U.S. patent application number 09/902861 was filed with the patent office on 2001-11-29 for system and method for converting light hydrocarbons into heavier hydrocarbons with a plurality of synthesis gas subsystems.
This patent application is currently assigned to Syntroleum Corporation, Delaware corporation. Invention is credited to Agee, Kenneth L., Agee, Mark A..
Application Number | 20010047040 09/902861 |
Document ID | / |
Family ID | 22427790 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010047040 |
Kind Code |
A1 |
Agee, Kenneth L. ; et
al. |
November 29, 2001 |
System and method for converting light hydrocarbons into heavier
hydrocarbons with a plurality of synthesis gas subsystems
Abstract
A system and method for converting normally gaseous, light
hydrocarbons into heavier, longer-chain hydrocarbons includes a
turbine; a first synthesis gas subsystem; a second synthesis gas
subsystem that receives thermal energy from the turbine and which
preferably includes a steam reformer; and a synthesis subsystem for
receiving synthesis gas from the first synthesis gas subsystem and
the second synthesis gas subsystem and for producing the heavier
hydrocarbons. A method includes using a plurality of synthesis gas
subsystems to prepare synthesis gas for delivery to and conversion
in a synthesis subsystem.
Inventors: |
Agee, Kenneth L.; (Bixby,
OK) ; Agee, Mark A.; (Tulsa, OK) |
Correspondence
Address: |
Bradley P. Williams, Esq.
Baker Botts L.L.P.
Suite 600
2001 Ross Avenue
Dallas
TX
75201-2980
US
|
Assignee: |
Syntroleum Corporation, Delaware
corporation
|
Family ID: |
22427790 |
Appl. No.: |
09/902861 |
Filed: |
July 11, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09902861 |
Jul 11, 2001 |
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09538609 |
Mar 29, 2000 |
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6277894 |
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60126996 |
Mar 30, 1999 |
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Current U.S.
Class: |
518/704 ;
422/600 |
Current CPC
Class: |
C01B 2203/0255 20130101;
C01B 2203/84 20130101; C01B 2203/82 20130101; C01B 2203/0877
20130101; C01B 2203/0244 20130101; C01B 2203/1258 20130101; C01B
2203/0415 20130101; C01B 2203/0833 20130101; C01B 2203/0811
20130101; C01B 2203/1241 20130101; C01B 3/382 20130101; C01B
2203/0238 20130101; C01B 2203/1011 20130101; C01B 2203/0822
20130101; C01B 2203/0475 20130101; C01B 2203/0405 20130101; C01B
2203/065 20130101; C01B 2203/142 20130101; C07C 1/0485 20130101;
C01B 2203/0883 20130101; C01B 2203/0894 20130101; C01B 2203/062
20130101; C01B 2203/1047 20130101; C01B 2203/1052 20130101; Y02P
20/10 20151101; C01B 2203/0233 20130101; C01B 2203/061 20130101;
C01B 2203/0844 20130101; C01B 2203/143 20130101; Y02P 20/128
20151101; C01B 2203/0861 20130101; C01B 2203/141 20130101; C10G
2/30 20130101; C01B 2203/1041 20130101; C01B 2203/148 20130101;
C01B 2203/0866 20130101; C01B 2203/0827 20130101; C01B 2203/1247
20130101; C01B 2203/127 20130101 |
Class at
Publication: |
518/704 ;
422/189 |
International
Class: |
C07C 027/06; B01J
008/04 |
Claims
What is claimed is:
1. A hydrocarbon conversion system for converting normally gaseous
light hydrocarbons into heavier hydrocarbons, which are liquid or
solid or gaseous at standard temperature and pressure, the system
comprising: a turbine unit having a compressor and an expander; a
first synthesis gas subsystem having a first feedstock inlet for
receiving normally gaseous light hydrocarbons and a first synthesis
gas outlet, the first synthesis gas subsystem for preparing
synthesis gas; a second synthesis gas subsystem thermally coupled
to the expander for receiving thermal energy from the expander and
having a second feedstock inlet for receiving light hydrocarbons, a
steam/water inlet, and a second synthesis gas outlet, the second
synthesis gas subsystem for preparing synthesis gas, and wherein
the second synthesis gas subsystem comprises a steam reformer; and
a Fischer-Tropsch synthesis subsystem having a synthesis gas inlet
fluidly coupled to the first synthesis gas subsystem and fluidly
coupled to the second synthesis subsystem for receiving synthesis
gas from the first synthesis gas outlet and the second synthesis
gas outlet and having a product outlet for emitting heavier
hydrocarbons.
2. The system of claim 1 wherein the first synthesis gas subsystem
comprises an autothermal reformer and wherein the first synthesis
gas subsystem is coupled to the compressor of the turbine for
receiving compressed air therefrom.
3. The system of claim 1 wherein the first synthesis gas subsystem
comprises a partial oxidation reactor.
4. The system of claim 1 wherein the first synthesis gas subsystem
comprises an autothermal reformer reactor.
5. The system of claim 1 wherein the first synthesis gas subsystem
comprises an autothermal reformer and wherein the first synthesis
gas subsystem is coupled to the compressor of the turbine for
receiving compressed enriched air therefrom.
6. The system of claim 1 further comprising a duct burner thermally
coupled to the second synthesis gas subsystem for enhancing the
thermal energy from the turbine before delivery to the second
synthesis gas subsystem.
7. The system of claim 1 wherein the turbine further comprises a
combustor, and wherein the combustor comprises the first synthesis
gas subsystem that is an autothermal reformer.
8. The system of claim 7 wherein the turbine comprises a gas
turbine.
9. The system of claim 1 further comprising: a third synthesis gas
subsystem having a third feedstock inlet for receiving light
hydrocarbons and a third synthesis gas outlet, the third synthesis
gas subsystem thermally coupled to the first synthesis gas
subsystem for receiving thermal energy therefrom; and wherein the
third synthesis gas subsystem is fluidly coupled to the
Fischer-Tropsch synthesis subsystem.
10. A method for converting normally gaseous hydrocarbons into
heavier hydrocarbons that are normally solid or liquid at standard
temperature and pressure, the method comprising the steps of:
preparing a synthesis gas in a first synthesis gas generator;
preparing a synthesis gas in a second synthesis gas generator that
is a steam reformer; delivering thermal energy from a turbine to
the steam reformer; delivering the synthesis gas from the first
synthesis gas generator and the steam reformer to a Fischer-Tropsch
unit; and converting synthesis gas to heavier hydrocarbons in the
Fischer-Tropsch unit.
