Purified gas production system with purity analizer

Abstract

A purified gas production system includes a molten carbonate fuel cell configured to output an anode exhaust stream including hydrogen and carbon dioxide, a gas separation system configured to receive the anode exhaust stream and to output a purified gas stream including one of purified hydrogen or purified carbon dioxide, a gas purity analyzer configured to detect concentrations of a plurality of contaminants in the purified gas stream using Fourier Transform Infrared Spectroscopy, a valve assembly configured to selectively direct the purified gas stream toward one of a first flow path or a second flow path, and a controller communicably coupled to the gas purity analyzer and the valve assembly and configured to control the valve assembly based on the detected concentrations of the plurality of contaminants.

Description

Atty. Dkt. No.: 106876-2267PURITY ANALYZER FOR HYDROGEN GENERATION SYSTEMCROSS-REFERENCE TO RELATED PATENT APPLICATION

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 728,378, filed December 5, 2024, which is incorporated by reference herein in its entirety.BACKGROUND

[0002] The present disclosure relates generally to the field of electrochemical cells. In particular, the present disclosure relates to using fuel cells to produce high-purity hydrogen gas that may be utilized in a variety of applications.[00031 A fuel cell is a type of electrochemical cell that uses an electrochemical reaction to convert chemical energy stored in a fuel such as hydrogen or methane into electrical energy. In general, fuel cells typically include an anode and a cathode separated by an electrolyte contained in an electrolyte matrix. Fuel is supplied to the anode, and an oxidant is supplied to the cathode. The fuel cell may oxidize the fuel in an electrochemical reaction, which releases a flow of electrons between the anode and cathode, thereby converting chemical energy into electrical energy. Multiple fuel cells may be arranged in a stack or stacks and electrically coupled in order to produce a desired amount of power. Many types of fuel cells use hydrogen as fuel. For example, proton exchange membrane fuel cells, the type most often used in vehicles, require high-purity hydrogen to operate.[0004| Other types of fuel cells, including high-temperature fuel cells like molten carbonate fuel cells and solid oxide fuel cells, are able to generate hydrogen from methane fuel in addition to generating electricity. For example, in a molten carbonate fuel cell, the high operating temperatures cause methane and steam supplied to the anode to react to form hydrogen and carbon monoxide in a steam-methane reforming reaction. Precious metal catalysts may also be used within the fuel cell system to increase the amount of steam-methane reforming. Oxygen-1-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 and carbon dioxide supplied to the cathode form carbonate (CO32) ions, which are transported across the electrolyte to the anode. At the anode, the hydrogen generated in the reforming reaction reacts with the carbonate ions to form carbon dioxide and steam, while an electrical current is generated. To ensure that there is sufficient fuel across the anodes of all the cells in a stack, a significant amount more fuel may be provided to the stack than can be consumed before the fuel flows out of the stack. When methane is used as a fuel source and reformed in the fuel cells, the anodes of the fuel cells output a stream of excess hydrogen. Thus, in addition to generating power, fuel cells may be used to generate hydrogen from methane.

[0005] Hydrogen used in various applications, including scientific research, cutting and welding, and hydrogen-powered automobiles, is subject to strict purity standards. For example, SAE International has published an industry standard for hydrogen purity for use in fuel cell-powered automobiles, SAE J2719, which sets upper limits for various contaminants. These contaminants include water, methane, helium, oxygen, argon, nitrogen, carbon dioxide, carbon monoxide, sulfur compounds, formaldehyde, formic acid, ammonia, halogenated compounds, and particulates. Various industries and applications may have different standards and requirements for hydrogen purity. Accordingly, hydrogen produced for use in regulated industries must be analyzed to determine whether the concentration of any of these contaminants exceeds the limits set by the relevant standard.SUMMARY

[0006] One aspect of the present disclosure relates to a purified gas production system including a molten carbonate fuel cell configured to output an anode exhaust stream including hydrogen and carbon dioxide, a gas separation system configured to receive the anode exhaust stream and to output a purified gas stream including one of purified hydrogen or purified carbon dioxide, a gas purity analyzer configured to detect concentrations of a plurality of contaminants in the purified gas stream using Fourier Transform Infrared Spectroscopy, a valve assembly configured to selectively direct the purified gas stream toward one of a first flow path or a second flow path, and a controller communicably coupled to the gas purity analyzer and the valve assembly and-2-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 configured to control the valve assembly based on the detected concentrations of the plurality of contaminants.

[0007] In some embodiments, the system further includes a water separation system configured to remove water from the anode exhaust stream before the anode exhaust stream is received by the gas separation system.

[0008] In some embodiments, the controller is configured to cause the valve assembly to direct the purified gas stream toward the first flow path when each of the concentrations of the plurality of contaminants is below a respective maximum concentration. In some embodiments, the controller is configured to cause the valve assembly to direct the purified gas stream toward the second flow path when any one of the concentrations of the plurality of contaminants is above the respective maximum concentration.

[0009] In some embodiments, the controller is configured to monitor an average concentration of each of the plurality of contaminants over a predetermined time period, wherein the controller is configured to cause the valve assembly to direct the purified gas stream toward the first flow path while the average concentration of each of the plurality of contaminants is below a respective maximum concentration during the time period. In some embodiments, the controller is configured to cause the valve assembly to direct the purified gas stream toward the second flow path when any one of the average concentrations of the plurality of contaminants is above the respective maximum concentration.

[0010] In some embodiments, the gas separation system is a pressure swing adsorption system, and the purified gas stream is a purified hydrogen stream. In some embodiments, the plurality of contaminants detected by the gas purity analyzer includes carbon monoxide, carbon dioxide, methane, and water.[00111 In some embodiments, the gas separation system is a carbon dioxide separation system, and the purified gas stream is a purified carbon dioxide stream. In some embodiments, the plurality of contaminants detected by the gas purity analyzer includes carbon monoxide, water,-3-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 and methane. In some embodiments, the carbon dioxide separation system is configured to compress, cool, and liquefy carbon dioxide to separate the carbon dioxide from the anode exhaust stream and then vaporize the separated carbon dioxide to form the purified carbon dioxide stream.

[0012] In some embodiments, the gas separation system is a pressure swing adsorption system, the purified gas stream is a purified hydrogen stream, and the plurality of contaminants detected by the gas purity analyzer includes carbon monoxide, carbon dioxide, methane, and water. In some embodiments, the controller is configured to determine whether the concentration of total hydrocarbons other than methane exceeds a predetermined limit based on the detected concentrations of only carbon monoxide, carbon dioxide, and water, wherein controlling the valve assembly is further based on the determination. In some embodiments, the controller is configured to determine whether the concentration of total non-hydrogen gases exceeds a predetermined limit based on the detected concentrations of only carbon monoxide, carbon dioxide, methane, and water, wherein controlling the valve assembly is further based on the determination.[0(1131 Another aspect of the present disclosure relates to a purified gas production system including a gas purity analyzer configured to detect concentrations of a plurality of contaminants in a purified gas stream using Fourier transform infrared spectroscopy, a first gas buffer tank to temporarily store purified gas from the purified gas stream, a second gas buffer tank to temporarily store purified gas from the purified gas stream, a first valve assembly configured to selectively direct the purified gas stream toward one of the first gas buffer tank or the second gas buffer tank, a second valve assembly configured to selectively direct purified gas from the first gas buffer tank toward one of a first flow path or a second flow path, a third valve assembly configured to selectively direct purified gas from the second gas buffer tank toward one of the first flow path or the second flow path, and a controller communicably coupled to the gas purity analyzer, the first valve assembly, the second valve assembly, and the third valve assembly. The controller is configured to control the first valve assembly to direct the purified gas stream to the first gas buffer tank during a first time period, control the first valve assembly to direct the-4-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 purified gas stream to the second gas buffer tank during a second time period subsequent to the first time period, control the second valve assembly based on the detected concentrations of the plurality of contaminants in the purified gas stream during the first time period, and control the third valve assembly based on the detected concentrations of the plurality of contaminants in the purified gas stream during the second time period.[0014 J In some embodiments, the system further includes a molten carbonate fuel cell configured to receive an anode input stream including methane and to output an anode exhaust stream including hydrogen and carbon dioxide, and a gas separation system configured to receive the anode exhaust stream and to output the purified gas stream, the purified gas stream including one of purified hydrogen or purified carbon dioxide.

[0015] In some embodiments, the system further includes a water separation system configured to remove water from the anode exhaust stream before the anode exhaust stream is received by the gas separation system.

