Method and system for preparing synthesis gas through high-temperature co-electrolysis

Abstract

The invention relates to the technical field of synthesis gas preparation, in particular to a method and system for preparing synthesis gas through high-temperature co-electrolysis. The method comprises the following steps: introducing raw material gas into a solid oxide electrolysis reactor, and carrying out high-temperature electrolysis to obtain synthesis gas; wherein the raw material gas comprises mixed gas of carbon dioxide, superheated water vapor and hydrogen. Hydrogen is introduced into raw material gas on the fuel side to serve as protective gas, the activity of a catalytic electrode can be remarkably improved, oxidation of the catalytic electrode in the cathode reduction reaction process is effectively inhibited, and then the conversion rate of carbon dioxide is increased. Meanwhile, the functional layer is introduced between the electrolyte and the oxygen electrode in the SOEC electrolytic tank, so that further methanation of the synthesis gas can be effectively inhibited, and the selectivity of the synthesis gas is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of synthesis gas preparation, and in particular to a method and system for producing synthesis gas by high-temperature co-electrolysis. Background Art

[0002] Carbon dioxide (CO2) is a significant greenhouse gas, and its adverse global impacts are becoming increasingly evident as climate change intensifies. A significant portion of CO2 emissions originate from the power sector. Currently, the main methods for CO2 conversion include thermochemical, photochemical, electrochemical, and biological conversion. Thermochemical conversion typically requires high temperatures (above 1000°C) and high pressures, placing stringent demands on catalysts and reaction apparatus materials, resulting in low energy efficiency. Photochemical conversion typically has an efficiency of less than 1%, with a maximum efficiency of only 4.5%, and exhibits poor reaction selectivity. Biological CO2 conversion is still in its exploratory stages. Electrochemical conversion technology is the most attractive. It allows for product regulation by controlling the operating voltage and catalyst, and it can leverage environmentally friendly renewable energy sources (such as wind power, solar photovoltaics, and biomass power) as well as nuclear energy for CO2 electrochemical conversion.

[0003] Current commercially viable CO2 electrochemical conversion technologies primarily include low-temperature electrochemical conversion (-20–200°C) using alkaline solutions or proton exchange membranes as electrolytes, and high-temperature electrochemical conversion (600–1000°C) using solid oxides as electrolytes. Solid oxide electrolysis cells (SOECs) offer higher electrolysis rates and energy conversion efficiencies compared to low-temperature electrolysis, making them a more efficient and cost-effective energy conversion method. Furthermore, SOECs' all-solid-state structure facilitates the separation of gaseous products, avoiding the evaporation, corrosion, and electrolyte loss associated with liquid electrolytes. Due to their rapid electrode reaction rates, SOECs eliminate the need for precious metal electrodes such as Pt, significantly reducing costs. SOECs can also be designed as basic modules with a specific power output, allowing for flexible scaling based on demand. Therefore, high-temperature SOEC CO2 electrolysis is considered one of the most viable and promising technological pathways for CO2 conversion.

[0004] However, the current SOEC high-temperature electrolysis of carbon dioxide technology for preparing synthesis gas has problems such as low carbon dioxide conversion rate and low production efficiency, so there is still room for further improvement. Summary of the Invention

[0005] In order to solve the above problems in the prior art, the present invention provides a method and system for producing synthesis gas by high-temperature co-electrolysis.

[0006] Based on this, the present invention has the following technical solutions: In a first aspect, the present invention provides a method for producing synthesis gas by high-temperature co-electrolysis, which is characterized by comprising: introducing raw gas into a solid oxide electrolysis stack, and obtaining synthesis gas after high-temperature electrolysis; wherein the raw gas comprises a mixed gas of carbon dioxide, superheated water vapor and hydrogen.

[0007] In the present invention, when using SOEC to prepare synthesis gas, hydrogen is introduced into the raw gas on the fuel side as a protective gas, which can significantly improve the activity of the catalytic electrode, effectively inhibit the oxidation of the catalytic electrode during the cathode reduction reaction, and thus improve the conversion rate of carbon dioxide.