11. The method of claim 10 wherein the first synthesis gas
generator is an autothermal reformer and further comprising the
steps of: compressing air with a compressor; delivering the
compressed air from the compressor to the autothermal reformer;
combusting a fuel in a combustor with air; expanding gases from the
combustor in an expander; and transmitting energy from the expander
to the steam reformer to provide at least a portion of the energy
required therein for conversion of feedstocks to synthesis gas.
12. The method of claim 11 further comprising the step of disposing
of wastewater by using it in the steam reformer.
13. The method of claim 10 further comprising the step of:
preparing a synthesis gas in a third synthesis gas generator that
is thermally coupled to the first synthesis gas generator; and
delivering the synthesis gas from the third synthesis gas generator
to the Fischer-Tropsch unit.
14. A hydrocarbon conversion system for converting normally gaseous
light hydrocarbons into heavier hydrocarbons, which are liquid or
solid or gaseous at standard temperature and pressure, the system
comprising: a compressor for receiving air and compressing the air;
a first synthesis gas system coupled to the compressor for
receiving air therefrom, for receiving light hydrocarbons, and for
producing a synthesis gas; an expander coupled to the first
synthesis gas subsystem for receiving synthesis gas therefrom; a
second synthesis gas subsystem for receiving light hydrocarbons and
forming synthesis gas; a synthesis subsystem fluidly coupled to the
expander for receiving synthesis gas therefrom and also fluidly
coupled to the second synthesis gas subsystem for receiving
synthesis gas therefrom and producing heavier hydrocarbons and a
tail gas; and the second synthesis gas subsystem further comprising
a duct burner and wherein the second synthesis gas subsystem is
fluidly coupled to the synthesis system for receiving a tail gas
for use in the burner.
Description
BACKGROUND OF THE INVENTION
[0001] As concerns over pollution caused by traditional fossil
fuels increases and as sources of crude oil decrease, there has
been increased interest in other sources of energy. One promising
source of energy is the synthetic production of fuels, lubricants,
and other products from natural gas (referred to at times as
gas-to-liquids or GTL) preferably through the Fischer-Tropsch
process. See for example U.S. Pat. Nos. 4,883,170 and 4,973,453,
which are incorporated by reference herein for all purposes.
[0002] A. Introduction to the Fischer Tropsch Process
[0003] The synthetic production of hydrocarbons by the catalytic
reaction of synthesis gas is well known and is generally referred
to as the Fischer-Tropsch reaction. The Fischer-Tropsch process was
developed in early part of the 20.sup.th century in Germany. It was
practiced commercially in Germany during World War II and later has
been practiced in South Africa.
[0004] The Fischer-Tropsch reaction for converting synthesis gas
(primarily CO and H.sub.2) has been characterized in some instances
by the following general reaction: 1
[0005] The hydrocarbon products derived from the Fischer-Tropsch
reaction range from some methane to high molecular weight
paraffinic waxes containing more than 50 carbon atoms.
[0006] Numerous catalysts incorporating active metals, such as
iron, cobalt, ruthenium, rhenium, etc., have been used in carrying
out the reaction, and both saturated and unsaturated hydrocarbons
can be produced. The synthesis reaction is very exothermic and
temperature sensitive whereby temperature control is required to
maintain a desired hydrocarbon product selectivity.
[0007] B. Synthesis Gas Production
[0008] Synthesis gas may be made from natural gas, gasified coal,
and other sources. A number of basic methods have been employed for
producing the synthesis gas ("syngas"), which is substantially
carbon monoxide and molecular hydrogen, utilized as feedstock in
the Fischer-Tropsch reaction. The numerous methodologies and
systems that have been used to prepare synthesis gas include
partial oxidation, steam reforming, auto-reforming or autothermal
reforming. Both fixed and fluid bed systems have been employed.
[0009] The reforming reactions are endothermic and a catalyst
containing nickel is often utilized. Partial oxidation
(non-catalytic or catalytic) involves sub-stoichiometric combustion
of light hydrocarbons such as methane to produce the synthesis gas.
The partial oxidation reaction is typically carried out
commercially using high purity oxygen.
[0010] In some situations these synthesis gas production methods
may be combined to form another method. A combination of partial
oxidation and steam reforming, known as autothermal reforming,
wherein air may be used as the oxygen-containing gas for the
partial oxidation reaction has also been used for producing
synthesis gas heretofore. Autothermal reforming, the combination of
partial oxidation and steam reforming, allows the exothermic heat
of the partial oxidation to supply the necessary heat for the
endothermic steam reforming reaction. The autothermal reforming
process can be carried out in a relatively inexpensive refractory
lined carbon steel vessel whereby a relatively lower cost is
typically involved.
[0011] The autothermal reforming process results in lower hydrogen
to carbon monoxide ratio in the synthesis gas than does steam
reforming alone. That is, the steam reforming reaction with methane
results in a ratio of about 3:1 or higher while the partial
oxidation of methane results in a ratio of less than about
2:1--depending upon the extent of the water gas shift reaction. A
good ratio for the hydrocarbon synthesis reaction carried out at
low or medium pressure (i.e., in the range of about atmospheric to
500 psig) over a cobalt catalyst is about 2:1. When the feed to the
autothermal reforming process is a mixture of light shorter-chain
hydrocarbons such as a natural gas stream, some form of additional
control is desired to maintain the ratio of hydrogen to carbon
monoxide in the synthesis gas at the optimum ratio (for cobalt
based F-T catalysts) of about 2:1. For this reason steam and/or
CO.sub.2 may be added to the synthesis gas reactor to adjust the
H.sub.2/CO ratio to the desired value with the goal of optimizing
the process economics.
[0012] C. Improved Economics Desired
[0013] It has been a quest for many to improve the economics of
processes utilizing the Fischer-Tropsch reaction. Improved
economics will allow a wide-scale adoption of the process in
numerous sites and for numerous applications. Efforts have been
made toward that end, but further improvements are desirable.
SUMMARY OF THE INVENTION
[0014] A need has arisen for a system and method for converting
light hydrocarbons into heavier hydrocarbons (C.sub.5+) that
addresses disadvantages and problems associated with previously
developed systems and methods. According to an aspect of the
present invention, a system for converting normally gaseous
hydrocarbons into heavier hydrocarbons, which are liquid or solid
at standard temperature and pressure, includes: a turbine; a first
synthesis gas subsystem; a second synthesis gas subsystem that
receives thermal energy from the turbine and which includes a steam
reformer; and a synthesis subsystem for receiving synthesis gas
from the first synthesis gas subsystem and from the second
synthesis gas subsystem and which produce the heavier
hydrocarbons.
