Note: Descriptions are shown in the official language in which they were submitted.
CA 02494680 2002-03-26
HYDROGEN PURIFICATION DEVICES, COMPONENTS AND
FUEL PROCESSING SYSTEMS CONTAINING THE SAME
Related Applications
The present application claims priority from U.S. Patent Application
Serial No. 09/967,172, which was filed on September 27, 2001 and issued on
December 17, 2002 as U.S. Patent No. 6,494,937; from U.S. Patent Application
Serial
No. 10/067,275, which was filed on February 4, 2002 and issued on May 13, 2003
as
U.S. Patent No. 6,562,111; and from U.S. Patent Application Serial No.
10/086,680,
which was filed on February 28, 2002 and issued on May 27, 2003 as U.S. Patent
No.
6,569,227.
Field of the Invention
The present invention is related generally to the purification of
hydrogen gas, and more specifically to hydrogen purification devices,
components
and fuel processing and fuel cell systems containing the same.
Background of the Invention
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, fuel cells use purified hydrogen and an oxidant to
produce an
electrical potential. Various processes and devices may be used to produce the
hydrogen gas that is consumed by the fuel cells. However, many hydrogen
production processes produce an impure hydrogen stream, which may also be
referred
to as a mixed gas stream that contains hydrogen gas. Prior to delivering this
stream to
a fuel cell or stack of fuel cells, the mixed gas stream may be purified, such
as to
remove undesirable impurities.
Summary of the Invention
The present invention is directed to hydrogen purification devices,
components of hydrogen purification devices, and fuel processing and fuel cell
systems that include hydrogen purification devices. In accordance with one
aspect of
the invention, hydrogen purification devices include an enclosure that
contains a
separation assembly adapted to receive a mixed gas stream containing hydrogen
gas
and to produce a stream that contains pure or at least substantially pure
hydrogen gas
therefrom. The separation assembly includes at least one hydrogen-permeable
and/or
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CA 02494680 2002-03-26
hydrogen-selective membrane, and in some embodiments includes at least one
membrane envelope that includes a pair of generally opposed membrane regions
that
define a harvesting conduit therebetween and which are separated by a support.
The
device includes one or more components that are formed from materials having
similar or the same coefficients of thermal expansion as the membrane or
membranes.
In some embodiments, these components include at least a portion of the
support, and
in some embodiments, these components include at least a portion of the
enclosure.
In accordance with another aspect of the invention, there is provided a
hydrogen purification device, including an enclosure having a pair of spaced-
apart
end plates and a perimeter shell extending therebetween to define with the end
plates
an internal compartment. The enclosure includes at least one input port
through
which a mixed gas stream containing hydrogen gas is delivered to the
enclosure, at
least one product output port through which a permeate stream containing at
least
substantially pure hydrogen gas is removed from the enclosure, and at least
one
byproduct output port through which a byproduct stream containing at least a
substantial portion of the other gases is removed from the enclosure. The
hydrogen
purification device fizrther includes at least one hydrogen-selective membrane
within
the compartment. The at least one hydrogen-selective membrane includes a first
surface adapted to be contacted by the mixed gas stream and a permeate surface
generally opposed to the first surface. The permeate stream is formed from the
portion of the mixed gas stream that passes through the at least one hydrogen-
selective membrane to the permeate surface, and the byproduct stream is formed
from
the portion of the mixed gas stream that does not pass through the at least
one
hydrogen-selective membrane. Each of the end plates includes an interior
surface that
generally faces the compartment, an exterior surface that generally faces away
from
the enclosure, and a sealing region that forms at least a portion of a seal
with the
perimeter shell. At least one of the end plates includes a base plate
containing the
sealing region and a truss assembly projecting from the base plate.
In accordance with another aspect of the invention, there is provided a
hydrogen purification device, including an enclosure defining an internal
compartment. The enclosure includes at least one input port through which a
mixed
gas stream containing hydrogen gas is delivered to the enclosure, at least one
product
output port through which a product hydrogen stream containing at least
substantially
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CA 02494680 2002-03-26
pure hydrogen gas is removed from the enclosure, and at least one byproduct
output
port through which a byproduct stream containing at least a substantial
portion of the
other gases is removed from the enclosure. The hydrogen purification device
further
includes at least one hydrogen-selective membrane within the compartment. The
at
least one hydrogen-selective membrane includes a first surface adapted to be
contacted by the mixed gas stream and a permeate surface generally opposed to
the
first surface. The product hydrogen stream is formed from the portion of the
mixed
gas stream that passes through the at least one hydrogen-selective membrane to
the
permeate surface, and the byproduct stream is formed from the portion of the
mixed
gas stream that does not pass through the at least one hydrogen-selective
membrane.
The enclosure includes a pair of end plates and a shell portion that extends
at least
partially between the end plates to define at least a portion of the
enclosure, and the
shell portion is integrally formed with at least one of the end plates.
In accordance with another aspect of the invention, there is provided,
in a hydrogen purification device that is adapted to be operated at a selected
temperature of at least 200° C and a selected pressure of at least 50
psi and which
includes an enclosure with an internal, at least substantially fluid-tight
compartment
containing at least one hydrogen-selective membrane, an improvement including
at
least one truss-stiffened end plate forming a portion of the enclosure.
In accordance with another aspect of the invention, there is provided a
hydrogen purification device, including an enclosure having a pair of spaced-
apart
end plates and a perimeter shell extending therebetween to define with the end
plates
an internal compartment. The enclosure includes at least one input port
through
which a mixed gas stream containing hydrogen gas is delivered to the
enclosure, at
least one product output port through which a permeate stream containing at
least
substantially pure hydrogen gas is removed from the enclosure, and at least
one
byproduct output port through which a byproduct stream containing at least a
substantial portion of the other gases is removed from the enclosure. The
hydrogen
purification device includes at least one hydrogen-selective membrane within
the
compartment. The at least one hydrogen-selective membrane includes a first
surface
adapted to be contacted by the mixed gas stream and a permeate surface
generally
opposed to the first surface. The permeate stream is formed from the portion
of the
mixed gas stream that passes through the at least one hydrogen-selective
membrane to
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CA 02494680 2002-03-26
the permeate surface, and the byproduct stream is formed from the portion of
the
mixed gas stream that does not pass through the at least one hydrogen-
selective
membrane. Each of the end plates includes an interior surface that generally
faces the
compartment, an exterior surface that generally faces away from the enclosure,
and a
sealing region that forms at least a portion of a seal with the perimeter
shell. At least
one of the end plates includes a base plate containing the sealing region and
having a
central region with a removed region extending into the base plate generally
toward
the interior surface.
Many other features of the present invention will become manifest to
those versed in the art upon making reference to the detailed description
which
follows and the accompanying sheets of drawings in which preferred embodiments
incorporating the principles of this invention are disclosed as illustrative
examples
only.
Brief Description of the Drawings
Fig. 1 is a schematic view of a hydrogen purification device.
Fig. 2 is a schematic cross-sectional view of a hydrogen purification
device having a planar separation membrane.
Fig. 3 is a schematic cross-sectional view of a hydrogen purification
device having a tubular separation membrane.
Fig.4 is a schematic cross-sectional view of another hydrogen
purification device having a tubular separation membrane.
Fig. 5 is a schematic cross-sectional view of another enclosure for a
hydrogen purification device constructed according to an embodiment of the
present
invention.
Fig. 6 is a schematic cross-sectional view of another enclosure for a
hydrogen purification device constructed according to an embodiment of the
present
invention.
Fig. 7 is a fragmentary cross-sectional detail showing another suitable
interface between components of an enclosure for a purification device
according to
an embodiment of the present invention.
Fig. 8 is a fragmentary cross-sectional detail showing another suitable
interface between components of an enclosure for a purification device
according to
an embodiment of the present invention.
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CA 02494680 2002-03-26
Fig. 9 is a fragmentary cross-sectional detail showing another suitable
interface between components of an enclosure for a purification device
according to
the present invention.
Fig. 10 is a fragmentary cross-sectional detail showing another suitable
interface between components of an enclosure for a purification device
according to
the present invention.
Fig. 11 is a top plan view of an end plate for a hydrogen purification
device constructed according to the present invention, including those shown
in
Figs. 1-6.
Fig. 12 is a cross-sectional view of the end plate of Fig. 11.
Fig. 13 is a top plan view of an end plate for a hydrogen purification
device constructed according to the present invention, including those shown
in
Figs. 1-6.
Fig. 14 is a cross-sectional view of the end plate of Fig. 13.
Fig. 15 is a top plan view of an end plate for a hydrogen purification
device constructed according to the present invention, including those shown
in
Figs. 1-6.
Fig. 16 is a cross-sectional view of the end plate of Fig. 15.
Fig. 17 is a top plan view of an end plate for a hydrogen purification
device constructed according to the present invention, including those shown
in
Figs. 1-6.
Fig. 18 is a cross-sectional view of the end plate of Fig. 17.
Fig. 19 is a top plan view of an end plate for an enclosure for a
hydrogen purification device constructed according to the present invention,
including
those shown in Figs. 1-6.
Fig. 20 is a cross-sectional view of the end plate of Fig. 19.
Fig. 21 is a top plan view of an end plate for an enclosure for a
hydrogen purification device constructed according to the present invention,
including
those shown in Figs. 1-6.
Fig. 22 is a side elevation view of the end plate of Fig. 21.
Fig. 23 is an isometric view of the end plate of Fig. 21.
Fig. 24 is a cross-sectional view of the end plate of Fig. 21.
3
CA 02494680 2002-03-26
Fig. 25 is a partial cross-sectional side elevation view of an enclosure
for a hydrogen purification device constructed with a pair of the end plates
shown in
Figs. 21-24.
Fig. 26 is an isometric view of another hydrogen purification device
constructed according to the present invention.
Fig. 27 is a cross-sectional view of the device of Fig. 26.
Fig. 28 is a side elevation view of another end plate for a hydrogen
purification device constructed according to the present invention, including
those
shown in Figs. 1-6.
Fig. 29 is a side elevation view of another end plate for a hydrogen
purification device constructed according to the present invention, including
those
shown in Figs. 1-6.
Fig. 30 is a side elevation view of another end plate for a hydrogen
purification device constructed according to the present invention, including
those
shown in Figs. 1-6.
Fig. 31 is a fragmentary side elevation view of a pair of separation
membranes separated by a support.
Fig.32 is an exploded isometric view of a membrane envelope
constructed according to the present invention and including a support in the
form of a
screen structure having several layers.
Fig. 33 is an exploded isometric view of another membrane envelope
according to the present invention.
Fig. 34 is an exploded isometric view of another membrane envelope
constructed according to the present invention.
Fig. 35 is an exploded isometric view of another membrane envelope
constructed according to the present invention.
Fig. 36 is a cross-sectional view of a shell for an enclosure for a
hydrogen purification device constructed according to the present invention
with an
illustrative membrane frame and membrane module shown in dashed lines.
Fig. 37 is a top plan view of the end plate of Fig. 13 with an illustrative
separation membrane and frame shown in dashed lines.
Fig. 38 is a top plan view of the end plate of Fig. 21 with an illustrative
separation membrane and frame shown in dashed lines.
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Fig. 39 is an exploded isometric view of another hydrogen purification device
constructed according to the present invention.
Fig. 40 is a schematic diagram of a fuel processing system that includes a
fuel
processor and a hydrogen purification device constructed according to the
present invention.
S Fig. 41 is a schematic diagram of a fuel processing system that includes a
fuel
processor integrated with a hydrogen purification device according to the
present invention.
Fig.42 is a schematic diagram of another fuel processor that includes an
integrated hydrogen purification device constructed according to the present
invention.
Fig. 43 is a schematic diagram of a fuel cell system that includes a hydrogen
purification device constructed according to the present invention.
Detailed Description and Best Mode of the Invention
A hydrogen purification device is schematically illustrated in Fig. 1 and
generally indicated at 10. Device 10 includes a body, or enclosure, 12 that
defines an internal
compartment 18 in which a separation assembly 20 is positioned. A mixed gas
stream 24
containing hydrogen gas 26 and other gases 28 is delivered to the internal
compartment.
More specifically, the mixed gas stream is delivered to a mixed gas region 30
of the internal
compartment and into contact with separation assembly 20. Separation assembly
20 includes
any suitable structure adapted to receive the mixed gas stream and to produce
therefrom a
permeate, or hydrogen-rich, stream. Stream 34 typically will contain pure or
at least
substantially pure hydrogen gas. However, it is within the scope of the
invention that stream
34 may at least initially also include a Garner, or sweep, gas component.
In the illustrated embodiment, the portion of the mixed gas stream that passes
through the separation assembly enters a permeate region 32 of the internal
compartment.
This portion of the mixed gas stream forms hydrogen-rich stream 34, and the
portion of the
mixed gas stream that does not pass through the separation assembly forms a
byproduct
stream 36, which contains at least a substantial portion of the other gases.
