Electrical connection to an assembly

Abstract

There is provided an assembly, a reactor system and a method for catalysing an endothermic reaction of a feed gas being converted to a product gas. The assembly comprises a catalyst zone comprising a catalyst and an electrically conductive material for resistance heating of the catalyst. The electrically conductive material is arranged to form at least one electrically conductive pathway between conductors for connecting the electrically conductive material to at least one electrical supply. The assembly also comprises control circuitry configured to monitor an electrical characteristic associated with an electrical connectivity parameter between at least one of the conductors and an electrical ground, and to adjust an electrical supply parameter of the electrical supply such that the electrical characteristic meets a predefined threshold.

Description

[0001] ELECTRICAL CONNECTION TO AN ASSEMBLY

[0002] The present techniques relate to an assembly, a reactor system, and a method of providing an electrical supply to an assembly.

[0003] In electrically-heated catalytic reactors for endothermic reactions such as those disclosed in WO2019228797, W02021260108 and WO2023274939A1 (incorporated herein by reference), a feed gas to be processed is fed to a catalyst, for example, one or more structured catalysts, which provide heat to the endothermic chemical reaction (e.g. steam methane reforming or reverse water gas shift reactions) by resistance heating. Each structured catalyst comprises a macroscopic structure. The term “macroscopic structure” denotes a structure which is large enough to be visible with the naked eye, without magnification. The dimensions of the macroscopic structure are typically in the range of centimetres or meters. Each structured catalyst may comprise a single macroscopic structure or multiple macroscopic structures. Preferably, the macroscopic structure is extruded, fabricated from corrugated sheet metal or 3D printed, because the pressure drop from the inlet to the outlet may be reduced considerably compared to arrangements where the catalyst material is in the form of pellets or similar.

[0004] The macroscopic structure comprises an electrically conductive material for heating by resistance. The macroscopic structure also supports a catalytically active material, which may be on a ceramic coating such as in WO2023274939A1, and may be provided on at least part of the exposed surface area of the macroscopic structure. The surface area of the macroscopic structure itself, the fraction of the macroscopic structure coated with a ceramic coating, the type, features and structure (e.g. particle size, typically within the range of 2 nm - 250 nm, in some instances up to 1000 nm, thickness typically in the range of 10-500 pm) of the coating and the amount and composition of the catalytically active material may be suitably tailored to the reaction and operating conditions.

[0005] The electrical arrangements provided to supply electrical current to the electrically conductive material(s) are provided with electrical insulation resistance between the conductive portions of the reactor and a ground connection of the reactor. To help ensure continued operation of the reactor, there is a need to reduce a likelihood of earth faults, which may pose a danger to the assemblies and / or to their operators, when the assembly is connected to an electrical supply.

[0006] According to a first aspect of the present techniques there is provided an assembly for catalysing an endothermic reaction of a feed gas being converted to a product gas, the assembly comprising: a catalyst zone comprising a catalyst and an electrically conductive material for resistance heating of the catalyst, wherein the electrically conductive material is arranged to form at least one electrically conductive pathway between conductors for connecting the electrically conductive material to at least one electrical supply; and control circuitry configured to monitor an electrical characteristic associated with an electrical connectivity parameter between at least one of the conductors and an electrical ground, and to adjust an electrical supply parameter of the electrical supply such that the electrical characteristic meets a predefined threshold.

[0007] According to a second aspect of the present techniques there is provided a reactor system comprising: the assembly of the first aspect; and a reactor shell housing the assembly.

[0008] According to a further aspect of the present techniques there is provided a method of providing an electrical supply to an assembly for catalysing an endothermic reaction of a feed gas being converted to a product gas, the assembly comprising a catalyst zone, the catalyst zone comprising at least one catalyst and an electrically conductive material for resistance heating of the at least one catalyst, wherein the electrically conductive material is arranged to form at least one electrically conductive pathway between conductors for connecting the electrically conductive material to at least one electrical supply, the method comprising: monitoring an electrical characteristic associated with an electrical connectivity parameter between at least one of the conductors and an electrical ground; and adjusting an electrical supply parameter of the electrical supply such that the electrical characteristic meets a predefined threshold.

[0009] The present techniques will be described further, by way of example only, with reference to configurations thereof as illustrated in the accompanying drawings, in which:

[0010] Figure 1 schematically illustrates an assembly which may embody various examples of the present techniques;

[0011] Figure 2 schematically illustrates an assembly which may embody various examples of the present techniques;

[0012] Figure 3 schematically illustrates an electrical circuit illustrative of various examples of the present techniques;

[0013] Figure 4 schematically illustrates (A) a three phase electrical supply, (B) an electrical circuit illustrative of various examples of the present techniques, and (C) an electrical circuit illustrative of various examples of the present techniques;

[0014] Figure 5 schematically illustrates an electrical arrangement of an assembly which may embody various examples of the present techniques;

[0015] Figure 6 schematically illustrates an electrical arrangement of an assembly which may embody various examples of the present techniques;

[0016] Figure 7 schematically illustrates an electrical arrangement of an assembly which may embody various examples of the present techniques;

[0017] Figure 8 schematically illustrates an electrical arrangement of an assembly which may embody various examples of the present techniques;

[0018] Figure 9 schematically illustrates an electrical arrangement of an assembly which may embody various examples of the present techniques;

[0019] Figure 10 schematically illustrates a sequence of steps according to various examples of the present techniques; and

[0020] Figure 11 schematically illustrates a sequence of steps according to various examples of the present techniques. According to some configurations there is provided an assembly for catalysing an endothermic reaction of a feed gas being converted to a product gas. The assembly comprises a catalyst zone comprising a catalyst and an electrically conductive material for resistance heating of the catalyst. The electrically conductive material is arranged to form at least one electrically conductive pathway between conductors for connecting the electrically conductive material to at least one electrical supply. The assembly is also provided with control circuitry configured to monitor an electrical characteristic associated with an electrical connectivity parameter between at least one of the conductors and an electrical ground, and to adjust an electrical supply parameter of the electrical supply such that the electrical characteristic meets a predefined threshold.

