Device for the production of methane

Abstract

Apparatus for the production of methane comprising a reactor in which a catalyst for the production of methane from a hydrogen- and carbon dioxide-containing reactant gas is housed, a reactant gas supply line connected to the reactor inlet and supplying the reactant gas from a reactant gas source to the reactor, a compressor provided on the reactant gas supply line, an end-product gas tank, a product gas line connected to the reactor outlet and conveying methane-containing product gas exiting the reactor to the end-product gas tank, a methane supply line supplying product gas to the reactant gas source, a methane flow control device provided on the methane supply line, which regulates the methane supply to the reactant gas source, a temperature sensor that detects the temperature in the reactor, a flow sensor that detects the flow of the reactant gas entering the reactor, and a hydrogen flow control device.a device that regulates the hydrogen supply to the reactant gas source, a carbon dioxide flow control device that regulates the carbon dioxide supply to the reactant gas source, and a control device that controls the operating processes of the hydrogen flow control device, the carbon dioxide flow control device, the methane flow control device, and the compressor such that, when the temperature detected by the temperature sensor exceeds a predetermined temperature threshold, the methane supply is increased while maintaining the hydrogen and carbon dioxide supply to the reactant gas source unchanged, and the compressor's intake flow is increased in accordance with the increase in reactant gas flow associated with the increase in methane supply, as long as the flow detected by the flow sensor remains equal to or less than a predetermined flow threshold.

Description

field of technology The invention relates to a device for the production of methane, in which hydrogen is added to a carbon dioxide-containing reactant gas in order to produce methane. Technical background of the invention In the prior art, devices are known for producing methane from a carbon dioxide-containing reactant gas by means of a catalytic reaction (methanation reaction) that converts carbon dioxide (CO2) and hydrogen (H2) into methane (CH4). The following equation (Chem. 1) is the equation for the methanation reaction: CO2 + 4H2 ⇌ CH4 + 2H2O [Chem. 1] Since the methanation reaction is an exothermic reaction, the temperature of the reactant gas and its reaction gas increases as they pass through the reaction site. Furthermore, the methanation reaction is reversible, so the equilibrium of the reaction shifts to the left (reactant side) in Chem. 1 with increasing temperature. Therefore, limiting the temperature increase at the reaction site is effective in promoting the methanation reaction. A technique for limiting the temperature increase in the reactor is proposed, as exemplified in Patent Document 1. In the process for producing methane-rich gas according to patent document 1, a carbon monoxide- and hydrogen-containing reactant gas (feed gas) is reacted in the presence of a methanation catalyst to produce a methane-rich product gas containing methane, carbon dioxide, and water. The carbon dioxide is removed from the methane-rich product gas to produce a methane-rich, low-carbon-dioxide gas, and at least a portion of the methane-rich, low-carbon-dioxide gas is cooled and recirculated. In this process, the temperature rise in the reactor is limited by diluting the reactant gas entering the reactor with the recirculated methane-rich gas, thereby reducing the load on the compressor, etc., by decreasing the volume of the recirculated methane-rich gas. State of the art documents Patent documents Patent document 1: Translation of the published international PCT application JP2012 - 514039 General description of the invention The problem underlying the invention In patent document 1, the feed gas entering the reactor is continuously diluted with the recirculated methane-rich gas, so that the compressor, which compresses the reactant gas supplied to the reactor, requires a significantly larger intake flow compared to the supply of carbon dioxide and hydrogen during steady-state operation. This leads to a larger compressor and higher plant costs. The invention, which arose in light of the described circumstances, aims to limit the temperature increase in the reactor of a device for producing methane from a hydrogen and carbon dioxide-containing reactant gas by adding methane to the reactant gas, thereby avoiding an increase in the size of the compressor. Means of solving the problem The apparatus for producing methane according to an embodiment of the invention is characterized in that it comprises a reactor in which a catalyst for producing methane from a hydrogen- and carbon dioxide-containing