INTRODUCTION

[001] The present invention relates to a modular ammonia cracker for producing hydrogen from ammonia. The invention also relates to a system including one or more modular ammonia crackers and methods of using the modules and systems.

[002] Hydrogen fuel has been proposed as a clean energy solution that, if adopted, could reduce the CO2 emissions associated with the world’s energy production and consumption. Hydrogen is considered to be a ‘clean’ fuel as it can be consumed and produce water as the sole or major product under the correct conditions. Hydrogen can be stored in gaseous or liquid form and transported as a means of delivering energy to locations and end-users that may require energy to be provided to locations geographically distant from a source of hydrogen. The transportation of hydrogen presents various challenges. The cost of green hydrogen to the end-user in geographies where it is most in demand such as Europe, North America, and Asia is not economic which impedes the decarbonisation of major CO2 emitting industries such as transport and heating. Green hydrogen produced in the regions of demand is often made via the electrolysis of water using renewable electricity. Renewable electricity in these regions is often expensive and so the high cost of energy results in hydrogen with a similarly high associated cost. Much of the world’s energy infrastructure does not currently support hydrogen and remains directed towards the transportation and exploitation of hydrocarbons and fossil fuels. It is possible to convert existing hydrocarbon fuel infrastructure to transport hydrogen fuel into regions where electricity is expensive. However, such conversions have not occurred on a large scale and new technical solutions are needed to allow small-to-medium scale users and applications to utilise hydrogen effectively.

[003] The Haber-Bosch process is a well-known equilibrium process that is most commonly used to produce ammonia for applications such as fertiliser through the reaction of hydrogen and nitrogen. The reaction of hydrogen with nitrogen is a reversible reaction, with the forward reaction producing ammonia (the Haber-Bosch process). This is a reversible reaction, and so manipulation of reaction conditions allows for ammonia to be converted back into hydrogen and nitrogen (known as cracking). The hydrogen thus formed from the cracking of ammonia may be used as a fuel. The reliance of world agriculture upon ammonia-based fertilisers has created an ammonia transportation infrastructure that is well-established. Transportation of ammonia has various advantages when compared to the transportation of hydrogen. The boiling point of hydrogen is approximately -253 °C whereas the boiling point of ammonia is approximately -33 °C. The difference in boiling points means that ammonia is significantly less energy intensive to liquify and store in liquid form. Ammonia is less flammable than hydrogen and so is considered safer to transport. The energy density of liquid ammonia is also significantly greater than that of liquid hydrogen.

[004] The inventors of the present invention have appreciated that the transportation of ammonia, over long distances, as a means of providing hydrogen to end-users and applications is preferable to the transportation of hydrogen in gaseous or liquid form. However, current plans for the conversion of ammonia back to hydrogen are generally intended to be carried out in large-scale centralised facilities, that would then necessitate the further transport and distribution of the hydrogen produced by the facility to end-users further afield. The inventors have solved this problem by developing a modular ammonia cracker that may be used to convert ammonia efficiently into hydrogen at, or in proximity to, the point of use. A point-of-use system allows preferably green ammonia to be directly transported to the modular ammonia cracker system and then converted into hydrogen. The module, system, and associated methods disclosed herein provide the missing link in the existing infrastructure chain to allow hydrogen to be exploited for small and medium scale applications.

[005] Existing traditional ammonia cracking technology is relatively primitive and is generally either too small or too inefficient to allow for production of hydrogen on suitable scale for a small or medium industrial or commercial end user. Existing ’’off-the-shelf” ammonia crackers are used in industries including metallurgy and glass production and generally provide a hydrogen product of low purity at a high energy cost. The ammonia cracker module described herein allows modules to be brought together to form a system that is scalable in terms of hydrogen production capacity. The module also provides a means of hydrogen production that is highly responsive, energy efficient, and compact.

[006] According to one aspect of the invention, there is provided an ammonia cracker module for converting ammonia into hydrogen. The ammonia cracker module includes: (i) a heat exchange reactor including: (a) a first reaction zone including: a first working fluid flowpath therethrough; a first reactant flowpath therethrough; and one or more heat exchange surfaces positioned between the first working fluid flowpath and first reactant flowpath; (b) a second reaction zone including: a second working fluid flowpath therethrough; a second reactant flowpath therethrough; and one or more heat exchange surfaces positioned between the second working fluid flowpath and second reactant flowpath; (c) a catalyst positioned to contact reactant fluid flowing through the first and second reactant flowpaths to convert ammonia flowing through the first and second reactant flowpaths into hydrogen. The ammonia cracker module further includes: (ii) a heating system including: a first heat source, configured to heat working fluid to create a first heated working fluid to enter the first working fluid flowpath; and a second heat source, configured to receive a first thermally depleted working fluid from the first working fluid flowpath and output a second heated working fluid to the second working fluid flowpath when the cracker module is in use; wherein: an outlet of the first working fluid flowpath is in fluid communication with an inlet of the second working fluid flowpath; and an outlet of the first reactant flowpath is in fluid communication with an inlet of the second reactant fluid flowpath.

[007] The heat exchange reactor may include: (d) a third reaction zone including: a third working fluid flowpath therethrough; a third reactant flowpath therethrough; and one or more heat exchange surfaces positioned between the third working fluid flowpath and third reactant flowpath, further wherein, the heating system includes: a third heat source, configured to receive a second thermally depleted working fluid from the second working fluid flowpath and output a third heated working fluid to the third working fluid flowpath when the cracker module is in use; wherein: an outlet of the second working fluid flowpath is in fluid communication with an inlet of the third working fluid flowpath; and an outlet of the second reactant flowpath is in fluid communication with an inlet of the third reactant fluid flowpath.

[008] The first working fluid flowpath and first reactant flowpath may be at least partially transverse to each other. The second working fluid flowpath and the second reactant flowpath may be at least partially transverse to each other. The first working fluid flowpath and first reactant flowpath may be positioned such that fluid flowing through the first reactant flowpath is at least partially counter-current to fluid flowing through the first working fluid flowpath. The first working fluid flowpath and first reactant flowpath may be positioned such that fluid flowing through the first reactant flowpath is at least partially co-current to fluid flowing through the first working fluid flowpath.

[009] The catalyst may be coated onto at least part of the one or more heat exchange surfaces of the first reaction zone and/or the second reaction zone. The catalyst may include a precious metal and/or a base metal. The surface area of the one or more heat exchange surfaces in the first reaction zone and/or the surface area of the one or more heat exchange surfaces in the second reaction zone may be at, or in excess of, about 200 square meters per cubic meter (m ² nr ³ ).

[010] The first heat source and/or second heat source and/or third heat source, where present, may include electric heating elements. The first heat source and/or second heat source and/or third heat source, where present, may include one or more catalytic combustors and/or one or more non-catalytic burners. The first heat source may include a first catalytic combustor configured to receive a fuel and air and combust the fuel in air to form the first heated working fluid. The second heat source may include a second catalytic combustor configured to receive fuel in the first thermally depleted working fluid and air and combust the fuel in the first thermally depleted working fluid in air to form the second heated working fluid. The third heat source, where present, may include a third catalytic combustor configured to receive fuel in the second thermally depleted working fluid and air and combust the fuel in the second thermally depleted working fluid in air to form the third heated working fluid.

[011] The fuel may include hydrocarbonaceous fuel. The fuel may include hydrogen. The fuel may include ammonia. The ammonia cracker module may be configured such that fuel is provided to the cracker module upstream of, or at the position of, the first heat source only. At least one catalytic combustor may be in fluid communication and/or in thermal communication with a hot waste gas stream from one or more processes outside the ammonia cracker module such that at least part of the energy and/or fuel required to initiate combustion within the at least one catalytic combustor is provided by the hot waste gas stream. The heat exchange reactor and heating system may be integral to each other.

[012] According to another aspect of the invention, there is provided a system comprising a plurality of ammonia cracker modules as described herein. The plurality of ammonia cracker modules may include 2, 3, 4, 5, 6, 7, 8, 9, or 10 ammonia cracker modules. In some systems at least some of the plurality of ammonia cracker modules may be stacked on others of the plurality of ammonia cracker modules to reduce the ground footprint required. The modules may be stacked so that they are vertically aligned or may be offset. In some systems the plurality of ammonia cracker modules may be stacked vertically such that the spatial footprint of the system does not exceed the spatial footprint of the ammonia cracker module at the base of the stack.

[013] The system may include a shared ammonia feed system. At least some of the ammonia cracker modules, and possibly each of the ammonia cracker modules may be configured to receive ammonia from a shared ammonia feed system. The hydrogen produced by some or each of the plurality of ammonia cracker modules may be combined into a single hydrogen output stream. The system may include one or more hydrogen purification systems. The system may include one or more nitrogen oxide removal systems. The system may include one or more gas turbines. The one or more gas turbines may be configured to receive and combust hydrogen produced by at least one module of the plurality of ammonia cracker modules. The system may include one or more other types of combustion engines such as compression engines or spark ignition engines. [014] According to a further aspect of the invention, there is provided a method for producing hydrogen from ammonia in a cascading cracker unit. The method includes:(1 ) generating a first heated working fluid in a first heating apparatus; (2) passing the first heated working fluid to a first reaction zone of a cracker unit; (3) feeding ammonia to the first reaction zone of the cracker unit; (4) heating the ammonia in the first reaction zone of the cracker unit using the first heated working fluid to produce a first thermally depleted working fluid stream and a first product stream including hydrogen and uncracked ammonia; (5) feeding the first product stream to a second reaction zone of the cracker unit; (6) sending the first thermally depleted working fluid to a second heating apparatus to generate a second heated working fluid; (7) passing the second heated working fluid to the second reaction zone of the cracker unit; (8) heating the first product stream in the second reaction zone of the cracker unit using the second heated working fluid to produce a second thermally depleted working fluid stream and a second product stream including hydrogen; wherein: the concentration of ammonia in the second product stream is less than the concentration of ammonia in the first product stream; the concentration of hydrogen in the second product stream is greater than the concentration of hydrogen in the first product stream; and the first and second product streams do not directly contact the first or second heated working fluids.

