U.S. patent application number 10/228516 was filed with the patent office on 2004-03-04 for stripping process and apparatus.
Invention is credited to Hunt, Harold R..
Application Number | 20040040893 10/228516 |
Document ID | / |
Family ID | 31976045 |
Filed Date | 2004-03-04 |
United States Patent
Application |
20040040893 |
Kind Code |
A1 |
Hunt, Harold R. |
March 4, 2004 |
Stripping process and apparatus
Abstract
A process and apparatus for stripping a hydrocarbon feedstock
comprising: heating the feedstock forming a vapor stream and a
liquid stream, separating the vapor stream from the liquid stream
and then stripping the liquid stream with a counter-current flow of
a gas.
Inventors: |
Hunt, Harold R.;
(Bartlesville, OK) |
Correspondence
Address: |
c/o RICHMOND, HITCHCOCK,
FISH & DOLLAR
P.O. Box 2443
Bartlesville
OK
74005
US
|
Family ID: |
31976045 |
Appl. No.: |
10/228516 |
Filed: |
August 27, 2002 |
Current U.S.
Class: |
208/347 ;
208/364 |
Current CPC
Class: |
C10G 47/00 20130101;
C10G 31/06 20130101; C10G 7/00 20130101 |
Class at
Publication: |
208/347 ;
208/364 |
International
Class: |
C10G 007/00 |
Claims
That which is claimed:
1. A process comprising the steps of: (a) heating a hydrocarbon
feedstock wherein at least a portion of said hydrocarbon feedstock
is vaporized so as to form a first vapor stream and a first liquid
stream; (b) separating said first vapor stream and said first
liquid stream; (c) stripping said first liquid stream with a
counter-current flow of a gas so as to form a second vapor stream
and a second liquid stream; and (d) recovering said second vapor
stream and said second liquid stream.
2. A process in accordance with claim 1 wherein said stripping
occurs in a stripper column comprising in the range of from 2 to 4
theoretical trays.
3. A process in accordance with claim 1 wherein said second liquid
stream comprises compounds having at least 5 carbon atoms per
molecule.
4. A process in accordance with claim 1 wherein said second liquid
stream comprises compounds having at least 12 carbon atoms per
molecule.
5. A process in accordance with claim 1 wherein said hydrocarbon
feedstock is heated in step (a) to a temperature in the range of
from about 100.degree. F. to about 800.degree. F.
6. A process in accordance with claim 1 wherein said hydrocarbon
feedstock is mixed with a diluent gas prior to said heating in step
(a).
7. A process in accordance with claim 6 wherein the ratio of said
diluent gas to said hydrocarbon feedstock is in the range of from
about 0.1:1 to about 8:1.
8. A process in accordance with claim 6 wherein said diluent gas is
selected from the group consisting of hydrogen, nitrogen, carbon
dioxide, methane, ethane, fuel gas, and combinations of any two or
more thereof.
9. A process in accordance with claim 1 further comprising the step
of: (e) reboiling at least a portion of said second liquid stream
to form a boil-up vapor stream and a bottoms residue stream for
return of said boil-up vapor stream to said stripper column.
10. A process in accordance with claim 1 wherein said hydrocarbon
feedstock is heated in step (a) such that from about 75% to about
99% of said hydrocarbon feedstock is vaporized.
11. A process in accordance with claim 1 wherein said hydrocarbon
feedstock is heated in step (a) such that from 85% to 90% of said
hydrocarbon feedstock is vaporized.
12. A process in accordance with claim 1 wherein said gas in step
(c) is selected from the group consisting of hydrogen, nitrogen,
carbon dioxide, methane, ethane, fuel gas, and combinations of any
two or more thereof.
13. A process in accordance with claim 12 wherein the ratio of said
gas in step (c) to said first liquid stream is in the range of from
about 0.05:1 to about 6:1.
14. A process in accordance with claim 12 wherein the ratio of said
gas in step (c) to said first liquid stream is in the range of from
0.1:1 to 2.4:1.
15. A process in accordance with claim 1 wherein said hydrocarbon
feedstock comprises gasoline.
16. A process in accordance with claim 15 wherein said second
liquid stream comprises compounds having in the range of from 12 to
35 carbon atoms per molecule.
17. A process in accordance with claim 15 wherein said second
liquid stream comprises compounds having in the range of from 12 to
25 carbon atoms per molecule.
18. A process in accordance with claim 15 wherein said gasoline is
heated in step (a) to a temperature in the range of from about
400.degree. F to about 600.degree. F.
19. A process in accordance with claim 15 wherein said gasoline is
heated in step (a) to a temperature in the range of from about
440.degree. F. to about 550.degree. F.
