Method and device for resource utilization of co2 coke oven gas

Abstract

The application relates to the field of environmental protection, and discloses a CO2 coke oven gas resource utilization method, which is characterized by the following steps: heating fresh coke oven gas to obtain a first reaction gas; performing a first reaction to obtain a first reaction product gas; performing cooling treatment to obtain a first reaction product cooling gas; performing gas-gas heat exchange treatment on the first reaction product cooling gas and first CO2 gas to obtain first first reaction product cooling gas, second first reaction product cooling gas and second reaction gas; mixing the first first reaction product cooling gas and second CO2 gas, performing water separation and compression treatment to obtain a first reaction product mixed gas, mixing the first reaction product mixed gas with fresh coke oven gas, and performing heating treatment; performing a second reaction on the second reaction gas to obtain a second reaction product gas; and performing heat exchange and condensation separation treatment to obtain substitute natural gas. The method can effectively utilize coke oven gas and CO2, and obtain substitute natural gas with a methane content of more than 95%.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental protection, in particular to a CO2 coke oven gas resource utilization method and device. BACKGROUND

[0002] In recent years, the consumption proportion of natural gas in China is increasing, and according to the prediction of China Petroleum Economic and Technical Research Institute, the consumption of natural gas in China will reach 330 billion cubic meters at the end of 2020, and the supply-demand gap is serious. Due to the energy characteristics of "rich coal, poor oil and less gas" in China, the preparation of synthetic natural gas not only can produce high-grade clean gas resources, but also can reduce the pollution caused by coal combustion to the environment, and has great social and economic benefits.

[0003] At the same time, China is the largest coke producer in the world, and the coke production accounts for more than 60% of the total global production. The coke oven gas produced by coking enterprises is about 120 billion cubic meters per year, in addition to the self-use, civil use and production of synthetic ammonia or methanol, about 20 billion cubic meters of coke oven gas is discharged every year, and the total heat quantity is equivalent to 60% of the total heat quantity of the West-East Gas Transmission Project. The coke oven gas composed of CH4, H2, CO and CO2 is an ideal raw material gas for preparing SNG / LNG. The coke oven gas discharged can be made into natural gas, and the investment is about 1 / 5 of the same scale synthetic natural gas prepared by coal, which can produce good economic and social benefits. In view of the composition of coke oven gas, supplementing CO2 and developing suitable coke oven gas supplementing CO2 to prepare methane technology is an effective way to realize the resource utilization of CO2, which is of great significance.

[0004] In recent years, due to the large decline of international oil price, combined with the close linkage between natural gas pricing and oil price in Asian region, the natural gas market is not prosperous, which makes it difficult to popularize the coal-to-SNG technology, and a coke oven gas supplementing carbon to prepare SNG process which can be applied in industry is needed. SUMMARY

[0005] The purpose of the present application is to overcome the problem of utilization of coke oven gas in the prior art, and to provide a CO2 coke oven gas resource utilization method and device.

[0006] In order to achieve the above purpose, the first aspect of the present application provides a CO2 coke oven gas resource utilization method, which comprises:

[0007] (1) heating fresh coke oven gas to obtain a first reaction gas;

[0008] (2) carrying out first reaction on the first reaction gas to obtain a first reaction product gas;

[0009] (3) cooling the first reaction product gas to obtain a first reaction product cooling gas;

[0010] (4) the first reverse product cooling gas and the first CO2 gas are mixed and then subjected to gas-gas heat exchange treatment with the one-reverse product cooling gas to obtain a first one-reverse product cooling gas, a second one-reverse product cooling gas and a two-reverse reaction gas;

[0011] (5) the first one-reverse product cooling gas and the second CO2 gas are mixed and then subjected to water separation treatment and compression treatment to obtain the one-reverse product mixed gas, and the one-reverse product mixed gas is returned to step (1) to be mixed with the fresh coke oven gas and then subjected to the heating treatment;

[0012] (6) the two-reverse reaction gas is subjected to a second reaction to obtain a two-reverse product gas;

[0013] (7) the two-reverse product gas is subjected to heat exchange treatment and condensation separation treatment to obtain a substitute natural gas.

[0014] The second aspect of the present application provides a CO2 coke oven gas resource utilization device, which comprises an electric heater, a first reactor, a first heat exchanger, a gas-gas heat exchanger, a mixing tank, a front buffer tank, a circulating compressor, a rear buffer tank, a second reactor, a second heat exchanger and a condensation tank.

