U.S. patent application number 11/839693 was filed with the patent office on 2008-04-03 for hydrocarbon gas processing.
This patent application is currently assigned to Ortloff Engineers, Ltd.. Invention is credited to Kyle T. Cuellar, Hank M. Hudson, Joe T. Lynch, Tony L. Martinez, John D. Wilkinson.
Application Number | 20080078205 11/839693 |
Document ID | / |
Family ID | 39259824 |
Filed Date | 2008-04-03 |
United States Patent
Application |
20080078205 |
Kind Code |
A1 |
Cuellar; Kyle T. ; et
al. |
April 3, 2008 |
Hydrocarbon Gas Processing
Abstract
A process and apparatus for the recovery of ethane, ethylene,
propane, propylene, and heavier hydrocarbon components from a
hydrocarbon gas stream is disclosed. The stream is cooled and
divided into first and second streams. The first stream is further
cooled to condense substantially all of it and is thereafter
expanded to the fractionation tower pressure and supplied to the
fractionation tower at a first mid-column feed position. The second
stream is expanded to the tower pressure and is then supplied to
the column at a second mid-column feed position. A distillation
stream is withdrawn from the column below the feed point of the
second stream and compressed to higher pressure, and is then
directed into heat exchange relation with the tower overhead vapor
stream to cool the distillation stream and condense substantially
all of it, forming a condensed stream. At least a portion of the
condensed stream is directed to the fractionation tower as its top
feed. The quantities and temperatures of the feeds to the
fractionation tower are effective to maintain the overhead
temperature of the fractionation tower at a temperature whereby the
major portion of the desired components is recovered. In other
embodiments, the distillation stream is withdrawn from the column
above the feed point of the second stream.
Inventors: |
Cuellar; Kyle T.; (Katy,
TX) ; Martinez; Tony L.; (Odessa, TX) ;
Wilkinson; John D.; (Midland, TX) ; Lynch; Joe
T.; (Midland, TX) ; Hudson; Hank M.; (Midland,
TX) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
Ortloff Engineers, Ltd.
Midland
TX
|
Family ID: |
39259824 |
Appl. No.: |
11/839693 |
Filed: |
August 16, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60897683 |
Jan 25, 2007 |
|
|
|
60848299 |
Sep 28, 2006 |
|
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Current U.S.
Class: |
62/620 |
Current CPC
Class: |
F25J 2220/66 20130101;
F25J 2200/02 20130101; F25J 2230/60 20130101; F25J 3/0238 20130101;
F25J 2230/08 20130101; F25J 3/0233 20130101; F25J 2200/30 20130101;
F25J 3/0209 20130101; F25J 2200/78 20130101; F25J 2205/04 20130101;
F25J 2210/06 20130101; F25J 2240/02 20130101; F25J 2290/40
20130101 |
Class at
Publication: |
62/620 |
International
Class: |
F25J 3/00 20060101
F25J003/00; F25J 1/00 20060101 F25J001/00 |
Claims
1. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered; the improvement wherein following cooling, said cooled
stream is divided into first and second streams; and (1) said first
stream is cooled to condense substantially all of it and is
thereafter expanded to said lower pressure whereby it is further
cooled; (2) said expanded cooled first stream is thereafter
supplied at a first mid-column feed position to said distillation
column; (3) said second stream is expanded to said lower pressure
and is supplied to said distillation column at a second mid-column
feed position; (4) a vapor distillation stream is withdrawn from a
region of said distillation column below said expanded second
stream and is compressed to higher pressure; (5) said compressed
vapor distillation stream is cooled sufficiently to condense at
least a part of it, thereby forming a condensed stream; (6) at
least a portion of said condensed stream is expanded to said lower
pressure and is thereafter supplied to said distillation column at
a top feed position; (7) an overhead vapor stream is withdrawn from
an upper region of said distillation column and is directed into
heat exchange relation with said compressed vapor distillation
stream and heated, thereby to supply at least a portion of the
cooling of step (5), and thereafter discharging at least a portion
of said heated overhead vapor stream as said volatile residue gas
fraction; and (8) the quantities and temperatures of said feed
streams to said distillation column are effective to maintain the
overhead temperature of said distillation column at a temperature
whereby the major portions of the components in said relatively
less volatile fraction are recovered.
2. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered; the improvement wherein prior to cooling, said gas is
divided into first and second streams; and (1) said first stream is
cooled to condense substantially all of it and is thereafter
expanded to said lower pressure whereby it is further cooled; (2)
said expanded cooled first stream is thereafter supplied at a first
mid-column feed position to said distillation column; (3) said
second stream is cooled and thereafter expanded to said lower
pressure and supplied to said distillation column at a second
mid-column feed position; (4) a vapor distillation stream is
withdrawn from a region of said distillation column below said
expanded cooled second stream and is compressed to higher pressure;
(5) said compressed vapor distillation stream is cooled
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (6) at least a portion of said condensed stream
is expanded to said lower pressure and is thereafter supplied to
said distillation column at a top feed position; (7) an overhead
vapor stream is withdrawn from an upper region of said distillation
column and is directed into heat exchange relation with said
compressed vapor distillation stream and heated, thereby to supply
at least a portion of the cooling of step (5), and thereafter
discharging at least a portion of said heated overhead vapor stream
as said volatile residue gas fraction; and (8) the quantities and
temperatures of said feed streams to said distillation column are
effective to maintain the overhead temperature of said distillation
column at a temperature whereby the major portions of the
components in said relatively less volatile fraction are
recovered.
3. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered; the improvement wherein said gas stream is cooled
sufficiently to partially condense it; and (1) said partially
condensed gas stream is separated thereby to provide a vapor stream
and at least one liquid stream; (2) said vapor stream is thereafter
divided into first and second streams; (3) said first stream is
cooled to condense substantially all of it and is thereafter
expanded to said lower pressure whereby it is further cooled; (4)
said expanded cooled first stream is thereafter supplied at a first
mid-column feed position to said distillation column; (5) said
second stream is expanded to said lower pressure and is supplied to
said distillation column at a second mid-column feed position; (6)
at least a portion of said at least one liquid stream is expanded
to said lower pressure and is supplied to said distillation column
at a third mid-column feed position; (7) a vapor distillation
stream is withdrawn from a region of said distillation column below
said expanded second stream and is compressed to higher pressure;
(8) said compressed vapor distillation stream is cooled
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (9) at least a portion of said condensed stream
is expanded to said lower pressure and is thereafter supplied to
said distillation column at a top feed position; (10) an overhead
vapor stream is withdrawn from an upper region of said distillation
column and is directed into heat exchange relation with said
compressed vapor distillation stream and heated, thereby to supply
at least a portion of the cooling of step (8), and thereafter
discharging at least a portion of said heated overhead vapor stream
as said volatile residue gas fraction; and (11) the quantities and
temperatures of said feed streams to said distillation column are
effective to maintain the overhead temperature of said distillation
column at a temperature whereby the major portions of the
components in said relatively less volatile fraction are
recovered.
4. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered; the improvement wherein said gas stream is cooled
sufficiently to partially condense it; and (1) said partially
condensed gas stream is separated thereby to provide a vapor stream
and at least one liquid stream; (2) said vapor stream is thereafter
divided into first and second streams; (3) said first stream is
combined with at least a portion of said at least one liquid stream
to form a combined stream, and said combined stream is cooled to
condense substantially all of it and is thereafter expanded to said
lower pressure whereby it is further cooled; (4) said expanded
cooled combined stream is thereafter supplied at a first mid-column
feed position to said distillation column; (5) said second stream
is expanded to said lower pressure and is supplied to said
distillation column at a second mid-column feed position; (6) any
remaining portion of said at least one liquid stream is expanded to
said lower pressure and is supplied to said distillation column at
a third mid-column feed position; (7) a vapor distillation stream
is withdrawn from a region of said distillation column below said
expanded second stream and is compressed to higher pressure; (8)
said compressed vapor distillation stream is cooled sufficiently to
condense at least a part of it, thereby forming a condensed stream;
(9) at least a portion of said condensed stream is expanded to said
lower pressure and is thereafter supplied to said distillation
column at a top feed position; (10) an overhead vapor stream is
withdrawn from an upper region of said distillation column and is
directed into heat exchange relation with said compressed vapor
distillation stream and heated, thereby to supply at least a
portion of the cooling of step (8), and thereafter discharging at
least a portion of said heated overhead vapor stream as said
volatile residue gas fraction; and (11) the quantities and
temperatures of said feed streams to said distillation column are
effective to maintain the overhead temperature of said distillation
column at a temperature whereby the major portions of the
components in said relatively less volatile fraction are
recovered.
5. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered; the improvement wherein prior to cooling, said gas is
divided into first and second streams; and (1) said first stream is
cooled to condense substantially all of it and is thereafter
expanded to said lower pressure whereby it is further cooled; (2)
said expanded cooled first stream is thereafter supplied at a first
mid-column feed position to said distillation column; (3) said
second stream is cooled under pressure sufficiently to partially
condense it; (4) said partially condensed second stream is
separated thereby to provide a vapor stream and at least one liquid
stream; (5) said vapor stream is expanded to said lower pressure
and supplied to said distillation column at a second mid-column
feed position; (6) at least a portion of said at least one liquid
stream is expanded to said lower pressure and is supplied to said
distillation column at a third mid-column feed position; (7) a
vapor distillation stream is withdrawn from a region of said
distillation column below said expanded vapor stream and is
compressed to higher pressure; (8) said compressed vapor
distillation stream is cooled sufficiently to condense at least a
part of it, thereby forming a condensed stream; (9) at least a
portion of said condensed stream is expanded to said lower pressure
and is thereafter supplied to said distillation column at a top
feed position; (10) an overhead vapor stream is withdrawn from an
upper region of said distillation column and is directed into heat
exchange relation with said compressed vapor distillation stream
and heated, thereby to supply at least a portion of the cooling of
step (8), and thereafter discharging at least a portion of said
heated overhead vapor stream as said volatile residue gas fraction;
and (11) the quantities and temperatures of said feed streams to
said distillation column are effective to maintain the overhead
temperature of said distillation column at a temperature whereby
the major portions of the components in said relatively less
volatile fraction are recovered.
6. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered; the improvement wherein following cooling, said cooled
stream is divided into first and second streams; and (1) said first
stream is cooled to condense substantially all of it and is
thereafter expanded to said lower pressure whereby it is further
cooled; (2) said expanded cooled first stream is thereafter
supplied at a mid-column feed position to a contacting and
separating device that produces an overhead vapor stream and a
bottom liquid stream, whereupon said bottom liquid stream is
supplied to said distillation column; (3) said second stream is
expanded to said lower pressure and is supplied to said contacting
and separating device at a first lower feed position; (4) a vapor
distillation stream is withdrawn from an upper region of said
distillation column to form at least a first distillation stream;
(5) said first distillation stream is compressed to higher
pressure; (6) said compressed first distillation stream is cooled
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (7) at least a portion of said condensed stream
is expanded to said lower pressure and is thereafter supplied to
said contacting and separating device at a top feed position; (8)
any remaining portion of said vapor distillation stream is directed
to said contacting and separating device at a second lower feed
position; (9) said overhead vapor stream is directed into heat
exchange relation with said compressed first distillation stream
and heated, thereby to supply at least a portion of the cooling of
step (6), and thereafter discharging at least a portion of said
heated overhead vapor stream as said volatile residue gas fraction;
and (10) the quantities and temperatures of said feed streams to
said contacting and separating device are effective to maintain the
overhead temperature of said contacting and separating device at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
7. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered; the improvement wherein prior to cooling, said gas is
divided into first and second streams; and (1) said first stream is
cooled to condense substantially all of it and is thereafter
expanded to said lower pressure whereby it is further cooled; (2)
said expanded cooled first stream is thereafter supplied at a
mid-column feed position to a contacting and separating device that
produces an overhead vapor stream and a bottom liquid stream,
whereupon said bottom liquid stream is supplied to said
distillation column; (3) said second stream is cooled and
thereafter expanded to said lower pressure and is supplied to said
contacting and separating device at a first lower feed position;
(4) a vapor distillation stream is withdrawn from an upper region
of said distillation column to form at least a first distillation
stream; (5) said first distillation stream is compressed to higher
pressure; (6) said compressed first distillation stream is cooled
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (7) at least a portion of said condensed stream
is expanded to said lower pressure and is thereafter supplied to
said contacting and separating device at a top feed position; (8)
any remaining portion of said vapor distillation stream is directed
to said contacting and separating device at a second lower feed
position; (9) said overhead vapor stream is directed into heat
exchange relation with said compressed first distillation stream
and heated, thereby to supply at least a portion of the cooling of
step (6), and thereafter discharging at least a portion of said
heated overhead vapor stream as said volatile residue gas fraction;
and (10) the quantities and temperatures of said feed streams to
said contacting and separating device are effective to maintain the
overhead temperature of said contacting and separating device at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
8. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered; the improvement wherein said gas stream is cooled
sufficiently to partially condense it; and (1) said partially
condensed gas stream is separated thereby to provide a vapor stream
and at least one liquid stream; (2) said vapor stream is thereafter
divided into first and second streams; (3) said first stream is
cooled to condense substantially all of it and is thereafter
expanded to said lower pressure whereby it is further cooled; (4)
said expanded cooled first stream is thereafter supplied at a
mid-column feed position to a contacting and separating device that
produces an overhead vapor stream and a bottom liquid stream,
whereupon said bottom liquid stream is supplied to said
distillation column; (5) said second stream is expanded to said
lower pressure and is supplied to said contacting and separating
device at a first lower feed position; (6) said at least one liquid
stream is expanded to said lower pressure and supplied to said
distillation column at a mid-column feed position; (7) a vapor
distillation stream is withdrawn from an upper region of said
distillation column to form at least a first distillation stream;
(8) said first distillation stream is compressed to higher
pressure; (9) said compressed first distillation stream is cooled
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (10) at least a portion of said condensed stream
is expanded to said lower pressure and is thereafter supplied to
said contacting and separating device at a top feed position; (11)
any remaining portion of said vapor distillation stream is directed
to said contacting and separating device at a second lower feed
position; (12) said overhead vapor stream is directed into heat
exchange relation with said compressed first distillation stream
and heated, thereby to supply at least a portion of the cooling of
step (9), and thereafter discharging at least a portion of said
heated overhead vapor stream as said volatile residue gas fraction;
and (13) the quantities and temperatures of said feed streams to
said contacting and separating device are effective to maintain the
overhead temperature of said contacting and separating device at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
9. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered; the improvement wherein said gas stream is cooled
sufficiently to partially condense it; and (1) said partially
condensed gas stream is separated thereby to provide a vapor stream
and at least one liquid stream; (2) said vapor stream is thereafter
divided into first and second streams; (3) said first stream is
combined with at least a portion of said at least one liquid stream
to form a combined stream, and said combined stream is cooled to
condense substantially all of it and is thereafter expanded to said
lower pressure whereby it is further cooled; (4) said expanded
cooled combined stream is thereafter supplied at a mid-column feed
position to a contacting and separating device that produces an
overhead vapor stream and a bottom liquid stream, whereupon said
bottom liquid stream is supplied to said distillation column; (5)
said second stream is expanded to said lower pressure and is
supplied to said contacting and separating device at a first lower
feed position; (6) any remaining portion of said at least one
liquid stream is expanded to said lower pressure and supplied to
said distillation column at a mid-column feed position; (7) a vapor
distillation stream is withdrawn from an upper region of said
distillation column to form at least a first distillation stream;
(8) said first distillation stream is compressed to higher
pressure; (9) said compressed first distillation stream is cooled
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (10) at least a portion of said condensed stream
is expanded to said lower pressure and is thereafter supplied to
said contacting and separating device at a top feed position; (11)
any remaining portion of said vapor distillation stream is directed
to said contacting and separating device at a second lower feed
position; (12) said overhead vapor stream is directed into heat
exchange relation with said compressed first distillation stream
and heated, thereby to supply at least a portion of the cooling of
step (9), and thereafter discharging at least a portion of said
heated overhead vapor stream as said volatile residue gas fraction;
and (13) the quantities and temperatures of said feed streams to
said contacting and separating device are effective to maintain the
overhead temperature of said contacting and separating device at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
10. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered; the improvement wherein prior to cooling, said gas is
divided into first and second streams; and (1) said first stream is
cooled to condense substantially all of it and is thereafter
expanded to said lower pressure whereby it is further cooled; (2)
said expanded cooled first stream is thereafter supplied at a
mid-column feed position to a contacting and separating device that
produces an overhead vapor stream and a bottom liquid stream,
whereupon said bottom liquid stream is supplied to said
distillation column; (3) said second stream is cooled under
pressure sufficiently to partially condense it; (4) said partially
condensed second stream is separated thereby to provide a vapor
stream and at least one liquid stream; (5) said vapor stream is
expanded to said lower pressure and is supplied to said contacting
and separating device at a first lower feed position; (6) said at
least one liquid stream is expanded to said lower pressure and
supplied to said distillation column at a mid-column feed position;
(7) a vapor distillation stream is withdrawn from an upper region
of said distillation column to form at least a first distillation
stream; (8) said first distillation stream is compressed to higher
pressure; (9) said compressed first distillation stream is cooled
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (10) at least a portion of said condensed stream
is expanded to said lower pressure and is thereafter supplied to
said contacting and separating device at a top feed position; (11)
any remaining portion of said vapor distillation stream is directed
to said contacting and separating device at a second lower feed
position; (12) said overhead vapor stream is directed into heat
exchange relation with said compressed first distillation stream
and heated, thereby to supply at least a portion of the cooling of
step (9), and thereafter discharging at least a portion of said
heated overhead vapor stream as said volatile residue gas fraction;
and (13) the quantities and temperatures of said feed streams to
said contacting and separating device are effective to maintain the
overhead temperature of said contacting and separating device at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
11. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered and a first overhead vapor stream is produced; the
improvement wherein following cooling, said cooled stream is
divided into first and second streams; and (1) said first stream is
cooled to condense substantially all of it and is thereafter
expanded to said lower pressure whereby it is further cooled; (2)
said expanded cooled first stream is thereafter supplied at a
mid-column feed position to a contacting and separating device that
produces a second overhead vapor stream and a bottom liquid stream,
whereupon said bottom liquid stream is supplied to said
distillation column; (3) said second stream is expanded to said
lower pressure and is supplied to said contacting and separating
device at a first lower feed position; (4) a vapor distillation
stream is withdrawn from a region of said contacting and separating
device above said expanded second stream and is compressed to
higher pressure; (5) said compressed vapor distillation stream is
cooled sufficiently to condense at least a part of it, thereby
forming a condensed stream; (6) at least a portion of said
condensed stream is expanded to said lower pressure and is
thereafter supplied to said contacting and separating device at a
top feed position; (7) said first overhead vapor stream is directed
to said contacting and separating device at a second lower feed
position; (8) said second overhead vapor stream is directed into
heat exchange relation with said compressed vapor distillation
stream and heated, thereby to supply at least a portion of the
cooling of step (5), and thereafter discharging at least a portion
of said heated second overhead vapor stream as said volatile
residue gas fraction; and (9) the quantities and temperatures of
said feed streams to said contacting and separating device are
effective to maintain the overhead temperature of said contacting
and separating device at a temperature whereby the major portions
of the components in said relatively less volatile fraction are
recovered.
12. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered and a first overhead vapor stream is produced; the
improvement wherein prior to cooling, said gas is divided into
first and second streams; and (1) said first stream is cooled to
condense substantially all of it and is thereafter expanded to said
lower pressure whereby it is further cooled; (2) said expanded
cooled first stream is thereafter supplied at a mid-column feed
position to a contacting and separating device that produces a
second overhead vapor stream and a bottom liquid stream, whereupon
said bottom liquid stream is supplied to said distillation column;
(3) said second stream is cooled and thereafter expanded to said
lower pressure and is supplied to said contacting and separating
device at a first lower feed position; (4) a vapor distillation
stream is withdrawn from a region of said contacting and separating
device above said expanded cooled second stream and is compressed
to higher pressure; (5) said compressed vapor distillation stream
is cooled sufficiently to condense at least a part of it, thereby
forming a condensed stream; (6) at least a portion of said
condensed stream is expanded to said lower pressure and is
thereafter supplied to said contacting and separating device at a
top feed position; (7) said first overhead vapor stream is directed
to said contacting and separating device at a second lower feed
position; (8) said second overhead vapor stream is directed into
heat exchange relation with said compressed vapor distillation
stream and heated, thereby to supply at least a portion of the
cooling of step (5), and thereafter discharging at least a portion
of said heated second overhead vapor stream as said volatile
residue gas fraction; and (9) the quantities and temperatures of
said feed streams to said contacting and separating device are
effective to maintain the overhead temperature of said contacting
and separating device at a temperature whereby the major portions
of the components in said relatively less volatile fraction are
recovered.
13. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered and a first overhead vapor stream is produced; the
improvement wherein said gas stream is cooled sufficiently to
partially condense it; and (1) said partially condensed gas stream
is separated thereby to provide a vapor stream and at least one
liquid stream; (2) said vapor stream is thereafter divided into
first and second streams; (3) said first stream is cooled to
condense substantially all of it and is thereafter expanded to said
lower pressure whereby it is further cooled; (4) said expanded
cooled first stream is thereafter supplied at a mid-column feed
position to a contacting and separating device that produces a
second overhead vapor stream and a bottom liquid stream, whereupon
said bottom liquid stream is supplied to said distillation column;
(5) said second stream is expanded to said lower pressure and is
supplied to said contacting and separating device at a first lower
feed position; (6) said at least one liquid stream is expanded to
said lower pressure and supplied to said distillation column at a
mid-column feed position; (7) a vapor distillation stream is
withdrawn from a region of said contacting and separating device
above said expanded second stream and is compressed to higher
pressure; (8) said compressed vapor distillation stream is cooled
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (9) at least a portion of said condensed stream
is expanded to said lower pressure and is thereafter supplied to
said contacting and separating device at a top feed position; (10)
said first overhead stream is directed to said contacting and
separating device at a second lower feed position; (11) said second
overhead vapor stream is directed into heat exchange relation with
said compressed vapor distillation stream and heated, thereby to
supply at least a portion of the cooling of step (8), and
thereafter discharging at least a portion of said heated second
overhead vapor stream as said volatile residue gas fraction; and
(12) the quantities and temperatures of said feed streams to said
contacting and separating device are effective to maintain the
overhead temperature of said contacting and separating device at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
14. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered and a first overhead vapor stream is produced; the
improvement wherein said gas stream is cooled sufficiently to
partially condense it; and (1) said partially condensed gas stream
is separated thereby to provide a vapor stream and at least one
liquid stream; (2) said vapor stream is thereafter divided into
first and second streams; (3) said first stream is combined with at
least a portion of said at least one liquid stream to form a
combined stream, and said combined stream is cooled to condense
substantially all of it and is thereafter expanded to said lower
pressure whereby it is further cooled; (4) said expanded cooled
combined stream is thereafter supplied at a mid-column feed
position to a contacting and separating device that produces a
second overhead vapor stream and a bottom liquid stream, whereupon
said bottom liquid stream is supplied to said distillation column;
(5) said second stream is expanded to said lower pressure and is
supplied to said contacting and separating device at a first lower
feed position; (6) any remaining portion of said at least one
liquid stream is expanded to said lower pressure and supplied to
said distillation column at a mid-column feed position; (7) a vapor
distillation stream is withdrawn from a region of said contacting
and separating device above said expanded second stream and is
compressed to higher pressure; (8) said compressed vapor
distillation stream is cooled sufficiently to condense at least a
part of it, thereby forming a condensed stream; (9) at least a
portion of said condensed stream is expanded to said lower pressure
and is thereafter supplied to said contacting and separating device
at a top feed position; (10) said first overhead stream is directed
to said contacting and separating device at a second lower feed
position; (11) said second overhead vapor stream is directed into
heat exchange relation with said compressed vapor distillation
stream and heated, thereby to supply at least a portion of the
cooling of step (8), and thereafter discharging at least a portion
of said heated second overhead vapor stream as said volatile
residue gas fraction; and (12) the quantities and temperatures of
said feed streams to said contacting and separating device are
effective to maintain the overhead temperature of said contacting
and separating device at a temperature whereby the major portions
of the components in said relatively less volatile fraction are
recovered.
15. In a process for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in which process (a) said gas stream is
cooled under pressure to provide a cooled stream; (b) said cooled
stream is expanded to a lower pressure whereby it is further
cooled; and (c) said further cooled stream is directed into a
distillation column and fractionated at said lower pressure whereby
the components of said relatively less volatile fraction are
recovered and a first overhead vapor stream is produced; the
improvement wherein prior to cooling, said gas is divided into
first and second streams; and (1) said first stream is cooled to
condense substantially all of it and is thereafter expanded to said
lower pressure whereby it is further cooled; (2) said expanded
cooled first stream is thereafter supplied at a mid-column feed
position to a contacting and separating device that produces a
second overhead vapor stream and a bottom liquid stream, whereupon
said bottom liquid stream is supplied to said distillation column;
(3) said second stream is cooled under pressure sufficiently to
partially condense it; (4) said partially condensed second stream
is separated thereby to provide a vapor stream and at least one
liquid stream; (5) said vapor stream is expanded to said lower
pressure and is supplied to said contacting and separating device
at a first lower feed position; (6) said at least one liquid stream
is expanded to said lower pressure and supplied to said
distillation column at a mid-column feed position; (7) a vapor
distillation stream is withdrawn from a region of said contacting
and separating device above said expanded vapor stream and is
compressed to higher pressure; (8) said compressed vapor
distillation stream is cooled sufficiently to condense at least a
part of it, thereby forming a condensed stream; (9) at least a
portion of said condensed stream is expanded to said lower pressure
and is thereafter supplied to said contacting and separating device
at a top feed position; (10) said first overhead stream is directed
to said contacting and separating device at a second lower feed
position; (11) said second overhead vapor stream is directed into
heat exchange relation with said compressed vapor distillation
stream and heated, thereby to supply at least a portion of the
cooling of step (8), and thereafter discharging at least a portion
of said heated second overhead vapor stream as said volatile
residue gas fraction; and (12) the quantities and temperatures of
said feed streams to said contacting and separating device are
effective to maintain the overhead temperature of said contacting
and separating device at a temperature whereby the major portions
of the components in said relatively less volatile fraction are
recovered.
16. The improvement according to claim 1, 3, or 4 wherein said
vapor distillation stream is withdrawn from a region of said
distillation column above said expanded second stream and is
thereafter compressed to higher pressure.
17. The improvement according to claim 2 wherein said vapor
distillation stream is withdrawn from a region of said distillation
column above said expanded cooled second stream and is thereafter
compressed to higher pressure.
18. The improvement according to claim 5 wherein said vapor
distillation stream is withdrawn from a region of said distillation
column above said expanded vapor stream and is thereafter
compressed to higher pressure.
19. The improvement according to claim 1, 3, or 4 wherein (1) said
condensed stream is divided into at least a first portion and a
second portion; (2) said first portion is expanded to said lower
pressure and is thereafter supplied to said distillation column at
said top feed position; and (3) said second portion is expanded to
said lower pressure and is thereafter supplied to said distillation
column at a mid-column feed position above that of said expanded
second stream.
20. The improvement according to claim 2 wherein (1) said condensed
stream is divided into at least a first portion and a second
portion; (2) said first portion is expanded to said lower pressure
and is thereafter supplied to said distillation column at said top
feed position; and (3) said second portion is expanded to said
lower pressure and is thereafter supplied to said distillation
column at a mid-column feed position above that of said expanded
cooled second stream.
21. The improvement according to claim 5 wherein (1) said condensed
stream is divided into at least a first portion and a second
portion; (2) said first portion is expanded to said lower pressure
and is thereafter supplied to said distillation column at said top
feed position; and (3) said second portion is expanded to said
lower pressure and is thereafter supplied to said distillation
column at a mid-column feed position above that of said expanded
vapor stream.
22. The improvement according to claim 6, 8, or 9 wherein (1) said
condensed stream is divided into at least a first portion and a
second portion; (2) said first portion is expanded to said lower
pressure and is thereafter supplied to said contacting and
separating device at said top feed position; and (3) said second
portion is expanded to said lower pressure and is thereafter
supplied to said contacting and separating device at a mid-column
feed position above that of said expanded second stream.
23. The improvement according to claim 7 wherein (1) said condensed
stream is divided into at least a first portion and a second
portion; (2) said first portion is expanded to said lower pressure
and is thereafter supplied to said contacting and separating device
at said top feed position; and (3) said second portion is expanded
to said lower pressure and is thereafter supplied to said
contacting and separating device at a mid-column feed position
above that of said expanded cooled second stream.
24. The improvement according to claim 10 wherein (1) said
condensed stream is divided into at least a first portion and a
second portion; (2) said first portion is expanded to said lower
pressure and is thereafter supplied to said contacting and
separating device at said top feed position; and (3) said second
portion is expanded to said lower pressure and is thereafter
supplied to said contacting and separating device at a mid-column
feed position above that of said expanded vapor stream.
25. The improvement according to claim 11, 12, 13, 14, or 15
wherein (1) said condensed stream is divided into at least a first
portion and a second portion; (2) said first portion is expanded to
said lower pressure and is thereafter supplied to said contacting
and separating device at said top feed position; and (3) said
second portion is expanded to said lower pressure and is thereafter
supplied to said contacting and separating device at a mid-column
feed position above the region wherein said vapor distillation
stream is withdrawn.
26. The improvement according to claim 16 wherein (1) said
condensed stream is divided into at least a first portion and a
second portion; (2) said first portion is expanded to said lower
pressure and is thereafter supplied to said distillation column at
said top feed position; and (3) said second portion is expanded to
said lower pressure and is thereafter supplied to said distillation
column at a mid-column feed position above the region wherein said
vapor distillation stream is withdrawn.
27. The improvement according to claim 17 or 18 wherein (1) said
condensed stream is divided into at least a first portion and a
second portion; (2) said first portion is expanded to said lower
pressure and is thereafter supplied to said distillation column at
said top feed position; and (3) said second portion is expanded to
said lower pressure and is thereafter supplied to said distillation
column at a mid-column feed position above the region wherein said
vapor distillation stream is withdrawn.
28. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into an overhead
vapor stream and said relatively less volatile fraction; the
improvement wherein said apparatus includes (1) dividing means
connected to said first cooling means to receive said cooled stream
and to divide it into first and second streams; (2) second cooling
means connected to said dividing means to receive said first stream
and to cool it sufficiently to substantially condense it; (3)
second expansion means connected to said second cooling means to
receive said substantially condensed first stream and to expand it
to said lower pressure, said second expansion means being further
connected to said distillation column to supply said expanded
cooled first stream to said distillation column at a first
mid-column feed position; (4) said first expansion means being
connected to said dividing means to receive said second stream and
to expand it to said lower pressure, said first expansion means
being further connected to said distillation column to supply said
expanded second stream to said distillation column at a second
mid-column feed position; (5) vapor withdrawing means connected to
said distillation column to receive a vapor distillation stream
from a region of said distillation column below said expanded
second stream; (6) compressing means connected to said vapor
withdrawing means to receive said vapor distillation stream and to
compress it to higher pressure; (7) heat exchange means connected
to said compressing means to receive said compressed vapor
distillation stream and to cool it sufficiently to condense at
least a part of it, thereby forming a condensed stream; (8) third
expansion means connected to said heat exchange means to receive at
least a portion of said condensed stream and to expand it to said
lower pressure, said third expansion means being further connected
to said distillation column to supply said at least a portion of
said expanded condensed stream to said distillation column at a top
feed position; (9) said distillation column being further connected
to said heat exchange means to direct at least a portion of said
overhead vapor stream separated therein into heat exchange relation
with said compressed vapor distillation stream and to heat said
overhead vapor stream, thereby to supply at least a portion of the
cooling of step (7), and thereafter discharging at least a portion
of said heated overhead vapor stream as said volatile residue gas
fraction; and (10) control means adapted to regulate the quantities
and temperatures of said feed streams to said distillation column
to maintain the overhead temperature of said distillation column at
a temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
29. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into an overhead
vapor stream and said relatively less volatile fraction; the
improvement wherein said apparatus includes (1) dividing means
prior to said first cooling means to divide said feed gas into
first and second streams; (2) second cooling means connected to
said dividing means to receive said first stream and to cool it
sufficiently to substantially condense it; (3) second expansion
means connected to said second cooling means to receive said
substantially condensed first stream and to expand it to said lower
pressure, said second expansion means being further connected to
said distillation column to supply said expanded cooled first
stream to said distillation column at a first mid-column feed
position; (4) said first cooling means being connected to said
dividing means to receive said second stream and to cool it; (5)
said first expansion means being connected to said first cooling
means to receive said cooled second stream and to expand it to said
lower pressure, said first expansion means being further connected
to said distillation column to supply said expanded cooled second
stream to said distillation column at a second mid-column feed
position; (6) vapor withdrawing means connected to said
distillation column to receive a vapor distillation stream from a
region of said distillation column below said expanded cooled
second stream; (7) compressing means connected to said vapor
withdrawing means to receive said vapor distillation stream and to
compress it to higher pressure; (8) heat exchange means connected
to said compressing means to receive said compressed vapor
distillation stream and to cool it sufficiently to condense at
least a part of it, thereby forming a condensed stream; (9) third
expansion means connected to said heat exchange means to receive at
least a portion of said condensed stream and to expand it to said
lower pressure, said third expansion means being further connected
to said distillation column to supply said at least a portion of
said expanded condensed stream to said distillation column at a top
feed position; (10) said distillation column being further
connected to said heat exchange means to direct at least a portion
of said overhead vapor stream separated therein into heat exchange
relation with said compressed vapor distillation stream and to heat
said overhead vapor stream, thereby to supply at least a portion of
the cooling of step (8), and thereafter discharging at least a
portion of said heated overhead vapor stream as said volatile
residue gas fraction; and (11) control means adapted to regulate
the quantities and temperatures of said feed streams to said
distillation column to maintain the overhead temperature of said
distillation column at a temperature whereby the major portions of
the components in said relatively less volatile fraction are
recovered.
30. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into an overhead
vapor stream and said relatively less volatile fraction; the
improvement wherein said apparatus includes (1) said first cooling
means being adapted to cool said feed gas under pressure
sufficiently to partially condense it; (2) separating means
connected to said first cooling means to receive said partially
condensed feed and to separate it into a vapor stream and at least
one liquid stream; (3) dividing means connected to said separating
means to receive said vapor stream and to divide it into first and
second streams; (4) second cooling means connected to said dividing
means to receive said first stream and to cool it sufficiently to
substantially condense it; (5) second expansion means connected to
said second cooling means to receive said substantially condensed
first stream and to expand it to said lower pressure, said second
expansion means being further connected to said distillation column
to supply said expanded cooled first stream to said distillation
column at a first mid-column feed position; (6) said first
expansion means being connected to said dividing means to receive
said second stream and to expand it to said lower pressure, said
first expansion means being further connected to said distillation
column to supply said expanded second stream to said distillation
column at a second mid-column feed position; (7) third expansion
means connected to said separating means to receive at least a
portion of said at least one liquid stream and to expand it to said
lower pressure, said third expansion means being further connected
to said distillation column to supply said expanded liquid stream
to said distillation column at a third mid-column feed position;
(8) vapor withdrawing means connected to said distillation column
to receive a vapor distillation stream from a region of said
distillation column below said expanded second stream; (9)
compressing means connected to said vapor withdrawing means to
receive said vapor distillation stream and to compress it to higher
pressure; (10) heat exchange means connected to said compressing
means to receive said compressed vapor distillation stream and to
cool it sufficiently to condense at least a part of it, thereby
forming a condensed stream; (11) fourth expansion means connected
to said heat exchange means to receive at least a portion of said
condensed stream and to expand it to said lower pressure, said
fourth expansion means being further connected to said distillation
column to supply said at least a portion of said expanded condensed
stream to said distillation column at a top feed position; (12)
said distillation column being further connected to said heat
exchange means to direct at least a portion of said overhead vapor
stream separated therein into heat exchange relation with said
compressed vapor distillation stream and to heat said overhead
vapor stream, thereby to supply at least a portion of the cooling
of step (10), and thereafter discharging at least a portion of said
heated overhead vapor stream as said volatile residue gas fraction;
and (13) control means adapted to regulate the quantities and
temperatures of said feed streams to said distillation column to
maintain the overhead temperature of said distillation column at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
31. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into an overhead
vapor stream and said relatively less volatile fraction; the
improvement wherein said apparatus includes (1) said first cooling
means being adapted to cool said feed gas under pressure
sufficiently to partially condense it; (2) separating means
connected to said first cooling means to receive said partially
condensed feed and to separate it into a vapor stream and at least
one liquid stream; (3) dividing means connected to said separating
means to receive said vapor stream and to divide it into first and
second streams; (4) combining means connected to said dividing
means and said separating means to receive said first stream and at
least a portion of said at least one liquid stream and form a
combined stream; (5) second cooling means connected to said
combining means to receive said combined stream and to cool it
sufficiently to substantially condense it; (6) second expansion
means connected to said second cooling means to receive said
substantially condensed combined stream and to expand it to said
lower pressure, said second expansion means being further connected
to said distillation column to supply said expanded cooled combined
stream to said distillation column at a first mid-column feed
position; (7) said first expansion means being connected to said
dividing means to receive said second stream and to expand it to
said lower pressure, said first expansion means being further
connected to said distillation column to supply said expanded
second stream to said distillation column at a second mid-column
feed position; (8) third expansion means connected to said
separating means to receive any remaining portion of said at least
one liquid stream and to expand it to said lower pressure, said
third expansion means being further connected to said distillation
column to supply said expanded liquid stream to said distillation
column at a third mid-column feed position; (9) vapor withdrawing
means connected to said distillation column to receive a vapor
distillation stream from a region of said distillation column below
said expanded second stream; (10) compressing means connected to
said vapor withdrawing means to receive said vapor distillation
stream and to compress it to higher pressure; (11) heat exchange
means connected to said compressing means to receive said
compressed vapor distillation stream and to cool it sufficiently to
condense at least a part of it, thereby forming a condensed stream;
(12) fourth expansion means connected to said heat exchange means
to receive at least a portion of said condensed stream and to
expand it to said lower pressure, said fourth expansion means being
further connected to said distillation column to supply said at
least a portion of said expanded condensed stream to said
distillation column at a top feed position; (13) said distillation
column being further connected to said heat exchange means to
direct at least a portion of said overhead vapor stream separated
therein into heat exchange relation with said compressed vapor
distillation stream and to heat said overhead vapor stream, thereby
to supply at least a portion of the cooling of step (11), and
thereafter discharging at least a portion of said heated overhead
vapor stream as said volatile residue gas fraction; and (14)
control means adapted to regulate the quantities and temperatures
of said feed streams to said distillation column to maintain the
overhead temperature of said distillation column at a temperature
whereby the major portions of the components in said relatively
less volatile fraction are recovered.
32. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into an overhead
vapor stream and said relatively less volatile fraction; the
improvement wherein said apparatus includes (1) dividing means
prior to said first cooling means to divide said feed gas into
first and second streams; (2) second cooling means connected to
said dividing means to receive said first stream and to cool it
sufficiently to substantially condense it; (3) second expansion
means connected to said second cooling means to receive said
substantially condensed first stream and to expand it to said lower
pressure, said second expansion means being further connected to
said distillation column to supply said expanded cooled first
stream to said distillation column at a first mid-column feed
position; (4) said first cooling means being connected to said
dividing means to receive said second stream, said first cooling
means being adapted to cool said second stream under pressure
sufficiently to partially condense it; (5) separating means
connected to said first cooling means to receive said partially
condensed second stream and to separate it into a vapor stream and
at least one liquid stream; (6) said first expansion means being
connected to said separating means to receive said vapor stream and
to expand it to said lower pressure, said first expansion means
being further connected to said distillation column to supply said
expanded vapor stream to said distillation column at a second
mid-column feed position; (7) third expansion means connected to
said separating means to receive at least a portion of said at
least one liquid stream and to expand it to said lower pressure,
said third expansion means being further connected to said
distillation column to supply said expanded liquid stream to said
distillation column at a third mid-column feed position; (8) vapor
withdrawing means connected to said distillation column to receive
a vapor distillation stream from a region of said distillation
column below said expanded vapor stream; (9) compressing means
connected to said vapor withdrawing means to receive said vapor
distillation stream and to compress it to higher pressure; (10)
heat exchange means connected to said compressing means to receive
said compressed vapor distillation stream and to cool it
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (11) fourth expansion means connected to said
heat exchange means to receive at least a portion of said condensed
stream and to expand it to said lower pressure, said fourth
expansion means being further connected to said distillation column
to supply said at least a portion of said expanded condensed stream
to said distillation column at a top feed position; (12) said
distillation column being further connected to said heat exchange
means to direct at least a portion of said overhead vapor stream
separated therein into heat exchange relation with said compressed
vapor distillation stream and to heat said overhead vapor stream,
thereby to supply at least a portion of the cooling of step (10),
and thereafter discharging at least a portion of said heated
overhead vapor stream as said volatile residue gas fraction; and
(13) control means adapted to regulate the quantities and
temperatures of said feed streams to said distillation column to
maintain the overhead temperature of said distillation column at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
33. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into a vapor
distillation stream and said relatively less volatile fraction; the
improvement wherein said apparatus includes (1) dividing means
connected to said first cooling means to receive said cooled stream
and to divide it into first and second streams; (2) second cooling
means connected to said dividing means to receive said first stream
and to cool it sufficiently to substantially condense it; (3)
second expansion means connected to said second cooling means to
receive said substantially condensed first stream and to expand it
to said lower pressure, said second expansion means being further
connected to a contacting and separating means to supply said
expanded cooled first stream to said contacting and separating
means at a mid-column feed position, said contacting and separating
means being adapted to produce an overhead vapor stream and a
bottom liquid stream; (4) said first expansion means being
connected to said dividing means to receive said second stream and
to expand it to said lower pressure, said first expansion means
being further connected to said contacting and separating means to
supply said expanded second stream to said contacting and
separating means at a first lower feed position; (5) said
distillation column being connected to said contacting and
separating means to receive at least a portion of said bottom
liquid stream; (6) vapor withdrawing means connected to said
distillation column to receive said vapor distillation stream and
form at least a first distillation stream; (7) compressing means
connected to said vapor withdrawing means to receive said first
distillation stream and to compress it to higher pressure; (8) heat
exchange means connected to said compressing means to receive said
compressed first distillation stream and to cool it sufficiently to
condense at least a part of it, thereby forming a condensed stream;
(9) third expansion means connected to said heat exchange means to
receive at least a portion of said condensed stream and to expand
it to said lower pressure, said third expansion means being further
connected to said contacting and separating means to supply said at
least a portion of said expanded condensed stream to said
contacting and separating means at a top feed position; (10) said
vapor withdrawing means being further connected to said contacting
and separating means to direct any remaining portion of said vapor
distillation stream to said contacting and separating means at a
second lower feed position; (11) said contacting and separating
means being further connected to said heat exchange means to direct
at least a portion of said overhead vapor stream separated therein
into heat exchange relation with said compressed first distillation
stream and to heat said overhead vapor stream, thereby to supply at
least a portion of the cooling of step (8), and thereafter
discharging at least a portion of said heated overhead vapor stream
as said volatile residue gas fraction; and (12) control means
adapted to regulate the quantities and temperatures of said feed
streams to said contacting and separating means to maintain the
overhead temperature of said contacting and separating means at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
34. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into a vapor
distillation stream and said relatively less volatile fraction; the
improvement wherein said apparatus includes (1) dividing means
prior to said first cooling means to divide said feed gas into
first and second streams; (2) second cooling means connected to
said dividing means to receive said first stream and to cool it
sufficiently to substantially condense it; (3) second expansion
means connected to said second cooling means to receive said
substantially condensed first stream and to expand it to said lower
pressure, said second expansion means being further connected to a
contacting and separating means to supply said expanded cooled
first stream to said contacting and separating means at a
mid-column feed position, said contacting and separating means
being adapted to produce an overhead vapor stream and a bottom
liquid stream; (4) said first cooling means being connected to said
dividing means to receive said second stream and to cool it; (5)
said first expansion means being connected to said first cooling
means to receive said cooled second stream and to expand it to said
lower pressure, said first expansion means being further connected
to said contacting and separating means to supply said expanded
cooled second stream to said contacting and separating means at a
first lower feed position; (6) said distillation column being
connected to said contacting and separating means to receive at
least a portion of said bottom liquid stream; (7) vapor withdrawing
means connected to said distillation column to receive said vapor
distillation stream and form at least a first distillation stream;
(8) compressing means connected to said vapor withdrawing means to
receive said first distillation stream and to compress it to higher
pressure; (9) heat exchange means connected to said compressing
means to receive said compressed first distillation stream and to
cool it sufficiently to condense at least a part of it, thereby
forming a condensed stream; (10) third expansion means connected to
said heat exchange means to receive at least a portion of said
condensed stream and to expand it to said lower pressure, said
third expansion means being further connected to said contacting
and separating means to supply said at least a portion of said
expanded condensed stream to said contacting and separating means
at a top feed position; (11) said vapor withdrawing means being
further connected to said contacting and separating means to direct
any remaining portion of said vapor distillation stream to said
contacting and separating means at a second lower feed position;
(12) said contacting and separating means being further connected
to said heat exchange means to direct at least a portion of said
overhead vapor stream separated therein into heat exchange relation
with said compressed first distillation stream and to heat said
overhead vapor stream, thereby to supply at least a portion of the
cooling of step (9), and thereafter discharging at least a portion
of said heated overhead vapor stream as said volatile residue gas
fraction; and (13) control means adapted to regulate the quantities
and temperatures of said feed streams to said contacting and
separating means to maintain the overhead temperature of said
contacting and separating means at a temperature whereby the major
portions of the components in said relatively less volatile
fraction are recovered.
35. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into a vapor
distillation stream and said relatively less volatile fraction; the
improvement wherein said apparatus includes (1) said first cooling
means being adapted to cool said feed gas under pressure
sufficiently to partially condense it; (2) separating means
connected to said first cooling means to receive said partially
condensed feed and to separate it into a vapor stream and at least
one liquid stream; (3) dividing means connected to said separating
means to receive said vapor stream and to divide it into first and
second streams; (4) second cooling means connected to said dividing
means to receive said first stream and to cool it sufficiently to
substantially condense it; (5) second expansion means connected to
said second cooling means to receive said substantially condensed
first stream and to expand it to said lower pressure, said second
expansion means being further connected to a contacting and
separating means to supply said expanded cooled first stream to
said contacting and separating means at a mid-column feed position,
said contacting and separating means being adapted to produce an
overhead vapor stream and a bottom liquid stream; (6) said first
expansion means being connected to said dividing means to receive
said second stream and to expand it to said lower pressure, said
first expansion means being further connected to said contacting
and separating means to supply said expanded second stream to said
contacting and separating means at a first lower feed position; (7)
said distillation column being connected to said contacting and
separating means to receive at least a portion of said bottom
liquid stream; (8) third expansion means connected to said
separating means to receive at least a portion of said at least one
liquid stream and to expand it to said lower pressure, said third
expansion means being further connected to said distillation column
to supply said expanded liquid stream to said distillation column
at a mid-column feed position; (9) vapor withdrawing means
connected to said distillation column to receive said vapor
distillation stream and form at least a first distillation stream;
(10) compressing means connected to said vapor withdrawing means to
receive said first distillation stream and to compress it to higher
pressure; (11) heat exchange means connected to said compressing
means to receive said compressed first distillation stream and to
cool it sufficiently to condense at least a part of it, thereby
forming a condensed stream; (12) fourth expansion means connected
to said heat exchange means to receive at least a portion of said
condensed stream and to expand it to said lower pressure, said
fourth expansion means being further connected to said contacting
and separating means to supply said at least a portion of said
expanded condensed stream to said contacting and separating means
at a top feed position; (13) said vapor withdrawing means being
further connected to said contacting and separating means to direct
any remaining portion of said vapor distillation stream to said
contacting and separating means at a second lower feed position;
(14) said contacting and separating means being further connected
to said heat exchange means to direct at least a portion of said
overhead vapor stream separated therein into heat exchange relation
with said compressed first distillation stream and to heat said
overhead vapor stream, thereby to supply at least a portion of the
cooling of step (11), and thereafter discharging at least a portion
of said heated overhead vapor stream as said volatile residue gas
fraction; and (15) control means adapted to regulate the quantities
and temperatures of said feed streams to said contacting and
separating means to maintain the overhead temperature of said
contacting and separating means at a temperature whereby the major
portions of the components in said relatively less volatile
fraction are recovered.
36. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into a vapor
distillation stream and said relatively less volatile fraction; the
improvement wherein said apparatus includes (1) said first cooling
means being adapted to cool said feed gas under pressure
sufficiently to partially condense it; (2) separating means
connected to said first cooling means to receive said partially
condensed feed and to separate it into a vapor stream and at least
one liquid stream; (3) dividing means connected to said separating
means to receive said vapor stream and to divide it into first and
second streams; (4) combining means connected to said dividing
means and said separating means to receive said first stream and at
least a portion of said at least one liquid stream and form a
combined stream; (5) second cooling means connected to said
combining means to receive said combined stream and to cool it
sufficiently to substantially condense it; (6) second expansion
means connected to said second cooling means to receive said
substantially condensed combined stream and to expand it to said
lower pressure, said second expansion means being further connected
to a contacting and separating means to supply said expanded cooled
combined stream to said contacting and separating means at a
mid-column feed position, said contacting and separating means
being adapted to produce an overhead vapor stream and a bottom
liquid stream; (7) said first expansion means being connected to
said dividing means to receive said second stream and to expand it
to said lower pressure, said first expansion means being further
connected to said contacting and separating means to supply said
expanded second stream to said contacting and separating means at a
first lower feed position; (8) said distillation column being
connected to said contacting and separating means to receive at
least a portion of said bottom liquid stream; (9) third expansion
means connected to said separating means to receive any remaining
portion of said at least one liquid stream and to expand it to said
lower pressure, said third expansion means being further connected
to said distillation column to supply said expanded liquid stream
to said distillation column at a mid-column feed position; (10)
vapor withdrawing means connected to said distillation column to
receive said vapor distillation stream and form at least a first
distillation stream; (11) compressing means connected to said vapor
withdrawing means to receive said first distillation stream and to
compress it to higher pressure; (12) heat exchange means connected
to said compressing means to receive said compressed first
distillation stream and to cool it sufficiently to condense at
least a part of it, thereby forming a condensed stream; (13) fourth
expansion means connected to said heat exchange means to receive at
least a portion of said condensed stream and to expand it to said
lower pressure, said fourth expansion means being further connected
to said contacting and separating means to supply said at least a
portion of said expanded condensed stream to said contacting and
separating means at a top feed position; (14) said vapor
withdrawing means being further connected to said contacting and
separating means to direct any remaining portion of said vapor
distillation stream to said contacting and separating means at a
second lower feed position; (15) said contacting and separating
means being further connected to said heat exchange means to direct
at least a portion of said overhead vapor stream separated therein
into heat exchange relation with said compressed first distillation
stream and to heat said overhead vapor stream, thereby to supply at
least a portion of the cooling of step (12), and thereafter
discharging at least a portion of said heated overhead vapor stream
as said volatile residue gas fraction; and (16) control means
adapted to regulate the quantities and temperatures of said feed
streams to said contacting and separating means to maintain the
overhead temperature of said contacting and separating means at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
37. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into a vapor
distillation stream and said relatively less volatile fraction; the
improvement wherein said apparatus includes (1) dividing means
prior to said first cooling means to divide said feed gas into
first and second streams; (2) second cooling means connected to
said dividing means to receive said first stream and to cool it
sufficiently to substantially condense it; (3) second expansion
means connected to said second cooling means to receive said
substantially condensed first stream and to expand it to said lower
pressure, said second expansion means being further connected to a
contacting and separating means to supply said expanded cooled
first stream to said contacting and separating means at a
mid-column feed position, said contacting and separating means
being adapted to produce an overhead vapor stream and a bottom
liquid stream; (4) said first cooling means being connected to said
dividing means to receive said second stream, said first cooling
means being adapted to cool said second stream under pressure
sufficiently to partially condense it; (5) separating means
connected to said first cooling means to receive said partially
condensed second stream and to separate it into a vapor stream and
at least one liquid stream; (6) said first expansion means being
connected to said separating means to receive said vapor stream and
to expand it to said lower pressure, said first expansion means
being further connected to said contacting and separating means to
supply said expanded vapor stream to said contacting and separating
means at a first lower feed position; (7) said distillation column
being connected to said contacting and separating means to receive
at least a portion of said bottom liquid stream; (8) third
expansion means connected to said separating means to receive at
least a portion of said at least one liquid stream and to expand it
to said lower pressure, said third expansion means being further
connected to said distillation column to supply said expanded
liquid stream to said distillation column at a mid-column feed
position; (9) vapor withdrawing means connected to said
distillation column to receive said vapor distillation stream and
form at least a first distillation stream; (10) compressing means
connected to said vapor withdrawing means to receive said first
distillation stream and to compress it to higher pressure; (11)
heat exchange means connected to said compressing means to receive
said compressed first distillation stream and to cool it
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (12) fourth expansion means connected to said
heat exchange means to receive at least a portion of said condensed
stream and to expand it to said lower pressure, said fourth
expansion means being further connected to said contacting and
separating means to supply said at least a portion of said expanded
condensed stream to said contacting and separating means at a top
feed position; (13) said vapor withdrawing means being further
connected to said contacting and separating means to direct any
remaining portion of said vapor distillation stream to said
contacting and separating means at a second lower feed position;
(14) said contacting and separating means being further connected
to said heat exchange means to direct at least a portion of said
overhead vapor stream separated therein into heat exchange relation
with said compressed first distillation stream and to heat said
overhead vapor stream, thereby to supply at least a portion of the
cooling of step (11), and thereafter discharging at least a portion
of said heated overhead vapor stream as said volatile residue gas
fraction; and (15) control means adapted to regulate the quantities
and temperatures of said feed streams to said contacting and
separating means to maintain the overhead temperature of said
contacting and separating means at a temperature whereby the major
portions of the components in said relatively less volatile
fraction are recovered.
38. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into a first
overhead vapor stream and said relatively less volatile fraction;
the improvement wherein said apparatus includes (1) dividing means
connected to said first cooling means to receive said cooled stream
and to divide it into first and second streams; (2) second cooling
means connected to said dividing means to receive said first stream
and to cool it sufficiently to substantially condense it; (3)
second expansion means connected to said second cooling means to
receive said substantially condensed first stream and to expand it
to said lower pressure, said second expansion means being further
connected to a contacting and separating means to supply said
expanded cooled first stream to said contacting and separating
means at a mid-column feed position, said contacting and separating
means being adapted to produce a second overhead vapor stream and a
bottom liquid stream; (4) said first expansion means being
connected to said dividing means to receive said second stream and
to expand it to said lower pressure, said first expansion means
being further connected to said contacting and separating means to
supply said expanded second stream to said contacting and
separating means at a first lower feed position; (5) vapor
withdrawing means connected to said contacting and separating means
to receive a vapor distillation stream from a region of said
contacting and separating means above said feed position of said
expanded second stream; (6) compressing means connected to said
vapor withdrawing means to receive said vapor distillation stream
and to compress it to higher pressure; (7) heat exchange means
connected to said compressing means to receive said compressed
vapor distillation stream and to cool it sufficiently to condense
at least a part of it, thereby forming a condensed stream; (8)
third expansion means connected to said heat exchange means to
receive at least a portion of said condensed stream and to expand
it to said lower pressure, said third expansion means being further
connected to said contacting and separating means to supply said at
least a portion of said expanded condensed stream to said
contacting and separating means at a top feed position; (9) said
distillation column being connected to said contacting and
separating means to receive at least a portion of said bottom
liquid stream; (10) said distillation column being further
connected to said contacting and separating means to direct said
first overhead vapor stream to said contacting and separating means
at a second lower feed position; (11) said contacting and
separating means being further connected to said heat exchange
means to direct at least a portion of said second overhead vapor
stream separated therein into heat exchange relation with said
compressed vapor distillation stream and to heat said second
overhead vapor stream, thereby to supply at least a portion of the
cooling of step (7), and thereafter discharging at least a portion
of said heated second overhead vapor stream as said volatile
residue gas fraction; and (12) control means adapted to regulate
the quantities and temperatures of said feed streams to said
contacting and separating means to maintain the overhead
temperature of said contacting and separating means at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
39. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into a first
overhead vapor stream and said relatively less volatile fraction;
the improvement wherein said apparatus includes (1) dividing means
prior to said first cooling means to divide said feed gas into
first and second streams; (2) second cooling means connected to
said dividing means to receive said first stream and to cool it
sufficiently to substantially condense it; (3) second expansion
means connected to said second cooling means to receive said
substantially condensed first stream and to expand it to said lower
pressure, said second expansion means being further connected to a
contacting and separating means to supply said expanded cooled
first stream to said contacting and separating means at a
mid-column feed position, said contacting and separating means
being adapted to produce a second overhead vapor stream and a
bottom liquid stream; (4) said first cooling means being connected
to said dividing means to receive said second stream and to cool
it; (5) said first expansion means being connected to said first
cooling means to receive said cooled second stream and to expand it
to said lower pressure, said first expansion means being further
connected to said contacting and separating means to supply said
expanded cooled second stream to said contacting and separating
means at a first lower feed position; (6) vapor withdrawing means
connected to said contacting and separating means to receive a
vapor distillation stream from a region of said contacting and
separating means above said feed position of said expanded cooled
second stream; (7) compressing means connected to said vapor
withdrawing means to receive said vapor distillation stream and to
compress it to higher pressure; (8) heat exchange means connected
to said compressing means to receive said compressed vapor
distillation stream and to cool it sufficiently to condense at
least a part of it, thereby forming a condensed stream; (9) third
expansion means connected to said heat exchange means to receive at
least a portion of said condensed stream and to expand it to said
lower pressure, said third expansion means being further connected
to said contacting and separating means to supply said at least a
portion of said expanded condensed stream to said contacting and
separating means at a top feed position; (10) said distillation
column being connected to said contacting and separating means to
receive at least a portion of said bottom liquid stream; (11) said
distillation column being further connected to said contacting and
separating means to direct said first overhead vapor stream to said
contacting and separating means at a second lower feed position;
(12) said contacting and separating means being further connected
to said heat exchange means to direct at least a portion of said
second overhead vapor stream separated therein into heat exchange
relation with said compressed vapor distillation stream and to heat
said second overhead vapor stream, thereby to supply at least a
portion of the cooling of step (8), and thereafter discharging at
least a portion of said heated second overhead vapor stream as said
volatile residue gas fraction; and (13) control means adapted to
regulate the quantities and temperatures of said feed streams to
said contacting and separating means to maintain the overhead
temperature of said contacting and separating means at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
40. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into a first
overhead vapor stream and said relatively less volatile fraction;
the improvement wherein said apparatus includes (1) said first
cooling means being adapted to cool said feed gas under pressure
sufficiently to partially condense it; (2) separating means
connected to said first cooling means to receive said partially
condensed feed and to separate it into a vapor stream and at least
one liquid stream; (3) dividing means connected to said separating
means to receive said vapor stream and to divide it into first and
second streams; (4) second cooling means connected to said dividing
means to receive said first stream and to cool it sufficiently to
substantially condense it; (5) second expansion means connected to
said second cooling means to receive said substantially condensed
first stream and to expand it to said lower pressure, said second
expansion means being further connected to a contacting and
separating means to supply said expanded cooled first stream to
said contacting and separating means at a mid-column feed position,
said contacting and separating means being adapted to produce a
second overhead vapor stream and a bottom liquid stream; (6) said
first expansion means being connected to said dividing means to
receive said second stream and to expand it to said lower pressure,
said first expansion means being further connected to said
contacting and separating means to supply said expanded second
stream to said contacting and separating means at a first lower
feed position; (7) vapor withdrawing means connected to said
contacting and separating means to receive a vapor distillation
stream from a region of said contacting and separating means above
said feed position of said expanded second stream; (8) compressing
means connected to said vapor withdrawing means to receive said
vapor distillation stream and to compress it to higher pressure;
(9) heat exchange means connected to said compressing means to
receive said compressed vapor distillation stream and to cool it
sufficiently to condense at least a part of it, thereby forming a
condensed stream; (10) third expansion means connected to said heat
exchange means to receive at least a portion of said condensed
stream and to expand it to said lower pressure, said third
expansion means being further connected to said contacting and
separating means to supply said at least a portion of said expanded
condensed stream to said contacting and separating means at a top
feed position; (11) said distillation column being connected to
said contacting and separating means to receive at least a portion
of said bottom liquid stream; (12) fourth expansion means connected
to said separating means to receive at least a portion of said at
least one liquid stream and to expand it to said lower pressure,
said fourth expansion means being further connected to said
distillation column to supply said expanded liquid stream to said
distillation column at a mid-column feed position; (13) said
distillation column being further connected to said contacting and
separating means to direct said first overhead vapor stream to said
contacting and separating means at a second lower feed position;
(14) said contacting and separating means being further connected
to said heat exchange means to direct at least a portion of said
second overhead vapor stream separated therein into heat exchange
relation with said compressed vapor distillation stream and to heat
said second overhead vapor stream, thereby to supply at least a
portion of the cooling of step (9), and thereafter discharging at
least a portion of said heated second overhead vapor stream as said
volatile residue gas fraction; and (15) control means adapted to
regulate the quantities and temperatures of said feed streams to
said contacting and separating means to maintain the overhead
temperature of said contacting and separating means at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
41. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into a first
overhead vapor stream and said relatively less volatile fraction;
the improvement wherein said apparatus includes (1) said first
cooling means being adapted to cool said feed gas under pressure
sufficiently to partially condense it; (2) separating means
connected to said first cooling means to receive said partially
condensed feed and to separate it into a vapor stream and at least
one liquid stream; (3) dividing means connected to said separating
means to receive said vapor stream and to divide it into first and
second streams; (4) combining means connected to said dividing
means and said separating means to receive said first stream and at
least a portion of said at least one liquid stream and form a
combined stream; (5) second cooling means connected to said
combining means to receive said combined stream and to cool it
sufficiently to substantially condense it; (6) second expansion
means connected to said second cooling means to receive said
substantially condensed combined stream and to expand it to said
lower pressure, said second expansion means being further connected
to a contacting and separating means to supply said expanded cooled
combined stream to said contacting and separating means at a
mid-column feed position, said contacting and separating means
being adapted to produce a second overhead vapor stream and a
bottom liquid stream; (7) said first expansion means being
connected to said dividing means to receive said second stream and
to expand it to said lower pressure, said first expansion means
being further connected to said contacting and separating means to
supply said expanded second stream to said contacting and
separating means at a first lower feed position; (8) vapor
withdrawing means connected to said contacting and separating means
to receive a vapor distillation stream from a region of said
contacting and separating means above said feed position of said
expanded second stream; (9) compressing means connected to said
vapor withdrawing means to receive said vapor distillation stream
and to compress it to higher pressure; (10) heat exchange means
connected to said compressing means to receive said compressed
vapor distillation stream and to cool it sufficiently to condense
at least a part of it, thereby forming a condensed stream; (11)
third expansion means connected to said heat exchange means to
receive at least a portion of said condensed stream and to expand
it to said lower pressure, said third expansion means being further
connected to said contacting and separating means to supply said at
least a portion of said expanded condensed stream to said
contacting and separating means at a top feed position; (12) said
distillation column being connected to said contacting and
separating means to receive at least a portion of said bottom
liquid stream; (13) fourth expansion means connected to said
separating means to receive any remaining portion of said at least
one liquid stream and to expand it to said lower pressure, said
fourth expansion means being further connected to said distillation
column to supply said expanded liquid stream to said distillation
column at a mid-column feed position; (14) said distillation column
being further connected to said contacting and separating means to
direct said first overhead vapor stream to said contacting and
separating means at a second lower feed position; (15) said
contacting and separating means being further connected to said
heat exchange means to direct at least a portion of said second
overhead vapor stream separated therein into heat exchange relation
with said compressed vapor distillation stream and to heat said
second overhead vapor stream, thereby to supply at least a portion
of the cooling of step (10), and thereafter discharging at least a
portion of said heated second overhead vapor stream as said
volatile residue gas fraction; and (16) control means adapted to
regulate the quantities and temperatures of said feed streams to
said contacting and separating means to maintain the overhead
temperature of said contacting and separating means at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
42. In an apparatus for the separation of a gas stream containing
methane, C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components into a volatile residue gas fraction and a
relatively less volatile fraction containing a major portion of
said C.sub.2 components, C.sub.3 components, and heavier
hydrocarbon components or said C.sub.3 components and heavier
hydrocarbon components, in said apparatus there being (a) a first
cooling means to cool said gas under pressure connected to provide
a cooled stream under pressure; (b) a first expansion means
connected to receive at least a portion of said cooled stream under
pressure and to expand it to a lower pressure, whereby said stream
is further cooled; and (c) a distillation column connected to
receive said further cooled stream, said distillation column being
adapted to separate said further cooled stream into a first
overhead vapor stream and said relatively less volatile fraction;
the improvement wherein said apparatus includes (1) dividing means
prior to said first cooling means to divide said feed gas into
first and second streams; (2) second cooling means connected to
said dividing means to receive said first stream and to cool it
sufficiently to substantially condense it; (3) second expansion
means connected to said second cooling means to receive said
substantially condensed first stream and to expand it to said lower
pressure, said second expansion means being further connected to a
contacting and separating means to supply said expanded cooled
first stream to said contacting and separating means at a
mid-column feed position, said contacting and separating means
being adapted to produce a second overhead vapor stream and a
bottom liquid stream; (4) said first cooling means being connected
to said dividing means to receive said second stream, said first
cooling means being adapted to cool said second stream under
pressure sufficiently to partially condense it; (5) separating
means connected to said first cooling means to receive said
partially condensed second stream and to separate it into a vapor
stream and at least one liquid stream; (6) said first expansion
means being connected to said separating means to receive said
vapor stream and to expand it to said lower pressure, said first
expansion means being further connected to said contacting and
separating means to supply said expanded vapor stream to said
contacting and separating means at a first lower feed position; (7)
vapor withdrawing means connected to said contacting and separating
means to receive a vapor distillation stream from a region of said
contacting and separating means above said feed position of said
expanded vapor stream; (8) compressing means connected to said
vapor withdrawing means to receive said vapor distillation stream
and to compress it to higher pressure; (9) heat exchange means
connected to said compressing means to receive said compressed
vapor distillation stream and to cool it sufficiently to condense
at least a part of it, thereby forming a condensed stream; (10)
third expansion means connected to said heat exchange means to
receive at least a portion of said condensed stream and to expand
it to said lower pressure, said third expansion means being further
connected to said contacting and separating means to supply said at
least a portion of said expanded condensed stream to said
contacting and separating means at a top feed position; (11) said
distillation column being connected to said contacting and
separating means to receive at least a portion of said bottom
liquid stream; (12) fourth expansion means connected to said
separating means to receive at least a portion of said at least one
liquid stream and to expand it to said lower pressure, said fourth
expansion means being further connected to said distillation column
to supply said expanded liquid stream to said distillation column
at a mid-column feed position; (13) said distillation column being
further connected to said contacting and separating means to direct
said first overhead vapor stream to said contacting and separating
means at a second lower feed position; (14) said contacting and
separating means being further connected to said heat exchange
means to direct at least a portion of said second overhead vapor
stream separated therein into heat exchange relation with said
compressed vapor distillation stream and to heat said second
overhead vapor stream, thereby to supply at least a portion of the
cooling of step (9), and thereafter discharging at least a portion
of said heated second overhead vapor stream as said volatile
residue gas fraction; and (15) control means adapted to regulate
the quantities and temperatures of said feed streams to said
contacting and separating means to maintain the overhead
temperature of said contacting and separating means at a
temperature whereby the major portions of the components in said
relatively less volatile fraction are recovered.