[0008] Preferably, the hydrogen content in the mixed gas is 5~20vol%; further preferably, the hydrogen content is 5~15vol%; for example, it can be 5vol%, 6vol%, 7vol%, 8vol%, 9vol%, 10vol%, 11vol%, 12vol%, 13vol%, 14vol% or 15vol%.

[0009] Preferably, in the mixed gas, the molar ratio of the carbon dioxide to the superheated water vapor is (1-4): (1-4).

[0010] Preferably, the method for producing synthesis gas by high-temperature co-electrolysis comprises: On the fuel side: the raw gas exchanges heat with the high-temperature gas product at the outlet of the solid oxide electrolysis stack, and then enters the solid oxide electrolysis stack after further heating; the high-temperature gas at the outlet of the fuel side of the solid oxide electrolysis stack exchanges heat with the raw gas to recover heat, and then exchanges heat with chilled water for further cooling and gas-liquid separation.

[0011] In the present invention, the high-temperature product gas exchanges heat with the raw gas through a high-temperature heat exchanger. The raw gas is further heated by an electric heater and enters the fuel cell stack to undergo an electrochemical reaction. The product gas becomes a medium-temperature gas after heat exchange, and is further cooled by a cooler. Finally, the synthesis gas is separated from the liquid water by a steam-water separation device to obtain pure synthesis gas. Compressed air is introduced into the oxygen electrode side, and the process is similar to that on the hydrogen electrode side. It is heated by heat exchange to produce oxygen-enriched air and then discharged. The above arrangement can effectively improve the efficiency of the system and efficiently prepare synthesis gas.

[0012] And / or, on the air side: the raw air is heated by heat exchange with the high-temperature oxygen-rich air at the air side outlet of the solid oxide electrolysis stack, and then further heated to enter the solid oxide electrolysis stack; the high-temperature oxygen-rich air at the air side outlet of the solid oxide electrolysis stack is heated by heat exchange with the raw air to recover heat, and then is cooled by heat exchange with chilled water and then directly discharged at a high point.

[0013] Preferably, the temperature of the high temperature electrolysis is 600-900°C, and the current density is 0.1-2 A / cm 2 , the single-chip electrolysis voltage is 1~2V.

[0014] In the present invention, carbon dioxide in the flue gas of a coal-fired power plant can be enriched by adsorption capture to obtain carbon dioxide in the raw gas, wherein the purity of the enriched carbon dioxide is above 97wt%, and the S and Si contents therein are at the ppm level.

[0015] Adsorption capture is a technology for separating gases. It uses chemical adsorbents or physical adsorbents to separate specific gases from mixed gases. Preferably, the adsorbent includes one or more of activated carbon, molecular sieves, solid amines and alkaline substances. Activated carbon is a porous adsorbent with a high surface area and porosity. During the adsorption process, the flue gas passes through the activated carbon bed, and carbon dioxide is adsorbed on the surface of the activated carbon. When the activated carbon is saturated, the adsorbed carbon dioxide can be released by heating or reducing pressure for subsequent treatment. Molecular sieve is an adsorbent with regular pore size and high selectivity. During the adsorption process, the flue gas passes through the molecular sieve bed, and carbon dioxide is selectively adsorbed in the pores of the molecular sieve. When the molecular sieve is saturated, the adsorbed carbon dioxide can be released by heating or reducing pressure for subsequent treatment.

[0016] In a second aspect, the present invention provides a system for producing synthesis gas through high-temperature co-electrolysis, comprising a gas supply unit, a heat exchange unit, a heating unit, an electrolysis unit, and an electronic control unit; the gas supply unit comprises a superheated steam preparation device, a carbon dioxide adsorption and capture device, and a hydrogen delivery device; the electrolysis unit comprises a plurality of SOEC modules; each SOEC module comprises a plurality of single SOEC electrolytic cells; the single electrolytic cell comprises a hydrogen electrode, an electrolyte, a functional layer, and an oxygen electrode arranged in contact with each other in sequence, and the material of the functional layer is GDC (Ce 0.8 Gd 0.2 O 2-δ ).

[0017] Preferably, in the monomer electrolytic cell, the amount of the functional layer is 1 to 20 wt%; for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%.

