System for co-producing LNG (Liquefied Natural Gas) and methanol from coke oven gas and blast furnace gas

Abstract

The utility model discloses a system for co-producing LNG (Liquefied Natural Gas) and methanol from coke oven gas and blast furnace gas. Comprising a purification and separation device, a methanation device, a cryogenic liquefaction device, a purification and desulfurization device, a CO2 separation and purification device, a first pressure swing adsorption device, a second pressure swing adsorption device, a first gas mixing device, a methanol synthesis device, a rectification device, a third gas mixing device, a blast furnace and a compressor. The coke oven gas pipeline is sequentially communicated with the purification and separation device, the methanation device and the cryogenic liquefaction device through pipelines; the blast furnace gas pipeline is sequentially communicated with the purification and desulfurization device, the CO2 separation and purification device, the first pressure swing adsorption device, the third gas mixing device and the blast furnace through pipelines; a tail gas outlet of the methanation device is communicated with the second pressure swing adsorption device and the third gas mixing device. The system effectively realizes the effects of high-efficiency cyclic utilization of blast furnace gas and coke oven gas, high-efficiency utilization of effective components in the gas and CO2 emission reduction.

Description

Technical Field

[0001] The utility model relates to a coal gas resource utilization technology, in particular to a system for co-producing LNG and methanol from coke oven gas and blast furnace gas. Background Art

[0002] The steel industry is a major emitter of CO2, accounting for about 15% of the country's carbon emissions, of which blast furnace gas has the largest carbon emission among by-product gases. At present, by-product gas, mainly blast furnace gas, is mainly used for combustion heating and power generation, with high carbon emissions, environmental pollution, low added value, and resource waste. Therefore, how to make high-value utilization and reduce CO2 emissions has become an urgent need for the sustainable development of the steel industry.

[0003] The Action Plan for Peak Carbon Reaching by 2030 issued by the State Council in October 2021 clearly proposed to "promote advanced and applicable technologies, tap the potential for energy conservation and carbon reduction, and encourage the joint production of steel and petrochemicals." Methanol is widely used as a chemical raw material and green fuel with a large market capacity. Separating and purifying CO2 and H2 from steel plant gas through the joint production of steel and petrochemicals to synthesize high-value methanol is an effective way to reduce carbon emissions and increase efficiency.

[0004] The patent application with publication number CN108265145A provides a method and system for utilizing carbon dioxide-rich blast furnace gas. The method obtains rich CO2 from blast furnace gas, mixes it with hydrogen produced after purification of coke oven gas to produce methanol, and the purge gas produced by methanol synthesis, the coke oven gas residual gas produced by desulfurization purification treatment, and the analysis gas produced by hydrogen pressure swing adsorption purification are used for power generation; the process of this scheme is simple, but the use of the gas produced in the process for power generation causes a waste of resources.

[0005] The patent application with publication number CN116397062A provides a near-zero carbon emission blast furnace long-process tempering co-production process and system, in which blast furnace gas is decarbonized by pressure swing adsorption to separate desorbed gas and decarbonized gas; the desorbed gas is purified by liquefied 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 to light hydrocarbons to separate CO+N2 and H2 logistics for the synthesis of ethylene glycol. This solution solidifies "carbon" emissions into products through steel-coke fusion and tempering co-production, achieving "carbon fixation and emission reduction" and increasing value and efficiency; however, this solution does not directly fix CO2 into chemical products, and a CO2 treatment process needs to be added later. Utility Model Content

[0006] The technical problem to be solved by the utility model is to provide a system for co-producing LNG and methanol with coke oven gas and blast furnace gas, which can realize efficient utilization of effective components in the gas and CO2 emission reduction.