[0021] The application of a voltage, generated by the electrical supply, across the electrically conductive material causes a current to pass through the electrically conductive material which generates heat due to the resistance of the electrically conductive material which heats the catalyst. The catalyst may be any catalytically active material (or any combination of plural catalytically active materials) and may be suitably tailored to the reaction and operating conditions required for operation of the assembly. The electrical pathway that the current takes through the catalyst zone can be manufactured to form a variety of different configurations as will be disclosed in further detail below. However, the electrical pathway need not coincide with a fluidic pathway taken by the feed gas as it passes through the catalyst zone and can be designed independently from the fluidic pathway. Monitoring the electrical characteristic based on the electrical connectivity parameter is performed whilst the system is online (i.e., whilst it is in operation) and provides an indication of electrical connectivity between the conductors and the electrical ground. The provision of control circuitry to adjust, based on this monitoring, the electrical supply parameter of the electrical supply, provides feedback between the electrical characteristics of the assembly and the electrical supply. The properties of the electrical supply can therefore be varied (either globally (e.g., by adjusting supply parameter associated with all electrical pathways in the assembly), or locally, (e.g., by adjusting a supply parameter associated with a subset of the electrical pathways in the assembly)). Performing these adjustments whilst the system is in operation enables the control circuitry to account for variation in the electrical connectivity parameter within the catalyst zone. The electrical connectivity parameters may vary during operation due to, for example, thermal effects, chemical effects, phase transitions, and aging of the system. Hence, this approach can reduce the likelihood of an electrical fault, for example, an earth fault, occurring between the electrical conductors and the electrical ground during operation of the assembly.

[0022] Whilst the control circuitry can be arranged to monitor any electrical connectivity parameter, in some preferred configurations the electrical connectivity parameter is based on insulation resistance. Electrical insulation may be provided between the electrically conductive material and the ground connection. Under ideal operating conditions, the insulation resistance should be sufficient to ensure that any current flow between the electrically conductive material and the ground connection is below a minimum acceptable threshold. However, where the electrical insulation is either damaged or degraded, the insulation resistance may be reduced which could result in an earth fault which may pose a safety hazard and require maintenance or replacement of part or all of the assembly. By monitoring an electrical connectivity parameter that is based on the insulation resistance, the control circuitry can take steps to mitigate this possibility by adjusting the electrical supply parameter to ensure that the insulation resistance meets the predefined threshold. As a result, electrical safety is improved, the likelihood of the assembly requiring maintenance is reduced and the overall lifetime of the assembly is improved. In some alternative configurations the insulation resistance is measured by superimposing a measuring DC voltage between the phase and ground connection. In other alternative configurations the insulation resistance is measured by an adaptive measuring pulse. In some configurations of the invention, where said endothermic reaction is a steam methane reforming reaction and consequently the reactant gas will require steam, monitoring said insulation resistance may be particularly important, because a sudden temperature drop or cold spot in the catalyst zone could lead to a phase transition of the reactant gas to form liquid water which could, in turn, lead to said earth fault if not managed properly. As discussed, the monitoring of the electrical characteristic associated with the electrical connectivity parameter, would mitigate against such a scenario and would avoid a potentially hazardous scenario. In some configurations the electrical characteristic is derived from the insulation resistance divided by the electrical supply parameter. The insulation resistance may be measured, for example, by calculating a current flowing from the conductors (electrical connections to the assembly) to the electrical ground. Based on a known voltage applied to the system, the insulation resistance can be determined using Ohm’s law. The known voltage applied to the system may be, for example, 300 Volts, 600 Volts, 1000 Volts, 2000 Volts, 3000 Volts, or higher. Ensuring that the insulation resistance divided by the electrical supply parameter such that the electrical characteristic meets the predefined threshold ensures that the earth fault current flowing between the conductor and the electrical ground is reduced when the electrical supply parameter is reduced, thereby providing a direct link between the parameters that can be adjusted by the control circuitry and the electrical characteristic.

[0023] Whilst in some configurations the electrical characteristic may be measured between a single one of the conductors and the electrical ground, in some configurations the control circuitry is configured to monitor the electrical characteristic between each of the conductors and the electrical ground. This allows the control circuitry to determine a particular location within the at least one electrically conductive pathway at which an earth fault may have occurred.

[0024] As discussed, the adjustment of the electrical supply parameter may be performed globally, i.e., for all electrical connections to the assembly. Alternatively, in some configurations the control circuitry is configured, for each given conductor of the conductors, to adjust the electrical supply parameter associated with the at least one electrical supply connected to the given conductor. This fine-grained control of the electrical supply parameters allows the electrical supply to provide an electrical current having an electrical supply parameter tailored to each of the electrical conductors. As a result, the control circuitry is able to maintain optimal operating conditions for those conductors where the electrical characteristic meets the predefined threshold and to provide an adjusted electrical supply parameter for those conductors where the electrical characteristic does not meet the predefined threshold. In some configurations the electrical supply parameter is a voltage. The voltage may be a peak voltage or a Root Mean Square (RMS) voltage. Alternatively, the electrical supply parameter may be a current.

[0025] The at least one electrical supply may comprise a single electrical supply or a plurality of electrical supplies. The plurality of electrical supplies may be identical supplies or different supplies providing different types of electrical current. In some configurations the electrical supply comprises at least one AC supply. The at least one AC supply may be provided in combination with other AC supplies, either operating on a same voltage or a different voltage and on a same phase or a different phase. Alternatively, the at least one AC supply may be provided in combination with one or more different electrical supplies providing a different type of electrical current.

[0026] In some configurations the AC supply comprises an N phase AC supply; and each phase of the N phase AC supply is phase shifted by 2 N with respect to another phase of the N phase AC supply. In some configurations N is equal to three such that the AC supply is a three phase AC supply with each phase shifted by 120 degrees with respect to another of the phases. However, in other configurations N could be any number, e.g., 2, 4, 5, etc.

[0027] In some configurations the electrical characteristic is based on measurements over at least one period of the multi-phase AC supply. Hence, the electrical characteristic is not an instant characteristic measured at a single point in time. Rather, it represents a time averaged characteristic over at least one period (duty cycle) of the AC supply.