[0016] In some embodiments, the controller is configured to cause the second valve assembly or the third valve assembly to direct the purified gas stream toward the first flow path when each of the concentrations of the plurality of contaminants is below a respective maximum concentration. In some embodiments, the controller is configured to cause the second valve assembly or the third valve assembly to direct the purified gas stream toward the second flow path when any one of the concentrations of the plurality of contaminants is above the respective maximum concentration.|00.17J In some embodiments, the gas separation system is a pressure swing adsorption system, and the purified gas stream is a purified hydrogen stream. In some embodiments, the plurality of contaminants detected by the gas purity analyzer includes carbon monoxide, carbon dioxide, methane, and water.[0018| In some embodiments, the gas separation system is a carbon dioxide separation system, and the purified gas stream is a purified carbon dioxide stream. In some embodiments, the-5-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 plurality of contaminants detected by the gas purity analyzer includes carbon monoxide, water, and methane. In some embodiments, the carbon dioxide separation system is configured to compress, cool, and liquefy carbon dioxide to separate the carbon dioxide from the anode exhaust stream and then vaporize the separated carbon dioxide to form the purified carbon dioxide stream.[0019 J Another aspect of the present disclosure relates to a method of producing a purified gas stream. The method includes generating a gas stream, separating hydrogen or carbon dioxide from the gas stream to form a purified gas stream, measuring concentrations of a plurality of contaminants in the purified gas stream using Fourier Transform Infrared Spectroscopy, and supplying the purified gas stream to one of a first flow path or a second flow path based on the measured concentrations.[0020| In some embodiments, generating the gas stream includes generating an anode exhaust stream from a molten carbonate fuel cell. In some embodiments, the method further includes removing water from the anode exhaust stream.(0021] In some embodiments, the method further includes supplying the purified gas stream to a first buffer tank during a first time period, wherein supplying the purified gas stream toward one of the first flow path or the second flow path includes supplying the purified gas in the first buffer tank to one of the first flow path or the second flow path based on average concentrations of the plurality of contaminants during the first time period. In some embodiments, the method further includes supplying the purified gas stream to a second buffer tank during a second time period, wherein supplying the purified gas stream toward one of the first flow path or the second flow path includes supplying the purified gas in the second buffer tank toward one of the first flow path or the second flow path based on average concentrations of the plurality of contaminants during the second time period.(0022] In some embodiments, the concentrations of the plurality of contaminants are measured before the purified gas stream is supplied to a purified gas storage system.-6-4867-2383-6145.1Atty. Dkt. No.: 106876-2267[00231 In some embodiments, separating hydrogen or carbon dioxide from the gas stream includes separating hydrogen from the gas stream using a pressure swing adsorption system such that the purified gas stream is a purified hydrogen stream.

[0024] In some embodiments, separating hydrogen or carbon dioxide from the gas stream includes cooling and compressing the gas stream to liquefy carbon dioxide and vaporizing the liquefied carbon dioxide such that the purified gas stream is a purified carbon dioxide stream.[0025| The foregoing is a summary of the disclosure and thus by necessity contains simplifications, generalizations, and omissions of detail. Consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, features, and advantages of the devices and / or processes described herein, as defined by the claims, will become apparent in the detailed description set forth herein and taken in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS[0026J FIG. l is a schematic diagram of a purified hydrogen production system, according to an exemplary embodiment.[0027| FIG. 2 is a schematic diagram of a purified hydrogen production system, according to an exemplary embodiment.

[0028] FIG. 3 is a schematic diagram of a purified carbon dioxide production system, according to an exemplary embodiment.

[0029] FIG. 4 is a schematic diagram of a purified carbon dioxide production system, according to an exemplary embodiment.

[0030] FIGS. 5 and 6 illustrate methods of producing a purified gas, according to exemplary embodiments.-7-4867-2383-6145.1Atty. Dkt. No.: 106876-2267[00311 It will be recognized that the figures are schematic representations for purposes of illustration. The figures are provided for the purpose of illustrating one or more implementations with the explicit understanding that the figures will not be used to limit the scope of the meaning of the claims.DETAILED DESCRIPTION[0032J In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure.

[0033] Disclosed herein are systems and methods for producing purified gas streams, for example, purified hydrogen streams and purified carbon dioxide streams. An anode exhaust stream from a molten carbonate fuel cell may be purified to generate a purified hydrogen stream, for example, via compression and Pressure Swing Adsorption. Alternatively or additionally, the anode exhaust stream may be purified to generate a purified carbon dioxide stream, for example, via compression and mechanical chilling, liquefaction, and cryogenic distillation of carbon dioxide. The systems may include a gas purity analyzer configured to measure contaminant concentrations in the purified hydrogen stream or purified and vaporized carbon dioxide stream. The contaminant concentrations may be measured in real-time or substantially in real-time, meaning the contaminant concentrations may be measured before the purified gas stream is supplied to a gas storage system, such that purified gas with contaminant concentrations that exceed maximum concentration limits can be diverted before reaching the hydrogen storage system. The systems may include buffer tanks to temporarily store purified gas while-8-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 contaminant concentration measurements are being taken. Based on the measurements, the purified gas in the buffer tanks may be released to the gas storage system or diverted. These systems may reduce the likelihood that a large quantity of stored gas must be discarded or reprocessed because a contaminant concentration is above a maximum limit. By diverting contaminated gas before it reaches the storage system, only the gas detected in real time to have contaminant concentrations exceeding the limits may be discarded. This may ensure that the gas that reaches the storage system has contaminant concentrations within acceptable limits and may eliminate the costs associated with discarding or reprocessing a large quantity of gas.

[0034] According to an exemplary embodiment, a hydrogen production system includes a hydrogen purity analyzer that measures the concentrations of several contaminants in a hydrogen stream in real time using Fourier Transform Infrared Spectroscopy (FTIR). The hydrogen stream may be generated by supplying anode exhaust from a molten carbonate fuel cell to a pressure swing adsorption system. Because molten carbonate fuel cell anode exhaust is used to generate the hydrogen stream, several contaminants, including those listed in the SAE J2719 standard, can be presumed to not be present in quantities sufficient to exceed the maximum concentration limits. For example, sulfur compounds and particulates should be removed from the input streams of molten carbonate fuel cells before they are input into the fuel cells, as high concentrations of these contaminants would inhibit the fuel cell reactions and cause damage to the fuel cells. Other potential contaminants, such as formaldehyde, formic acid, ammonia, and halogenated compounds are not present in the raw material streams provided to the molten carbonate fuel cells and are not introduced at any point in the system, upstream or downstream of the fuel cells. While argon, nitrogen, and helium may be present in the input stream supplied to the cathode, additional process controls may ensure that they do not cross over to the anode and mix with the gases in the anode exhaust stream. The use of a molten carbonate fuel cell and a pressure swing adsorption system to generate the purified hydrogen stream, as well as the upstream process controls employed, allow for the use of a single FTIR purity analyzer configured to measure only a subset of the listed contaminants to determine in real-time and with a high degree of confidence that the hydrogen generated meets all of the purity requirements set-9-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 out in the SAE J2719 standard. The measured contaminants may be compared directly to their respective maximum concentration limits and may also act as a proxy to determine whether the untested contaminants meet their respective maximum concentration limits. For example, the purity analyzer may measure the concentrations of carbon monoxide, carbon dioxide, methane, and water. These measurements may be directly compared to their respective purity standards and also used to determine, for example, whether the total non-hydrogen gases or total hydrocarbons other than methane exceed their respective maximum concentration limits.

[0035] The hydrogen generation system may cut off a flow of hydrogen to downstream storage when a contaminant concentration exceeds the maximum concentration limit so that larger volumes of purified hydrogen do not become contaminated. By diverting hydrogen with any contaminants exceeding the maximum concentration limits rather than mixing it with hydrogen meeting the purity requirements, the discarding of large amounts of sufficiently pure hydrogen may be avoided. In some cases, testing of the hydrogen stream for the presence of sulfur compounds, particulates, or the other potential compounds and gases listed may not be performed, as these contaminants can be presumed not to exceed the maximum concentration limits. Alternatively, the hydrogen may be tested for these additional contaminants after a large quantity of hydrogen has been stored with little to no risk that these previously untested contaminants will exceed the maximum concentration limits.

[0036] Another exemplary embodiment includes a similar system configured to produce purified carbon dioxide. A carbon dioxide purity analyzer may use FTIR to detect several contaminants listed in the Compressed Gas Association standard for beverage-grade carbon dioxide, CGA G- 6.2-2011, in real-time. This purified carbon dioxide generation system may cut off a flow of carbon dioxide to downstream storage when a contaminant concentration exceeds the maximum concentration limits so that larger volumes of carbon dioxide do not become contaminated.

