Hydrogen Generation Assembly

Abstract

A hydrogen generation assembly and method are disclosed. In one embodiment, the method includes receiving a feed stream at a fuel processing assembly and heating a hydrogen-producing region of the fuel processing assembly to at least a minimum hydrogen-producing temperature via one or more burners. The method additionally includes generating an output stream in the heated hydrogen-producing region of the fuel processing assembly from the received feed stream and generating a product hydrogen stream and a by-product stream from the output stream in a purification region of the fuel processing assembly. The method further includes separating at least a portion of the carbon dioxide gas from the by-product stream to generate a fuel stream having a lower carbon dioxide concentration than the by-product stream and supplying the fuel stream to the one or more burners.

Description

[Background technology]

[0001] A hydrogen generation assembly is an assembly that converts one or more feedstocks into a product stream containing hydrogen gas as a primary component. The feedstock may include a carbon-containing feedstock and, in some embodiments, may also include water. The feedstock is delivered to the hydrogen-producing region of the hydrogen generation assembly from a feedstock delivery system, typically under pressure and at an elevated temperature. The hydrogen-producing region is often associated with a temperature regulation assembly, such as a heating or cooling assembly, that consumes one or more fuel streams to maintain the hydrogen-producing region within an appropriate temperature range for effective production of hydrogen gas. The hydrogen generation assembly may generate hydrogen gas via any suitable mechanism, such as steam reforming, autothermal reforming, pyrolysis, and / or catalytic partial oxidation.

[0002] However, the generated or produced hydrogen gas may contain impurities. The gas may be referred to as a mixed gas stream containing hydrogen gas and other gases. Before the mixed gas stream can be used, it must be purified, such as by removing at least a portion of the other gases. Therefore, a hydrogen generation assembly may 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 for separating the mixed gas stream into a product stream and a by-product stream. The product stream contains a higher concentration of hydrogen gas and / or reduced concentrations of one or more 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 within a pressure vessel. The mixed gas stream contacts the mixed gas surface of the membrane, and a product stream is formed from at least a portion of the mixed gas stream that permeates the membrane. The pressure vessel is typically sealed to prevent gas from entering or exiting the pressure vessel except through defined inlet and outlet ports or conduits.

[0003] The product stream can be used in a variety of applications. One such application is energy production, such as in electrochemical fuel cells. Electrochemical fuel cells are devices that convert fuel and oxidant into electricity, reaction products, and heat. For example, fuel cells can convert hydrogen and oxygen into water and electricity. In these fuel cells, hydrogen is the fuel, oxygen is the oxidant, and water is the reaction product. Fuel cell stacks include multiple fuel cells and can be utilized with a hydrogen generation assembly to provide an energy production assembly.

[0004] Examples of hydrogen generation assemblies, hydrogen processing assemblies, and / or components of those assemblies are described in U.S. Patent Nos. 5,627,592; 5,727,597 ... [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 5,861,137 [Patent Document 2] U.S. Patent No. 6,319,306 [Patent Document 3] U.S. Patent No. 6,494,937 [Patent Document 4] U.S. Patent No. 6,562,111 [Patent Document 5] U.S. Patent No. 7,063,047 [Patent Document 6] U.S. Patent No. 7,306,868 [Patent Document 7] U.S. Patent No. 7,470,293 [Patent Document 8] U.S. Patent No. 7,601,302 [Patent Document 9] U.S. Patent No. 7,632,322 [Patent Document 10] U.S. Patent No. 8,961,627 [Patent Document 11] U.S. Patent No. 9,187,324 [Patent Document 12] U.S. Patent No. 9,914,641 [Patent Document 13] U.S. Patent No. 10,717,040 [Patent Document 14] US Patent Application Publication No. 2006 / 0090397 [Patent Document 15] US Patent Application Publication No. 2006 / 0272212 [Patent Document 16] US Patent Application Publication No. 2007 / 0266631 [Patent Document 17] US Patent Application Publication No. 2007 / 0274904 [Patent Document 18] US Patent Application Publication No. 2008 / 0085434 [Patent Document 19] US Patent Application Publication No. 2008 / 0138678 [Patent Document 20] US Patent Application Publication No. 2008 / 0230039 [Patent Document 21] US Patent Application Publication No. 2010 / 0064887 [Patent Document 22] U.S. Patent No. 5,997,594 [Patent Document 23] U.S. Patent No. 6,221,117 [Patent Document 24] U.S. Patent No. 9,605,224 Summary of the Invention [Means for solving the problem]

[0006] Some embodiments include a method for producing hydrogen. In one embodiment, the method includes receiving a feed stream at a fuel processing assembly. The feed stream includes a carbon-containing feedstock. The method additionally includes heating a hydrogen-producing region of the fuel processing assembly to at least a minimum hydrogen-producing temperature via one or more burners. The method further includes generating an output stream within the heated hydrogen-producing region of the fuel processing assembly from the received feed stream. The output stream includes hydrogen gas and carbon dioxide gas.

[0007] The method additionally includes producing a product hydrogen stream and a by-product stream from the output stream in a purification region of the fuel processing assembly. The product hydrogen stream has a higher hydrogen concentration than the output stream and a lower carbon dioxide concentration than the output stream, and the by-product stream has a lower hydrogen concentration than the output stream and a higher carbon dioxide concentration than the output stream. The method further includes separating at least a portion of the carbon dioxide gas from the by-product stream to produce a fuel stream having a lower carbon dioxide concentration than the by-product stream. The method additionally includes supplying the fuel stream to one or more burners.

[0008] Some embodiments include a hydrogen generation assembly. In one embodiment, the assembly includes an enclosure and a hydrogen-production region housed within the enclosure. The hydrogen-production region is configured to produce an output stream from at least one feed stream. The output stream includes hydrogen gas and carbon dioxide gas, and the at least one feed stream includes a carbon-containing feedstock. The assembly additionally includes a heating assembly configured to receive at least one air stream and at least one fuel stream, combust the at least one fuel stream in a combustion region housed within the enclosure, and produce a heated exhaust stream for heating the hydrogen-production region to at least a minimum hydrogen-production temperature.

[0009] The assembly further includes a purification region housed within the enclosure. The purification region is configured to produce a product hydrogen stream and a by-product stream, the product hydrogen stream having a higher hydrogen concentration and a lower carbon dioxide concentration than the output stream, and the by-product stream having a lower hydrogen concentration and a higher carbon dioxide concentration than the output stream. The assembly additionally includes a gas removal assembly configured to separate at least a portion of the carbon dioxide gas from the by-product stream and produce at least a portion of the at least one fuel stream therefrom. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of an example hydrogen generation assembly. [Figure 2] FIG. 2 is a schematic diagram of an example of the hydrogen generation assembly of FIG. 1. [Figure 3] 3 is a schematic diagram of an example gas removal assembly of the hydrogen generation assembly of FIG. 2. [Figure 4] FIG. 4 is a schematic diagram of an example of the gas removal assembly of FIG. 3. [Figure 5] 4 is a schematic diagram of another example of the gas removal assembly of FIG. 3. [Figure 6] 4 is a schematic diagram of an additional example of the gas removal assembly of FIG. 3. [Figure 7] FIG. 4 is an additional further schematic view of the gas removal assembly of FIG. 3. [Figure 8] FIG. 4 is an additional further schematic view of the gas removal assembly of FIG. 3. [Figure 9] FIG. 9 is a schematic diagram of an example membrane contactor of the gas removal assembly of FIG. 8. [Figure 10] FIG. 10 is a schematic diagram of an example of a membrane of the membrane contactor of FIG. [Figure 11] FIG. 10 is a schematic diagram of another example of a membrane for the membrane contactor of FIG. 9. [Figure 12] 4 is a schematic diagram of an additional example of the gas removal assembly of FIG. 3. [Figure 13] 1 is a flow chart of an example method for producing hydrogen. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1 illustrates an example of a hydrogen generation assembly 20. Unless specifically excluded, the hydrogen generation assembly 20 may include one or more components of the 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.

[0012] In some embodiments, feedstock delivery system 22 may further 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 portions of the fuel processing assembly. The feedstock delivery system may include any suitable delivery mechanism, such as a positive displacement or other suitable pump or mechanism for propelling fluid flow. In some embodiments, the feedstock delivery system may be configured to deliver feed stream 26 and / or fuel stream 28 without requiring the use of a pump and / or other powered fluid delivery mechanism. Examples of suitable feedstock delivery systems that may be used with hydrogen generation assembly 20 include the feedstock delivery systems described in U.S. Patent Nos. 5,629,999; 5,729,999; and 5,729,999. The complete disclosures of the above-referenced patents and patent applications are incorporated herein by reference for all purposes.

[0013] Feed stream 26 may include at least one hydrogen-production fluid 30, which may include one or more fluids that can be utilized as reactants to generate product hydrogen stream 21. For example, the hydrogen-production fluid may include at least one carbon-containing feedstock, such as a 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 the fuel processing assembly 24 generates the product hydrogen stream via steam reforming and / or autothermal reforming. When the fuel processing assembly 24 generates the product hydrogen stream via pyrolysis or catalytic partial oxidation, feed stream 26 does not include water.

[0014] In some embodiments, the feedstock delivery system 22 can be configured to deliver a hydrogen-production fluid 30 comprising a mixture of water and a water-miscible carbon-containing feedstock (such as methanol and / or another water-soluble alcohol). The ratio of water to carbon-containing feedstock in such a fluid stream can vary according to one or more factors, such as the particular carbon-containing feedstock used, user preference, the design of the fuel processing assembly, the mechanism used by the fuel processing assembly to generate the product hydrogen stream, etc. For example, the water-to-carbon molar ratio can be about 1:1 to 3:1. Additionally, a mixture of water and methanol can be delivered at or near a 1:1 molar ratio (37% water, 63% methanol by weight), and a mixture of hydrocarbons or other alcohols can be delivered at a water-to-carbon molar ratio greater than 1:1.