[015] Where the second product stream includes ammonia, the method may further include: (9) feeding the second product stream to a third reaction zone of the cracker unit; (10) sending the second thermally depleted working fluid to a third heating apparatus to generate a third heated working fluid; (11 ) passing the third heated working fluid to the third reaction zone of the cracker unit; (12) heating the second product stream in the third reaction zone of the cracker unit using the third heated working fluid to produce a third thermally depleted working fluid stream and a third product stream including hydrogen; wherein: the concentration of ammonia in the third product stream is less than the concentration of ammonia in each of the first and second product streams; the concentration of hydrogen in the third product stream is greater than the concentration of hydrogen in each of the first and second product streams; and the third product stream does not directly contact the third heated working fluid.

[016] All of the reaction zones of the cracker unit may be within a single heat exchanger apparatus. At least one of the heating apparatus may heat the working fluid using electrical heating. At least one of the heating apparatus may heat the working fluid by combusting fuel. At least one of the heating apparatus may heat the working fluid using waste gases from one or more further processes. [017] The method may include controlling the heat energy carried by the first heated working fluid and/or the second heated working fluid by regulating the rate at which air and/or fuel is introduced to the first heating apparatus and/or the second heating apparatus, respectively. Heating the ammonia in the first reaction zone of the cracker unit using the first heated working fluid may include transferring heat between the second heated working fluid and the first product stream via a first solid heat transfer interface. Heating the first product stream in the second reaction zone of the cracker unit using the second heated working fluid may include transferring heat between the second heated working fluid and the first product stream via a second solid heat transfer interface. The first solid heat transfer interface may include catalyst positioned to contact the ammonia. The second solid heat transfer interface may include a catalyst positioned to contact the first product stream.

BRIEF DESCRIPTION OF THE DRAWINGS

[018] Examples of the present disclosure will now be described with reference to the following drawings, in which:

[019] Figure 1 shows an example simplified schematic representation of an ammonia cracker module including three reaction zones;

[020] Figure 2 shows another example simplified schematic of an ammonia cracker module including three reaction zones;

[021] Figure 3 shows an example schematic simplification of a system including a plurality of ammonia cracker modules;

[022] Figure 4 shows another example of a system including an ammonia cracker module;

[023] Figure 5 shows a flow diagram of a method for producing hydrogen from ammonia in a cascading cracker unit; and

[024] Figures 6A, 6B, and 6C show simplified representations of portions of the internal configuration of various heat exchange reactors.

DETAILED DESCRIPTION

[025] The ammonia cracker module, systems and methods disclosed herein aim to provide a simple and scalable means of producing hydrogen which may be used, for example at a point-of-use application, where it is not possible, or not feasible, or not economic, to obtain hydrogen from a large scale production facility or fixed hydrogen supply infrastructure. The modular configuration allows an end user to use one or more modules as part of a single hydrogen production system with the number of modules included being scalable to provide the amount or rate of hydrogen production required to meet the user’s needs. The modules are further advantageous in that they are energy efficient. The modules may be yet further advantageous as they may operate at a lower temperature than many existing hydrogen production systems. Lower temperatures of operation result in reductions in energy losses which, in turn, enhance the energy efficiency of the module and reduce thermal stresses experienced by the equipment. Many of the features of the ammonia cracker modules described herein may work together synergistically to maintain a high efficiency of operation when cracking or converting ammonia into hydrogen.

[026] The term ‘modular’ as used herein refers to the capability for two or more ammonia cracker modules to be used together in a single scalable system. In this example, a ‘modular’ system is formed from one or more modules that may be fitted into a single system using one or more different configurations of module. The modular nature of the system means that additional modules may be added to, or some modules may be removed from, an existing system with relative ease. The simplest system includes a single ammonia cracker module whereas a more complex system may include 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, 20, or more than 20 modules. In this manner, one or more ammonia cracker modules may be assembled into an ammonia cracker system. The configuration of one or more modules may be standardised. Standardised modules and associated components may be consistent in their components such that a module may be replaced with an equivalent or identical module that performs the same function while occupying the same spatial footprint. Standardised modules may also each have the same fixtures, fittings, and connectors such that a module, or additional modules, can be easily integrated into a system. Standardised modules may also allow modules to be easily removed from a system and replaced with another module quickly and with relative ease. Two or more or each module of a plurality of modules in a system may be identical. In other examples, one or more or each of the modules in a system may be different from one or more or each other module in the system. For example, one or more modules may have different components, efficiency, production capacity, throughput, control methodology, material of constructions, operating conditions, or any other parameter of difference when compared to another module used within a modular system. [027] The term ‘cascading’ as used herein refers to the flow of one or more process streams in a system or module through multiple steps or stages in succession. Each step through which a process stream ‘cascades’ in a system or module may be substantially identical. In other examples, one or more or each step in the cascading system or module through which an input cascades may be different. A cascading process may take place within a single component of an apparatus such as an ammonia cracker module. In an example, a heat exchanger which flows a working fluid stream through multiple process zones within the single heat exchanger may be referred to as a ‘cascading’ process. In another example, passing a reactant stream through multiple reaction zones within a single reactor may be considered to be a cascading process. The term ‘cascading’ is often used in association with the flow of fluid in the direction of gravity and, for the avoidance of doubt, it should be noted that no such limitation is intended upon the system and processes described herein. In particular, the terms ‘cascading’, ‘cascade’, and the like as used here are not intended to describe the relative orientation or spatial arrangement of a process and are merely intended to relate to the principle of sequential stages for a given material, process stream, or the like in the systems and processes described.

[028] The ammonia cracker modules described herein may be any suitable size. However, the ammonia cracker modules and accompanying systems are intended to be suitable for use as ‘point-of-use’ systems with dimensions such that the ammonia cracker module and associated systems may be deployed and utilised within a range of industries and utilities with relative ease and a low spatial footprint. The ammonia cracker module may occupy a spatial volume with a length, width, and/or height of about 0.8 metres, about 0.9 metres, about 1.0 metres, about 1.1 metres, about 1.2 metres, about 1.3 metres, about 1.4 metres, about 1.5 metres, about 1 .6 metres, about 1 .7 metres, about 1 .8 metres, about 1 .9 metres, about 2.0 metres, or more than 2.0 metres. The ammonia cracker module may therefore occupy a volume of about 0.5 m ³ , about 75 m ³ , about 1 m ³ , about 2 m ³ , about 3 m ³ , about 4 m ³ , about 5 m ³ , about 6 m ³ , about 7 m ³ , about 8 m ³ , about 9 m ³ , about 10 m ³ , or any other suitable volume. The ammonia cracker module may include a housing with any of the dimensions or spatial volume previously described. The housing may contain, support, and/or arrange the other components of the ammonia cracker module within a fixed space. The dimensions of the housing of the ammonia cracker module may be a pre-determined size such that each ammonia cracker module is of the same pre-determined housing size. The use of ammonia cracker modules with housings of the same pre-determined size may facilitate the use of consistent mountings, connectors, and/or supports for each module and the easy removal and replacement of modules if or when required. [029] The ammonia cracker module includes a heat exchange reactor. The term ‘heat exchange reactor’ as used herein is intended to refer to an apparatus that combines the function of a heat exchanger and a reactor or reaction vessel within a single apparatus unit. A heat exchange reactor will therefore provide a means by which heat energy is exchanged between at least two mediums while also enclosing, or facilitating, a chemical or physiochemical reaction inside at least part of the heat exchange reactor. The heat exchange reactor of the ammonia cracker module described herein is configured to receive ammonia as at least part of a reactant stream and to convert at least part of the ammonia in the reactant stream into hydrogen and nitrogen. The conversion of ammonia into hydrogen and nitrogen in the heat exchange reactor may be carried out by heating the ammonia in the reactant stream inside the heat exchange reactor via transfer of heat energy to the ammonia from a heated working fluid stream also flowing through the heat exchange reactor. The heat exchange reactor includes a plurality of reaction zones. The heat exchange reactor is configured such that the cracking or conversion of ammonia into hydrogen will take place within each reaction zone. The heat exchange reactor may include 2, 3, 4, 5, 6, 7, 8, 9, 10, or more than 10 reaction zones. In one example, the heat exchange reactor may include 2 reaction zones. In another example, the heat exchange reactor may include 3 reactions zones. In a further example, the heat exchange reactor may include 4 reaction zones.

[030] The hydrogen output of an ammonia cracker module may be at least partially proportionate to the number of reaction zones in the heat exchange reactor of the ammonia cracker module. A greater number of reaction zones may allow for a greater maximum hydrogen output across a fixed period of time than an ammonia cracker module with fewer reaction zones, particularly where the reaction zones are identical or comparable. Each reaction zone of the heat exchange reactor may be identical or substantially identical. Alternatively, one or more or each of the reaction zones of the heat exchange reactor may be different. The heat exchange reactor may comprise a plurality of sub-heat exchanger reactors, each of which may define a reaction zone. Each sub-heat exchanger reactor may be a separate unit or may be defined regions within the heat exchanger reactor. A baffle may be present between any two reaction zones. A reaction zone generally includes a first working fluid flowpath that, in use, carries a heated working fluid in a heated working fluid stream through the reaction zone of the heat exchange reactor. A reaction zone further includes a reactant flowpath through the reaction zone of the heat exchange reactor that, in use, carries a reactant stream including ammonia through the reaction zone of the heat exchange reactor. Each reaction zone includes one or more heat exchange interfaces through which heat energy may pass from the heated working fluid flowing through the working fluid flowpath to the reactant stream flowing through the reactant flowpath. The or each heat exchange interface includes at least one surface in contact with the heated working fluid in the working fluid flowpath and at least one surface in contact with the reactant stream flowing through the reactant flowpath.