[0037] Referring to FIG. 1, a purified hydrogen production system 100 is shown, according to an exemplary embodiment. The hydrogen production system 100 includes a fuel cell module 102 that includes an anode portion 104 and a cathode portion 106. As shown in FIG. 1, the fuel cell-10-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 module 102 is a molten carbonate fuel cell module. The fuel cell module 102 may include multiple fuel cells, each including an anode and a cathode separated by an electrolyte (e.g., a molten carbonate electrolyte). An anode input stream 108 containing steam and natural gas (the natural gas being primarily methane) and / or other chemical fuels is supplied to the anode portion 104 and thereby to the anodes of each fuel cell in the module 102. The cathode input stream 110 containing oxygen and carbon dioxide is supplied to the cathode portion 106 and thereby to the cathodes of each fuel cell in the module 102. At the cathodes, the oxygen and carbon dioxide in the cathode input stream 110 react to form carbonate ions (CCh2' ions). The carbonate ions are transported across the electrolyte to the corresponding anode. At the anodes, the methane and steam react in the presence of precious metal catalysts to form hydrogen and carbon dioxide (i.e., a steam-methane reforming reaction) as well as carbon monoxide. Other hydrocarbons (e.g., ethane, propane, and butane) that may be present in the natural gas in the anode input stream may similarly be converted to hydrogen, carbon dioxide, and carbon monoxide in reforming reactions. In some embodiments, the hydrogen production system 100 may have an external reformer upstream of the anode portion 104 instead of or in addition to the internal reforming catalyst in the anode portion 104. A portion of the hydrogen then reacts with the carbonate ions that have been transported across the electrolyte to form steam and carbon dioxide. Electrons are released as a result of the reaction of the hydrogen and the carbonate ions. The electrons travel through an external circuit back to the cathode, generating an electrical current. The cathode portion 106 outputs a cathode output stream 114 including unreacted oxygen. The anode portion 104 outputs an anode exhaust stream 112 including carbon dioxide and steam (which are formed in the reaction between the hydrogen and the carbonate ions) as well as hydrogen formed in the steam-methane reforming reaction. Excess hydrogen passes through the anode portion 104 without reacting with the carbonate ions.

[0038] The anode exhaust stream 112 is then supplied to a water separation system 118 and a compression system 116. Water is removed by the water separation system 118, and the remaining components of the anode exhaust stream are compressed by the compression system 116, before the compressed dehumidified anode exhaust stream 122 is supplied to the gas-11-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 separation system 124. For example, the water separation system 118 may include a chiller configured to cool and condense water out of the anode exhaust stream 112 or may include a water separation membrane. In some embodiments, the water separation system 118 may include a regenerative bed dryer configured to reduce the moisture content of the anode exhaust stream to below 10 parts per million. The compression system 116 may include multiple compressor stages, and additional water may be removed between successive compressor stages and / or after the anode exhaust stream 112 has passed through all of the compressor stages. The water separation system outputs a water stream 120 (which may also include the water removed within or downstream of the compression system 116), and the compression system 116 outputs a dehumidified anode exhaust stream 122.[0039| The dehumidified anode exhaust stream 122, which includes hydrogen and carbon dioxide, is then supplied to a gas separation system 124, shown in FIG. 1 as a pressure swing adsorption (PSA) system. The gas separation system 124 separates the dehumidified anode exhaust stream 122 into a purified gas stream, shown as a purified hydrogen stream 126, and a carbon dioxide stream 128. The carbon dioxide stream 128 may include carbon dioxide, some unrecovered hydrogen, and various other contaminants from the dehumidified anode exhaust stream 122. The carbon dioxide stream 128 may be used elsewhere in the system, represented in FIG. 1 as the balance-of-plant (BOP) 130. For example, the unrecovered hydrogen in the carbon dioxide stream 128 may be burned to preheat the cathode input stream 110 before it is input into the cathode portion 106, the carbon dioxide in the carbon dioxide stream 128 may be captured and compressed for other purposes. In other embodiments, the gas separation system may separate the dehumidified anode exhaust stream 122 using other methods, such as cryogenic distillation or membrane separation.

[0040] The purified hydrogen stream 126 may then be supplied to a hydrogen purity testing and storage system 132. A small portion (e.g., less than 0.1%) of the purified hydrogen stream 126 may be supplied to a gas purity analyzer, shown as a hydrogen purity analyzer 134, while the remainder is directed to a first valve assembly 136. As shown in FIG. 1, the first valve assembly 136 is configured to selectively direct the purified hydrogen stream 126 via a first flow path to a -12-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 hydrogen storage tank 129 or via a second flow path to the balance-of-plant 130 using one or more valves. In other embodiments, rather than being directed to the hydrogen storage tank 129, the purified hydrogen stream 126 may be directed to another location for immediate use. The hydrogen purity testing and storage system 132 includes a controller 142 configured to receive data from the hydrogen purity analyzer 134, including detected contaminant concentrations for one or more contaminants, and to control the first valve assembly 136 based on the data. The controller 142 may include at least one processor and at least one memory storing instructions that, when executed by the processor, cause the processor to execute the functions of the controller 142 described herein.[00411 The hydrogen purity analyzer 134, which is discussed in further detail below, may use Fourier Transform Infrared Spectroscopy (FTIR) to detect the concentrations of various contaminants in a sample of the purified hydrogen stream 126. The controller 142 may receive the measurements from the hydrogen purity analyzer 134 and determine whether the measured contaminant concentrations exceed upper limits, which may be defined, for example, based on SAE J2719 or any other suitable standard. The hydrogen purity analyzer 134 may continuously sample and test the purified hydrogen stream 126 and provide measurements to the controller 142. While the measurements indicate that all of the contaminant concentrations are below the maximum concentration limits, the controller 142 may control the first valve assembly 136 to supply the purified hydrogen stream 126 to the hydrogen storage tank 129 via a first flow path. The hydrogen stored in the hydrogen storage tank 129 may then be used in applications requiring high-purity hydrogen, such as in automobiles. Upon receiving the measurements indicating that any one or more contaminant concentration exceeds a maximum concentration limit, the controller 142 may control the first valve assembly 136 to stop supplying the purified hydrogen stream 126 to the hydrogen storage tank 129 and begin supplying the purified hydrogen stream to the balance-of-plant 130 via a second flow path. Hydrogen supplied to the balance-of-plant 130 may be used by systems that do not require high-purity hydrogen. For example, the less pure hydrogen may be burned to preheat the cathode input stream 110. In some embodiments, at-13-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 least a portion of the less pure hydrogen may be returned to the gas separation system 124 and reprocessed to further purify the hydrogen.

[0042] In conventional automotive hydrogen purification systems, samples are taken, and contaminant concentrations are measured after a large volume of purified hydrogen has been supplied to a storage tank. If a contaminant concentration exceeds an upper limit, all of the purified hydrogen in the hydrogen tank must be discarded, repurposed, or reprocessed, as the hydrogen is not suitable for use in automobiles. Thus, even if the hydrogen supplied to the storage tank has contaminant concentrations below the upper limits for 90 percent of the storage tank fill time, if the hydrogen supplied to the storage tank for the remaining 10 percent of the fill time has contaminant concentrations that cause the overall contaminant concentration in the storage tank to exceed the upper limits, all of the hydrogen in the storage tank will be rejected. In contrast, the hydrogen purity testing and storage system 132 diverts hydrogen that exceeds the contaminant concentration limits away from the hydrogen storage tank 129 and to the balance- of-plant 130. Thus, only hydrogen with contaminant concentrations below the upper limits may be allowed to reach the hydrogen storage tank 129.[00431 In some embodiments, rather than diverting hydrogen with contaminant concentrations exceeding the upper limits, the controller 142 may monitor the average contaminant concentrations over time (e.g., over a predetermined time period, over a time period in which a purified gas storage tank is being filled, etc.), allowing some hydrogen with contaminant concentrations that exceed the upper limits to be supplied in the hydrogen storage tank 129, as long as the overall contaminant concentrations of hydrogen supplied to the hydrogen storage tank 129 do not exceed the upper limits. For example, if a particular contaminant has a limit of 100 ppm, and the controller 142 determines, based on continuous or periodic data from the hydrogen purity analyzer 134 and other sensors or flow meters, that the hydrogen storage tank 129 is 90 percent full and the contaminant concentration is 80 ppm, the controller 142 may allow hydrogen with a contaminant concentration exceeding 100 ppm to be supplied to the hydrogen storage tank. For example, if the remaining 10 percent of the tank volume is filled with hydrogen having a contaminant concentration of 200 ppm, the total contaminant concentration of-14-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 the hydrogen in the hydrogen storage tank 129 will still fall below the upper limit of 100 ppm (e.g., 80 ppm x 0.9 + 200 ppm x 0.1 = 92 ppm). Monitoring the total contaminant concentration in the storage tank may allow less purified hydrogen to be diverted to the balance-of-plant 130 or recycled for further processing while still maintaining the concentrations of contaminants in the hydrogen storage tank 129 below the upper limits. The valve assembly 136 may be controlled by the controller 142 to direct the purified hydrogen stream 126 via the first flow path to the hydrogen storage system 129 as long as the average contaminant concentrations since the beginning of the time period are below their respective maximum concentration limits.

