A method for reducing CO2 emissions in blast furnace ironmaking process and tuyere injection structure

Abstract

The present invention provides a method for reducing CO2 emissions in a blast furnace ironmaking process and a tuyere injection structure. The method comprises the following steps: (1) using coke oven gas as raw material gas to produce hydrogen, and removing CO2 from tail gas to obtain methane-rich gas; (2) using converter gas as a gas source, utilizing the hydrogen obtained in step (1), hydrogenating and converting the synthesized methane to obtain coal gas containing high concentration of methane; (3) using the methane-rich gas obtained in step (1) as tail gas after treatment of coke oven gas, and using the coal gas containing high concentration of methane obtained in step (2) as methanogenic product gas, mixing them in a volume ratio of methanogenic product gas: tail gas after treatment of coke oven gas = (1-3):1, to obtain a mixed gas containing methane, hydrogen and CO; and (4) injecting the mixed gas obtained in step (3) into the blast furnace through an injection system to replace coal powder or part of coke.

Description

Technical Field

[0001] The invention belongs to the technical field of low-carbon metallurgy, and in particular relates to a method for reducing CO2 emissions in a blast furnace ironmaking process and a tuyere injection structure. Background Art

[0002] It has become a general consensus of the international community that global warming and frequent extreme weather events are closely related to the significant increase in CO2 emissions. China's steel industry accounts for about 15% of the country's energy consumption and CO2 emissions, and is a key industry for the country to promote CO2 emission reduction actions. my country's steel production is mainly based on the blast furnace-converter long process, coal and electricity are the main energy sources, and about 70% of energy consumption and CO2 emissions are generated in the blast furnace ironmaking process. Therefore, low-carbon ironmaking is the key direction for technological breakthroughs in reducing CO2 emissions in the steel industry. In addition to developing and applying the gas-based vertical furnace direct reduction + electric furnace short-process steelmaking process, an effective way to reduce blast furnace CO2 emissions in the short term is to further reduce the consumption of carbon fuels (including pulverized coal and coke) in blast furnaces, and to use other low-carbon hydrogen-rich fuels to replace carbon fuels, so that the direct combustion CO2 emissions of the top gas (containing CO and CO2) generated by the blast furnace are further reduced.

[0003] Blast furnaces can be injected with natural gas, coke oven gas, waste grease, biomass fuel, chemical waste (waste plastics, etc.), hydrogen, etc., but due to resource source and other conditions, natural gas and coke oven gas are more suitable injection materials. However, my country's natural gas resources are seriously lacking, imported natural gas is in short supply, the price is high, and steel mills are limited in their use. Coke oven gas, as a by-product of steel mills containing H2 and CH4, although the resources are guaranteed and the unit price is low, its ability to save carbon when directly injected into the blast furnace is not as good as natural gas, and the acceptable injection volume of the blast furnace is far less than that of natural gas.

[0004] The following are some of the related prior art.

[0005] Prior art 1: Chinese patent document CN100552046C, whose applicant is Japan JFE, discloses a mechanism for injecting gas reducing agent (natural gas, etc.) into a blast furnace and a method for injecting gas into a blast furnace, using two spray guns to spray solid fuel and gas fuel respectively, the outlet of the solid fuel spray gun is upstream of the hot air supply direction, the outlet of the gas spray gun is downstream, and the gas spray gun port is 0-50mm away from the inner side of the front end face of the tuyere. In its embodiment, a design is proposed in which a gas nozzle is inserted into the water cavity in front of the tuyere, and then hot air is injected from a position 50mm away from the front end face of the tuyere.

[0006] Prior art 2: Chinese patent document CN103328657B, the applicant of which is Japan JFE, discloses a mechanism and operation method for injecting gas and solid fuel into a blast furnace, using a three-layer casing spray gun for tuyere injection, wherein the inner tube carries pulverized coal, the middle tube seam carries city gas, and the outer tube annular seam carries oxygen. The preferential mixed combustion of oxygen and city gas promotes the heating and combustion of pulverized coal.

