CN118599578A - A comprehensive utilization method and system for synthesizing methanol from blast furnace gas and coke oven gas - Google Patents

Abstract

The present invention discloses a comprehensive utilization method and system for synthesizing methanol from blast furnace gas and coke oven gas, comprising the following steps: (1) purifying and desulfurizing the blast furnace gas, and then separating and purifying _CO2 to obtain a _CO2- rich product gas and a _CO2- poor gas; the _CO2- poor gas is subjected to CO separation and purification to obtain a 1# CO-rich product gas and a carbon oxide-poor tail gas; (2) the coke oven gas is subjected to a methanogenic reaction after being purified and separated, and then the gas is separated to obtain a methane-rich gas and a _H2- rich gas; (3) the _CO2- rich product gas and the methane-rich gas are subjected to a dry reforming reaction to obtain a synthesis gas; a portion of CO is separated from the synthesis gas to obtain a 2# CO-rich product gas and a CO2-poor product gas; (4) the CO2-poor product gas is subjected to methanol synthesis to obtain a methanol product; (5) the 1# CO2-rich product gas, the 2# CO2-rich product gas and the _H2- rich gas are mixed and then sprayed back into the blast furnace for recycling. The method and system can reduce _CO2 emissions while realizing the efficient recycling of each effective component of the gas.

Description

A comprehensive utilization method and system for synthesizing methanol from blast furnace gas and coke oven gas

Technical Field

The invention relates to the field of coal gas resource utilization, in particular to a comprehensive utilization method and system for synthesizing methanol from blast furnace gas and coke oven gas.

Background Art

The steel industry is a major _CO2 emitter, accounting for about 15% of the country's carbon emissions, of which by-product gas (blast furnace gas, converter gas, coke oven gas) is the main source of carbon emissions. At present, using it through power generation, combustion and other means not only causes waste of resources, but also pollutes the environment. Therefore, improving the utilization rate of gas resources and reducing carbon emissions have become urgent needs for the sustainable development of the steel industry.

The steel and petrochemical co-production not only enables efficient utilization of by-product gas from steel mills, but also promotes the diversified supply of chemical raw materials. Most importantly, it can fix the carbon elements emitted by the steel industry and achieve the goal of carbon reduction. The development of steel and petrochemical co-production in the steel industry focuses on separating and purifying the effective components ( _H2 , CO, _CO2 , _CH4 , etc.) in the by-product gas of steel mills as raw materials, and synthesizing chemical products such as methanol, ethanol, ethylene glycol, urea, etc. Methanol is widely used as a chemical raw material and green fuel, and has a large market capacity. Separating and purifying _CO2 and _H2 from steel mill gas through steel and petrochemical co-production and synthesizing high-value methanol is an effective way to reduce carbon and increase efficiency.

The patent application with publication number CN116397062A provides a near-zero carbon emission blast furnace long-process tempering co-production process and system thereof, in which blast furnace gas is decarbonized by pressure swing adsorption to separate desorbed gas and decarbonized gas; desorbed gas is purified by liquefaction distillation to obtain liquid carbon dioxide; part of the decarbonized gas is recycled to the blast furnace, and the other part is mixed with refined converter gas and coke oven gas converted by light hydrocarbons to separate CO+ _N2 and _H2 logistics for synthesizing ethylene glycol. The process and system solidify the "carbon" emission into liquid carbon dioxide products through steel-coke fusion and tempering co-production; but _CO2 is not directly fixed as a high-value product, which increases the subsequent treatment process of _CO2 .

The patent application with publication number CN116947619A provides a process and system for producing acetic acid from methane-rich gas through dry reforming and carbonylation synthesis. The method uses methane-rich gas and _CO2 as raw materials, and obtains acetic acid products through dry reforming reaction, _CO2 separation, CO separation, methanol synthesis, carbonylation synthesis and other processes. The process and system make full use of methane-rich gas to produce acetic acid, reducing the emission of greenhouse gas _CO2 in the traditional acetic acid preparation process; however, the source of _CO2 raw gas is unknown, the process flow is long, and no effective treatment is performed on steel plant gas.