[031] The working fluid flowpath and the reactant flowpath in each reaction zone in the heat exchange reactor are configured such that heat energy is transferred between the working fluid in the working fluid flowpath and the reactant stream flowing through the reactant flowpath via the one or more heat exchange interfaces. The working fluid flowpath and the reactant flowpath may be arranged such that they are at least partially transverse to each other. In an example, the working fluid flowpath and the reactant flowpath may be at least partially transverse to each other at the point of, or around, at least one heat exchange interface. The working fluid flowpath and reactant flowpath may be mostly, or wholly, transverse to each other. The term ‘transverse’ refers to the interaction of the working fluid flowpath and the reactant flowpath at an angle of 90 degrees, substantially 90 degrees, or close to 90 degrees. Additionally, or alternatively, the working fluid flowpath and the reactant flowpath may be arranged such that they are at least partially in a counter-current configuration relative to each other. In an example, the working fluid flowpath and the reactant flowpath may be arranged such that they are at least partially in a counter-current configuration to each other at the point of, or around, the heat exchange interface.

[032] The working fluid flowpath and reactant flowpath may be mostly, or wholly, arranged counter-current to each other. Additionally, or alternatively, the working fluid flowpath and the reactant flowpath may be arranged such that they are at least partially in a co-current configuration relative to each other. In an example, the working fluid flowpath and the reactant flowpath may be arranged such that they are at least partially in a co-current configuration to each other at the point of, or around, the heat exchange interface.

[033] The working fluid flowpath and reactant flowpath may be mostly, or wholly, arranged co-current to each other. The arrangement of the working fluid flowpath and reactant fluid flowpaths may be complex in that the working fluid flowpath and reactant flowpath may be at least partially transverse, co-current, and/or counter current in their arrangement within a reaction zone of the heat exchange reactor.

[034] The arrangement of the working fluid flowpath relative to the reactant flowpath in each reaction zone of the heat exchange reactor may the same. In another example, two or more reaction zones in the heat exchange reactor may be configured such that the arrangement of the working fluid flowpath relative to the reactant flowpath is different. [035] The internal configuration of any or each reaction zone of the heat exchange reactor may be any suitable configuration that allows sufficient heat energy to be transferred from the heated working fluid to reactant stream such that ammonia is converted or cracked to form hydrogen within the portion of the reaction zone carrying the reactant stream. It may be advantageous to use a reaction zone with a particular configuration or properties. It may be advantageous to configure one or more or each reaction zone such that the surface of the reaction zone, or the heat exchange interface in particular, in contact with at least part of the reactant in the reaction flow path is greater than many known heat exchange systems used for the cracking of ammonia. For example, the surface of the reaction zone and/or the heat exchange interface may have a surface area of about 100 m ² nr ³ , about 110 m ² nr ³ , about 120 m ² m' ³ , about 130 m ² nr ³ , about 140 m ² m' ³ , about 150 m ² m' ³ , about 160 m ² nr ³ , about 170 m ² nr ³ , about 180 m ² m' ³ , about 190 m ² m' ³ , about 200 m ² m' ³ , about 210 m ² nr ³ , about 220 m ² nr ³ , about 230 m ² nr ³ , about 240 m ² nr ³ or greater than about 240 m ² m' ³ . It may be advantageous for the surface area of the reaction zone, the heat exchange interface, or the entire working portion of the heat exchanger to be at, or to be in excess of, about 200 square meters per cubic meter (m ² nr ³ ). It may be advantageous to configure one or more or each reaction zone such that the working fluid stream flowing through the working fluid flowpath and/or the reactant stream flowing through the reactant flowpath experience a low extent of pressure drop. For example, the pressure drop experienced by the working fluid stream and/or the reactant stream may be less than or equal to about 40%, less than or equal to about 35%, less than or equal to about 30%, less than or equal to about 25%, less than or equal to about 20%, less than or equal to about 15%, less than or equal to about 10%, or less than or equal to about 5%. It may be advantageous to configure each reaction zone of the heat exchange reactor to have a high surface area while also imparting a low pressure drop to the working fluid stream and/or reactant stream flowing through the reaction zone. In an example, each reaction zone and/or heat exchange interface may have a surface area of about 150 m ² nr ³ and a pressure drop of less than or equal to about 20%. In another example, each reaction zone may have a surface area of about 200 m ² nr ³ with a pressure drop of less than or equal to about 10%. In yet another example, each reaction zone may have a surface area of about 220 m ² nr ³ with a pressure drop of less than or equal to about 15%. Each reaction zone may be configured with any combination of surface area and pressure drop characteristics described herein.

[036] The heat exchange reactor may be any suitable heat exchange system suffice that the cracking or conversion of ammonia to hydrogen may occur within the heat exchange reactor. For example, the heat exchange reactor may be configured in the manner of a plate type heat exchanger, a shell and tube type heat exchanger, a spiral heat exchanger, or any other suitable type of heat exchanger. The heat exchanger may include one or more tubes or plates defining a heat exchange interface which separate the reactant and working fluid flowpaths and through which the heat may be transferred between the flowpaths, for example the heat exchange reactor may be, or may comprise, a multi-tubular heat exchanger or a plate type heat exchanger. The heat exchange reactor may further include one or more heat transfer enhancing elements including one or a plurality of fins, pins, radiative elements, or any combination thereof. The one or a plurality of fins, pins, radiative elements, or combination thereof may be present on any suitable portion of the heat exchanger to enhance the surface area and/or heat transfer capability of the heat exchange reactor. For example, the surface area of one or more plates, or other heat exchange interface surface, may be increased or enhanced by the addition of one or more such heat transfer enhancing elements. The heat transfer enhancing elements may extend from a main surface of a separating element, for example a plate surface, into the flow path of the working and I or the reactant fluid.

[037] The heat exchange reactor includes a first reaction zone and a second reaction zone. The first reaction zone of the heat exchange reactor generally includes a first inlet in fluid communication with a first outlet via a first flowpath and a second inlet in fluid communication with a second outlet via a second flowpath. A heat exchange interface, or multiple heat exchange interfaces, are positioned between the first flowpath and second flowpath such that heat energy will be carried from the working fluid flowing through the first flowpath to the reactant stream flowing through the second flowpath when the ammonia cracker module is in use. One or more surfaces of the or each heat exchange interface will become heated by the hot working fluid in the first flowpath and heat will transfer through the or each heat exchange interface to heat one or more surfaces of the or each heat exchange interface in contact with the reactant stream flowing through the second flowpath.

[038] The second reaction zone of the heat exchange reactor generally includes a third inlet in fluid communication with a third outlet via a third flowpath and a fourth inlet in fluid communication with a fourth outlet via a fourth flowpath. A heat exchange interface, or multiple heat exchange interfaces, are positioned between the third flowpath and fourth flowpath such that heat energy will be carried from working fluid flowing through the third flowpath to the reactant stream flowing through the fourth flowpath when the ammonia cracker module is in use. One or more surfaces of the or each heat exchange interface will become heated by the hot working fluid in the third flowpath and heat will transfer through the or each heat exchange interface to heat one or more surfaces of the or each heat exchange interface in contact with the reactant stream flowing through the fourth flowpath. The first outlet and third inlet are in fluid communication such that thermally depleted working fluid leaving the first reaction zone may will be routed to the second reaction zone. The second outlet and fourth inlet are in fluid communication such that the reactant stream including any unreacted ammonia, hydrogen product or other reaction products leaving the first reaction zone are routed to the second reaction zone. The first and third inlets and outlets are not in fluid communication with the second or fourth inlets and outlets such that the working fluid and reactant stream do not directly interact, mix, or the like.

[039] The first reaction zone is configured such that the first flowpath and second flowpath do not interact within the first reaction zone aside from the exchange of heat via the heat exchange interface of the first reaction zone. Similarly, the second reaction zone is configured such that the third flowpath and fourth flowpath do not interact within the second reaction zone aside from the exchange of heat via the heat exchange interface of the second reaction zone. In this manner, the working fluid and reactant entering the heat exchange reactor will ‘cascade’ from the first reaction zone to the second reaction zone and then to any subsequent reaction zone. The first and second reaction zones are configured such that the working fluid stream and reactant stream do not touch, mix, or interact while the ammonia cracker module is in use. The first, second, third, and/or fourth flowpaths may be at least partially formed by one or more conduits, pipes, channels, apertures, plates, supporting structural elements, or any combination thereof.

[040] The heat exchange reactor may include any number of additional reaction zones such as a third reaction zone, fourth reaction zone, fifth reaction zone, or any number of further reaction zones. In the interests of conciseness, the following passage will describe only the features of a third reaction zone when present alongside the first reaction zone and second reaction zone as previously described. The skilled person, with the benefit of this disclosure, will understand that the features of the third reaction zone and those of the first and second reaction zone may be essentially replicated in configuration and structure to form a fourth, fifth, or any number of further reaction zones as desired through which working fluid and/or reactant may cascade. The third reaction zone, where present, includes a fifth inlet in fluid communication with a fifth outlet via a fifth flowpath and a sixth inlet in fluid communication with a sixth outlet via a sixth flowpath. The third outlet of the second reaction zone and the fifth inlet of the third reaction zone are in fluid communication such that thermally depleted working fluid leaving the second reaction zone will be routed to the third reaction zone. The fourth outlet of the second reaction zone and the sixth inlet of the third reaction zone are in fluid communication such that the reactant stream including any unreacted ammonia, hydrogen product or other reaction products leaving the first reaction zone are routed to the second reaction zone. A heat exchange interface, or multiple heat exchange interfaces, are positioned between the fifth flowpath and sixth flowpath such that heat energy will be carried from working fluid flowing through the fifth flowpath to the reactant stream flowing through the sixth flowpath when the ammonia cracker module is in use. One or more surfaces of the or each heat exchange interface will become heated by the hot working fluid in the fifth flowpath and heat will transfer through the or each heat exchange interface to heat one or more surfaces of the or each heat exchange interface in contact with the reactant stream flowing through the sixth flowpath. The first, third, and fifth inlets and outlets are not in fluid communication with the sixth inlets and outlets such that the working fluid and reactant stream do not directly interact, mix, or the like.