[0015] According to another aspect of the present invention, a
method for converting normally gaseous hydrocarbons to heavier
hydrocarbons that are normally solid or liquid at standard
temperature and pressure is provided that includes the steps of:
preparing a synthesis gas in a first synthesis gas unit; providing
a steam reformer having a primary reforming zone; providing a
turbine having a compressor section, cumbustor, and expansion
section; thermally coupling the expansion section of the turbine to
the steam reformer to provide at least a portion of the reaction
energy required in the steam reformer to produce synthesis gas;
preparing a synthesis gas in the steam reformer; delivering the
synthesis gas from the first synthesis gas unit and the steam
reformer to a synthesis subsystem for conversion to the heavier
hydrocarbons. According to another aspect of the present invention,
the combustor section of the gas turbine may be combined with the
first synthesis gas unit, which may be an autothermal reformer or a
steam reformer.
[0016] The present invention provides a number of advantages. A few
examples follow. A technical advantage of the present invention is
that it allows more efficient use of energy in a turbine-powered
synthesis system. Another technical advantage of the present
invention is that it lowers the nitrogen content in the synthesis
gas compared to a straight air-blown autothermal reformer based
conversion system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] For a more complete understanding of the present invention
and advantages thereof, reference is now made to the following
description taken in conjunction with the accompanying drawings in
which like reference numbers indicate like features, and
wherein:
[0018] FIG. 1 is a schematic diagram of a conversion system
according to one embodiment of the present invention;
[0019] FIG. 2 is a schematic diagram of an embodiment of a
conversion system according to another embodiment of the present
invention;
[0020] FIG. 3 is a schematic diagram of a first synthesis gas
subsystem according to an aspect of the present invention;
[0021] FIG. 4 is a schematic diagram of a second synthesis gas
subsystem, which is a steam reformer, according to an aspect of the
present invention;
[0022] FIG. 5 is a schematic diagram of a synthesis subsystem
according to an aspect of the present invention; and
[0023] FIG. 6 is a schematic diagram of another embodiment of a
system for converting light hydrocarbons to heavier hydrocarbons
according to an aspect of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The preferred embodiment of the present invention and its
advantages are best understood by referring to FIGS. 1-6 of the
drawings, like numerals being used for like and corresponding parts
of the various drawings.
[0025] Referring to FIG. 1, a system 10 for converting normally
gaseous hydrocarbons into heavier hydrocarbons, which are primarily
liquid or solid at standard temperature and pressure, is presented.
System 10 includes a turbine unit 12, a first synthesis gas
subsystem 14, a second synthesis gas subsystem 16, which is
preferably a steam reformer, and a synthesis subsystem 18, which
reacts synthesis gas to form heavier, longer-chain hydrocarbons
(e.g., C.sub.5+).
[0026] Turbine 12 has an air inlet 20 and an exhaust outlet 22.
While "air" is referenced in this application, it is to be
understood that other oxygen-containing gases might be used as
well, e.g., enriched air. Turbine 12 generates mechanical energy
that may be used to run additional compressors or to generate
electricity or for other uses (e.g, power for plasma synthesis
techniques), as is represented by power offtake 24. Turbine 12 may
be a gas turbine or a compressor/steam turbine combination. As will
be described below, turbine 12 includes a compressed air outlet
26.
[0027] The first synthesis gas subsystem 14 and the second
synthesis gas subsystem 16 generate synthesis gas. First synthesis
gas subsystem 14 may be any of a number of types of subsystems for
generating synthesis gas, such as a partial oxidation (POX)
subsystem or steam reformer, or preferably, an autothermal
reformer. Still another acceptable method for generating synthesis
gas would be use of a plasma technique; for example, excess
electrical energy from the system might be used with a steam
reformer or POX with plasma. Other acceptable systems include
gasification systems.
[0028] Gasification systems normally start with raw materials such
as coal, petroleum based materials (crude oil, high sulfur fuel
oil, petroleum coke, and other refinery residuals), gases, or
materials that would otherwise be disposed of as waste. The
feedstock is prepared and fed to the gasifier in either dry or
slurried form where it reacts with steam and oxygen at high
temperature and pressure in a reducing (oxygen starved) environment
to make synthesis gas (mainly carbon monoxide and hydrogen). The
high temperature and pressure in the gasifier convert the inorganic
materials in the feedstock (such as ash and metals) into a
vitrified material (slag) like course sand. Valuable metals may be
concentrated and recovered for reuse from some feedstocks. The
synthesis gas produced in gasifiers of this type are used on
occasion as fuel for producing electricity, such as in an
integrated gasification combined cycle (IGCC) power generation
configuration. The combined cycle of an IGCC has a high efficiency
gas turbine that burns synthesis gas to produce electricity.
[0029] One acceptable gasification process uses an entrained-bed,
non-catalytic, partial oxidation process in which carbonaceous
substances react at elevated temperatures and pressures to produce
synthesis gas. Inorganic materials in the feed melt and are removed
as a glass-like slag. Pressures and temperatures may be above 20
atmospheres and with temperatures between 2,200 F and 2,800 F.
Slurred waste may be pumped to burners mounted at the top of a
refractory-line gasifier. The feed, oxygen, and an auxiliary fuel,
such as coal, react and are downwardly flowed through the gasifier
to a quench chamber, which collects the slag. A lockhopper is
eventually used to remove the slag. A scrubber cleans and further
cools the resultant synthesis gas. The scrubber removes fine
particulate matter which may be recycled to the gasifier. A sulfur
recovery system may also be used in the gasification system. After
the gasification process, the resultant synthesis gas can be
delivered and used as described below. As noted above other systems
may be used, and an autothermal reformer remains the preferred
first synthesis gas subsystem.
[0030] First synthesis gas subsystem 14 has a compressed air inlet
28 that may be provided from an external source of compressed air
30, or from compressed air outlet 26 of turbine 12, or both. Light
hydrocarbons (e.g., normally gaseous at standard temperature and
pressure) such as methane are provided to the first synthesis gas
subsystem through a first feedstock inlet 32. An embodiment of
first synthesis gas subsystem 14, which includes an autothermal
reformer, is described in more detail below in connection with FIG.
3. Subsystem 14 develops synthesis gas that is delivered to a first
synthesis gas outlet 34.
[0031] Second synthesis gas subsystem 16 is preferably a steam
reformer, but other substantially endothermic systems for
generating synthesis gas (or that benefit from the transfer of
thermal energy) may be used. As an important aspect to the present
invention, the second synthesis gas subsystem 16 is thermally
coupled to the turbine such that the thermal energy of the turbine
exhaust is delivered to the second synthesis gas subsystem 16. In
this example, the thermal coupling is accomplished by delivering
the exhaust energy from turbine 12 to second synthesis gas
subsystem 16. The thermal exhaust energy is shown delivered by
exhaust outlet 22 and may be delivered by numerous types of beat
exchange devices associated with the synthesis gas subsystem 16.
