Carbon capture coupling electrolytic hydrogen production methanation device and method

Abstract

The invention discloses a carbon capture coupling electrolytic hydrogen production methanation device and method. The device comprises a membrane separator, a synthesis gas compressor, an electrolytic bath, a 1 # methane synthesis reactor, a 2 # methane synthesis reactor, a methane purification system, a purification system and the like. The method can simultaneously couple an absorption method carbon capture technology, a water electrolysis hydrogen production technology and a carbon dioxide hydrogenation technology, and has the characteristics of high process flow integration level, realization of system wastewater recycling and the like.

Description

Technical Field

[0001] This invention relates to the fields of carbon dioxide capture and utilization and green chemical technology, specifically to a carbon capture coupled with electrolytic hydrogen production and methanation apparatus and method. Background Technology

[0002] my country's energy structure is characterized by "abundant coal, scarce oil, and limited natural gas." With the strengthening of environmental protection policies and the implementation of sustainable development strategies, my country's demand for natural gas will increase daily, projected to reach 300 billion cubic meters by 2030. 3 Meanwhile, natural gas production during the same period was approximately 140-160 billion cubic meters. 3 In the future, there will be a contradiction between natural gas supply and demand.

[0003] Natural gas's main component is methane. Currently, traditional natural gas production processes primarily use coal as a raw material to obtain syngas (carbon monoxide and hydrogen), which are then further reacted to produce methane. At present, my country has four large-scale coal-to-natural gas plants in operation: Datang Keqi, Liaoning Fuxin, Inner Mongolia Huineng, and Xinjiang Qinghua coal-to-natural gas projects, with a total capacity of 51.4 billion cubic meters. 3 The commissioning of these facilities can alleviate natural gas demand to some extent. However, under the dual-carbon context, carbon reduction in coal chemical plants has become a key area of ​​concern.

[0004] Carbon dioxide capture, utilization and storage (CCUS) has become an important pathway to achieve dual carbon targets. It is estimated that by 2028, the emission reduction from coal-fired power plants through CCUS will reach 6 million tons per year, and will peak at 200-500 million tons per year by 2040.

[0005] High-purity CO2 obtained from power plant flue gas through carbon capture and coupled with green hydrogen produced by water electrolysis to produce methanol is one of the important ways to realize the resource utilization of carbon dioxide. It is also a realistic choice to solve the greenhouse effect, develop green energy and achieve sustainable economic development, and plays an important supporting role in the development of the CCUS industrial chain.

[0006] Patent CN120714610A discloses a cerium oxide-supported non-precious metal catalyst for the carbon dioxide methanation reaction and its preparation method. The cerium oxide support is synthesized via a hydrothermal method, and the cerium oxide-supported non-precious metal catalyst is prepared via an impregnation method. The preparation method is simple, the reaction conditions are controllable, the raw material cost is low, and the equipment requirements are minimal.

[0007] Patent CN116899572B discloses a method for preparing a high-temperature resistant CO2 methanation catalyst and its application. The method uses a melting method to prepare a high-temperature resistant carbon dioxide methanation catalyst precursor in an inert atmosphere in one step. The prepared methanation catalyst has good high-temperature stability, strong resistance to carbon deposition and sintering, and is suitable for coal-to-natural gas synthesis technology under different operating conditions.

[0008] Currently, research on carbon dioxide methanation technology is still in the laboratory research stage, mainly focusing on catalyst technology research and development, with less development and research on process flow, and few researchers have organically combined carbon dioxide capture technology with water electrolysis to produce hydrogen. Summary of the Invention

[0009] This invention provides a method for carbon capture coupled with electrolytic hydrogen production and methanation. This method couples absorption carbon capture technology, water electrolysis for hydrogen production, and carbon dioxide hydrogenation technology, and features high process integration and wastewater recycling.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] A carbon capture coupled with electrolysis to produce hydrogen methanation apparatus includes a syngas compressor. Flue gas from a power plant is connected to a membrane separator via a buffer tank, and the separated CO2 gas enters the syngas compressor. Demineralized water from outside the plant is connected to an electrolyzer, and the hydrogen obtained from the electrolyzer is also connected to the syngas compressor via a hydrogen storage tank.

