U.S. patent application number 10/979698 was filed with the patent office on 2006-05-04 for pre-processing assembly for pre-processing fuel feedstocks for use in a fuel cell system.
Invention is credited to Joseph M. Daly, Sai P. Katikaneni.
Application Number | 20060090398 10/979698 |
Document ID | / |
Family ID | 36260198 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060090398 |
Kind Code |
A1 |
Katikaneni; Sai P. ; et
al. |
May 4, 2006 |
Pre-processing assembly for pre-processing fuel feedstocks for use
in a fuel cell system
Abstract
A pre-processing assembly and method for processing fuel
feedstock containing oxygen and hydrocarbons having higher and
lower hydrocarbon content for a fuel cell, wherein the
pre-processing assembly has a deoxidizing bed for reducing oxygen
in the fuel feedstock and a pre-reforming bed for reducing higher
hydrocarbon content in the fuel feedstock and wherein the
deoxidizing bed and the pre-reforming bed are disposed within a
common reaction vessel such that the fuel feedstock first passes
through the deoxidizing bed and thereafter through the
pre-reforming bed. The pre-reforming assembly may further include a
propane processor bed for processing propane and propylene in the
fuel feedstock, where the propane processor bed is disposed within
the common reaction vessel with the deoxidizing bed and the
pre-reforming bed.
Inventors: |
Katikaneni; Sai P.;
(Brookfield, CT) ; Daly; Joseph M.; (Bethel,
CT) |
Correspondence
Address: |
COWAN LIEBOWITZ & LATMAN, P.C;JOHN J TORRENTE
1133 AVENUE OF THE AMERICAS
NEW YORK
NY
10036
US
|
Family ID: |
36260198 |
Appl. No.: |
10/979698 |
Filed: |
November 2, 2004 |
Current U.S.
Class: |
48/127.9 |
Current CPC
Class: |
H01M 2008/147 20130101;
B01J 2208/025 20130101; C01B 2203/143 20130101; C01B 3/382
20130101; B01J 2219/0004 20130101; B01J 19/2485 20130101; C01B
2203/127 20130101; C01B 2203/0233 20130101; C01B 2203/066 20130101;
H01M 8/0618 20130101; Y02E 60/50 20130101; C01B 2203/1258 20130101;
B01J 2208/00176 20130101; C01B 3/386 20130101; C01B 2203/1241
20130101; Y02E 60/526 20130101; B01J 8/0453 20130101; C01B
2203/0261 20130101; C01B 3/38 20130101; H01M 2008/1293 20130101;
C01B 2203/1247 20130101; H01M 8/0675 20130101; B01J 2208/00884
20130101 |
Class at
Publication: |
048/127.9 |
International
Class: |
B01J 8/00 20060101
B01J008/00 |
Claims
1. A pre-processing assembly for processing fuel feedstock for a
fuel cell, the fuel feedstock including oxygen and hydrocarbons
having higher and lower hydrocarbon content, said pre-processing
assembly comprising: a deoxidizing unit for reducing the oxygen in
said fuel feedstock; and a pre-reforming unit for reducing the
higher hydrocarbon content in said fuel feedstock; and a common
vessel; wherein said deoxidizing unit and said pre-reforming unit
are disposed within said common vessel such that said fuel
feedstock passes through said deoxidizing unit first and thereafter
through said pre-reforming unit.
2. A pre-processing assembly according to claim 1, wherein said
deoxidizing unit comprises a deoxidizing bed and said pre-reforming
unit comprises a pre-reforming bed, said pre-reforming bed
following said deoxidizing bed along the flow path of said fuel
feedstock.
3. A pre-processing assembly according to claim 2, wherein said
deoxidizing bed comprises a deoxidizing catalyst and said
pre-reforming bed comprises a pre-reforming catalyst.
4. A pre-processing assembly according to claim 3, wherein said
deoxidizing catalyst is one of Pt--Pd on alumina catalyst,
Pt--Rh-based catalyst and Rh--Pd-based alumina catalyst.
5. A pre-processing assembly according to claim 4, wherein said
deoxidizing catalyst is G-74D.
6. A pre-processing assembly according to claim 4, wherein said
pre-reforming catalyst is a nickel-based catalyst.
7. A pre-processing assembly according to claim 6, wherein said
pre-reforming catalyst is one of C11-PR, CRG-F, CRG-LH and
G-180.
8. A pre-processing assembly according to claim 7, wherein said
deoxidizing catalyst and said pre-reforming catalyst are
pellet-shaped catalysts.
9. A pre-processing assembly according to claim 7, wherein each of
said deoxidizing catalyst and said pre-reforming catalyst comprises
a catalyst-coated ceramic monolith.
10. A pre-processing assembly according to claim 1, wherein said
deoxidizing bed in reducing said oxygen produces hydrogen and said
pre-reforming bed converts said lower hydrocarbon content to
hydrogen to maintain a reducing environment in said pre-reforming
bed.
11. A pre-processing assembly according to claim 10, wherein the
space velocity of the fuel feedstock in said pre-reforming bed is
such that hydrogen back diffusion is developed and maintained in
said pre-reforming bed.
12. A pre-processing assembly according to claim 11, wherein the
space velocity of said fuel feedstock in said pre-reforming bed is
between 2,000 and 5,000 h.sup.-1.
13. A pre-processing assembly according to claim 12, wherein the
space velocity of said fuel feedstock in said deoxidizer bed is
between 5,000 and 12,000 h.sup.-1.
14. A pre-processing assembly according to claim 13, wherein: said
deoxidizer bed has a volume of 0.7 cubic feet; and said
pre-reforming bed has a volume of 2.5 cubic feet.
15. A pre-processing assembly according to claim 14, wherein the
temperature of said fuel feedstock upon entry into said assembly is
approximately 375.degree. C.
16. A pre-processing assembly according to claim 15, wherein the
deoxidizer bed operates at temperatures between 300.degree. C. and
600.degree. C., and said pre-reforming bed operates at temperatures
between 320.degree. C. and 540.degree. C.
17. A pre-processing assembly according to claim 16, wherein the
steam to carbon ratio of the fuel feedstock is between 2.9 and
3.4.
18. A pre-processing assembly according to claim 17, wherein the
superficial velocity of the fuel feedstock in said pre-reforming
bed is 1.3 ft/s at STP conditions.
19. A pre-processing assembly in accordance with claim 1, wherein
said pre-reforming unit is further adapted to remove
sulfur-containing compounds from said fuel feedstock.
