Systems and methods for processing ammonia and starting a fuel cell

Abstract

The present disclosure provides systems and methods for processing ammonia (NH3). A heater may heat reformers and NH3 reforming catalysts therein. NH3 may be directed to the reformers from storage tanks, and the NH3 may be decomposed or cracked to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2). At least part of the reformate stream may be burned in combustors to heat the reformers. Before the reformate stream is burned in the combustors, a mixture of hydrogen and nitrogen may be used as a heat transfer gas to heat up the reformers. An exhaust valve may be used to vent part of the reformate stream or heat transfer gas before directing at least part of the reformate stream to a fuel cell, thereby preventing the overheating of the combustors or reformers.

Description

SYSTEMS AND METHODS FOR PROCESSING AMMONIAAND STARTING A FUEL CELLCROSS-REFERENCE

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 639,467, filed April 26, 2024, which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] Various embodiments of this disclosure relate generally to systems and methods for reforming ammonia to produce a reformate stream that can be processed in a fuel cell.BACKGROUND

[0003] Ammonia can be reformed (e.g., decomposed or dissociated) into a reformate containing hydrogen gas and nitrogen gas, for example, by contacting the ammonia with a catalyst in a reformer. Part of the reformate can be provided to a fuel cell to generate electricity, and another part of the reformate can be burned in a combustor to heat the reformer (in a self- sustaining, autothermal process).

[0004] In conventional systems, before the fuel cell is turned on, all of the reformate is combusted to heat the reformer as the flow rate of ammonia to the reformer is increased to a target ammonia flow rate. The combustion may operate with a relatively high air-fuel equivalence ratio (e.g., lambda of 4-5), and air flow can be used to control the reformer temperature to avoid overheating the reformer (for example, by diluting the combustion).

[0005] Several problems occur during fuel cell startup in a conventional system. First, even though the flow rate of the feed ammonia is fixed at the target ammonia flow rate, reformate fuel consumption in the combustor can drop suddenly from 100% to, for example, 50%, 40%, 30%, etc., after the fuel cell starts consuming the reformate. To avoid reducing the temperature of the reformer, which can depress the ammonia conversion rate, air flow can be rapidly reduced to a lambda of around 1.1 to 1.5. Pressure drops in the reformer as the feed ammonia valve takes time to restrict (due to reduced reformate flow to the combustor). These sudden changes in temperature and pressure can damage the walls of the reactor vessels over time, which may result in dangerous situations such as sudden fractures.

[0006] Additionally, during fuel cell startup in a conventional system, process control may need to switch from a scheme based on flow rate control to one based on pressure control. Before the fuel cell is turned on, the quantity of feed ammonia supplied to the reformer may bemeasured and controlled based on flow rate. Because conventional fuel cells rely on pressurebased control schemes to maintain a target pressure differential ratio between the anode and the cathode, during startup and operation of the fuel cell, the quantity of reformate supplied to the fuel cell anode is measured and controlled based on pressure, however, such methods can be complex and difficult to implement.

[0007] These problems are solved by various embodiments of the systems and methods described below.SUMMARY

[0008] It may be desirable to rely on flow rate-based control before fuel cell startup, such that the quantity of feed ammonia supplied to the reformer is measured and controlled based on flow rate rather than pressure, which may simplify and improve the operation of conventional systems. For example, to avoid the sudden changes in temperature and pressure described above, a large portion of the reformate may be vented before turning on the fuel cell (for example, 60% or 70% of the reformate) and the rest of the reformate may be combusted in a combustion heater (for example, 30% of the reformate). The reformate may be vented at a point along a fuel line upstream of the combustion heater (known as a trim fuel line). This venting avoids the need to dilute the combustion heater with air to reduce the temperature of the combustion heater, and therefore enables using a lower air-fuel equivalence ratio (for example, 1.0 to 1.5 with venting instead of 4.0 to 5.0 without venting) and a smaller air supply unit footprint (e.g., smaller by physical volume and electrical power consumption). Additionally, venting hydrogen upstream of the combustion heater before initiating combustion may avoid venting a mixture of hydrogen and oxygen through the combustion heater in the case of a failed ignition, which can be dangerous due to the flammability of the mixture.

[0009] To start the fuel cell in various embodiments of the systems disclosed herein, reformate is redirected from the exhaust valve to the fuel cell. After the fuel cell starts, the amount of reformate vented through the exhaust valve may decrease as the hydrogen utilization rate of the fuel cell increases. When the fuel cell reaches or exceeds a target hydrogen utilization rate, the exhaust valve may be fully closed by controlling the exhaust valve. For example, the exhaust valve may be turned off once the fuel cell consumes 75% of the hydrogen in the part of the reformate provided to the fuel cell, in a pass from the anode inlet to the anode outlet of the fuel cell.

[0010] In this way, the percentage of the reformate combusted (as well as the air-fuel equivalence ratio) before the fuel cell starts is maintained to be about the same as after the fuel cell starts. For example, the combustion may be maintained at about 30% of the reformate andthe air-fuel equivalence ratio may be maintained at between about 1.1 and 1.5, thereby preventing damage to the combustion heater or reformer that may be caused by large swings in temperature and pressure.

[0011] Additionally, by venting hydrogen before starting the fuel cell, a flow of feed ammonia and reformate may be maintained and static pressure may be prevented, thereby maintaining flow control and avoiding pressure control before starting the fuel cell.

[0012] Additionally, by venting hydrogen downstream of the anode exhaust, a consistent delivery of feed ammonia to the reformer may be maintained during the transition to fuel cell operation. Otherwise, if all of the anode exhaust is directed to the combustion heater, a relatively higher air-fuel equivalence ratio may be required to fully combust hydrogen and prevent overheating of the reformer. Venting downstream of the anode exhaust enables 30% of the reformate to be burned in the combustion heater during the initialization period of the fuel cell. Once the fuel cell reaches a target hydrogen utilization rate, the trim fuel flow reduces and NH3 flow reduces slightly to maintain constant reformate fuel to the combustion heater and constant pressure upstream of the fuel cell.

[0013] In one aspect, the present disclosure is directed to a method comprising the following steps: (a) reforming ammonia in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2); (b) combusting a first portion of the reformate stream in at least one combustion heater; (c) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater; (d) controlling the first valve to decrease a percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining a percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a fuel cell comprising an anode and a cathode; (e) processing the at least part of the second portion in the fuel cell at a hydrogen utilization rate; and (f) increasing the hydrogen utilization rate of the fuel cell, wherein the percentage of the reformate stream directed to the exhaust vent as the second portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the first valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the second portion as the hydrogen utilization rate increases.

[0014] In some embodiments, the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9% of the second portion. In some embodiments, the threshold hydrogen utilization rate is about 75%.

[0015] In some embodiments, an air-fuel equivalence ratio (X) of the combustion occurring in step (b) is greater than about 1.0 and less than about 1.5, wherein the method further comprises substantially maintaining the air-fuel equivalence ratio (X) after initiating step (d).

[0016] In some embodiments, the percentage of the reformate stream combusted as the first portion is greater than about 15% and less than about 60% of the reformate stream. In some embodiments, the percentage of the reformate stream combusted as the first portion is about 30% of the reformate stream.

[0017] In some embodiments, in step (c), the percentage of the reformate stream directed to the exhaust vent as the second portion is greater than about 40% and less than about 85% of the reformate stream.

[0018] In another aspect, the present disclosure is directed to a method comprising the following steps: (a) reforming ammonia in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2); (b) combusting a first portion of the reformate stream in at least one combustion heater; (c) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater; (d) controlling the first valve to decrease a percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining a percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a fuel cell comprising an anode and a cathode; (e) processing the at least part of the second portion in the fuel cell at a hydrogen utilization rate; (f) controlling a second valve to direct a remaining portion of the reformate stream to the exhaust vent, wherein the remaining portion comprises the percentage of the at least part of the second portion not processed by the fuel cell, wherein the second valve is positioned downstream of the fuel cell anode; and (g) increasing the hydrogen utilization rate of the fuel cell, wherein the percentage of the reformate stream directed to the exhaust vent as the remaining portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the second valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the remaining portion as the hydrogen utilization rate increases.

[0019] In another aspect, the present disclosure is directed to a method comprising the following steps: (a) reforming ammonia in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2); (b) combusting a first portion of the reformate stream in at least one combustion heater; (c) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the firstvalve is positioned upstream of the at least one combustion heater; (d) controlling the first valve to decrease a percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining a percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a fuel cell comprising an anode and a cathode; (e) processing the at least part of the second portion in the fuel cell at a hydrogen utilization rate; (f) controlling a second valve to direct a siphoned portion of the reformate stream to the exhaust vent, wherein the siphoned portion comprises a percentage of the at least part of the second portion that is directed upstream of the fuel cell anode, wherein the second valve is positioned upstream of the fuel cell anode; and (g) increasing the hydrogen utilization rate of the fuel cell, wherein the percentage of the reformate stream directed to the exhaust vent as the siphoned portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the second valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the siphoned portion as the hydrogen utilization rate increases.

