U.S. patent application number 15/027648 was filed with the patent office on 2016-09-08 for split feed addition to iso-pressure open refrigeration lpg recovery.
The applicant listed for this patent is LUMMUS TECHNOLOGY INC.. Invention is credited to Robert Huebel, Ayyalasomayajula Kumar, Michael Malsam.
Application Number | 20160258675 15/027648 |
Document ID | / |
Family ID | 52813613 |
Filed Date | 2016-09-08 |
United States Patent
Application |
20160258675 |
Kind Code |
A1 |
Kumar; Ayyalasomayajula ; et
al. |
September 8, 2016 |
SPLIT FEED ADDITION TO ISO-PRESSURE OPEN REFRIGERATION LPG
RECOVERY
Abstract
A process is disclosed herein for recovery of natural gas
liquids from a feed gas stream, comprising forming a first portion
of the feed gas stream and a second portion of the feed gas stream,
wherein the mass ratio of the first portion to the second portion
is in the range of 95:5 to 5:95, cooling the first portion in a
heat exchanger and at least partially condensing the first portion,
and feeding the second portion and the cooled and at least
partially condensed first portion to a distillation column wherein
lighter components are removed from the distillation column as an
overhead vapor stream and heavier components are removed from the
distillation column in the bottoms as a product stream, and wherein
the second portion is fed into the distillation column at a point
one or more vapor-liquid equilibrium stages below the first
portion, thereby allowing mass transfer exchange between liquids of
the cooled second portion and vapors of the second portion within
the column. A corresponding apparatus is also disclosed.
Inventors: |
Kumar; Ayyalasomayajula;
(Richmond, TX) ; Huebel; Robert; (Sugar Land,
TX) ; Malsam; Michael; (Sugar Land, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LUMMUS TECHNOLOGY INC. |
Bloomfield |
NJ |
US |
|
|
Family ID: |
52813613 |
Appl. No.: |
15/027648 |
Filed: |
October 8, 2014 |
PCT Filed: |
October 8, 2014 |
PCT NO: |
PCT/US14/59682 |
371 Date: |
April 6, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61888901 |
Oct 9, 2013 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25J 2200/02 20130101;
F25J 2200/40 20130101; F25J 2200/94 20130101; F25J 3/0242 20130101;
C10L 2290/46 20130101; C10L 2290/06 20130101; F25J 2205/02
20130101; F25J 2270/12 20130101; F25J 3/0233 20130101; F25J 2210/06
20130101; F25J 2270/60 20130101; F25J 3/0219 20130101; F25J 2210/12
20130101; F25J 3/0209 20130101; F25J 2200/76 20130101; F25J 2260/60
20130101; C10L 2290/543 20130101; F25J 3/0238 20130101; F25J
2215/62 20130101; F25J 3/0257 20130101; C10L 3/12 20130101; F25J
2200/70 20130101; C10L 2290/541 20130101; F25J 3/0247 20130101;
F25J 2270/02 20130101; F25J 2200/30 20130101; F25J 2200/78
20130101; C10L 2290/48 20130101 |
International
Class: |
F25J 3/02 20060101
F25J003/02 |
Claims
1. A process for recovery of natural gas liquids from a feed gas
stream, comprising: (a) forming a first portion of the feed gas
stream and a second portion of the feed gas stream, wherein the
mass ratio of the first portion to the second portion is in the
range of 95:5 to 5:95; (b) cooling the first portion in a heat
exchanger and at least partially condensing the first portion; (c)
feeding the second portion and the cooled and at least partially
condensed first portion to a distillation column wherein lighter
components are removed from the distillation column as an overhead
vapor stream and heavier components are removed from the
distillation column in the bottoms as a product stream, and wherein
the second portion is fed into the distillation column at a point
one or more vapor-liquid equilibrium stages below the first
portion, thereby allowing mass transfer exchange between liquids of
the cooled first portion and vapors of the second portion within
the column; (d) feeding the distillation column overhead stream to
the heat exchanger and cooling the distillation column overhead
stream to at least partially liquefy the distillation column
overhead stream; (e) feeding the at least partially liquefied
distillation column overhead stream to a first separator; (f)
separating the vapor and liquid in the first separator to produce
an overhead vapor stream comprising sales gas and a bottoms stream
comprising a mixed refrigerant; (g) feeding the mixed refrigerant
stream to the heat exchanger to provide cooling, wherein the mixed
refrigerant stream vaporizes as it passes through the heat
exchanger; (h) compressing the vaporized mixed refrigerant stream
and passing the compressed mixed refrigerant stream through the
heat exchanger; and (i) feeding at least a portion of the
compressed mixed refrigerant stream to the distillation column as a
reflux stream.
2. The process of claim 1, further comprising, before (i), feeding
the compressed mixed refrigerant stream to a second separator, and
feeding the bottoms from the second separator to the distillation
column as the reflux stream.
3. The process of claim 1, further comprising reducing the
temperature of the mixed refrigerant stream before the mixed
refrigerant stream enters the heat exchanger by reducing the
pressure of the mixed refrigerant using a control valve.
4. The process of claim 1, further comprising combining the
overhead stream from the second separator with the overhead stream
from the distillation column and feeding the combined stream to the
first separator.
5. The process of claim 1, further comprising cooling the
compressed mixed refrigerant in a cooler before passing the
compressed mixed refrigerant stream through the heat exchanger.
6. The process of claim 1, wherein the first separator is an
absorber.
7. The process of claim 1, wherein the feed gas stream is one of
natural gas or refinery gas.
8. The process of claim 1, wherein the distillation column operates
at a pressure of between about 100 psia and 450 psia.
9. The process of claim 1, wherein the first and second portions of
the feed gas stream have the same composition.
10. The process of claim 1, wherein the first portion and second
portion of the feed gas streams have a mass ratio in the range of
95:5 to 65:35.
11. The process of claim 1, wherein the first portion and second
portion of the feed gas streams have a mass ratio in the range of
95:5 to 70:30.
12. The process of claim 1, wherein a portion of compressed mixed
refrigerant stream is removed as a supplemental product stream.
13. The process of claim 1, wherein separating the vapors and
liquids in the separator further includes producing a side draw
fraction.
14. The process of claim 13, wherein the overhead vapor stream is
enriched in nitrogen and depleted in propane, the bottoms fraction
is depleted in nitrogen and enriched in propane, and the side draw
fraction has intermediate propane and nitrogen content.
15. The process of claim 1 further comprising reboiling a portion
of the distillation column bottoms in a distillation column
reboiler, wherein the energy input to the distillation column
reboiler is at least 5% lower than the energy input for a process
with the same volumes and compositions of the feed gas stream,
product stream and sales gas stream, and in which no second portion
is formed from the feed gas stream.
16. The process of claim 1 further comprising reboiling a portion
of the distillation column bottoms in a distillation column
reboiler, wherein the energy input to the distillation column
reboiler is at least 10% lower than the energy input for a process
with the same volumes and compositions of the feed gas stream,
product stream and sales gas stream, and in which no second portion
is formed from the feed gas stream.
17. The process of claim 1, wherein the total compressor duty of
the process is at least 5% lower than the compressor duty for a
process with the same volumes and compositions of the feed gas
stream, product stream and sales gas stream, but in which no second
portion is formed from the feed gas stream.
18. The process of claim 1, wherein the total compressor duty of
the process is at least 10% lower than the compressor duty for a
process with the same volumes and compositions of the feed gas
stream, product stream and sales gas stream, but in which no second
portion is formed from the feed gas stream.
19. An apparatus for separating natural gas liquids from a feed gas
stream, the apparatus comprising: (a) a primary feed gas line
configured to deliver a feed gas stream; (b) a heat exchanger
operable to provide the heating and cooling necessary for
separation of natural gas liquids from a feed gas stream by heat
exchange contact between the feed gas stream and one or more
process streams thus forming a cooled feed gas stream; (c) a
distillation column configured to receive the feed gas stream and
to separate the feed gas stream into a column overhead stream
comprising a substantial amount of the lighter hydrocarbon
components of the feed gas stream and a column bottoms stream
comprising a substantial amount of the heavier hydrocarbon
components; (d) a first separator configured to receive the
distillation column overhead stream and to separate the column
overhead stream into an overhead sales gas stream and a bottoms
stream comprising a mixed refrigerant configured to provide process
cooling in the heat exchanger; (e) a compressor configured to
compress the mixed refrigerant stream after the mixed refrigerant
stream has provided process cooling in the heat exchanger; and (f)
a feed gas bypass line configured to remove a portion of the feed
gas stream prior to it being sent to the heat exchanger, wherein
the feed gas bypass line is fluidly connected to the distillation
column at a point one or more vapor-liquid equilibrium stages below
the point at which the cooled feed gas stream from the heat
exchanger is fluidly connected, thereby allowing mass transfer
exchange between the liquids of the cooled feed gas stream from the
heat exchanger and the vapors of the bypass feed gas stream within
the column.
20. The apparatus of claim 19, further including a second separator
configured to receive the compressed mixed refrigerant stream and
separate the compressed mixed refrigerant into an overhead stream
and a bottoms stream that is fed to the distillation column as a
reflux stream.
21. The apparatus of claim 19, further including a splitter
configured to provide that the stream entering the feed gas bypass
line has the same composition as the portion of the feed gas stream
sent to the heat exchanger.
22. The apparatus of claim 19, wherein the splitter is configured
to provide that the bypass line receives about 5 to 35 weight % of
the feed gas from the primary feed gas line.
23. The apparatus of claim 19, further including a splitter
configured to remove a portion of the compressed mixed refrigerant
as a product stream.
24. The apparatus of claim 19, wherein the first separator is an
absorber.
25. The apparatus of claim 24, wherein the absorber has a side draw
line configured to remove a side draw stream.
Description
RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Application No. 61/888,901 filed Oct. 9, 2013.
FIELD
[0002] The embodiments described herein relate to improved
processes for recovery of natural gas liquids from gas feed streams
containing hydrocarbons, and in particular to recovery of propane
and ethane from gas feed streams.
BACKGROUND
[0003] Natural gas contains various hydrocarbons, including
methane, ethane and propane.
[0004] Natural gas usually has a major proportion of methane and
ethane, i.e. methane and ethane together typically 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. In addition to natural gas, other gas
streams containing hydrocarbons may contain a mixture of lighter
and heavier hydrocarbons. For example, gas streams formed in the
refining process can contain mixtures of hydrocarbons to be
separated. Separation and recovery of these hydrocarbons can
provide valuable products that may be used directly or as
feedstocks for other processes. These hydrocarbons are typically
recovered as natural gas liquids (NGL).
[0005] The embodiments described herein are primarily directed to
recovery of C.sub.3+ components in gas streams containing
hydrocarbons, and in particular to recovery of propane from these
gas streams. A typical natural gas feed to be processed in
accordance with the processes described below typically may
contain, in approximate mole percent, 92.12% methane, 3.96% ethane
and other C.sub.2 components, 1.05% propane and other C.sub.3
components, 0.15% iso-butane, 0.21% normal butane, 0.11% pentanes
or heavier, and the balance made up primarily of nitrogen and
carbon dioxide. Refinery gas streams may contain less methane and
higher amounts of heavier hydrocarbons.