20. A pre-processing assembly for processing fuel feedstock for a
fuel cell, the fuel feedstock including oxygen and hydrocarbons
having higher and lower hydrocarbon content, said pre-processing
assembly comprising: a deoxidizing unit for reducing the oxygen in
said fuel feedstock; a propane processor unit for reducing the
propylene in said fuel feedstock; and a pre-reforming unit for
reducing the higher hydrocarbon content in said fuel feedstock.
21. A pre-processing assembly according to claim 20, wherein said
propane processor unit comprises a nickel-based carbon resistant
catalyst.
22. A pre-processing assembly according to claim 21, wherein said
deoxidizing unit, said propane processor unit and said
pre-reforming unit are disposed within a common vessel.
23. A pre-processing assembly according to claim 22, wherein said
deoxidizing unit comprises a deoxidizing bed, said pre-reforming
unit comprises a pre-reforming bed and said propane processor unit
comprises a propane processor bed.
24. A pre-processing assembly according to claim 23, wherein said
deoxidizing bed, said propane processor bed and said pre-reforming
bed are disposed within said common vessel such that said fuel
feedstock passes through said deoxidizing bed first, then through
one of said propane processor bed and said pre-reforming bed, and
thereafter through the other of said propane processor bed and said
pre-reforming bed.
25. A pre-processing assembly according to claim 24, wherein said
deoxidizing bed, said propane processor bed and said pre-reforming
bed are disposed within said common vessel such that said fuel
feedstock passes through said deoxidizing bed first, then through
said propane processor bed, and thereafter through said
pre-reforming bed.
26. A pre-processing assembly according to claim 24, wherein said
deoxidizing bed comprises a deoxidizing catalyst and said
pre-reforming bed comprises a pre-reforming catalyst.
27. A pre-processing assembly according to claim 26, wherein said
deoxidizing catalyst is one of Pt--Pd on alumina catalyst,
Pt--Rh-based catalyst and Rh--Pd-based alumina catalyst.
28. A pre-processing assembly according to claim 27, wherein said
deoxidizing catalyst is G-74D.
29. A pre-processing assembly according to claim 27, wherein said
pre-reforming catalyst is a nickel based catalyst.
30. A pre-processing assembly according to claim 29, wherein said
pre-reforming catalyst is one of C11-PR, CRG-F, CRG-LH and
G-180.
31. A pre-processing assembly according to claim 30, wherein said
carbon resistant catalyst is FCR-HC59.
32. A pre-processing assembly according to claim 31, wherein: said
deoxidizing bed has a volume of 0.7 cubic feet; said propane
processor bed has a volume of 0.75 cubic feet; said pre-reforming
bed has a volume of 1.7 cubic feet.
33. A pre-processing assembly according to claim 32, wherein: the
space velocity of said fuel feedstock in said deoxidizing bed is
between 5,000 and 10,000 h.sup.-1; the space velocity of said fuel
feedstock in said propane processor bed is between 1900 and 10,000
h.sup.-1; and the space velocity of said fuel feedstock in said
pre-reforming processor bed is between 2,000 and 5,000
h.sup.-1.
34. A pre-processing assembly according to claim 33, wherein the
fuel inlet temperature is between 300 and 450.degree. C.
35. A pre-processing assembly according to claim 34, wherein said
deoxidizer bed is adapted to operate at a temperature between
300.degree. C. and 600.degree. C., said propane processor bed is
adapted to operate at a temperature between 300.degree. C. and
540.degree. C., and said pre-reforming bed is adapted to operate at
temperature between 300.degree. C. and 540.degree. C.
36. A pre-processing assembly according to claim 35, wherein the
steam to carbon ratio in said fuel feedstock is between 2.9 and
3.4.
37. A pre-processing assembly according to claim 20, wherein said
pre-reforming unit is further adapted to remove sulfur-containing
compounds from said fuel feedstock.
38. A fuel processing method for processing fuel feedstock for a
fuel cell, the fuel feedstock including oxygen and hydrocarbons
having higher and lower hydrocarbon content, the fuel processing
method comprising the steps of: providing said fuel feedstock;
reducing oxygen in said fuel feedstock using a deoxidizing unit;
reducing said higher hydrocarbon content in said fuel feedstock
using a pre-reforming unit; wherein said deoxidizing unit and said
pre-reforming unit are disposed within a common vessel such that
said fuel feedstock first flows through said deoxidizing unit and
thereafter through said pre-reforming unit.
39. A fuel processing method according to claim 38, wherein said
deoxidizing unit comprises a deoxidizing bed and said pre-reforming
unit comprises a pre-reforming bed, said pre-reforming bed
following said deoxidizing bed along the flow path of said fuel
feedstock.
40. A fuel processing method according to claim 39, wherein said
deoxidizing bed comprises a deoxidizing catalyst and said
pre-reforming bed comprises a pre-reforming catalyst.
41. A fuel processing method according to claim 40, wherein said
deoxidizing catalyst is one of Pt--Pd on alumina catalyst,
Pt--Rh-based catalyst and Rh--Pd-based alumina catalyst, and
wherein said pre-reforming catalyst is a nickel-based catalyst.
42. A fuel processing method according to claim 41, wherein said
deoxidizing catalyst is G-74D.
43. A fuel processing method according to claim 41, wherein said
pre-reforming catalyst is one of C11-PR, CRG-F, CRG-LH and
G-180.
44. A fuel processing method according to claim 39, further
comprising a step of reducing the propylene in said fuel feedstock
using a propane processor unit.
45. A fuel processing method according to claim 34, wherein said
propane processor unit is disposed in said common vessel and
comprises a propane processing bed.
46. A fuel processing method according to claim 45, wherein said
deoxidizer bed, said pre-reforming bed and said propane processing
bed are disposed in said common vessel such that said fuel
feedstock flows first through said deoxidizing bed, and then
through one of said propane processing bed and said pre-reforming
bed, and thereafter through the other of said propane processing
bed and said pre-reforming bed.
47. A fuel processing method according to claim 46, wherein said
propane processing bed comprises a nickel-based carbon resistant
catalyst.
48. A fuel processing method according to claim 43, wherein said
carbon resistant catalyst is FCR-HC59.
49. A fuel processing method according to claim 38, wherein
reducing said oxygen in said deoxidizing bed produces hydrogen, and
said lower hydrocarbon content is converted to produce hydrogen in
said pre-reforming bed.
50. A fuel processing method according to claim 49, wherein the
space velocity of said fuel feedstock in said pre-reforming bed is
such that hydrogen back diffusion is developed and maintained in
said pre-reforming bed.
51. A fuel processing method according to claim 38, further
comprising removing sulfur-containing compounds from said fuel
feedstock in said pre-reforming unit.