reactant gas is housed, a reactant gas supply line which is connected to the inlet of the reactor and supplies the reactant gas to the reactor from a reactant gas source, a compressor provided on the reactant gas supply line, an end-product gas tank, a product gas line which is connected to the outlet of the reactor and conveys a methane-containing product gas exiting the reactor to the end-product gas tank, a methane supply line which supplies the product gas to the reactant gas source, a methane flow control device provided on the methane supply line which regulates the methane supply to the reactant gas source, a temperature sensor which detects the temperature in the reactor, and a control device.which controls the control process of the methane flow control device in such a way that the methane supply to the reactant gas source is increased when the temperature detected by the temperature sensor exceeds a predetermined temperature threshold. With the methane production device described above, the methanation reaction in the reactor shifts to the reactant side by adding methane to the reactant gas, thus limiting the temperature rise in the reactor. The methane is not added continuously, but only when the temperature in the reactor exceeds the temperature threshold. This reduces the need for a compressor with an excessively large intake flow, calculated based on the supply of carbon dioxide and hydrogen during steady-state operation. Therefore, by adding methane to the reactant gas, it is possible to limit the temperature rise in the reactor and avoid increasing the size of the compressor. The above-described device for producing methane may additionally include a flow sensor that detects the flow of the reactant gas entering the reactor, a hydrogen flow control device that regulates the hydrogen supply to the reactant gas source, and a carbon dioxide flow control device that regulates the carbon dioxide supply to the reactant gas source.And the control device can control the operating processes of the hydrogen flow control device, the carbon dioxide flow control device, the methane flow control device and the compressor in such a way that, when the temperature detected by the temperature sensor exceeds the temperature threshold, the methane supply is increased while maintaining the hydrogen and carbon dioxide supply to the reactant gas source unchanged, and the intake flow of the compressor is increased in accordance with the increase in reactant gas flow associated with the increase in methane supply, as long as the flow detected by the flow sensor remains equal to or less than a predetermined flow threshold. This increases the flow rate of the reactant gas due to the added methane within the compressor's capacity, thus preventing the compressor from being overloaded. In the above-described device for the production of methane, the control device can perform the control in such a way that, when the flow rate detected by the flow sensor exceeds the flow rate threshold, the hydrogen supply and the carbon dioxide supply to the reactant gas source are reduced and the methane supply is increased without increasing the flow rate of the reactant gas. This allows the proportion of methane in the reactant gas to be further increased while keeping the reactant gas flow rate within the compressor's capacity. Consequently, the temperature increase in the reactor can be counteracted even more effectively. The above-described apparatus for the production of methane may additionally include a separating device provided on the product gas line for separating components other than methane from the product gas, wherein the upstream end of the methane supply line may be connected to the final product gas tank or to the product gas line downstream of the separating device. This allows gas with a higher methane concentration to be conveyed to the reactant gas source via the methane feed line. This effectively counteracts the temperature increase in the reactor, provided the compressor load is not significantly increased. The above-described apparatus for the production of methane can additionally include a pressure sensor that detects the gas pressure of the reactant gas source, wherein, in the event of a pressure detected by the pressure sensor exceeding a predetermined pressure threshold, the control device can reduce at least one of the hydrogen supply, the carbon dioxide supply and the methane supply to the reactant gas source until the pressure detected by the pressure sensor is equal to or less than the pressure threshold. This prevents the compressor from being overloaded. Advantages of the invention The invention makes it possible, in a device for producing methane from a hydrogen and carbon dioxide-containing reactant gas, to limit the temperature increase in the reactor by adding methane to the reactant gas