[0007] Prior art 3: The Chinese utility model patent with publication number CN204039421U discloses a process equipment for mixed injection of petroleum-associated natural gas and pulverized coal in a blast furnace. The petroleum-associated natural gas is injected into the blast furnace through an injection system after pretreatment and pressurization. The natural gas injection system is provided with a main delivery pipe and a surrounding pipe arranged on the tuyere platform, and injection branches of each tuyere are connected from the surrounding pipe. Natural gas and pulverized coal are injected into the tuyere of the blast furnace at the same time by means of a sleeve-type spray gun (with pulverized coal in the inner pipe and natural gas in the outer pipe) and by injecting pulverized coal or natural gas at intervals in the tuyere of the blast furnace.

[0008] Prior art 4: The Chinese utility model patent with publication number CN204039426U discloses a process equipment for injecting natural gas with oxygen-enriched gas in a blast furnace, wherein a natural gas nozzle and an oxygen nozzle pass through the rear cavity of the tuyere, extend from the front end of the front water cavity, and inject into the furnace at the front end of the tuyere at a certain angle, and the two nozzles are symmetrically arranged in the tuyere water cavity. By mixing and burning oxygen and natural gas at the front end of the tuyere (in the furnace), the natural gas is prevented from being pyrolyzed in the hot air channel of the tuyere to form carbon black, thereby improving the combustion effect.

[0009] Prior art 5: The Chinese patent document with application number 201580055083.7 and invention name “Method for injecting alternative reducing agent into blast furnace” uses fuel gas (CO, H2, hydrocarbon, natural gas, COG) as carrier gas (fuel gas accounts for 2-25%), densely transports powdered alternative reducing agent (coal powder) and sprays it into the blast furnace by means of a spray gun. Oxygen is transported through the spray gun, which is a double-layer casing, with coal powder and conveying gas passing through the inner tube, and oxygen passing through the annular seam, and the mixing of coal powder and oxygen is promoted by the vortex structure; or coal powder and conveying gas are sprayed by a single-tube spray gun, and oxygen is sprayed through another spray gun.

[0010] Prior art 6: A Chinese patent document with application number 201210391487.1 and invention name “Blast furnace coal injection method using coke oven gas as a coal injection transport carrier”, in which the coke oven gas is dehydrated and pressurized, and then sent to a coal powder injection tank, where it is mixed with coal powder and sprayed out, and then sprayed into the blast furnace through a coal powder distributor, a coal powder injection pipeline, and a tuyere spray gun.

[0011] Prior art 7: According to a Chinese patent document with application number 201210101057.1 and invention name “A blast furnace injection process”, CO2 is removed from converter gas by adsorption and the gas is heated to 400°C; CO2 and SO2 are removed from coke oven gas and the gas is then heated to 400°C; the two treated gases are mixed in a mixing tank and then pressurized and sprayed into the middle of the blast furnace shaft.

[0012] Prior art 8: A Chinese patent document with application number 201110160190.X and invention name “A process for composite injection of coke oven gas and pulverized coal into a blast furnace”, in which the coke oven gas is detarred and pressurized, and then enters the outer tube of a double-layer sleeve type spray gun through a buffer tank, a gas main pipe and a gas surrounding pipe, and the pulverized coal enters the inner tube of the double-layer sleeve type coal gun, and the two are mixed and burned in the hot air channel at the outlet of the spray gun.

[0013] Prior art 9: Chinese patent document with application number 201080022850.1 and invention name “Method for preparing synthesis gas” relates to a method for preparing synthesis gas containing H2 and CO, wherein coke oven gas is separated into hydrogen and gas containing hydrocarbons, CO-enriched gas is separated from blast furnace top gas, and then the hydrogen is mixed with the CO-enriched gas to prepare synthesis gas. Gas containing hydrocarbons is also separately fed into the blast furnace as raw gas.

[0014] Prior art 10: A Chinese patent document with application number 201410619526.8 and invention name “Method for producing natural gas and liquid ammonia by cooperating with coke oven gas and blast furnace gas”, one of the technical contents of which is to pressurize the coke oven gas, remove tar and naphthalene by temperature swing adsorption, perform secondary pressure swing adsorption decarbonization, perform tertiary desulfurization, and then enter the methane synthesis unit to obtain natural gas by pressure swing adsorption.