In some
embodiments, byproduct stream 36 may contain a portion of the hydrogen gas
present in the
mixed gas stream. It is also within the scope of the invention that the
separation assembly is
adapted to trap or otherwise retain at least a
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CA 02494680 2002-03-26
substantial portion of the other gases, which will be removed as a byproduct
stream as
the assembly is replaced, regenerated or otherwise recharged. In Fig. 1,
streams 24-
28 are meant to schematically represent that each of streams 24-28 may include
more
than one actual stream flowing into or out of device 10. For example, device
10 may
receive plural feed streams 24, a single stream 24 that is divided into plural
streams
prior to contacting separation assembly 20, or simply a single stream that is
delivered
into compartment 18.
Device 10 is typically operated at elevated temperatures and/or
pressures. For example, device 10 may be operated at (selected) temperatures
in the
range of ambient temperatures up to 700° C or more. In many
embodiments, the
selected temperature will be in the range of 200° C and 500° C,
in other embodiments,
the selected temperature will be in the range of 250° C and 400°
C. and in still other
embodiments, the selected temperature will be 400° C ~ either
25° C, 50° C or 75° C.
Device 10 may be operated at (selected) pressures in the range of
approximately
50 psi and 1000 psi or more. In many embodiments, the selected pressure will
be in
the range of 50 psi and 250 or 500 psi, in other embodiments, the selected
pressure
will be less than 300 psi or less than 250 psi, and in still other
embodiments, the
selected pressure will be 175 psi ~ either 25 psi, 50 psi or 75 psi. As a
result, the
enclosure must be sufficiently well sealed to achieve and withstand the
operating
pressure.
It should be understood that as used herein with reference to operating
parameters like temperature or pressure, the term "selected" refers to defined
or
predetermined threshold values or ranges of values, with device 10 and any
associated
components being configured to operate at or within these selected values. For
further illustration, a selected operating temperature may be an operating
temperature
above or below a specific temperature, within a specific range of
temperatures, or
within a defined tolerance from a specific temperature, such as within 5%,
10%, etc.
of a specific temperature.
In embodiments of the hydrogen purification device in which the
device is operated at an elevated operating temperature, heat needs to be
applied to
the device to raise the temperature of the device to the selected operating
temperature.
For example, this heat may be provided by any suitable heating assembly 42.
Illustrative examples of heating assembly 42 have been schematically
illustrated in
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CA 02494680 2002-03-26
Fig. 1. It should be understood that assembly 42 may take any suitable form,
including mixed gas stream 24 itself. Illustrative examples of other suitable
heating
assemblies include one or more of a resistance heater, a burner or other
combustion
region that produces a heated exhaust stream, heat exchange with a heated
fluid
stream other than mixed gas stream 24, etc. When a burner or other combustion
chamber is used, a fuel stream is consumed and byproduct stream 36 may form
all or
a portion of this fuel stream. At 42' in Fig. 1, schematic representations
have been
made to illustrate that the heating assembly may deliver the heated fluid
stream
external device 10, such as within a j acket that surrounds or at least
partially
surrounds the enclosure, by a stream that extends into the enclosure or
through
passages in the enclosure, or by conduction, such as with an electric
resistance heater
or other device that radiates or conducts electrically generated heat.
A suitable structure for separation assembly 20 is one or more
hydrogen-permeable and/or hydrogen-selective membranes 46. The membranes may
be formed of any hydrogen-permeable material suitable for use in the operating
environment and parameters in which purification device 10 is operated.
Examples of
suitable materials for membranes 46 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,
such as a
membrane that contains 40 wt% copper. These membranes are typically formed
from
a thin foil that is approximately 0.001 inches thick. It is within the scope
of the
present invention, however, that the membranes may be formed from other
hydrogen-
permeable and/or hydrogen-selective materials, including metals and metal
alloys
other than those discussed above as well as non-metallic materials and
compositions,
and that the membranes may have thicknesses that are greater or less than
discussed
above. For example, the membrane may be made thinner, with commensurate
increase in hydrogen flux. Examples of suitable mechanisms for reducing the
thickness of the membranes include rolling, sputtering and etching. A suitable
etching process is disclosed in U.S. Patent No. 6,152,995. Examples of various
membranes, membrane configurations, and methods for preparing the same are
disclosed in U.S. Patent No. 6,221,117 and U.S. Patent No. 6,319,306.
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CA 02494680 2002-03-26
In Fig.2, illustrative examples of suitable configurations for
membranes 46 are shown. As shown, membrane 46 includes a mixed-gas surface 48
which is oriented for contact by mixed gas stream 24, and a permeate surface
50,
which is generally opposed to surface 48. Also shown at 52 are schematic
representations of mounts, which may be any suitable structure for supporting
and/or
positioning the membranes or other separation assemblies within compartment
18.
The patents referred to immediately above also disclose illustrative examples
of
suitable mounts 52. At 46', membrane 46 is illustrated as a foil or film. At
46", the
membrane is supported by an underlying support 54, such as a mesh or expanded
metal screen or a ceramic or other porous material. At 46"', the membrane is
coated
or formed onto or otherwise bonded to a porous member 56. It should be
understood
that the membrane configurations discussed above have been illustrated
schematically
in Fig. 2 and are not intended to represent every possible configuration
within the
scope of the invention.
For example, although membrane 46 is illustrated in Fig. 2 as having a
planar configuration, it is within the scope of the invention that membrane 46
may
have non-planar configurations as well. For example, the shape of the membrane
may
be defined at least in part by the shape of a support 54 or member 56 upon
which the
membrane is supported and/or formed. As such, membranes 46 may have concave,
convex or other non-planar configurations, especially when device 10 is
operating at
an elevated pressure. As another example, membrane 46 may have a tubular
configuration, such as shown in Figs. 3 and 4.
In Fig. 3, an example of a tubular membrane is shown in which the
mixed gas stream is delivered to the interior of the membrane tube. In this
configuration, the interior of the membrane tube defines region 30 of the
internal
compartment, and the permeate region 32 of the compartment lies external the
tube.
An additional membrane tube is shown in dashed lines in Fig.3 to represent
graphically that it is within the scope of the present invention that device
10 may
include more than one membrane and/or more than one mixed-gas surface 48. It
is
within the scope of the invention that device 10 may also include more than
two
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CA 02494680 2002-03-26
membranes, and that the relative spacing and/or configuration of the membranes
may
vary.
In Fig. 4, another example of a hydrogen purification device 10 that
includes tubular membranes is shown. In this illustrated configuration, device
10 is
configured so that the mixed gas stream is delivered into compartment 18
external to
the membrane tube or tubes. In such a configuration, the mixed-gas surface of
a
membrane tube is exterior to the corresponding permeate surface, and the
permeate
region is located internal the membrane tube or tubes.
The tubular membranes may have a variety of configurations and
constructions, such as those discussed above with respect to the planar
membranes
shown in Fig. 2. For example, illustrative examples of various mounts 52,
supports
54 and porous members 56 are shown in Figs. 3 and 4, including a spring 58,
which
has been schematically illustrated. It is further within the scope of the
invention that
tubular membranes may have a configuration other than the straight cylindrical
tube
shown in Fig. 3. Examples of other configurations include U-shaped tubes and
spiral
or helical tubes.
As discussed, enclosure 12 defines a pressurized compartment 18 in
which separation assembly 20 is positioned. In the embodiments shown in Figs.
2-4,
enclosure 12 includes a pair of end plates 60 that are joined by a perimeter
shell 62. It
should be understood that device 10 has been schematically illustrated in
Figs. 2-4 to
show representative examples of the general components of the device without
intending to be limited to geometry, shape and size. For example, end plates
60
typically are thicker than the walls of perimeter shell 62, but this is not
required.
Similarly, the thickness of the end plates may be greater than, less than or
the same as
the distance between the end plates. As a further example, the thickness of
membrane
46 has been exaggerated for purposes of illustration.
In Figs. 2-4, it can be seen that mixed gas stream 24 is delivered to
compartment 18 through an input port 64, hydrogen-rich (or permeate) stream 34
is
removed from device 10 through one or more product ports 66, and the byproduct
stream is removed from device 10 through one or more byproduct ports 68. In
Fig. 2,
the ports are shown extending through various ones of the end plates to
illustrate that
the particular location on enclosure 12 from which the gas streams are
delivered to
and removed from device 10 may vary. It is also within the scope of the
invention
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CA 02494680 2002-03-26
that one or more of the streams may be delivered or withdrawn through shell
62, such as
illustrated in dashed lines in Fig. 3. It is further within the scope of the
invention that ports
64-68 may include or be associated with flow-regulating and/or coupling
structures.
Examples of these structures include one or more of valves, flow and pressure
regulators,
S connectors or other fittings and/or manifold assemblies that are configured
to permanently or
selectively fluidly interconnect device 10 with upstream and downstream
components. For
purposes of illustration, these flow-regulating and/or coupling structures are
generally
indicated at 70 in Fig. 2. For purposes of brevity, structures 70 have not
been illustrated in
every embodiment. Instead, it should be understood that some or all of the
ports for a
particular embodiment of device 10 may include any or all of these structures,
that each port
does not need to have the same, if any, structure 70, and that two or more
ports may in some
embodiments share or collectively utilize structure 70, such as a common
collection or
delivery manifold, pressure relief valve, fluid-flow valve, etc.
End plates 60 and perimeter shell 62 are secured together by a retention
structure 72. Structure 72 may take any suitable form capable of maintaining
the components
of enclosure 12 together in a fluid-tight or substantially fluid-tight
configuration in the
operating parameters and conditions in which device 10 is used. Examples of
suitable
structures 72 include welds 74 and bolts 76, such as shown in Figs. 2 and 3.
In Fig. 3, bolts
76 are shown extending through flanges 78 that extend from the components of
enclosure 12
to be joined. In Fig. 4, bolts 76 are shown extending through compartment 18.
It should be
understood that the number of bolts may vary, and typically will include a
plurality of bolts or
similar fastening mechanisms extending around the perimeter of enclosure 12.
Bolts 76
should be selected to be able to withstand the operating parameters and
conditions of device
10, including the tension imparted to the bolts when device 10 is pressurized.
In the lower halves of Figs. 3 and 4, gaskets 80 are shown to illustrate that
enclosure 12 may, but does not necessarily, include a seal member 82
interconnecting or
spanning the surfaces to be joined to enhance the leak-resistance of the
enclosure. The seal
member should be selected to reduce or eliminate leaks when used at the
operating parameters
and under the operating conditions of the device. Therefore, in many
embodiments, high-
pressure and/or high-temperature seals should be selected. An illustrative,
non-exclusive
example of such a seal structure is a
CA 02494680 2002-03-26
graphite gasket, such as sold by Union Carbide under the trade name GRAFOIL~.
As used
herein, "seal member" and "sealing member" are meant to refer to structures or
materials
applied to, placed between, or placed in contact with the metallic end plates
and shell (or shell
portions) to enhance the seal established therebetween. Gaskets or other
sealing members
may also be used internal compartment 18, such as to provide seals between
adjacent
membranes, fluid conduits, mounts or supports, andlor any of the above with
the internal
surface of enclosure 12.
In Figs. 2-4, the illustrated enclosures include a pair of end plates 60 and a
shell 62. With reference to Fig. 4, it can be seen that the end plates include
sealing regions 90,
which form an interface 94 with a corresponding sealing region 92 of shell 62.
In many
embodiments, the sealing region of end plate 60 will be a perimeter region,
and as such,
sealing region 90 will often be referred to herein as a perimeter region 90 of
the end plate.
However, as used herein, the perimeter region is meant to refer to the region
of the end plate
that extends generally around the central region and which forms an interface
with a portion
of the shell, even if there are additional portions or edges of the end plate
that proj ect beyond
this perimeter portion. Similarly, sealing region 92 of shell 62 will
typically be an end region
of the shell. Accordingly, the sealing region of the shell will often be
referred to herein as end
region 92 of the shell. It is within the scope of the invention, however, that
end plates 60 may
have portions that project outwardly beyond the sealing region 90 and
interface 94 formed
with shell 62, and that shell 62 may have regions that project beyond end
plate 60 and the
interface formed therewith. These portions are illustrated in dashed lines in
Fig. 4 at 91 and
93 for purposes of graphical illustration.
As an alternative to a pair of end plates 60 joined by a separate perimeter
shell
62, enclosure 12 may include a shell that is at least partially integrated
with either or both of
the end plates. For example, in Fig. 5, a portion 63 of shell 62 is integrally
formed with each
end plate 60. Described another way, each end plate 60 includes shell
portions, or collars, 63
that extend from the perimeter region 90 of the end plate. As shown, the shell
portions
include end regions 92 which intersect at an interface 94. In the illustrated
embodiment, the
end regions abut each other without a region of overlap; however, it is within
the scope of the
invention that interface 94 may have other configurations, such as those
illustrated and/or
described subsequently. End regions 92 are secured together via any suitable
mechanism,
such
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CA 02494680 2002-03-26
as by any of the previously discussed retention structures 72, and may (but do
not
necessarily) include a seal member 82 in addition to the mating surfaces of
end
regions 92.
