U.S. patent application number 10/412709 was filed with the patent office on 2003-12-04 for steam reforming fuel processor, burner assembly, and methods of operating the same.
Invention is credited to Edlund, David J., Elliott, Darrell J., Hayes, Alan E., Pledger, William A., Renn, Curtiss, Stephens, Redwood, Studebaker, R. Todd.
Application Number | 20030223926 10/412709 |
Document ID | / |
Family ID | 29255339 |
Filed Date | 2003-12-04 |
United States Patent
Application |
20030223926 |
Kind Code |
A1 |
Edlund, David J. ; et
al. |
December 4, 2003 |
Steam reforming fuel processor, burner assembly, and methods of
operating the same
Abstract
Diffusion and atomizing burner assemblies and fuel processing
and fuel cell systems containing the same. The burner assembly
receives at least one liquid and/or gaseous fuel stream, mixes the
stream with air, and combusts the mixed stream to provide heat for
a fuel processor. In some embodiments, the burner assembly receives
at least one combustible fuel stream produced by the fuel
processing and/or fuel cell system. In some embodiments, the burner
assembly receives a fuel stream having the same composition as a
stream that is delivered for non-combustion purposes to another
portion of the fuel processing and/or fuel cell system. In some
embodiments, the burner assembly receives and vaporizes a fuel
stream that includes the same carbon-containing feedstock and/or
has the same overall composition as the feed stream from which the
steam reformer or other fuel processor produces hydrogen gas.
Methods of use are also disclosed.
Inventors: |
Edlund, David J.; (Bend,
OR) ; Elliott, Darrell J.; (Bend, OR) ; Hayes,
Alan E.; (Bend, OR) ; Pledger, William A.;
(Sisters, OR) ; Renn, Curtiss; (Bend, OR) ;
Stephens, Redwood; (Bend, OR) ; Studebaker, R.
Todd; (Bend, OR) |
Correspondence
Address: |
KOLISCH HARTWELL, P.C.
520 S.W. YAMHILL STREET
SUITE 200
PORTLAND
OR
97204
US
|
Family ID: |
29255339 |
Appl. No.: |
10/412709 |
Filed: |
April 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60372748 |
Apr 14, 2002 |
|
|
|
60392397 |
Jun 27, 2002 |
|
|
|
Current U.S.
Class: |
422/198 ;
422/211 |
Current CPC
Class: |
B01J 2208/00309
20130101; F23D 14/22 20130101; F23D 91/02 20150701; B01J 2208/0053
20130101; B01J 2208/00141 20130101; C01B 3/384 20130101; C01B
2203/048 20130101; H01M 8/0631 20130101; C01B 2203/047 20130101;
C01B 2203/0811 20130101; C01B 2203/0233 20130101; C01B 3/501
20130101; B01J 8/0285 20130101; B01J 2208/00504 20130101; H01M
8/0687 20130101; Y02E 60/50 20130101; H01M 8/04022 20130101; C01B
2203/0485 20130101; B01J 8/0221 20130101; C01B 2203/041 20130101;
C01B 2203/0475 20130101; H01M 8/0668 20130101; B01J 2208/00132
20130101; H01M 8/0612 20130101; C01B 2203/0465 20130101; C01B
2203/0495 20130101 |
Class at
Publication: |
422/198 ;
422/211 |
International
Class: |
B01J 008/02 |
Claims
We claim:
1. A steam reforming fuel processor, comprising: a reforming region
containing a reforming catalyst, wherein the reforming region is
adapted to receive a feed stream comprising water and a
carbon-containing feedstock and to produce a mixed gas stream
containing hydrogen gas and other gases therefrom; a burner
assembly adapted to receive an air stream and a combustible fuel
stream and to produce a combustion stream for heating at least the
reforming region of the fuel processor; wherein the feed stream and
the fuel stream both comprise a carbon-containing feedstock and at
least 25% water.
2. The fuel processor of claim 1, wherein at least one of the feed
stream and the fuel stream further comprise at least one additional
component.
3. The fuel processor of claim 1, wherein the feed stream and the
fuel stream have the same composition.
4. The fuel processor of claim 1, wherein the fuel processor
further includes a valve assembly that is adapted to receive a
stream containing water and a liquid carbon-containing feedstock
and to apportion the ed stream into feed stream for the reforming
region and the combustible fuel stream for the burner assembly.
5. The fuel processor of claim 1, wherein the fuel processor
further includes at least one separation region adapted to receive
at least a portion of the mixed gas stream and to produce therefrom
a hydrogen-rich stream containing at least substantially pure
hydrogen gas and a byproduct stream containing at least a
substantial portion of the other gases.
6. The fuel processor of claim 5, wherein the burner assembly is
further adapted to receive at least a portion of the byproduct
stream as a gaseous combustible fuel stream.
7. The fuel processor of claim 5, wherein the at least one
separation region includes at least one hydrogen-selective
membrane.
8. The fuel processor of claim 5, wherein the at least one
separation region includes at least one carbon monoxide removal
assembly adapted to reduce the concentration of any carbon monoxide
present in the mixed gas stream.
9. The fuel processor of claim 1, wherein the burner assembly is
adapted to receive a liquid combustible fuel stream, and further
wherein the burner assembly includes an atomization assembly that
is adapted to receive and atomize the liquid combustible fuel
stream.
10. The fuel processor of claim 1, wherein the burner assembly is
adapted to receive a liquid combustible fuel stream, and further
wherein the burner assembly includes a vaporization region that is
adapted to receive and vaporize the liquid combustible fuel stream
to form a vaporized fuel stream therefrom.
11. The fuel processor of claim 10, wherein the burner assembly
further includes a diffusion region adapted to receive and mix the
vaporized fuel stream and the air stream to form an oxygenated
combustible fuel stream.
12. A fuel processor, comprising: a hydrogen-producing region
adapted to receive a feed stream and to produce a mixed gas stream
containing hydrogen gas and other gases therefrom; a burner
assembly adapted to produce a heated exhaust stream for heating at
least the hydrogen-producing region of the fuel processor, wherein
the burner assembly is adapted to receive a combustible fuel stream
and an air stream and to combust the fuel and air streams to
produce the heated exhaust stream; and means for controlling the
amount of heat produced by the burner assembly by controlling the
rate at which the air stream is delivered to the burner
assembly.
13. The fuel processor of claim 12, wherein the fuel stream and the
feed stream share a common carbon-containing feedstock
component.
14. The fuel processor of claim 12, wherein the fuel stream and the
feed stream have the same composition.
15. The fuel processor of claim 12, wherein the fuel stream and the
feed stream contain at least 25% water.
16. The fuel processor of claim 12, wherein the hydrogen-producing
region includes at least one reforming catalyst bed containing a
steam reforming catalyst, and further wherein the feed stream
comprises water and a carbon-containing feedstock.
17. The fuel processor of claim 12, wherein the fuel processor
further includes at least one separation region adapted to receive
at least a portion of the mixed gas stream and to produce a
hydrogen-rich stream containing at least substantially pure
hydrogen gas and at least one byproduct stream containing at least
a substantial portion of the other gases.
18. The fuel processor of claim 17, wherein the at least one
separation region includes at least one hydrogen-selective
membrane.
19. The fuel processor of claim 17, wherein the at least one
separation region includes a membrane module that contains a
compartment into which the mixed gas stream is delivered under
pressure, and further wherein the compartment contains at least one
hydrogen-selective membrane, the hydrogen-rich stream is formed
from a portion of the mixed gas stream that passes through the at
least one hydrogen-selective membrane, and the byproduct stream is
formed form a portion of the mixed gas stream that does not pass
through the at least one membrane.
20. The fuel processor of claim 19, wherein the at least one
separation region further includes at least one carbon monoxide
removal assembly adapted to reduce the concentration of any carbon
monoxide present in the hydrogen-rich stream.
21. The fuel processor of claim 12, wherein the burner assembly is
adapted to selectively receive both liquid and gaseous combustible
fuel streams.
22. The fuel processor of claim 12, wherein the burner assembly is
adapted to receive a liquid combustible fuel stream, and further
wherein the burner assembly includes an atomization assembly that
is adapted to receive and atomize the liquid combustible fuel
stream.
23. The fuel processor of claim 12, wherein the burner assembly is
adapted to receive a liquid combustible fuel stream, and further
wherein the burner assembly includes a vaporization region that is
adapted to receive and vaporize the liquid combustible fuel stream
to form a vaporized fuel stream therefrom.
24. The fuel processor of claim 23, wherein the burner assembly
further includes a diffusion region adapted to receive and mix the
vaporized fuel stream and the air stream to form an oxygenated
combustible fuel stream.
25. A fuel processor, comprising: a hydrogen-producing region
adapted to receive a feed stream and to produce a mixed gas stream
containing hydrogen gas and other gases therefrom; at least one
separation region adapted to receive at least a portion of the
mixed gas stream and to produce a hydrogen-rich stream containing
at least substantially pure hydrogen gas and at least one byproduct
stream containing at least a substantial portion of the other
gases; a diffusion burner assembly adapted to produce a heated
exhaust stream for heating at least the hydrogen-producing region
of the fuel processor, wherein the diffusion burner assembly is
adapted to receive an air stream and a combustible fuel stream,
wherein the diffusion burner assembly comprises: a diffusion region
adapted to mix the combustible fuel stream and the air stream to
form an oxygenated combustible fuel stream; and a combustion region
adapted to receive the oxygenated combustible fuel stream; and at
least one ignition region adapted to initiate combustion of the
oxygenated combustible fuel stream.
26. The fuel processor of claim 25, wherein the distribution region
includes a diffusion structure adapted to promote the formation of
a plurality of oxygenated combustible fuel streams.
27. The fuel processor of claim 26, wherein the diffusion structure
is adapted to divide the air stream into a plurality of air streams
and to divide the combustible fuel stream into a plurality of
combustible fuel streams.
28. The fuel processor of claim 27, wherein each of the plurality
of air streams contains no more than 10% of the air stream.
29. The fuel processor of claim 27, wherein each of the plurality
of combustible fuel streams contains no more than 10% of the
combustible fuel stream.
30. The fuel processor of claim 27, wherein the diffusion structure
includes a fuel distribution manifold containing a plurality of
fuel apertures into which the combustible fuel stream is divided
into the plurality of combustible fuel streams, and further wherein
the plurality of fuel apertures are in communication with a
plurality of fuel tubes having fuel outlets adapted to deliver the
plurality of fuel streams to the combustion region.
31. The fuel processor of claim 30, wherein the diffusion region
further includes an air distribution chamber.
32. The fuel processor of claim 31, wherein the air distribution
chamber is adapted to receive the air stream and permit the air
stream to flow around the plurality of fuel tubes.
33. The fuel processor of claim 32, wherein the diffusion region
includes a combustion manifold separating the air diffusion chamber
and the combustion region, wherein the combustion manifold includes
a plurality of apertures through which the air stream is divided
into the plurality of air streams, and further wherein each of the
fuel outlets of the plurality of fuel tubes is associated with one
of the plurality of apertures.
34. The fuel processor of claim 33, wherein each fuel outlet
extends at least partially through one of the plurality of
apertures.
35. The fuel processor of claim 33, wherein each fuel outlet
extends through one of the plurality of apertures.
36. The fuel processor of claim 33, wherein the combustion manifold
is adapted to maintain the air distribution chamber at a pressure
that is greater than the pressure within the combustion region.
37. The fuel processor of claim 33, wherein the diffusion burner
assembly is adapted to receive a combustible fuel stream in the
form of a liquid combustible fuel stream, and further wherein the
diffusion burner assembly includes a vaporization region that is
adapted to vaporize the liquid combustible fuel stream.
38. The fuel processor of claim 37, wherein the vaporization region
includes at least one reservoir adapted to receive a volume of the
liquid combustible fuel stream.
39. The fuel processor of claim 37, wherein the fuel distribution
manifold is adapted to maintain the vaporization region at a
pressure that is greater than the pressure in the plurality of fuel
tubes.
40. The fuel processor of claim 33, wherein the diffusion burner
assembly is adapted to receive a combustible fuel stream in the
form of a gaseous combustible fuel stream.
41. The fuel processor of claim 40, wherein the gaseous combustible
fuel stream includes at least a portion of the byproduct
stream.
42. The fuel processor of claim 25, wherein a stream that contains
a carbon-containing feedstock is delivered to the fuel processor as
a single stream and thereafter divided into a stream that forms at
least a portion of the feed stream and a stream that forms at least
a portion of the fuel stream.
43. The fuel processor of claim 25, wherein the fuel stream and the
feed stream both contain water and a carbon-containing
feedstock.
44. The fuel processor of claim 43, wherein the fuel stream and the
feed stream both contain at least 25 wt % water and a
carbon-containing feedstock.
45. The fuel processor of claim 25, wherein the fuel stream and the
feed stream have the same composition.
46. The fuel processor of claim 25, wherein at least one of the
fuel stream and the feed stream further comprise at least one
additional component.
47. The fuel processor of claim 25, wherein the fuel processor is
adapted to produce the mixed gas stream via a steam reforming
reaction, wherein the hydrogen-producing region includes at least
one reforming region that contains a reforming catalyst, and
further wherein the feed stream contains water and a
carbon-containing feedstock.
48. The fuel processor of claim 47, wherein the feed stream is
delivered to the fuel processor as an at least substantially liquid
stream and divided into the feed stream for the hydrogen-producing
region of the fuel processor and the fuel stream for the burner
assembly.
49. The fuel processor of claim 48, wherein the fuel processor
includes a vaporization region in which the feed stream is
vaporized at least partially responsive to thermal contact with the
heated exhaust stream from the burner assembly.
50. The fuel processor of claim 25, wherein the burner assembly is
further adapted to receive a gaseous fuel stream.
51. The fuel processor of claim 25, wherein the burner assembly is
further adapted to receive at least a portion of the byproduct
stream as a gaseous fuel stream.
52. A fuel processor, comprising: a hydrogen-producing region
adapted to receive a feed stream and to produce a mixed gas stream
containing hydrogen gas and other gases therefrom; at least one
separation region adapted to receive at least a portion of the
mixed gas stream and to produce a hydrogen-rich stream containing
at least substantially pure hydrogen gas and at least one byproduct
stream containing at least a substantial portion of the other
gases; and an atomizing burner assembly adapted to produce a heated
exhaust stream for heating at least the hydrogen-producing region
of the fuel processor, wherein the atomizing burner assembly is
adapted to receive an air stream and to receive under pressure a
liquid combustible fuel stream, and further wherein the atomizing
burner assembly comprises: an atomization assembly adapted to
receive the liquid combustible fuel stream and to produce an
atomized fuel stream therefrom; and an ignition region with at
least one ignition source adapted to initiate combustion of the
atomized fuel stream and the air stream.
53. The fuel processor of claim 52, wherein the liquid combustible
fuel stream is delivered to the fuel atomization assembly at a
pressure of at least 50 psi.
54. The fuel processor of claim 52, wherein the atomization
assembly includes an atomization orifice adapted to produce the
atomized fuel stream from the liquid combustible fuel stream as the
liquid combustible fuel stream passes through the orifice.
55. The fuel processor of claim 52, wherein the atomization
assembly includes at least one impingement surface adapted to
produce the atomized fuel stream as the liquid combustible fuel
stream is urged under pressure into contact with the impingement
surface.
56. The fuel processor of claim 52, wherein the atomizing burner
assembly is adapted to promote mixing of the atomized fuel stream
and the air stream prior to combustion of the atomized fuel
stream.
57. The fuel processor of claim 52, wherein the ignition region
includes a constricted outlet through which the heated exhaust
stream exits the ignition region, and further wherein the outlet is
adapted to promote greater mixing of the atomized fuel stream and
the air stream.
58. The fuel processor of claim 52, wherein the atomizing burner
assembly includes a distribution plate adapted to promote turbulent
mixing of the atomized fuel stream and the air stream.
59. The fuel processor of claim 58, wherein the distribution plate
includes a plurality of angularly oriented passages through which
the air stream and the atomized fuel stream pass prior to reaching
the ignition region.
60. The fuel processor of claim 52, wherein a stream that contains
a carbon-containing feedstock is delivered to the fuel processor as
a single stream and thereafter divided into a stream that forms at
least a portion of the feed stream and a stream that forms at least
a portion of the fuel stream.
61. The fuel processor of claim 52, wherein the fuel stream and the
feed stream both contain water and a carbon-containing
feedstock.
62. The fuel processor of claim 61, wherein the fuel stream and the
feed stream both contain at least 25 wt % water and a
carbon-containing feedstock.
63. The fuel processor of claim 52, wherein the fuel stream and the
feed stream have the same composition.
64. The fuel processor of claim 52, wherein at least one of the
fuel stream and the feed stream further comprise at least one
additional component.
65. The fuel processor of claim 52, wherein the fuel processor is
adapted to produce the mixed gas stream via a steam reforming
reaction, with the fuel processor including at least one reforming
region that contains a reforming catalyst, and further wherein the
feed stream contains water and a carbon-containing feedstock.
66. The fuel processor of claim 65, wherein the feed stream is
delivered to the fuel processor as an at least substantially liquid
stream and divided into the feed stream for the hydrogen-producing
region of the fuel processor and the fuel stream for the burner
assembly.