The exhaust from the turbine delivered through conduit 22 exits the
second synthesis gas subsystem 16 through conduit 23. Synthesis gas
subsystem 16 has a second feedstock inlet 36 and a steam inlet 38.
In the preferred embodiment, synthesis subsystem 16 is a steam
reformer operating in the rang of 1000 to 1600 degrees Fahrenheit.
Because the turbine exhaust 22 may not be sufficiently heated, a
burner may be added that burns a tail gas or natural gas or both or
other waste gases or liquids or combinations (see, e.g., burner 160
of FIG. 2). An embodiment of second synthesis gas subsystem 16,
which includes a steam reformer, is described in more detail in
connection with FIG. 4 below.
[0032] Subsystem 16 develops a synthesis gas that is delivered to
second synthesis gas outlet 40. Outlets 34 and 40 deliver synthesis
gas to conduit 42. Between synthesis gas subsystem 16 and conduit
42 may be a number of gas treatment devices for such things as the
removal of a portion of the hydrogen as will be described further
below. Synthesis gas within conduit 42 is delivered to synthesis
subsystem 18.
[0033] Synthesis subsystem 18 receives synthesis gas from at least
two sources (e.g., synthesis gas subsystems 14 and 16) and converts
it to heavier hydrocarbons that are normally liquid or solid at
standard temperature and pressure (but may also include gaseous
products), and which may be referred to generally as a synthesis
product. The liquid synthesis products are delivered through
conduit 44 to storage 46 (or to a product upgrading unit).
Synthesis subsystem 18 has a tail gas (low-BTU residue
gas--typically below 100 BTU/scf when air is used) in offtake 48
and a water offtake 50. Tail gas produced by synthesis subsystem 18
and delivered to tail gas offtake 48 may be used elsewhere within
system 10. For example, the tail gas may be used to provide or help
provide reactive energy to second synthesis gas subsystem 16 or to
a combustor, which is included as a part of turbine 12. Similarly,
water from synthesis subsystem 18 delivered to water offtake 50 may
be used elsewhere within system 10. For example, water may be used
to generate steam for use with second synthesis gas subsystem
16.
[0034] Referring now to FIG. 2, another embodiment of a system 52
for converting normally gaseous, light hydrocarbons into heavier
hydrocarbons is presented. System 52 includes a turbine 56; a first
synthesis gas subsystem 60; a second synthesis gas subsystem 64,
which preferably includes a steam reformer 132; and a synthesis
subsystem 68.
[0035] Turbine 56 includes a compressor section 72 having an air
inlet 76 and a compressor exhaust outlet 80. Compressor section 72
may include a number of compressors with components as is known in
the art. Turbine 56 also includes an expander section 84 fluidly
coupled to a combustor section 90, and having an expander exhaust
outlet 94. Expander section 84 may include numerous expansion
sections and components as is known in the art. Expander section 84
is preferably mechanically linked by linkage 98, such as a shaft,
to compressor section 72. The net power generated by expander, or
turbine, section 84, is depicted by power offtake 102. The net
power generated, if any, may be used elsewhere in system 52 and/or
be exported. Turbine 56 may be a gas turbine or may be a
compressor/steam turbine combination.
[0036] Compressor exhaust in the form of compressed air from
compressor section 72 is delivered into compressor exhaust outlet
80. The exhaust is delivered, at least in part, to combustor
section 90 through conduit 106. In the embodiment shown, a portion
may also be delivered through compressed air inlet 108 to first
synthesis gas subsystem 60. In addition, a portion of the exhaust
in outlet 80 may be delivered to expander section 84 by conduit 112
to assist with cooling of expander section 84. Thus, there may be a
three-way split as shown at junction 116. It is to be understood
that the components of the turbine/combustor/compressor may be
included in a housing and are presented as such for illustrative
reasons.
[0037] First synthesis gas subsystem 60 receives compressed air
through an inlet, which may be from any source but preferably is
from compressor exhaust 80 of turbine 56. In addition, first
synthesis gas subsystem 60 receives light hydrocarbons, e.g.,
natural gas, from a first feedstock inlet 120. The light
hydrocarbons may be preheated and conditioned before delivery to
subsystem 60. Subsystem 60 produces a synthesis gas that is
delivered to first synthesis gas outlet 124 preferably at about
1700-1800 degrees Fahrenheit. Synthesis gas subsystem 60 may have
additional substances added, such as steam, to control the hydrogen
to carbon monoxide ratio of the synthesis gas delivered to outlet
124. Water is typically created as a by-product and is preferably
delivered by conduit 125 to the second synthesis gas subsystem 64.
Conduit 125 may include a water treatment subsystem on part of
it.
[0038] Synthesis gas subsystem 60 produces synthesis gas. Outlet
124 delivers the synthesis gas to a first portion of a synthesis
gas conduit 128. A high steam pressure drum and other devices known
in the art may be included as part of conduit 128. The hydrogen to
carbon monoxide ratio is preferably about 2:1 (for cobalt-based
catalyst, but other catalyst may be used with other ratios).
[0039] In an optional modification to system 52, a third synthesis
gas subsystem 127, which is preferably a pressurized reformer, may
be added downstream of first synthesis gas subsystem 60. The third
synthesis gas subsystem 127 uses primarily the thermal energy of
the synthesis gas from the first synthesis gas subsystem 60 to
reform natural gas 129. Subsystem 127 may be what is referred to as
a compact reformer. See, e.g., U.S. Pat. No. 5,980,840. The third
synthesis gas subsystem 127 would deliver its synthesis gas to
conduit 128 at about 1400 degrees. Conduit 128 may further contain
a boiler.131. Thus the synthesis gas from subsystem 60 (and
optionally subsystem 127) is delivered to conduit 128.
