Two-stage coke oven gas carbon supplementation methanation process system

Abstract

The invention aims to provide a two-stage coke oven gas carbon supplementation methanation process system, and belongs to the technical field of coke oven gas methanation processes, rich H2 resources in coke oven gas are combined with CO and CO2 to be converted into high-added-value synthetic natural gas (SNG), cyclic utilization of carbon resources is achieved, and greenhouse gas emission is reduced. And industrial discharged CO2 such as tail gas of a power plant is used as a carbon supplementing source, so that the carbon source cost is reduced, and wide development prospects are achieved.

Description

Technical Field

[0001] This invention belongs to the technical field of coke oven gas methanation process, specifically relating to a two-stage coke oven gas carbon supplementation methanation process system. Background Technology

[0003] For the commercial application of methanation technology, several representative technologies include TREMP methanation, Davy methanation, and Lurgi methanation (these three technologies are mainly monopolized by foreign projects), as well as the adiabatic multi-stage methanation technology developed by the Southwest Chemical Research and Design Institute in my country. These methanation technologies are all based on multi-stage (three or more stages) reactors and generally face three common challenges: First, high catalyst costs, weak resistance to poisoning, and easy sintering and carbon deposition at high temperatures increase operating costs; second, low thermal cycle efficiency, with the overall system thermal efficiency generally below 65%; third, stringent feedstock adaptability, requiring only CO or CO2 as carbon sources, and strict hydrogen-to-carbon ratio requirements; fourth, in industrial operations, to control temperature rise and reduce catalyst carbon deposition, a certain amount of process steam is usually added to the feed gas, and the feed gas / steam ratio is strictly controlled to prevent catalyst pulverization, but this also reduces catalytic conversion efficiency. Therefore, by supplementing the feed gas with CO2 to match the H2 concentration and optimizing the methanation process, the development of low-temperature methanation technology is crucial. Currently, my country still lags significantly behind advanced international levels in the field of methanation technology, and large-scale industrial operation is still under development. Summary of the Invention

[0004] The purpose of this invention is to provide a two-stage coke oven gas carbon supplementation methanation process system, which combines the abundant H2 resources in coke oven gas with CO and CO2 to convert them into high-value-added synthetic natural gas (SNG), realizing the recycling of carbon resources and reducing greenhouse gas emissions. By utilizing CO2 emitted from industrial sources such as power plant tail gas as a carbon supplementation source, the cost of carbon sources is reduced, and it has broad development prospects.

[0005] The present invention adopts the following technical solution: A two-stage coke oven gas carbon supplementation methanation process system includes heat exchanger 1, heat exchanger 2, heat exchanger 3, heat exchanger 4, reactor 1, reactor 2, and condenser; one end of heat exchanger 1 is the raw gas inlet, and the other end is connected to a deaerator. One end of the deaerator is connected to the inlet of heat exchanger 2. The cold stream outlet of heat exchanger 2 is connected to the inlet of reactor 1 via a mixer. The outlet of reactor 1 is connected to heat exchanger 3. The outlet of heat exchanger 3 is connected to gas-water separator 1 via heat exchanger 2, heat exchanger 4, and condenser in sequence. The outlet of gas-water separator 1 is connected to cooling water heat exchanger 1 to form cooling water. One end of the outlet of gas-water separator 1 is connected to reactor 1 via compressor 1, the cold flow outlet of heat exchanger 4, a distributor, and a mixer. The other end is connected to reactor 2 via the cold flow outlet of heat exchanger 3. The outlet of reactor 2 is sequentially connected to deoxygenated water heat exchanger, cooling water heat exchanger 2, and gas-water separator 2. One end of the outlet of gas-water separator 2 is connected to compressor 2 to obtain synthetic natural gas, and the other end is the cooling water outlet. Both reactor one and reactor two contain methane catalysts.