and thereby avoid increasing the size of the compressor. Brief description of the drawings [Fig. 1] Fig. 1 shows the general structure of the apparatus for producing methane according to one embodiment of the invention. [Fig. 2] Fig. 2 is a block diagram illustrating the structure of the control system of the apparatus for producing methane. [Fig. 3] Fig. 3 is a flowchart illustrating the control flow for limiting the temperature rise in the reactor. [Fig. 4] Fig. 4 is a flowchart illustrating the control flow for limiting the temperature rise in the reactor. embodiment of the invention An embodiment of the invention will now be described with reference to the drawings. Fig. 1 shows the general structure of the apparatus for producing methane 100 according to one embodiment of the invention. The apparatus for producing methane 100 shown in Fig. 1 comprises a reactor R in which a catalyst is housed, a reactant gas supply line 2 that supplies reactant gas to the reactor R, an end-product gas tank 7, a product gas line 3 that conveys product gas exiting the reactor R to the end-product gas tank 7, a methane supply line 5 that conveys the product gas to the reactant gas supply line 2, and a control device 6 that controls the apparatus for producing methane 100. The product gas contains a high concentration of methane. [Reactant gas supply line 2] The reactant gas supply line 2 is formed, among other things, by a line that connects a reactant gas source 21 to the inlet of the first reactor R1. The reactant gas supply line 2 is equipped with a compressor 22 and a heat exchanger 23. A flow sensor 88 is provided on the reactant gas supply line 2 downstream of the compressor 22 and upstream of the heat exchanger 23, according to the flow of the reactant gas. The reactant gas supply line 2 is also equipped with a pressure sensor 89, which detects the gas pressure of the reactant gas source 21. A carbon dioxide supply line 25, connected to a carbon dioxide supply source (not shown), is connected to the reactant gas source 21, and carbon dioxide is supplied to the reactant gas source 21 via the carbon dioxide supply line 25. The carbon dioxide supply line 25 is equipped with a carbon dioxide flow control device 83, which is controlled by the control device 6. This carbon dioxide flow control device 83 regulates the flow of carbon dioxide supplied to the reactant gas source 21. A hydrogen supply line 24, connected to a hydrogen supply source (not shown), is connected to the reactant gas source 21, and hydrogen is supplied to the reactant gas source 21 via the hydrogen supply line 24. The hydrogen supply line 24 is equipped with a hydrogen flow control device 82, which is controlled by the control device 6. This hydrogen flow control device 82 regulates the flow of hydrogen supplied to the reactant gas source 21. In the reactant gas source 21, the hydrogen and carbon dioxide mix in a predetermined ratio to produce the reactant gas. As described below, the reactant gas may also contain methane. During steady-state operation, the hydrogen and carbon dioxide are supplied such that the hydrogen and carbon dioxide have a molar ratio of 3.2 to 4.0 (hydrogen / carbon dioxide = 3.2 - 4.0). The reactant gas source 21 is preferably a tank with a capacity sufficient to ensure that the supplied carbon dioxide and hydrogen mix uniformly. However, the design of the reactant gas source 21 is not limited to this; it can also be formed as part of the reactant gas supply line 2. Compressor 22 compresses the reactant gas so that it has a predetermined pressure suitable for the methanation reaction. The pressure suitable for the methanation reaction depends on the type of methanation catalyst and the design of reactor R. For example, the pressure requirement for the reactant gas flowing into reactor R1 is 0 to 3 MPa absolute pressure. In heat exchanger 23, heat exchange takes place between the hot oil used to cool reactor R1 and the reactant gas, thereby adjusting the reactant gas to a predetermined temperature suitable for the methanation reaction. The temperature suitable for the methanation reaction depends on the type of methanation catalyst and the stage of reactor R. [Reactor R] The reactant gas is pressurized in the compressor 22 and its temperature is adjusted in the heat exchanger 23 before flowing into the first reactor R1. The device for producing methane 100 according to this embodiment has two reactors R, namely a first reactor R1 and a second reactor R2, connected in series. The reactors R1, R2, ..., have essentially the same design. The number of reactors R can be one or a plurality of three or more. A catalyst (methanation catalyst) is housed in the reactor R, which promotes the methanation reaction in which methane and water are produced from hydrogen and carbon dioxide. The catalyst, which is not subject to any particular