U.S. patent application number 13/641847 was filed with the patent office on 2013-06-20 for apparatus and method for conducting a fischer-tropsch synthesis reaction.
This patent application is currently assigned to GTL.F1 AG. The applicant listed for this patent is Roger Hansen. Invention is credited to Roger Hansen.
Application Number | 20130158136 13/641847 |
Document ID | / |
Family ID | 42245446 |
Filed Date | 2013-06-20 |
United States Patent
Application |
20130158136 |
Kind Code |
A1 |
Hansen; Roger |
June 20, 2013 |
APPARATUS AND METHOD FOR CONDUCTING A FISCHER-TROPSCH SYNTHESIS
REACTION
Abstract
In order to avoid fouling (precipitation of solid matter on cold
surfaces) in heat-exchangers down-stream of the gas outlet of a
Fischer-Tropsch reactor, the reactor gas stream containing
hydrocarbon products that are solid at lower temperatures is fed
into a liquid wash tank. Condensation of heavy oil in the liquid
wash tank is effected by feeding an evaporable light oil into the
liquid wash tank. Heavy oil is recovered as a bottom product from
the liquid wash tank while a gaseous product is taken out of the
liquid wash tank as the top product. The light oil is obtained from
the wash tank top product.
Inventors: |
Hansen; Roger; (Ranheim,
NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hansen; Roger |
Ranheim |
|
NO |
|
|
Assignee: |
GTL.F1 AG
Zurich
CH
|
Family ID: |
42245446 |
Appl. No.: |
13/641847 |
Filed: |
April 18, 2011 |
PCT Filed: |
April 18, 2011 |
PCT NO: |
PCT/GB2011/000596 |
371 Date: |
March 4, 2013 |
Current U.S.
Class: |
518/700 ;
422/187; 518/728 |
Current CPC
Class: |
C10G 5/06 20130101; C10G
2/34 20130101; C10G 2/30 20130101; C10G 2300/1022 20130101 |
Class at
Publication: |
518/700 ;
422/187; 518/728 |
International
Class: |
C10G 5/06 20060101
C10G005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 19, 2010 |
GB |
1006526.6 |
Claims
1. A process for recovering condensable products contained within
an outlet gas stream from a Fischer-Tropsch reactor, comprising the
steps: conveying a Fischer-Tropsh reactor gas stream to a
condensation and separation unit; subjecting the F-T gases to
direct heat exchange in the condensation and separation unit
against a stream of evaporable hydrocarbon liquid, thereby cooling
the F-T gases; condensing higher boiling components in the F-T
gases; separating the condensed higher boiling components from
gaseous components; and removing a gaseous fraction and a condensed
higher boiling fraction; wherein at least a portion of the
evaporable hydrocarbon liquid stream is obtained from subsequent
processing of the gaseous fraction obtained in the removing
step.
2. A process as claimed in claim 1, wherein the reactor gas stream
is pre-cooled in order to produce a mixture of gaseous and liquid
components before it is conveyed to the condensation and separation
unit.
3. A process as claimed in claim 2, wherein the pre-cooling
comprises indirect heat exchange between the reactor gas stream and
a syngas feed stream to the reactor.
4. A process as claimed in claim 1, wherein one or more operating
parameters are controlled in order to avoid condensation of water
in the condensation and separation unit.
5. A process as claimed in claim 1, wherein the gaseous fraction
obtained from the removing step is subjected to a first separation
step wherein the gaseous fraction is separated into a gas phase, a
liquid hydrocarbon phase and an aqueous phase.
6. A process as claimed in claim 5, wherein prior to the first
separation step, the gaseous fraction is subjected to a cooling
step to form a stream of gas and liquid products.
7. A process as claimed in claim 5, wherein at least a portion of
the liquid hydrocarbon phase from the first separation step
constitutes the evaporable hydrocarbon liquid conveyed to the
separation unit.
8. A process as claimed in claim 5, wherein the gas phase from the
first separation step is subjected to a second separation step
wherein the gas phase is separated into a gas phase, a liquid
hydrocarbon phase and an aqueous phase.
9. A process as claimed in claim 8, wherein prior to the second
separation step, the gas phase from the first separation step is
subjected to a cooling step to form a second stream of gas and
liquid products.
10. A process for conducting a Fischer-Tropsch synthesis reaction
to produce Fischer-Tropsch wax which comprises supplying H.sub.2
and CO to a Fischer-Tropsch reactor, conducting the process set out
in claim 1, and removing a wax product stream from the reactor.