[0006] Furthermore, the methane catalyst is Ni / MgO-Sm2O3-CeO2 / Al2O3, with Ni having a mass percentage of 38-42%; MgO having a doping amount of 6-8%; Sm2O3 having a doping amount of 6-8%; CeO2 having a doping amount of 14-16%; and Al2O3 having a doping amount of 30-32%. The preparation method is as follows: S1. Weigh out Ni(NO3)2·6H2O, Mg(NO3)2·6H2O, Sm(NO3)3·6H2O, Ce(NO3)3·6H2O and Al(NO3)3·9H2O respectively according to the proportions, and dissolve them together in 1000mL of deionized water to prepare a nitrate metal solution. S2. Dissolve 1.875 mol Na2CO3 in 2500 mL of deionized water, and slowly add the metal nitrate solution dropwise to the Na2CO3 solution while stirring continuously to obtain a mixed solution; S3. Adjust the pH of the mixed solution with 1.5 mol / L NaOH solution until the metal is completely precipitated to obtain a mixture; the pH adjustment range is 10.5-11.5. S4. The resulting mixture is stirred, sonicated, washed, and dried, and then calcined in a muffle furnace to obtain a fresh catalyst NiO / MgO-Sm2O3-CeO2 / Al2O3 catalyst precursor. The stirring time is 30-60 min; the ultrasonic time is 30-60 min; the drying temperature is 80-120℃ and the drying time is 12-24 h; the calcination temperature in the muffle furnace is 500℃ and the calcination time is 2-4 h. S5. The catalyst precursor is reduced in a hydrogen atmosphere to obtain a Ni / MgO-Sm2O3-CeO2 / Al2O3 catalyst; the reduction temperature is 550℃ and the reduction time is 2-3h.

[0007] Furthermore, the raw material gas is purified coke oven gas, supplemented with CO2.

[0008] Furthermore, the amount of CO2 supplemented accounts for 9-11% of the total amount of coke oven gas and supplemented CO2.

[0009] Furthermore, the reaction temperature of reactor one is 300°C and the reaction pressure is 15 bar.

[0010] Furthermore, the reaction temperature of reactor two is 275°C, and the reaction pressure is 15 bar.

[0011] Furthermore, the deaerator has a pressure of 1.76 MPa, a temperature of 165.5 °C, and a deaeration efficiency of 100%.

[0012] Furthermore, the pressure of the heat exchanger is 1.77 MPa and the temperature is 165 °C.

[0013] Furthermore, the pressure of the second heat exchanger is 1.5 MPa, and the outlet temperature of the cold stream is 260°C.

[0014] Furthermore, the pressure of the heat exchanger is 1.5 MPa, and the outlet temperature of the cold stream is 280°C.

[0015] Furthermore, the pressure of the heat exchanger four is 1.5 MPa, and the outlet temperature of the cold stream is 230°C.

[0016] Furthermore, the pressure of the gas-water separator is 1.57 MPa, and the outlet temperature of the cold stream is 101°C.

[0017] Furthermore, the pressure of the second gas-water separator is 1.5 MPa, and the outlet temperature of the cold stream is 36°C.

[0018] Furthermore, the condenser has a pressure of 1.5 MPa and a temperature of 101 °C.

[0019] Furthermore, the pressure of the cooling water heat exchanger is 0.1 MPa and the temperature is 36°C.

[0020] Furthermore, the pressure of the second cooling water heat exchanger is 1.5 MPa, and the temperature is 101 °C.

[0021] Furthermore, the deoxygenated water heat exchanger has a pressure of 1.5 MPa and a temperature of 130°C.

[0022] Furthermore, both compressor one and compressor two are isentropic compression compressors, and their discharge pressures are both 1.74 MPa.

[0023] The one- or two-stage coke oven gas carbon supplementation methanation process system of this invention adopts a two-stage series reactor with an increased circulating flow structure. Through hot gas recirculation technology, part of the reacted gas is recycled back to the reactor inlet to dilute the CO and CO2 concentrations in the feed gas, control the reaction temperature rise, and increase the CH4 yield. Furthermore, by producing medium-pressure steam as a byproduct and preheating the feed gas, the heat of reaction is efficiently recovered to reduce energy consumption.

[0024] Meanwhile, process simulation software is used to optimize the process system, ensuring efficient utilization of heat and energy and further improving the economics of the process. To achieve efficient utilization of the abundant H2 resources in coke oven gas, this invention introduces CO2 as a carbon supplement feedstock in the primary reactor. This design not only optimizes the carbon-hydrogen ratio and increases the CH4 yield, but also realizes the recycling of carbon resources. The integration of the carbon supplement process does not require large-scale modification of existing equipment; only a CO2 inlet section needs to be added, which has high economic efficiency and feasibility. Using Aspen Plus process simulation software, the process flow and its parameters are accurately calculated and optimized to ensure the efficient and stable operation of the system. By simulating the reaction process under different operating conditions, the optimal process scheme is calculated, reducing trial and error costs and shortening the time to industrial application.

