CN118491444A - A synthesis device and method for preparing methane based on electric and thermochemical hybrid method - Google Patents

Abstract

The present invention relates to a synthesis device and method for preparing methane based on an electrochemical and thermochemical mixed method. The reaction chamber of the device is at least provided with a first input chamber, a second input chamber, a first output chamber and an electrocatalytic reactor, wherein the first input chamber is in close contact with the circumferential side wall of the reaction chamber; the second input chamber is located at the center of the reaction chamber; the electrocatalytic reactor is sleeved to the outside of the second input chamber, and the second input chamber is connected to the electrocatalytic reactor; the inner wall of the catalytic unit is provided with a catalytic layer for catalyzing a methanation reaction; the first output chamber is located between the first input chamber and the electrocatalytic reactor, and the first output chamber is connected to the first input chamber; methane/synthesis gas is synthesized by reacting carbon dioxide with hydrogen generated by electrolysis of water, thereby converting carbon dioxide into fuel to replace traditional fossil fuels, thereby realizing the effective utilization of carbon dioxide resources and reducing greenhouse gas emissions.

Description

A synthesis device and method for preparing methane based on electric and thermochemical hybrid method

Technical Field

The present invention relates to the technical field of synthetic natural gas or synthesis gas preparation, and in particular to a synthesis device and method for preparing methane based on an electric and thermochemical mixed mode.

Background Art

As climate change and energy depletion become increasingly serious, the need to replace fossil fuels and reduce greenhouse gas emissions is becoming more and more urgent. Among them, the use of carbon dioxide for methanation reaction to synthesize natural gas is of great research significance, which is of great significance to energy consumption and reducing greenhouse gas emissions.

At present, in terms of synthesizing green methane, SOEC co-electrolysis of CO ₂ /H ₂ O technology for preparing methane/synthesis gas has great application potential. The main method is to pass a certain proportion of CO ₂ and water vapor into an oxygen ion conductor SOEC electrolysis device, and an electrochemical reduction reaction occurs at high temperature to generate H ₂ , CO and O ^2- , among which H ₂ and CO are catalyzed by a catalyst to generate methane under medium and low temperature conditions; O ^2- passes through the electrolyte layer and undergoes an oxidation reaction to generate O ₂ ;

At present, the oxygen ion conductor SOEC synthesis system for preparing methane/syngas has the following problems:

The synthesis of methane from syngas is a highly exothermic reaction. Lowering the reaction temperature is conducive to the forward reaction. However, the operating temperature of the SOEC stack is higher than 600°C, making it difficult for the methanation reaction to occur in the stack. Therefore, due to the mismatch between the SOEC electrolysis and methanation reaction temperatures, the existing co-electrolysis methane production mostly divides the electrolysis preparation and methane synthesis processes into two reaction stages, which are carried out in the stack and the external reactor respectively, resulting in a complex process, a bulky overall structure of the equipment, and a large occupied volume. The electrolysis equipment, the methane synthesis equipment, and the heat exchanger used to heat the materials are independent of each other, resulting in the inability to achieve cascade utilization of thermal energy in the same equipment, making it difficult for the waste heat of the stack and the methanation reactor to fully meet the large amount of low-grade thermal energy required for the evaporation process of liquid water, limiting the improvement of the overall energy utilization efficiency.

Summary of the invention

In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a synthesis device and method for preparing methane based on an electric and thermochemical hybrid method, which specifically adopts the following technical solutions:

A synthesis device for preparing methane based on an electrothermal chemical mixing method comprises a reaction chamber, wherein the reaction chamber is provided with at least a first input chamber, a second input chamber, a first output chamber and an electrocatalytic reactor.

The first input chamber is close to the circumferential side wall of the reaction chamber; the first input chamber is used to input water vapor;

The second input chamber is located at the center of the reaction chamber; the second input chamber is used to input carbon dioxide gas;

The electrocatalytic reactor is sleeved to the outside of the second input chamber, and the second input chamber is connected to the electrocatalytic reactor; the electrocatalytic reactor comprises a coaxially connected electrolytic unit and a catalytic unit, the circumferential inner surface of the electrolytic unit contacts the carbon dioxide gas input by the second input chamber, and the circumferential outer surface of the electrolytic cell contacts the water vapor input by the first input chamber; the inner wall of the catalytic unit is provided with a catalytic layer for catalyzing the methanation reaction;

The first output chamber is located between the first input chamber and the electrocatalytic reactor, and the first output chamber is communicated with the first input chamber; the first output chamber is used to output the remaining water vapor and the oxygen generated by the electrolytic cell.

