Turbocharged Methanation

Abstract

The present invention relates to an improved methanation process in which energy released during the methanation process is used to drive a turbocharger for carrying out and / or maintaining the process. The present invention further relates to a system for producing methane-rich gas and electricity from hydrogen and a carbon-containing starting material, comprising at least one methanation reactor and at least one turbocharger.

Description

[Technical field]

[0001] The present invention relates to an improved methanation process, in which energy released during the methanation process is used to drive a turbocharger for carrying out and / or maintaining the process.The present invention further relates to a system for producing methane-rich gas and optionally electricity from hydrogen and a carbon-containing starting material, comprising at least one methanation reactor and at least one turbocharger. [Background technology]

[0002] Methanation is the conversion of carbon monoxide (CO) and / or carbon dioxide (CO2) to methane (CH4) by hydrogenation. The process was discovered in the early 20th century. Example reactions for methanation of carbon monoxide and carbon dioxide, respectively, are given below.

[0003] [ka]

[0004] Methanation reactions are classified as exothermic.

[0005] Examples of possible starting materials are CO2 from biogas plants and H2 from high temperature electrolysis plants. Examples of prior art methanation processes include the Topsoe Recycle Energy-efficient Methanation Process (TREMP™) by Haldor Topsoe.

[0006] The TREMP process can be carried out at high temperatures up to 973 K due to the MCR-2X methanation catalyst used in the process. This catalyst allows the recovery of the heat of reaction in the form of high pressure superheated steam, ensuring energy savings at low recycle rates. CO methanation is carried out in an adiabatic fixed bed reactor.

[0007] The heat generated by the reaction causes high temperatures to rise. The product of this process, methane-rich gas, is partly recycled to reduce the temperature rise in the methanation reactor. Over the past decade, interest in natural gas alternatives has increased. Work on this technology has been relaunched, and knowledge gained over the years is being used to improve tried and tested techniques and catalysts.

[0008] A demonstration plant (Westfield Coal Gasification plant) was built in Scotland and will produce 2.46 million Nm 3 / h SNG production. The methanator used in this plant consisted of a fixed bed reactor with gas recycle.

[0009] A further development from British Gas was the HICOM process, in which methane-rich gas is produced directly from purified gasifier product gas by reaction with steam over a catalyst, with the temperature increase controlled by hot gas recycle and split-stream operation.

[0010] In Germany, Linde has developed an isothermal fixed-bed reactor with indirect heat exchange. The reactor itself can generate steam from the heat of the exothermic methanation reaction. Part of the steam is added to the synthesis gas mixture to minimize the risk of carbon deposition before being fed to the isothermal and adiabatic methanation reactor.

[0011] All the above mentioned processes use fixed bed reactors with cooled product gas recycle and / or steam addition, which is necessary in order to efficiently dissipate the high reaction enthalpy (about 20% of the heating value of the feed gas) and to use it advantageously, if necessary, especially for steam generation and optionally for superheated steam generation.

[0012] On the other hand, in smaller systems, a single stage near-isothermal reactor arrangement is frequently used, often in combination with a thermal power plant. The heat generated in the methanation process is used to heat the working medium in the thermal power plant. Usually the working medium is water, and a boiling water reactor is used to control the reaction temperature in the methanation reactor. Alternative working media are thermal oil and molten salt. The water is heated to produce steam. A large portion of this steam is then expanded in a steam turbine to generate electricity.

[0013] CO / CO2 methanation has many practical applications. It is a means of removing carbon oxides from process gases and is also being considered as an alternative to catalytic preferential oxidation of carbon monoxide (PROX) in gas mixtures in fuel processors for mobile fuel cells. Methanation as a means of producing synthetic natural gas has been explored since the 1970s.

[0014] More recently, it has been explored as a way to store energy generated by solar or wind power using power-to-gas systems, in combination with existing natural gas storage. As part of the energy transition, the need for seasonal energy storage may increase. In Germany, it is expected that 30 TWh of storage capacity would be needed if 80% of electricity was generated from renewable sources.

[0015] Power-to-gas processes, which store energy by synthesizing gas using surplus electricity, are the most promising technology for seasonal energy storage. The main storage media are hydrogen and methane. Methane has the advantage over hydrogen that it can use existing infrastructure (gas pipes and natural gas tanks). In 2018, there were 128 research and demonstration plants for power-to-gas processes in Europe, indicating a great interest in this technology.

[0016] In order to provide an economically viable and technically feasible method of methanation, the methane produced needs to fulfil several requirements. The methane produced in the methanation process needs to be of high purity, since methane of insufficient purity must not be fed into the natural gas network. Furthermore, methane needs to be pressurised before being fed into the natural gas network. A satisfactory methanation process therefore needs to produce pressurised methane of high purity.

[0017] However, possible sources of starting material for the methanation process are biogas plants supplying CO2 and high-temperature electrolysis plants supplying H2. These plants usually provide their product at low pressure. Thus, some prior art methanation plants are operated at low pressure, which reduces the purity of the methane. This methane needs to be purified and pressurized before it can be fed into the natural gas network.

[0018] Therefore, processes have been developed to compress the starting material to produce pressurized methane. Methanation is often carried out at high pressure to shift the equilibrium towards methane according to Le Châtelier's principle. Depending on the application, the goal is usually a maximum residual hydrogen content of 2-5%.

[0019] For feed gases with low initial inlet pressures, motor-driven compressors are mostly used. To improve the equilibrium position, (partial) intermediate condensation of the water vapor formed between the two methanation stages can also be provided. This shifts the balance accordingly to the right-hand side of the equation.

[0020] Energy is required to pressurize the starting material so that compressed pure methane can be obtained. In the prior art, motor-driven compressors that require external energy, such as electrical energy, are usually employed to pressurize the starting material. The costs associated with this part account for 50% of the total system costs. Therefore, a process is needed to minimize the costs associated with the process of pressurizing the starting material. To achieve this goal, energy must be utilized efficiently to make the process economically and technically viable.