67. The fuel processor of claim 66, wherein the fuel processor
includes a vaporization region in which the feed stream is
vaporized at least partially responsive to thermal contact with the
heated exhaust stream from the burner assembly.
68. The fuel processor of claim 52, wherein the burner assembly is
further adapted to receive a gaseous fuel stream.
69. The fuel processor of claim 52, wherein the burner assembly is
further adapted to receive at least a portion of the byproduct
stream as a gaseous fuel stream.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application Serial No. 60/372,748, which was filed on Apr. 14, 2002
and is entitled "Steam Reforming Fuel Processor, Burner Assembly,
and Methods of Operating the Same," and to U.S. Provisional Patent
Application Serial No. 60/392,397, which was filed on Jun. 27, 2002
and is entitled "Fuel Processing System with Diffusion Burner
Assembly." The complete disclosures of these priority applications
are hereby incorporated by reference for all purposes.
FIELD OF THE DISCLOSURE
[0002] The present disclosure is directed generally to fuel
processing and fuel cell systems, and more particularly, to burner
assemblies for use in such systems and to fuel processing and fuel
cell systems containing these burner assemblies.
BACKGROUND OF THE DISCLOSURE
[0003] Purified hydrogen is used in the manufacture of many
products including metals, edible fats and oils, and semiconductors
and microelectronics. Purified hydrogen is also an important fuel
source for many energy conversion devices. For example, many fuel
cells use purified hydrogen and an oxidant to produce an electrical
potential. A series of interconnected fuel cells is referred to as
a fuel cell stack, and this stack may be referred to as a fuel cell
system when combined with sources of oxidant and hydrogen gas.
Various processes and devices may be used to produce the hydrogen
gas that is consumed by the fuel cells.
[0004] As used herein, a fuel processor is a device that produces
hydrogen gas from a feed stream that includes one or more
feedstocks. Examples of fuel processors include steam and
autothermal reformers, in which the feed stream contains water and
a carbon-containing feedstock, such as an alcohol or a hydrocarbon,
and partial oxidation and pyrolysis reactors, in which the feed
stream is a carbon-containing feedstock. Fuel processors typically
operate at elevated temperatures. Because the reforming and other
fuel processing reactions are overall endothermic, the heat
required to heat the fuel processors needs to be provided by a
heating assembly, such as a burner, electrical heater or the like.
When burners are used to heat the fuel processor, the burners
typically utilize a combustible fuel stream, such as a combustible
gas or a combustible liquid.
[0005] One such hydrogen-producing fuel processor is a steam
reformer, in which hydrogen gas is produced from a feed stream that
includes a carbon-containing feedstock and water. Steam reforming
is performed at elevated temperatures and pressures, and therefore
steam reformers typically include a heating assembly that provides
heat for the steam reforming reaction, such as to maintain the
reforming catalyst bed at a selected reforming temperature and to
vaporize the feed stream. One type of heating assembly is a burner,
in which a combustible fuel stream is combusted with air. Steam
reformers conventionally utilize a feed stream that is vaporized
and reformed to produce a mixed gas stream containing hydrogen gas
and other gases, and a fuel stream that has a different composition
that the feed stream and which is delivered to, and consumed by,
the burner or other heating assembly to heat the steam
reformer.
SUMMARY OF THE DISCLOSURE
[0006] The present disclosure is directed to a burner assembly,
such as may be used in fuel processing and fuel cell systems, and
to fuel processing and fuel cell systems containing burner
assemblies according to the present disclosure. The burner assembly
receives at least one fuel stream, mixes the stream with air and
ignites the mixed stream to provide heat for a fuel processor. In
some embodiments, the burner assembly is adapted to receive and
vaporize a liquid combustible fuel stream, in other embodiments,
the burner assembly is adapted to receive a gaseous combustible
fuel stream, and in still other embodiments, the burner assembly is
adapted to receive both liquid and gaseous combustible fuel
streams. In some embodiments, the burner assembly receives at least
one combustible fuel stream that is produced by the fuel processing
and/or fuel cell system with which the burner is used. In some
embodiments, the burner assembly receives a fuel stream having the
same composition as a stream that is delivered for non-combustion
purposes to another portion of the fuel processing and/or fuel cell
system with which the burner assembly is used. In some embodiments,
the burner assembly is adapted to receive and vaporize a fuel
stream that includes the same carbon-containing feedstock and/or
the same overall composition as the feed stream from which the
steam reformer or other fuel processor produces hydrogen gas. In
some embodiments, the feed stream and the fuel stream have the same
composition, and optionally are selectively delivered from the same
supply. In some embodiments, the burner assembly is a diffusion
burner assembly. In some embodiments, the burner assembly is an
atomizing burner assembly. Methods for operating a steam reformer
and burner assembly are also disclosed herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a schematic diagram of a fuel processing system
with a burner assembly according to the present disclosure.
[0008] FIG. 2 is a schematic diagram of a fuel processing system
with a chemical carbon monoxide removal assembly according to the
present disclosure.
[0009] FIG. 3 is a schematic diagram of a fuel cell system with a
burner assembly according to the present disclosure.
[0010] FIG. 4 is a schematic diagram of another fuel processor with
a burner assembly according to the present disclosure.
[0011] FIG. 5 is a schematic view of another burner assembly
according to the present disclosure.
[0012] FIG. 6 is a schematic view of another burner assembly
according to the present disclosure.
[0013] FIG. 7 is a schematic view of a fuel processor according to
the present disclosure in which the hydrogen-producing region and
the burner assembly both receive the same liquid carbon-containing
feedstock.
[0014] FIG. 8 is a schematic view showing a variation of the fuel
processor of FIG. 7, with a carbon-containing feedstock being
delivered to the hydrogen-producing region and the burner assembly
from the same supply stream.
[0015] FIG. 9 is a schematic view of a fuel processor according to
the present disclosure in which the hydrogen-producing region and
the burner assembly both receive fuel, or feed, streams containing
water and a liquid carbon-containing feedstock.
[0016] FIG. 10 is a schematic view showing a variation of the fuel
processor of FIG. 9, with the hydrogen-producing region and the
burner assembly both receiving fuel, or feed, streams containing
water and a carbon-containing feedstock from the same supply
stream.
[0017] FIG. 11 is a schematic view showing another variation of the
fuel processors of FIGS. 9 and 10.
[0018] FIG. 12 is a schematic view showing another burner assembly
according to the present disclosure.
[0019] FIG. 13 is a schematic view showing an ignition region of a
burner assembly that includes an atomization assembly that includes
an atomizing orifice.
[0020] FIG. 14 is a schematic view of an ignition region of a
burner assembly that includes an atomization assembly that includes
a nozzle with an atomizing orifice.
[0021] FIG. 15 is a schematic view of another ignition region of a
burner assembly that includes an atomization assembly that includes
a nozzle with an atomizing orifice.
[0022] FIG. 16 is a schematic view of an ignition region of a
burner assembly that includes an atomization assembly that includes
an impingement member that atomizes the feed stream.
[0023] FIG. 17 is a schematic view of another ignition region of a
burner assembly that includes an impingement member that atomizes
the feed stream.
[0024] FIG. 18 is a schematic view of another ignition region of a
burner assembly according to the present disclosure that includes
an impingement member that atomizes the feed stream.
[0025] FIG. 19 is a cross-sectional view of an ignition region of
another burner assembly that includes an impingement member.
[0026] FIG. 20 is a cross-sectional view of the region of FIG. 19
taken along the line 20-20 in FIG. 19.
[0027] FIG. 21 is a cross-sectional view of another ignition region
of a burner assembly according to the present disclosure that also
combusts a byproduct stream from the fuel processor.
[0028] FIG. 22 is a cross-sectional view of the region of FIG. 21,
taken along the line 22-22 in FIG. 21.
[0029] FIG. 23 is a cross-sectional view of another ignition region
of a burner assembly according to the present disclosure.
[0030] FIG. 24 is a top plan view of the ignition region of FIG. 23
taken along the line 24-24 in FIG. 23.
[0031] FIG. 25 is a cross-sectional view of a portion of the
distribution plate of the ignition region of FIG. 23 taken along
the line 25-25 in FIG. 24.
[0032] FIG. 26 is a cross-sectional view of a variation of the
ignition regions of FIGS. 20 and 22 that includes an extension
sleeve with a reduced-area outlet.
[0033] FIG. 27 is a top plan view of extension sleeve of the
ignition region of FIG. 26.
[0034] FIG. 28 is a cross-sectional view showing another variation
of the ignition regions of FIGS. 23 and 26.
[0035] FIG. 29 is an exploded cross-sectional view of the ignition
region of FIG. 28.
[0036] FIG. 30 is a cross-sectional view of a fuel processor that
includes a burner assembly according to the present disclosure.
[0037] FIG. 31 is a cross-sectional view of another fuel processor
that includes a burner assembly according to the present
disclosure,
[0038] FIG. 32 is a cross-sectional view of the fuel processor of
FIG. 31 taken along the line 32-32 in FIG. 31.
[0039] FIG. 33 is an isometric view of another fuel processor with
a burner assembly according to the present disclosure.
[0040] FIG. 34 is an exploded isometric view of the fuel processor
of FIG. 34.
[0041] FIG. 35 is a side elevation view of the fuel processor of
FIGS. 33 and 34 with the shroud, or cover assembly, removed.
[0042] FIG. 36 is bottom plan view of the fuel processor of FIG.
33.
[0043] FIG. 37 is a cross-sectional view of the fuel processor of
FIG. 33 taken along the line 37-37 in FIG. 36 and with the legs of
the support assembly removed.
[0044] FIG. 38 is a cross-sectional view of the fuel processor of
FIG. 33 taken along the line 38-38 in FIG. 36.
[0045] FIG. 39 is a cross-sectional view of the fuel processor of
FIG. 33.
[0046] FIG. 40 is a schematic diagram of another burner assembly
according to the present disclosure.
[0047] FIG. 41 is a schematic diagram of another burner assembly
according to the present disclosure.
[0048] FIG. 42 is a schematic diagram of another burner assembly
according to the present disclosure.
[0049] FIG. 43 is a side cross-sectional view of another burner
assembly according to the present disclosure.
[0050] FIG. 44 is a fragmentary cross-sectional view showing
variations of the burner assembly of FIG. 43.
[0051] FIG. 45 is a top plan view of another burner assembly
according to the present disclosure.
[0052] FIG. 46 is a side cross-sectional view of the burner
assembly of FIG. 45, taken along the line 46-46 in FIG. 45.
[0053] FIG. 47 is an isometric view of a variant of the burner
assembly of FIG. 45.
[0054] FIG. 48 is an exploded isometric view of the burner assembly
of FIG. 47.
[0055] FIG. 49 is an isometric view of a variation of the burner
assembly of FIGS. 45 and 47.
[0056] FIG. 50 is an isometric view of the burner assembly of FIG.
49 with an installed heating assembly.
[0057] FIG. 51 is an exploded isometric view of the burner assembly
of FIG. 50.
[0058] FIG. 52 is an isometric view of another burner assembly
according to the present disclosure.
[0059] FIG. 53 is a cross-sectional isometric view of the burner
assembly of FIG. 52.
[0060] FIG. 54 is a cross-sectional isometric view showing a
variation of the burner assembly of FIG. 53.
[0061] FIG. 55 is a schematic diagram of a steam reformer with a
burner assembly according to the present disclosure.
[0062] FIG. 56 is a flowchart showing illustrative methods for
using burner assemblies according to the present disclosure.
DETAILED DESCRIPTION AND BEST MODE OF THE DISCLOSURE
[0063] A fuel processing system is shown in FIG. 1 and indicated
generally at 10. System 10 includes a fuel processor 12 that is
adapted to produce a product hydrogen stream 14 containing hydrogen
gas, and preferably at least substantially pure hydrogen gas, from
one or more feed streams 16. Fuel processor 12 is any suitable
device, or combination of devices, that is adapted to produce
hydrogen gas from feed stream(s) 16. Accordingly, processor 12
includes a hydrogen-producing region 19, in which a resultant
stream 20 containing hydrogen gas is produced by utilizing any
suitable hydrogen-producing mechanism(s). By this it is meant that
hydrogen gas is at least a primary constituent of stream 20.
[0064] Examples of suitable mechanisms for producing hydrogen gas
from feed stream(s) 16 include steam reforming and autothermal
reforming, in which reforming catalysts are used to produce
hydrogen gas from a feed stream containing a carbon-containing
feedstock and water. Other suitable mechanisms for producing
hydrogen gas include pyrolysis and catalytic partial oxidation of a
carbon-containing feedstock, in which case the feed stream does not
contain water. Still another suitable mechanism for producing
hydrogen gas is electrolysis, in which case the feedstock is water.
Examples of suitable carbon-containing feedstocks include at least
one hydrocarbon or alcohol. Examples of suitable hydrocarbons
include methane, propane, natural gas, diesel, kerosene, gasoline
and the like. Examples of suitable alcohols include methanol,
ethanol, and polyols, such as ethylene glycol and propylene
glycol.
[0065] Feed stream(s) 16 may be delivered to fuel processor 12 via
any suitable mechanism. While a single feed stream 16 is shown in
FIG. 1, it is within the scope of the disclosure that more than one
stream 16 may be used and that these streams may contain the same
or different feedstocks. This is schematically illustrated by the
inclusion of a second feed stream 16 in dashed lines in FIG. 1.
When feed stream 16 contains two or more components, such as a
carbon-containing feedstock and water, the components may be
delivered in the same or different feed streams. For example, when
the fuel processor is adapted to produce hydrogen gas from a
carbon-containing feedstock and water, these components are
typically delivered in separate streams when they are not miscible
with each other. This is schematically illustrated in dashed lines
in FIG. 1, in which reference numeral 17 represents water and
reference numeral 18 represents a carbon-containing feedstock, such
as many hydrocarbons, that is not miscible with water. When the
carbon-containing feedstock is miscible with water, the feedstock
is typically, but not required to be, delivered with the water
component of feed stream 16, such as shown in the subsequently
described FIG. 2. For example, when the fuel processor receives a
feed stream containing water and a water-soluble alcohol, such as
methanol, these components may be premixed and delivered as a
single stream.
[0066] In FIG. 1, feed stream 16 is shown being delivered to fuel
processor 12 by a feedstock delivery system 22, which schematically
represents any suitable mechanism, device or combination thereof
for selectively delivering the feed stream to the fuel processor.
For example, the delivery system may include one or more pumps that
deliver the components of stream 16 from one or more supplies.
Additionally, or alternatively, system 22 may include a valve
assembly adapted to regulate the flow of the components from a
pressurized supply. The supplies may be located external of the
fuel processing system, or may be contained within or adjacent the
system. When feed stream 16 is delivered to the fuel processor in
more than one stream, the streams may be delivered by the same or
separate feed stream delivery systems.
[0067] An example of a hydrogen-producing mechanism in which feed
stream 16 comprises water and a carbon-containing feedstock is
steam reforming. In a steam reforming process, hydrogen-producing
region 19 contains a reforming catalyst 23, as indicated in dashed
lines in FIGS. 1 and 2. In such an embodiment, the fuel processor
may be referred to as a steam reformer, hydrogen-producing region
19 may be referred to as a reforming region, and resultant, or
mixed gas, stream 20 may be referred to as a reformate stream.
Examples of suitable steam reforming catalysts include copper-zinc
formulations of low temperature shift catalysts and a chromium
formulation sold under the trade name KMA by Sud-Chemie, although
others may be used. The other gases that are typically present in
the reformate stream include carbon monoxide, carbon dioxide,
methane, steam and/or unreacted carbon-containing feedstock.
[0068] Steam reformers typically operate at temperatures in the
range of 200.degree. C. and 700.degree. C., and at pressures in the
range of 50 psi and 300 psi, although temperatures and pressures
outside of this range are within the scope of the invention. When
the carbon-containing feedstock is an alcohol, the steam reforming
reaction will typically operate in a temperature range of
approximately 200-500.degree. C., and when the carbon-containing
feedstock is a hydrocarbon, a temperature range of approximately
400-800.degree. C. will be used for the steam reforming reaction.
As such, feed stream 16 is typically delivered to the fuel
processor at a selected pressure, such as a pressure within the
illustrative range presented above.
[0069] In many applications, it is desirable for the fuel processor
to produce at least substantially pure hydrogen gas. Accordingly,
the fuel processor may utilize a process that inherently produces
sufficiently pure hydrogen gas. When the resultant stream contains
sufficiently pure hydrogen gas and/or sufficiently low
concentrations of one or more non-hydrogen components for a
particular application, product hydrogen stream 14 may be formed
directly from resultant stream 20. However, in many
hydrogen-producing processes, resultant stream 20 will be a mixed
gas stream that contains hydrogen gas and other gases. Similarly,
in many applications, the product hydrogen stream may be
substantially pure but still contain concentrations of one or more
non-hydrogen components that are harmful or otherwise undesired for
the application for which the product hydrogen stream is intended
to be used.