[0044] Referring to FIG. 2, a purified hydrogen production system 200 is shown, according to another exemplary embodiment. The hydrogen production system 200 is substantially similar to the hydrogen production system 100, except as shown and described herein. In the hydrogen production system 200, rather than supplying the purified hydrogen stream 126 directly to the hydrogen storage tank 129, the valve assembly 136 may supply the purified hydrogen stream 126 to a first gas (e.g., hydrogen) buffer tank 138 or a second gas (e.g., hydrogen) buffer tank 140. In some embodiments, a first valve may control the flow of purified hydrogen to either the balance- of-plant 130 or the hydrogen buffer tanks 138, 140, and a second valve may control the flow of purified hydrogen to one of the first hydrogen buffer tank 138 or the second hydrogen buffer tank 140. The hydrogen buffer tanks 138, 140 may temporarily store hydrogen to account for any delay in the purity analysis by the hydrogen purity analyzer 134. Second and third valve assemblies 144, 146 couple the hydrogen buffer tanks 138, 140 to the hydrogen storage tank 129. The controller 142 may be configured to control the valve assemblies 144, 146 to selectively supply the hydrogen in the buffer tanks 138, 140 to either the hydrogen storage tank 129 or the balance-of-plant 130.

[0045] While the hydrogen purity analyzer 134 detects contaminant concentrations in the purified hydrogen stream 126 below the upper limits, the controller 142 may control the valve assembly 136 to alternate between supplying the purified hydrogen stream to the first hydrogen buffer tank 138 and the second hydrogen buffer tank 140. As the hydrogen buffer tanks 138, 140 become full, the controller 142 may open the respective valve assembly 144, 146 to release the-15-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 hydrogen into hydrogen storage tank 129. For example, the controller 142 may control the first valve assembly 136 to begin supplying the purified hydrogen stream 126 to the first hydrogen buffer tank 138 during a first period of time. When the first hydrogen buffer tank 138 becomes full or the measurements by the hydrogen purity analyzer 134 are complete, the controller 142 may control the first valve assembly 136 to begin supplying the purified hydrogen stream 126 to the second hydrogen buffer tank 140 during a second period of time. During the second period of time (or simultaneously with controlling the first valve assembly 136 to begin supplying purified hydrogen stream to the second hydrogen buffer tank), the controller 142 may open the second valve assembly 144 to release the hydrogen in the first hydrogen buffer tank 138 via a first flow path into the hydrogen storage tank 129 if the detected contaminant concentrations during the first time period are all below their respective maximum concentration limits, or via a second flow path to the balance-of-plant 130 if any one of the detected contaminant concentrations during the first time period is above its maximum concentration limit.

[0046] When the second hydrogen buffer tank 140 becomes full, the controller 142 may control the valve assembly 136 to again begin supplying the purified hydrogen stream 126 to the first hydrogen buffer tank 138 during the third period of time. The controller 142 may open the third valve assembly 146 to release the hydrogen in the first hydrogen buffer tank 138 via a first flow path into the hydrogen storage tank 129 if the detected contaminant concentrations during the first time period are all below their respective maximum concentration limits, or via a second flow path to the balance-of-plant 130 if any one of the detected contaminant concentrations during the first time period is above its maximum concentration limit. The controller 142 may thus repeatedly alternate between supplying the purified hydrogen stream to the first hydrogen buffer tank 138 and the second hydrogen buffer tank 140, releasing the hydrogen in the respective buffer tank 138, 140 to the hydrogen storage tank 129 upon receiving a measurement from the hydrogen purity analyzer 134 indicating that contaminant concentrations do not exceed the limits.

[0047] When the hydrogen purity analyzer 134 detects contaminant concentrations in the purified hydrogen stream 126 that exceed the upper limits, the controller 142 may control the-16-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 valve assemblies 136, 144, 146 to divert the purified hydrogen to the balance-of-plant 130. For example, during the first period of time, the controller 142 may control the first valve assembly 136 to supply the purified hydrogen stream 126 to the first hydrogen buffer tank 138. Also during the first period of time, hydrogen purity analyzer 134 may analyze one or more samples of the purified hydrogen stream 126. The controller 142 may maintain the second valve assembly 144 in a closed position until the controller 142 receives the measurement data from the hydrogen purity analyzer 134, thus retaining the purified hydrogen associated with the sample being analyzed in the first hydrogen buffer tank 138. As discussed above, if the hydrogen purity analyzer 134 detects contaminant concentrations in the purified hydrogen stream 126 below the upper limits, the controller 142 may open the second valve assembly 144, allowing the purified hydrogen to flow into the hydrogen storage tank 129. However, if the hydrogen purity analyzer 134 detects contaminant concentrations in the purified hydrogen stream 126 that exceed the upper limits, the controller 142 may control the second valve assembly 144 to release the hydrogen stored in the first hydrogen buffer tank 138 to the balance-of-plant 130.[Q048| At the same time, the controller 142 may control the first valve assembly 136 to begin supplying the purified hydrogen stream 126 to the second hydrogen buffer tank 140, maintaining the third valve assembly 146 in the closed position until another measurement is received from the hydrogen purity analyzer 134. The controller 142 may thus repeatedly alternate between supplying the purified hydrogen stream to the first hydrogen buffer tank 138 and the second hydrogen buffer tank 140, releasing the hydrogen in the respective buffer tank 138, 140 to the balance-of-plant 130 upon receiving a measurement from the hydrogen purity analyzer 134 indicating that contaminant concentrations exceed the limits. The volume of the hydrogen buffer tanks 138, 140 may be determined based on the flow rate of the purified hydrogen stream 126 and the amount of time required for the hydrogen purity analyzer 134 to analyze a sample. The hydrogen buffer tanks 138, 140 may ensure that purified hydrogen having contaminant concentrations that exceed the upper limits do not reach the hydrogen storage tank 129 while the hydrogen purity analyzer 134 is in the process of analyzing the sample. As discussed above with respect to the hydrogen production system 100, the controller 142 may monitor the average-17-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 contaminant concentrations in the purified hydrogen supplied to the hydrogen storage tank 129, and may allow some hydrogen having contaminant concentrations that exceed the limits to be supplied to the hydrogen storage tank 129 as long as the average contaminant concentrations do not exceed the limits when the hydrogen storage tank 129 is completely filled.