[0021] There is therefore a need for an improved methanation method and system that efficiently uses the energy provided by the exothermic reaction and minimizes the need for the use of external energy, thereby efficiently providing pressurized methane-enriched gas sufficiently pure for supply to the natural gas network. Summary of the Invention

[0022] The present invention provides an improved methanation method and system that efficiently uses the energy provided by the exothermic reaction and minimizes the need for the use of external energy, thereby efficiently providing methane-enriched gas that is pressurized to pure methane that can be fed into the natural gas network or for other downstream uses.

[0023] The present invention uses a turbocharger driven by the heat of reaction generated in the methanation reactor to compress the starting material and / or methane-rich gas generated in the system, thereby significantly reducing the costs that would be incurred if a motor-driven compressor were used.

[0024] The improved methanation method and system of the present invention uses a novel combination of one or more methanation stages with one or more turbochargers, which may be complemented with heat exchangers. The methanation stages may be adiabatic in all stages. However, the methanation stages may also be isothermal in one or more stages.

[0025] The improved methanation method and system of the present invention can be accomplished in several ways.

[0026] In one embodiment, the gas to be methanated (feed gas) or the methane-enriched (methanized) gas (product gas) flows completely through both components of the turbocharger.

[0027] In another embodiment, the gas to be methanated or the methanated gas passes only through the compressor of the turbocharger.

[0028] In one embodiment of the present invention, the methanation gas is not returned to the methanation reactor where it was produced. The methanation gas proceeds downstream through the continuous gas line and is completely removed from the system. In other words, at the outlet of the continuous gas line, all of the produced methanation gas can be removed. Removing all of the methanation gas from the system means that the methane-rich gas produced in the process is not returned from the outlet of the continuous gas line to one or more methanation reactors. Avoiding recirculation simplifies the system structure and eliminates the need to use a relatively expensive high-temperature compressor or intermediate cooling step, as in the prior art TREMP process.

[0029] In another embodiment, a portion of the methane-rich gas can be recycled back to the methanation reactor to control the reaction temperature.

[0030] In another embodiment, a portion of the methane-rich gas can be recirculated without the need for an additional recirculation compressor by a simple control valve, since the compression of the main gas stream by the turbocharger results in a higher pressure at the outlet of the system than at the inlet.

[0031] The main advantage of the present invention is that at the outlet of the system an increased pressure is obtained compared to the initial pressure of the starting material. The pressurized methane-enriched gas can be used directly for downstream applications. For example, the methane-enriched gas can be fed into the natural gas network without the need for further compression.

[0032] Thus, the methods and systems of the present invention can use starting materials at low pressures, such as atmospheric pressure, and still provide pressurized methane-enriched gas. Thus, the methods and systems of the present invention do not require high pressure starting materials, and thus can avoid expensive process costs associated with or caused by using, for example, electrical energy for a compressor to pressurize the starting material.

[0033] Additionally, the methods and systems of the present invention eliminate the need to further compress the methane-rich gas prior to use in downstream processes, thus avoiding the costs associated with this compression step.

[0034] The present invention therefore provides an improved methanation method and system that efficiently uses the energy provided by the exothermic reaction, minimizing the need for the use of external energy, thereby efficiently providing methane-enriched gas pressurized to pure methane that can be supplied to the natural gas network. [Brief description of the drawings]

[0035] [Figure 1] 1 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention. The system includes a turbocharger (2) and an integrated adiabatic methanation reactor (1). [Diagram 2] 2 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention. The system includes a turbocharger, an integrated adiabatic methanation reactor and a heat exchanger (8). The heat exchanger is a recuperator, in which the produced methane-rich gas heats the hydrogen and carbon-containing starting material leaving the compressor (3). [Diagram 3] 3 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention. The system comprises a turbocharger, a methanation reactor (1) arranged downstream of the turbocharger, and a heat exchanger (8). The heat exchanger is a recuperator, in which the produced methane-rich gas heats the hydrogen and carbon-containing starting material leaving the compressor. [Figure 4] 4 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention. The system comprises a turbocharger and a methanation reactor (1) located upstream of the turbocharger. The system further comprises two heat exchangers (8). [Diagram 5] Figure 5 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the invention. The system is similar to the system shown in Figure 4. The heat stream (10) from the methanation reaction is used for recovery of the produced methane-rich gas leaving the compressor before entering the turbine. [Figure 6] 6 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention, the system including a turbocharger with a counterflow of the produced methane-rich gas into a turbine before entering the compressor of the turbocharger. [Figure 7] Figure 7 shows a schematic diagram of a system for producing methane-enriched gas from hydrogen and carbon-containing starting materials according to the present invention similar to the system of Figure 1. It further comprises the injection of water (11) pressurized by a pump (12) and preheated and / or partially or fully evaporated in a preheating element / evaporator (8c / 8d) into the methanation reactor for temperature control and increased mass flow rate. [Figure 8] Figure 8 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of Figure 7, but including two methanation reactors. The first methanation reactor is an adiabatic methanation reactor and the second methanation reactor is an isothermal methanation reactor. [Figure 9] 9 shows a schematic diagram of a system for producing methane-rich gas and electricity from hydrogen and a carbon-containing starting material according to the present invention, comprising two methanation reactors. The first methanation reactor is cooled by a boiling water cooler. The methanation process in the first methanation reactor is isothermal. The second methanation reactor is an adiabatic methanation reactor. [Figure 10] FIG. 10 shows a schematic diagram of a system for producing methane-enriched gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 1, but including two turbochargers with an intermediate cooling element (8b) located between the compressors of each turbocharger. [Figure 11] FIG. 11 shows a schematic diagram of a system for producing methane-enriched gas and electricity from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 10, but including a second adiabatic methanation reactor located between the turbines of each turbocharger. [Figure 12] FIG. 12 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 11, but including an additional recuperator. [Figure 13] FIG. 13 shows a schematic diagram of a system for producing methane-rich gas and electricity from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 12, but including a third methanation reactor in which the isothermal methanation step takes place and a thermal power plant for the production of electricity. [Figure 14] FIG. 14 shows a schematic diagram of a system for producing methane-enriched gas from hydrogen and a carbon-containing starting material according to the present invention, including two turbochargers, both of which are positioned upstream of an adiabatic methanation reactor, and heat is transferred from the product gas to the feed gas in a recuperator before entering the first turbine. [Figure 15] FIG. 15 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 14, but including an additional adiabatic methanation reactor and an additional recuperator. [Figure 16]FIG. 16 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and carbon-containing starting materials according to the present invention, comprising a two-stage methanation process with recovery and turbocharging, located downstream of each methanation reactor, where the methane-rich gas produced in each methanation reactor enters a turbine (counterflow) before entering the compressor. [Figure 17] FIG. 17 shows a schematic diagram of a system for producing methane-rich gas and electricity from hydrogen and a carbon-containing starting material according to the present invention, which is a combination of a first stage corresponding to the system of FIG. 1, a second stage with counterflow of the methane-rich gas produced in the second methanation reactor with a downstream turbocharger, and a third stage including a third methanation reactor using an isothermal methanation process controlled by a steam circuit and a fourth methanation reactor polished to obtain a very high methane content in the methane-rich gas leaving the system. [Figure 18] FIG. 18 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention, including a turbocharger located downstream of a methanation reactor. [Figure 19] FIG. 19 shows a schematic diagram of a system for producing methane from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 18, including an additional recuperator located between the compressor and the heat exchanger using the heat stream of the methanation reactor. [Figure 20] FIG. 20 shows a schematic diagram of a system for producing methane-enriched gas and electricity from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 18 including an additional methanation stage. [Figure 21] FIG. 21 is a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 18, but including an adiabatic methanation reactor and a downstream recuperator. [Figure 22] FIG. 22 shows a schematic diagram of a system for producing methane-enriched gas and electricity from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 21, but including an additional isothermal methanation stage and a thermal power plant. [Figure 23]FIG. 23 shows a schematic diagram of a system for producing methane-enriched gas and electricity from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 16, but including an additional third methanation stage. [Figure 24] FIG. 24 shows a schematic diagram of a hybrid exemplary system for producing methane-rich gas from hydrogen and carbon-containing starting materials according to the present invention, combining some of the advantages of the systems shown in the previous figures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Description of the invention The present invention relates to a method for producing methane-rich gas or methane and optionally electricity from hydrogen and a carbon-containing starting material in a system comprising at least one single or multi-stage methanation process, comprising the following steps: a) providing: one methanation reactor (1) for each of at least one single-stage or multi-stage methanation steps, each methanation reactor comprising an inlet for the introduction of a feed gas comprising hydrogen and a carbon-containing starting material or a methane-enriched gas from a previous methanation stage, and an outlet for a methane-enriched product gas; a continuous gas line having an inlet (6) for the introduction of hydrogen and a carbon-containing starting material and an outlet (7) for removing methane-rich gas from the system; and at least one turbocharger (2) having a compressor (3) and a turbine (4) mechanically connected by a common shaft (5), the at least one turbocharger being connected to a methanation reactor via a continuous gas line; (at least one compressor is connected to the continuous gas line and is located in a portion of the continuous gas line defining a path from the introduction of the starting material to the removal of the methane-rich gas, in particular upstream of the methanation reactors, between the methanation reactors or downstream of the methanation reactors);