Summary of the invention

The technical problem to be solved by the present invention is to provide a comprehensive utilization method for synthesizing methanol from blast furnace gas and coke oven gas by circulating and efficiently utilizing various gas components; the present invention also provides a comprehensive utilization system for synthesizing methanol from blast furnace gas and coke oven gas.

In order to solve the above technical problems, the technical solution adopted by the method of the present invention comprises the following steps:

(1) After blast furnace gas is purified and desulfurized, _CO2 is separated and purified to obtain CO2 _- rich product gas and _CO2 -lean gas; the CO2 _- lean gas is subjected to CO separation and purification to obtain 1# CO-rich product gas and carbon oxide-lean tail gas;

(2) After the coke oven gas is purified and separated, it is subjected to a methanogenic reaction, and then the gas is separated to obtain methane-rich gas and _H2- rich gas;

(3) The _CO2- rich product gas and the methane-rich gas are subjected to dry reforming reaction to obtain synthesis gas; a portion of CO is separated from the synthesis gas to obtain 2# CO2-rich product gas and CO-lean product gas;

(4) synthesizing methanol from the CO-depleted product gas to obtain a methanol product;

(5) The 1# CO-rich product gas, the 2# CO-rich product gas and the _H2- rich gas are mixed and then sprayed back into the blast furnace for recycling.

Furthermore, in step (1), the _CO2 content in the _CO2- rich product gas is greater than 85 vol%, and the CO content in the 1# CO-rich product gas is greater than 85 vol%.

Furthermore, in step (2), the _CH4 content in the methane-rich gas is greater than 85 vol%, and the _H2 content in the H2 _- rich gas is greater than 80 vol%.

Furthermore, in step (3), the CO content in the 2# CO-rich product gas is greater than 90 vol%, and the hydrogen-carbon molar ratio in the CO-lean product gas is 2 to 2.8:1.

Furthermore, in step (4), the methanol purge gas generated by methanol synthesis is returned to the methanol synthesis process.

Furthermore, in step (1), the carbon oxide-depleted tail gas is returned to the gas network.

The technical scheme adopted by the system of the present invention is: comprising a purification and desulfurization device, a _CO2 separation and purification device, a No. 1 pressure swing adsorption device, a purification and separation device, a methanation device, a No. 2 pressure swing adsorption device, a dry reforming reaction device, a No. 3 pressure swing adsorption device, a methanol synthesis device, a rectification device, a compressor, a No. 1 gas mixing device, a No. 2 gas mixing device and a blast furnace; the blast furnace gas pipeline network is sequentially connected to the purification and desulfurization device and the _CO2 separation and purification device through pipelines, the _CO2 -poor gas outlet of the _CO2 separation and purification device is connected to the inlet of the No. 1 pressure swing adsorption device, and the CO2 _- rich gas outlet is connected to the No. 1 gas mixing device, and the CO2-rich gas outlet of the No. 1 pressure swing adsorption device is connected to the gas inlet of the blast furnace through the No. 2 gas mixing device; the coke oven gas pipeline network is sequentially connected to the purification and separation device, the methanation device and the No. 2 pressure swing adsorption device through pipelines, and the H2-rich gas outlet of the No. 2 pressure swing adsorption device is connected to the No. 1 gas mixing device. The methane-rich gas outlet is connected to the inlet of the No. ₂ gas mixing device, and the methane-rich gas outlet is connected to the inlet of the No. 1 gas mixing device; the outlet of the No. 1 gas mixing device is connected to the dry reforming reaction device and the No. 3 pressure swing adsorption device in sequence, and the lean CO gas outlet of the No. 3 pressure swing adsorption device is connected to the methanol synthesis device and the distillation device in sequence; the CO-rich gas outlet of the No. 3 pressure swing adsorption device is connected to the inlet of the No. 2 gas mixing device; the compressor provides power.