11. A process as claimed in claim 10, wherein the reaction is
carried out in a slurry bubble column reactor, and wherein the
H.sub.2 and CO are supplied to a slurry in the reactor, the slurry
comprising catalyst in suspension in a liquid including the
reaction products of the H.sub.2 and CO, the catalyst being
maintained in suspension in the slurry at least partly by the
motion of the gas supplied to the slurry.
12. A process as claimed in claim 11, wherein a reaction
temperature is in the range of 190-250.degree. C. and a reaction
pressure is in the range of 10-60 bar.
13. A process as claimed in claim 11, wherein a H.sub.2/CO ratio of
the gases supplied to the Fischer-Tropsch synthesis reactor is in
the range of 1.1 to 2.2.
14. A process as claimed in claim 11, wherein a superficial gas
velocity in the reactor is in the range of 5 to 60 cm/s.
15. A process as claimed in claim 11 wherein, the product of the
Fischer-Tropsch synthesis reaction is subsequently subjected to
post-processing.
16. A process as claimed in claim 15, wherein the post-processing
is selected from de-waxing, hydro-isomerisation, hydro-cracking,
and combinations thereof.
17. An apparatus for recovering condensable products contained
within an outlet gas stream from a Fischer-Tropsch reactor,
comprising a Fischer-Tropsch reactor; a condensation and separation
unit; a gas/liquid separator; a line arranged to convey a
Firscher-Tropsch reactor gas stream to the condensation and
separations unit; a condensed higher boiling fraction outlet from
the condensation and separation unit; a gaseous fraction outlet
line from the condensation and separation unit arranged to convey
at least a portion of the gaseous fraction to the gas/liquid
separator; and a recycle line arranged to convey evaporable
hydrocarbon liquid from the gas/liquid separator to the
condensation and separation unit, thereby subjecting the reactor
gas stream to direct heat exchange in the condensation and
separation unit against the stream of evaporable hydrocarbon
liquid.
18. The apparatus as claimed in claim 17, wherein the condensation
and separation unit is a liquid wash column.
19. The apparatus as claimed in claim 17, wherein the reactor is a
slurry bubble column reactor.
20. The apparatus as claimed in claim 17, wherein the gas/liquid
separator is a liquid flash tank.
21. The apparatus as claimed in claim 17, further comprising a heat
exchanger facilitating indirect heat exchange between the reactor
gas stream and a syngas feed stream to the reactor.
22. The apparatus as claimed in claim 17, further comprising a
second gas/liquid separator arranged to receive a gas stream from
the first gas/liquid separator.
23. The apparatus as claimed in claim 22, wherein the second
gas/liquid separator is a liquid flash tank.
Description
RELATED APPLICATIONS
[0001] The present application is a National Phase entry of PCT
Application No. PCT/GB2011/000596, filed Apr. 18, 2011, which
claims priority from Great Britain Application No. 1006526.6, filed
Apr. 19, 2010, the disclosures of which are hereby incorporated by
reference in their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to an apparatus and method for
conducting a Fischer-Tropsch ("F-T") synthesis reaction and is
particularly concerned with recovering condensable products in the
top gas stream from an F-T reactor.
BACKGROUND OF THE INVENTION
[0003] The F-T synthesis process is used for converting natural
gas, coal or biomass via a syngas unit, into longer chain
hydrocarbon waxes. One problem associated with the F-T system is
fouling of heat exchangers and other equipment down stream of the
reactor gas outlet by the precipitation of higher boiling products
in solid form on cold surfaces.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to address this
difficulty.
[0005] According to one aspect of the present invention, there is
provided a process for recovering condensable products contained
within an outlet gas stream from a Fischer-Tropsch reactor,
comprising the steps: conveying the reactor gas stream to a
condensation and separation unit; subjecting the F-T gases to
direct heat exchange in the condensation and separation unit
against a stream of evaporable hydrocarbon liquid, thereby cooling
the F-T gases; condensing higher boiling components in the F-T
gases; separating the condensed higher boiling components from
gaseous components; and removing a gaseous fraction and a condensed
higher boiling fraction; and in which at least a portion of the
evaporable hydrocarbon liquid stream is obtained from subsequent
processing of the gaseous fraction obtained in the removing
step.