[0037] b) introducing hydrogen and a carbon-containing starting material into an inlet of a continuous gas line; c) producing a methane-enriched gas in a methanation reactor; and d) Using the energy released during the methanation process to increase the system pressure in the continuous gas line via at least one compressor.

[0038] The present invention also relates to a system for producing methane-rich gas or methane and optionally electricity from hydrogen and a carbon-containing starting material in at least one single-stage or multi-stage methanation process.The present invention also relates to a system for sustaining the production of methane-rich gas or methane and electricity from hydrogen and a carbon-containing starting material in at least one single-stage or multi-stage methanation process.

[0039] The system is for use in the method of the present invention and comprises: one methanation reactor (1) for each of at least one single-stage or multi-stage methanation steps, each methanation reactor comprising an inlet for the introduction of a feed gas comprising hydrogen and a carbon-containing starting material or a methane-enriched gas from a previous methanation stage, and an outlet for a methane-enriched product gas; a continuous gas line having an inlet (6) for the introduction of hydrogen and a carbon-containing starting material and an outlet (7) for removing methane-rich gas from the system; and

[0040] At least one turbocharger (2) in which the compressor (3) and turbine (4) are mechanically connected by a common shaft (5) (The at least one compressor is connected to the continuous gas line and is located in a portion of the continuous gas line defining a path from the introduction of the starting material to the removal of the methane-rich gas, in particular upstream of the methanation reactors, between the methanation reactors, or downstream of the methanation reactors).

[0041] Another aspect of the present invention is the use of the system of the present invention for the methanation process of the present invention.

[0042] In the method or system of the present invention, the heat generated in the methanation reactor can be used to drive a turbocharger and increase the pressure in the system, thereby efficiently maintaining the methanation process. Therefore, the present invention can also be described as a method or system for maintaining the production of methane-rich gas or methane and optionally electricity from hydrogen and carbon-containing starting materials in a system comprising at least one single-stage or multi-stage methanation process as described above.

[0043] Feed gas in the context of the present invention is the gas entering the methanation reactor, the feed gas entering the methanation reactor prior to the first methanation stage comprises hydrogen and carbon-containing starting material, the feed gas in the subsequent methanation stage comprises the product gas of the previous methanation stage, which is the methane-rich gas produced in the previous methanation stage.

[0044] Product gas in the context of the present invention is the gas leaving the methanation reactor. The product gas is a methane-enriched gas or methanated gas, which has an increased content of methane compared to the feed gas entering the same methanation reactor.

[0045] Depending on the composition of the feed gas, e.g., the content of methane in the feed gas, and the reaction conditions in the methanation reactor, the methane-enriched product gas can have a methane concentration of more than about 97%. The carbon-containing starting material is preferably CO2 and / or CO.

[0046] The method and system can be operated using parameters used by those skilled in the art.

[0047] The carbon-containing starting material is preferably provided at atmospheric pressure. By using the compressor according to the present invention, the pressure at the outlet of the continuous gas line is higher than the pressure at the inlet of the continuous gas line. Preferably, the pressure may be in the range of 0.1 to 100 bar, more preferably 1.5 to 25 bar, even more preferably 2 to 8 bar.