[0006] Recovery of natural gas liquids from a gas feed stream has
been performed using various processes, such as cooling and
refrigeration of gas, oil absorption, refrigerated oil absorption
or through the use of multiple distillation towers. More recently,
cryogenic expansion processes utilizing Joule-Thompson valves or
turbo expanders have become preferred processes for recovery of NGL
from natural gas.
[0007] 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 the desired
components.
[0008] The high-pressure liquids may be expanded to a lower
pressure and fractionated. The expanded stream, comprising a
mixture of liquid and vapor, is fractionated in a distillation
column. In the distillation column volatile gases and lighter
hydrocarbons are removed as overhead vapors and heavier hydrocarbon
components exit as liquid product in the bottoms.
[0009] The feed gas is typically not totally condensed, and the
vapor remaining from the partial condensation may be passed through
a Joule-Thompson valve or a turbo expander to a lower pressure at
which further liquids are condensed as a result of further cooling
of the stream. The expanded stream is supplied as a feed stream to
the distillation column.
[0010] A reflux stream is provided to the distillation column,
typically a portion of partially condensed feed gas after cooling
but prior to expansion. Various processes have used other sources
for the reflux, such as a recycled stream of residue gas supplied
under pressure.
[0011] While various improvements to the general cryogenic
processes described above have been attempted, these improvements
continue to use a turbo expander or Joule-Thompson valve to expand
the feed stream to the distillation column. It would be desirable
to have an improved process for enhanced recovery of NGLs from a
natural gas feed stream.
SUMMARY
[0012] The embodiments described herein relate to improved
processes for recovery of NGLs from a feed gas stream. The process
utilizes an open loop mixed refrigerant process to achieve the low
temperatures necessary for high levels of NGL recovery. A single
distillation column is utilized to separate heavier hydrocarbons
from lighter components such as sales gas. The overhead stream from
the distillation column is cooled to partially liquefy the overhead
stream. The partially liquefied overhead stream is separated into a
vapor stream comprising lighter hydrocarbons, such as sales gas,
and a liquid component that serves as a mixed refrigerant. The
mixed refrigerant provides process cooling and a portion of the
mixed refrigerant is used as a reflux stream to enrich the
distillation column with key components. With the gas in the
distillation column enriched, the overhead stream of the
distillation column condenses at warmer temperatures, and the
distillation column runs at warmer temperatures than typically used
for high recoveries of NGLs. The process achieves high recovery of
desired NGL components without expanding the gas as in a
Joule-Thompson valve or turbo expander based plant, and with only a
single distillation column.
[0013] In one embodiment, C.sub.3+ hydrocarbons, and in particular
propane, are recovered. Temperatures and pressures are maintained
as required to achieve the desired recovery of C.sub.3+
hydrocarbons based upon the composition of the incoming feed
stream. In this embodiment of the process, feed gas enters a main
heat exchanger and is cooled. The cooled feed gas is fed to a
distillation column, which in this embodiment functions as a
deethanizer. Cooling for the feed stream may be provided primarily
by a warm refrigerant such as propane. The overhead stream from the
distillation column enters the main heat exchanger and is cooled to
the temperature required to produce the mixed refrigerant and to
provide the desired NGL recovery from the system.
[0014] The cooled overhead stream from the distillation column is
combined with an overhead stream from a reflux drum and separated
in a distillation column overhead drum. The overhead vapor from the
distillation column overhead drum is sales gas (i.e. methane,
ethane and inert gases) and the liquid bottoms are the mixed
refrigerant. The mixed refrigerant is enriched in C.sub.2 and
lighter components as compared to the feed gas. The sales gas is
fed through the main heat exchanger where it is warmed. The
temperature of the mixed refrigerant is reduced to a temperature
cold enough to facilitate the necessary heat transfer in the main
heat exchanger. The temperature of the refrigerant is lowered by
reducing the refrigerant pressure across a control valve. The mixed
refrigerant is fed to the main heat exchanger where it is
evaporated and super-heated as it passes through the main heat
exchanger.
[0015] After passing through the main heat exchanger, the mixed
refrigerant is compressed. Preferably, the compressor discharge
pressure is greater than the distillation column pressure so no
reflux pump is necessary. The compressed gas passes through the
main heat exchanger, where it is partially condensed. The partially
condensed mixed refrigerant is routed to a reflux drum. The bottom
liquid from the reflux drum is used as a reflux stream for the
distillation column. The vapors from the reflux drum are combined
with the distillation column over head stream exiting the main heat
exchanger and the combined stream is routed to the distillation
column overhead drum. In this embodiment, the process can achieve
over 99 percent recovery of propane from the feed gas.
[0016] In another embodiment of the process, the feed gas is
treated as described above and a portion of the mixed refrigerant
is removed from the plant following compression and cooling. The
portion of the mixed refrigerant removed from the plant is fed to a
C.sub.2 recovery unit to recover the ethane in the mixed
refrigerant. Removal of a portion of the mixed refrigerant stream
after it has passed through the main heat exchanger and been
compressed and cooled has minimal effect on the process provided
that enough C.sub.2 components remain in the system to provide the
required refrigeration. In some embodiments, as much as 95 percent
of the mixed refrigerant stream may be removed for C.sub.2
recovery. The removed stream may be used as a feed stream in an
ethylene cracking unit.
[0017] In another embodiment of the process, an absorber column is
used to separate the distillation column overhead stream. The
overhead stream from the absorber is sales gas, and the bottoms are
the mixed refrigerant.
[0018] In yet another embodiment, only one separator drum is used.
In this embodiment, the compressed, cooled mixed refrigerant is
returned to the distillation column as a reflux stream.
[0019] The process described above may be modified to achieve
separation of hydrocarbons in any manner desired. For example, the
plant may be operated such that the distillation column separates
C.sub.4+ hydrocarbons, primarily butane, from C.sub.3 and lighter
hydrocarbons. In another embodiment, the plant may be operated to
recover both ethane and propane. In this embodiment, the
distillation column is used as a demethanizer, and the plant
pressures and temperatures are adjusted accordingly. In this
embodiment, the bottoms from the distillation tower contain
primarily the C.sub.2+ components, while the overhead stream
contains primarily methane and inert gases. In this embodiment,
recovery of as much as 55 percent of the C.sub.2+ components in the
feed gas can be obtained.
[0020] Among the advantages of the process is that the reflux to
the distillation column is enriched, for example in ethane,
reducing loss of propane from the distillation column. The reflux
also increases the mole fraction of lighter hydrocarbons, such as
ethane, in the distillation column making it easier to condense the
overhead stream. This process uses the liquid condensed in the
distillation column overhead twice, once as a low temperature
refrigerant and the second time as a reflux stream for the
distillation column. Other advantages of the processes described
herein will be apparent to those skilled in the art based upon the
detailed description of preferred embodiments provided below.
[0021] In yet another embodiment, a process is provided for
recovery of natural gas liquids from a feed gas stream, comprising
forming a first portion of the feed gas stream and a second portion
of the feed gas stream, wherein the mass ratio of the first portion
to the second portion is in the range of 95:5 to 5:95; cooling the
first portion in a heat exchanger and at least partially condensing
the first portion; and feeding the second portion and the cooled
and at least partially condensed first portion to a distillation
column wherein lighter components are removed from the distillation
column as an overhead vapor stream and heavier components are
removed from the distillation column in the bottoms as a product
stream, and wherein the second portion is fed into the distillation
column at a point one or more vapor-liquid equilibrium stages below
the first portion, thereby allowing mass transfer exchange between
liquids of the cooled first portion and vapors of the second
portion within the column. The process further includes feeding the
distillation column overhead stream to the heat exchanger and
cooling the distillation column overhead stream to at least
partially liquefy the distillation column overhead stream, feeding
the at least partially liquefied distillation column overhead
stream to a first separator, separating the vapor and liquid in the
first separator to produce an overhead vapor stream comprising
sales gas and a bottoms stream comprising a mixed refrigerant,
feeding the mixed refrigerant stream to the heat exchanger to
provide cooling, wherein the mixed refrigerant stream vaporizes as
it passes through the heat exchanger, compressing the vaporized
mixed refrigerant stream and passing the compressed mixed
refrigerant stream through the heat exchanger, and feeding at least
a portion of the compressed mixed refrigerant stream to the
distillation column as a reflux stream. In embodiments, energy
inputs are about 5-30% lower, or about 10-20% lower, than the
energy inputs for processes in which the feed stream is not split
and the entire feed stream passes through the heat exchanger for
cooling. The decrease in energy input results in significant
savings in operational costs.
[0022] In a further embodiment, an apparatus is provided for
separating natural gas liquids from a feed gas stream, the
apparatus comprising a primary feed gas line configured to deliver
a feed gas stream, a heat exchanger operable to provide the heating
and cooling necessary for separation of natural gas liquids from a
feed gas stream by heat exchange contact between the feed gas
stream and one or more process streams thus forming a cooled feed
gas stream, and a distillation column configured to receive the
feed gas stream and to separate the feed gas stream into a column
overhead stream comprising a substantial amount of the lighter
hydrocarbon components of the feed gas stream and a column bottoms
stream comprising a substantial amount of the heavier hydrocarbon
components. The apparatus further includes a first separator
configured to receive the distillation column overhead stream and
to separate the column overhead stream into an overhead sales gas
stream and a bottoms stream comprising a mixed refrigerant
configured to provide process cooling in the heat exchanger, a
compressor configured to compress the mixed refrigerant stream
after the mixed refrigerant stream has provided process cooling in
the heat exchanger, and a feed gas bypass line configured to remove
a portion of the feed gas stream prior to it being sent to the heat
exchanger, wherein the feed gas bypass line is fluidly connected to
the distillation column at a point one or more vapor-liquid
equilibrium stages below the point at which the cooled feed gas
stream from the heat exchanger is fluidly connected, thereby
allowing mass transfer exchange between the liquids of the cooled
feed gas stream from the heat exchanger and the vapors of the
bypass feed gas stream within the column.
DESCRIPTION OF THE FIGURES
[0023] FIG. 1 is a schematic drawing of a plant for performing
embodiments of a method in which the mixed refrigerant stream is
compressed and returned to the reflux separator.
[0024] FIG. 2 is a schematic drawing of a plant for performing
embodiments of a method in which a portion of the compressed mixed
refrigerant stream is removed from the plant for ethane
recovery.
[0025] FIG. 3 is a schematic drawing of a plant for performing
embodiments in which an absorber is used to separate the
distillation overhead stream.
[0026] FIG. 4 is a schematic drawing of a plant for performing
embodiments in which only one separator drum is used.
[0027] FIG. 5 is a schematic drawing of a plant for performing
embodiments of a method in which the feed stream to the
distillation column is split and fed to different locations of the
column, and the mixed refrigerant is compressed and returned to the
reflux separator.
[0028] FIG. 6 is a schematic drawing of a plant for performing
embodiments of a method in which the feed stream to the
distillation column is split and fed to different locations of the
column, and a portion of the compressed mixed refrigerant stream is
removed from the plant for ethane recovery.