[0070] Accordingly, fuel processing system 10 may (but is not
required to) further include a separation region 24, in which the
resultant, or mixed gas, stream is separated into a hydrogen-rich
stream 26 and at least one byproduct stream 28. Hydrogen-rich
stream 26 contains at least one of a greater hydrogen purity than
the resultant stream and a reduced concentration of one or more of
the other gases or impurities that were present in the resultant
stream. Separation region 24 is schematically illustrated in FIG.
1, where resultant stream 20 is shown being delivered to an
optional separation region 24. As shown in FIG. 1, product hydrogen
stream 14 is formed from hydrogen-rich stream 26. Byproduct stream
28 may be exhausted, sent to a burner assembly or other combustion
source, used as a heated fluid stream, stored for later use, or
otherwise utilized, stored or disposed of. It is within the scope
of the disclosure that byproduct stream 28 may be emitted from the
separation region as a continuous stream responsive to the delivery
of resultant stream 20 to the separation region, or intermittently,
such as in a batch process or when the removed portion of the
resultant stream is retained at least temporarily in the separation
region.
[0071] Separation region 24 includes any suitable device, or
combination of devices, that are adapted to reduce the
concentration of at least one component of resultant stream 20. In
most applications, hydrogen-rich stream 26 will have a greater
hydrogen purity than resultant stream 20. However, it is also
within the scope of the disclosure that the hydrogen-rich stream
will have a reduced concentration of one or more non-hydrogen
components that were present in resultant stream 20, yet have the
same, or even a reduced overall hydrogen purity as the resultant
stream. For example, in some applications where product hydrogen
stream 14 may be used, certain impurities, or non-hydrogen
components, are more harmful than others. As a specific example, in
conventional fuel cell systems, carbon monoxide may damage a fuel
cell stack if it is present in even a few parts per million, while
other possible non-hydrogen components, such as water, will not
damage the stack even if present in much greater concentrations.
Therefore, in such an application, a suitable separation region may
not increase the overall hydrogen purity, but it will reduce the
concentration of a non-hydrogen component that is harmful, or
potentially harmful, to the desired application for the product
hydrogen stream.
[0072] Illustrative examples of suitable devices for separation
region 24 include one or more hydrogen-selective membranes 30,
chemical carbon monoxide removal assemblies 32, and pressure swing
adsorption systems 38. It is within the scope of the disclosure
that separation region 24 may include more than one type of
separation device, and that these devices may have the same or
different structures and/or operate by the same or different
mechanisms.
[0073] Hydrogen-selective membranes 30 are permeable to hydrogen
gas, but are largely impermeable to other components of resultant
stream 20. Membranes 30 may be formed of any hydrogen-permeable
material suitable for use in the operating environment and
parameters in which separation region 24 is operated. Examples of
suitable materials for membranes 30 include palladium and palladium
alloys, and especially thin films of such metals and metal alloys.
Palladium alloys have proven particularly effective, especially
palladium with 35 wt % to 45 wt % copper. A palladium-copper alloy
that contains approximately 40 wt % copper has proven particularly
effective, although other relative concentrations and components
may be used within the scope of the invention.
[0074] Hydrogen-selective membranes are typically formed from a
thin foil that is approximately 0.001 inches thick. It is within
the scope of the present invention, however, that the membranes may
be formed from other hydrogen-permeable and/or hydrogen-selective
materials, including metals and metal alloys other than those
discussed above as well as non-metallic materials and compositions,
and that the membranes may have thicknesses that are greater or
less than discussed above. For example, the membrane may be made
thinner, with commensurate increase in hydrogen flux. Examples of
suitable mechanisms for reducing the thickness of the membranes
include rolling, sputtering and etching. A suitable etching process
is disclosed in U.S. Pat. No. 6,152,995, the complete disclosure of
which is hereby incorporated by reference for all purposes.
Examples of various membranes, membrane configurations, and methods
for preparing the same are disclosed in U.S. Pat. Nos. 6,221,117,
6,319,306, and 6,537,352, the complete disclosures of which are
hereby incorporated by reference for all purposes.
[0075] Chemical carbon monoxide removal assemblies 32 are devices
that chemically react carbon monoxide, if present in resultant
stream 20, to form other compositions that are not as potentially
harmful as carbon monoxide. Examples of chemical carbon monoxide
removal assemblies include water-gas shift reactors and other
devices that convert carbon monoxide to carbon dioxide, and
methanation catalyst beds that convert carbon monoxide and hydrogen
to methane and water. It is within the scope of the disclosure that
fuel processing system 10 may include more than one type and/or
number of chemical removal assemblies 32. FIG. 2 provides a
graphical depiction of a fuel processing system that includes a
separation region 24 with a chemical removal assembly 32. In the
illustrated example, assembly 32 includes a methanation region 34
that includes a methanation catalyst 35. Methanation catalyst 35
converts carbon monoxide and carbon dioxide into methane and water,
both of which will not damage a PEM fuel cell stack. Accordingly,
region 34 may be referred to as including at least one methanation
catalyst bed. Separation region 32 may also include a reforming
region 36 that contains reforming catalyst 23 to convert any
unreacted feedstock into hydrogen gas. In such an embodiment, it is
preferable that the reforming catalyst is upstream from the
methanation catalyst so as not to reintroduce carbon dioxide or
carbon monoxide downstream of the methanation catalyst. When used
to treat the hydrogen-rich stream from one or more
hydrogen-selective membranes, reforming region 36 may be described
as being a secondary, or polishing, reforming region, and it may
also be described as being downstream from the primary reforming
region and/or the hydrogen selective membrane(s).
[0076] Pressure swing adsorption (PSA) is a chemical process in
which gaseous impurities are removed from resultant stream 20 based
on the principle that certain gases, under the proper conditions of
temperature and pressure, will be adsorbed onto an adsorbent
material more strongly than other gases. Typically, it is the
impurities that are adsorbed and thus removed from resultant stream
20. The success of using PSA for hydrogen purification is due to
the relatively strong adsorption of common impurity gases (such as
CO, CO.sub.2, hydrocarbons including CH.sub.4, and N.sub.2) on the
adsorbent material. Hydrogen adsorbs only very weakly and so
hydrogen passes through the adsorbent bed while the impurities are
retained on the adsorbent material. Impurity gases such as
NH.sub.3, H.sub.2S, and H.sub.2O adsorb very strongly on the
adsorbent material and are therefore removed from stream 20 along
with other impurities. Impurity gases such as NH.sub.3, H.sub.2S,
and H.sub.2O adsorb very strongly on the adsorbent material and are
therefore removed from stream 20 along with other impurities. If
the adsorbent material is going to be regenerated and these
impurities are present in stream 20, separation region 24
preferably includes a suitable device that is adapted to remove
these impurities prior to delivery of stream 20 to the adsorbent
material because it is more difficult to desorb these
impurities.
[0077] Adsorption of impurity gases occurs at elevated pressure.
When the pressure is reduced, the impurities are desorbed from the
adsorbent material, thus regenerating the adsorbent material.
Typically, PSA is a cyclic process and requires at least two beds
for continuous (as opposed to batch) operation. Examples of
suitable adsorbent materials that may be used in adsorbent beds are
activated carbon and zeolites, especially 5 .ANG. (5 angstrom)
zeolites. The adsorbent material is commonly in the form of pellets
and it is placed in a cylindrical pressure vessel utilizing a
conventional packed-bed configuration. It should be understood,
however, that other suitable adsorbent material compositions, forms
and configurations may be used.
[0078] PSA system 38 also provides an example of a device for use
in separation region 24 in which the byproducts, or removed
components, are not directly exhausted from the region as a gas
stream concurrently with the separation of the resultant stream.
Instead, these components are removed when the adsorbent material
is regenerated or otherwise removed from the separation region.
[0079] In FIG. 1, separation region 24 is shown within fuel
processor 12. It is within the scope of the disclosure that region
24, when present, may alternatively be separately located
downstream from the fuel processor, as is schematically illustrated
in dash-dot lines in FIG. 1. It is also within the scope of the
disclosure that separation region 24 may include portions within
and external fuel processor 12.
[0080] In the context of a fuel processor that is adapted to
produce a product hydrogen stream that will be used as a feed, or
fuel, stream for a fuel cell stack, the fuel processor preferably
is adapted to produce substantially pure hydrogen gas, and even
more preferably, the fuel processor is adapted to produce pure
hydrogen gas. For the purposes of the present disclosure,
substantially pure hydrogen gas is greater than 90% pure,
preferably greater than 95% pure, more preferably greater than 99%
pure, and even more preferably greater than 99.5% pure. Suitable
fuel processors for producing streams of at least substantially
pure hydrogen gas are disclosed in U.S. Pat. Nos. 6,319,306,
6,221,117, 5,997,594, 5,861,137, pending U.S. patent application
Ser. No. 09/802,361, which was filed on Mar. 8, 2001 and is
entitled "Fuel Processor and Systems and Devices Containing the
Same," and U.S. patent application Ser. No. ______, which was filed
on Apr. 4, 2003, is entitled "Steam Reforming Fuel Processor," and
which claims priority to U.S. Provisional Patent Application Serial
No. 60/372,258. The complete disclosures of the above-identified
patents and patent applications are hereby incorporated by
reference for all purposes.
[0081] Product hydrogen stream 14 may be used in a variety of
applications, including applications where high purity hydrogen gas
is utilized. An example of such an application is as a fuel, or
feed, stream for a fuel cell stack. A fuel cell stack is a device
that produces an electrical potential from a source of protons,
such as hydrogen gas, and an oxidant, such as oxygen gas.
Accordingly, a fuel cell stack may be adapted to receive at least a
portion of product hydrogen stream 14 and a stream of oxygen (which
is typically delivered as an air stream), and to produce an
electric current therefrom. This is schematically illustrated in
FIG. 3, in which a fuel cell stack is indicated at 40 and produces
an electric current, which is schematically illustrated at 41. In
such a configuration, in which the fuel processor or fuel
processing system is coupled to a fuel cell stack, the resulting
system may be referred to as a fuel cell system 42 because it
includes a fuel cell stack and a source of fuel for the fuel cell
stack. It is within the scope of the present disclosure that fuel
processors and burner assemblies according to the present
disclosure may be used in applications that do not include a fuel
cell stack.
[0082] When stream 14 is intended for use in a fuel cell stack,
compositions that may damage the fuel cell stack, such as carbon
monoxide and carbon dioxide, may be removed from the hydrogen-rich
stream, if necessary, such as by separation region 24. For fuel
cell stacks, such as proton exchange membrane (PEM) and alkaline
fuel cell stacks, the concentration of carbon monoxide is
preferably less than 10 ppm (parts per million). Preferably, the
concentration of carbon monoxide is less than 5 ppm, and even more
preferably, less than 1 ppm. The concentration of carbon dioxide
may be greater than that of carbon monoxide. For example,
concentrations of less than 25% carbon dioxide may be acceptable.
Preferably, the concentration is less than 10%, and even more
preferably, less than 1%. Especially preferred concentrations are
less than 50 ppm. It should be understood that the acceptable
minimum concentrations presented herein are illustrative examples,
and that concentrations other than those presented herein may be
used and are within the scope of the present invention. For
example, particular users or manufacturers may require minimum or
maximum concentration levels or ranges that are different than
those identified herein.
[0083] Fuel cell stack 40 contains at least one, and typically
multiple, fuel cells 44 that are adapted to produce an electric
current from the portion of the product hydrogen stream 14
delivered thereto. A fuel cell stack typically includes multiple
fuel cells joined together between common end plates 48, which
contain fluid delivery/removal conduits. Examples of suitable fuel
cells include proton exchange membrane (PEM) fuel cells and
alkaline fuel cells. Others include solid oxide fuel cells,
phosphoric acid fuel cells, and molten carbonate fuel cells.
[0084] The electric current produced by stack 40 may be used to
satisfy the energy demands, or applied load, of at least one
associated energy-consuming device 46. Illustrative examples of
devices 46 include, but should not be limited to motor vehicles,
recreational vehicles, construction or industrial vehicles, boats
or other seacraft, tools, lights or lighting assemblies, appliances
(such as household or other appliances), households or other
dwellings, offices or other commercial establishments, computers,
signaling or communication equipment, etc. Similarly, stack 40 may
be used to satisfy the power requirements of fuel cell system 42.
It should be understood that device 46 is schematically illustrated
in FIG. 3 and is meant to represent one or more devices, or
collection of devices, that are adapted to draw electric current
from the fuel cell system.
[0085] Fuel cell stack 40 may receive all of product hydrogen
stream 14. Some or all of stream 14 may additionally, or
alternatively, be delivered, via a suitable conduit, for use in
another hydrogen-consuming process, burned for fuel or heat, or
stored for later use. As an illustrative example, a hydrogen
storage device 50 is shown in dashed lines in FIG. 3. Device 50 is
adapted to store at least a portion of product hydrogen stream 14.
For example, when the demand for hydrogen gas by stack 40 is less
than the hydrogen output of fuel processor 12, the excess hydrogen
gas may be stored in device 50. Illustrative examples of suitable
hydrogen storage devices include hydride beds and pressurized
tanks. Although not required, a benefit of system 10 or 42
including a supply of stored hydrogen is that this supply may be
used to satisfy the hydrogen requirements of stack 40, or the other
application for which stream 14 is used, in situations when
processor 12 is not able to meet these hydrogen demands. Examples
of these situations include when the fuel processor is starting up
from a cold, or inactive state, ramping up from an idle state,
offline for maintenance or repair, and when the stack or
application is demanding a greater flow rate of hydrogen gas than
the maximum available production from the fuel processor.
Additionally or alternatively, the stored hydrogen may also be used
as a combustible fuel stream to heat the fuel processing or fuel
cell system. Fuel processing systems that are not directly
associated with a fuel cell stack may still include at least one
hydrogen-storage device, thereby enabling the product hydrogen
streams from these fuel processing systems to also be stored for
later use.
[0086] Fuel cell system 42 may also include a battery 52 or other
suitable electricity-storing device that is adapted to store
electricity produced by stack 40. Similar to the above discussion
regarding excess hydrogen, stack 40 may produce electricity in
excess of that necessary to satisfy the load exerted, or applied,
by device 46, including the load required to power system 42. In
further similarity to the above discussion of excess hydrogen gas,
this excess supply may be transported from the system for use in
other applications and/or stored for later use by the system. For
example, the battery or other storage device may provide power for
use by system 42 during startup or other applications in which the
system is not producing electricity and/or hydrogen gas. In FIG. 3,
flow-regulating structures are generally indicated at 54 and
schematically represent any suitable manifold, valves, controllers
and the like for selectively delivering hydrogen and electricity to
device 50 and battery 52, respectively, and to draw the stored
hydrogen and electricity therefrom.
[0087] In FIG. 1, fuel processor 10 is shown including a shell 68
in which at least the hydrogen-producing region, and optionally the
separation region, is contained. Shell 68, which also may be
referred to as a housing, enables the components of the steam
reformer or other fuel processor to be moved as a unit. It also
protects the components of the fuel processor from damage by
providing a protective enclosure and reduces the heating demand of
the fuel processor because the components of the fuel processor may
be heated as a unit. Shell 68 may, but does not necessarily,
include insulating material 70, such as a solid insulating
material, blanket insulating material, and/or an air-filled cavity.
It is within the scope of the invention, however, that the fuel
processor may be formed without a housing or shell. When fuel
processor 10 includes insulating material 70, the insulating
material may be internal the shell, external the shell, or both.
When the insulating material is external a shell containing the
above-described reforming, separation and/or polishing regions, the
steam reformer may further include an outer cover or jacket 72
external the insulation, as schematically illustrated in FIG.
1.
[0088] It is further within the scope of the invention that one or
more of the components of fuel processor 10 may either extend
beyond the shell or be located external at least shell 68. For
example, and as discussed, separation region 24 may be located
external shell 68, such as with the separation being coupled
directly to the shell (as schematically illustrated in FIG. 4) or
being spaced-away from the shell but in fluid communication
therewith by suitable fluid-transfer conduits (as indicated in
dash-dot lines in FIG. 1). As another example, a portion of
hydrogen-producing region 19 (such as portions of one or more
reforming catalyst beds) may extend beyond the shell, such as
indicated schematically with a dashed line in FIG. 1.
[0089] Fuel cell and fuel processing systems have been very
schematically illustrated in FIGS. 1-4, and it should be understood
that these systems often include additional components, such as
air/oxidant supplies and delivery systems, heat exchange assemblies
and/or sources, controllers, sensors, valves and other flow
controllers, power management modules, etc. Similarly, although a
single fuel processor 12 and/or a single fuel cell stack 40 are
shown in various ones of FIGS. 1-4, it is within the scope of the
disclosure that more than one of either or both of these components
may be used.