[0015] The outlet of the electric heater and the middle inlet of the first reactor are communicated, and are used for heating treatment of fresh coke oven gas to obtain a one-reverse reaction gas; in the first reactor, the one-reverse reaction gas is subjected to a first reaction to obtain a one-reverse product gas;

[0016] The inlet of the first heat exchanger is communicated with the outlet of the first reactor, and is used for cooling treatment of the one-reverse product gas to obtain a one-reverse product cooling gas;

[0017] The first inlet and the second inlet of the gas-gas heat exchanger are respectively communicated with the outlet of the first heat exchanger and the bottom outlet of the mixing tank, and are used for introducing the one-reverse product cooling gas and the first CO2 gas into the gas-gas heat exchanger to perform gas-gas heat exchange treatment, and a first one-reverse product cooling gas, a second one-reverse product cooling gas and a two-reverse reaction gas are obtained at the first outlet, the second outlet and the third outlet of the gas-gas heat exchanger;

[0018] The first outlet of the gas-gas heat exchanger and the upper inlet of the front buffer tank are communicated, and the middle outlet of the front buffer tank and the inlet of the circulating compressor are communicated, which are used for mixing the first one-reverse product cooling gas and the second CO2 gas to perform water separation treatment and compression treatment to obtain a one-reverse product mixed gas;

[0019] The outlet of the circulating compressor and the middle inlet of the rear buffer tank are communicated, the middle outlet of the rear buffer tank and the inlet of the electric heater are communicated, for mixing the one-reaction product gas with the fresh coke oven gas after passing through the rear buffer tank, and introducing into the electric heater for the heating treatment;

[0020] The second outlet of the gas-gas heat exchanger and the middle inlet of the mixing tank are communicated, for mixing the second one-reaction product cooling gas with the first CO2 gas, and introducing into the gas-gas heat exchanger for the gas-gas heat exchange treatment with the one-reaction product cooling gas;

[0021] The third outlet of the gas-gas heat exchanger and the middle inlet of the second reactor are communicated, in the second reactor, the two-reaction reaction gas is subjected to the second reaction to obtain the two-reaction product gas;

[0022] The middle outlet of the second reactor and the inlet of the second heat exchanger are communicated, the outlet of the second heat exchanger and the upper inlet of the condensing tank are communicated, for the heat exchange treatment and the condensing separation treatment of the two-reaction product gas, to obtain the substitute natural gas.

[0023] Through the above technical scheme, the CO2 coke oven gas resource utilization method and device provided by the application have the following beneficial effects:

[0024] (1) By circulating the first one-reaction product cooling gas and performing the first reaction with the fresh coke oven gas, the total concentration of CO and CO2 in the one-reaction reaction gas is reduced, the temperature rise of the first reaction is reduced, and the temperature of the two-reaction reaction gas is reduced through the gas-gas heat exchange treatment, which is helpful for the second reaction, the two-stage methanation reaction process is short, and the product gas concentration is finally improved;

[0025] (2) The first one-reaction product cooling gas and the second CO2 gas are mixed and subjected to the water separation treatment, which promotes the reaction;

[0026] (3) In view of the condition that hydrogen is more and carbon is less in the coke oven gas, the hydrogen is excessive for the first reaction and the second reaction, therefore, the first CO2 gas and the second CO2 gas are used for two-stage carbon supplement, the effective utilization of CO2 and H2 in the coke oven gas is realized, the total conversion rate of CO in the coke oven gas is ≥96%, the total conversion rate of CO2 is ≥84%, and the substitute natural gas with a methane content of more than 95% is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a process flow chart of the CO2 coke oven gas resource utilization provided by a preferred embodiment of the application.

[0028] REFERENCE SIGNS

[0029] 1, electric heater 2, first reactor 3, first heat exchanger

[0030] 4. Gas-gas heat exchanger 5. Mixing tank 6. Front buffer tank

[0031] 7. Circulating compressor 8. Back buffer tank 9. Second reactor

[0032] 10. Second heat exchanger 11. Condensing tank 12. First inlet

[0033] 13. Second inlet 14. First outlet 15. Second outlet

[0034] 16. Third outlet DETAILED DESCRIPTION

[0035] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the properties. The endpoints of the ranges and the individual values are not to be understood as limited to the precise values recited as the exact dimensions are not critical unless expressly stated otherwise. The ranges, endpoints thereof, and individual values thereof, can be combined with one another even if not specifically stated in combination with each other.