[0040] Second synthesis gas subsystem 64 preferably includes a
steam reformer 132. As an important aspect of the present
invention, steam reformer 132 receives thermal exhaust energy from
turbine 56 through exhaust conduit 94 and conduit 96. After
transferring thermal energy to subsystem 64, the exhaust may be
released through outlet 143. Steam reformer 132 receives light
hydrocarbons through a second feedstock inlet 136. In addition, it
receives steam/water through steam/water inlet 140. Steam reformer
132 preferably utilizes a steam reformer catalyst to convert the
light hydrocarbons delivered through conduit 136 into synthesis gas
that is delivered to second synthesis gas outlet 144, which
preferably delivers it into synthesis gas preparation unit 152 and
then to a portion of the synthesis gas conduit 148. Other synthesis
gas generator types could be used, such as plasma synthesis gas
generator. On conduit 144 between steam reformer 132 and the second
portion of the synthesis gas conduit 148, there may be located a
number of components that may be referred to as a synthesis gas
preparation unit 152. Synthesis gas preparation unit 152 may
include carbon dioxide removal devices and/or hydrogen removal
devices. If a CO.sub.2 removal device is included, the CO.sub.2 may
be transferred to the first synthesis gas system through conduit
147 to assist in adjusting the molar ratio (it may also be
delivered to the second subsystem 64 and third subsystem 127). If a
hydrogen removal device is included, the hydrogen removed may be
used to assist with hydrocracking or hydro-treating elsewhere in
system 52 or downstream from it, or may be used as fuel in a
burner. As an example of the latter, hydrogen from synthesis gas
preparation unit 152 may be delivered into conduit 156 and
delivered to burner 160. CO.sub.2 can also be removed from conduit
172 with a membrane and be delivered to one or more of the
synthesis gas generators 60, 64, or 127 as feedstock to adjust the
H.sub.2/CO ratio.
[0041] Exhaust from turbine 56, which is delivered through expander
exhaust conduit 94 to conduit 96, may need to have its temperature
increased to provide adequate feeding energy to the heat exchanger
elements of steam reformer 132. Thus, duct burner 160 may be
included for further heating the exhaust. Burner 160 has a fuel
inlet 164. Fuel delivered through inlet 164 may be a hydrocarbon
fuel feedstock delivered through conduit 166 or a low BTU residue
gas, or tail gas, prepared as may be appropriate from synthesis
subsystem 68 and delivered to inlet 164 through conduit 168 from
tail gas outlet 172. Burner 160 thus may burn fuel from inlet 164
and/or hydrogen delivered through conduit 156. Exhaust gases from
subsystem 64 may be delivered to combustor 90 or directly to
expander section 84 by a return conduit 100.
[0042] Synthesis gas from first synthesis gas subsystem 60 is mixed
with synthesis gas from second synthesis gas subsystem 64 in the
synthesis gas conduit 128, 148. The combined synthesis gas is
delivered to synthesis subsystem 68. A synthesis gas booster
compressor 149 may be used to increase the pressure of the
synthesis gas. Synthesis subsystem 68 may be, and preferably is, a
Fischer-Tropsch system, as will be described in further detail in
connection with FIG. 5. (it could also be other synthesis system
such as methanol). Synthesis subsystem 68 produces a heavier,
longer chain hydrocarbon product stream that is delivered to
product outlet 176 where it may be delivered to storage and/or
further processed.
[0043] Synthesis subsystem 68 also produces a low-BTU residual or
tail gas (preferably C.sub.<6 with 150 BTU/scf and more
preferably 100 BTU/scf or lower) that is delivered to a tail gas
outlet 172. Tail gas delivered to conduit 172 may be treated and
prepared for use as fuel in either burner 160 or in combustor
section 90. Conduit 172 delivers tail gas to conduit 168 and/or
conduit 180. A control unit 184 (e.g., a valve system) may be
optionally included at the junction between conduit 172, 168, and
180 to vary the portions of tail gas provided to conduits 168 and
180. Unit 184 can, by moving tail gas from the combustor (conduit
180) to the burner 160, allow for adjustments to the ratio of
product to be obtained from synthesis subsystem 68 to the amount of
electricity generated (off take 102). Water is made as a by-product
in synthesis subsystem 68 and is preferably delivered by conduit
177 to steam/water inlet 140 of the second synthesis gas subsystem
64. Conduit 177 may include a water treatment subsystem to remove
contaminants.
[0044] In an alternative embodiment, the reactor of first synthesis
gas subsystem 60 may be combined with the combustor section 90 as
shown by reference line 91. If, for example, the subsystem 60
includes an autothermal-reformer-reactor, the reactor and combustor
may be combined with the combustor 90 to form a combined
autothermal reformer combustor. In that case, substantially all the
air from compressor section 72 is delivered to the
autothermal-reformer-combustor where synthesis gas is prepared and
all the exhaust (i.e., the synthesis gas) is delivered to the
expander 84 (i.e., conduit 124 would be modified to deliver it to
the expander 84). The synthesis gas that is exhausted from the
turbine may then be used to assist with the thermal energy demands
of the second synthesis gas subsystem before being delivered along
with synthesis gas from the second synthesis gas subsystem to the
synthesis subsystem. A booster compressor may be added to boost the
synthesis gas from the first synthesis gas subsystem after it has
exited the expander 84 and before the synthesis subsystem 68. See
also FIG. 6 and the accompanying discussion below. A combined steam
reformer combustor might also be used.
[0045] Referring now to FIG. 3, one illustrative embodiment of a
first synthesis gas subsystem 190 is presented. Subsystem 190
includes an autothermal reformer reactor (ATR) 194. Reactor 194
contains an appropriate catalyst, such as a nickel catalyst, as is
known in the art. Subsystem 190 has an inlet 198. Inlet 198 may
deliver air or enriched air (i.e., having an oxygen content greater
than standard air) to ATR 194. Air inlet 198 is preferably
preheated by heat exchanger 202.
[0046] Subsystem 190 has a first feedstock inlet 206 for receiving
lighter hydrocarbons such as natural gas. Feedstock inlet 206
delivers the feedstock to a pretreatment unit 210. Unit 210
represents a number of components that may be used to treat the
feedstock prior to delivery to ATR 194; for example, a separator,
devices (such as an activated carbon vessel) for removing mecaptan
sulfur, a device (such as a zinc oxide vessel) for removing
H.sub.2S, etc. Conduit 214 delivers the feedstock to ATR 194. Heat
exchanger 218 may be included on conduit 214 to preheat the
feedstock. A water inlet 222 may deliver water or steam or other
substances into conduit 214 to help control hydrogen to carbon
monoxide ratios within ATR 194. Autothermal reformer 194 produces a
synthesis gas that is delivered into first synthesis gas outlet
226. Outlet 226 may be coupled to heat exchangers 218, 202 to
provide heat energy to air (or enriched air) in conduit 198 and
feedstock in conduit 214. Additional heat exchangers, such as heat
exchanger 230, may be provided to adjust temperature of the
synthesis gas within conduit 226 as desired. Synthesis gas within
conduit 226 is delivered to a synthesis subsystem such as 18 in
FIG. 1.