[0029] FIG. 7 is a schematic drawing of a plant for performing
embodiments of a method in which the feed stream to the
distillation column is split and fed to different locations of the
column, and an absorber is used to separate the distillation column
overhead stream.
[0030] FIG. 8 is a schematic drawing of a plant for performing
embodiments of a method in which the feed stream to the
distillation column is split and fed to different locations of the
column, and in which only one separator drum is used.
[0031] FIG. 9 is a schematic drawing of a plant for performing
embodiments of another method in which the feed stream to the
distillation column is split and fed to different locations of the
column.
DETAILED DESCRIPTION OF EMBODIMENTS
[0032] The embodiments described herein relate to improved
processes for recovery of natural gas liquids (NGL) from gas feed
streams containing hydrocarbons, such as natural gas or gas streams
from petroleum processing. In embodiments, the process runs at
approximately constant pressures with no intentional reduction in
gas pressures through the plant. The process uses a single
distillation column to separate lighter hydrocarbons and heavier
hydrocarbons. An open loop mixed refrigerant provides process
cooling to achieve the temperatures required for high recovery of
NGL gases. The mixed refrigerant is comprised of a mixture of the
lighter and heavier hydrocarbons in the feed gas, and is generally
enriched in the lighter hydrocarbons as compared to the feed
gas.
[0033] The open loop mixed refrigerant is also used to provide an
enriched reflux stream to the distillation column, which allows the
distillation column to operate at higher temperatures and enhances
the recovery of NGLs. The overhead stream from the distillation
column is cooled to partially liquefy the overhead stream. The
partially liquefied overhead stream is separated into a vapor
stream comprising lighter hydrocarbons, such as sales gas, and a
liquid component that serves as a mixed refrigerant.
[0034] In embodiments, the process may be used to obtain the
desired separation of hydrocarbons in a mixed feed gas stream. In
one embodiment, the process of the present application may be used
to obtain high levels of propane recovery. Recovery of as much as
99 percent or more of the propane in the feed case may be recovered
in the process. The process can also be operated in a manner to
recover significant amounts of ethane with the propane or reject
most of the ethane with the sales gas. Alternatively, the process
can be operated to recover a high percentage of C.sub.4+ components
of the feed stream and discharge C.sub.3 and lighter
components.
[0035] In embodiments, a substantial reduction in energy usage can
be obtained using the split feed configuration described herein. In
embodiments, compressor duty can be reduced by at least 5%, or at
least 10, or by 5-20% as compared to a system in which a split feed
is not used. In embodiments, the reboiler duty can be reduced by at
least 10%, or at least 20%, or at least 30% as compared to a system
that does not have a split feed. In embodiments, the size of the
distillation column also can be reduced, resulting in lower capital
cost. In embodiments, the mass ratio of the first portion of the
feed stream, which is cooled and partially condensed before being
fed to the distillation column, and the second portion of the feed
stream, which is not cooled and not partially condensed, is in the
range of 95:5 to 5:95, or in the range of 95:5 to 65:35, or in the
range of 95:5 to 70:30.
[0036] A plant for performing some embodiments is shown
schematically in FIG. 1. It should be understood that the operating
parameters for the plant, such as the temperature, pressure, flow
rates and compositions of the various streams, are established to
achieve the desired separation and recovery of the NGLs. The
required operating parameters also depend on the composition of the
feed gas. The required operating parameters can be readily
determined by those skilled in the art using known techniques,
including for example computer simulations. Accordingly, the
descriptions and ranges of the various operating parameters
provided below are intended to provide a description of specific
embodiments, and they are not intended to limit the scope of the
disclosure in any way.
[0037] Feed gas is fed through line (12) to main heat exchanger
(10). The feed gas may be natural gas, refinery gas or other gas
stream requiring separation. The feed gas is typically filtered and
dehydrated prior to being fed into the plant to prevent freezing in
the NGL unit. The feed gas is typically fed to the main heat
exchanger at a temperature between about 110.degree. F. and
130.degree. F. and at a pressure between about 100 psia and 450
psia. The feed gas is cooled and partially liquefied in the main
heat exchanger (10) by making heat exchange contact with cooler
process streams and with a refrigerant which may be fed to the main
heat exchanger through line (15) in an amount necessary to provide
additional cooling necessary for the process. A warm refrigerant
such as propane may be used to provide the necessary cooling for
the feed gas. The feed gas is cooled in the main heat exchanger to
a temperature between about 0.degree. F. and -40.degree. F.
[0038] The cool feed gas (12) exits the main heat exchanger (10)
and enters the distillation column (20) through feed line (13). The
distillation column operates at a pressure slightly below the
pressure of the feed gas, typically at a pressure of between about
5 psi and 10 psi less than the pressure of the feed gas. In the
distillation column, heavier hydrocarbons, such as for example
propane and other C.sub.3+ components, are separated from the
lighter hydrocarbons, such as ethane, methane and other gases. The
heavier hydrocarbon components exit in the liquid bottoms from the
distillation column through line (16), while the lighter components
exit through vapor overhead line (14). Preferably, the bottoms
stream (16) exits the distillation column at a temperature of
between about 150.degree. F. and 300.degree. F., and the overhead
stream (14) exits the distillation column at a temperature of
between about -10.degree. F. and -80.degree. F.
[0039] The bottoms stream (16) from the distillation column is
split, with a product stream (18) and a recycle stream (22)
directed to a reboiler (30) which receives heat input (Q).
Optionally, the product stream (18) may be cooled in a cooler to a
temperature between about 60.degree. F. and 130.degree. F. The
product stream (18) is highly enriched in the heavier hydrocarbons
in the feed gas stream. In the embodiment shown in FIG. 1, the
product stream may highly enriched in propane and heavier
components, and ethane and lighter gases are removed as sales gas
as described below. Alternatively, the plant may be operated such
that the product stream is heavily enriched in C.sub.4+
hydrocarbons, and the propane is removed with the ethane in the
sales gas. The recycle stream (22) is heated in reboiler (30) to
provide heat to the distillation column. Any type of reboiler
typically used for distillation columns may be used.
[0040] The distillation column overhead stream (14) passes through
main heat exchanger (10), where it is cooled by heat exchange
contact with process gases to partially liquefy the stream. The
distillation column overhead stream exits the main heat exchanger
through line (19) and is cooled sufficiently to produce the mixed
refrigerant as described below. Preferably, the distillation column
overhead stream is cooled to between about -30.degree. F. and
-130.degree. F. in the main heat exchanger.
[0041] In the embodiment of the process shown in FIG. 1, the cooled
and partially liquefied stream (19) is combined with the overhead
stream (28) from reflux separator (40) in mixer (100) and is then
fed through line (32) to the distillation column overhead separator
(60). Alternatively, stream (19) may be fed to the distillation
column overhead separator (60) without being combined with the
overhead stream (28) from reflux separator (40). Overhead stream
(28) may be fed to the distillation column overhead separator
directly, or in other embodiments of the process, the overhead
stream (28) from reflux separator (40) may be combined with the
sales gas (42). Optionally, the overhead stream from reflux
separator (40) may be fed through control valve (75) prior to being
fed through line (28a) to be mixed with distillation column
overhead stream (19). Depending upon the feed gas used and other
process parameters, control valve (75) may be used to hold pressure
on the ethane compressor (80), which can ease condensing this
stream and to provide pressure to transfer liquid to the top of the
distillation column. Alternatively, a reflux pump can be used to
provide the necessary pressure to transfer the liquid to the top of
the column.
[0042] In the embodiment shown in FIG. 1, the combined distillation
column overhead stream and reflux drum overhead stream (32) is
separated in the distillation column overhead separator (60) into
an overhead stream (42) and a bottoms stream (34). The overhead
stream (42) from the distillation column overhead separator (60)
contains product sales gas (e.g. methane, ethane and lighter
components). The bottoms stream (34) from the distillation column
overhead separator is the liquid mixed refrigerant used for cooling
in the main heat exchanger (10).
[0043] The sales gas flows through the main heat exchanger (10)
through line (42) and is warmed. In a typical plant, the sales gas
exits the deethanizer overhead separator at a temperature of
between about -40.degree. F. and -120.degree. F. and a pressure of
between about 85 psia and 435 psia, and exits the main heat
exchanger at a temperature of between about 100.degree. F. and
120.degree. F. The sales gas is sent for further processing through
line (43).
[0044] The mixed refrigerant flows through the distillation column
overhead separator bottoms line (34). The temperature of the mixed
refrigerant may be lowered by reducing the pressure of the
refrigerant across control valve (65). The temperature of the mixed
refrigerant is reduced to a temperature cold enough to provide the
necessary cooling in the main heat exchanger (10). The mixed
refrigerant is fed to the main heat exchanger through line (35).
The temperature of the mixed refrigerant entering the main heat
exchanger is typically between about -60.degree. F. to -175.degree.
F. Where the control valve (65) is used to reduce the temperature
of the mixed refrigerant, the temperature is typically reduced by
between about 20.degree. F. to 50.degree. F. and the pressure is
reduced by between about 90 psi to 250 psi. The mixed refrigerant
is evaporated and superheated as it passes through the main heat
exchanger (10) and exits through line (35a). The temperature of the
mixed refrigerant exiting the main heat exchanger is between about
80.degree. F. and 100.degree. F.
[0045] After exiting the main heat exchanger, the mixed refrigerant
is fed to ethane compressor (80). The mixed refrigerant is
compressed to a pressure about 15 psi to 25 psi greater than the
operating pressure of the distillation column at a temperature of
between about 230.degree. F. to 350.degree. F. By compressing the
mixed refrigerant to a pressure greater than the distillation
column pressure, there is no need for a reflux pump. The compressed
mixed refrigerant flows through line (36) to cooler (90) where it
is cooled to a temperature of between about 70.degree. F. and
130.degree. F. Optionally, cooler (90) may be omitted and the
compressed mixed refrigerant may flow directly to main heat
exchanger (10) as described below. The compressed mixed refrigerant
then flows through line (38) through the main heat exchanger (10)
where it is further cooled and partially liquefied. The mixed
refrigerant is cooled in the main heat exchanger to a temperature
of between about 15.degree. F. to -70.degree. F. The partially
liquefied mixed refrigerant is introduced through line (39) to the
reflux separator (40). As described previously, in the embodiment
of FIG. 1, the overhead (28) from reflux separator (40) is combined
with the overheads (14) from the distillation column and the
combined stream (32) is fed to the distillation column overhead
separator. The liquid bottoms (26) from the reflux separator (40)
are fed back to the distillation column as a reflux stream (26).
Control valves (75, 85) may be used to hold pressure on the
compressor to promote condensation.
[0046] The open loop mixed refrigerant used as reflux enriches the
distillation column with gas phase components. With the gas in the
distillation column enriched, the overhead stream of the column
condenses at warmer temperatures, and the distillation column runs
at warmer temperatures than normally required for high recovery of
NGLs.
[0047] The reflux to the distillation column also reduces losses of
heavier hydrocarbons from the column. For example, in processes for
recovery of propane, the reflux increases the mole fraction of
ethane in the distillation column, which makes it easier to
condense the overhead stream. The process uses the liquid condensed
in the distillation column overhead drum twice, once as a low
temperature refrigerant and the second time as a reflux stream for
the distillation column.