[0025] The beneficial effects of this invention are as follows: 1. By using the two-stage coke oven gas carbon supplementation methanation process system of the present invention, H2, CO and CO2 in the feed gas are all completely converted; CH4 accounts for 89.90% of the product gas at the outlet, which meets the industrial SNG implementation standard.

[0026] 2. The two-stage coke oven gas carbon supplementation methanation process system of the present invention, compared with the traditional three-stage and multi-stage coke oven gas methanation process, can achieve a 39.1% reduction in heat energy consumption and a 31.2% reduction in cooling water consumption under the condition of unchanged raw material processing volume, and can reduce the total investment capital of the project by 24.3%. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the two-stage coke oven gas carbon supplementation methanation process system of the present invention; Figure 2 A simplified schematic diagram of a two-stage coke oven gas carbon supplementation and methanation process system; Figure 3 This is a schematic diagram illustrating the simulation and determination of the optimal CO2 supplementation amount for the simplified two-stage coke oven gas carbon supplementation methanation process system described in Embodiment 1 of the present invention. Figure 4 This is a schematic diagram of the traditional three-stage coke oven gas carbon supplementation methanation process system described in Comparative Example 1 of the present invention. Figure 5 This is a schematic diagram illustrating the reduction of thermal energy consumption in Embodiment 1 and Comparative Example 1 of the present invention; Figure 6 This is a schematic diagram illustrating the reduction in cooling water consumption in Embodiment 1 and Comparative Example 1 of the present invention; Figure 7 This is a schematic diagram illustrating the economic benefits of Embodiment 1 and Comparative Example 1 of the present invention; Wherein: 1-Heat Exchanger 1; 2-Heat Exchanger 2; 3-Heat Exchanger 3; 4-Heat Exchanger 4; 5-Reactor 1; 6-Reactor 2; 7-Condenser; 8-Deaerator; 9-Mixer; 10-Gas-Water Separator 1; 11-Cooling Water Heat Exchanger 1; 12-Compressor 1; 13-Diverter; 14-Deaerator Water Heat Exchanger; 15-Cooling Water Heat Exchanger 2; 16-Gas-Water Separator 2; 17-Compressor 2; 18-Gas-Liquid Separator; 19-Heat Exchanger 5; 20-Condenser 1; 21-Condenser 2; 22-Reactor 3. Detailed Implementation

[0028] The following embodiments are merely preferred technical solutions of the present invention and are not intended to limit the present invention in any way. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0029] The purpose of this invention is to provide a two-stage coke oven gas carbon supplementation and methanation process system, including heat exchanger 1, heat exchanger 2, heat exchanger 3, heat exchanger 4, reactor 5, reactor 6, and condenser 7; one end of heat exchanger 1 is the raw gas inlet, and the other end is connected to a deaerator 8. One end of the deaerator 8 is connected to the inlet of heat exchanger 2. The cold stream outlet of heat exchanger 2 is connected to the inlet of reactor 5 via a mixer 9. The outlet of reactor 5 is connected to heat exchanger 3. The outlet of heat exchanger 3 is connected to a gas-water separator 10 via heat exchanger 2, heat exchanger 4, and condenser 7 in sequence. The outlet of gas-water separator 10 is connected to a cooling water heat exchanger 11 to form cooling water. One end of the outlet of the gas-water separator 10 is connected to the reactor 5 via the compressor 12, the cold stream outlet of the heat exchanger 4, the distributor 13, and the mixer 9. The other end is connected to the reactor 6 via the cold stream outlet of the heat exchanger 3. The outlet of the reactor 6 is connected in sequence to the deoxygenated water heat exchanger 14, the cooling water heat exchanger 2 15, and the gas-water separator 2 16. One end of the outlet of the gas-water separator 2 16 is connected to the compressor 2 17 to obtain synthetic natural gas, and the other end is the cooling water outlet. Both reactor 5 and reactor 2 5 contain methane catalysts.

[0030] The system works as follows: The raw gas is first preheated by heat exchanger 1 and then enters deoxygenator 8 to remove oxygen from the components. It then enters reactor 5 through heat exchanger 2 for the first stage reaction. The tail gas from reactor 5 is circulated back to heat exchanger 2 through heat exchanger 3 for parallel heat exchange to save energy. After passing through heat exchanger 4, condenser 7 for precooling, and gas-water separator 10 for water removal, it is split into two streams. One stream flows back into reactor 5 through heat exchanger 4, and the other stream flows into reactor 2 through heat exchanger 3 for the second stage reaction. Finally, after cooling, gas-water separation, and compression, high-purity SNG is obtained.

