Patent Publication Number: US-2021162335-A1

Title: Hydrogen generation assemblies

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/891,477, filed Jun. 3, 2020 and entitled “Hydrogen Generation Assemblies,” which is a continuation of U.S. patent application Ser. No. 15/985,175, filed May 21, 2018 and entitled “Hydrogen Generation Assemblies,” which issued as U.S. Pat. No. 10,710,022 on Jul. 14, 2020, which is a continuation of U.S. patent application Ser. No. 15/483,265, which was filed Apr. 10, 2017 and entitled “Hydrogen Generation Assemblies and Hydrogen Purification Devices,” which issued as U.S. Pat. No. 10,166,506 on Jan. 1, 2019, which is a continuation application of U.S. patent application Ser. No. 14/931,585, filed Nov. 3, 2015 and entitled “Hydrogen Generation Assemblies and Hydrogen Purification Devices,” which issued as U.S. Pat. No. 9,616,389 on Apr. 11, 2017, which is a divisional application of U.S. patent application Ser. No. 13/829,766, filed Mar. 14, 2013 and entitled “Hydrogen Generation Assemblies and Hydrogen Purification Devices,” which issued as U.S. Pat. No. 9,187,324 on Nov. 17, 2015, which is a continuation-in-part application of U.S. patent application Ser. No. 13/600,096, filed Aug. 30, 2012 and entitled “Hydrogen Generation Assemblies.” The complete disclosures of the above applications are hereby incorporated by reference for all purposes. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     A hydrogen generation assembly is an assembly that converts one or more feedstocks into a product stream containing hydrogen gas as a majority component. The feedstocks may include a carbon-containing feedstock and, in some embodiments, also may include water. The feedstocks are delivered to a hydrogen-producing region of the hydrogen generation assembly from a feedstock delivery system, typically with the feedstocks being delivered under pressure and at elevated temperatures. The hydrogen-producing region is often associated with a temperature modulating assembly, such as a heating assembly or cooling assembly, which consumes one or more fuel streams to maintain the hydrogen-producing region within a suitable temperature range for effectively producing hydrogen gas. The hydrogen generation assembly may generate hydrogen gas via any suitable mechanism(s), such as steam reforming, autothermal reforming, pyrolysis, and/or catalytic partial oxidation. 
     The generated or produced hydrogen gas may, however, have impurities. That gas may be referred to as a mixed gas stream that contains hydrogen gas and other gases. Prior to using the mixed gas stream, it must be purified, such as to remove at least a portion of the other gases. The hydrogen generation assembly may therefore include a hydrogen purification device for increasing the hydrogen purity of the mixed gas stream. The hydrogen purification device may include at least one hydrogen-selective membrane to separate the mixed gas stream into a product stream and a byproduct stream. The product stream contains a greater concentration of hydrogen gas and/or a reduced concentration of one or more of the other gases from the mixed gas stream. Hydrogen purification using one or more hydrogen-selective membranes is a pressure driven separation process in which the one or more hydrogen-selective membranes are contained in a pressure vessel. The mixed gas stream contacts the mixed gas surface of the membrane(s), and the product stream is formed from at least a portion of the mixed gas stream that permeates through the membrane(s). The pressure vessel is typically sealed to prevent gases from entering or leaving the pressure vessel except through defined inlet and outlet ports or conduits. 
     The product stream may be used in a variety of applications. One such application is energy production, such as in electrochemical fuel cells. An electrochemical fuel cell is a device that converts fuel and an oxidant to electricity, a reaction product, and heat. For example, fuel cells may convert hydrogen and oxygen into water and electricity. In those fuel cells, the hydrogen is the fuel, the oxygen is the oxidant, and the water is a reaction product. Fuel cell stacks include a plurality of fuel cells and may be utilized with a hydrogen generation assembly to provide an energy production assembly. 
     Examples of hydrogen generation assemblies, hydrogen processing assemblies, and/or components of those assemblies are described in U.S. Pat. Nos. 5,861,137; 6,319,306; 6,494,937; 6,562,111; 7,063,047; 7,306,868; 7,470,293; 7,601,302; 7,632,322; U.S. Patent Application Publication Nos. 2006/0090397; 2006/0272212; 2007/0266631; 2007/0274904; 2008/0085434; 2008/0138678; 2008/0230039; 2010/0064887; and U.S. patent application Ser. No. 13/178,098. The complete disclosures of the above patents and patent application publications are hereby incorporated by reference for all purposes. 
     SUMMARY OF THE DISCLOSURE 
     Some embodiments may provide a hydrogen generation assembly. In some embodiments, the hydrogen generation assembly may include a fuel processing assembly configured to receive a feed stream and produce a product hydrogen stream from the feed stream. The hydrogen generation assembly may additionally include a feed assembly configured to deliver the feed stream to the fuel processing assembly. The feed assembly may include a feed tank configured to contain feedstock for the feed stream, and a feed conduit fluidly connecting the feed tank and the fuel processing assembly. The feed assembly may additionally include a pump configured to deliver the feed stream at a plurality of flowrates to the fuel processing assembly via the feed conduit. The hydrogen generation assembly may further include a control system. The control system may include a feed sensor assembly configured to detect pressure in the feed conduit downstream from the pump. The control system may additionally include a pump controller configured to select a flowrate from the plurality of flowrates based on the detected pressure in the feed conduit, and to operate the pump at the selected flowrate. 
     In some embodiments, the hydrogen generation assembly may include a fuel processing assembly configured to receive a feed stream and produce a product hydrogen stream from the feed stream. The hydrogen generation assembly may additionally include a pressurized gas assembly configured to receive at least one container of pressurized gas that is configured to purge the fuel processing assembly. The hydrogen generation assembly may further include a purge conduit configured to fluidly connect the pressurized gas assembly and the fuel processing assembly. The hydrogen generation assembly may additionally include a purge valve assembly configured to allow the at least one pressurized gas to flow through the purge conduit from the pressurized gas assembly to the fuel processing assembly when power to the fuel processing assembly is interrupted. 
     In some embodiments, the hydrogen generation assembly may include a fuel processing assembly configured to receive a feed stream and to be operable among a plurality of modes, including a run mode in which the fuel processing assembly produces a product hydrogen stream from the feed stream, and a standby mode in which the fuel processing assembly does not produce the product hydrogen stream from the feed stream. The hydrogen generation assembly may additionally include a buffer tank configured to contain the product hydrogen stream, and a product conduit fluidly connecting the fuel processing assembly and the buffer tank. The hydrogen generation assembly may further include a tank sensor assembly configured to detect pressure in the buffer tank, and a control assembly configured to operate the fuel processing assembly between the run and standby modes based, at least in part, on the detected pressure in the buffer tank. 
     Some embodiments may provide a steam reforming hydrogen generation assembly configured to receive at least one feed stream and generate a reformate stream containing hydrogen gas as a majority component and other gases. In some embodiments, the steam reforming hydrogen generation assembly may include an enclosure having an exhaust port, and a hydrogen-producing region contained within the enclosure and configured to produce, via a steam reforming reaction, the reformate stream from the at least one feed stream. The steam reforming hydrogen generation assembly may additionally include a reformer sensor assembly configured to detect temperature in the hydrogen-producing region. The steam reforming hydrogen generation assembly may further include a heating assembly configured to receive at least one air stream and at least one fuel stream and to combust the at least one fuel stream within a combustion region contained within the enclosure producing a heated exhaust stream for heating at least the hydrogen-producing region to at least a minimum hydrogen-producing temperature. The steam reforming hydrogen generation assembly may additionally include a damper moveably connected to the exhaust port and configured to move among a plurality of positions including a fully open position in which the damper allows the heated exhaust stream to flow through the exhaust port, a closed position in which the damper prevents the heated exhaust stream from flowing through the exhaust port, and a plurality of intermediate open positions between the fully open and closed positions. The steam reforming hydrogen generation assembly may further include a damper controller configured to move the damper between the fully open and closed positions based, at least in part, on the detected temperature in the hydrogen-producing region. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an example of a hydrogen generation assembly. 
         FIG. 2  is a schematic view of another example of a hydrogen generation assembly. 
         FIG. 3  is a partial schematic view of an additional example of a hydrogen generation assembly. 
         FIG. 4  is a schematic view of an example of a control assembly. 
         FIG. 5  is a graph showing an example of the control assembly of  FIG. 4  receiving a detection signal and conditioning the detection signal to generate a conditioned signal. 
         FIG. 6  is a partial schematic view of a further example of a hydrogen generation assembly. 
         FIG. 7  is an example of a purge assembly of a hydrogen generation assembly. 
         FIG. 8  is another example of a purge assembly of a hydrogen generation assembly. 
         FIG. 9  is a partial schematic view of an additional example of a hydrogen generation assembly. 
         FIGS. 10-12  are partial schematic views of the hydrogen generation assembly of  FIG. 9  showing another example of a damper and examples of positions for that damper. 
         FIG. 13  is a partial schematic view of a further example of a hydrogen generation assembly. 
         FIG. 14  is a partial schematic view of another example of a hydrogen generation assembly. 
         FIG. 15  is a partial schematic view of the hydrogen generation assembly of  FIG. 14  showing a three-way valve in a flow position. 
         FIG. 16  is a partial schematic view of the hydrogen generation assembly of  FIG. 14  showing the three-way valve of  FIG. 15  in a vent position. 
         FIG. 17  is a partial schematic view of a further example of a hydrogen generation assembly. 
         FIG. 18  is a partial schematic view of the hydrogen generation assembly of  FIG. 17  showing a first valve in an open position and a second valve in a closed position. 
         FIG. 19  is a partial schematic view of the hydrogen generation assembly of  FIG. 17  showing the first valve of  FIG. 18  in a closed position and the second valve of  FIG. 18  in an open position. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
       FIG. 1  shows an example of a hydrogen generation assembly  20 . Unless specifically excluded hydrogen generation assembly may include one or more components of other hydrogen generation assemblies described in this disclosure. The hydrogen generation assembly may include any suitable structure configured to generate a product hydrogen stream  21 . For example, the hydrogen generation assembly may include a feedstock delivery system  22  and a fuel processing assembly  24 . The feedstock delivery system may include any suitable structure configured to selectively deliver at least one feed stream  26  to the fuel processing assembly. 
     In some embodiments, feedstock delivery system  22  may additionally include any suitable structure configured to selectively deliver at least one fuel stream  28  to a burner or other heating assembly of fuel processing assembly  24 . In some embodiments, feed stream  26  and fuel stream  28  may be the same stream delivered to different parts of the fuel processing assembly. The feedstock delivery system may include any suitable delivery mechanisms, such as a positive displacement or other suitable pump or mechanism for propelling fluid streams. In some embodiments, feedstock delivery system may be configured to deliver feed stream(s)  26  and/or fuel stream(s)  28  without requiring the use of pumps and/or other electrically powered fluid-delivery mechanisms. Examples of suitable feedstock delivery systems that may be used with hydrogen generation assembly  20  include the feedstock delivery systems described in U.S. Pat. Nos. 7,470,293 and 7,601,302, and U.S. Patent Application Publication No. 2006/0090397. The complete disclosures of the above patents and patent application are hereby incorporated by reference for all purposes. 
     Feed stream  26  may include at least one hydrogen-production fluid  30 , which may include one or more fluids that may be utilized as reactants to produce product hydrogen stream  21 . For example, the hydrogen-production fluid may include a carbon-containing feedstock, such as at least one hydrocarbon and/or alcohol. Examples of suitable hydrocarbons include methane, propane, natural gas, diesel, kerosene, gasoline, etc. Examples of suitable alcohols include methanol, ethanol, polyols (such as ethylene glycol and propylene glycol), etc. Additionally, hydrogen-production fluid  30  may include water, such as when fuel processing assembly generates the product hydrogen stream via steam reforming and/or autothermal reforming. When fuel processing assembly  24  generates the product hydrogen stream via pyrolysis or catalytic partial oxidation, feed stream  26  does not contain water. 