[0015] When fuel processing assembly 24 generates product hydrogen stream 21 via reforming, feed stream 26 may contain, for example, about 25% to 75% by volume of methanol or ethanol (or another suitable water-miscible carbon-containing feedstock) and about 25% to 75% by volume of water. For feed streams at least substantially containing methanol and water, they may contain about 50% to 75% by volume of methanol and about 25% to 50% by volume of water. Streams containing ethanol or other water-miscible alcohols may contain about 25% to 60% by volume of alcohol and about 40% to 75% by volume of water. An example feed stream for hydrogen generation assembly 20 utilizing steam reforming or autothermal reforming contains 69% by volume of methanol and 31% by volume of water.

[0016] Although the feedstock delivery system 22 is shown configured to deliver a single feed stream 26, the feedstock delivery system may be configured to deliver two or more feed streams 26. The feed streams may contain the same or different feedstocks, have different compositions, have at least one common component, no common components, or the same composition. For example, a first feed stream may contain a first component, such as a carbon-containing feedstock, and a second feed stream may contain a second component, such as water. Additionally, while the feedstock delivery system 22 may be configured to deliver a single fuel stream 28 in some embodiments, the feedstock delivery system may be configured to deliver two or more fuel streams. The fuel streams may have different compositions, have at least one common component, no common components, or the same composition. Furthermore, the feed stream and the fuel stream may exit the feedstock delivery system at different stages. For example, one of the feed stream and the fuel stream may be a liquid stream, and the other is a gas stream. In some embodiments, both the feed stream and the fuel stream can be liquid streams, while in other embodiments, both the feed stream and the fuel stream can be gas streams. Additionally, although hydrogen generation assembly 20 is shown as including a single feedstock delivery system 22, the hydrogen generation assembly can include two or more feedstock delivery systems 22.

[0017] Fuel processing assembly 24 may include a hydrogen-producing region 32 configured to produce an output stream 34 comprising hydrogen gas via any suitable hydrogen-producing mechanism. The output stream may include hydrogen gas as at least a major component and may include additional gaseous components. Thus, output stream 34 may be referred to as a "mixed gas stream" that includes hydrogen gas as its major component but also includes other gases.

[0018] Hydrogen-producing region 32 may include any suitable catalyst-containing bed or region. When the hydrogen production mechanism is steam reforming, hydrogen-producing region 32 may include a suitable steam reforming catalyst 36 to facilitate production of output stream 34 from feed stream 26 comprising the carbon-containing feedstock and water. In such embodiments, 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 "reformed stream." Other gases that may be present in the reformed stream may include carbon monoxide, carbon dioxide, methane, steam, and / or unreacted carbon-containing feedstock.

[0019] When the hydrogen production mechanism is autothermal reforming, hydrogen-producing region 32 may include a suitable autothermal reforming catalyst to promote production of output stream 34 from feed stream 26 comprising water and carbon-containing feedstock in the presence of air. Additionally, fuel processing assembly 24 may include an air delivery assembly 38 configured to deliver an air stream to the hydrogen-producing region.

[0020] 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 contain a higher hydrogen concentration than output stream 34 and / or a reduced concentration of one or more other gases (or impurities) that were present in the 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 may have the same composition and flow rate. Alternatively, a portion 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 may also be referred to as a “hydrogen purification device” or a “hydrogen processing assembly.”

[0021] In some embodiments, purification region 40 may produce at least one by-product stream 44, which may contain no hydrogen gas or may contain some hydrogen gas. The by-product stream may be discharged, 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 of. Additionally, purification region 40 may emit the by-product stream as a continuous stream in response to delivery of output stream 34, or may emit the stream intermittently, such as in a batch process or when a by-product portion of the output stream is at least temporarily retained in the purification region.

[0022] Fuel processing assembly 24 may include one or more purification regions configured to produce one or more by-product streams containing a sufficient amount of hydrogen gas suitable for use as a fuel stream (or feed stream) for a heating assembly for the fuel processing assembly. In some embodiments, the by-product streams may have a fuel value or hydrogen content sufficient to enable the heating assembly to maintain the hydrogen-producing region at a desired operating temperature or within a selected temperature range. For example, the by-product streams may contain hydrogen gas at 10% to 30% by volume, 15% to 25% by volume, 20% to 30% by volume, at least 10% or 15% by volume, at least 20% by volume, etc.

[0023] Purification region 40 may include any suitable structure configured to concentrate (and / or increase) the concentration of at least one component of output stream 21. In most applications, hydrogen-rich stream 42 will have a higher hydrogen concentration than output stream (or mixed gas stream) 34. The hydrogen-rich stream may also include reduced concentrations of one or more non-hydrogen components that were present in output stream 34 when the hydrogen-rich stream had a higher, the same, or lower hydrogen concentration than the output stream. For example, in conventional fuel cell systems, the presence of even a few ppm of carbon monoxide can damage the fuel cell stack, while other non-hydrogen components present in output stream 34, such as water, can be present in much higher concentrations without damaging the stack. Thus, in such applications, 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 use of the product hydrogen stream.

[0024] Examples of devices suitable for purification region 40 include one or more hydrogen-selective membranes 46, a chemical carbon monoxide removal assembly 48, and / or a pressure swing adsorption (PSA) system 50. Purification region 40 may include two or more types of purification devices, and the devices may have the same or different structures and / or operate by the same or different mechanisms. Fuel processing assembly 24 may include at least one restrictive orifice and / or other flow restrictor downstream of the purification region, such as associated with one or more product hydrogen streams, a hydrogen-rich stream, and / or a by-product stream.

[0025] The hydrogen-selective membrane 46 is permeable to hydrogen gas but at least substantially (if not completely) impermeable to other components of the output stream 34. The membrane 46 may be formed from any hydrogen-permeable material suitable for use in the operating environment and parameters in which the purification region 40 will be operated. Examples of suitable materials for the membrane 46 include palladium and palladium alloys, particularly thin films of such metals and metal alloys. Palladium alloys, particularly palladium containing 35% to 45% copper by weight, have proven particularly effective. A palladium-copper alloy containing approximately 40% copper by weight has proven particularly effective, although other relative concentrations and compositions may be used. Three other particularly effective alloys are palladium with 2 to 20% gold by weight, specifically 5% gold by weight; palladium with 3 to 10% indium and 0 to 10% ruthenium by weight, specifically 6% indium and 0.5% ruthenium by weight; and palladium with 20 to 30% silver by weight. When palladium and palladium alloys are used, the hydrogen-selective membrane 46 is sometimes referred to as a "foil." Typical thicknesses of hydrogen-permeable metal foils are less than 25 microns (micrometers), preferably 15 microns or less, and most preferably between 5 and 12 microns. The foil can be any suitable size, such as 110 mm by 270 mm.

[0026] The chemical carbon monoxide removal assembly 48 is a device that chemically reacts carbon monoxide and / or other undesirable components of the output stream 34 to form other, less potentially harmful compositions. Examples of chemical carbon monoxide removal assemblies include a water-gas shift reactor configured to produce hydrogen gas and carbon dioxide from water and carbon monoxide, a partial oxidation reactor configured to convert carbon monoxide and oxygen (typically from air) to carbon dioxide, and a methanation reactor configured to convert carbon monoxide and hydrogen to methane and water. The fuel processing assembly 24 may include more than one type and / or number of chemical removal assemblies 48.

[0027] Pressure swing adsorption (PSA) is a chemical process in which gaseous impurities are removed from the output stream 34 based on the principle that, under appropriate conditions of temperature and pressure, certain gases are more strongly adsorbed onto an adsorbent material than others. Typically, non-hydrogen impurities are adsorbed and removed from the output stream 34. Adsorption of impurity gases occurs at high pressure. As the pressure is reduced, the impurities desorb from the adsorbent material, thus regenerating the adsorbent material. Typically, PSA is a cyclic process, requiring at least two beds for continuous (as opposed to batch) operation. Examples of suitable adsorbent materials that can be used in the adsorption beds are activated carbon and zeolites. PSA system 50 also provides an example of a device for use in the purification region 40 in which by-products or removed components are not directly discharged from the region as a gas stream upon purification of the output stream. Instead, these by-product components are removed when the adsorbent material is regenerated or otherwise removed from the purification region.

[0028] In Figure 1, a purification region 40 is shown within the fuel processing assembly 24. Alternatively, the purification region may be located separately downstream from the fuel processing assembly, as shown schematically in dashed lines in Figure 1. The purification region 40 may also include internal and external portions of the fuel processing assembly.

[0029] Fuel processing assembly 24 may also include a temperature regulation assembly in the form of a heating assembly 52. ​​The heating assembly may be configured to generate at least one heated exhaust stream (or combustion stream) 54 from at least one fuel stream 28, typically combusted in the presence of air. Heated exhaust stream 54 is shown schematically in FIG. 1 as heating hydrogen-producing region 32. Heating assembly 52 may include any suitable structure configured to generate a heated exhaust stream, such as a burner or combustion catalyst in which fuel is combusted with air to generate the heated exhaust stream. The heating assembly may include an igniter or ignition source 58 configured to initiate combustion of the fuel. Examples of suitable ignition sources include one or more spark plugs, glow plugs, combustion catalysts, pilot lights, piezoelectric igniters, spark igniters, hot surface igniters, etc.