Furthermore, a No. 3 gas mixing device is provided between the No. 3 pressure swing adsorption device and the methanol synthesis device; the purge gas outlet of the methanol synthesis device is connected to the inlet of the No. 3 gas mixing device.

Furthermore, the tail gas outlet of the No. 1 pressure swing adsorption device is connected to the gas pipeline network.

The beneficial effects of the above technical solution are as follows: the present invention uses _CO2 in blast furnace gas and methane-rich gas obtained by methanation of coke oven gas as raw materials for dry reforming, and synthesizes methanol products after separating part of CO from the obtained synthesis gas, which solves the problem of large-scale emission of _CO2 from blast furnace gas in steel plants and makes high-value utilization. The CO separated from blast furnace gas, the CO separated from synthesis gas, and the hydrogen-rich gas produced by methanation of coke oven gas described in the present invention are sprayed back into the blast furnace, realizing the efficient and cyclic utilization of each effective component of steel plant gas, the process flow is simple, and the blast furnace process is carbon-reduced from the source. While reducing _CO2 emissions, the present invention realizes the efficient and cyclic utilization of each effective component of coal gas, improves the economic benefits of steel plants, and is of great significance to the realization of the "dual carbon" goal.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a schematic diagram of the process flow of the present invention;

FIG. 2 is a schematic diagram of the system structure of the present invention.

DETAILED DESCRIPTION

As shown in FIG1 , the comprehensive utilization method of synthesizing methanol from blast furnace gas and coke oven gas comprises the following steps:

(1) After blast furnace gas is purified and desulfurized, _CO2 is separated and purified to obtain CO2 _- rich product gas and _CO2- lean gas; the CO2 _- lean gas is subjected to CO separation and purification to obtain 1# CO-rich product gas and carbon oxide-lean tail gas; the carbon oxide-lean tail gas is returned to the gas pipeline network for combustion and power generation, and the gas pipeline network is a blast furnace gas pipeline network and/or a coke oven gas pipeline network;

The main components of the blast furnace gas are (vol): CO 20-30%, CO ₂ 15-25%, CH ₄ 0.4-1.5%, H ₂ 1.5-3.5%, O ₂ 0.2-1.0%, N ₂ 46-60%. The blast furnace gas is purified and desulfurized to a sulfur content of <0.1ppm and an oxygen content of <300ppm. The CO ₂ content in the CO ₂ -rich product gas is >85vol%, and the CO content in the 1# CO-rich product gas is >85vol%.

(2) After the coke oven gas is purified and separated, it is subjected to a methanogenic reaction, and then the gas is separated to obtain methane-rich gas and _H2- rich gas;

The main components of the coke oven gas are (vol): H ₂ 50-65%, CO 4-10%, CO ₂ 1-6%, CH ₄ 15-23%, O ₂ ～1%, N ₂ 5-8%. The coke oven gas is purified and separated to a sulfur content of <0.1ppm and an oxygen content of <300ppm. The main reactions of the methanation reaction are: CO+3H ₂ →CH ₄ +H ₂ O, CO ₂ +4H ₂ →CH ₄ +2H ₂ O; the methanation reaction conditions are: reaction temperature 500-700°C, pressure 1-4MPa. The separation adopts a combination of one or more of pressure swing adsorption separation, membrane separation and cryogenic separation. The CH ₄ content in the methane-rich gas is >85vol%; the main components of the H ₂ -rich gas are (vol): H ₂ >80%, CO <10ppm, CO ₂ <20ppm, CH ₄ 0.5-3%, O ₂ <10ppm.