     In some embodiments, feedstock delivery system  22  may be configured to deliver a hydrogen-production fluid  30  that contains a mixture of water and a carbon-containing feedstock that is miscible with water (such as methanol and/or another water-soluble alcohol). The ratio of water to carbon-containing feedstock in such a fluid stream may vary according to one or more factors, such as the particular carbon-containing feedstock being used, user preferences, design of the fuel processing assembly, mechanism(s) used by the fuel processing assembly to generate the product hydrogen stream etc. For example, the molar ratio of water to carbon may be approximately 1:1 to 3:1. Additionally, mixtures of water and methanol may be delivered at or near a 1:1 molar ratio (37 weight % water, 63 weight % methanol), while mixtures of hydrocarbons or other alcohols may be delivered at a water-to-carbon molar ratio greater than 1:1. 
     When fuel processing assembly  24  generates product hydrogen stream  21  via reforming, feed stream  26  may include, for example, approximately 25-75 volume % methanol or ethanol (or another suitable water-miscible carbon-containing feedstock) and approximately 25-75 volume % water. For feed streams that at least substantially include methanol and water, those streams may include approximately 50-75 volume % methanol and approximately 25-50 volume % water. Streams containing ethanol or other water-miscible alcohols may contain approximately 25-60 volume % alcohol and approximately 40-75 volume % water. An example of a feed stream for hydrogen generating assembly  20  that utilizes steam reforming or autothermal reforming contains 69 volume % methanol and 31 volume % water. 
     Although feedstock delivery system  22  is shown to be configured to deliver a single feed stream  26 , the feedstock delivery system may be configured to deliver two or more feed streams  26 . Those streams may contain the same or different feedstocks and may have different compositions, at least one common component, no common components, or the same compositions. For example, a first feed stream may include a first component, such as a carbon-containing feedstock and a second feed stream may include a second component, such as water. Additionally, although feedstock delivery system  22  may, in some embodiments, be configured to deliver a single fuel stream  28 , the feedstock delivery system may be configured to deliver two or more fuel streams. The fuel streams may have different compositions, at least one common component, no common components, or the same compositions. Moreover, the feed and fuel streams may be discharged from the feedstock delivery system in different phases. For example, one of the streams may be a liquid stream while the other is a gas stream. In some embodiments, both of the streams may be liquid streams, while in other embodiments both of the streams may be gas streams. Furthermore, although hydrogen generation assembly  20  is shown to include a single feedstock delivery system  22 , the hydrogen generation assembly may include two or more feedstock delivery systems  22 . 
     Fuel processing assembly  24  may include a hydrogen-producing region  32  configured to produce an output stream  34  containing hydrogen gas via any suitable hydrogen-producing mechanism(s). The output stream may include hydrogen gas as at least a majority component and may include additional gaseous component(s). Output stream  34  may therefore be referred to as a “mixed gas stream” that contains hydrogen gas as its majority component but which includes other gases. 
     Hydrogen-producing region  32  may include any suitable catalyst-containing bed or region. When the hydrogen-producing mechanism is steam reforming, the hydrogen-producing region may include a suitable steam reforming catalyst  36  to facilitate production of output stream(s)  34  from feed stream(s)  26  containing a carbon-containing feedstock and water. In such an embodiment, fuel processing assembly  24  may be referred to as a “steam reformer,” hydrogen-producing region  32  may be referred to as a “reforming region,” and output stream  34  may be referred to as a “reformate stream.” The other gases that may be present in the reformate stream may include carbon monoxide, carbon dioxide, methane, steam, and/or unreacted carbon-containing feedstock. 
     When the hydrogen-producing mechanism is autothermal reforming, hydrogen-producing region  32  may include a suitable autothermal reforming catalyst to facilitate the production of output stream(s)  34  from feed stream(s)  26  containing water and a carbon-containing feedstock in the presence of air. Additionally, fuel processing assembly  24  may include an air delivery assembly  38  configured to deliver air stream(s) to the hydrogen-producing region. 
     In some embodiments, fuel processing assembly  24  may include a purification (or separation) region  40 , which may include any suitable structure configured to produce at least one hydrogen-rich stream  42  from output (or mixed gas) stream  34 . Hydrogen-rich stream  42  may include a greater hydrogen concentration than output stream  34  and/or a reduced concentration of one or more other gases (or impurities) that were present in that output stream. Product hydrogen stream  21  includes at least a portion of hydrogen-rich stream  42 . Thus, product hydrogen stream  21  and hydrogen-rich stream  42  may be the same stream and have the same composition and flow rates. Alternatively, some of the purified hydrogen gas in hydrogen-rich stream  42  may be stored for later use, such as in a suitable hydrogen storage assembly and/or consumed by the fuel processing assembly. Purification region  40  also may be referred to as a “hydrogen purification device” or a “hydrogen processing assembly.” 
     In some embodiments, purification region  40  may produce at least one byproduct stream  44 , which may contain no hydrogen gas or some hydrogen gas. The byproduct stream may be exhausted, sent to a burner assembly and/or other combustion source, used as a heated fluid stream, stored for later use, and/or otherwise utilized, stored, and/or disposed. Additionally, purification region  40  may emit the byproduct stream as a continuous stream responsive to the deliver of output stream  34 , or may emit that stream intermittently, such as in a batch process or when the byproduct portion of the output stream is retained at least temporarily in the purification region. 
     Fuel processing assembly  24  may include one or more purification regions configured to produce one or more byproduct streams containing sufficient amounts of hydrogen gas to be suitable for use as a fuel stream (or a feedstock stream) for a heating assembly for the fuel processing assembly. In some embodiments, the byproduct stream may have sufficient fuel value or hydrogen content to enable a heating assembly to maintain the hydrogen-producing region at a desired operating temperature or within a selected range of temperatures. For example, the byproduct stream may include hydrogen gas, such as 10-30 weight % hydrogen gas, 15-25 weight % hydrogen gas, 20-30 weight % hydrogen gas, at least 10 or 15 weight % hydrogen gas, at least 20 weight % hydrogen gas, etc. 
     Purification region  40  may include any suitable structure configured to reduce the concentration of at least one component of output stream  21 . In most applications, hydrogen-rich stream  42  will have a greater hydrogen concentration than output stream (or mixed gas stream)  34 . The hydrogen-rich stream also may have a reduced concentration of one or more non-hydrogen components that were present in output stream  34  with the hydrogen concentration of the hydrogen-rich stream being more, the same, or less than the output stream. For example, in conventional fuel cell systems, carbon monoxide may damage a fuel cell stack if it is present in even a few parts per million, while other non-hydrogen components that may be present in output stream  34 , such as water, will not damage the stack even if present in much greater concentrations. Therefore, in such an application, the purification region may not increase the overall hydrogen concentration but will reduce the concentration of one or more non-hydrogen components that are harmful, or potentially harmful, to the desired application for the product hydrogen stream. 
     Examples of suitable devices for purification region  40  include one or more hydrogen-selective membranes  46 , chemical carbon monoxide removal assemblies  48 , and/or pressure swing adsorption (PSA) systems  50 . Purification region  40  may include more than one type of purification device and the devices may have the same or different structures and/or operate by the same or difference mechanism(s). Fuel processing assembly  24  may include at least one restrictive orifice and/or other flow restrictor downstream of the purification region(s), such as associated with one or more product hydrogen stream(s), hydrogen-rich stream(s), and/or byproduct stream(s). 
     Hydrogen-selective membranes  46  are permeable to hydrogen gas, but are at least substantially (if not completely) impermeable to other components of output stream  34 . Membranes  46  may be formed of any hydrogen-permeable material suitable for use in the operating environment and parameters in which purification region  40  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 weight % to 45 weight % copper. A palladium-copper alloy that contains approximately 40 weight % copper has proven particularly effective, although other relative concentrations and components may be used. Another especially effective alloy is palladium with 2 weight % to 10 weight % gold, especially palladium with 5 weight % gold. When palladium and palladium alloys are used, hydrogen-selective membranes  46  may sometimes be referred to as “foils.” 
     Chemical carbon monoxide removal assemblies  48  are devices that chemically react carbon monoxide and/or other undesirable components of output stream  34  to form other compositions that are not as potentially harmful. Examples of chemical carbon monoxide removal assemblies include water-gas shift reactors that are configured to produce hydrogen gas and carbon dioxide from water and carbon monoxide, partial oxidation reactors that are configured to convert carbon monoxide and oxygen (usually from air) into carbon dioxide, and methanation reactors that are configured to convert carbon monoxide and hydrogen to methane and water. Fuel processing assembly  24  may include more than one type and/or number of chemical removal assemblies  48 . 
     Pressure swing adsorption (PSA) is a chemical process in which gaseous impurities are removed from output stream  34  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, the non-hydrogen impurities are adsorbed and removed from output stream  34 . 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. PSA system  50  also provides an example of a device for use in purification region  40  in which the byproducts, or removed components, are not directly exhausted from the region as a gas stream concurrently with the purification of the output stream. Instead, these byproduct components are removed when the adsorbent material is regenerated or otherwise removed from the purification region. 
     In  FIG. 1 , purification region  40  is shown within fuel processing assembly  24 . The purification region may alternatively be separately located downstream from the fuel processing assembly, as is schematically illustrated in dash-dot lines in  FIG. 1 . Purification region  40  also may include portions within and external to the fuel processing assembly. 
     Fuel processing assembly  24  also may include a temperature modulating assembly in the form of a heating assembly  52 . The heating assembly may be configured to produce at least one heated exhaust stream (or combustion stream)  54  from at least one heating fuel stream  28 , typically as combusted in the presence of air. Heated exhaust stream  54  is schematically illustrated in  FIG. 1  as heating hydrogen-producing region  32 . Heating assembly  52  may include any suitable structure configured to generate the heated exhaust stream, such as a burner or combustion catalyst in which a fuel is combusted with air to produce the heated exhaust stream. The heating assembly may include an ignitor or ignition source  58  that is configured to initiate the combustion of fuel. Examples of suitable ignition sources include one or more spark plugs, glow plugs, combustion catalyst, pilot lights, piezoelectric ignitors, spark igniters, hot surface igniters, etc. 
     In some embodiments, heating assembly  52  may include a burner assembly  60  and may be referred to as a combustion-based, or combustion-driven, heating assembly. In a combustion-based heating assembly, heating assembly  52  may be configured to receive at least one fuel stream  28  and to combust the fuel stream in the presence of air to provide a hot combustion stream  54  that may be used to heat at least the hydrogen-producing region of the fuel processing assembly. Air may be delivered to the heating assembly via a variety of mechanisms. For example, an air stream  62  may be delivered to the heating assembly as a separate stream, as shown in  FIG. 1 . Alternatively, or additionally, air stream  62  may be delivered to the heating assembly with at least one of the fuel streams  28  for heating assembly  52  and/or drawn from the environment within which the heating assembly is utilized. 
     Combustion stream  54  may additionally, or alternatively, be used to heat other portions of the fuel processing assembly and/or fuel cell systems with which the heating assembly is used. Additionally, other configuration and types of heating assemblies  52  may be used. For example, heating assembly  52  may be an electrically powered heating assembly that is configured to heat at least hydrogen-producing region  32  of fuel processing assembly  24  by generating heat using at least one heating element, such as a resistive heating element. In those embodiments, heating assembly  52  may not receive and combust a combustible fuel stream to heat the hydrogen-producing region to a suitable hydrogen-producing temperature. Examples of heating assemblies are disclosed in U.S. Pat. No. 7,632,322, the complete disclosure of which is hereby incorporated by reference for all purposes. 