[0015] Prior art 11: Chinese patent document with application number 200810045866.9 and invention name “A method for producing methanol synthesis gas using coke oven gas and blast furnace gas” discloses a method for producing methanol synthesis gas using coke oven gas and blast furnace gas as raw materials, wherein H2 is extracted from the coke oven gas by pressure swing adsorption, CO and CO2 are extracted from the blast furnace gas using an adsorbent that can simultaneously adsorb CO and CO2, and then H2, CO and CO2 are mixed to prepare a gas for synthesizing methanol. Summary of the invention

[0016] The technical problem to be solved by the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a method for reducing CO2 emissions from the blast furnace ironmaking process by methanating and spraying the by-product coal gas of the steel plant into the blast furnace to replace coal. The coke oven gas and converter gas produced by the steel plant are used as gas sources, and the coal gas containing CH4 is produced by chemical conversion, and then sprayed into the blast furnace to replace the pulverized coal and part of the coke used in the blast furnace to the greatest extent, thereby reducing the CO2 emissions from the coal gas in the blast furnace ironmaking process. It includes a process for methanating the converter gas by extracting hydrogen from the coke oven gas, and removing CO2 from the tail gas after hydrogen extraction from the coke oven gas and then mixing it with the methanated gas, and spraying it into the blast furnace through a designed tuyere injection mechanism / structure to control the lower part of the blast furnace operation.

[0017] The technical problem to be solved can be implemented through the following technical solutions.

[0018] A method for reducing CO2 emissions in a blast furnace ironmaking process, characterized in that it comprises the following steps:

[0019] (1) Using coke oven gas as raw gas to produce hydrogen, removing CO2 from tail gas to obtain methane-rich gas;

[0020] (2) Using converter gas as a gas source, the hydrogen obtained in step (1) is hydrogenated and converted into methane to obtain gas containing a high concentration of methane;

[0021] (3) The methane-rich gas obtained in step (1) is used as the tail gas after the treatment of coke oven gas, and the coal gas containing high concentration of methane obtained in step (2) is used as the methanogenic product gas, and the mixture is mixed in a volume ratio of methanogenic product gas: tail gas after the treatment of coke oven gas = (1-3):1 to obtain a mixed gas containing methane, hydrogen and CO;

[0022] (4) The mixed gas obtained in step (3) is injected into the blast furnace through an injection system to replace coal powder or part of the coke.

[0023] As a further improvement of the technical solution, in step (1), the hydrogen is produced by purifying the coke oven gas to meet the standards and then entering the pressure swing adsorption hydrogen extraction system to extract hydrogen. The purification includes the removal of benzene, naphthalene, tar and sulfur. The removal condition (requirement) is that the naphthalene is reduced to 50 mg / Nm 3 Below, tar drops to 10mg / Nm 3 Below, and the organic sulfur in coke oven gas is reduced to 10mg / Nm 3 Below, the olefin component is reduced to <0.5%; the hydrogen pressure of the obtained product is ≥0.8MPa.

[0024] As a further improvement of the present technical solution, in step (1), an alcohol amine method is used to remove CO2; after CO2 is removed, the volume concentration of CO is 21-22%.

[0025] As a further improvement of the present technical solution, in step (2), when the converter gas is hydrogenated to synthesize methane, the converter gas is mixed with the produced hydrogen at a molar ratio of (CO+CO2) / H2 of 2:7.2 to 2:7.6 as the raw gas for the methanation reaction; and water vapor is added at a water / gas ratio of 2-3% by volume.

[0026] As a further improvement of the technical solution, a 2-3 stage series fixed bed reactor is used to carry out hydrogenation and methanation of the converter gas.

[0027] Preferably, the medium-pressure superheated steam generated during the methanation reaction is used as a heat source for heating the regeneration tower of various adsorbents and catalysts in the coke oven gas pressure swing adsorption hydrogen extraction system and the converter gas methanation synthesis system.

[0028] Preferably, the mixed gas is injected from the blast furnace tuyere, and the outlet position of the nozzle port in the blast furnace tuyere is set downstream of the pulverized coal injection gun port, and the distance between the two is controlled at 200-250mm.

