Patent Application
20060037476
The present disclosure 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.
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.
A hydrogen purification device is schematically illustrated in
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 disclosure that the separation assembly is adapted to trap or otherwise retain at least a substantial portion of the other gases, which will be removed as a byproduct stream as the assembly is replaced, regenerated or otherwise recharged. In
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., 800° 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
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 disclosure, however, that the membranes may be formed from other hydrogen-permeable and/or hydrogen-selective materials, including metals and metal alloys other than those discussed above as well as non-metallic materials and compositions, and that the membranes may have thicknesses that are greater or less than discussed above. For example, the membrane may be made thinner, with commensurate increase in hydrogen flux. Examples of suitable mechanisms for reducing the thickness of the membranes include rolling, sputtering and etching. A suitable etching process is disclosed in U.S. Pat. No. 6,152,995, the complete disclosure of which is hereby incorporated by reference for all purposes. Examples of various membranes, membrane configurations, and methods for preparing the same are disclosed in U.S. Pat. No. 6,221,117 and U.S. Pat. No. 6,319,306, the complete disclosures of which are hereby incorporated by reference for all purposes.
In
For example, although membrane 46 is illustrated in
In
In
The tubular membranes may have a variety of configurations and constructions, such as those discussed above with respect to the planar membranes shown in
As discussed, enclosure 12 defines a pressurized compartment 18 in which separation assembly 20 is positioned. In the embodiments shown in
In
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
In the lower halves of
In
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
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
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 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
In
It should be understood that any of these interfaces may be used with an enclosure constructed according to the present disclosure. 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
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 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 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 to monitor on an end plate include the deflection of the end plate, especially at the perimeter regions that form interface(s) 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 weights 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 disclosure is shown in
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
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) 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
In
For purposes of comparison, consider an end plate 120 having the configuration shown in
In
Also shown in dashed lines in
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 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
In
For purposes of comparison, both end plates 150 and 150′ have reduced weights compared to end plates 120, 120′ and 120″. Plate 150 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 deflections of the plates were 0.0098 inches and 0.008 inches, respectively, and the displacements at perimeter regions 90 were 0.0061 inches and 0.0059 inches, respectively.
Another end plate 60 constructed according to the present disclosure is shown in
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
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.
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 160 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
In
It is also within the scope of the present disclosure 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
Although not required or essential to all devices 10 according to the present disclosure, 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 from a solid slab of uniform thickness of same material as end plate 60 and exposed to the same operating parameters:
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
An example of a membrane envelope is shown in
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 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
An example of a suitable support 54 for membrane envelopes 200 is shown in
The screen members may be of similar or the same construction, and more or less screen members may be used than shown in
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-incorporated U.S. Pat. No. 6,319,306. For purposes of illustration, adhesive is generally indicated in dashed lines at 218 in
Supports 54, including screen structure 210, may include a coating 219 on the surfaces 211 that engage membranes 46, such as indicated in dash-dot lines in
The hydrogen purification devices 10 described, illustrated and/or incorporated 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 withdraw 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 further 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 plates, that are adapted to seal, support and/or interconnect the membrane envelopes. An illustrative example of suitable frame members 230 is shown in
Continuing the above illustration of exemplary frame members 230, permeate 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
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
In
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
Shell 62 has been described as interconnecting the end plates to define therewith internal compartment 18. It is within the scope of the present disclosure that the 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
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 disclosure 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 present disclosure 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 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 (μm/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 component(s) 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
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 and/or 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 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
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 configuration 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 16.0. 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 present disclosure, 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 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 ±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 ±1.2, 1, 0.5, 0.2, 0.1 or less than 0.1 μm/m/° 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 present disclosure.
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 310S 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 μm/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 μm/m/° C. As another example, consider a membrane having a CTE of 13.4 μm/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 310S 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.
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-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
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
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 and/or 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.
A hydrogen purification device 10 constructed according to the present disclosure 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 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
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 of such a configuration is shown in
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
Feed stream 316 may be delivered to fuel processor 300 via any suitable mechanism. A single feed stream 316 is shown in solid lines in
As generally indicated at 332 in
The reformate, or mixed gas, stream 24 typically contains hydrogen gas and impurities, and therefore is delivered to hydrogen purification device 10, where stream 24 is separated into one or more byproduct streams, which are collectively illustrated at 36, and at least one hydrogen-rich stream 34 by any suitable pressure-driven separation process. The hydrogen-rich stream(s) will contain at least one of a greater concentration of hydrogen gas and a lower concentration of at least certain ones of the impurities than the mixed gas stream. Similarly, the byproduct stream(s) will contain at least a substantial portion of the impurities.