[0048] In a typical setup, a turbocharger's compressor increases the pressure by a factor of 2-8, while the turbine reduces the pressure by a factor of 1.5-3. The specific performance depends on the quality of the turbocharger. You can expect a pressure increase of about 1.5-3 times for each stage of the turbocharger.

[0049] In the system shown in Example 1 and in Figure 1, the inlet pressure is 1 bar. After the compressor, the pressure rises to 3 bar. The methanation step is carried out at 3 bar. In the turbine, the pressure drops to 1.5 bar. The product gas leaves the system at a pressure of 1.5 bar.

[0050] In the two-stage system shown in Example 12 and FIG. 12, the pressure of 3 bar after the first compressor increases to 9 bar after the second compressor (3 times for each stage). The first methanation step is performed at 9 bar. In the first turbine, the pressure is reduced to 4.5 bar. The second methanation step is performed at 4.5 bar with decreasing temperature. In the second turbine, the pressure is reduced to 2.25 bar. The product gas leaves the system at a pressure of 2.25 bar.

[0051] The methods and systems of the present invention are particularly useful for maintaining an ongoing methanation process, however, they can also be used to start up new methanation reactions.

[0052] To initiate a new methanation reaction, the method of the present invention may further comprise preheating the methanation reactor prior to introducing hydrogen and the carbon-containing starting material into the inlet of the continuous gas line.

[0053] The temperature range of the starting material at the inlet of the continuous gas line can range from ambient temperature, such as room temperature, to 100° C. The temperature at the inlet of the first methanation reactor is preferably at least about 130-150° C., as this is the temperature range in which the exothermic reaction in the reactor will sustain itself.

[0054] The methanation process begins with a reactor temperature of about 200° C., more preferably about 250° C. A feed gas containing hydrogen and a carbon-containing starting material can be electrically heated to about 200° C. and fed into the system to begin the process.

[0055] The method of the invention may further comprise the additional step between steps b) and c) of injecting water or steam directly into the at least one methanation reactor or into a continuous gas line upstream of the inlet for introducing the feed gas of the at least one methanation reactor, which has the advantage of increasing the mass flow rate in the turbine compared to the compressor and thus the compression ratio of the compressor.

[0056] Additionally, the temperature in the reactor can also be limited, if desired, by direct injection of steam or water into the methanation reactor or injection before the inlet of the methanation reactor. In those embodiments including a water / steam injection step, the system of the invention includes a water / steam injection unit for injecting water or steam directly into at least one methanation reactor or into a continuous gas line upstream of the inlet for introduction of the feed gas. The water / steam injection unit includes a line carrying water and / or steam.

[0057] Water is pumped by a pump to the methanation reactor or to a continuous gas line at a location before the inlet of the methanation reactor, and the water is converted to steam or hot water in a heat exchanger element using heat provided by the product gas before the product gas leaves the system.

[0058] The process of the present invention may additionally or alternatively further comprise supplying external energy to the compressor to facilitate initial compression of the hydrogen and carbon-containing starting material prior to the initiation of the methanation step.

[0059] The installation location of the compressor in the method and system of the present invention is not particularly limited as long as it is installed at a position where it can compress the gas in the continuous gas line.

[0060] In one option, the compressor increases the pressure in the continuous gas line at a location located between the inlet of the continuous gas line and the inlet of the methanation reactor, i.e., the compressor can be located at a location in the continuous gas line prior to the methanation reactor.

[0061] This provides the advantage of carrying out the methanation step at an increased pressure level. Alternatively, the compressor increases the pressure in the continuous gas line at a location located between the outlet of the methanation reactor and the outlet of the continuous gas line. That is, the compressor can also be located at a position in the continuous gas line located after the methanation reactor.

[0062] This has the advantage of reducing the volumetric flow rate in the compressor. In the methanation reaction, four molecules of H2 react with one molecule of CO2 to produce two molecules of water and one molecule of methane, which corresponds to a reduction in volume of about 3 / 5. Reducing the volumetric flow rate in the compressor can improve the compressor's performance.

[0063] Alternatively, the turbine can be located upstream of the compressor, which has the advantage of further reducing the volumetric flow rate in the compressor. The gas leaving the turbine can be cooled and water vapor can be condensed out and removed before entering the compressor. This further reduces the gas volume, especially when comparing the gas volume in the turbine with the gas volume in the compressor.

[0064] In embodiments having one or more turbochargers, one compressor may be located before the first methanation reactor and another compressor may be located after the last methanation reactor, and one or more compressors may be located between any two methanation reactors.

[0065] In the method or system of the present invention, at least one turbocharger can be disposed upstream of the methanation reactor, and heat generated in the methanation reactor can be supplied to the turbocharger at a location between the turbine and the compressor via at least one heat exchanger.

[0066] Alternatively, at least one turbocharger can be located downstream of the methanation reactor and heat generated in the methanation reactor can be supplied to the turbocharger at a location between the turbine and the compressor via at least one heat exchanger.

[0067] The heat exchanger ensures that heat can be transferred between the compressor and turbine components to the turbocharger, whether the turbocharger is located upstream or downstream of the methanation reactor.

[0068] Alternatively, at least one turbocharger can be arranged between the two methanation reactors, and heat generated in the methanation reactor arranged upstream of the turbocharger is supplied to the turbocharger via at least one heat exchanger prior to the turbine inlet of the turbocharger, preferably at a location between the turbine and the compressor.

[0069] The methods or systems of the present invention include at least one turbocharger. They may also include multiple turbochargers. In certain embodiments, two, three, or more turbochargers may be used. Each additional stage of turbocharger may increase the pressure in the system.

[0070] The method or system of the present invention can be further controlled by inter-cooling or inter-heating the continuous gas lines via heat exchanger elements.

[0071] The term "heat exchange element / heat exchanger" as used herein may refer to an intermediate cooling element, intermediate heating element, recuperator, gas cooling element, preheating element, condenser, and / or evaporator. In a preferred embodiment, the heat exchanger may be a recuperator, which transfers heat from the gas exiting the turbine to the hydrogen and carbon-containing starting material for entry into the methanation reactor.