[0049] As discussed above, the hydrogen purity analyzer 134 may use FTIR to detect the concentrations of a specific set of contaminants in the purified hydrogen stream 126. For example, the hydrogen purity analyzer 134 may be configured to detect the concentrations of carbon monoxide, carbon dioxide, methane, and water. SAE J2719, a hydrogen fuel quality standard for fuel cell vehicles, includes maximum concentration limits for these four contaminants, in addition to maximum concentration limits for other contaminants including, helium, oxygen, argon, nitrogen, sulfur compounds formaldehyde, formic acid, ammonia, halogenated compounds, and particulates. Because the source of the hydrogen in the hydrogen production system 100 is the anode portion 104 of a molten carbonate fuel cell module 102, certain contaminants are necessarily eliminated or substantially eliminated by process controls upstream of the fuel cell module 102 or simply not present or not present significant amounts in the system 100 (e g., not included in the anode input stream 108 or the cathode input stream 110). For example, sulfur compounds and particulates are removed from the input streams of the fuel cell module 102 before they are input into the fuel cell module 102, as high concentrations of these contaminants would inhibit the fuel cell reactions and cause damage to the fuel cells. In the event that sulfur or sulfur compounds do break through and reach the fuel cell, the sulfur or sulfur compounds may inhibit the reforming reactions in the fuel cells, increasing the temperature in the fuel cell module 102 and triggering temperature alarms to shut down the fuel cell module 102. Thus, sulfur compounds are very unlikely to be present in the anode exhaust stream 112.[0(>50| Other potential contaminants, such as formaldehyde, formic acid, ammonia, and halogenated compounds are not present in the raw material streams and are not introduced at any point in the system, upstream or downstream of the fuel cell module 102. Thus, these components can be presumed to be below their respective maximum concentration limits in the -18-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 purified hydrogen stream 126. As discussed above, nitrogen, argon, and helium may be present in the cathode input stream 110, and, without proper controls may cross over to the anode portion 104 of the fuel cell module 102 through cracks and in the electrolytes of the fuel cells or through imperfect seals. However, by operating the fuel cell module with the anode portion 104 at a higher pressure than the cathode portion 106, any crossover of gases across the electrolyte may be substantially ensured to flow from the anode portion 104 to the cathode portion 106 rather than vice versa. Thus, components of the anode input stream 108 or products of reactions in the anode portion 104 may cross over to the cathode portion 106, but gases in the cathode portion 106 may be substantially prevented from crossing over to the anode portion 104. A controller (e g., controller 142) may control valves upstream or downstream of the fuel cell module 102 to adjust the respective pressures of the anode portion 104 and the cathode portion 106 to ensure that the pressure in the anode portion 104 remains higher than the pressure in the cathode portion 106 during operation. Nitrogen may be used in various additional situations in the hydrogen production system 100, but in each case, process controls ensure that it does not mix with the anode exhaust stream 112 or any of the downstream gas streams between the anode portion 104 and the hydrogen storage system 129. For example, nitrogen may be used as a purge gas when hydrogen production is stopped. In other cases, sensors may be used to detect a loss of pressure indicating a leak of nitrogen and trigger a shutdown of the entire hydrogen production system 100.[0051 J Another set of potential contaminants can be presumed to be below the maximum concentration limits based on the measured concentrations of carbon monoxide, carbon dioxide, water, and methane. For example, the contaminant category listed in the SAE J2719 standard as “Total hydrocarbons except methane (Cl equivalent)” can be presumed to be below the maximum concentration limit if the sum of the concentrations of carbon monoxide, carbon dioxide, and water is below the maximum concentration limit for Total hydrocarbons except methane. Hydrocarbons other than methane (e.g., ethane, propane, and butane) may be present in the natural gas fuel in the anode input stream 108 in small concentrations. However, reforming reactions that occur in the anode portion 104 (and / or upstream of the anode portion-19-4867-2383-6145.1Atty. Dkt. No.: 106876-2267104 in an external reformer), which are fundamental and intrinsic parts of the hydrogen generation process that allow the molten carbonate fuel cells to function by absorbing heat generated in the fuel cell reactions, convert the higher hydrocarbons (e.g., ethane, propane, and butane) to methane, carbon monoxide, carbon dioxide, and water. Due to these reactions, the total concentration of the higher hydrocarbons will necessarily be lower than the total concentration of carbon monoxide, carbon dioxide, and water. Thus, the sum of the concentrations of carbon monoxide, carbon dioxide, and water can be used as a proxy for total hydrocarbons except methane. As another example, if the total of carbon monoxide, water, carbon dioxide, and methane (indicator species) is below the sum of their respective maximum concentration limits, it can be presumed that the total non-hydrogen gases, of which only carbon monoxide, water, carbon dioxide, and methane can be present in the system in substantial quantities, is also below its maximum concentration limit. For example, the maximum concentration limit for total non-hydrogen gases in SAE J2719 is 300 ppm, and the respective maximum concentration limits for carbon monoxide, water, carbon dioxide, and methane are 0.2 ppm, 5.0 ppm, 2.0 ppm, and 100.0 ppm. Thus, if each of these contaminants are at their respective maximum concentration limits, the total will be 107.2 ppm. With total hydrocarbons except methane confirmed to be below the maximum concentration limit of 2 ppm and there being no other significant contaminants, the hydrogen generated can be presumed to be no higher than 109.2 ppm, well below the 300 ppm limit.[00521 In summary, the contaminants listed in the SAE J2719 standard may fall into three categories: 1) those directly measured by the hydrogen purity analyzer 134, 2) those with concentrations that can be presumed to be below the maximum concentration limits based on the measured contaminant concentrations, and 3) those that cannot be present in concentrations exceeding the maximum concentration limits based on their absence from the process or based on upstream process controls.[00531 Referring now to FIG. 3, a purified carbon dioxide production system 300 is shown, according to another exemplary embodiment. The carbon dioxide production system 300 is configured to produce purified carbon dioxide, such as beverage-grade carbon dioxide meeting -20-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 the Compressed Gas Association standard CGA G-6.2-2011. The carbon dioxide production system 300 is substantially similar to the hydrogen production system 100, except as shown and described herein. As discussed above, the anode exhaust stream 112 includes carbon dioxide, water, and hydrogen. Like the hydrogen production system 100, the carbon dioxide production system 300 includes a water separation system 118 that cools the anode exhaust stream 112 to condense water, which is then removed via the water stream 120. The dehumidified anode exhaust stream 122, rather than being supplied to a gas separation system 124 (e.g., a PSA system), is instead supplied to a gas separation system, shown in FIG. 3 as a carbon dioxide separation system 224. The carbon dioxide separation system 224 may be a cryogenic carbon dioxide separation system that pressurizes and cools the dehumidified anode exhaust stream 122 to liquefy the carbon dioxide. The liquefied carbon dioxide is then separated from the hydrogen and most other constituent gases of the dehumidified anode exhaust stream 122. The carbon dioxide separation system 224 may then release the pressure on the liquefied carbon dioxide, which may vaporize and return to the gas phase. The carbon dioxide separation system 224 may then release a gaseous purified carbon dioxide stream 226. The remaining gases, including mainly hydrogen, may be supplied to the balance-of-plant 130 via the hydrogen stream 228.

[0054] The purified carbon dioxide stream 226 may be supplied to the valve assembly 136, while a sample of the purified carbon dioxide stream 226 is supplied to a carbon dioxide purity analyzer 234. Similar to the hydrogen purity analyzer 134, the carbon dioxide purity analyzer 234 may use Fourier transform infrared spectroscopy to measure the concentrations of several contaminants in the purified carbon dioxide stream 226. For example, the carbon dioxide purity analyzer 234 may detect the concentrations of carbon monoxide, methane, and water. The concentrations of the contaminants measured by the carbon dioxide purity analyzer 234 are communicated to the controller 142. Based on the measurements, the controller 142 may control the valve assembly 136 to direct the purified carbon dioxide stream 226 to either a carbon dioxide storage system 229 or to the balance-of-plant 130. Like in the hydrogen production system 100, certain contaminants may be presumed to not be present in the purified carbon dioxide stream 226 due to their correlation to the measured contaminants. Other contaminants-21-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 may be presumed to not be present in concentrations exceeding the maximum contamination limits due to upstream process controls. For example, hydrogen and nitrogen may be presumed to not be present in significant concentrations due to the carbon dioxide liquefaction process in the carbon dioxide separation system 224.

[0055] Similar to the hydrogen production system 100, the controller 142 in the purified carbon dioxide production system 300 may control the valve assembly 136 based on real-time measurements from the carbon dioxide purity analyzer 234. So, for example, if the concentration of one of the contaminants exceeds the maximum concentration limit for that contaminant, the controller 142 may control the valve assembly 136 to direct the purified carbon dioxide stream 226 to the balance-of-plant 130. If all of the measured contaminant concentrations are below their respective maximum concentration limits, the controller 142 may control the valve assembly 136 to direct the purified carbon dioxide stream 226 to the carbon dioxide storage system 229. In other embodiments, rather than supplying the purified carbon dioxide to the carbon dioxide storage system 229, the valve assembly 136 may direct the purified carbon dioxide to another system or may be used immediately rather than being stored. Like in the hydrogen production system 100, the controller 142 may monitor the measured concentrations of the contaminants over a period of time to determine whether the average concentrations of the contaminants during that time period exceed the maximum concentration limits. Thus, if a contaminant concentration exceeds a maximum concentration limit for a brief period of time, the purified carbon dioxide stream may still be supplied to the carbon dioxide storage system 229 as long as the average concentration of that contaminant remains below the maximum concentration limit during the period of time.

[0056] Referring to FIG. 4, a purified carbon dioxide production system 400 is shown, according to some embodiments. The carbon dioxide production system 400 may be substantially similar to the carbon dioxide production system 300, with a pair of carbon dioxide buffer tanks 238, 240 similar to the hydrogen buffer tanks in the hydrogen production system 200. Similar to the hydrogen production system 200, the carbon dioxide production system 400 of FIG. 4 includes a valve assembly 136 controlled by the controller 142 to selectively supply the purified carbon-22-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 dioxide stream 226 to one of the first carbon dioxide buffer tank 238 or the second carbon dioxide buffer tank 240. In some embodiments, a first valve assembly may control the flow of purified carbon dioxide to either the balance-of-plant 130 or the carbon dioxide buffer tanks 238, 240, and a second valve assembly may control the flow of purified carbon dioxide to one of the first carbon dioxide buffer tank 238 or the second carbon dioxide buffer tank 240. The carbon dioxide buffer tanks 238, 240 may temporarily store carbon dioxide to account for any delay in the purity analysis by the carbon dioxide purity analyzer 234. Second and third valve assemblies 144, 146 couple the carbon dioxide buffer tanks 238, 240 to the carbon dioxide storage tank 229. The controller 142 may be configured to control the valve assemblies 144, 146 to selectively supply the carbon dioxide in the buffer tanks 238, 240 to either the carbon dioxide storage tank 229 or the balance-of-plant 130.