[0028] In some configurations the electrical characteristic is based on at least one of an average measured over the at least one period; a maximum measured over the at least one period; and a minimum measured over the at least one period. In some configurations, where an average electrical characteristic is measured, the electrical characteristic is a Root Mean Square characteristic obtained by taking measurements over a period of the AC supply, squaring those measurements, averaging the result of the squaring, and taking the square root of the average. The use of RMS measurements avoids the possibility of AC parameters averaging to zero. Where the electrical characteristic is measured as a minimum or a maximum characteristic, the minimum or maximum characteristic may correspond to a minimum or maximum in terms of absolute value of the electrical characteristic.

[0029] The electrically conductive pathway between the conductors may be variously arranged dependent on the particular implementation. In some configurations the at least one electrically conductive pathway comprises a plurality of electrically conductive pathways arranged in a star configuration. A star configuration (also referred to as a wye configuration) refers to an electrical arrangement in which each of N conductors is connected to one of N phases with the N conductors forming N independent pathways to a neutral point (otherwise referred to as a star point or star bridge) at which the N phases cancel out resulting (at least in the idealised case where all of the N independent pathways are electrically identical) in net zero volts. The neutral point may be provided with a further conductor providing a neutral return connection back to the electrical supply. Alternatively, the neutral point may be left floating and not connected back to the electrical supply.

[0030] In some configurations the at least one electrically conductive pathway comprises a plurality of electrically conductive pathways arranged in a delta configuration. The delta configuration is an electrical configuration in which each given conductor is electrically connected, via at least part of the electrically conductive pathway, to two other conductors, each of the two other conductors connected to one of the electrical supplies having a phase shift of 2 N relative to the given conductor. In the delta configuration, there is no fixed neutral point.

[0031] The delta configuration and the star configuration need not be exclusively used. In some configurations some of the conductors may be connected to one another, via the electrically conductive material, in a delta configuration and others of the conductors may be connected to one another, via the electrically conductive material in a star configuration.

[0032] In some configurations the electrical supply comprises a DC supply. The DC supply may be provided as the only source of electrical power or as one of a plurality of sources of electrical power which may also include other DC supplies, single-phase and / or multi-phase AC supplies. The plurality of supplies may be set to a same peak voltage or a plurality of different peak voltages.

[0033] In some configurations the DC supply comprises a plurality of DC outputs and a common neutral point; the conductors comprise a plurality of input conductors for connection to the plurality of DC outputs, and at least one output conductor for connection to the common neutral point; the at least one electrically conductive pathway comprises a plurality of electrically conductive pathways, the plurality of electrically conductive pathways connecting each of the plurality of input conductors in parallel to the at least one output conductor. The at least one output conductor may be a single output conductor. Alternatively, the at least one output conductor may be a plurality of output conductors that are each suitable for connection to the common neutral point.

[0034] In some configurations the catalyst comprises a structured catalyst, having a macroscopic structure; and / or the catalyst comprises the electrically conductive material; or the electrically conductive material is separate from the catalyst. For configurations in which the catalyst (e.g., the structured catalyst, an unstructured catalyst, or a fixed bed of catalyst particle) comprises the electrically conductive material, the catalyst itself contains the electrically conductive material and provides the at least one electrically conductive pathway. For example, the catalyst may be fabricated (fully or partly) from materials including (comprising) the electrically conductive material, or may have the electrically conductive material embedded / integrated or impregnated into the entirety or a part its structure. In this way, the catalyst can be directly heated through application of current from the electrical supply. For configurations in which the electrically conductive material comprises the electrical heating element separate from the catalyst, the catalyst may be arranged in any manner. For example, the catalyst may comprise one or a plurality of structured catalysts, and / or one or a plurality of unstructured catalysts, and / or a fixed bed of catalyst particles. In such configurations, the electrical heating elements are independent of (e.g., are physically distinct from) the structured catalysts and may provide heat to the structured catalysts through, e.g., heat conduction and / or radiation. Such an approach enables independent design of the catalyst elements and the heating elements. The heating elements may be designed, for example, to take a tortuous pathway through the catalyst elements to provide a uniform heating. Alternatively, the heating elements may be arranged in particular regions of the catalyst zone to provide a more concentrated application of heat in some regions.

[0035] In some configurations, comprising a plurality of structured catalysts, the plurality of structured catalysts are grouped in a plurality of arrays, each array comprising two or more structured catalysts; and each of the at least one electrically conductive pathway comprises at least one of the plurality of arrays. Each structured catalyst comprises a macroscopic structure. The dimensions of the macroscopic structure are typically in the range of centimetres or meters. Each structured catalyst may comprise a single macroscopic structure or multiple macroscopic structures. Preferably, the macroscopic structure is extruded, fabricated from corrugated sheet metal or 3D printed, because the pressure drop from the inlet to the outlet may be reduced considerably compared to arrangements where the catalyst material is in the form of pellets or similar. Each of the structured catalysts provides a whole or part of a fluidic pathway for the feed gas to pass through whilst being heated by the structured catalyst. The structured catalysts are grouped into arrays which may contain any number (1, 2,3, ...) of structured catalysts. The number, size and geometry of the structured catalysts in each array may be the same, however, this is not necessarily the case and in some configurations one or more of the arrays may contain a different number of structured catalysts to the others. Alternatively, or in addition, the size and geometry of the structured catalysts may vary within the array or between arrays. The electrically conductive pathways formed by the arrays may be arranged according to any of the configurations described above. For example, each array may form an electrically conductive pathway that forms part of a star configuration or a delta configuration. As discussed above, the fluid pathways through the structured catalysts may coincide with the electrically conductive pathways. Alternatively, the fluid pathways through the structured catalysts may be independent from the electrically conductive pathways.

[0036] In a preferred embodiment the control circuitry comprises a programable power supply comprising a thyristor. In some configurations the control circuitry comprises a programmable power supply comprising a thyristor, a step transformer, a variable transformer, a linear voltage regulator, and / or a switching regulator. For configurations in which multiple AC or DC supplies are provided to the conductors, the control circuitry may be configured to provide individual control to each of the supplies based on measurement of the electrical characteristic associated with the electrical connectivity parameter between a respective conductor and the ground. Alternative arrangements for an electrically controllable power supply may be used as would be known to the person skilled in the art.