[0012] The output end of the syngas compressor is connected to the preheater. One output end of the preheater is connected to the No. 1 methanation reactor, and the other output end is connected to the No. 2 methanation reactor. The output ends at the bottom of both the No. 1 and No. 2 methanation reactors are connected to the gas-liquid separator through the preheater. The gas output end of the gas-liquid separator is connected to the methane purification system.

[0013] In the above-mentioned device, the liquid output end of the gas-liquid separator is connected to the electrolytic cell through a purification system.

[0014] In the above-mentioned apparatus, the No. 1 methanation reactor and the No. 2 methanation reactor adopt a tubular fixed bed structure.

[0015] A method for producing hydrogen via carbon capture coupled with electrolytic methanation using the above-described apparatus, the method comprising the following steps:

[0016] 1) Desalinated water from outside the boundary enters the electrolytic cell and undergoes an electrochemical reaction to produce high-purity hydrogen;

[0017] 2) Flue gas from the power plant outside the boundary passes through a buffer tank and a membrane separator in sequence to obtain high-purity carbon dioxide;

[0018] 3) The hydrogen and carbon dioxide gases obtained in steps 1) and 2) are sequentially passed through the syngas compressor and preheater and then split into two branches, which enter the No. 1 methanation reactor and the No. 2 methanation reactor respectively. The methane-containing process gases are then combined and passed through the preheater into the gas-liquid separator for gas-liquid separation. The methane gas at the top outlet is then purified by the methane purification system to obtain methane products which are then sent to the outside.

[0019] 4) The wastewater generated at the bottom of the gas-liquid separator in step 3) is returned to the electrolytic cell for reuse via a purification system.

[0020] In the above method: the hydrogen obtained in step 1) and the high-purity carbon dioxide obtained in step 2) are mixed in such a ratio that the volume fraction ratio of hydrogen to carbon monoxide entering the methanation reactor 1 and the methanation reactor 2 is 4.0~4.3:1.

[0021] In the above method: the operating temperature of the No. 1 methanation reactor and the No. 2 methanation reactor in step 3) is 200℃~400℃, and the operating pressure is 3.0~5.0MPa.

[0022] In the above method: the outlet of the preheater is divided into two branches, and the volume flow rate ratio of entering the No. 1 methanation reactor and the No. 2 methanation reactor is 0.5~0.7.

[0023] The beneficial effects of this invention are:

[0024] This invention provides a carbon capture coupled with electrolytic hydrogen production and methanation process device and method. This method can simultaneously couple absorption carbon capture technology, water electrolysis hydrogen production and carbon dioxide hydrogenation technology, and has the characteristics of high process integration and system wastewater recycling. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0026] In the diagram: 1-Buffer tank, 2-Membrane separator, 3-Synthesis gas compressor, 4-Electrolyzer, 5-Hydrogen storage tank, 6-Preheater, 7-1# Methanation reactor, 8-2# Methanation reactor, 9-Gas-liquid separator, 10-Methane purification system, 11-Purification system. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto:

[0028] The membrane separator used in this embodiment is a mixed matrix carbon dioxide capture membrane provided by Zhongxin Membrane (Beijing) Technology Co., Ltd.

[0029] A process apparatus for carbon capture coupled with electrolysis to produce hydrogen and methanation, the apparatus comprising a buffer tank (1), a membrane separator (2), a syngas compressor (3), an electrolyzer (4), a hydrogen storage tank (5), a preheater (6), a No. 1 methane synthesis reactor (7), a No. 2 methane synthesis reactor (8), a gas-liquid separator (9), a methane purification system (10), and a purification system (11).

[0030] The output end of the buffer tank (1) is connected in sequence to the membrane separator (2), the syngas compressor (3), the preheater (6), the No. 1 methanation reactor (7), and the No. 2 methanation reactor (8); the output end of the electrolyzer (4) is connected in sequence to the hydrogen storage tank (5) and the syngas compressor (3); the gas phase output end of the gas-liquid separator (9) enters the methane purification system for purification and obtains methane products which are then sent to the outside; the liquid phase output end of the gas-liquid separator (9) is connected to the electrolyzer (4) via the purification system (11).