[0090] As also shown in various ones of FIGS. 1-4, fuel processing
(and fuel cell) systems according to the present disclosure include
a heating assembly 60 that is adapted to heat at least the
hydrogen-producing region 19 of the fuel processor. In systems
according to the present disclosure, heating assembly 60 includes a
burner assembly 62. Burner assembly 62 is adapted to receive at
least one fuel stream 64 and to combust the fuel stream in the
presence of air to provide a hot combustion stream 66 that may be
used to heat at least the hydrogen-producing region 19 of the fuel
processor. As discussed in more detail herein, air may be delivered
to the burner assembly via a variety of mechanisms. In FIG. 4, an
air stream 74 is shown in solid lines, with a dashed line being
used to graphically indicate that it is within the scope of the
disclosure for the air stream to additionally or alternatively be
delivered to the burner assembly with at least one of the fuel
streams 64 for the burner assembly. It is within the scope of the
disclosure that combustion stream 66 may additionally or
alternatively be used to heat other portions of the fuel processing
and/or fuel cell systems with which burner assembly 62 is used. In
FIGS. 1-4, burner assembly 62 is shown in an overlapping
relationship with fuel processor 12 to graphically represent that
it is within the scope of the disclosure that the burner assembly
may be located partially or completely within the fuel processor,
such as being at least partially within shell 68, and/or that at
least a portion, or all, of the burner assembly may be located
external the fuel processor. In this latter embodiment, the hot
combustion gases from the burner assembly will be delivered via
suitable heat transfer conduits to the fuel processor or other
portion of the systems to be heated.
[0091] As indicated in FIG. 4 in dashed lines, fuel processors 12
according to the present disclosure may include a vaporization
region 69 that is adapted to receive a liquid feed stream 16 (or a
liquid component of feed stream 16, such as a stream of water 17 or
a stream of a liquid carbon-containing feedstock 76) and to
vaporize the feed stream (or portion thereof) prior to delivery to
the hydrogen-producing region of the fuel processor. As indicated
schematically in FIG. 4, heated exhaust stream 66 from the heating
assembly may be used to vaporize the feed stream in vaporization
region 69 and/or otherwise heat the feed stream. It is within the
scope of the disclosure that fuel processor 12 may be constructed
without a vaporization region and/or that the fuel processor is
adapted to receive a feed stream that is gaseous or that has
already been vaporized.
[0092] In FIG. 5, another illustrative heating assembly 60 with a
burner assembly 62 is schematically illustrated. As shown, burner
assembly 62 includes an ignition region 86 in which the fuel and
air streams (64 and 74) are ignited to initiate the combustion
thereof. Region 86 includes an ignition source 88, which is any
suitable structure or device for igniting the fuel and air streams.
Examples of suitable ignition sources 88 include at least one of a
spark plug, a glow plug, a pilot light, a combustion catalyst, glow
plugs in combination with combustion catalysts, electrically heated
ceramic igniters, and the like. The streams are ignited and the
combustion thereof produces a heated exhaust stream 66, which
typically is exhausted from the ignition region to a combustion
chamber 92 or other heat transfer region of the steam reformer or
fuel processing system. It is within the scope of the disclosure
that the combustion initiated in ignition region 86 may be
completed in a variety of locations within the burner assembly
and/or fuel processor being heated by the burner assembly. For
example, the combustion may be fully completed in the ignition
region, partially completed in the ignition region and partially
completed in the combustion region, partially completed in the
ignition region, the combustion region and a portion of the fuel
processor external the combustion region, etc.
[0093] When fuel stream 64 is a gaseous stream, it can be mixed and
ignited with air stream 74 to produce exhaust stream 66. However,
some fuel streams 64 are liquid-phase fuel streams at the operating
parameters at which the fuel stream is delivered to burner assembly
62, namely a temperature in the range of ambient (approximately
25.degree. C.) to approximately 100.degree. C. and a pressure in
the range of 50-200 psi, and more typically 100-150 psi. It should
be understood that the operating parameters discussed above are not
intended to be exclusive examples. Instead, they are meant to
illustrate typical parameters, with parameters outside of these
ranges still being within the scope of the invention. For example,
the fuel stream may be heated, through heat exchange or otherwise,
before being delivered to the burner assembly, but this heating is
not required, nor necessarily useful in many embodiments.
[0094] In the context of liquid-phase, or liquid, fuel streams,
such as an alcohol like methanol or ethanol or a hydrocarbon like
methane, ethane, gasoline, kerosene, diesel, etc., the burner
assembly preferably includes an atomization assembly 94. This is
illustrated graphically in FIG. 6, in which the liquid fuel stream
is indicated at 82 and contains a liquid carbon-containing
feedstock 76, and in which the burner assembly that is adapted to
receive and atomize the liquid fuel stream is indicated at 80 and
may be referred to as an atomizing burner assembly. As used herein,
"liquid" is meant to refer to fuel streams that are at least 95%
liquid-phase at the operating parameters at which the fuel stream
is delivered to the burner assembly, and preferably at least
approximately 99% liquid. It should be understood that even a
"completely" liquid-phase stream may include a small (typically
less than 1%) gas phase, such as produced by off gassing as the
stream is heated. Atomization assembly 94 includes any suitable
device or combination of devices that are adapted to convert liquid
fuel stream 82 into an aerosol fuel stream 82' that can be mixed
with air stream 74 and combusted, or ignited, to produce heated
exhaust stream 66. This is contrasted with vaporizing burner
assemblies that heat a liquid fuel stream until the fuel stream
changes phases to a vapor phase. Illustrative examples of suitable
atomization assemblies are discussed in more detail herein.
[0095] As discussed, many conventional fuel processors, such as
steam and autothermal reformers and pyrolysis and partial oxidation
reactors, require a carbon-containing feedstock that is used in the
hydrogen-producing reaction, and then a separate fuel stream that
is used as a fuel source for the burner assembly. As such, these
fuel processors require a separate source, pump or other delivery
assembly, transport conduits and flow-regulating devices, etc.
According to an aspect of the present disclosure, a liquid-phase
carbon-containing feedstock 76 is used for both the
carbon-containing feedstock portion of feed stream 16 and fuel
stream 82 for burner assembly 80, such as schematically illustrated
in FIG. 7. As shown, liquid carbon-containing feedstock 76 is
delivered to both burner assembly 80 and hydrogen-producing region
19. FIG. 7 has been shown in fragmentary view because fuel
processor 12 may have a wide variety of configurations, such as
configurations that do not include a separation region, that
utilize more than one type or number of separation mechanism, etc.
It is intended that the fragmentary fuel processor shown in FIG. 7
(and subsequent Figures) schematically represents any of these
configurations, as well as any of the steam reformers and other
fuel processors described, illustrated and/or incorporated
herein.
[0096] FIG. 8 is similar to FIG. 7, except that the liquid
carbon-containing feedstock 76 is delivered as a single stream to
valve assembly 96, in which the carbon-containing feedstock is
selectively delivered to at least one of the burner assembly and
the hydrogen-producing region. Valve assembly 96 may include any
suitable structure for selectively dividing the stream of
carbon-containing feedstock between the burner assembly and the
hydrogen-producing region. The range of possible configurations
includes the burner assembly receiving all of the carbon-containing
feedstock, the hydrogen-producing region receiving all of the
carbon-containing feedstock, or both the burner assembly and the
hydrogen-producing region receiving carbon-containing feedstock. As
discussed herein, the distribution of the carbon-containing
feedstock depends at least in part upon the particular
carbon-containing feedstock being used, whether byproduct stream 28
is also used as a fuel for burner assembly 80 and the particular
mode of operation of the fuel processor, such as an idle mode, a
startup mode, or a hydrogen-producing mode.
[0097] The distribution of feedstock 76 between the
hydrogen-producing region and the burner assembly may be manually
controlled. However, in many embodiments, it may be desirable for
the distribution to be at least partially automated, such as by
system 10 including a controller 98 that selectively regulates the
delivery of feedstock 76 between the hydrogen-producing region and
the burner assembly. An example of a suitable controller for a
steam reforming fuel processor is disclosed in U.S. Pat. No.
6,383,670, the complete disclosure of which is hereby incorporated
by reference.
[0098] Further reduction in the supplies, delivery systems, flow
regulators, delivery conduits and the like may be achieved
according to another aspect of the present disclosure by feed
stream 16 and fuel stream 82 both containing the same liquid
carbon-containing feedstock 76 and water 17, with the water forming
at least approximately 25% of the stream and the carbon-containing
feedstock preferably being miscible in water. This is schematically
illustrated in FIGS. 9 and 10, in which this composite stream is
indicated at 78. Streams 16 and 82 may have nearly, or completely,
identical compositions, and may be entirely formed from stream 78.
It is within the scope of the disclosure, however, that at least
one of streams 16 and 82 may have at least one additional component
or additional amount of water or carbon-containing feedstock added
thereto prior to consumption of the stream by the burner assembly
or hydrogen-producing region. As discussed previously, in the
context of a steam reformer or other fuel processor that produces
hydrogen gas from water and a carbon-containing feedstock, feed
stream 16 is at least substantially, and typically essentially
entirely, comprised of a mixture of water and a liquid-phase
carbon-containing feedstock 76 that is preferably water-soluble. As
such, a single stream containing water 17 and carbon-containing
feedstock 76 can be consumed as both the hydrogen-producing feed
stream 16, as well as the burner fuel stream 82.
[0099] Similar to the previously discussed alternatives of FIGS. 7
and 8 (where only the carbon-containing feedstock component of feed
stream 16 was delivered to burner assembly 80), feed stream 78 may
be selectively delivered to burner assembly 80 and
hydrogen-producing region 19 in separate streams from the same or a
different source. Alternatively, and as schematically illustrated
in FIG. 10, a single feed stream 78 may be delivered to the fuel
processor, and more specifically to a valve assembly 96, where the
stream is selectively divided between the burner assembly and the
hydrogen-producing region. A controller 98, which may be a
computerized or other electronic controller or preprogrammed
controller, is also shown in dashed lines in FIG. 10. Controller 98
may be located internal or external fuel processor 12, and/or may
include both internal and external components.
[0100] The relative amounts of water 17 and liquid
carbon-containing feedstock 76 in streams 16 and 78 may vary, and
in part will depend upon the particular carbon-containing feedstock
being used. The relative concentrations of these components may be
expressed in terms of a ratio of water to carbon. When feedstock 76
is methanol, a 1:1 ratio has proven effective. When feedstock 76 is
ethanol, a ratio of 2-3:1 has proven effective. When feedstock 76
is a hydrocarbon, a ratio of approximately 3:1 is typically used.
However, the illustrative ratios described above are not meant to
be exclusive ratios within the scope of the invention.
[0101] In FIG. 11, a variation of the configuration of FIG. 10 is
shown to illustrate that it is within the scope of the invention
that the valve assembly may be located either internal or external
fuel processor 10. FIG. 11 also illustrates that when the fuel
processor includes or is otherwise associated with a separation
region 24 that produces a gaseous byproduct stream 28, the gaseous
byproduct stream 28 may be delivered to the burner assembly to be
used as a gaseous fuel for the burner assembly. This gaseous fuel
may supplement the liquid fuel discussed above (such as
carbon-containing feedstock 76 or feed stream 16), or may itself
contain sufficient heating value for certain steam reformers or
other fuel processors and/or certain operating configurations of
the fuel processors.
[0102] As discussed above, in the context of burner assemblies 80
according to the present disclosure, the carbon-containing
feedstock consumed in both the hydrogen-producing region and the
burner assembly is a liquid at the operating parameters at which it
is delivered to the burner assembly. As also discussed, burner
assembly 80 includes an atomization assembly 94 that is adapted to
atomize the liquid fuel stream (82) to produce a gaseous, or
aerosol, stream (82') that is ignited in ignition region 86 with
air stream 74. When the liquid fuel steam has the same composition
as the feed stream for a steam reformer or other fuel processor
that produces hydrogen gas from water and a carbon-containing
feedstock, the liquid fuel stream therefore contains a substantial
water component (typically at least 25%), the stream is a liquid
stream, and atomization assembly 94 produces an aerosol, or
gaseous, stream 78' therefrom, as schematically illustrated in FIG.
12. For the purpose of brevity, the following discussion of
atomization assembly 94 will discuss a fuel stream in the form of a
liquid stream 78 of water 17 and carbon-containing feedstock 76,
with stream 78 having the same composition as the feed stream 16
for a steam reformer or other fuel processor that is adapted to
produce from water and a carbon-containing feedstock a resultant
stream 20 in which hydrogen gas is a primary component. However, it
is within the scope of the present disclosure that the burner
assemblies 80 and/or atomization assemblies 94 illustrated and/or
described herein may also be used with a liquid carbon-containing
feedstock without water, such as when the feedstock is a
hydrocarbon that is not miscible in water. Similarly, and as
discussed previously, it is also within the scope of the disclosure
that stream 78 may be used to form the feed/fuel streams for both
the fuel processor and the burner assembly, but at least one of
these streams may have at least one additional component or
additional amount of water or carbon-containing feedstock added
thereto.
[0103] An illustrative example of a suitable structure for
atomization assembly 94 is shown in FIG. 12 and includes an orifice
100 to which feed stream 78 is delivered under pressure, such as at
a pressure in the range of 50-200 psi, and more typically
approximately 100-150 psi. Orifice 100 is sized to reduce the
liquid feed stream into an aerosol, or gaseous, stream 78' having
sufficiently small droplets that the stream will tend to mix and
disperse with air stream 74 instead of condensing or pooling in the
burner assembly. The particular orifice size to be used in a
particular application will tend to vary with the composition of
the feed stream (or stream of carbon-containing feedstock), the
flow rate of the stream, and the delivery pressure of the stream.
As an illustrative example, for a feed stream containing methanol
and water in the above-discussed mix ratio flowing at a feed rate
of 15-20 mL/min and a pressure in the preferred range presented
above, an orifice 100 having an opening in the range of 0.001-0.015
inches, and more preferably 0.006-0.007 inches, in diameter has
proven effective.
[0104] In FIG. 13, orifice 100 is illustrated schematically as
forming part of the boundary of ignition region 86 through which
stream 78 must pass before reaching ignition source 88. Another
example of a suitable configuration for orifice 100 is a nozzle 102
that optionally extends into region 86 and includes orifice 100,
such as shown in FIG. 14. Regardless of the configuration or
placement of orifice 100, it is preferable that the orifice be
preceded with a filter 106, as schematically illustrated in FIGS.
13 and 14. Filter 106 is sized to remove from stream 78 particulate
that is large enough to clog orifice 100. Filter 106 may be located
at any suitable location upstream from orifice 100.
[0105] FIGS. 13 and 14 also demonstrate that it may be preferable
for the atomized feed stream 78' and air 74 to be introduced into
ignition region 86 at generally intersecting orientations to
promote mixing of the streams as, or prior to, the streams being
ignited by ignition source 88. The amount of heat provided by feed
stream 78 will increase as the percentage of the feed stream that
is fully combusted increases. One mechanism for increasing this
value is to orient the streams or otherwise include structure
within the burner assembly that promotes turbulence, and thus
mixing, of the gas streams.
[0106] In FIG. 14, ignition source 88 is located near the point of
intersection of atomized feed stream 78' and air stream 74. While
effective for igniting the streams, for at least some ignition
sources, it may be desirable for the ignition source to be
positioned within assembly 80 so that it is not in the direct, or
at least primary, combustion (flame) region. An example of such a
configuration is shown schematically in FIG. 15, in which ignition
source 88 is located away from the region at which the streams
intersect. Another example of such a position is shown in dashed
lines in FIG. 15. Because these illustrative configurations locate
the ignition source away from a position where they will be in the
direct flame as the streams are burned, the ignition source will
not be exposed to as high of temperatures as if the source was
located in a region of direct flame. FIG. 15 also graphically
illustrates that ignition region 86 may have an outlet 108 for
heated exhaust stream 66 that has a smaller cross-sectional area
than the ignition region. Expressed in other terms, the ignition
region may promote greater mixing and combustion of the atomized
feed stream and the air stream by restricting the size of the
outlet through which the gases may exit the ignition region after
combustion has been initiated.
[0107] As somewhat schematically illustrated in at least FIGS.
13-15, the fuel and air streams are introduced into the ignition
region via input ports, or delivery conduits, which are indicated
at 101 and 103, respectively. The illustrative examples of the
delivery conduits demonstrate graphically that the conduits include
at least one opening or orifice through which the fluid contained
therein is released into the ignition region, with the conduits
terminating at the boundary of the ignition region, or optionally,
extending into the ignition region. It is within the scope of the
disclosure that any suitable delivery conduits may be used, and
that burner assemblies 80 according to the present disclosure may
include more than one of conduits 101 and 103, with the burner
assemblies thereby being adapted to receive and combust more than
one fuel and/or air stream.
[0108] Another example of a suitable atomization assembly 94 is an
impingement member 110, as schematically illustrated in FIG. 16. In
such an embodiment, stream 78 is delivered under pressure into the
ignition region such that the pressurized liquid stream strikes the
impingement member 110, where it is atomized and produces an
aerosol stream 78' as it ricochets from the surface. In FIG. 16,
member 110 has a contact surface 112 that extends generally
transverse the direction of flow of stream 78. However, it should
be understood that it is within the scope of the invention that
member 110 may have other configurations relative to the feed
stream. FIG. 16 also graphically illustrates that the ignition
region may include one or more baffles or other suitable
turbulent-promoting structures 114.