[0030] In some embodiments, the 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, the heating assembly 52 may be configured to receive at least one fuel stream 28 and combust the fuel stream in the presence of air to provide a high-temperature combustion stream 54 that may be used to heat at least the hydrogen-producing region of the fuel processing assembly. The air may be delivered to the heating assembly via various 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, the air stream 62 may be delivered to the heating assembly along with at least one of the fuel streams 28 for the heating assembly 52 and / or may be drawn from the environment in which the heating assembly is utilized.

[0031] Combustion stream 54 may additionally or alternatively be used to heat other portions of the fuel processing assembly and / or fuel cell system in which the heating assembly is used. Additionally, other configurations and types of heating assembly 52 may be used. For example, heating assembly 52 may be an electrically powered heating assembly 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. An example of a heating assembly is disclosed in U.S. Patent No. 6,229,999, the complete disclosure of which is incorporated herein by reference for all purposes.

[0032] Heating assembly 52 may be housed within a common shell or housing with the hydrogen-producing region and / or the separation region (discussed further below). The heating assembly may be located separately from 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 outside of the shell. If the heating assembly is located outside of the shell, hot combustion gases from burner assembly 60 may be transported to one or more components within the shell via appropriate heat transfer conduits.

[0033] The heating assembly may also be configured to heat feedstock delivery system 22, the feedstock feed stream, hydrogen-producing region 32, purification (or separation) region 40, or any suitable combination of these systems, streams, and regions. Heating the feedstock feed stream may include vaporizing a liquid reactant stream 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 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 heated fuel and / or hydrogen-production fluid that forms at least a portion of feed stream 26 and fuel stream 28.

[0034] Heating assembly 52 may achieve and / or maintain any suitable temperature in hydrogen-producing region 32. Steam reformers typically operate at temperatures ranging from 200°C to 900°C. However, temperatures outside this range are within the scope of the present disclosure. When the carbon-containing feedstock is methanol, the steam reforming reaction typically operates in a temperature range of approximately 200°C to 500°C. Exemplary subsets of that range include 350°C to 450°C, 375°C to 425°C, and 375°C to 400°C. When the carbon-containing feedstock is a hydrocarbon, ethanol, or another alcohol, a temperature range of approximately 400°C to 900°C is typically used for the steam reforming reaction. Exemplary subsets of that range include 750°C to 850°C, 725°C to 825°C, 650°C to 750°C, 700°C to 800°C, 700°C to 900°C, 500°C to 800°C, 400°C to 600°C, and 600°C to 800°C. Hydrogen-producing region 32 may include two or more zones or sections, each of which may be operated at the same or different temperatures. For example, if the hydrogen-production fluid includes hydrocarbons, hydrogen-producing region 32 may include two different hydrogen-producing sections or regions, one operating at a lower temperature than the other to provide a pre-reforming region. In these embodiments, the fuel processing assembly may be referred to as including two or more hydrogen-producing regions.

[0035] Fuel stream 28 may include any combustible liquid and / or gas suitable for consumption 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 other fuel streams may be delivered to the heating assembly as a liquid stream. Examples of suitable heating fuels for fuel stream 28 include carbon-containing feedstocks such as methanol, methane, ethane, ethanol, ethylene, propane, propylene, butane, and the like. Additional examples include low molecular weight condensable fuels such as liquefied petroleum gas, ammonia, light amines, dimethyl ether, and low molecular weight hydrocarbons. Still other examples include hydrogen and carbon monoxide. In embodiments of the hydrogen generation assembly 20 that include a temperature regulation assembly in the form of a cooling assembly instead of a heating assembly (such as may be used when an exothermic hydrogen production 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 the fuel or coolant stream to the assembly. Any suitable fuel or coolant may be used.

[0036] Fuel processing assembly 24 may additionally include a shell or housing 66 in which at least hydrogen-producing region 32 is housed, as shown in FIG. 1 . In some embodiments, vaporization region 64 and / or purification region 40 may additionally be housed within the shell. Shell 66 may allow components of a steam reformer or other fuel processing mechanism to be moved as a unit. The shell may also protect the fuel processing assembly components from damage by providing a protective enclosure and / or reduce the heating demands of the fuel processing assembly because the components are heated as a unit. Shell 66 may include insulating material 68, such as solid insulating material, blanket insulating material, and / or air-filled cavities. The insulating material may be internal to the shell, external to the shell, or both. If the insulating material is external to the shell, fuel processing assembly 24 may further include an outer cover or jacket 70 outside the insulating material, as shown schematically in FIG. 1 . The fuel processing assembly may include a different shell containing additional components of the fuel processing assembly, such as feedstock delivery system 22 and / or other components.

[0037] One or more components of fuel processing assembly 24 may extend beyond the shell or may be located external to the shell. For example, purification region 40 may be located external to shell 66, such as spaced apart from the shell but in fluid communication with it via an appropriate fluid communication conduit. As another example, a portion of hydrogen-producing region 32 (such as a portion of one or more reforming catalyst beds) may extend beyond the shell, as shown schematically by the dashed lines representing an alternative shell configuration in FIG. 1. Examples of suitable hydrogen generation assemblies and their components are disclosed in U.S. Patent Nos. 5,629,999, 5,729,979, 5,729,989, 5,729,999, and 5,729,989, the complete disclosures of which are incorporated herein by reference for all purposes.

[0038] Another example of hydrogen generation assembly 20 is shown in FIG. 2 and is generally designated 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, a heating assembly 80, and a purification region 82, as shown in FIG.

[0039] The feedstock delivery system may include any suitable structure configured to deliver one or more feed streams and / or fuel streams to one or more other components of the hydrogen generation assembly. For example, the 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 / or a carbon-containing feedstock (e.g., a methanol / water mixture). The 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 including water and a carbon-containing feedstock, to the vaporization region 76 and / or the hydrogen-production region 78. In some embodiments, the feedstock delivery system may be configured to deliver the feed stream 90 without requiring the use of a pump and / or other powered fluid delivery mechanism.

[0040] 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 convert liquid-containing feed stream 90 into one or more vapor feed streams. The vapor feed stream may, in some embodiments, include a liquid. One example of a suitable vaporizer is a coiled tubing vaporizer, such as a coiled stainless steel tubing.

[0041] The hydrogen-producing region 78 may include any suitable structure configured to receive one or more feed streams, such as a steam feed stream from a vaporization region, to produce one or more output streams 96 comprising hydrogen gas as a primary component and other gases, such as carbon dioxide. The hydrogen-producing region may produce the output stream(s) via any suitable mechanism. For example, the hydrogen-producing region 78 may produce the output stream 96 via a steam reforming reaction, an autothermal reforming reaction, or a partial oxidation reaction. If the output stream 96 is produced via a steam reforming reaction, the hydrogen-producing region 78 may include a steam reforming region 97 having a reforming catalyst 98 configured to facilitate and / or promote the steam reforming reaction. If the hydrogen-producing region 78 produces the output stream 96 via a steam reforming reaction, the hydrogen generation assembly 72 may be referred to as a “steam reforming hydrogen generation assembly,” and the output stream 96 may be referred to as a “reformed stream.”

[0042] Heating assembly 80 may include any suitable structure configured to generate at least one heated exhaust stream 99 for heating one or more other components of hydrogen generation assembly 72. For example, the heating assembly may heat the vaporization region to any suitable temperature, such as at least a minimum vaporization temperature or a temperature at which at least a portion of the liquid-containing feed stream is vaporized to form a vapor feed stream. Additionally or alternatively, heating assembly 80 may heat the hydrogen-production region to any suitable temperature, such as at least a minimum hydrogen-production temperature or a temperature at which at least a portion of the vapor feed stream is reacted to produce hydrogen gas to form an 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 the hydrogen-production region.

[0043] The heating assembly may include a burner assembly 100 and at least one blower 102, 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 107 and combust the at least one fuel stream in a combustion region 110 to generate a heated exhaust stream 99. The fuel streams may be provided by feedstock delivery system 74 and / or purification region 82, as discussed further below. The combustion region may be housed within an enclosure of the hydrogen generation assembly. The blower 102 may include any suitable structure configured to generate the air stream 106. In some embodiments, the heating assembly may include an igniter assembly (not shown) configured to ignite the fuel stream 107.

[0044] Purification region 82 may include any suitable structure configured to produce at least one hydrogen-rich or product hydrogen stream 112, which may contain a higher hydrogen concentration than output stream 96 and / or reduced concentrations of one or more other gases or impurities, such as carbon dioxide, that were present in the output stream. The purification region may produce at least one by-product stream 108, which contains a lower hydrogen concentration than output stream 96 and / or increased concentrations of one or more other gases or impurities. Purification region 82 may include a membrane assembly 114. In some embodiments, purification region 82 may also include a methanation reactor assembly, such as downstream of the membrane assembly, to convert carbon monoxide and hydrogen into methane and water.

[0045] The membrane assembly 114 may include any suitable structure configured to receive the output or mixed gas stream 96, which includes hydrogen gas and other gases, and produce a permeate or hydrogen-rich stream 112, which includes a higher concentration of hydrogen gas than the mixed gas stream and / or a lower concentration of the other gas than the mixed gas stream. The membrane assembly 114 may incorporate planar or tubular hydrogen-permeable (or hydrogen-selective) membranes, and two or more hydrogen-permeable membranes may be incorporated into the membrane assembly 114. The permeate stream may be used for any suitable application, such as one or more fuel cells. In some embodiments, the membrane assembly may produce at least one by-product stream 108, which includes at least a substantial portion of other gases, such as carbon dioxide gas. While the purification region 82 is shown to include the membrane assembly 114, the purification region may alternatively or additionally include one or more other components configured to purify the output stream 96 and / or produce one or more product hydrogen streams and / or one or more by-product streams.