Optionally: a second output chamber is provided between the electrocatalytic reactor and the circumferential side wall of the second input chamber, one end of the electrolysis unit in the electrocatalytic reactor is closed, and a first notch is provided at one end of the second input chamber close to the closed end of the electrolysis unit, and the carbon dioxide gas in the second input chamber flows into the second output chamber through the first notch.

Optionally, the electrocatalytic reactor is in close contact with the circumferential side wall of the second input chamber, and the second input chamber is connected through both ends of the reaction chamber.

Optionally: the electrolysis unit adopts a tubular electrolysis cell structure, and the electrolysis unit includes an anode layer, a cathode layer and an electrolyte layer located therebetween, the anode layer is located on a side close to the first input chamber, and the cathode layer is located on a side close to the second input chamber.

Optionally: the reaction chamber is provided with at least a first input port, a second input port, a first output port and a second output port;

The first input port is connected to the first input chamber, and water vapor flows into the first input chamber through the first input port;

The first output port is connected to the first output chamber, and the remaining water vapor and oxygen in the first output chamber are discharged through the first output port;

The second input port is connected to the second input chamber, and the carbon dioxide gas flows into the second input chamber through the second input port;

The second output port is connected to the catalytic unit of the electrocatalytic reactor, and the methane gas in the catalytic unit is discharged through the second output port.

Optionally: a first partition is provided between the first input chamber and the first output chamber, and an end of the first partition close to the first input port is connected to the inner wall of the reaction chamber; a second notch is provided at an end of the first partition away from the first input port, and the water vapor in the first input chamber flows into the side of the first output chamber close to the electrolysis unit through the second notch.

Optionally: the electrolysis unit and the catalytic unit of the electrocatalytic reactor are connected by integral molding, and the cathode layer of the electrolysis unit and the catalytic layer of the catalytic unit are made of the same material.

Optionally: the operating temperature of the electrolysis unit in the electrocatalytic reactor is 450-650°C; the operating temperature of the catalytic unit in the electrocatalytic reactor is 400-500°C.

Optionally: the synthesis device also includes an external power supply, wherein the positive electrode of the external power supply is connected to the anode layer of the electrolysis unit, and the negative electrode of the external power supply is connected to the cathode layer of the electrolysis unit.

The present invention also discloses a synthesis method for preparing methane based on an electrothermal chemical mixing method, which is implemented using the above-mentioned synthesis device and comprises the following steps:

The water vapor is uniformly introduced into the reaction chamber from the first input chamber, and the carbon dioxide gas is uniformly introduced into the reaction chamber from the second input chamber; after waiting for a predetermined time, the working temperature of the electrolysis unit is increased to 450-650°C;

The external power supply supplies power to the electrolysis unit, and after the water vapor contacts the anode layer of the electrolysis unit, an oxidation reaction occurs in the anode layer of the electrolysis cell to produce protons H ⁺ and oxygen O ₂ ; the protons H ⁺ are conducted to the cathode layer through the electrolyte layer of the electrolysis unit, and obtain electrons to produce hydrogen H ₂ ; the oxygen O ₂ and the residual water vapor are discharged from the reaction chamber through the first output chamber;

The hydrogen _H2 produced by the electrolysis unit is mixed with the carbon dioxide input from the second input chamber and transported to the catalytic unit; the operating temperature of the catalytic unit is maintained at 400-500°C, and the hydrogen _H2 and carbon dioxide undergo methanation reaction and reverse water vapor change reaction under the action of the catalyst in the catalytic layer to obtain the reaction product methane/synthesis gas;

The methane/synthesis gas produced by the catalytic unit is output from the reaction chamber and stored by a subsequent gas storage device.

Beneficial Effects

The technical solution of the present invention achieves the following beneficial effects:

(1) The synthesis device of the present invention synthesizes methane/synthesis gas by reacting carbon dioxide with hydrogen produced by electrolysis of water, thereby converting carbon dioxide into fuel, which is more beneficial for replacing traditional fossil fuels, realizing the effective utilization of carbon dioxide resources and reducing greenhouse gas emissions.