[0109] Other examples are shown in FIG. 17 and include an
impingement member 110 with a contact surface 116 that extends at
an angle in the range of 15-75.degree. relative to the direction at
which feed steam 78 flows into contact with the surface. At 118, an
example of a non-planar contact surface for impingement member 110
is shown. Surface 118 tends to produce a greater dispersion
pattern, or a more random dispersion pattern than a planar
impingement member, and thereby tends to create greater turbulence
in the stream. At 120, FIG. 17 depicts that a wall of the ignition
region may itself form an impingement member. In FIG. 18, an
impingement member 110 with a non-static contact surface 122 is
shown. By this, it is meant that surface 122 is configured to
rotate, pivot or otherwise move as it is impacted by the
pressurized feed stream. For example, surface 122 may include fins
or other contact surfaces 124 that are rotatably mounted on an axis
126, about which the surfaces rotate as they are acted upon by feed
stream 78 and/or the gas streams flowing within region 86.
[0110] Another example of a burner assembly 80 according to the
present invention is shown in FIGS. 19 and 20. As shown in FIGS. 19
and/or 20, the burner assembly includes an ignition region 86 with
an ignition source 88 that is positioned away from the primary
region in which the atomized feed stream is mixed with air stream
74. Described in other words, the ignition source, which in FIGS.
19 and 20 takes the form of a spark plug, is positioned against a
wall of the ignition region, while feed stream 78 is delivered to
the region approximately in the center of the region relative to
the ignition source. The burner assembly of FIGS. 19 and 20 also
demonstrates an atomization assembly 94 that includes a nozzle 102
with a reduced-diameter orifice 100, as well as an impingement
member 110 with a contact surface 112 positioned to be struck by
feed stream 78 as the feed stream is delivered under pressure into
the ignition region. As also shown, air stream 74 is delivered at
an angle to the region. As shown, the air stream is oriented to
promote swirling, and thus mixing, within the ignition region.
[0111] Another burner assembly 80 according to the invention is
shown in FIGS. 21 and 22 and demonstrates an example of a burner
assembly that is adapted to receive a liquid fuel stream (which in
some embodiments is feed stream 78 and in others is
carbon-containing feedstock 76), as well as a gaseous fuel stream,
such as (but not limited to) byproduct stream 28. As perhaps best
seen in FIG. 21, the illustrated burner assembly also demonstrates
a valve assembly 96 that selectively apportions feed stream 78 to
form a feed stream 16 for the hydrogen-producing region of the
associated fuel processor, and/or to form a fuel stream 82 for the
burner assembly. Another valve assembly 96' is also shown
selectively regulating the flow of byproduct stream 28 to the
burner assembly. While it is within the scope of the disclosure
that the valve assembly may be manually actuated and/or controlled,
it is preferable that the burner assembly and associated fuel
processor include a computerized, or otherwise automated controller
98, such as is shown in FIG. 21 communicating with the valve
assemblies via communication linkages 128, which may be any
suitable form of communication line for control signals or any
suitable mechanical linkage.
[0112] It is within the scope of the disclosure that burner
assembly 80 is located external and spaced-apart from an associated
fuel processor, in which case heated exhaust stream 66 is delivered
to the fuel processor via suitable gas transport conduits, which
preferably are insulated to reduce the heat loss during transfer of
the exhaust stream. Typically, the burner assembly will be directly
coupled to the fuel processor, and optionally at least partially
contained within the shell or other housing of the fuel processor.
In FIGS. 21 and 22, a mounting plate is shown at 130. Plate 130 is
configured to be secured to the fuel processor to position and
retain the burner assembly in an operative position therewith.
Plate 130 may be welded to the fuel processor or otherwise secured
thereto by another mechanism for fixedly securing the burner
assembly to the fuel processor. By "fixedly securing" and "fixedly
secured," it is meant that although it is possible to remove the
plate, the fastening mechanism is not intended to be repeatedly
removed and replaced, and commonly will be damaged during removal.
Alternatively, a selectively removable fastening mechanism, such as
bolts, threaded fittings, etc. may be used. By "selectively
removable" and "removably received," it is meant that the fastening
mechanism is designed to be repeatedly removed and reconnected.
[0113] Another burner assembly 80 according to the present
disclosure is shown in FIG. 23. Similar to the burner assembly
shown in FIGS. 21 and 22, the burner assembly of FIG. 23 is also
adapted to receive byproduct stream 28 or another gaseous
combustible fuel, such as to be used as an auxiliary fuel source to
supplement, or in some applications, replace the fuel stream
comprised of carbon-containing feedstock 76, and more typically
feed stream 78. In FIG. 23, ignition source 88 is again illustrated
as a spark plug, with the spark plug coupled to the burner assembly
by an igniter mount 132. As positioned in FIG. 23, the spark plug
is positioned beneath the level at which the atomized feed stream
is introduced into the ignition region. Accordingly, the spark plug
is sheltered from much of the heat that would otherwise be
transferred to the spark plug if it was mounted within a region of
the burner assembly where it was generally continuously within the
flame produced as the feed and/or byproduct streams are
combusted.
[0114] FIG. 23 also demonstrates a distribution plate 140 that is
adapted to promote the turbulent mixing of byproduct stream 28 and
air stream 74. As shown, the air stream is introduced into a
chamber 142 on the opposite side of the plate as the orifice 100 of
atomization assembly 94, which as shown includes a nozzle 102. In
FIG. 23, atomization assembly 94 has been illustrated as a
removable nozzle 102 that is threadingly received within a socket
143; however, it should be understood that any other suitable
atomization member, such as those described and/or illustrated
herein, may be used. As perhaps best seen in FIGS. 24 and 25, air
stream 74 is delivered into the ignition region by a plurality of
angularly oriented passages 144. The passages have outlets 146 that
are oriented to direct the air flow into intersecting paths, and
inlets 148 through which the air in the previously described and
illustrated chamber 142 enters the passages. Although four sets of
intersecting passages are shown in FIG. 24, it should be understood
that the number of passages may vary, from a single passage to more
than four sets of passages. Also shown in FIGS. 24 and 25 are
distribution conduits 150 within the plate for delivering byproduct
stream 28 to outlets 152, which are oriented to exhaust the
byproduct gas stream in an intersecting path with at least a pair
of the air streams, as perhaps best seen in FIG. 25, in which the
intersection is schematically illustrated at 154.
[0115] It should be understood that the burner assemblies
illustrated in FIGS. 21-26 are not required to utilize byproduct
stream 28. As illustrated, the burner assemblies 80 are configured
to receive and use liquid and gas fuel streams. Therefore, if
byproduct stream 28 is delivered to the burner assemblies, then the
byproduct stream is introduced into the ignition region. However,
if no byproduct stream is delivered to the burner assemblies, then
liquid feed stream 78 (or 82) can still be used.
[0116] As discussed previously with respect to FIG. 15, burner
assemblies according to the present invention may include a
reduced-area outlet 108 from the ignition region to promote
additional mixing and/or combustion or within the ignition region.
Similarly, because the combusting gas streams will be discharged
from region 86 from the reduced-area opening, the combustion that
occurs within heating chamber 92 will also tend to be more
complete. In FIG. 26, the burner assembly of FIG. 23 is shown
including an extension sleeve 160 that essentially extends the
ignition region to provide additional space for combustion and/or
mixing to occur before the gas stream is discharged into the
heating chamber, or combustion region, 92. In FIG. 26, sleeve 160
is shown as a separately formed component from the rest of the
housing for the burner assembly. Sleeve 160 may alternatively be
integrally formed with other portions of the burner assembly's
housing, such as shown in the subsequently discussed FIG. 28. As
perhaps best seen by comparing FIGS. 26 and 27, sleeve 160 includes
a neck 162 with outlet 108, which has a smaller cross-sectional
area than the regions of ignition region 86 leading to the
outlet.
[0117] Although the size of burner assembly 80 may vary within the
scope of the disclosure, it is possible for burner assembly 80 to
be relatively compact and yet still provide sufficient durability
(such as for ignition source 88), mixing and combustion. For
example, when the burner assembly shown in FIG. 26 is sized to
receive 15-20 mL/min of feed stream 78, the ignition region may
have an inside diameter of approximately 2.19 inches, an outlet 108
with an inside diameter of approximately 1.125 inches, a sleeve 160
length of approximately 1.125 inches, and an overall burner
assembly length (measuring in the general direction of flow of feed
stream 78) of approximately 3 inches.
[0118] In FIGS. 23 and 26, atomization assembly 94 was illustrated
as including a removable nozzle 102 that is threadingly received
into a socket within distribution plate 140. To illustrate that
this configuration is but one of many suitable configurations that
are within the scope of the invention, a variation of this
structure is shown in FIGS. 28 and 29. As shown, the atomization
assembly still includes a removable, threaded nozzle 102. However,
in the burner assembly of FIGS. 28 and 29, the nozzle is adapted to
be removably received into a nozzle plug 170, which is itself
removably received into a nozzle sleeve 172 within chamber 142.
[0119] As discussed, burner assemblies 80 according to the present
disclosure are configured to receive a liquid fuel stream that
contains a carbon-containing feedstock, and which may also include
water, such as when the burner assembly and the hydrogen-producing
region of the associated fuel processor utilize the same (or nearly
the same) feed stream. A benefit of such a construction is that the
a steam reformer or other fuel processor that produces hydrogen gas
from water and a carbon-containing feedstock does not need to
include more than a single supply, if the water and water-soluble
liquid carbon-containing feedstock are premixed. If not, then the
fuel processor still only requires a water supply and a
carbon-containing feedstock supply. In contrast, conventional steam
reformers with burner assemblies to heat the reformer require a
fuel supply and associated delivery and monitoring systems for the
burner assembly, and this fuel supply is independent from the fuel
supply for the steam reformer.
[0120] As an illustrative example, startup of a fuel processor 12
in the form of a steam reformer is discussed below. During startup
of a steam reformer or other fuel processor with burner assembly
80, at least a portion (if not all) of feed stream 78 is delivered
to the burner assembly and combusted with air stream 74 to produce
a heated exhaust stream that is used to heat the steam reformer.
When the reformer has been heated to a selected, or predetermined,
temperature, then the feed stream may be instantaneously switched
to the reforming region instead of the burner assembly.
Alternatively, a gradual transition may be used, in which the steam
reformer begins receiving some, and then greater and greater
amounts of the feed stream, while the burner assembly receives less
and less of the feed stream. As hydrogen gas is produced in the
reforming region of the steam reformer, and then purified in one or
more separation regions 24, a gaseous byproduct stream 28 may be
produced and may be delivered to the burner assembly to be used as
a fuel stream. Typically, the predetermined temperature at which
feed stream 78 begins to be delivered to the reforming region is
less than the selected, or predetermined, reforming temperature,
such as 25-125.degree. C., and more typically 50-100.degree. C.,
less than the reforming temperature. One reason for this is that
the reforming reaction typically yields a resultant, or mixed gas
stream, 20 that is hotter than the vaporized feed stream 78'
delivered thereto. Therefore, there is a tendency for the reforming
region to increase in temperature as the feed stream is reformed.
Therefore, heating the reforming region to above the desired
reforming temperature not only results in waste of fuel, but also
may result in the reformer being overheated.
[0121] In some applications, such as most steam reformers in which
the carbon-containing feedstock is methanol, the byproduct stream
should have sufficient heating value that burner assembly 80 will
not require any of feed stream 78 to maintain the reformer within
its selected operating temperatures. However, when other
carbon-containing feedstocks, and especially hydrocarbons, are
used, it may be necessary to either continue to supply the burner
assembly with some of feed stream 78 and/or use some of the product
hydrogen steam as a fuel stream in order to provide sufficient fuel
to maintain the temperature of the reformer.
[0122] In FIGS. 30-39, various illustrative examples of fuel
processors 12 with burner assemblies 80 according to the present
invention are shown. Still other examples of suitable steam
reformers with which burner assemblies according to the present
invention may be used are disclosed in the above-incorporated
patents and patent applications, as well as in U.S. Provisional
Patent Application Serial No. 60/372,258, which was filed on Apr.
12, 2002 and is entitled "Steam Reforming Fuel Processor." The
complete disclosure of each of these references is hereby
incorporated by reference for all purposes. For the purpose of
brevity, each of the above-discussed elements, variants thereof,
and optional additional elements for burner assemblies and fuel
processors according to the present disclosure will not be
indicated and discussed in the following illustrative examples. For
correlational purposes, illustrative ones of the reference numerals
introduced above have been included in FIGS. 30-39; however, and as
discussed, each of these numerals is not rediscussed below. It is
within the scope of the disclosure that other burner assemblies
described, illustrated and/or incorporated herein may be used in
place of the illustrative examples of atomizing burner assemblies
depicted in FIGS. 30-39. For example, any of the previously
described atomizing burner assemblies or any of the subsequently
described diffusion burner assemblies may be used in place of the
illustrative examples depicted in FIGS. 30-39. As discussed, it is
also within the scope of the disclosure that the burner assemblies
illustrated in FIGS. 30-39 may be utilized in other applications,
including in other types and/or configurations of fuel
processors.
[0123] In FIG. 30, an illustrative fuel processor 12 is shown that
is adapted to produce a mixed gas stream containing hydrogen gas
and other gases by steam reforming a feed stream 16 containing
water 17 and a carbon-containing feedstock 76. Steam reforming fuel
processor 200, which may be referred to as a steam reformer,
includes a hydrogen-producing region 19 that contains steam
reforming catalyst 23. As shown, the hydrogen-producing region and
atomizing burner assembly 80 are adapted to receive feed/fuel
streams 82 and 16, respectively, that contain water and a
carbon-containing feedstock. Fuel processor 200 also provides an
illustrative example of a vaporization region 69, in which feed
stream 16 is vaporized prior to delivery to the hydrogen-producing
region of the fuel processor. Fuel stream 82 is combusted with air
stream 74, and the heat produced thereby is used to vaporize the
feed stream and to heat the reforming catalyst in the
hydrogen-producing region to a selected reforming temperature, or
range of temperatures. In the illustrated embodiment, the heated
exhaust stream from the burner assembly flows through passages that
extend through the hydrogen-producing region. As shown, reforming
catalyst 23 surrounds the conduits containing the heated exhaust
stream. It is within the scope of the disclosure that other
configurations may be used, such as in which the reforming catalyst
is housed in conduits, or beds, around which the heated exhaust
stream passes.
[0124] As also indicated in FIG. 30, atomizing burner assembly 80
is also adapted to receive the gaseous byproduct stream 28 from
separation region 24, such as may be produced by one or more
hydrogen-selective membranes 30 that are schematically illustrated
in FIG. 30. As discussed, burner assembly 80 (or one of the
subsequently described diffusion burner assemblies 262) may be
adapted to utilize liquid and/or gasesous combustible fuel streams.
It is within the scope of the disclosure that the burner assembly
may use one type and/or composition of fuel stream during some
operating states of the fuel processor, such as during start up of
the fuel processor, and other types and/or compositions of fuel
stream during other operating states of the fuel processor, such as
during a hydrogen-producing state and/or an idle, or standby,
operating state.
[0125] FIGS. 31 and 32 depict another example of a fuel processor
12 that is adapted to produce hydrogen gas via a steam reforming
reaction. As shown, the steam reforming fuel processor is generally
indicated at 210 and is configured to have a vertical orientation,
in contrast to the illustrative horizontal configuration shown in
FIG. 30. Although not required, a benefit of a vertical orientation
in which the burner assembly introduces the heated exhaust stream
generally within a chamber or annulus defined by at least the
hydrogen-producing region of the steam reformer is that the
reforming catalyst beds (or other hydrogen-producing region used in
other fuel processors within the scope of the present disclosure)
are provided with a thermal symmetry relative to the heated exhaust
stream. As shown, the burner assembly extends generally beneath the
hydrogen-producing region of the fuel processor and produces a
heated exhaust stream that flows into a combustion region 92 that
is at least partially surrounded by the hydrogen-producing and
vaporizing regions of the fuel processor. The illustrated burner
assembly 80 has the configuration of the burner assembly that was
previously described with respect to FIGS. 21 and 22. As discussed,
however, any of the atomizing and diffusion burner assemblies
described, illustrated and/or incorporated herein may be used in
place of the illustrated burner assembly.
[0126] Reformer 210 provides a graphical example of a fuel
processor that includes at least one insulated shell 68. As
indicated in solid lines, the reformer may be described as
including an insulating shell 68 that encloses at least a
substantial portion of the reformer. In the illustrated example,
shell 68 defines a compartment into which the hydrogen-producing,
vaporization and vaporization regions of the fuel processor are
housed, with the shell defining an opening 211 to which a base, or
mount, for the fuel processor is coupled to the shell. As shown,
shell 68 includes various types of insulating material 70, such as
an air-filled cavity, or passage, 212 and a layer of solid
insulating material 214. The depicted examples of insulating
materials are separated by inner layers of shell 68, although it is
within the scope of the disclosure that other shell and/or
insulating configurations maybe used, including fuel processors
that do not include an external shell. As indicated in dashed lines
in FIGS. 31 and 32, shell 68 may alternatively be described as
being surrounded by an insulating jacket 72, such as with
air-filled cavity 212 separating the shell from jacket 72.