[0037] In some configurations the control circuitry is configured to adjust the electrical supply parameter to maintain a continued electrical supply between the at least one of the conductors and the electrical ground. In other words, adjusting the electrical supply parameter involves reducing or increasing the electrical supply parameter without switching the electrical supply off. The continued electrical supply may be a continued DC or AC electrical supply. The term continued electrical supply in relation to an AC supply denotes an AC electrical supply that continues to provide a non-zero peak or root mean square (RMS) voltage. Hence, whilst the voltage may drop to zero instantaneously (e.g., twice per period of the AC voltage signal), the peak and RMS voltage associated with the supply is still non-zero and is classified as a continued electrical supply.

[0038] Whilst the predefined threshold may be based on any parameter, for example, a maximum power usage constraint, or a quality of service constraint, in some configurations the predefined threshold is an electrical safety threshold, the electrical safety threshold being: greater than 10 Ohms per Volt; preferably greater than 20 Ohms per Volt; and particularly preferably greater than 300 Ohms per Volt. The electrical safety threshold relates to an insulation resistance between the conductor and the ground connection is selected to avoid earth faults which occur when one of the conductors becomes electrically connected to the ground connection. Prevention of such faults is achieved by determining, as the electrical connectivity parameter between at least one of the conductors and the electrical ground, a measure of impedance (e.g. a measure of insulation resistance). The electrical characteristic can then be determined based on the supply voltage (for example, a peak voltage or an RMS voltage in the case of an AC supply) by dividing the impedance by that supply voltage. The resulting electrical characteristic (measured in Ohms per Volt, also equal to Amperes'1) can then be compared against the predefined threshold. The greater the electrical characteristic (Ohms per Volt) the lower the current passing between the at least one of the conductors and the electrical ground. The electrical safety threshold may be chosen dependent on the particular implementation and maybe greater than 10 Ohms per Volt, greater than 20 Ohms per Volt, greater than 30 Ohms per Volt, greater than 40 Ohms per Volt, greater than 50 Ohms per Volt, greater than 75 Ohms per Volt, greater than 100 Ohms per Volt, greater than 150 Ohms per Volt, greater than 200 Ohms per Volt, or greater than 250 Ohms per Volt.

[0039] In some configurations there is provided a reactor system comprising: the assembly according to any of the configurations described herein; and a reactor shell housing the assembly. The shell may comprise an inlet for receiving the feed gas and an outlet for the product gas. The reactor may also comprise a thermal insulation layer between the catalyst zone and the shell (the thermal insulation layer preferably having a thermal conductivity of < 20 W / (mK), more preferably < 1 W / (mK)). The reactor may be used for any suitable reaction, but particularly may be used for one or more endothermic reactions such as steam methane reforming, hydrogen cyanide formation, methanol cracking, ammonia cracking, reverse water gas shift and dehydrogenation. The reactor may be configured according to the low voltage directive (2014 / 35 / EU).

[0040] In some configurations the reactor system may further comprise the at least one electrical supply connected to the conductors; and / or wherein the conductors are provided outside of the reactor shell; and / or wherein the conductors are connected to electrical supply using a feedthrough; and / or wherein the electrical reactor shell is connected to the ground connection. Connecting the electrical supply using a feedthrough allows for the reactor to operate at pressures above atmospheric pressure. The feedthrough may be provided as a single feedthrough housing plural electrical connection pathways (for example, cables or conductive elements). Alternatively, plural feedthroughs may be provided. For example, where an N phase supply is used, N feedthroughs, 2 times N feedthroughs, or N+l feedthroughs may be provided dependent on the type of electrical supply and the electrical configuration provided between conductors. Where multiple electrical supplies are provided within a single feedthrough using a plurality of electrical connection pathways, the plurality of connection pathways may be arranged, for example, in a linear configuration within the feedthrough. Alternatively, the plurality of connection pathways may be arranged in a trefoil configuration within the feedthrough, where a trefoil configuration refers to an arrangement of connection pathways in which a shortest distance between all possible pairs of the connection pathways is the same. It would be readily apparent to the skilled person that any number of feedthroughs may be provided and that different configurations of feedthrough may be appropriate based on, for example, the electrical supplies used, the electrical configuration within the reactor, and arrangement of electrical equipment in an installation environment for the reactor. In some configurations the feedthroughs are purged with a substantially dry process gas to keep the feedthrough free of condensate. This allows for the system to be applied for operation with gases prospective of condensation.

[0041] The assembly disclosed in this application provides the technical advantage of reducing the likelihood of an electrical fault, for example, an earth fault, occurring between the electrical conductors and the electrical ground during operation of the assembly. In some example applications of the assembly described herein it is possible to engineer a reactor in which all constituents are assembled into a complete construct, which also can be a pressure bearing construct. For example, applications in which electrical feedthroughs are provided, an improved means of mechanical attachment of the feedthroughs to the reactor can be achieved through appropriate choice of electrical insulation materials. Similarly, through appropriate choice of electrical insulation, the assembly can be mechanically attached but still electrically insulated from said reactor. Some examples of electrical insulation materials include ceramics and polymers between the different constituent parts to provide a high electrical resistance towards the reactor shell. Using the assembly described herein, it is consequently possible to design a total reactor installation that is compact and that, through the provision of the control circuitry to mitigate against electrical faults, allows overdesign of the electrical insulation layers to be reduced whilst providing an approach for monitoring unexpected operating scenarios which could result in potentially hazardous situations arising.

[0042] Some configurations of the invention will now be described with reference to the accompanying drawings.

[0043] Figure 1 schematically illustrates an assembly 10 according to various configurations of the present techniques. The assembly 10 is provided with a catalyst zone comprising a plurality of structured catalysts 12 including a first structured catalyst 12(A) and a second structured catalyst 12(B). The plurality of structured catalysts 12 support a catalytically active material. The structured catalysts 12 are arranged to provide a fluid pathway and receive a feed gas at one end of the fluid pathway and may be configured, for example, according to any of the examples set out in WO2019228797, W02021260108 and WO2023274939A1. The feed gas is heated as it passes through the plurality of structured catalysts 12 to cause a reaction to take place resulting in a product gas being produced at the far end of the fluid pathway. The plurality of structured catalysts 12 are electrically connected to one another between one or more conductors 14 which, in the illustrated configuration, comprise conductor 14(A) and conductor 14(B). The conductors 14 are provided to enable connection to a power supply 18 which provides power to the plurality of structured catalysts 12 to generate heat through resistance heating. The power supply is also connected to control circuitry 16 which measures an electrical characteristic associated with an electrical connectivity parameter between at least one of the plurality of conductors 14 and the electrical ground 11. The control circuitry 16 is arranged to control the power supply 18 to adjust at least one electrical supply parameter such that the electrical characteristic meets a predefined threshold. Whilst, in the illustrated configuration, the catalyst zone is provided with a plurality of structured catalysts that comprise an electrically conductive material, in alternative configurations, the catalyst zone may be provided with structured or unstructured catalysts which may be heated by a heating element, separate from the catalysts, which comprises an electrically conductive material.