(3) The _CO2- rich product gas and the methane-rich gas are subjected to dry reforming reaction to obtain synthesis gas; a portion of CO is separated from the synthesis gas to obtain 2# CO2-rich product gas and CO-lean product gas;

The main reaction of the dry reforming reaction is: CO ₂ +CH ₄ →2CO+2H ₂ ; the reaction conditions of the dry reforming reaction are: reaction temperature 600-1200°C, pressure 0.1-4MPa; the catalyst used in the dry reforming reaction includes: a combination of one or more of platinum-based catalysts, rhodium-based catalysts, palladium-based catalysts, ruthenium-based catalysts, nickel-based catalysts and copper-based catalysts; the CO _2- rich product gas: methane-rich gas = 1:0.5-5; the volume ratio of CO/H ₂ in the synthesis gas = 0.2-5:1. The CO content in the 2# CO-rich product gas is >90vol%, and the hydrogen-carbon molar ratio in the CO-poor product gas is H/C = 2-2.8:1.

(4) synthesizing methanol from the CO-depleted product gas to obtain a methanol product; the methanol purge gas generated by the methanol synthesis is returned and mixed with the CO-depleted product gas to perform methanol synthesis again;

The main reaction of the methanol synthesis is: CO+2H ₂ →CH ₃ OH; the reaction conditions of the methanol synthesis are: temperature 200-300° C., pressure 2-8 MPa; the purity of the methanol product is >98%.

(5) The 1# CO-rich product gas, the 2# CO-rich product gas and the _H2- rich gas are mixed and then sprayed back into the blast furnace for recycling.

As shown in Figure 2, the comprehensive utilization system for synthesizing methanol from blast furnace gas and coke oven gas includes a purification and desulfurization device, a _CO2 separation and purification device, a No. 1 pressure swing adsorption device, a purification and separation device, a methanation device, a No. 2 pressure swing adsorption device, a dry reforming reaction device, a No. 3 pressure swing adsorption device, a methanol synthesis device, a distillation device, a No. 1 gas mixing device, a No. 2 gas mixing device, a No. 3 gas mixing device, a blast furnace, a No. 1 compressor, a No. 2 compressor, a No. 3 compressor, a No. 4 compressor and a No. 5 compressor. The blast furnace gas pipeline network is connected to the inlet of the purification and desulfurization device through a pipeline, and the outlet of the purification and desulfurization device is connected to the inlet of the _CO2 separation and purification device through compressor No. 1; the lean _CO2 gas outlet of the _CO2 separation and purification device is connected to the inlet of the No. 1 pressure swing adsorption device through compressor No. 2, and the rich CO2 gas outlet of the No. 1 pressure swing adsorption device is connected to the inlet of the No. 2 gas mixing device, and the outlet of the No. 2 gas mixing device is connected to the gas inlet of the blast furnace; the rich _CO2 gas outlet of the _CO2 separation and purification device is connected to the No. 1 gas mixing device; the tail gas outlet of the No. 1 pressure swing adsorption device is connected to the gas pipeline network. After adopting such a structure, the blast furnace gas is purified and desulfurized by the purification and desulfurization device, and then the _CO2 separation and purification device is used to obtain _{CO2 -} rich product gas and _CO2- lean gas; the CO2 _- lean gas is subjected to CO separation and purification by the No. 1 pressure swing adsorption device to obtain 1# CO-rich product gas and carbon oxide-lean tail gas; the 1# CO-rich product gas is sent to the No. 2 mixing device to be mixed with the following 2# CO-rich product gas and _H2- rich gas, and then sent to the blast furnace for use as coal gas; the _CO2- rich product gas is sent to the No. 1 mixing device; the carbon oxide-lean tail gas is sent to the gas pipeline network.