A benefit of shell 62 being integrally formed with at least one of the
end plates is that the enclosure has one less interface that must be sealed.
This benefit
may be realized by reduced leaks due to the reduced number of seals that could
fail,
fewer components, and/or a reduced assembly time for device 10. Another
example
of such a construction for enclosure 12 is shown in Fig. 6, in which the shell
62 is
integrally formed with one of the end plates, with a shell portion 63 that
extends
integrally from the perimeter region 90 of one of the end plates. Shell
portion 63
includes an end region 92 that forms an interface 94 with the perimeter region
90 of
the other end plate via any suitable retention structure 72, such as those
described
above. The combined end plate and shell components shown in Figs. 5 and 6 may
be
formed via any suitable mechanism, including machining them from a solid bar
or
block of material. For purposes of simplicity, separation assembly 20 and the
input
and output ports have not been illustrated in Figs. 5 and 6 and only
illustrative, non-
exclusive examples of suitable retention structure 72 are shown. Similar to
the other
enclosures illustrated and described herein, it should be understood that the
relative
dimensions of the enclosure may vary and still be within the scope of the
invention.
For example, shell portions 63 may have lengths that are longer or shorter
than those
illustrated in Figs. 5 and 6.
Before proceeding to additional illustrative configurations for end
plates 60, it should be clarified that as used herein in connection with the
enclosures
of devices 10, the term "interface" is meant to refer to the interconnection
and sealing
region that extends between the portions of enclosure 12 that are separately
formed
and thereafter secured together, such as (but not necessarily) by one of the
previously
discussed retention structures 72. The specific geometry and size of interface
94 will
tend to vary, such as depending upon size, configuration and nature of the
components being joined together. Therefore, interface 94 may include a metal-
on-
metal seal formed between corresponding end regions and perimeter regions, a
metal-
on-metal seal formed between corresponding pairs of end regions, a metal-
gasket (or
other seal member 82)-metal seal, etc. Similarly, the interface may have a
variety of
12
CA 02494680 2002-03-26
shapes, including linear, arcuate and rectilinear configurations that are
largely defined by the
shape and relative position of the components being joined together.
For example, in Fig. 6, an interface 94 extends between end region 92 of shell
portion 63 and perimeter region 90 of end plate 60. As shown, regions 90 and
92 intersect
with parallel edges. As discussed, a gasket or other seal member may extend
between these
edges. In Figs. 7-10, nonexclusive examples of additional interfaces 94 that
are within the
scope of the invention are shown. Embodiments of enclosure 12 that include an
interface 94
formed between adjacent shell regions may also have any of these
configurations. In Fig. 7,
perimeter region 90 defines a recess or corner into which end region 92 of
shell 62 extends to
form an interface 94 that extends around this comer. Also shown in Fig. 7 is
central region 96
of end plate 60, which as illustrated extends within shell 62 and defines a
region of overlap
therewith.
In Fig. 8, perimeter region 90 defines a corner that opens generally toward
compartment 18, as opposed to the corner of Fig. 7, which opens generally away
from
compartment 18. In the configuration shown in Fig. 8, perimeter region 90
includes a collar
portion 98 that extends at least partially along the outer surface 100 of
shell 62 to define a
region of overlap therewith. Central region 96 of plate 60 is shown in solid
lines extending
along end region 92 without extending into shell 62, in dashed lines extending
into shell 62,
and in dash-dot lines including an internal support 102 that extends at least
partially along the
inner surface 104 of shell 62. Figs. 9 and 10 are similar to Figs. 7 and 8
except that perimeter
region 90 and end region 92 are adapted to threadingly engage each other, and
accordingly
include corresponding threads 106 and 108. In dashed lines in Fig. 9, an
additional example
of a suitable configuration for perimeter region 90 of end plate 60 is shown.
As shown, the
outer edge 110 of the end plate does not extend radially (or outwardly) to or
beyond the
exterior surface of shell 62.
It should be understood that any of these interfaces may be used with an
enclosure constructed according to the present invention. However, for
purposes of brevity,
every embodiment of enclosure 12 will not be shown with each of these
interfaces. Therefore,
although the subsequently described end plates shown in Figs. 11-31 are shown
with the
interface configuration of Fig. 7, it is within the scope of the invention
that the end plates and
corresponding shells may be configured to have any of the interfaces described
and/or
illustrated herein, as well as the integrated shell
13
CA 02494680 2002-03-26
configuration described and illustrated with respect to Figs. 5 and 6.
Similarly, it
should be understood that the devices constructed according to the present
invention
may have any of the enclosure configurations, interface configurations,
retention
structure configurations, separation assembly configurations, flow-regulating
and/or
coupling structures, seal member configurations, and port configurations
discussed,
described and/or referred to herein. Similarly, although the following end
plate
configurations are illustrated with circular perimeters, it is within the
scope of the
invention that the end plates may be configured to have perimeters with any
other
geometric configuration, including arcuate, rectilinear, and angular
configurations, as
well as combinations thereof.
As discussed, the dimensions of device 10 and enclosure 12 may also
vary. For example, an enclosure designed to house tubular separation membranes
may need to be longer (i.e. have a greater distance between end plates) than
an
enclosure designed to house planar separation membranes to provide a
comparable
amount of membrane surface area exposed to the mixed gas stream (i.e., the
same
amount of effective membrane surface area). Similarly, an enclosure configured
to
house planar separation membranes may tend to be wider (i.e., have a greater
cross-
sectional area measured generally parallel to the end plates) than an
enclosure
designed to house tubular separation membranes. However, it should be
understood
that neither of these relationships are required, and that the specific size
of the device
and/or enclosure may vary. Factors that may affect the specific size of the
enclosure
include the type and size of separation assembly to be housed, the operating
parameters in which the device will be used, the flow rate of mixed gas stream
24, the
shape and configuration of devices such as heating assemblies, fuel processors
and the
like with which or within which the device will be used, and to some degree,
user
preferences.
As discussed previously, hydrogen purification devices may be
operated at elevated temperatures and/or pressures. Both of these operating
parameters may impact the design of enclosures 12 and other components of the
devices. For example, consider a hydrogen purification device 10 operated at a
selected operating temperature above an ambient temperature, such as a device
operating at 400° C. As an initial matter, the device, including
enclosure 12 and
separation assembly 20, must be constructed from a material that can withstand
the
14
CA 02494680 2002-03-26
selected operating temperature, and especially over prolonged periods of time
and/or
with repeated heating and cooling off cycles. Similarly, the materials that
are exposed
to the gas streams preferably are not reactive or at least not detrimentally
reactive with
the gases. An example of a suitable material is stainless steel, such as Type
304
stainless steel, although others may be used.
Besides the thermal and reactive stability described above, operating
device 10 at a selected elevated temperature requires one or more heating
assemblies
42 to heat the device to the selected operating temperature. When the device
is
initially operated from a shutdown, or unheated, state, there will be an
initial startup
or preheating period in which the device is heated to the selected operating
temperature. During this period, the device may produce a hydrogen-rich stream
that
contains more than an acceptable level of the other gases, a hydrogen-rich
stream that
has a reduced flow rate compared to the byproduct stream or streams (meaning
that a
greater percentage of the hydrogen gas is being exhausted as byproduct instead
of
product), or even no hydrogen-rich stream at all. In addition to the time to
heat the
device, one must also consider the heat or thermal energy required to heat the
device
to the selected temperature. The heating assembly or assemblies may add to the
operating cost, materials cost, and/or equipment cost of the device. For
example, a
simplified end plate 60 is a relatively thick slab having a uniform thickness.
In fact,
Type 304 stainless steel plates having a uniform thickness of 0.5" or 0.75
inches have
proven effective to support and withstand the operating parameters and
conditions of
device 10. However, the dimensions of these plates add considerable weight to
device 10, and in many embodiments require considerable thermal energy to be
heated to the selected operating temperature. As used herein, the term
"uniform
thickness" is meant to refer to devices that have a constant or at least
substantially
constant thickness, including those that deviate in thickness by a few (less
than 5%)
along their lengths. In contrast, and as used herein, a "variable thickness"
will refer to
a thickness that varies by at least 10%, and in some embodiments at least 25%,
40%
or 50%.
The pressure at which device 10 is operated may also affect the design
of device 10, including enclosure 12 and separation assembly 20. Consider for
example a device operating at a selected pressure of 175 psi. Device 10 must
be
constructed to be able to withstand the stresses encountered when operating at
the
CA 02494680 2002-03-26
selected pressure. This strength requirement affects not only the seals formed
between the components of enclosure 12, but also the stresses imparted to the
components themselves. For example, deflection or other deformation of the end
plates and/or shell may cause gases within compartment 18 to leak from the
enclosure. Similarly, deflection and/or deformation of the components of the
device
may also cause unintentional mixing of two or more of gas streams 24, 34 and
36.
For example, an end plate may deform plastically or elastically when subjected
to the
operating parameters under which device 10 is used. Plastic deformation
results in a
permanent deformation of the end plate, the disadvantage of which appears
fairly
evident. Elastic deformation, however, also may impair the operation of the
device
because the deformation may result in internal and/or external leaks. More
specifically, the deformation of the end plates or other components of
enclosure 12
may enable gases to pass through regions where fluid-tight seals previously
existed.
As discussed, device 10 may include gaskets or other seal members to reduce
the
tendency of these seals to leak, however, the gaskets have a finite size
within which
they can effectively prevent or limit leaks between opposing surfaces. For
example,
internal leaks may occur in embodiments that include one or more membrane
envelopes or membrane plates compressed (with or without gaskets) between the
end
plates. As the end plates deform and deflect away from each other, the plates
and/or
gaskets may in those regions not be under the same tension or compression as
existed
prior to the deformation. Gaskets, or gasket plates, may be located between a
membrane envelope and adjacent feed plates, end plates, and/or other adjacent
membrane envelopes. Similarly, gaskets or gasket plates may also be positioned
within a membrane envelope to provide additional leak prevention within the
envelope.
In view of the above, it can be seen that there are two or three
competing factors to be weighed with respect to device 10. In the context of
enclosure 12, the heating requirements of the enclosure will tend to increase
as the
materials used to form the enclosure are thickened. To some degree using
thicker
materials may increase the strength of the enclosure, however, it may also
increase the
heating and material requirements, and in some embodiments actually produce
regions to which greater stresses are imparted compared to a thinner
enclosure. Areas
16
CA 02494680 2002-03-26
to monitor on an end plate include the deflection of the end plate, especially
at the
perimeter regions that form interfaces) 94, and the stresses imparted to the
end plate.
Consider for example a circular end plate formed from Type 304
stainless steel and having a uniform thickness of 0.75 inches. Such an end
plate
weighs 7.5 pounds. A hydrogen purification device containing this end plate
was
exposed to operating parameters of 400° C and 175 psi. Maximum stresses
of 25,900
psi were imparted to the end plate, with a maximum deflection of 0.0042 inches
and a
deflection at perimeter region 90 of 0.0025 inches.
Another end plate 60 constructed according to the present invention is
shown in Figs. 11 and 12 and generally indicated at 120. As shown, end plate
120 has
interior and exterior surfaces 122 and 124. Interior surface 122 includes
central
region 96 and perimeter region 90. Exterior surface 124 has a central region
126 and
a perimeter region 128, and in the illustrated embodiment, plate 120 has a
perimeter
130 extending between the perimeter regions 90 and 128 of the interior and
exterior
surfaces. As discussed above, perimeter region 90 may have any of the
configurations illustrated or described above, including a configuration in
which the
sealing region is at least partially or completely located along perimeter
130. In the
illustrated embodiment, perimeter 130 has a circular configuration. However,
it is
within the scope of the invention that the shape may vary, such as to include
rectilinear and other arcuate, geometric, linear, andlor cornered
configurations.
Unlike the previously illustrated end plates, however, the central
region of the end plate has a variable thickness between its interior and
exterior
surfaces, which is perhaps best seen in Fig. 12. Unlike a uniform slab of
material, the
exterior surface of plate 120 has a central region 126 that includes an
exterior cavity,
or removed region, 132 that extends into the plate and generally toward
central region
96 on interior surface 122. Described another way, the end plate has a
nonplanar
exterior surface, and more specifically, an exterior surface in which at least
a portion
of the central region extends toward the corresponding central region of the
end
plate's interior surface. Region 132 reduces the overall weight of the end
plate
compared to a similarly constructed end plate that does not include region
132. As
used herein, removed region 132 is meant to exclude ports or other bores that
extend
completely through the end plates. Instead, region 132 extends into, but not
through,
the end plate.