[0044] Figure 2 schematically illustrates an assembly 20 according to various configurations of the present technique. The assembly 20 is provided with a power supply, a catalyst zone 24 comprising a catalyst, control circuitry 26 and a test resistor 28 (also denoted RT). Details of the electrical arrangement of the catalyst zone 24 are not illustrated. However, it would be readily apparent to the person skilled in the art that any of the electrical arrangements of the catalyst zone disclosed herein could be provided. In an ideal system, the electrical power supplied by the power supply 22 would be completely insulated from the electrical ground. However, in any real system there may be a small leakage current with current from the power supply 22 passing through the insulation resistance provided around the electrically conductive material in the catalyst zone 24 and to the electrical ground. In the illustrated configuration, the control circuitry 26 is able to measure the leakage current using the test resistor 28 which as a value of electrical resistance that is known to the control circuitry 26. The control circuitry 26 measures the voltage VTacross the test resistor 28 and is able to determine the current flowing through that test resistor using Ohm’s law, IT= VT / RT. Where the current ITis larger than expected, the control circuitry is able to determine that the insulation resistance of the catalyst zone 24 is not performing as expected and may choose to reduce the voltage supplied by the power supply 22. For example, the current ITmay, in some configurations, be the electrical connectivity parameter, and the control circuitry 26 may derive the electrical characteristic of the circuit by dividing the known voltage of the power supply by that current to estimate the insulation resistance. The control circuitry may be configured to adjust the power supply 22, for example, by reducing a supply voltage, such that a total resistance per volt meets a predefined threshold.

[0045] Figure 3 schematically illustrates an electrical configuration of an assembly according to some configurations of the present technique. The assembly is illustrated as three resistors connected between three AC supply voltages. The assembly comprises a first structured catalyst, a second structured catalyst, and a third structured catalyst. A first AC voltage VAC 1is supplied to one terminal of the first structured catalyst, a second AC voltage VAC 2is supplied to one terminal of the second structured catalyst, and a third AC voltage VAC 3is supplied to one terminal of the third structured catalyst. The second terminals of each of the structured catalysts are connected to one another. In an ideal circuit, the potential difference between the AC voltages supplied to each of the structured catalysts would result in a current flowing through the structured catalysts with no loss to the electrical ground connection.

[0046] In any real circuit this is not the case and, as in the case of figure 2, the illustrated configuration is provided with a test resistance RT. As shown in the illustrated configuration, there is the potential that electrical current could flow through the insulation resistance, through the test resistor and to the electrical ground connection. For example, current from the first AC supply could flow through insulation resistance / / ?! to the electrical ground, current from the second AC supply could flow through the insulation resistance IR2to ground, and current from the third AC supply could flow through the insulation resistance IR3to ground. The illustrated configuration is a simplified configuration that is provided for illustrative purpose only. In any real system, there may be any number of electrical pathways between each of the electrical supplies and the ground connection.

[0047] In order to operate the electrical supply so that the electrical characteristic (in this case the resistance per volt) meets a predefined threshold, the current flowing through the resistor RTis determined and, the control circuitry is configured to determine which electrical supply parameter to adjust. In some configurations, the control circuitry may perform a coarse granularity control in which all voltage supplies are reduced to ensure that the resistance per volt meets the predefined threshold. Whilst this approach offers reduced complexity, it may result in a sub-optimal operation of the assembly. For example, if the majority of the leakage current is due to a degradation of insulation resistance IR2then reducing all supply voltages will result in an unnecessary reduction of VAC 1and VAC 3. In order to provide improved control and maximise the system efficiency, the control circuitry may be arranged to measure the insulation resistance associated with each supply voltage separately and to control the power supply to modify each of the AC supply voltages independently. Independent electrical measurements of the current leaking from each supply can be achieved in a variety of ways. In some configurations, the control circuitry is configured to add a perturbation voltage to each supply voltage in turn. The perturbation voltage is an additional voltage signal supplied at the same connector as the input voltage supply. The perturbation may be an additional voltage (e.g., <1% of the supply voltage, <0.1%, of the supply voltage etc.) provided at the same frequency and phase as the supply voltage. Alternatively, the perturbation may be an additional voltage (e.g., <1% of the supply voltage, <0.1%, of the supply voltage etc.) provided at a different frequency or phase to the supply voltage. The additional of the perturbation voltage will result in a change in current measured across the test resistor. For example, the voltage supplied to the first structured catalyst may be modified from tc,i to VACi + <5F, . As a result, the measured current across the test resistor RTmay change to IT+ 8I . The increase in current is attributed to the increase in the voltage supplied to the first structured catalysts. As a result, the insulation resistance seen by the first supply voltage can be estimated to be IR1« 8V- 8I . The control circuitry can then modify VAC 1such that IR-L / VACI1is greater than the predefined threshold, for example, by reducing the peak or RMS value of VAC 1. The same procedure can be applied to each of the supply voltages in turn allowing an independent control of the supply voltage.

[0048] It would be readily apparent to the skilled person that the technique for adjusting the electrical supply parameter to ensure that the electrical characteristic associated with the insulation resistance meets the predefined threshold can be applied independent of the particular electrical connections between the structured catalysts. Furthermore, it would be readily apparent to the skilled person that, whilst the described technique considers each supply voltage in turn, plural supply voltages could be considered in parallel, for example, by applying different frequency perturbation voltages to each of the supply voltages. In some configurations of the above techniques may be used to ensure that the electrical supply parameter is adjusted to meet the predefined threshold. For example, where a large current ITis detected, the supply voltages may be globally lowered to ensure that the current is reduced quickly. The supply voltages could then be fine-tuned, e.g., increased or decreased to maximise the supplied voltage whilst ensuring that the predefined threshold is met.