An example of a suitable structure for use in device 10 is a separation assembly 20, such as a membrane module, that contains one or more hydrogen permeable metal membranes 46. Illustrative, non-exclusive examples of suitable hydrogen purification devices 10 and separation assemblies 20 have been described above. Examples of suitable membrane modules formed from a plurality of hydrogen-selective metal membranes are disclosed in U.S. Pat. No. 6,221,117, the complete disclosure of which was previously incorporated by reference for all purposes. In that application, a plurality of generally planar membranes are assembled together into a membrane module having flow channels through which an impure gas stream is delivered to the membranes, a purified gas stream is harvested from the membranes and a byproduct stream is removed from the membranes. Gaskets, such as flexible graphite gaskets, are used to achieve seals around the feed and permeate flow channels. Also disclosed in the above-identified application are tubular hydrogen-selective membranes, which also may be used. Other suitable membranes and membrane modules are disclosed in U.S. Pat. No. 6,547,858, the complete disclosure of which is hereby incorporated by reference in its entirety for all purposes. Other suitable, non-exclusive examples of fuel processors are also disclosed in the other incorporated patents and patent applications.
Another example of a suitable pressure-separation process for use in a hydrogen purification device 10 is pressure swing absorption (PSA). In a pressure swing adsorption (PSA) process, gaseous impurities are removed from a stream containing hydrogen gas. PSA is based on the principle that certain gases, under the proper conditions of temperature and pressure, will be adsorbed onto an adsorbent material more strongly than other gases. Typically, it is the impurities that are adsorbed and thus removed from reformate stream 24. The success of using PSA for hydrogen purification is due to the relatively strong adsorption of common impurity gases (such as CO, CO2, hydrocarbons including CH4, and N2) on the adsorbent material. Hydrogen adsorbs only very weakly and so hydrogen passes through the adsorbent bed while the impurities are retained on the adsorbent. Impurity gases such as NH3, H2S, and H2O adsorb very strongly on the adsorbent material and are therefore removed from stream 24 along with other impurities. If the adsorbent material is going to be regenerated and these impurities are present in stream 24, device 10 preferably includes a suitable device that is adapted to remove these impurities prior to delivery of stream 24 to the adsorbent material because it is more difficult to desorb these impurities.
Adsorption of impurity gases occurs at elevated pressure. When the pressure is reduced, the impurities are desorbed from the adsorbent material, thus regenerating the adsorbent material. Typically, PSA is a cyclic process and requires at least two beds for continuous (as opposed to batch) operation. Examples of suitable adsorbent materials that may be used in adsorbent beds are activated carbon and zeolites, especially 5 Å (5 angstrom) zeolites. The adsorbent material is commonly in the form of pellets and it is placed in a cylindrical pressure vessel utilizing a conventional packed-bed configuration. It should be understood, however, that other suitable adsorbent material compositions, forms and configurations may be used.
Fuel processor 300 may, but does not necessarily, further include a polishing region 348, such as shown in dashed lines in
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 900° 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 present disclosure, 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
It is further within the scope of the present disclosure 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
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
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 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
As described herein, hydrogen purification device 10 may receive mixed gas stream 24 from any number of sources, such as hydride beds or fuel processors. During operation, some particulate may be carried with the fluid streams to the hydrogen purification device, which contains the separation assembly 20. This particulate may be in the form of dust from catalysts upstream from the hydrogen purification device, such as the (steam or autothermal) reforming catalyst. It may also be from impurities in the feedstock, either as delivered to the fuel processor, or from the recycled byproduct stream which could contain dust from upstream or downstream catalysts (such as reforming or methanation catalysts). Another source of particulate is coke, which may be formed as a byproduct of the reforming reactions.