[0127] FIGS. 31 and 32 depict examples of several different types
of filters that may be used with fuel processors according to the
present disclosure. For example, at 215 in FIG. 31 a filter is
shown positioned to remove particulate or other types of impurities
from reformate (mixed gas) stream 20 prior to delivery to
separation assembly 24. Also shown in both FIGS. 31 and 32 is an
exhaust filter 216 that is adapted to remove selected impurities or
other materials from the heated exhaust stream produced by the
burner assembly before the exhaust stream exits shell 68, such as
through exhaust opening 218. As indicated in dashed lines, one type
of suitable exhaust filter is a catalytic converter 220, although
others may be used. Also shown in FIGS. 31 and 32 is an orifice 221
through which the exhaust stream passes from an inner chamber of
the shell.
[0128] Similar to the exemplary atomizing burner assembly 80 shown
in FIG. 30, the burner assembly shown in FIGS. 31 and 32 is adapted
to combust with air (such as from air stream 74) and at least one
of a gaseous and a liquid fuel stream. As perhaps best seen in FIG.
31, a common feed stream 78 may be used to supply both a liquid
fuel stream 82 to the burner assembly and a reforming feed stream
16 to the hydrogen-producing (steam reforming) region 19 of the
fuel processor. In such an embodiment, stream 78 contains both
water and a liquid carbon-containing feedstock. As also shown, the
gaseous byproduct stream 28 from a separation region 24 also may be
consumed as fuel for the burner assembly.
[0129] In the illustrated embodiment, the fuel processor utilizes a
separation region that contains at least one hydrogen-selective
membrane 30 to separate the reformate (mixed gas) stream produced
in the hydrogen-producing region into a hydrogen-rich stream 26 and
a byproduct stream 28. As shown, this separation region takes the
form of a module, or housing, 225 that defines a compartment 227
into which reformate stream 20 is delivered under pressure and
separated into streams 26 and 28. In FIGS. 31 and 32, this membrane
module utilizes generally planar membranes 30 that extend generally
transverse to the reforming catalyst beds and the central axis of
the burner assembly. The feed stream for the reformer is vaporized
in vaporization region 69, which takes the form of a central coil
that surrounds at least a portion of combustion region 92. The
vaporized feed stream is distributed to a plurality of reforming
catalyst beds 222 by a distribution manifold 224. The reformate
stream produced in beds 222 is collected in a collection manifold
226 and thereafter delivered to an internal compartment 227 of the
membrane module. At 228, an optional fluid transfer conduit is
shown. Conduits 228, which extend generally between upper and lower
portions of the hydrogen-producing region of the reformer may be
used to control whether various fluid streams flow generally in the
direction of the heated exhaust stream (away from the burner
assembly) or generally toward the burner assembly. For example, the
selected direction of flow may be used to control the temperature
of the fluid within the stream or that is delivered to various
regions of the reformer. As also shown, an insulating member, or
heat shield, 230 may be used to protect the membrane module from
being overheated by the burner assembly. For example, in the
context of hydrogen-selective palladium-copper membranes, it is
generally preferable (although not required) to maintain the
membranes at a temperature that is less than approximately
450.degree. C.
[0130] Reformer 200 also provides an example of a fuel processor
that includes more than one type of separation region 24. As shown
in FIG. 30, the fuel processor also includes a separation region
that includes a carbon monoxide removal assembly 32, such as a
methanation region that contains methanation catalyst 34, with this
second separation region being positioned downstream from a
separation region 24 that contains hydrogen-selective membranes 30.
Accordingly, methanation region 34 is positioned to further purify
the hydrogen-rich stream produced by the hydrogen-selective
membranes.
[0131] In FIGS. 33-39 another illustrative example of a steam
reforming fuel processor utilizing a burner assembly according to
the present disclosure is shown and generally indicated at 240.
Reformer 240 has a similar configuration to reformer 210. Reformer
240 is shown including a burner assembly 80 that is similar in
configuration to the burner assembly shown in FIGS. 28 and 29 to
provide a graphical example that the illustrative reformer may be
used with any of the burner assemblies described, illustrated
and/or incorporated herein. For the purpose of continuity, many of
the above discussed structure and reference numerals are depicted
in FIGS. 33-39. However, each of these structures and/or reference
numerals will not be rediscussed below.
[0132] Reformer 240 provides a graphical illustration that the
steam reformers and other fuel processors with burner assemblies
according to the present disclosure may include heat distribution
structure that is adapted to normalize, or even out the temperature
distribution produced by the heated exhaust stream from the burner
assembly in the combustion region. In this region, even when there
is thermal symmetry of the vaporization region and/or
hydrogen-producing region, it is possible that "hot spots" or
localized regions of elevated temperature may occasionally occur
within the combustion region and/or vaporization region. As shown
in FIGS. 34 and 37-39, reformer 240 includes a pair of heat
diffusion structures 250 and 252. Structure 250 is adapted to
reduce and/or dissipate these hot spots as heat is transferred from
combustion region 92 to vaporization region 69. Diffuser 250 is
adapted to provide a more even temperature distribution to
vaporization region 69 than if the diffuser was not present.
Because the diffuser will conduct and radiate heat, hot spots will
tend to be reduced in temperature, with the heat in hotter areas
distributed to surrounding areas of the diffuser and surrounding
structure. An example of a suitable material for diffuser 250 is
FeCrAlY or one of the other oxidation-resistant alloys discussed
above.
[0133] In embodiments of reformer 240 (or other fuel processors)
that include a diffuser, a suitable position for the diffuser is
generally between the vaporization region and the heating assembly,
as indicated with diffuser 250 in FIGS. 34 and 37-39. The diffuser
typically will extend at least substantially, if not completely,
around the vaporization region and/or the heating assembly. Another
suitable position is for the diffuser to surround
hydrogen-producing region 19, as illustrated at 252. It is within
the scope of the disclosure that one or more diffusers may be used,
such as in an overlapping, spaced-apart and/or concentric
configuration, including a reformer that includes both of the
illustrative diffuser positions shown in FIGS. 34 and 37-39.
[0134] In the illustrative configurations shown in FIGS. 34 and
37-39, the plurality of reforming catalyst beds 222 may be
described as collectively defining inner and outer perimeters, with
the diffuser extending at least substantially around at least one
of the inner and/or the outer perimeters of the plurality of
reforming catalyst beds. At least diffuser 250 should be formed
from a material through which the combustion exhaust may pass.
Examples of suitable materials include woven or other metal mesh or
metal fabric structures, expanded metal, and perforated metal
materials. The materials used should be of sufficient thickness or
durability that they will not oxidize or otherwise adversely react
when exposed to the operating parameters within reformer 240. As an
illustrative example, metal mesh in the range of 20-60-mesh has
proven effective, with mesh in the range of 40-mesh being
preferred. If the mesh is too fine, the strands forming the
material will tend to oxidize and/or will not have sufficient
heat-conducting value to effectively diffuse the generated
heat.
[0135] As discussed herein, steam reformers and other fuel
processors with burner assemblies according to the present
disclosure will often be in communication with a controller that
regulates the operation of at least a portion of the burner
assembly and/or the entire fuel processor, fuel processing system,
or fuel cell system responsive to one or more measured operating
states. An example of a suitable controller for a steam reforming
fuel processor is disclosed in U.S. Pat. No. 6,383,670, the
complete disclosure of which is hereby incorporated by reference
for all purposes. Accordingly, the reformers may include various
sensors 254, such as temperature sensors, pressure sensors, flow
meters, and the like, of which several illustrative examples are
shown in FIGS. 34-39.
[0136] Also shown in FIGS. 34-35 and 37-38 is an optional
evaporator 256 that is adapted to vaporize any residual
liquid-water content in exhaust stream 66. In many embodiments,
evaporator 256 will not be necessary. However, in some embodiments,
additional fluid streams are mixed with the exhaust stream external
hydrogen-producing region 19 to reduce the temperature of the
resulting stream. As an example, the cathode air exhaust from a
fuel cell stack may be mixed with stream 66. This air exhaust
stream has a vapor pressure of water that exceeds the stream's
saturation point. Accordingly, it contains a mixture of liquid
water and water vapor. To prevent water from condensing or
otherwise depositing within the reformer or other fuel processor,
such as on separation region 24, evaporator 256 may be used.
[0137] Another burner assembly 62 according to the present
disclosure is schematically illustrated in FIG. 40 and generally
indicated at 262. As shown, burner assembly 262 includes a
diffusion region 270 in which a combustible fuel stream 64 is mixed
with an air stream 74 to form an oxygenated combustible fuel stream
74. Therefore, and in contrast to burner assemblies that receive
premixed streams of fuel and oxidant, burner assemblies according
to at least this aspect of the present disclosure receive at least
one combustible fuel stream and at least one air/oxygen stream, and
then mix these streams in diffusion region 270. Although described
herein as an air stream 74, it is within the scope of the
disclosure that stream 74 may have a greater oxygen content than
air, that the stream may be otherwise depleted in components
present in air, enriched in one or more of these components, and/or
contain one or more components that are not normally present in
air. In the illustrated embodiment, the fuel stream is a gaseous
combustible fuel stream 276.
[0138] Diffusion region 270 includes diffusion structure 278 that
is adapted to promote the formation of one, and typically a
plurality of, oxygenated combustible fuel streams 274, as
schematically indicated in FIG. 40. The oxygenated combustible fuel
stream, which may also be referred to as the oxygenated fuel stream
is then delivered to a combustion region 92, where it is ignited to
produce a heated exhaust stream 66, which may also be referred to
herein as a combustion stream 66. Combustion region 92 includes at
least one ignition source 88, which is adapted to ignite the
oxygenated fuel stream. Ignition source 88 may optionally be
described as being within an ignition region 86 within the
combustion region. An example of a suitable diffusion structure 278
is a structure that promotes mixing of the gaseous streams into a
relatively uniform mixture of air/oxygen and gaseous fuel. The
resulting stream 274 will tend to burn cleaner and more efficiently
than if the diffusion structure is not present.
[0139] As shown in FIG. 41, burner assemblies 262 according to the
present disclosure may additionally or alternatively include a
distribution region 284, in which at least one of the air and/or
fuel streams is divided into a plurality of smaller streams.
Accordingly, distribution region 84 includes distribution structure
86, which is adapted to receive and divide at least one of the fuel
and air streams into a plurality of smaller streams. Although not
required, burner assemblies 262 that receive a primary air stream
and a primary fuel stream preferably include distribution regions
284 that are adapted to receive and divide each of these streams
into a plurality of smaller streams. This is schematically
illustrated in FIG. 41, where air stream 74 is divided into a
plurality of smaller air streams 74' and fuel stream 276 is divided
into a plurality of smaller fuel streams 276'. As shown, streams
72' and 276' are mixed in diffusion region 270 to produce a
plurality of oxygenated fuel streams 274, which are ignited in
combustion region 92. As used herein in the context of the flows of
fluid streams, "smaller" refers to the mass/molar flow rate of the
streams compared to the corresponding mass/molar flow rate of the
primary stream.
[0140] An example of a suitable distribution structure 286 is
structure that subdivides the air and combustible fuel streams into
a plurality of smaller streams that are delivered in pairs or other
groupings of at least one of each subdivided stream to an ignition
source. This configuration provides cleaner, more efficient
combustion of the original fuel stream because the overall flow of
the fuel stream is divided into smaller streams that are mixed with
one or more corresponding air streams. This configuration enables
better overall diffusion, or mixing, of the streams and enables
combustion to be completed with a smaller flame than a comparative
burner assembly in which the fuel and oxidant streams are not
divided prior to combustion. As indicated in dashed lines in FIG.
41, distribution region 284 is preferably configured to divide the
fuel and air streams without mixing, or enabling diffusion, of the
streams. Therefore, although illustrated schematically as a single
box in FIG. 41, the distribution region may be implemented as
separate regions for the air and the fuel streams and/or may
include distribution structure that is adapted to maintain the fuel
and air streams separate from one another until the smaller streams
are delivered to diffusion region 270.
[0141] Burner assemblies 262 according to the present disclosure
may additionally or alternatively be configured to receive a
combustible fuel stream 64 in the form of a liquid combustible fuel
stream 82. Illustrative, non-exclusive examples of liquid
combustible fuel streams 82 include streams that contain as at
least a majority component one or more liquid alcohols or
hydrocarbons. An example of such a burner assembly is schematically
illustrated in FIG. 42. As shown, fuel stream 82 is delivered to a
vaporization region 92, in which the stream is vaporized to form a
vaporized fuel stream 294. The vaporized fuel stream is delivered
to distribution region 284, where it is divided into a plurality of
smaller fuel streams 294'. As shown, distribution region 284 also
receives air stream 74 and divides the air stream into a plurality
of smaller air streams 74'. Streams 74' and 294' are delivered to
diffusion region 270, where they are mixed in selective pairs or
similar groupings to produce a plurality of oxygenated fuel streams
274'.
[0142] FIG. 42 also graphically illustrates in dashed lines that
burner assemblies 262 according to the present disclosure may
additionally or alternatively be configured to receive and combust
both liquid and gaseous combustible fuel streams 82 and 276. In
embodiments where the burner assembly also receives a combustible
gaseous fuel stream 276, streams 294, 294' and 274' will contain
both vaporized and gaseous combustible fuels.
[0143] As shown in FIG. 42, the burner assembly includes a
vaporizing heating assembly 296 that is adapted to heat the
vaporizing region to vaporize the liquid combustible fuel stream.
Also shown in FIG. 42 is a fuel stream 298 for the vaporizing
heating assembly. Stream 298 will tend to vary in composition
and/or form depending upon the particular structure of vaporizing
heating assembly 296. For example, when assembly 296 is adapted to
combust a combustible fuel stream, then stream 298 will contain
such a stream. Similarly, when assembly 296 is an electrically
powered heating assembly, then stream 298 will include an
electrical connection to a power source (including, but not
required to be or limited to, fuel cell stack 40 and/or battery
52).
[0144] For purposes of illustration, the components of the burner
assemblies shown in FIGS. 40-42 have been illustrated as being
spaced-apart from each other, with the corresponding streams being
delivered between these components. Although not required, actual
burner assemblies will typically have at least one, if not all of
these components housed together within, and/or collectively
define, a common shell or housing. For example, the entire burner
assembly may be contained within a shell or housing. As another
example, two or more of the burner assemblies' functional regions
may be integrated or otherwise contained within a common shell or
housing. As an illustrative example of this alternative, the
diffusion and combustion regions may be integrated together so that
the air and fuel streams are separately introduced into the
combustion region, but introduced in a manner that promotes
diffusion of the streams as they are introduced and ignited.
[0145] FIG. 43 provides a less schematic example of a diffusion
burner assembly 262 according to the present disclosure. As shown
and generally indicated at 300, the burner assembly is configured
to receive gaseous and/or liquid combustible fuel streams 64
through respective gas and liquid input ports 302 and 304. Although
only a single one of each port is shown in FIG. 43, it is within
the scope of the disclosure that two or more of each port may be
used. When burner assembly 300 is adapted to receive both liquid
and gaseous fuel streams, the burner assembly will typically be
installed with each port connected via suitable conduits to
respective supplies from which the fuel streams are obtained. When
the burner assembly is adapted to receive only a gaseous or only a
liquid fuel stream, one of the ports may be eliminated, blocked, or
otherwise not functionally present in the burner assembly.
[0146] As shown in FIG. 43, liquid stream 82 is delivered to
vaporization region 292, where it is vaporized and forms vaporized
fuel stream 294, such as by heat provided by vaporizing heating
assembly 296. Instead of being delivered as a single vaporized gas
stream to combustion region 92 (with or without premixing of air),
the vaporized gas stream must pass through distribution region 284,
where distribution structure 286 divides the vaporized fuel stream
294 into a plurality of streams 294'. Furthermore, streams 294' are
then mixed through diffusion with a corresponding plurality of air
streams 74', and the resulting oxygenated fuel streams 274' are
combusted to collectively produce hot combustion stream 66.
Therefore, burner assembles 262 according to the present disclosure
are configured to receive combustible fuel and air streams, and
divide these streams into a plurality of streams that each contain
only a minority, and often 10% or less, of the original flow. The
smaller streams are then mixed, ignited, and recombined to form
combustion stream 66.
[0147] As shown in FIG. 43, distribution structure 286 includes a
fuel distribution manifold 310, which includes a plurality of fuel
apertures 312 into which the vaporized fuel stream may flow into a
corresponding plurality of fuel tubes 314. In the illustrated
embodiment, apertures 312 define the inlets to tubes 314. As shown,
the tubes are spaced-apart from each other and extend from manifold
310 to combustion region 92, where the tubes terminate at outlets
316 from which the fuel streams are delivered into the combustion
region. Therefore, instead of receiving a single vaporized fuel
stream with a flow rate that is at least approximately equal to the
flow rate of the original liquid fuel stream that was delivered to
vaporization region 292, the combustion region receives a plurality
of vaporized fuel streams that each contain only a minority
fraction of the original flow. For example, each stream may contain
25% or less of the original flow. It is within the scope of the
disclosure that each stream may contain less than 20%, less than
15%, less than 10%, less than 5%, between 1-10%, or between 2-5% of
the original flow. It should be understood that the percentage of
the original flow that passes through the individual tubes is
largely dependent upon the number of such tubes that are present
and available to receive the vaporized fuel stream. Accordingly, it
should also be understood that the number of tubes shown in FIG. 43
has been selected for representation purposes only and that the
actual number may vary, such as depending upon one or more of the
desired flow rate through each tube and the desired proportion of
the total flow desired through each tube.