[0047] Referring now to FIG. 4, one embodiment of a second
synthesis gas subsystem 234 is presented. Subsystem 234 preferably
includes a steam-reforming reactor 238. Steam reforming itself, the
catalytic conversion of hydrocarbons by reaction with steam at
elevated temperature, is known in the art. In this process, a fluid
hydrocarbon, such as natural gas, is converted to a hot reformed
gas mixture, or synthesis gas, containing hydrogen and carbon
monoxide. The reaction may be generally represented as follows:
CH.sub.4+H.sub.2O.fwdarw.CO+3H.sub.2
[0048] This reaction is known generally as primary reforming and
widely used in the production of synthesis gas or pure hydrogen.
The primary reforming reaction is endothermic in nature, and the
conventional operation is usually carried out by passing a gaseous
mixture of fluid hydrocarbons and steam through an externally
heated reaction tube or group of tubes. The tubes are packed with a
suitable catalyst composition, such as solid catalyst granules
deposited on an inert carrier material. The resulting reformed gas
mixture discharges from said tubes as a hot reformer tube effluent
from which heat may be recovered in a waste heat recovery zone. The
hot reformer tube effluent from primary steam reforming is often
passed directly to a secondary reforming zone. There the reformed
gas mixture is passed, together with oxygen or air, through a bed
of reforming catalyst so that the oxygen or air reacts with
unconverted methane present in the reformed gas mixture. The gas
mixture from such secondary reforming can then be cooled in a waste
heat recovery zone prior to any further processing.
[0049] In the illustrative embodiment of FIG. 4, reactor 238 may
include a shell 242 with a plurality of reformer tubes 246 within
it. Tubes 246 are filled with a reforming catalyst 250, such as
metals of Group VIII of the periodic system having an atomic number
not greater than 28 and/or oxides thereof and metals of the
left-hand elements of Group VI and/or oxides thereof, which are
known to be good reforming catalysts, or other catalysts known in
the art. Other catalysts include, but are not limited to, nickel,
nickel oxide, cobalt oxide, chromia, and molybdenum oxide.
Promoters and treatments may be used as is known in the art. A
promoted nickel oxide catalyst is preferred.
[0050] A feedstock inlet 254 delivers a feedstock of light
hydrocarbons, such as natural gas, to tube inlets 260. The
feedstock delivered to inlet 254 may be preheated. A steam inlet
264 provides steam to tube inlets 260 as well. The feedstock and
steam delivered tubes 260 pass through the reforming catalyst
contained within reformer tubes 246 to produce a synthesis gas
which is delivered to second synthesis gas outlet 268. As known in
the art, a secondary reformer, such as secondary reformer 270, may
be included. Secondary reformer receives air or oxygen through
inlet 274. Secondary reformer 270 typically contains a reforming
catalyst to react the unconverted methane present in the reformed
gas mixture introduced therein. The thermal energy of the synthesis
gas in conduit 268 may be used to create the steam in conduit 264.
For example, water may be delivered to water inlet 276 and steam
produced in heat exchanger 278 and delivered into conduit 264.
[0051] The steam reforming reaction is endothermic and the
necessary energy to sustain the reaction is provided by heated
fluid or flue gas 272 passing over and about reformer tubes 246. A
portion of the feedstock (i.e., light hydrocarbon and air) may also
be delivered to shell 242 for combustion on the shell side of tubes
246. Heated fluid 272 is preferably provided in a substantial part
by a turbine as discussed in connection with FIGS. 1 and 2--but a
burner may also be used in further energize the fluid. The
synthesis gas delivered to synthesis gas outlet 268 may then be
delivered to a synthesis subsystem as previously described.
[0052] While subsystem 234 shows a single reforming zone and shows
the use of reforming tubes, it is to be understood that numerous
other embodiments may be used with the systems of FIGS. 1 and 2.
For example, a fluidized bed may be used or a partial oxidation
system.
[0053] In the embodiment of FIG. 4, the steam to hydrocarbon ratio
will vary, as is known in the art, depending on the overall
conditions employed in the primary reforming zone. The amount of
steam employed is influenced by the requirement of avoiding carbon
deposition on the catalyst and by the acceptable methane content of
the effluent at the reforming conditions.
[0054] Many stream reforming operations are carried out in
superatmospheric pressure conditions. Pressures between about 50 to
about 800 p.s.i.g. are generally preferred.
[0055] Referring now to FIG. 5, an illustrative embodiment of a
synthesis subsystem 280 is presented that may be used as part of
systems 10 (FIG. 1) or 52 (FIG. 2). In a preferred embodiment,
subsystem 280 uses a Fischer-Tropsch reaction to convert synthesis
gas into heavier hydrocarbons that are normally solids or liquids
or gaseous at standard temperatures and pressures. Those skilled in
the art will appreciate that numerous embodiments may be used to
carry out such a reaction, and the one presented here is merely
illustrative. It is possible to utilize other synthesis reactions
as an aspect of the present invention.
[0056] Synthesis gas is delivered to subsystem 280 through a
synthesis gas conduit 284. According to an important aspect of the
present invention, the synthesis gas delivered to conduit 284 is
synthesis gas combined from a plurality of synthesis gas subsystems
as described previously in connection with FIGS. 1 and 2. It may be
necessary in some situations to boost the pressure of the synthesis
gas delivered to conduit 284. For this purpose, a booster
compressor 288 may receive the synthesis gas, compress it, and
deliver it to conduit 292. The energy to power booster compressor
288 may be provided by a turbine, such as turbine 56 in FIG. 2.
Synthesis gas in conduit 292 is delivered to Fischer-Tropsch
reactor 296.
[0057] Reactor 296 may take any of a number of forms known in the
art, e.g., moving bed, fixed bed, etc., but as presented, is a form
of a moving-bed reactor, having liquid circulated within it.
Reactor 296 contains an appropriate Fischer-Tropsch catalyst, such
as a cobalt-based, an iron-based, rhenium-based or a
ruthenium-based case catalyst and may be supported on alumina,
titania, or another inert support. The catalyst is ebullated within
the reactor as gas and liquid are flowed up through the reactor.
The heavy hydrocarbon liquid that is up-flowed is delivered through
conduit 300. The gas and liquid product from reactor 296 is
delivered through conduit 304 to separator 308, which separates the
product into a gas effluent and a liquid effluent. The gas effluent
is delivered through conduit 312, which is delivered to cooler 316.
When cooled, some of the light hydrocarbons and water condense and
the condensation products come out and go through conduit 324 to a
cold separator 320. There, the water is removed and delivered into
conduit 328, the liquid hydrocarbon product stream is removed and
delivered to conduit 332, and a residual gas or tail gas is removed
and delivered to conduit 336. The light liquid hydrocarbon products
of conduit 332 may be delivered to storage 340 and/or to other
units for further processing.