52. A fuel cell system for use with a fuel feedstock, said fuel
feedstock including oxygen and hydrocarbons having higher and lower
hydrocarbon content, said fuel cell system comprising:
pre-processing assembly for processing said fuel feedstock
comprising: a deoxidizing unit for reducing the oxygen in said fuel
feedstock; a pre-reforming unit for reducing the higher hydrocarbon
content in said fuel feedstock; and a common vessel; wherein said
deoxidizing unit and said pre-reforming unit are disposed within
said common vessel such that said fuel feedstock passes through
said deoxidizing unit first and thereafter through said
pre-reforming unit; and a fuel cell for receiving said fuel
feedstock after passage through said pre-processing assembly.
53. A fuel cell system according to claim 52, wherein said
pre-processing assembly further comprises a propane processor unit
for processing propane and propylene in said fuel, said propane
processor unit being disposed in said common reaction vessel.
54. A fuel cell system according to claim 53, wherein said
deoxidizing unit comprises a deoxidizing bed, said pre-reforming
unit comprises a pre-reforming bed and said propane processor unit
comprises a propane processor bed.
55. A fuel cell system according to claim 54, wherein: said
deoxidizing bed, said propane processor bed and said pre-reforming
bed are disposed within a common vessel such that said fuel
feedstock passes through said deoxidizing bed first, then through
one of said propane processor bed and said pre-reforming bed, and
thereafter through the other of said propane processor bed and said
pre-reforming bed.
56. A fuel cell system according to claim 55, further comprising: a
preheater for preheating said fuel feedstock before said fuel
feedstock is processed by said pre-processing assembly.
57. A fuel cell system according to claim 56, further comprising: a
desulfurizer for reducing the sulfur content in said fuel feedstock
before said fuel feedstock is processed by said pre-processing
assembly.
58. A fuel cell system according to claim 57, wherein said
desulfurizer precedes said preheater.
59. A fuel cell system in accordance with claim 56, wherein said
preheater heats said fuel feedstock to approximately 375.degree.
C.
60. A fuel cell system in accordance with claim 54, wherein: said
deoxidizer bed comprises one of Pt--Pd on alumina catalyst,
Pt--Rh-based catalyst and Rh--Pd-based alumina catalyst; said
pre-reforming bed comprises a nickel based catalyst; and said
propane processor bed comprises a nickel-based carbon resistant
catalyst.
61. A fuel cell system in accordance with claim 60, wherein said
nickel-based carbon resistant catalyst is doped with promoters
comprising at least one of cerium oxide, lanthanum oxide, palladium
and platinum.
62. A fuel cell system in accordance with claim 61, wherein:
deoxidizing bed comprises a G-74D catalyst; said pre-reforming bed
comprises one of C11-PR, CRG-F, CRG-LH and G-180; and said propane
processor bed comprises FCR-HC59 catalyst.
63. A fuel cell system according to claim 52, wherein said
deoxidizing unit in reducing said oxygen produces hydrogen and said
pre-reforming unit converts a portion of said lower hydrocarbon
content to hydrogen to maintain a reducing environment in said
pre-reforming unit.
64. A fuel cell system according to claim 63, wherein the space
velocity of the fuel feedstock in said pre-reforming unit is such
that hydrogen back diffusion is developed and maintained in said
pre-reforming unit.
65. A fuel cell system according to claim 52, wherein said
pre-reforming unit is further adapted to remove sulfur-containing
compounds from said fuel feedstock.
66. A fuel cell system according to claim 52, wherein said fuel
cell is one of a molten carbonate fuel cell and solid oxide fuel
cell.
67. A pre-processing assembly according to claim 1, wherein said
fuel feedstock is a multi fuel such as natural gas, peak shaving
gas, coal bed methane, digester gas, propane, LPG, and HD-5.
68. A pre-processing assembly according to claim 20, wherein said
assembly is adapted to process natural gas, HD-5 and LPG
hydrocarbon fuel feedstocks to produce methane rich gas for use in
a high temperature fuel cell.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to processing of fuel feedstocks
containing hydrocarbons for use in fuel cell systems and, in
particular, to pre-processing assemblies for performing
pre-processing of the fuel feedstocks.
[0002] A fuel cell is a device which directly converts chemical
energy stored in hydrocarbon fuel into electrical energy by means
of an electrochemical reaction. Generally, a fuel cell comprises an
anode and a cathode separated by an electrolyte, which serves to
conduct electrically charged ions. Molten carbonate fuel cells
operate by passing a reactant fuel gas through the anode, while
oxidizing gas is passed through the cathode. In order to produce a
useful power level, a number of individual fuel cells are stacked
in series with an electrically conductive separator plate between
each cell.
[0003] Current fuel cells require as the reactant fuel gas a clean
gas composed of hydrogen or a mixture of hydrogen and carbon
monoxide. The reactant fuel gas is generally developed from a
hydrocarbon-containing feedstock using a reforming process. The
hydrocarbon-containing feedstock usually contains substantial
amounts of lower hydrocarbons, i.e., hydrocarbons with 2 or less
carbons, such as methane, as well as small amounts of hydrogen,
carbon dioxide, nitrogen and higher hydrocarbons, i.e. hydrocarbons
with more than 2 carbons. This is true, for example, when the fuel
feedstock is natural gas, peak shaving gas, digester gas and coal
bed methane.
[0004] The fuel feedstock is usually subjected to pre-processing to
reduce or eliminate the higher hydrocarbons and to convert a
portion of the lower hydrocarbons to methane, hydrogen and carbon
dioxide. The feedstock is then further processed in a reforming
unit to generate a fuel gas rich in hydrogen.
[0005] Conventional pre-processing is carried out using a
deoxidizer assembly followed by a pre-reforming assembly. The
deoxidizer assembly reduces the concentration of oxygen in the fuel
feedstock before the feedstock enters the pre-reforming assembly.
This protects the catalyst (usually, a Ni-based catalyst) used in
the pre-reforming assembly, which otherwise would be deactivated in
the presence of oxygen.
[0006] In the pre-reforming assembly, the reforming reaction is a
conversion process which may inadvertently result in carbon
formation based on fuel composition and steam. Carbon formation is
of a particular concern when the fuel feedstock contains propylene,
since the propensity to form carbon increases as the concentration
of propylene increases. The carbon which is produced deposits at
the active sites of the reforming catalyst of the pre-reforming
assembly, thereby deactivating the catalyst. This reduces the life
of the pre-reforming assembly.
[0007] In order to reduce carbon formation in conventional
pre-reforming assemblies, special catalysts either containing
alkali or based on an active magnesia support have been proposed.