restrictions, can, for example, be a commercially available nickel catalyst. The reactor R1 and R2 are equipped with a temperature sensor 86 and 87, respectively, to detect the internal temperature.87 The temperature of the catalyst in reactor R can be measured. In reactor R1, the methanation reaction of hydrogen and carbon dioxide takes place in the reactant gas in the presence of the catalyst, producing methane and water. The product gas, which contains the methane and water produced in reactor R1 as well as the unreacted hydrogen and carbon dioxide, flows into connecting line 1. The connecting line 1 is formed, among other things, from a line that connects the outlet of the first reactor R1 to the inlet of the second reactor R2. In this embodiment, the number of connecting lines 1 is 1, since the number of reactors R is 2, and the device for producing methane 100 has a number of connecting lines 1 corresponding to the number of reactors R. The connecting line 1 is equipped with a first heat exchanger 11, a water separator 12, and a second heat exchanger 13. In the first heat exchanger 11, heat exchange takes place between the product gas and the cooling water. In the water separator 12, the water condensed in the product gas during cooling in the first heat exchanger 11 is separated from the product gas. In the second heat exchanger 13, heat exchange takes place between the hot oil used to cool the second reactor R2 and the product gas. The product gas exiting reactor R1 flows through connecting line 1 into reactor R2. The temperature of the product gas entering reactor R2 is adjusted by heat exchangers 11 and 13 to a temperature equal to or higher than the temperature at which the methanation reaction begins, and below the temperature at which the methanation reaction ends. In reactor R2, the methanation reaction of hydrogen and carbon dioxide in the product gas also takes place in the presence of the catalyst, producing methane and water. The product gas, containing the methane and water produced in reactor R2 as well as the unreacted hydrogen and carbon dioxide, flows into product gas line 3. [Product gas line 3] The product gas exiting reactor R2 is conveyed via product gas line 3 to the final product gas tank 7. Product gas line 3 is formed, among other things, by a line that connects the outlet of reactor R2, which is switched on in the last stage, to the inlet of the final product gas tank 7. Product gas line 3 is equipped with a heat exchanger 31, a water separator 32, a separation device 9, and a hydrogen separation device 42. In heat exchanger 31, heat exchange takes place between the product gas exiting reactor R2, which is switched on in the last stage, and water. In water separator 32, the water condensed in the product gas due to cooling in heat exchanger 31 is separated. In the separation device 9, components other than methane are separated from the product gas. The product gas, whose methane concentration has increased during its passage through the separation device 9, is conveyed to the final product gas tank 7. The exhaust gas (the components other than methane) removed from the product gas is released into the atmosphere or fed to the reactant gas source 21 and reused as part of the reactant gas. The separation device 9 can be a previously known gas separation device with pressure swing adsorption, which utilizes the principle of pressure swing adsorption. Typically, the gas separation device with pressure swing adsorption comprises a plurality of adsorption vessels filled with adsorbent and a compressor that pressurizes the feed gas (product gas) to be conveyed to the adsorption vessels (both not shown). A cycle of pressure equalization, adsorption, regeneration, and pressure equalization steps is carried out alternately in the adsorption vessels. In the pressure equalization step, the adsorption vessels are connected to each other to equalize pressure by moving the gas within the vessels. In the adsorption step, the feed gas is supplied to the adsorption vessel, thereby increasing the internal pressure, and the final product gas is extracted by supplying the feed gas.In the regeneration step, the adsorbent is regenerated by lowering the pressure in the adsorption container, which allows more easily adsorbed components to be desorbed from the adsorbent. The product gas exiting the separating device 9, the main component of which is methane, is contaminated with a small amount of hydrogen. Therefore, the product gas line 3 downstream of the separating device 9 is equipped with a hydrogen separator 42, which separates the hydrogen from the product gas. By separating the hydrogen in the hydrogen separator 42, the purity of the methane in the product gas, which is collected in the final product gas tank 7, is further increased. [Methane supply line 5] The methane supply line 5 is