[0018] The present invention has found that introducing the above-mentioned functional layer into the electrolyte layer in the SOEC electrolytic cell can effectively inhibit the further methanation of the synthesis gas and improve the selectivity of the synthesis gas.

[0019] Preferably, the structure of the single electrolytic cell is a hydrogen electrode supported type, an electrolyte supported type or an oxygen electrode supported type; And / or, the electrolyte material includes YSZ ((Y2O3) 0.08 (ZrO2) 0.92 ), the hydrogen electrode material includes Ni / YSZ, and the oxygen electrode material includes LSCF (La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ ) and GDC (Ce 0.8 Gd 0.2 O 2-δ ) formed composite materials.

[0020] In the present invention, an electrolytic stack is equipped with 1 to 500 SOEC modules in parallel, series, or mixed connection. Each SOEC module is composed of 1 to 500 single SOEC electrolytic cells. The single electrolytic cells are connected in series via metal connectors or ceramic connectors. The metal connectors may be made of Cr5Fe1Y2O3, ferritic steel, Inconel 625, Ni22Cr, austenitic steel, or the like. The ceramic connectors may be made of LaCrO3, YCrO3, or materials doped with elements such as Sr, Ca, and Mg. The single electrolytic cells and the connectors are encapsulated by glass-based, alumina-based, or YSZ-based ceramic sealing materials. Each single electrolytic cell is rectangular or circular, with the side length of the rectangular cell being 5 to 50 cm and the diameter of the circular cell being 5 to 50 cm.

[0021] Preferably, the heat exchange unit includes a first heat exchanger and a second heat exchanger, and the first heat exchanger and the second heat exchanger are plate heat exchangers; the first heat exchanger is used to exchange heat between the raw gas and the high-temperature gas product at the fuel side outlet of the solid oxide electrolysis stack; the second heat exchanger is used to exchange heat between the air and the high-temperature oxygen-rich air at the air side outlet of the solid oxide electrolysis stack.

[0022] In the present invention, for the selection of heat exchangers, considering the large temperature difference between the two gas paths and the low pressure, a plate heat exchanger is considered. At the same time, the plate heat exchanger has a high heat transfer coefficient and a compact structure, which is more conducive to system integration. Since the high-temperature gas is as high as 650°C and one of the gas paths is a hydrogen-water mixture, the material is designed to be Inconel material, which can meet the requirements of high temperature resistance and corrosion resistance. The low-temperature section can be made of 316 stainless steel, which meets the requirements while reducing costs. The heat exchanger interface is a butt welding joint, and a sealing test is performed after butt welding.

[0023] Preferably, the heating unit includes a first electric heater and a second electric heater; the first electric heater and the second electric heater are made of Inconel 625 material; the first electric heater is used to heat the mixed gas of carbon dioxide, superheated water vapor and hydrogen after heat exchange; the second electric heater is used to heat the raw air.

[0024] In the present invention, the first and second electric heaters are made of Inconel 625, which meets the requirements of high temperature resistance and corrosion resistance. Ceramic fiber is used on the outside of the heater for thermal insulation. Thermocouples are respectively installed in the middle of the electric heating tube and at the outlet to monitor the center temperature and outlet gas temperature, ensuring safe operation and achieving the expected temperature. In addition, to ensure the safety of electrical appliances, explosion-proof functions are designed to minimize possible safety hazards. The electric heater interface is a butt-welded interface, which is tested for sealing after butt welding.

[0025] Preferably, the superheated water vapor preparation device includes a third electric heater for heating water in sequence to saturated steam in the saturation section and superheated water vapor in the superheating section.

[0026] In the present invention, purified water from a water purifier enters the saturation section of the steam generator, where it is heated by an electric heating tube to produce saturated steam. The liquid level in the saturated section is controlled by a regulating valve at the outlet of the water purifier. The saturated section of the steam generator is pressure-controlled, and the power of the electric heater is adjusted by the pressure of the water vapor. The saturated steam enters the superheating section of the steam generator, where it is further heated to superheated steam by the electric heating tube. The power of the electric heater is then adjusted by the temperature of the superheated steam.