[0007] In order to solve the above technical problems, the technical scheme adopted by the system of the utility model is: including a purification and separation device, a methanation device, a cryogenic liquefaction device, a purification and desulfurization device, a CO2 separation and purification device, a No. 1 pressure swing adsorption device, a No. 2 pressure swing adsorption device, a No. 1 gas mixing device, a methanol synthesis device, a distillation device, a No. 3 gas mixing device, a blast furnace and a compressor; the coke oven gas pipeline is connected to the purification and separation device, the methanation device and the cryogenic liquefaction device in sequence through pipelines; the blast furnace gas pipeline is connected to the purification and desulfurization device, the CO2 separation and purification device, the No. 1 pressure swing adsorption device, the No. 3 gas mixing device and the blast furnace in sequence through pipelines; the tail gas outlet of the methanation device is connected to the No. 2 pressure swing adsorption device and the No. 3 gas mixing device; the product gas outlet of the No. 2 pressure swing adsorption device is connected to the No. 1 gas mixing device, the methanol synthesis device and the distillation device in sequence; the product gas outlet of the CO2 separation and purification device is connected to the No. 1 gas mixing device; the compressor provides power.

[0008] Furthermore, it also includes a No. 2 gas mixing device; the No. 2 gas mixing device is connected in series between the tail gas outlet of the methanation device and the No. 2 pressure swing adsorption device, and the relaxation gas outlet of the methanol synthesis device is connected to the inlet of the No. 2 gas mixing device.

[0009] Furthermore, it also includes a No. 4 gas mixing device and a fuel gas blending device; the decomposition gas outlet of the No. 2 pressure swing adsorption device and the decomposition gas outlet of the No. 1 pressure swing adsorption device are both connected to the inlet of the No. 4 gas mixing device, and the outlet of the No. 4 gas mixing device is connected to the fuel gas blending device.

[0010] The beneficial effects of adopting the above-mentioned technical scheme are as follows: the utility model uses CO2 in blast furnace gas and H2 in coke oven gas as raw materials to produce methanol, uses coke oven gas as raw material to produce LNG, and uses CO in blast furnace gas, hydrogen-rich tail gas produced by the methanation process and the purge gas of methanol synthesis as reducing gas to spray back into the blast furnace, effectively realizing the efficient recycling of blast furnace gas and coke oven gas, the efficient utilization of each effective component in the gas and the effect of CO2 emission reduction, thereby improving the overall economic benefits of the steel plant, which is of great significance to the realization of the "dual carbon" goal. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0012] Figure 1 It is a schematic diagram of the system structure of the utility model. DETAILED DESCRIPTION

[0013] Figure 1As shown, the system for co-producing LNG and methanol with coke oven gas and blast furnace gas includes a purification and separation device, a methanation device, a cryogenic liquefaction device, a purification and desulfurization device, a CO2 separation and purification device, a No. 1 pressure swing adsorption device, a No. 2 pressure swing adsorption device, a No. 1 gas mixing device, a No. 2 gas mixing device, a methanol synthesis device, a distillation device, a No. 3 gas mixing device, a No. 4 gas mixing device, a fuel gas blending 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 coke oven gas pipeline is connected to the inlet of the purification and separation device, the outlet of the purification and separation device is connected to the inlet of the methanation device through the No. 1 compressor, and the methane outlet of the methanation device is connected to the cryogenic liquefaction device; the tail gas outlet of the methanation device is connected to the inlet of the No. 2 gas mixing device and the No. 3 gas mixing device. In this way, the coke oven gas is removed of sulfur and oxygen through the purification and separation device, and then compressed by compressor No. 1 before entering the methanation device for methanation reaction. The generated methane is deep-cold liquefied through the deep-cold liquefaction device to obtain LNG products; the H2-rich tail gas generated by the methanation device partially enters the No. 2 mixing device and partially enters the No. 3 mixing device.