[0006] According to another aspect of the present invention, there
is provided an apparatus for recovering condensable products
contained within an outlet gas stream from a Fischer-Tropsch
reactor, comprising a Fischer-Tropsch reactor; a condensation and
separation unit; a gas/liquid separator; a line arranged to convey
the reactor gas stream to the condensation and separations unit; a
condensed higher boiling fraction outlet from the condensation and
separation unit; a gaseous fraction outlet line from the
condensation and separation unit arranged to convey at least a
portion of the gaseous fraction to the gas/liquid separator; and a
recycle line arranged to convey evaporable hydrocarbon liquid from
the gas/liquid separator to the condensation and separation unit,
thereby subjection the reactor gas stream to direct heat exchange
in the condensation and separation unit against the stream of
evaporable hydrocarbon liquid.
[0007] Thus, waxy material which might otherwise foul downstream
equipment is removed from the overhead gas stream from the reactor
by direct heat exchange with a liquid obtained from the lighter
fractions of the gas stream.
[0008] Preferably, the reactor gas stream is pre-cooled in order to
produce a mixture of gaseous and liquid components before it is
conveyed to the condensation and separation unit. Preferably, the
pre-cooling comprises indirect heat exchange between the reactor
gas stream and a syngas feed stream to the reactor. Preferably, the
gaseous fraction obtained from the removing step is subjected to a
first separation step in which it is separated into a gas phase, a
liquid hydrocarbon phase and an aqueous phase. (It will be
understood that there will inevitably be a small amount of water in
the hydrocarbon phase and vice-versa.) Preferably, prior to the
first separation step, the gaseous fraction is subjected to a
cooling step to form a stream of gas and liquid products.
Preferably, at least a portion of the liquid hydrocarbon phase from
the first separation step constitutes the evaporable hydrocarbon
liquid conveyed to the separation unit.
[0009] Preferably, the higher boiling fraction removed from the
condensation and separation unit is a heavy oil and the liquid
hydrocarbon phase from the separation step is a light oil. The
products received at the highest temperature (typically in the
range 110-150 degrees C.) are referred to as "Heavy Oil" (HO),
while product recovered at the lowest temperature (defined by the
availability of cooling water) and at typically 30-50 degrees C.,
are referred to as "Light Oil" (LO).
[0010] Preferably, the gas phase from the first separation step is
subjected to a second separation step in which it is separated into
a gas phase, a liquid hydrocarbon phase and an aqueous phase.
Preferably, prior to the second separation step, the gas phase from
the first separation step is subjected to a cooling step to form a
second stream of gas and liquid products. However, while product
recovery has been described as being achieved in two cooling steps,
there could be only one, or several such steps.
[0011] Preferably, the condensation and separation unit is a liquid
wash column. Preferably, the reactor is a slurry bubble column
reactor. Preferably, the gas/liquid separator is a liquid flash
tank. The apparatus may further include a heat exchanger
facilitating indirect heat exchange between the reactor gas stream
and a syngas feed stream to the reactor and a second gas/liquid
separator arranged to receive a gas stream from the first
gas/liquid separator. Preferably, the second gas/liquid separator
is a liquid flash tank.
[0012] Thus, the present invention may be considered to reside in
the use of the liquid wash column where recycled LO is utilized to
condense the HO products, while LO is vaporized in a column. The
cooling duty to condense HO is scuffed into the cold section with
the recycled LO. This design will reduce the partial pressure of
heavy components into the cold section of the product recovery
section.
[0013] The present invention may also be considered to reside in a
general non-cryogenic process for the recovery of condensable
hydrocarbon components included in a blend of hydrocarbons that may
pose a risk of fouling by precipitation of components having a
melting point above ambient temperatures (approx. 20.degree. C.)
though direct heat-exchange against a stream of evaporable
hydrocarbon liquids in a condensation and separation zone and
recovery of a liquid fraction of higher-boiling hydrocarbons and a
gaseous fraction, from which one or more fractions of lower-boiling
hydrocarbons are obtained by subsequent processing of the gaseous
fraction. Typically, the condensable hydrocarbon components have
boiling points in the ranges corresponding to those of light and
heavy oil.
[0014] The present invention also extends to a process from
conducting an F-T synthesis reaction adopting the aspects of the
present invention set out above, in which H.sub.2 and CO are
supplied to the F-T reactor and a wax product stream is recovered
from the reactor.