[0031] Example The optimized simulation process system of this invention simulates the methanation conversion process under the condition of coke oven gas supplemented with CO2 mixed components. The optimization and simulation steps are as follows: S1. Select a suitable thermodynamic property method and define the relevant chemical components. (1) Using Aspen Plus software, select the property method GASPROC in the property menu, the basic method is PR-BM, the free water method is STEAM-TA, and the water solubility is 3. The chemical components used include: CO, CO2, H2, O2, N2, CH4, and H2O.

[0032] The components of coke oven gas are 6.56% CO, 2.03% CO2, 62.32% H2, 24.23% CH4, and 4.56% N2.

[0033] (2) According to Figure 1 To form a complete process system.

[0034] S2. Construct the corresponding steady-state process flow model. (1) In the simplified two-stage coke oven gas carbon supplementation methanation process system, a steady-state process simulation model is established, and a sensitivity analysis module is set up to simulate and determine the optimal CO2 supplementation amount.

[0035] (2) Under the condition that the total feed flow rate is kept constant at 50 mL / min, the CO2 supplementation is gradually increased in intervals of 1 unit, with a variation range of 0-25 mL / min, to simulate the feed process.

[0036] (3) It was finally determined that the best simulated methane conversion performance could be achieved under the conditions of coke oven gas feed flow rate of 46 mL / min and CO2 supplement feed flow rate of 4 mL / min.

[0037] Table 1. Summary of Simulation Data on Optimal CO2 Supplementation for the Two-Stage Coke Oven Gas Carbon Supplementation and Methanation Process System S3. Based on the actual feeding conditions and operating parameters in production, the model is solved and preliminary calculation results are obtained.

[0038] (1) The composition of each component in the total feed after the optimal CO2 supplementation of coke oven gas was determined by simulation to be 6.05% CO, 9.87% CO2, 57.51% H2, 22.36% CH4, and 4.21% N2. Simulation calculations were performed under these feed parameters.

[0039] (2) The simulation results show that H2, CO and CO2 in the feed gas are completely converted; CH4 accounts for 89.90% of the product gas in the outlet gas, which meets the industrial SNG implementation standard.

[0040] Table 2 Summary of the simulation results of the two-stage coke oven gas carbon supplementation and methanation process system. S4. On the basis of ensuring that the simulation results meet the process design requirements, further optimize the process by adjusting the parameter settings of key operation units through the system.

[0041] The parameters of operating units such as process heat exchange networks, hot and cold flow heat exchangers, distributors, mixers, compressors, separators, condensers, and flash evaporators are optimized and adjusted to reduce process energy consumption.

[0042] The reaction temperature of reactor one is 300℃, and the reaction pressure is 15 bar. The reaction temperature of reactor two is 275℃, and the reaction pressure is 15 bar. The deaerator has a pressure of 1.76 MPa, a temperature of 165.5℃, and a deaeration efficiency of 100%. The pressure of heat exchanger one is 1.77 MPa, and the temperature is 165℃. The pressure of heat exchanger two is 1.5 MPa, and the cold stream outlet temperature is 260℃. The pressure of heat exchanger three is 1.5 MPa, and the cold stream outlet temperature is 280℃. The pressure of heat exchanger four is 1.5 MPa, and the cold stream outlet temperature is 230℃. The pressure of gas-water separator one is 1.57 MPa, and the cold stream outlet temperature is 101℃. The pressure of gas-water separator two is 1.5 MPa, and the cold stream outlet temperature is 36℃. The pressure of the condenser is 1.5 MPa, and the temperature is 101℃. The first cooling water heat exchanger has a pressure of 0.1 MPa and a temperature of 36°C. The second cooling water heat exchanger has a pressure of 1.5 MPa and a temperature of 101°C. The deoxygenated water heat exchanger has a pressure of 1.5 MPa and a temperature of 130°C. Both compressors, compressor one and compressor two, use isentropic compression and have a discharge pressure of 1.74 MPa.