As shown in Figure 2, the comprehensive utilization system of blast furnace gas and coke oven gas for synthesizing methanol, the coke oven gas pipeline network is connected to the inlet of the purification and separation device through a pipeline, the outlet of the purification and separation device is connected to the inlet of the methanation device through compressor No. 3, and the outlet of the methanation device is connected to the inlet of the No. 2 pressure swing adsorption device; the methane-rich gas outlet of the No. 2 pressure swing adsorption device is connected to the inlet of the No. 1 gas mixing device, the outlet of the No. 1 gas mixing device is connected to the inlet of the dry reforming reaction device through compressor No. 4, the outlet of the dry reforming reaction device is connected to the inlet of the No. 3 pressure swing adsorption device, the lean CO gas outlet of the No. 3 pressure swing adsorption device is connected to the inlet of the No. 3 gas mixing device, the outlet of the No. 3 gas mixing device is connected to the inlet of the methanol synthesis device through compressor No. 5, and the outlet of the methanol synthesis device is connected to the inlet of the distillation device; the relaxation gas outlet of the methanol synthesis device is connected to the inlet of the No. 3 gas mixing device; the H2-rich gas outlet of the No. ₂ pressure swing adsorption device is connected to the inlet of the No. 2 gas mixing device; the CO-rich gas outlet of the No. 3 pressure swing adsorption device is connected to the inlet of the No. 2 gas mixing device. After adopting such a structure, the coke oven gas is purified and separated by the purification and separation device, then enters the methanation device for methanation reaction, and then enters the No. 2 pressure swing adsorption device to separate the gas to obtain methane-rich gas and _H2- rich gas; the methane-rich gas is mixed with the above-mentioned _CO2- rich product gas in the No. 1 gas mixing device, and then enters the dry reforming reaction device for dry reforming reaction to obtain synthesis gas; the synthesis gas is separated from part of CO by the No. 3 pressure swing adsorption device to obtain 2# CO-rich product gas and CO-lean product gas; the CO-lean product gas enters the methanol synthesis device to be synthesized into crude methanol, and the crude methanol enters the distillation device for distillation to obtain methanol product; the methanol purge gas generated by the methanol synthesis device returns to the No. 3 gas mixing device to be mixed with the CO-lean product gas, and methanol synthesis is carried out again; the _H2- rich gas and 2# CO-rich product gas enter the No. 2 gas mixing device, and after being mixed with the above-mentioned 1# CO-rich product gas, they are sent to the blast furnace for use as coal gas.

Example 1: The comprehensive utilization method and system for synthesizing methanol from blast furnace gas and coke oven gas are described as follows.

A steel company uses blast furnace gas and coke oven gas as raw materials:

The main components of blast furnace gas are: CO 26%, CO ₂ 20%, CH ₄ 0.75%, H ₂ 2.1%, O ₂ 0.43%, N ₂ 49.2%; temperature 40°C, pressure 6000Pa(A), flow rate 111000Nm ³ /h;

The main components of coke oven gas are: H ₂ 60%, CO 6%, CO ₂ 2%, CH ₄ 22%, O ₂ 0.72%, N ₂ 7.6%; temperature 40°C, pressure 6000Pa(A), flow rate 275000Nm ³ /h;

Plant scale: Annual production of 400,000 tons of methanol, plant operation time 8,000 hours/year.

As shown in Figures 1 and 2, the method includes the following specific steps:

(1) Separation and purification of _CO2 and CO from blast furnace gas:

The blast furnace gas with a flow rate of ^111000Nm3 /h is purified and desulfurized to remove sulfur and oxygen in the gas, until the sulfur content is less than 0.1ppm and the oxygen content is less than 300ppm, and then enters the _CO2 separation and purification device for organic amine circulation absorption. In the device, the blast furnace gas and N-methyldiethanolamine (MEDA- _CO2 ) are countercurrently contacted to absorb _CO2 through mass transfer and chemical reaction, and then the pressure is reduced and heated for desorption to obtain a _CO2 -rich product gas with a flow rate of ^24000Nm3 /h and a _CO2 concentration of 91.1%; then it is transported to the No. 1 gas mixing device to mix with the methane-rich gas. The adsorbed gas generated by the _CO2 separation and purification device enters the No. 1 pressure swing adsorption device for pressure swing adsorption to purify CO, and obtains a No. 1 CO2-rich product gas with a flow rate of ^30000Nm3 /h and a CO concentration of 96.2%.

