Note: Descriptions are shown in the official language in which they were submitted.
CA 02536110 2003-04-11
STEAM REFORMING FUEL PROCESSOR, BURNER ASSEMBLY,
AND METHODS OF OPERATING THE SAME
Field of the Disclosure
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
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.
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.
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
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CA 02536110 2003-04-11
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
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.
CA 02536110 2012-01-11
In accordance with an illustrative embodiment, a fuel processor includes a
hydrogen-
producing region containing a reforming catalyst and adapted to receive a feed
stream
containing at least a carbon-containing feedstock and to produce a mixed gas
stream
containing hydrogen gas and other gases therefrom. The fuel processor also
includes a
burner assembly adapted to produce a heated exhaust stream for heating at
least the
hydrogen-producing region of the fuel processor. 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. The combustible fuel stream includes at
least one of the
feed stream and at least a portion of the mixed gas stream. The fuel processor
also includes
means for selectively controlling the rate at which air is delivered to the
burner assembly to
actively control the temperature of the hydrogen-producing region independent
of the flow
rate of the feed stream to the hydrogen-producing region. The means for
selectively
controlling includes means for increasing the rate at which the air is
delivered to the burner
assembly to decrease the temperature of the hydrogen-producing region.
In accordance with another illustrative embodiment, a fuel processor includes
a
hydrogen-producing region containing a reforming catalyst and adapted to
receive a feed
stream containing at least a carbon-containing feedstock and to produce a
mixed gas stream
containing hydrogen gas and other gases therefrom. The fuel processor also
includes a
burner assembly adapted to produce a heated exhaust stream for heating at
least the
hydrogen-producing region of the fuel processor. 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. The combustible fuel stream includes at
least one of the
feed stream and at least a portion of the mixed gas stream. The fuel processor
also includes
means for selectively controlling the rate at which air is delivered to the
burner assembly to
actively control the temperature of the hydrogen-producing region without
actively
controlling the rate at which the feed stream is delivered to the hydrogen-
producing region.
The means for selectively controlling includes means for increasing the rate
at which the air
is delivered to the burner assembly to decrease the temperature of the
hydrogen-producing
region.
2A
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In accordance with another illustrative embodiment, a fuel processor includes
a
hydrogen-producing region containing a reforming catalyst and adapted to
receive a feed
stream containing at least a carbon-containing feedstock and to produce a
mixed gas stream
containing hydrogen gas and other gases therefrom. The fuel processor also
includes a
burner assembly adapted to produce a heated exhaust stream for heating at
least the
hydrogen-producing region of the fuel processor. 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. The combustible fuel stream includes at
least one of the
feed stream and at least a portion of the mixed gas stream. The fuel processor
also includes
means for selectively controlling the rate at which air is delivered to the
burner assembly to
selectively control the amount of heat produced by the burner assembly. The
air stream is
delivered to the burner assembly at a rate sufficient to provide at least 200%
of a
stoichiometrically required amount of oxygen gas to combust the combustible
fuel stream to
produce the heated exhaust stream. The means for selectively controlling
includes means for
increasing the rate at which the air is delivered to the burner assembly to
decrease the
temperature of the hydrogen-producing region.
In accordance with another illustrative embodiment, a method for operating a
hydrogen-producing fuel processing system includes heating a hydrogen-
producing region of
a fuel processing system to a hydrogen-producing temperature. The hydrogen-
producing
region contains a catalyst adapted to catalyze the formation of a mixed gas
stream including
hydrogen gas from water and a carbon-containing feedstock via an endothermic
reaction at
the hydrogen-producing temperature. The method further includes providing a
feed stream
including water and a carbon-containing feedstock to the hydrogen-producing
region, and
producing the mixed gas stream in the hydrogen-producing region via the
endothermic
reaction catalyzed by the catalyst. The mixed gas stream further includes
other gases. The
method further includes separating the mixed gas stream into a product
hydrogen stream
containing a greater concentration of hydrogen gas than the mixed gas stream
and at least one
byproduct stream containing at least a substantial portion of the other gases.