[0020] In another aspect, the present disclosure is directed to a method comprising the following steps: (a) passing a gas through an electric heater to heat the gas to a temperature greater than about 400° C and less than about 900° C; (b) passing the heated gas through a reactor comprising an ammonia-reforming catalyst to heat the catalyst; and (c) passing the heated gas through a recirculation line in fluid communication with the electric heater; and (d) repeating steps (a), (b), and (c) until the catalyst is heated to a temperature greater than about 400° C and less than about 900° C.

[0021] In some embodiments, a ratio of hydrogen to nitrogen in the gas is about 3:1. In some embodiments, the method further comprises the step of combusting the gas in a combustion heater in thermal communication with the reactor.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. Methods and materials are described herein for use in the present application; other suitable methods and materials known in the art can also be used. The materials, methods, and examples are illustrative only and not intended to be limiting. Other features and advantages of the present application will be apparent from the following detailed description and figures, and from the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 schematically shows a system in accordance with various embodiments of the present disclosure.

[0024] FIG. 2 is a flowchart illustrating a process for starting the fuel cell of the system schematically shown in FIG. 1 in accordance with various embodiments of the present disclosure.

[0025] FIG. 3 schematically shows a system in accordance with various embodiments of the present disclosure.

[0026] FIG. 4 is a flowchart illustrating a process for starting the fuel cell of the system schematically shown in FIG. 1, in accordance with various embodiments of the present disclosure.

[0027] FIG. 5 schematically shows a system in accordance with various embodiments of the present disclosure.

[0028] FIG. 6 schematically shows a system in accordance with various embodiments of the present disclosure.

[0029] FIG. 7 schematically shows a system in accordance with various embodiments of the present disclosure.

[0030] FIG. 8 is a flowchart illustrating a process for heating the reformers of the systems schematically shown in FIGS. 1, 3, and 5-7, in accordance with various embodiments of the present disclosure.DETAILED DESCRIPTION

[0031] While various embodiments of the methods and systems have been shown and described herein, it will be understood by those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions, including various combinations and subcombinations, may occur to those skilled in the art without departing from this disclosure. It should be understood that various alternatives to the embodiments of the methods and systems described herein may be employed. It should be understood that any of the embodiments, configurations and / or components described with respect to a particular figure may be combined with other embodiments, configurations, and / or components described with respect to other figures.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments.

[0033] As used herein, the singular forms “a,” “an” and “the” include plural references unless the context clearly indicates or dictates otherwise. For example, “a,” “an,” and “the” may be construed to mean “one or more.”

[0034] Any range described in the present disclosure may also describe subrange(s) within the range. For example, a range described as “greater than about 10% and less than about 90%” may also describe “greater than about 20% and less than about 80%, ” and “greater than about 30% and less than about 70%. ”

[0035] As used herein, the terms “reform ammonia,” “decompose ammonia,” “dissociate ammonia,” “crack ammonia,” “dehydrogenate ammonia,” and their grammatical variations may be construed or used interchangeably, and refer to the conversion of ammonia (NH3) to hydrogen (H2) and nitrogen (N2) by way of the following endothermic reaction: 2NH3 — > N2 + 3H2.

[0036] As used herein, the terms “reformer” and “reformers” mean a vessel or unit configured for one or more of reforming, dehydrogenation, cracking, catalytic reforming, or autothermal reforming of ammonia or any other material capable of being reformed to generate at least hydrogen (H2), such as methanol or methane.

[0037] As used herein, the terms “reformate” and “reformate stream” may be used interchangeably to refer to any mixture comprising hydrogen (H2) and nitrogen (N2) that is a product of the endothermic reaction that converts ammonia (NH3) to hydrogen (H2) and nitrogen (N2). The reformate or reformate stream may also include water.

[0038] As used herein, the terms “catalyst” and “catalysts” refer to a material that promotes a chemical reaction (i.e., increases the rate of reaction by decreasing the activation energy of the reaction) without being consumed in the reaction. The term “catalyst” includes a material or materials capable of promoting the following endothermic reaction: 2NH3 — > N2 + 3H2.

[0039] As used herein, the terms “valve” and “valves” refer to one or more flow-control devices by which the flow of fluids can be started, stopped, or regulated by partially or wholly obstructing or limiting the fluid flow across or through one or more flow paths. For example, and without limitation, valves may be on / off valves, variable valves, solenoid valves, proportional valves, two-way valves, three-way valves, four-way valves, or valves associated with any other number of flow paths.

[0040] As used herein, the terms “control,” “controls,” “controlled,” and “controlling” with respect to a valve or valves refer to opening, closing, partially opening, partially closing, turning on, turning off, or adjusting or regulating flow or pressure of fluids through one or morevalves, as well as any other action that affects the flow of fluids through one or more valves. A valve may be controlled manually or automatically.

[0041] As used herein, the terms “vent” or “exhaust vent” may refer to an opening or port anywhere along a flow path that allows a fluid moving along the flow path to pass through into an open space (such as the atmosphere or surrounding environment) or a closed space (such as a storage vessel or tank).

[0042] As used herein, the terms “upstream” and “downstream” refer to the intended flow direction of a fluid or the location of a component within a system relative to another component in the system based on the intended flow direction of a fluid between the components. As an example, for a fluid that flows through component A, then to component B, then to component C, and then to component D, in that order (i.e., A a B a C a D), the component B is upstream of the component C, and the component D is downstream of the component C.

[0043] As used herein, the term “hydrogen utilization rate” with respect to a fuel cell means the percentage of hydrogen (e.g., mole percent or volume percent) that is processed, consumed, or reacted in the fuel cell anode, in a pass from the anode inlet to the anode outlet, without taking into account any recycled anode exhaust stream. The hydrogen utilization rate may be calculated as follows: (the amount of hydrogen consumed by the fuel cell / the total amount of hydrogen provided to the fuel cell) x 100. For example, a hydrogen utilization rate of 75% means that 75% of the hydrogen provided to the fuel cell is processed, consumed, or reacted by the fuel cell.

[0044] As used herein, the term “threshold hydrogen utilization rate” means the hydrogen utilization rate that when reached or exceeded results in a predetermined action (for example, stopping the directing of hydrogen to an exhaust vent) and / or condition (e.g., 0% of the hydrogen being directed to the exhaust vent).

[0045] As used herein, the terms “air-fuel equivalence ratio,” “lambda,” or “A” refers to the relative stoichiometric ratio of air (or another oxygen-containing gas) to fuel. For example, A = 1.0 represents a stoichiometric mixture of air and fuel, A < 1.0 represents a richer mixture, and A > 1.0 represents a leaner mixture.

[0046] As used herein, the term “in fluid communication” means connected by one or more conduits, manifolds, valves, flow paths, fluid lines and the like for the transfer of fluid. A component such as a pump or a compressor may be present between a first component in fluid communication with a second component unless explicitly stated otherwise.

[0047] As used herein, the term “in thermal communication” refers to a configuration of two or more components or systems being in relatively close proximity to each other or in contact with each other such that heat can be directly or indirectly transferred between the components or systems.

[0048] Directional terms may be used herein (e.g., upper, lower, top, bottom, left, right). These directional terms are merely intended to assist in describing components or features of various embodiments described herein and are not intended to limit the various embodiments in any way.

[0049] FIG. 1 schematically shows a system 100, in accordance with various embodiments of the present disclosure, that may comprise an ammonia (NH3) storage vessel 101a, a nitrogen storage vessel 101b, a hydrogen storage vessel 101c, an electric heater 115, a heat transfer device 106, one or more reformers 108, one or more combustion heaters 109, a temperature swing adsorption (TSA) system 122, a TSA heat transfer device 130, a separation device 180, a fuel cell 124, an exhaust vent 170, an exhaust valve 172, and valves 105a-105f. Any pair of the valves 105a-105f may instead be replaced by a three-way valve to achieve a similar functionality of dividing fluid streams.

[0050] The NH3 storage vessel 101a may be configured to store NH3 under pressure (e.g., 7- 25 barg) and / or at a low temperature (e.g., about -30 °C). The NH3 storage vessel 101a may comprise a metallic material that is resistant to corrosion by ammonia (e.g., steel). The NH3 storage vessel 101a may comprise one or more insulating layers (e.g., perlite or glass wool). An additional heater may be positioned adjacent to, on, or inside the NH3 storage vessel 101a to heat and / or pressurize the NH3 stored therein. In some cases, the ammonia is anhydrous ammonia (e.g., >99.9% ammonia by mole). In some cases, contaminants (e.g., <1% each of water or oil) may be contained in the NH3 storage vessel 101a. Industrial ammonia, for example, may be contaminated with water, so the NH3 storage vessel 101a may also include an amount of water as a contaminant when filled with industrial ammonia. In some cases, contaminants in the NH3 storage vessel 101a may accumulate over time (for example, water may accumulate due to the polarity / hygroscopicity of ammonia). During operation, the NH3 storage vessel 101a provides an NH3 stream 104 (for example, by controlling a valve) to be reformed in the reform er(s) 108.