[0043] The preparation method of methane catalyst is as follows: S1: Weigh a certain amount of Ni(NO3)2·6H2O (0.511 mol), Mg(NO3)2·6H2O (0.128 mol), Sm(NO3)3·6H2O (0.016 mol), Ce(NO3)3·6H2O (0.065 mol) and Al(NO3)3·9H2O (0.225 mol) reagents and dissolve them in 1000 mL of deionized water to prepare a nitrate solution; S2: Weigh 1.875 mol Na2CO3 reagent and dissolve it in 2500 mL of deionized water to prepare a precipitant solution; S3: Slowly add the metal nitrate solution dropwise to the above Na2CO3 solution while stirring continuously, and then adjust the pH value with 1.5 mol / L NaOH solution until the metal is completely precipitated; S4: The resulting mixture was stirred (stirring time was 40 min), sonicated (sonication time was 40 min), washed, and dried (drying temperature was 100℃, drying time was 15 h), and then calcined in a muffle furnace at 500 ℃ to obtain a fresh catalyst NiO / MgO-Sm2O3-CeO2 / Al2O3. S5: Reduction was carried out at 550 °C in a hydrogen atmosphere for 2 hours to obtain a nickel-based catalyst, denoted as Ni / MgO-Sm2O3-CeO2 / Al2O3.

[0044] The methanation catalyst, under industrial conditions of 300℃ and 15 bar, can achieve a CO conversion rate of 90-100%, a CO2 conversion rate of 85-95%, and a CH4 selectivity of 90-95%.

[0045] Under industrial conditions of 275℃ and 15 bar, a CO conversion rate of 90-100%, a CO2 conversion rate of 80-90%, and a CH4 selectivity of 90-95% can be achieved.

[0046] S5. Compare the optimized process with the traditional process route and conduct an economic benefit analysis.

[0047] (1) The public works used include medium-pressure steam, cooling water, and electricity; and equipment costs, installation costs, operating costs, and raw material costs are all analyzed for economic benefits based on average market prices.

[0048] Table 3 Summary of Economic Benefits of the Optimized Two-Stage Coke Oven Gas Carbon Supplementation and Methanation Process System Comparative Example The difference between this comparative example and the embodiment is that a traditional three-stage coke oven gas carbon supplementation methanation process system is used for simulation, and the feed parameters are exactly the same as those in the embodiment.

[0049] The three-stage coke oven gas carbon supplementation methanation process system has a reactor temperature of 500℃ and a reaction pressure of 15 bar.

[0050] The three-stage coke oven gas carbon supplementation methanation process system has a reactor second reaction temperature of 400℃ and a reaction pressure of 15 bar.

[0051] The three-stage coke oven gas carbon supplementation methanation process system has a reactor reaction temperature of 300℃ and a reaction pressure of 15 bar.

[0052] Table 4 Summary of Economic Benefits of Optimized Traditional Three-Stage Coke Oven Gas Carbon Supplementation and Methanation Process System Table 5. Comparison of Utilities for Two-Stage and Traditional Three-Stage Coke Oven Gas Carbon Supplementation and Methanation Process Systems The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A two-stage coke oven gas carbon supplementation methanation process system, characterized in that: It includes heat exchanger 1 (1), heat exchanger 2 (2), heat exchanger 3 (3), heat exchanger 4 (4), reactor 1 (5), reactor 2 (6) and condenser (7); one end of heat exchanger 1 (1) is the raw material gas inlet, and the other end is connected to deaerator (8). One end of deaerator (8) is connected to the inlet of heat exchanger 2 (2). The cold flow outlet of heat exchanger 2 (2) is connected to the inlet of reactor 1 (5) through mixer (9). The outlet of reactor 1 (5) is connected to heat exchanger 3 (3). The outlet of heat exchanger 3 (3) is connected to gas-water separator 1 (10) through heat exchanger 2 (2), heat exchanger 4 (4) and condenser (7) in sequence. The outlet of gas-water separator 1 (10) is connected to cooling water heat exchanger 1 (11) to form cooling water. One end of the outlet of gas-water separator 1 (10) is connected to reactor 1 (5) via compressor 1 (12), cold stream outlet of heat exchanger 4 (4), distributor (13), and mixer (9), and the other end is connected to reactor 2 (6) via cold stream outlet of heat exchanger 3 (3). The outlet of reactor 2 (6) is connected in sequence to deoxygenated water heat exchanger (14), cooling water heat exchanger 2 (15), and gas-water separator 2 (16). One end of the outlet of gas-water separator 2 (16) is connected to compressor 2 (17) to obtain synthetic natural gas, and the other end is the cooling water outlet. Both reactor one (5) and reactor two (5) contain methane catalysts.