[0031] A method for carbon capture coupled with electrolysis to produce hydrogen via methanation, the main process of which is as follows: Demineralized water from outside the boundary enters the water electrolysis unit and undergoes an electrochemical reaction to obtain high-purity hydrogen; flue gas from the power plant outside the boundary passes through a buffer tank and a membrane separator to obtain high-purity carbon dioxide; the obtained high-purity hydrogen and carbon dioxide are pressurized by a syngas compressor in a certain proportion, and then heated by a preheater before being divided into two branches that enter the No. 1 methanation reactor and the No. 2 methanation reactor respectively, to obtain methane-containing process gases. After merging, the gases enter a gas-liquid separator through a preheater for gas-liquid separation. The methane gas at the top outlet is purified by a methane purification system to obtain methane product, which is then sent outside the boundary; the wastewater generated at the bottom of the gas-liquid separator is returned to the electrolyzer for reuse through a purification system.

[0032] A method for synthesizing methanol by coupling carbon capture with electrolytic hydrogen production includes the following specific steps:

[0033] Example 1:

[0034] Demineralized water with a flow rate of 15000 kg / h from outside the boundary enters the water electrolysis unit and undergoes an electrochemical reaction to produce 4245 Nm³. 3 High-purity hydrogen (99.9%) per hour, with a flow rate of 10000 Nm³. 3 Power plant flue gas at 53℃ (containing CO2: 11%, N2: 5%, O2: 68%, H2O: 16%) is passed through a buffer tank and membrane separator at a rate of / h to obtain 1060 Nm³ / h. 3The high-purity carbon dioxide gas is produced at a ratio of 4:1. The resulting high-purity hydrogen and carbon dioxide gases are fed into the syngas compressor, pressurized, and then preheated before being divided into two streams with a volumetric flow rate ratio of 0.5. These streams enter the No. 1 and No. 2 methanation reactors, respectively, at an operating temperature of 200℃ and an operating pressure of 3.0 MPa. The resulting methane-containing process gases are then combined and preheated before entering a gas-liquid separator for gas-liquid separation. The top outlet methane gas is purified by a methane purification system to obtain 950 Nm³ / h of high-purity hydrogen. 3 The methane product with a volume fraction of 99.5% is delivered outside the boundary at a rate of 1 / h; the 165 kg / h wastewater generated at the bottom of the gas-liquid separator is returned to the electrolyzer for reuse through a purification system.

[0035] Example 2:

[0036] Demineralized water with a flow rate of 17500 kg / h from outside the boundary enters the water electrolysis unit and undergoes an electrochemical reaction to produce 6150 Nm³. 3 High-purity hydrogen (99.9%), flow rate 15200 Nm³ / h. 3 Power plant flue gas at 53℃ (containing CO2: 11%, N2: 5%, O2: 68%, H2O: 16%) is passed through a buffer tank and membrane separator at a rate of / h to obtain 1500Nm³ / h. 3 The high-purity carbon dioxide gas is produced at a ratio of 4.1:1 and fed into the syngas compressor. After being pressurized and heated in a preheater, the gas is divided into two streams with a volumetric flow rate ratio of 0.6. These streams then enter the No. 1 and No. 2 methanation reactors, respectively, at an operating temperature of 280℃ and an operating pressure of 4.0MPa. The resulting methane-containing process gases are then combined and preheated before entering a gas-liquid separator for gas-liquid separation. The methane gas from the top outlet is purified by a methane purification system to obtain 1360 Nm³ / h of high-purity hydrogen and carbon dioxide gas. 3 The 99.5% methane product is delivered outside the boundary at a rate of 1000 kg / h; the 225 kg / h wastewater generated at the bottom of the gas-liquid separator is returned to the electrolyzer for reuse through a purification system.