[0057] While the carbon dioxide purity analyzer 234 detects contaminant concentrations in the purified carbon dioxide stream 226 below the upper limits, the controller 142 may control the valve assembly 136 to alternate between supplying the purified carbon dioxide stream 226 to the first carbon dioxide buffer tank 238 and the second carbon dioxide buffer tank 240. As the carbon dioxide buffer tanks 238, 240 become full, the controller 142 may open the respective valve assembly 144, 146 to release the carbon dioxide into the carbon dioxide storage tank 229. For example, the controller 142 may control the first valve assembly 136 to begin supplying the purified carbon dioxide stream 226 to the first carbon dioxide buffer tank 238 during a first period of time. When the first carbon dioxide buffer tank 238 becomes full, the controller 142 may control the first valve assembly 136 to begin supplying the purified carbon dioxide stream 226 to the second carbon dioxide buffer tank 240 during a second period of time.

[0058] During the second period of time (or simultaneously with controlling the first valve to begin supplying purified carbon dioxide stream to the second carbon dioxide buffer tank 240), the controller 142 may open the second valve assembly 144 to release the carbon dioxide in the first carbon dioxide buffer tank 238 into the carbon dioxide storage tank 229. When the second carbon dioxide buffer tank 240 becomes full, the controller 142 may control the valve assembly 136 to again begin supplying the purified carbon dioxide stream 226 to the first carbon dioxide-23-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 buffer tank 238 during the third period of time. The controller 142 may open the third valve assembly 146 to release the carbon dioxide in the second carbon dioxide buffer tank 240 into the carbon dioxide storage tank 229. The controller 142 may thus repeatedly alternate between supplying the purified carbon dioxide stream 226 to the first carbon dioxide buffer tank 238 and the second carbon dioxide buffer tank 240, releasing the carbon dioxide in the respective buffer tank 238, 240 to the carbon dioxide storage tank 229 upon receiving a measurement from the carbon dioxide purity analyzer 234 indicating that contaminant concentrations do not exceed the limits.

[0059] If the carbon dioxide purity analyzer 234 detects contaminant concentrations in the purified carbon dioxide stream 226 that exceed the upper limits, the controller 142 may control the valve assemblies 136, 144, 146 to divert the purified carbon dioxide to the balance-of-plant 130. For example, during the first period of time, the controller 142 may control the first valve assembly 136 to supply the purified carbon dioxide stream 226 to the first carbon dioxide buffer tank 238. Also during the first period of time, the carbon dioxide purity analyzer 234 may analyze one or more samples of the purified carbon dioxide stream 226. The controller 142 may maintain the second valve assembly 144 in a closed position until the controller 142 receives the measurement data from the carbon dioxide purity analyzer 234, thus retaining the purified carbon dioxide associated with the sample being analyzed in the first carbon dioxide buffer tank 238.

[0060] As discussed above, if the carbon dioxide purity analyzer 234 detects contaminant concentrations in the purified carbon dioxide stream 226 below the upper limits, the controller 142 may open the second valve assembly 144, allowing the purified carbon dioxide to flow into the carbon dioxide storage tank 229. However, if the carbon dioxide purity analyzer 234 detects contaminant concentrations in the purified carbon dioxide stream 226 that exceed the upper limits, the controller 142 may control the second valve assembly 144 to release the carbon dioxide stored in the first carbon dioxide buffer tank 238 to the balance-of-plant 130. At the same time, the controller 142 may control the first valve assembly 136 to begin supplying the purified carbon dioxide stream 226 to the second carbon dioxide buffer tank 240, maintaining the third valve assembly 146 in the closed position until another measurement is received from the-24-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 carbon dioxide purity analyzer 234. The controller 142 may thus repeatedly alternate between supplying the purified carbon dioxide stream 226 to the first carbon dioxide buffer tank 238 and the second carbon dioxide buffer tank 240, releasing the carbon dioxide in the respective buffer tank 238, 240 to the balance-of-plant 130 upon receiving a measurement from the carbon dioxide purity analyzer 234 indicating that contaminant concentrations exceed the limits.[0061 j The volume of the carbon dioxide buffer tanks 238, 240 may be determined based on the flow rate of the purified carbon dioxide stream 226 and the amount of time required for the carbon dioxide purity analyzer 234 to analyze a sample. The carbon dioxide buffer tanks 238, 240 may ensure that purified carbon dioxide having contaminant concentrations that exceed the upper limits do not reach the carbon dioxide storage tank 229 while the carbon dioxide purity analyzer 234 is in the process of analyzing the sample. As discussed above with respect to the carbon dioxide production system 300 of FIG. 3, the controller 142 may monitor the average contaminant concentrations in the purified carbon dioxide supplied to the carbon dioxide storage tank 229, and may allow some carbon dioxide having contaminant concentrations that exceed the limits to be supplied to the carbon dioxide storage tank 229 as long as the average contaminant concentrations do not exceed the limits when the carbon dioxide storage tank 229 is completely filled.[0062J In some embodiments, a purified gas production system may include components of the hydrogen production system 100 or 200 and components of the carbon dioxide production system 300 or 400. For example, the dehumidified anode exhaust stream 122 may be supplied to a valve assembly configured to selectively supply the dehumidified anode exhaust stream to either a carbon dioxide separation system 224 or a gas separation system 124, depending on whether hydrogen production or carbon dioxide production is desired at a particular time. In some embodiments, both purified carbon dioxide and purified hydrogen may be produced in series. For example, the hydrogen production system 100 may be modified such that the carbon dioxide stream 128 is supplied to a carbon dioxide separation system (e.g., similar to the carbon dioxide separation system 224) rather than to the balance-of-plant 130. The carbon dioxide separation system may then cryogenically separate the carbon dioxide from the other-25-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 components of the carbon dioxide stream 128 to form a purified carbon dioxide stream, analyze the purified carbon dioxide stream to determine whether the contaminants exceed the maximum concentration levels (e.g., using a carbon dioxide purity analyzer 234), and store the purified carbon dioxide in a carbon dioxide storage system (e.g., the carbon dioxide storage system 229). Similarly, the carbon dioxide production system 300 may be modified such that the hydrogen stream 228 is supplied to a pressure swing adsorber system (e.g., similar to the gas separation system 124) rather than to the balance-of-plant 130. The hydrogen separation system may then cryogenically separate the hydrogen from the other components of the hydrogen stream 228 to form a purified hydrogen stream, analyze the purified hydrogen stream to determine whether the contaminants exceed the maximum concentration levels (e.g., using a hydrogen purity analyzer 134), and store the purified hydrogen in a hydrogen storage system (e.g., the hydrogen storage system 129).|0063J Referring now to FIG. 5, a method 500 of producing a purified gas is shown, according to an exemplary embodiment. The method 500 may be performed, for example, with the hydrogen production system 100 or the carbon dioxide production system 300. At operation 502 of the method 500, a gas stream including hydrogen and / or carbon dioxide is generated. For example, the gas stream may be an anode exhaust stream generated by a molten carbonate fuel cell including both hydrogen and carbon dioxide. In other embodiments, the gas stream may be produced by other methods. For example, the gas stream may be a flue gas stream from an industrial burner including carbon dioxide. As another example, the gas stream may be an anode exhaust stream from a solid oxide fuel cell including hydrogen.[0064| At operation 504 of the method 500, water is removed from the gas stream. For example, a gas stream including steam may be compressed and cooled to condense the steam to liquid water, which may then be removed from the gas stream. In some embodiments, the gas stream may not include steam, and the method 500 may not include operation 504. At operation 506 of the method 500, hydrogen or carbon dioxide is separated from the gas stream to form a purified gas stream, for example, a purified hydrogen stream or a purified carbon dioxide stream. In some embodiments, a purified hydrogen stream may be formed by separating hydrogen from -26-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 the gas stream using a gas separation system (e.g., a pressure swing adsorber system). In other embodiments, the purified hydrogen stream may be formed using other methods of separating hydrogen, for example, cryogenic distillation or membrane separation. In some embodiments, a purified carbon dioxide stream may be formed by cooling and compressing the gas stream to liquefy the gaseous carbon dioxide. The liquid carbon dioxide may then be separated from the residual gases in the gas stream. In other embodiments, the purified carbon dioxide stream may be formed using other methods of separating carbon dioxide, for example, adsorption or membrane separation.