[0029] Preferably, after the blast furnace starts to supply air, purge gas is introduced into the inner tube of the coal gun and the gas injection pipeline through the pulverized coal injection system and the mixed gas injection system respectively to prevent hot air from flowing back and cool the steel pipe;

[0030] After the blast furnace starts to inject fuel, coal injection and mixed gas injection are started successively. The mixed gas is injected at a speed of <10000Nm 3 / h low flow injection; after the blast furnace returns to normal planned blast parameters and furnace conditions, priority is given to increasing the pulverized coal injection rate, and the injection rate of the mixed gas is >10000Nm 3 / h flow rate spray;

[0031] When the pulverized coal injection rate reaches an acceptable level for the blast furnace and the furnace conditions, furnace temperature and airflow distribution are normal and stable, continue to increase the gas injection rate and reduce the pulverized coal injection rate; gas injection rate <50Nm 3 / t, press 1.1-1.3Nm 3 The principle of replacing 1kg of coal powder with gas reduces the amount of coal injection; gas injection 50-100Nm 3 / t, press 1.3-1.5Nm 3 The principle of replacing 1kg of coal powder with gas can reduce the amount of coal injection.

[0032] Another technical problem to be solved by the present invention is to provide a tuyere blowing structure for realizing the above-mentioned method.

[0033] The structure includes a blast furnace tuyere and a straight blowing pipe matched with the blast furnace tuyere, and is characterized in that it includes a nozzle for blowing the mixed gas, a part of the nozzle is buried in the rear water cavity of the blast furnace tuyere, and an air inlet end is used to connect to an external mixed gas source pipeline; the port of the nozzle jet end is flush with the inner wall of the straight blowing pipe, and the pipe opening of the nozzle air inlet end forms an angle of 35-40° with the center line of the blast furnace tuyere.

[0034] Preferably, the jet end of the nozzle is arranged downstream of the coal powder injection gun port (towards the furnace), and the distance between the two is controlled at 200-250 mm.

[0035] Furthermore, the blast furnace tuyere is a cross-flow tuyere.

[0036] In the technical scheme of the present invention, the converter gas produced in the steelmaking process contains 50-60% CO and 15-20% CO2, which is an important source of carbonaceous gas for methane synthesis; at the same time, the coke oven gas produced in the coking process of the steel plant contains 55% hydrogen, 25% CH4, and 5-8% CO, wherein the H2 is the source of hydrogen for chemically converting CO and CO2 in the converter gas into CH4. The converter gas is converted into CH4 through a catalytic reaction process, and becomes a carbon fuel substitute for the blast furnace, so that its chemical energy can be fully utilized. In addition, the tail gas after hydrogen extraction from the coke oven gas is rich in CH4, and the residual CO2 is removed from the tail gas, which also becomes a gas fuel containing CH4 for blast furnace injection.

[0037] The present invention aims at the process equipment of injecting CH4-rich coal gas into the blast furnace and the smelting operation of injecting CH4-rich gas into the blast furnace, and proposes a process mechanism for injecting coal gas at the tuyere of the blast furnace and an operation method for adjusting the parameters of the lower part of the blast furnace to make the blast furnace run smoothly and stabilize, and minimize the amount of CO+CO2 per ton of iron generated by the top coal gas. By reasonably controlling the injection amount of coal gas and coal powder, and controlling appropriate operating parameters of the lower part of the blast furnace, the carbon consumption of the blast furnace is reduced.

[0038] This further reduces CO2 emissions during the blast furnace ironmaking process.

[0039] The beneficial effects of the technical solution of this application are as follows:

[0040] (1) CO and CO2 in converter gas are used as gas sources and converted into methane through hydrogenation reaction, making it a gas injection fuel for the blast furnace. This makes rational use of the chemical energy of converter gas and expands the source of reducing gas for the blast furnace.

[0041] (2) The technical method of the present application does not extract CO from converter gas and H2 from coke oven gas, and then mix them into gas and inject them into the blast furnace, but converts all CO and CO2 in the converter gas into CH4. The theoretical replacement rate of CH4 for coal powder is 0.8kg / Nm3 The replacement rate of coke is about 0.7kg / Nm 3 However, the direct injection of CO+H2 mixed gas has little ability to replace coal powder and coke, and its effect of reducing CO2 emissions from blast furnaces is poor, because it basically does not release heat in front of the blast furnace tuyere.