[041] The heat exchange reactor may form each reaction zone from one or more structural components shared between two or more reaction zones of the heat exchange reactor. Alternatively, each reaction zone of the heat exchange reactor may be formed individually and then connected, coupled, bolted, or otherwise combined into a single heat exchange reactor apparatus. The single heat exchange reactor apparatus may therefore be formed from multiple heat exchanger sub-components or modules which are combined, stacked, closely coupled, or otherwise integrated into a single unit. The use of a single heat exchange reactor apparatus within a given module may be advantageous as it allows the ammonia cracker module to inhabit a smaller spatial footprint than may be achievable if using separate heat exchange reactors for each reaction zone. The distance that the working fluid and/or reactant stream flows between each reaction zone may be minimised. For example, the distance that the working fluid must flow between the first outlet of the first reaction zone and the third inlet of the second reaction zone may be minimised. In another example, the distance that the reactant stream must flow between the second outlet of the first reaction zone and the fourth inlet of the second reaction zone may be minimised. The distance that the working fluid and/or reactant stream flow between any pair of outlets and inlets may be less than about 0.01 m, about 0.01 m, about 0.03 m, about 0.05 m, about 0.07 m, about 0.1 m, about 0.2 m, about 0.3 m, about 0.4 m, about 0.5 m, any distance up to 0.5 m, or any other suitable distance. Confining each reaction zone in the ammonia cracker module within a single heat exchange reactor apparatus and/or minimising the distance travelled by the working fluid and/or reactant stream between each reaction zone may be advantageous for the pressure drop of the system or the provision of an ammonia cracker with a low spatial footprint. A compact configuration may also allow reaction zones, flowpaths, or other components of the heat exchange reactor and/or ammonia cracker module to share components such as internal or external walls, structural supports, or the like. [042] Each of the reaction zones in the heat exchange reactor includes a catalyst. The catalyst is positioned such that it contacts at least a portion of the reactant flowing through the reactant flowpath in each reaction zone such that ammonia present in the reactant may be converted or cracked to hydrogen. The use of a catalyst allows the cracking or conversion of ammonia to take place at lower temperatures and/or using a reduced amount of energy when compared to conversion or cracking carried out without the presence of a catalyst. The catalyst may be positioned upon one or more surfaces of the one or more heat exchange interfaces in a reaction zone in contact with the reactant flowing through the reactant flowpath. Where the catalyst is positioned upon one or more surfaces of the one or more heat exchange interfaces, the catalyst may be present in the form of a coating that covers at least part, or all, of the one or more surfaces in contact with the reactant in the reactant flowpath which may include heat transfer enhancing elements. Additionally, or alternatively, the catalyst may be positioned free from the one or more heat transfer interfaces and in contact with the reactant flowing through the reactant flowpath. In an example, the catalyst may be positioned in a basket positioned within the reactant flowpath such that the reactant stream flowing through the reactant flowpath at least partially contacts the catalyst in the basket. In another example, the catalyst may be present as part of a protrusion extending into the reactant flowpath such that the protrusion contacts at least part of the reactant flowing through the reactant flowpath. In a yet further example, the catalyst may form at least part of the inner wall of a pipe, conduit, channel, aperture, or the like which forms part of the reactant flowpath and through which reactant flows. Any suitable position and configuration of catalyst may be used suffice that the catalyst is positioned such that it can catalyse the conversion or cracking of ammonia in the reactant stream into hydrogen. The catalyst may include one or more metals which may include precious metals. For example, the catalyst may include nickel, cobalt, iron, ruthenium, or any combination thereof. The catalyst may be a supported catalyst in that the catalyst may include, be supported upon, and/or dispersed throughout a support material such as a substrate. Suitable support materials may include porous materials such as zeolites, carbon materials such as activated carbons, inorganic materials such as calcium imide, any other suitable support material, or any combination thereof. In an example, the support material may include carbon. In another example, the support material may include alumina. In another example, the support material may include ceria. In another example, the support material may include zirconia. In another example, the support material may include yttria. In a further example, the support material may include a basic material.

[043] The configuration of the two or more reaction zones in the heat exchange reactor provides a cascading and/or multi-pass mode of operation. Working fluid flowing through a reaction zone will become depleted of heat energy in that reaction zone. Thermally depleted working fluid may carry sufficient residual exploitable heat energy such that passing the thermally depleted working fluid to a further and subsequent reaction zone, where present, allows for the residual exploitable heat energy to be utilised within the ammonia cracker in the further and subsequent reaction zone. Similarly, the reactant stream flowing through a reaction zone will become depleted of ammonia due to the cracking or conversion of ammonia into hydrogen within the reaction zone. The ammonia depleted reactant stream may carry sufficient residual uncracked or unconverted ammonia such that the residual uncracked or unconverted ammonia may be cracked or converted to hydrogen when passed to the further or subsequent reaction zone. The flow of the working fluid and/or the reactant stream through two reaction zones in sequence may be referred to as a ‘two pass’ heat exchange reactor. Similarly, the flowing of the working fluid and/or the reactant stream through three reaction zones in sequence may be referred to as a ‘three pass’ heat exchange reactor. The number of passes may generally be equivalent to the number of reaction zones in the heat exchange reactor. The cascading or multi-pass configuration of the heat exchange reactor to flow working fluid and/or reactant through each reaction zone may be advantageous for the efficient use of heat energy in the working fluid and/or the efficiency of cracking or conversion of the ammonia reactant entering the heat exchange reactor of the ammonia cracker module.

[044] The ammonia cracker module includes a heating system. The heating system may be any heating system capable of heating the working fluid entering, or flowing through, the ammonia cracker module to a sufficient temperature that it may impart sufficient heat energy to the ammonia flowing through the heat exchange reactor via one or more heat transfer interfaces to crack or convert the ammonia to form hydrogen. The heating system includes a plurality of heat sources. The plurality of heat sources heat the working fluid entering and/or flowing through the ammonia cracker module. The first heat source of the plurality of heat sources is configured to heat working fluid to create a first heated working fluid that will subsequently enter first reaction zone of the heat exchange reactor and flow through the first working fluid flowpath. The first heated working fluid may therefore enter the first reaction zone via the first inlet and flow through the first reaction zone to the first outlet. The second, and subsequent heat sources, where present, will heat the working fluid depleted of heat energy by passing through one or more reaction zones of the heat exchange reactor to form a further heated working fluid which will subsequently be passed to one or more further reaction zones of the heat exchange reactor. In an example, the heating system includes a second heat source that is positioned and configured to heat thermally depleted working fluid leaving the first reaction zone to create a second heated working fluid which will subsequently enter the second reaction zone of the heat exchange reactor and flow through the second working fluid flowpath. The second heated working fluid may therefore enter the second reaction zone via the third inlet and flow through the second reaction zone to the third outlet. The heat sources of the plurality of heat sources beyond the first heat source may generally be positioned between reaction zones of the heat exchange reactor to introduce additional heat energy into the working fluid depleted of heat energy by a preceding reaction zone.

[045] The cracking or conversion of ammonia to form hydrogen is an endothermic process and so heat energy is generally consumed within each reaction zone of the heat exchange reactor. For example, where the heat exchange reactor includes two reaction zones, the first heat source will be positioned in the working fluid flowpath upstream of the first reaction zone of the heat exchange reactor such that the working fluid is heated prior to entering the first reaction zone where the endothermic cracking of ammonia will cause heat to be consumed. In this example, the second heat source is positioned between the first reaction zone and the second reaction zone such that the thermally depleted working fluid exiting the first reaction zone can be imparted additional heat energy prior to it entering the second reaction zone where the endothermic cracking of ammonia will cause it to become further depleted. As noted previously, the ammonia cracker module described herein may include any number of reaction zones beyond two. Where further reactions zones are present, heat sources may be positioned between each reaction zone along the flowpath of the working fluid such that the working fluid may be further heated and imparted with additional heat energy prior to each reaction zone of the heat exchange reactor. The heat sources may be integrated with the heat exchange reactor. More particularly, the heat sources and heat exchange reactor may share at least part of a housing, wall, boundary, or support structure. An ammonia cracker module in which one or more heat sources are integral with at least part of the heat exchange reactor may advantageous as it may reduce the quantity of material required to realise the ammonia cracker module, may reduce the distance through which working fluid must flow when passing through the ammonia cracker module, and/or may reduce the spatial footprint of the ammonia cracker module by reducing the need for additional piping, conduits, channels, or the like between the heat sources and the reaction zones of the heat exchange reactor. One or more or each heat source may also be separate and distinct from the heat exchange reactor while still forming part of the ammonia cracker module. Heat sources distinct from the heat exchange reactor may allow for the use of less complex components and/or may provide ease of component replacement or maintenance should it be required by the module. In an example, the heat exchange reactor and each heat source of the heating system are integral to each other.

[046] The working fluid heated by one or more or each of the plurality of heat sources of the heating system will increase in temperature from a first temperature to a second temperature. In an example, the first temperature may be -33°C to 700°C. For example, the first temperature may be about -30°C, about -10°C, about 0°C, about 25°C, about 50°C, about 100°C, about 150°C, about 200°C, about 250°C, about 300°C, about 350°C, about 400°C, about 450°C, about 500°C, about 550°C, about 650°C, about 700°C, or about any suitable temperature between -33°C and 700°C. In further examples, the second temperature may be 300°C to 1 ,000°C. For example, the second temperature may be about 300°C, about 350°C, about 400°C, about 450°C, about 500°C, about 550°C, about 600°C, about 650°C, about 700°C, about 750°C, about 800°C, about 850°C, about 900°C, about 950°C, about 1 ,000°C, or any other suitable temperature between 300°C and 1 ,000°C. The one or more or each heat source may increase the temperature of the working fluid it heats by 50°C to 600°C. For example, the one or more or each heat source may increase the temperature of the working fluid by about 50°C, about 100°C, about 150°C, about 200°C, about 250°C, about 300°C, about 350°C, about 400°C, about 450°C, about 500°C, about 550°C, about 600°C, or any other suitable temperature increase between 50°C and 600°C. Two or more or each of the plurality of heat sources may heat the working fluid to different extents such that the temperature increase experienced by the first working fluid when heated by the first heat source may be different to the temperature increase experienced by the thermally depleted working fluid when heated by a second or subsequent heat source. In another example, each heat source may heat the working fluid to an equivalent extent. Each of the plurality of heat sources may be any suitable form of heater. In an example, one or more or each heat source may include, or consist essentially of, an electric heater. Where at least one heat source includes, or consists essentially of, an electric heater, the at least one electric heater may include one or more electric heating elements. Electric heating elements may include wire elements, foil elements, film elements, semiconductor elements, composite heating elements, any other suitable type of heating element, or any combination thereof. In another example, one or more or each heat source may include, or consist essentially of, a combustion heater. A combustion heater may combust one or more fuels in the presence of oxygen to generate heat energy which is then used to directly, or indirectly heat the working fluid. The rate at which fuel and/or oxygen is introduced to the combustion heater and/or the ratio of fuel to oxygen may be used to control the rate of combustion, the extent of combustion of the fuel, and the amount of, and rate at which, heat energy is generated by the combustion heater. Air may be used a source of oxygen. Where at least one heat source includes, or consists essentially of, a combustion heater, the combustion heater may include a catalytic combustor and/or a non-catalytic burner. A catalytic combustor may include one or more combustion catalysts which may improve the efficiency of combustion and/or reduce the temperature at which combustion of a fuel occurs. The combustion catalyst, where present, may include a metal catalyst. A metal combustion catalyst may include metals such as platinum, palladium, or any other suitable metal capable of catalysing the combustion of a fuel. One or more or each heat source may include multiple means of heating a working fluid. For example, one or more or each heat source may include electric heating elements configured to heat the working fluid and include combustion heating apparatus such that working fluid may be heated by electric heating, combustion heating, or both electric and combustion heating.