(2) Methanation of coke oven gas to obtain methane-rich gas and _H2- rich gas:

The coke oven gas with a flow rate of ^275000Nm3 /h is purified and separated to remove sulfur from the gas to <0.1ppm and oxygen content <300ppm; then it enters the methanation unit for reaction, and at 650℃ and 2.0MPa, CO, _CO2 and _H2 in the unit are converted into methane under catalytic action; then it enters the No. 2 pressure swing adsorption unit for hydrogen extraction and gas separation, obtaining methane-rich gas with a flow rate of ^70000Nm3 /h and a _CH4 concentration of 88.26%, and _{H2 -} rich gas with a flow rate of ^205000Nm3 /h and a H2 concentration of 81.05%.

(3) Dry reforming reaction to obtain synthesis gas:

The methane-rich gas with a flow rate of 70,000 Nm ³ /h and a CH ₄ concentration of 88.26% was mixed with the CO ₂ -rich product gas with a flow rate of 24,000 Nm ³ /h and a CO ₂ concentration of 91.1%, and then dry reformed over a nickel-based catalyst at 800°C and 1.0 MPa to obtain a synthesis gas with a flow rate of 170,000 Nm ³ /h and CO and H ₂ concentrations of 49.0% and 49.0%, respectively. The synthesis gas was sent to the No. 3 pressure swing adsorption unit for pressure swing adsorption to extract part of CO, and a No. 2 CO-rich product gas with a flow rate of 48,000 Nm ³ /h and a CO concentration of 90.45% was obtained, as well as a CO-lean product gas with a flow rate of 120,000 Nm ³ /h and CO and H ₂ concentrations of 33.0% and 66.0%, respectively.

(4) Methanol synthesis:

The CO-depleted product gas with a flow rate of 120,000 Nm ³ /h and CO and H ₂ concentrations of 33.0% and 66.0% respectively is synthesized by copper-based catalyst at 250°C and 6MPa to produce crude methanol. The synthesized crude methanol is pumped to the distillation unit to separate water to produce methanol product (purity 99%) with an annual output of 400,000 tons. The methanol purge gas produced by the methanol synthesis unit is returned to the methanol synthesis unit.

(5) Back-spraying blast furnace:

The 1# CO-rich product gas with a flow rate of ^30000Nm3 /h and a CO concentration of 96.2%, the 2# CO-rich product gas with a flow rate of ^48000Nm3 /h and a CO concentration of 90.45%, and the _{H2 -} rich gas with a flow rate of ^205000Nm3 /h and a H2 concentration of 81.05% are mixed and sprayed back into the blast furnace.

(6) Exhaust gas treatment:

The carbon oxide-poor tail gas from blast furnace gas after CO and _CO2 are removed is returned to the gas network for use as fuel gas in various steel production processes and power generation equipment.

Claims (9)