20. A process in accordance with claim 15 wherein said gasoline is
heated in step (a) to a temperature in the range of from
460.degree. F. to 510.degree. F.
21. A process in accordance with claim 15 wherein said gasoline is
mixed with a diluent gas prior to said heating in step (a).
22. A process in accordance with claim 21 wherein the ratio of said
diluent gas to said gasoline is in the range of from 0.1:1 to
2:1.
23. An apparatus comprising: (a) a vessel defining a vaporization
zone; (b) a vessel defining a liquid-vapor separation zone and a
stripping zone, said vessel being in fluid flow communication with
said vaporization zone.
24. An apparatus in accordance with claim 23 further comprising a
reboiler in fluid flow communication with said vessel.
25. An apparatus in accordance with claim 23 wherein said vessel
comprises from 2 to 4 theoretical trays.
26. An apparatus comprising: (a) a vaporization vessel defining a
vaporization zone; (b) a liquid-vapor separation vessel defining a
liquid-vapor separation zone in fluid flow communication with said
vaporization zone; and (c) a stripping vessel defining a stripping
zone in fluid flow communication with said liquid-vapor separation
vessel.
27. An apparatus in accordance with claim 26 further comprising a
reboiler in fluid flow communication with said stripping
vessel.
28. An apparatus in accordance with claim 26 wherein said stripping
vessel comprises from 2 to 4 theoretical trays.
29. An apparatus comprising: (a) A first vessel defining a
vaporization zone and a liquid-vapor separation zone; (b) a second
vessel defining a stripping zone wherein said second vessel is in
fluid flow communication with said first vessel.
30. An apparatus in accordance with claim 29 further comprising a
reboiler in fluid flow communication with said second vessel.
31. An apparatus in accordance with claim 29 wherein said second
vessel comprises from 2 to 4 theoretical trays.
Description
BACKGROUND
[0001] This invention relates to the field of hydrocarbon refining.
More particularly, this invention relates to the purification of
hydrocarbon streams.
[0002] It is well known in the art to strip hydrocarbon feedstocks
with a gas. However, there are ever-present incentives for the
development of new and/or more effective processes for stripping
hydrocarbons since heavy components in hydrocarbon feedstocks can
clog equipment.
[0003] In many refining processes, the hydrocarbon feedstocks are
mixed with hydrogen and heated to a high temperature using heat
exchangers and furnaces. Heavy components contained in some
hydrocarbon feedstocks can cause coke formation in areas where a
dry point occurs. The coke can plug the tubes in heat exchangers,
furnaces, or other equipment. Therefore, it is necessary for heavy
components to be removed from these hydrocarbon feedstocks to avoid
problems with clogged equipment.
[0004] In addition, incomplete vaporization can cause problems in
refining processes that do not tolerate liquids.
[0005] Therefore, a novel stripping process and apparatus that
effectively strips hydrocarbon feedstocks and also provides for a
substantially vaporized feedstock for refining processes would be a
significant contribution to the art and economy.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide an
improved process for removing heavy components from a hydrocarbon
feedstock which is economical and efficient.
[0007] A further object of the present invention is to provide an
improved apparatus to be used in removing heavy components from a
hydrocarbon feedstock which is economical in construction and
reliable and efficient in operation.
[0008] In accordance with the first embodiment of the present
invention, a process is provided for removing heavy components from
a hydrocarbon feedstock. The process comprises, consists of, or
consists essentially of:
[0009] (a) heating a hydrocarbon feedstock wherein at least a
portion of the hydrocarbon feedstock is vaporized so as to form a
first vapor stream and a first liquid stream;
[0010] (b) separating the first vapor stream and the first liquid
stream;
[0011] (c) stripping the first liquid stream with a counter current
flow of a gas so as to form a second vapor stream and a second
liquid stream; and
[0012] (d) recovering the second vapor stream and the second liquid
stream from the stripper column.
[0013] In accordance with the second embodiment of the present
invention a system or apparatus is provided for removing heavy
components from a hydrocarbon feedstock comprising, consisting of,
or consisting essentially of:
[0014] (a) a vaporization zone; and
[0015] (b) a vessel defining a liquid vapor separation zone and a
stripping zone, the vessel being in fluid flow communication with
the vaporization zone.
[0016] The third embodiment of the present invention is an
apparatus comprising, consisting of, or consisting essentially
of;
[0017] (a) a vaporization zone;
[0018] (b) a liquid-vapor separation vessel in fluid flow
communication with the vaporization zone; and
[0019] (c) a stripping vessel in fluid flow communication with the
liquid-vapor separation vessel.
[0020] The fourth embodiment of the present invention is an
apparatus comprising, consisting of, or consisting essentially
of:
[0021] (a) A first vessel defining a vaporization zone and a
liquid-vapor separation zone;
[0022] (b) a second vessel defining a stripping zone wherein the
second vessel is in fluid flow communication with the first
vessel.