[0049] Figure 4 schematically illustrates some different arrangements of the structured catalysts according to some configurations of the present techniques. Figure 4(A) schematically illustrates a three phase electrical supply that may be used to power the structured catalysts. The three phase electrical supply comprises three different AC voltages including a first phase 40, a second phase 42, and a third phase 44. Each of the three phases is out of phase with respect to the others by 120 degrees.

[0050] Figure 4(B) schematically illustrates a first electrical configuration of the present techniques in which the structured catalysts are electrically connected in a delta configuration. In the delta configuration, the structured catalysts (or arrays of structured catalysts) are arranged to form a loop with each of the structured catalysts (or arrays of structured catalysts) being provided between two of the electrical supplies. In the illustrated configuration the first structured catalyst is provided between the first electrical supply and the second electrical supply, the second structured catalyst is provided between the second electrical supply and the third electrical supply, and the third structured catalyst is provided between the third electrical supply and the first electrical supply.

[0051] Figure 4(C) schematically illustrates a second electrical configuration of the present techniques in which the structured catalysts are electrically connected in a star configuration (otherwise referred to as a wye configuration). In the star configuration each of the structured catalysts (or arrays of structured catalysts) are electrically connected between a single one of the voltage supplies and a neutral point. In the illustrated configuration the first structured catalyst is provided between the first electrical supply and the neutral point, the second structured catalyst is provided between the second electrical supply and the neutral point, and the third structured catalyst is provided between the third electrical supply and the neutral point. The star configuration may optionally be provided with a return cable connected between the neutral point of the star configuration and a return terminal of the electrical supply.

[0052] Whilst the star and delta configurations have been illustrated using three phases, it would be readily apparent to the skilled person that these configurations could be modified to include any number of electrical phases, for example, 2 phase, 4, phases, etc. Furthermore, any suitable combination of delta and star configurations may be used. For example, where plural electrical supplies are provided, a first electrical supply may be connected to catalysts arranged in a delta configuration and a second electrical supply may be connected to structured catalysts arranged in a star configuration. Alternatively, or in addition, one or more electrical supplies may be connected, in parallel, to a first set of structured catalysts arranged in a delta configuration and to a second set of structured catalysts arranged in a star configuration.

[0053] Figure 5 schematically illustrates an electrical arrangement of an assembly 50 according to some configurations of the present techniques. The assembly is provided with a plurality of structured catalysts 12 including a first structured catalyst 12(A), a second structured catalyst 12(B), and a third structured catalyst 12(C). The structured catalysts are electrically connected to one another and to a plurality of conductors 56 for connection to an electrical supply 52. The electrical conductors comprise a first conductor 56(A), a second conductor 56(B), and a third conductor 56(C). The plurality of structured catalysts 12 are arranged to form a delta configuration as described in relation to figure 4(B). The assembly 50 is also provided with control circuitry 54 configured to monitor the electrical characteristic of the assembly and to adjust the electrical supply 52 to ensure that a predefined threshold is met.

[0054] Figure 6 schematically illustrates an electrical arrangement of an assembly 60 according to some configurations of the present techniques. The assembly is provided with a plurality of structured catalysts 12 including a first structured catalyst 12(A), a second structured catalyst 12(B), and a third structured catalyst 12(C). The structured catalysts are electrically connected to one another and to a plurality of conductors 66 for connection to an electrical supply 62. The electrical conductors comprise a first conductor 66(A), a second conductor 66(B), a third conductor 66(C), and (optionally) a fourth conductor 66(D) to supply a return feed to the electrical supply 62. The plurality of structured catalysts 12 are arranged to form a star configuration as described in relation to figure 4(C). The assembly 60 is also provided with control circuitry 64 configured to monitor the electrical characteristic of the assembly and to adjust the electrical supply 62 to ensure that a predefined threshold is met.

[0055] Figure 7 schematically illustrates an electrical arrangement of an assembly 70 according to some configurations of the present techniques. The assembly is provided with a plurality of structured catalysts 12 including a first structured catalyst 12(A), a second structured catalyst 12(B), and a third structured catalyst 12(C). The structured catalysts are electrically connected to one another and to a plurality of conductors 76 for connection to an electrical supply 72. The electrical conductors comprise a first conductor 76(A), a second conductor 76(B), a third conductor 76(C), and a fourth conductor 76(D) to supply a return feed to the electrical supply 72. In the illustrated configuration, the electrical supply is a DC electrical supply and the plurality of structured catalysts 12 are arranged in parallel to one another with a common return signal being routed to the conductor 76(D) for return to the electrical supply 72. The assembly 70 is also provided with control circuitry 74 configured to monitor the electrical characteristic of the assembly and to adjust the electrical supply 72 to ensure that a predefined threshold is met.

[0056] Figure 8 schematically illustrates an electrical arrangement of structured catalysts with an assembly 80. The structured catalysts are grouped into arrays 82 including a first array 82(A), a second array 82(B), and a third array 82(C). The structured catalysts within each array are arranged in series with one another and the plurality of arrays 82 are connected to one another in a delta configuration.

[0057] Figure 9 schematically illustrates an electrical arrangement of structured catalysts with an assembly 90. The structured catalysts are grouped into arrays 92 including a first array 92(A), a second array 92(B), and a third array 92(C). The structured catalysts within each array are arranged in series with one another and the plurality of arrays 92 are connected to one another in a star configuration.

[0058] It would be readily apparent to the skilled person that each array within the arrangements shown in figures 8 and 9 need not be identical. Taking figure 8 as an illustrative example, the first array 82(A) may be arranged with more or fewer structured catalysts than the second array 82(B) or the third array 82(C). Alternatively, or in addition, the structured catalysts within one or more of the arrays may be arranged in parallel rather than in series. In addition, whilst in the illustrated configurations the electrically conductive material is comprised within the catalysts, it would be readily apparent to the skilled person that the electrically conductive material may be provided as a heating element separate to the catalysts which may be structured catalysts or unstructured catalysts.