[0046] In some embodiments, hydrogen generation assembly 72 may include a shell or housing 120 that may at least partially contain one or more other components of the assembly. For example, shell 120 may at least partially house 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 exhaust at least one combustion exhaust stream 124 generated by heating assembly 80.

[0047] In some embodiments, hydrogen generation assembly 72 may include a gas removal assembly 126 configured to separate at least a portion of the carbon dioxide gas from byproduct stream 108 to produce a fuel stream 128 having a lower concentration of carbon dioxide gas than the byproduct stream and an off-gas stream 129 having a higher concentration of carbon dioxide gas than the byproduct stream. The off-gas stream may be compressed and / or liquefied, stored as a compressed gas, discharged to a pipeline, chemically converted to other compounds, etc. Fuel stream 128 may form all or a portion of fuel stream 107 used or combusted by burner assembly 100. A fuel restriction orifice 130 may restrict the flow of fuel stream 128 to burner assembly 100. Gas removal assembly 126 may include any suitable components, as discussed further below.

[0048] 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. For example, heat exchange assembly 136 may transfer heat from by-product stream 108 to feed stream 90 to increase the temperature of the feed stream before it enters vaporization region 76 and to cool by-product stream 108.

[0049] An example of a gas removal assembly 126 is shown in FIG. 3 and is generally designated 184. Unless specifically excluded, gas removal assembly 184 may include one or more components of other gas removal assemblies described in this disclosure. Gas removal assembly 184 may include at least one gas isolation assembly 186.

[0050] Gas separation assembly 186 may include any suitable structure configured to separate carbon dioxide gas from by-product stream 108 to produce fuel stream 128 having a reduced concentration of carbon dioxide gas and / or elevated concentrations of other gases compared to by-product stream 108. For example, gas separation assembly 186 may include at least one absorber 194 configured to receive at least one chemical or absorbent 196 adapted to absorb at least a portion of the carbon dioxide gas from by-product stream 108 via reversible chemical bonding and / or physical dissolution.

[0051] The absorber is configured to receive an absorbent 196 and direct the flow of by-product stream 108 through the absorbent to absorb carbon dioxide gas from by-product stream 108. As used herein, "absorb" means that carbon dioxide gas is bound to or fixed by the absorbent through reversible or irreversible processes involving weak chemical bonding and / or solvation, and the bound carbon dioxide gas may include surface interactions with the absorbent, bulk interactions with the absorbent, or both. The absorbent 196 may be in fluid form, solid form, or a combination thereof. Suitable examples of absorbents for carbon dioxide include metal hydroxides (e.g., sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, etc.), metal oxides (e.g., sodium oxide, potassium oxide, calcium oxide, magnesium oxide, iron oxide, etc.), organic amines, particularly alkanolamines (e.g., monoethanolamine and diethanolamine, both of which are liquids under normal temperature and pressure), UCARSOL® formulated solvent for acid gas removal (manufactured and sold by Dow Chemical Company), aqueous solutions of metal hydroxides, Ascarite® (Thomas Scientific), CarboLime™ (Allied Health Products Inc.), SodaLime (Airgas Corp.), immobilized organic amines (such as organic amines bound to polymeric substrates, especially polymeric beads), dimethyl polyethylene glycol, propylene carbonate, polyethylene glycol dialkyl ethers (e.g., Genosorb® 1753 sold by Clariant), organic ionic liquids, mixtures of the above chemicals and / or chemical agents, as well as other agents or mixtures of agents that reversibly absorb carbon dioxide by weak chemical interactions and / or physical dissolution.

[0052] The fuel stream 128 exiting the absorber 194 may contain a reduced concentration of carbon dioxide gas and / or an elevated concentration of other gases compared to the by-product stream 108. Preferably, the fuel stream contains less than 25% carbon dioxide, with less than 10% carbon dioxide being particularly preferred. The absorber 194 may be operated at pressures above 50 psig, preferably between 100 and 500 psig.

[0053] If the absorbent 196 is in solid form, the absorber 194 may include two or more absorbent beds 197 and may be configured to direct the flow of the by-product stream 108 to a first of those absorbent beds. When that bed becomes nearly saturated with carbon dioxide, the absorber may be configured to direct the flow to another of the absorbent beds to allow the absorbent of the previous absorbent bed to be recharged and / or regenerated. If the absorbent 196 is in fluid form, the absorbent may be configured to absorb or bind carbon dioxide gas at a relatively low temperature and then release or desorb the gas at a higher temperature. This process is known as temperature swing absorption, or TSA. Alternatively, a carbon dioxide absorbent may be selected that binds carbon dioxide at a high pressure and releases the carbon dioxide at a lower pressure (known as pressure swing absorption).

[0054] Gas separation assembly 186 may alternatively or additionally include one or more permeable membranes 200 (such as one or more carbon dioxide selective membranes). Membrane contactor assembly 198 may be configured to separate carbon dioxide gas from by-product stream 108. For example, permeable membrane 200 may have a relatively high permeability to carbon dioxide gas compared to other gases to allow carbon dioxide gas from by-product stream 108 to pass from the feed side to the permeate side of the permeable membrane.

[0055] The membrane contactor assembly 198 may additionally be configured to receive at least one liquid chemical or liquid absorbent 202 adapted to absorb at least a portion of the carbon dioxide gas separated from the by-product stream 108 (such as carbon dioxide gas passing from the feed side to the permeate side of the permeable membrane). For example, the membrane contactor assembly may receive the absorbent on the permeate side of the permeable membrane 200. The liquid absorbent 202 may be configured to absorb or bind carbon dioxide gas at relatively low temperatures and release or desorb the gas at elevated temperatures. Examples of preferred liquid absorbents include alkanolamines, such as monoethanolamine or diethanolamine, or aqueous solutions thereof. However, other organic amines, solutions of organic amines, or solutions of inorganic and / or organic hydroxide salts may be used.

[0056] If the gas separation assembly 186 includes an absorber 194 and / or a permeable membrane 200 that receives a liquid absorbent, the gas separation assembly may produce at least one liquid absorbent stream 204 having absorbed carbon dioxide gas (sometimes referred to as a "spent liquid absorbent stream" or a "gas-containing liquid absorbent stream"). If a spent liquid absorbent stream 204 is produced and the absorption of gas in the spent liquid absorbent stream is irreversible, the gas removal assembly 184 may additionally include at least one gas extraction assembly 206.

[0057] Gas extraction assembly 206 may include any suitable structure configured to extract (or desorb) absorbed gas from liquid absorbent stream 204. For example, gas extraction assembly 206 may include one or more strippers 208. In some embodiments, when the liquid absorbent includes absorbed carbon dioxide gas, the gas extraction assembly may be configured to extract or desorb at least a substantial portion of the absorbed carbon dioxide gas to form an at least substantially regenerated liquid absorbent stream (or stripped liquid absorbent stream) 210 from which at least a substantial portion of the carbon dioxide gas has been extracted, and an off-gas stream 212 having the extracted carbon dioxide gas.

[0058] Stripped liquid absorbent stream 210 may be pumped or otherwise transported to gas separation assembly 186 for further absorption of carbon dioxide gas from by-product stream 108. Alternatively or additionally, stripped liquid absorbent stream 210 may be stored for later use. Off-gas stream 212 may be pumped or otherwise transported to one or more other components of the purification assembly, such as to supplement one or more heating fuel streams. Alternatively, off-gas stream 212 may be stored, vented to the atmosphere, or otherwise disposed of.

[0059] The gas extraction assembly 206 may use any suitable mechanism to regenerate the liquid absorbent stream 204 with the absorbed gas. If the liquid absorbent used in the gas separation assembly 186 is configured to absorb or bind carbon dioxide gas at a relatively low temperature and then release or desorb the gas at a high temperature, the gas removal assembly 184 may further include at least one heating assembly 214. The heating assembly may be configured to generate at least one heated exhaust stream (or combustion stream) 216 from at least one heating fuel stream 218, which is typically combusted in the presence of air. The heated exhaust stream 216 is shown schematically in FIG. 3 as the heated gas extraction assembly 206. The heated exhaust stream may alternatively or additionally heat the spent liquid absorbent stream 204 prior to the gas extraction assembly 206, as shown in FIG. 3.

[0060] The heating assembly 214 may include any suitable structure configured to generate a heated exhaust stream, such as a burner or combustion catalyst in which fuel is combusted with air to generate a heated exhaust stream. The heating assembly may include an igniter or ignition source 220 configured to initiate combustion of the fuel. The heating assembly 214 may achieve and / or maintain any suitable temperature in the gas extraction assembly 206 and / or the piping preceding that assembly. For example, the heating assembly 214 may heat the gas extraction assembly to at least a target operating temperature and / or at least a minimum extraction or desorption temperature for the particular liquid absorbent used.

[0061] In some embodiments, the heating assembly 214 may include a burner assembly 222 and may be configured to receive at least one fuel stream 218 and combust the fuel stream in the presence of air to provide a high-temperature combustion stream 214 that may be used to heat the gas removal reactor. The air may be delivered to the heating assembly via various mechanisms. For example, the air stream 224 may be delivered to the heating assembly as a separate stream, as shown in FIG. 3. Alternatively or additionally, the air stream 224 may be delivered to the heating assembly along with at least one of the fuel streams 218 for the heating assembly 214 and / or may be drawn from the environment in which the heating assembly is utilized.