[0042] (3) The technical method of the present application does not directly inject coke oven gas into the blast furnace, but extracts H2 from the coke oven gas for methanation reaction of converter gas. This is because injecting CH4 saves carbon more than directly injecting coke oven gas (the replacement rate of coke oven gas to coke is about 0.4-0.5kg / Nm 3 ) is much better, and the more economical injection volume exceeds that of coke oven gas (usually, the injection volume of natural gas can reach 100Nm 3 / t, while the injection rate of coke oven gas is only 50Nm 3 / t), and its ability to replace coal powder and coke far exceeds that of coke oven gas. The H2 in coke oven gas does not burn and release heat in the blast furnace, and the actual effect of H2 in reducing iron ore and the utilization efficiency of H2 are lower than those of CO. Therefore, extracting H2 from coke oven gas for the synthesis of methane has a better utilization effect.

[0043] (4) The technical method of the present application uses the CH4-rich gas remaining after H2 is extracted from coke oven gas for blast furnace injection, which can more effectively utilize the coke oven gas and give full play to its greater role in saving coal and reducing carbon emissions.

[0044] (5) The mechanism for spraying CH4-rich gas with a built-in nozzle in the tuyere water jacket proposed in the present application is that the nozzle is only arranged in the rear water cavity of the tuyere, and has no effect on the waterway structure, water flow rate and water flow form of the front cavity of the tuyere, which can ensure the water speed and cooling capacity of the front cavity of the tuyere and the longevity of the tuyere. Moreover, the nozzle of CH4-rich gas is at a long distance from the front face of the tuyere, and the gas can be mixed and burned with CH4 and hot air in the tuyere channel, and the ignition and combustion effect is much better than that of spraying into the front end of the tuyere, which can reduce CH4 cracking, increase the gas spraying amount, and also improve its heat release and coal powder replacement effect.

[0045] (6) Compared with direct methanation of coke oven gas or methanation after mixing coke oven gas with converter gas, the technical solution of the present application simplifies the treatment process of coke oven gas and simplifies the process and equipment of the methanation system. The technology of extracting hydrogen from coke oven gas is mature, but if all coke oven gas is used for methanation, its impurities including benzene, naphthalene, CnHm, sulfur, etc. need to be thoroughly treated to prevent the catalyst in the methanation reactor from affecting the conversion efficiency due to carbon deposition, poisoning, etc. The methanation of hydrogen extracted from coke oven gas mixed with converter gas greatly simplifies the equipment and treatment process of the methanation reaction system, which can well avoid the influence of impurities in coke oven gas. In addition, coke oven gas contains about 25% CH4, which does not participate in the synthesis reaction during the methanation process. Instead, it is easy to increase the reverse reaction of CO+CO2+H2→CH4 due to the excessive concentration of CH4 during the conversion process, thereby reducing the conversion rate of CH4. Involving CH4 in coke oven gas in the methanation reaction will increase the reactor volume, reduce the conversion productivity, and increase equipment investment.

[0046] (7) The smelting operation method of the blast furnace for simultaneously injecting pulverized coal and CH4-rich gas described in the present application can reasonably control the theoretical combustion temperature and the amount of gas in the furnace belly of the blast furnace, so that when the amount of gas injection is increased, the blast furnace can run smoothly and the pressure difference does not increase significantly, and more gas can be injected, thereby replacing more pulverized coal or coke; based on material balance-heat balance and carbon balance calculations, the lower system of the blast furnace is comprehensively adjusted, and the injection amount of pulverized coal and gas fuel is reasonably coordinated to reduce the solid fuel ratio to the minimum, and the amount of CO+CO2 per ton of iron discharged from the blast furnace top gas is reduced as much as possible.

[0047] The present invention develops a process for producing CH4-containing gas by chemical conversion of steel mill byproduct gas, and an operating technology for spraying the produced CH4-containing gas into a blast furnace to minimize carbon fuel consumption. This is an important way to solve the problem of lack of oil and natural gas supply to blast furnaces and achieve CO2 emission reduction in blast furnaces. The converter gas (containing 50-60% CO and 15-20% CO2) produced in the steelmaking process of the steel mill is an important gas source that can be fully utilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is a process flow chart of the method of the present invention;

[0049] Figure 2 It is a schematic diagram of the structure of the tuyere injection mechanism for composite injection of gas and solid fuel in a blast furnace of the present invention; DETAILED DESCRIPTION

[0050] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0051] The present invention provides a method for reducing CO2 emissions in a blast furnace ironmaking process, further comprising catalytically converting coke oven gas and converter gas produced as by-products of a steel plant to produce a gas containing CH4, which is then injected into the blast furnace to replace coal powder or part of the coke, thereby reducing CO2 emissions in the blast furnace ironmaking process.