The method
further includes delivering a fuel stream and an air stream to a heating
assembly, combusting
the fuel stream to produce a hot combustion stream, and heating at least the
hydrogen-
producing region with the hot combustion stream to maintain the hydrogen-
producing region
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CA 02536110 2012-01-11
at a temperature of at least the hydrogen-producing temperature. The method
further
includes controlling the rate at which the air stream is delivered to the
heating assembly to
selectively increase or decrease the temperature of the hot combustion stream
produced by
the heating assembly. The controlling includes controlling the rate at which
the air stream is
delivered to the heating assembly independent of the flow rate of the feed
stream to the
hydrogen-producing region. The controlling includes increasing the rate at
which the air is
delivered to the burner assembly to decrease the temperature of the hydrogen-
producing
region.
In accordance with another illustrative embodiment, a method for operating a
hydrogen-producing fuel processing system includes heating a hydrogen-
producing region of
a fuel processing system to a hydrogen-producing temperature. The hydrogen-
producing
region contains a catalyst adapted to catalyze the formation of a mixed gas
stream including
hydrogen gas from water and a carbon-containing feedstock via an endothermic
reaction at
the hydrogen-producing temperature. The method further includes providing a
feed stream
including water and a carbon-containing feedstock to the hydrogen-producing
region, and
producing the mixed gas stream in the hydrogen-producing region via the
endothermic
reaction catalyzed by the catalyst. The mixed gas stream further includes
other gases. The
method further includes separating the mixed gas stream into a product
hydrogen stream
containing a greater concentration of hydrogen gas than the mixed gas stream
and at least one
byproduct stream containing at least a substantial portion of the other gases.
The method
further includes delivering a fuel stream and an air stream to a heating
assembly, combusting
the fuel stream to produce a hot combustion stream, and heating at least the
hydrogen-
producing region with the hot combustion stream to maintain the hydrogen-
producing region
at a temperature of at least the hydrogen-producing temperature. The method
further
includes controlling the rate at which the air stream is delivered to the
heating assembly to
selectively increase or decrease the temperature of the hot combustion stream
produced by
the heating assembly. The controlling includes controlling the rate at which
the air stream is
delivered to the heating assembly independent of the flow rate of the fuel to
the heating
assembly. The controlling includes increasing the rate at which the air is
delivered to the
burner assembly to decrease the temperature of the hydrogen-producing region.
2C
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Other aspects and features of illustrative embodiments will become apparent to
those
ordinarily skilled in the art upon review of the following description of such
embodiments in
conjunction with the accompanying figures.
2D
CA 02536110 2003-04-11
Brief Description of the Drawings
Fig. I is a schematic diagram of a fuel processing system with a burner
assembly according to the present disclosure.
Fig. 2 is a schematic diagram of a fuel processing system with a chemical
carbon monoxide removal assembly according to the present disclosure.
Fig. 3 is a schematic diagram of a fuel cell system with a burner assembly
according to the present disclosure.
Fig. 4 is a schematic diagram of another fuel processor with a burner
assembly according to the present disclosure.
Fig. 5 is a schematic view of another burner assembly according to the
present disclosure.
Fig. 6 is a schematic view of another burner assembly according to the
present disclosure.
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.
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.
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.
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.
Fig. I1 is a schematic view showing another variation of the fuel
processors of Figs. 9 and 10.
Fig. 12 is a schematic view showing another burner assembly according
to the present disclosure.
Fig. 13 is a schematic view showing an ignition region of a burner
assembly that includes an atomization assembly that includes an atomizing
orifice.
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CA 02536110 2003-04-11
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.
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.
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.
Fig. 17 is a schematic view of another ignition region of a burner
assembly that includes an impingement member that atomizes the feed stream.
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.
Fig. 19 is a cross-sectional view of an ignition region of another burner
assembly that includes an impingement member.
Fig. 20 is a cross-sectional view of the region of Fig. 19 taken along the
line 20-20 in Fig. 19.
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.
Fig. 22 is a cross-sectional view of the region of Fig. 21, taken along the
line 22-22 in Fig. 21.
Fig. 23 is a cross-sectional view of another ignition region of a burner
assembly according to the present disclosure.
Fig. 24 is a top plan view of the ignition region of Fig. 23 taken along the
line 24-24 in Fig. 23.
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.
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.
Fig. 27 is a top plan view of extension sleeve of the ignition region of
Fig. 26.
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CA 02536110 2003-04-11
Fig. 28 is a cross-sectional view showing another variation of the ignition
regions of Figs. 23 and 26.
Fig. 29 is an exploded cross-sectional view of the ignition region of
Fig. 28.
Fig. 30 is a cross-sectional view of a fuel processor that includes a burner
assembly according to the present disclosure.