     Heating assembly  52  may be housed in a common shell or housing with the hydrogen-producing region and/or separation region (as further discussed below). The heating assembly may be separately positioned relative to hydrogen-producing region  32  but in thermal and/or fluid communication with that region to provide the desired heating of at least the hydrogen-producing region. Heating assembly  52  may be located partially or completely within the common shell, and/or at least a portion (or all) of the heating assembly may be located external that shell. When the heating assembly is located external the shell, the hot combustion gases from burner assembly  60  may be delivered via suitable heat transfer conduits to one or more components within the shell. 
     The heating assembly also may be configured to heat feedstock delivery system  22 , the feedstock supply streams, hydrogen-producing region  32 , purification (or separation) region  40 , or any suitable combination of those systems, streams, and regions. Heating of the feedstock supply streams may include vaporizing liquid reactant streams or components of the hydrogen-production fluid used to produce hydrogen gas in the hydrogen-producing region. In that embodiment, fuel processing assembly  24  may be described as including a vaporization region  64 . The heating assembly may additionally be configured to heat other components of the hydrogen generation assembly. For example, the heated exhaust stream may be configured to heat a pressure vessel and/or other canister containing the heating fuel and/or the hydrogen-production fluid that forms at least portions of feed stream  26  and fuel stream  28 . 
     Heating assembly  52  may achieve and/or maintain in hydrogen-producing region  32  any suitable temperatures. Steam reformers typically operate at temperatures in the range of 200° C. and 900° C. However, temperatures outside this range are within the scope of this disclosure. When the carbon-containing feedstock is methanol, the steam reforming reaction will typically operate in a temperature range of approximately 200-500° C. Example subsets of that range include 350-450° C., 375-425° C., and 375-400° C. When the carbon-containing feedstock is a hydrocarbon, ethanol or another alcohol, a temperature range of approximately 400-900° C. will typically be used for the steam reforming reaction. Example subsets of that range include 750-850° C., 725-825° C., 650-750° C., 700-800° C., 700-900° C., 500-800° C., 400-600° C., and 600-800° C. Hydrogen-producing region  32  may include two or more zones, or portions, each of which may be operated at the same or at different temperatures. For example, when the hydrogen-production fluid includes a hydrocarbon, hydrogen-producing region  32  may include two different hydrogen-producing portions, or regions, with one operating at a lower temperature than the other to provide a pre-reforming region. In those embodiments, the fuel processing assembly may also be referred to as including two or more hydrogen-producing regions. 
     Fuel stream  28  may include any combustible liquid(s) and/or gas(es) that are suitable for being consumed by heating assembly  52  to provide the desired heat output. Some fuel streams may be gases when delivered and combusted by heating assembly  52 , while others may be delivered to the heating assembly as a liquid stream. Examples of suitable heating fuels for fuel streams  28  include carbon-containing feedstocks, such as methanol, methane, ethane, ethanol, ethylene, propane, propylene, butane, etc. Additional examples include low molecular weight condensable fuels, such as liquefied petroleum gas, ammonia, lightweight amines, dimethyl ether, and low molecular weight hydrocarbons. Yet other examples include hydrogen and carbon monoxide. In embodiments of hydrogen generation assembly  20  that include a temperature modulating assembly in the form of a cooling assembly instead of a heating assembly (such as may be used when an exothermic hydrogen-generating process—e.g., partial oxidation—is utilized instead of an endothermic process such as steam reforming), the feedstock delivery system may be configured to supply a fuel or coolant stream to the assembly. Any suitable fuel or coolant fluid may be used. 
     Fuel processing assembly  24  may additionally include a shell or housing  66  in which at least hydrogen-producing region  32  is contained, as shown in  FIG. 1 . In some embodiments, vaporization region  64  and/or purification region  40  may additionally be contained within the shell. Shell  66  may enable components of the steam reformer or other fuel processing mechanism to be moved as a unit. The shell also may protect components of the fuel processing assembly from damage by providing a protective enclosure and/or may reduce the heating demand of the fuel processing assembly because components may be heated as a unit. Shell  66  may include insulating material  68 , such as a solid insulating material, blanket insulating material, and/or an air-filled cavity. The insulating material may be internal the shell, external the shell, or both. When the insulating material is external a shell, fuel processing assembly  24  may further include an outer cover or jacket  70  external the insulation, as schematically illustrated in  FIG. 1 . The fuel processing assembly may include a different shell that includes additional components of the fuel processing assembly, such as feedstock delivery system  22  and/or other components. 
     One or more components of fuel processing assembly  24  may either extend beyond the shell or be located external the shell. For example, purification region  40  may be located external shell  66 , such as being spaced-away from the shell but in fluid communication by suitable fluid-transfer conduits. As another example, a portion of hydrogen-producing region  32  (such as portions of one or more reforming catalyst beds) may extend beyond the shell, such as indicated schematically with a dashed line representing an alternative shell configuration in  FIG. 1 . Examples of suitable hydrogen generation assemblies and its components are disclosed in U.S. Pat. Nos. 5,861,137; 5,997,594; and 6,221,117, the complete disclosures of which are hereby incorporated by reference for all purposes. 
     Another example of hydrogen generation assembly  20  is shown in  FIG. 2 , and is generally indicated at  72 . Unless specifically excluded, hydrogen generation assembly  72  may include one or more components of hydrogen generation assembly  20 . Hydrogen-generation assembly  72  may include a feedstock delivery system  74 , a vaporization region  76 , a hydrogen-producing region  78 , and a heating assembly  80 , as shown in  FIG. 2 . In some embodiments, hydrogen generation assembly  20  also may include a purification region  82 . 
     The feedstock delivery system may include any suitable structure configured to deliver one or more feed and/or fuel streams to one or more other components of the hydrogen-generation assembly. For example, feedstock delivery system may include a feedstock tank (or container)  84  and a pump  86 . The feedstock tank may contain any suitable hydrogen-production fluid  88 , such as water and a carbon-containing feedstock (e.g., a methanol/water mixture). Pump  86  may have any suitable structure configured to deliver the hydrogen-production fluid, which may be in the form of at least one liquid-containing feed stream  90  that includes water and a carbon-containing feedstock, to vaporization region  76  and/or hydrogen-producing region  78 . 
     Vaporization region  76  may include any suitable structure configured to receive and vaporize at least a portion of a liquid-containing feed stream, such as liquid-containing feed stream  90 . For example, vaporization region  76  may include a vaporizer  92  configured to at least partially transform liquid-containing feed stream  90  into one or more vapor feed streams  94 . The vapor feed streams may, in some embodiments, include liquid. An example of a suitable vaporizer is a coiled tube vaporizer, such as a coiled stainless steel tube. 
     Hydrogen-producing region  78  may include any suitable structure configured to receive one of more feed streams, such as vapor feed stream(s)  94  from the vaporization region, to produce one or more output streams  96  containing hydrogen gas as a majority component and other gases. The hydrogen-producing region may produce the output stream via any suitable mechanism(s). For example, hydrogen-producing region  78  may generate output stream(s)  96  via a steam reforming reaction. In that example, hydrogen-producing region  78  may include a steam reforming region  97  with a reforming catalyst  98  configured to facilitate and/or promote the steam reforming reaction. When hydrogen-producing region  78  generates output stream(s)  96  via a steam reforming reaction, hydrogen generation assembly  72  may be referred to as a “steam reforming hydrogen generation assembly” and output stream  96  may be referred to as a “reformate stream.” 
     Heating assembly  80  may include any suitable structure configured to produce at least one heated exhaust stream  99  for heating one or more other components of the hydrogen generation assembly  72 . For example, the heating assembly may heat the vaporization region to any suitable temperature(s), such as at least a minimum vaporization temperature or the temperature in which at least a portion of the liquid-containing feed stream is vaporized to form the vapor feed stream. Additionally, or alternatively, heating assembly  80  may heat the hydrogen-producing region to any suitable temperature(s), such as at least a minimum hydrogen-producing temperature or the temperature in which at least a portion of the vapor feed stream is reacted to produce hydrogen gas to form the output stream. The heating assembly may be in thermal communication with one or more components of the hydrogen generation assembly, such as the vaporization region and/or hydrogen-producing region. 
     The heating assembly may include a burner assembly  100 , at least one air blower  102 , and an igniter assembly  104 , as shown in  FIG. 2 . The burner assembly may include any suitable structure configured to receive at least one air stream  106  and at least one fuel stream  108  and to combust the at least one fuel stream within a combustion region  110  to produce heated exhaust stream  99 . The fuel stream may be provided by feedstock delivery system  74  and/or purification region  82 . The combustion region may be contained within an enclosure of the hydrogen generation assembly. Air blower  102  may include any suitable structure configured to generate air stream(s)  106 . Igniter assembly  104  may include any suitable structure configured to ignite fuel stream(s)  108 . 
     Purification region  82  may include any suitable structure configured to produce at least one hydrogen-rich stream  112 , which may include a greater hydrogen concentration than output stream  96  and/or a reduced concentration of one or more other gases (or impurities) that were present in that output stream. The purification region may produce at least one byproduct stream or fuel stream  108 , which may be sent to burner assembly  100  and used as a fuel stream for that assembly, as shown in  FIG. 2 . Purification region  82  may include a flow restricting orifice  111 , a filter assembly  114 , a membrane assembly  116 , and a methanation reactor assembly  118 . The filter assembly (such as one or more hot gas filters) may be configured to remove impurities from output stream  96  prior to the hydrogen purification membrane assembly. 
     Membrane assembly  116  may include any suitable structure configured to receive output or mixed gas stream(s)  96  that contains hydrogen gas and other gases, and to generate permeate or hydrogen-rich stream(s)  112  containing a greater concentration of hydrogen gas and/or a lower concentration of other gases than the mixed gas stream. Membrane assembly  116  may incorporate hydrogen-permeable (or hydrogen-selective) membranes that are planar or tubular, and more than one hydrogen-permeable membrane may be incorporated into membrane assembly  116 . The permeate stream(s) may be used for any suitable applications, such as for one or more fuel cells. In some embodiments, the membrane assembly may generate a byproduct or fuel stream  108  that includes at least a substantial portion of the other gases. Methanation reactor assembly  118  may include any suitable structure configured to convert carbon monoxide and hydrogen to methane and water. Although purification region  82  is shown to include flow restricting orifice  111 , filter assembly  114 , membrane assembly  116 , and methanation reactor assembly  118 , the purification region may have less than all of those assemblies, and/or may alternatively, or additionally, include one or more other components configured to purify output stream  96 . For example, purification region  82  may include only membrane assembly  116 . 
     In some embodiments, hydrogen generation assembly  72  may include a shell or housing  120  which may at least partially contain one or more other components of that assembly. For example, shell  120  may at least partially contain vaporization region  76 , hydrogen-producing region  78 , heating assembly  80 , and/or purification region  82 , as shown in  FIG. 2 . Shell  120  may include one or more exhaust ports  122  configured to discharge at least one combustion exhaust stream  124  produced by heating assembly  80 . 
     Hydrogen generation assembly  72  may, in some embodiments, include a control system  126 , which may include any suitable structure configured to control operation of hydrogen generation assembly  72 . For example, control assembly  126  may include a control assembly  128 , at least one valve  130 , at least one pressure relief valve  132 , and one or more temperature measurement devices  134 . Control assembly  128  may detect temperatures in the hydrogen-producing region and/or purification regions via the temperature measurement device  134 , which may include one or more thermocouples and/or other suitable devices. Based on the detected temperatures, the control assembly and/or an operator of the control system may adjust delivery of feed stream  90  to vaporization region  76  and/or hydrogen-producing region  78  via valve(s)  130  and pump(s)  86 . Valve(s)  130  may include a solenoid valve and/or any suitable valve(s). Pressure relief valve(s)  132  may be configured to ensure that excess pressure in the system is relieved. 
     In some embodiments, hydrogen generation assembly  72  may include a heat exchange assembly  136 , which may include one or more heat exchangers  138  configured to transfer heat from one portion of the hydrogen generation assembly to another portion. For example, heat exchange assembly  136  may transfer heat from hydrogen-rich stream  112  to feed stream  90  to raise the temperature of the feed stream prior to entering vaporization region  76 , as well as to cool hydrogen-rich stream  112 . 