formed, among other things, by a line that connects the product gas line 3 or the end product gas tank 7 to the reactant gas source 21. The methane-containing product gas is conveyed to the reactant gas supply line 2 via the methane supply line 5. The methane supply line 5 is equipped with a methane flow control device 81, which operates controlled by the control device 6. This methane flow control device 81 regulates the flow of the methane supplied from the end product gas tank 7 to the reactant gas supply line 2. In the case of the configuration shown in Fig.In the apparatus for the production of methane 100 shown in Fig. 1, the upstream end of the methane supply line 5 is connected to the end-product gas tank 7, but the upstream end of the methane supply line 5 can also be connected to the product gas line 3 (preferably downstream of the separating device 9 on the product gas line 3, so that methane with the highest possible concentration is supplied to the reactant gas supply line 2). Furthermore, in the apparatus for the production of methane 100 shown in Fig. 1, the downstream end of the methane supply line 5 is connected to the reactant gas source 21, but it is sufficient if the downstream end of the methane supply line 5 is connected to the reactant gas supply line 2 upstream of the compressor 22 in the direction of the reactant gas flow. [Control device 6] Fig. 2 is a block diagram illustrating the structure of the control system of the methane 100 production device. This diagram shows the elements related to the control of the temperature rise in reactor R; other elements are omitted. The control device 6 shown in Fig. 2 is a so-called computer and comprises an arithmetic logic unit (ALU) such as a CPU and a memory element such as ROM, RAM, or similar (both not shown). The memory element stores programs executed by the ALU, various fixed data, etc. The ALU sends and receives data to and from external devices. Furthermore, the ALU receives data from various communication-capable measuring instruments (including the 1st temperature sensor 86, the 2nd...).The arithmetic logic unit (ALU) receives detection signals from temperature sensor 87, flow sensor 88, pressure sensor 89, pressure sensor 91, and temperature sensor 92. The ALU outputs control signals to various connected devices (including the methane flow control device 81, the hydrogen flow control device 82, the carbon dioxide flow control device 83, and the compressor 22). The ALU performs the processes for controlling the operation of the methane production device 100 by reading and executing software, such as the programs stored in the memory element. The ALU can execute these processes either as a centralized control system operated by a single computer or as a decentralized control system through the cooperation of multiple computers.Finally, the control device 6 can also consist of a microcontroller, a programmable logic controller (PLC) or the like. [Control system to limit the temperature increase in reactor R] This section describes the control system for limiting the temperature rise in the device for producing methane 100, as described above. Figures 3 and 4 are flowcharts illustrating the control process for limiting the temperature rise in the reactor. As shown in Fig. 3, the control device 6 receives the temperature T1 in reactor R1 from temperature sensor 86 and the temperature T2 in reactor R2 from temperature sensor 87 (step S1). The control device 6 then compares the received temperature T1 and T2 with a predetermined temperature threshold Tα (step S2). The temperature threshold Tα is a temperature below the temperature at which the methanation reaction ceases and can, for example, be the upper limit of a temperature range within which the methanation reaction proceeds at a suitable rate. The temperature threshold Tα is determined depending on the type of catalyst. The control device 6 returns to step S1 and continues the process if neither of the obtained temperatures T1, T2 exceeds the temperature threshold Tα (NO in step S2). That is, if the temperatures T1, T2 are equal to or less than the temperature threshold Tα, the processes for limiting the temperature rise in the reactor R are not executed. The number of temperatures checked against the temperature threshold Tα is singular if the reactor R is singular. If, however, at least one of the obtained temperatures T1, T2 exceeds the temperature threshold Tα (YES in step S2), the control device 6 actuates the methane flow control device 81 such that, while maintaining the carbon dioxide and hydrogen supplies unchanged, the methane supply is increased by a predetermined amount (step S3). The methane supply can be zero in the initial phase (in steady-state operation). This maintains the carbon dioxide-to-hydrogen ratio in the reactant gas at the predetermined level, while the