[047] Where the heat source combusts one or more fuels, the one or more fuels may include liquid fuel, gaseous fuel, mixed-phase fuel, or any other suitable type of fuel. The fuel may include, or consist essentially of, a single fuel species. In other examples, the fuel may include a mix of fuel species. The fuel may include hydrocarbonaceous fuel. The hydrocarbonaceus fuel may include natural gas, methane, ethane, propane, any other suitable hydrocarbonaceous fuel, or any combination thereof. The fuel may include hydrogen. The hydrogen may be hydrogen previously produced from ammonia cracked or converted using one or more ammonia cracker modules as described here. The fuel may include ammonia. Where the fuel includes ammonia, the ammonia may be of the same composition as the ammonia fed to the heat exchange reactor as a reactant. In another example, at least part of the ammonia passing through the heat exchange reactor that was not cracked or converted into hydrogen by the heat exchange reactor may be directed towards the combustion heater for use as a fuel. The fuel may include a combination of hydrocarbonaceous fuel, hydrogen, ammonia, and/or any other suitable fuel. Fuel may be introduced to the ammonia cracker module directly into the working fluid flowpath upstream of the first heat source. Additionally, or alternatively, the fuel may be introduced into the working fluid flowpath at the point of the first heat source. Additional fuel may be introduced to the working fluid upstream of each heat source or at the point of each heat source as desired.

[048] Alternatively, the ammonia cracker module may introduce fuel only upstream of, or at the position of, the first heat source. In this example, excess fuel is introduced into the working fluid and a portion of this fuel is consumed by the first heat source to heat the working fluid to form the heated working fluid. The remainder of the fuel not consumed by the first heat source flows through the heat exchange reactor with the working fluid until it reaches the second heat source where it is at least partially combusted to heat the working fluid prior to the working fluid entering the second reaction zone. In such examples the amount of fuel consumed in each heat source can be controlled by the volume of oxygen provided to the heat source, which may be provided in the form of air.

[049] In examples where a third or further reaction zone are present in the heat exchange reactor, a sufficient excess of fuel may be introduced upstream of, or at the position of the first heat source such that there is sufficient fuel in the working fluid to fuel combustion in each heat source prior to each reaction zone. Additional fuel may be introduced into the working fluid at any suitable point in the process. For example, if an excess of fuel was provided to the working fluid upstream of the first reaction zone then additional fuel may only be added upstream of the third, fourth, fifth, or sixth reaction zone as needed. Additional fuel may therefore be introduced upstream of, or at the position of, one or more heat sources.

[050] Additionally, or alternatively, additional heat energy may be provided to the working fluid using non-combustion heating methods such as electric heating. In such an example, a controlled amount of fuel may be consumed in one or more or each heat source with any additional heat energy being provided via other means. In another example, additional hot working fluid from a source outside the ammonia cracker module may be introduced into the working fluid flowpath to provide additional heat energy to the working fluid at any suitable point in the process such as upstream of, or at the position of, one or more heat sources. An ammonia cracker module including a combustion heat source such as a catalytic combustor may therefore be configured such that the heat source is in fluid communication and/or thermal communication with a hot waste gas stream from one or more processes outside the ammonia cracker module. In an example, the combustor may be in thermal communication with the hot waste gas stream via a heat exchanger or the like. In examples where a gas stream is in fluid and/or thermal communication with the combustor, at least part of the energy and/or fuel required to initiate combustion within the at least one combustor and/or the heat required to induct the cracking or conversion of ammonia in one or more reaction zones is provided by the hot waste gas stream.

[051] The working fluid may be any suitable working fluid capable of being heated in the heating system by the plurality of heat sources. The working fluid may include, or consist essentially of, one or more gases. Where the working fluid includes a gas, the working fluid may include air. An output gas stream produced, or resulting from, one or more processes may be used as, and/or combined with, the working fluid entering the ammonia cracker module and/or flowing through the ammonia cracker module stream. For example, at least part of the product formed from the reactant stream of the ammonia cracker module, or another ammonia cracker module, as described herein may be used to form the working fluid used, and/or recycled, in the ammonia cracker module. Other suitable output gas streams may include one or more outputs of any suitable process. For example, an output gas stream of a turbine, generator, purifier, heat exchanger, chemical reactor, abatement system, or the like may be at least partially used to form the working fluid used, and/or recycled, in the ammonia cracker module. Where the output stream is a gas stream at elevated temperature (above ambient temperature), the heat energy carried by the output stream may contribute at least part of the heat energy required for the working fluid to heat the ammonia stream in the heat exchange reactor. The use of a hot output stream at elevated temperature may reduce the amount of energy to be provided, and/or the magnitude of temperature change needed, to cause the working fluid to reach the energy loading or temperature required to incite cracking or conversion of ammonia into hydrogen when the working fluid is passed to a reaction zone of the heat exchange reactor. Where the output gas stream contains ammonia, hydrogen, and/or hydrocarbon species, these species may be consumed as at least part of the fuel in examples where the working fluid with which the output gas stream is combined is passed to a combustion heater. In ammonia cracker modules where the heat sources are combustion heat sources then the fuel consumed by the combustion heat sources may form at least part of the working fluid. As previous described, an ammonia cracker module including multiple combustion heat sources may introduce fuel into the working fluid upstream, or at the position of, a number of heat sources less than the total number of heat sources. For example, fuel may be introduced upstream of, or at the position of, the first heat source only. In ammonia cracker modules configured in this manner, the fuel that is not consumed within any combustion heat source will act at least in part as the working fluid in that it will become heated as a result of the heat source and will carry this heat energy further into the process within the working fluid stream. In this manner, unconsumed fuel may form part of a heated working fluid formed using a heat source and the thermally depleted working fluid formed when the heated working fluid is passed through a reaction zone of the heat exchange reactor.

[052] The working fluid and/or reactant stream may be moved through the ammonia cracker module using any suitable technique. For example, the ammonia cracker module may include one or more fans, compressors, pumps, impellers, any other suitable means of moving a fluid, or any combination thereof. The conduits, pipes, channels, or other components of the ammonia cracker module defining the flowpath of the working fluid and/or ammonia reactant stream may include one or more valves, gates, doors, or the like that allow the passage of working fluid and/or the reactant stream to be limited, stopped, or otherwise controlled. The flow rate of working fluid through the working fluid flowpath passing through the heat exchange reactor may be 20 kg/hr to 10,000 kg/hr. For example, the flow rate of working fluid through the working fluid flowpath passing through the heat exchange reactor may be about 20 kg/hr, about 50 kg/hr, about 100 kg/hr, about 200 kg/hr, about 300 kg/hr, about 400 kg/hr, about 500 kg/hr, about 1 ,000 kg/hr, about 1 ,500 kg/hr, about 2,000 kg/hr, about 2,500 kg/hr, about 3,000 kg/hr, about 3,500 kg/hr, about 4,000 kg/hr, about 4,500 kg/hr, about 5,000 kg/hr, about 5,500 kg/hr, about 6,000 kg/hr, about 6,500 kg/hr, about 7,000 kg/hr, about 7,500 kg/hr, about 8,000 kg/hr, about 8,500 kg/hr, about 9,000 kg/hr, about 9,500 kg/hr, about 10,000 kg/hr, or any other suitable flow rate between 20 kg/hr and 10,000 kg/hr. The flow rate of ammonia through the heat exchange reactor may be 10 kg/hr to 3,000 kg/hr. For example, the flow rate of ammonia through the heat exchange reactor may be about 10 kg/hr, about 50 kg/hr, about 100 kg/hr, about 150 kg/hr, about 200 kg/hr, about 250 kg/hr, about 500kg/hr, about 1 ,000 kg/hr, about 1 ,500 kg/hr about 2,000 kg/hr, about 2,500 kg/hr, about 3,000 kg/hr, or any other suitable flow rate between 10 kg/hr and 3,000 kg/hr. The pressure of ammonia in the heat exchange reactor may be 50 kPa (0.5 bar abs) to 10,000 kPa (100 bar abs). For example, the pressure of ammonia in the heat exchange reactor may be about 50 kPa, about 100 kPa, about 150 kPa, about 200 kPa, about 250 kPa, about 300 kPa, about 350 kPa, about 400 kPa, about 450 kPa, about 500 kPa, about 1 ,000 kPa, about 1 ,500 kPa, about 2,000 kPa, about 2,500 kPa, about 3,000 kPa, about 3,500 kPa, about 4,000 kPa, about 4,500 kPa, about 5,000 kPa, or any other suitable pressure between 50 kPa and 10,000 kPa.