[0036] The first aspect of the present application provides a method for resource utilization of CO2 coke oven gas, the method comprising:

[0037] (1) heating treatment of fresh coke oven gas to obtain a first reaction gas;

[0038] (2) first reaction of the first reaction gas to obtain a first product gas;

[0039] (3) cooling treatment of the first product gas to obtain a first product cooling gas;

[0040] (4) gas-gas heat exchange treatment of the first product cooling gas and first CO2 gas to obtain first first product cooling gas, second first product cooling gas and second reaction gas;

[0041] (5) mixing of the first first product cooling gas and second CO2 gas, then water separation treatment and compression treatment to obtain the first product mixed gas, and returning the first product mixed gas to step (1) to mix with the fresh coke oven gas for the heating treatment;

[0042] (6) second reaction of the second reaction gas to obtain a second product gas;

[0043] (7) heat exchange treatment and condensation separation treatment of the second product gas to obtain substitute natural gas.

[0044] In the present application, by circulating the first one-reaction product cooling gas and performing the first reaction with fresh coke oven gas, the total concentration of CO and CO2 in the one-reaction gas is reduced, the temperature rise of the first reaction is reduced, and the temperature of the two-reaction gas is reduced by gas-gas heat exchange treatment, which helps the second reaction to proceed, the two-stage methanation reaction process is short, and the product gas concentration is finally improved.

[0045] In the present application, the first one-reaction product cooling gas and the second one-reaction product cooling gas are obtained by distributing the one-reaction product cooling gas after the gas-gas heat exchange treatment; and the two-reaction gas is obtained by mixing the first CO2 gas or the second one-reaction product cooling gas with the first CO2 gas and then performing the gas-gas heat exchange treatment.

[0046] In one specific embodiment of the present application, preferably, the second one-reaction product cooling gas is mixed with the first CO2 gas and then subjected to the gas-gas heat exchange treatment with the one-reaction product cooling gas.

[0047] In the present application, in view of the fact that the coke oven gas contains more hydrogen and less carbon, the hydrogen is excessive for the first reaction and the second reaction, and therefore, the first CO2 gas and the second CO2 gas are used for two-stage carbon supplementation to realize the effective utilization of CO2 and H2 in the coke oven gas.

[0048] In one preferred embodiment of the present application, the total volume concentration of CO and CO2 in the one-reaction gas is 11-13%.

[0049] In one preferred embodiment of the present application, the volume ratio of CO2 to CO in the one-reaction gas is less than or equal to 3.

[0050] In one preferred embodiment of the present application, the temperature of the one-reaction gas is 250-320℃.

[0051] In one preferred embodiment of the present application, the first reaction is an adiabatic reaction.

[0052] In one preferred embodiment of the present application, the adiabatic reaction is carried out under the following conditions: the pressure is 2.5-3.5 MPa, the space velocity is 5000-15000 h -1 .

[0053] In one preferred embodiment of the present application, the volume ratio of the first one-reaction product cooling gas to the second one-reaction product cooling gas is 1:0-3, preferably 1:1-3.

[0054] In the present application, the first one-reaction product cooling gas and the second CO2 gas are mixed and then subjected to water removal treatment in step (5), which can promote the subsequent reaction.

[0055] In a preferred embodiment of the present application, the total volume concentration of CO and CO2 in the second reverse reaction gas is 8-10%.

[0056] In a preferred embodiment of the present application, the volume ratio of CO2 to CO in the second reverse reaction gas is less than or equal to 8.

[0057] In a preferred embodiment of the present application, the second reaction is an isothermal reaction.

[0058] In a preferred embodiment of the present application, the isothermal reaction is carried out under the following conditions: pressure 2.5-3.5 MPa, space velocity 5000-15000 h-1. -1 .

[0059] In a preferred embodiment of the present application, the temperature of the second reverse reaction gas is 250-350℃.

[0060] In a preferred embodiment of the present application, the temperature of the second reverse product gas is 250-350℃.

[0061] The second aspect of the present application provides a CO2 coke oven gas resource utilization device, which comprises: an electric heater 1, a first reactor 2, a first heat exchanger 3, a gas-gas heat exchanger 4, a mixing tank 5, a front buffer tank 6, a circulating compressor 7, a rear buffer tank 8, a second reactor 9, a second heat exchanger 10, and a condensing tank 11.

[0062] The outlet of the electric heater 1 is connected to the middle inlet of the first reactor 2, which is used for heating and treating fresh coke oven gas to obtain a first reverse reaction gas; in the first reactor 2, the first reverse reaction gas is subjected to a first reaction to obtain a first reverse product gas.