1. A method for comprehensive utilization of blast furnace gas and coke oven gas to synthesize methanol, characterized in that it comprises the following steps: (1) After blast furnace gas is purified and desulfurized, _CO2 is separated and purified to obtain CO2 _- rich product gas and _CO2 -lean gas; the CO2 _- lean gas is subjected to CO separation and purification to obtain 1# CO-rich product gas and carbon oxide-lean tail gas; (2) After the coke oven gas is purified and separated, it is subjected to a methanogenic reaction, and then the gas is separated to obtain methane-rich gas and _H2- rich gas; (3) The _CO2- rich product gas and the methane-rich gas are subjected to dry reforming reaction to obtain synthesis gas; a portion of CO is separated from the synthesis gas to obtain 2# CO2-rich product gas and CO-lean product gas; (4) synthesizing methanol from the CO-depleted product gas to obtain a methanol product; (5) The 1# CO-rich product gas, the 2# CO-rich product gas and the _H2- rich gas are mixed and then sprayed back into the blast furnace for recycling. 2. A method for comprehensive utilization of blast furnace gas and coke oven gas to synthesize methanol according to claim 1, characterized in that: in said step (1), the _CO2 content in the _CO2- rich product gas is greater than 85 vol%, and the CO content in the 1# CO-rich product gas is greater than 85 vol%. 3. The method for comprehensive utilization of blast furnace gas and coke oven gas to synthesize methanol according to claim 1, characterized in that: in the step (2), the _CH4 content in the methane-rich gas is greater than 85 vol%, and the _H2 content in the H2 _- rich gas is greater than 80 vol%. 4. The method for comprehensive utilization of blast furnace gas and coke oven gas to synthesize methanol according to claim 1, characterized in that: in the step (3), the CO content in the 2# CO-rich product gas is greater than 90 vol%, and the hydrogen-carbon molar ratio in the CO-poor product gas is 2 to 2.8:1. 5. The method for comprehensive utilization of blast furnace gas and coke oven gas to synthesize methanol according to claim 1, characterized in that: in said step (4), the methanol purge gas generated by methanol synthesis is returned to the methanol synthesis process. 6. A method for comprehensive utilization of blast furnace gas and coke oven gas to synthesize methanol according to any one of claims 1 to 5, characterized in that: in step (1), the carbon oxide-poor tail gas is returned to the gas pipeline network. 7. A comprehensive utilization system for synthesizing methanol from blast furnace gas and coke oven gas, characterized in that it comprises a purification and desulfurization device, a _CO2 separation and purification device, a No. 1 pressure swing adsorption device, a purification and separation device, a methanation device, a No. 2 pressure swing adsorption device, a dry reforming reaction device, a No. 3 pressure swing adsorption device, a methanol synthesis device, a rectification device, a compressor, a No. 1 gas mixing device, a No. 2 gas mixing device and a blast furnace; the blast furnace gas pipeline network is sequentially connected to the purification and desulfurization device and the _CO2 separation and purification device through pipelines, the _CO2- poor gas outlet of the _CO2 separation and purification device is connected to the inlet of the No. 1 pressure swing adsorption device, and the CO2-rich gas outlet is connected to the No. 1 gas mixing device, and the _CO2- rich gas outlet of the No. 1 pressure swing adsorption device is connected to the gas inlet of the blast furnace through the No. 2 gas mixing device; the coke oven gas pipeline network is sequentially connected to the purification and separation device, the methanation device and the No. 2 pressure swing adsorption device through pipelines, and the H2-rich gas outlet of the No. 2 pressure swing adsorption device is connected to the No. 1 gas mixing device. The methane-rich gas outlet is connected to the inlet of the No. ₂ gas mixing device, and the methane-rich gas outlet is connected to the inlet of the No. 1 gas mixing device; the outlet of the No. 1 gas mixing device is connected to the dry reforming reaction device and the No. 3 pressure swing adsorption device in sequence, and the lean CO gas outlet of the No. 3 pressure swing adsorption device is connected to the methanol synthesis device and the distillation device in sequence; the CO-rich gas outlet of the No. 3 pressure swing adsorption device is connected to the inlet of the No. 2 gas mixing device; the compressor provides power. 8. A comprehensive utilization system for synthesizing methanol from blast furnace gas and coke oven gas according to claim 7, characterized in that a No. 3 gas mixing device is also provided between the No. 3 pressure swing adsorption device and the methanol synthesis device; and the purge gas outlet of the methanol synthesis device is connected to the inlet of the No. 3 gas mixing device. 9. A comprehensive utilization system for synthesizing methanol from blast furnace gas and coke oven gas according to claim 7 or 8, characterized in that the tail gas outlet of the No. 1 pressure swing adsorption device is connected to the gas pipeline network.