[053] The components of the ammonia cracker module may be made from any suitable materials suffice that the materials are capable of withstanding the temperatures at which the ammonia cracker module is operated. For example, a suitable material may have a melting point in excess of the maximum operating temperature of the ammonia cracker module and be able to at least partially resist any thermal shock associated with heating and cooling of the material. In an example, the heat exchange reactor, heating system, and/or any conduits, piping, or the like may be at least partially formed from steel, stainless steel, high nickel alloy steels, Hastalloy, Monel, Inconel, titanium, titanium alloys, any other suitable material, or any combination thereof.

[054] A multi-pass or cascading ammonia cracker module as described herein may be used to produce hydrogen from ammonia. A method of producing hydrogen from ammonia in a cascading cracker unit includes generating a first heated working fluid in a first heating apparatus. The first heated working fluid is then passed to the first reaction zone of a cracker unit to which ammonia is also fed. The ammonia fed to the first reaction zone of the cracker unit is heated using the first heated working fluid to produce a first thermally depleted working fluid stream and a first product stream including hydrogen, nitrogen and uncracked ammonia. The first product stream is fed to a second reaction zone of the cracker unit while the first thermally depleted working fluid is fed to a second heating apparatus where it is heated to form a second heated working fluid. The second heated working fluid is then passed to the second reaction zone of the cracker unit where it is used to heat the first product stream which forms a second thermally depleted working fluid. The first product stream including ammonia and hydrogen is heated and the ammonia is cracked to form a second product stream including hydrogen. The second product stream may also include uncracked ammonia if sufficient ammonia was fed to the first reaction zone such that it has not been fully cracked in the first and second reaction zones. In general, the concentration of ammonia in the second product stream will be less than the concentration of ammonia in the first product stream due to the cracking of ammonia in the first reaction zone. The concentration of hydrogen in the second product stream will also be greater than the concentration of hydrogen in the first product stream. The first and second product streams do not directly contact the first or second heated working fluids such that the working fluid and product streams do not mix. Heating the ammonia in the first reaction zone of the cracker unit using the first heated working fluid may include transferring heat between the first heated working fluid and the ammonia via a first solid heat transfer interface. Heating the first product stream in the second reaction zone of the cracker unit using the second heated working fluid includes transferring heat between the second heated working fluid and the first product stream via a second solid heat transfer interface. The first solid heat transfer interface and/or the second solid heat transfer interface may include a catalyst positioned to contact the ammonia and/or the first product stream, respectively.

[055] The method of producing hydrogen from ammonia in a cascading cracker unit may include one or more further steps. Where the second product stream includes ammonia, the method may include feeding the second product stream to a third reaction zone of a cracker unit, where present. In this method, the second thermally depleted working fluid may be sent to a third heating apparatus to generate a third heated working fluid. The third heated working fluid may then be passed to the third reaction zone of the cracker unit to heat the second product stream in the third reaction zone. The ammonia in the second product stream in the third reaction zone is then cracked to produce a third product stream including hydrogen. Generally, the concentration of ammonia in the third product stream will be less than the concentration of ammonia in each of the first and second product streams. The concentration of hydrogen in the third product stream will therefore be greater than the concentration of hydrogen in each of the first and second product streams. The third product stream does not directly contact the third heated working fluid such that the working fluid and product streams do not mix.

[056] All reaction zones of the cracker unit may be within a single heat exchanger apparatus such that the method can be carried out within a single ammonia cracker module as described herein. The method may involve heating the working fluid and/or any thermally depleted working fluids using any suitable means. At least one of the heating apparatus may heat the working fluid using electrical heating. In another example, at least one of the heating apparatus may heat the working fluid by combusting fuel. The method may utilise any heat source or heating system as substantially described herein. The method may include directing waste gases from one or more further processes into the working fluid to impart heat energy to the working fluid. Where this method step is used, the waste gases may become part of the working fluid and/or any thermally depleted working fluid depending upon the point in the method at which the waste gases are introduced and/or utilised.

[057] The ammonia cracker module may include a control system to control at least part of the operation of the ammonia cracker module. The control system, where present, may include one or more measurement instruments positioned to determine one or more properties of the ammonia cracker module and/or flow streams and/or one or more processes occurring in the ammonia cracker module. The control system may include one or more temperature measurement devices such as a thermometer, thermocouple, infrared temperature sensor, thermistor, or any other suitable temperature measurement device. The one or more temperature measurement devices may be present in the ammonia cracker module in any position where it may be desirable to measure the temperature of the ammonia cracker module. Suitable positions include, but are not limited to: the working fluid stream upstream of one or more or each heat source; the working fluid stream within or at the position of one or more or each heat source; the working fluid stream downstream of one or more or each heat source; the working fluid stream at the inlet and/or outlet of one or more or each reaction zone of the heat exchange reactor; the reactant stream at the inlet and/or outlet of each reaction zone of the heat exchange reactor, or at any other suitable position. The control system may include one or more pressure measurement devices such as a hydrostatic device, an aneroid gauge, an electronic pressure sensor, or any other suitable type of pressure measurement device. The one or more pressure measurement devices may be present in the ammonia cracker module in any position where it may be desirable to measure the pressure of the ammonia cracker module. Suitable positions include, but are not limited to: the working fluid stream upstream of one or more or each heat source; the working fluid stream within or at the position of one or more or each heat source; the working fluid stream downstream of one or more or each heat source; the working fluid stream at the inlet and/or outlet of one or more or each reaction zone of the heat exchange reactor; the reactant stream at the inlet and/or outlet of each reaction zone of the heat exchange reactor, or at any other suitable position. The control system may include one or more flow rate measurement devices such as a flow meter, differential pressure measurement device, a positive displacement measurement device, a velocity measurement device, or any other suitable device for measuring flow rate. The one or more flow rate measurement devices may be present in the ammonia cracker module in any position where it may be desirable to measure the flow rate of a fluid flowing through the ammonia cracker module. Suitable positions include, but are not limited to: the working fluid stream upstream of one or more or each heat source; the working fluid stream within or at the position of one or more or each heat source; the working fluid stream downstream of one or more or each heat source; the working fluid stream at the inlet and/or outlet of one or more or each reaction zone of the heat exchange reactor; the reactant stream at the inlet and/or outlet of each reaction zone of the heat exchange reactor, or at any other suitable position.

[058] The control system may include a controller, central controller, or the like. The controller may include, or may consist of, a computing device such as a computer, a programmable logic controller (PLC), distributed control system (DCS), any other type of computing and control system, or any combination thereof. The computing device may include a processor. The computing device may include a non-transient computer readable medium. The non-transient computer readable medium may be any electronic, magnetic, optical or other physical storage device that stores executable instructions, sometimes referred to as a memory. Thus, the non-transient computer readable medium may be, for example, Random Access Memory (RAM), and Electrically-Erasable Programmable Read-Only Memory (EEPROM), a storage drive, an optical disc, or the like. A computing device may allow the methods and processes of operation of the ammonia cracker module as described herein to be carried out with minimal or no interaction from a user. In one example, a user may input a start command into the computing device using a switch, user interface, or other input means to start the operation of the ammonia cracker module. Once the start command has been issued, the computing device may carry out the instructions stored on the non-transient computer readable medium to automatically control the ammonia cracker module by: opening, closing, or adjusting the position of one or more values, opening or closing one or more electrical circuits to provide or remove electrical energy to or from one or more components of the ammonia cracker module; any other suitable control operation; or any combination thereof. Various control methods may be used. In an example, the temperature to which the working fluid is heated by one or more or each of the heat sources of the heating system and/or the heat energy carried by the working fluid may be controlled. Where the heating apparatus or heat source includes a combustion heating device, controlling the heat energy carried by the first heated working fluid, the second heated working fluid, and/or the working fluid heated by any heating apparatus of the ammonia cracker module may be carried out by regulating the rate at which air and/or fuel is introduced to the heating apparatus. Regulation of air entering the heating apparatus may control the timing, duration, and/or extent of combustion of fuel. Where the heating apparatus or heat source includes an electric heating device, control of the heat energy imparted to the working fluid may be achieved by altering the amount and/or duration of supply of electrical energy to the electrical heating device. In other examples, the flow rate of working fluid and/or ammonia reactant through any portion of the ammonia cracker module may be controlled by opening, closing, or actuating valves along the flowpath of the working fluid and/or ammonia reactant. Flow rates may also be adjusted by controlling the speed of fans, the operation of compressors, or the operation of any other means through which working fluid and/or ammonia reactant is moved through the ammonia cracker module. Control may be achieved via instructions issued by the controller to one or more components of the ammonia cracker module. The controller may be communicably coupled to one or more or each component of the ammonia cracker module that may need to be controlled, change state, or be otherwise adjusted during operation of the ammonia cracker module. Additionally, or alternatively, control may be achieved via manual interactions and/or adjustments performed by a user.

[059] The ammonia cracker module may be part of a larger system. A system may include a plurality of ammonia cracker modules within a single system. The modular nature of the ammonia cracker modules means that any number of ammonia cracker modules may be combined to provide a desired rate of production of hydrogen gas from the ammonia. In general, a greater number of modules will provide a great rate of hydrogen production suffice that sufficient ammonia can be provided to each module in the system. A system may therefore include a plurality of ammonia cracker modules such as 2, 3, 4, 5, 6, 7, 8, 9, 10, up to 15, up to 20, or more than 20 ammonia cracker modules. A system including a greater number of ammonia cracker modules may be able to crack or convert a greater amount of ammonia within a fixed time period than a system with fewer ammonia cracker modules. The maximum rate of production of hydrogen may therefore be greater in a system with a greater number of ammonia cracker modules. The ammonia cracker modules may each be configured and operated in parallel. When the ammonia cracker modules are configured and operated in parallel, each ammonia cracker module will be provided with an ammonia reactant stream and will produce an output of hydrogen independently from the other ammonia cracker modules in the system. For the avoidance of doubt, the ammonia cracker modules may additionally, or alternatively, be operated in series. In series operation, the product stream leaving a first ammonia cracker module may be fed as the reactant input to a second ammonia cracker module. Series operation may be advantageous if the ammonia reactant fed to a first ammonia cracker module is not sufficiently cracked or converted to hydrogen within the first ammonia cracker module leaving sufficient ammonia for cracking or conversion to hydrogen in the second ammonia cracker module. The ammonia cracker modules in a system may be arranged partially in series and partially in parallel. The ammonia cracker modules may be arranged in any suitable manner. In an example, where a plurality of ammonia cracker modules are used together, the ammonia cracker modules may be arranged side-by-side along a plane perpendicular to the direction of gravity. However, it may be advantageous to stack the ammonia cracker modules vertically such that the spatial footprint of the system does not exceed, or does not greatly exceed, the spatial footprint of a single ammonia cracker module such as the ammonia cracker module at the base of the stack. When two or more ammonia cracked modules are stacked vertically then they may be arranged in a plane parallel to the direction of gravity.