[0051] The heat transfer device 106 may be configured to cool the reformate stream 120, and may comprise, for example, a chiller and / or one or more heat exchangers. In some cases, the heat transfer device 106 may be a heat exchanger that is configured to transfer heat from a reformate stream 120, which may be relatively warm at a temperature > 400 °C, output by thereformer(s) 108 to the ammonia stream 104, which may be relatively cold at a temperature < 100 °C. In some cases, the heat transfer device 106 is a heat exchanger that transfers heat from the reformate stream 120 to air, water or a gly col-containing solution to cool the reformate stream 120. The heat transfer device 106 may be a plate heat exchanger, a shell-and-tube heat exchanger, or a tube-in-tube heat exchanger, although the present disclosure is not limited thereto.

[0052] The reform er(s) 108 may be configured to generate and output the reformate stream 120, which may include a ratio of H2 to N2 of about 3 : 1 at a relatively high ammonia conversion rate (e.g., >90% and preferably >99% or >99.9%). The reformate stream 120 may be generated by contacting the ammonia stream 104 with a catalyst in the reform er(s) 108. The catalyst may comprise an active metal such as ruthenium or nickel, a support material such as alumina or zirconia, and additional materials such as potassium, lanthanum, or cerium. The reformer(s) 108 and the catalyst therein may be heated to a sufficient target temperature in a target temperature range to facilitate catalytic ammonia reforming (for example, a temperature from about 400 °C to about 650 °C) using a startup heating method (for example, the startup heating method described with respect to FIG. 8). The temperature of the reformer(s) 108 and / or catalyst may be measured, for example, by positioning temperature sensor(s) (e.g., thermocouples) adjacent to the reformer(s) 108 and / or the catalyst, or by positioning temperature sensor(s) at an exhaust outlet of the combustion heater(s) 109 or at a reformate outlet of the reform er(s) 108.

[0053] The reformer(s) 108 may comprise a plurality of reformers, which may be in fluid communication in various series and / or parallel arrangements. The reform er(s) 108 may have a cylindrical or rectangular-cuboid shape and may be constructed of a metallic material (e.g., steel) and / or ceramic material (e.g., silicon carbide or alumina). In some cases, a reformer 108 may comprise a vessel with a single chamber containing catalyst therein. In some cases, a reformer 108 may comprise a vessel with multiple chambers, and at least one of the chambers may contain catalyst therein. In some cases, the reformer(s) 108 comprise a single vessel having multiple reaction tubes, with each of the reaction tubes having catalyst therein. In some cases, the reformer(s) 108 may be affixable or attachable to the combustion heater(s) 109 using a flange plate, screws, nuts, and / or bolts. The combustion heater(s) 109 may be in thermal communication with the reform er(s) 108 to heat, for example, the catalyst in the reformer(s) 108. The combustion heater(s) 109 may react part of the reformate stream 120 (e.g., the hydrogen in trim fuel stream 120d) with an air stream 118 (e.g., a gas containing at least oxygen (O2)). The combustion heater(s) 109 may have a cylindrical or rectangular-cuboid shape andmay be constructed of a metallic (e.g., steel) and / or ceramic material (e.g., silicon carbide or alumina). In some cases, the combustion heater(s) 109 may at least partially surround the reformer(s) 108, such that the combustion heater(s) 109 heat the reform er(s) 108 externally. In some cases, the reform er(s) 108 may at least partially surround the combustion heater(s) 109, such that the combustion heater(s) 109 heat the reform er(s) 108 internally. In some cases, the combustion heater(s) 109 may not surround the reform er(s) 108 and may instead generate combustion exhaust that is transferred via an exhaust conduit to heat the reformer(s) 108.

[0054] The heat from the exothermic oxidation reaction in the combustion heater(s) 109 may be transferred to the catalyst in the reform er(s) 108. For example, the relatively hot combustion exhaust 114 may contact walls of the reformer(s) 108 thereby transferring heat across the walls of the reform er(s) 108 to the catalyst. After transferring heat, the combustion exhaust 114 may be subsequently output from the combustion heater(s) 109 and / or the reformer(s) 108. The combustion heater(s) 109 may comprise a separate component from the reformer(s) 108 and may be slidably insertable or removable in the reformer(s) 108. In some cases, the combustion heater(s) 109 are a unitary structure with the reformer(s) 108. For example, both the reformer(s) 108 and the combustion heater(s) 109 may be manufactured via 3D printing and / or casting or otherwise fabricated or manufactured as a unitary structure or single part.

[0055] The air stream 118 (which may be sourced from the atmosphere and comprise at least about 20% oxygen by molar fraction) may be provided to the combustion heater(s) 109 using an air supply unit (for example, a compressor, a pump, a blower, a fan, a turbocharger, etc.). The air stream 118 may comprise pure oxygen by molar fraction, or substantially pure oxygen by molar fraction, for example, at least about 99% pure oxygen, and may include contaminants such as lubricants, oils, etc.

[0056] After exiting the reform er(s) 108, the reformate stream 120 may be cooled using the heat transfer device 106. The reformate stream 120 may be cooled to a temperature sufficient for further processing downstream of the reform er(s) 108, including passing the reformate stream 120 through the TSA system 122, which may include adsorbent vessels, to adsorb at least part of the reformate stream 120 (e.g., ammonia and / or water) onto an adsorbent material.

[0057] After cooling, the reformate stream 120 may be directed to and passed through the TSA system 122. The TSA system 122 may filter or remove ammonia and / or water from the reformate stream 120. The TSA system 122 may be configured to reduce the concentration of NH3 in the reformate stream 120, for example, from greater than about 10,000 parts per million (ppm) to less than about 0.1 ppm, thereby preventing damage to the fuel cell 124. The TSA system 122 may contain a bed comprising a plurality of particles or pellets of adsorbentmaterial. The adsorbent material may include, for example, bentonite, natural or synthetic zeolite, clay, biochar, activated carbon, silica gel, or metal organic frameworks (MOFs) therein. The adsorbent material may be cartridge-based (for simple replaceability, for example, after the adsorbent material is saturated with ammonia). In some cases, the adsorbent material is a monolith structure, for example, a honeycomb structure.

[0058] After exiting the TSA system 122, the reformate stream 120 may then pass through a separation device 180 that separates the hydrogen from the nitrogen and generates a purified stream 120b and a tail gas stream 120a. In some cases, after exiting the TSA system 122, a bypass conduit 162 may direct at least part of the reformate stream 120 to the tail gas stream 120a, for example, via valve 161. Bypassing the separation device 180 may advantageously increase the concentration of hydrogen in the tail gas stream 120a, thereby increasing the proportion of hydrogen combusted in the combustion heater(s) 109 downstream of the separation device 180. In some cases, all of the reformate stream 120 may be directed through the bypass conduit 162, and therefore all of the reformate stream 120 may bypass the separation device 180, which may be advantageous when the fuel cell 124 is turned off, or when the separation device 180 is damaged or non-functional. In some cases, the separation device 180 may be a pressure swing adsorption (PSA) system. In some cases, the separation device 180 may be a membrane capable of separating hydrogen and nitrogen, and the purified stream 120b may be a permeate stream and the tail gas stream 120a may be a retentate stream. In some embodiments, the system 100 may not include the TSA system 122, and the reformate stream 120 may pass through the separation device 180 without passing through the TSA system 122. The membrane may comprise, for example, a layer of palladium or platinum on a ceramic or metallic substrate. In some cases, the membrane may comprise a ceramic or polymeric material. In some cases, the membrane may be placed in an insulated, heated container to improve the hydrogen separation efficiency and hydrogen purity.

[0059] The purified stream 120b may contain mostly hydrogen (for example, 40-85% of the H2 in the reformate stream 120 by mole with a hydrogen purity of > 95% H2 by mole) and the tail gas stream 120a may comprise mostly nitrogen and with some remaining hydrogen (for example, 15-60% of the H2 in the reformate stream 120 by mole). The purified stream 120b may be provided to the fuel cell 124 by, for example, controlling the valve 105f. A valve 105c may be controlled to mix some of the purified stream 120b with the tail gas stream 120a via a return conduit. For example, in response to an increased fuel demand of the combustion heater(s) 109, more hydrogen may be added to the tail gas stream 120a and may therefore also be added to the trim fuel stream 120d downstream of the separation device 180.

[0060] The fuel cell 124 may comprise a polymer electrolyte membrane fuel cell (PEMFC), a solid oxide fuel cell (SOFC), a molten carbonate fuel cell (MCFC), a phosphoric acid fuel cell (PAFC), or an alkaline fuel cell (AFC), although the present disclosure is not limited thereto. The fuel cell 124 may comprise an anode, a cathode, and an electrolyte between the anode and the cathode.