[0063] The inlet of the first heat exchanger 3 is connected to the outlet of the first reactor 2, which is used for cooling and treating the first reverse product gas to obtain a first reverse product cooling gas.

[0064] The first inlet 12 and the second inlet 13 of the gas-gas heat exchanger 4 are respectively connected to the outlet of the first heat exchanger 3 and the bottom outlet of the mixing tank 5, which are used for introducing the first reverse product cooling gas and the first CO2 gas into the gas-gas heat exchanger 4 for gas-gas heat exchange treatment, and obtaining a first first reverse product cooling gas, a second first reverse product cooling gas, and a second reverse reaction gas at the first outlet 14, the second outlet 15, and the third outlet 16 of the gas-gas heat exchanger 4, respectively.

[0065] The first outlet 14 of the gas-gas heat exchanger 4 is connected to the upper inlet of the front buffer tank 6, and the middle outlet of the front buffer tank 6 is connected to the inlet of the circulating compressor 7, which are used for mixing the first first reverse product cooling gas and the second CO2 gas, and then performing water separation treatment and compression treatment to obtain a first reverse product mixed gas.

[0066] The outlet of the circulating compressor 7 is connected to the middle inlet of the rear buffer tank 8, and the middle outlet of the rear buffer tank 8 is connected to the inlet of the electric heater 1, so as to mix the first-product mixed gas with the fresh coke oven gas after passing through the rear buffer tank, and introduce the mixed gas into the electric heater for the heating treatment;

[0067] The second outlet 15 of the gas-to-gas heat exchanger 4 is connected to the middle inlet of the mixing tank 5, and is used to mix the second first-reverse product cooling gas with the first CO2 gas and then introduce it into the gas-to-gas heat exchanger 4 to perform the gas-to-gas heat exchange treatment with the first-reverse product cooling gas;

[0068] The third outlet 16 of the gas-to-gas heat exchanger 4 is connected to the middle inlet of the second reactor 9. In the second reactor 9, the second reaction gas undergoes a second reaction to obtain a second reaction product gas.

[0069] The middle outlet of the second reactor 9 is connected to the inlet of the second heat exchanger 10, and the outlet of the second heat exchanger 10 is connected to the upper inlet of the condensation tank 11, which is used to perform heat exchange treatment and condensation separation treatment on the secondary reaction product gas to obtain substitute natural gas.

[0070] In a preferred embodiment of the present invention, the first reactor 2 is an adiabatic reactor.

[0071] In a preferred embodiment of the present invention, the second reactor 9 is an isothermal reactor.

[0072] In a preferred embodiment of the present invention, a pipeline is connected in parallel at both ends of the circulation compressor 7, which can be used to short-circuit the circulation compressor 7; the circulation compressor 7 can be turned on as needed according to the intake load; preferably, the circulation compressor 7 is resistant to high temperatures and can withstand a maximum temperature of 190°C.

[0073] According to a preferred embodiment of the present invention, the method for resource utilization of CO2 coke oven gas provided by the present invention is as follows: Figure 1 The process flow chart shown is as follows:

[0074] (1) Fresh coke oven gas is fed into an electric heater 1 for heating treatment to obtain a reaction gas; wherein the temperature of the reaction gas is 250-320° C.;

[0075] (2) The first reaction gas is subjected to an adiabatic reaction in the first reactor (which is an adiabatic reactor) 2 to obtain a first reaction product gas; wherein the conditions of the adiabatic reaction are: a pressure of 2.5-3.5 MPa, a space velocity of 5000-15000 h -1 ;

[0076] (3) the first product gas is sent into the first heat exchanger 3 for cooling treatment, to obtain a first product cooling gas;

[0077] (4) the first product cooling gas and the first CO2 gas are sent into the gas-gas heat exchanger 4 for gas-gas heat exchange treatment, and the first first product cooling gas, the second first product cooling gas and the second reaction gas are obtained at the first outlet 14, the second outlet 15 and the third outlet 16 of the gas-gas heat exchanger 4 respectively; wherein the volume ratio of the first first product cooling gas and the second first product cooling gas is 1:1-3; preferably, the second first product cooling gas is mixed with the first CO2 gas in the mixing tank 5, and then the gas-gas heat exchange treatment is performed with the first product cooling gas in the gas-gas heat exchanger 4, wherein the total volume concentration of CO and CO2 in the second reaction gas is 8-10%, the volume ratio of CO2 and CO in the second reaction gas is less than or equal to 8, and the temperature of the second reaction gas is 250-350℃;