[060] A system including a plurality of ammonia cracker modules may include a shared ammonia feed system. The shared ammonia feed system may be configured to deliver ammonia from one or more ammonia sources or reservoirs to each ammonia cracker module of the system. The flowpath and associated piping, conduits, or the like used to deliver ammonia from an ammonia source or reservoir to two or more ammonia cracker modules may therefore be partially shared with different branches or sub-divisions of flowpaths delivering ammonia to each ammonia cracker module only when the flowpath approaches the two or more ammonia cracker modules. Alternatively, individual flowpaths may carry ammonia from the ammonia source or reservoir to each ammonia cracker module. Each ammonia cracker module may therefore be configured to receive ammonia from a shared ammonia feed system. A system including a plurality of ammonia cracker modules may include a shared hydrogen output system such that hydrogen output from each of the plurality of ammonia cracker modules is combined in a single hydrogen output stream. A shared hydrogen output system may be implemented simply by directing the output of each ammonia cracker module carrying the hydrogen into a single flowpath.

[061] A system may include one or more additional components that may enhance the functionality of the system or that may benefit from use of hydrogen produced by one or more ammonia cracker modules. In an example, a system may include one or more hydrogen purification systems. A single hydrogen purification system may be used where a shared hydrogen output allows the entirety of the hydrogen product by the system to be directed towards a single purification system. In other examples, a hydrogen purification system may be used to purify the hydrogen produced by one or more ammonia cracker modules without necessary receiving the output of every ammonia cracker module within a system. Such a configuration may be adopted where the output of at least one ammonia cracker module is directed back into the system for use as fuel in one or more or each ammonia cracker modules in the system. Suitable purification systems may include pressure swing adsorption (PSA) systems, temperature swing adsorption (TSA) systems, membrane systems, any other suitable purification system, or any combination thereof. In another example, a system may include one or more nitrogen oxide (NO _X ) removal systems. Nitrogen oxides may be produced with an ammonia cracker module and may be removed from a gas stream via a removal system. Nitrogen oxide removal systems may include scrubbers, catalytic conversion systems, solid pellet and/or granular NO _X adsorbers, solid pellet and/or granular NO _X reactants, any system which may form an inert product via interaction with NO _X , any other suitable NO _X removal system, or any combination thereof. An output of one or more ammonia cracker units may be directed to one or more nitrogen oxide removal systems in order to produce a gas stream with lower nitrogen oxide content. In a yet further example, a system may include one or more turbines such as a gas turbine. Where present, the one or more turbines may be configured to receive and combust hydrogen produced by at least one of the plurality of ammonia cracker modules present in the system. The one or more turbines may be used to generate electricity or may be used to generate harnessable energy for other uses. In another yet further example, the system may include one or more engines. Where present, the one or more engines may include piston engines, reciprocating engines, compression engines, spark ignition engines, or any other suitable engines. The one or more engines may consume hydrogen and/or ammonia in one or more outputs of an ammonia cracker module in order to operate the engine.

[062] Figure 1 shows an example simplified schematic representation of an ammonia cracker module 100 including three reaction zones 101 , 102, 103 within heat exchange reactor 130. Heat sources 104, 105, 106 are positioned along the working fluid flowpath upstream of each reaction zone 101 , 102, 103. Working fluid enters the ammonia cracker module 100 via inlet 107 and flows in a flow direction 108 towards the first heat source 104. The heat source 104 heats the working fluid before passing the heated working fluid along flowpath 109 to the first reaction zone 101. The working fluid flows through the working fluid flowpath 110 of the first reaction zone 101 and heats the reactant stream flowing through the reactant flowpath 120 of the first reaction zone 101 to crack or convert ammonia in the reactant stream into hydrogen. Reactant enters the ammonia cracker module 100 via an inlet 118 and then flows towards the first reaction zone along a flowpath in a flow direction 119. The working fluid at least partially thermally depleted in the first reaction zone 101 leaves the first reaction zone 101 via flowpath 111 and is directed to second heat source 105 where it is again heated. The working fluid heated by the second heat source 105 passes to the second reaction zone 102 via flowpath 112. The working fluid flows through the second reaction zone 102 via working fluid flowpath 113 and heats the reactant stream flowing through the flowpath 122 of the second reaction zone 102 to crack or convert ammonia in the reactant stream into hydrogen. The reactant stream leaving the first reaction zone 101 flows into the second reaction 102 zone via flowpath 121 and then through the second reaction zone 102 via flowpath 122. Working fluid flowing through the second reaction zone 102 flows to third heat source 106 via flowpath 114. The working fluid is heated by the third heat source 106 before being passed to the third reaction zone 103 via flowpath 115. The working fluid flows through working fluid flowpath 116 of the third reaction zone where it heats the reactant flowing through reactant flowpath 124. The working fluid then leaves the third reaction zone 103 and leaves the ammonia cracker module via outlet 117. The reactant leaving the second reaction zone 102 is passed to the third reaction zone 103 via flowpath 123 before flowing through the reactant flowpath 124 of the third reaction zone 103. Ammonia in the reactant flowpath 124 of the third reaction zone 103 is cracked or converted to hydrogen using heat transferred to the reactant from the working fluid flowing through working fluid flowpath 116. The reactant leaving the third reaction zone 103 leaves the ammonia cracker module via outlet 125. Each working fluid flowpath 110, 113, 116 in each reaction zone 101 , 102, 103, is transverse to the reactant flowpath 120, 122, 124 in each respective reaction zone. The reaction zones, heat source, and flowpaths may be any type, configuration, or arrangement of reaction zone, heat source, and/or flowpath as described herein.

[063] Figure 2 shows another simplified schematic example of an ammonia cracker module 200. The ammonia cracker module 200 of Figure 2 is similar to the ammonia cracker module 100 shown in Figure 1 except that the heat sources 204, 205, 206 of ammonia cracker module 200 are combustion heat sources. Much like the ammonia cracker module 100 of Figure 1 , reactant enters the ammonia cracker module 200 of Figure 2 via inlet 218 and flows in flow direction 219 into the first reaction zone 201 of heat exchange reactor 230. The reactant flows through the first reaction zone 201 , second reaction zone 202, and the third reaction zone 203 before leaving the ammonia cracker module alongside any hydrogen produced in the module via outlet 224. The reactant is heated by the working fluid flowing through each reaction zone which results in ammonia in the reactant being cracked or converted into hydrogen. Working fluid enters the ammonia cracker module 200 via inlet 207 and flows through the ammonia cracker module 200 in flow direction 207. The working fluid is heated by combustion heat source 204 which combusts fuel present in the working fluid in the presence of air. Air is provided to the combustion heat source 204 via air intake 225. The heated working fluid heats the reactant in the first reaction zone 201 being passed to second combustion heat source 205 where it is again heated. The second combustion heat source combusts fuel in the working fluid in the presence of air which is provided to the second combustion heat source via ait inlet 226. The working fluid heated by the second combustion heat source 205 flows through the second reaction zone 202 and heats the reactant therein. The thermally depleted working fluid leaving the second reaction zone is heated via third combustion heat source 206 by combustion of fuel in the working fluid in the presence of air. Air is provided to the third combustion heat source 206 via air inlet 227. The working fluid used to heat the reactant in the third reaction zone then flows out of the ammonia cracker module via outlet 217. [064] Figure 3 shows an example schematic simplification of a system 300 including a plurality of ammonia cracker modules 304, 305, and 306. Although three ammonia cracker modules are shown, additional ammonia cracker modules may be included. An ammonia source 301 provides ammonia to each of the ammonia cracker modules 304, 305, 306 by flowing ammonia through shared ammonia feed system 302 in flow direction 303. The ammonia fed to the ammonia cracker modules 304, 305, 306 by the shared ammonia feed system is cracked in the heat exchange reactor 307, 308, 309 of each respective ammonia cracker module 304, 305, 306. A working fluid system (not shown) provides working fluid to each ammonia cracker module 304, 305, 306 and the working fluid is heated by heating systems 310, 311 , 312 to provide the energy to drive the conversion of ammonia to hydrogen. The hydrogen produced in the ammonia cracker modules 304, 305, 306 is leaves the modules via the combined hydrogen output system 313 and flows in flow direction 314 to a hydrogen purification system 315.

[065] Figure 4 shows another example of a system 400 including an ammonia cracker module 405. Although only a single ammonia cracker module 405 is shown, it should be understood that a plurality of ammonia cracker modules may be present without significantly altering the principles and arrangement of system 400. The system 400 includes an ammonia supply 401 which provides ammonia to the heat exchange reactor 403 and combustion heating system 404 of ammonia cracker module 405. The ammonia supply 401 also supplies ammonia to a turbine 406. Air is drawn into the combustion heating system via air inlet 407 and ammonia is combusted in the air to heat the gases flowing through heating system 404. The hot gases are passed through the heat exchange reactor 403 to crack the ammonia introduced directly to the heat exchange reactor 403 from the ammonia supply 401. The exhaust gas leaving the heat exchange reactor via flowpath 408 is directed towards NO _X removal unit 409. The hydrogen produced in the heat exchange reactor 403 and any residual ammonia is sent to the turbine 406 where it is used to drive the turbine. A portion of the hot exhaust gases leaving the turbine are directed to the heating system of the ammonia cracker module via flowpath 410 where the residual heat energy and any residual ammonia and/or hydrogen is combusted alongside fresh ammonia from the ammonia supply to heat the working fluid flowing through the ammonia cracker module. The remainder of the exhaust gases leaving the turbine are directed to the NOx removal unit to be treated.