Another technique is to use adiabatic processing. In such case, a
fixed bed adiabatic pre-reforming assembly converts the higher
hydrocarbon content at low temperature with steam into methane,
hydrogen and carbon oxides.
[0008] Propylene-containing fuel feedstocks generally have a high
concentration of sulfur-containing compounds. These compounds also
tend to deactivate the reforming catalysts in the pre-reforming
assembly. Although fuel feedstocks are typically desulfurized in a
desulfurizer unit before being carried to the pre-reforming
assembly, high sulfur concentration and the propylene in the fuel
feedstocks reduce the capacity of the desulfurizer unit.
[0009] Fuel feedstocks supplied to the pre-reforming assembly must
also be supplied with additional hydrogen from a hydrogen supply.
This is required to provide a sufficient concentration of hydrogen
in the feedstocks to maintain a reducing environment for the
reforming catalyst, thereby maintaining the catalyst activity.
[0010] As can be appreciated, conventional pre-processing of fuel
feedstocks is complex and costly, due to the need for additional
units or special components for supplying hydrogen, for reducing
carbon formation and for removing propylene and an additional unit
to remove oxygen entering into the pre-reforming assembly. A
pre-processing assembly of simpler design, less cost and longer
life would thus be desirable.
[0011] It is therefore an object of the present invention to
provide a pre-processing assembly which is better able to process
fuel feedstocks containing hydrocarbons and oxygen without
deactivation of the pre-processing catalyst.
[0012] It is a further object of the invention to provide a
pre-processing assembly which is capable of operating without an
additional hydrogen supply and has an increased operating life.
[0013] It is yet a further object of the invention to provide a
pre-processing assembly which is specifically adapted to retard the
affects of propylene and other olefins in hydrocarbon containing
fuel feedstocks.
SUMMARY OF THE INVENTION
[0014] In accordance with the principles of the present invention,
the above and other objectives are realized in a pre-processing
assembly and method for pre-processing a fuel feedstock containing
hydrocarbons including higher hydrocarbon content in which a common
vessel houses both a deoxidizing unit for reducing the oxygen
content in the fuel feedstock and a pre-forming unit for receiving
the fuel feedstock after passage through the deoxidizing unit and
for reducing the higher hydrocarbon content in the fuel feedstock.
In performing this pre-processing the assembly also reduces a
portion of the lower hydrocarbon content in the feedstock and
increases the hydrogen content.
[0015] In the embodiment of the invention disclosed herein, the
pre-reforming unit is arranged to follow the deoxidizing unit along
the flow path of the fuel feedstock and both units are in bed form.
Also, in this embodiment, the catalyst of the deoxidizing bed is
one of a Pt--Pd on alumina catalyst or a Pt--Rh-based catalyst or a
Rh--Pt-based alumina catalyst and the catalyst of the pre-reforming
bed is nickel-based and one of C11-PR (Sud Chemie), CRG-F (Johnson
Matthey), CRG-LH (Johnson Matthey) and G-180 (BASF).
[0016] In a further aspect of the invention, the pre-processing
assembly further includes a propane processor unit for processing
propane and propylene in the fuel feedstock. In the embodiment
disclosed, the propane processor unit is in bed form and arranged
between the deoxidizing bed and the pre-reforming bed. The propane
processor bed has a nickel-based carbon resistant catalyst, such as
FCR-HC59 (Sud Chemie).
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The above and other features and aspects of the present
invention will become more apparent upon reading the following
detailed description in conjunction with the accompanying drawings,
in which:
[0018] FIG. 1 shows a fuel cell system having a fuel delivery
system which uses a pre-processing assembly in accordance with the
principles of the present invention;
[0019] FIG. 2 shows a detailed schematic view of a first embodiment
of the pre-processing assembly of FIG. 1;
[0020] FIG. 3 shows a table of performance data of a deoxidizer of
FIG. 2;
[0021] FIG. 4 shows a detailed schematic view of a second
embodiment of the pre-processing assembly of FIG. 1;
[0022] FIG. 5 shows a graph of performance data of the
pre-processing assembly of FIG. 4;
[0023] FIG. 6 shows a graph of residual concentration of propane in
pre-processed fuel feedstock leaving the assembly of FIG. 4 at
different fuel inlet temperatures;
[0024] FIG. 7 shows a bar graph of component concentrations in
exiting pre-processed fuel feedstocks at different gas space
velocities of inlet HD-5 propane fuel feedstock gas;
[0025] FIG. 8 shows a bar graph of component concentrations in
exiting pre-processed fuel feedstock at different gas space
velocities of inlet HD-5 propane fuel feedstock gas with five
percent propylene;
[0026] FIG. 9 shows a table summarizing conditions during
performance test and performance results of the assembly of FIG.
4;
[0027] FIG. 10 shows a bar graph of component concentrations in
exiting pre-processed fuel feedstock at different steam to carbon
ratios of inlet HD-5 propane fuel feedstock with five percent
propylene;
[0028] FIG. 11 shows a graph of the effect of adding hydrogen to
the fuel feedstock gas input to the assembly of FIG. 4 on the
exiting pre-processed fuel feedstock gas component
concentrations.
DETAILED DESCRIPTION
[0029] FIG. 1 shows a fuel cell system 100 comprising a fuel
delivery system 101 having a pre-processing assembly 108 in
accordance with the principles of the present invention. The fuel
delivery system 101 delivers hydrogen rich fuel to a fuel cell
assembly 112 and includes a fuel supply 102. The fuel supply 102
provides a fuel feedstock containing substantial amounts of methane
and carbon oxides (CO and CO.sub.2), and a higher hydrocarbon
content, such as, for example, ethane, propane and C.sub.4+
hydrocarbons, and amounts of oxygen and hydrogen. Typically, the
fuel feedstock might be natural gas, peak shaving gas, digester
gas, propane, coal bed methane, HD-5 or LPG.
[0030] The fuel delivery system 101 also includes a desulfurizer
104, a preheater 106 and a reformer 110. The fuel feedstock from
the fuel supply 102 is passed to the desulfurizer 104, where
sulfur-containing compounds in the fuel feedstock are physically
and/or chemically removed. Desulfurized fuel feedstock then flows
to the pre-heater 106 where it is preheated to a suitable
temperature, e.g., approximately 375.degree. C., before being
carried to the fuel pre-processing assembly 108. Pre-processed fuel
feedstock exiting the assembly 108 is suitable for use in a fuel
cell assembly 112. In the fuel cell assembly 112, the hydrogen-rich
fuel undergoes an electrochemical reaction to produce power.