[0072] In the method or system of the present invention, at least one single stage methanation step can be adiabatic, or at least one stage of the multi-stage methanation step can be adiabatic. In an adiabatic step, the gas temperature is increased, which improves the performance of the turbine. In a preferred embodiment, the first stage is carried out in an adiabatic methanation reactor to maximize the temperature in the system.

[0073] The maximum temperature reached in the reactor can be in the range of 350 to 800°C, for example 500 to 800°C, depending on the gas composition and pressure. A preferred maximum temperature is in the range of about 430 to about 720°C, for example 630 to about 720°C.

[0074] An adiabatic process is preferably used since the heat flow generated in the adiabatic process can be used to drive a turbocharger, in particular the compressor of the turbocharger. Further stages can also be adiabatic.

[0075] In the method or system of the present invention, at least one single stage methanation step can be isothermal, or at least one stage of the multi-stage methanation step can be isothermal. Isothermal reactions have the advantage that they are carried out at low temperatures in the range of about 200-300° C., providing a better gas composition that can be used in downstream applications without further treatment.

[0076] Better gas composition means that more of the starting material is reacted to methane. The product gas of an isothermal process contains more methane than the product gas of an adiabatic process using the same starting material. This is because the reaction balance at the high temperatures reached in the adiabatic process of reaction to methane is not optimal.

[0077] In a preferred embodiment of the present invention, the method or system includes a combination of at least one adiabatic step and at least one isothermal step, benefiting from the advantages provided by both of these steps. The number of methanation stages can be selected by the skilled person depending on the requirements of the methane-rich gas produced in the system. Additional stages can increase the methane concentration in the product gas.

[0078] In the isothermal methanation process of the present invention, the temperature in the methanation reactor is controlled by the thermal power plant.

[0079] A thermal power plant in the context of the present invention is a system capable of converting thermal energy into electricity. When a thermal power plant is present in the system or method of the present invention, the system or method of the present invention can be used to generate methane-enriched gas and electricity. For example, a steam-driven turbine can convert heat into mechanical power as an intermediate to electricity. The steam turbine is connected to the lines of the thermal power plant, in which the working medium moves. In a preferred embodiment, the working medium is water and / or steam.

[0080] Alternatively, the working medium can be thermal oil or molten salt. Thermal oil or molten salt is usually used in an intermediate circuit that stores heat. The heat stored in the thermal oil / molten salt circuit is transferred to the steam circuit. Therefore, compared to systems using direct cooling with water / steam, this system includes an additional circuit, making the system more complex. On the other hand, with indirect cooling with thermal oil / molten salt circuits, the reactor does not need to be designed for high pressures, such as up to 80 bar, as in the case of direct cooling with water / steam circuits. This is because the thermal oil circuit does not require pressure.

[0081] In thermal power plants, a working medium such as water is heated and turned into steam to drive a steam turbine, which can drive a generator. In some embodiments of the present invention, the heat flow generated in the isothermal methanation reactor can be used to heat the working medium in the thermal power plant system. Additionally, the working medium can be preheated in a heat exchanger element, and the heated methanation gas preheats the working medium before the methanation gas exits the system. After the steam passes through the turbine, it is condensed in a condenser and recycled to where it was heated.

[0082] In the method or system of the present invention, the turbine of the turbocharger can reduce the pressure of the gas leaving the methanation reactor. Additionally or alternatively, a turbine can be placed in the steam circuit of the thermal power plant to reduce the pressure of the working medium moving in the lines of the thermal power plant used to control the temperature of another methanation reactor.

[0083] In the method or system of the present invention, a portion of the heat generated in the methanation step can be used in the turbocharger and another portion, preferably a larger portion, can be used to generate steam or electricity. Since it is thermodynamically impossible to use all of the heat generated in the methanation step in the turbocharger, it is advantageous to use the remaining heat to generate electricity. This makes the method and system more efficient.

[0084] The present invention is further illustrated in the following examples. EXAMPLES

[0085] Example 1 One example of the system and method of the present invention is shown in FIG.

[0086] Figure 1 shows a schematic diagram of a system for producing methane-enriched gas from hydrogen and a carbon-containing starting material according to the invention. The system comprises a turbocharger including a compressor (3) and a turbine (4) mechanically connected by a common shaft (5), and an adiabatic (uncooled) methanation reactor (1) arranged between the compressor and the turbine. The inlet pressure is 1 bar (a) and the temperature is 20°C. The feed gas consists, for example, of 4 mol / s H2 and 1 mol / s CO2. The hydrogen and the carbon-containing starting material pass through the compressor. The pressure at the outlet of the compressor is, for example, 3 bar (a). The isentropic efficiency of the compressor and the turbine is assumed to be 90%.

[0087] Then, in an adiabatic methanation reactor at 3 bar(a), a methanation gas with about 0.48 mol / s of methane and an outlet temperature of 628°C is produced. The produced methane-rich gas leaves the methanation reactor and enters the turbine. This gas is expanded in the turbine to about 1.5 bar(a) to drive the compressor. About 17.5 kW of power is transmitted via the turbocharger shaft. The expanded methane-rich gas is then discharged from the system. In order to achieve a complete conversion of the starting gas, in the example shown, at least one additional methanation reactor can be added after the turbine. This can be operated isothermally at, for example, 280°C, the temperature in the methanation being controlled via the thermal power plant.

[0088] Example 2 Figure 2 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and carbon-containing starting material according to the present invention. The system includes a turbocharger (2) including a compressor (3) and a turbine (4) mechanically connected by a common shaft (5), and an adiabatic methanation reactor (1) located between the compressor and the turbine. The system further includes a heat exchanger (8). The heat exchanger is a recuperator, which heats the hydrogen and carbon-containing starting material exiting the compressor with the produced methane-rich gas. The recuperator (50 K pinch) increases the inlet temperature to the methanation reactor to about 513°C (compared to about 131°C in the system shown in Figure 1).

[0089] The methanated gas leaving the reactor is at a temperature of about 702°C (compared to about 628°C in the system shown in Figure 1). This reduces the methane production (0.26 mol / s methane at the reactor outlet). However, the increased temperature allows the turbine to operate with a reduced pressure differential to drive the compressor. The methane-rich gas can therefore be given an increased pressure of 1.7 bar (compared to 1.5 bar in the system shown in Figure 1). The methane-rich gas leaving the system after passing through the recuperator is at a temperature of about 181°C.