Regardless of its source, this particulate may interfere with the operation of the hydrogen-selective membrane or membranes used in hydrogen purification device 10. Additionally or alternatively, the particulate may interfere with the operation of the absorbent material used in hydrogen purification devices incorporating PSA separation assemblies. Continuing with the example of membrane separation, this particulate may plug the gas flow channels in the membranes. As this occurs, the pressure drop through the membranes increases and eventually requires replacement of the membranes. It should be understood that the time required for the membrane to need replacing will vary, depending upon such factors as the operating conditions of the fuel processor, the concentration and size of particulate being delivered to the membranes, etc. To prevent this particulate from impairing the operation of separation assembly 20, fuel processor 300 may include a filter assembly 360 intermediate its hydrogen producing region and the hydrogen purification device, such as shown in
Filter assembly 360 is adapted to remove or reduce the amount of particulate in reformate stream 24 prior to delivery of the stream to the fuel processor's hydrogen purification device 10. As such, filter assembly 360 may also be described as a particle-gas separator. As shown, filter assembly 360 receives reformate stream 24 and a filtered stream 364 is delivered to hydrogen purification device 10 from the filter assembly. Filter assembly 360 includes at least one filter element 362. Filter element 362 includes any suitable device adapted to remove particulates from reformate stream 24 at the elevated temperatures at which the fuel processor operates. An example of a suitable filter element is a porous medium through which the reformate stream may flow, and in which particulates contained in the reformate stream are retained.
An example of a suitable form for filter element 362 is a sintered metal tube or disc. Another example is a woven metal mesh, such as filter cloth that is fabricated into the shape of a tube or disc. Ceramic tubes and discs are also suitable filter elements. A 2-micron filter that operates at temperatures in the range of 700° C. has proven effective as a filter element, however, it should be understood that the size (namely, the size of the smallest particulate that will be trapped by the filter) and the composition of the filter may vary. Another suitable filter element is a device in which the reformate stream passes through an elbow or other conduit containing a trap, which retains the particulate. Filter assembly 360 may also include two or more filter elements 362, such as filter elements that may have the same or different sizing and/or different types of filter elements. Particulate that may be present in the hot reformate gas as it exits the hydrogen producing region are retained on the filter element.
Also shown in
Heating assembly 370 consumes a fuel stream 376, which may be a combustible fuel stream or an electric current, depending upon the type of heating element used in the heating assembly. In the illustrated embodiment, the heating assembly forms part of a combustion chamber, or region, 377, and the fuel stream includes a combustible fuel and air from an air stream 378. The fuel may come from an external source, such as schematically illustrated at 380, or may be at least partially formed from the byproduct stream 36 from hydrogen purification device 10. It is within the scope of the present disclosure that at least a portion of the fuel stream may also be formed from product hydrogen stream 314. In the illustrated embodiment, the exhaust from combustion region 377 flows through heating conduits 384 in hydrogen-producing region 332 to provide additional heating to the hydrogen producing region. Conduits 384 may take a variety of forms, including finned tubes and spirals, to provide sufficient surface area and desirable uniform distribution of heat throughout hydrogen-producing region 332.
As discussed, hydrogen purification device 10 may include a separation assembly 20 that contains one or more hydrogen-selective metal membranes 46, which may also be referred to as hydrogen-permeable metal membranes. Hydrogen purification device 10 may include one or more of the separation assemblies 20 discussed above, including assemblies incorporating membrane separation technologies, PSA separation technologies, polishing regions, a combination of membrane and PSA separation technologies, a combination of membrane or PSA separation technologies with polishing regions, or other separation technologies.
As discussed, fuel processor 300, which may, but does not necessarily, take the form of a steam reformer, may be housed in a shell 312. As further discussed, a shell provides greater heating efficiency of the components of the fuel processor or reformer, as well as enabling these components to be more readily transported as a unit and protecting these components from damage caused by physical forces applied to the fuel processor or reformer. A disadvantage of housing the components of fuel processor 300 in a shell is that it is more difficult to access the individual components of the fuel processor, such as for inspection, maintenance, removal or repair. Typically, the fuel processor or reformer needs to be shut down, cooled, opened through the removal of at least a portion of the shell, sufficiently disassembled to access and remove or repair the particular component, and then reassembled.