[0014] Figure 1 As shown, in the system of co-producing LNG and methanol with coke oven gas and blast furnace gas, the inlet of the blast furnace gas pipeline purification and desulfurization device, the outlet of the purification and desulfurization device is connected to the inlet of the CO2 separation and purification device through compressor No. 2, the desorption 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. 5, the product gas outlet of the No. 1 pressure swing adsorption device is connected to the inlet of the No. 3 gas mixing device, and the outlet of the No. 3 gas mixing device is connected to the gas inlet of the blast furnace; the product gas outlet of the CO2 separation and purification device is connected to the inlet of the No. 1 gas mixing device; the desorption gas outlet of the No. 1 pressure swing adsorption device is connected to the inlet of the No. 4 gas mixing device. In this way, the blast furnace gas is purified and desulfurized to remove sulfur and oxygen, and then compressed by compressor No. 2 before entering the CO2 separation and purification device. The obtained CO2-rich analysis gas is compressed by compressor No. 5 before entering the No. 1 pressure swing adsorption device to purify CO. The obtained CO2-rich product gas is mixed with part of the H2-rich tail gas in the No. 3 mixing device and then sent to the blast furnace for use as coal gas; the CO2-rich product gas obtained by the CO2 separation and purification device enters the No. 1 mixing device; the carbon oxide-rich analysis gas obtained by the No. 1 pressure swing adsorption device enters the No. 4 mixing device.

[0015] Figure 1As shown, in the system of co-producing LNG and methanol with coke oven gas and blast furnace gas, the outlet of the No. 2 gas mixing device is connected to the inlet of the No. 2 pressure swing adsorption device through compressor No. 3, the product 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 methanol synthesis device through compressor No. 4, the methanol 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. 2 gas mixing device; the desorption gas outlet of the No. 2 pressure swing adsorption device is connected to the inlet of the No. 4 gas mixing device. In this way, a part of the H2-rich tail gas generated by the methanation unit is mixed with the methanol synthesis purge gas generated by the methanol synthesis unit in the No. 2 gas mixing unit, and then sent to the No. 2 pressure swing adsorption unit for H2 purification after passing through compressor No. 3. The obtained H2-rich gas is mixed with the CO2-rich product gas generated by the CO2 separation and purification unit in the No. 1 gas mixing unit, and then sent to the methanol synthesis unit and the distillation unit after passing through compressor No. 4 to obtain methanol product; the methanol synthesis purge gas generated by the methanol synthesis unit is sent to the No. 2 gas mixing unit to be mixed with a part of the H2-rich tail gas; the H2-rich analysis gas obtained by the No. 2 pressure swing adsorption unit enters the No. 4 gas mixing unit.

[0016] Figure 1 As shown, in the system for co-producing LNG and methanol with coke oven gas and blast furnace gas, the outlet of the No. 4 gas mixing device is connected to the inlet of the fuel gas blending device. In this way, the carbon oxide-extracted desorption gas obtained by the No. 1 pressure swing adsorption device and the H2-extracted desorption gas obtained by the No. 2 pressure swing adsorption device are mixed in the No. 4 gas mixing device, and then after the components are blended in the fuel gas blending device, they are used as fuel gas in various steel production processes and power generation devices.

[0017] Figure 1 As shown, the production process of the system for co-producing LNG and methanol with coke oven gas and blast furnace gas is as follows:

[0018] (1) The coke oven gas is purified and separated in a purification and separation device to remove sulfur and oxygen therein to a sulfur content of <0.1ppm and an oxygen content of <300ppm; then a methanation reaction is carried out in a methanation device to generate methane and H2-rich tail gas; the methane is liquefied and cryogenically cooled in a cryogenic liquefaction device to obtain an LNG product;

[0019] The main components of the coke oven gas are (vol): H2 50-65%, CO 4-10%, CO2 1-6%, CH4 15-23%. The main reactions of the methanation reaction are: CO+3H2→CH4+H2O, CO2+4H2→CH4+2H2O. The main components of the hydrogen-rich tail gas are (vol): H2 70-90%, CO<10ppm, CO2<20ppm, CH4 0.5-3%, O2<10ppm.

[0020] (2) A portion of the H2-rich tail gas is mixed with the subsequent methanol synthesis purge gas in the No. 2 gas mixing device, and then the hydrogen is purified in the No. 2 pressure swing adsorption to obtain H2-rich gas. The remaining gas after purification is H2-extracted analytical gas. This portion of the H2-rich tail gas accounts for 50% or more of the total volume of the H2-rich tail gas; the H2 content in the H2-rich gas is greater than 99.5 vol%.