     Another example of hydrogen generation assembly  20  is generally indicated at  140  in  FIG. 3 . Unless specifically excluded, hydrogen generation assembly  140  may include one or more components of one or more other hydrogen generation assemblies described in this disclosure. Hydrogen generation assembly  140  may include a feedstock delivery system or feed assembly  142  and a fuel processing assembly  144  configured to receive at least one feed stream from the feedstock delivery system and produce one or more product hydrogen stream(s), such as a hydrogen gas stream, from the feed stream(s). 
     The feedstock delivery system may include any suitable structure configured to deliver one or more feed and/or fuel streams to one or more other components of the hydrogen generation assembly, such as fuel processing assembly  144 . For example, the feedstock delivery system may include a feedstock tank or feed tank (and/or container)  146 , a feed conduit  148 , a pump  150 , and a control system  152 . The feed tank may contain feedstock for one or more feed streams of the fuel processing assembly. For example, feed tank  146  may contain any suitable hydrogen-production fluid, such as water and a carbon-containing feedstock (e.g., a methanol/water mixture). 
     Feed conduit  148  may fluidly connect feed tank  146  with fuel processing assembly  144 . The feed conduit may include a feed portion  154  and a bypass portion  156 . The bypass portion may be configured to prevent overpressurization in the feed conduit, in the fuel processing assembly, and/or in one or more other components of hydrogen generation assembly  140 . For example, bypass portion  156  may include a valve assembly  158 , such as a pressure relief valve or a check valve. 
     Pump  150  may have any suitable structure configured to deliver one or more feed and/or fuel streams to the fuel processing assembly at a plurality of flowrates to fuel processing assembly  144  via, for example, feed conduit  148 . For example, pump  150  may be a variable-speed pump (or a pump that includes a variable speed motor) that injects the feed and/or fuel streams into the fuel processing assembly under pressure. The pump may operate at a speed based on a control signal from the control system. For example, pump  150  may operate or turn at a higher speed (which results in the pump discharging the feed and/or fuel streams at a higher flowrate) when the control signal increases in magnitude, while the pump may operate or turn at a lower speed (which results in the pump discharging the feed and/or fuel streams at a lower flowrate) when the control signal decreases in magnitude. 
     Pressure in the fuel processing assembly (such as in the hydrogen-producing region of the fuel processing assembly) may increase with higher pump flowrates and may decrease with lower pump flowrates. For example, one or more fixed flow restriction devices in the fuel processing assembly may cause a proportional increase in pressure with higher pump flowrates, and a proportional decrease in pressure with lower pump flowrates. Because feed conduit  148  fluidly connects the feedstock delivery system and the fuel processing assembly, an increase (or decrease) in pressure in the fuel processing assembly may result in an increase (or decrease) in pressure in the feed conduit downstream from pump  150 . 
     Control system  152  may include any suitable structure configured to control and/or operate pump  150  and/or other controlled devices of hydrogen generation assembly  140 . For example, control system  152  may include a sensor assembly  160 , a control assembly  162 , and communication linkages  164 . 
     The sensor assembly may include any suitable structure configured to detect and/or measure one or more suitable operating variables and/or parameters in the hydrogen generation assembly and/or generate one or more signals based on the detected and/or measured operating variable(s) and/or parameter(s). For example, the sensor assembly may detect mass, volume, flow, temperature, electrical current, pressure, refractive index, thermal conductivity, density, viscosity, optical absorbance, electrical conductivity, and/or other suitable variable(s), and/or parameter(s). In some embodiments, the sensor assembly may detect one or more triggering events. A “triggering event,” as used herein, is a measurable event in which a predetermined threshold value or range of values representative of a predetermined amount of one or more of the components forming one or more streams associated with the hydrogen generation assembly is reached or exceeded. 
     For example, sensor assembly  160  may include one or more sensors  166  configured to detect pressure, temperature, flowrate, volume, and/or other parameters. Sensors  166  may, for example, include at least one feed sensor  168  configured to detect one or more suitable operating variables, parameters, and/or triggering events in feed conduit  148 . The feed sensor may be configured to detect, for example, pressure in the feed conduit and/or generate one or more signals based on the detected pressure. 
     Control assembly  162  may be configured to communicate with sensor assembly  160  and pump  150  (and/or other controlled devices of hydrogen generation assembly  140 ) via communication linkages  164 . For example, control assembly  162  may include any suitable structure configured to select a flowrate from the plurality of flowrates of pump  150  based on the detected pressure in the feed conduit, and/or to operate the pump at the selected flowrate. Communication linkages  164  may be any suitable wired and/or wireless mechanism for one- or two-way communication between the corresponding devices, such as input signals, command signals, measured parameters, etc. 
     Control assembly  162  may, for example, include at least one processor  170 , as shown in  FIG. 4 . The processor may communicate with sensor assembly  160  and pump  150  and/or other controlled-devices via communication linkages  148 . Processor  170  may have any suitable form, such as a computerized device, software executing on a computer, an embedded processor, programmable logic controller, an analog device (with one or more resistors), and/or functionally equivalent devices. The control assembly may include any suitable software, hardware, and/or firmware. For example, control assembly  162  may include memory device(s)  172  in which preselected, preprogrammed, and/or user-selected operating parameters may be stored. The memory device may include volatile portion(s), nonvolatile portion(s), and/or both. 
     In some embodiments, processor  170  may be in the form of a signal conditioner  174 , which may include any suitable structure configured to condition one or more signals received from sensor assembly  160 . The signal conditioner may amplify, filter, convert, invert, range match, isolate, and/or otherwise modify one or more signals received from the sensor assembly such that the conditioned signals are suitable for downstream components. For example, signal conditioner  174  may invert one or more signals received from sensor assembly  160 . “Invert,” as used herein, refers to one or more of the following: converting a signal with a characteristic having ascending values to a signal with the characteristic having descending values, converting a signal with a characteristic having descending values to a signal with the characteristic having ascending values, converting a signal with a characteristic having a high value to a signal with the characteristic having a low value (or having the highest value to the lowest value), and/or converting a signal with a characteristic having a low value to a signal with the characteristic having a high value (or having the lowest value to the highest value). Characteristics of the signals may include voltage, current, etc. One or more of the converted values may match and/or correspond to values from the original signal, such as converting the highest original value to the lowest original value and/or converting the lowest original value to the highest original value. Alternatively, one or more of the converted values may be different from the original values of the signals. 
     In some embodiments, control assembly  162  may include a user interface  176 , as shown in  FIG. 4 . The user interface may include any suitable structure configured to allow a user to monitor and/or interact with operation of processor  170 . For example, user interface  176  may include a display region  178 , a user input device  180 , and/or a user-signaling device  182 , as shown in  FIG. 4 . The display region may include a screen and/or other suitable display mechanism in which information is presented to the user. For example, display region  178  may display current values measured by one or more sensors  166 , current operating parameters of the hydrogen generation assembly, stored threshold values or ranges, previously measured values, and/or other information regarding the operation and/or performance of the hydrogen generation assembly. 
     User input device  180  may include any suitable structure configured to receive input from the user and send that input to processor  170 . For example, the user input device may include rotary dials, switches, push-buttons, keypads, keyboards, a mouse, touch screens, etc. User input device  180  may, for example, enable a user to specify how signals from sensor assembly  160  will be conditioned, such as whether the signal will be inverted, what the range of values of the inverted signal should be, etc. User-signaling device  182  may include any suitable structure configured to alert a user when an acceptable threshold level has been exceeded. For example, the user-signaling device may include an alarm, lights, and/or other suitable mechanism(s) for alerting a user. 
     In some embodiments, control assembly  162  may be configured to only condition signals received from sensor assembly  160  via signal conditioner  168  without additional processing of the signal and/or sending a different signal. In other words, the signal(s) from sensor assembly  160  may be conditioned via signal conditioner  168  and the conditioned signals may be sent to pump  150  and/or other controlled device(s) via communication linkages  164  to operate the pump and/or other controlled devices without additional processing by the control assembly and/or other assemblies. 
     The conditioned signal (such as an inverted signal) may be configured, for example, to select a flowrate for pump  150  from the plurality of flowrates. When the conditioned signal is configured to select a flowrate for the pump, the control assembly may be described as being configured to select the flowrate based on (or based solely on) the conditioned signal. 
     An example of controlling pump  150  with a conditioned signal is shown in graph  184  in  FIG. 5 . Sensor assembly  160  may include feed sensor  168  that detects pressure and sends a detection signal  186  to control assembly  162  based on the detected pressure. The detection signal may be a voltage signal as shown in  FIG. 5 , a current signal, and/or other suitable signals that are proportional to the detected pressure. The detection signal(s) may be any suitable voltage(s) and/or current(s), such as 0-5 volts and/or 4-20 milliampere (mA). 
     Control assembly  162  may condition (such as invert) the detection signal into a conditioned signal  188  such that the conditioned signal is configured to select one or more parameters (such as flowrate and/or speed) for pump  150  and/or other controlled devices. The conditioned signal(s) may be any suitable voltage(s) and/or current(s), such as 0-5 volts and/or 4-20 mA. The voltages and pressure shown in  FIG. 5  are only one example of the various voltages and pressures that may be generated and/or detected by control system  152 . In other words, control system  152  is not limited to operation in the voltages and pressures shown in that figure. 
     Another example of hydrogen generation assembly  20  is generally indicated at  190  in  FIG. 6 . Unless specifically excluded, hydrogen generation assembly  190  may include one or more components of one or more other hydrogen generation assemblies described in this disclosure. Hydrogen generation assembly  190  may include a feedstock delivery system or feed assembly  192  and a fuel processing assembly  194  configured to receive at least one feed stream from the feedstock delivery system and produce one or more product hydrogen stream(s), such as a hydrogen gas stream, from the feed stream(s). 
     The feedstock delivery system may include a feedstock tank or feed tank (and/or container)  196 , a feed conduit  198 , a pump  200 , and a control system  202 . The feed tank may contain feedstock for one or more feed streams of the fuel processing assembly. Feed conduit  198  may fluidly connect feed tank  196  with fuel processing assembly  194 . The feed conduit may include a feed portion  204  and a bypass portion  206 . The bypass portion may be configured to prevent overpressurization in hydrogen generation assembly  190 . For example, bypass portion  206  may include a pressure relief valve  208 . 
     Pump  200  may have any suitable structure configured to deliver one or more feed and/or fuel streams to the fuel processing assembly at a plurality of flowrates to fuel processing assembly  194  via, for example, feed conduit  198 . For example, pump  200  may be a variable-speed pump (or a pump that includes a variable speed motor) that injects the feed and/or fuel streams into the fuel processing assembly under pressure. The pump may operate at a speed based on a control signal from the control system. 
     Control system  202  may include any suitable structure configured to control and/or operate pump  200  and/or other controlled devices of hydrogen generation assembly  190 . For example, control system  202  may include at least one pressure transducer  210 , a control assembly  212 , and communication linkages  214 . Pressure transducer  210  may be configured to detect pressure in feed conduit  198 . Although pressure transducer  210  is shown to be adjacent to pump  200  and/or bypass portion  206 , the pressure transducer may be positioned in any suitable portions along the feed portion. 
     Control assembly  212  may include a power supply assembly  216  and a signal conditioner assembly  218 . The power supply assembly may include any suitable structure configured to provide suitable power to the signal conditioner assembly. For example, the power supply assembly may include one or more batteries, one or more solar panels, one or more connectors for connecting to a DC or AC power source, etc. In some embodiments, power supply assembly  216  may include a DC power supply, which may provide the same voltage as is required to operate pump  200  and/or pressure transducer  210 . 