reactant gas flow rate increases by the amount of methane. Therefore, the control device 6 increases the power of the compressor 22 so that the intake flow rate increases accordingly. Meanwhile, the control device 6 monitors the value detected by the pressure sensor 89. When the pressure sensor 89 detects a value exceeding a predetermined pressure threshold, the control device 6 actuates the methane flow control device 81, the hydrogen flow control device 82, and the carbon dioxide flow control device 83 such that the total gas supply to the reactant gas source 21 is throttled until the value detected by the pressure sensor 89 is equal to or less than the pressure threshold. The pressure threshold can be a pressure value corresponding to the upper limit of the intake flow of the compressor 22. Furthermore, the control device 6 receives the flow rate F of the reactant gas from the flow sensor 88, the pressure P of the reactant gas from the pressure sensor 91 and the temperature T0 of the reactant gas from the temperature sensor 92 (step S4). The control device 6 compares the flow rate F with a predetermined flow rate threshold Fα (step S5). The flow rate threshold Fα can, for example, be a value resulting from correcting the compressor 22's outlet flow, corresponding to 70 to 90% of the rated power of the electric motor used in the compressor 22, according to the pressure P, the temperature T0, and the given humidity, to a flow rate on the compressor 22's outlet side. The flow rate threshold Fα is determined depending on the compressor 22's performance. Although the flow rate threshold Fα is determined here as a value corrected according to the pressure P, the temperature T0, and the given humidity, the flow rate F can also be converted into an outlet flow rate according to the pressure P, the temperature T0, and the given humidity. In this case, the pressure P or...The temperature T0 should not only be a recorded value, but also a predefined estimated value. The control device 6 returns to step S1 and continues the process if the flow rate F is equal to or less than the flow rate threshold Fα (NO in step S5). If, however, the flow rate F exceeds the flow rate threshold Fα (YES in step S5), the control device 6 enters the flow hold phase in the process. As shown in Fig. 4, the control device 6 first begins timing in the flow-hold phase (step S11). The control device 6 then actuates the methane flow control device 81, the hydrogen flow control device 82, and the carbon dioxide flow control device 83 such that the carbon dioxide supply is reduced by a predetermined amount, the hydrogen supply is reduced by a predetermined amount, and the methane supply is increased by a predetermined amount (step S12). This regulates the reduction in carbon dioxide, the reduction in hydrogen, and the increase in methane such that the flow rate of the reactant gas flowing through the reactant gas supply line 2 (i.e., the intake flow of the compressor 22) remains unchanged, while the proportions of carbon dioxide and hydrogen in the reactant gas are reduced and the proportion of methane is increased. The control device 6 receives the temperature T1 in the first reactor R1 from the first temperature sensor 86 and the temperature T2 in the second reactor R2 from the second temperature sensor 87 (step S13). The control device 6 then compares the received temperature T1 and T2 with the predefined temperature threshold Tα (step S14). If none of the obtained temperatures T1, T2 exceeds the temperature threshold Tα (NO in step 14), the control device 6 actuates the methane flow control device 81, the hydrogen flow control device 82, and the carbon dioxide flow control device 83 such that the carbon dioxide and hydrogen supply are increased and thus returned to the initial state (or a predetermined normal state), and the methane supply is decreased and thus returned to the initial state (step S17). Furthermore, in accordance with the decrease in the flow rate of the reactant gas flowing through the reactant gas supply line 2, the control device 6 reduces the power of the compressor 22 and returns to step S1 to repeat the process. If, however, at least one of the obtained temperatures T1, T2 exceeds the temperature threshold Tα (YES in step S14), the control device 6 compares the time k elapsed since the start of the time measurement with a predefined time threshold kα (step S15). The time threshold kα is the permissible duration of the flow holding phase and can be any value. The control device 6 returns to step S12 and continues the process if the elapsed time k is equal to or less than the time threshold kα (NO in step S15). If, however, the elapsed time k exceeds the time threshold kα (YES in step S15), the control device 6 forces the shutdown of the methane 100 production device (step S16) and terminates the process. The forced