2. The two-stage coke oven gas carbon supplementation methanation process system according to claim 1, characterized in that: The methane catalyst is Ni / MgO-Sm2O3-CeO2 / Al2O3, with Ni having a mass percentage of 38-42%; MgO having a doping amount of 6-8%; Sm2O3 having a doping amount of 6-8%; CeO2 having a doping amount of 14-16%; and Al2O3 having a doping amount of 30-32%. The preparation method is as follows: S1. Weigh out Ni(NO3)2·6H2O, Mg(NO3)2·6H2O, Sm(NO3)3·6H2O, Ce(NO3)3·6H2O and Al(NO3)3·9H2O respectively according to the proportions, and dissolve them together in 1000mL of deionized water to prepare a nitrate metal solution. S2. Dissolve 1.875 mol Na2CO3 in 2500 mL of deionized water, and slowly add the metal nitrate solution dropwise to the Na2CO3 solution while stirring continuously to obtain a mixed solution; S3. Adjust the pH of the mixed solution with 1.5 mol / L NaOH solution until the metal is completely precipitated to obtain a mixture; the pH adjustment range is 10.5-11.

5. S4. The resulting mixture is stirred, sonicated, washed, and dried, and then calcined in a muffle furnace to obtain a fresh catalyst NiO / MgO-Sm2O3-CeO2 / Al2O3 catalyst precursor. The stirring time is 30-60 min; the ultrasonic time is 30-60 min; the drying temperature is 80-120℃ and the drying time is 12-24 h; the calcination temperature in the muffle furnace is 500℃ and the calcination time is 2-4 h. S5. The catalyst precursor is reduced in a hydrogen atmosphere to obtain a Ni / MgO-Sm2O3-CeO2 / Al2O3 catalyst; the reduction temperature is 550℃ and the reduction time is 2-3h.

3. The two-stage coke oven gas carbon supplementation methanation process system according to claim 1, characterized in that: The raw material gas is purified coke oven gas, supplemented with CO2; The amount of CO2 supplemented accounts for 9-11% of the total amount of coke oven gas and supplemented CO2.

4. The two-stage coke oven gas carbon supplementation methanation process system according to claim 1, characterized in that: The reaction temperature of reactor 1 (5) is 300°C and the reaction pressure is 15 bar; The reaction temperature of reactor two (6) is 275°C and the reaction pressure is 15 bar. The deaerator (8) has a pressure of 1.76 MPa, a temperature of 165.5 °C, and a deaeration efficiency of 100%.

5. The two-stage coke oven gas carbon supplementation methanation process system according to claim 1, characterized in that: The pressure of the heat exchanger (1) is 1.77 MPa and the temperature is 165 °C. The pressure of the heat exchanger (2) is 1.5 MPa, and the outlet temperature of the cold stream is 260°C. The pressure of the heat exchanger (3) is 1.5 MPa, and the outlet temperature of the cold stream is 280°C. The pressure of the heat exchanger (4) is 1.5 MPa, and the outlet temperature of the cold stream is 230°C.

6. The two-stage coke oven gas carbon supplementation methanation process system according to claim 1, characterized in that: The pressure of the gas-water separator (10) is 1.57 MPa, and the outlet temperature of the cold stream is 101 °C. The pressure of the gas-water separator (16) is 1.5 MPa, and the outlet temperature of the cold stream is 36°C.

7. The two-stage coke oven gas carbon supplementation methanation process system according to claim 1, characterized in that: The condenser (7) has a pressure of 1.5 MPa and a temperature of 101 °C.

8. The two-stage coke oven gas carbon supplementation methanation process system according to claim 1, characterized in that: The pressure of the cooling water heat exchanger (11) is 0.1 MPa and the temperature is 36 °C. The pressure of the second cooling water heat exchanger (15) is 1.5 MPa and the temperature is 101 °C.

9. A two-stage coke oven gas carbon supplementation methanation process system according to claim 1, characterized in that: The deoxygenated water heat exchanger (14) has a pressure of 1.5 MPa and a temperature of 130 °C.

10. A two-stage coke oven gas carbon supplementation methanation process system according to claim 1, characterized in that: Both compressor one (12) and compressor two (17) are isentropic compression, and their discharge pressure is 1.74 MPa.

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