     Signal conditioner assembly  218  may include any suitable structure configured to condition one or more signals received from pressure transducer  210  such that one or more of the conditioned signals may be used to operate pump  200 . For example, signal conditioner assembly  218  may invert the pressure signals (or transducer signals) received from the pressure transducer and relay the inverted signals via communication linkages  214  to pump  200 . The inverted signals may be configured to select a speed and/or flowrate for pump  200  among the plurality of speeds and/or flowrates for the pump. When the inverted signals are used to control the pump&#39;s speed, the signals may be referred to as “speed control signals.” 
     An example of a purge assembly of the hydrogen generation assemblies described in the present disclosure is shown in  FIG. 7  and is generally indicated at  220 . The purge assembly may include any suitable structure configured to purge one or more other portions of a hydrogen generation assembly. Purge assembly  220  may be configured to purge one or more gases from reactor(s), purifier(s), fuel processing assembly(ies), and/or other component(s) and/or device(s) of hydrogen generation assemblies of the present disclosure and/or other hydrogen generation assemblies. For example, purge assembly  220  may include a pressurized gas assembly  222 , a purge conduit  224 , and a valve assembly  226 . Purge conduit  224  may be configured to fluidly connect the pressurized gas assembly and one or more other portions of the hydrogen generation assembly. 
     Pressurized gas assembly  222  may include any suitable structure configured to connect to and/or receive at least one gas supply assembly  228 . For example, pressurized gas assembly  222  may include any suitable connectors, piping, valves, and/or other components configured to connect to and/or receive gas supply assembly  228 . The gas supply assembly may include one or more containers of pressurized gas (such as one or more cartridges and/or cylinders) and/or one or more tanks of pressurized gas. The gas supply assembly may include any suitable pressurized gas configured to purge one or more other components of the hydrogen generation assemblies described in the present disclosure. For example, gas supply assembly may include compressed carbon dioxide or compressed nitrogen. 
     Purge conduit  224  may be configured to fluidly connect the pressurized gas assembly and one or more other portions of the hydrogen generation assembly, such as the fuel processing assembly. The purge conduit may include any suitable connectors, piping, valves, and/or other components to provide for the fluid connection between the above assemblies. 
     Valve assembly  226  may include any suitable structure configured to manage flow of the pressurized gas through purge conduit  224  from pressurized gas assembly  222  to one or more other portions of the hydrogen generation assembly. For example, valve assembly  226  may be configured to allow at least one pressurized gas to flow through the purge conduit from the pressurized gas assembly to one or more other portions of the hydrogen generation assembly and/or to prevent the at least one pressurized gas to flow through the purge conduit from the pressurized gas assembly to one or more other portions of the hydrogen generation assembly. The valve assembly may be configured to allow or prevent flow based on one or more detected variable(s), parameter(s) and/or triggering event(s). For example, the valve assembly may be configured to allow flow of at least one pressurized gas from the pressurized gas assembly to one or more other portions of the hydrogen generation assembly when power to one or more portions of the hydrogen generation assembly is interrupted. 
     In some embodiments, a control system  230  may control one or more valves of valve assembly  226 . Control system  230  may also control one or more other components of the hydrogen generation assembly, or may be dedicated to controlling only purge assembly  220 . In some embodiments, valve assembly  226  may be configured to manage flow in the purge conduit independent of control system  230  and/or any control system of the hydrogen generation assembly. In other words, valve assembly  226  may be configured to selectively allow and prevent flow without direction from control system  230  and/or any control system of the hydrogen generation assembly. 
     The purge assembly may be located within enclosure or shell  66 , external to the shell, or partially within the shell and partially external the shell. In some embodiments, at least a portion of the fuel processing assembly may be contained within an enclosure and at least a portion of the purge assembly may be contained within the enclosure, as shown in  FIG. 1 . 
     Purge assembly  220  may be connected to any suitable other component(s) of the hydrogen generation assembly. For example, as shown in  FIG. 2 , purge assembly  220  may be connected to the feed conduit either upstream of heat exchange assembly  136  (such as shown via purge conduit  224 ), and/or downstream of the heat exchange assembly (such as shown via a purge conduit  225 ). In some embodiments, the feed conduit of the hydrogen generation assembly may include a check valve  232  to prevent backflow of the pressurized gas into the feedstock delivery system, such as when the pump does not prevent backflow. The pressurized gas from the purge assembly may exit the hydrogen generation assembly at any suitable portions, such as the burner and/or the product hydrogen line. 
     Another example of purge assembly  220  is shown in  FIG. 8  and is generally indicated at  232 . Purge assembly  232  may include a pressurized gas assembly  234 , a purge conduit  236 , and a valve assembly  238 . The pressurized gas assembly may include any suitable structure configured to receive at least one pressurized gas container  240  having at least one pressurized gas. Purge conduit  236  may include any suitable structure configured to fluidly connect pressurized gas assembly  234  and one or more other portions of the hydrogen generation assembly. 
     Valve assembly  238  may include any suitable structure configured to manage flow of the at least one pressurized gas through the purge conduit from the pressurized gas assembly to one or more other portions of the hydrogen generation assembly. For example, valve assembly  238  may include a manual valve  240  and a solenoid valve (or purge solenoid valve)  242 , as shown in  FIG. 8 . The manual valve may be closed to isolate the pressurized gas assembly from one or more other portions of the hydrogen generation assembly, such as when installing or connecting a compressed or pressurized gas canister to the pressurized gas assembly. Manual valve  240  may then be opened to allow the solenoid valve to manage flow of the gas through the purge conduit from the pressurized gas assembly to one or more other portions of the hydrogen generation assembly. Manual valve  240  may sometimes be referred to as a “manual isolation valve.” 
     Solenoid valve  242  may include at least one solenoid or purge solenoid  244  and at one valve or purge valve  246 . The valve may be configured to move among a plurality of positions, including between a closed position and an open position. In the closed position, the pressurized gas assembly is isolated from one or more other portions of the hydrogen generation assembly and the pressurized gas does not flow through the purge conduit from the pressurized gas assembly. In the open position, the pressurized gas assembly is in fluid communication with one or more other portions of the hydrogen generation assembly and pressurized gas is allowed to flow through the purge conduit from the pressurized gas assembly. Solenoid  244  may be configured to move valve  226  between the open and closed positions based on one or more detected variable(s), parameter(s) and/or triggering event(s). Solenoid valve  242  may, for example, be configured to allow flow of at least one pressurized gas from the pressurized gas assembly to one or more other portions of the hydrogen generation assembly when power to the solenoid and/or one or more portions of the hydrogen generation assembly is interrupted, such as when power to the fuel processing assembly is interrupted. 
     For example, valve  246  may be configured to be in the open position without power to solenoid  244  (may also be referred to as “normally open”), such as via urging of one or more bias elements or springs (not shown). Additionally, valve  246  may be configured to be in the closed position with power to solenoid  244  (which may move the valve to the closed position against urging of the bias element(s)). Thus, a loss of electrical power to one or more portions of the hydrogen generation assembly (and/or a loss of electrical power to solenoid  244 ) may cause valve  246  to automatically move from the closed position to the open position. In other words, valve  246  of solenoid valve  242  may be configured to be in the closed position when there is power to the solenoid and/or one or more portions of the hydrogen generation assembly (such as the fuel processing assembly), and may automatically move to the open position when power to the solenoid and/or one or more portions of the hydrogen generation assembly is interrupted. 
     In some embodiments, solenoid valve  242  may be controlled by a control system  248 . For example, control system  248  may be configured to send a control signal to solenoid  244  and the solenoid may be configured to move valve  246  to the closed position when the control signal is received. Additionally, valve  246  may be configured to automatically move to the open position when the solenoid does not receive a control signal from the control system. Control system  248  may control one or more other components of the hydrogen generation assembly or may be separate from any control system. The solenoid valve may, in some embodiments, be controlled by both the control system and whether power is supplied to the solenoid. 
     In some embodiments, purge assembly  220  may include a flow-restriction orifice  250 , which may be configured to reduce or limit flow rate of the pressurized gas discharged from the pressurized gas assembly. For example, when the pressurized gas is nitrogen, the flow-restriction orifice may reduce or limit flow rate of the nitrogen gas to avoid overpressure in one or more other components of the hydrogen generation assembly, such as in the reformer and/or purifier. However, when the pressurized gas is liquefied compressed gas, such as carbon dioxide, the purge assembly may not include the flow-restriction orifice. 
     The purge assemblies of the present disclosure may be used as part of (or in) any suitable hydrogen generation assembly, such as a hydrogen generation assembly with a reformer but without a hydrogen purifier, a hydrogen generation assembly with a hydrogen purifier but without a reformer, a hydrogen generation assembly with a methanol/water reformer, a natural gas reformer, a LPG reformer, etc. 
     Another example of hydrogen generation assembly  20  is generally indicated at  252  in  FIG. 9 . Unless specifically excluded, hydrogen generation assembly  252  may include one or more components of one or more other hydrogen generation assemblies described in this disclosure. Hydrogen generation assembly  252  may include an enclosure or shell  254 , a hydrogen-producing region  256 , a heating assembly  258 , and an exhaust management assembly  260 . The enclosure or shell may include any suitable structure configured to at least partially contain one or more other components of hydrogen generation assembly  252  and/or provide insulation (such as thermal insulation) for those component(s). The enclosure may define an insulated zone or insulated hot zone  261  for the components within the enclosure. Enclosure  254  may include at least one exhaust port  262  configured to exhaust gases within the enclosure to the environment and/or to an exhaust collection system. 
     Hydrogen-producing region  256  may be partially or fully contained within the enclosure. The hydrogen-producing region may receive one or more feed streams  264  and produce an output stream  266  containing hydrogen gas via any suitable hydrogen-producing mechanism(s), such as steam reforming, autothermal reforming, etc. The output stream may include hydrogen gas as at least a majority component and may include additional gases. When hydrogen generation assembly  252  is a steam reforming hydrogen generation assembly, then the hydrogen-producing region may be referred to as being configured to produce, via a steam reforming reaction, a reformate stream  266 . 
     In some embodiments, hydrogen generation assembly  252  may include a purification region  268 , which may include any suitable structure configured to produce at least one hydrogen-rich (or permeate) stream  270  from output (or reformate) stream  266  and at least one byproduct stream  272  (which may contain no or some hydrogen gas). For example, the purification region may include one or more hydrogen-selective membranes  274 . The hydrogen-selective membrane(s) may be configured to produce at least part of the permeate stream from the portion of the reformate stream that passes through the hydrogen-selective membrane(s), and to produce at least part of the byproduct stream from the portion of the reformate stream that does not pass through the hydrogen-selective membrane(s). In some embodiments, hydrogen generation assembly  252  may include a vaporization region  276 , which may include any suitable structure configured to vaporize the feed stream(s) containing one or more liquid(s). 
     Heating assembly  258  may be configured to receive at least one air stream  278  and at least one fuel stream  280  and to combust the fuel stream(s) within a combustion region  282  contained within enclosure  254 . Fuel stream  280  may be produced from the hydrogen-producing region (and/or the purification region), and/or may be produced independent of the hydrogen generation assembly. The combustion of the fuel stream(s) may produce one or more heated exhaust streams  284 . The heated exhaust stream(s) may heat, for example, hydrogen-producing region  256 , such as to at least a minimum hydrogen-producing temperature. Additionally, the heated exhaust stream(s) may heat vaporization region  276 , such as to at least a minimum vaporization temperature. 
     Exhaust management assembly  260  may include any suitable structure configured to manage exhaust streams in enclosure  254 , such as heated exhaust streams  284 . For example, the exhaust management assembly may include a sensor assembly  286 , a damper assembly  288 , and a control assembly  290 , as shown in  FIG. 9 . 
     Sensor assembly  286  may include any suitable structure configured to detect and/or measure one or more suitable operating variables and/or parameters in the hydrogen generation assembly and/or generate one or more signals based on the detected and/or measured operating variable(s) and/or parameter(s). For example, the sensor assembly may detect mass, volume, flow, temperature, electrical current, pressure, refractive index, thermal conductivity, density, viscosity, optical absorbance, electrical conductivity, and/or other suitable variable(s), and/or parameter(s). In some embodiments, the sensor assembly may detect one or more triggering events. 