17
CA 02494680 2002-03-26
A reduction in weight means that a purification device 10 that includes
the end plate will be lighter than a corresponding purification device that
includes a
similarly constructed end plate formed without region 132. With the reduction
in
weight also comes a corresponding reduction in the amount of heat (thermal
energy)
S that must be applied to the end plate to heat the end plate to a selected
operating
temperature. In the illustrated embodiment, region 132 also increases the
surface area
of exterior surface 124. Increasing the surface area of the end plate compared
to a
corresponding end plate may, but does not necessarily in all embodiments,
increase
the heat transfer surface of the end plate, which in turn, can reduce the
heating
requirements and/or time of a device containing end plate 120.
In some embodiments, plate 120 may also be described as having a
cavity that corresponds to, or includes, the region of maximum stress on a
similarly
constructed end plate in which the cavity was not present. Accordingly, when
exposed to the same operating parameters and conditions, lower stresses will
be
imparted to end plate 120 than to a solid end plate formed without region 132.
For
example, in the solid end plate with a uniform thickness, the region of
maximum
stress occurs within the portion of the end plate occupied by removed region
132 in
end plate 120. Accordingly, an end plate with region 132 may additionally or
alternatively be described as having a stress abatement structure 134 in that
an area of
maximum stress that would otherwise be imparted to the end plate has been
removed.
For purposes of comparison, consider an end plate 120 having the
configuration shown in Figs. 11 and 12, formed from Type 304 stainless steel,
and
having a diameter of 6.5 inches. This configuration corresponds to maximum
plate
thickness of 0.75 inches and a removed region 132 having a length and width of
3
inches. When utilized in a device 10 operating at 400° C and 175 psi,
plate 120 has a
maximum stress imparted to it of 36,000 psi, a maximum deflection of 0.0078
inches,
a displacement of 0.0055 inches at perimeter region 90, and a weight of 5.7
pounds.
It should be understood that the dimensions and properties described above are
meant
to provide an illustrative example of the combinations of weight, stress and
displacement experienced by end plates according to the present invention, and
that
the specific perimeter shape, materials of construction, perimeter size,
thickness,
removed region shape, removed region depth and removed region perimeter all
may
vary within the scope of the invention.
18
CA 02494680 2002-03-26
In Fig. 11, it can be seen that region 132 (and/or stress abatement
structure 134) has a generally square or rectilinear configuration measured
transverse
to surfaces 122 and 124. As discussed, other geometries and dimensions may be
used
and are within the scope of the invention. To illustrate this point,
variations of end
plate 120 are shown in Figs. 13-16 and generally indicated at 120' and 120".
In these
figures, region 132 is shown having a circular perimeter, with the dimensions
of the
region being smaller in Figs. 13 and 14 than in Figs. 15 and 16.
For purposes of comparison, consider an end plate 120 having the
configuration shown in Figs. 13 and 14 and having the same materials of
construction,
perimeter and thickness as the end plate shown in Figs. 11 and 12. Instead of
the
generally square removed region of Figs. 11 and 12, however, end plate 120'
ha.s a
removed region with a generally circular perimeter and a diameter of 3.25
inches.
End plate 120' weighs the same as end plate 120, but has reduced maximum
stress
and deflections. More specifically, while end plate 120 had a maximum stress
greater
than 35,000 psi, end plate 120' had a maximum stress that is less than 30,000
psi, and
in the illustrated configuration less than 25,000 psi, when subjected to the
operating
parameters discussed above with respect to plate 120. In fact, plate 120'
demonstrated approximately a 35% reduction in maximum stress compared to plate
120. The maximum and perimeter region deflections of plate 120' were also less
than
plate 120, with a measured maximum deflection of 0.007 inches and a measured
deflection at perimeter region 90 of 0.0050 inches.
End plate 120", which is shown in Figs. 15 and 16 is similar to end
plate 120', except region 132 (and/or structure 134) has a diameter of 3.75
inches
instead of 3.25 inches. This change in the size of the removed region
decreases the
weight of the end plate to 5.3 pounds and produced the same maximum
deflection.
End plate 120" also demonstrated a maximum stress that is less than 25,000
psi,
although approximately 5% greater than that of end plate 120' (24,700 psi,
compared
to 23,500 psi). At perimeter region 90, end plate 120" exhibited a maximum
deflection of 0.0068 inches.
In Figs. 13-16, illustrative port configurations have been shown. In
Figs. 13 and 14, a port 138 is shown in dashed lines extending from interior
surface
122 through the end plate to exterior surface 124. Accordingly, with such a
configuration a gas stream is delivered or removed via the exterior surface of
the end
19
CA 02494680 2002-03-26
plate of device 10. In such a configuration, fluid conduits andlor flow-
regulating
and/or coupling structure 70 typically will project from the exterior surface
124 of the
end plate. Another suitable configuration is indicated at 140 in dashed lines
in
Figs. 15 and 16. As shown, port 140 extends from the interior surface of the
end plate
then through perimeter 130 instead of exterior surface 124. Accordingly, port
140
enables gas to be delivered or removed from the perimeter of the end plate
instead of
the exterior surface of the end plate. It should be understood that ports 64-
68 may
have these configurations illustrated by ports 138 and 140. Of course, ports
64-68
may have any other suitable port configuration as well, including a port that
extends
through shell 62 or a shell portion. For purposes of simplicity, ports will
not be
illustrated in many of the subsequently described end plates, just as they
were not
illustrated in Figs. 5 and 6.
Also shown in dashed lines in Figs. 13-15 are guide structures 144.
Guide structures 144 extend into compartment 18 and provide supports that may
be
used to position and/or align separation assembly 20, such as membranes 46. In
some
embodiments, guide structures 144 may themselves form mounts 52 for the
separation
assembly. In other embodiments, the device includes mounts other than guide
structures 144. Guide structures may be used with any of the end plates
illustrated,
referred to or described herein, regardless of whether any such guide
structures are
shown in a particular drawing figure. However, it should also be understood
that
hydrogen purification devices according to the present invention may be formed
without guide structures 144. In embodiments of device 10 that include guide
structures 144 that extend into or through compartment 18, the number of such
structures may vary from a single support to two or more supports. Similarly,
while
guide structures 144 have been illustrated as cylindrical ribs or projections,
other
shapes and configurations may be used within the scope of the invention.
Guide structures 144 may be formed from the same materials as the
corresponding end plates. Additionally or alternatively, the guide structures
may
include a coating or layer of a different material. Guide structures 144 may
be either
separately formed from the end plates and subsequently attached thereto, or
integrally
formed therewith. Guide structures 144 may be coupled to the end plates by any
suitable mechanism, including attaching the guide structures to the interior
surfaces of
the end plates, inserting the guide structures into bores extending partially
through the
CA 02494680 2002-03-26
end plates from the interior surfaces thereof, or inserting the guide
structures through
bores that extend completely through the end plates. In embodiments where the
end
plates include bores that extend completely through the end plates (which are
graphically illustrated for purposes of illustration at 146 in Fig. 14), the
guide
structures may be subsequently affixed to the end plates. Alternatively, the
guide
structures may be inserted through compartment 18 until the separation
assembly is
properly assigned and secured therein, and then the guide structures may be
removed
and the bores sealed (such as by welding) to prevent leaks.
In Figs. 17 and 18, another end plate 60 constructed according to the
present invention is shown and generally indicated at 150. Unless otherwise
specified, it should be understood that end plates 150 may have any of the
elements,
subelements and variations as any of the other end plates shown, described
and/or
referred to herein. Similar to end plate 120', plate 150 includes an exterior
surface
124 with a removed region 132 (andlor stress abatement structure 134) having a
circular perimeter with a diameter of 3.25 inches. Exterior surface 124
further
includes an outer removed region 152 that extends from central region 126 to
perimeter portion 128. Outer removed region 152 decreases in thickness as it
approaches perimeter 130. In the illustrated embodiment, region 152 has a
generally
linear reduction in thickness, although other linear and arcuate transitions
may be
used. For example, a variation of end plate 150 is shown in Figs. 19 and 20
and
generally indicated at 150'. End plate 150' also includes central and exterior
removed
regions 132 and 152, with exterior surface 124 having a generally semitoroidal
configuration as it extends from central region 126 to perimeter region 128.
To
demonstrate that the size of region 132 (which will also be referred to as a
central
removed region, such as when embodied on an end plate that also includes an
outer
removed region), may vary, end plate 150' includes a central removed region
having a
diameter of 3 inches.
For purposes of comparison, both end plates 150 and 1 SO' have
reduced weights compared to end plates 120, 120' and 120". Plate 1 SO weighed
4.7
pounds, and plate 150' weighed 5.1 pounds. Both end plates 150 and 150'
experienced maximum stresses of 25,000 psi or less when subjected to the
operating
parameters discussed above (400° C and 175 psi), with plate 150' having
a 5% lower
stress than plate 150 (23,750 psi compared to 25,000 psi). The maximum
deflection
21
CA 02494680 2002-03-26
of the plates were 0.0098 inches and 0.008 inches, respectively, and the
displacement
at perimeter regions 90 were 0.0061 inches and 0.0059 inches, respectively.
Another end plate 60 constructed according to the present invention is
shown in Figs. 21-24 and generally indicated at 160. Unless otherwise
specified, end
plate 160 may have the same elements, subelements and variations as the other
end
plates illustrated, described or referred to herein. End plate 160 may be
referred to as
a truss-stiffened end plate because it includes a truss assembly 162 that
extends from
the end plate's exterior surface 124. As shown, end plate 160 has a base plate
164
with a generally planar configuration, similar to the end plates shown in
Figs. 2-5.
However, truss assembly 162 enables, but does not require, that the base plate
may
have a thinner construction while still providing comparable if not reduced
maximum
stresses and deflections. It is within the scope of the invention that any of
the other
end plates illustrated, described or referred to herein also may include a
truss
assembly 162.
Truss assembly 162 extends from exterior surface 124 of base plate
164 and includes a plurality of projecting ribs 166 that extend from exterior
surface
124. In Figs. 21-24, it can be seen that ribs 166 are radially spaced around
surface
124. Nine ribs 166 are shown in Figs. 21 and 23, but it is within the scope of
the
invention that truss assembly 162 may be formed with more or fewer ribs.
Similarly,
in the illustrated embodiment, ribs 166 have arcuate configurations, and
include
flanges 168 extending between the ribs and surface 124. Flanges 168 may also
be
described as heat transfer fins because they add considerable heat transfer
area to the
end plate. Truss assembly 162 further includes a tension collar 170 that
interconnects
the ribs. As shown, collar 170 extends generally parallel to surface base
plate 164 and
has an open central region 172. Collar 170 may be formed with a closed or
internally
or externally proj ecting central portion without departing from the
invention. To
illustrate this point, members 174 are shown in dashed lines extending across
collar
170 in Fig. 21. Similarly, collar 170 may have configurations other than the
circular
configuration shown in Figs. 21-24. As a further alternative, base plate 164
has been
indicated in partial dashed lines in Fig. 22 to graphically illustrate that
the base plate
may have a variety of configurations, such as those described, illustrated and
referred
to herein, including the configuration shown if the dashed region is removed.
22
CA 02494680 2002-03-26
End plate 160 may additionally, or alternatively, be described as having a
support 170 that extends in a spaced-apart relationship beyond exterior
surface 124 of base
plate 164 and which is adapted to provide additional stiffness and/or strength
to the base plate.
Still another additional or alternative description of end plate 160 is that
the end plate includes
heat transfer structure 162 extending away from the exterior surface of the
base plate, and that
the heat transfer structure includes a surface 170 that is spaced-away from
surface 124 such
that a heated fluid stream may pass between the surfaces.
Truss assembly 162 may also be referred to as an example of a deflection
abatement structure because it reduces the deflection that would otherwise
occur if base plate
164 were formed without the truss assembly. Similarly, truss assembly 162 may
also provide
another example of a stress abatement restructure because it reduces the
maximum stresses
that would otherwise be imparted to the base plate. Furthermore, the open
design of the truss
assembly increases the heat transfer area of the base plate without adding
significant weight to
the base plate.
1 S Continuing the preceding comparisons between end plates, plate 160 was
subjected to the same operating parameters as the previously described end
plates. The
maximum stresses imparted to base plate 164 were 10,000 psi or less.
Similarly, the
maximum deflection of the base plate was only 0.0061 inches, with a deflection
of 0.0056
inches at perimeter region 90. It should be noted, that base plate 164
achieved this significant
reduction in maximum stress while weighing only 3.3 pounds. Similarly, base
plate 164
experienced a smaller maximum displacement and comparable or reduced perimeter
displacement yet had a base plate that was only 0.25 inches thick. Of course,
plate 160 may
be constructed with thicker base plates, but the tested plate proved to be
sufficiently strong
and rigid under the operating parameters with which it was used.