[0048] In another embodiment shown in FIG. 2, in which like numbers
indicate like components and flow streams described above, the
process is used to separate propane and other C.sub.3+ hydrocarbons
from ethane and light components. A tee (110) is provided in line
(38) after the mixed refrigerant compressor (80) and the mixed
refrigerant cooler to split the mixed refrigerant into a return
line (45) and an ethane recovery line (47). The return line (45)
returns a portion of the mixed refrigerant to the process through
main heat exchanger (10) as described above. Ethane recovery line
(47) supplies a portion of the mixed refrigerant to a separate
ethane recovery unit for ethane recovery. Removal of a portion of
the mixed refrigerant stream has minimal effect on the process
provided that enough C.sub.2 components remain in the system to
provide the required refrigeration. In some embodiments, as much as
95 percent of the mixed refrigerant stream may be removed for
C.sub.2 recovery. The removed stream may be used, for example, as a
feed stream in an ethylene cracking unit.
[0049] In another embodiment, the NGL recovery unit can recover
significant amounts of ethane with the propane. In this embodiment
of the process, the distillation column is a demethanizer, and the
overhead stream contains primarily methane and inert gases, while
the column bottoms contain ethane, propane and heavier
components.
[0050] In another embodiment of the process, the deethanizer
overhead drum may be replaced by an absorber. As shown in FIG. 3,
in which like numbers indicate like components and flow streams
described above, in this embodiment, the overhead stream (14) from
the distillation column (20) passes through main heat exchanger
(10) and the cooled stream (19) is fed to absorber (120). The
overhead stream (28) from reflux separator (40) is also fed to the
absorber (120). The overhead stream (42) from the absorber is the
sales gas and the bottoms stream (34) from the absorber is the
mixed refrigerant. The other streams and components shown in FIG. 3
have the same flow paths as described above.
[0051] In yet another embodiment shown in FIG. 4, in which like
numbers indicate like components and flow streams described above,
the second separator and the cooler are not used in the process. In
this embodiment, the compressed mixed refrigerant (36) is fed
through the main heat exchanger (10) and fed to the distillation
tower through line (39) to provide reflux flow.
[0052] In the embodiment shown in FIG. 5, the gas feed stream (112)
is split to create a first feed stream (112a) and a second feed
stream (112b). The first feed stream (112a) enters the heat
exchanger (110) for cooling to form a cold feed stream (113) from
the heat exchanger (110) that is partially liquefied to form a
stream (113) containing a mixture of liquid and vapor. The second
feed stream (112b) is a warm gas by-pass feed stream that is not
pre-cooled and typically is entirely in a gas phase, with no
liquid. A valve (195) is provided for the second feed stream (112b)
for process control purposes, including controlling the relative
flow rates of the first and second feed streams (112a) and (112b)
into the distillation column (120). When liquids condense in the
first feed stream (112a), a portion of the condensed liquid is
methane and ethane. Normally methane and ethane are overhead vapor
products from the process. The second feed stream (112b) has the
same overall composition as first feed stream (112a) and the cooled
feed stream (113) but typically does not contain any liquid. As a
result, there is a higher concentration of propane vapor and butane
vapor in the by-pass gas of the second feed stream (112b) than in
the cold feed stream (113). Feeding the warm by-pass gas of the
second feed stream (112b) to the distillation column one or more,
or 1 to 10, or 1 to 7, or 1 to 4 vapor-liquid equilibrium stages
below the cold feed stream (113) allows mass transfer to exchange
liquid methane and ethane for propane and butane vapor within the
distillation column (120). This vaporizes methane and ethane while
condensing propane and butane. By doing this, it unexpectedly
increases the overall efficiency of the process by substantially
reducing the refrigeration duty and reboiler duty. In embodiments,
the size of the distillation column can be reduced as compared to a
system that does not include second feed stream (112b).
[0053] The feed gas (112) may be natural gas, refinery gas or other
gas stream requiring separation. The feed gas is typically filtered
and dehydrated prior to being fed into the plant to prevent
freezing in the NGL unit. The feed gas in the first feed stream
(112a) is typically fed to the main heat exchanger at a temperature
between about 110.degree. F. and 130.degree. F. and at a pressure
between about 100 psia and 450 psia. The feed as is cooled and
partially liquefied in the main heat exchanger (110) by making heat
exchange contact with cooler process streams and with a refrigerant
which may be fed to the main heat exchanger through line (115) in
an amount necessary to provide additional cooling necessary for the
process. A warm refrigerant such as propane may be used to provide
the necessary cooling for the feed gas. The feed gas is cooled in
the main heat exchanger to a temperature between about 0.degree. F.
and -40.degree. F.
[0054] The cool feed gas (112a) exits the main heat exchanger (110)
and enters the distillation column (120) through feed line (113).
The distillation column operates at a pressure slightly below the
pressure of the feed gas, typically at a pressure of between about
5 psi and 10 psi less than the pressure of the feed gas. In the
distillation column, heavier hydrocarbons, such as for example
propane and other C.sub.3+ components, are separated from the
lighter hydrocarbons, such as ethane, methane and other gases. The
heavier hydrocarbon components exit in the liquid bottoms from the
distillation column through line (116), while the lighter
components exit through vapor overhead line (114). Preferably, the
bottoms stream (116) exits the distillation column at a temperature
of between about 150.degree. F. and 300.degree. F., and the
overhead stream (114) exits the distillation column at a
temperature of between about -10.degree. F. and -80.degree. F.
[0055] The bottoms stream (116) from the distillation column is
split, with a product stream (118) and a recycle stream (122)
directed to a reboiler (130) which receives heat input (Q).
Optionally, the product stream (118) may be cooled in a cooler to a
temperature between about 60.degree. F. and 130.degree. F. The
product stream (118) is highly enriched in the heavier hydrocarbons
in the feed gas stream. In the embodiment shown in FIG. 5, the
product stream may be highly enriched in propane and heavier
components, and ethane and lighter gases are removed as sales gas
in the sales gas line (143) as described below. Alternatively, the
plant may be operated such that the product stream is heavily
enriched in C.sub.4+ hydrocarbons, and the propane is removed with
the ethane in the sales gas. The recycle stream (122) is heated in
reboiler (130) to provide heat to the distillation column. Any type
of reboiler typically used for distillation columns may be
used.
[0056] The distillation column overhead stream (114) passes through
main heat exchanger (110), where it is cooled by heat exchange
contact with process gases to partially liquefy the stream. The
distillation column overhead stream exits the main heat exchanger
through line (119) and is cooled sufficiently to produce the mixed
refrigerant as described below. Preferably, the distillation column
overhead stream is cooled to between about -30.degree. F. and
-130.degree. F. in the main heat exchanger.
[0057] In the embodiment of the process shown in FIG. 5, the cooled
and partially liquefied stream (119) is combined with the overhead
stream (128) from reflux separator (140) in mixer (200) and is then
fed through line (132) to the distillation column overhead
separator (160). Alternatively, stream (119) may be fed to the
distillation column overhead separator (160) without being combined
with the overhead stream (128) from reflux separator (140).
Overhead stream (128) may be fed to the distillation column
overhead separator directly, or in other embodiments of the
process, the overhead stream (128) from reflux separator (140) may
be combined with the sales gas (142). Optionally, the overhead
stream from reflux separator (140) may be fed through control valve
(175) prior to being fed through line (128a) to be mixed with
distillation column overhead stream (119). Depending upon the feed
gas used and other process parameters, control valve (175) may be
used to hold pressure on the ethane compressor (180), which can
ease condensing this stream and to provide pressure to transfer
liquid to the top of the distillation column. Alternatively, a
reflux pump can be used to provide the necessary pressure to
transfer the liquid to the top of the column.
[0058] In the embodiment shown in FIG. 5, the combined distillation
column overhead stream and reflux drum overhead stream (132) is
separated in the distillation column overhead separator (160) into
an overhead stream (142) and a bottoms stream (134). The overhead
stream (142) from the distillation column overhead separator (160)
contains product sales gas (e.g. methane, ethane and lighter
components). The bottoms stream (134) from the distillation column
overhead separator is the liquid mixed refrigerant used for cooling
in the main heat exchanger (110).
[0059] The sales gas flows through the main heat exchanger (110)
through line (142) and is warmed. In a typical plant, the sales gas
exits the deethanizer overhead separator at a temperature of
between about -40.degree. F. and -120.degree. F. and a pressure of
between about 85 psia and 435 psia, and exits the main heat
exchanger at a temperature of between about 100.degree. F. and
120.degree. F. The sales gas is sent for further processing through
line (143).
[0060] The mixed refrigerant flows through the distillation column
overhead separator bottoms line (134). The temperature of the mixed
refrigerant may be lowered by reducing the pressure of the
refrigerant across control valve (165). The temperature of the
mixed refrigerant is reduced to a temperature cold enough to
provide the necessary cooling in the main heat exchanger (110). The
mixed refrigerant is fed to the main heat exchanger through line
(135). The temperature of the mixed refrigerant entering the main
heat exchanger is typically between about -60.degree. F. to
-175.degree. F. Where the control valve (165) is used to reduce the
temperature of the mixed refrigerant, the temperature is typically
reduced by between about 20.degree. F. to 50.degree. F. and the
pressure is reduced by between about 90 psi to 250 psi. The mixed
refrigerant is evaporated and superheated as it passes through the
main heat exchanger (110) and exits through line (135a). The
temperature of the mixed refrigerant exiting the main heat
exchanger is between about 80.degree. F. and 100.degree. F.
[0061] After exiting the main heat exchanger, the mixed refrigerant
is fed to ethane compressor (180). The mixed refrigerant is
compressed to a pressure about 15 psi to 25 psi greater than the
operating pressure of the distillation column at a temperature of
between about 230.degree. F. to 350.degree. F. By compressing the
mixed refrigerant to a pressure greater than the distillation
column pressure, there is no need for a reflux pump. The compressed
mixed refrigerant flows through line (136) to cooler (190) where it
is cooled to a temperature of between about 70.degree. F. and
130.degree. F. Optionally, cooler (190) may be omitted and the
compressed mixed refrigerant may flow directly to main heat
exchanger (110) as described below. The compressed mixed
refrigerant then flows through line (138) through the main heat
exchanger (110) where it is further cooled and partially liquefied.
The mixed refrigerant is cooled in the main heat exchanger to a
temperature of between about 15.degree. F. to -70.degree. F. The
partially liquefied mixed refrigerant is introduced through line
(139) to the reflux separator (140). As described previously, in
the embodiment of FIG. 5, the overhead (128) from reflux separator
(140) is combined with the overheads (114) from the distillation
column and the combined stream (132) is fed to the distillation
column overhead separator. The liquid bottoms (126) from the reflux
separator (140) are fed back to the distillation column as a reflux
stream (126). Control valves (175, 185) may be used to hold
pressure on the compressor to promote condensation.