[0062] Fuel stream 218 may include any combustible liquid and / or gas suitable for consumption by heating assembly 214 to provide the desired heat output. Some fuel streams may be gases when delivered and combusted by heating assembly 214, while other fuel streams may be delivered to the heating assembly as liquid streams. Examples of suitable heating fuels for fuel stream 218 include carbon-containing feedstocks, low molecular weight condensable fuels, and low molecular weight hydrocarbons. Other examples include carbon dioxide gas from one or more by-product streams 226. For example, one or more by-product streams 226 from other components and / or assemblies of the fuel processing system may be used as a suitable heating fuel for fuel stream 218. In some examples, at least a portion of fuel stream 218 is used for by-product stream 226.

[0063] The combustion stream 216 may additionally or alternatively be used to heat other portions of the fuel processing system and / or other systems in which the heating assembly is used. Additionally, other configurations and types of heating assembly 214 may be used. For example, the heating assembly 214 may be an electrically powered heating assembly configured to heat the gas extraction assembly 206 and / or piping upstream of that assembly by generating heat using at least one heating element (such as a resistive heating element), a waste heat stream, solar heating, electric heating, etc. In those embodiments, the heating assembly 214 need not receive and combust a combustible fuel stream to heat the vaporizer to the appropriate vaporization temperature and / or heat the methanation reactor to the appropriate methanation temperature.

[0064] The heating assembly may also be configured to heat other components and / or assemblies, such as the feedstock delivery system, the feedstock feed stream, the methane production assembly, and / or other assemblies of the purification assembly, or any suitable combination of those systems, streams, and regions. The heating assembly may additionally be configured to heat other components of the purification assembly. For example, the heated exhaust stream may be configured to heat a pressure vessel and / or other canister containing heated fuel and / or hydrogen-production fluid that forms at least a portion of the feed stream and / or fuel stream for the fuel processing system.

[0065] The heating assembly 214 may be housed within an assembly shell or housing 227 along with the gas isolation assembly and gas extraction assembly. The heating assembly may be located separately from one or both of the assemblies, but may be in thermal and / or fluid communication with one or both to provide the desired heating. The heating assembly 214 may be located partially or completely within a common shell, and / or at least a portion (or all) of the heating assembly may be located outside of the shell. If the heating assembly is located outside of the shell, hot combustion gases from the burner assembly 222 may be transported to one or more components within the shell via appropriate heat transfer conduits.

[0066] Although gas removal assembly 184 ( FIG. 3 ) and hydrogen-producing region 78 and / or vaporization region 76 ( FIG. 2 ) are shown as each including a heating assembly, gas removal assembly 184, vaporization region 76, and hydrogen-producing region may have a common heating assembly that may be located within shell 120, within the shell of one or more of the gas removal assemblies, or external to those shells. If a common heating assembly is present, the heating assembly may include appropriate heat transfer conduits for transferring heat to the components of the gas removal assembly, the vaporization region, and / or the hydrogen-producing region. Additionally, if gas extraction assembly 206 includes two or more strippers 208, the gas extraction assembly may include a common heating assembly 214 for two or more of the strippers (in some embodiments, for all of the strippers). Additionally, although the gas removal assembly 184 is shown to include a single gas separation assembly 186, a single gas extraction assembly 206, and a single heating assembly 214, the gas removal assembly may include two or more gas separation assemblies, two or more gas extraction assemblies, and / or two or more heating assemblies, as shown by the dashed lines in FIG. 3 .

[0067] 4 and generally designated 350. Unless specifically excluded, gas removal assembly 350 may include other gas removal assemblies and / or one or more components of other assemblies in this disclosure. Gas removal assembly 350 may include at least one absorber 352, at least one stripper 354, at least one heating assembly 356, at least one pump 358, and at least one heat exchanger 360.

[0068] The absorber 352 may include any suitable structure configured to receive a liquid absorbent stream 362 adapted to absorb at least a portion of the carbon dioxide gas from the by-product stream 108 and / or to direct the by-product stream through a liquid absorbent stream. For example, the absorber 352 may include at least one spray nozzle 364 configured to at least partially atomize the liquid absorbent stream into one or more atomized liquid absorbent streams 366. The absorber may be configured to direct the by-product stream 108 through the atomized liquid absorbent stream 366 in any suitable flow configuration, such as countercurrent, cross-current, or co-current. As the by-product stream 108 flows through the atomized liquid absorbent stream, the carbon dioxide gas may be at least partially absorbed by the atomized stream to form a fuel stream 128 free of absorbed carbon dioxide gas and a spent liquid absorbent stream 368 having absorbed carbon dioxide gas. The absorber 352 may be operated at a pressure greater than 50 psig, preferably between 100 psig and 500 psig.

[0069] An alternative suitable configuration is to return the liquid absorbent stream 362 to the absorber without using spray nozzles. For example, the liquid absorbent stream 362 may enter the top, middle, or bottom of the absorber 352 via a suitable tubing or pipe connection, and the liquid absorbent may be allowed to accumulate to fill a volume at the bottom of the absorber. The by-product stream 108 may be directed to bubble through a volume of the liquid absorbent to remove at least a portion of the carbon dioxide gas to form the fuel stream 128.

[0070] Stripper 354 may include any suitable structure configured to receive one or more spent liquid absorbent streams 368, strip absorbed carbon dioxide gas from those spent liquid absorbent streams, and / or deliver one or more stripped liquid absorbent streams 370 to absorber 352. For example, stripper 354 may include at least one spray nozzle 372 configured to at least partially atomize the spent liquid absorbent stream into one or more atomized spent liquid absorbent streams 374. Stripper 354 may strip absorbed carbon dioxide gas via any suitable mechanism. For example, if the liquid absorbent used for liquid absorbent stream 362 absorbs or binds carbon dioxide gas within a first temperature range and releases or desorbs carbon dioxide gas within a second temperature range higher than the first temperature range, stripper 354 may be configured to receive one or more heated exhaust streams 376 from heating assembly 356 and direct the heated exhaust streams through the atomized spent liquid absorbent streams.

[0071] For example, the atomized spent liquid absorbent stream may be heated by a heated exhaust stream between 60° C. and 200° C., preferably between 80° C. and 150° C., to drive off absorbed carbon dioxide gas to produce or provide an at least partially regenerated liquid absorbent stream 370. The released or desorbed gas may form at least one off-gas stream 377. Stripper 354 may be operated within a range of 0 psig to 50 psig, preferably 0 psig to 10 psig.

[0072] The heating assembly 356 may include any suitable structure configured to generate at least one heated exhaust stream 376 for heating the atomized spent liquid absorbent stream 374. For example, the heating assembly may heat the stripper to any suitable temperature, such as at least the minimum release temperature or desorption temperature of carbon dioxide gas in the atomized spent liquid absorbent stream.

[0073] The heating assembly 356 may include at least one heater 394 powered by at least one power assembly (not shown). The heater 394 may include at least one heating element 398 (such as a resistive heating element). The heating element may heat the spent liquid absorbent stream 368 prior to the stripper 354 (and / or the spray nozzles 372) and / or may heat the spent liquid absorbent stream within the stripper. The power assembly may include one or more electrical cords (to allow a user to plug the heater into an electrical outlet), solar panels, wind turbines, fuel cells, etc.

[0074] Additionally, other configurations and types of heating assembly 356 may be used. For example, heating assembly 356 may include a burner assembly 378, at least one blower 380, and an igniter assembly 382, ​​as shown in FIG. 5 . The burner assembly may include any suitable structure configured to receive at least one air stream 384 and at least one fuel stream 386 and combust the at least one fuel stream to generate heated exhaust stream 376. The fuel stream may be provided by feedstock delivery system 74, absorber 352, and / or one or more other gas removal assemblies. Additionally, at least a portion of off-gas stream 377 may be used as its by-product fuel stream. Fuel stream 386 may be delivered to burner assembly 378 via a pump and / or another suitable device. Blower 380 may include any suitable structure configured to generate air stream 384. Igniter assembly 382 may include any suitable structure configured to ignite fuel stream 386.

[0075] Pump 358 may be configured to deliver or transport spent liquid absorbent stream 368 to stripper 354 for desorbing at least a portion of the carbon dioxide gas absorbed from the liquid absorbent stream, as shown in FIG. 4. Alternatively, pump 358 may be configured to deliver or transport stripped liquid absorbent stream 370 to absorber 352 for absorbing at least a portion of the carbon dioxide gas from by-product stream 108, as shown in FIG. 5. In some embodiments, the spent liquid absorbent stream and / or the stripped liquid absorbent stream flow between the absorber and the stripper without requiring the use of a pump and / or other powered fluid delivery mechanism. Heat exchanger 360 may include any suitable structure configured to transfer heat from the stripped liquid absorbent stream to the spent liquid absorbent stream.

[0076] In some embodiments, gas removal assembly 350 may include a shell or housing 392 that may at least partially house one or more other components of the assembly. For example, shell 392 may at least partially house absorber 352, stripper 354, heating assembly 356, pump 358, and / or heat exchanger 360, as shown in FIG. 5 . The shell or housing may include insulation and / or a jacket. Alternatively, the gas removal assembly may be housed within a common shell or housing of the other components of the fuel processing assembly.

[0077] Another example of gas removal assembly 184 is shown in FIG. 6 and is generally designated 400. Unless specifically excluded, gas removal assembly 400 may include one or more components of the other gas removal assemblies described in this disclosure. For example, gas removal assembly 400 may include one or more absorbers 402.

[0078] The absorber 402 may include at least one solid absorbent 406 (e.g., in a solid absorbent bed) adapted to absorb at least a portion of the carbon dioxide gas from the by-product stream 108 and / or to direct the flow of the by-product stream through the solid absorbent. As the by-product stream 108 flows through the solid absorbent, the carbon dioxide gas may be at least partially absorbed, forming the fuel stream 128 without absorbed carbon dioxide gas. The gas removal assembly 400 may include any suitable number of absorbers 402. For example, the gas removal assembly may include a first absorber 408 and a second absorber 410, as shown in FIG. 6. Although the second gas removal assembly 400 is shown as including two absorbers 402, the assembly may include any suitable number of absorbers, such as one absorber or three or more absorbers.