shutdown of the methane 100 production device means the shutdown of the supply of carbon dioxide and hydrogen to the reactant gas source 21, while the supply of methane continues until the temperatures T1 and T2 are equal to or less than the temperature threshold Tα. As described above, the apparatus for producing methane 100 according to this embodiment comprises the reactor R, in which the catalyst for generating methane from the hydrogen- and carbon dioxide-containing reactant gas is housed; the reactant gas supply line 2, which is connected to the inlet of the reactor R and supplies the reactant gas from the reactant gas source 21 to the reactor R; the compressor 22 provided on the reactant gas supply line 2; the end-product gas tank 7; the product gas line 3, which is connected to the outlet of the reactor R and conveys the methane-containing product gas exiting the reactor R to the end-product gas tank 7; and the methane supply line 5, which supplies the product gas to the reactant gas source 21. The product gas contains a high methane content. And the device for the production of methane 100 described above comprises the methane flow control device 81 provided on the methane supply line 5, which regulates the methane supply to the reactant gas source 21, the temperature sensor 86, 87, which detects the temperature in the reactor R, and the control device 6, which, depending on the value detected by the temperature sensor 86, 87, controls the control process of the methane flow control device 81 in such a way that the methane supply to the reactant gas source 21 is increased when the temperature detected by the temperature sensor 86, 87 exceeds the predetermined temperature threshold. With the device for producing methane 100 described above, the proportion of methane in the reactant gas increases by adding methane to the reactant gas, thus shifting the methanation reaction in reactor R to the reactant side and limiting the temperature rise in reactor R. The methane is not added to the reactant gas continuously, but only when the temperature in reactor R exceeds the temperature threshold. This reduces the need for a compressor 22 with an excessively large intake flow, calculated based on the supply of carbon dioxide and hydrogen during steady-state operation. Therefore, by adding methane to the reactant gas, it is possible to limit the temperature rise in reactor R and thus avoid increasing the size of the compressor 22. The device for producing methane 100 according to this embodiment additionally comprises the flow sensor 88, which detects the flow of the reactant gas flowing into the reactor R, the hydrogen flow control device 82, which regulates the hydrogen supply to the reactant gas source 21, and the carbon dioxide flow control device 83, which regulates the carbon dioxide supply to the reactant gas source 21.And the control device 6 controls the operating processes of the hydrogen flow control device 82, the carbon dioxide flow control device 83, the methane flow control device 81 and the compressor 22 such that, when the temperature T1, T2 detected by the temperature sensor 86, 87 exceeds the temperature threshold Tα, the methane supply is increased while maintaining the hydrogen and carbon dioxide supply to the reactant gas source 21 unchanged, and the intake flow of the compressor 22 is increased in accordance with the increase in the reactant gas flow rate associated with the increase in the methane supply, as long as the flow rate F detected by the flow sensor 88 remains equal to or less than the predetermined flow threshold Fα. This results in an increase in the flow rate of the reactant gas due to the added methane within the capacity of the compressor 22, so that an overload of the compressor 22 can be avoided. Furthermore, in the device for producing methane 100 according to this embodiment, the control device 6 performs the control in such a way that, in the event of a flow rate F exceeding the flow threshold Fα detected by the flow sensor 88, the hydrogen supply and the carbon dioxide supply to the reactant gas source 21 are reduced and the methane supply is increased without increasing the flow rate of the reactant gas. This allows the proportion of methane in the reactant gas to be further increased while maintaining the reactant gas flow rate within the capacity of compressor 22. Consequently, the temperature increase in reactor R can be counteracted even more effectively. Furthermore, the device for producing methane 100 according to this embodiment additionally includes the separating device 9 provided on the product gas line 3 for separating components other than methane from the product gas, wherein the upstream end of the methane supply line 5 is connected to the end product gas tank 7 or to the product gas line 3 downstream of the separating device 9. This allows gas with