(2) The synthesis device of the present invention integrates the electrolysis unit and the catalytic unit of the methanation reaction into the same device, which simplifies the process flow and equipment of carbon dioxide to methane/synthesis gas, and effectively reduces the investment cost of the carbon dioxide to methane/synthesis gas device.

(3) The electrolysis unit in the synthesis device of the present invention adopts a proton conductor electrolysis cell, which electrolyzes water at a relatively high temperature to produce hydrogen, and the gas is directly mixed with _CO2 to form a reaction gas without cooling. At the same time, oxygen is produced on the steam side through the partitioned and directional transport of protons and oxygen ions, and finally high-purity oxygen is formed, realizing the co-production of multiple substances.

(4) The synthesis device of the present invention realizes the step-by-step utilization of heat through a multi-stream countercurrent heat exchange method, and can construct multiple reaction temperature zones in the reaction chamber, thereby solving the problems faced by the electrolysis hydrogen production- _CO2 methanation synthesis process in the traditional green methane preparation, such as complex energy management and large conversion losses of multiple energy flows across the device. The thermodynamic-kinetic matching of the electrochemical process and the thermochemical process is achieved through multiple temperature zones, and a high material conversion rate from electricity to hydrogen and hydrogen to methane is achieved in a single device. At the same time, the comprehensive energy utilization efficiency is improved by the in-situ utilization of thermal energy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a synthesis device for preparing methane based on a hybrid electric and thermochemical method in Example 1 of the present invention.

FIG2 is a schematic diagram of the structure of a synthesis device for preparing methane based on a hybrid electric and thermochemical method in Example 2 of the present invention.

FIG3 is a cross-sectional schematic diagram of an electrolytic unit in Example 2 of the present invention.

The specific meanings of the reference numerals in the accompanying drawings are:

1-first input chamber; 2-first output chamber; 3-second input chamber; 4-second output chamber; 5-electrolysis unit; 501-anode layer; 502-electrolyte layer; 503-cathode layer; 6-catalytic unit; 7-first partition; 8-first input port; 9-first output port; 10-second input port; 11-second output port; 12-first gap; 13-second gap.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the scope of protection of the present invention. It should be pointed out that the following detailed description is exemplary and is intended to provide further explanation of the present application.

In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Since the current equipment for the methanation reaction of carbon dioxide mainly realizes methane synthesis through the electrolysis of water to produce hydrogen, and the methanation reaction of hydrogen and carbon dioxide, and the electrolysis hydrogen production process and the methanation reaction process in the existing equipment are divided into two stages, which are carried out in stages in different equipment, corresponding equipment needs to be designed for different stages, which leads to the problem of complex overall structure of the equipment and large occupied volume. The present invention integrates the electrolysis hydrogen production process and the methanation reaction process into the same equipment, that is, the electrolysis unit for hydrogen production and the catalytic unit for methanation reaction are integrated into the same device, so that the equipment structure is simpler to reduce the equipment investment cost. In addition, the present invention also transfers the heat carried by water vapor to the inside of the device through a countercurrent heat exchange scheme, realizes the change of heat gradient in the reaction chamber, forms a plurality of different temperature zones, and applies the heat to the methanation reaction of the catalytic unit, realizing efficient energy utilization.

Embodiment 1:

As shown in Figure 1, this embodiment 1 discloses a synthesis device for preparing methane based on an electric and thermochemical mixed method, which includes a reaction chamber. The reaction chamber can adopt a structure such as a circular column or a prismatic column. At least a first input chamber 1, a second input chamber 3, a first output chamber 2 and an electrocatalytic reactor are provided in the reaction chamber. Similarly, the first input chamber 1, the second input chamber 3, the first output chamber 2 and the electrocatalytic reactor can also adopt a structure with the same shape but different sizes as the reaction chamber, for example, all adopt a circular column shape, and the above-mentioned chambers are stacked and nested.

The first input chamber 1 is close to the circumferential side wall of the reaction chamber; the first input chamber 1 is used to input water vapor; the second input chamber 3 is located at the center of the reaction chamber; the second input chamber 3 is used to input carbon dioxide gas. The first input chamber 1 and the first output chamber 2 are separated by a first partition 7, and the first partition 7 has high thermal conductivity, which can realize heat exchange between the first input chamber 1 and the first output chamber 2. In this embodiment 1, the water vapor input by the first input chamber 1 has a high temperature, and the heat can be transferred to the first output chamber 2 through the first partition 7 during its flow.