As discussed, enclosure 12 may include a pair of end plates 60 and a perimeter
shell. In Fig. 25, an example of an enclosure 12 formed with a pair of end
plates 160 is shown
for purposes of illustration and indicated generally at 180. Although
enclosure 180 has a pair
of truss-stiffened end plates 160, it is within the scope of the invention
that an enclosure may
have end plates having different constructions and/or configurations. In fact,
in some
operating environments it may
23
CA 02494680 2002-03-26
be beneficial to form enclosure 12 with two different types of end plates. In
others, it
may be beneficial for the end plates to have the same construction.
In Figs. 26 and 27 another example of an enclosure 12 is shown and
generally indicated at 190 and includes end plates 120"'. End plate 120"' has
a
configuration similar to Figs. 13-16, except removed region 132 is shown
having a
diameter of 4 inches to further illustrate that the shape and size of the
removed region
may vary within the scope of the invention. Both end plates include shell
portions 63
extending integrally therefrom to illustrate that any of the end plates
illustrated,
described, or referred to herein may include a shell portion 63 extending
integrally
therefrom. To illustrate that any of the end plates described, illustrated or
referred to
herein may also include truss assemblies (or heat transfer structure) 162
and/or
projecting supports 170 or deflection abatement structure, members 194 are
shown
projecting across removed region 132 in a spaced-apart configuration from the
exterior surface 124 of the end plate.
It is also within the scope of the invention that enclosure 12 may
include stress and/or deflection abatement structures that extend into
compartment 18
as opposed to, or in addition to, corresponding structures that extend from
the exterior
surface of the end plates. In Figs. 28-30, end plates 60 are shown
illustrating
examples of these structures. For example, in Fig. 28, end plate 60 includes a
removed region 132 that extends into the end plate from the interior surface
122 of the
end plate. It should be understood that region 132 may have any of the
configurations
described, illustrated or referred to herein with respect to removed regions
that extend
from the exterior surface of a base plate. Similarly, in dashed lines at 170
in Fig. 28,
supports are shown extending across region 132 to provide additional support
and/or
rigidity to the end plate. In Fig. 29, end plate 60 includes internal supports
196 that
are adapted to extend into compartment 18 to interconnect the end plate with
the
corresponding end plate at the other end of the compartment. As discussed,
guide
structures 144 may form such a support. In Fig. 30, an internally projecting
truss
assembly 162 is shown.
Although not required or essential to the invention, in some
embodiments, device 10 includes end plates 60 that exhibit at least one of the
following properties or combinations of properties compared to an end plate
formed
24
CA 02494680 2002-03-26
from a solid slab of uniform thickness of same material as end plate 60 and
exposed to
the same operating parameters:
- a projecting truss assembly;
- an internally projecting support;
- an externally projecting support;
- an external removed region;
- an internal removed region;
- an integral shell portion;
- an integral shell;
- a reduced mass and reduced maximum stress;
- a reduced mass and reduced maximum displacement;
- a reduced mass and reduced perimeter displacement;
- a reduced mass and increased heat transfer area;
- a reduced mass and internally projecting supports;
- a reduced mass and externally projecting supports;
- a reduced maximum stress and reduced maximum displacement;
- a reduced maximum stress and reduced perimeter displacement;
- a reduced maximum stress and increased heat transfer area;
- a reduced maximum stress and a projecting truss assembly;
- a reduced maximum stress and a removed region;
- a reduced maximum displacement and reduced perimeter displacement;
- a reduced maximum displacement and increased heat transfer area;
- a reduced perimeter displacement and increased heat transfer area;
- a reduced perimeter displacement and a projecting truss assembly;
- a reduced perimeter displacement and a removed region;
- a mass/maximum displacement ratio that is less than 1500 lb/psi;
- a mass/maximum displacement ratio that is less than 1000 lb/psi;
- a mass/maximum displacement ratio that is less than 750 lb/psi;
- a mass/maximum displacement ratio that is less than 500 lb/psi;
- a mass/perimeter displacement ratio that is less than 2000 lb/psi;
- a mass/perimeter displacement ratio that is less than 1500 lb/psi;
- a mass/perimeter displacement ratio that is less than 1000 lb/psi;
- a mass/perimeter displacement ratio that is less than 800 lb/psi;
CA 02494680 2002-03-26
- a mass/perimeter displacement ratio that is less than 600 lb/psi;
- a cross-sectional area/mass ratio that is at least 6 inzlpound;
- a cross-sectional area/mass ratio that is at least 7 in2/pound; and/or
- a cross-sectional area/mass ratio that is at least 10 inz/pound.
For example, device 10 according to the present disclosure may
include at least one end plate that includes a base plate that is adapted to
receive
stresses of less than 12,000 psi when the device is operated at a selected
temperature
of at least 200° C and a selected pressure of at least 50 psi, a
selected temperature of at
least 300° C and a selected pressure of at least 100 psi, a selected
temperature of at
least 300° C and a selected pressure of at least at least 125 psi,
and/or a selected
temperature of at least 400° C and a selected pressure of at least 175
psi. The at least
one end plate may have a variety of weights, including weighing less than 5
pounds or
even less than 4 pounds. Similarly, the at least one end plate may have a
variety of
sizes, including having a cross-sectional area of at least 10 in2, or even at
least 20 in2
and/or a thickness of at least 1/3 inch.
As discussed, when device 10 is used, pressures will be exerted to the
device,
including its end plates, that will tend to deflect or otherwise deform the
end plates.
For example, as measured with reference to a device 10 having a first
configuration at
a temperature of 25° C and a pressure within its compartment of 1 atm,
the device
may have a second configuration at a suitable temperature and pressure for
purifying
hydrogen gas, such as a temperature of 400° C and a pressure within the
compartment
of 175 psi. In this second configuration, the base plate of the at least one
end plate
may be adapted to have a maximum displacement from the first configuration of
less
than 0.001 inches, and optionally less than 0.0008 inches, and further
optionally less
than 0.00065 inches. As a further illustrative example, at these conditions,
the base
plate of the at least one end plate may be adapted to have at its sealing
region a
displacement of less than 0.001 inches compared to the first configuration,
and
optionally less than 0.0008 inches compared to the first configuration, and
further
optionally less than 0.0006 inches compared to the first configuration. As yet
another
illustrative example, at these or other operative conditions, the at least one
end plate
may be adapted to have a maximum displacement measured relative to its first
configuration and a mass/maximum displacement ratio of less than 800 lb/psi
when
26
CA 02494680 2002-03-26
the device is operated at a selected temperature of at least 300° C and
a selected
pressure of at least 125 psi.
As discussed, enclosure 12 contains an internal compartment 18 that houses
separation assembly 20, such as one or more separation membranes 46, which are
supported within the enclosure by a suitable mount 52. In the illustrative
examples
shown in Figs. 2 and 4, the separation membranes 46 were depicted as
independent
planar or tubular membranes. It is also within the scope of the invention that
the
membranes may be arranged in pairs that define permeate region 32
therebetween. In
such a configuration, the membrane pairs may be referred to as a membrane
envelope,
in that they define a common permeate region 32 in the form of a harvesting
conduit,
or flow path, extending therebetween and from which hydrogen-rich stream 34
may
be collected.
An example of a membrane envelope is shown in Fig. 31 and generally
indicated at 200. It should be understood that the membrane pairs may take a
variety
of suitable shapes, such as planar envelopes and tubular envelopes. Similarly,
the
membranes may be independently supported, such as with respect to an end plate
or
around a central passage. For purposes of illustration, the following
description and
associated illustrations will describe the separation assembly as including
one or more
membrane envelopes 200. It should be understood that the membranes forming the
envelope may be two separate membranes, or may be a single membrane folded,
rolled or otherwise configured to define two membrane regions, or surfaces,
202 with
permeate surfaces 50 that are oriented toward each other to define a conduit
204
therebetween from which the hydrogen-rich permeate gas may be collected and
withdrawn. Conduit 204 may itself form permeate region 32, or a device 10
according to the present invention may include a plurality of membrane
envelopes
200 and corresponding conduits 204 that collectively define permeate region
32.
To support the membranes against high feed pressures, a support 54 is
used. Support 54 should enable gas that permeates through membranes 46 to flow
therethrough. Support 54 includes surfaces 211 against which the permeate
surfaces
50 of the membranes are supported. In the context of a pair of membranes
forming a
membrane envelope, support 54 may also be described as defining harvesting
26A
CA 02494680 2002-03-26
conduit 204. In conduit 204, permeated gas preferably may flow both transverse
and parallel
to the surface of the membrane through which the gas passes, such as
schematically illustrated
in Fig. 31. The permeate gas, which is at least substantially pure hydrogen
gas, may then be
harvested or otherwise withdrawn from the envelope to form hydrogen-rich
stream 34.
Because the membranes lie against the support, it is preferable that the
support does not
obstruct the flow of gas through the hydrogen-selective membranes. The gas
that does not
pass through the membranes forms one or more byproduct streams 36, as
schematically
illustrated in Fig. 31.
An example of a suitable support 54 for membrane envelopes 200 is shown in
Fig. 32 in the form of a screen structure 210. Screen structure 210 includes
plural screen
members 212. In the illustrated embodiment, the screen members include a
coarse mesh
screen 214 sandwiched between fme mesh screens 216. It should be understood
that the terms
"fine" and "coarse" are relative terms. Preferably, the outer screen members
are selected to
support membranes 46 without piercing the membranes and without having
sufficient
apertures, edges or other projections that may pierce, weaken or otherwise
damage the
membrane under the operating conditions with which device 10 is operated.
Because the
screen structure needs to provide for flow of the permeated gas generally
parallel to the
membranes, it is preferable to use a relatively coarser inner screen member to
provide for
enhanced, or larger, parallel flow conduits. In other words, the finer mesh
screens provide
better protection for the membranes, while the coarser mesh screen provides
better flow
generally parallel to the membranes and in some embodiments may be selected to
be stiffer,
or less flexible, than the finer mesh screens.
The screen members may be of similar or the same construction, and more or
less screen members may be used than shown in Fig. 32. Preferably, support 54
is formed
from a corrosion-resistant material that will not impair the operation of the
hydrogen
purification device and other devices with which device 10 is used. Examples
of suitable
materials for metallic screen members include stainless steels, titanium and
alloys thereof,
zirconium and alloys thereof, corrosion-resistant alloys, including Inconel~
alloys, such as
800H~, and HastelloyTM alloys, and alloys of copper and nickel, such as
Monel~.
Hastelloy~ and Inconel~ alloys are nickel-based alloys. Inconel~ alloys
typically contain
nickel alloyed with chromium and iron. Money alloys typically are alloys of
nickel, copper,
iron and manganese.
27
CA 02494680 2002-03-26
Additional examples of structure for supports 54 include porous ceramics,
porous carbon,
porous metal, ceramic foam, carbon foam, and metal foam, either alone, or in
combination with
one or more screen members 212. As another example, some or all of the screen
members may
be formed from expanded metal instead of a woven mesh material. In view of the
above, the
support may, but is not required to, be described as including one or more
(i.e., at least one),
screen member, with the illustrative examples provided herein demonstrating
one, two and
three screen members. These screen members may be formed from any of the
material
described herein, including a material that does not include an alloy of
nickel and copper.
During fabrication of the membrane envelopes, adhesive may be used to secure
membranes 46 to the screen structure and/or to secure the components of screen
structure 210
together, as discussed in more detail in the above-mentioned U.S. Patent No.
6,319,306. For
purposes of illustration, adhesive is generally indicated in dashed lines at
218 in Fig. 32. An
example of a suitable adhesive is sold by 3M under the trade name SUPER 77.
Typically, the
adhesive is at least substantially, if not completely, removed after
fabrication of the membrane
envelope so as not to interfere with the permeability, selectivity and flow
paths of the
membrane envelopes. An example of a suitable method for removing adhesive from
the
membranes and/or screen structures or other supports is by exposure to
oxidizing conditions
prior to initial operation of device 10. The objective of the oxidative
conditioning is to burn
out the adhesive without excessively oxidizing the palladium-alloy membrane. A
suitable
procedure for such oxidizing is disclosed in the above-mentioned patent.
Supports 54, including screen structure 210, may include a coating 219 on the
surfaces that engage membranes 46, such as indicated in dash-dot lines in Fig.
32. Examples
of suitable coatings include aluminum oxide, tungsten carbide, tungsten
nitride, titanium
carbide, titanium nitride, and mixtures thereof. These coatings are generally
characterized as
being thermodynamically stable with respect to decomposition in the presence
of hydrogen.