[0031] As discussed in detail herein below, in accordance with the
principles of the present invention, the pre-processing assembly
108 includes a plurality of fuel processing units disposed or
housed in a common vessel for deoxidizing the fuel feedstock and
for pre-reforming the deoxidized fuel feedstock to reduce or
substantially eliminate the higher hydrocarbon content. This
pre-reforming processing also reduces the lower hydrocarbon content
by converting it to hydrogen so that the resultant pre-processed
fuel feedstock exiting the assembly 108 has increased hydrogen
content and methane suitable for high temperature fuel cell
applications.
[0032] A detailed schematic view of a first embodiment of the
pre-processing assembly 108 is shown in FIG. 2. As shown, the
pre-processing assembly 108 includes two fuel processing units in
the form of a deoxidizer bed 204 and a pre-reforming bed 206. These
beds are arranged or housed in a common vessel 202 having an inlet
208 for receiving the preheated fuel feedstock from the preheater
106 and an outlet 210 for discharging the pre-processed fuel
feedstock to the fuel cell assembly 112.
[0033] As shown, the pre-reforming bed 206 is arranged to follow
the deoxidizer bed 204 along the flow path 201 of the feedstock.
Also, a porous member, shown as a screen 212 which typically can be
made of Nickel mesh having a mesh size of 10-14, separates the beds
and provides support for the bed 204. The pre-processing bed 206,
in turn, is supported on the lower surface 202a of the vessel
202.
[0034] The deoxidizer bed 204 comprises a deoxidizing catalyst
which typically might be Pt/Pd on Alumina, or G-74D, manufactured
by Sud Chemie Inc. Other catalysts such as Pt--Rh based catalysts
and Rh--Pd based Alumina catalysts also may be used.
[0035] The catalyst used in the pre-reforming bed 206 may be a
standard nickel based catalyst. Examples are nickel-based alumina
catalysts, or C11-PR catalyst, manufactured by Sud-Chemie Inc.
Additionally, other nickel-based catalysts such as CRG-F and
CRG-LH, manufactured by Johnson Matthey or G-180 manufactured by
BASF may likewise be used.
[0036] The shapes of the catalysts used in both beds may vary. For
example, in the case shown, pellet-shaped catalysts are employed in
both the deoxidizer bed 204 and the pre-reforming bed 206. In
addition, monolith-based catalyst structures, comprising a ceramic
monolith substrate with a catalyst coating, are suitable for use in
each bed.
[0037] As mentioned above, the pre-processing assembly 108 reduces
or substantially eliminates the higher hydrocarbon content and the
oxygen content in the fuel feedstock. It also reduces the lower
hydrocarbon content and increases the hydrogen content in the
feedstock. Due to the arrangement of the deoxidizer and
pre-reforming beds 204 and 206 in the common vessel 202, the
pre-processing reduces the possibility of deactivating the
catalysts in the beds and is carried out without the need of adding
hydrogen from a hydrogen supply to the fuel feedstock.
[0038] In particular, the catalyst of the deoxidizer bed 204
facilitates the removal of oxygen from the fuel feedstock. Where
the feedstock is coal mine methane or digester gas, the oxygen is
removed by reacting the oxygen with the methane in the feedstock
aided by the catalyst, as follows:
2CH.sub.4+O.sub.2.fwdarw.2CO+4H.sub.2+heat
CH.sub.4+O.sub.2.fwdarw.CO.sub.2+2H.sub.2+heat Where the feedstock
is peakshaving gas, the oxygen is removed in the deoxidizer bed 204
by reacting the propane in the feedstock with oxygen, as follows:
C.sub.3H.sub.8+2O.sub.2.fwdarw.2CO+2CO.sub.2+4H.sub.2+heat
[0039] Removal of oxygen in the deoxidizer bed 204 prevents the
deactivation of the catalyst in the pre-reforming bed 206. It also
produces additional hydrogen needed to maintain a reducing
environment for such catalyst. In the pre-reforming bed 206, the
reduction of the higher hydrocarbon content in the deoxidized
feedstock is aided by the catalyst and occurs by conversion of the
higher hydrocarbon content into a mixture of hydrogen, carbon
oxides and methane. A reduction in the lower hydrocarbon content
also occurs through conversion and results in increased hydrogen
and carbon oxides. Particularly, approximately 10% of the methane
in the fuel is reformed to provide hydrogen for the electrochemical
reaction in the fuel cell assembly. The remainder of the methane in
the fuel is internally reformed in the fuel cell assembly. The
following reactions exemplify the conversion processing:
CnHm+nH.sub.2O.fwdarw.nCO+(m/2+n)H.sub.2
CH.sub.4+H.sub.2O.fwdarw.CO+3H.sub.2
C.sub.3H.sub.8+2H.sub.2.fwdarw.CO.sub.2+2CH.sub.4+2H.sub.2
[0040] As mentioned above, the deoxidizer bed 204 is firstly
disposed in the vessel 202 in relation to the direction of the flow
or flow path 201 of the fuel feedstock and to the inlet of the
vessel 202. The pre-reforming bed 206 then follows the deoxidizer
bed 204 in the direction of the flow path 201. As was stated
previously, this arrangement causes the removal of oxygen from the
fuel feedstock before entering the pre-reforming bed, thereby
preventing deactivation of the catalyst in the bed. The life of the
pre-processing assembly 108 is thus extended.
[0041] As can also be seen from the above, the deoxidizing and
pre-reforming reactions in the beds 204 and 206 increase the
hydrogen content in the feedstock. This maintains a reducing
environment in the pre-reforming bed 206. In particular, back
diffusion of hydrogen in the pre-reforming bed 206 provides this
reducing environment, thereby allowing the assembly 108 to operate
without an additional supply of hydrogen to the fuel feedstock.
[0042] The amount of back diffusion of hydrogen in the bed 206 is
inversely related to the space velocity of the fuel feedstock.
Accordingly, maintaining a low space velocity of the fuel feedstock
through the pre-reforming bed 206 is desired in order to realize
sufficient hydrogen back diffusion in the bed.
[0043] As can be appreciated, the space velocity is directly
proportional to the flow of the fuel through the pre-reforming bed
206 and inversely proportional to the volume of the catalyst in the
pre-reforming bed 206. Accordingly, the space velocity of the fuel
feedstock can be controlled by adjusting the volume of the catalyst
in the pre-reforming bed 206 and/or by changing the amount of the
fuel flowing through the reforming bed 206, using the following
relationship: SV = Fuel .times. .times. Flow .times. .times. per
.times. .times. Hour Catalyst .times. .times. Volume ##EQU1##
[0044] In addition to controlling the space velocity of the fuel
feedstock, the superficial velocity of the fuel needs to be
controlled for a desired amount of hydrogen back diffusion.