[0052] Reference Figure 1 and Figure 2 The specific technical solution of the present invention includes the following three steps:

[0053] Step 1: Use coke oven gas as raw gas to produce hydrogen and obtain tail gas rich in CH4. Hydrogen is used as gas for converting converter gas into methane by hydrogenation, and the tail gas is used as gas for blast furnace injection after CO2 is removed.

[0054] The coke oven gas (pressure of about 7KPa) from the pipeline is pressurized and then pre-purified. It passes through a pre-purification system consisting of two crude naphthalene removers (one for use and one for regeneration) and a heater to remove most of the benzene, naphthalene and tar in the coke oven gas (COG). Then, a screw compressor is used to pressurize the pre-purified gas to 1.0MPa, and deep naphthalene removal, tar removal and desulfurization treatment are carried out respectively. The TSA temperature swing adsorption process, multifunctional adsorbent and high-efficiency deoiling agent are used to reduce naphthalene from ≤500mg / Nm 3 Reduced to 50mg / Nm 3 Below, tar from ≤50mg / Nm 3 Reduced to 10mg / Nm 3 Below. Using activated carbon desulfurization process, H2S is reduced from 100mg / Nm 3 Reduced to 10mg / Nm 3 The coal gas from the deep purification system enters the CnHm removal system to remove high hydrocarbon components such as C4 and C5 to ensure the stable operation of the pressure swing adsorption (PSA) hydrogen production system. Nickel-zinc adsorbent is used to reduce the organic sulfur in COG from 350mg / Nm 3 Reduced to 10mg / Nm 3 , the olefin component dropped from 2-3% to <0.5%.

[0055] After purification, COG enters the PSA system to extract hydrogen. In the pressure swing adsorption system, each adsorber goes through adsorption, balanced pressure reduction, forward release, reverse release, flushing, balanced pressure increase, and final pressure increase to complete adsorption and desorption, and obtain product hydrogen and desorbed gas. Product hydrogen ≥0.8MPa is sent to the methanation unit for use, and the desorbed gas is sent to the storage tank. The desorbed gas pressure is ≥0.02MPa, containing about 20% H2, about 38-40% CH4, about 13% CO, about 3-4% CnHm, about 12-13% N2, and a certain amount of O2 and CO2.

[0056] The desorbed gas is passed through an amine system to remove CO2, so as to eliminate the gasification and strength damage to the coke in front of the tuyere after it is injected into the blast furnace, and to reduce the drop in the temperature in front of the tuyere caused by the heat absorption during the gasification process, which increases the consumption of coke. After removing CO2, the CO concentration is increased to 21-22%, and other components do not change much.

[0057] Step 2: Using converter gas as the gas source, synthesize methane through a hydrogenation reaction device to obtain gas containing high concentration of CH4 for blast furnace injection.

[0058] A 2-3 stage series fixed bed reactor is used to hydrogenate and methanate converter gas (50-60% CO, 15-20% CO2, 10-20% N2 and a small amount of O2). According to the reaction formula CO+CO2+7H2→2CH4+3H2O and the molar ratio of (CO+CO2) / H2 of 2:7.2 to 2:7.6, the converter gas is mixed with the prepared hydrogen to become the raw gas for the methanation reaction, which is pressurized to 2-4MPa by a gas compressor, and water vapor is added according to a water / gas ratio of 2-3% by volume, preheated to 300-350°C, and enters the first stage reactor. Since the methanation reaction is a highly exothermic process, each reactor is filled with a CeO2-modified Ni-Al2O3 catalyst that is highly active at low temperatures (300°C), resistant to high temperatures (800°C), and resistant to carbon deposition. The temperature in the reactor bed is controlled within 450-550°C by controlling the carbon-hydrogen ratio (CO+CO2) / H2 of the raw gas and adjusting the proportion of water vapor added to the raw gas. In addition, a waste heat boiler is set between each reactor level to cool the outlet gas (temperature 400-450°C) of the previous reactor and recover waste heat to generate medium-pressure steam (180-200°C). The gas (20KPa) at the outlet of the last reactor is separated from gas and water (and cooled) before entering the product gas storage tank.