Suitable coatings are formed from materials, such as oxides, nitrides,
carbides, or intermetallic
compounds, that can be applied as a coating and which are thermodynamically
stable with
respect to decomposition in the presence of hydrogen under the operating
parameters
(temperature, pressure, etc.) under which the hydrogen purification device
will be
28
CA 02494680 2002-03-26
operated. Suitable methods for applying such coatings to the screen or
expanded metal screen
member include chemical vapor deposition, sputtering, thermal evaporation,
thermal spraying,
and, in the case of at least aluminum oxide, deposition of the metal (e.g.,
aluminum) followed
by oxidation of the metal to give aluminum
28A
CA 02494680 2002-03-26
oxide. In at least some embodiments, the coatings may be described as
preventing
intermetallic diffusion between the hydrogen-selective membranes and the
screen
structure.
The hydrogen purification devices 10 described, illustrated and/or
referred to herein may include one or more membrane envelopes 200, typically
along
with suitable input and output ports through which the mixed gas stream is
delivered
and from which the hydrogen-rich and byproduct streams are removed. In some
embodiments, the device may include a plurality of membrane envelopes. When
the
separation assembly includes a plurality of membrane envelopes, it may include
fluid
conduits interconnecting the envelopes, such as to deliver a mixed gas stream
thereto,
to withdxaw the hydrogen-rich stream therefrom, and/or to withdraw the gas
that does
not pass through the membranes from mixed gas region 30. When the device
includes
a plurality of membrane envelopes, the permeate stream, byproduct stream, or
both,
from a first membrane envelope may be sent to another membrane envelope for
fiurther purification. The envelope or plurality of envelopes and associated
ports,
supports, conduits and the like may be referred to as a membrane module 220.
The number of membrane envelopes 200 used in a particular device 10
depends to a degree upon the feed rate of mixed gas stream 24. For example, a
membrane module 220 containing four envelopes 200 has proven effective for a
mixed gas stream delivered to device 10 at a flow rate of 20 liters/minute. As
the
flow rate is increased, the number of membrane envelopes may be increased,
such as
in a generally linear relationship. For example, a device 10 adapted to
receive mixed
gas stream 24 at a flow rate of 30 liters/minute may preferably include six
membrane
envelopes. However, these exemplary numbers of envelopes are provided for
purposes of illustration, and greater or fewer numbers of envelopes may be
used. For
example, factors that may affect the number of envelopes to be used include
the
hydrogen flux through the membranes, the effective surface area of the
membranes,
the flow rate of mixed gas stream 24, the desired purity of hydrogen-rich
stream 34,
the desired efficiency at which hydrogen gas is removed from mixed gas stream
24,
user preferences, the available dimensions of device 10 and compartment 18,
etc.
Preferably, but not necessarily, the screen structure and membranes
that are incorporated into a membrane envelope 200 include frame members 230,
or
29
CA 02494680 2002-03-26
plates, that are adapted to seal, support and/or interconnect the membrane
envelopes. An
illustrative example of suitable frame members 230 is shown in Fig. 33. As
shown, screen
structure 210 fits within a frame member 230 in the form of a permeate frame
232. The
screen structure and frame 232 may collectively be referred to as a screen
plate or permeate
plate 234. When screen structure 210 includes expanded metal members, the
expanded metal
screen members may either fit within permeate frame 232 or extend at least
partially over the
surface of the frame. Additional examples of frame members 230 include
supporting frames,
feed plates and/or gaskets. These frames, gaskets or other support structures
may also define,
at least in part, the fluid conduits that interconnect the membrane envelopes
in an embodiment
of separation assembly 20 that contains two or more membrane envelopes.
Examples of
suitable gaskets are flexible graphite gaskets, including those sold under the
trade name
GRAFOIL~ by Union Carbide, although other materials may be used, such as
depending
upon the operating conditions under which device 10 is used.
Continuing the above illustration of exemplary frame members 230, permeate
1 S gaskets 236 and 236' are attached to permeate frame 232, preferably but
not necessarily, by
using another thin application of adhesive. Next, membranes 46 are supported
against screen
structure 210 and/or attached to screen structure 210 using a thin application
of adhesive, such
as by spraying or otherwise applying the adhesive to either or both of the
membrane and/or
screen structure. Care should be taken to ensure that the membranes are flat
and firmly
attached to the corresponding screen member 212. Feed plates, or gaskets, 238
and 238' are
optionally attached to gaskets 236 and 236', such as by using another thin
application of
adhesive. The resulting membrane envelope 200 is then positioned within
compartment 18,
such as by a suitable mount 52. Optionally, two or more membrane envelopes may
be stacked
or otherwise supported together within compartment 18.
As a further alternative, each membrane 46 may be fixed to a frame member
230, such as metal frames 240 and 240', as shown in Fig. 34. If so, the
membrane is fixed to
the frame, for instance by ultrasonic welding or another suitable
CA 02494680 2002-03-26
attachment mechanism. The membrane-frame assembly may, but is not required to
be,
attached to screen structure 210 using adhesive. Other examples of attachment
mechanisms
that achieve gas-tight seals between plates forming membrane envelope 200, as
well as between
the membrane envelopes, include one or more of brazing, gasketing, and
welding. The
membrane and attached frame may collectively be referred to as a membrane
plate, such as
indicated at 242 and 242' in Fig. 34. It is within the scope of the invention
that the various
frames discussed herein do not all need to be formed from the same materials
and/or that the
frames may not have the same dimensions, such as the same thicknesses. For
example, the
permeate and feed frames may be formed from stainless steel or another
suitable structural
member, while the membrane plate may be formed from a different material, such
as copper,
alloys thereof, and other materials discussed in the above-mentioned patents
and applications.
Additionally and/or alternatively, the membrane plate may, but is not required
to be, thinner than
the feed and/or permeate plates.
For purposes of illustration, a suitable geometry of fluid flow through
membrane envelope 200 is described with respect to the embodiment of envelope
200 shown
in Fig. 33. As shown, mixed gas stream 24 is delivered to the membrane
envelope and
contacts the outer surfaces 50 of membranes 46. The hydrogen-rich gas that
permeates
through the membranes enters harvesting conduit 204. The harvesting conduit is
in fluid
communication with conduits 250 through which the permeate stream may be
withdrawn
from the membrane envelope. The portion of the mixed gas stream that does not
pass through
the membranes flows to a conduit 252 through which this gas may be withdrawn
as byproduct
stream 36. In Fig. 33, a single byproduct .conduit 252 is shown, while in Fig.
34 a pair of
conduits 252 are shown to illustrate that any of the conduits described herein
may
alternatively include more than one fluid passage. It should be understood
that the arrows
used to indicate the flow of streams 34 and 36 have been schematically
illustrated, and that the
direction of flow through conduits 250 and 252 may vary, such as depending
upon the
configuration of a particular membrane envelope 200, module 220 and/or device
10.
31
CA 02494680 2002-03-26
In Fig. 35, another example of a suitable membrane envelope 200 is shown. To
graphically illustrate that end plates 60 and shell 62 may have a variety of
configurations,
envelope 200 is shown having a generally rectangular configuration. The
envelope of Fig. 35
also provides another example of a membrane envelope having a pair of
byproduct conduits 252
and a pair of hydrogen conduits 250. As shown, envelope 200 includes feed, or
spacer, plates
238 as the outer most frames in the envelope. Generally, each of plates 238
includes a frame 260
that defines an inner open region 262. Each inner open region 262 couples
laterally to conduits
252. Conduits 250, however, are closed relative to open region 262, thereby
isolating hydrogen-
rich stream
31A
CA 02494680 2002-03-26
34. Membrane plates 242 lie adjacent and interior to plates 238. Membrane
plates 242
each include as a central portion thereof a hydrogen-selective membrane 46,
which may
be secured to an outer frame 240, which is shown for purposes of graphical
illustration.
In plates 242, all of the conduits are closed relative to membrane 46. Each
membrane
lies adjacent to a corresponding one of open regions 262, i.e., adjacent to
the flow of
mixed gas arriving to the envelope. This provides an opportunity for hydrogen
gas to
pass through the membrane, with the non-permeating gases, i.e., the gases
forming
byproduct stream 36, leaving open region 262 through conduit 252. Screen plate
234 is
positioned intermediate membranes 46 and/or membrane plates 242, i.e., on the
interior
or permeate side of each of membranes 46. Screen plate 234 includes a screen
structure
210 or another suitable support 54. Conduits 252 are closed relative to the
central region
of screen plate 234, thereby isolating the byproduct stream 36 and mixed gas
stream 24
from hydrogen-rich stream 34. Conduits 250 are open to the interior region of
screen
plate 234. Hydrogen gas, having passed through the adjoining membranes 46,
travels
along and through screen structure 210 to conduits 250 and eventually to an
output port
as the hydrogen-rich stream 34.
As discussed, device 10 may include a single membrane 46 within
shell 62, a plurality of membranes within shell 62, one or more membrane
envelopes
200 within shell 62 and/or other separation assemblies 20. In Fig. 36, a
membrane
envelope 200 similar to that shown in Fig. 34 is shown positioned within shell
62 to
illustrate this point. It should be understood that envelope 200 may also
schematically
represent a membrane module 220 containing a plurality of membrane envelopes,
and/or a single membrane plate 242. Also shown for purposes of illustration is
an
example of a suitable position for guide structures 144. As discussed,
structures 144
also represent an example of internal supports 196. Fig. 36 also illustrates
graphically
an example of suitable positions for ports 64-68. To further illustrate
suitable
positions of the membrane plates and/or membrane envelopes within devices 10
containing end plates according to the present invention, Figs. 37 and 38
respectively
illustrate in dashed lines a membrane plate 242, membrane envelope 200 and/or
membrane module 220 positioned within a device 10 that includes the end plates
shown in Figs. 13-14 and 21-25.
Shell 62 has been described as interconnecting the end plates to define
therewith internal compartment 18. It is within the scope of the invention
that the
32
CA 02494680 2002-03-26
shell may be formed from a plurality of interconnected plates 230. For
example, a
membrane module 220 that includes one or more membrane envelopes 200 may form
shell 62 because the perimeter regions of each of the plates may form a fluid-
tight, or
at least substantially fluid-tight seal therebetween. An example of such a
construction
is shown in Fig. 39, in which a membrane module 220 that includes three
membrane
envelopes 200 is shown. It should be understood that the number of membrane
envelopes may vary, from a single envelope or even a single membrane plate
242, to a
dozen or more. In Fig. 39, end plates 60 are schematically represented as
having
generally rectangular configurations to illustrate that configurations other
than
circular configurations are within the scope of the invention. It should be
understood
that the schematically depicted end plates 60 may have any of the end plate
configurations discussed, illustrated or referred to herein.
In the preceding discussion, illustrative examples of suitable materials
of construction and methods of fabrication for the components of hydrogen
purification devices according to the present invention have been discussed.
It should
be understood that the examples are not meant to represent an exclusive, or
closed, list
of exemplary materials and methods, and that it is within the scope of the
invention
that other materials and/or methods may be used. For example, in many of the
above
examples, desirable characteristics or properties are presented to provide
guidance for
selecting additional methods and/or materials. This guidance is also meant as
an
illustrative aid, as opposed to reciting essential requirements for all
embodiments.
As discussed, in embodiments of device 10 that include a separation
assembly that includes hydrogen-permeable and/or hydrogen-selective membranes
46,
suitable materials for membranes 46 include palladium and palladium alloys. As
also
discussed, the membranes may be supported by frames and/or supports, such as
the
previously described frames 240, supports 54 and screen structure 210.
Furthermore,
devices 10 are often operated at selected operating parameters that include
elevated
temperatures and pressures. In such an application, the devices typically
begin at a
startup, or initial, operating state, in which the devices are typically at
ambient
temperature and pressure, such as atmospheric pressure and a temperature of
approximately 25° C. From this state, the device is heated (such as
with heating
assembly 42) and pressurized (via any suitable mechanism) to selected
operating
33
CA 02494680 2002-03-26
parameters, such as temperatures of 200° C or more, and selected
operating pressures, such as
a pressure of 50 psi or more.
When devices 10 are heated, the components of the devices will expand. The
degree to which the components enlarge or expand is largely defined by the
coefficient of
thermal expansion (CTE) of the materials from which the components are formed.
Accordingly, these differences in CTE's will tend to cause the components to
expand at
different rates, thereby placing additional tension or compression on some
components and/or
reduced tension or compression on others.
For example, consider a hydrogen-selective membrane 46 formed from an
alloy of 60 wt% palladium and 40 wt% copper (Pd-40Cu). Such a membrane has a
coefficient
of thermal expansion of 14.9 (~m/m)/°C. Further consider that the
membrane is secured to a
structural frame 230 or other mount, or retained against a support 54 formed
from a material
having a different CTE than Pd-40Cu or another material from which membrane 46
is formed.
When a device 10 in which these components are operated is heated from an
ambient or
resting configuration, the components will expand at different rates.