Fig. 31 is a cross-sectional view of another fuel processor that includes a
burner assembly according to the present disclosure,
Fig. 32 is a cross-sectional view of the fuel processor of Fig. 31 taken
along the line 32-32 in Fig. 31.
Fig. 33 is an isometric view of another fuel processor with a burner
assembly according to the present disclosure.
Fig. 34 is an exploded isometric view of the fuel processor of Fig. 34.
Fig. 35 is a side elevation view of the fuel processor of Figs. 33 and 34
with the shroud, or cover assembly, removed.
Fig. 36 is bottom plan view of the fuel processor of Fig. 33.
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.
Fig. 38 is a cross-sectional view of the fuel processor of Fig. 33 taken
along the line 38-38 in Fig. 36.
Fig. 39 is a cross-sectional view of the fuel processor of Fig. 33.
Fig. 40 is a schematic diagram of another burner assembly according to
the present disclosure.
Fig. 41 is a schematic diagram of another burner assembly according to
the present disclosure.
Fig. 42 is a schematic diagram of another burner assembly according to
the present disclosure.
Fig. 43 is a side cross-sectional view of another burner assembly
according to the present disclosure.
Fig. 44 is a fragmentary cross-sectional view showing variations of the
burner assembly of Fig. 43.
Fig. 45 is a top plan view of another burner assembly according to the
present disclosure.
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Fig. 46 is a side cross-sectional view of the burner assembly of Fig. 45,
taken along the line 46-46 in Fig. 45.
Fig. 47 is an isometric view of a variant of the burner assembly of Fig. 45.
Fig. 48 is an exploded isometric view of the burner assembly of Fig. 47.
Fig. 49 is an isometric view of a variation of the burner assembly of
Figs. 45 and 47.
Fig. 50 is an isometric view of the burner assembly of Fig. 49 with an
installed heating assembly.
Fig. 51 is an exploded isometric view of the burner assembly of Fig. 50.
Fig. 52 is an isometric view of another burner assembly according to the
present disclosure.
Fig. 53 is a cross-sectional isometric view of the burner assembly of
Fig. 52.
Fig. 54 is a cross-sectional isometric view showing a variation of the
burner assembly of Fig. 53.
Fig. 55 is a schematic diagram of a steam reformer with a burner
assembly according to the present disclosure.
Fig. 56 is a flowchart showing illustrative methods for using burner
assemblies according to the present disclosure.
6
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Detailed Description and Best Mode of the Disclosure
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.
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.
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
7
CA 02536110 2003-04-11
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.
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.
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. I 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.
Steam reformers typically operate at temperatures in the range of 200 C
and 700 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.
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When the carbon-containing feedstock is an alcohol, the steam reforming
reaction will
typically operate in a temperature range of approximately 200-500 C, and when
the
carbon-containing feedstock is a hydrocarbon, a temperature range of
approximately
400-800 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.
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.
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.
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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.
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.
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.
CA 02536110 2003-04-11
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 suitable mechanisms for
reducing the
thickness of the membranes include rolling, sputtering and etching. A suitable
etching process is
disclosed in U.S. Patent No. 6,152,995. Examples of various membranes,
membrane
configurations, and methods for preparing the same are disclosed in U.S.
Patent Nos. 6,221,117,
6,319,306 and 6,537,352.
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 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-
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CA 02536110 2003-04-11
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).
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, C02, hydrocarbons including
CH4, and N2) 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 NH3, H2S, and H2O adsorb very
strongly
on the adsorbent material and are therefore removed from stream 20 along with
other
impurities. Impurity gases such as NH3, H2S, and H2O 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.
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 A (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.
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
12
CA 02536110 2003-04-11
the resultant stream. Instead, these components are removed when the adsorbent
material is
regenerated or otherwise removed from the separation region.
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.
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. Patent Nos. 6,319,306,
6,221,117,
5,997,594, 5,861,137, U.S. Patent Publication No. US 2001/0045061 and U.S.
patent
application Publication No. US 2003/019225 1.
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 form 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 derived
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
13
CA 02536110 2003-04-11
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.
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.
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.
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
14
CA 02536110 2003-04-11
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.
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.
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
CA 02536110 2003-04-11
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.
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.
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.
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
16
CA 02536110 2003-04-11
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.
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.
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
17
CA 02536110 2003-04-11
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.
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.
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 C) to approximately 100 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.
18
CA 02536110 2003-04-11
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.