[0065] At operation 508 of the method 500, the concentrations of a plurality of contaminants in the purified gas stream are measured. The contaminant concentrations may be measured using FTIR. If the purified gas stream is a purified hydrogen stream, the concentrations of carbon monoxide, carbon dioxide, methane, and water may be measured. If the gas stream generated in operation 502 is an anode exhaust stream from a molten carbonate fuel cell, these contaminants may be representative of any other relevant contaminants that may be present in the purified hydrogen stream. For example, the concentrations of carbon monoxide, carbon dioxide, methane, and water may be representative of the contaminants listed in the SAE J2719 standard for vehicle-grade hydrogen. The other contaminants listed in the SAE J2719 standard may be effectively eliminated by upstream processes and by using the molten carbonate fuel cell to generate the gas stream in operation 502.

[0066] If the purified gas stream is a purified carbon dioxide stream, the concentrations of carbon monoxide, methane, and water may be measured. If the gas stream generated in operation 502 is an anode exhaust stream from a molten carbonate fuel cell, these contaminants may be representative of any other relevant contaminants that may be present in the purified carbon dioxide stream. For example, the concentrations of carbon monoxide, methane, and water may be representative of the contaminants listed in the CGA G-6.2-2011 standard for beverage-grade carbon dioxide. The other contaminants listed in the CGA G-6.2-2011 standard may be effectively eliminated by upstream processes and by using the molten carbonate fuel cell to generate the gas stream in operation 502. In other embodiments where additional-27-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 contaminants can be eliminated, operation 508 may include measuring the concentration of only one contaminant.

[0067] At operation 514 of the method 500, the purified gas stream is supplied to one of a first flow path or a second flow path based on the contaminant concentrations measured in operation 508. For example, the purified gas stream may be supplied via the first flow path to a gas storage system for later use while the measured contaminant concentrations measured in operation 508 remain below maximum concentration limits. If the measured contaminant concentrations exceed the maximum concentration limits, the purified gas stream may instead be supplied via a second flow path to a balance-of-plant, where it may be used for other purposes, or it may be recycled and purified a second time. The contaminant concentration measurements taken in operation 508 may be taken substantially in real-time, such that the purified gas stream can be supplied to the first flow path to a storage system based on the measurements, rather than supplying the purified gas stream to a gas storage system first, then later measuring the contaminant concentrations.

[0068] The method 500 may not include all of the operations shown in FIG. 5. For example, in some embodiments, the method 500 may not include the water removal operation 504. The method 500 may include additional operations not shown in FIG. 5. For example, the method may include storing the purified gas supplied to the first flow path or burning the purified gas supplied to the second flow path. The method 500 may further include monitoring the average contaminant concentrations over a period of time such that the purified gas stream may be supplied to one of the first or second flow paths in operation 514 based on the average contaminant concentrations over the period of time. For example, if a contaminant concentration exceeds its maximum concentration limit for a portion of the period of time, but the average concentration of that contaminant over the entire period of time is below the maximum concentration limit, the purified gas may still be supplied via the first flow path to the purified gas storage system, as the average concentration in the storage system will still be below the maximum concentration limit.-28-4867-2383-6145.1Atty. Dkt. No.: 106876-2267[0069| Referring now to FIG. 6, a method 600 of producing a purified gas is shown, according to an exemplary embodiment. The method 600 may be performed, for example, with the hydrogen production system 200 or the carbon dioxide production system 400. The method 600 is substantially the same as the method 500, except as shown and described herein. For example, as shown in FIG. 6, the method 600 includes operations 502, 504, 506, 508, and 514. However, the method 600 also includes operations 510 and 512, in which the purified gas stream is supplied to a first buffer tank or a second buffer tank before being supplied to the first flow path or the second flow path.

[0070] At operation 510 of the method 600, the purified gas stream is supplied to a first buffer tank during a first time period while the contaminant concentrations are being measured (e.g., in operation 508). The contaminant concentrations may be measured one or more times during the first time period while the purified gas stream is being supplied to the first buffer tank. If the contaminant concentrations are measured more than one time during the first time period, the measurements may be averaged to determine the average concentrations of the contaminants in the buffer tank. At operation 512 of the method 500, the purified gas stream is supplied to a second buffer tank during a second time period while the contaminant concentrations are being measured (e.g., in operation 508). The second time period may be subsequent to the first time period. For example, the purified gas stream may be supplied to the first buffer tank while the contaminant concentrations are being measured in the first time period; then, the second time period may begin, and the purified gas stream may be supplied to the second buffer tank while new measurements for the contaminants are taken.

[0071] In operation 514 of the method 600, the first and second buffer tanks may release the purified gas stored therein to the first or second flow path based on the contaminant concentrations measured in the first and second time periods, respectively. For example, the purified gas stream may be supplied to the first buffer tank during the first time period (operation 510) while the concentrations of the contaminants are being measured (operation 508). Then, at the beginning of the second time period, the purified gas stream may begin to be supplied to the second buffer tank (operation 512). If the contaminant concentrations or average contaminant -29-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 concentrations measured in the first time period are all below their respective maximum concentration limits, in operation 514, the purified gas stored in the first buffer tank may be supplied to the first flow path, which may lead to a gas storage system. If the contaminant concentration or average contaminant concentration measured in the first time period for any one of the measured contaminants is above the maximum concentration limit, in operation 514, the purified gas stored in the first buffer tank may be supplied to the second flow path, which leads somewhere other than the purified gas storage system. Thus, while the purified gas stream is being supplied to the second buffer tank during the second time period, the first buffer tank may release the purified gas stored therein to the first flow path or the second flow path. At the end of the second time period, a third time period may begin that is substantially the same as the first time period, with the purified gas again being supplied to the first buffer tank. During the third time period, the second buffer tank may release the purified gas stored therein to either the first flow path or the second flow path based on the contaminant concentrations or average contaminant concentrations measured during the second time period. The method 600 may continue (repeat, etc.) indefinitely, with the purified gas stream being altematingly supplied to the first buffer tank and the second buffer tank while purified gas is altematingly being released from the opposite buffer tank.[0072J The method 600 may further include monitoring the average contaminant concentrations over multiple time periods (e.g., the first time period and the second time period discussed above) such that the purified gas stream may be supplied to one of the first or second flow paths in operation 514 based on the average contaminant concentrations over the multiple time periods. For example, if a contaminant concentration exceeds its maximum concentration limit during the second time period, but the average concentration of that contaminant over both the first and second time periods is below the maximum concentration limit, the second buffer tank may still release the purified gas via the first flow path to the purified gas storage system, as the average concentration in the storage system will still be below the maximum concentration limit. Like the method 500, the method 600 may not include all of the operations shown in FIG. 6. For example, in some embodiments, the method 500 may not include the water removal operation-30-4867-2383-6145.1Atty. Dkt. No.: 106876-2267504. The method 500 may include additional operations not shown in FIG. 5. For example, the method may include storing the purified gas supplied to the first flow path or burning (combusting, etc.) the purified gas supplied to the second flow path.

[0073] As utilized herein, the terms “approximately,” “about,” “substantially”, and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims.[0074J The terms “coupled,” “connected,” and the like as used herein mean the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.

[0075] References herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below,” etc.) are merely used to describe the orientation of various elements in the Figures. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.[0076| The hardware and data processing components used to implement the various processes, operations, illustrative logics, logical blocks, modules and circuits described in connection with the embodiments disclosed herein (e.g., the controller 142) may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an-31-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or, any conventional processor, or state machine. A processor also may be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, the one or more processors may be shared by multiple circuits (e.g., the controller may include or otherwise share the same processor which, in some example embodiments, may execute instructions stored, or otherwise accessed, via different areas of memory). Alternatively or additionally, the one or more processors may be structured to perform or otherwise execute certain operations independent of one or more co-processors. In other example embodiments, two or more processors may be coupled via a bus to enable independent, parallel, pipelined, or multi-threaded instruction execution. All such variations are intended to fall within the scope of the present disclosure.[0077J The memory device (e g., memory, memory unit, storage device) may include one or more devices (e.g., RAM, ROM, Flash memory, hard disk storage) for storing data and / or computer code for completing or facilitating the various processes, layers and modules described in the present disclosure. The memory device may be communicably connected to the processor to provide computer code or instructions to the processor for executing at least some of the processes described herein. Moreover, the memory device may be or include tangible, nontransient volatile memory or non-volatile memory. Accordingly, the memory device may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described herein.[0078| It is important to note that the construction and arrangement of the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate -32-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process or method steps may be varied or resequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may also be made in the design, operating conditions, and arrangement of the various exemplary embodiments without departing from the scope of the present invention.4867-2383-6145.1

Claims

Atty. Dkt. No.: 106876-2267WHAT IS CLAIMED IS:

1. A purified gas production system comprising: a molten carbonate fuel cell configured to output an anode exhaust stream comprising hydrogen and carbon dioxide; a gas separation system configured to receive the anode exhaust stream and to output a purified gas stream comprising one of purified hydrogen or purified carbon dioxide; a gas purity analyzer configured to detect concentrations of a plurality of contaminants in the purified gas stream using Fourier Transform Infrared Spectroscopy; a valve assembly configured to selectively direct the purified gas stream toward one of a first flow path or a second flow path; and a controller communicably coupled to the gas purity analyzer and the valve assembly and configured to control the valve assembly based on the detected concentrations of the plurality of contaminants.