Superficial velocity is a function of a diameter of the vessel
through which the fuel is flowing. Particularly, superficial
velocity is directly proportional to the fuel flow and inversely
proportional to the diameter of the pre-reforming bed 206.
[0045] In the pre-processing assembly 108 of the present invention,
space velocities between 2,000 to 5,000 h.sup.-1 and maximum
superficial velocities of approximately 1.3 ft/s have been found
desirable in operation of the pre-reforming bed 206.
[0046] Moreover, the pre-reforming bed 206 may additionally be
adapted to act as a guard to trap sulfur-containing compounds
present in the fuel feedstock which are not removed by the
desulfurizer unit 104 of FIG. 1. In particular, the nickel in
pre-reforming catalyst is suitable for trapping sulfur-containing
compounds effectively. With this additional sulfur removal, the
operating life of the reforming catalyst in the fuel cell assembly
112 can be increased.
[0047] The optimal design of the pre-reforming assembly 108 will
depend upon the particular application. Some of the important
factors to be considered are the requirements of the fuel cell
assembly 112, the type of fuel gas being processed, and the amount
of gas to be treated. An illustrative example of a pre-reforming
assembly 108 is described herein below.
EXAMPLE 1
[0048] The pre-processing assembly 108 has been optimized for
processing fuel feedstock comprising oxygen and methane for use in
a 300 kW Direct Fuel Cell power plant. The deoxidizer bed 204
comprises a G-74D catalyst and has a volume of 0.7 cubic feet. The
pre-reforming bed 206 comprises a C11-PR catalyst and has a volume
of 2.5 cubic feet. The deoxidizer bed 204 is approximately 4 inches
in thickness and the pre-reforming bed 206 is approximately 14.5
inches in thickness. The common vessel 202 is made from 304/310
stainless steel and has a volume of 4 cubic feet and a diameter of
20 inches.
[0049] The optimal temperatures of the fuel feedstock entering the
vessel 202 through the inlet 208 and of the pre-processed fuel
feedstock exiting the vessel 202 through the outlet 210 are
approximately 300 to 490.degree. C. The optimal operating
temperature range of the deoxidizer bed 204 is between 300.degree.
C. and 600.degree. C., and the optimal operating temperature range
of the pre-reforming bed 206 is between 320.degree. C. and
540.degree. C. The space velocity of the fuel feedstock flowing
through the deoxidizer bed 204 is between 5,000 and 12,000 h.sup.-1
and the space velocity of the fuel feedstock flowing through the
pre-reforming bed 206 is between 2,000 and 5,000 h.sup.-1.
Moreover, in order to maintain a desired hydrogen back diffusion in
the pre-reforming bed 206, the desired maximum superficial velocity
of the fuel feedstock flowing through the bed 206 is 1.3 ft/s at
STP conditions.
[0050] The performance of the pre-processing assembly 108 was
tested by passing through the assembly 108 fuel feedstock
comprising 6.31 lb-mole/hr of methane, 0.06 lb-mole/hr of carbon
dioxide, 12.48 lb-mole/hr water, 0.08 lb-mole/hr of nitrogen, 0.17
lb-mole/hr of ethane and 0.03 lb-mole/hr of propane. The
temperature of the fuel feedstock entering the deoxidizer bed 204
was approximately 425.degree. C. and the space velocity of the fuel
feedstock was approximately 10,000 hr.sup.-1. The temperature of
the pre-processed fuel leaving the pre-reforming bed 206 was about
320.degree. C., and the space velocity of the pre-reformed fuel
leaving the pre-reforming bed 206 was about 3,000 hr.sup.-1. Fuel
pre-processed using the pre-processing assembly comprised about
1.67 lb-mole/hr of hydrogen, 6.25 lb-mole/hr of methane, 0.53
lb-mole/hr of carbon dioxide, 11.54 lb-mole/hr of water and 0.08
lb-mole/hr of nitrogen. From these performance results, it can be
seen that all of the ethane or propane present in the fuel
feedstock was converted to methane, hydrogen and carbon dioxide in
the assembly 108.
EXAMPLE 2
[0051] In this example, the pre-processing assembly 108 of Example
1 has also been optimized for processing hydrocarbon fuels
contaminated with up to 10% oxygen. The optimal temperature range
of the fuel feedstock entering the vessel 202 through inlet 208 is
approximately 310.degree. C. to 500.degree. C.
[0052] The deoxidizing function of the pre-processing assembly 108
of FIG. 2 has been demonstrated with fuels containing oxygen such
as anaerobic digester gas, coal mine methane, and peak shave gas.
The deoxidizing performance of the assembly 108 of this example was
tested at varied inlet temperatures of the fuel feedstock entering
the assembly 108, and varied oxygen contents of the hydrocarbon
fuels. FIG. 3 shows tabulated data of deoxidizer performance
summarizing the results of these tests. In the testing procedure,
the oxygen content of the inlet fuel feedstock was measured, and
the fuel feedstock was pre-heated to various temperatures ranging
from 312.degree. C. to 439.degree. C. before entering the assembly
108. The concentration of oxygen in the pre-processed fuel
feedstock gas exiting the deoxidizer bed 204 and the temperature,
at deoxidizer and pre-reformer bed interface were measured. The
flow rate of the fuel feedstock through the assembly was 15
standard cubic feet per minute (scfm) of natural gas, with the
diluents, such as carbon dioxide, nitrogen, propane and air, added
as listed in FIG. 3, or, for peak shave gas, at a predetermined
ratio so as to give the same heating value. The fuel feedstock used
during these tests had a steam to carbon ratio of 2.0.
[0053] As the tabulated data of FIG. 3 show, pre-processed fuel
feedstock leaving the assembly 108 was depleted of all oxygen. The
temperature rise across the deoxidizer bed 204 is an indication of
the reaction of oxygen with the hydrocarbon fuel feedstock.
Accordingly, these tests show that the deoxidizer bed 204 is
capable of removing oxygen from fuel feedstock over a wide
temperature range and over a wide variation in concentration of
contaminant oxygen in the inlet fuel feedstock.
[0054] A pre-processing assembly 108 having this construction is
estimated to have a life of approximately 5 years as compared to an
average 3-year operating life of a conventional assembly. The life
of the pre-processing assembly 108 is increased partly due to the
maintenance of the pre-reforming bed 206 in a reducing atmosphere
by providing hydrogen from the deoxidizer and from optimized
hydrogen back diffusion, thereby increasing the overall life of the
pre-reforming catalyst.