     For example, sensor assembly  286  may include one or more sensors  292  configured to detect pressure, temperature, flowrate, volume, and/or other parameters in any suitable portion(s) of the hydrogen generation assembly. Sensors  292  may, for example, include at least one hydrogen-producing region sensor  294  configured to detect one or more suitable operating variables, parameters, and/or triggering events in hydrogen-producing region  256 . The hydrogen-producing region sensor may be configured to detect, for example, temperature in the hydrogen-producing region and/or generate one or more signals based on the detected temperature in the hydrogen-producing region. 
     Additionally, sensors  292  may include at least one purification region sensor  296  configured to detect one or more suitable operating variables, parameters, and/or triggering events in purification region  268 . The purification region sensor may be configured to detect, for example, temperature in the purification region and/or generate one or more signals based on the detected temperature in the purification region. 
     Damper assembly  288  may include any suitable structure configured to manage flow, such as the flow of exhaust gases (or heated exhaust stream(s)  284 ), through exhaust port  262 . For example, damper assembly  288  may include at least one damper  298  and at least one actuator  300 . The damper may be moveably connected to exhaust port  262 . For example, damper  298  may be slidably, pivotably, and/or rotatably connected to the exhaust port. 
     Additionally, the damper may be configured to move among a plurality of positions. Those positions may include, for example, a fully open position  302 , a closed position  304 , and a plurality of intermediate open positions  306  between the fully open and closed positions, as shown in  FIGS. 10-12 . In the fully open position, damper  298  may allow one or more exhaust streams  307  (such as heated exhaust stream(s)  284  and/or other exhaust gases in the enclosure) to flow through exhaust port  262 . In the closed position, damper  298  may block the exhaust port and prevent exhaust stream(s) from flowing through the exhaust port. The intermediate open positions may allow the exhaust stream(s) to flow through exhaust port  262  at slower rate(s) than when the damper is in the fully open position. During operation, the temperature in the hydrogen-producing region may decrease when the exhaust stream(s) are restricted by the damper. 
     Damper  298  may include any suitable structure. For example, damper  298  may be a gate-type damper with one or more plates that slide across the exhaust port, such as shown in  FIGS. 10-12 . Additionally, damper  298  may be a flapper-type damper, such as shown in  FIG. 9 . The flapper-type damper may, for example, include full circle or half-circle inserts that pivot to open or close the exhaust. Actuator  300  may include any suitable structure configured to move damper  298  among the plurality of positions. In some embodiments, the actuator may move the damper incrementally between the fully open and closed positions. Although damper assembly  288  is shown to include a single damper and a single actuator, the damper assembly may include two or more dampers and/or two or more actuators. 
     Control assembly  290  may include any suitable structure configured to control damper assembly  288  based, at least in part, on input(s) from sensor assembly  286 , such as based, at least in part, on detected and/or measured operating variable(s) and/or parameter(s) by the sensor assembly. Control assembly  290  may receive input(s) only from sensor assembly  286  or the control assembly may receive input(s) from other sensor assemblies of the hydrogen generation assembly. Control assembly  290  may control only damper assembly, or the control assembly may control one or more other components of the hydrogen generation assembly. 
     Control assembly  290  may, for example, be configured to move damper  298 , such as via actuator  300 , between the fully open and closed positions based, at least in part, on the detected temperature in the hydrogen-producing region and/or the purification region. When control assembly  290  receives inputs from two or more sensors, the control assembly may select the input with a higher value, may select the input with a lower value, may calculate an average of the input values, may calculate a median of the input values, and/or perform other suitable calculation(s). For example, control assembly  290  may be configured to move the damper toward (or incrementally toward) the closed position when detected temperature in the hydrogen-producing and/or purification regions are above a predetermined maximum temperature, and/or to move the damper toward (or incrementally toward) the fully open position when the detected temperature in the hydrogen-producing and/or purification regions are below a predetermined minimum temperature. The predetermined maximum and minimum temperatures may be any suitable maximum and minimum temperatures. For example, the maximum and minimum temperatures may be set based on a desired range of temperatures for operating the vaporization, hydrogen-producing, and/or purification regions. 
     Another example of hydrogen generation assembly  20  is generally indicated at  308  in  FIG. 13 . Unless specifically excluded, hydrogen generation assembly  308  may include one or more components of one or more other hydrogen generation assemblies described in this disclosure. The hydrogen generation assembly may provide or supply hydrogen to one or more hydrogen consuming devices  310 , such as a fuel cell, hydrogen furnace, etc. Hydrogen generation assembly  308  may, for example, include a fuel processing assembly  312  and a product hydrogen management system  314 . 
     Fuel processing assembly  312  may include any suitable structure configured to generate one or more product hydrogen streams  316  (such as one or more hydrogen gas streams) from one or more feed streams  318  via one or more suitable mechanisms, such as steam reforming, autothermal reforming, electrolysis, thermolysis, partial oxidation, plasma reforming, photocatalytic water splitting, sulfur-iodine cycle, etc. For example, fuel processing assembly  312  may include one or more hydrogen generator reactors  320 , such as reformer(s), electrolyzer(s), etc. Feed stream(s)  318  may be delivered to the fuel processing assembly via one or more feed conduits  317  from one or more feedstock delivery systems (not shown). 
     Fuel processing assembly  312  may be configured to be operable among a plurality of modes, such as a run mode and a standby mode. In the run mode, the fuel processing assembly may produce or generate the product hydrogen stream(s) from the feed stream(s). For example, in the run mode, the feedstock delivery system may deliver the feed stream to the fuel processing assembly and/or may perform other operation(s). Additionally, in the run mode, the fuel processing assembly may receive the feed stream, may combust the fuel stream via the heating assembly, may vaporize the feed stream via the vaporization region, may generate the output stream via the hydrogen producing region, may generate the product hydrogen stream and the byproduct stream via the purification region, and/or may perform other operations. 
     In the standby mode, fuel processing assembly  312  may not produce the product hydrogen stream(s) from the feed stream(s). For example, in the standby mode, the feedstock delivery system may not deliver the feed stream to the fuel processing assembly and/or may not perform other operation(s). Additionally, in the standby mode, the fuel processing assembly may not receive the feed stream, may not combust the fuel stream via the heating assembly, may not vaporize the feed stream via the vaporization region, may not generate the output stream via the hydrogen producing region, may not generate the product hydrogen stream and the byproduct stream via the purification region, and/or may not perform other operations. The standby mode may include when the fuel processing assembly is powered down or when there is no power to the fuel processing assembly. 
     In some embodiments, the plurality of modes may include one or more reduced output modes. For example, fuel processing assembly  312  may produce or generate product hydrogen stream(s)  316  at a first output rate when in the run mode (such as at a maximum output rate or normal output rate), and produce or generate the product hydrogen stream(s) at second, third, fourth, or more rates that are lower (or higher) than the first rate when in the reduced output mode (such as at a minimum output rate). 
     Product hydrogen management system  314  may include any suitable structure configured to manage product hydrogen generated by fuel processing assembly  312 . Additionally, the product hydrogen management system may include any suitable structure configured to interact with fuel processing assembly  312  to maintain any suitable amount of product hydrogen available for hydrogen consuming device(s)  310 . For example, product hydrogen management system  314  may include a product conduit  322 , a buffer tank  324 , a buffer tank conduit  325 , a sensor assembly  326 , and a control assembly  328 . 
     Product conduit  322  may be configured to fluidly connect fuel processing assembly  312  with buffer tank  324 . Buffer tank  324  may be configured to receive product hydrogen stream  316  via product conduit  322 , to retain a predetermined amount or volume of the product hydrogen stream, and/or to provide the product hydrogen stream to one or more hydrogen consuming devices  310 . In some embodiments, the buffer tank may be a lower-pressure buffer tank. The buffer tank may be any suitable size based on one or more factors, such as expected or actual hydrogen consumption by the hydrogen consuming device(s), cycling characteristics of the hydrogen generator reactor, fuel processing assembly, etc. 
     In some embodiments, buffer tank  324  may be sized to provide enough hydrogen for a minimum amount of time of operation of the hydrogen consuming device(s) and/or for a minimum amount of time of operation for the fuel processing assembly, such as a minimum amount of time of operation for the vaporization region, hydrogen-producing region, and/or purification region. For example, the buffer tank may be sized for two, five, ten, or more minutes of operation of the fuel processing assembly. Buffer tank conduit  325  may be configured to fluidly connect buffer tank  324  with hydrogen consuming device(s)  310 . 
     Sensor assembly  326  may include any suitable structure configured to detect and/or measure one or more suitable operating variables and/or parameters in the buffer tank and/or generate one or more signals based on the detected and/or measured operating variable(s) and/or parameter(s). For example, the sensor assembly may detect mass, volume, flow, temperature, electrical current, pressure, refractive index, thermal conductivity, density, viscosity, optical absorbance, electrical conductivity, and/or other suitable variable(s), and/or parameter(s). In some embodiments, the sensor assembly may detect one or more triggering events. 
     For example, sensor assembly  326  may include one or more sensors  330  configured to detect pressure, temperature, flowrate, volume, and/or other parameters. Sensors  330  may, for example, include at least one buffer tank sensor  332  configured to detect one or more suitable operating variables, parameters, and/or triggering events in the buffer tank. The buffer tank sensor may be configured to detect, for example, pressure in the buffer tank and/or generate one or more signals based on the detected pressure. For example, unless product hydrogen is being withdrawn from the buffer tank at a flow rate that is equal to, or greater than, the incoming flow rate into the buffer tank, the pressure of the buffer tank may increase and the tank sensor may detect the increase of pressure in the buffer tank. 
     Control assembly  328  may include any suitable structure configured to control fuel processing assembly  312  based, at least in part, on input(s) from sensor assembly  326 , such as based, at least in part, on detected and/or measured operating variable(s) and/or parameter(s) by the sensor assembly. Control assembly  328  may receive input(s) only from sensor assembly  326  or the control assembly may receive input(s) from other sensor assemblies of the hydrogen generation assembly. Control assembly  328  may control only the fuel processing assembly, or the control assembly may control one or more other components of the hydrogen generation assembly. The control assembly may communicate with the sensor assembly, the fuel processing assembly, and/or a product valve assembly (further described below) via communication linkages  333 . 
     Communication linkages  333  may be any suitable wired and/or wireless mechanism for one- or two-way communication between the corresponding devices, such as input signals, command signals, measured parameters, etc. 
     Control assembly  328  may, for example, be configured to operate fuel processing assembly  312  between the run and standby modes based, at least in part, on the detected pressure in buffer tank  324 . For example, control assembly  328  may be configured to operate the fuel processing assembly in the standby mode when the detected pressure in the buffer tank is above a predetermined maximum pressure, and/or to operate the fuel processing assembly in the run mode when the detected pressure in the buffer tank is below a predetermined minimum pressure. 
     The predetermined maximum and minimum pressures may be any suitable maximum and minimum pressures. Those predetermined pressures may be independently set, or set without regard to other predetermined pressure(s) and/or other predetermined variable(s). For example, the predetermined maximum pressure may be set based on the operating pressure range of the fuel processing assembly, such as to prevent overpressure in the fuel processing assembly because of back pressure from the product hydrogen management system. Additionally, the predetermined minimum pressure may be set based on the pressure required by the hydrogen consuming device(s). Alternatively, control assembly  328  may operate the fuel processing assembly to operate in the run mode within a predetermined range of pressure differentials (such as between the fuel processing assembly and the buffer tank and/or between the buffer tank and the hydrogen consuming device(s)), and in the standby mode when outside the predetermined range of pressure differentials. 