[0061] The fuel cell 124 may receive hydrogen (e.g., at least part of the reformate stream 120) via one or more anode inlets and may receive oxygen (e.g., at least part of the air stream 118 or a separate air stream) via one or more cathode inlets. The fuel cell 124 may process the EE in the purified stream 120b at the anode and process the O2 in an air stream at the cathode to generate electricity (e.g., to power an electrical load). The fuel cell 124 may also include a cathode exhaust and a coolant loop (not shown). In the embodiment schematically shown in FIG. 1, the fuel cell 124 may include an anode recirculation loop (not shown) that recycles the anode exhaust into the purified stream 120b.

[0062] The tail gas stream 120a may be directed to a TSA heat transfer device 130 by, for example, controlling valve 105d. The TSA heat transfer device 130 may be configured to heat the tail gas stream 120a to a temperature capable of desorbing ammonia and / or water from the adsorbent material in an adsorbent vessel of the TSA system 122. In some cases, the TSA heat transfer device 130 is a heat exchanger which may transfer heat from the combustion exhaust 114 to the tail gas stream 120a, thereby generating a heated regeneration stream 120c.

[0063] In some cases, the TSA heat transfer device 130 is instead an electric heater configured to heat the tail gas stream 120a. In some cases, a bypass conduit 116 may direct the tail gas stream 120a directly to an adsorbent vessel (e.g., by opening valve 105e and closing valve 105d), which may cool the adsorbent material, for example, after desorption in the TSA system 122. In some cases, a heat exchanger may transfer heat from the combustion exhaust 114 to the ammonia stream 104 after the combustion exhaust 114 heats the tail gas stream 120a via the TSA heat transfer device 130 (thereby increasing the overall energy efficiency of the system 100).

[0064] The heated regeneration stream 120c may then be directed to an adsorbent vessel of the TSA system 122. The heated regeneration stream 120c may then be passed through an adsorbent vessel in the TSA system 122 to desorb at least part of the adsorbed ammonia and / or the adsorbed water, thereby generating the trim fuel stream 120d, which may then be combusted in the combustion heater(s) 109 to heat the reform er(s) 108.

[0065] The adsorbent vessels of the TSA system 122 may each alternately cycle between adsorption and desorption. For example, when a first adsorbent vessel is saturated withammonia and / or water adsorbed from the reformate stream 120, the first adsorbent vessel may then start desorption and a second adsorbent vessel may start adsorption.

[0066] In some cases, after exiting the separation device 180, at least part of the tail gas stream 120a may be directed through a bypass conduit 167 to the combustion heater(s) 109, for example, via valve 166. Bypassing the TSA system 122 may be advantageous in cases where the TSA device 122 is non-functional, or to reduce the combustion of ammonia and thereby reduce nitrogen oxide emissions.

[0067] FIG. 2 is a flowchart illustrating a method 200 of starting the fuel cell 124 described with respect to and schematically shown in FIG. 1, in accordance with one or more embodiments of the present disclosure. The method 200 may advantageously reduce thermal damage to the combustion heater(s) 109 and / or the reformer(s) 108 that may be caused by overheating by venting excess hydrogen that is not required to be combusted to heat the reformer(s) 108 to a target temperature range (before the fuel cell 124 is turned on or reaches or exceeds a threshold hydrogen utilization rate).

[0068] At step 201, the ammonia stream 104 is reformed in the reformer(s) 108 to generate the reformate stream 120.

[0069] At step 202, a first portion of the reformate stream 120 (for example, at least part of trim fuel stream 120d) is combusted in the combustion heater(s) 109 to heat the reformer(s) 108. The percentage of the reformate stream 120 combusted as the first portion may be greater than about 15% and less than about 60% of the reformate stream 120. In one example, the percentage of the reformate stream 120 combusted as the first portion may comprise about 30% of the reformate stream 120.

[0070] At step 203, a second portion of the reformate stream 120 (for example, at least part of the trim fuel stream 120d) may be directed to the exhaust vent 170 by controlling valve 172. The percentage of the reformate stream 120 directed to the exhaust vent 170 as the second portion may be greater than about 40% and less than about 85% of the reformate stream 120. In one example, the first portion that is combusted may be about 30% of the reformate stream 120, and the second portion that is vented may be about 70% of the reformate stream 120. Step 203 may occur simultaneously with step 202.

[0071] In some cases, the exhaust vent 170 may be in fluid communication with an open space, for example, the atmosphere or surrounding environment. If the second portion of the reformate stream 120 is vented to the atmosphere or surrounding environment, it may be desirable to dilute the second portion of the reformate stream 120, for example, with air (e.g., to avoid emitting a dangerously flammable vapor and / or to comply with greenhouse gasemission regulations). In some cases, the exhaust vent 170 is in fluid communication with the hydrogen storage vessel 101c and / or the nitrogen storage vessel 101b, which may store at least part of the second portion of the reformate stream 120.

[0072] In some cases, the exhaust vent 170 is in fluid communication with a storage tank that may store at least part of the second portion of the reformate stream 120. The storage tank may provide hydrogen to the combustion heater(s) 109 and / or the fuel cell 124 in response to a deficit in hydrogen demand, for example, to achieve a target temperature in the combustion heater(s) 109 and / or the reformer(s) 108 or to achieve a target electrical power output by the fuel cell 124. In some cases, the storage tank may provide at least part of the second portion of the reformate stream 120 to the TSA heat transfer device 130, for example, to generate at least part of the heated regeneration stream 120c. In some cases, the storage tank may provide at least part of the second portion of the reformate stream 120 to components or fluid lines of the system 100 or the system 600 (described with respect to FIG. 6) for purging residual gases, for example, to the reform er(s) 108 to remove oxygen therein.

[0073] In some cases, the exhaust vent 170 comprises a plurality of exhaust vents, for example, where each of the plurality of exhaust vents comprising exhaust vent 170 corresponds to a different outlet or a different fluid line or flow path. In some cases, the exhaust vent 170 is in fluid communication with a flare stack configured to combust hydrogen and emit water vapor. The flare stack may be constructed of materials to withstand, for example, temperatures greater than 500 °C, and fluctuations in temperature, such as a high-grade steel (e.g., ferritic steel grades 4713 and 472, or higher alloyed 4736, 4742, 4762).

[0074] At step 204, the percentage of the reformate stream 120 that is directed to the exhaust vent 170 via the valve 172 as the second portion is decreased, while the percentage of the reformate stream 120 combusted as the first portion is substantially maintained at a predetermined percentage or within a predetermined range of percentages (e.g., at about 30%, or at or above about 30%), thereby redirecting at least part of the second portion from the exhaust vent 170 to the fuel cell 124.

[0075] In some cases, the percentage of the reformate stream 120 that is directed to the exhaust vent 170 as the second portion is decreased, for example, by controlling the valve 172.

[0076] In some cases, the percentage of the reformate stream 120 combusted as the first portion is maintained within a tolerance. For example, if the percentage combusted is 30% and the tolerance is ±1%, the percentage combusted may deviate within a range from greater than about 29% to less than about 31%.

[0077] At step 205, at least part of the second portion of the reformate stream 120 may be processed in the fuel cell 124 at a hydrogen utilization rate. The hydrogen utilization rate may be increased, and the valve 172 may be controlled to decrease by any suitable amount the percentage of the reformate stream 120 that is directed to the exhaust vent 170 as the second portion as the hydrogen utilization rate increases at any suitable rate. Step 204 may occur simultaneously with step 205.

[0078] The percentage of the reformate stream 120 directed to the exhaust vent 170 as the second portion may be decreased to 0% or about 0% when the hydrogen utilization rate reaches or exceeds a threshold hydrogen utilization rate. In some cases, the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9% of the second portion (for example, about 75%).

[0079] An air-fuel equivalence ratio (X) of the combustion occurring at step 202 may be greater than about 1.0 and less than about 1.5 (in other words, fuel lean). The method 200 may further comprise substantially maintaining the air-fuel equivalence ratio after initiating step 204. The air-fuel equivalence ratio may be maintained within a tolerance. For example, if the air-fuel equivalence ratio is intended to be maintained at 1.2 with a tolerance of ±0.05, the air-fuel equivalence ratio may deviate within a range from greater than about 1.15 to less than about 1.25.

[0080] FIG. 3 schematically shows a system 300, in accordance with various embodiments of the present disclosure, that may comprise the NH3 storage vessel 101a, the nitrogen storage vessel 101b, the hydrogen storage vessel 101c, the electric heater 115, the heat transfer device 106, the reformer(s) 108, the combustion heater(s) 109, the TSA system 122, the TSA heat transfer device 130, the fuel cell 124, exhaust vents 171a and 171b, and valves 105a-105f.

[0081] Additionally, the system 300 may comprise a compressor 301, an electric heater 315, a water removal device 302, a stripper vessel 303, which is an optional component of the system 300, exhaust valves 370a-370b, and three-way valves 350a-350b.