[0078] (5) the first first product cooling gas and the second CO2 gas are mixed and then sent into the front buffer tank 6 for water separation treatment, and then sent into the circulating compressor 7 for compression treatment to obtain the first product mixed gas, which is returned to step (1) after passing through the rear buffer tank 8, mixed with the fresh coke oven gas and then subjected to the heating treatment in the electric heater 1 to obtain the first reaction gas; wherein the total volume concentration of CO and CO2 in the first reaction gas is 11-13%, and the volume ratio of CO2 and CO in the first reaction gas is less than or equal to 3;

[0079] (6) the second reaction gas is sent into the second reactor (isothermal reactor) 9 for isothermal reaction to obtain a second product gas; wherein the temperature of the second product gas is 250-350℃, and the conditions of the isothermal reaction are as follows: the pressure is 2.5-3.5 MPa, the space velocity is 5000-15000 h-1, and the temperature is 250-350℃; -1 ;

[0080] (7) the second product gas is sent into the second heat exchanger 10 for heat exchange treatment, and then sent into the condensation tank 11 for condensation separation treatment to obtain the substitute natural gas.

[0081] The application will be described in detail below by way of examples. In the following examples and comparative examples, the composition of the fresh coke oven gas (by volume fraction) is as follows: CO 5.3%, CO2 2.3%, H2 3.79%, CH4 1.58%, H2O 3.83%, N2 3.2%.

[0082] Example 1

[0083] S1, the fresh coke oven gas is sent into the electric heater 1 for heating treatment to obtain a reverse reaction gas; wherein the temperature of the reverse reaction gas is 280℃;

[0084] S2, the reverse reaction gas is subjected to adiabatic reaction in the first reactor (adiabatic reactor) 2 to obtain a reverse product gas; wherein the adiabatic reaction conditions are: pressure 3 MPa, space velocity 9000h -1 , the hot spot temperature is maintained at 640-660℃.

[0085] S3, the reverse product gas is sent into the first heat exchanger 3 for cooling treatment to obtain a reverse product cooling gas;

[0086] S4, the reverse product cooling gas and the first CO2 gas are sent into the gas-gas heat exchanger 4 for gas-gas heat exchange treatment, and the first reverse product cooling gas, the second reverse product cooling gas and the second reverse reaction gas are obtained at the first outlet 14, the second outlet 15 and the third outlet 16 of the gas-gas heat exchanger 4 respectively; wherein the volume ratio of the first reverse product cooling gas to the second reverse product cooling gas is 1:2;

[0087] S5, the second reverse product cooling gas is mixed with the first CO2 gas in the mixing tank 5, and then returned to step S4 to replace the first CO2 gas and the reverse product cooling gas in the gas-gas heat exchanger 4 for gas-gas heat exchange treatment; wherein the total volume concentration of CO and CO2 in the second reverse reaction gas is 8%, the volume ratio of CO2 to CO in the second reverse reaction gas is 6, and the temperature of the second reverse reaction gas is 280℃;

[0088] S6, the first reverse product cooling gas and the second CO2 gas are mixed and then sent into the front buffer tank 6 for water separation treatment, and then sent into the circulating compressor 7 for compression treatment to obtain the reverse product mixed gas; the reverse product mixed gas is sent into the rear buffer tank 8 and then returned to step S1 to mix with the fresh coke oven gas and then subjected to the heating treatment in the electric heater 1 to obtain the reverse reaction gas; wherein the total volume concentration of CO and CO2 in the reverse reaction gas is 11%, and the volume ratio of CO2 to CO in the reverse reaction gas is 2;

[0089] S7, the second reverse reaction gas is sent into the second reactor (isothermal reactor) 9 for isothermal reaction to obtain a second reverse product gas; wherein the temperature of the second reverse product gas is 280℃, and the isothermal reaction conditions are: pressure 3 MPa, space velocity 9000h -1 ;

[0090] S8, the second reverse product gas is sent into the second heat exchanger 10 for heat exchange treatment, and then sent into the condensation tank 11 for condensation separation treatment to obtain the substitute natural gas with a methane content of 97.3%.

[0091] Example 2-11

[0092] The same method as Example 1 was adopted, except that the reaction conditions were as shown in Table 1.