43. The improvement according to claim 28 wherein said vapor
withdrawing means is connected to said distillation column to
receive a vapor distillation stream from a region of said
distillation column above said expanded second stream.
44. The improvement according to claim 29 wherein said vapor
withdrawing means is connected to said distillation column to
receive a vapor distillation stream from a region of said
distillation column above said expanded cooled second stream.
45. The improvement according to claim 30 or 31 wherein said vapor
withdrawing means is connected to said distillation column to
receive a vapor distillation stream from a region of said
distillation column above said expanded second stream.
46. The improvement according to claim 32 wherein said vapor
withdrawing means is connected to said distillation column to
receive a vapor distillation stream from a region of said
distillation column above said expanded vapor stream.
47. The improvement according to claim 28 wherein (1) a second
dividing means is connected to said heat exchange means to receive
said condensed stream and to divide it into at least a first
portion and a second portion, said second dividing means being
further connected to said third expansion means to supply said
first portion to said third expansion means; (2) said third
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said distillation column at said top feed position; and
(3) fourth expansion means connected to said second dividing means
to receive said second portion and to expand it to said lower
pressure, said fourth expansion means being further connected to
said distillation column to supply said expanded second portion to
said distillation column at a mid-column feed position above that
of said expanded second stream.
48. The improvement according to claim 29 wherein (1) a second
dividing means is connected to said heat exchange means to receive
said condensed stream and to divide it into at least a first
portion and a second portion, said second dividing means being
further connected to said third expansion means to supply said
first portion to said third expansion means; (2) said third
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said distillation column at said top feed position; and
(3) fourth expansion means connected to said second dividing means
to receive said second portion and to expand it to said lower
pressure, said fourth expansion means being further connected to
said distillation column to supply said expanded second portion to
said distillation column at a mid-column feed position above that
of said expanded cooled second stream.
49. The improvement according to claim 30 or 31 wherein (1) a
second dividing means is connected to said heat exchange means to
receive said condensed stream and to divide it into at least a
first portion and a second portion, said second dividing means
being further connected to said fourth expansion means to supply
said first portion to said fourth expansion means; (2) said fourth
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said distillation column at said top feed position; and
(3) fifth expansion means connected to said second dividing means
to receive said second portion and to expand it to said lower
pressure, said fifth expansion means being further connected to
said distillation column to supply said expanded second portion to
said distillation column at a mid-column feed position above that
of said expanded second stream.
50. The improvement according to claim 32 wherein (1) a second
dividing means is connected to said heat exchange means to receive
said condensed stream and to divide it into at least a first
portion and a second portion, said second dividing means being
further connected to said fourth expansion means to supply said
first portion to said fourth expansion means; (2) said fourth
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said distillation column at said top feed position; and
(3) fifth expansion means connected to said second dividing means
to receive said second portion and to expand it to said lower
pressure, said fifth expansion means being further connected to
said distillation column to supply said expanded second portion to
said distillation column at a mid-column feed position above that
of said expanded vapor stream.
51. The improvement according to claim 33 wherein (1) a second
dividing means is connected to said heat exchange means to receive
said condensed stream and to divide it into at least a first
portion and a second portion, said second dividing means being
further connected to said third expansion means to supply said
first portion to said third expansion means; (2) said third
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said contacting and separating means at said top feed
position; and (3) fourth expansion means connected to said second
dividing means to receive said second portion and to expand it to
said lower pressure, said fourth expansion means being further
connected to said contacting and separating means to supply said
expanded second portion to said contacting and separating means at
a mid-column feed position above that of said expanded second
stream.
52. The improvement according to claim 34 wherein (1) a second
dividing means is connected to said heat exchange means to receive
said condensed stream and to divide it into at least a first
portion and a second portion, said second dividing means being
further connected to said third expansion means to supply said
first portion to said third expansion means; (2) said third
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said contacting and separating means at said top feed
position; and (3) fourth expansion means connected to said second
dividing means to receive said second portion and to expand it to
said lower pressure, said fourth expansion means being further
connected to said contacting and separating means to supply said
expanded second portion to said contacting and separating means at
a mid-column feed position above that of said expanded cooled
second stream.
53. The improvement according to claim 35 or 36 wherein (1) a
second dividing means is connected to said heat exchange means to
receive said condensed stream and to divide it into at least a
first portion and a second portion, said second dividing means
being further connected to said fourth expansion means to supply
said first portion to said fourth expansion means; (2) said fourth
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said contacting and separating means at said top feed
position; and (3) fifth expansion means connected to said second
dividing means to receive said second portion and to expand it to
said lower pressure, said fifth expansion means being further
connected to said contacting and separating means to supply said
expanded second portion to said contacting and separating means at
a mid-column feed position above that of said expanded second
stream.
54. The improvement according to claim 37 wherein (1) a second
dividing means is connected to said heat exchange means to receive
said condensed stream and to divide it into at least a first
portion and a second portion, said second dividing means being
further connected to said fourth expansion means to supply said
first portion to said fourth expansion means; (2) said fourth
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said contacting and separating means at said top feed
position; and (3) fifth expansion means connected to said second
dividing means to receive said second portion and to expand it to
said lower pressure, said fifth expansion means being further
connected to said contacting and separating means to supply said
expanded second portion to said contacting and separating means at
a mid-column feed position above that of said expanded vapor
stream.
55. The improvement according to claim 38 or 39 wherein (1) a
second dividing means is connected to said heat exchange means to
receive said condensed stream and to divide it into at least a
first portion and a second portion, said second dividing means
being further connected to said third expansion means to supply
said first portion to said third expansion means; (2) said third
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said contacting and separating means at said top feed
position; and (3) fourth expansion means connected to said second
dividing means to receive said second portion and to expand it to
said lower pressure, said fourth expansion means being further
connected to said contacting and separating means to supply said
expanded second portion to said contacting and separating means at
a mid-column feed position above the region wherein said vapor
withdrawing means is connected to said contacting and separating
means to receive said vapor distillation stream.
56. The improvement according to claim 40, 41, or 42 wherein (1) a
second dividing means is connected to said heat exchange means to
receive said condensed stream and to divide it into at least a
first portion and a second portion, said second dividing means
being further connected to said third expansion means to supply
said first portion to said third expansion means; (2) said third
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said contacting and separating means at said top feed
position; and (3) fifth expansion means connected to said second
dividing means to receive said second portion and to expand it to
said lower pressure, said fifth expansion means being further
connected to said contacting and separating means to supply said
expanded second portion to said contacting and separating means at
a mid-column feed position above the region wherein said vapor
withdrawing means is connected to said contacting and separating
means to receive said vapor distillation stream.
57. The improvement according to claim 43 or 44 wherein (1) a
second dividing means is connected to said heat exchange means to
receive said condensed stream and to divide it into at least a
first portion and a second portion, said second dividing means
being further connected to said third expansion means to supply
said first portion to said third expansion means; (2) said third
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said distillation column at said top feed position; and
(3) fourth expansion means connected to said second dividing means
to receive said second portion and to expand it to said lower
pressure, said fourth expansion means being further connected to
said distillation column to supply said expanded second portion to
said distillation column at a mid-column feed position above the
region wherein said vapor withdrawing means is connected to said
distillation column to receive said vapor distillation stream.
58. The improvement according to claim 45 wherein (1) a second
dividing means is connected to said heat exchange means to receive
said condensed stream and to divide it into at least a first
portion and a second portion, said second dividing means being
further connected to said fourth expansion means to supply said
first portion to said fourth expansion means; (2) said fourth
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said distillation column at said top feed position; and
(3) fifth expansion means connected to said second dividing means
to receive said second portion and to expand it to said lower
pressure, said fifth expansion means being further connected to
said distillation column to supply said expanded second portion to
said distillation column at a mid-column feed position above the
region wherein said vapor withdrawing means is connected to said
distillation column to receive said vapor distillation stream.
59. The improvement according to claim 46 wherein (1) a second
dividing means is connected to said heat exchange means to receive
said condensed stream and to divide it into at least a first
portion and a second portion, said second dividing means being
further connected to said fourth expansion means to supply said
first portion to said fourth expansion means; (2) said fourth
expansion means being adapted to expand said first portion to said
lower pressure, and thereafter to supply said expanded first
portion to said distillation column at said top feed position; and
(3) fifth expansion means connected to said second dividing means
to receive said second portion and to expand it to said lower
pressure, said fifth expansion means being further connected to
said distillation column to supply said expanded second portion to
said distillation column at a mid-column feed position above the
region wherein said vapor withdrawing means is connected to said
distillation column to receive said vapor distillation stream.
Description
[0001] This invention relates to a process for the separation of a
gas containing hydrocarbons. The applicants claim the benefits
under Title 35, United States Code, Section 119(e) of prior U.S.
Provisional Application Nos. 60/848,299 which was filed on Sep. 28,
2006 and 60/897,683 which was filed on Jan. 25, 2007.
BACKGROUND OF THE INVENTION
[0002] Ethylene, ethane, propylene, propane, and/or heavier
hydrocarbons can be recovered from a variety of gases, such as
natural gas, refinery gas, and synthetic gas streams obtained from
other hydrocarbon materials such as coal, crude oil, naphtha, oil
shale, tar sands, and lignite. Natural gas usually has a major
proportion of methane and ethane, i.e., methane and ethane together
comprise at least 50 mole percent of the gas. The gas also contains
relatively lesser amounts of heavier hydrocarbons such as propane,
butanes, pentanes, and the like, as well as hydrogen, nitrogen,
carbon dioxide, and other gases.
[0003] The present invention is generally concerned with the
recovery of ethylene, ethane, propylene, propane, and heavier
hydrocarbons from such gas streams. A typical analysis of a gas
stream to be processed in accordance with this invention would be,
in approximate mole percent, 90.5% methane, 4.1% ethane and other
C.sub.2 components, 1.3% propane and other C.sub.3 components, 0.4%
iso-butane, 0.3% normal butane, 0.5% pentanes plus, and 2.6% carbon
dioxide, with the balance made up of nitrogen. Sulfur containing
gases are also sometimes present.
[0004] The historically cyclic fluctuations in the prices of both
natural gas and its natural gas liquid (NGL) constituents have at
times reduced the incremental value of ethane, ethylene, propane,
propylene, and heavier components as liquid products. This has
resulted in a demand for processes that can provide more efficient
recoveries of these products, for processes that can provide
efficient recoveries with lower capital investment and lower
operating costs, and for processes that can be easily adapted or
adjusted to vary the recovery of a specific component over a broad
range. Available processes for separating these materials include
those based upon cooling and refrigeration of gas, oil absorption,
and refrigerated oil absorption. Additionally, cryogenic processes
have become popular because of the availability of economical
equipment that produces power while simultaneously expanding and
extracting heat from the gas being processed. Depending upon the
pressure of the gas source, the richness (ethane, ethylene, and
heavier hydrocarbons content) of the gas, and the desired end
products, each of these processes or a combination thereof may be
employed.
[0005] The cryogenic expansion process is now generally preferred
for natural gas liquids recovery because it provides maximum
simplicity with ease of startup, operating flexibility, good
efficiency, safety, and good reliability. U.S. Pat. Nos. 3,292,380;
4,061,481; 4,140,504; 4,157,904; 4,171,964; 4,185,978; 4,251,249;
4,278,457; 4,519,824; 4,617,039; 4,687,499; 4,689,063; 4,690,702;
4,854,955; 4,869,740; 4,889,545; 5,275,005; 5,555,748; 5,568,737;
5,771,712; 5,799,507; 5,881,569; 5,890,378; 5,983,664; 6,182,469;
6,712,880; 6,915,662; 7,191,617; 7,219,513; reissue U.S. Pat. No.
33,408; and co-pending application Ser. No. 11/430,412 describe
relevant processes (although the description of the present
invention in some cases is based on different processing conditions
than those described in the cited patents and applications).
[0006] In a typical cryogenic expansion recovery process, a feed
gas stream under pressure is cooled by heat exchange with other
streams of the process and/or external sources of refrigeration
such as a propane compression-refrigeration system. As the gas is
cooled, liquids may be condensed and collected in one or more
separators as high-pressure liquids containing some of the desired
C.sub.2+ or C.sub.3+ components. Depending on the richness of the
gas and the amount of liquids formed, the high-pressure liquids may
be expanded to a lower pressure and fractionated. The vaporization
occurring during expansion of the liquids results in further
cooling of the stream. Under some conditions, pre-cooling the high
pressure liquids prior to the expansion may be desirable in order
to further lower the temperature resulting from the expansion. The
expanded stream, comprising a mixture of liquid and vapor, is
fractionated in a distillation (demethanizer or deethanizer)
column. In the column, the expansion cooled stream(s) is (are)
distilled to separate residual methane, nitrogen, and other
volatile gases as overhead vapor from the desired C.sub.2
components, C.sub.3 components, and heavier hydrocarbon components
as bottom liquid product, or to separate residual methane, C.sub.2
components, nitrogen, and other volatile gases as overhead vapor
from the desired C.sub.3 components and heavier hydrocarbon
components as bottom liquid product.
[0007] If the feed gas is not totally condensed (typically it is
not), a portion of the vapor remaining from the partial
condensation can be passed through a work expansion machine or
engine, or an expansion valve, to a lower pressure at which
additional liquids are condensed as a result of further cooling of
the stream. The pressure after expansion is essentially the same as
the pressure at which the distillation column is operated. The
combined vapor-liquid phases resulting from the expansion are
supplied as feed to the column.
[0008] The remaining portion of the vapor is cooled to substantial
condensation by heat exchange with other process streams, e.g., the
cold fractionation tower overhead. Some or all of the high-pressure
liquid may be combined with this vapor portion prior to cooling.
The resulting cooled stream is then expanded through an appropriate
expansion device, such as an expansion valve, to the pressure at
which the demethanizer is operated. During expansion, a portion of
the liquid will vaporize, resulting in cooling of the total stream.
The flash expanded stream is then supplied as top feed to the
demethanizer. Typically, the vapor portion of the expanded stream
and the demethanizer overhead vapor combine in an upper separator
section in the fractionation tower as residual methane product gas.
Alternatively, the cooled and expanded stream may be supplied to a
separator to provide vapor and liquid streams. The vapor is
combined with the tower overhead and the liquid is supplied to the
column as a top column feed.
[0009] In the ideal operation of such a separation process, the
residue gas leaving the process will contain substantially all of
the methane in the feed gas with essentially none of the heavier
hydrocarbon components and the bottoms fraction leaving the
demethanizer will contain substantially all of the heavier
hydrocarbon components with essentially no methane or more volatile
components. In practice, however, this ideal situation is not
obtained for two main reasons. The first reason is that the
conventional demethanizer is operated largely as a stripping
column. The methane product of the process, therefore, typically
comprises vapors leaving the top fractionation stage of the column,
together with vapors not subjected to any rectification step.