[0037] Example 3:

[0038] Demineralized water with a flow rate of 20,500 kg / h from outside the boundary enters the water electrolysis unit and undergoes an electrochemical reaction to produce 9460 Nm³. 3 High-purity hydrogen (99.9%), flow rate 20500 Nm³ / h. 3 Power plant flue gas at 53℃ (containing CO2: 11%, N2: 5%, O2: 68%, H2O: 16%) is passed through a buffer tank and membrane separator at a rate of / h to obtain 2200 Nm³ / h. 3The high-purity carbon dioxide gas is produced at a ratio of 4.3:1. The resulting high-purity hydrogen and carbon dioxide gases are fed into the syngas compressor, where they are pressurized and then preheated before being divided into two streams with a volumetric flow rate ratio of 0.7. These streams enter the No. 1 and No. 2 methanation reactors, respectively, at an operating temperature of 400℃ and an operating pressure of 5.0MPa. The resulting methane-containing process gases are then combined and preheated before entering a gas-liquid separator for gas-liquid separation. The top outlet methane gas is purified by a methane purification system to obtain 1840 Nm³ / h of high-purity hydrogen. 3 The methane product with a volume fraction of 99.5% is sent outside the boundary at a rate of 1000 kg / h; the 415 kg / h wastewater generated at the bottom of the gas-liquid separator is returned to the electrolyzer for reuse through a purification system.

Claims

1. A carbon capture coupled with electrolytic hydrogen production and methanation apparatus, characterized in that, The device includes a syngas compressor. Flue gas from the power plant is connected to a membrane separator via a buffer tank, and the CO2 gas obtained after separation enters the syngas compressor. Demineralized water from outside the plant is connected to an electrolyzer, and the hydrogen obtained from the electrolyzer is also connected to the syngas compressor via a hydrogen storage tank. The output end of the syngas compressor is connected to the preheater. One output end of the preheater is connected to the No. 1 methanation reactor, and the other output end is connected to the No. 2 methanation reactor. The output ends at the bottom of both the No. 1 and No. 2 methanation reactors are connected to the gas-liquid separator through the preheater. The gas output end of the gas-liquid separator is connected to the methane purification system.

2. The carbon capture coupled electrolytic hydrogen production methanation apparatus according to claim 1, characterized in that, The liquid output end of the gas-liquid separator is connected to the electrolytic cell through a purification system.

3. The carbon capture coupled electrolytic hydrogen production methanation apparatus according to claim 1, characterized in that, The No. 1 methanation reactor and the No. 2 methanation reactor adopt a tubular fixed bed structure.

4. A method for producing hydrogen via carbon capture coupled with electrolytic methanation using the apparatus of claim 1, characterized in that: The method includes the following steps: 1) Desalinated water from outside the boundary enters the electrolytic cell and undergoes an electrochemical reaction to produce high-purity hydrogen; 2) Flue gas from the power plant outside the boundary passes through a buffer tank and a membrane separator in sequence to obtain high-purity carbon dioxide; 3) The hydrogen and carbon dioxide gases obtained in steps 1) and 2) are sequentially passed through the syngas compressor and preheater and then split into two branches, which enter the No. 1 methanation reactor and the No. 2 methanation reactor respectively. The methane-containing process gases are then combined and passed through the preheater into the gas-liquid separator for gas-liquid separation. The methane gas at the top outlet is then purified by the methane purification system to obtain methane products which are then sent to the outside. 4) The wastewater generated at the bottom of the gas-liquid separator in step 3) is returned to the electrolytic cell for reuse via a purification system.

5. The method for carbon capture coupled with electrolytic hydrogen production and methanation according to claim 4, characterized in that: The hydrogen obtained in step 1) is mixed with the high-purity carbon dioxide obtained in step 2) so that the volume fraction ratio of hydrogen to carbon monoxide entering the methanation reactor 1 and the methanation reactor 2 is 4.0~4.3:

1.

6. The method for carbon capture coupled with electrolytic hydrogen production and methanation according to claim 4, characterized in that: The operating temperature of the No. 1 methanation reactor and the No. 2 methanation reactor mentioned in step 3) is 200℃~400℃, and the operating pressure is 3.0~5.0MPa.

7. The method for carbon capture coupled with electrolytic hydrogen production and methanation according to claim 4, characterized in that: The preheater outlet is divided into two branches, with a volumetric flow rate ratio of 0.5 to 0.7 entering the No. 1 methanation reactor and the No. 2 methanation reactor.

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