[0090] Example 3 Figure 3 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention. The system comprises a turbocharger including a compressor (3) and a turbine (4) mechanically connected by a common shaft (5), and a methanation reactor (1) located downstream of the compressor and the turbine. The system further comprises a heat exchanger (8). The heat exchanger is a recuperator, in which the produced methane-rich gas heats the hydrogen and carbon-containing starting material leaving the compressor.

[0091] Example 4 Figure 4 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the invention. The system comprises a turbocharger, including a compressor (3) and a turbine (4), mechanically connected by a common shaft (5), and a methanation reactor (1) located upstream of the compressor and the turbine. The system further comprises two heat exchangers (8 / 8a). The produced methane-rich gas passes through one heat exchanger, a recuperator (8), located between the compressor and the turbine, and the product methane-rich gas leaving the compressor flows countercurrently with the product methane-rich gas leaving the methanation reactor. The vapors produced in the reaction are condensed in a further heat exchange element, the gas cooling element (8a), so that the condensate (9) leaves the system before the methane-rich gas enters the compressor.

[0092] Example 5 Figure 5 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the invention. The system is similar to the system shown in Figure 4. The heat stream (10) from the methanation reaction is used for recovery of the produced methane-rich gas leaving the compressor before entering the turbine.

[0093] Example 6 Figure 6 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the invention. The system comprises a turbocharger with a counterflow of the produced methane-rich gas entering a turbine before entering the compressor of the turbocharger. The produced methane-rich gas enters the turbine and is then cooled in a recuperator by the counterflow of hydrogen and the carbon-containing starting material. The vapors produced in the reaction are condensed in a further heat exchange element, the intermediate cooling element (8b), so that the condensate (9) leaves the system before the methane-rich gas enters the compressor. The methane-rich gas leaving the compressor leaves the system.

[0094] Example 7 Figure 7 shows a schematic diagram of a system for producing methane-enriched gas from hydrogen and carbon-containing starting materials according to the invention, similar to the system of Figure 1. It further includes a water / steam injection unit including a line through which water travels. Water (11) pumped by pump (12) through a heat exchanger (8c / 8d), which can be a preheating element (8c) or an evaporator (8d), where the steam produced in the methanation reaction condenses and the condensate flows out of the system, is heated to hot water / steam (13) and injected into the methanation reactor.

[0095] Example 8 Figure 8 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of Figure 7, but including two methanation reactors. The first methanation reactor is an adiabatic methanation reactor. The heated methane-rich gas produced in the first methanation reactor is used to heat the methane-rich gas exiting the second methanation reactor before the methane-rich gas enters the turbine.

[0096] The second methanation reactor is cooled by a boiling water cooler. The methanation process in the second methanation reactor is isothermal. The water / steam injection unit is similar to the water / steam injection unit shown in FIG. 7. Before leaving the system, the pumped water is heated in a preheating heat exchanger using the residual heat of the produced methane-rich gas to hot water (14), and the hot water is heated in an additional heat exchanger using the heat flow produced in the second methanation reactor to obtain steam (15). The steam is injected into the continuous gas line at a point downstream of the second methanation reactor but upstream of the turbine.

[0097] Example 9 FIG. 9 shows a schematic diagram of a system for producing methane-rich gas and electricity from hydrogen and a carbon-containing starting material according to the present invention, comprising two methanation reactors. The first methanation reactor is cooled by a boiling water cooler. The methanation process in the first methanation reactor is isothermal. The second methanation reactor is an adiabatic methanation reactor. The heated methane produced in the first methanation reactor is used to heat water in a thermal power plant that includes a steam circuit. In one part of the circuit, the water is pumped through the lines of the thermal power plant to a heat exchanger and is heated by countercurrent flow of the water with the methane-rich gas produced in the first methanation reactor.

[0098] Condensate from the methane-rich gas stream leaves the system at this point in the circuit. In another part of the circuit, water is pumped through the thermal power plant lines to another heat exchanger where it is heated by countercurrent flow of water with the methane-rich gas produced in the second methanation reactor. The heated water from both parts of the circuit enters an additional heat exchanger to generate steam. The heat flow from the first methanation reactor is used to heat the water, which in turn cools the first methanation reactor. The steam is used to drive the turbocharger turbine (4). The residual pressure is used in the steam turbine (16) to generate electricity. The residual steam is cooled in a condenser and pumped to the pump, thereby completing the circuit. The electricity generated by the steam turbine can be used in part to drive the pumps in the steam circuit and / or for other purposes, such as pumping to the power grid.

[0099] Hydrogen and carbon-containing starting material enter the first methanation reactor. The methane-rich gas produced exits the first methanation reactor and is cooled in a heat exchanger, resulting in a condensate flowing out of the system. The methane-rich gas then enters a compressor before entering the second methanation reactor. The methane-rich gas produced exits the second methanation reactor and is used to heat water flowing from a pump to the turbine of a turbocharger, before exiting the system.

[0100] Example 10 FIG. 10 shows a schematic diagram of a system for producing methane-enriched gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 1, but including two turbochargers with an intermediate cooling element disposed between the compressors of each turbocharger.

[0101] Example 11 FIG. 11 shows a schematic diagram of a system for producing methane-enriched gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 10, but including a second adiabatic methanation reactor disposed between the turbines of each turbocharger.

[0102] Example 12 Figure 12 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of Figure 11, but including an additional recuperator, in which the produced methane-rich gas is used to heat the hydrogen and carbon-containing starting material before it exits the system and enters a first methanation reactor.

[0103] Example 13 Figure 13 shows a schematic diagram of a system for producing methane-enriched gas and electricity from hydrogen and a carbon-containing starting material according to the invention similar to the system of Figure 12, but including a third methanation reactor in which an isothermal methanation step is carried out. The third methanation reactor interacts with a thermal power plant including a steam turbine for generating electricity using the heat stream produced in the third methanation reactor.