[0148] The number and size of tubes 314 is preferably, but not
required to be, selected to maintain the flow velocity of the
combustible fuel passing through the tubes to be below the
flame-front velocity of the particular fuel. By this it is meant
that the combustible fuel streams preferably are not flowing at
such a velocity, or fluid flow rate, that the flames lift off of
the outlets 316 of the tubes. For purposes of illustration a flame
is shown in FIG. 43 at 318. As shown, the flame may be described as
being attached to outlet 316 because combustion is initiated at the
outlet, as opposed to at a region spaced above the outlet. This
latter, less desirable situation is schematically illustrated in
FIG. 44 at 318'. Flame 318' tends to be less stable than flame 318,
and will often result in less efficient combustion and a less
uniform flame. As such, the flame is more likely to flameout and
may also impinge against adjacent structure that would not be
impinged against by flame 318. This impingement may produce
undesirable combustion byproducts, lower the heating value of the
combustible fuel stream, and/or damage or weaken the impinged upon
structure. Although tubes 314 are shown in FIGS. 43 and 44 as
having right cylindrical configurations, it is within the scope of
the disclosure that other cross-sectional and lengthwise
configurations may be used. Similarly, stainless steel tubes have
proven effective in experiments, but it is within the scope of the
disclosure that any other suitable material may be used. Preferably
the tubes are not configured so that the vaporized fuel stream is
cooled to the point of condensing, as the condensed liquid may
obstruct the tubes and prevent further passage of vaporized fuel
therethrough.
[0149] Preferably, each tube 314 forms a portion of manifold 310 or
is otherwise in fluid communication therewith such that any gas
passing through one of apertures 312 passes into the tube and
cannot flow into the subsequently described air distribution
chamber 322. Fuel distribution manifold 310 may, in at least some
embodiments, be referred to as a distribution plenum, in that it
maintains the pressure within vaporization region 292 at least
slightly greater than the pressure in the plurality of fuel tubes.
This pressure differential promotes distribution of the vaporized
fuel stream between the tubes, and in embodiments where both
gaseous and vaporized fuel streams are present in vaporization
region 292, promotes mixing of the streams within vaporization
region 292.
[0150] When burner assembly 300 receives a gaseous combustible fuel
stream 276 in addition to liquid combustible fuel stream 82, the
gaseous fuel stream is also delivered to the vaporization region,
where it mixes with the vaporized fuel stream and the resultant
stream is distributed between the fuel tubes. This is schematically
illustrated in dashed lines in FIG. 43, where the tubes are shown
including streams 294", which contain both gaseous and vaporized
combustible fuels. It is within the scope of the disclosure that
the gaseous and vaporized fuel streams may be only partially mixed
prior to entering the fuel tubes and that further mixing or
diffusion of the streams may occur within the individual fuel
tubes. Similar to the above discussion of the flow rates of streams
294', it should be understood that each of the streams 294" will
include a minority fraction of the original flows of the liquid and
gaseous combustible fuel streams, with the above-described
illustrative percentages being again applicable.
[0151] As discussed, the burner assembly additionally or
alternatively may be implemented or configured so that it only
receives a gaseous combustible fuel stream 276. In such an
application or implementation, the vaporization region may be
referred to as a staging region, in that the gaseous combustible
fuel stream is delivered into the region and then divided into a
plurality of smaller streams 276' by fuel distribution manifold (or
plenum) 310.
[0152] Burner assembly 300 also includes at least one air input
port 320 through which air stream 74 is delivered into distribution
region 284. As shown in FIG. 43, the air stream is delivered into
an air distribution chamber 322 in which the air may flow around
the plurality of fuel tubes. As also shown in FIG. 43, the
distribution structure includes a combustion distribution manifold
324. Manifold 324 is adapted to divide the air stream 74 that is
delivered into chamber 322 into a plurality of air streams 74',
with each stream 74' containing only a minority fraction of the
original air stream. For example, each stream may contain 25% or
less of the original flow. It is within the scope of the disclosure
that each stream may contain less than 20%, less than 15%, less
than 10%, less than 5%, between 1-10%, or 2-5% of the original
flow. In at least some embodiments of the burner assembly,
combustion distribution manifold 324 may be referred to as a
combustion plenum, in that it maintains the pressure within chamber
322 at least slightly greater than the pressure within combustion
region 92. This pressure differential promotes the even flow of air
into the combustion region and restricts the flow of the fuel
streams into the air distribution chamber.
[0153] As shown in FIG. 43, manifold (or plenum) 324 includes a
plurality of apertures 326 through which air streams 74' flow into
the combustion region. As also shown, the apertures are sized so
that tubes 314 may extend into, and in the illustrated embodiment
through, the apertures. As shown, the tubes are concentrically
located within apertures 326 so that each fuel stream (such as
276', 294' or 294") is surrounded by a corresponding air stream 74'
as it exits the corresponding tube 314. As each fuel stream exits
its corresponding tube 314, it is mixed through diffusion with the
surrounding air stream 74' to produce an oxygenated fuel stream
274', which is ignited, such as by ignition source 86. As such, the
region in which the air and fuel streams are diffused together may
be referred to as the diffusion region of the burner assembly, with
the configuration of outlets 316 and apertures 326 providing the
diffusion structure, which enables the pairs of air and fuel
streams to diffuse together. The hot combustion gases produced from
the plurality of streams 274' collectively form a hot combustion
stream 66.
[0154] The distribution of the combustible fuel and air streams
into a plurality of smaller, and optionally concentric, streams
enables the burner assembly to complete combustion of the fuel
streams with a smaller flame than otherwise would be obtained if
the original streams were not divided. As the number of tube and
aperture assemblies is increased for a fixed feed of fuel/air, the
proportional flow through each tube decreases. As such, the
distance required for complete diffusion and combustion of the fuel
delivered by that assembly will tend to be reduced. For example,
the subsequently described and illustrated burner assembly shown in
FIGS. 45-50 is adapted to complete combustion of combustible fuel
delivered at a flow rate of 60 mL/min within 6 inches, and more
commonly within approximately 4 inches of outlets 316.
[0155] Similar to the above discussion about the velocity at which
the plurality of fuel streams are delivered to the diffusion and
combustion regions, air streams 74' are also preferably delivered
to the diffusion and combustion regions at velocities that do not
cause or promote flameout or separation of the flames from outlets
316. It should be understood that the size of apertures 326 may be
selected to provide the desired mass/molar flow of oxygen without
producing an undesirable velocity for the air stream.
[0156] Preferably, air streams 74' are delivered so that at least
the stoichiometric amount of oxygen required for complete
combustion is delivered to each combustible fuel stream. For
example, a liquid combustible fuel stream that contains a mixture
of approximately 70% (by volume) methanol and the balance water
stoichiometrically requires approximately 40 L/min air. Preferably,
and to provide an excess, or buffer, of oxygen, more than the
stoichiometrically required amount of oxygen is delivered. For
example, the oxygen in streams 74' may be present at greater than
approximately 1, 2, 3 or more times the stoichiometrically required
amount of oxygen for a particular composition of combustible fuel.
An air stream 74' that contains an oxygen component that is present
in the range of 1.1-1.3 times the stoichiometrically required
amount of oxygen has proven effective, but other oxygen flow rates
that are above and below this amount may be used and are within the
scope of the disclosure.
[0157] Burner assemblies 262 constructed according to the present
disclosure may be effectively utilized with several times the
stoichiometrically required amount of oxygen. For example, when
200-500% excess air is delivered to the burner assembly, the burner
assembly still effectively combusts the fuel streams and produces a
hot combustion stream. The impact of this excess air is that the
flame will be cooler, or in other words, hot combustion stream 66
will not be as hot as a comparative stream produced with less
excess air. The amount of excess air provides a mechanism by which
the amount of heat produced by the burner assembly may be
controlled by controlling the rate at which air is delivered to the
burner assembly. As discussed above, when it is envisioned that the
burner assembly will be utilized in such an excess air
configuration, apertures 126 may be sized so that the resulting
streams 74' of excess air do not travel at sufficient velocities to
cause flameout, and preferably are sized so that the flames are not
separated from outlets 316.
[0158] In the embodiment illustrated in FIG. 43, each fuel tube 314
extends through one of apertures 326 in combustion manifold 324. In
this configuration for diffusion structure 278, the portion of air
stream 74 that passes through each aperture 326 produces an airflow
that surrounds the respective outlets of the fuel streams. A
benefit of such a configuration is that the combustible fuel stream
is delivered above combustion manifold 324, thereby reducing the
chance that the combustible fuel will flow into the diffusion
region external the tubes. It is within the scope of the
disclosure, however, that one or more of the fuel tubes may have
outlets 316 that ate co-terminus with the combustion- or
distribution-faces (330 and 332, respectively) of combustion
manifold 324, anywhere in between, or even that the tubes terminate
prior to reaching manifold 324. Because the air stream is delivered
into the distribution region external the tubes and cannot flow
into vaporization region 292, the air stream will create a positive
flow of gas from distribution region 284 to the diffusion and
combustion regions 270 and 92. Examples of several of the
above-described variations are graphically illustrated in FIG. 44.
As shown, tubes 314 on the left side of FIG. 44 do not extend
beyond the combustion-surface 330 of manifold 324, and the tubes
314 on the right side of FIG. 44 terminate generally between the
combustion- and distribution-surfaces 332 and 330 of manifold
324.
[0159] As discussed, burner assemblies 262 according to the present
disclosure may be configured to receive only one of a gaseous or a
liquid combustible fuel stream. In embodiments or applications
where only a gaseous combustible fuel stream is received, it should
be understood that heating assembly 96 is not required. In fact,
when the burner is configured to only receive gaseous combustible
fuel streams, the burner assembly may be formed without the
vaporizing heating assembly, as shown on the left side of FIG. 44.
When the burner assembly is selectively used with either or both of
the above fuel streams, the burner assembly will tend to be
present, but will generally not be used when only a gaseous fuel
stream is received into the vaporization region.
[0160] On the right side of FIG. 44, several optional
configurations are shown for vaporization region 292 and the
corresponding vaporizing heating assembly 296 of burner assemblies
that are configured to receive a liquid combustible fuel stream,
either alone or in addition to a gaseous combustible fuel stream
276. As shown, vaporization region 292 includes a base 340 and a
partition 342 that extends from the base generally toward fuel
distribution manifold 310. Partition 342 creates a well, or
reservoir, 344 into which liquid combustible fuel stream 82 is
initially delivered upon introduction into the vaporization region.
Reservoir 344 enables a volume of liquid combustible fuel stream 82
to be delivered into the vaporization region and to pool or
accumulate, in the reservoir. The level of the pooled stream will
rise until it reaches the height of the partition, at which point
the delivery of an additional amount of stream 82 will cause some
of the stream to pour over the partition. When this occurs, then at
least the portion that pours (or spatters) over the partition will
contact the region 352 of base 340 that does not extend under
reservoir 344, where it is vaporized by heat provided by heating
assembly 296.
[0161] A benefit of this configuration is that the burner assembly
has a "reserve" or "buffer" 346 of liquid combustible fuel. For
example, should the flow rate of stream 82 to burner assembly 300
be interrupted or otherwise non-uniform, the reserve can be
vaporized as it is heated to maintain a flow of vaporized fuel to
the combustion region. While the flow of vaporized fuel from the
reservoir when no new liquid combustible fuel is being delivered to
the reservoir may be less than the corresponding flow that would be
produced if stream 82 was uniformly delivered to the burner
assembly, it still provides a mechanism by which the flame created
in combustion region 92 is less likely to be extinguished.
Therefore, the reservoir may be described as a mechanism for
leveling, or equalizing, the flow of combustible fuel to combustion
region 92 relative to the rate at which it is delivered to
vaporization region 292. A benefit of this construction is that
unstable delivery of combustible fuel to the combustion region may
cause flameouts, such as when there is no flow of combustible fuel
or a period of low flow followed immediately by a period of much
greater flow. Even when these fluctuations do not cause the flame
to be completely extinguished, they will still tend to cause
instability in the flame, such as flare-ups and periods of
incomplete combustion. Therefore, burner assemblies with the
structure shown in FIG. 44 are less likely to encounter flameout,
or unstable combustion, situations than conventional liquid-fuel
burners that do not have this structure.
[0162] As a variation of the above construction, partition 342 may
include one or more ports, channels or similar conduits 348
therethrough that enables some of the liquid combustible fuel
stream to flow through the partition. Preferably, the conduit or
conduits are sized such that the flow rate of combustible liquid
fuel that flows through the conduits per unit time is not greater
than the flow rate of stream 82 into the vaporization region. In
other words, when partition 342 includes one or more conduits 348,
stream 82 is preferably delivered into the vaporization region at a
flow rate that exceeds the rate at which the liquid fuel flows
through the one or more conduits 348. In this configuration, a
reserve of liquid fuel will be established and continuously
replenished as long as the flow of stream 82 is not interrupted or
diminished for a sufficient time that the reserve of liquid fuel is
depleted, such as by flowing through the partition and/or being
vaporized. However, as long as the reservoir contains a supply of
liquid fuel that may flow through the partition and be vaporized,
the net flow of vaporized fuel to distribution region 284 will be
comparatively stable or normalized, even if the flow rate of stream
82 tends to vary over time.
[0163] For example, one suitable mechanism for delivering stream 82
to vaporization region2 92 is to use a pump. Some pumps, such as
reciprocating piston pumps, deliver liquid in intervals (such as
during half of each piston cycle) and therefore do not provide a
constant flow of stream 82. Accordingly, a reciprocating piston
pump will tend to deliver flows of stream 82 in intervals, and the
use of partition 342 (with or without conduit(s) 348) can stabilize
or normalize the flow of vaporized fuel produced therefrom.
[0164] As indicated at the bottom of FIG. 44, it can be seen that
the vaporization heating assembly may be configured to heat the
entire base 340 of the vaporization region, including the portion
of the base that underlies reservoir 344. A benefit of this
construction is that all of the liquid fuel stream will be
eventually vaporized by the vaporizing heating assembly. An
alternative configuration is schematically illustrated in dashed
lines. In this alternative configuration, the vaporization heating
assembly is adapted to either not directly heat the portion 350 of
the base beneath the reservoir, or to not heat that region to as
high of temperature as the portion 352 of the base upon which the
liquid combustible fuel stream is intended to be vaporized. For
example, the vaporization heating assembly may be located generally
beneath only portion 352. Expressed in different terms, the
reservoir may be offset or otherwise located distal the heating
assembly. As an additional or alternative implementation, portion
350 may be insulated or formed from a material which is not as
conductive as the material from which the rest of the base is
formed.
[0165] Another burner assembly 262 constructed according to the
present disclosure is shown in FIGS. 35 and 36 and generally
indicated at 400. As used herein, similar elements and subelements
will retain the same reference numerals between the various
illustrative embodiments of the burner assemblies, fuel processing
and fuel cell systems disclosed and/or illustrated herein. It is
within the scope of the disclosure that these later-referenced
structures may (but are not required to) have the same elements,
subelements and variations as the earlier presented structure. As
an illustrative example, burner assembly 400 includes a
vaporization region 292 with a partition 342. However, and similar
to previously discussed embodiments, it is within the scope of the
disclosure that burner assembly 400 may be formed without a
reservoir and/or with a reservoir that includes one or more
conduits 348 that extend through the partition. As another example,
although the fuel tubes shown in FIG. 46 extend through combustion
distribution manifold 324, it is within the scope of the disclosure
that the tubes may have any of the other relative positions,
geometries and the like that are illustrated and/or described
herein. For the purpose of simplifying the drawings, every
subelement and/or optional structure will not be repeatedly
discussed and/or labeled in each illustrated view of burner
assemblies according to the present disclosure.
[0166] As shown in FIGS. 45 and/or 46, burner assembly 400 includes
a housing 402 within which its combustion, diffusion and
distribution regions are housed. In the illustrated embodiment,
housing 402 has a generally cylindrical configuration and includes
a mount 404 that is sized to couple the burner assembly with a fuel
processor. As shown, mount 404 takes the form of a reduced-diameter
neck 406, although it is within the scope of the disclosure that
the mount may have other configurations, such as projecting
flanges, struts, threads, and the like, and that the housing may be
formed without a mount. It is also within the scope of the
disclosure that housing 402 may have any other suitable shape and
that the housing may be formed from a greater number of components
than is shown in FIGS. 45 and/or 46. Also shown are a fuel supply
conduit 408 for combustible fuel stream 64 (such as gaseous
combustible fuel stream 276) and an air supply conduit 410 for air
stream 74. In the illustrated embodiment shown in solid lines, the
burner assembly is adapted to receive only gaseous combustible fuel
streams. However, a vaporizing heating assembly 296, supply conduit
411 for a liquid combustible fuel stream 82, and optional partition
342 are shown in dashed lines and would generally be present in a
version of burner assembly 400 that is configured to receive and
vaporize a liquid combustible fuel stream.