[0023] Other objects and advantages of the invention will be
apparent from the detailed description of the invention and the
appended claims.
BRIEF DESCRIPTION OF THE DRAWING
[0024] The drawing is a partially cut away elevation of an
apparatus representing one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The process of this invention involves the removal of heavy
components from a hydrocarbon feedstock.
[0026] The hydrocarbon feedstock can be any hydrocarbon feedstock
containing heavy components. This can include hydrocarbon streams
in refineries such as naphtha, straight run naphtha, coker naphtha,
catalytic gasoline, visbreaker naphtha, alkylate, isomerate,
reformate, and the like and combinations thereof. This can also
include gasoline such as, but not limited to, coker gasoline,
thermally cracked gasoline, visbreaker gasoline, fluid
catalytically cracked gasoline, heavy oil cracked gasoline, and the
like and combinations thereof. Diesel fuels can also be used.
Suitable diesel fuels include, but are not limited to, light cycle
oil, kerosene, jet fuel, straight-run diesel, hydrotreated diesel,
and the like and combinations thereof.
[0027] The number of carbon atoms per molecule of heavy components
in a particular hydrocarbon feedstock depends upon the boiling
range of that feedstock. For example, heavy components will
generally be heavier in diesel fuel than in gasoline.
[0028] Generally, a heavy component can be any compound having at
least 12 carbon atoms per molecule. In gasoline, the heavy
components contain in the range of from 12 to 35 carbon atoms per
molecule. More often, the heavy components in gasoline contain in
the range of from 12 to 25 carbon atoms per molecule.
[0029] In the present invention a hydrocarbon feedstock is charged
to a vaporization zone where it is heated. Optionally, the
hydrocarbon feedstock can be mixed with a diluent gas prior to the
heating. Generally, the ratio of diluent gas to the hydrocarbon
feedstock is in the range of from about 0.1:1 to about 8:1. For
gasoline in particular, the ratio of diluent gas to the hydrocarbon
feedstock is preferably in the range of from 0.1:1 to 2:1. The
diluent gas is selected from the group consisting of hydrogen,
nitrogen, carbon dioxide, methane, ethane, fuel gas, and
combinations of any two or more thereof. Preferably, the diluent
gas is hydrogen. The hydrocarbon feedstock is preferably heated
such that from about 75% to about 99% of the feedstock is
vaporized. More preferably, 85% to 90% of the hydrocarbon feedstock
is vaporized as a result of such heating. The temperature to which
the hydrocarbon feedstock is heated can depend upon a variety of
factors. Such factors can include the type of hydrocarbon
feedstock, the pressure, and the amount of diluent gas used.
Generally, the hydrocarbon feedstock can be heated to a temperature
in the range of from about 100.degree. F. to about 800.degree. F.
Generally, gasoline can be heated to a temperature in the range of
from about 400.degree. F. to about 600.degree. F. More preferably,
the gasoline is heated to a temperature in the range of from about
440.degree. F. to about 550.degree. F. Most preferably, the
gasoline is heated to a temperature in the range of 460.degree. F.
to 510.degree. F.
[0030] The hydrocarbon feedstock is vaporized so as to form a first
vapor stream and a first liquid stream. These streams pass into a
liquid vapor separation zone, which is in fluid flow communication
with the vaporization zone. Within the liquid-vapor separation
zone, the first vapor stream and the first liquid stream are
separated. The first vapor stream leaves the liquid-vapor
separation zone overhead, while the first liquid stream flows from
the liquid-vapor separation zone into the stripping zone which is
in fluid flow communication with the liquid-vapor separation zone,
in order to be stripped. In the second embodiment of the invention,
the liquid-vapor separation zone and stripping zone are in the same
vessel, which is in fluid flow communication with the vaporization
zone. In the third embodiment of the invention, the vaporization
zone, liquid-vapor separation zone, and stripping zone are all in
separate vessels that are in fluid flow communication with each
other. In the fourth embodiment, the vaporization zone and
liquid-vapor separation zone are in the same vessel. The stripping
zone is located in a separate vessel. Both vessels are in fluid
flow communication with each other. The stripping zone comprises,
consists of, or consists essentially of, in the range of from 2 to
4 theoretical trays.