[0058] Returning now to separator 308, the liquid product, or
ebullating oil, is delivered into conduit 344, which delivers it to
a control unit 348. Control unit 348, according to the amount of
ebullating oil within system 280, may send some of the ebullating
oil to storage through a slip stream conduit 352 or to a recycle
loop 356. Ebullating oil in the recycle loop 356 is delivered to a
pump 360 which moves the ebullating oil through conduit 364 where
it is delivered to heat exchanger 368. Heat exchanger 368 is used
to adjust the temperature of the ebullating oil by adding or
removing heat as necessary. The heat transfer fluid enters
exchanger 368 at 372 and exits at 376. Ebullating oil from heat
exchanger 368 is delivered in part through conduit 300 to
Fischer-Tropsch reactor 296 as previously mentioned. Another
portion is delivered through conduit 380 back to the suction side
of pump 360 to keep a high velocity there as needed.
[0059] Referring now to FIG. 6, another system 400 for converting
ligher hydrocarbons to heavier hydrocarbons with a plurality of
synthesis gas subsystems is shown. An important aspect of system
400 is that synthesis gas from a first synthesis gas subsystem 412
is delivered to an expander 408 before being delivered to a
synthesis subsystem 428.
[0060] Air is introduced through conduit 402 to a compressor 404
(which may or may not be part of a steam turbine). The compressor
is driven through mechanical linkage 406 that is powered by a
turbine expander 408. Expander 408 may be a steam turbine or
together with compressor 404 may be part of a gas turbine.
[0061] Compressor air from compressor 404 is delivered through
conduit 410 to a first synthesis gas subsystem 412, which is
preferably an autothermal reformer reactor. Light hydrocarbons,
such as natural gas, are delivered through conduit 414 to the first
synthesis gas subsystem 412. Steam may be delivered to first
synthesis gas subsystem 412 through conduit 416 to help adjust the
CO:H.sub.2 ratio. With these feeds, first synthesis gas subsystem
412 generates a synthesis gas that is delivered by conduit 418 to
expander 408. The expanding synthesis gas imparts mechanical energy
that may be transmitted by linkage 406 to compressor 404 and any
net energy may be exported.
[0062] The expanded synthesis gas is delivered by conduit 420 to
condenser 421 and separator 422. The synthesis gas then continues
through conduit 424 to conduit 426 and onto a synthesis subsystem
428, which is preferably a Fischer-Tropsch unit. Conduit 426 may
include a synthesis gas booster compressor (like 149 in FIG.
2).
[0063] The by-product water knocked out at separator 422 is
delivered by conduit 430 to a second synthesis gas subsystem 432. A
water treatment subsystem 434 may be included on conduit 430 to
remove any contaminants such as alcohols from it. Water treatment
subsystem 434 may be a biological treatment system or a
concentrator followed by a stripper tower unit.
[0064] Second synthesis gas subsystem 432 receives water through
conduit 430 as previously noted, but also light hydrocarbons
through conduit 414. The water/steam and light hydrocarbons are
used to make synthesis gas that is delivered to conduit 436.
Conduit 436 delivers the synthesis gas to conduit 426 from where it
is introduced into synthesis subsystem 428. A low-BTU tail gas
produced in the synthesis subsystem 428 is delivered by conduit 438
to second synthesis gas subsystem 432. Light hydrocarbons may also
be introduced as needed into conduit 438 by conduit 440 to help
supply the energy content thereof. The energy from the tail gas
delivered into conduit 438 and/or the light hydrocarbons delivered
through conduit 440 may fuel burners within second synthesis gas
subsystem 432, which is preferably a steam reformer.
[0065] Synthesis subsystem 428 produces heavier hydrocarbons such
as those mentioned further below and delivers them to one or more
conduits such as conduit 442 from where they may go to storage,
e.g, 444, or for downstream processing. Synthesis subsystem 428 is
preferably subsystem that uses a Fischer-Tropsch reaction to
convert synthesis gas to heavier hydrocarbons. By-product water may
also be produced and is delivered to conduit 446, which is
preferably fluidly coupled to conduit 430.
[0066] The systems and methods of the present invention are
preferably used to convert synthesis gas into heavier, longer-chain
hydrocarbons, e.g., the full spectrum of C.sub.5+ products through
the Fischer-Tropsch reaction (but other reactions might be used in
some situations). The heavier Fischer-Tropsch products that may be
made directly or with downstream processing include numerous
products for numerous uses. Furthermore, a number changes may be
anticipated as the system is applied in different environments. A
number of examples of each are presented below.
[0067] The Fischer-Tropsch products may include synthetic alpha
olefins adapted for many applications, including, without
limitation, PAO feedstock (alpha olefins in the range of C.sub.6 to
C.sub.12 and preferably C.sub.10 are used to produce poly alpha
olefins); alpha olefins for laundry and other detergents
(preferably C.sub.12-C.sub.16); chlorination stock to be used in
textiles, pharmaceuticals and transportation lubricants/hydraulic
fluids (preferably C.sub.18-C.sub.24); alpha olefins used to
produce particle board emulsions and poly vinyl chloride lubricants
(C.sub.24-C.sub.28); and alpha olefins used to manufacture
decorative and industrial candles, particle board emulsions and PVC
lubricants (C.sub.30+ alpha olefins, which are considered a
synthetic paraffin wax and therefore used in many of the markets
where paraffin waxes are used). The Fischer-Tropsch products are
also well suited for use as synthetic white oils because
Fischer-Tropsch liquid normal paraffins meet FDA specifications
governing their use in direct food contact applications, which
gives them a wide range of potential markets to enter, including
markets which traditionally use food grade mineral oils. Similarly,
the Fischer-Tropsch product may be used for technical grade mineral
or white oils that are used to produce paints, stains and inks,
among other end-use products and may be used as a pharmaceutical
(USP) grade white oil to be used to produce cosmetics and
healthcare products. In these applications, Fischer-Tropsch
products are better because the liquid or hydroisomerized product
can probably satisfy ASTM standards with little effort.
[0068] The Fischer-Tropsch products may also be used for synthetic
liquid n-paraffins in numerous applications. The Fischer-Tropch
product may be used as a chlorination feedstock to be used, for
example, to produce chlorinated normal paraffins for use in
textiles and industrial lubricants. The product may also be used as
a linear alkyl benzene (LAB) feedstock (C.sub.10 to C.sub.13) which
may be used for laundry detergents. The Fischer-Tropsch product may
also be used as an aluminum rolling oil (C.sub.14 to C.sub.17),
e.g., for cold rolling oils for aluminum foil. Further the
Fischer-Tropsch product N-paraffin may be used for "liquid"
candles.