Considerable losses of C.sub.3 and C.sub.4+ components occur
because the top liquid feed contains substantial quantities of
these components and heavier hydrocarbon components, resulting in
corresponding equilibrium quantities of C.sub.3 components, C.sub.4
components, and heavier hydrocarbon components in the vapors
leaving the top fractionation stage of the demethanizer. The loss
of these desirable components could be significantly reduced if the
rising vapors could be brought into contact with a significant
quantity of liquid (reflux) capable of absorbing the C.sub.3
components, C.sub.4 components, and heavier hydrocarbon components
from the vapors.
[0010] The second reason that this ideal situation cannot be
obtained is that carbon dioxide contained in the feed gas
fractionates in the demethanizer and can build up to concentrations
of as much as 5% to 10% or more in the tower even when the feed gas
contains less than 1% carbon dioxide. At such high concentrations,
formation of solid carbon dioxide can occur depending on
temperatures, pressures, and the liquid solubility. It is well
known that natural gas streams usually contain carbon dioxide,
sometimes in substantial amounts. If the carbon dioxide
concentration in the feed gas is high enough, it becomes impossible
to process the feed gas as desired due to blockage of the process
equipment with solid carbon dioxide (unless carbon dioxide removal
equipment is added, which would increase capital cost
substantially). The present invention provides a means for
generating a liquid reflux stream that will improve the recovery
efficiency for the desired products while simultaneously
substantially mitigating the problem of carbon dioxide icing.
[0011] In recent years, the preferred processes for hydrocarbon
separation use an upper absorber section to provide additional
rectification of the rising vapors. The source of the reflux stream
for the upper rectification section is typically a recycled stream
of residue gas supplied under pressure. The recycled residue gas
stream is usually cooled to substantial condensation by heat
exchange with other process streams, e.g., the cold fractionation
tower overhead. The resulting substantially condensed stream is
then expanded through an appropriate expansion device, such as an
expansion valve, to the pressure at which the demethanizer is
operated. During expansion, a portion of the liquid will usually
vaporize, resulting in cooling of the total stream. The flash
expanded stream is then supplied as top feed to the demethanizer.
Typically, the vapor portion of the expanded stream and the
demethanizer overhead vapor combine in an upper separator section
in the fractionation tower as residual methane product gas.
Alternatively, the cooled and expanded stream may be supplied to a
separator to provide vapor and liquid streams, so that thereafter
the vapor is combined with the tower overhead and the liquid is
supplied to the column as a top column feed. Typical process
schemes of this type are disclosed in U.S. Pat. Nos. 4,889,545;
5,568,737; and 5,881,569, and in Mowrey, E. Ross, "Efficient, High
Recovery of Liquids from Natural Gas Utilizing a High Pressure
Absorber", Proceedings of the Eighty-First Annual Convention of the
Gas Processors Association, Dallas, Tex., Mar. 11-13, 2002.
Unfortunately, these processes require the use of a large amount of
compression power to provide the motive force for recycling the
reflux stream to the demethanizer, adding to both the capital cost
and the operating cost of facilities using these processes.
[0012] The present invention also employs an upper rectification
section (or a separate rectification column in some embodiments).
However, the reflux stream for this rectification section is
provided by using a side draw of the vapors rising in a lower
portion of the tower. By modestly elevating its pressure, a
significant quantity of liquid can be condensed in this side draw
stream, often using only the refrigeration available in the cold
vapor leaving the upper rectification section. This condensed
liquid, which is predominantly liquid methane, can then be used to
absorb C.sub.2 components, C.sub.3 components, C.sub.4 components,
and heavier hydrocarbon components from the vapors rising through
the upper rectification section and thereby capture these valuable
components in the bottom liquid product from the demethanizer.
[0013] Heretofore, such a side draw feature has been employed in
C.sub.2+ recovery systems, as illustrated in the assignee's U.S.
Patent No. 7,191,617. Surprisingly, applicants have found that
elevating the pressure of the side draw feature of the assignee's
U.S. Pat. No. 7,191,617 invention improves C.sub.3+ recoveries
without sacrificing C.sub.2 component recovery levels and improves
the system efficiency, while simultaneously substantially
mitigating the problem of carbon dioxide icing.
[0014] In accordance with the present invention, it has been found
that C.sub.3 and C.sub.4+ recoveries in excess of 99 percent can be
obtained with no loss in C.sub.2+ component recovery. The present
invention provides the further advantage of being able to maintain
in excess of 99 percent recovery of the C.sub.3 and C.sub.4+
components as the recovery of C.sub.2 components is adjusted from
high to low values. In addition, the present invention makes
possible essentially 100 percent separation of methane and lighter
components from the C.sub.2 components and heavier components while
maintaining the same recovery levels as the prior art and improving
the safety factor with respect to the danger of carbon dioxide
icing. The present invention, although applicable at lower
pressures and warmer temperatures, is particularly advantageous
when processing feed gases in the range of 400 to 1500 psia [2,758
to 10,342 kPa(a)] or higher under conditions requiring NGL recovery
column overhead temperatures of -50.degree. F. [-46.degree. C.] or
colder.
[0015] For a better understanding of the present invention,
reference is made to the following examples and drawings. Referring
to the drawings:
[0016] FIG. 1 is a flow diagram of a prior art natural gas
processing plant in accordance with U.S. Pat. No. 7,191,617;
[0017] FIG. 2 is a flow diagram of a natural gas processing plant
in accordance with the present invention;
[0018] FIG. 3 is a concentration-temperature diagram for carbon
dioxide showing the effect of the present invention;
[0019] FIG. 4 is a flow diagram illustrating an alternative means
of application of the present invention to a natural gas
stream;
[0020] FIG. 5 is a concentration-temperature diagram for carbon
dioxide showing the effect of the present invention with respect to
the process of FIG. 4;
[0021] FIGS. 6 through 9 are flow diagrams illustrating alternative
means of application of the present invention to a natural gas
stream; and
[0022] FIG. 10 is a partial flow diagram illustrating alternative
means of accomplishing the splitting of the vapor feed in
accordance with the present invention.
[0023] In the following explanation of the above figures, tables
are provided summarizing flow rates calculated for representative
process conditions. In the tables appearing herein, the values for
flow rates (in moles per hour) have been rounded to the nearest
whole number for convenience. The total stream rates shown in the
tables include all non-hydrocarbon components and hence are
generally larger than the sum of the stream flow rates for the
hydrocarbon components. Temperatures indicated are approximate
values rounded to the nearest degree. It should also be noted that
the process design calculations performed for the purpose of
comparing the processes depicted in the figures are based on the
assumption of no heat leak from (or to) the surroundings to (or
from) the process. The quality of commercially available insulating
materials makes this a very reasonable assumption and one that is
typically made by those skilled in the art.
[0024] For convenience, process parameters are reported in both the
traditional British units and in the units of the Systeme
International d'Unites (SI). The molar flow rates given in the
tables may be interpreted as either pound moles per hour or
kilogram moles per hour. The energy consumptions reported as
horsepower (HP) and/or thousand British Thermal Units per hour
(MBTU/Hr) correspond to the stated molar flow rates in pound moles
per hour. The energy consumptions reported as kilowatts (kW)
correspond to the stated molar flow rates in kilogram moles per
hour.
DESCRIPTION OF THE PRIOR ART
[0025] FIG. 1 is a process flow diagram showing the design of a
processing plant to recover C.sub.2+ components from natural gas
using prior art according to assignee's U.S. Pat. No. 7,191,617. In
this simulation of the process, inlet gas enters the plant at
120.degree. F. [49.degree. C.] and 1040 psia [7,171 kPa(a)] as
stream 31. If the inlet gas contains a concentration of sulfur
compounds which would prevent the product streams from meeting
specifications, the sulfur compounds are removed by appropriate
pretreatment of the feed gas (not illustrated). In addition, the
feed stream is usually dehydrated to prevent hydrate (ice)
formation under cryogenic conditions. Solid desiccant has typically
been used for this purpose.
[0026] The feed stream 31 is cooled in heat exchanger 10 by heat
exchange with cool residue gas at -28.degree. F. [-33.degree. C.]
(stream 48a), demethanizer reboiler liquids at 35.degree. F.
[2.degree. C.] (stream 41), demethanizer lower side reboiler
liquids at -10.degree. F. [-23.degree. C.] (stream 40), and
demethanizer upper side reboiler liquids at -79.degree. F.
[-62.degree. C.] (stream 39). The cooled stream 31a enters
separator 11 at -15.degree. F. [-26.degree. C.] and 1030 psia
[7,102 kPa(a)] where the vapor (stream 32) is separated from the
condensed liquid (stream 33). The separator liquid (stream 33) is
expanded to the operating pressure (approximately 432 psia [2,976
kPa(a)]) of fractionation tower 19 by expansion valve 12, cooling
stream 33a to -39.degree. F. [-39.degree. C.] before it is supplied
to fractionation tower 19 at a lower mid-column feed point.
[0027] The vapor (stream 32) from separator 11 is divided into two
streams, 35 and 36. Stream 35, containing about 36% of the total
vapor, passes through heat exchanger 15 in heat exchange relation
with the cold residue gas at -127.degree. F. [-88.degree. C.]
(stream 48) where it is cooled to substantial condensation. The
resulting substantially condensed stream 35a at -123.degree. F.
[-86.degree. C.] is then flash expanded through expansion valve 16
to the operating pressure of fractionation tower 19. During
expansion a portion of the stream is vaporized, resulting in
cooling of the total stream to -134.degree. F. [-92.degree. C.].
The expanded stream 35b is supplied to fractionation tower 19 at an
upper mid-column feed point.
[0028] The remaining 64% of the vapor from separator 11 (stream 36)
enters a work expansion machine 17 in which mechanical energy is
extracted from this portion of the high pressure feed. The machine
17 expands the vapor substantially isentropically to the tower
operating pressure, with the work expansion cooling the expanded
stream 36a to a temperature of approximately -90.degree. F.
[-68.degree. C.]. The typical commercially available expanders are
capable of recovering on the order of 80-88% of the work
theoretically available in an ideal isentropic expansion. The work
recovered is often used to drive a centrifugal compressor (such as
item 18) that can be used to re-compress the residue gas (stream
48b), for example. The partially condensed expanded stream 36a is
thereafter supplied as feed to fractionation tower 19 a second
lower mid-column feed point.
[0029] The demethanizer in tower 19 is a conventional distillation
column containing a plurality of vertically spaced trays, one or
more packed beds, or some combination of trays and packing. The
demethanizer tower consists of two sections: an upper absorbing
(rectification) section 19a that contains the trays and/or packing
to provide the necessary contact between the vapor portion of the
expanded streams 35b and 36a rising upward and cold liquid falling
downward to condense and absorb the C.sub.2 components, C.sub.3
components, and heavier components; and a lower stripping
(demethanizing) section 19b that contains the trays and/or packing
to provide the necessary contact between the liquids falling
downward and the vapors rising upward. The stripping section 19b
also includes reboilers (such as trim reboiler 20 and the reboiler
and side reboilers described previously) which heat and vaporize a
portion of the liquids flowing down the column to provide the
stripping vapors which flow up the column to strip the liquid
product, stream 42, of methane and lighter components. Stream 36a
enters demethanizer 19 at an intermediate feed position located in
the lower region of absorbing section 19a of demethanizer 19. The
liquid portion of the expanded stream commingles with liquids
falling downward from the absorbing section 19a and the combined
liquid continues downward into the stripping section 19b of
demethanizer 19. The vapor portion of the expanded stream rises
upward through absorbing section 19a and is contacted with cold
liquid falling downward to condense and absorb the C.sub.2
components, C.sub.3 components, and heavier components.
[0030] A portion of the distillation vapor (stream 43) is withdrawn
from the upper region of stripping section 19b. This stream is then
cooled from -112.degree. F. [-80.degree. C.] to -130.degree. F.
[-90.degree. C.] and partially condensed (stream 43a) in heat
exchanger 22 by heat exchange with the cold demethanizer overhead
stream 38 exiting the top of demethanizer 19 at -134.degree. F.
[-92.degree. C]. The cold demethanizer overhead stream is warmed
slightly to -126.degree. F. [-88.degree. C.] (stream 38a) as it
cools and condenses at least a portion of stream 43.
[0031] The operating pressure in reflux separator 23 (428 psia
[2,951 kPa(a)]) is maintained slightly below the operating pressure
of demethanizer 19. This provides the driving force which causes
distillation vapor stream 43 to flow through heat exchanger 22 and
thence into the reflux separator 23 wherein the condensed liquid
(stream 45) is separated from the uncondensed vapor (stream 44).
Stream 44 then combines with the warmed demethanizer overhead
stream 38a from heat exchanger 22 to form cold residue gas stream
48 at -127.degree. F. [-88.degree. C.].
[0032] The liquid stream 45 from reflux separator 23 is pumped by
pump 24 to a pressure slightly above the operating pressure of
demethanizer 19, and stream 45a is then supplied as cold top column
feed (reflux) to demethanizer 19. This cold liquid reflux absorbs
and condenses the propane and heavier components rising in the
upper rectification region of absorbing section 19a of demethanizer
19.
[0033] In stripping section 19b of demethanizer 19, the feed
streams are stripped of their methane and lighter components. The
resulting liquid product (stream 42) exits the bottom of tower 19
at 52.degree. F. [11.degree. C.], based on a typical specification
of a methane to ethane ratio of 0.025:1 on a molar basis in the
bottom product. The distillation vapor stream forming the tower
overhead (stream 38) is warmed in heat exchanger 22 as it provides
cooling to distillation stream 43 as described previously, then
combines with stream 44 to form the cold residue gas stream 48. The
residue gas passes countercurrently to the incoming feed gas in
heat exchanger 15 where it is heated to -28.degree. F. [-33.degree.
C.] (stream 48a), and in heat exchanger 10 where it is heated to
107.degree. F. [42.degree. C.] (stream 48b) as it provides cooling
as previously described. The residue gas is then re-compressed in
two stages, compressor 18 driven by expansion machine 17 and
compressor 27 driven by a supplemental power source. After stream
48d is cooled to 120.degree. F. [49.degree. C.] in discharge cooler
28, the residue gas product (stream 48e) flows to the sales gas
pipeline at 1040 psia [7,171 kPa(a)].
[0034] A summary of stream flow rates and energy consumption for
the process illustrated in FIG. 1 is set forth in the following
table:
TABLE-US-00001 TABLE I (FIG. 1) Stream Flow Summary - Lb. Moles/Hr
[kg moles/Hr] C. Stream Methane Ethane Propane Butanes+ Dioxide
Total 31 25,382 1,161 362 332 743 28,055 32 25,241 1,131 336 220
733 27,736 33 141 30 26 112 10 319 35 9,087 407 121 79 264 9,985 36
16,154 724 215 141 469 17,751 43 3,598 96 5 1 113 3,816 44 2,963 33
0 0 59 3,058 45 635 63 5 1 54 758 38 22,395 164 5 0 262 22,897 48
25,358 197 5 0 321 25,955 42 24 964 357 332 422 2,100 Recoveries*
Ethane 83.05% Propane 98.50% Butanes+ 99.94% Power Residue Gas
Compression 12,464 HP [20,490 kW] *(Based on un-rounded flow
rates)
DESCRIPTION OF THE INVENTION
EXAMPLE 1
[0035] FIG. 2 illustrates a flow diagram of a process in accordance
with the present invention. The feed gas composition and conditions
considered in the process presented in FIG. 2 are the same as those
in FIG. 1. Accordingly, the FIG. 2 process can be compared with
that of the FIG. 1 process to illustrate the advantages of the
present invention.
[0036] In the simulation of the FIG. 2 process, inlet gas enters
the plant as stream 31 and is cooled in heat exchanger 10 by heat
exchange with cool residue gas at -66.degree. F. [-54.degree. C.]
(stream 38b), demethanizer reboiler liquids at 48.degree. F.
[9.degree. C.] (stream 41), demethanizer lower side reboiler
liquids at 5.degree. F. [-15.degree. C.] (stream 40), and
demethanizer upper side reboiler liquids at -70.degree. F.
[-57.degree. C.] (stream 39). The cooled stream 31a enters
separator 11 at -38.degree. F. [-39.degree. C.] and 1030 psia
[7,102 kPa(a)] where the vapor (stream 32) is separated from the
condensed liquid (stream 33). The separator liquid (stream 33) may
in some cases be divided into two streams, stream 47 and stream 37.