[0059] Figure 10 schematically illustrates a sequence of steps carried out by control circuitry of an assembly according to some configurations of the present techniques. Flow begins at step S 100 where the electrical characteristics associated with an electrical connectivity parameter between at least one conductor and the electrical ground are monitored. Flow then proceeds to step SI 02 where a parameter of the electrical supply is adjusted such that the electrical characteristic meets a predefined threshold.

[0060] Figure 11 schematically illustrates further details of a method of adjusting a supply voltage of an electrical supply according to some configurations of the present techniques. Flow begins at step SI 10 where the control circuitry controls the electrical supply to supply voltage to N conductors. Flow then proceeds to step SI 12 where a test current ITis calculated, for example, by measuring a voltage drop across a resistor of known resistance. Flow then proceeds to step SI 14, where a variable i is set to one. Flow then proceeds to step SI 16 where control circuitry causes the electrical supply to perturb the ithvoltage to Vt+ <5F(-. Flow then proceeds to step SI 18 where the current flowing to the ground as a result of the perturbed voltage is measured as IT+ 8It. Flow then proceeds to step S120 where the insulation resistance between the conductor and ground is estimated as Rt = SVi / SI . Flow then proceeds to step S122 where the electrical characteristic of resistance per volt is measured for the insulation resistance of the ithsupply, Xt= Rt / Vt. Flow then proceeds to step S124 where it is determined whether or not the electrical characteristic Xtis larger than the predetermined threshold. If, at step S124, it is determined that Xtis not larger than the predetermined threshold, then flow proceeds to step S130, where the supply voltage Vtis decreased before flow returns to step SI 16. If, at step S124, it is determined that Xtis larger than the predetermined threshold, then flow proceeds to step S126, where it is determined if there are any more phases left to consider, i.e., it is determined if i>N. If, at step S126, it is determined that i is greater than N, then flow returns to step SI 10. If, at step S126, it is determined that i is not greater than N, then flow proceeds to step S128, where i is incremented before flow returns to step SI 16.

[0061] In brief overall summary there is provided an assembly, a reactor system and a method for catalysing an endothermic reaction of a feed gas being converted to a product gas. The assembly comprises a catalyst zone comprising a catalyst and an electrically conductive material for resistance heating of the catalyst. The electrically conductive material is arranged to form at least one electrically conductive pathway between conductors for connecting the electrically conductive material to at least one electrical supply. The assembly also comprises control circuitry configured to monitor an electrical characteristic associated with an electrical connectivity parameter between at least one of the conductors and an electrical ground, and to adjust an electrical supply parameter of the electrical supply such that the electrical characteristic meets a predefined threshold.

[0062] In the present application, the words “configured to. ..” are used to mean that an element of an apparatus has a configuration able to carry out the defined operation. In this context, a “configuration” means an arrangement or manner of interconnection of hardware or software. For example, the apparatus may have dedicated hardware which provides the defined operation, or a processor or other processing device may be programmed to perform the function. “Configured to” does not imply that the apparatus element needs to be changed in any way in order to provide the defined operation. In the present application, lists of features preceded with the phrase “at least one of’ mean that any one or more of those features can be provided either individually or in combination. For example, “at least one of: [A], [B] and [C]” encompasses any of the following options: A alone (without B or C), B alone (without A or C), C alone (without A or B), A and B in combination (without C), A and C in combination (without B), B and C in combination (without A), or A, B and C in combination.

[0063] Although illustrative configurations have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise configurations, and that various changes, additions and modifications can be effected therein by one skilled in the art without departing from the scope and spirit of the invention as defined by the appended claims. For example, various combinations of the features of the dependent claims could be made with the features of the independent claims without departing from the scope of the present invention.

[0064] Some configurations of the invention may also be provided according to the following numbered clauses:

[0065] Clause 1. An assembly for catalysing an endothermic reaction of a feed gas being converted to a product gas, the assembly comprising: a catalyst zone comprising a catalyst and an electrically conductive material for resistance heating of the catalyst, wherein the electrically conductive material is arranged to form at least one electrically conductive pathway between conductors for connecting the electrically conductive material to at least one electrical supply; and control circuitry configured to monitor an electrical characteristic associated with an electrical connectivity parameter between at least one of the conductors and an electrical ground, and to adjust an electrical supply parameter of the electrical supply such that the electrical characteristic meets a predefined threshold. Clause 2. The assembly of clause 1, wherein the electrical connectivity parameter is based on insulation resistance.

[0066] Clause 3. The assembly of clause 2, wherein the electrical characteristic is derived from the insulation resistance divided by the electrical supply parameter.

[0067] Clause 4. The assembly of any preceding clause, wherein the control circuitry is configured to monitor the electrical characteristic between each of the conductors and the electrical ground.

[0068] Clause 5. The assembly of clause 4, wherein the control circuitry is configured, for each given conductor of the conductors, to adjust the electrical supply parameter associated with the at least one electrical supply connected to the given conductor.

[0069] Clause 6. The assembly of any preceding clause, wherein the electrical supply parameter is a voltage.

[0070] Clause 7. The assembly of any preceding clause, wherein the electrical supply comprises at least one AC supply.

[0071] Clause 8. The assembly of clause 7, wherein: the AC supply comprises an N phase AC supply; and each phase of the N phase AC supply is phase shifted by 2 N with respect to another phase of the N phase AC supply.

[0072] Clause 9. The assembly of clause 7 or clause 8, wherein the electrical characteristic is based on measurements over at least one period of the multi-phase AC supply.

[0073] Clause 10. The assembly of clause 9, wherein the electrical characteristic is based on at least one of: an average measured over the at least one period; a maximum measured over the at least one period; and a minimum measured over the at least one period.

[0074] Clause 11. The assembly of any of any preceding clause, wherein the at least one electrically conductive pathway comprises a plurality of electrically conductive pathways arranged in a star configuration.

[0075] Clause 12. The assembly of any preceding clause, wherein the at least one electrically conductive pathway comprises a plurality of electrically conductive pathways arranged in a delta configuration.

[0076] Clause 13. The assembly of any preceding clause, wherein the electrical supply comprises a DC supply.

[0077] Clause 14. The assembly of clause 13, wherein: the DC supply comprises a plurality of DC outputs and a common neutral point; the conductors comprise a plurality of input conductors for connection to the plurality of DC outputs, and at least one output conductor for connection to the common neutral point; the at least one electrically conductive pathway comprises a plurality of electrically conductive pathways, the plurality of electrically conductive pathways connecting each of the plurality of input conductors in parallel to the at least one output conductor.