A fuel processor and steam reformer that offers the benefits of a shell without the disadvantages discussed above is shown in
As shown in
The modular component may, but is not necessarily in all embodiments, be described as being adapted to receive a fluid-containing stream, and in those embodiments may, but is not necessarily in all embodiments, be described as outputting a gas-containing stream having a different composition that the fluid-containing stream received by the modular component. Typically, the fluid-containing stream will be a gas-containing stream, such as the reformate stream, mixed gas stream, hydrogen-rich stream, product hydrogen stream, filtered stream, byproduct stream, or other streams described or illustrated herein. Similar to the above discussion with respect to feed stream 316, this description of a modular component is meant to include, but not require, more than one fluid- or gas-containing stream being received and/or outputted by the modular component.
In the illustrated embodiment, the components include fittings 420 that are positioned for access from external shell 312, such as through access ports 422. Fittings 420 may take any suitable construction that enables the cartridge-based components to be removed in whole or in part. An example of a suitable fitting 420 is a coupling in a fluid communication line to and/or from a particular component. By disconnecting the fitting, the component may be removed in its entirety. Another example of a fitting is a seal, mounting bracket, receptacle or other releasable retainer that receives a replaceable cartridge, such as a cartridge containing a filter element, reforming catalyst, or other portion of the fuel processor or reformer that may need to be periodically replaced or recharged.
As discussed above, fuel processor 300 operates at elevated temperatures and pressures. Fittings 420 may include subcomponents or parts adapted to maintain the coupling between the components of the fuel processor under the operating conditions of the fuel processor. Additionally or alternatively, fitting 420 may be adapted to create a seal between two or more components. In the example of fitting 420 embodied as a coupling in a fluid communication line, fitting 420 may include two or more members, such as at least one body member and at least one seal member, adapted to at least substantially seal the fitting, such as to prevent leakage of the fluid. For purposes of illustration, the at least one body member may include a male connector and the at least one seal member may include a female connector adapted to be threadingly engaged, frictionally engaged, or otherwise coupled to seal the fitting. The configurations of the fitting on the modular component side and on the fuel processor component side may be varied and adapted suitable for the location and function of the fitting. For example, the fitting may include at least one body member associated with the modular component, the first fuel processor component, or both the modular component and the first fuel processor component. Similarly, the fitting may include at least one seal member associated with the modular component, the first fuel processor component, or both the modular component and the first fuel processor component. One or more portions of the body member and/or the seal member may not participate in the coupling of the components but may still be part of fitting 420. For example, the body member and/or the seal member may include or be formed by a gasket, a washer, or other sealing mechanism that does not actively couple the two components.
Additionally or alternatively, fittings 420 may be considered to be, or otherwise form, an interface between two components of fuel processor 300. For example, fitting 420 may be an interface between hydrogen-producing region 332 and hydrogen purification device 10. Fitting 420 may be an interface between hydrogen purification device 10 and shell 312 or an interface between a membrane envelope and a membrane module. The interface may be formed between any two components of the fuel processor. The interface may be formed between a first interface member associated with a first fuel processor component and a second interface member associated with a second fuel processor component. At least one of the first fuel processor component and the second fuel processor component is a modular component. Additionally or alternatively, one or more of the first and second fuel processor components may be a sub-component of another component. For example, the first component may be a membrane module and the second component may be a membrane envelope. The first and second interface members may be a part of the respective first and second fuel processor component. Alternatively, the interface member may be associated with, but not a part of, the respective fuel processor component. For example, one or more of the first and second interface members may include a gasket, a washer, or other member disposed between the first and second fuel processor components, in which case the gasket may be associated with either or both fuel processor component.
Whether the one or more modular components of fuel processor 300 are operatively coupled via one or more body members and seal members or via an interface between two or more interface members, the elevated pressure and temperature in fuel processor 300 may affect the coupling between the components. As discussed above, fuel processors 300 may thermally cycle during the course of operation causing expansion or contraction of the components due to the coefficients of thermal expansion of the components' materials. At the elevated operating temperatures of fuel processor 300, the CTE of the members and the differences in the CTE's of two adjacent members may cause one member to expand greater or less than another member. As discussed above, the varying degrees of expansion may affect the seal or coupling between the members in a number of ways, potentially leading to undesirable fluid or gas leaks or unexpected heat loss.