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
19
CA 02536110 2003-04-11
configurations, as well as any of the steam reformers and other processors
described,
illustrated and/or referenced herein.
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.
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. Patent No. 6,383,670.
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
CA 02536110 2003-04-11
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.
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.
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.
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
21
CA 02536110 2003-04-11
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.
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.
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
22
CA 02536110 2003-04-11
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 mLmin
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.
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.
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.
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,
23
CA 02536110 2003-04-11
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.
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.
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.
24
CA 02536110 2003-04-11
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 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.
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.
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
CA 02536110 2003-04-11
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.
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.
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-
26
CA 02536110 2003-04-11
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.
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.
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.
-27
CA 02536110 2003-04-11
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.
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.
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.
28
CA 02536110 2003-04-11
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.
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 C, and more typically 50-100 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
29
CA 02536110 2009-02-26
desired reforming temperature not only results in waste of fuel, but also may
result in the
reformer being overheated.
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 reformmmer.
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 patents and patent' applications, as well as
in U_S- Provisional
Patent Application Serial No. 60/372,258, which was filed on April 12, 2002,
is entitled
"Steam Reforming Fuel Processor", and is available to the public upon request
from the
World Intellectual Property Organization as a result of having served as time
basis for a
priority claim for PCT International Application No. PCT/US03/10943.
(publication no. WO
2003/086964). 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 rediseussed below. It is within the scope of the disclosure that other
burner assemblies
described, illustrated and/or referenced 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. -30-19. 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.
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
CA 02536110 2003-04-11
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.
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.
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
31
CA 02536110 2003-04-11
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 referenced herein may be used in place of the
illustrated burner
assembly.
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 Fig. 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.
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
32
CA 02536110 2003-04-11
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.
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.
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
33
CA 02536110 2003-04-11
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 C.
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.
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
referenced 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. The illustrated example of a steam reforming fuel
processor includes
an optional base, or base plate, 242 having a plurality of supports, or legs,
246. Several
optional sensors 254 are also illustrated.
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.
34
CA 02536110 2003-04-11
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 FeCrAIY or one of the other
oxidation-resistant alloys discussed above.
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.
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.
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
CA 02536110 2003-04-11
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. Patent No. 6,383,670.
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.
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.
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 re not normally present
in air. In
the illustrated embodiment, the fuel stream is a gaseous combustible fuel
stream 276.
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
36
CA 02536110 2003-04-11
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.
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.
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
37
CA 02536110 2003-04-11
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.
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'.
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.
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
38
CA 02536110 2003-04-11
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).
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.
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.
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
39
CA 02536110 2003-04-11
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.
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.
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
CA 02536110 2003-04-11
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.
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.
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
41
CA 02536110 2003-04-11
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.
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.
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.
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
42
CA 02536110 2003-04-11
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.
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.
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.
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
43
CA 02536110 2010-12-23
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.
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. Thus, the burner assembly may include mechanisms 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. 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.
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 are 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
44
CA 02536110 2003-04-11
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.
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.
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.
CA 02536110 2003-04-11
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.
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
46
CA 02536110 2003-04-11
comparatively stable or normalized, even if the flow rate of stream 82 tends
to vary over
time.
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.
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.
Another burner assembly 262 constructed according to the present disclosure
is shown in Figs. 45 and 46 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
47
CA 02536110 2003-04-11
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.
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.
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.
48
CA 02536110 2003-04-11
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.
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.
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.
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
49
CA 02536110 2003-04-11
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 example, 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.
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.
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 411. 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
CA 02536110 2003-04-11
discussed passage and sleeve 430 are shown in Figs. 49-5 1, 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.
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.
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.
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
51
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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 guides
470 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.
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.
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
52
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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.
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.
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 C and
typically less
than 500 C has proven effective. Preheating the vaporization region to
approximately
200-250 C has proven particularly effective for methanol and methanol/water
liquid
combustible fuel streams. Although not required, it may be
53
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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.
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.
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).
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CA 02536110 2003-04-11
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 C, and more
preferably,
325-350 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.
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.
This illustrative utilization of a burner assembly 262 is depicted in flow
chart 560 in Fig. 56. As shown, at 562, the burner assembly is preheated. At
564, 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 566, 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 568, the
reformate stream
is separated into a hydrogen-rich stream and a byproduct stream, and at 570,
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
CA 02536110 2003-04-11
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
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.
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.
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.
56