[0104] Example 14 Figure 14 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention, comprising two turbochargers, with an intermediate cooling element (8b) arranged between the compressors of each turbocharger. The hydrogen and carbon-containing starting material are heated in a recuperator with the produced methane-rich gas leaving the methanation reactor. The methanation reactor is arranged downstream of the turbochargers.

[0105] Example 15 Figure 15 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of Figure 14, but including an additional adiabatic methanation reactor. The methane-rich gas produced in the second methanation reactor is used to heat the hydrogen and carbon-containing starting material at a location between the two turbines.

[0106] Example 16 FIG. 16 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and carbon-containing starting materials according to the present invention, comprising a two-stage methanation process with recovery and turbocharging, located downstream of each methanation reactor, where the methane-rich gas produced in each methanation reactor enters a turbine (counterflow) before entering the compressor.

[0107] Example 17 FIG. 17 shows a schematic diagram of a system for producing methane-rich gas and electricity from hydrogen and a carbon-containing starting material according to the present invention, which is a combination of a first stage corresponding to the system of FIG. 1, a second stage with counterflow of the methane-rich gas produced in the second methanation reactor with a downstream turbocharger, and a third stage including a third methanation reactor using an isothermal methanation process controlled by a steam circuit and a fourth methanation reactor as a grinding device to obtain a very high methane content in the methane-rich gas leaving the system.

[0108] Example 18 FIG. 18 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention, including a turbocharger located downstream of a methanation reactor. The heat flow from the methanation reactor is used to heat the methane-rich gas leaving the compressor before it enters the turbine. The methane-rich gas produced in the methanation reactor is cooled before it enters the compressor. The condensate leaves the system. A recuperator is used to heat the hydrogen and the carbon-containing starting material before it enters the methanation reactor.

[0109] Example 19 FIG. 19 shows a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of FIG. 18, but including an additional recuperator located between the compressor and the heat exchanger using the heat stream from the methanation reactor.

[0110] Example 20 Figure 20 shows a schematic diagram of a system for producing methane-rich gas and electricity from hydrogen and a carbon-containing starting material according to the invention similar to the system of Figure 18 including an additional methanation stage. The additional methanation reactor is cooled by a thermal power plant by using the heat flow to vaporize water in the steam circuit of the thermal power plant to generate electricity.

[0111] Example 21 Figure 21 is a schematic diagram of a system for producing methane-rich gas from hydrogen and a carbon-containing starting material according to the present invention similar to the system of Figure 18, but including an adiabatic methanation reactor and a downstream heat exchanger. The methane-rich gas exiting the methanation reactor is used to heat the methane-rich gas exiting the compressor.

[0112] Example 22 Figure 22 shows a schematic diagram of a system for producing methane-rich gas and electricity from hydrogen and a carbon-containing starting material according to the invention similar to the system of Figure 21, but including an additional methanation stage. The additional methanation reactor is cooled by a thermal power plant by using the heat flow to vaporize water in the steam circuit of the thermal power plant to generate electricity.

[0113] Example 23 Figure 23 shows a schematic diagram of a system for producing methane-rich gas and electricity from hydrogen and a carbon-containing starting material according to the invention similar to the system of Figure 16, but including an additional third methanation stage. The additional third methanation reactor is cooled by a thermal power plant by using the heat flow to vaporize water in the steam circuit of the thermal power plant to generate electricity.

[0114] Example 24 24 shows a schematic diagram of a composite exemplary system for producing methane-rich gas from hydrogen and carbon-containing starting materials according to the present invention. The adiabatic methanation stage is followed by recovery and utilization of the heat stream produced in the first methanation reactor, then intercooling to allow the condensate to flow out of the system, then two-stage compression in two turbocharger compressors.

[0115] A second adiabatic methanation stage with hot water / steam injection is followed by recovery heating and expansion in the respective turbocharger turbine. After a further expansion step in the third turbocharger turbine, the methane is compressed in the third turbocharger compressor and enters the third methanation reactor. The heat stream of the third methanation reactor is used to generate steam for injection into the second methanation reactor.

[0116] The advantage of this combined system is that the mass flow rate through the expansion turbine is significantly increased. This allows very high outlet pressures to be achieved at the end of the system, for example up to 50 bar(a) with an inlet pressure of 1 bar(a). A two-stage compression before the second methanation stage allows pressures of about 5-20 bar(a) to be obtained. By combining intermediate cooling and separation of the condensate very high methane concentrations (>97%) can be achieved. Another advantage is that the methanation stage is adiabatic, so no complex cooling circuits are required. As the first stage (high temperature) operates only at atmospheric pressure, the outlet temperature is essentially limited to about 600 °C.

[0117] Reference List 1: Methanation reactor 2: Turbocharger 3: Compressor 4: Turbine 5: Shaft 6: Inlet of a continuous gas line for introducing hydrogen and carbon-containing starting materials (feed gases) 7: Outlet for removing the produced methane-enriched gas (produced gas) 8: Heat exchanger / recuperator 8a: Gas cooling element 8b: Intermediate cooling element 8c: Preheating element 8d: Evaporator 8e: Condenser 9: Condensate drainage 10: Heat flow 11:Water 12: Pump 13: Hot water / steam 14:Hot water 15: Steam 16: Power generation steam turbine

Claims

1. 1. A method for producing methane-rich gas from hydrogen and a carbon-containing starting material in a system comprising at least one single or multi-stage methanation step, comprising: The method includes the steps of: a) providing: one methanation reactor (1) for at least one single-stage or multi-stage methanation step, each methanation reactor comprising an inlet for the introduction of a feed gas comprising hydrogen and a carbon-containing starting material or a methane-enriched gas from a previous methanation stage, and an outlet for a methane-enriched product gas; a continuous gas line having an inlet (6) for the introduction of hydrogen and carbon-containing starting material and an outlet (7) for removing methane-rich gas from the system; and at least one turbocharger (2) having a compressor (3) and a turbine (4) mechanically connected by a common shaft (5), the at least one turbocharger being connected to a methanation reactor via a continuous gas line; wherein the at least one compressor is disposed in a continuous gas line, the continuous gas line defining a path from the introduction of the starting material to the removal of the methane-enriched gas; b) introducing hydrogen and a carbon-containing starting material into an inlet of a continuous gas line; c) producing a methane-enriched gas in a methanation reactor; and d) Using the energy released during the methanation process to increase the system pressure in the continuous gas line via at least one compressor.