To illustrate the effect of materials of differing expansion rates in a fitting or interface, consider a friction-fitted (i.e., press fit) or threaded coupling on a fluid line having a male connector and a female connector. If the female connector has a CTE greater than the CTE of the male connector, the male connector will not expand to the same degree as the female connector and the seal between the two may be broken. Alternatively, if the relative CTE's were reversed, the male connector would expand greater than the female connector applying stresses on both connector members. While such a scenario may not cause an immediate leak, the pressure between the connectors may crack, break, or otherwise deform one or both connectors. In the case of a fitting or interface between a modular component such as a hydrogen purification device 10 and a shell 312, such differences in expansion may not leak process fluids but may contribute to undesirable heat loss through the gaps and may vary the heating patterns within fuel processor 300. At the elevated operating pressures of fuel processor 300, even relatively minor expansion differences may lead to undesirable consequences.
One or more of the interfaces between components of the fuel processor may not be sensitive to varying rates of expansion between adjacent members. For example, one or more interface between components may be adapted to secure the components in the operational positions regardless of the different expansion rates. And when the interface between the components is not a coupling in a fluid or gas line, there is minimal or no risk of a fluid or gas leak due the differing expansion rates. Moreover, some interfaces between fuel processor components may be amenable to the use of deformable gaskets or other accommodating structures adapted to minimize the impact of the varied expansion rates.
However, other interfaces between fuel processor components may be sensitive to potentially differing rates of expansion between adjacent members. An interface may be sensitive to expansion rate differences if the difference would leak fluids or gases. Additionally or alternatively, an interface would be sensitive to the differences in coefficients of thermal expansion if the difference would apply fatiguing or deforming stresses on one or more components. Additionally or alternatively, an interface may be sensitive to CTE differences if the differences weaken or loosen the coupling between two components.
In interfaces or fittings that are sensitive to different rates of expansion between adjacent members, the materials of the interface or fittings may be selected to minimize the differences in the coefficients of thermal expansion between two adjacent members. For example, at least a portion of the body member may be selected to have a CTE that is sufficiently close to or equal to the CTE of at least a portion of the seal member such that upon thermal cycling of the fuel processor within a temperature range of at least 200° C. the relationship between the body member and the seal member at least substantially maintains the seal of the fitting. First and second interface members may be similarly selected to have CTE's sufficient close to or equal to each other to maintain the seal of the interface. The acceptable degree of difference may vary depending on the location of the fitting or interface, the components being coupled, and the configuration of the components and the members of the fitting or interface. For example, the CTE of the first interface member of the interface, or the body member of the fitting, may be within 10-20% of the CTE of the second interface member, or the seal member. For some fittings, it may be preferred to have the CTE of the body member within about 10% of the CTE of the seal member. In other situations, it may be preferred to be within about 5%.
To illustrate the use of cartridge-based, or discrete, components, consider filter assembly 360. Filter assembly 360 may include a housing 361 that receives one or more filter elements 362 in the form of a cartridge. In the illustrated embodiment, two filter elements are shown, but it is within the scope of the present disclosure that this number may vary from a single filter element, to multiple filter elements within the same cartridge, to multiple filter elements each forming a separate cartridge. Via access port 422, the filter element may be removed from filter housing 361, such as to replace the filter with a fresh filter. Alternatively or additionally, the entire filter assembly, including housing 361, may be removed as a unit by disconnecting fittings 420. Similarly, other components of the fuel processor, or steam reformer, may include similar cartridge-based components and sub-components. For example, hydrogen separation device 10 may include one or more membrane envelopes as discussed above. One or more of the membrane envelopes may be a cartridge-based sub-component adapted to be accessed, removed from, and replaced as a unit into an operational position in the membrane module. As a further example, the hydrogen-separation device 10 itself may be a cartridge-based component that is adapted to accessed, removed from, and replaced as a unit into an operational position relative to the fuel processor.
It is also within the scope of the present disclosure that the cartridge-based components may be located at least partially or completely outside of the shell or otherwise accessible from external the shell, in which case an access port is not needed. The terms “cartridge,” “cartridge-based,” “modular,” “discrete” and “compartmentalized” are meant to refer to components of a fuel processor that may be readily removed as a unit from the fuel processor without requiring the level of disassembly traditionally required. The use of cartridge-based components enables a component that requires servicing or repair to be quickly removed and replaced, even by individuals, such as consumers, that are not trained in the operation and maintenance of the fuel processor. A replacement cartridge may be inserted in place of the removed cartridge, with only minor effort required and only minor, if any, downtime. The removed cartridge may then be discarded, serviced or otherwise repaired. Similarly, the use of replaceable cartridges enables outdated components to be replaced or augmented, such as when improved modules become available or as operational requirements or parameters change. When access ports are used, the fittings should be located in a position for ready access and disconnection of the component or subcomponent, and in some embodiments should enable the component or subcomponent to be accessed and/or removed and replaced without shutting down the fuel processor.