[0027] In the present invention, the electronic control unit adopts a distributed system structure, capable of independently controlling the raw gas system, electrolysis, and other process flows, while also enabling the coordinated operation of various units. A rigorously designed state machine program enables process automation and editable scheduling. An independently designed electrolysis interlocking protection system ensures that indicators such as power consumption, temperature, pressure, and leakage are below predetermined values. Protective measures are implemented for various factors that affect the safe operation of the equipment to ensure the safety of personnel and equipment during operation. The control system has a three-layer structure: Layer 0 is the field instrument layer, Layer 1 is the process control layer, and Layer 2 is the operation layer. The process control layer uses a commercial PLC controller, which collects and sends feedback and control signals through the IO module. The included configuration and programming software enables programming of process control logic such as ladder diagrams and module diagrams. The operation layer software uses the EPICS software suite, which implements human-machine interface display, as well as control functions such as real-time data interaction, alarm management, historical data archiving, and log reports. The system's automatic operation mode is developed through state machine design, including automated control of processes such as system startup, normal operation, and normal shutdown. In addition, the control system can achieve safe shutdown operations in response to possible system failures such as gas leakage, pressure overload, etc.

[0028] The method and system for producing syngas through high-temperature co-electrolysis provided by the present invention utilizes a SOEC (Sodium Electrolyzer) to produce syngas. By introducing hydrogen as a shielding gas into the fuel-side feed gas, the activity of the catalytic electrode is significantly enhanced, effectively suppressing oxidation of the catalytic electrode during the cathode reduction reaction, thereby increasing the carbon dioxide conversion rate. Furthermore, the introduction of the aforementioned functional layer between the electrolyte and the oxygen electrode in the SOEC electrolytic cell effectively suppresses further methanation of the syngas, thereby improving syngas selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is a flow chart of high-temperature co-electrolysis of carbon dioxide / H2O to produce synthesis gas provided by the present invention.

[0031] Figure 2 This is a detailed flow chart of the high-temperature co-electrolysis of carbon dioxide / H2O to produce synthesis gas provided by the present invention. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0033] Unless otherwise specified, the various raw materials used in the examples and comparative examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0034] Example 1

[0035] This embodiment provides a method and system for producing synthesis gas by high-temperature co-electrolysis (see the flow diagram for details). Figure 1~Figure 2 ),include: The purified flue gas emitted from the gas-fired power plant is passed into an absorption tower equipped with adsorbent, where pure carbon dioxide gas is produced through adsorption-desorption by alcoholamine solid base. The purity of the enriched carbon dioxide is above 97wt%, and the S and Si contents are at the ppm level.

[0036] The enriched carbon dioxide is fed into the solid oxide electrolysis stack together with high-temperature superheated steam and hydrogen protective gas; the high-temperature electrolysis temperature is 750°C and the current density is 1A / cm 2 The single-chip electrolysis voltage is 1.32 V. In the mixed gas, the content of hydrogen is 10 vol %, and the molar ratio of carbon dioxide to superheated steam is 1:2.

[0037] Applying direct current for high-temperature co-electrolysis produces a mixed gas containing carbon dioxide, carbon monoxide, hydrogen, and water vapor. This mixed gas enters a cooler, where it undergoes heat exchange with chilled water for further cooling before entering a gas-water separator for gas-liquid separation. The liquid phase of the gas-water separator is directly discharged from the device, leaving the gas phase containing hydrogen, carbon monoxide, carbon dioxide, and a small amount of water vapor. This gaseous mixture is then further separated and purified to produce pure synthesis gas.

[0038] Among them, on the fuel side: the purified liquid water enters the steam generator to generate superheated steam, which is mixed with hydrogen from the hydrogen network / gas cylinder and carbon dioxide from the carbon dioxide network / gas cylinder and then enters the static mixer for uniform mixing. The mixed gas of water vapor, hydrogen and carbon dioxide enters the high-temperature heat exchanger on the fuel side to exchange heat with the high-temperature gas product at the outlet of the fuel side of the fuel stack. Then the mixed gas enters the fuel side electric heater for further heating and then enters the fuel stack. The high-temperature gas at the outlet of the fuel side of the fuel stack enters the high-temperature heat exchanger on the fuel side for heat exchange and heat recovery, and then enters the fuel side cooler, exchanges heat with chilled water for further cooling and enters the gas-water separator for gas-liquid separation. The gas phase contains hydrogen, CO, carbon dioxide and a small amount of water vapor. The liquid water in the gas-water separator is directly discharged from the device.