The electrocatalytic reactor is sleeved to the outside of the second input chamber 3, and the second input chamber 3 is connected to the electrocatalytic reactor; the electrocatalytic reactor includes a coaxially connected electrolytic unit 5 and a catalytic unit 6. In this embodiment 1, the electrolytic unit 5 adopts a tubular electrolytic cell structure, as shown in FIG3 , the electrolytic unit 5 includes an anode layer 501, a cathode layer 503 and an electrolyte layer 502 located therebetween, the anode layer 501 is located on the side close to the first input chamber 1, and the cathode layer 503 is located on the side close to the second input chamber 3. The circumferential inner surface of the electrolytic unit 5 contacts the carbon dioxide gas input from the second input chamber 3, and the circumferential outer surface of the electrolytic unit 5 contacts the water vapor input from the first input chamber 1.

The electrolysis unit 5 is connected to an external power source, the positive electrode of the external power source is connected to the anode layer 501 of the electrolysis unit 5, and the negative electrode of the external power source is connected to the cathode layer 503 of the electrolysis unit 5. When the external power source is powered on to the electrolysis unit 5, the water vapor transported through the first input chamber 1 contacts the anode layer 501 of the electrolysis unit 5, and the water vapor undergoes an electrochemical reaction in the anode layer 501 of the electrolysis unit 5 to produce protons H ⁺ and oxygen O ₂ : 2H ₂ O→4H ⁺ +O ₂ +4e ^- . Since the electrolyte layer 502 of the electrolysis unit 5 adopts a proton conductor electrolyte layer 502, which has the ability to conduct protons, the protons H ⁺ produced in the anode layer 501 can be conducted to the cathode layer 503 of the electrolysis unit 5 through the electrolyte layer 502, and the protons H ⁺ obtain electrons in the cathode layer 503 to produce hydrogen: 4H ⁺ +4e ^- →2H ₂ . The overall reaction of the electrolysis unit 5 is: 2H ₂ O→2H ₂ +O ₂ .

In addition, in this embodiment 1, the first output chamber 2 is located between the first input chamber 1 and the electrocatalytic reactor, and the first output chamber 2 is connected to the first input chamber 1; the first output chamber 2 is used to output the remaining water vapor and the oxygen generated by the electrolytic cell. After being transported through the first input chamber 1, the water vapor will flow to the first output chamber 2. During the flow, the water vapor will first contact the anode layer 501 of the electrolysis unit 5. After the electrolysis of the electrolysis unit 5, part of the water vapor will be decomposed into oxygen, and the oxygen will flow to the discharge port of the first output chamber 2 together with the residual water vapor.

Furthermore, the oxygen generated in the anode layer 501 of the electrolysis unit 5 is discharged outward through the first output chamber 2, and part of the water vapor is also discharged along with the first output chamber 2. The hydrogen generated in the cathode layer 503 of the electrolysis unit 5 flows to the catalytic unit 6 together with the carbon dioxide. The inner wall of the catalytic unit 6 is provided with a catalytic layer for catalyzing the methanogenic reaction. Under the action of the catalyst in the catalytic layer, the two react to generate methane gas through a methanogenic reaction.

It should be noted that the electrolysis unit 5 and the catalytic unit 6 of the electrocatalytic reactor described in this embodiment 1 are connected by integral molding, and the cathode layer 503 of the electrolysis unit 5 and the catalytic layer of the catalytic unit 6 are made of the same material. When the cathode layer 503 of the electrolysis unit 5 produces hydrogen, the carbon dioxide delivered by the second input chamber 3 will be mixed with the hydrogen. At this time, the catalyst is evenly arranged on the inner wall of the catalytic unit 6. When the mixed gas enters, the catalyst will promote the forward methanation reaction to occur methanation reaction and reverse water vapor change reaction, obtain the reaction product methane/synthesis gas, and improve the methane productivity.