[0021] (3) The blast furnace gas is treated by a purification and desulfurization device to remove sulfur and oxygen therein; then the blast furnace gas enters a CO2 separation and purification device for CO2 separation and purification to obtain a CO2-rich product gas and a CO2-rich analysis gas; the CO2-rich analysis gas enters a No. 1 pressure swing adsorption device to purify CO to obtain a CO-rich product gas and a carbon oxide-rich analysis gas;

[0022] The main components of the blast furnace gas are (vol): CO 20-30%, CO2 15-25%, CH4 0.4-1.5%, H2 1.5-3.5%, O2 0.2-1.0%, N2 46-60%; the blast furnace gas is purified and desulfurized to a sulfur content of <0.1ppm and an oxygen content of <300ppm; the CO2 content in the CO2-rich product gas is >85vol%; the CO content in the CO-rich product gas is >85vol%.

[0023] (4) The CO2-rich gas and the H2-rich gas are mixed in the No. 1 gas mixing device and enter the methanol synthesis device for methanol synthesis to obtain a methanol product; methanol synthesis purge gas is generated during the methanol synthesis process. The main reaction in the methanol synthesis is: CO2+4H2→CH3OH+2H2O; the main components of the methanol purge gas are (volume): H2 60-75%, inert gas 0-20%, CO 1-7%, CO2 1-10%.

[0024] (5) The CO-rich product gas and another portion of the H2-rich tail gas are mixed in the No. 3 gas mixing device and sprayed back into the blast furnace for recycling.

[0025] (6) The H2-extracted desorption gas obtained in step (2) and the carbon oxide-extracted desorption gas obtained in step (3) are mixed in a No. 4 gas mixing device and used as fuel gas for various steel production processes and power generation equipment.

[0026] Specific application examples:

[0027] The main components of blast furnace gas are: CO 26%, CO2 20%, CH4 0.75%, H2 2.1%, O2 0.43%, N2 49.2%, temperature 40℃, pressure 6000Pa(A), flow rate 55000Nm 3 / h;

[0028] The main components of coke oven gas are: H2 60%, CO 6%, CO2 2%, CH4 22%, O2 0.72%, N2 7.6%, temperature 40℃, pressure 6000Pa(A), flow rate 55000Nm 3 / h;

[0029] The main components of hydrogen-rich tail gas are: H286.7%, CO<10ppm, CO2<20ppm, CH41.6%, O2<10ppm, temperature 27℃, pressure 1.3MPa(A);

[0030] Plant scale: Annual production of 120,000 tons of methanol, 92,000 tons of LNG, and 14,500 Nm of CO product gas 3 / h back-spraying blast furnace, the device operation time is 8000h / year.

[0031] Figure 1 As shown, the specific steps include:

[0032] (1) Coke oven gas methanation to produce LNG and hydrogen extraction from hydrogen-rich tail gas:

[0033] The flow rate is 75000Nm 3 / h of coke oven gas is purified and separated to remove sulfur to <0.1ppm and oxygen content to <300ppm, and then enters the methanation device for methanation reaction. Under the conditions of 600-650℃ and 1.5-2.0MPa, CO, CO2 and H2 in the methanation device are converted into methane under the action of catalytic materials, and methane is liquefied and deep-cooled to produce LNG products.

[0034] The methanogenation device produces a flow rate of 52000Nm 3 / h, H2-rich tail gas with a H2 concentration of 86.7% and a flow rate of 37000Nm 3 / h of hydrogen-rich tail gas is compressed and sent to pressure swing adsorption for hydrogen purification, and the flow rate is 32000Nm 3 / h, H2 rich gas with a H2 concentration of 99.5%.