[0055] In accordance with a further aspect of the invention and to
further improve the performance and the operating life of the
pre-processing assembly 108 when the fuel feedstock includes
propane and/or propylene, the assembly 108 is additionally adapted
as shown in FIG. 4. More particularly, FIG. 4 shows a second
embodiment of the pre-processing assembly 108 of FIG. 2 modified to
include a propane processor bed 301, adapted to convert propane and
propylene in the fuel feedstock to methane and carbon oxides.
[0056] As shown in FIG. 4, the propane processor bed 301 is
disposed in the vessel 202 between the deoxidizer bed 204 and the
pre-reforming bed 206. In particular, the bed 301 is situated below
the screen 212 and rests on a further like screen 302 which
separates the bed 301 from the bed 206. The fuel feedstock thus now
flows through the deoxidizer bed 204 in which oxygen reduction
occurs, through the bed 301 in which propane and propylene are
removed through conversion to methane and carbon oxides and through
the bed 206 in which pre-reforming causes a reduction in the higher
hydrocarbon content and conversion of a part of the lower
hydrocarbon content to hydrogen.
[0057] In the embodiment of FIG. 4, the beds 204 and 206 contain
the same catalysts as those discussed above for the first
embodiment of FIG. 2. The propane processor bed 301, in turn,
comprises a nickel-based carbon resistant catalyst doped with
promoters such as cerium oxide, lanthanum oxide, palladium,
platinum, or a combination of these compounds. An example of a
suitable nickel-based carbon resistant catalyst is FCR-HC59
manufactured by Sud Chemie. The carbon resistant catalyst in the
propane processor bed 305 is selective towards propane and
propylene and promotes the conversion of propane and propylene in
the fuel feedstock to methane and carbon oxides, as follows:
C.sub.3H.sub.6+2H.sub.2O.fwdarw.CO.sub.2+2CH.sub.4+H.sub.2
C.sub.3H.sub.8+2H.sub.2O.fwdarw.CO.sub.2+2CH.sub.4+2H.sub.2
[0058] The pre-processing assembly 108 of FIG. 4 is able to process
commercial grade propane fuel comprising up to 5% propylene, or
HD-5 gas. The performance of the pre-processing assembly will vary
depending on the fuel feedstock inlet temperature, the space
velocity of the fuel feedstock in the beds 204, 301, 206, and the
steam to carbon ("S/C") ratio of the fuel feedstock.
[0059] As with the embodiment of FIG. 2, the optimal design of the
pre-reforming assembly 108 of FIG. 4 will vary depending on the
factors discussed for the embodiment of FIG. 2 and the additional
factor of the propylene concentration. An illustrative example of a
configuration of the pre-processing assembly 108 of FIG. 4 is
described in Example 3 below.
EXAMPLE 3
[0060] The pre-processing assembly of FIG. 4 has been optimized for
processing fuel comprising propane and up to 5% propylene for use
in a 300 kW Direct Fuel Cell power plant. The deoxidizer bed 204
comprises a G-74D catalyst and has a volume of 0.7 cubic feet. The
propane processor bed 301 comprises an FCR-HC59 anti-carbon
catalyst manufactured by Sud Chemie and has a volume of 0.75 cubic
feet, and the pre-reforming bed 206 comprises a C11-PR catalyst and
has a volume of 1.7 cubic feet. The vessel 202 is made from 304/310
stainless steel and has a volume of 4 cubic feet.
[0061] The optimal temperature of the fuel feedstock entering the
vessel 202 through the inlet 208 is approximately 350.degree. C.
and the temperature of the pre-processed fuel exiting the vessel
202 through the outlet 210 is approximately 350.degree. C. The
deoxidizer bed 204 is adapted to operate at a temperature between
300.degree. and 600.degree. C., while the propane processor bed 301
and the pre-reforming bed 206 are adapted to operate at temperature
between 300.degree. and 540.degree. C. The optimal operating
temperature range of beds 204, 301 and 206 of the assembly 108 is
between 300.degree. C. and 400.degree. C. The desired space
velocity of the fuel feedstock flowing through the deoxidizer bed
204 is between 5,000 and 12,000 h.sup.-1. The desired space
velocity of the fuel feedstock flowing through the propane
processor bed 301 is between 5,000 and 11,000 h.sup.-1, while the
desired space velocity of the fuel feedstock flowing through the
pre-processing bed 206 is between 2,000 and 5,000 h.sup.-1.
Moreover, it is preferred that the steam to carbon ratio of the
fuel feedstock entering the assembly is approximately 3.
[0062] The performance of the pre-processing assembly 108 of FIG. 4
was tested using propane fuel feedstock having various
concentrations of propylene. Fuel feedstock used during these tests
comprised pure propane with no propylene, HD-5 gas having 2538 ppm
of propylene, and HD-5+ gas having approximately 5% propylene. The
tests were performed at varied inlet temperatures of the fuel
feedstock entering the assembly 108, varied space velocities and
varied steam to carbon ratios.
[0063] FIG. 5 shows a graph of performance data resulting from the
testing of the assembly 108 of FIG. 4 at different fuel feedstock
inlet temperatures. In the testing procedure, fuel feedstock was
pre-heated to various temperatures before entering the assembly 108
and the concentrations of the various components of the
pre-processed fuel feedstock gas exiting the assembly were
measured. The fuel feedstock used during this testing had a steam
to carbon ratio of 3.0. The flow rate of the pure propane fuel
feedstock gas through the assembly was at 5.0 standard cubic feet
per minute ("scfm"), the flow rates of the HD-5 fuel feedstock gas
and the HD-5+ fuel feedstock gas were at 4.5 scfm and the inlet
temperatures of the fuel feedstock gas entering the assembly 108
ranged between 300 and 450.degree. C.
[0064] As shown in FIG. 5, pre-processed fuel feedstock leaving the
assembly 108 included methane, hydrogen and carbon dioxide content.
The X-axis in FIG. 5 represents the pre-processing assembly inlet
temperature, while the Y-axis represents the exit concentration of
each of the components exiting in the pre-processed fuel feedstock
gas.
[0065] As can be seen from FIG. 5, the respective concentrations of
methane, hydrogen and carbon dioxide in the exiting pre-processed
fuel feedstock gas resulting from the pure propane input feedstock
are approximately the same as the respective concentrations of
methane, hydrogen and carbon dioxide in the exiting pre-processed
fuel feedstock gas resulting from the HD-5 and HD-5+ input
feedstocks. Accordingly, these tests show that the assembly 108 is
capable of pre-processing fuel feedstock with high propylene
concentrations without degradation in performance.