[0093] Comparative Example 1

[0094] The same method as Example 1 was adopted, except that in step S6, no second CO2 gas was supplemented, and the reaction conditions were as shown in Table 1.

[0095] Comparative Example 2

[0096] The same method as Example 1 was adopted, except that in step S4, the first outlet of the gas-gas heat exchanger was closed, and the one-reaction product cooling gas and the first CO2 gas were fed into the gas-gas heat exchanger for gas-gas heat exchange treatment, and a one-reaction product secondary cooling gas and a two-reaction reaction gas were obtained at the second outlet and the third outlet of the gas-gas heat exchanger, respectively.

[0097] In step S5, the one-reaction product secondary cooling gas was mixed with the first CO2 gas in a mixing tank, and then returned to step S4 to replace the aforementioned gas-gas heat exchange treatment of the first CO2 gas and the one-reaction product cooling gas in the gas-gas heat exchanger.

[0098] And the processing of step S6 was cancelled accordingly, and the reaction conditions were as shown in Table 1.

[0099] The total CO conversion rate of the coke oven gas, the total CO2 conversion rate of the coke oven gas, and the methane content in the substitute natural gas in Examples 1-11 and Comparative Examples 1-2 were shown in Table 2.

[0100] Table 1

[0101]

[0102]

[0103] Table 1 (continued)

[0104]

[0105] Table 2

[0106]

[0107]

[0108] As can be seen from the results in Table 1 and Table 2, compared with Comparative Examples 1-2, the total CO conversion rate of the coke oven gas and the methane content in the substitute natural gas were improved by using the method and device provided in Examples 1-11 of the present application.

[0109] From the comparison of examples 1-9 and examples 10-11, it can be seen that, by limiting the total volume concentration of CO and CO2 of the first reaction gas and the second reaction gas and the volume ratio of CO2 and CO in the preferred range of the present application, the total conversion rate of CO and CO2 of the coke oven gas and the methane content in the substitute natural gas can be further improved, and finally the total conversion rate of CO of the coke oven gas is ≥99.5%, the total conversion rate of CO2 is ≥90%, and the substitute natural gas with a methane content greater than 96% is obtained.

[0110] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and belong to the protection scope of the present application.

Claims

1. A method for resource utilization of CO2 coke oven gas, characterized in that: The method comprises: (1) Heating fresh coke oven gas to obtain a reaction gas; (2) subjecting the first reaction gas to a first reaction to obtain a first reaction product gas; (3) cooling the first reaction product gas to obtain a first reaction product cooling gas; (4) subjecting the first reaction product cooling gas to a gas-to-gas heat exchange treatment with the first CO2 gas to obtain a first reaction product cooling gas, a second reaction product cooling gas, and a second reaction gas; after the second reaction product cooling gas is mixed with the first CO2 gas, the gas-to-gas heat exchange treatment is returned to step (4) to replace the first CO2 gas with the first reaction product cooling gas; (5) The first first-product cooling gas and the second CO2 gas are mixed and then subjected to water separation and compression to obtain the first-product mixed gas, and the first-product mixed gas is returned to step (1) to be mixed with the fresh coke oven gas and then subjected to the heating treatment; (6) subjecting the second reaction gas to a second reaction to obtain a second reaction product gas; (7) subjecting the secondary reaction product gas to heat exchange treatment and condensation separation treatment to obtain substitute natural gas; The total volume concentration of CO and CO2 in the first reaction gas is 11-13%; the volume ratio of CO2 to CO in the first reaction gas is less than or equal to 3; The first reaction is an adiabatic reaction; The total volume concentration of CO and CO2 in the second reaction gas is 8-10%; the volume ratio of CO2 to CO in the second reaction gas is less than or equal to 8; The second reaction is an isothermal reaction.

2. The method according to claim 1, wherein The temperature of the primary reaction gas is 250-320°C.

3. The method according to claim 1 or 2, wherein: The conditions of the adiabatic reaction are: pressure of 2.5-3.5 MPa, space velocity of 5000-15000 h -1 .

4. The method according to claim 1 or 2, wherein: The volume ratio of the first counter-product cooling gas to the second counter-product cooling gas is 1:0-3.

5. The method according to claim 1 or 2, wherein: The isothermal reaction conditions are: pressure of 2.5-3.5 MPa, space velocity of 5000-15000 h -1 .

6. The method according to claim 1 or 2, wherein: The temperature of the secondary reaction gas is 250-350°C.

7. The method according to claim 1 or 2, wherein: The temperature of the secondary reaction product gas is 250-350°C.

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