[0079] If gas removal assembly 400 includes two or more absorbers 402, the gas removal assembly may include two or more control valves (not shown) and / or other structures for isolating one or more absorbers 402 and / or directing flow to one or more other absorbers 402. For example, by-product stream 108 may be directed to flow through a first absorber 408 until the solid sorbent in the first absorber is saturated or substantially saturated with carbon dioxide gas. At that point, a control valve may isolate first absorber 408 and direct the flow of by-product stream 108 through a second absorber 410 until the solid sorbent in the second absorber is saturated or substantially saturated. While by-product stream 108 is flowing through the second absorber, the solid sorbent in the isolated first absorber may be recharged or regenerated, or vice versa. In some embodiments, gas removal assembly 400 may include a shell or housing 413 that may at least partially house one or more other components of the assembly. For example, the shell 413 may at least partially house the absorber 402, as shown in Figure 6. The shell or housing may include insulation and / or a jacket. Alternatively, the gas removal assembly may be housed within a common shell or housing of the other components of the fuel processing assembly.

[0080] Another example of gas removal assembly 184 is shown in FIG. 7 and is generally designated 414. Unless specifically excluded, gas removal assembly 414 may include other gas removal assemblies and / or one or more components of other assemblies in this disclosure. Gas removal assembly 414 may include a membrane assembly 418.

[0081] Membrane assembly 418 may include any suitable structure configured to separate at least a portion of the carbon dioxide gas from by-product stream 108 to form fuel stream 128. The separated carbon dioxide gas may form off-gas stream 333. For example, membrane assembly 418 may include one or more carbon dioxide-selective membranes 428 configured to separate at least a portion of the carbon dioxide gas from by-product stream 108. Membrane assembly 418 may include any suitable number of membranes 428, as shown by the dashed lines in FIG. 7. When membrane assembly 418 includes two or more membranes 428, the membranes may be arranged in parallel or in series. In some embodiments, gas removal assembly 414 may include a shell or housing 429 that may at least partially house one or more other components of the assembly. For example, shell 429 may at least partially house membrane assembly 418, as shown in FIG. 7. The shell or housing may include insulation and / or a jacket. Alternatively, the gas removal assembly may be housed within a common shell or housing of other components of the fuel processing assembly.

[0082] Another example of gas removal assembly 184 is shown in FIG. 8 and is generally designated 430. Unless specifically excluded, gas removal assembly 430 may include other gas removal assemblies and / or one or more components of other assemblies in this disclosure. Gas removal assembly 430 may include a membrane contactor assembly 434, at least one stripper 436, at least one heating assembly 438, at least one heat exchanger 440, and at least one pump 442.

[0083] The membrane contactor assembly 434 may include any suitable structure configured to separate carbon dioxide gas from the by-product stream 108 to form the fuel stream 128. For example, the membrane contactor assembly 434 may include one or more membrane contactors 452. The membrane contactors may include a plurality of carbon dioxide selective membranes 454 configured to separate at least a portion of the carbon dioxide gas from the by-product stream 108.

[0084] The membranes 454 may be hollow fibers or small diameter tubular membranes that may be sealed (or potted) into a shell 456, as shown in Figure 9. The shell 456 may include inlet and outlet ports 457 and any suitable number of membranes 454, such as hundreds to thousands of membranes 454. The membranes 454 may have any suitable length, such as from about 1 centimeter to about 2 to 3 meters, and / or any suitable diameter, such as from 0.1 millimeter to 5 millimeters. The membranes may be configured to be microporous and / or highly permeable to carbon dioxide gas.

[0085] Membrane 454 may be constructed of a material that is chemically inert to the components of by-product stream 108, regardless of whether the components are in the gas and / or liquid phase. Additionally, if membrane 454 is microporous, it may be constructed of one or more materials that are not wetted by the liquid phase of the components of by-product stream 108 and / or liquid absorbent stream 470. In other words, the liquid phase of those components is not drawn into the micropore structure by capillary forces. Otherwise, if the membrane's micropore structure were to fill with liquid, the relatively slow diffusion of carbon dioxide gas from the liquid-filled pores could adversely affect the membrane's overall performance. One example of a suitable microporous polypropylene membrane is manufactured by Celgard®, LLC (Charlotte, North Carolina).

[0086] The membrane contactor 452 may direct the flow of the by-product stream 108 through holes or lumens 458 in the membrane 454, as shown in Figure 10. At least a portion of the carbon dioxide gas may pass through one or more walls 460 and enter the membrane contactor shell, as shown at 462 in Figure 10. When the by-product stream 108 is directed to flow into and / or through the lumen 458 of the membrane 454, the interior of the lumen may be referred to as the "feed side 466," and the interior of the shell (and / or exterior of the membrane) may be referred to as the "permeate side 468."

[0087] Alternatively, as shown in Figure 11, the membrane contactor may direct the flow of the by-product stream 108 through the membrane contactor shell and / or over the membrane. At least a portion of the carbon dioxide gas may pass through the wall 460 and into the lumen 458 of the membrane 454, as shown at 464 in Figure 11. When the by-product stream 108 is directed to flow into and / or through the membrane contactor shell and / or over the membrane, the interior of the membrane contactor shell or the exterior of the membrane may be referred to as the "feed side 466," and the interior of the lumen may be referred to as the "permeate side 468." Preferably, the by-product stream 108 is directed to flow through the lumen of the membrane when the lumen diameter is small and the membrane length is long to prevent the high pressure drop that would be encountered if the liquid absorbent stream 470 were directed through the lumen.

[0088] Additionally, membrane contactor 452 may receive at least one liquid absorbent stream 470 on the permeate side of the membrane. The liquid absorbent stream may be adapted to absorb at least a portion of the carbon dioxide gas passing from the feed side to the permeate side of membrane 454 to form liquid absorbent stream 472 having absorbed carbon dioxide gas (sometimes referred to as "spent liquid absorbent stream 472"). For example, if membrane contactor 452 is configured to receive by-product stream 108 through lumen 458 of membrane 454, the membrane contactor may receive liquid absorbent stream 470 within membrane contactor shell 456. Alternatively, if membrane contactor 452 is configured to receive by-product stream 108 through membrane contactor shell 456, the membrane contactor may receive liquid absorbent stream 470 through lumen 458 of membrane 454. The liquid absorbent in liquid absorbent stream 470 may be configured to absorb (or bind) at least a portion of the carbon dioxide gas at a relatively low temperature and then release (or desorb) those gases at an elevated temperature. Alternatively, the liquid absorbent in liquid absorbent stream 470 is driven by a pressure cycle, in which case carbon dioxide absorption at 434 can be at a relatively high pressure of 50 psig to 100 psig, or particularly 100 psig to 500 psig, and desorption at 436 occurs at a lower pressure.

[0089] The membrane contactor assembly 434 may include any suitable number of membrane contactors 452, as shown by the dashed lines in Figure 8. The membrane contactor assembly 434 may include two or more membrane contactors 452, which may be arranged in parallel or in series.

[0090] Stripper 436 may include any suitable structure configured to receive one or more spent liquid absorbent streams 472, strip absorbed carbon dioxide gas from those spent liquid absorbent streams, and / or deliver one or more stripped liquid absorbent streams 474 to membrane contactor 452. For example, stripper 436 may include at least one spray nozzle 476 configured to at least partially atomize the spent liquid absorbent streams into one or more atomized spent liquid absorbent streams 478. Stripper 436 may strip absorbed carbon dioxide gas via any suitable mechanism. For example, if the liquid absorbent used for liquid absorbent stream 470 absorbs or binds carbon dioxide gas within a first temperature range and releases or desorbs carbon dioxide gas within a second temperature range higher than the first temperature range, stripper 436 may be configured to receive one or more heated exhaust streams 480 from heating assembly 438 and direct the flow of those heated exhaust streams through the atomized spent liquid absorbent streams.

[0091] The atomized spent liquid absorbent stream may be heated by a heated exhaust stream between 60° C. and 200° C., preferably between 80° C. and 150° C., to drive off absorbed carbon dioxide gas to produce or provide an at least partially regenerated liquid absorbent stream 474. The released or desorbed gas may form at least one off-gas stream 333. The stripper 436 may be operated within a range of 0 psig to 50 psig, most preferably within a range of 0 psig to 10 psig.

[0092] The heating assembly 438 may include any suitable structure configured to generate at least one heated exhaust stream 480 for heating the atomized spent liquid absorbent stream 478. For example, the heating assembly may heat the stripper to any suitable temperature, such as at least the minimum release temperature or desorption temperature of carbon dioxide gas in the atomized spent liquid absorbent stream.

[0093] The heating assembly may include a burner assembly 484, at least one blower 486, and an igniter assembly 488, as shown in FIG. 8 . The burner assembly may include any suitable structure configured to receive at least one air stream 490 and at least one fuel stream 492 and combust the at least one fuel stream to generate heated exhaust stream 480. Fuel stream 492 may be provided by one or more of feedstock delivery system 232, a membrane contactor assembly (such as from at least a portion of fuel stream 128), and / or a gas removal assembly. In some embodiments, at least a portion of off-gas stream 333 may supplement fuel stream 492. Fuel stream 492 may be delivered to burner assembly 378 via a pump and / or other suitable device. Blower 486 may include any suitable structure configured to generate air stream 492. Igniter assembly 488 may include any suitable structure configured to ignite fuel stream 492.