[0039] On the air side: Air from the air compressor or pipeline gas is metered by a mass flow controller and then enters the air-side high-temperature heat exchanger, where it exchanges heat with the high-temperature, oxygen-enriched air at the stack air-side outlet. This heat-exchanged air then enters the air-side electric heater for further heating before entering the stack. The high-temperature, oxygen-enriched air at the stack air-side outlet enters the air-side high-temperature heat exchanger for heat recovery, then enters the air-side cooler, where it exchanges heat with chilled water for cooling before being discharged directly to the air at a high point.

[0040] The system for producing synthesis gas through high-temperature co-electrolysis provided in this embodiment includes a gas supply unit, a heat exchange unit, a heating unit, an electrolysis unit, and an electronic control unit. The gas supply unit includes a superheated steam production device, a carbon dioxide adsorption and capture device, and a hydrogen delivery device. The electrolysis unit includes 10 SOEC modules, each of which includes four individual SOEC electrolytic cells. The individual electrolytic cells are of a hydrogen electrode support type. The individual electrolytic cells are connected in series via metal connectors, and the individual electrolytic cells and connectors are encapsulated with glass-based, alumina-based, and YSZ-based ceramic sealing materials. Each individual electrolytic cell is rectangular, with a side length of 12 cm.

[0041] The single electrolytic cell is composed of a hydrogen electrode, an electrolyte, a functional layer, and an oxygen electrode that are sequentially contacted. The material of the functional layer is GDC (Ce 0.8 Gd 0.2 O 2-δ );In the monomer electrolytic cell, the amount of the functional layer is 10wt%. The material of the electrolyte includes YSZ ((Y2O3) 0.08 (ZrO2) 0.92 ), the hydrogen electrode material includes Ni / YSZ, and the oxygen electrode material includes LSCF (La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ ) and GDC (Ce0.8 Gd 0.2 O 2-δ ) formed composite materials.

[0042] The electrolysis unit also includes a DC regulated power supply, which can convert AC power, unstable power, or power with substandard current and voltage into stable DC power suitable for the system. A high-temperature electrolyzer is installed within the hot box of the solid oxide electrolysis cell, serving as the core reactor for high-temperature co-electrolysis synthesis gas production.

[0043] The heat exchange unit includes a first heat exchanger and a second heat exchanger, and the first heat exchanger and the second heat exchanger are plate heat exchangers; the first heat exchanger is used to exchange heat between the raw gas and the high-temperature gas product at the fuel side outlet of the solid oxide electrolysis stack; the second heat exchanger is used to exchange heat between the air and the high-temperature oxygen-rich air at the air side outlet of the solid oxide electrolysis stack.

[0044] Regarding heat exchanger selection, considering the large temperature difference between the two gas lines and the low pressure, a plate heat exchanger was considered. Plate heat exchangers also offer a high heat transfer coefficient and compact structure, making them more conducive to system integration. Because the high-temperature gas reaches 650°C, and one of the gas lines is a hydrogen-water mixture, Inconel was chosen to meet the requirements for high-temperature and corrosion resistance. The low-temperature section can be made of 316 stainless steel, meeting the requirements while reducing costs. The heat exchanger interfaces are butt-welded, and the seals are tested after welding.

[0045] The heating unit includes a first electric heater and a second electric heater; the first electric heater and the second electric heater are made of Inconel 625 material; the first electric heater is used to heat the mixed gas of carbon dioxide, superheated water vapor and hydrogen after heat exchange; the second electric heater is used to heat the raw air.

[0046] The first and second electric heaters are made of Inconel 625, which meets the requirements for high-temperature and corrosion resistance. Ceramic fiber is used on the exterior of the heater for thermal insulation. Thermocouples are installed in the center of the electric heating tube and at the outlet to monitor the center temperature and outlet gas temperature, ensuring safe operation and achieving the desired temperature. In addition, to ensure the safety of the appliance, an explosion-proof function is designed to minimize potential safety hazards. The electric heater interface is a butt-welded joint, which is then tested for sealing.