[0078] Clause 15. The assembly of any preceding clause, wherein: the catalyst comprises a structured catalyst, having a macroscopic structure; and / or the catalyst comprises the electrically conductive material; or the electrically conductive material is separate from the catalyst.

[0079] Clause 16. The assembly of clause 15, comprising a plurality of structured catalysts, wherein: the plurality of structured catalysts are grouped in a plurality of arrays, each array comprising two or more structured catalysts; and each of the at least one electrically conductive pathway comprises at least one of the plurality of arrays.

[0080] Clause 17. The assembly of any preceding clause, wherein the control circuitry comprises a programmable power supply comprising a thyristor controller, a variable transformer, a linear voltage regulator, a switching regulator and / or a step transformer.

[0081] Clause 18. The assembly of any preceding clause, wherein the control circuitry is configured to adjust the electrical supply parameter to maintain a continued electrical supply between the at least one of the conductors and the electrical ground.

[0082] Clause 19. The assembly of any preceding clause, wherein the predefined threshold is an electrical safety threshold, the electrical safety threshold being: greater than 10 Ohms per Volt; preferably greater than 20 Ohms per Volt; and particularly preferably greater than 300 Ohms per Volt.

[0083] Clause 20. A reactor system comprising: the assembly of any preceding clause; and a reactor shell housing the assembly.

[0084] Clause 21. The reactor system of clause 20, comprising the at least one electrical supply connected to the conductors; and / or wherein the conductors are provided outside of the reactor shell; and / or wherein the conductors are connected to electrical supply using a feedthrough; and / or wherein the electrical reactor shell is connected to the ground connection.

[0085] Clause 22. A method of providing an electrical supply to an assembly for catalysing an endothermic reaction of a feed gas being converted to a product gas, the assembly comprising a catalyst zone, the catalyst zone comprising at least one catalyst and an electrically conductive material for resistance heating of the at least one catalyst, wherein the electrically conductive material is arranged to form at least one electrically conductive pathway between conductors for connecting the electrically conductive material to at least one electrical supply, the method comprising: monitoring an electrical characteristic associated with an electrical connectivity parameter between at least one of the conductors and an electrical ground; and adjusting an electrical supply parameter of the electrical supply such that the electrical characteristic meets a predefined threshold.

Claims

CLAIMS1. An assembly for catalysing an endothermic reaction of a feed gas being converted to a product gas, the assembly comprising: a catalyst zone comprising a catalyst and an electrically conductive material for resistance heating of the catalyst, wherein the electrically conductive material is arranged to form at least one electrically conductive pathway between conductors for connecting the electrically conductive material to at least one electrical supply; and control circuitry configured to monitor an electrical characteristic associated with an electrical connectivity parameter between at least one of the conductors and an electrical ground, and to adjust an electrical supply parameter of the electrical supply such that the electrical characteristic meets a predefined threshold.

2. The assembly of claim 1, wherein the electrical connectivity parameter is based on insulation resistance.

3. The assembly of claim 2, wherein the electrical characteristic is derived from the insulation resistance divided by the electrical supply parameter.

4. The assembly of any preceding claim, wherein the control circuitry is configured to monitor the electrical characteristic between each of the conductors and the electrical ground.

5. The assembly of claim 4, wherein the control circuitry is configured, for each given conductor of the conductors, to adjust the electrical supply parameter associated with the at least one electrical supply connected to the given conductor.

6. The assembly of any preceding claim, wherein the electrical supply parameter is a voltage.

7. The assembly of any preceding claim, wherein the electrical supply comprises at least one AC supply.

8. The assembly of claim 7, wherein: the AC supply comprises an N phase AC supply; and each phase of the N phase AC supply is phase shifted by 2 N with respect to another phase of the N phase AC supply.

9. The assembly of claim 7 or claim 8, wherein the electrical characteristic is based on measurements over at least one period of the multi-phase AC supply.

10. The assembly of any of any preceding claim, wherein the at least one electrically conductive pathway comprises a plurality of electrically conductive pathways arranged in a star configuration and / or a plurality of electrically conductive pathways arranged in a delta configuration.

11. The assembly of any preceding claim, wherein the electrical supply comprises a DC supply.

12. The assembly of claim 11, wherein: the DC supply comprises a plurality of DC outputs and a common neutral point; the conductors comprise a plurality of input conductors for connection to the plurality of DC outputs, and at least one output conductor for connection to the common neutral point; the at least one electrically conductive pathway comprises a plurality of electrically conductive pathways, the plurality of electrically conductive pathways connecting each of the plurality of input conductors in parallel to the at least one output conductor.

13. The assembly of any preceding claim, wherein: the catalyst comprises a structured catalyst, having a macroscopic structure; and / orthe catalyst comprises the electrically conductive material; or the electrically conductive material is separate from the catalyst.

14. The assembly of claim 13, comprising a plurality of structured catalysts, wherein: the plurality of structured catalysts are grouped in a plurality of arrays, each array comprising two or more structured catalysts; and each of the at least one electrically conductive pathway comprises at least one of the plurality of arrays.

15. A reactor system comprising: the assembly of any preceding claim; and a reactor shell housing the assembly.

16. The reactor system of claim 15, comprising the at least one electrical supply connected to the conductors; and / or wherein the conductors are provided outside of the reactor shell; and / or wherein the conductors are connected to electrical supply using a feedthrough; and / or wherein the electrical reactor shell is connected to the ground connection.

17. A method of providing an electrical supply to an assembly for catalysing an endothermic reaction of a feed gas being converted to a product gas, the assembly comprising a catalyst zone, the catalyst zone comprising at least one catalyst and an electrically conductive material for resistance heating of the at least one catalyst, wherein the electrically conductive material is arranged to form at least one electrically conductive pathway between conductors for connecting the electrically conductive material to at least one electrical supply, the method comprising: monitoring an electrical characteristic associated with an electrical connectivity parameter between at least one of the conductors and an electrical ground; andadjusting an electrical supply parameter of the electrical supply such that the electrical characteristic meets a predefined threshold.

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