[0082] After the NH3 stream 104 starts flowing from the NH3 storage vessel 101a, the NH3 stream 104 may be pressurized by the compressor 301 (for example, to a pressure greater than about 7 barg and less than about 25 barg). In some cases, the compressor 301 may be powered using electrical power and / or mechanical power. In some cases, the compressor 301 may be a passive device that is not powered by electrical or mechanical energy (for example, one or more fluid jet injectors).

[0083] After being compressed, the NH3 stream 104 may be heated by a heat exchanger that transfers heat from the reformate stream 120 to the NH3 stream 104. Since the heat providedby the heat exchanger may not be sufficient for separation in the water removal device 302, an electric heater 315 (e.g., fluid heater or line heater) may heat the NH3 stream 104 to a temperature capable of volatilizing or vaporizing ammonia at a given pressure (for example, at the pressure between 7 barg and 25 barg). In some cases, the temperature is greater than about 40 °C and less than about 95 °C.

[0084] After being heated and pressurized, the NH3 stream 104 may pass through a water removal device 302 which may be, for example, a condenser or a water-selective adsorbent. In some cases, the water removal device 302 may be a flash drum that may separate water from the ammonia vapor by, for example, passing the NH3 stream 104 through a throttling device (e.g., diffuser). The separated water may then be provided to an ammonia disposal or release mitigation system or may optionally be provided to the stripper vessel 303.

[0085] After exiting the water removal device 302, the NH3 stream 104 may be directed to the heat transfer device 106 and then to the reform er(s) 108 to be reformed into the reformate stream 120. The reformate stream 120 may then pass through the heat transfer device 106 and the TSA system 122.

[0086] After exiting the TSA system 122, the reformate stream 120 may be split by the three- way valve 350a into a regeneration portion 320a and a fuel cell portion 320b. The regeneration portion 320a may be heated by the TSA heat transfer device 130 to generate a heated regeneration stream 320c. The three-way valve 350b may direct part of the heated regeneration stream 320c to the combustion heater(s) 109 as a trim fuel stream 320d, and the remaining part of the heated regeneration stream 320c to the TSA system 122 for desorption. In some cases, the three-way valve 350b may be positioned upstream of the TSA heat transfer device 130 and may instead divide the regeneration portion 320a into the trim fuel stream 320d and the regeneration stream 320c (which is subsequently heated by the TSA heat transfer device 130). The fuel cell portion 320b may be directed to the fuel cell 124 and processed by the fuel cell 124 to generate electrical power. The anode exhaust 310, which may include hydrogen not processed by the fuel cell 124, may be directed to the combustion heater(s) 109. After exiting the TSA system 122, the contaminated regeneration stream 320e may be cooled by a cooler, which may be a chiller and / or a heat exchanger, and directed to the ammonia stream 104.

[0087] In some cases, the contaminated regeneration stream 320e may optionally be directed to the stripper vessel 303. The stripper vessel 303 may include a solution that removes water from the contaminated regeneration stream 320e. Ammonia vapor may exit the stripper vessel 303 from an outlet at or near the top of the stripper vessel 303 (e.g., overhead stream) which may then be directed (or recycled) to the ammonia stream 104. The removed water 305, whichmay include ammonia, may exit the stripper vessel 303 from an outlet at or near the bottom of the stripper vessel 303 (e.g., bottoms stream) and be directed to an ammonia disposal or release mitigation system.

[0088] FIG. 4 is a flowchart illustrating a method 400 of starting the fuel cell 124 described with respect to and schematically shown in FIG. 3, in accordance with one or more embodiments of the present disclosure. The method 400 may advantageously reduce thermal damage to the combustion heater(s) 109 and / or the reformer(s) 108 that may be caused by overheating by venting excess hydrogen that is not required to be combusted to heat the reformer(s) 108 to the target temperature range (before the fuel cell 124 is turned on, or reaches or exceeds a threshold hydrogen utilization rate). Additionally, by venting the anode exhaust 310, a consistent delivery of the ammonia stream 104 to the reformer(s) 108 may be maintained during a transition to operation of the fuel cell 124. Otherwise, if all of the anode exhaust 310 is directed to the combustion heater(s) 109, a relatively higher lambda is required to fully combust the hydrogen in the anode exhaust 310 and prevent overheating of the reform er(s) 108. Venting the anode exhaust 310 enables 30% of the reformate stream 120 to be combusted in the combustion heater(s) 109 during the initialization period of the fuel cell 124. Once the fuel cell 124 reaches a target hydrogen utilization rate, the flow rate of the trim fuel stream 320d reduces, and flow rate of the ammonia stream 104 reduces slightly, to maintain a constant quantity of fuel provided to the combustion heater(s) 109 and a constant pressure upstream of the fuel cell 124.

[0089] At step 401, the ammonia stream 104 is reformed in the reformer(s) 108 to generate the reformate stream 120.

[0090] At step 402, a first portion of the reformate stream 120 (for example, at least part of trim fuel stream 120d) is combusted in the combustion heater(s) 109 to heat the reformer(s) 108. The percentage of the reformate stream 120 combusted as the first portion may be greater than about 15% and less than about 60% of the reformate stream 120. In one example, the percentage of the reformate stream 120 combusted as the first portion may comprise about 30% of the reformate stream 120.

[0091] At step 403, a second portion of the reformate stream 120 (for example, at least part of the trim fuel stream 120d) may be directed to the exhaust vent 171b by controlling valve 370b. The percentage of the reformate stream 120 directed to the exhaust vent 171b as the second portion via the valve 370b may be greater than about 40% and less than about 85% of the reformate stream 120. In one example, the first portion that is combusted may be about 30%of the reformate stream 120, and the second portion that is vented may be about 70% of the reformate stream 120. Step 403 may occur simultaneously with step 402.

[0092] In some cases, one or more of the exhaust vents 171a-b may be in fluid communication with an open space, for example, the atmosphere or surrounding environment. If the second portion of the reformate stream 120 is vented to the atmosphere or surrounding environment, it may be desirable to dilute the second portion of the reformate stream 120, for example, with air (e.g., to avoid emitting a dangerously flammable vapor and / or to comply with greenhouse gas emission regulations). In some cases, one or more of the exhaust vents 171a-b is in fluid communication with the hydrogen storage vessel 101c and / or the nitrogen storage vessel 101b, which may store at least part of the second portion of the reformate stream 120.

[0093] In some cases, one or more of the exhaust vents 171a-b is in fluid communication with a storage tank that may store at least part of the second portion of the reformate stream 120. The storage tank may provide hydrogen to the combustion heater(s) 109 and / or the fuel cell 124 in response to a deficit in hydrogen demand, for example, to achieve a target temperature in the combustion heater(s) 109 and / or the reformer(s) 108 or to achieve a target electrical power output by the fuel cell 124. In some cases, the storage tank may provide at least part of the second portion of the reformate stream 120 to the TSA heat transfer device 130, for example, to generate at least part of the heated regeneration stream 320c. In some cases, the storage tank may provide at least part of the second portion of the reformate stream 120 to components or fluid lines of the system 300, system 500 (described with respect to FIG. 5), or system 700 (described with respect to FIG. 7) for purging residual gases, for example, to the reformer(s) 108 to remove oxygen therein.

[0094] In some cases, one or more of the exhaust vents 171a-b comprises a plurality of exhaust vents, for example, where each of the plurality of exhaust vents corresponds to a different outlet or a different fluid line or flow path. In some cases, the one or more of the exhaust vents 171a- b is in fluid communication with a flare stack configured to combust hydrogen and emit water vapor. The flare stack may be constructed of materials to withstand, for example, temperatures greater than 500 °C, and fluctuations in temperature, such as a high-grade steel (e.g., ferritic steel grades 4713 and 472, or higher alloyed 4736, 4742, 4762).

[0095] At step 404, the percentage of the reformate stream 120 that is directed to the exhaust vent 171b as the second portion is decreased (e.g., by controlling the valve 370b), while the percentage of the reformate stream 120 combusted as the first portion is substantially maintained at a predetermined percentage or within a predetermined range of percentages (e.g.,at about 30%, or at or above about 30%), thereby redirecting at least part of the second portion from the exhaust vent 171b to the fuel cell 124.

[0096] In some cases, the percentage of the reformate stream 120 combusted as the first portion is substantially maintained within a tolerance. For example, if the percentage combusted is 30% and the tolerance is ±1%, the percentage combusted may deviate within a range from greater than about 29% to less than about 31%.

[0097] At step 405, at least part of the second portion of the reformate stream 120 may be processed in the fuel cell 124 at a hydrogen utilization rate. The hydrogen utilization rate may be increased, and the valve 370b may be controlled to decrease, by any suitable amount, the percentage of the reformate stream 120 that is directed to the exhaust vent 171b as the second portion as the hydrogen utilization rate increases at any suitable rate. In some cases, instead of decreasing the venting, the valve 370b may be controlled to immediately decrease the percentage of the reformate stream 120 that is directed to the exhaust vent 171b to a predetermined percentage, including 0% or about 0%. Step 404 may occur simultaneously with step 405.