[066] Figure 5 shows a flow diagram of a method 500 for producing hydrogen from ammonia in a cascading cracker unit such as the ammonia cracker module of Figures 1 or Figure 2 or the systems of Figure 3 or Figure 4. The method 500 includes generating 501 a first heated working fluid in a first heating apparatus. The method further includes passing 502 the first heated working fluid to a first reaction zone of a cracker unit. The method yet further includes feeding 503 ammonia to the first reaction zone of the cracker unit. Heating 504 the ammonia in the first reaction zone of the cracker unit using the first heated working fluid to produce a first thermally depleted working fluid stream and a first product stream including hydrogen and uncracked ammonia also forms part of the method 500. The method 500 also includes feeding 505 the first product stream to a second reaction zone of the cracker unit, and sending 506 the first thermally depleted working fluid to a second heating apparatus to generate a second heated working fluid. The method 500 also further includes passing 507 the second heated working fluid to the second reaction zone of the cracker unit, and heating 508 the first product stream in the second reaction zone of the cracker unit using the second heated working fluid to produce a second thermally depleted working fluid stream and a second product stream including hydrogen. The method 500 shows the method steps involved in cracking ammonia in two reactions zones but it will be understood that the method 500 may further include further method steps relating to a third reaction zone if such a reaction zone is present. The method 500 is merely an example and so may also include any method step or feature as substantially described here.

[067] Figures 6A, 6B, and 6C show simplified representations of portions of the internal configuration of various heat exchange reactors that may be used in the modules and/or systems described herein and/or shown in Figures 1 , 2, 3, or 4. Figure 6A shows a portion of the internal configuration of heat exchange reactor 600. Heat exchange reactor 600 includes plates 601 , 602, 603 arranged in parallel planes with gaps between each plate. The gaps between each plate form fluid flowpaths through which fluid may flow when the heat exchange reactor 600 is in use. For example, ammonia reactant may flow between plate 601 and 602 in a flow direction 604 when the heat exchange reactor is in use. Working fluid, and/or ammonia reactant may flow between plate 602 and plate 603 in a flow direction 605. In examples where working fluid flows between plate 602 and 603, heat may be exchanged between the working fluid flowing between plate 602 and 603 and the ammonia reactant flowing between plate 601 and plate 602 by transfer of heat through the plate 602. The heat exchange reactor 600 includes heat transfer enhancing elements 606. Heat transfer enhancing elements 606 may be of circular, oval, or rounded cross section. In an example, heat transfer enhancing elements 606 may be cylindrical or substantially cylindrical. In some examples the heat transfer enhancing elements 606 may include sub-elements extending from them, or cavities extending into them to further increase their surface area. The heat transfer enhancing elements 606 are protrusions which increase the surface area available for the absorption and subsequent transfer of heat from the working fluid to the ammonia reactant. Although the heat transfer enhancing elements 606 are shown arranged in a repeating pattern relative to each plate 601 , 602, and 603, any suitable pattern of heat transfer enhancing elements may be used. For example, each plate 601 , 602, and 603 may have an alternating arrangement of heat transfer enhancing elements. In another example, each plate 601 , 602, and 603 may have an irregular arrangement of heat transfer enhancing elements such that the arrangement of heat transfer enhancing elements is, or appears to be, substantially random. Surfaces 607a of the plates 601 , 602, and 603 in contact with the ammonia reactant when the heat exchange reactor 600 is in use and surfaces 607b of the heat transfer enhancing elements 606 in contact with the ammonia reactant when the heat exchange reactor 600 is in use are coated with a catalyst that can catalyse the cracking or conversion of the ammonia reactant to hydrogen. In the heat exchange reactor 600 of Figure 6A, substantially all of the surfaces 607a and 607b in contact with the ammonia reactant are coated with the catalyst although configurations where only portions of the surfaces 607a and/or 607b are coated are also contemplated. In examples where ammonia reactant flows between each of plate 601 , 602, and 603, working fluid may flow through a conduit or channel defined by the heat transfer enhancing elements 606 in a flow direction transverse to flow direction 604 and flow direction 605. In this example the heat transfer enhancing elements 606 are shown as extending all the way across the gaps between plates 601 , 602, and 603, but in other examples some or all of the heat transfer enhancing elements 606 may extend into the gap from one or both sides, but not extend all the way across the gap.

[068] Figure 6B shows an alternative configuration of a portion of the internal configuration of a heat exchange reactor 610. In a similar manner to the heat exchange reactor of Figure 6A, heat exchange reactor 610 includes plates 611 , 612, 613 arranged in parallel planes with gaps between each plate. The gaps between each plate forms fluid flowpaths through which fluid may flow when the heat exchange reactor 610 is in use. For example, ammonia reactant may flow between plate 611 and 612 in a flow direction 614 when the heat exchange reactor is in use. Working fluid, and/or ammonia reactant may flow between plate 612 and plate 613 in a flow direction 615. In examples where working fluid flows between plate 612 and 613, heat may be exchanged between the working fluid flowing between plate 612 and 613 and the ammonia reactant flowing between plate 611 and plate 612 by transfer of heat through the plate 612. The heat exchange reactor 610 includes heat transfer enhancing elements 616. Heat transfer enhancing elements 616 differ from those shown in Figure 6A in that heat transfer enhancing elements 616 are protrusions with an equiangular quadrilateral cross section. For example, the cross section of heat transfer enhancing elements 616 may be square or rectangular. In an example, heat transfer enhancing elements 616 may be cubes, rectangular prisms, or the like. The heat transfer enhancing elements 616 are protrusions which increase the surface area available for the absorption and subsequent transfer of heat from the working fluid to the ammonia reactant. Although the heat transfer enhancing elements 616 are shown arranged in a repeating pattern relative to each plate 611 , 612, and 613, any suitable pattern of heat transfer enhancing elements may be used. For example, each plate 611 , 612, and 613 may have an alternating arrangement of heat transfer enhancing elements. In another example, each plate 611 , 612, and 613 may have an irregular arrangement of heat transfer enhancing elements 616 such that the arrangement of heat transfer enhancing elements 616 is, or appears to be, substantially random. Surfaces of portions of the plates 611 , 612, and 613 in contact with the ammonia reactant when the heat exchange reactor 610 is in use include a coating 617 with a catalyst that can catalyse the cracking or conversion of the ammonia reactant to hydrogen. In some examples also some or all surfaces of the heat transfer enhancing elements 616 in contact with the ammonia reactant when the heat exchange reactor 610 is in use may include the coating 617. Only portions of the surfaces in contact with the ammonia reactant are coated with a catalyst in the example of Figure 6B but additional portions of the surfaces, or all of the surfaces, may be coated in other examples. In examples where ammonia reactant flows between each of plate 611 , 612, and 613, working fluid may flow through a conduit or channel defined by the heat transfer enhancing elements 616 in a flow direction transverse to flow direction 614 and flow direction 615.

[069] Figure 6C shows an alternative configuration of a portion of the internal configuration of a heat exchange reactor 620. In a similar manner to the heat exchange reactor of Figures 6A and 6B, heat exchange reactor 620 includes plates 621 , 622, 623 arranged in parallel planes with gaps between each plate. The gaps between each plate 621 , 622, 623 form fluid flowpaths through which fluid may flow when the heat exchange reactor 620 is in use. For example, ammonia reactant may flow between plate 621 and 622 in a flow direction 624 when the heat exchange reactor is in use. Working fluid, and/or ammonia reactant may flow between plate 622 and plate 623 in a flow direction 625. In examples where working fluid flows between plate 622 and 623, heat may be exchanged between the working fluid flowing between plate 622 and 623 and the ammonia reactant flowing between plate 621 and plate 622 by transfer of heat through the plate 622. The heat exchange reactor 620 includes heat transfer enhancing elements 626. Heat transfer enhancing elements 626 differ from those shown in Figures 6A and 6B in that heat transfer enhancing elements 626 are fin-like protrusions having a dimension such as thickness which is greatly exceeded by the height and width. For example, the fin-like protrusions may be thin, plate like protrusions having a broad face and a narrow edge. In this example the fin-like protrusions are arranged with the broad face facing the fluid flow, which may increase turbulence, but they could be arranged with the narrow edge facing into the flow, which may reduce pressure drop. The fin-like projections may all be arranged in the same orientation, in random orientations or at angles to cause fluid to flow in a desired direction or pattern. The heat transfer enhancing elements 626 are protrusions which increase the surface area available for the absorption and subsequent transfer of heat from the working fluid to the ammonia reactant. Although the heat transfer enhancing elements are shown arranged in an irregular or substantially random pattern relative to each plate, a regular, repeating, or similarly ordered pattern may also be used such as those shown in respect of the heat transfer enhancing elements of Figures 6A and 6B. Surfaces 627a of the plates 621 , 622, and 623 in contact with the ammonia reactant when the heat exchange reactor 620 is in use and surfaces 627b of the heat transfer enhancing elements 626 in contact with the ammonia reactant when the heat exchange reactor 620 is in use are coated with a catalyst that can catalyse the cracking or conversion of the ammonia reactant to hydrogen. All of surfaces 627a and 627b, or only portions of the surfaces 627a and/or 627b in contact with the ammonia reactant may be coated in the manner shown in Figure 6A or 6B relative to heat exchange reactors 600 and 610.

[070] The ammonia cracker module, systems, and methods described herein are therefore well suited to the production of hydrogen. The ammonia cracker module and accompanying systems and methods provide an efficient point of use system that can be easily scaled by using multiple ammonia cracker modules to produce hydrogen. The ammonia cracker modules described herein may provide a high efficiency due to the synergistic combination of any number of the following features, where present: a high surface area for heat exchange; the cascading nature of the reactant and working fluid streams through the heat exchange reactor; the transverse or cross-flow, or counter-current, or co-current arrangement of working fluid to reactant in the reaction zones; the ability to control the rate of heat energy provided to the system via combustion heat sources; the use of a catalyst within the heat exchange reactor; and/or the use of recycled heat, fuel, and/or ammonia from other processes to reduce the burden of new heat, fuel, and/or ammonia required by the process. These and other advantages will be apparent to the skilled person with the benefit of this disclosure.