[0062] In the embodiment shown in FIG. 6, the gas feed stream (212)
is split to create a first feed stream (212a) and a second feed
stream (212b). The first feed stream (212a) enters the heat
exchanger (210) for cooling to form a cold feed stream (213) from
the heat exchanger (210) that is partially liquefied. The second
feed stream (212b) is a warm gas by-pass feed stream that is not
pre-cooled and typically is in an entirely gas phase, with no
liquid. A valve (295) is provided for the second feed stream (212b)
for process control purposes. When liquids condense, a portion of
the condensed liquid is methane and ethane. Normally methane and
ethane are overhead vapor products from the process. The second
feed stream (212b) has the same composition as the first feed
stream (212a) but contains less liquid (and typically is entirely
in the gas phase). As a result, there is a higher concentration of
propane vapor and butane vapor in the by-pass gas of second feed
stream (212b) than in the cold feed stream (213). Placing the warm
by-pass gas of the second feed stream (212b) one or more, or 1 to
10, or 1 to 7, or 1 to 4 vapor-liquid equilibrium stages below the
cold feed stream (213) allows mass transfer to exchange liquid
methane and ethane for propane and butane vapor within the
distillation column (220). This vaporizes methane and ethane while
condensing propane and butane. By doing this, it unexpectedly
increases the overall efficiency of the process by substantially
reducing the refrigeration duty and reboiler duty. In embodiments,
the size of the distillation column can be reduced as compared to a
system that does not include stream (212b).
[0063] In the embodiment of FIG. 6, the process is used to separate
propane and other C.sub.3+ hydrocarbons from ethane and light
components. A tee (310) is provided in line (238) after the mixed
refrigerant compressor (280) and the mixed refrigerant cooler to
split the mixed refrigerant into a return line (245) and an ethane
recovery line (247). The return line (245) returns a portion of the
mixed refrigerant to the process through main heat exchanger (210)
as described above. Ethane recovery line (247) supplies a portion
of the mixed refrigerant to a separate ethane recovery unit for
ethane recovery. Removal of a portion of the mixed refrigerant
stream has minimal effect on the process provided that enough
C.sub.2 components remain in the system to provide the required
refrigeration. In some embodiments, as much as 95 percent of the
mixed refrigerant stream may be removed for C.sub.2 recovery. The
removed stream may be used, for example, as a feed stream in an
ethylene cracking unit.
[0064] In the embodiment shown in FIG. 7, the gas feed stream (312)
is split to create a first feed stream (312a) that enters the heat
exchanger (310) for cooling to form a cold feed stream (313) from
the heat exchanger (310) that is partially liquefied, and a second
feed stream (312b) that is a warm gas by-pass feed stream that is
not pre-cooled. A valve (395) is provided for the second feed
stream (312b) for process control purposes. When liquids condense
in first feed stream (312a), a portion of the condensed liquid is
methane and ethane. Normally methane and ethane are overhead vapor
products from the process. The second feed stream (312b) has the
same composition as the first feed stream (312a) but contains less
liquid. As a result, there is a higher concentration of propane
vapor and butane vapor in the by-pass gas of second feed stream
(312b) than in the cold feed stream (313). Placing the warm by-pass
gas of the second feed stream (312b) one or more, or 1 to 10, or 1
to 7, or 1 to 4, vapor-liquid equilibrium stages below the cold
feed stream (313) allows mass transfer to exchange liquid methane
and ethane for propane and butane vapor within the distillation
column (320). This vaporizes methane and ethane while condensing
propane and butane. By doing this, it unexpectedly increases the
overall efficiency of the process by substantially reducing the
refrigeration duty and reboiler duty. In embodiments, the size of
the distillation column can be reduced as compared to a system that
does not include stream (312b).
[0065] As is shown in FIG. 7, the deethanizer overhead drum may be
replaced by an absorber. In this embodiment, the overhead stream
(314) from the distillation column (320) passes through main heat
exchanger (310) and the cooled stream (319) is fed to an absorber
(321). The overhead stream (328) from reflux separator (340) is
also fed to the absorber (321) through line (332). The overhead
stream (342) from the absorber (321) is the sales gas and the
bottoms stream (334) from the absorber (321) is the mixed
refrigerant. The other streams and components shown in FIG. 7 have
the same flow paths as described above.
[0066] In yet another embodiment shown in FIG. 8 the second
separator and the cooler are not used in the process. In this
embodiment, the compressed mixed refrigerant (436) is fed through
the main heat exchanger (410) and fed to the distillation column
(420) through line (439) to provide reflux flow.
[0067] In the embodiment shown in FIG. 8, the gas feed stream (412)
is split to create a first feed stream (412a) that enters the heat
exchanger (410) for cooling to form a cold feed stream (413) from
the heat exchanger (410) that is partially liquefied, and a second
feed stream (412b) that is a warm gas by-pass feed stream that is
not pre-cooled. A valve (495) is provided for the second feed
stream (412b) for process control purposes. When liquids condense,
a portion of the condensed liquid is methane and ethane. Normally
methane and ethane are overhead vapor products from the process.
The second feed stream (412b) has the same composition as the first
feed stream (412a) but contains less liquid. As a result, there is
a higher concentration of propane vapor and butane vapor in the
by-pass gas of second feed stream (412b) than in the cold feed
stream (413). Placing the warm by-pass gas of the second feed
stream (412b) one or more, or 1 to 10, or 1 to 7, or 1 to 4
vapor-liquid equilibrium stages below the cold feed stream (413)
allows mass transfer to exchange liquid methane and ethane for
propane and butane vapor within the distillation column (420). This
vaporizes methane and ethane while condensing propane and butane.
By doing this, it unexpectedly increases the overall efficiency of
the process by substantially reducing the refrigeration duty and
reboiler duty. In embodiments, the size of the distillation column
can be reduced as compared to a system that does not include stream
(412b).
[0068] In yet another embodiment shown in FIG. 9, the split feed
scheme is incorporated into a system that is somewhat similar to a
process described in U.S. Pat. No. 8,627,681, the contents of which
are incorporated herein by reference in their entirety. The
benefits of the embodiment of FIG. 9 are surprisingly and
unexpectedly discovered that there will be a decrease in
refrigeration duty specification, decrease in deethanizer reboiler
duty specification, decrease in deethanizer vapor and liquid
traffic thus providing for a distillation column sizing decrease,
and a decrease in the refrigeration and reboiler duty specification
with high pressure feeds. The total propane and mixed refrigerant
compressor duty is over 11 percent higher without the split feed.
As is shown, considerable economic benefits from reduced total
invested cost and operational costs can be obtained as a result of
these unexpected improvements.
[0069] More specifically, the overall process of FIG. 9 is
designated as 502. Feed stream (512) is split to create first feed
stream (512a) and second feed stream (512b). First feed stream
(512a) enters the heat exchanger (510) for cooling to form a cold
or high pressure stream (513) from the heat exchanger (510) that is
partially liquefied. Warm vapor by-pass stream (512b) is a second
stream that is not pre-cooled. Stream (512b) passes through control
valve (605) to reduce its pressure and is then fed to the middle of
a distillation column (520) at a location that is one or more, or 1
to 10, or 1 to 7, or 1 to 4 vapor-liquid equilibrium stages below
the entry point of stream 513.
[0070] Although a multi-pass heat exchanger (510) is illustrated,
use of multiple heat exchangers may be used to achieve similar
results, as is also the case with the embodiments shown in FIGS.
5-8. The feed stream (512) may be natural gas, refinery gas or
other gas stream requiring separation. The feed gas is typically
filtered and dehydrated prior to being fed into the plant to
prevent freezing in the NGL unit. In embodiments, the first feed
stream (512a) is typically fed to the main heat exchanger at a
temperature between about 43.degree. C. and 54.degree. C.
(110.degree. F. and 130.degree. F.) and at a pressure between about
7 bar and 31 bar (100 psia and 450 psia). The first feed stream
(512a) is cooled and partially liquefied in the main heat exchanger
510 via indirect heat exchange with cooler process streams and/or
with a refrigerant which may be fed to the main heat exchanger via
line (515) in an amount necessary to provide additional cooling
necessary for the process. A warm refrigerant such as propane, for
example, may be used to provide the necessary cooling for the feed
gas. The feed gas may be cooled in the main heat exchanger to a
temperature between about -18.degree. C. and -40.degree. C.
(0.degree. F. and -40.degree. F.).
[0071] The cool feed gas exits the main heat exchanger (510) and is
fed to distillation column (520) via feed line (513). Distillation
column (520) operates at a pressure slightly below the pressure of
the feed gas, typically at a pressure about 0.3 to 0.7 bar (5 to 10
psi) less than the pressure of the feed gas. In the distillation
column, heavier hydrocarbons, such as propane and other C.sub.3+
components, are separated from the lighter hydrocarbons, such as
ethane, methane and other gases. The heavier hydrocarbon components
exit in the liquid bottoms from the distillation column through
line (516), while the lighter components exit through vapor
overhead line (514). In embodiments, the bottoms stream 516 exits
the distillation column at a temperature between about 65.degree.
C. and 149.degree. C. (150.degree. F. and 300.degree. F.), and the
overhead stream 14 exits the distillation column at a temperature
of between about -23.degree. C. and -62.degree. C. (-10.degree. F.
and -80.degree. F.).
[0072] The bottoms stream (516) from the distillation column is
split, with a product stream (518) and a reboil stream (522)
directed to a reboiler (530). Optionally, the product stream (518)
may be cooled in a cooler (not shown) to a temperature between
about 515.degree. C. and 554.degree. C. (60.degree. F. and
130.degree. F.). The product stream (518) is highly enriched in the
heavier hydrocarbons in the feed gas stream. In the embodiment
shown in FIG. 9, the product stream may be enriched in propane and
heavier components, and ethane and lighter gases are further
processed as described below. Alternatively, the plant may be
operated such that the product stream is heavily enriched in
C.sub.4+ hydrocarbons, and the propane is removed with the ethane
in the sales gas produced. The reboil stream (522) is heated in
reboiler (530) to provide heat to the distillation column. Any type
of reboiler typically used for distillation columns may be
used.
[0073] The distillation column overhead stream (514) passes through
main heat exchanger (510), where it is cooled by indirect heat
exchange with process gases to at least partially liquefy or
completely (100%) liquefy the stream. The distillation column
overhead stream exits the main heat exchanger (510) through line
(519) and is cooled sufficiently to produce the mixed refrigerant
as described below. In some embodiments, the distillation column
overhead stream is cooled to between about -34.degree. C. and
-90.degree. C. (-30.degree. F. and -130.degree. F.) in main heat
exchanger 510.
[0074] The cooled and partially liquefied stream (519) and the
overhead stream (528) (stream 532 following control valve 575) from
reflux separator (540) may be fed to distillation column overhead
separator (585).
[0075] The components in distillation column overhead stream (519)
and reflux drum overhead stream (532) are separated in overhead
separator (585) into an overhead stream (542), a side draw fraction
(551), and a bottoms stream (534). The overhead stream (542) from
distillation column overhead separator (585) contains methane,
ethane, nitrogen, and other lighter components, and is enriched in
nitrogen content. Side draw fraction (551) may be of intermediate
nitrogen content. The bottoms stream (534) from distillation column
overhead separator (585) is the liquid mixed refrigerant used for
cooling in the main heat exchanger (510), which may be depleted in
nitrogen content. The side draw fraction may be reduced in pressure
across flow valve (595), fed to heat exchanger (510) for use in the
integrated heat exchange system, and recovered via flow line
(552).