A second output chamber 4 is provided between the electrocatalytic reactor and the circumferential side wall of the second input chamber 3 in this embodiment 1, so the electrolysis unit 5 and the catalytic unit 6 in this embodiment 1 are substantially both located in the second output chamber 4, and the second output chamber 4 is mainly used to discharge the methane, residual carbon dioxide and hydrogen produced by the catalytic unit 6; one end of the electrolysis unit 5 in the electrocatalytic reactor in this embodiment 1 is closed, and a first notch 12 is provided at one end of the second input chamber 3 close to the closed end of the electrolysis unit 5, and the carbon dioxide gas located in the second input chamber 3 flows into the second output chamber 4 through the first notch 12.

More specifically, in this embodiment 1, at least a first input port 8, a second input port 10, a first output port 9 and a second output port 11 are provided on the reaction chamber; wherein the first input port 8 is connected to the first input chamber 1, and water vapor flows into the first input chamber 1 through the first input port 8; the first output port 9 is connected to the first output chamber 2, and the remaining water vapor and oxygen in the first output chamber 2 are discharged through the first output port 9; the second input port 10 is connected to the second input chamber 3, and carbon dioxide gas flows into the second input chamber 3 through the second input port 10; the second output port 11 is connected to the catalytic unit 6 of the electrocatalytic reactor, and the methane gas in the catalytic unit 6 is discharged through the second output port 11. One end of the first partition 7 close to the first input port 8 is connected to the inner wall of the reaction chamber; one end of the first partition 7 far from the first input port 8 is provided with a second notch 13, and the water vapor of the first input chamber 1 flows into the side of the first output chamber 2 close to the electrolysis unit 5 through the second notch 13.

As shown in FIG1 , water vapor enters the first input chamber 1 through the first input port 8 at the right end of the reaction chamber, and the water vapor flows from the right end to the left end of the first input chamber 1. When the water vapor flows through the second notch 13, the water vapor will enter the first output chamber 2 through the second notch 13. Subsequently, the water vapor in the first output chamber 2 will flow from the left end to the right end. At this time, the water vapor contacts the electrolysis unit 5, and generates oxygen and hydrogen after electrolysis, wherein the oxygen flows to the right end with the first output chamber 2 and is finally discharged from the first output port 9. At this time, the hydrogen generated by the cathode layer 503 of the electrolysis unit 5 fills the position near the electrolysis unit 5 in the second output chamber 4, and the carbon dioxide gas flows through the first notch 503 at the right end of the reaction chamber. The second input port 10 is transported to the second input chamber 3, and the carbon dioxide gas flows from the right end to the left end of the second input chamber 3. When the carbon dioxide gas reaches the first notch 12, it will enter the second output chamber 4 through the first notch 12. At this time, the carbon dioxide gas is mixed with the hydrogen produced by the cathode layer 503 of the electrolysis unit 5, and the mixed gas continues to flow to the right end of the second output chamber 4. The mixed gas reaches the catalytic unit 6. The catalyst in the catalytic unit 6 will accelerate the methanation reaction process between the carbon dioxide gas and the hydrogen to generate methane gas. Subsequently, the methane, residual carbon dioxide gas and hydrogen are discharged to the gas storage device through the second output port 11 to facilitate subsequent gas separation.

The above-mentioned synthesis device synthesizes methane/synthesis gas by reacting carbon dioxide with hydrogen generated by electrolysis of water, which converts carbon dioxide into methane fuel, realizes the effective utilization of carbon dioxide resources, and reduces greenhouse gas emissions, which is beneficial to the demand for replacing traditional fossil fuels and reducing greenhouse gas emissions. In addition, the device integrates the electrolysis unit 5 and the catalytic unit 6 of the methanation reaction into the same device, which simplifies the process and equipment of carbon dioxide to methane/synthesis gas, and effectively reduces the investment cost of the device for carbon dioxide to methane/synthesis gas.

In addition, it should be further mentioned that the working temperature of the electrolytic unit 5 in the electrocatalytic reactor described in this embodiment 1 is 450-650°C; the working temperature of the catalytic unit 6 in the electrocatalytic reactor is 400-500°C. Since the first input chamber 1, the first output chamber 2, the second input chamber 3, and the second output chamber 4 in this embodiment 1 are stacked and nested with each other, the internal gas changes its flow direction multiple times in the reaction chamber, and the reaction chamber is provided with multiple temperature zones through a multi-stream countercurrent heat exchange method, so that there is a difference between the temperature of the electrolytic unit 5 and the temperature of the catalytic unit 6, which meets the temperature requirements of the corresponding regions, realizes energy ladder utilization and high-efficiency material conversion, improves energy utilization efficiency, and effectively reduces energy input costs.