Typically, device 10 is
thermally cycled within a temperature range of at least 200° C, and
often within a range of at
least 250° C, 300° C or more. If the CTE of the membrane is less
than the CTE of the
adjoining structural component, then the membrane will tend to be stretched as
the
components are heated.
In addition to this initial stretching, it should be considered that hydrogen
purification devices typically experience thermal cycling as they are heated
for use, then
cooled or allowed to cool when not in use, then reheated, recooled, etc. In
such an
application, the stretched membrane may become wrinkled as it is compressed
toward its
original configuration as the membrane and other structural components) are
cooled.
On the other hand, if the CTE of the membrane is greater than the CTE of the
adjoining structural component, then the membrane will tend to be compressed
during heating
of the device, and this compression may cause wrinkling of the membrane.
During cooling,
or as the components cool, the membrane is then drawn back to its original
configuration.
As an illustrative example, consider membrane plate 242 shown in Fig. 34. If
the CTE of membrane 46 is greater than the CTE of frame member 230,
34
CA 02494680 2002-03-26
which typically has a different composition than membrane 46, then the
membrane
will tend to expand faster when heated than the frame. Accordingly,
compressive
forces will be imparted to the membrane from frame 230, and these forces may
produce wrinkles in the membrane. In contrast, if the CTE of membrane 46 is
less
than the CTE of frame 230, then the frame will expand faster when heated than
membrane 46. As this occurs, expansive forces will be imparted to the
membrane, as
the expansion of the frame in essence tries to stretch the membrane. While
neither of
these situations is desirable, compared to an embodiment in which the frame
and
membrane have the same or essentially the same CTE, the former scenario may in
some embodiments be the more desirable of the two because it may be less
likely to
produce wrinkles in the membrane.
Wrinkling of membrane 46 may cause holes and cracks in the
membrane, especially along the wrinkles where the membrane is fatigued. In
regions
where two or more wrinkles intersect, the likelihood of holes and/or cracks is
increased because that portion of the membrane has been wrinkled in at least
two
different directions. It should be understood that holes and cracks lessen the
selectivity of the membrane for hydrogen gas because the holes and/or cracks
are not
selective for hydrogen gas and instead allow any of the components of the
mixed gas
stream to pass thereto. During repeated thermal cycling of the membrane, these
points or regions of failure will tend to increase in size, thereby further
decreasing the
purity of the hydrogen-rich, or permeate, stream. It should be further
understood that
these wrinkles may be caused by forces imparted to the membrane from portions
of
device 10 that contact the membrane directly, and which accordingly may be
referred
to as membrane-contacting portions or structure, or by other portions of the
device
that do not contact the membrane but which upon expansion andlor cooling
impart
forces that are transmitted to the membrane. Examples of membrane-contacting
structure include frames or other mounts 52 and supports 54 upon which the
membrane is mounted or with which membrane 46 is in contact even if the
membrane
is not actually secured or otherwise mounted thereon. Examples of portions of
device
10 that may, at least in some embodiments, impart wrinkle-inducing forces to
membrane 46 include the enclosure 12, and portions thereof such as one or more
end
plates 60 and/or shell 62. Other examples include gaskets and spacers between
the
end plates and the frames or other mounts for the membrane, and in embodiments
of
CA 02494680 2002-03-26
device 10 that include a plurality of membranes, between adjacent frames or
other
supports or mounts for the membranes.
One approach to guarding against membrane failure due to differences
in CTE between the membranes and adjoining structural components is to place
deformable gaskets between the membrane and any component of device 10 that
contacts the membrane and has sufficient stiffness or structure to impart
compressive
or tensile forces to the membrane that may wrinkle the membrane. For example,
in
Fig. 33, membrane 46 is shown sandwiched between feed plate 238 and permeate
gasket 236, both of which may be formed from a deformable material. In such an
embodiment and with such a construction, the deformable gaskets buffer, or
absorb, at
least a significant portion of the compressive or tensile forces that
otherwise would be
exerted upon membrane 46.
In embodiments where either or both of these frames are not formed
from a deformable material (i.e., a resilient material that may be compressed
or
expanded as forces are imparted thereto and which returns to its original
co~guration
upon removal of those forces), when membrane 46 is mounted on a plate 242 that
has
a thickness and/or composition that may exert the above-described wrinkling
tensile
or compressive forces to membrane 46, or when support 54 is bonded (or secured
under the selected operating pressure) to membrane 46, a different approach
may
additionally or alternatively be used. More specifically, the life of the
membranes
may be increased by forming components of device 10 that otherwise would
impart
wrinkling forces, either tensile or compressive, to membrane 46 from materials
having a CTE that is the same or similar to that of the material or materials
from
which membrane 46 is formed.
For example, Type 304 stainless steel has a CTE of 17.3 and Type 316
stainless steel has a CTE of 16Ø Accordingly, Type 304 stainless steel has a
CTE
that is approximately 15% greater than that of Pd-40Cu, and Type 316 stainless
steel
has a CTE that is approximately 8% greater than that of Pd-40Cu. This does not
mean that these materials may not be used to form the various supports,
frames,
plates, shells and the like discussed herein. However, in some embodiments of
the
invention, it may be desirable to form at least some of these components from
a
material that has a CTE that is the same as or more similar to that of the
material from
which membrane 46 is formed. More specifically, it may be desirable to have a
CTE
36
CA 02494680 2002-03-26
that is the same as the CTE of the material from which membrane 46 is formed,
or a material
that has a CTE that is within a selected range of the CTE of the material from
which
membrane 46 is selected, such as within t 0.5%, 1%, 2%, 5%, 10%, or 15%.
Expressed
another way, in at least some embodiments, it may be desirable to form the
membrane-
contacting portions or other elements of the device from a material or
materials that have a
CTE that is within X1.2, 1, 0.5, 0.2, 0.1 or less than 0.1 pm/ml°C of
the CTE from which
membrane 46 is at least substantially formed. Materials having one of the
above compositions
and/or CTE's relative to the CTE of membrane 46 may be referred to herein as
having one of
the selected CTE's within the context of this disclosure.
In the following table, exemplary alloys and their corresponding CTE's and
compositions are presented. It should be understood that the materials listed
in the following
table are provided for purposes of illustration, and that other materials may
be used, including
combinations of the below-listed materials and/or other materials, without
departing from the
scope of the invention.
Table 1
Allo CTE No minalCom
osition
e/Grade m1m/C C n Ni Cr Co Mo W Nb Cu Ti A1 Fe Si
d-40Cu 14.9
onel 400
(LTNS
04400 13.9 .0 1.565 3 2.
onel 401
(UNS
04401 13.7 .052.42 5 0.5
onel 405
(UNS
04405 13.7 .021.565 32 2.
onel 500
(UNS
05500 13.7 .0 1.65 32 0. 1.5
ype 304
Stainless
(UNS
530400 17.3 .051.59. 19. Bal0.5
37
CA 02494680 2002-03-26
ype 316
tainless
(LTNS
31600 16.0 .051.512. 17. 2.5 Bal 0.5
ype 310S
Stainless
(UNS
531008 15.9 .051.520.525. Bal 1.1
ype 330
Stainless
(IJNS
08330 14.4 .OS1.535.518.5 Bal 1.1
ISI Type
661
Stainless
(LTNS
0155 14.0 .1 1.520. 21. 20.53. 2.51. 31. 0.8
conel 600
(LJNS
06600 13.3 .08 76. 15.5 8.
conel 601
(LJNS
06601 13.75 .05 60.523. 0.5 1.3514.1
conel 625
(UNS
06625 12.8 .05 61. 21.5 9. 3. 0. 0.2 2.5
coloy 800
(UrTS
08800 14.4 .050.832.5 0. 0. 0. 46. 0.5
imonic
lloy 901
(UNS
09901 13.5 .05 42.512.5 6. 2.7 36.2
astelloy
X
(LTNS
06002 13.3 .15 49. 22. 1.5 9. 0. 2 15.8
conel 718
UNS
07718 13.0 .05 52.519. 3. 5.1 0. 0.5 18.5
aynes 230
(UNS
06002 12.7 0.1 55. 22. 5. 2. 1 0.353.
38
CA 02494680 2002-03-26
From the above information, it can be seen that alloys such as Type 330
stainless steel and Incoloy 800 have CTE's that are within approximately 3% of
the CTE of
Pd40Cu, and Monel 400 and Types 3105 stainless steel have CTE's that deviate
from the
CTE of Pd40Cu by less than 7%.
To illustrate that the selection of materials may vary with the CTE of the
particular membrane being used, consider a material for membrane 46 that has a
coefficient of
thermal expansion of 13.8 ~,m/m/° C. From the above table, it can be
seen that the Monel and
Inconel 600 alloys have CTE's that deviate, or differ from, the CTE of the
membrane by 0.1
pmlm/°C. As another example, consider a membrane having a CTE of 13.4
pm/m/°C.
Hastelloy X has a CTE that corresponds to that of the membrane, and that the
Monel and
Inconel 601 alloys have CTE's that are within approximately 1 % of the CTE of
the
membrane. Of the illustrative example of materials listed in the table, all of
the alloys other
than Hastelloy X, Incoloy 800 and the Type 300 series of stainless steel
alloys have CTE's
that are within 2% of the CTE of the membrane, and all of the alloys except
Type 304, 316
and 3105 stainless steel alloys have CTE's that are within 5% of the CTE of
the membrane.
Examples of components of device 10 that may be formed from a material
having a selected CTE relative to membrane 46, such as a CTE corresponding to
or within one
of the selected ranges of the CTE of membrane 46, include one or more of the
following:
support 54, screen members 212, fine or outer screen or expanded metal member
216, inner
screen member 214, membrane frame 240, permeate frame 232, permeate plate 234,
feed
plate 238. By the above, it should be understood that one of the above
components may be
formed from such a material, more than one of the above components may be
formed from
such a material, but that none of the above components are required to be
formed from such a
material. Similarly, the membranes 46 may be formed from materials other than
Pd-40Cu,
and as such the selected CTE's will vary depending upon the particular
composition of
membranes 46. Although not required, many hydrogen-selective membranes will
have a CTE
in the range of approximately 13.6 ~m/m/°C and 16 pm/m/°C.
39
CA 02494680 2002-03-26
In view of the above, membrane-contacting structures according to the present
disclosure may have, or may be completely or at least substantially formed
from one or more
materials that have, a CTE that is greater than 13 ~.m/m/°C, less than
16 ~,m/m/°C, within the
range of 13 ~,m/m/°C and 16 um/m/°C. The membrane-contacting
structure may have, or may
be completely or at least substantially formed from one or more materials that
have, a CTE
that is the same as, greater than, or less than the CTE of the membrane that
is contacted by the
structure. Although not required, the membrane-contacting structure will
typically be formed
from a material that is not hydrogen-selective. The membrane-contacting
structures described
herein, as well as the supports, mounts, and other structure that assist in
supporting the
membranes even if they do not directly contact the membranes may collectively
be referred to
as means for supporting the hydrogen-selective membrane(s). Accordingly, it is
within the
scope of the present disclosure for the means for supporting the hydrogen-
selective
membranes to be described as having any of the illustrative compositions,
CTE's,
configurations, etc. described herein with respect to one or more of the
illustrative membrane
contacting structures.
By way of further illustration, a device 10 may be formed with a membrane
module 220 that includes one or more membrane envelopes 200 with a support
that includes a
screen structure which is entirely formed from a material having one of the
selected CTE's.
As another example, only the outer, or membrane-
39A
CA 02494680 2002-03-26
contacting, screen members (such as members 216) may be formed from a material
having one of the selected CTE's, with the inner member or members being
formed
from a material that does not have one of the selected CTE's. As still another
illustrative example, the inner screen member 214 may be formed from a
material
having one of the selected CTE's, with the membrane-contacting members being
formed from a material that does not have one of the selected CTE's, etc.
In some embodiments, it may be sufficient for only the portions of the
support that have sufficient stiffness to cause wrinkles in the membranes
during the
thermal cycling and other intended uses of the purification device to be
formed from a
material having one of the selected CTE's. As an illustrative example,
consider
screen structure 210, which is shown in Fig. 32. In the illustrative
embodiment, the
screen structure is adapted to be positioned between a pair of membranes 46,
and the
screen structure includes a pair of outer, or membrane-contacting screen
members
216, and an inner screen member 214 that does not contact the membranes.
Typically, but not exclusively, the outer screen members are formed from a
material
that is less stiff and often more fine than the inner screen member, which
tends to
have a stiffer and often coarser, construction. In such an embodiment, the
inner
screen member may be formed from a material having one of the selected CTE's,
such as an alloy that includes nickel and copper, such as Monel, with the
outer screen
members being formed from conventional stainless steel, such as Type 304 or
Type
316 stainless steel. Such a screen structure may also be described as having a
membrane-contacting screen member with a CTE that differs from the CTE of
membrane 46 more than the CTE of the material from which the inner screen
member
is formed. As discussed, however, it is also within the scope of the invention
that all
of the screen members may be formed from an alloy that includes nickel and
copper,
such as Monel, or another material having one of the selected CTE's.