[0047] The superheated steam generation device includes a third electric heater, which sequentially heats water to saturated steam in the saturation section and superheated steam in the superheated section. Specifically, purified water from the water purifier enters the saturation section of the steam generator, where it is heated by an electric heating tube to produce saturated steam. The liquid level in the saturated section is controlled by a regulating valve at the outlet of the water purifier. The saturated section of the steam generator is pressure-controlled, and the power of the electric heater is adjusted by the pressure of the water vapor. The saturated steam enters the superheated section of the steam generator, where it is further heated by the electric heating tube to produce superheated steam. The power of the electric heater is adjusted by the temperature of the superheated steam.

[0048] The electronic control unit utilizes a distributed system architecture, enabling independent control of the feed gas system, electrolysis, and other process flows while also enabling coordinated operation of various units. A rigorously designed state machine program enables process automation and editable scheduling. An independently designed electrolysis interlocking protection system ensures that indicators such as power consumption, temperature, pressure, and leakage remain below predetermined values. Protective measures are implemented for various factors that affect safe equipment operation, ensuring the safety of personnel and equipment during operation. The control system is structured in three layers: Layer 0 is the field instrumentation layer, Layer 1 is the process control layer, and Layer 2 is the operation layer. The process control layer utilizes a commercial PLC controller, collecting and transmitting feedback and control signals through I / O modules. Included configuration and programming software enables programming of process control logic using ladder diagrams and block diagrams. The operation layer utilizes the EPICS software suite, providing a human-machine interface display, as well as control functions such as real-time data interaction, alarm management, historical data archiving, and log reporting. State machine design has been used to develop the system's automatic operation modes, including automated control of system startup, normal operation, and normal shutdown. Furthermore, the control system implements safe shutdown operations for potential system failures such as gas leaks and pressure overloads.

[0049] Example 2

[0050] This embodiment provides a method and system for producing synthesis gas by high-temperature co-electrolysis. The only difference between this method and the first embodiment is that the enriched carbon dioxide is introduced into the solid oxide electrolysis stack together with high-temperature superheated steam, i.e., the mixed gas does not contain hydrogen.

[0051] Comparative Example 1

[0052] This comparative example provides a method and system for producing synthesis gas by high-temperature co-electrolysis, which differs from Example 1 only in that the single electrolytic cell consists of a hydrogen electrode, an electrolyte, and an oxygen electrode arranged in contact with each other in sequence, and does not contain a functional layer.

[0053] Test example

[0054] The present invention tests the carbon dioxide conversion rate and the synthesis gas selectivity in the methods of the above embodiment and comparative example. The results are shown in Table 1: Table 1

[0055] The method and system for producing syngas through high-temperature co-electrolysis provided by the present invention utilizes a SOEC (Sodium Electrolyzer) to produce syngas. By introducing hydrogen as a shielding gas into the fuel-side feed gas, the activity of the catalytic electrode is significantly enhanced, effectively suppressing oxidation of the catalytic electrode during the cathode reduction reaction, thereby increasing the carbon dioxide conversion rate. Furthermore, the introduction of the aforementioned functional layer between the electrolyte and the oxygen electrode in the SOEC electrolytic cell effectively suppresses further methanation of the syngas, thereby improving syngas selectivity.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for producing synthesis gas by high temperature co-electrolysis, characterized in that: include: The raw gas is introduced into a solid oxide electrolysis stack and subjected to high-temperature electrolysis to obtain synthesis gas; wherein the raw gas includes a mixed gas of carbon dioxide, superheated water vapor and hydrogen.

2. The method for producing synthesis gas by high temperature co-electrolysis according to claim 1, characterized in that: In the mixed gas, the content of hydrogen is 5-20 vol%.

3. The method for producing synthesis gas by high temperature co-electrolysis according to claim 1, characterized in that: In the mixed gas, the molar ratio of the carbon dioxide to the superheated water vapor is (1-4): (1-4).