[0066] As can also be seen, as the inlet temperature of the
feedstock increased, the concentration of hydrogen in the exiting
pre-processed fuel feedstock gas also increased, while the
concentration of methane in the exiting pre-processed fuel
feedstock gas decreased. Moreover, as shown, at all inlet
temperatures the pre-processed fuel feedstock gas exiting the
assembly included a sufficient concentration of hydrogen to
maintain the pre-reforming catalyst in a reducing atmosphere, thus
extending the operating life of the assembly 108.
[0067] FIG. 6 shows a graph of residual propane concentration in
the exiting pre-processed fuel feedstock gas of the assembly 108 of
FIG. 4 corresponding to various inlet temperatures of the
feedstock. As shown in FIG. 6, the X-axis represents the inlet
temperature of the feedstock entering the pre-processing assembly
108, and the Y-axis represents a percent concentration of propane
in the exiting pre-processed fuel feedstock gas. As can be
appreciated, the performance of the assembly is inversely related
to the residual propane concentration in the exiting pre-processed
fuel feedstock gas.
[0068] FIG. 6 shows that in all cases, even with lower inlet
temperatures of approximately 300.degree. C., the concentration of
propane in the exiting pre-processed fuel is acceptably low.
Furthermore, the concentration of propane in the exiting
pre-processed fuel feedstock gas decreases as the inlet temperature
of the fuel feedstock increases, to a point where propane is
non-detectable at inlet temperatures above 425.degree. C.
[0069] Based on the above tests performed at different fuel
feedstock inlet temperatures, it can be seen that the performance
of the assembly 108 is excellent over a wide temperature range,
allowing the inlet temperature to be varied according to the
desired outlet concentrations of hydrogen and methane. The optimal
operating temperatures for the pre-processing assembly of FIG. 4
are between 300 and 450.degree. Celsius.
[0070] The effect of fuel feedstock space velocity on the
performance of the pre-processing assembly 108 of FIG. 4 was also
tested using HD-5 and HD-5+ input fuel feedstock gases. During
these tests, fuel feedstocks were passed through the assembly 108
with the gas space velocities of 1900 h.sup.-1, 2660 h.sup.-1, 3420
h.sup.-1, and 9082 h.sup.-1. The inlet temperature of the fuel
feedstock was kept constant at 375.degree. C. Percent
concentrations of methane, hydrogen and carbon dioxide in the
pre-processed fuel feedstock gas exiting the assembly 108 were
recorded.
[0071] FIGS. 7 and 8 show bar graphs of exit gas concentrations,
with constant inlet temperature of 375.degree. C., at different
feedstock space velocities of HD-5 and HD-5+ fuel feedstocks,
respectively, flowing through the assembly 108. The Y-axis in FIGS.
7 and 8 represents the percent concentration of each component in
the exiting pre-processed fuel feedstock gas. As can be seen, the
assembly 108 is able to effectively pre-process fuel feedstock
flowing through it with a space velocity in the range of 1900
h.sup.-1 and 9082 h.sup.-1 and demonstrates excess capacity in this
space velocity range. Additionally, these tests show that the
performance of the assembly 108 is not greatly affected by an
increase in the concentration of propylene in the HD-5+ fuel
feedstock when its space velocity is in the range of 1900 h.sup.-1
to 9044 h.sup.-1.
[0072] The performance of the assembly 108 of FIG. 4 has also been
tested at other inlet temperatures with high space velocity for
both HD-5 propane with added propylene and natural gas. FIG. 9
shows a table summarizing specific conditions during these tests,
including fuel feedstock composition and inlet temperatures, and
exit compositions of pre-processed natural gas and HD-5 propane
with added propylene gas exiting the assembly 108 of FIG. 4. In
particular, the inlet feedstock composition of natural gas includes
2.23% of ethane, 0.36% of propane and 0.16% of butanes, while the
inlet feedstock composition of HD-5 propane with added propylene
includes 7.2% of ethane, 88% of propane, 4.02% of propylene and
0.6% of butanes. As shown in FIG. 9, all of these higher
hydrocarbons were removed by the pre-processing assembly 108. As
these tests show, the assembly 108 of FIG. 4 has excellent
performance at space velocities in the range of 12,000 h.sup.-1 for
the deoxidizer 204, 11,000 h.sup.-1 for the propane processor 301,
and 5,000 h.sup.-1 for the pre-reformer 206.
[0073] Furthermore, the performance of the assembly 108 of FIG. 4
was tested at different steam to carbon ratios. FIG. 10 shows a bar
graph of the component concentrations in the exiting pre-processed
fuel feedstock gas derived from HD-5+ fuel feedstock at different
steam to carbon ratios. The tests were conducted with a constant
fuel feedstock inlet temperature of 375.degree. C. In FIG. 10, the
Y-axis represents the percent concentration of the exit gas
components. Performance testing was carried out by passing a
mixture of HD-5+ fuel feedstock and steam with steam to carbon
ratios of 2.9, 3.0, 3.2 and 3.4 through the assembly 108.
Concentrations of methane, hydrogen and carbon dioxide in the
exiting pre-processed fuel feedstock gas were measured at the
outlet of the assembly 108. As can be seen, an increase in the
steam to carbon ratio from 3.0 to 3.4 resulted in an increased
hydrogen production by the assembly.
[0074] The performance of the assembly 108 was also tested with
propane fuel feedstock to which was added different hydrogen
concentrations. Fuel feedstock used during this test comprised 5
scfm of propane and 39 scfm of steam (steam to carbon ratio of 2.6)
and had an inlet temperature of 310.degree. C. Different amounts of
hydrogen were added to the fuel feedstock at the inlet of the
assembly 108. FIG. 11 shows a graph of the effect of hydrogen added
to the fuel feedstock on the concentrations of methane, propane,
hydrogen and carbon dioxide in the exiting pre-processed fuel
feedstock gas. As shown, the concentration of propane increased as
the amount of hydrogen added at the inlet of the assembly 108
increased. These tests show that the assembly 108 is capable of
operating without an additional hydrogen supply, and that the
addition of hydrogen resulted in decreased conversion of propane,
thus detracting from the performance of the assembly.
[0075] In all cases it is understood that the above-described
arrangements are merely illustrative of the many possible specific
embodiments which represent applications of the present invention.
Numerous and varied other arrangements can be readily devised in
accordance with the principles of the present invention without
departing from the spirit and the scope of the invention. For
example, various modifications of the catalyst bed construction of
the invention may be made to optimize the space velocity and the
superficial velocity of the fuel feedstock gas as it is being
passed through the pre-reforming bed. Moreover, other deoxidizing
and pre-reforming catalysts may be used in the beds 202 and 204 in
lieu of those discussed above.
* * * * *