[0069] The Fischer-Tropsch product may be used as a synthetic wax
in numerous applications. For example, the product may be used to
make thermostat wax, which is used primarily to control automobile
thermostats. The wax is particularly suitable for this since it
must be uniform in molecular weight, carbon number distribution and
molecular structure. The Fischer-Tropsch wax may be used to make
hotmelt adhesives, i.e., used as a viscosity modifier for
industrial hotmelt adhesives. The synthetic wax may be used in
printing inks. In that case, the wax is used as an antiscuff
surface modifier for fine grade web offset and gravure inks. It may
also be used for paints and stains. The wax is used to enhance
water repellency of water-based paints and stains. The
Fischer-Tropsch product may be used to make corrugated board in
which the waxes are used to add strength and water repellency to
the corrugated board. Similarly, the Fischer-Tropsch product may
also be used as a wax for packaging and food additives.
[0070] The synthetic wax may be used as a PVC lubricant/extrusion
aid; the high melting point waxes are used as internal/external
lubricants for PVC extrusion. The wax may be used as a flushing
compound, to impart the dripless quality to decorative candles,
with cosmetics as a viscosity modifier and melting point enhancer,
to bind various drugs which are in powdered form into tablet form
(they also impart a slippery surface to tablets such as aspirin,
etc.). Waxy Fischer-Tropsch products may also be used as
plasticizers and extrusion aids for various plastics such as high
density polyethylene, PET linear low density polyethylene and
polypropylene. Another use is as anti-ozone additives to protect
the outside surfaces of rubber products from packing and ozone
damages.
[0071] Fischer-Tropsch product in the form of synthetic lubricants
may be used in numerous additional applications. For example, the
synthetic lubricants may be used as environmentally friendly
drilling fluids. Fischer-Tropsch oils may be used to produce highly
stable high temperature operation automatic transmission fluids.
They may also be used as a hydraulic fluid that is very stable at
high temperatures and ideally suited for use in vehicular and
industrial hydraulic compounds. The synthetic lubricants may also
be used as vehicular lubricants (PCMO and HDD). The Fischer-Tropsch
product in the form of a synthetic lubricant may be used as a
quenching oil or cutting oil. Further they may be used for a
plurality of specialty lubricants such as for two-cycle, marine
lubricants, or baroil. They may also be used as a vehicle for
lubricant-additives.
[0072] An exciting aspect of the products that may be made from or
as part of the Fischer-Tropsch products are synthetic fuels and
blends, including Fischer-Tropsch compression ignition fuels,
Fischer-Tropsch spark ignition fuels, feedstocks for fuel cells,
aviation fuel (turbine and spark-ignition) and railroad fuels. The
sulfur-free clean nature of the synthetic fuels thus made are
advantageous.
[0073] The Fischer-Tropsch products may also be used as synthetic
solvents. As such, the uses of the synthetic solvents include as
printing inks, paints, stains, drying agents, dye transfer agents,
synthetic heptane, hexane, and de-waxing agents.
[0074] The process, such as that presented in connection with the
figures, may be adapted with other plants for additional purposes
and may also be modified for application in the various
environments throughout the world. Fischer-Tropsch plants can be
built in a number of different settings, which will, by definition,
determine some of the plant characteristics. The following is a
list of some of the settings in which Fischer-Tropsch plants may be
applied. The character of these plants will be controlled by
factors including weather conditions, specifically whether it is
tropical or temperate, or arctic settings, as well as local
conditions, such as wind, wave action, altitude and
precipitation.
[0075] Land-based plants imply the absence of water, and can have
permanent or temporary foundations. Sites will range from sea level
to elevations limited by turbine capability. Further adjustments
are made for certain plant conditions such as arctic weather
conditions on the North Slope. Riverine/Deltaic Fischer-Tropsch
plants generally are capable of accommodating fluctuating water
levels due to flood conditions, consolidated soil, regional
subsidence, and other dynamic conditions common to this setting.
Intratidal Fischer-Tropsch plants include many of the same
conditions as Riverine/Deltaic Fischer-Tropsch plants, but also
include design consideration known in the art for tides and wave
motion. Open water Fischer-Tropsch plants are engineered to
accommodate wind and waves motions found in open marine
conditions.
[0076] Numerous platform options are available for Fischer-Tropsch
plants to help accommodate their application in the various
settings and conditions. The following listing is a brief
characterization of bases or platforms on Fischer-Tropsch plants
may be mounted. A barge-mounted Fischer-Tropsch plant may be used
in marine, intratidal, and Deltaic/Riverine settings. The
Fischer-Tropsch plants may be made from material ranging from metal
to concrete. A plant may be mounted on a ship primarily for an open
marine condition(s), and may be utilized under conditions similar
to oil production from ships today. The plants may be modular
(e.g., steel skid-mounted containers). These modular
Fischer-Tropsch plants are subdivided into modules on steel
skid-mounted containers for efficient transport, setup, connect and
disconnect. Modular Fischer-Tropsch plants may range in sizes from
small enough for shipment by rail to large enough to be carried as
a heavy lift from a barge or ship. The plants may also be
spar/offshore platform mounted Fischer-Tropsch plants. These
Fischer-Tropsch plants are mounted on offshore and open marine
settings spar or platforms, either retrofitted onto platforms that
were previously designed for offshore oil and gas production or on
platforms built specifically for the Fischer-Tropsch plant. The
Fischer-Tropsch plant on a vessel may also be modified for use in
recovering and converting hydrates from the ocean floor. These are
but a few examples.
[0077] In addition to these platforms and settings, the plants may
be oriented toward numerous other or additional applications. For
example, the plant may be an aspect of a desalination plant. These
Fischer-Tropsch plants are designed to use Fischer-Tropsch process
heat (the Fischer-Tropsch and syngas reactions) to convert
available water into water suitable for agriculture, industrial or
portable water. The desalination may be by reverse osmosis or
thermal desalination.
[0078] Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alterations can be made therein without departing
from the spirit and scope of the invention as defined by the
appended claims. For example, while FIG. 5 presents one embodiment
of a synthesis subsystem, numerous embodiments of such subsystems
are possible, including those shown in U.S. Pat. No. 4,973,453,
which is incorporated herein by reference for all purposes. As
another example, components and subsystems shown in one embodiment
may be used in other embodiments; as a specific example of this,
the CO2 recycle 147 mentioned in FIG. 2 may be practiced with all
the embodiments.
* * * * *