[0098] At step 406, a second valve 370a may be controlled to direct a remaining portion of the reformate stream 120 to the exhaust vent 171a. The remaining portion comprises the percentage of the at least part of the second portion not processed by the fuel cell 124 and may be part of the anode exhaust 310. The second valve 370a may be positioned downstream of the anode of the fuel cell 124 as shown in FIGS. 3, 5, and 7. The percentage of the reformate stream 120 directed to the exhaust vent 171a via the second valve 370a as the remaining portion may be greater than about 0% and less than about 85% of the reformate stream 120. In one example, the first portion that is combusted may be about 30% of the reformate stream 120, and the remaining portion that is vented via the second valve 370a may be about 70% of the reformate stream 120. Step 406 may occur simultaneously with step 405. In some cases, as shown in FIG. 7, the second valve 370a may be positioned upstream of the anode of the fuel cell 124, and the second valve 370a may be controlled to direct a siphoned portion 380 (instead of the remaining portion) of the reformate stream 120 to the exhaust vent 171a. The siphoned portion 380 may comprise a percentage of the second portion directed from a position upstream of the fuel cell 124. The percentage of the reformate stream 120 directed to the exhaust vent 171a via the second valve 370a as the siphoned portion 380 may be greater than about 0% and less than about 85% of the reformate stream 120. In one example, the first portion that is combusted may be about 30% of the reformate stream 120, and the siphoned portion 380 that is vented via the second valve 370a may be about 70% of the reformate stream 120.

[0099] At step 407, the percentage of the reformate stream 120 directed to the exhaust vent 171a as the remaining portion (or the siphoned portion 380) via the exhaust valve 370a may be decreased to 0% or about 0% when the hydrogen utilization rate reaches or exceeds a threshold hydrogen utilization rate. In some cases, the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9% of the second portion (for example, about 75%).

[0100] An air-fuel equivalence ratio (X) of the combustion occurring at step 402 may be greater than about 1.0 and less than about 1.5 (in other words, fuel lean). The method 400 may further comprise substantially maintaining the air-fuel equivalence ratio after initiating step 404. The air-fuel equivalence ratio may be maintained within a tolerance. For example, if the air-fuel equivalence ratio is intended to be maintained at 1.2 with a tolerance of ±0.05, the air-fuel equivalence ratio may deviate within a range from greater than about 1.15 to less than about 1.25.

[0101] FIG. 5 schematically shows a system 500, in accordance with various embodiments of the present disclosure. The components described with respect to system 500 may be substantially similar in structure and function to the identically identified components of system 100 described with respect to FIG. 1 and the identically identified components of system 300 described with respect to FIG. 3.

[0102] In contrast to system 100, the membrane 180 may instead be replaced with the three- way valve 350a that divides the reformate stream 120 into the regeneration portion 320a and the fuel cell portion 320b. The regeneration portion 320a may be heated by the TSA heat transfer device 130 to generate the heated regeneration stream 120c. The anode exhaust 310 may be directed to the combustion heater(s) 109. The fuel cell 124 may be started using the method 400 described with respect to FIG. 4, for example, by controlling the valves 370a and 370b.

[0103] FIG. 6 schematically shows a system 600, in accordance with various embodiments of the present disclosure. The components described with respect to system 600 may be substantially similar in structure and function to the identically identified components of system 500 described with respect to FIG. 5.

[0104] Instead of separate flow paths that lead to the combustion heater(s) 109, the trim fuel stream 120d and the anode exhaust 310 may be mixed to form a combined stream 610 at a mixing position 605 before being directed to the combustion heater(s) 109. The valve 172 may be positioned downstream of the mixing position 605 and upstream of the combustion heater(s) 109. The fuel cell 124 may be started using the method 200 described with respect to FIG. 2, for example, by controlling the valve 172.

[0105] FIG. 7 schematically shows a system 700, in accordance with various embodiments of the present disclosure. The components described with respect to system 700 may be substantially similar in structure and function to the identically identified components of system 100 described with respect to FIG. 1 and the identically identified components of system 300 described with respect to FIG. 3.

[0106] In contrast to system 300, the valve 370a may be positioned upstream of the anode of the fuel cell 124. The fuel cell 124 may be started using the method 400 described with respect to FIG. 4, for example, by controlling the valves 370a and 370b.

[0107] FIG. 8 is a flowchart illustrating a method 800 of heating the reformer(s) 108 schematically shown in FIG. 1 and FIG. 3 by passing a gas 107 that is heated through the reformer(s) 108, in accordance with various embodiments of the present disclosure. The gas 107 may be continuously recirculated in a fluid recirculation line (e.g., in a loop) until the reformer(s) 108 and / or a catalyst therein are heated to a target temperature. The fluid recirculation line may trace the path from the outlet of the reformer(s) 108, to the heat transfer device 106, to the electric heater 115, back to the heat transfer device 106, and finally to the inlet of the reformer(s) 108. In some cases, the gas 107 may bypass the heat transfer device 106. In some cases, the gas 107 may pass through a blower, a pump, fan, or the like (not shown).

[0108] In some cases, the gas 107 may comprise a mixture of hydrogen (H2) gas (e.g., sourced from the hydrogen storage vessel 101c) and nitrogen (N2) gas (e.g., sourced from the nitrogen storage vessel 101b). The hydrogen and nitrogen of the gas 107 may be mixed upstream of the electric heater 115. In some cases, a ratio of hydrogen to nitrogen in the gas 107 may be about 3: 1. Nitrogen gas acquired from industrial producers may be contaminated with oxygen (O2) gas (e.g., < 0.5% by mole O2). This oxygen may damage the catalyst in the reformer(s) 108 and may cause oxidative stress (e.g., rust) in other components of the systems 100 and 300. Even though nitrogen is more abundant and simpler to source compared to hydrogen gas, it may be disadvantageous to use pure nitrogen or only nitrogen without another gas as the gas 107 for the aforementioned reason. Therefore, it is contemplated that by diluting the nitrogen gas with hydrogen gas (or another gas), damage to the catalyst or other components of the systems 100 and 300 may be significantly reduced.

[0109] In some cases, the gas 107 may comprise a mixture of nitrogen (N2) gas (e.g., sourced from the nitrogen storage vessel 101b) and ammonia (NH3) gas (e.g., sourced from the ammonia storage vessel 101a after vaporizing liquid ammonia). For example, the gas 107 may comprise greater than about 90% (e.g., about 99%) nitrogen gas by mole or by volume and lessthan about 10% (e.g., about 1%) ammonia gas by mole or by volume. In some cases, the gas107 may comprise substantially pure nitrogen (for example, greater than about 99% nitrogen by mole or by volume).

[0110] At step 801, the gas 107 may be passed through the electric heater 115 (e.g., a fluid heater, a line heater, or inline heater) to heat the gas 107 to a temperature greater than about 400° C and less than about 900° C. The electric heater 115 may be, for example, a resistance heater, an induction heater, a radiant (infrared) heater, or a heat pump.[OHl] At step 802, the gas 107, after being heated, is passed through the reactor(s) 108 to heat the catalyst therein. The gas 107 may heat the catalyst by convection.

[0112] At step 803, the gas 107 is passed through the recirculation line in fluid communication with the electric heater 115 (for example, by controlling valve 105a to be open and controlling valve 105b to be closed). The gas 107 may pass through the heat transfer device 106 and may also pass through a blower (not shown).

[0113] At step 804, steps 801, 802 and 803 are repeated until the catalyst in the reform er(s)108 is heated to a target temperature greater than about 400° C and less than about 900° C.

[0114] In some cases, after the catalyst in the reformer(s) 108 is heated to the target temperature greater than about 400° C and less than about 900° C, the valve 105a may be controlled to be closed and the valve 105b may be controlled to be open. The heated gas 107 may then be combusted in the combustion heater(s) 109, and the ammonia stream 104 may be directed to the reformer(s) 108 to generate the reformate stream 120. In this way, the gas 107 may advantageously be used to heat the reform er(s) 108 by convection in addition to being combusted to heat the reform er(s) 108.

[0115] In some cases, after the catalyst in the reformer(s) 108 is heated to the target temperature greater than about 400° C and less than about 900° C, the valve 105a may be controlled to be partially open and the valve 105b may be controlled to be at least partially open. The ammonia stream 104 may be directed to the reformer(s) 108 to generate the reformate stream 120. At least part of the gas 107 may be directed to the exhaust vent 170 (for example, via the valve 172) or the exhaust vent 171b (for example, via the valve 370b). At least part of the reformate stream 120 may be passed through the recirculation line. This process may continue until substantially all or all of the fluid passing through the recirculation line comprises the reformate stream 120, at which point the valve 105a may be controlled to be closed and the reformate stream 120 may be directed to the combustion heater(s) 109 by controlling the valve 105b.