Embodiment 2:

As shown in FIG2 , this embodiment 2 also discloses a synthesis device for preparing methane based on an electric and thermochemical mixed method, and its basic structure is the same as that of embodiment 1, and it includes a reaction chamber, and the reaction chamber can adopt a structure such as a circular column or a prismatic column, and the reaction chamber is provided with at least a first input chamber 1, a second input chamber 3, a first output chamber 2 and an electrocatalytic reactor.

The difference is that in this embodiment 2, the second output chamber is shared with the second input chamber 3, the electrocatalytic reactor is close to the circumferential side wall of the second input chamber 3, and the second input chamber 3 is connected through the two ends of the reaction chamber. As shown in Figure 2, the water vapor flow mode is basically the same as that in embodiment 1, and the carbon dioxide gas is transported to the first input chamber 1 from the first input port 8 located at the left end of the reaction chamber. In essence, in this embodiment 2, the first input chamber 1 is shared with the internal cavity of the electrolytic catalytic unit 6. After the carbon dioxide gas enters the first input chamber 1, the carbon dioxide gas contacts the cathode layer 503 of the electrolytic unit 5. At this time, the carbon dioxide gas is mixed with hydrogen. The mixed gas flows to the right end of the first input chamber 1 to the catalytic unit 6, and a methanogenic reaction is carried out in the catalytic unit 6 to generate methane gas. Subsequently, methane, residual carbon dioxide gas and hydrogen are discharged to the gas storage device through the second output port 11 to facilitate subsequent gas separation.

This embodiment 2 further simplifies the structure of the synthesis device, making the device easier to manufacture, while also meeting the process flow and equipment for producing methane/synthesis gas from carbon dioxide, effectively reducing the investment cost of the device for producing methane/synthesis gas from carbon dioxide.

Embodiment 3:

This embodiment 3 also discloses a synthesis method for preparing methane based on a hybrid method of electricity and thermochemistry, which is implemented using the synthesis device of the above embodiment 1 or 2, and includes the following steps:

The water vapor is uniformly introduced into the reaction chamber from the first input chamber 1, and the carbon dioxide gas is uniformly introduced into the reaction chamber from the second input chamber 3; after waiting for a predetermined time, the working temperature of the electrolysis unit 5 is increased to 450-650°C;

The external power source supplies power to the electrolysis unit 5. After the water vapor contacts the anode layer 501 of the electrolysis unit 5, an oxidation reaction occurs in the anode layer 501 of the electrolysis cell to produce protons H ⁺ and oxygen O ₂ ; the protons H ⁺ are conducted to the cathode layer 503 through the electrolyte layer 502 of the electrolysis unit 5, and obtain electrons to produce hydrogen H ₂ ; the oxygen O ₂ and the residual water vapor are discharged from the reaction chamber through the first output chamber 2;

The hydrogen _H2 generated by the electrolysis unit 5 is mixed with the carbon dioxide input from the second input chamber 3 and transported to the catalytic unit 6, and the gas volume ratio of carbon dioxide to hydrogen is maintained at 1:0.2-0.3; the operating temperature of the catalytic unit 6 is maintained at 400-500°C, and the hydrogen _H2 and carbon dioxide undergo methanogenic reaction and reverse water vapor change reaction under the action of the catalyst in the catalytic layer to obtain the reaction product methane/synthesis gas;

The methane/synthesis gas produced by the catalytic unit 6 is output from the reaction chamber and stored by a subsequent gas storage device.

The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims (10)