This construction also may be applied to supports that include more
than one screen member or layer, but which only support one membrane. For
example, and with reference to Fig.2, the support may include a membrane-
contacting layer or screen member 214', which may have a construction like a
screen
member 214. Layer 214' engages and extends across at least a substantial
portion of
the face of the membrane, but typically does not itself provide sufficient
support to
the membrane when the purification device is pressurized and in use. The
support
CA 02494680 2002-03-26
may further include a second layer or second screen member 216', which may
have a
construction like screen member 216 and which extends generally parallel to
the first layer but
on the opposite side of the first layer than the membrane. This second layer
is stiffer than the
first layer so that it provides a composite screen structure that has
sufficient strength, or
stiffness, to support the membrane when in use. When such a construction is
utilized, it may
(but is not required to be) implemented with the second layer, or screen
member to be formed
from an alloy of nickel and copper, such as Monel, or another material having
a selected CTE,
and with the membrane-contacting layer, or screen member, being formed from a
material
having a CTE that differs from the CTE of the membrane by a greater amount
than the
material from which the second layer is formed. Additionally, the membrane-
contacting layer
may be described as being formed from a material that does not include an
alloy of nickel and
copper.
Another example of exemplary configurations, a device 10 may have a single
membrane 46 supported between the end plates 60 of the enclosure by one or
more mounts 52
and/or one or more supports 54. The mounts andJor the supports may be formed
from a
material having one of the selected CTE's. Similarly, at least a portion of
enclosure 12, such
as one or both of end plates 60 or shell 62, may be formed from a material
having one of the
selected CTE's.
In embodiments of device 10 in which there are components of the device that
do not directly contact membrane 46, these components may still be formed from
a material
having one of the selected CTE's. For example, a portion or all of enclosure
12, such as one
or both of end plates 60 or shell 62, may be formed from a material, including
one of the
alloys listed in Table 1, having one of the selected CTE's relative to the CTE
of the material
from which membrane 46 is formed even though these portions do not directly
contact
membrane 46. As such, it is within the scope of the disclosure to describe the
enclosure being
adapted to not impart wrinkle-inducing forces to the at least one hydrogen-
selective
membrane supported within the enclosure. With reference to the prior
discussion of
illustrative materials, one such material from which the enclosure may be
partially or
completely formed is an alloy that contains nickel and copper.
41
CA 02494680 2002-03-26
A hydrogen purification device 10 constructed according to the present
invention may be coupled to, or in fluid communication with, any source of
impure hydrogen
gas. Examples of these sources include gas storage devices, such as hydride
beds and
pressurized tanks. Another source is an apparatus that produces as a
byproduct, exhaust or
waste stream a flow of gas from which hydrogen gas may be recovered. Still
another source
is a fuel processor, which as used herein, refers to any device that is
adapted to produce a
mixed gas stream containing hydrogen gas from at
.41 A
CA 02494680 2002-03-26
least one feed stream containing a feedstock. Typically, hydrogen gas will
form a
majority or at least a substantial portion of the mixed gas stream produced by
a fuel
processor.
A fuel processor may produce mixed gas stream 24 through a variety
of mechanisms. Examples of suitable mechanisms 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.
A hydrogen purification device 10 adapted to receive mixed gas stream
24 from a fuel processor is shown schematically in Fig. 40. As shown, the fuel
processor is generally indicated at 300, and the combination of a fuel
processor and a
hydrogen purification device may be referred to as a fuel processing system
302.
Also shown in dashed lines at 42 is a heating assembly, which as discussed
provides
heat to device 10 and may take a variety of forms. Fuel processor 300 may take
any
of the forms discussed above. To graphically illustrate that a hydrogen
purification
device according to the present invention may also receive mixed gas stream 24
from
sources other than a fuel processor 300, a gas storage device is schematically
illustrated at 306 and an apparatus that produces mixed gas stream 24 as a
waste or
byproduct stream in the course of producing a different product stream 308 is
shown
at 310. It should be understood that the schematic representation of fuel
processor
300 is meant to include any associated heating assemblies, feedstock delivery
systems, air delivery systems, feed stream sources or supplies, etc.
Fuel processors are often operated at elevated temperatures and/or
pressures. As a result, it may be desirable to at least partially integrate
hydrogen
purification device 10 with fuel processor 300, as opposed to having device 10
and
fuel processor 300 connected by external fluid transportation conduits. An
example
42
CA 02494680 2002-03-26
of such a configuration is shown in Fig. 42, in which the fuel processor
includes a
shell or housing 312, which device 10 forms a portion of and/or extends at
least
partially within. In such a configuration, fuel processor 300 may be described
as
including device 10. Integrating the fuel processor or other source of mixed
gas
stream 24 with hydrogen purification device 10 enables the devices to be more
easily
moved as a unit. It also enables the fuel processor's components, including
device 10,
to be heated by a common heating assembly and/or for at least some if not all
of the
heating requirements of device 10 be to satisfied by heat generated by
processor 300.
As discussed, fuel processor 300 is any suitable device that produces a
mixed gas stream containing hydrogen gas, and preferably a mixed gas stream
that
contains a majority of hydrogen gas. For purposes of illustration, the
following
discussion will describe fuel processor 300 as being adapted to receive a feed
stream
316 containing a carbon-containing feedstock 318 and water 320, as shown in
Fig. 42.
However, it is within the scope of the invention that the fuel processor 300
may take
other forms, as discussed above, and that feed stream 316 may have other
compositions, such as containing only a carbon-containing feedstock or only
water.
Feed stream 316 may be delivered to fuel processor 300 via any
suitable mechanism. A single feed stream 316 is shown in Fig. 42, but it
should be
understood that more than one stream 316 may be used and that these streams
may
contain the same or different components. When the carbon-containing feedstock
318
is miscible with water, the feedstock is typically delivered with the water
component
of feed stream 316, such as shown in Fig. 42. When the carbon-containing
feedstock
is immiscible or only slightly miscible with water, these components are
typically
delivered to fuel processor 300 in separate streams, such as shown in dashed
lines in
Fig. 42. In Fig. 42, feed stream 316 is shown being delivered to fuel
processor 300 by
a feed stream delivery system 317. Delivery system 31? includes any suitable
mechanism, device, or combination thereof that delivers the feed stream to
fuel
processor 300. For example, the delivery system may include one or more pumps
that
deliver the components of stream 316 from a supply. Additionally, or
alternatively,
system 317 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 cell system, or may be contained within or adjacent the system.
43
CA 02494680 2002-03-26
As generally indicated at 332 in Fig.42, fuel processor 300 includes a
hydrogen-producing region in which mixed gas stream 24 is produced from feed
stream 316.
As discussed, a variety of different processes may be utilized in hydrogen-
producing region
332. An example of such a process is steam reforming, in which region 332
includes a steam
reforming catalyst 334. Alternatively, region 332 may produce stream 24 by
autothermal
reforming, in which case region 332 includes an autothermal reforming
catalyst. In the
context of a steam or autothermal reformer, mixed gas stream 24 may also be
referred to as a
reformate stream. Preferably, the fuel processor 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 invention, 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. Examples of suitable
fuel processors
are disclosed in U.S. Patent No. 6,221,117, U.S. Patent Application
Publication No. US
2001/0045061 A1 entitled "Fuel Processor and Systems and Devices Containing
the Same,"
and U.S. Patent No. 6,319,306.
Fuel processor 300 may, but does not necessarily, further include a polishing
region 348, such as shown in dashed lines in Fig. 42. Polishing region 348
receives hydrogen-
rich stream 34 from device 10 and further purifies the stream by reducing the
concentration
of, or removing, selected compositions therein. In Fig. 42, the resulting
stream is indicated at
314 and may be referred to as a product hydrogen stream or purified hydrogen
stream. When
fuel processor 300 does not include polishing region 348, hydrogen-rich stream
34 forms
product hydrogen stream 314. For example, when stream 34 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. The
concentration of
carbon monoxide should be less than 10 ppm (parts per million) to prevent the
control system
from isolating the fuel cell stack. Preferably, the system limits the
concentration of carbon
monoxide to less than 5 ppm, and even more preferably, to less than 1 ppm. The
concentration of carbon dioxide may be greater than that of carbon monoxide.
44
CA 02494680 2002-03-26
For example, concentrations of less than 25% carbon dioxide may be acceptable.
Preferably, the concentration is less than 10%, 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.
Region 348 includes any suitable structure for removing or reducing
the concentration of the selected compositions in stream 34. For example, when
the
product stream is intended for use in a PEM fuel cell stack or other device
that will be
damaged if the stream contains more than determined concentrations of carbon
monoxide or carbon dioxide, it may be desirable to include at least one
methanation
catalyst bed 350. Bed 350 converts carbon monoxide and carbon dioxide into
methane and water, both of which will not damage a PEM fuel cell stack.
Polishing
region 348 may also include another hydrogen-producing region 352, such as
another
reforming catalyst bed, to convert any unreacted feedstock into hydrogen gas.
In such
an embodiment, it is preferable that the second reforming catalyst bed is
upstream
from the methanation catalyst bed so as not to reintroduce carbon dioxide or
carbon
monoxide downstream of the methanation catalyst bed.
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
1000 psi, although
temperatures outside of this range are within the scope of the invention, such
as
depending upon the particular type and configuration of fuel processor being
used.
Any suitable heating mechanism or device may be used to provide this heat,
such as a
heater, burner, combustion catalyst, or the like. The heating assembly may be
external the fuel processor or may form a combustion chamber that forms part
of the
fuel processor. The fuel for the heating assembly may be provided by the fuel
processing or fuel cell system, by an external source, or both.
In Fig. 42, fuel processor 300 is shown including a shell 312 in which
the above-described components are contained. Shell 312, which also may be
referred to as a housing, enables the components of the fuel processor to be
moved as
a unit. It also protects the components of the fuel processor from damage by
CA 02494680 2002-03-26
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 312 may,
but does not
necessarily, include insulating material 333, such as a solid insulating
material, blanket
insulating material, 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 300
includes insulating material 333, 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 fuel processor may further
include an outer
cover or jacket external the insulation.
It is further within the scope of the invention that one or more of the
components of fuel processor 300 may either extend beyond the shell or be
located external at
least shell 312. For example, device 10 may extend at least partially beyond
shell 312, as
indicated in Fig.4l. As another example, and as schematically illustrated in
Fig.42,
polishing region 348 may be external shell 312 andlor a portion of hydrogen-
producing region
332 (such as portions of one or more reforming catalyst beds) may extend
beyond the shell.
As indicated above, fuel processor 300 may be adapted to deliver hydrogen-
rich stream 34 or product hydrogen stream 314 to at least one fuel cell stack,
which produces
an electric current therefrom. In such a configuration, the fuel processor and
fuel cell stack
may be referred to as a fuel cell system. An example of such a system is
schematically
illustrated in Fig. 43, in which a fuel cell stack is generally indicated at
322. The fuel cell
stack is adapted to produce an electric current from the portion of product
hydrogen stream
314 delivered thereto. In the illustrated embodiment, a single fuel processor
300 and a single
fuel cell stack 322 are shown and described, however, it should be understood
that more than
one of either or both of these components may be used. It should also be
understood that
these components have been schematically illustrated and that the fuel cell
system may
include additional components that are not specifically illustrated in the
figures, such as feed
pumps, air delivery systems, heat exchangers, heating assemblies and the like.
Fuel cell stack 322 contains at least one, and typically multiple, fuel cells
324
that are adapted to produce an electric current from the portion of the
product hydrogen
stream 314 delivered thereto. This electric current may be used to
46
CA 02494680 2002-03-26
satisfy the energy demands, or applied load, of an associated energy-consuming
device 325. Illustrative examples of devices 325 include, but should not be
limited to,
a motor vehicle, recreational vehicle, boat, tools, lights or lighting
assemblies,
appliances (such as a household or other appliance), household, signaling or
communication equipment, etc. It should be understood that device 325 is
schematically illustrated in Fig. 43 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. A fuel cell stack typically includes multiple fuel cells joined
together
between common end plates 323, which contain fluid delivery/removal conduits
(not
shown). Examples of suitable fuel cells include proton exchange membrane (PEM)
fuel cells and alkaline fuel cells. Fuel cell stack 322 may receive all of
product
hydrogen stream 314. Some or all of stream 314 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.
Industrial A,pplicabilitv
The invented hydrogen purification devices, components and fuel
processing systems are applicable to the fuel processing and other industries
in which
hydrogen gas is produced and/or utilized.
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 andlor properties may be
claimed
through amendment of the present claims or presentation of new claims in this
or a
47
CA 02494680 2002-03-26
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.
48