[0116] In some cases, instead of performing the method 800 or in addition to performing the method 800, the combustion heater(s) 109 may be heated by combusting ammonia (forexample, using an ammonia combustion catalyst that promotes the combustion of ammonia and / or a pilot fuel such as diesel, natural gas or hydrogen). In some cases, instead of performing the method 800 or in addition to performing the method 800, the combustion heater(s) 109 may be heated by combusting reformate that is stored in a buffer tank.

[0117] In an example embodiment (or aspect), a method comprises (a) reforming ammonia (NH3) in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2); (b) combusting a first portion of the reformate stream in at least one combustion heater; (c) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater; (d) controlling the first valve to decrease a percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining a percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a membrane to generate a purified stream and a tail gas stream; (e) processing at least part of the purified stream in a fuel cell at a hydrogen utilization rate; and (f) increasing the hydrogen utilization rate of the fuel cell, wherein the percentage of the reformate stream directed to the exhaust vent as the second portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the first valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the second portion as the hydrogen utilization rate increases.

[0118] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9%.

[0119] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), an air-fuel equivalence ratio ( ) of the combustion occurring in (b) is greater than about 1.0 and less than about 1.5, wherein the method further comprises substantially maintaining the air-fuel equivalence ratio ( ) after initiating (d).

[0120] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the percentage of the reformate stream combusted as the first portion is greater than about 15% and less than about 60% of the reformate stream.

[0121] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), in (c), the percentage of the reformate stream directed to the exhaust vent as the second portion is greater than about 40% and less than about 85% of the reformate stream.

[0122] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the method further comprises combusting at least part of the tail gas stream in the at least one combustion heater.

[0123] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the purified stream comprises greater than 95% H2 by mole.

[0124] In an example embodiment (or aspect), a method comprises (g) reforming ammonia (NH3) in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2); (h) combusting a first portion of the reformate stream in at least one combustion heater; (i) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater; (j) controlling the first valve to decrease a percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining a percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a fuel cell comprising an anode and a cathode; (k) processing the at least part of the second portion in the fuel cell at a hydrogen utilization rate; (1) controlling a second valve to direct a remaining portion of the reformate stream to the exhaust vent, wherein the remaining portion comprises a percentage of the at least part of the second portion not processed by the fuel cell, wherein the second valve is positioned downstream of the fuel cell anode; and (m) increasing the hydrogen utilization rate of the fuel cell, wherein a percentage of the reformate stream directed to the exhaust vent as the remaining portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the second valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the remaining portion as the hydrogen utilization rate increases.

[0125] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9%.

[0126] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), an air-fuel equivalence ratio ( ) of the combustion occurring in (h) is greater than about 1.0 and less than about 1.5, and the method further comprises substantially maintaining the air-fuel equivalence ratio (X) after initiating (j).

[0127] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the percentage of the reformate stream combusted as the first portion is greater than about 15% and less than about 60% of the reformate stream.

[0128] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), in (i), the percentage of the reformate stream directed to the exhaust vent as the second portion is greater than about 40% and less than about 85% of the reformate stream.

[0129] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), in (j), the percentage of the reformate stream directed to the exhaust vent as the second portion is decreased to about 0% of the reformate stream.

[0130] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), in (1), the percentage of the reformate stream directed to the exhaust vent as the remaining portion is greater than about 40% and less than about 85% of the reformate stream.

[0131] In an example embodiment (or aspect), a method comprises (n) reforming ammonia (NH3) in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2); (o) combusting a first portion of the reformate stream in at least one combustion heater; (p) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater; (q) controlling the first valve to decrease a percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining a percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a fuel cell comprising an anode and a cathode; (r) processing the at least part of the second portion in the fuel cell at a hydrogen utilization rate; (s) controlling a second valve to direct a siphoned portion of the reformate stream to the exhaust vent, wherein the siphoned portion comprises a percentage of the at least part of the second portion that is directed upstream of the fuel cell anode to the exhaust vent, wherein the second valve is positioned upstream of the fuel cell anode; and (t) increasing the hydrogen utilization rate of the fuel cell, wherein a percentage of the reformate stream directed to the exhaust vent as the siphoned portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the second valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the siphoned portion as the hydrogen utilization rate increases.

[0132] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9%.

[0133] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), an air-fuel equivalence ratio (X) of the combustion occurring in (o) isgreater than about 1.0 and less than about 1.5, wherein the method further comprises substantially maintaining the air-fuel equivalence ratio (X) after initiating (q).

[0134] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the percentage of the reformate stream combusted as the first portion is greater than about 15% and less than about 60% of the reformate stream.

[0135] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), in (p), the percentage of the reformate stream directed to the exhaust vent as the second portion is greater than about 40% and less than about 85% of the reformate stream.

[0136] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), in (q), the percentage of the reformate stream directed to the exhaust vent as the second portion is decreased to about 0% of the reformate stream.

[0137] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), in (s), the percentage of the reformate stream directed to the exhaust vent as the siphoned portion is greater than about 40% and less than about 85% of the reformate stream.

[0138] In an example embodiment (or aspect), a method comprises (u) passing a gas through an electric heater to heat the gas to a temperature greater than about 400° C and less than about 900° C; (v) passing the heated gas through a reformer comprising a catalyst to heat the catalyst; and (w) passing the heated gas through a recirculation line in fluid communication with the electric heater; and (x) repeating steps (u), (v) and (w) until the catalyst is heated to a temperature greater than about 400° C and less than about 900° C.

[0139] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the gas comprises hydrogen (H2) and nitrogen (N2).

[0140] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), a ratio of hydrogen to nitrogen in the gas is about 3: 1.

[0141] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), combusting the gas in a combustion heater in thermal communication with the reformer.

[0142] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the gas comprises nitrogen (N2) and ammonia (NH3).

[0143] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the gas comprises nitrogen (N2).

[0144] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the gas comprises ammonia (NH3).

[0145] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the gas comprises hydrogen (H2).

[0146] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), passing an ammonia stream through the reformer and the recirculation line to generate a reformate stream, and directing at least part of the heated gas to an exhaust vent.

[0147] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the method further comprises combusting ammonia to heat the reformer and / or the catalyst.

[0148] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the ammonia is combusted using an ammonia combustion catalyst or a pilot fuel.

[0149] In an example embodiment (or aspect) combinable with any other example embodiment (or aspect), the pilot fuel is natural gas, diesel, or hydrogen.EXEMPLARY EMBODIMENTS