In this example of the present invention, all of the separator
liquid in stream 33 is directed to stream 37 and is expanded to the
operating pressure (approximately 470 psia [3,238 kPa(a)]) of
fractionation tower 19 by expansion valve 12, cooling stream 37a to
-68.degree. F. [-56.degree. C.] before it is supplied to
fractionation tower 19 at a lower mid-column feed point. In other
embodiments of the present invention, all of the separator liquid
in stream 33 may be directed to stream 47, or a portion of stream
33 may be directed to stream 37 with the remaining portion directed
to stream 47.
[0037] The vapor (stream 32) from separator 11 is divided into two
streams, 34 and 36. Stream 34, containing about 22% of the total
vapor, may in some embodiments be combined with a portion (stream
47) of separator liquid stream 33 to form combined stream 35.
Stream 34 or 35, as the case may be, passes through heat exchanger
15 in heat exchange relation with the cold residue gas at
-105.degree. F. [-76.degree. C.] (stream 38a) where it is cooled to
substantial condensation. The resulting substantially condensed
stream 35a at -101.degree. F. [-74.degree. C.] is then flash
expanded through expansion valve 16 to the operating pressure of
fractionation tower 19. During expansion a portion of the stream is
vaporized, resulting in cooling of the total stream. In the process
illustrated in FIG. 2, the expanded stream 35b leaving expansion
valve 16 reaches a temperature of -128.degree. F. [-89.degree. C.]
and is supplied to fractionation tower 19 at an upper mid-column
feed point.
[0038] The remaining 78% of the vapor from separator 11 (stream 36)
enters a work expansion machine 17 in which mechanical energy is
extracted from this portion of the high pressure feed. The machine
17 expands the vapor substantially isentropically to the tower
operating pressure, with the work expansion cooling the expanded
stream 36a to a temperature of approximately -102.degree. F.
[-74.degree. C.]. The partially condensed expanded stream 36a is
thereafter supplied as feed to fractionation tower 19 a second
lower mid-column feed point.
[0039] The demethanizer in tower 19 is a conventional distillation
column containing a plurality of vertically spaced trays, one or
more packed beds, or some combination of trays and packing. The
demethanizer tower consists of two sections: an upper absorbing
(rectification) section 19a that contains the trays and/or packing
to provide the necessary contact between the vapor portion of the
expanded streams 35b and 36a rising upward and cold liquid falling
downward to condense and absorb the C.sub.2 components, C.sub.3
components, and heavier components; and a lower stripping
(demethanizing) section 19b that contains the trays and/or packing
to provide the necessary contact between the liquids falling
downward and the vapors rising upward. The stripping section 19b
also includes reboilers (such as trim reboiler 20 and the reboiler
and side reboilers described previously) which heat and vaporize a
portion of the liquids flowing down the column to provide the
stripping vapors which flow up the column to strip the liquid
product, stream 42, of methane and lighter components. Stream 36a
enters demethanizer 19 at an intermediate feed position located in
the lower region of absorbing section 19a of demethanizer 19. The
liquid portion of the expanded stream commingles with liquids
falling downward from the absorbing section 19a and the combined
liquid continues downward into the stripping section 19b of
demethanizer 19. The vapor portion of the expanded stream rises
upward through absorbing section 19a and is contacted with cold
liquid falling downward to condense and absorb the C.sub.2
components, C.sub.3 components, and heavier components.
[0040] A portion of the distillation vapor (stream 43) is withdrawn
from the upper region of stripping section 19b at -108.degree. F.
[-78.degree. C.] below expanded stream 36a and is compressed to
approximately 609 psia [4,199 kPa(a)] by vapor compressor 21. The
compressed stream 43a is then cooled from -78.degree. F.
[-61.degree. C.] to -125.degree. F. [-87.degree. C.] and
substantially condensed (stream 43b) in heat exchanger 22 by heat
exchange with the cold demethanizer overhead stream 38 exiting the
top of demethanizer 19 at -129.degree. F. [-89.degree. C.]. The
cold demethanizer overhead stream is warmed to -105.degree. F.
[-76.degree. C.] (stream 38a) as it cools and condenses stream
43a.
[0041] Since substantially condensed stream 43b is at a pressure
greater than the operating pressure of demethanizer 19, it is flash
expanded through expansion valve 25 to the operating pressure of
fractionation tower 19. During expansion a small portion of the
stream is vaporized, resulting in cooling of the total stream to
-132.degree. F. [-91.degree. C.]. The expanded stream 43c is then
supplied as cold top column feed (reflux) to demethanizer 19. The
vapor portion (if any) of stream 43c combines with the distillation
vapor rising from the upper fractionation stage to form residue gas
stream 38, while the cold liquid reflux portion absorbs and
condenses the C.sub.2 components, C.sub.3 components, and heavier
components rising in the upper rectification region of absorbing
section 19a of demethanizer 19.
[0042] In stripping section 19b of demethanizer 19, the feed
streams are stripped of their methane and lighter components. The
resulting liquid product (stream 42) exits the bottom of tower 19
at 66.degree. F. [19.degree. C.]. The distillation vapor stream
forming cold residue gas stream 38 is warmed in heat exchanger 22
as it provides cooling to compressed distillation stream 43a as
described previously. The residue gas (stream 38a) passes
countercurrently to the incoming feed gas in heat exchanger 15
where it is heated to -66.degree. F. [-54.degree. C.] (stream 38b),
and in heat exchanger 10 where it is heated to 110.degree. F.
[43.degree. C.] (stream 38c) as it provides cooling as previously
described. The residue gas is then re-compressed in two stages,
compressor 18 driven by expansion machine 17 and compressor 27
driven by a supplemental power source. After stream 38e is cooled
to 120.degree. F. [49.degree. C.] in discharge cooler 28, the
residue gas product (stream 38f) flows to the sales gas pipeline at
1040 psia [7,171 kPa(a)].
[0043] A summary of stream flow rates and energy consumption for
the process illustrated in FIG. 2 is set forth in the following
table:
TABLE-US-00002 TABLE II (FIG. 2) Stream Flow Summary - Lb. Moles/Hr
[kg moles/Hr] C. Stream Methane Ethane Propane Butanes+ Dioxide
Total 31 25,382 1,161 362 332 743 28,055 32 25,050 1,096 310 180
720 27,431 33 332 65 52 152 23 624 34/35 5,473 239 68 39 157 5,994
36 19,577 857 242 141 563 21,437 43 3,936 114 7 1 109 4,171 38
25,358 197 2 0 403 26,034 42 24 964 360 332 340 2,021 Recoveries*
Ethane 83.06% Propane 99.33% Butanes+ 99.97% Power Residue Gas
Compression 11,111 HP [18,266 kW] Vapor Compression 278 HP [457 kW]
Total Compression 11,389 HP [18,723 kW] *(Based on un-rounded flow
rates)
[0044] A comparison of Tables I and II shows that, compared to the
prior art, the present invention maintains essentially the same
ethane recovery (83.05% versus 83.06%), but improves both the
propane recovery (99.33% versus 98.50%) and butanes+ recovery
(99.97% versus 99.94%). Comparison of Tables I and II further shows
that these increased yields were achieved using less horsepower
than the prior art (11,389 HP versus 12,464 HP, or more than 8%
less).
[0045] There are three primary factors that account for the
improved efficiency of the present invention. First, the boost in
pressure provided by vapor compressor 21 allows the column overhead
(stream 38) to condense all of distillation vapor stream 43, unlike
the prior art process which can condense only a fraction of the
stream. As a result, the top reflux stream (stream 43c) for the
present invention is more than 5 times greater than that of the
prior art (stream 45a), providing much more efficient rectification
in the upper region of absorbing section 19a. Second, with the
increase in the quantity of the top reflux stream possible with the
present invention, the quantity of secondary reflux stream 35b can
be correspondingly less without reducing the product yields. This
in turn results in more flow (stream 36) to expansion machine 17
and the resultant increase in the energy recovered to power
compressor 18, thereby reducing the power requirements of
compressor 27. Third, the more efficient rectification provided by
stream 43c in the upper region of absorbing section 19a allows
operating demethanizer 19 at a higher pressure without reducing the
product yields, further reducing the power requirements of
compressor 27.
[0046] A further advantage of the present invention is a reduced
likelihood of carbon dioxide icing. FIG. 3 is a graph of the
relation between carbon dioxide concentration and temperature. Line
71 represents the equilibrium conditions for solid and liquid
carbon dioxide in methane. (The liquid-solid equilibrium line in
this graph is based on the data given in FIG. 16-33 on page 16-24
of the Engineering Data Book, Twelfth Edition, published in 2004 by
the Gas Processors Suppliers Association, which is often used as a
reference when checking for potential icing conditions.) A liquid
temperature on or to the right of line 71, or a carbon dioxide
concentration on or above this line, signifies an icing condition.
Because of the variations which normally occur in gas processing
facilities (e.g., feed gas composition, conditions, and flow rate),
it is usually desired to design a demethanizer with a considerable
safety factor between the expected operating conditions and the
icing conditions. (Experience has shown that the conditions of the
liquids on the fractionation stages of a demethanizer, rather than
the conditions of the vapors, typically govern the allowable
operating conditions in most demethanizers. For this reason, the
corresponding vapor-solid equilibrium line is not shown in FIG.
3.)
[0047] Also plotted in FIG. 3 is a line representing the conditions
for the liquids on the fractionation stages of demethanizer 19 in
the prior art FIG. 1 process (line 72). As can be seen, a portion
of this operating line lies above the liquid-solid equilibrium
line, indicating that the prior art FIG. 1 process cannot be
operated at these conditions without encountering carbon dioxide
icing problems. As a result, it is not possible to use the FIG. 1
process under these conditions, so the prior art FIG. 1 process
cannot actually achieve the recovery efficiencies stated in Table I
in practice without removal of at least some of the carbon dioxide
from the feed gas. This would, of course, substantially increase
capital cost.
[0048] Line 73 in FIG. 3 represents the conditions for the liquids
on the fractionation stages of demethanizer 19 in the present
invention as depicted in FIG. 2. In contrast to the prior art FIG.
1 process, there is a minimum safety factor of 1.2 between the
carbon dioxide concentration in the column liquids for the
anticipated operating conditions of the FIG. 2 process versus the
concentrations at the liquid-solid equilibrium line. That is, it
would require a 20 percent increase in the carbon dioxide content
of the liquids to cause icing. Thus, the present invention could
tolerate a 20% higher concentration of carbon dioxide in its feed
gas than the prior art FIG. 1 process could tolerate without risk
of crossing the liquid-solid equilibrium line. Further, whereas the
prior art FIG. 1 process cannot be operated to achieve the recovery
levels given in Table I because of icing, the present invention
could in fact be operated at even higher recovery levels than those
given in Table II without risk of icing.
[0049] The shift in the operating conditions of the FIG. 2
demethanizer as indicated by line 73 in FIG. 3 can be understood by
comparing the distinguishing features of the present invention to
the prior art process of FIG. 1. While the shape of the operating
line for the prior art FIG. 1 process (line 72) is similar to the
shape of the operating line for the present invention (line 73),
there is a key difference. The operating temperatures of the
critical upper fractionation stages in the demethanizer in the FIG.
2 process are warmer than those of the corresponding fractionation
stages in the demethanizer in the prior art FIG. 1 process,
effectively shifting the operating line of the FIG. 2 process away
from the liquid-solid equilibrium line. The warmer temperatures of
the fractionation stages in the FIG. 2 demethanizer are mainly the
result of operating the tower at higher pressure than the prior art
FIG. 1 process. However, the higher tower pressure does not cause a
loss in C.sub.2+ component recovery levels because the distillation
vapor stream 43 in the FIG. 2 process is in essence an open
direct-contact compression-refrigeration cycle for the demethanizer
using a portion of the inter-column vapor as the working fluid,
supplying refrigeration to the process needed to overcome the loss
in recovery that normally accompanies an increase in demethanizer
operating pressure.
[0050] Another advantage of the present invention is a reduction in
the amount of carbon dioxide leaving demethanizer 19 in liquid
product stream 42. Comparing stream 42 in Table I for the prior art
FIG. 1 process to stream 42 in Table II for the FIG. 2 embodiment
of the present invention reveals that there is nearly a 20%
reduction in the quantity of carbon dioxide captured in stream 42
with the present invention. This generally reduces the product
treating requirements by a corresponding amount, reducing both the
capital cost and the operating cost of the treating system.
[0051] One of the inherent features in the operation of a
demethanizer column to recover C.sub.2 components is that the
column must fractionate between the methane that is to leave the
tower in its overhead product (vapor stream 38) and the C.sub.2
components that are to leave the tower in its bottom product
(liquid stream 42). However, the relative volatility of carbon
dioxide lies between that of methane and C.sub.2 components,
causing the carbon dioxide to appear in both terminal streams.
Further, carbon dioxide and ethane form an azeotrope, resulting in
a tendency for carbon dioxide to accumulate in the intermediate
fractionation stages of the column and thereby cause large
concentrations of carbon dioxide to develop in the tower
liquids.
[0052] The reflux streams for absorbing section 19a in demethanizer
19 of the prior art FIG. 1 process are streams 45a and 35b, while
those for the present invention shown in the FIG. 2 process are
streams 43c and 35b. Comparing these streams in Table I and Table
II, note that the total amounts of C.sub.2 components and carbon
dioxide in the reflux streams in the prior art FIG. 1 process are
470 and 318 Lb. Moles/Hr [470 and 318 kg moles/Hr], respectively,
versus 353 and 266 Lb. Moles/Hr [353 and 266 kg moles/Hr],
respectively, for the reflux streams in the FIG. 2 process of the
present invention. Thus, significantly less of the azeotrope
forming components enter absorbing section 19a in the cold liquid
reflux streams, entering instead into the warmer, lower region of
absorbing section 19a with stream 36a so that there is less
accumulation of carbon dioxide in the fractionation stages of
absorbing section 19a. This allows more of the carbon dioxide to
escape in overhead stream 38 instead of being captured in liquid
product stream 42.
EXAMPLE 2
[0053] An alternative embodiment of the present invention is shown
in FIG. 4. The feed gas composition and conditions considered in
the process presented in FIG. 4 are the same as those in FIGS. 1
and 2. Accordingly, FIG. 4 can be compared with the prior art FIG.
1 process to illustrate the advantages of the present invention,
and can likewise be compared to the embodiment displayed in FIG.
2.
[0054] In the simulation of the FIG. 4 process, inlet gas enters
the plant as stream 31 and is cooled in heat exchanger 10 by heat
exchange with cool residue gas at -66.degree. F. [-55.degree. C.]
(stream 38b), demethanizer reboiler liquids at 51.degree. F.
[11.degree. C.] (stream 41), demethanizer lower side reboiler
liquids at 10.degree. F. [-12.degree. C.] (stream 40), and
demethanizer upper side reboiler liquids at -65.degree. F.
[-54.degree. C.] (stream 39). The cooled stream 31a enters
separator 11 at -38.degree. F. [-39.degree. C.] and 1030 psia
[7,102 kPa(a)] where the vapor (stream 32) is separated from the
condensed liquid (stream 33). The separator liquid (stream 33) may
in some cases be divided into two streams, stream 47 and stream 37.
In this example of the present invention, all of the separator
liquid in stream 33 is directed to stream 37 and is expanded to the
operating pressure (approximately 480 psia [3,309 kPa(a)]) of
fractionation tower 19 by expansion valve 12, cooling stream 37a to
-67.degree. F. [-55.degree. C.] before it is supplied to
fractionation tower 19 at a lower mid-column feed point. In other
embodiments of the present invention, all of the separator liquid
in stream 33 may be directed to stream 47, or a portion of stream
33 may be directed to stream 37 with the remaining portion directed
to stream 47.
[0055] The vapor (stream 32) from separator 11 is divided into two
streams, 34 and 36. Stream 34, containing about 23% of the total
vapor, may in some embodiments be combined with a portion (stream
47) of separator liquid stream 33 to form combined stream 35.
Stream 34 or 35, as the case may be, passes through heat exchanger
15 in heat exchange relation with the cold residue gas at
-106.degree. F. [-77.degree. C.] (stream 38a) where it is cooled to
substantial condensation. The resulting substantially condensed
stream 35a at -102.degree. F. [-74.degree. C.] is then flash
expanded through expansion valve 16 to the operating pressure of
fractionation tower 19. During expansion a portion of the stream is
vaporized, resulting in cooling of the total stream. In the process
illustrated in FIG. 4, the expanded stream 35b leaving expansion
valve 16 reaches a temperature of -127.degree. F. [-88.degree. C.]
and is supplied to fractionation tower 19 at an upper mid-column
feed point.