1. A synthesis device for preparing methane based on an electrochemical and thermochemical hybrid method, characterized in that it comprises a reaction chamber, wherein the reaction chamber is provided with at least a first input chamber, a second input chamber, a first output chamber and an electrocatalytic reactor, The first input chamber is close to the circumferential side wall of the reaction chamber; the first input chamber is used to input water vapor; The second input chamber is located at the center of the reaction chamber; the second input chamber is used to input carbon dioxide gas; The electrocatalytic reactor is sleeved to the outside of the second input chamber, and the second input chamber is connected to the electrocatalytic reactor; the electrocatalytic reactor comprises a coaxially connected electrolytic unit and a catalytic unit, the circumferential inner surface of the electrolytic unit contacts the carbon dioxide gas input by the second input chamber, and the circumferential outer surface of the electrolytic cell contacts the water vapor input by the first input chamber; the inner wall of the catalytic unit is provided with a catalytic layer for catalyzing the methanation reaction; The first output chamber is located between the first input chamber and the electrocatalytic reactor, and the first output chamber is communicated with the first input chamber; the first output chamber is used to output the remaining water vapor and the oxygen generated by the electrolytic cell. 2. The synthesis device according to claim 1 is characterized in that a second output chamber is provided between the electrocatalytic reactor and the circumferential side wall of the second input chamber, one end of the electrolysis unit in the electrocatalytic reactor is closed, and a first notch is provided at one end of the second input chamber close to the closed end of the electrolysis unit, and the carbon dioxide gas in the second input chamber flows into the second output chamber through the first notch. 3. The synthesis device according to claim 1 is characterized in that the electrocatalytic reactor is closely attached to the circumferential side wall of the second input chamber, and the second input chamber is connected through both ends of the reaction chamber. 4. The synthesis device according to claim 1 is characterized in that the electrolysis unit adopts a tubular electrolysis cell structure, and the electrolysis unit includes an anode layer, a cathode layer and an electrolyte layer located therebetween, the anode layer is located on a side close to the first input chamber, and the cathode layer is located on a side close to the second input chamber. 5. The synthesis device according to claim 2 or 3, characterized in that the reaction chamber is provided with at least a first input port, a second input port, a first output port and a second output port; The first input port is connected to the first input chamber, and water vapor flows into the first input chamber through the first input port; The first output port is connected to the first output chamber, and the remaining water vapor and oxygen in the first output chamber are discharged through the first output port; The second input port is connected to the second input chamber, and the carbon dioxide gas flows into the second input chamber through the second input port; The second output port is connected to the catalytic unit of the electrocatalytic reactor, and the methane gas in the catalytic unit is discharged through the second output port. 6. The synthesis device according to claim 5 is characterized in that a first partition is provided between the first input chamber and the first output chamber, and an end of the first partition close to the first input port is connected to the inner wall of the reaction chamber; a second notch is provided at an end of the first partition away from the first input port, and the water vapor in the first input chamber flows into the first output chamber through the second notch. 7. The synthesis device according to claim 4 is characterized in that the electrolysis unit and the catalytic unit of the electrocatalytic reactor are connected by integral molding, and the cathode layer of the electrolysis unit and the catalytic layer of the catalytic unit are made of the same material. 8. The synthesis device according to claim 1 is characterized in that the working temperature of the electrolysis unit in the electrocatalytic reactor is 450-650°C; the working temperature of the catalytic unit in the electrocatalytic reactor is 400-500°C. 9. The synthesis device according to claim 4 is characterized in that it also includes an external power supply, wherein the positive electrode of the external power supply is connected to the anode layer of the electrolysis unit, and the negative electrode of the external power supply is connected to the cathode layer of the electrolysis unit. 10. A method for preparing methane based on a hybrid electro-thermochemical method, which is implemented using the synthesis device according to any one of claims 1 to 9, characterized in that it comprises the following steps: The water vapor is uniformly introduced into the reaction chamber from the first input chamber, and the carbon dioxide gas is uniformly introduced into the reaction chamber from the second input chamber; after waiting for a predetermined time, the working temperature of the electrolysis unit is increased to 450-650°C; The external power supply supplies power to the electrolysis unit, and after the water vapor contacts the anode layer of the electrolysis unit, an oxidation reaction occurs in the anode layer of the electrolysis cell to produce protons H ⁺ and oxygen O ₂ ; the protons H ⁺ are conducted to the cathode layer through the electrolyte layer of the electrolysis unit, and obtain electrons to produce hydrogen H ₂ ; the oxygen O ₂ and the residual water vapor are discharged from the reaction chamber through the first output chamber; The hydrogen _H2 produced by the electrolysis unit is mixed with the carbon dioxide input from the second input chamber and transported to the catalytic unit; the operating temperature of the catalytic unit is maintained at 400-500°C, and the hydrogen _H2 and carbon dioxide undergo methanation reaction and reverse water vapor change reaction under the action of the catalyst in the catalytic layer to obtain the reaction product methane/synthesis gas; The methane/synthesis gas produced by the catalytic unit is output from the reaction chamber and stored by a subsequent gas storage device.