[0094] Additionally, other configurations and types of heating assembly 438 may be used. For example, heating assembly 438 may include at least one heater 498 powered by at least one power assembly 500, as shown in FIG. 12 . Heater 498 may include at least one heating element 502 (e.g., a resistive heating element, etc.). The heating element may heat the spent liquid absorbent stream 472 prior to stripper 436 (and / or spray nozzle 476) and / or may heat the spent liquid absorbent stream within the stripper. Power assembly 500 may include one or more electrical cords (to allow a user to plug the heater into an electrical outlet), solar panels, wind turbines, fuel cells, etc.

[0095] Heat exchanger 440 may include any suitable structure configured to transfer heat from the stripped liquid absorbent stream to the spent liquid absorbent stream. Pump 442 may include suitable structure configured to deliver or transport stripped liquid absorbent stream 474 to membrane contactor 452 for additional absorption of carbon dioxide gas from by-product stream 108. In some embodiments, the spent liquid absorbent stream and / or the stripped liquid absorbent stream flow between the absorber and stripper without requiring the use of a pump and / or other powered fluid delivery mechanism.

[0096] In some embodiments, the gas removal assembly 430 may include a shell or housing 508 that may at least partially house one or more other components of the assembly. For example, the shell 508 may at least partially house the membrane contactor assembly 434, the stripper 436, the heating assembly 438, the heat exchanger 440, and / or the pump 442, as shown in Figures 8 and 12. In some embodiments, the shell 508 may include insulation and / or a jacket. Alternatively, the gas removal assembly may be housed within a common shell or housing of the other components of the fuel processing assembly.

[0097] The gas removal assembly 184 may additionally or alternatively include one or more structures and / or components such as those described in U.S. Patent Application Publication No. 2007 / 0129990, which is incorporated herein by reference for all purposes. While the gas removal assemblies of the present disclosure are discussed as separating and / or removing carbon dioxide, they may additionally separate and / or remove carbon monoxide and / or other gases. While the hydrogen generation assemblies and gas removal assemblies of the present disclosure include streams delivered via pumps, one or more of the streams may be delivered without a pump, or vice versa.

[0098] An example of a method 600 for producing hydrogen is shown in Figure 13. Although certain steps are shown in Figure 13, other examples of method 600 may omit, substitute, modify, duplicate, and / or add one or more steps. Additionally, the steps may be performed in any suitable order.

[0099] At 602, one or more feedstreams including a carbon-containing feedstock and / or water may be received at a fuel processing assembly. At 604, a hydrogen-producing region of the fuel processing assembly may be heated, such as via one or more burners, to at least a minimum hydrogen-producing temperature.

[0100] At 606, one or more output streams may be produced from the feed stream in the heated hydrogen-producing region. The output stream may include hydrogen gas, carbon dioxide, and one or more other gases. At 608, a product hydrogen stream and a by-product stream may be produced from the output stream in a purification region of the fuel processing assembly. The product hydrogen stream may have a higher hydrogen concentration than the output stream and a lower carbon dioxide concentration than the output stream. Additionally, the by-product stream may have a lower hydrogen concentration than the output stream and a higher carbon dioxide concentration than the output stream. In some examples, the purification region may include one or more hydrogen-selective membranes where the product hydrogen stream is produced from a portion of the output stream that passes through the hydrogen-selective membrane, and the by-product stream is produced from a portion of the output stream that does not pass through the hydrogen-selective membrane.

[0101] At 610, at least a portion of the carbon dioxide gas may be separated or removed from the by-product stream to produce a fuel stream. The fuel stream may have a lower carbon dioxide concentration than the by-product stream. For example, at least a portion of the carbon dioxide may be absorbed from the by-product stream by or through at least one absorbent, such as at least one solid absorbent or at least one liquid absorbent stream. In some examples, the spent liquid absorbent stream, or the liquid absorbent stream having absorbed carbon dioxide gas, may be heated to strip at least a substantial portion of the absorbed carbon dioxide gas to form a stripped liquid absorbent stream and an off-gas stream comprising stripped carbon dioxide gas.

[0102] In other examples, the by-product stream flows through one or more carbon dioxide selective membranes to remove carbon dioxide gas. At least a portion of the carbon dioxide gas passes from the feed side to the permeate side of the membrane to form a fuel stream, while the portion of the by-product stream that does not pass through the membrane (i.e., does not pass from the feed side to the permeate side) forms an off-gas stream. In some examples, the liquid absorbent stream flows through the permeate side of the carbon dioxide selective membrane to produce a spent liquid absorbent stream, or a liquid absorbent stream having absorbed carbon dioxide gas. In some examples, the spent liquid absorbent stream, or the liquid absorbent stream having absorbed carbon dioxide gas, can be heated to strip at least a substantial portion of the absorbed carbon dioxide gas to form a stripped liquid absorbent stream and an off-gas stream comprising stripped carbon dioxide gas. At 612, the fuel stream can be supplied to a burner for combustion.

[0103] Some examples of method 600 may additionally or alternatively include one or more other steps. For example, at 614, a vaporization region of the fuel processing assembly may be heated to at least a minimum vaporization temperature, such as via one or more burners. The burners used to heat the vaporization region may be the same or different from the one or more burners used to heat the hydrogen-producing region. Additionally, at 616, at least a portion of the feed stream may be vaporized in the vaporization region of the fuel processing assembly to form one or more at least substantially vaporized streams. Once at least a portion of the feed stream is vaporized, the output stream generated at 606 may be at least partially generated from the at least substantially vaporized streams.

[0104] The disclosed hydrogen generation assembly and method provides an effective way to reduce carbon dioxide emissions produced when producing hydrogen from carbon-containing feedstocks, such as producing hydrogen from methanol. Carbon dioxide can alternatively be removed from the flue gas stream. However, flue gas streams have relatively low carbon dioxide concentrations and are at very low pressures due to, for example, dilution of the combustion gases with excess air supplied for combustion.

[0105] In one example, a 1.575 L / min methanol / water mixture (62.5 wt% methanol / balance water) yields 1396 std. L / min product hydrogen at a lower heating value (LHV) energy efficiency of 83%. The by-product stream from the purification section is about 1.5 MPa to about 2.0 MPa and about 1.0 Nm3 / min. Additionally, the by-product stream is composed of about 25.7% hydrogen, 15.8% water, 1.8% methanol, 47.8% carbon dioxide, and 10% carbon monoxide. The by-product stream is about 400°C and exits the heat exchanger at about 30°C. The feed stream enters the same heat exchanger at about 25°C and exits at about 195°C. The heat exchanger has a heat duty of about 578 kJ / min. In contrast, the flue gas stream has a carbon dioxide concentration of 19% to 22% at about 110 kPa and about 3.2 Nm3 / min. [Industrial Applicability]

[0106] The present disclosure, including hydrogen generation devices and components of those devices, is applicable to fuel processing and other industries where hydrogen gas is refined, produced, and / or utilized.

[0107] The above disclosure encompasses multiple separate inventions with independent utility. While each of these inventions is disclosed in its preferred form, the specific embodiments thereof disclosed and illustrated herein are susceptible to numerous variations and should not be considered in a limiting sense. 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, if any claim recites "a" or "first" element or the equivalent, such claim should be understood to include the incorporation of one or more such elements, and neither requires nor excludes more than one such element.

[0108] Inventions embodied in various combinations and subcombinations of features, functions, elements, and / or properties may be claimed by presenting new claims in the related application, and such new claims, whether directed to different inventions or the same invention, and whether of different, broader, narrower, or equal scope to the original claims, will also be deemed to fall within the scope of the inventive subject matter of this disclosure. [Explanation of symbols]