     In some embodiments, product hydrogen management system  314  may include a product valve assembly  334 , which may include any suitable structure configured to manage and/or direct flow in product conduit  322 . For example, the product valve assembly may allow the product hydrogen stream to flow from the fuel processing assembly to the buffer tank, as indicated at  335 . Additionally, product valve assembly  334  may be configured to vent product hydrogen stream  316  from fuel processing assembly  312 , as indicated at  337 . The vented product hydrogen stream may be discharged to atmosphere and/or to a vented product hydrogen management system (not shown). 
     Product valve assembly  334  may, for example, include one or more valves  336  that are configured to operate between a flow position in which the product hydrogen stream from the fuel processing assembly flows through the product conduit and into the buffer tank, and a vent position in which the product hydrogen stream from the fuel processing assembly is vented. Valve(s)  336  may be positioned along any suitable portion(s) of the product conduit prior to the buffer tank. 
     Control assembly  328  may be configured to operate the product valve assembly based on, for example, input(s) from sensor assembly. For example, the control assembly may direct or control the product valve assembly (and/or valve(s)  336 ) to vent the product hydrogen stream from the fuel processing assembly when the fuel processing assembly is in the standby mode. Additionally, control assembly  328  may direct or control product valve assembly  334  (and/or valve(s)  336 ) to allow the product hydrogen stream to flow from the fuel processing assembly to the buffer tank when fuel processing assembly  312  is in the run mode and/or reduced output mode(s). 
     Another example of hydrogen generation assembly  20  is generally indicated at  338  in  FIG. 14 . Unless specifically excluded, hydrogen generation assembly  338  may include one or more components of one or more other hydrogen generation assemblies described in this disclosure. The hydrogen generation assembly may provide or supply hydrogen to one or more hydrogen consuming devices  340 , such as a fuel cell, hydrogen furnace, etc. Hydrogen generation assembly  338  may, for example, include a fuel processing assembly  342  and a product hydrogen management system  344 . Fuel processing assembly  342  may include any suitable structure configured to generate one or more product hydrogen streams  346  (such as one or more hydrogen gas streams) from one or more feed streams  348  via one or more suitable mechanisms. 
     Product hydrogen management system  344  may include any suitable structure configured to manage product hydrogen generated by fuel processing assembly  342 . Additionally, the product hydrogen management system may include any suitable structure configured to interact with fuel processing assembly  342  to maintain any suitable amount of product hydrogen available for hydrogen consuming device(s)  340 . For example, product hydrogen management system  344  may include a product conduit  349 , a buffer tank  352 , a buffer tank conduit  353 , a buffer tank sensor assembly  354 , a product valve assembly  355 , and a control assembly  356 . 
     Product conduit  349  may be configured to fluidly connect fuel processing assembly  342  with buffer tank  352 . The product conduit may include any suitable number of valves, such as check valve(s) (such as check valve  350 ), control valve(s), and/or other suitable valves. Check valve  350  may prevent backflow from the buffer tank toward the fuel processing assembly. The check valve may open at any suitable pressures, such as 1 psi or less. Buffer tank  352  may be configured to receive product hydrogen stream  346  via product conduit  349 , to retain a predetermined amount or volume of the product hydrogen stream, and/or to provide the product hydrogen stream to one or more hydrogen consuming devices  340 . 
     Buffer tank conduit  353  may be configured to fluidly connect buffer tank  352  and hydrogen consuming device(s)  340 . The buffer tank conduit may include any suitable number of valves, such as check valve(s), control valve(s), and/or other suitable valve(s). For example, the buffer tank conduit may include one or more control valves  351 . Control valve  351  may allow isolation of the buffer tank and/or other components of the hydrogen generation assembly. The control valve may, for example, be controlled by control assembly  356  and/or other control assembly(ies). 
     Tank sensor assembly  354  may include any suitable structure configured to detect and/or measure one or more suitable operating variables and/or parameters in the buffer tank and/or generate one or more signals based on the detected and/or measured operating variable(s) and/or parameter(s). For example, the buffer tank sensor assembly may detect mass, volume, flow, temperature, electrical current, pressure, refractive index, thermal conductivity, density, viscosity, optical absorbance, electrical conductivity, and/or other suitable variable(s), and/or parameter(s). In some embodiments, the buffer tank sensor assembly may detect one or more triggering events. For example, buffer tank sensor assembly  354  may include one or more tank sensors  358  configured to detect pressure, temperature, flowrate, volume, and/or other parameters. Buffer tank sensors  358  may, for example, be configured to detect pressure in the buffer tank and/or generate one or more signals based on the detected pressure. 
     Product valve assembly  355  may include any suitable structure configured to manage and/or direct flow in product conduit  349 . For example, the product valve assembly may allow the product hydrogen stream to flow from the fuel processing assembly to the buffer tank, as indicated at  359 . Additionally, product valve assembly  355  may be configured to vent product hydrogen stream  346  from fuel processing assembly  342 , as indicated at  361 . The vented product hydrogen stream may be discharged to atmosphere and/or to a vented product hydrogen management system (not shown) including discharging vented product hydrogen back to the fuel processing assembly. 
     Product valve assembly  355  may, for example, include a three-way solenoid valve  360 . The three-way solenoid valve may include a solenoid  362  and a three-way valve  364 . The three-way valve may be configured to move between a plurality of positions. For example, three-way valve  364  may be configured to move between a flow position  363  and a vent position  365 , as shown in  FIGS. 15-16 . In the flow position, the product hydrogen stream is allowed to flow from the fuel processing assembly to the buffer tank, as indicated at  359 . In the vent position, the product hydrogen stream from the fuel processing assembly is vented, as indicated at  361 . Additionally, the three-way valve may be configured to isolate the buffer tank from the product hydrogen stream when the valve is in the vent position. Solenoid  362  may be configured to move valve  364  between the flow and vent positions based on input(s) received from control assembly  356  and/or other control assembly(ies). 
     Control assembly  356  may include any suitable structure configured to control fuel processing assembly  342  and/or product valve assembly  355  based, at least in part, on input(s) from buffer tank sensor assembly  354 , such as based, at least in part, on detected and/or measured operating variable(s) and/or parameter(s) by the buffer tank sensor assembly. Control assembly  356  may receive input(s) only from buffer tank sensor assembly  354  and/or the control assembly may receive input(s) from other sensor assemblies of the hydrogen generation assembly. Additionally, control assembly  356  may control only the fuel processing assembly, only the product valve assembly, only both the fuel processing assembly and the product valve assembly, or the fuel processing assembly, product valve assembly and/or one or more other components of the hydrogen generation assembly. Control assembly  356  may communicate with the fuel processing assembly, the buffer tank sensor assembly, and the product valve assembly via communication linkages  357 . Communication linkages  357  may be any suitable wired and/or wireless mechanism for one- or two-way communication between the corresponding devices, such as input signals, command signals, measured parameters, etc. 
     Control assembly  356  may, for example, be configured to operate fuel processing assembly  342  among or between the run and standby modes (and/or reduced output mode(s)) based, at least in part, on the detected pressure in buffer tank  352 . For example, control assembly  356  may be configured to operate the fuel processing assembly in the standby mode when the detected pressure in the buffer tank is above a predetermined maximum pressure, to operate the fuel processing assembly in one or more reduced output mode(s) when the detected pressure in the buffer tank is below a predetermined maximum pressure and/or above a predetermined operating pressure, and/or to operate the fuel processing assembly in the run mode when the detected pressure in the buffer tank is below a predetermined operating pressure and/or predetermined minimum pressure. The predetermined maximum and minimum pressures and/or predetermined operating pressure(s) may be any suitable pressures. For example, the one or more of the above pressures may be independently set based on a desired range of pressures for the fuel processing assembly, product hydrogen in the buffer tank, and/or the pressure requirements of the hydrogen consuming device(s). Alternatively, control assembly  356  may operate the fuel processing assembly to operate in the run mode within a predetermined range of pressure differentials (such as between the fuel processing assembly and the buffer tank), and in the reduced output and/or standby mode when outside the predetermined range of pressure differentials. 
     Additionally, control assembly  356  may be configured to operate the product valve assembly based on, for example, input(s) from sensor assembly. For example, the control assembly may direct or control solenoid  362  to move three-way valve  364  to the vent position when the fuel processing assembly is in the standby mode. Additionally, control assembly  356  may direct or control the solenoid to move three-way valve  364  to the flow position when fuel processing assembly  342  is in the run mode. 
     Control assembly  356  may, for example, include a controller  366 , a switching device  368 , and a power supply  370 . Controller  366  may have any suitable form, such as a computerized device, software executing on a computer, an embedded processor, programmable logic controller, an analog device, and/or functionally equivalent devices. Additionally, the controller may include any suitable software, hardware, and/or firmware. 
     Switching device  368  may include any suitable structure configured to allow controller  366  to control solenoid  362 . For example, the switching device may include a solid-state relay  372 . The solid-state relay may allow controller  366  to control solenoid  362  via power supply  370 . For example, when solenoid  362  is controlled with 24 volts, the solid-state relay may allow controller  366  to use a voltage signal less than 24 volts (such as 5 volts) to control solenoid  362 . Power supply  370  may include any suitable structure configured to provide power sufficient to control solenoid  362 . For example, power supply  370  may include one or more batteries, one or more solar panels, etc. In some embodiments, the power supply may include one or more electrical outlet connectors and one or more rectifiers (not shown). Although the solenoid and controller are described to operate at certain voltages, the solenoid and controller may operate at any suitable voltages. 
     Another example of hydrogen generation assembly  20  is generally indicated at  374  in  FIG. 17 . Unless specifically excluded, hydrogen generation assembly  374  may include one or more components of one or more other hydrogen generation assemblies described in this disclosure. The hydrogen generation assembly may provide or supply hydrogen to one or more hydrogen consuming devices  376 , such as a fuel cell, hydrogen furnace, etc. Hydrogen generation assembly  374  may, for example, include a fuel processing assembly  378  and a product hydrogen management system  380 . Fuel processing assembly  378  may include any suitable structure configured to generate one or more product hydrogen streams  382  (such as one or more hydrogen gas streams) from one or more feed streams  384  via one or more suitable mechanisms. 
     Product hydrogen management system  380  may include any suitable structure configured to manage product hydrogen generated by fuel processing assembly  382  and/or interact with fuel processing assembly  382  to maintain any suitable amount of product hydrogen available for hydrogen consuming device(s)  376 . For example, product hydrogen management system  380  may include a product conduit  386 , a buffer tank  388 , a buffer tank conduit  389 , a tank sensor assembly  390 , a product valve assembly  392 , and a control assembly  394 . 
     Product conduit  386  may be configured to fluidly connect fuel processing assembly  378  with buffer tank  388 . The product conduit may include a flow portion or leg  395  and a vent portion or leg  396 . Additionally, product conduit  386  may include any suitable number of valves, such as check valve(s) (such as check valve  397 ), control valve(s), and/or other suitable valve(s). Buffer tank  388  may be configured to receive product hydrogen stream  382  via product conduit  386 , to retain predetermined amount(s) or volume(s) of the product hydrogen stream, and/or to provide the product hydrogen stream to one or more hydrogen consuming devices  376 . 
     Buffer tank conduit  389  may be configured to fluidly connect buffer tank  388  with hydrogen consuming device(s)  376 . The buffer tank conduit may include any suitable number of valves, such as check valve(s), control valve(s), and/or other suitable valve(s). For example, the buffer tank conduit may include one or more control valves  398 . Control valve  398  may allow isolation of the buffer tank and/or other components of the hydrogen generation assembly. The control valve may, for example, be controlled by control assembly  394  and/or other control assembly(ies). 