[0076] The components in overhead stream (542) are fed to main heat
exchanger (510) and warmed. In a typical plant, the overhead
fraction recovered via stream (542) from overhead separator (585)
is at a temperature between about -40.degree. C. and -84.degree. C.
(-40.degree. F. and -120.degree. F.) and at a pressure between
about 5 bar and 30 bar (85 psia and 435 psia). Following heat
exchange in main heat exchanger (510), the overhead fraction
recovered from heat exchanger 510 via stream (543) may be at a
temperature between about 37.degree. C. and 49.degree. C.
(100.degree. F. and 120.degree. F.). The overhead fraction is
enriched in nitrogen content and may be recovered via stream (543)
as a low-btu natural gas stream.
[0077] The mixed refrigerant, as mentioned above, is recovered from
distillation column overhead separator (585) via bottoms line
(534). The temperature of the mixed refrigerant may be lowered by
reducing the pressure of the refrigerant across control valve
(565). The temperature of the mixed refrigerant is reduced to a
temperature cold enough to provide the necessary cooling in the
main heat exchanger (510). The mixed refrigerant is fed to the main
heat exchanger through line (535). The temperature of the mixed
refrigerant entering the main heat exchanger is typically between
about -51.degree. C. and -115.degree. C. (-60.degree. F. to
-175.degree. F.).
[0078] Where the control valve (565) is used to reduce the
temperature of the mixed refrigerant, the temperature is typically
reduced by about 6.degree. C. to 10.degree. C. (20.degree. F. to
50.degree. F.) and the pressure is reduced by about 6 bar to 17 bar
(90 to 250 psi). The mixed refrigerant is evaporated and
superheated as it passes through the main heat exchanger 510 and
exits through line (535a).
[0079] The temperature of the mixed refrigerant exiting the main
heat exchanger is between about 26.degree. C. and 38.degree. C.
(80.degree. F. and 100.degree. F.).
[0080] After exiting main heat exchanger (510), the mixed
refrigerant is fed to compressor (580). The mixed refrigerant is
compressed to a pressure 1 bar to 2 bar (15 psi to 25 psi) greater
than the operating pressure of the distillation column, and at a
temperature between about 110.degree. C. to 177.degree. C.
(230.degree. F. to 350.degree. F.). By compressing the mixed
refrigerant to a pressure greater than the distillation column
pressure, there is no need for a reflux pump. The compressed mixed
refrigerant flows through line (536) to cooler (590) where it is
cooled to a temperature between about 21.degree. C. and 54.degree.
C. (70.degree. F. and 130.degree. F.). Optionally, cooler (590) may
be omitted and the compressed mixed refrigerant may flow directly
to main heat exchanger (510). The compressed mixed refrigerant then
flows via line (538) through the main heat exchanger (510) where it
is further cooled and partially liquefied.
[0081] The mixed refrigerant is cooled in the main heat exchanger
to a temperature from about -9.degree. C. to -57.degree. C.
(15.degree. F. to -70.degree. F.) The partially liquefied mixed
refrigerant is introduced through line (539) to reflux separator
(540). As described previously, the overheads (528) from reflux
separator (540) and overheads (514) from the distillation column
(520) are fed to the distillation column overhead separator (585).
The liquid bottoms (526) from the reflux separator (540) are fed
back to the distillation column (520) as a reflux stream (526).
Control valves (575), (586) may be used to hold pressure on the
compressor to promote condensation.
[0082] The mixed refrigerant used as reflux (fed via stream 526)
enriches distillation column (520) with gas phase components. With
the gas in the distillation column enriched, the overhead stream of
the column condenses at warmer temperatures, and the distillation
column runs at warmer temperatures than normally required for a
high recovery of NGLs.
[0083] The reflux to distillation column (520) also reduces heavier
hydrocarbons in the overheads fraction. For example, in processes
for recovery of propane, the reflux increases the mole fraction of
ethane in the distillation column, which makes it easier to
condense the overhead stream. The process uses the liquid condensed
in the distillation column overhead separator twice, once as a low
temperature refrigerant and the second time as a reflux stream for
the distillation column.
[0084] At least a portion of the mixed refrigerant in flow line
(528), having a very low nitrogen content, may be withdrawn via
flow stream (532ex) prior to separator (585). In some embodiments,
the portion withdrawn via flow stream (532ex) may be used for
pipeline sales. In other embodiments, a mixed refrigerant stream
(532ex), having less than 1 mole % nitrogen, may be mixed with a
high or intermediate btu natural gas process stream having greater
than 4% nitrogen to result in a pipeline sales stream having 4% or
less nitrogen.
[0085] For example, mixed refrigerant stream (532ex) may be
combined with intermediate btu natural gas in stream (551) (side
draw) to result in a natural gas stream suitable for pipeline
sales. The flow rates of streams (532ex) and (551) may be such that
the resulting product stream (548) has a nitrogen (inert) content
of less than 4 mole %. In some embodiments, flow stream (532ex) may
be fed to main heat exchanger (510); and following heat transfer,
the mixed refrigerant may be recovered from heat exchanger (510)
via flow line (541) for admixture with intermediate btu stream
(551). Other process streams may also be admixed with mixed
refrigerant stream (532ex) in other embodiments.
[0086] Processes according to the embodiment of FIG. 9 allows for
substantial process flexibility, providing for the ability to
efficiently process feed gas streams having a wide range of
nitrogen content. The embodiment described with regard to FIG. 9
allows for recovery of a majority of the feed gas btu value as a
natural gas sales stream. Iso-pressure open refrigeration processes
according to embodiments disclosed herein may additionally include
separation of nitrogen from high or intermediate nitrogen content
streams, allowing for additional recovery of btu value or
additional flexibility with regard to process conditions and feed
gas nitrogen content.
[0087] Examples of specific embodiments of the processes are
described below. These examples are provided to further describe
the processes described herein and they are not intended to limit
the full scope of the disclosure in any way.
CONTROL EXAMPLE 1
[0088] In the following examples, operation of the processing plant
shown in FIG. 1 with different types and compositions of feed gas
were computer simulated using process the Apsen HYSYS simulator. In
this example, the operating parameters for C.sub.3+ recovery using
a relatively lean feed gas are provided. Table 1 shows the
operating parameters for propane recovery using a lean feed gas.
The composition of the feed gas, the sales gas stream and the
C.sub.3+ product stream, and the mixed refrigerant stream in mole
fractions are provided in Table 2. Energy inputs for this
embodiment included about 3.717.times.10.sup.55 Btu/hr (Q) to the
reboiler (30) and about 459 horsepower (P) to the ethane compressor
(80).
[0089] As can be seen in Table 2, the product stream (18) from the
bottom of the distillation column is highly enriched in C.sub.3+
components, while the sales gas stream (43) contains almost
entirely C.sub.2 and lighter hydrocarbons and gases. Approximately
99.6% of the propane in the feed gas is recovered in the product
stream. The mixed refrigerant is comprised primarily of methane and
ethane, but contains more propane than the sales gas.
CONTROL EXAMPLE 2
[0090] In this example, operating parameters are provided for the
processing plant shown in
[0091] FIG. 1 using a refinery feed gas for recovery of C.sub.3+
components in the product stream. Table 3 shows the operating
parameters using the refinery feed gas. The composition of the feed
gas, the sales gas stream and the C.sub.3+ product stream, and the
mixed refrigerant stream in mole fractions are provided in Table 4.
Energy inputs for this embodiment included about
2.205.times.10.sup.6 Btu/hr (Q) to the reboiler (30) and about 228
horsepower (P) to the ethane compressor (80).
[0092] As can be seen in Table 4, the product stream (18) from the
bottom of the distillation column is highly enriched in C.sub.3+
components, while the sales gas stream (43) contains almost
entirely C.sub.2 and lighter hydrocarbons and gases, in particular
hydrogen. This stream could be used to feed a membrane unit or PSA
to upgrade this stream to useful hydrogen. Approximately 97.2% of
the propane in the feed gas is recovered in the product stream. The
mixed refrigerant is comprised primarily of methane and ethane, but
contains more propane than the sales gas.
CONTROL EXAMPLE 3
[0093] In this example, operating parameters are provided for the
processing plant shown in
[0094] FIG. 1 using a refinery feed gas for the recovery of
C.sub.4+ components in the product stream, with the C.sub.3
components removed in the sales gas stream. Table 5 shows the
operating parameters for this embodiment of the process. The
composition of the feed gas, the sales gas stream and the C.sub.4+
product stream, and the mixed refrigerant stream in mole fractions
are provided in Table 6. Energy inputs for this embodiment included
about 2.512.times.10.sup.6 Btu/hr (Q) to the reboiler (30) and
about 198 horsepower (P) to the ethane compressor (80).
[0095] As can be seen in Table 6, in this embodiment, the product
stream (18) from the bottom of the distillation column is highly
enriched in C.sub.4+ components, while the sales gas stream (43)
contains almost entirely C.sub.3 and lighter hydrocarbons and
gases. Approximately 99.7% of the C.sub.4+ components in the feed
gas is recovered in the product stream. The mixed refrigerant is
comprised primarily of C.sub.3 and lighter components, but contains
more butane than the sales gas.
CONTROL EXAMPLE 4
[0096] In this example, operating parameters are provided for the
processing plant shown in FIG. 2 using a refinery feed gas for
recovery of C.sub.3+ components in the product stream, with the
C.sub.2 and lighter components removed in the sales gas stream. In
this embodiment, a portion of the mixed refrigerant is removed
through line (47) and fed to an ethane recovery unit for further
processing. Table 7 shows the operating parameters for this
embodiment of the process. The composition of the feed gas, the
sales gas stream and the C.sub.3+ product stream, and the mixed
refrigerant stream in mole fractions are provided in Table 8.
Energy inputs for this embodiment included about
2.089.times.10.sup.6 Btu/hr (Q) to the reboiler (30) and about 391
horsepower (P) to the ethane compressor (80).
[0097] As can be seen in Table 8, in this embodiment, the product
stream (18) from the bottom of the distillation column is highly
enriched in C.sub.3+ components, while the sales gas stream (43)
contains almost entirely C.sub.2 and lighter hydrocarbons and
gases. The mixed refrigerant is comprised primarily of C.sub.2 and
lighter components, but contains more propane than the sales
gas.
CONTROL EXAMPLE 5
[0098] In this example, operating parameters are provided for the
processing plant shown in
[0099] FIG. 3 using a lean feed gas for recovery of C.sub.3+
components in the product stream, with the C.sub.2 and lighter
components removed in the sales gas stream. In this embodiment, an
absorber (120) is used to separate the distillation column overhead
stream and the reflux separator overhead stream to obtain the mixed
refrigerant. Table 9 shows the operating parameters for this
embodiment of the process. The composition of the feed gas, the
sales gas stream and the C.sub.3+ product stream, and the mixed
refrigerant stream in mole fractions are provided in Table 10.
Energy inputs for this embodiment included about
3.734.times.10.sup.5 Btu/hr (Q) to the reboiler (30) and about 316
horsepower (P) to the ethane compressor (80).