[0167] Burner assembly 400 also demonstrates another suitable
configuration for tubes 314 and gas distribution manifold (or
plenum) 310. Unlike the previously illustrated embodiments, such as
illustrated in FIGS. 43 and 44, in which tubes 314 extended from
apertures 312 in manifold 310, burner assembly 400 demonstrates
that the tubes may project though the apertures in manifold 310. As
such, tubes 314 include inlets 412 that are located within
vaporization region 292.
[0168] As perhaps best seen in FIG. 45, the burner assembly
includes a plurality of tubes 314 concentrically positioned within
a corresponding plurality of apertures 326 in combustion
distribution manifold 324. Although not required, burner assembly
400 illustrates that manifold 324 may include a portion 420
proximate air input port 320 that contains no apertures and
corresponding tubes, or proportionally less apertures and tubes. As
shown, portion 420 corresponds to an area where the distribution of
apertures 326 (and therefore tubes 314) would be present in a
symmetrical distribution. However, portion 420 corresponds to an
area where the apertures are asymmetrically distributed, and as
shown in FIG. 45, not present. A benefit of this configuration is
that absence (or optional reduced number) of apertures 326 in
manifold 324 proximate input port 320 promotes the distribution of
the air stream throughout air distribution chamber 322.
[0169] FIGS. 45 and 46 also demonstrate that burner assemblies 262
according to the present disclosure may include a chamber, or
passage, 422 through which ignition source 88 may be mounted and/or
inserted into and removed from the burner assembly. When ignition
source 88 is within passage 422 it will tend to be shielded from
direct contact with the flames that are produced as the fuel
streams are ignited. Although not required, it can be seen in FIGS.
45 and 46 that the air streams 74' surrounding the passage 422 will
provide a flow of air that will tend to shield the ignition source
from the flames produced as the fuel streams are ignited.
[0170] As perhaps best seen in FIG. 46, passage 422 extends through
the burner assembly to base 340, thereby enabling the ignition
source to be removed from a burner assembly that is mounted (such
as via a mount 404) to a fuel processor. A benefit of this
construction is that ignition sources which require periodic
servicing or replacement may be used with burner assemblies
according to the disclosure without requiring the entire burner
assembly to be removed from the fuel processor simply to inspect,
service or remove/replace the ignition source. Instead, and as
perhaps best seen in FIG. 46, the ignition source may be inserted
within the passage, and selectively removed therefrom through base
340, such as for inspection, maintenance or replacement.
[0171] A variation of burner assembly 400 is shown in FIGS. 47 and
48. As shown, the burner assembly includes a sleeve 430 that
extends from vaporization region 292 through combustion region 92
and into which one or more temperature sensors 432, such as
thermocouples or other suitable temperature sensors, may be
inserted. The inclusion of temperature sensors enables the
operating state of the burner assembly to be determined by a
processor or other suitable monitor in communication with sensor(s)
432. For example, the sensor(s) may be used to detect if combustion
has commenced in the combustion region. As another examples, if the
burner assembly is no longer generating (or maintaining) heat, such
as if the supply of combustible fuel has been interrupted, the
flames have been extinguished, etc., this may be detected using the
temperature sensors. Furthermore, the measured temperatures from
one or more regions of the burner assembly may be used to control
or adjust the operating state of the burner assembly. For example,
when the burner assembly is initially preheated by vaporization
heating assembly 296 (as will be discussed subsequently), a
temperature sensor 432 may be used to determine when a selected
preheat temperature has been reached. As another possible, but not
required, application of temperature sensors 432, the sensors may
be used for safety reasons, namely, to sense if a region of the
burner assembly has exceeded a predetermined threshold temperature.
Sleeve 430 may also be referred to as a sensor port or a mount for
one or more thermocouples or other temperature sensors.
[0172] In the illustrated embodiment, sleeve 430 defines a passage
434 that is accessible through base 340 of the burner assembly.
Similar to the above discussion regarding passage 422, this
configuration enables temperature sensors or other measuring
equipment to be inserted into and removed from the burner assembly
while the burner assembly is mounted on a fuel processor. In the
illustrated embodiment, sleeve 430 extends through each of the
above-discussed regions of the burner assembly, thereby enabling
the temperature of each of these regions to be selectively measured
through the insertion of suitable sensors 432 at the appropriate
location within the sleeve. Also shown in FIG. 48 is a mount 436
that retains sleeve 430 and/or sensor(s) 432 within the burner
assembly.
[0173] In FIGS. 49-51, another version of the burner assemblies of
FIGS. 45-48 is shown and generally indicated at 400'. As shown, the
burner assembly is adapted to receive and vaporize a liquid
combustible fuel stream 82 through liquid fuel supply conduit 412.
Burner assembly 400' may be configured to only receive liquid
combustible fuel streams, in which case supply conduit 408 and its
corresponding input port may be omitted. Similarly, although the
previously discussed passage and sleeve 430 are shown in FIGS.
49-51, burner assembly 400' may be formed without these components
and/or with any of the other elements, subelements and/or
variations described and/or illustrated herein.
[0174] In FIG. 49, the burner assembly is shown including a
vaporization heating assembly 296 that includes a plurality of
ports, or mounts, 460 that are adapted to receive electrically
powered heaters 462, such as electric resistance heaters. As shown,
heating assembly 296 includes four ports 460, but it is within the
scope of the disclosure that the number and configuration of the
ports may vary. For example, even in the context of electrically
powered resistance heaters, such heaters can have disc or flat
configurations, as opposed to the cylindrical cartridge heaters
shown in FIG. 50. Similarly, the power requirements and/or heat
output of the heaters may affect the number and configuration of
heaters to be used. In FIG. 50, heaters 462 are shown received
within the ports and include electrical leads 464 that are
connected to a source of electricity, such as a battery, fuel cell
stack, electrical outlet, generator, etc.
[0175] Heating assembly 296 preferably heats the vaporized fuel
stream to a sufficient temperature that the stream does not
condense prior to being ignited in combustion region 92. As such,
heating assembly 296 may be configured to superheat the vaporized
fuel stream. For liquid combustible fuel streams containing
methanol, or optionally methanol and up to 50 vol % water, four
heaters 462 that are designed to output 100 watts at 10.6 volts
have proven effective. It should be understood, however, that the
number of heaters and/or amount of heat to be supplied therefrom
will tend to vary depending upon the composition of the liquid
combustible fuel stream, the flow rate thereof, and/or the
configuration of the vaporization region. The heaters may be
configured to provide a constant output, or alternatively may be
selectively controlled to provide a selected amount of heat from
within a predetermined range of outputs. For example, by
selectively energizing between none and all of the heaters, the
output of the heating assembly is varied. As another example, the
power provided to the heaters may be controlled, such as by pulse
width modulation of the DC voltage delivered thereto to selectively
scale the power.
[0176] When heaters 462 are removably received within the
vaporizing heating assembly, the heating assembly may (but is not
required to) include a suitable retainer 466 that is adapted to
retain the heaters therein and thereby prevent unintentional
removal of the heaters. An illustrative example of a suitable
retainer 466 is shown in FIGS. 50 and 51 in the form of a pin 468
that is selectively passed through the guides that are positioned
so that the openings of the ports are at least partially obstructed
by the pin after the pin is inserted through the guides. In such a
configuration, vaporizing heating assembly 96 may include at least
one such pin 468 at each end of the ports. As a variation of this
configuration, the mounts may be keyed so that the heaters may only
be inserted into (or removed from) one end of the ports. For
example, one end of the ports may be obstructed, or even closed, so
that the heaters cannot pass completely through the ports.
[0177] FIG. 50 also demonstrates an example of a modular, or
cartridge-based, ignition source 88 that may be selectively
inserted into and removed from operative positions relative to
combustion region 92 via passage 422. As shown, the ignition source
includes a housing 480 within which the particular igniting
element(s) 482 is/are located. For example, housing 480 may contain
a combustion catalyst, spark plug, electrically heated ceramic
element, etc. As shown, housing 480 includes a mount 484 that is
adapted to be releasably coupled to the burner assembly, such as to
base 340.
[0178] In FIGS. 52 and 53, another example of a burner assembly 262
according to the present disclosure is shown and generally
indicated at 500. In the illustrated embodiment, burner assembly
500 is adapted to receive a gaseous combustible fuel stream through
fuel port 302 and an air stream through air port 320. However, it
is within the scope of the disclosure that burner assembly 500 may
additionally or alternatively receive a liquid combustible fuel
stream through port 302 or an additional port within
vaporization/staging region 292, with burner assembly 500 in such
an embodiment also being heated such that the liquid fuel is
vaporized in region 292. As perhaps best seen in FIG. 53, burner
assembly 500 demonstrates a bifurcated, or distributed, air
distribution chamber 322. More specifically, and as perhaps best
seen in FIG. 53, an air stream is delivered into a primary
distribution region 510, which in the illustrated embodiment takes
the form of an annulus that surrounds tubes 314 and is separated
therefrom by a wall structure 512. As shown, wall structure 512
includes a plurality of ports 514 through which the air stream may
be introduced into a secondary distribution region 516, in which
the air stream may flow around the tubes and be distributed between
the apertures 326 in combustion distribution manifold 324.
Preferably, ports 514 are spaced at intervals around wall structure
512 so that air entering region 510 is circulated within the region
and introduced into secondary distribution region 516 from a
plurality of radially spaced-apart ports. The distributed design of
air distribution chamber 322 is designed to promote distribution of
the air stream throughout region 516.
[0179] As discussed, burner assembly 500 may be adapted to receive
and vaporize a liquid combustible fuel stream. An illustrative
example of such a version of the burner assembly is shown in FIG.
54 and generally indicated at 500'. As shown in solid lines, the
burner assembly includes a vaporizing heating assembly 296 and is
adapted to receive a liquid combustible fuel stream through an
input port, such as the port that was previously utilized for a
gaseous combustible fuel stream in FIG. 52. When the burner
assembly is adapted to selectively receive either or both of
gaseous and liquid combustible fuel streams, vaporization region
292 will typically include a pair of fuel input ports, with the
second such port indicated in dashed lines in FIG. 54. Although
vaporizing heating assembly 296 has been illustrated in FIG. 54 as
being mounted on, or integrated with, the rest of burner assembly
500', such as being within or forming a portion of a common shell
or housing 402, it is within the scope of the disclosure that
vaporizing heating assembly 296 may be a separate structure that is
merely positioned to deliver sufficient heat to the vaporization
region to vaporize the liquid combustible fuel stream. For example,
instead of generating heat itself, such as electrically or through
combustion, the heating assembly may deliver a heated fluid stream
that vaporizes the liquid combustible fuel stream.
[0180] In operation, burner assemblies 262 according to the present
disclosure that are adapted to receive a liquid combustible fuel
stream (either alone or in combination with a gaseous combustible
fuel stream) are typically preheated, such as by vaporizing heating
assembly 296. A reason for preheating the burner assembly is so
that the liquid combustible fuel stream does not fill or overflow
the vaporization region while the region is heated. For most
suitable liquid fuels, such as alcohols and shorter chain
hydrocarbons, preheating the vaporization region to at least
150.degree. C. and typically less than 500.degree. C. has proven
effective. Preheating the vaporization region to approximately
200-250.degree. C. has proven particularly effective for methanol
and methanol/water liquid combustible fuel streams. Although not
required, it may be desirable to preheat the vaporization region to
a temperature that will produce thin film boiling of the liquid
combustible fuel stream that is delivered thereto.
[0181] As discussed, burner assemblies 262 according to the present
disclosure may be used to heat the hydrogen-producing regions of a
variety of fuel processors. For purposes of illustration, the
following discussion will describe a liquid/gaseous burner assembly
according to the present disclosure being used with a fuel
processor in the form of a steam reformer that is adapted to
receive a feed stream 16 containing a carbon-containing feedstock
and water. However, it is within the scope of the disclosure that
fuel processor 12 may take other forms, as discussed above. An
example of a suitable steam reformer is schematically illustrated
in FIG. 55 and indicated generally at 530. Reformer 530 includes a
hydrogen-producing region 19 in the form of a reforming region that
includes a steam reforming catalyst 23. In the reforming region, a
resultant stream 20, which may in this context also be referred to
as a reformate stream, is produced from the water and
carbon-containing feedstock forming feed stream 16.
[0182] As discussed previously, feed stream 16 may be a single
stream containing both water and a water-soluble carbon-containing
feedstock, or it may be two or more streams that collectively
contain the water and carbon-containing feedstock(s) that are
consumed in the reforming region. As shown in dashed lines in FIG.
55, it is within the scope of the disclosure that at least the
carbon-containing feedstock component of feed stream 16 may also
form a combustible fuel stream 64 that is delivered to burner
assembly 262. It is also within the scope of the disclosure that
the complete feed stream (i.e. water and carbon-containing
feedstock) may be used as the combustible fuel stream for burner
assembly 262. For example, a reforming feed stream may contain
approximately 50-75 vol % methanol and approximately 25-50 vol %
water. An example of a particularly well-suited feed stream
contains 69 vol % methanol and 31 vol % water. This stream may
effectively be used as the feed stream for reformer 530 and the
combustible fuel stream for a burner assembly according to the
present disclosure. A benefit of this common feed/fuel is that the
overall size of the fuel processing system may be reduced by not
having to store and deliver a fuel stream 64 having a different
composition than feed stream 16 (or its components).
[0183] When a burner assembly 262 is used to heat steam reformer
530 from an off, or cold, state, the burner assembly is initially
preheated using vaporizing heating assembly 296. As an illustrative
example, reformers that receive a feed stream 16 containing
methanol will typically be preheated to at least 300.degree. C.,
and more preferably, 325-350.degree. C. After this temperature is
reached, a liquid combustible fuel stream 82 is delivered to the
vaporization region and vaporized, and an air stream 74 is
delivered to distribution region 284. The vaporized fuel streams
and air streams are distributed, diffused together and ignited, as
discussed herein, with the resulting hot combustion stream 66 being
used to heat at least the reforming region of steam reformer
530.
[0184] When the reforming region has been heated to a predetermined
reforming temperature, which as discussed will tend to vary
depending upon the composition of feed stream 16, feed stream 16 is
delivered to the reforming region to produce reformate stream 20.
Although feed stream 16 (or at least the carbon-containing
feedstock component thereof) may continue to be used as the
combustible fuel stream for the burner assembly, at least part, or
even all, of the fuel stream may be formed by byproduct stream 28.
In such an embodiment, the burner assembly will initially be used
with a liquid combustible fuel stream during startup of the
reformer, and then will be used with a gaseous burner assembly
after the reforming region is preheated and producing a reformate
stream.
[0185] This illustrative utilization of a burner assembly 262 is
depicted in flow chart 560 in FIG. 56. As shown, at 560, the burner
assembly is preheated. At 562, the burner assembly preheats the
reforming region using a liquid combustible fuel stream. As
discussed, this fuel stream may contain the same composition as the
feed stream for the reformer. At 564, the preheated reforming
region receives a feed stream containing a carbon-containing
feedstock and water. The feed stream is reformed to produce a
reformate stream containing hydrogen gas and other gases. At 566,
the reformate stream is separated into a hydrogen-rich stream and a
byproduct stream, and at 568, the byproduct stream is delivered to
the burner assembly for use as a gaseous combustible fuel stream.
If the byproduct stream contains sufficient heating value to
maintain the reforming region at a suitable reforming temperature,
then the flow of liquid combustible fuel stream may be stopped.
When byproduct stream 28 does not contain sufficient heating value,
it may be supplemented, such as with another gaseous combustible
fuel stream (including a portion of reformate stream 20,
hydrogen-rich stream 26 or product hydrogen stream 14) and/or the
liquid combustible fuel stream may continue to be delivered to the
burner assembly, typically at a reduced flow compared to its
startup flow rate. It should be understood, however, that the above
implementation is but one of many uses for burner assemblies
according to the present disclosure.
INDUSTRIAL APPLICABILITY
[0186] Burner assemblies, steam reformers, fuel processing systems
and fuel cell systems according to the present disclosure are
applicable to the fuel processing, fuel cell and other industries
in which hydrogen gas is produced, and in the case of fuel cell
systems, consumed by a fuel cell stack to produce an electric
current.
[0187] It is believed that the disclosure set forth above
encompasses multiple distinct inventions with independent utility.
While each of these inventions has been disclosed in its preferred
form, the specific embodiments thereof as disclosed and illustrated
herein are not to be considered in a limiting sense as numerous
variations are possible. The subject matter of the inventions
includes all novel and non-obvious combinations and subcombinations
of the various elements, features, functions and/or properties
disclosed herein. Similarly, where the claims recite "a" or "a
first" element or the equivalent thereof, such claims should be
understood to include incorporation of one or more such elements,
neither requiring nor excluding two or more such elements.
[0188] It is believed that the following claims particularly point
out certain combinations and subcombinations that are directed to
one of the disclosed inventions and are novel and non-obvious.
Inventions embodied in other combinations and subcombinations of
features, functions, elements and/or properties may be claimed
through amendment of the present claims or presentation of new
claims in this or a related application. Such amended or new
claims, whether they are directed to a different invention or
directed to the same invention, whether different, broader,
narrower or equal in scope to the original claims, are also
regarded as included within the subject matter of the inventions of
the present disclosure.
* * * * *