4. The method for producing synthesis gas by high-temperature co-electrolysis according to any one of claims 1 to 3, characterized in that: include: Fuel side: the raw gas is heat exchanged with the high-temperature gas product at the outlet of the solid oxide electrolysis stack, and then further heated before entering the solid oxide electrolysis stack; the high-temperature gas at the outlet of the fuel side of the solid oxide electrolysis stack exchanges heat with the raw gas to recover heat, and then exchanges heat with chilled water for further cooling and gas-liquid separation; And / or, on the air side: the raw air is heated by heat exchange with the high-temperature oxygen-rich air at the outlet of the air side of the solid oxide electrolysis stack, and then is further heated and heated before entering the solid oxide electrolysis stack; the high-temperature oxygen-rich air at the outlet of the air side of the solid oxide electrolysis stack is heated by heat exchange with the raw air to recover heat, and then is cooled by heat exchange with chilled water and then directly discharged at a high point.

5. The method for producing synthesis gas by high temperature co-electrolysis according to any one of claims 1 to 4, characterized in that: The temperature of the high temperature electrolysis is 600-900°C, and the current density is 0.1-2A / cm 2 , the single-chip electrolysis voltage is 1~2V.

6. The method for producing synthesis gas by high temperature co-electrolysis according to any one of claims 1 to 5, characterized in that: The carbon dioxide in the flue gas of the coal-fired power plant is enriched by adsorption capture to obtain the carbon dioxide in the raw gas, wherein the purity of the enriched carbon dioxide is above 97wt%, and the S and Si contents contained therein are at the ppm level; Preferably, the adsorbent includes one or more of activated carbon, molecular sieves, solid amines and alkaline substances.

7. A system for producing synthesis gas by high temperature co-electrolysis, characterized in that: It includes a gas supply unit, a heat exchange unit, a heating unit, an electrolysis unit and an electronic control unit; the gas supply unit includes a superheated steam preparation device, a carbon dioxide adsorption capture device and a hydrogen delivery device; the electrolysis unit includes a plurality of SOEC modules; each SOEC module includes a plurality of single SOEC electrolytic cells; the single electrolytic cell is composed of a hydrogen electrode, an electrolyte, a functional layer and an oxygen electrode arranged in contact with each other in sequence, and the material of the functional layer is Ce 0.8 G 0.2 O 2-δ , the material can significantly inhibit the generation of methane and carbon deposits; preferably, in the monomer electrolytic cell, the amount of the functional layer is 1-20wt%.

8. The system for producing synthesis gas by high temperature co-electrolysis according to claim 7, characterized in that: The structure of the monomer electrolytic cell is a hydrogen electrode supported type, an electrolyte supported type or an oxygen electrode supported type; And / or, the material of the electrolyte includes ((Y2O3) 0.08 (ZrO2) 0.92 ), the hydrogen electrode material includes Ni / YSZ, and the oxygen electrode material includes (La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ ) and Ce 0.8 G 0.2 O 2-δ The formed composite material.

9. The system for producing synthesis gas by high temperature co-electrolysis according to claim 7 or 8, characterized in that: The heat exchange unit comprises a first heat exchanger and a second heat exchanger, wherein the first heat exchanger and the second heat exchanger are plate heat exchangers; The first heat exchanger is used for exchanging heat between the raw gas and the high-temperature gas product at the outlet of the fuel side of the solid oxide electrolysis stack; the second heat exchanger is used for exchanging heat between the air and the high-temperature oxygen-rich air at the outlet of the air side of the solid oxide electrolysis stack.

10. The system for producing synthesis gas by high temperature co-electrolysis according to any one of claims 7 to 9, characterized in that: The heating unit includes a first electric heater and a second electric heater; the first electric heater and the second electric heater are made of Inconel 625 material; the first electric heater is used to heat the mixed gas of carbon dioxide, superheated water vapor and hydrogen after heat exchange; the second electric heater is used to heat the raw air; And / or, the superheated water vapor preparation device comprises a third electric heater, which is used to heat water in sequence into saturated steam in the saturation section and superheated water vapor in the superheating section.

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