[0035] (2) Purification of CO2 and CO from blast furnace gas:

[0036] The flow rate is 55000Nm 3 / h blast furnace gas is purified and desulfurized. The sulfur in the blast furnace gas is removed to <0.1ppm and the oxygen content is <300ppm. Organic amine circulation absorption is used for CO2 separation and purification. MEDA-CO2 is used for separation and purification. The blast furnace gas is countercurrently contacted with N-methyldiethanolamine (MEDA-CO2) to absorb CO2 through mass transfer and chemical reaction, and then the pressure is reduced and heated for desorption to obtain a flow rate of 11000Nm 3 / h, CO2-rich product gas with a CO2 concentration of 98.0%. The CO2 separated and purified analytical gas is subjected to CO separation and purification by pressure swing adsorption, and a flow rate of 14500Nm 3 / h, CO-rich product gas with a CO concentration of 98.5%.

[0037] (3) Methanol synthesis:

[0038] The flow rate obtained in step (2) is 11000 Nm 3 / h, CO2 concentration of 98.0% CO2-rich product gas, and the flow rate obtained in step (1) is 32000Nm 3 / h, and part of the H2-rich gas with a hydrogen concentration of 99.5% are mixed, compressed to 8MPa and then enter the methanol synthesis unit for synthesis to produce crude methanol; the crude methanol is sent to the distillation unit to separate water to produce methanol products with an output of 140,000 tons / year.

[0039] The purge gas produced by the methanol synthesis device has a flow rate of 37000 Nm 3 / h of H2-rich tail gas is mixed and sent to pressure swing adsorption for hydrogen purification for methanol synthesis.

[0040] (4) Back-spraying blast furnace:

[0041] The CO-rich product gas obtained in step (2) is mixed with the remaining hydrogen-rich tail gas with a flow rate of 15000 Nm3 / h and sprayed back into the blast furnace.

[0042] (5) Exhaust gas treatment:

[0043] The desorption gas obtained by the pressure swing adsorption in step (1) and the carbon oxide-extracted desorption gas obtained by the CO separation and purification in step (1) are mixed and used as fuel gas for various processes in steel production and power generation equipment.

Claims

1. A system for co-producing LNG and methanol from coke oven gas and blast furnace gas, characterized in that: It includes a purification and separation device, a methanation device, a cryogenic liquefaction device, a purification and desulfurization device, a CO2 separation and purification device, a No. 1 pressure swing adsorption device, a No. 2 pressure swing adsorption device, a No. 1 gas mixing device, a methanol synthesis device, a distillation device, a No. 3 gas mixing device, a blast furnace and a compressor; the coke oven gas pipeline is connected to the purification and separation device, the methanation device and the cryogenic liquefaction device in sequence through pipelines; the blast furnace gas pipeline is connected to the purification and desulfurization device, the CO2 separation and purification device, the No. 1 pressure swing adsorption device, the No. 3 gas mixing device and the blast furnace in sequence through pipelines; the tail gas outlet of the methanation device is connected to the No. 2 pressure swing adsorption device and the No. 3 gas mixing device; the product gas outlet of the No. 2 pressure swing adsorption device is connected to the No. 1 gas mixing device, the methanol synthesis device and the distillation device in sequence; the product gas outlet of the CO2 separation and purification device is connected to the No. 1 gas mixing device; the compressor provides power.

2. The system for co-producing LNG and methanol from coke oven gas and blast furnace gas according to claim 1, characterized in that: It also includes a No. 2 gas mixing device; the No. 2 gas mixing device is connected in series between the tail gas outlet of the methanation device and the No. 2 pressure swing adsorption device, and the relaxation gas outlet of the methanol synthesis device is connected to the inlet of the No. 2 gas mixing device.

3. A system for co-producing LNG and methanol from coke oven gas and blast furnace gas according to claim 1 or 2, characterized in that: It also includes a No. 4 gas mixing device and a fuel gas blending device; the decomposition gas outlet of the No. 2 pressure swing adsorption device and the decomposition gas outlet of the No. 1 pressure swing adsorption device are both connected to the inlet of the No. 4 gas mixing device, and the outlet of the No. 4 gas mixing device is connected to the fuel gas blending device.

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