[0109] 20 Hydrogen Generation Assembly 21 Product hydrogen stream 22 Ingredient Delivery System 24 Fuel Processing Assembly 26 Feed stream 28 Fuel flow 30 Hydrogen-producing fluid 32 Hydrogen Generation Area 34 Output flow, output (or mixed gas) flow, output flow (or mixed gas flow) 36 Steam reforming catalyst 38 Air Delivery Assembly 40 Purification (or separation) area, purification area 42 Hydrogen-rich flow 44 By-product logistics 46 Hydrogen-selective membranes, membranes 48 Chemical carbon monoxide removal assembly, chemical removal assembly 50 Pressure Swing Adsorption (PSA) System, PSA System 52 Heating Assembly 54 Heated exhaust flow (or combustion flow), heated exhaust flow, high-temperature combustion flow 58 Igniters or ignition sources 60 Burner Assembly 62 Airflow 64 Vaporization Region 66 Shell or housing, shell 68 Insulation Materials 70 Outer cover or jacket 72 Hydrogen Generation Assembly 74 Ingredient Delivery System 76 Vaporization Region 78 Hydrogen Generation Area 80 Heating Assembly 82 Purification area 84 Raw material tank (or container) 86 Pump 88 Hydrogen-producing fluid 90 Liquid-containing feed stream, feed stream 92 Vaporizer 94 Steam Feed Stream 96 Output flow, output or mixed gas flow 97 Steam reforming area 98 Reforming catalyst 99 Heated exhaust flow 100 Burner Assembly 102 Blower 104 Igniter Assembly 106 Airflow 107 Fuel flow 108 By-product logistics 110 Combustion Zone 112 Hydrogen-rich stream or product hydrogen stream, permeate or hydrogen-rich stream 114 Membrane Assembly 120 Shell or housing, shell 122 Exhaust port 124 Combustion Exhaust Flow 126 Gas Removal Assembly 128 Fuel flow 129 Offgas Stream 130 Fuel Restriction Orifice 136 Heat Exchange Assembly 138 Heat exchanger 184 Gas Removal Assembly 186 Gas Separation Assembly 194 Absorber 196 Absorbent 197 Absorbent Bed 198 Membrane Contactor Assembly 200 Permeable membrane 202 Liquid chemical agents or liquid absorbents, liquid absorbents 204 Liquid absorbent flow, spent liquid absorbent flow 206 Gas extraction assembly, heated gas extraction assembly 210 Regenerated liquid absorbent stream (or stripped liquid absorbent stream), stripped liquid absorbent stream 212 Offgas Stream 214 Heating Assembly 216 Heated exhaust flow (or combustion flow), heated exhaust flow 218 Heated fuel flow, combustion flow 220 Igniters or Ignition Sources 222 Burner Assembly 224 Airflow 226 By-product logistics 227 Assembly Shell or Housing 232 Raw Material Delivery System 333 Offgas Stream 350 Gas Removal Assembly 352 Absorber 354 Stripper 356 Heating Assembly 358 Pump 360 heat exchanger 362 Liquid absorbent flow 364 Spray Nozzle 366 Sprayed Liquid Absorbent Flow 368 Spent Liquid Absorbent Flow 370 Stripped Liquid Absorbent Stream 372 spray nozzle 374 Sprayed spent liquid absorbent flow 376 Heated Exhaust Flow 377 Offgas Stream 378 Burner Assembly 380 Blower 382 Igniter Assembly 384 Airflow 386 Fuel flow 392 Shell or housing, shell 394 Heater 398 Heating Element 400 Gas Removal Assembly 402 Absorber 408 First absorber 410 Second absorber 413 Shell or housing, shell 414 Gas Removal Assembly 418 Membrane Assembly 428 Carbon dioxide selective membrane, membrane 429 Shell or housing, shell 430 Gas Removal Assembly 434 Membrane Contactor Assembly 436 Stripper 438 Heating Assembly 440 Heat exchanger 442 Pump 452 Membrane Contactor 454 Carbon dioxide selective membrane, membrane 456 Shell, membrane contactor shell 457 Inlet and Outlet Ports 458 Hole or bore, lumen 460 Wall 466 Supply Side 468 Transparent side 470 Liquid absorbent flow 472 Liquid absorbent flow, spent liquid absorbent flow 474 Stripped Liquid Absorbent Stream 476 Spray Nozzle 478 Sprayed spent liquid absorbent flow 480 heated exhaust flow 484 Burner Assembly 486 Blower 488 Igniter Assembly 490 Airflow 492 Fuel flow 498 Heater 500 Power Assembly 502 Heating Element 508 Shell or housing, shell

Claims

1. A process comprising the steps of: receiving a feed stream comprising a carbon-containing feedstock; heating the hydrogen-producing region to at least a minimum steam reforming temperature via one or more burners; generating an output stream in the heated hydrogen-producing region from the received feed stream via steam reforming, the output stream comprising primarily hydrogen gas and carbon dioxide gas; producing a product hydrogen stream and a by-product stream from the output stream in a purification region separately located downstream of the heated hydrogen-producing region, the product hydrogen stream having a higher hydrogen concentration and a lower carbon dioxide concentration than the output stream, and the by-product stream having a lower hydrogen concentration and a higher carbon dioxide concentration than the output stream; separating at least a portion of the carbon dioxide gas from the by-product stream to produce a fuel stream having a lower carbon dioxide concentration than the by-product stream; supplying the fuel stream to the one or more burners; A method for producing hydrogen, comprising:

2. 10. The method of claim 1, wherein separating at least a portion of the carbon dioxide gas from the by-product stream comprises absorbing the at least a portion of the carbon dioxide gas from the by-product stream via at least one absorbent.

3. 3. The method of claim 2, wherein absorbing at least a portion of the carbon dioxide gas comprises absorbing at least a portion of the carbon dioxide gas from the by-product stream via at least one solid sorbent.

4. 3. The method of claim 2, wherein absorbing at least a portion of the carbon dioxide gas from the by-product stream comprises absorbing at least a portion of the carbon dioxide gas from the by-product stream via a liquid absorbent stream.

5. 5. The method of claim 4, wherein separating at least a portion of the carbon dioxide gas from the by-product stream further comprises heating the liquid absorbent stream with absorbed carbon dioxide gas to strip at least a substantial portion of the absorbed carbon dioxide gas to form a stripped liquid absorbent stream and an off-gas stream comprising stripped carbon dioxide gas.

6. 10. The method of claim 1, wherein separating at least a portion of the carbon dioxide gas from the by-product stream comprises passing the at least a portion of the carbon dioxide gas from a feed side to a permeate side of at least one carbon dioxide-selective membrane.

7. 7. The method of claim 6, wherein separating at least a portion of the carbon dioxide gas from the by-product stream further comprises flowing a liquid absorbent stream through the permeate side of the at least one carbon dioxide selective membrane to produce a liquid absorbent stream having absorbed carbon dioxide gas therefrom.

8. 8. The method of claim 7, wherein separating at least a portion of the carbon dioxide gas from the by-product stream further comprises heating the liquid absorbent stream with absorbed carbon dioxide gas to strip at least a substantial portion of the absorbed carbon dioxide gas to form a stripped liquid absorbent stream and an off-gas stream comprising stripped carbon dioxide gas.

9. The method of claim 1, further comprising the step of vaporizing at least a portion of the supply stream to form an at least substantially vaporized stream in a vaporization region, and wherein generating an output stream in the heated hydrogen-producing region comprises generating the output stream from the at least substantially vaporized stream in the heated hydrogen-producing region.

10. The method of claim 9 further comprising heating the vaporization region to at least a minimum vaporization temperature via the one or more burners.

11. 10. The method of claim 1, wherein the purification region includes at least one hydrogen-selective membrane, and wherein generating a product hydrogen stream and a by-product stream in the purification region includes generating the product hydrogen stream and the by-product stream through the at least one hydrogen-selective membrane, wherein the product hydrogen stream is generated from a portion of the output stream that passes through the at least one hydrogen-selective membrane, and the by-product stream is generated from a portion of the output stream that does not pass through the at least one hydrogen-selective membrane.

12. A hydrogen-producing region configured to produce an output stream from at least one feed stream, the output stream comprising hydrogen gas and carbon dioxide gas as primary components, and the at least one feed stream comprising a carbon-containing feedstock; and a heating assembly configured to receive at least one air stream and at least one fuel stream, combust the at least one fuel stream in a combustion region, and generate a heated exhaust stream for heating the hydrogen-producing region to at least a minimum steam reforming temperature; a purification region disposed separately downstream of the hydrogen-producing region, the purification region configured to produce a product hydrogen stream and a by-product stream, the product hydrogen stream having a higher hydrogen concentration and a lower carbon dioxide concentration than the output stream, and the by-product stream having a lower hydrogen concentration and a higher carbon dioxide concentration than the output stream; a gas removal assembly configured to separate at least a portion of the carbon dioxide gas from the by-product stream and produce at least a portion of the at least one fuel stream therefrom; A hydrogen generation assembly comprising:

13. 13. The assembly of claim 12, wherein the gas removal assembly includes at least one absorber configured to receive at least one solid sorbent adapted to absorb at least a portion of the carbon dioxide gas from the by-product stream and produce therefrom said at least a portion of the at least one fuel stream.

14. 13. The assembly of claim 12, wherein the gas removal assembly includes at least one absorber configured to (a) receive a liquid absorbent stream adapted to absorb the at least a portion of the carbon dioxide gas, and (b) direct a flow of the by-product stream through the liquid absorbent stream.

15. 15. The assembly of claim 14, wherein the gas removal assembly further comprises at least one stripper configured to (a) receive the liquid absorbent stream having absorbed carbon dioxide gas, (b) strip carbon dioxide gas from the liquid absorbent stream to form an off-gas stream therefrom, and (c) deliver the stripped liquid absorbent stream to the at least one absorber.

16. 13. The assembly of claim 12, wherein the gas removal assembly includes at least one carbon dioxide selective membrane having a feed side and a permeate side, the feed side configured to receive the by-product stream, at least a portion of the carbon dioxide gas in the by-product stream configured to pass from the feed side to the permeate side, and a remaining portion of the by-product stream remaining on the feed side forming said at least a portion of the at least one fuel stream.

17. 17. The assembly of claim 16, wherein the gas removal assembly comprises at least one absorber configured to (a) receive a liquid absorbent stream adapted to absorb at least a portion of the carbon dioxide gas passing from the feed side to the permeate side, and (b) direct a flow of the by-product stream through the liquid absorbent stream.

18. 18. The assembly of claim 17, wherein the gas removal assembly further comprises at least one stripper configured to (a) receive the liquid absorbent stream having absorbed carbon dioxide gas, (b) strip carbon dioxide gas from the liquid absorbent stream to form an off-gas stream therefrom, and (c) deliver the stripped liquid absorbent stream to the at least one absorber.

19. The assembly described in claim 12, further comprising a vaporization region configured to receive the at least one feed stream to form at least a substantial vaporized stream, and the hydrogen-producing region configured to produce the product hydrogen stream from the at least substantially vaporized stream.

20. 20. The assembly of claim 19, wherein the heated exhaust stream is for heating the vaporization region to at least a minimum vaporization temperature and for heating the hydrogen-producing region to at least a minimum hydrogen-producing temperature.

21. The assembly of claim 12 , wherein the hydrogen-producing region comprises a catalyst.

22. 22. The assembly of claim 21, wherein the catalyst is a reforming catalyst.

23. 13. The assembly of claim 12, wherein the purification region comprises at least one hydrogen-selective membrane, the product hydrogen stream being produced from a portion of the output stream that passes through the at least one hydrogen-selective membrane, and the by-product stream being produced from a portion of the output stream that does not pass through the at least one hydrogen-selective membrane.

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