2. 10. The method of claim 1, wherein the at least one compressor is disposed in a section defining an upstream methanation reactor, between methanation reactors, or downstream of a methanation reactor.

3. 3. The method according to claim 1 or 2, further comprising the additional step between steps b) and c) of injecting water or steam directly into the at least one methanation reactor or injecting water or steam into a continuous gas line upstream of an inlet for introducing the feed gas of the at least one methanation reactor and / or the turbocharger turbine.

4. 4. The method according to any one of claims 1 to 3, wherein in step a) a thermal power plant is provided having a working medium moving in the lines of the thermal power plant, the thermal power plant being connected via at least one heat exchanger (8) to the at least one methanation reactor or a gas stream resulting therefrom, the thermal power plant generating electrical power, and optionally the thermal power plant being a steam turbine (16) having steam (15) moving in the lines of a steam turbine cycle.

5. At least one turbocharger turbine is connected to the continuous gas line or, if present, to one of the lines of the thermal power plant; and / or further comprising a step e) of removing methane-rich gas from the system at the outlet of the continuous gas line; and / or wherein the carbon-containing starting material is CO ２ and / or CO; and / or the hydrogen and the carbon-containing starting material are provided at atmospheric pressure; and / or the pressure at the outlet of the continuous gas line is higher than the pressure at the inlet of the continuous gas line.

6. 6. The method of any one of claims 1 to 5, further comprising pre-heating the methanation reactor prior to step b) of claim 1; and / or further comprising supplying external energy to a compressor to facilitate initial compression of the hydrogen and carbon-containing starting material prior to the methanation step.

7. 7. The method according to any one of claims 1 to 6, wherein one or more compressors increase the pressure in the continuous gas line at a location located between the inlet of the continuous gas line and the inlet of the first methanation reactor; and / or one or more compressors increase the pressure in the continuous gas line at a location located between the outlet of the methanation reactor and the outlet of the continuous gas line; and / or a turbine is disposed at a location upstream of the one or more compressors.

8. 8. The method according to any one of claims 1 to 7, wherein multiple turbochargers are used; or inter-cooling or inter-heating of successive gas lines is performed via a heat exchanger element (8); and / or at least one single-stage methanation process is adiabatic or at least one stage of the multi-stage methanation process is adiabatic.

9. The method of claim 8 wherein three or more turbochargers are used.

10. 10. The process according to any one of claims 2 to 9, wherein at least one single stage methanation process is isothermal or at least one stage of the multi-stage methanation process is isothermal, and in the isothermal process the temperature in the methanation reactor is controlled by a thermal power plant.

11. 11. The method according to any one of claims 1 to 10, wherein the turbine reduces the pressure of the gas leaving the methanation reactor; or, if present, the turbine reduces the pressure of the working medium moving in the lines of the thermal power plant used to control the temperature of the methanation reactor; and / or the heat exchanger (8), if present, is a recuperator, which transfers heat from the gas leaving the turbine to the hydrogen and the carbon-containing starting material before they enter the methanation reactor.

12. 12. The method according to any one of claims 1 to 11, wherein at least one turbocharger is located upstream of the methanation reactor and heat generated in the methanation reactor is supplied to the turbocharger at a position between the turbine and the compressor via at least one heat exchanger; or wherein at least one turbocharger is located downstream of the methanation reactor and heat generated in the methanation reactor is supplied to the turbocharger at a position between the turbine and the compressor via at least one heat exchanger; or wherein at least one turbocharger is located between two methanation reactors and heat generated in the methanation reactor located upstream of the turbocharger is supplied to the turbocharger via at least one heat exchanger before the turbine inlet of the turbocharger.

13. 13. The method of claim 12, wherein heat generated in a methanation reactor located upstream of the turbocharger is supplied to the turbocharger at a location between the turbine and the compressor.

14. A method according to any one of the preceding claims, wherein part of the heat produced in the methanation process is used in a turbocharger and another part is used to generate steam or electricity.

15. The method of claim 14, wherein the separate portion of heat generated in the methanation process that is used to generate steam or electricity is greater than the portion of heat generated in the methanation process that is used in the turbocharger.

16. 1. A system for producing a methane-rich gas from a hydrogen- and carbon-containing starting material in at least one single-stage or multi-stage methanation step, comprising: Systems including: one methanation reactor (1) for at least one single-stage or multi-stage methanation step, each methanation reactor comprising an inlet for the introduction of a feed gas comprising hydrogen and a carbon-containing starting material or a methane-enriched gas from a previous methanation stage, and an outlet for a methane-enriched product gas; a continuous gas line having an inlet (6) for the introduction of hydrogen and carbon-containing starting material and an outlet (7) for removing methane-rich gas from the system; and At least one turbocharger (2) having a compressor (3) and a turbine (4) mechanically connected by a common shaft (5); Here, at least one compressor is disposed in a continuous gas line, said continuous gas line defining a path from the introduction of the starting material to the removal of the methane-enriched gas.

17. 17. The system of claim 16, wherein the at least one compressor is disposed upstream of a methanation reactor, between methanation reactors, or in a section defining a downstream methanation reactor.

18. 18. The system of claim 16 or 17, further comprising a water / steam injection unit for injecting water or steam directly into the at least one methanation reactor or into a continuous gas line upstream of the inlet for the introduction of the feed gas.

19. 19. The system according to any one of claims 16 to 18, further comprising a thermal power plant having a working medium moving in a line of the thermal power plant, the methanation reactor and the at least one turbocharger being connected via a continuous gas line, the thermal power plant being connected to the at least one methanation reactor or a gas stream resulting therefrom via at least one heat exchanger (8), the thermal power plant being configured to generate electricity.

20. The system of claim 19, wherein the thermal power plant is a steam turbine (16) having lines of a steam turbine cycle.

21. A system according to any one of claims 16 to 20, wherein at least one turbine is connected to the continuous gas line or, if present, to one of the thermal power plant lines.

22. Use of a system according to any one of claims 16 to 21 for a method according to any one of claims 1 to 15.

Images