a higher methane concentration to be conveyed to the reactant gas source 21 via the methane supply line 5. This effectively counteracts the temperature increase in the reactor R, while limiting the increase in the load on the compressor 22. Furthermore, the device for producing methane 100 according to this embodiment additionally includes the pressure sensor 89, which detects the gas pressure of the reactant gas source 21. And the control device 6, when the pressure detected by the pressure sensor 89 exceeds the predetermined pressure threshold, controls the operating processes of the methane flow control device 81, the hydrogen flow control device 82, and the carbon dioxide flow control device 83 such that at least one of the hydrogen supply, the carbon dioxide supply, and the methane supply to the reactant gas source 21 is reduced until the value detected by the pressure sensor 89 is equal to or less than the pressure threshold. This prevents the compressor 22 from being overloaded. The foregoing describes a preferred embodiment of the invention, whereby modifications of the specific structure and / or function of the embodiment described above may also be included in the invention to an extent that does not deviate from the teaching of the invention. Explanation of reference symbols 1 Connecting line 2 Reactant gas supply line 3 Product gas line 5 Methane supply line 6 Control device 7 End product gas tank 9 Separation device 21 Reactant gas source 22 Compressor 23 Heat exchanger 24 Hydrogen supply line 25 Carbon dioxide supply line 81 Methane flow control device 82 Hydrogen flow control device 83 Carbon dioxide flow control device 86, 87 Temperature sensor 88 Flow sensor 89, 91 Pressure sensor 92 Temperature sensor 100 Methane production device R, R1, R2 reactor

Claims

Apparatus for the production of methane comprising a reactor in which a catalyst for the production of methane from a hydrogen- and carbon dioxide-containing reactant gas is housed, a reactant gas supply line connected to the reactor inlet and supplying the reactant gas from a reactant gas source to the reactor, a compressor provided on the reactant gas supply line, an end-product gas tank, a product gas line connected to the reactor outlet and conveying methane-containing product gas exiting the reactor to the end-product gas tank, a methane supply line supplying product gas to the reactant gas source, a methane flow control device provided on the methane supply line, which regulates the methane supply to the reactant gas source, a temperature sensor that detects the temperature in the reactor, a flow sensor that detects the flow of the reactant gas entering the reactor, and a hydrogen flow control device.a device that regulates the hydrogen supply to the reactant gas source, a carbon dioxide flow control device that regulates the carbon dioxide supply to the reactant gas source, and a control device that controls the operating processes of the hydrogen flow control device, the carbon dioxide flow control device, the methane flow control device, and the compressor such that, when the temperature detected by the temperature sensor exceeds a predetermined temperature threshold, the methane supply is increased while maintaining the hydrogen and carbon dioxide supply to the reactant gas source unchanged, and the compressor's intake flow is increased in accordance with the increase in reactant gas flow associated with the increase in methane supply, as long as the flow detected by the flow sensor remains equal to or less than a predetermined flow threshold. Apparatus for the production of methane according to claim 1, wherein the control device, in the event of a flow rate exceeding the flow threshold as detected by the flow sensor, reduces the hydrogen supply and the carbon dioxide supply to the reactant gas source and increases the methane supply without increasing the flow rate of the reactant gas. Apparatus for the production of methane according to one of claims 1 or 2, further comprising a separating device provided on the product gas line for separating components other than methane from the product gas, wherein the upstream end of the methane supply line is connected to the final product gas tank or to the product gas line downstream of the separating device. Apparatus for the production of methane according to one of claims 1 to 3, further comprising a pressure sensor which detects the gas pressure of the reactant gas source, wherein the control device, in the event of a pressure detected by the pressure sensor exceeding a predetermined pressure threshold, reduces at least one of the hydrogen supply, the carbon dioxide supply and the methane supply to the reactant gas source until the pressure detected by the pressure sensor is equal to or less than the pressure threshold.

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