2. The purified gas production system of claim 1, further comprising a water separation system configured to remove water from the anode exhaust stream before the anode exhaust stream is received by the gas separation system.

3. The purified gas production system of claim 1, wherein the controller is configured to cause the valve assembly to direct the purified gas stream toward the first flow path when each of the concentrations of the plurality of contaminants is below a respective maximum concentration.

4. The purified gas production system of claim 3, wherein the controller is configured to cause the valve assembly to direct the purified gas stream toward the second flow path when any one of the concentrations of the plurality of contaminants is above the respective maximum concentration.-34-4867-2383-6145.1Atty. Dkt. No.: 106876-22675. The purified gas production system of claim 1, wherein the controller is configured to monitor an average concentration of each of the plurality of contaminants over a predetermined time period, wherein the controller is configured to cause the valve assembly to direct the purified gas stream toward the first flow path while the average concentration of each of the plurality of contaminants is below a respective maximum concentration during the time period.

6. The purified gas production system of claim 5, wherein the controller is configured to cause the valve assembly to direct the purified gas stream toward the second flow path when any one of the average concentrations of the plurality of contaminants is above the respective maximum concentration.

7. The purified gas production system of any one of claims 1-6, wherein the gas separation system is a pressure swing adsorption system, and the purified gas stream is a purified hydrogen stream.

8. The purified gas production system of claim 7, wherein the plurality of contaminants detected by the gas purity analyzer comprises carbon monoxide, carbon dioxide, methane, and water.

9. The purified gas production system of claim 8, wherein the controller is configured to determine whether the concentration of total hydrocarbons other than methane exceeds a predetermined limit based on the detected concentrations of only carbon monoxide, carbon dioxide, and water, wherein controlling the valve assembly is further based on the determination.

10. The purified gas production system of claim 8, wherein the controller is configured to determine whether the concentration of total non-hydrogen gases exceeds a predetermined limit based on the detected concentrations of only carbon monoxide, carbon dioxide, methane, and water, wherein controlling the valve assembly is further based on the determination.-35-4867-2383-6145.1Atty. Dkt. No.: 106876-226711. The purified gas production system of any one of claims 1-6, wherein the gas separation system is a carbon dioxide separation system, and the purified gas stream is a purified carbon dioxide stream.

12. The purified gas production system of claim 11, wherein the plurality of contaminants detected by the gas purity analyzer comprises carbon monoxide, water, and methane.

13. The purified gas production system of claim 11, wherein the carbon dioxide separation system is configured to compress, cool, and liquefy carbon dioxide to separate the carbon dioxide from the anode exhaust stream and then vaporize the separated carbon dioxide to form the purified carbon dioxide stream.

14. A purified gas production system comprising: a gas purity analyzer configured to detect concentrations of a plurality of contaminants in a purified gas stream using Fourier transform infrared spectroscopy; a first gas buffer tank to temporarily store purified gas from the purified gas stream; a second gas buffer tank to temporarily store purified gas from the purified gas stream; a first valve assembly configured to selectively direct the purified gas stream toward one of the first gas buffer tank or the second gas buffer tank; a second valve assembly configured to selectively direct purified gas from the first gas buffer tank toward one of a first flow path or a second flow path; a third valve assembly configured to selectively direct purified gas from the second gas buffer tank toward one of the first flow path or the second flow path; and a controller communicably coupled to the gas purity analyzer, the first valve assembly, the second valve assembly, and the third valve assembly and configured to: control the first valve assembly to direct the purified gas stream to the first gas buffer tank during a first time period;-36-4867-2383-6145.1Atty. Dkt. No.: 106876-2267 control the first valve assembly to direct the purified gas stream to the second gas buffer tank during a second time period subsequent to the first time period; control the second valve assembly based on the detected concentrations of the plurality of contaminants in the purified gas stream during the first time period; and control the third valve assembly based on the detected concentrations of the plurality of contaminants in the purified gas stream during the second time period.

15. The purified gas production system of claim 14, further comprising: a molten carbonate fuel cell configured to receive an anode input stream comprising methane and to output an anode exhaust stream comprising hydrogen and carbon dioxide; and a gas separation system configured to receive the anode exhaust stream and to output the purified gas stream, the purified gas stream comprising one of purified hydrogen or purified carbon dioxide.

16. The purified gas production system of claim 15, further comprising a water separation system configured to remove water from the anode exhaust stream before the anode exhaust stream is received by the gas separation system.

17. The purified gas production system of claim 14, wherein the controller is configured to cause the second valve assembly or the third valve assembly to direct the purified gas stream toward the first flow path when each of the concentrations of the plurality of contaminants is below a respective maximum concentration.

18. The purified gas production system of claim 17, wherein the controller is configured to cause the second valve assembly or the third valve assembly to direct the purified gas stream toward the second flow path when any one of the concentrations of the plurality of contaminants is above the respective maximum concentration.-37-4867-2383-6145.1Atty. Dkt. No.: 106876-226719. The purified gas production system of either one of claims 15 or 16, wherein the gas separation system is a pressure swing adsorption system, and the purified gas stream is a purified hydrogen stream.

20. The purified gas production system of claim 19, wherein the plurality of contaminants detected by the gas purity analyzer comprises carbon monoxide, carbon dioxide, methane, and water.

21. The purified gas production system of either one of claims 15 or 16, wherein the gas separation system is a carbon dioxide separation system, and the purified gas stream is a purified carbon dioxide stream.

22. The purified gas production system of claim 21, wherein the plurality of contaminants detected by the gas purity analyzer comprises carbon monoxide, water, and methane.

23. The purified gas production system of claim 21, wherein the carbon dioxide separation system is configured to compress, cool, and liquefy carbon dioxide to separate the carbon dioxide from the anode exhaust stream and then vaporize the separated carbon dioxide to form the purified carbon dioxide stream.

24. A method of producing a purified gas stream, the method comprising: generating a gas stream; separating hydrogen or carbon dioxide from the gas stream to form a purified gas stream; measuring concentrations of a plurality of contaminants in the purified gas stream using Fourier Transform Infrared Spectroscopy; and supplying the purified gas stream to one of a first flow path or a second flow path based on the measured concentrations.-38-4867-2383-6145.1Atty. Dkt. No.: 106876-226725. The method of claim 24, wherein generating the gas stream comprises generating an anode exhaust stream from a molten carbonate fuel cell.

26. The method of claim 25, further comprising removing water from the anode exhaust stream.

27. The method of claim 24 further comprising supplying the purified gas stream to a first buffer tank during a first time period, wherein supplying the purified gas stream toward one of the first flow path or the second flow path comprises supplying the purified gas in the first buffer tank to one of the first flow path or the second flow path based on average concentrations of the plurality of contaminants during the first time period.

28. The method of claim 27, further comprising supplying the purified gas stream to a second buffer tank during a second time period, wherein supplying the purified gas stream toward one of the first flow path or the second flow path comprises supplying the purified gas in the second buffer tank toward one of the first flow path or the second flow path based on average concentrations of the plurality of contaminants during the second time period.

29. The method of claim 26, wherein the concentrations of the plurality of contaminants are measured before the purified gas stream is supplied to a purified gas storage system.

30. The method of any one of claims 24-29, wherein separating hydrogen or carbon dioxide from the gas stream comprises separating hydrogen from the gas stream using a pressure swing adsorption system such that the purified gas stream is a purified hydrogen stream.

31. The method of any one of claims 24-29, wherein separating hydrogen or carbon dioxide from the gas stream comprises cooling and compressing the gas stream to liquefy carbon dioxide and vaporizing the liquefied carbon dioxide such that the purified gas stream is a purified carbon dioxide stream.-39-4867-2383-6145.1

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