[0150] Among the exemplary embodiments are:1. A method comprising:(a) reforming ammonia in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2);(b) combusting a first portion of the reformate stream in at least one combustion heater;(c) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater;(d) controlling the first valve to decrease the percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining the percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a fuel cell comprising an anode and a cathode;(e) processing the at least part of the second portion in the fuel cell at a hydrogen utilization rate; and(f) increasing the hydrogen utilization rate of the fuel cell, wherein the percentage of the reformate stream directed to the exhaust vent as the second portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the first valve is controlled to decrease the percentage of thereformate stream that is directed to the exhaust vent as the second portion as the hydrogen utilization rate increases.2. The method of embodiment 1, wherein the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9% of the second portion.3. The method of embodiment 1, wherein an air-fuel equivalence ratio (X) of the combustion occurring in step (b) is greater than about 1.0 and less than about 1.5, wherein the method further comprises substantially maintaining the air-fuel equivalence ratio (X) after initiating step (d).4. The method of embodiment 1, wherein the percentage of the reformate stream combusted as the first portion is greater than about 15% and less than about 60% of the reformate stream.5. The method of embodiment 1, wherein, in step (c), the percentage of the reformate stream directed to the exhaust vent as the second portion is greater than about 40% to less than about 85%.6. A method comprising:(a) reforming ammonia in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2);(b) combusting a first portion of the reformate stream in at least one combustion heater;(c) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater;(d) controlling the first valve to decrease the percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining the percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a fuel cell comprising an anode and a cathode;(e) processing the at least part of the second portion in the fuel cell at a hydrogen utilization rate;(f) controlling a second valve to direct a remaining portion of the reformate stream to the exhaust vent, wherein the remaining portion comprises the percentage of the at least part of the second portion not processed by the fuel cell, wherein the second valve is positioned downstream of the fuel cell anode; and(g) increasing the hydrogen utilization rate of the fuel cell, wherein the percentage of the reformate stream directed to the exhaust vent as the remaining portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the second valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the remaining portion as the hydrogen utilization rate increases.7. The method of embodiment 6, wherein the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9%.8. The method of embodiment 6, wherein an air-fuel equivalence ratio (X) of the combustion occurring in step (b) is greater than about 1.0 and less than about 1.5, wherein the method further comprises substantially maintaining the air-fuel equivalence ratio (X) after initiating step (d).9. The method of embodiment 6, wherein the percentage of the reformate stream combusted as the first portion is greater than about 15% and less than about 60% of the reformate stream.10. The method of embodiment 6, wherein, in step (c), the percentage of the reformate stream directed to the exhaust vent as the second portion is greater than about 40% to less than about 85%.11. The method of embodiment 6, wherein, in step (d), the percentage of the reformate stream directed to the exhaust vent as the second portion is decreased to about 0%.12. The method of embodiment 6, wherein, in step (f), the percentage of the reformate stream directed to the exhaust vent as the remaining portion is greater than about 40% to less than about 85%.13. A method compri sing :(a) reforming ammonia in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2);(b) combusting a first portion of the reformate stream in at least one combustion heater;(c) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater;(d) controlling the first valve to decrease the percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining the percentage of the reformate stream combusted as the first portion, thereby redirectingat least part of the second portion from the exhaust vent to a fuel cell comprising an anode and a cathode;(e) processing the at least part of the second portion in the fuel cell at a hydrogen utilization rate;(f) controlling a second valve to direct a siphoned portion of the reformate stream to the exhaust vent, wherein the siphoned portion comprises a percentage of the at least part of the second portion siphoned upstream of the fuel cell anode, wherein the second valve is positioned upstream of the fuel cell anode; and(g) increasing the hydrogen utilization rate of the fuel cell, wherein the percentage of the reformate stream directed to the exhaust vent as the siphoned portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the second valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the siphoned portion as the hydrogen utilization rate increases.14. The method of embodiment 13, wherein the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9%.15. The method of embodiment 13, wherein an air-fuel equivalence ratio (X) of the combustion occurring in step (b) is greater than about 1.0 and less than about 1.5, wherein the method further comprises substantially maintaining the air-fuel equivalence ratio (X) after initiating step (d).16. The method of embodiment 13, wherein the percentage of the reformate stream combusted as the first portion is greater than about 15% and less than about 60% of the reformate stream.17. The method of embodiment 13, wherein, in step (c), the percentage of the reformate stream directed to the exhaust vent as the second portion is greater than about 40% to less than about 85%.18. The method of embodiment 13, wherein, in step (d), the percentage of the reformate stream directed to the exhaust vent as the second portion is decreased to about 0%.19. The method of embodiment 13, wherein, in step (f), the percentage of the reformate stream directed to the exhaust vent as the siphoned portion is greater than about 40% to less than about 85%.20. A method comprising:(a) passing a gas through an electric heater to heat the gas to a temperature greater than about 400° C and less than about 900° C;(b) passing the heated gas through a reformer comprising a catalyst to heat the catalyst; and(c) passing the heated gas through a recirculation line in fluid communication with the electric heater; and(d) repeating steps (a), (b) and (c) until the catalyst is heated to a temperature greater than about 400° C and less than about 900° C.21. The method of embodiment 20, wherein the gas comprises hydrogen (H2) and nitrogen (N2).22. The method of embodiment 21, wherein a ratio of hydrogen to nitrogen in the gas is about 3: 1.23. The method of embodiment 21, further comprising the step of combusting the gas in a combustion heater in thermal communication with the reformer.24. The method of embodiment 20, wherein the gas comprises nitrogen (N2) and ammonia (NH3).25. The method of embodiment 20, wherein the gas comprises nitrogen (N2).26. The method of embodiment 20, further comprising the step of passing an ammonia stream through the reformer and the recirculation line to generate a reformate stream, and directing at least part of the heated gas to an exhaust vent.

[0151] The various embodiments of this disclosure are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. While various embodiments have been shown and described herein, it will be clear to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from this disclosure. Furthermore, it shall be understood that all aspects of the subject matter are not limited to the specific depictions, configurations, or relative proportions set forth herein, which depend upon a variety of conditions and variables. It should be understood that various alternatives to the embodiments described herein may be employed. It is therefore contemplated that the subject matter shall also cover any such alternatives, modifications, variations, or equivalents.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A method comprising:(g) reforming ammonia (NH3) in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2);(h) combusting a first portion of the reformate stream in at least one combustion heater;(i) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater;(j) controlling the first valve to decrease a percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining a percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a membrane to generate a purified stream and a tail gas stream;(k) processing at least part of the purified stream in a fuel cell at a hydrogen utilization rate; and(l) increasing the hydrogen utilization rate of the fuel cell, wherein the percentage of the reformate stream directed to the exhaust vent as the second portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the first valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the second portion as the hydrogen utilization rate increases.

2. The method of claim 1, wherein the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9%.

3. The method of claim 1, wherein an air- fuel equivalence ratio ( ) of the combustion occurring in (b) is greater than about 1.0 and less than about 1.5, wherein the method further comprises substantially maintaining the air-fuel equivalence ratio (X) after initiating (d).

4. The method of claim 1, wherein the percentage of the reformate stream combusted as the first portion is greater than about 15% and less than about 60% of the reformate stream.

5. The method of claim 1, wherein, in (c), the percentage of the reformate stream directed to the exhaust vent as the second portion is greater than about 40% and less than about 85% of the reformate stream.

6. The method of claim 1 , further comprising combusting at least part of the tail gas stream in the at least one combustion heater.

7. A method comprising:(h) reforming ammonia (NH3) in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2);(i) combusting a first portion of the reformate stream in at least one combustion heater;(j) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater;(k) controlling the first valve to decrease a percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining a percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a fuel cell comprising an anode and a cathode;(l) processing the at least part of the second portion in the fuel cell at a hydrogen utilization rate;(m) controlling a second valve to direct a remaining portion of the reformate stream to the exhaust vent, wherein the remaining portion comprises a percentage of the at least part of the second portion not processed by the fuel cell, wherein the second valve is positioned downstream of the fuel cell anode; and(n) increasing the hydrogen utilization rate of the fuel cell, wherein a percentage of the reformate stream directed to the exhaust vent as the remaining portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the second valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the remaining portion as the hydrogen utilization rate increases.

8. The method of claim 7, wherein the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9%.

9. The method of claim 7, wherein an air-fuel equivalence ratio (X) of the combustion occurring in (b) is greater than about 1.0 and less than about 1.5, wherein the method further comprises substantially maintaining the air-fuel equivalence ratio (X) after initiating (d).

10. The method of claim 7, wherein the percentage of the reformate stream combusted as the first portion is greater than about 15% and less than about 60% of the reformate stream.

11. The method of claim 7, wherein, in (c), the percentage of the reformate stream directed to the exhaust vent as the second portion is greater than about 40% and less than about 85% of the reformate stream.

12. The method of claim 7, wherein, in (d), the percentage of the reformate stream directed to the exhaust vent as the second portion is decreased to about 0% of the reformate stream.

13. The method of claim 7, wherein, in (f), the percentage of the reformate stream directed to the exhaust vent as the remaining portion is greater than about 40% and less than about 85% of the reformate stream.

14. A method comprising:(h) reforming ammonia (NH3) in at least one reformer that comprises a catalyst to generate a reformate stream comprising hydrogen (H2) and nitrogen (N2);(i) combusting a first portion of the reformate stream in at least one combustion heater;(j) controlling a first valve to direct a second portion of the reformate stream to an exhaust vent, wherein the first valve is positioned upstream of the at least one combustion heater;(k) controlling the first valve to decrease a percentage of the reformate stream directed to the exhaust vent as the second portion while substantially maintaining a percentage of the reformate stream combusted as the first portion, thereby redirecting at least part of the second portion from the exhaust vent to a fuel cell comprising an anode and a cathode;(l) processing the at least part of the second portion in the fuel cell at a hydrogen utilization rate;(m) controlling a second valve to direct a siphoned portion of the reformate stream to the exhaust vent, wherein the siphoned portion comprises a percentage of the at least part of the second portion that is directed upstream of the fuel cell anode to the exhaust vent, wherein the second valve is positioned upstream of the fuel cell anode; and(n) increasing the hydrogen utilization rate of the fuel cell, wherein a percentage of the reformate stream directed to the exhaust vent as the siphoned portion is decreased to about 0% when the hydrogen utilization rate is increased to a threshold hydrogen utilization rate, wherein the second valve is controlled to decrease the percentage of the reformate stream that is directed to the exhaust vent as the siphoned portion as the hydrogen utilization rate increases.

15. The method of claim 14, wherein the threshold hydrogen utilization rate is greater than about 55% and less than about 99.9%.

16. The method of claim 14, wherein an air-fuel equivalence ratio (X) of the combustion occurring in (b) is greater than about 1.0 and less than about 1.5, wherein the method further comprises substantially maintaining the air-fuel equivalence ratio (X) after initiating (d).

17. The method of claim 14, wherein the percentage of the reformate stream combusted as the first portion is greater than about 15% and less than about 60% of the reformate stream.

18. The method of claim 14, wherein, in (c), the percentage of the reformate stream directed to the exhaust vent as the second portion is greater than about 40% and less than about 85% of the reformate stream.

19. The method of claim 14, wherein, in (d), the percentage of the reformate stream directed to the exhaust vent as the second portion is decreased to about 0% of the reformate stream.

20. The method of claim 14, wherein, in (f), the percentage of the reformate stream directed to the exhaust vent as the siphoned portion is greater than about 40% and less than about 85% of the reformate stream.

Images