[0100] As can be seen in Table 10, in this embodiment, the product
stream (18) from the bottom of the distillation column is highly
enriched in C.sub.3+ components, while the sales gas stream (43)
contains almost entirely C.sub.2 and lighter hydrocarbons and
gases. The mixed refrigerant is comprised primarily of C.sub.2 and
lighter components, but contains more propane than the sales
gas.
CONTROL EXAMPLE 6
[0101] In this example, operating parameters are provided for the
processing plant shown in FIG. 1 using a rich feed gas for the
recovery of C.sub.3+ components in the product stream, with the
C.sub.2 components removed in the sales gas stream. Table 11 shows
the operating parameters for this embodiment of the process. The
composition of the feed gas, the sales gas stream and the C.sub.3+
product stream, and the mixed refrigerant stream in mole fractions
are provided in Table 12. Energy inputs for this embodiment
included about 1.458.times.10.sup.6 Btu/hr (Q) to the reboiler (30)
and about 226 horsepower (P) to the ethane compressor (80).
[0102] As can be seen in Table 12, in this embodiment, the product
stream (18) from the bottom of the distillation column is highly
enriched in C.sub.3+ components, while the sales gas stream (43)
contains almost entirely C.sub.2 and lighter hydrocarbons and
gases. The mixed refrigerant is comprised primarily of C.sub.2 and
lighter components, but contains more propane than the sales
gas.
EXAMPLE 7
[0103] In this example, operating parameters comparable to the
prior examples are provided for a simulated processing plant shown
in FIG. 5 using the rich feed gas of Control Example 6 for the
recovery of C.sub.3+ components in the product stream, with the
C.sub.2 components removed in the sales gas stream. Energy inputs
for this embodiment included about 1.117.times.10.sup.6 Btu/hr (Q)
to the reboiler (130) and a reduced horsepower to the ethane
compressor (180). In this embodiment, about 15 weight % of the gas
feed stream (112) formed the bypass stream (112b) and the remainder
of stream (112) formed the first feed stream (112a).
[0104] As was the case in the prior examples, in this embodiment,
the product stream (118) from the bottom of the distillation column
is highly enriched in C.sub.3+ components, while the sales gas
stream (143) contains almost entirely C.sub.2 and lighter
hydrocarbons and gases. The mixed refrigerant is comprised
primarily of C.sub.2 and lighter components, but contains more
propane than the sales gas. Based on process simulation data, with
the insertion of the feed stream (112b) into the column (120) as
shown, it was discovered that there was an unexpected and
surprising decrease in refrigeration duty specification, decrease
in deethanizer reboiler duty specification, decrease in deethanizer
vapor and liquid traffic thus providing for a distillation column
sizing decrease, and a decrease in the refrigeration and reboiler
duty specification with high pressure feeds. The total propane and
mixed refrigerant compressor duty is over 12 percent higher without
the split feed. This results in significant economic savings in
both total invested cost (TIC) in the plant and operational costs.
By way of illustration, in the USA, 200 MMSCFD gas plants are
fairly typical. Such a plant may have about 15,000 HP of
refrigeration compressors, depending of feed composition. Based on
the following calculation, configuration results in about a 12
percent saving in compressor duty. 15,000 HP.times.0.12
Savings.times.0.746 kw/hp.times.0.1 $/kwh=134 $/hr, which is over a
million dollars per year of electric power.
[0105] For a 200 MMSCFD plant, a reboiler duty without the split
feed is approximately 29.2 MMBTU/HR. In this Example, the reboiler
duty is about 22.2 MMBTU/HR. Assuming an energy cost of US 5.00
MMBTU, annual savings would be about $307,000.
EXAMPLE 8
[0106] In this set of examples, operating parameters comparable to
the prior examples were provided for a simulated processing plant
shown in FIG. 5 using the same lean feed gas and product stream
compositions as were used in Control Example 1 for the recovery of
C.sub.3+ components in the product stream, with the C.sub.2
components removed in the sales gas stream. The by-pass feed stream
contained about 10-15 weight % of the feed gas stream 112. Energy
inputs for this embodiment were about 20-27% lower than the energy
input for Control Example 1. This set of examples resulted in
significant economic savings in both total invested cost (TIC) in
the plant and operational costs.
PROPHETIC EXAMPLE 9
[0107] In this example, operating parameters comparable to the
prior examples are provided for a simulated processing plant shown
in FIG. 6 using the same lean feed gas and product stream
compositions as were used in Control Example 4 for the recovery of
C.sub.3+ components in the product stream, with the C.sub.2
components removed in the sales gas stream. The by-pass feed stream
contains about 10-15 weight % of the feed gas stream 212. Energy
inputs for this embodiment are lower than the energy input for
Control Example 4. This embodiment results in significant economic
savings in both total invested cost (TIC) in the plant and
operational costs.
PROPHETIC EXAMPLE 10
[0108] In this example, operating parameters comparable to the
prior examples are provided for a simulated processing plant shown
in FIG. 7 using the same lean feed gas and product stream
compositions as were used in Control Example 5 for the recovery of
C.sub.3+ components in the product stream, with the C.sub.2
components removed in the sales gas stream. The by-pass stream
contains about 10-15 weight % of the feed gas stream 312. Energy
inputs for this embodiment are lower than the energy input for
Control Example 5. This embodiment results in significant economic
savings in both total invested cost (TIC) in the plant and
operational costs.
[0109] While specific embodiments have been described above, one
skilled in the art will recognize that numerous variations or
changes may be made to the process described above without
departing from the scope as recited in the appended claims.
Accordingly, the foregoing description of preferred embodiments is
intended to describe the embodiments an exemplary, rather than a
limiting, sense.
TABLE-US-00001 TABLE 1 Material Streams 12 13 19 15 17 Vapour
1.0000 0.9838 0.3989 0.0000 0.5000 Fraction Temperature F. 120.0
-25.00 -129.0 -30.00 -29.68 Pressure psia 415.0 410.0 400.0 21.88
20.88 Molar Flow MMSCFD 10.00 10.00 11.76 1.317 1.317 Mass Flow
lb/hr 1.973e+004 1.973e+004 2.362e+004 6356 6356 Liquid barrel/day
4203 4203 5100 862.2 862.2 Volume Flow 14 18 32 34 42 Vapour 1.0000
0.0000 0.6145 0.0000 1.0000 Fraction Temperature F. -76.88 251.9
-118.6 -118.7 -118.7 Pressure psia 405.0 410.0 400.0 400.0 400.0
Molar Flow MMSCFD 11.76 0.2517 15.89 6.139 9.723 Mass Flow lb/hr
2.362e+004 1671 3.220e+004 1.414e+004 1.800e+004 Liquid barrel/day
5100 196.3 6931 2925 3995 Volume Flow 43 35 35a 36 38 Vapour 1.0000
0.2758 1.0000 1.0000 1.0000 Fraction Temperature F. 110.0 -165.0
90.00 262.2 120.0 Pressure psia 395.0 149.9 144.9 470.0 465.0 Molar
Flow MMSCFD 9.723 6.139 6.139 6.139 6.139 Mass Flow lb/hr
1.800e+004 1.414e+004 1.414e+004 1.414e+004 1.414e+004 Liquid
barrel/day 3995 2925 2925 2925 2925 Volume Flow 39 28 26 26a 28a
Vapour 0.6723 1.0000 0.0000 0.0452 .09925 Fraction Temperature F.
-63.00 -63.00 -63.00 -68.04 -69.27 Pressure psia 460.0 460.0 460.0
415.0 400.0 Molar Flow MMSCFD 6.139 4.127 2.011 2.011 4.127 Mass
Flow lb/hr 1.414e+004 8573 5566 5566 8573 Liquid barrel/day 2925
1831 1094 1094 1831 Volume Flow
TABLE-US-00002 TABLE 2 Mole Fractions of Components in Streams Feed
Gas Product Sales Gas Mixed (12) (18) (43) Refrigerant (35) Methane
0.9212 0.0000 0.9453 0.6671 Ethane 0.0396 0.0082 0.0402 0.3121
Propane 0.0105 0.4116 0.0001 0.0046 Butane 0.0036 0.1430 0.0000
0.0000 Pentane 0.0090 0.3576 0.0000 0.0000 Heptane 0.0020 0.0795
0.0000 0.0000 CO.sub.2 0.0050 0.0000 0.0051 0.0145 Nitrogen 0.0091
0.0000 0.0094 0.0017
TABLE-US-00003 TABLE 3 Material Streams 12 13 19 15 17 Vapour
0.9617 0.7601 0.7649 0.0000 0.5000 Fraction Temperature F. 120.0
-5.00 -85.00 -15.00 -14.37 Pressure psia 200.0 195.0 185.0 30.12
29.12 Molar Flow MMSCFD 10.00 10.00 9.821 8.498 8.498 Mass Flow
lb/hr 2.673e+004 2.673e+004 1.852e+004 4.102e+004 4.102e+004 Liquid
barrel/day 4723 4723 4252 5564 5564 Volume Flow 14 18 32 34 42
Vapour 1.0000 0.0000 0.7669 0.0000 1.0000 Fraction Temperature F.
-50.25 162.6 -84.09 -84.07 -84.07 Pressure psia 190.0 195.0 185.0
185.0 185.0 Molar Flow MMSCFD 9.821 2.377 9.937 2.314 7.617 Mass
Flow lb/hr 1.852e+004 1.559e+004 1.883e+004 7696 1.112e+004 Liquid
barrel/day 4252 1844 4314 1436 2876 Volume Flow 43 35 35a 36 38
Vapour 1.0000 0.0833 1.0000 1.0000 1.0000 Fraction Temperature F.
110.0 -103.0 90.00 260.4 120.0 Pressure psia 180.0 50.8 45.8 215.0
210.0 Molar Flow MMSCFD 7.617 2.314 2.314 2.314 2.314 Mass Flow
lb/hr 1.112e+004 7696 7696 7696 7696 Liquid barrel/day 2876 1436
1436 1436 1436 Volume Flow 39 28 26 26a 28a Vapour 0.0500 1.0000
0.0000 0.0032 1.0000 Fraction Temperature F. -29.77 -29.77 -29.77
-30.32 -33.30 Pressure psia 205.0 205.0 205.0 200.0 185.0 Molar
Flow MMSCFD 2.314 0.1157 2.198 2.198 0.1157 Mass Flow lb/hr 7696
308.1 7388 7388 308.1 Liquid barrel/day 1436 62.34 1373 1373 62.34
Volume Flow
TABLE-US-00004 TABLE 4 Mole Fractions of Components in Streams Feed
Gas Product Sales Gas Mixed (12) (18) (43) Refrigerant (35)
Hydrogen 0.3401 0.0000 0.4465 0.0038 Methane 0.2334 0.0000 0.3062
0.0658 Ethane 0.1887 0.0100 0.2439 0.8415 Propane 0.0924 0.3783
0.0034 0.0889 Butane 0.0769 0.3234 0.0000 0.0000 Pentane 0.0419
0.1760 0.0000 0.0000 Heptane 0.0267 0.1124 0.0000 0.0000 CO.sub.2
0.0000 0.0000 0.0000 0.0000 Nitrogen 0.0000 0.0000 0.0000
0.0000
TABLE-US-00005 TABLE 5 Material Streams 12 13 19 15 17 Vapour
0.9805 0.8125 0.8225 0.0000 0.5000 Fraction Temperature F. 120.0
0.00 -43.00 -20.00 -19.46 Pressure psia 135.0 130.0 120.0 27.15
26.15 Molar Flow MMSCFD 10.00 10.00 10.31 8.058 8.058 Mass Flow
lb/hr 2.673e+004 2.673e+004 2.339e+004 3.890e+004 3.890e+004 Liquid
barrel/day 4723 4723 4624 5276 5276 Volume Flow 14 18 32 34 42
Vapour 1.0000 0.0000 0.8234 0.0000 1.0000 Fraction Temperature F.