An example of a fuel processor 300 containing at least one cartridge-based component is shown in
The fuel processor shown in
In the illustrated embodiment, the vaporized feed stream 316 from vaporization coil 368 is delivered to a manifold 444 that distributes the feed stream between reforming catalyst tubes 432. As shown in dashed lines in
Another embodiment of a cartridge-based fuel processor is shown in
Also shown in dashed lines is a handle 454 that may be used to facilitate removal of the separation assembly from the shell, such as from within receptacle 452. Handle 454 may take any suitable form that is adapted to be grasped by a user to draw the separation assembly from the shell, such as finger holes, the projecting handle shown in
As a further alternative, the hydrogen producing region may be removed from the fuel processor by withdrawing the region from the other end of the shell, either along with cover plate 470 or after removal of the cover plate. As a further alternative, the hydrogen producing region may be removed though an access port in the shell generally between these two regions. It should be understood that various fittings 420 will need to be disconnected to remove the hydrogen producing region.
The fuel processor of
The fuel processor of
As discussed, fuel processor 300 may be jacketed with an insulating material. An example of such a fuel processor is shown in
Also shown in
In
In the embodiment illustrated in
Similar to the embodiment of the fuel processor shown in
It should be understood that the features described and illustrated herein may be used together or separately. For example, a fuel processor according to the present disclosure may be implemented with one or more cartridge-based components, with an air delivery system to control the operating temperature of the fuel processor, with a filter assembly, etc., either alone or in combination with these or other features and elements described herein.
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 and/or properties may be claimed through amendment of the present claims or presentation of new claims in this or a related application. Such amended or new claims, whether they are directed to a different invention or directed to the same invention, whether different, broader, narrower or equal in scope to the original claims, are also regarded as included within the subject matter of the inventions of the present disclosure.
This application is a continuation-in-part of, and claims priority to U.S. patent application Ser. No. 10/802,657, now U.S. Pat. No. 6,953,497, which was filed on Mar. 16, 2004, and which is a continuation of U.S. patent application Ser. No. 10/439,843, now U.S. Pat. No. 6,719,832, which was filed on May 15, 2003, and which is a continuation of U.S. patent application Ser. No. 10/086,680, now U.S. Pat. No. 6,569,227, which was filed on Feb. 28, 2002. This application is also a continuation-in-part of, and claims priority to U.S. patent application Ser. No. 09/802,361, which was filed on Mar. 8, 2001. U.S. Pat. application Ser. No. 10/086,680 is a continuation-in-part of: 1) U.S. patent application Ser. No. 10/003,164, now U.S. Pat. No. 6,458,189, which was filed on Nov. 14, 2001, and which is a continuation of U.S. patent application Ser. No. 09/812,499, now U.S. Pat. No. 6,319,306, which was filed on Mar. 19, 2002; 2) U.S. patent application Ser. No. 10/067,275, now U.S. Pat. No. 6,562,111, which was filed on Feb. 4, 2002, and which is a continuation-in-part of U.S. patent application Ser. No. 09/967,172, now U.S. Pat. No. 6,494,937, which was filed on Sep. 27, 2001; and 3) U.S. patent application Ser. No. 09/967,172, now U.S. Pat. No. 6,494,937, which was filed on Sep. 27, 2001. The complete disclosures of the above-identified patents and patent applications are hereby incorporated by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10439843 | May 2003 | US |
| Child | 10802657 | Mar 2004 | US |
| Parent | 10086680 | Feb 2002 | US |
| Child | 10439843 | May 2003 | US |
| Parent | 09812499 | Mar 2001 | US |
| Child | 10003164 | Nov 2001 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10802657 | Mar 2004 | US |
| Child | 11247744 | Oct 2005 | US |
| Parent | 09802361 | Mar 2001 | US |
| Child | 11247744 | Oct 2005 | US |
| Parent | 10003164 | Nov 2001 | US |
| Child | 11247744 | Oct 2005 | US |
| Parent | 09967172 | Sep 2001 | US |
| Child | 10439843 | US |