[0015] Preferably, the reaction is carried out in a slurry bubble
column reactor, in which the H.sub.2 and CO are supplied to a
slurry in the reactor, the slurry comprising the catalyst in
suspension in a liquid including the reaction products of the
H.sub.2 and CO, the catalyst being maintained in suspension in the
slurry at least partly by the motion of the gas supplied to the
slurry. Preferably, the reaction temperature is in the range
190-250.degree. C. and/or the reaction pressure is in the range
10-60 bar. Preferably, the H.sub.2/CO ratio of the gases supplied
to the Fischer-Tropsch synthesis reactor is in the range 1.1 to
2.2. Preferably, the superficial gas velocity in the reactor is in
the range 5 to 60 cm/s. Preferably, the product of the
Fischer-Tropsch synthesis reaction is subsequently subjected to
post-processing, such as de-waxing, hydro-isomerisation,
hydro-cracking, and combinations of these.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] For a detailed description of the preferred embodiments of
the present invention, reference will now be made to the
accompanying Figure, wherein:
[0017] FIG. 1 is a simplified flow diagram of a Fischer-Tropsch
synthesis installation embodying the present invention
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The present invention may be carried into practice in
various ways and one embodiment will now be described by way of
example, with reference to accompanying FIG. 1.
[0019] The F-T installation comprises a syngas unit 11, an F-T
slurry reactor 12, a liquid wash tank or column 13, first and
second flash and separator tanks 14, 15 and an optional cryogenic
tail gas recovery unit 16.
[0020] Natural gas 17, oxygen 18 and steam 19 are fed to the syngas
unit 11 where syngas is produced in the conventional manner and
leaves as a syngas outlet stream 21. Water is removed in a water
recovery stream 22 and directed to a utility system (not shown).
The syngas stream 21 is combined with a portion 23 of a gas recycle
stream 29 from the tail gas recovery unit 16, and the combined gas
stream 24 is heated in a first heat exchanger 25. The combined
stream is then fed to the F-T reactor 12 in a line 26 via a second
heat exchanger 27 in which it is further heated to about
150.degree. C. by indirect heat exchange with an overhead gas
stream 28 leaving the F-T reactor 12 at about 190-250.degree. C. Of
the remainder of the gas recycle stream 29, a portion 31 may be
purged to a fuel gas system, and a portion 32 is recycled to the
syngas unit 11.
[0021] The syngas is converted in the F-T reactor 12 to a wide
boiling point range of hydrocarbons. Those hydrocarbons that are in
the liquid phase at reactor conditions are extracted as liquid and
referred to as `wax` (since a substantial portion of the product
would normally be solid at ambient temperatures). They are removed
from the reactor 12 in a wax product line 33.
[0022] To avoid fouling of heat exchangers down stream of the
reactor top gas outlet by the precipitation of solid matter on cold
surfaces, the overhead gas stream 28, which also contains
hydrocarbon products that are solid at lower temperatures is fed to
the wash tank 13. After heat exchange with the syngas stream 24 in
the heat exchanger 27, the overhead stream 28 is a mixed stream of
gas and liquid components. An evaporable light oil stream 34 is fed
to the wash tank 13, which condenses heavy oil (which may contain
significant amounts of wax components) from the overhead gas stream
28. The heavy oil is removed from the wash tank 13 in a heavy oil
outlet stream 35. The feed streams 28, 34 to the wash tank 13 are
controlled in such a way that water does not condense in the tank
13.
[0023] A gas stream 36 is removed from the wash tank 13 and cooled
in a heat exchanger 37 to provide a three-phase stream of gas and
liquid products with water. This is fed to the first flash and
separator tank 14, from which water is recovered and removed in a
water stream 38 and light oil is recovered and removed in a light
oil stream 39. A portion of the light oil makes up the evaporable
light oil stream 34 that is fed to the wash tank 13; thus the
recycled light oil stream acts as a direct cooling medium on the
F-T reactor top gas stream in the wash tank 13. The remainder of
the light oil is removed in a light oil recovery stream 41.
[0024] The uncondensed product from the first flash tank 14 is
removed in a gas stream 42 and is cooled in a heat exchanger 43
whereby more liquid products are condensed out and the resulting
gas and liquid stream 44 is fed to the second flash and separator
tank 15. Water is recovered and removed from the second flash tank
15 in a water stream 45 and light oil is recovered and removed in a
light oil recovery stream 46.
[0025] Components that remain in the gas phase in the second flash
tank 15 are removed as a tail gas stream 47. This may be treated in
the tail gas recovery unit 16 to produce a LPG stream 48 and a C5+
stream 49 for upgrading.
* * * * *