-13.13 195.3 -42.52 -42.49 -42.49 Pressure psia 125.0 130.0 120.0
120.0 120.0 Molar Flow MMSCFD 10.31 1.462 10.38 1.840 8.557 Mass
Flow lb/hr 2.339e+004 1.119e+004 2.360e+004 8068 1.561e+004 Liquid
barrel/day 4624 1245 4661 1183 3490 Volume Flow 43 35 35a 36 38
Vapour 1.0000 0.0805 1.0000 1.0000 1.0000 Fraction Temperature F.
110.0 -62.0 90.00 238.2 120.0 Pressure psia 115.0 31.75 26.75 150.0
145.0 Molar Flow MMSCFD 8.557 1.840 1.840 1.840 1.840 Mass Flow
lb/hr 1.561e+004 8068 8068 8068 8068 Liquid barrel/day 3490 1183
1183 1183 1183 Volume Flow 39 28 26 26a 28a Vapour 0.0349 1.0000
0.0000 0.0038 1.0000 Fraction Temperature F. 15.00 15.00 15.00
14.31 11.44 Pressure psia 140.0 140.0 140.0 135.0 120.0 Molar Flow
MMSCFD 1.840 6.425e-002 1.776 1.776 6.425e-002 Mass Flow lb/hr 8068
211.4 7856 7856 211.4 Liquid barrel/day 1183 36.58 1147 1147 36.58
Volume Flow
TABLE-US-00006 TABLE 6 Mole Fractions of Components in Streams Feed
Gas Product Sales Gas Mixed (12) (18) (43) Refrigerant (35)
Hydrogen 0.3401 0.0000 0.3975 0.0022 Methane 0.2334 0.0000 0.2728
0.0257 Ethane 0.1887 0.0000 0.2220 0.2461 Propane 0.0924 0.0100
0.1074 0.7188 Butane 0.0769 0.5212 0.0003 0.0071 Pentane 0.0419
0.2861 0.0000 0.0000 Heptane 0.0267 0.1828 0.0000 0.0000 CO.sub.2
0.0000 0.0000 0.0000 0.0000 Nitrogen 0.0000 0.0000 0.0000
0.0000
TABLE-US-00007 TABLE 7 Material Streams 12 13 19 15 17 14 Vapour
0.9617 0.7202 0.6831 0.0000 0.5000 1.0000 Fraction Temperature F.
120.0 -25.00 -145.0 -30.00 -29.68 -22.80 Pressure psia 200.0 195.0
185.0 21.88 20.88 190.0 Molar Flow MMSCFD 10.00 10.00 8.153 7.268
7.628 8.153 Mass Flow lb/hr 2.673e+004 2.673e+004 1.367e+004
3.508e+004 3.508e+004 1.367e+004 Liquid barrel/day 4723 4723 3231
4758 4758 3231 Volume Flow 18 32 34 42 43 Vapour 0.0000 0.6833
0.0000 1.0000 1.000 Fraction Temperature F. 176.0 -144.9 -144.9
-144.9 110.0 Pressure psia 195.0 185.0 185.0 185.0 180.0 Molar Flow
MMSCFD 1.970 8.160 2.589 5.576 5.576 Mass Flow lb/hr 1.348e+004
1.369e+004 8758 4943 4943 Liquid barrel/day 1567 3234 1570 1661
1667 Volume Flow 35 35a 36 38 39 28 Vapour 0.0957 1.0000 1.0000
1.0000 0.0500 1.0000 Fraction Temperature F. -163.1 90.00 330.0
120.0 -61.75 -61.75 Pressure psia 28.00 23.00 215.0 210.0 205.0
205.0 Molar Flow MMSCFD 2.589 2.589 2.589 2.589 0.1294 6.472e-003
Mass Flow lb/hr 8758 8758 8758 8758 437.9 14.05 Liquid barrel/day
1570 1570 1570 1570 78.48 3.009 Volume Flow Vapour 26 26a 28a 45 47
Fraction 0.0000 0.0028 1.0000 1.000 1.0000 Temperature F. Pressure
psia -61.75 -62.15 -64.65 120.0 120.0 Molar Flow MMSCFD 205.0 200.0
185.0 210.0 210.0 Mass Flow lb/hr 0.1230 0.1230 6.472e-003 0.1294
2.459 Liquid barrel/day 423.8 423.8 14.05 437.9 8320 Volume 75.47
75.47 3.009 78.48 1491 Flow
TABLE-US-00008 TABLE 8 Mole Fractions of Components in Streams Feed
Gas Product Sales Gas Mixed (12) (18) (43) Refrigerant (35)
Hydrogen 0.3401 0.0000 0.6085 0.0034 Methane 0.2334 0.0000 0.3517
0.1520 Ethane 0.1887 0.0100 0.0392 0.6719 Propane 0.0924 0.2974
0.0006 0.1363 Butane 0.0769 0.3482 0.0000 0.0335 Pentane 0.0419
0.2087 0.0000 0.0028 Heptane 0.0267 0.1828 0.0000 0.0000 CO.sub.2
0.0000 0.1357 0.0000 0.0000 Nitrogen 0.0000 0.0000 0.0000
0.0000
TABLE-US-00009 TABLE 9 Material Streams 12 13 19 15 17 Vapour
1.0000 0.9838 0.6646 0.0000 0.5000 Fraction Temperature F. 120.0
-25.00 -119.0 -30.00 -29.68 Pressure psia 415.0 410.0 400.0 21.88
20.88 Molar Flow MMSCFD 10.00 10.00 11.83 1.263 1.263 Mass Flow
lb/hr 1.973e+004 1.973e+004 2.369e+004 6096 6096 Liquid barrel/day
4203 4203 5115 826.9 826.9 Volume Flow 14 18 32 34 42 Vapour 1.0000
0.0000 0.9925 0.0000 1.0000 Fraction Temperature F. -79.00 251.1
-77.01 -109.5 -118.9 Pressure psia 405.0 410.0 405.0 405.0 400.0
Molar Flow MMSCFD 11.83 0.2534 1.577 3.668 9.730 Mass Flow lb/hr
2.369e+004 1679 3206 8867 1.801e+004 Liquid barrel/day 5115 197.4
688.7 1804 3997 Volume Flow 35 35a 36 38 39 Vapour 0.3049 1.0000
1.0000 1.0000 0.4300 Fraction Temperature F. -162.0 90.00 280.9
120.0 -71.34 Pressure psia 128.30 123.30 470.0 465.0 460.0 Molar
Flow MMSCFD 3.668 3.668 3.668 3.668 3.688 Mass Flow lb/hr 8867 8867
8867 8867 8867 Liquid barrel/day 1804 1804 1804 1804 1804 Volume
Flow 28 26 26a 43 Vapour 1.0000 0.0000 0.0464 1.000 Fraction
Temperature F. -71.34 -71.34 -76.54 110.0 Pressure psia 460.0 460.0
415.0 395.0 Molar Flow MMSCFD 1.577 2.091 2.091 9.730 Mass Flow
lb/hr 3206 5661 5661 1.801e+004 Liquid barrel/day 688.7 1115 1115
3997 Volume Flow
TABLE-US-00010 TABLE 10 Mole Fractions of Components in Streams
Feed Gas Product Sales Gas Mixed (12) (18) (43) Refrigerant (35)
Methane 0.9212 0.0000 0.9457 0.5987 Ethane 0.0396 0.0083 0.0397
0.3763 Propane 0.0105 0.4154 0.0001 0.0054 Butane 00036. 0.1421
0.0000 0.0000 Pentane 0.0090 0.3552 0.0000 0.0000 Heptane 0.0020
0.0789 0.0000 0.0000 CO.sub.2 0.0050 0.0000 0.0051 0.0195 Nitrogen
0.0091 0.0000 0.0094 0.0001
TABLE-US-00011 TABLE 11 Material Streams 12 13 19 15 17 Vapour
1.0000 0.8833 0.7394 0.0000 0.5000 Fraction Temperature F. 120.0
-20.00 -85.5 -30.00 -29.68 Pressure psia 315.0 310.0 305.0 21.88
20.88 Molar Flow MMSCFD 10.00 10.00 11.37 5.018 5.018 Mass Flow
lb/hr 2.484e+004 2.484e+004 2.549e+004 2.422e+004 2.422e+004 Liquid
barrel/day 4721 4721 5338 3285 3285 Volume Flow 14 18 32 34 42
Vapour 1.0000 0.0000 0.7491 0.0000 1.0000 Fraction Temperature F.
-55.13 181.7 -84.23 -84.24 -84.24 Pressure psia 310.0 315.0 305.0
305.0 305.0 Molar Flow MMSCFD 11.37 1.139 11.81 2.952 8.844 Mass
Flow lb/hr 2.549e+004 6778 2.648e+004 8419 1.802e+004 Liquid
barrel/day 5338 834.5 5546 1660 3877 Volume Flow 43 35 35a 36 38
Vapour 1.0000 0.2044 1.0000 1.0000 1.0000 Fraction Temperature F.
110.0 -120.0 90.00 246.2 120.0 Pressure psia 300.0 113.9 108.9
375.0 370.0 Molar Flow MMSCFD 8.844 2.952 2952 2952 2952 Mass Flow
lb/hr 1.802e+004 8419 8419 8419 8419 Liquid barrel/day 3877 1660
1660 1660 1660 Volume Flow 39 28 26 26a 28a Vapour 0.1500 1.0000
0.0000 0.0434 .09975 Fraction Temperature F. -49.05 -49.05 -49.05
-54.73 -57.22 Pressure psia 365.0 365.0 365.0 320.0 305.0 Molar
Flow MMSCFD 2952 0.4429 2.510 2.510 0.4429 Mass Flow lb/hr 8419
990.7 7429 7429 990.7 Liquid barrel/day 1660 207.9 1452 1452 207.9
Volume Flow
TABLE-US-00012 TABLE 12 Mole Fractions of Components in Streams
Feed Gas Product Sales Gas Mixed (12)) (18) (43) Refrigerant (35)
Methane 0.7304 0.0000 0.8252 0.3071 Ethane 0.1429 0.0119 0.1566
0.6770 Propane 0.0681 0.5974 0.0003 0.0071 Butane 0.0257 0.2256
0.0000 0.0000 Pentane 0.0088 0.0772 0.0000 0.0000 Heptane 0.0100
0.0878 0.0000 0.0000 CO.sub.2 0.0050 0.0000 0.0056 0.0079 Nitrogen
0.0091 0.0000 0.0103 0.0009
* * * * *