[0031] The first liquid stream is stripped in the stripping zone
with a counter current flow of a gas so as to form a second vapor
stream and a second liquid stream. The stripping gas is selected
from the group consisting of hydrogen, nitrogen, carbon dioxide,
methane, ethane, fuel gas, and combinations of any two or more
thereof. Preferably, the gas is hydrogen. Preferably, the ratio of
the stripping gas to the first liquid stream is in the range of
from about 0.05:1 to about 6:1. More preferably, the ratio of the
stripping gas to the first liquid stream is in the range of from
0.1:1 to 2.4:1. The type of molecules contained in the second vapor
stream depends on the type of hydrocarbon feedstock. The molecules
can be heavier in diesel fuel than in gasoline. In diesel fuel for
example, the second vapor stream can contain molecules with up to
about 25 carbon atoms per molecule. For gasoline, the second vapor
stream can comprise compounds having in the range of from 2 to 15
carbon atoms per molecule. The type of molecules contained in the
second liquid stream depends on the type of hydrocarbon feedstock.
Generally, the second liquid stream can comprise compounds having
at least 5 carbon atoms per molecule. Preferably, the second liquid
stream comprises compounds having at least 12 carbon atoms per
molecule. For gasoline, the second liquid stream preferably
comprises compounds having in the range of from 12 to 35 carbon
atoms per molecule. More preferably for gasoline, the second liquid
stream comprises compounds having in the range of from 12 to 25
carbon atoms per molecule.
[0032] In another embodiment at least a portion of the second
liquid stream can optionally be reboiled to form a boil-up vapor
stream and a bottoms residue stream. The bottoms residue stream
passes out of the reboiling vessel, while the boil-up vapor stream
returns to the stripper column.
[0033] Referring to the drawing, therein is illustrated the second
embodiment of the present invention referred to as apparatus 10, a
hydrocarbon feedstock enters vaporizer 100, defining a vaporization
zone, via conduit 102, which is in fluid flow communication with
vaporizer 100. Optionally, hydrogen can be mixed with the
hydrocarbon feedstock via conduit 104, which is in fluid flow
communication with conduit 102. About 85-90% of the hydrocarbon
feedstock is vaporized in vaporizer 100 and passes to vessel 110
via conduit 108, wherein conduit 108 connects vaporizer 100 and
vessel 110 in fluid flow communication. Vessel 110 includes
liquid-vapor separation zone 112, where the vapor is separated from
the liquid, thereby forming a first vapor stream and a first liquid
stream. The first vapor stream passes out of vessel 110 via conduit
114, which is in fluid flow communication with vessel 110. The
first liquid stream is stripped in stripping zone 116 also located
in vessel 110, which contains in the range of from 2 to 4
theoretical trays. Hydrogen enters stripping zone 116 via conduit
106, which is in fluid flow communication with conduit 104 and
vessel 110. The stripping forms a second vapor stream and a second
liquid stream. The second vapor stream also passes through
liquid-vapor separation zone 112 and leaves vessel 110 via conduit
114. The second liquid stream leaves vessel 110 via conduit 118
which is in fluid flow communication with vessel 110. Optionally,
the second liquid stream can travel to reboiler 120 via conduit
118, which is also in fluid flow communication with reboiler 120.
The second liquid stream is reboiled to form a bottoms residue
stream, which leaves the reboiler via conduit 122 which is in fluid
flow communication with reboiler 120, and a boil up vapor stream
which returns to vessel 110 via conduit 124 which is in fluid flow
communication with reboiler 120 and vessel 110.
[0034] The following example is provided to further illustrate this
invention and is not to be considered as unduly limiting the scope
of this invention.
CALCULATED EXAMPLE
[0035] This example illustrates the stripping of hydrocarbons using
the inventive process.
[0036] A computer model was used to simulate the stripping of
naphtha. The naphtha composition used as an input to the computer
model was obtained from analyses of products from ASTM D-86
distillations of naphtha. The mass flow of the naphtha stream was
set at 487,256 pounds per hour. The heavy components for this
simulation were mainly modeled as C.sub.24H.sub.50. The heavy
components in the naphtha stream of this simulation had a mass flow
of 2424 pounds per hour. In this simulation, about 87.7% of the
naphtha feed was vaporized before stripping. The mass flow of the
stream containing hydrogen was set at 6190 pounds per hour. Seventy
percent of the hydrogen went to the vaporizer and thirty percent of
the hydrogen went to the stripper.
[0037] The mass flows of the heavy components are shown in the
table for the feedstock before being contacted with hydrogen,
before it is vaporized, for the first vapor stream and the first
liquid stream, and for the second vapor stream and the second
liquid stream.
1 Mass Flow (lb/hr) of Heavy Stream Components Before being
contacted with 2424 hydrogen Before vaporization 2424 1.sup.st
vapor stream 76.4 1.sup.st liquid stream 2348 2.sup.nd vapor stream
38.7 2.sup.nd liquid stream 2309
[0038] The second vapor stream has a significantly lower mass flow
of heavy components than the first liquid stream has before it is
stripped. Therefore, the inventive process is quite useful for
removing heavy components.
* * * * *