[0056] The remaining 77% of the vapor from separator 11 (stream 36)
enters a work expansion machine 17 in which mechanical energy is
extracted from this portion of the high pressure feed. The machine
17 expands the vapor substantially isentropically to the tower
operating pressure, with the work expansion cooling the expanded
stream 36a to a temperature of approximately -101.degree. F.
[-74.degree. C.]. The partially condensed expanded stream 36a is
thereafter supplied as feed to fractionation tower 19 a second
lower mid-column feed point.
[0057] A portion of the distillation vapor (stream 43) is withdrawn
from the lower region of absorbing section 19a of demethanizer 19
at -113.degree. F. [-81.degree. C.] above expanded stream 36a and
is compressed to approximately 619 psia [4,266 kPa(a)] by vapor
compressor 21. The compressed stream 43a is then cooled from
-84.degree. F. [-65.degree. C.] to -124.degree. F. [-87.degree. C.]
and substantially condensed (stream 43b) in heat exchanger 22 by
heat exchange with the cold demethanizer overhead stream 38 exiting
the top of demethanizer 19 at -128.degree. F. [-89.degree. C.]. The
cold demethanizer overhead stream is warmed to -106.degree. F.
[-77.degree. C.] (stream 38a) as it cools and condenses stream
43a.
[0058] Since substantially condensed stream 43b is at a pressure
greater than the operating pressure of demethanizer 19, it is flash
expanded through expansion valve 25 to the operating pressure of
fractionation tower 19. During expansion a small portion of the
stream is vaporized, resulting in cooling of the total stream to
-131.degree. F. [-91.degree. C.]. The expanded stream 43c is then
supplied as cold top column feed (reflux) to demethanizer 19. The
vapor portion (if any) of stream 43c combines with the distillation
vapor rising from the upper fractionation stage to form residue gas
stream 38, while the cold liquid reflux portion absorbs and
condenses the C.sub.2 components, C.sub.3 components, and heavier
components rising in the upper rectification region of absorbing
section 19a of demethanizer 19.
[0059] In stripping section 19b of demethanizer 19, the feed
streams are stripped of their methane and lighter components. The
resulting liquid product (stream 42) exits the bottom of tower 19
at 70.degree. F. [21.degree. C.]. The distillation vapor stream
forming cold residue gas stream 38 is warmed in heat exchanger 22
as it provides cooling to compressed distillation stream 43a as
described previously. The residue gas (stream 38a) passes
countercurrently to the incoming feed gas in heat exchanger 15
where it is heated to -66.degree. F. [-55.degree. C.] (stream 38b),
and in heat exchanger 10 where it is heated to 110.degree. F.
[43.degree. C.] (stream 38c) as it provides cooling as previously
described. The residue gas is then re-compressed in two stages,
compressor 18 driven by expansion machine 17 and compressor 27
driven by a supplemental power source. After stream 38e is cooled
to 120.degree. F. [49.degree. C.] in discharge cooler 28, the
residue gas product (stream 38f) flows to the sales gas pipeline at
1040 psia [7,171 kPa(a)].
[0060] A summary of stream flow rates and energy consumption for
the process illustrated in FIG. 4 is set forth in the following
table:
TABLE-US-00003 TABLE III (FIG. 4) Stream Flow Summary - Lb.
Moles/Hr [kg moles/Hr] C. Stream Methane Ethane Propane Butanes+
Dioxide Total 31 25,382 1,161 362 332 743 28,055 32 25,050 1,096
310 180 720 27,431 33 332 65 52 152 23 624 34/35 5,636 247 70 40
162 6,172 36 19,414 849 240 140 558 21,259 43 3,962 100 3 0 125
4,200 38 25,358 197 2 0 425 26,055 42 24 964 360 332 318 2,000
Recoveries* Ethane 83.06% Propane 99.50% Butanes+ 99.98% Power
Residue Gas Compression 10,784 HP [17,728 kW] Vapor Compression 260
HP [428 kW] Total Compression 11,044 HP [18,156 kW] *(Based on
un-rounded flow rates)
[0061] A comparison of Tables II and III shows that, compared to
the FIG. 2 embodiment of the present invention, the FIG. 4
embodiment maintains the same ethane recovery while improving the
propane recovery (99.50% versus 99.33%) and butanes+ recovery
(99.98% versus 99.97%) slightly. However, comparison of Tables II
and III further shows that these yields were achieved using about
3% less horsepower than that required by the FIG. 2 embodiment of
the present invention. The drop in the power requirements for the
FIG. 4 embodiment is mainly due to the lower content of C.sub.2+
components in top reflux stream 43c, which provides more efficient
rectification in the upper region of absorbing section 19a so that
demethanizer 19 can be operated at a slightly higher operating
pressure (thereby reducing compression requirements) without
reducing product yields. Comparing distillation vapor stream 43 in
Table III for the FIG. 4 embodiment of the present invention to
stream 43 in Table II for the FIG. 2 embodiment of the present
invention, the concentrations of C.sub.2 components and
particularly the C.sub.3+ components in stream 43 of the FIG. 4
embodiment are significantly lower, so that higher product yields
are achieved using less power than the FIG. 2 embodiment. The lower
concentrations of C.sub.2 components and C.sub.3+ components in
stream 43 of the FIG. 4 embodiment are the result of withdrawing
the distillation vapor from the lower region of absorbing section
19a rather than from the upper region of stripping section 19b as
in the FIG. 2 embodiment. The distillation vapor at the higher
column location has been subjected to more rectification than the
distillation vapor lower in the column, and so is closer to being
the pure methane stream that would be the ideal reflux stream for
the top of the column. In the prior art process of FIG. 1, the
column overhead (stream 38) could not condense a pure methane
stream, but with the elevation in pressure provided by vapor
compressor 21 of the present invention, column overhead stream 38
is cold enough to totally condense the distillation vapor stream 43
even though it is almost pure methane.
[0062] When the present invention is employed as in Example 2, the
advantage with respect to avoiding carbon dioxide icing conditions
is maintained compared to the FIG. 2 embodiment. FIG. 5 is another
graph of the relation between carbon dioxide concentration and
temperature, with line 71 as before representing the equilibrium
conditions for solid and liquid carbon dioxide in methane and line
72 representing the conditions for the liquids on the fractionation
stages of demethanizer 19 in the prior art process of FIG. 1. Line
74 in FIG. 5 represents the conditions for the liquids on the
fractionation stages of demethanizer 19 in the present invention as
depicted in FIG. 4, and shows a safety factor of 1.2 between the
anticipated operating conditions and the icing conditions for the
FIG. 4 process. Thus, this embodiment of the present invention
could also tolerate an increase of 20 percent in the concentration
of carbon dioxide without risk of icing. In practice, this
improvement in the icing safety factor could be used to advantage
by operating the demethanizer at lower pressure (i.e., with colder
temperatures on the fractionation stages) to raise the C.sub.2+
component recovery levels without encountering icing problems. The
shape of line 74 in FIG. 5 for the FIG. 4 embodiment is very
similar to that of line 73 in FIG. 3 for the FIG. 2 embodiment. The
primary difference is the significantly lower carbon dioxide
concentrations of the liquids on the fractionation stages in the
lower section of the FIG. 4 demethanizer due to withdrawing the
distillation vapor stream at a higher location on the column in
this embodiment. As can be seen by comparing stream 42 in Tables II
and III, even less of the carbon dioxide in the feed gas is
captured with the bottom liquid product in the FIG. 4 embodiment of
the present invention, which generally means still less product
treating will be required compared to the FIG. 2 embodiment of the
present invention.
Other Embodiments
[0063] In accordance with this invention, it is generally
advantageous to design the absorbing (rectification) section of the
demethanizer to contain multiple theoretical separation stages.
However, the benefits of the present invention can be achieved with
as few as one theoretical stage, and it is believed that even the
equivalent of a fractional theoretical stage may allow achieving
these benefits. For instance, all or a part of the expanded
substantially condensed distillation stream 43c from expansion
valve 25, all or a part of the expanded substantially condensed
stream 35b from expansion valve 16, and all or a part of the
expanded stream 36a from work expansion machine 17 can be combined
(such as in the piping joining the expansion valve to the
demethanizer) and if thoroughly intermingled, the vapors and
liquids will mix together and separate in accordance with the
relative volatilities of the various components of the total
combined streams. Such commingling of the three streams shall be
considered for the purposes of this invention as constituting an
absorbing section.
[0064] In some cases it may be advantageous to split the
substantially condensed distillation stream 43b into at least two
streams as shown in FIGS. 6 through 9. This allows a portion
(stream 51) to be supplied above the location where vapor
distillation stream 43 is withdrawn (and perhaps also above the
feed location of expanded stream 36a), either lower in the
absorbing section of fractionation tower 19 (FIGS. 6 and 7) or
lower on absorber column 19 (FIGS. 8 and 9), to increase the liquid
flow in that part of the distillation system and improve the
rectification of stream 43. In such cases, expansion valve 26 is
used to expand stream 51 to the column operating pressure (forming
stream 51a), while expansion valve 25 is used to expand the
remaining portion (stream 50) to the column operating pressure so
that the resulting stream 50a can then be supplied to the top of
the absorbing section in demethanizer 19 (FIGS. 6 and 7) or to the
top of absorber column 19 (FIGS. 8 and 9).
[0065] FIGS. 8 and 9 depict a fractionation tower constructed in
two vessels, absorber (rectifier) column 19 (a contacting and
separating device) and stripper column 29 (a distillation column).
In FIG. 8, the overhead vapor (stream 46) from stripper column 29
is split into two portions. One portion (stream 43) is routed to
compressor 21 and thence to heat exchanger 22 to generate reflux
for absorber column 19 as described earlier. The remaining portion
(stream 49) flows to the lower section of absorber column 19 to be
contacted by expanded substantially condensed stream 35b and the
expanded substantially condensed distillation stream (either stream
50a, or streams 50a and 51a). Pump 30 is used to route the liquids
(stream 52) from the bottom of absorber column 19 to the top of
stripper column 29 so that the two towers effectively function as
one distillation system. In FIG. 9, all of the overhead vapor
(stream 46) flows to the lower section of absorber column 19, and
distillation vapor stream 43 is withdrawn from a location higher in
absorber column 19, above the feed location of expanded stream 36a.
The decision whether to construct the fractionation tower as a
single vessel (such as demethanizer 19 in FIGS. 2, 4, 6, and 7) or
multiple vessels will depend on a number of factors such as plant
size, the distance to fabrication facilities, etc.
[0066] Feed gas conditions, plant size, available equipment, or
other factors may indicate that elimination of work expansion
machine 17, or replacement with an alternate expansion device (such
as an expansion valve), is feasible. Although individual stream
expansion is depicted in particular expansion devices, alternative
expansion means may be employed where appropriate. For example,
conditions may warrant work expansion of the substantially
condensed portion of the feed stream (stream 35a) and/or the
substantially condensed distillation stream (stream 43b).
[0067] As described in the earlier examples, distillation stream 43
is substantially condensed and the resulting condensate used to
absorb valuable C.sub.2 components, C.sub.3 components, and heavier
components from the vapors rising through the upper region of
absorbing section 19a of demethanizer 19 (FIGS. 2, 4, 6, and 7) or
absorber column 19 (FIGS. 8 and 9). However, the present invention
is not limited to this embodiment. It may be advantageous, for
instance, to treat only a portion of these vapors in this manner,
or to use only a portion of the condensate as an absorbent, in
cases where other design considerations indicate portions of the
vapors or the condensate should bypass absorbing section 19a of
demethanizer 19 (FIGS. 2, 4, 6, and 7) or absorber column 19 (FIGS.
8 and 9). Some circumstances may favor partial condensation, rather
than total condensation, of distillation stream 43a in heat
exchanger 22. Other circumstances may favor that distillation
stream 43 be a total vapor side draw from fractionation column 19
rather than a partial vapor side draw. It should also be noted
that, depending on the composition of the feed gas stream, it may
be advantageous to use external refrigeration to provide some
portion of the cooling of distillation stream 43a in heat exchanger
22.
[0068] Under some circumstances, it may be advantageous to heat
distillation stream 43 before it is compressed, as this may reduce
the capital cost of compressor 21. One means to accomplish this is
to use compressed distillation stream 43a (which is warmer due to
the heat of compression) to supply this heating using a cross
exchanger. In such cases, it may be possible to supplement the
cooling of compressed distillation stream 43a by the use of aerial
cooling or other means, thereby reducing the cooling that must be
supplied in heat exchanger 22 by overhead stream 38. The potential
reduction in the capital cost of compressor 21 must be weighed
against the capital cost of the additional heating and cooling
means for each application to determine whether this embodiment is
advantageous.
[0069] In accordance with this invention, the splitting of the
vapor feed may be accomplished in several ways. In some
embodiments, vapor splitting may be effected in a separator. In the
processes of FIGS. 2, 4, and 6 through 9, the splitting of the
vapor occurs following cooling, and perhaps after separation of any
liquids which may have been formed. The high pressure gas may be
split, however, prior to any cooling of the inlet gas as shown in
FIG. 10. Streams 35b, 36a, and 37a in FIG. 10 may all be fed to a
distillation column (such as demethanizer 19 in FIGS. 2, 4, 6, and
7), or streams 35b and 36a may be fed to a contacting and
separating device and stream 37a may be fed to a distillation
column (such as absorber column 19 and stripper column 29,
respectively, in FIGS. 8 and 9). The cooling of stream 53 in heat
exchanger 10 in FIG. 10 may be accomplished or supplemented by
additional process streams (such as streams 39, 40, and 41 in FIGS.
2, 4, and 6 through 9) and/or external refrigeration.
[0070] When the inlet gas is leaner, separator 11 in FIGS. 2, 4,
and 6 through 10 may not be needed. Depending on the quantity of
heavier hydrocarbons in the feed gas and the feed gas pressure, the
cooled feed stream 31a leaving heat exchanger 10 in FIGS. 2, 4, and
6 through 9 or the cooled stream 53a leaving heat exchanger 10 in
FIG. 10 may not contain any liquid (because it is above its
dewpoint, or because it is above its cricondenbar), so that
separator 11 shown in FIGS. 2, 4, and 6 through 10 is not
required.
[0071] The high pressure liquid (stream 33) in FIGS. 2, 4, and 6
through 9 need not be expanded and fed to a mid-column feed point
on the distillation column. Instead, all or a portion of it (dashed
stream 47) may be combined with the portion of the separator vapor
(stream 34) to form combined stream 35 that flows to heat exchanger
15. Any remaining portion of the liquid (dashed stream 37) may be
expanded through an appropriate expansion device, such as expansion
valve 12, to form stream 37a which is then fed to a mid-column feed
point on distillation column 19 (FIGS. 2, 4, 6, and 7) or stripper
column 29 (FIGS. 8 and 9). Stream 33 in FIGS. 2, 4, and 6 through 9
and/or stream 37 in FIGS. 2, 4, and 6 through 10 may also be used
for inlet gas cooling or other heat exchange service before or
after the expansion step prior to flowing to the demethanizer.
[0072] In accordance with this invention, the use of external
refrigeration to supplement the cooling available to the inlet gas
and/or the distillation stream from other process streams may be
employed, particularly in the case of a rich inlet gas. The use and
distribution of separator liquids and demethanizer side draw
liquids for process heat exchange, and the particular arrangement
of heat exchangers for inlet gas cooling must be evaluated for each
particular application, as well as the choice of process streams
for specific heat exchange services.
[0073] It will also be recognized that the relative amount of feed
found in each branch of the split vapor feed will depend on several
factors, including gas pressure, feed gas composition, the amount
of heat which can economically be extracted from the feed, and the
quantity of horsepower available. More feed to the top of the
column may increase recovery while decreasing power recovered from
the expander thereby increasing the recompression horsepower
requirements. Increasing feed lower in the column reduces the
horsepower consumption but may also reduce product recovery. The
relative locations of the mid-column feeds may vary depending on
inlet composition or other factors such as desired recovery levels
and amount of liquid formed during inlet gas cooling. Moreover, two
or more of the feed streams, or portions thereof, may be combined
depending on the relative temperatures and quantities of individual
streams, and the combined stream then fed to a mid-column feed
position.
[0074] The present invention provides improved recovery of C.sub.3
components and heavier hydrocarbon components per amount of utility
consumption required to operate the process. An improvement in
utility consumption required for operating the demethanizer process
may appear in the form of reduced power requirements for
compression or re-compression, reduced power requirements for
external refrigeration, reduced energy requirements for tower
reboilers, or a combination thereof.
[0075] While there have been described what are believed to be
preferred embodiments of the invention, those skilled in the art
will recognize that other and further modifications may be made
thereto, e.g. to adapt the invention to various conditions, types
of feed, or other requirements without departing from the spirit of
the present invention as defined by the following claims.
* * * * *