     Tank sensor assembly  390  may include any suitable structure configured to detect and/or measure one or more suitable operating variables and/or parameters in the buffer tank and/or generate one or more signals based on the detected and/or measured operating variable(s) and/or parameter(s). For example, the tank sensor assembly may detect mass, volume, flow, temperature, electrical current, pressure, refractive index, thermal conductivity, density, viscosity, optical absorbance, electrical conductivity, and/or other suitable variable(s), and/or parameter(s). In some embodiments, the tank sensor assembly may detect one or more triggering events. For example, tank sensor assembly  390  may include one or more tank sensors  400  configured to detect pressure, temperature, flowrate, volume, and/or other parameters. Tank sensors  400  may, for example, be configured to detect pressure in the buffer tank and/or generate one or more signals based on the detected pressure. 
     Product valve assembly  392  may include any suitable structure configured to manage and/or direct flow in product conduit  386 . For example, the product valve assembly may allow the product hydrogen stream to flow from the fuel processing assembly to the buffer tank (as indicated at  401 ), and/or vent product hydrogen stream  382  from fuel processing assembly  378  (as indicated at  403 ). The vented product hydrogen stream may be discharged to atmosphere and/or to a vented product hydrogen management system (not shown). 
     Product valve assembly  392  may, for example, include a first solenoid valve  402  and a second solenoid valve  404 . The first solenoid valve may include a first solenoid  406  and a first valve  408 , while the second solenoid valve may include a second solenoid  410  and a second valve  412 . As shown in  FIGS. 18-19 , the first valve may be configured to move between a plurality of positions, including a first open position  407  and a first closed position  409 . Additionally, the second valve may be configured to move between a plurality of positions, including a second open position  411  and a second closed position  413 . 
     When the first valve is in the open position, the product hydrogen stream is allowed to flow from the fuel processing assembly to the buffer tank. In contrast, when the first valve is in the closed position, buffer tank is isolated from the product hydrogen stream from the fuel processing assembly (or the product hydrogen stream from the fuel processing assembly is not allowed to flow to the buffer tank). When the second valve is in the open position, the product hydrogen stream from the fuel processing assembly is vented. In contrast, when the second valve is in the closed position, the product hydrogen stream from the fuel processing assembly is not vented. 
     First solenoid  406  may be configured to move first valve  408  between the open and closed positions based on input(s) received from control assembly  394 . Additionally, second solenoid  410  may be configured to move second valve  412  between the open and closed position based on input(s) received from the control assembly. 
     Control assembly  394  may include any suitable structure configured to control fuel processing assembly  378  and/or product valve assembly  392  based, at least in part, on input(s) from buffer tank sensor assembly  390 , such as based, at least in part, on detected and/or measured operating variable(s) and/or parameter(s) by the buffer tank sensor assembly. Control assembly  394  may receive input(s) only from buffer tank sensor assembly  390  and/or the control assembly may receive input(s) from other sensor assemblies of the hydrogen generation assembly. Additionally, control assembly  394  may control only the fuel processing assembly, only the product valve assembly, only both the fuel processing assembly and the product valve assembly, or the fuel processing assembly, product valve assembly and/or one or more other components of the hydrogen generation assembly. Control assembly  394  may communicate with the fuel processing assembly, the buffer tank sensor assembly, and/or the product valve assembly via communication linkages  393 . Communication linkages  393  may be any suitable wired and/or wireless mechanism for one- or two-way communication between the corresponding devices, such as input signals, command signals, measured parameters, etc. 
     Control assembly  394  may, for example, be configured to operate fuel processing assembly  378  between the run and standby modes (and/or reduced output mode(s)) based, at least in part, on the detected pressure in buffer tank  388 . For example, control assembly  394  may be configured to operate the fuel processing assembly in the standby mode when the detected pressure in the buffer tank is above a predetermined maximum pressure, to operate the fuel processing assembly in one or more reduced output mode(s) when the detected pressure in the buffer tank is below a predetermined maximum pressure and/or above a predetermined operating pressure, and/or to operate the fuel processing assembly in the run mode when the detected pressure in the buffer tank is below a predetermined operating pressure and/or predetermined minimum pressure. The predetermined maximum and minimum pressures and/or predetermined operating pressure(s) may be any suitable pressures. For example, the one or more of the above pressures may be independently set based on a desired range of pressures for the fuel processing assembly, the product hydrogen in the buffer tank, and/or the pressure requirements of the hydrogen consuming device(s). Alternatively, control assembly  394  may operate the fuel processing assembly to operate in the run mode within a predetermined range of pressure differentials (such as between the fuel processing assembly and the buffer tank and/or between the buffer tank and the hydrogen consuming device(s)), and in the reduced output and/or standby mode(s) when outside the predetermined range of pressure differentials. 
     Additionally, control assembly  394  may be configured to operate the product valve assembly based on, for example, input(s) from sensor assembly. For example, the control assembly may direct or control the first and/or second solenoids to move the first valve in the closed position and/or the second valve in the open position when the fuel processing assembly is in the standby mode. Additionally, control assembly  394  may direct or control the first and/or second solenoids to move the first valve in the open position and/or the second valve in the closed position when fuel processing assembly  378  is in the run mode and/or reduced output mode(s). 
     Control assembly  394  may, for example, include a controller  414 , a switching device  416 , and a power supply  418 . Controller  414  may have any suitable form, such as a computerized device, software executing on a computer, an embedded processor, programmable logic controller, an analog device, and/or functionally equivalent devices. Additionally, the controller may include any suitable software, hardware, and/or firmware. 
     Switching device  416  may include any suitable structure configured to allow controller  414  to control the first and/or second solenoids. For example, the switching device may include a solid-state relay  420 . Power supply  418  may include any suitable structure configured to provide power sufficient to control the first and/or second solenoids. 
     Hydrogen generation assemblies of the present disclosure may include one or more of the following:
         A feed assembly configured to deliver a feed stream to a fuel processing assembly.   A feed tank configured to contain feedstock for a feed stream.   A feed conduit fluidly connecting a feed tank and a fuel processing assembly.   A pump configured to deliver a feed stream at a plurality of flowrates to a fuel processing assembly via a feed conduit.   A feed sensor assembly configured to detect pressure in a feed conduit downstream from a pump.   A feed sensor assembly configured to generate a signal based on detected pressure.   A pump controller configured to select a flowrate from a plurality of flowrates based on detected pressure.   A pump controller configured to operate a pump at a selected flowrate.   A pump controller configured to select a flowrate for a pump based solely on detected pressure.   A pump controller configured to condition a signal received from a sensor assembly.   A pump controller configured to invert a signal received from a feed sensor assembly.   A pump controller configured to select a flowrate based on a conditioned signal.   A pump controller configured to select a flowrate based on an inverted signal.   A fuel processing assembly configured to receive a feed stream.   A fuel processing assembly configured to produce a product hydrogen stream from a feed stream.   A fuel processing assembly configured to be operable among a plurality of modes.   A fuel processing assembly configured to be operable among a run mode in which the fuel processing assembly produces a product hydrogen stream from a feed stream, and a standby mode in which the fuel processing assembly does not produce the product hydrogen stream from the feed stream.   A purge assembly.   A pressurized gas assembly configured to receive at least one container of pressurized gas that is configured to purge a fuel processing assembly.   A purge conduit configured to fluidly connect a pressurized gas assembly and a fuel processing assembly.   A purge valve assembly configured to allow at least one pressurized gas to flow through a purge conduit from a pressurized gas assembly to a hydrogen generation assembly when power to the hydrogen generation assembly is interrupted.   A solenoid valve that moves between a closed position in which at least one pressurized gas does not flow through a purge conduit from a pressurized gas assembly, and an open position in which the at least one pressurized gas is allowed to flow through the purge conduit from the pressurized gas assembly.   A solenoid valve that is in the closed position when there is power to a fuel processing assembly.   A solenoid valve that automatically moves to an open position when power to a fuel processing assembly is interrupted.   A solenoid valve configured to move to a closed position when the solenoid valve receives a control signal.   A solenoid valve configured to automatically move to an open position when the solenoid valve does not receive a control signal.   A control system configured to send a control signal to a solenoid valve.   An enclosure containing at least a portion of a fuel processing assembly and at least a portion of a purge assembly.   An enclosure having an exhaust port.   A hydrogen-producing region contained within an enclosure.   A hydrogen-producing region configured to produce, via a steam reforming reaction, a reformate stream from at least one feed stream.   A purification region contained within an enclosure.   A purification region including a hydrogen-selective membrane.   A purification region configured to produce a permeate stream comprised of the portion of a reformate stream that passes through a hydrogen-selective membrane, and a byproduct stream comprised of the portion of the reformate stream that does not pass through the membrane.   A reformer sensor assembly configured to detect temperature within a hydrogen-producing region.   A reformer sensor assembly configured to detect temperature in the purification region.   A heating assembly configured to receive at least one air stream and at least one fuel stream.   A heating assembly configured to combust at least one fuel stream within a combustion region contained within an enclosure producing a heated exhaust stream for heating at least a hydrogen-producing region to at least a minimum hydrogen-producing temperature.   A damper moveably connected to an exhaust port.   A damper configured to move among a plurality of positions.   A damper configured to move among a fully open position in which the damper allows a heated exhaust stream to flow through an exhaust port, a closed position in which the damper prevents the heated exhaust stream from flowing through the exhaust port, and a plurality of intermediate open positions between the fully open and closed positions.   A damper controller configured to move a damper between fully open and closed positions based, at least in part, on a detected temperature in a hydrogen-producing region.   A damper controller configured to move a damper between fully open and closed positions based, at least in part, on a detected temperature in at least one of a hydrogen-producing region and a purification region.   A damper controller configured to move a damper toward a closed position when a detected temperature is above a predetermined maximum temperature.   A damper controller configured to move a damper toward an open position when a detected temperature is below a predetermined minimum temperature.   A buffer tank configured to contain a product hydrogen stream.   A product conduit fluidly connecting a fuel processing assembly and a buffer tank.   A tank sensor assembly configured to detect pressure in a buffer tank.   A product valve assembly configured to manage flow in a product conduit.   At least one valve that is configured to operate between a flow position in which a product hydrogen stream from a fuel processing assembly flows through a product conduit and into a buffer tank, and a vent position in which the product hydrogen stream from the fuel processing assembly is vented prior to the buffer tank.   A three-way solenoid valve.   A first valve configured to control flow of a product hydrogen stream between a fuel processing assembly and a buffer tank.   A first valve configured to move between a first open position in which a product hydrogen stream flows between a fuel processing assembly and a buffer tank, and a first closed position in which the product hydrogen stream does not flow between the fuel processing assembly and the buffer tank.   A second valve configured to vent a product hydrogen stream from a fuel processing assembly.   A second valve configured to move between a second open position in which a product hydrogen stream is vented, and a second closed position in which the product hydrogen stream is not vented.   A control assembly configured to operate a fuel processing assembly between run and standby modes based, at least in part, on detected pressure.   A control assembly configured to operate a fuel processing assembly in a standby mode when detected pressure in a buffer tank is above a predetermined maximum pressure.   A control assembly configured to operate a fuel processing assembly in a run mode when detected pressure in a buffer tank is below a predetermined minimum pressure.   A control assembly configured to direct a product valve assembly to vent a product hydrogen stream from a fuel processing assembly when the fuel processing assembly is in the standby mode.   A control assembly configured to move at least one valve to a flow position when a fuel processing assembly is in a run mode.   A control assembly configured to move at least one valve to a vent position when a fuel processing assembly is in a standby mode.   A control assembly configured to move a first valve to a first open position and a second valve to a second closed position when a fuel processing assembly is in a run mode.   A control assembly configured to move a first valve to a first closed position and a second valve to a second open position when a fuel processing assembly is in a standby mode.       

     INDUSTRIAL APPLICABILITY 
     The present disclosure, including hydrogen generation assemblies, hydrogen purification devices, and components of those assemblies and devices, is applicable to the fuel-processing and other industries in which hydrogen gas is purified, produced, and/or utilized. 
     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 any claim recites “a” or “a first” element or the equivalent thereof, such claim should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. 
     Inventions embodied in various combinations and subcombinations of features, functions, elements, and/or properties may be claimed through presentation of new claims in a related application. Such 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.