[0059] After the converter gas is converted, washed and cooled by the methanation reactor system, the product gas contains 80-90% CH4, about 10-20% N2, and less than 50ppm CO2.

[0060] The medium-pressure superheated steam generated by the methanation reactor system is used as a heat source for heating the regeneration tower of various adsorbents and catalysts in the coke oven gas pressure swing adsorption hydrogen extraction system and the converter gas methanation synthesis system in the technical solution of the present application.

[0061] Step 3: The tail gas containing CH4 obtained after hydrogen extraction and CO2 removal from the coke oven gas by pressure swing adsorption is mixed with the product gas (containing CH4 and a small amount of N2) prepared by the converter gas methanation synthesis system to obtain a mixed gas containing CH4, H2 and CO. The mixed gas is injected into the blast furnace from the tuyere injection mechanism through the pressure regulation and injection system of the booster station to replace coal powder or part of the coke for low-carbon smelting.

[0062] Pipes are connected from the storage tank of tail gas after hydrogen extraction from coke oven gas and the storage tank of product gas of converter gas methanation system to the valve station of blast furnace gas fuel injection system. The two gases are connected in series and mixed here and then pressurized to 1.0-1.1MPa by gas compressor. A flow meter is set on each gas pipeline, and the mixed gas can be matched according to the ratio of methanation product gas: tail gas after COG treatment = (1-3): 1. The valve station is equipped with two sets of injection control valve groups, one is a large flow injection control valve group, and the other is a small flow control valve group. Each valve group is equipped with automatic shut-off valve, flow meter, pressure regulating valve, flow regulating valve, manual shut-off valve and pressure and temperature measuring instruments, and a nitrogen purge and release device between valves is also set. The small flow valve group is mainly used when the blast furnace starts to inject mixed gas, which is convenient for accurate control and adjustment of the injection flow. When the gas injection amount required by the blast furnace increases to a certain value, it is switched to the large flow valve group operation.

[0063] The gas main coming out of the valve station is connected to the blast furnace tuyere gas injection station. The injection station is equipped with gas injection branches in the same number as the blast furnace tuyere. Each branch is laid above the blast furnace tuyere platform and connected to the corresponding tuyere gas injection mechanism. In the gas injection station, each gas injection branch is equipped with a manual shut-off valve, an automatic shut-off valve and a nitrogen automatic purge valve. The automatic shut-off valve of the injection gas branch is interlocked with the nitrogen automatic purge valve. When the gas injection branch fails or stops spraying, the automatic shut-off valve of the injection gas branch is closed and the nitrogen automatic purge valve is opened to purge the gas injection branch (all the way to the blast furnace tuyere) to ensure safety. A certain number of flow meters are set on all gas injection branches to detect the actual flow of the branch and grasp the gas injection flow of a single tuyere.

[0064] Further, the present invention provides a tuyere injection mechanism (structure) for injecting gas fuel into a blast furnace, specifically Figure 2A 20# carbon steel pipe (i.e., the mixed gas nozzle 200 in the figure) is cast into the rear cavity of the through-flow tuyere 100 used in the blast furnace (i.e., the tuyere rear water cavity 120 in the figure, and the reference numeral 110 in the figure is the tuyere front water cavity) by a casting method, and its front end 210 is flush with the inner wall of the copper tuyere hot air channel (i.e., the channel formed by the straight blowing pipe 400 in the figure), and the pipe outlet 220 forms an angle of 35-40° with the tuyere center line (i.e., the dotted line in the figure), and its rear end extends out of the rear seat of the tuyere, and a short steel pipe 230 with internal threads is welded to connect with a longer gas injection pipeline. The diameter of the steel pipe cast in the tuyere and the external longer steel pipe to be connected thereto is determined according to the total gas injection flow rate of the blast furnace or the gas injection flow rate of a single tuyere. In general, the diameter size is φ28-38, and the gas outlet velocity is <250m / s to reduce the resistance of the injection branch pipe. The distance between the position of the front end (gas ejection end) of the steel pipe cast in the tuyere and the rear seat end face of the tuyere is determined according to the position of the coal gun for blast furnace coal injection inserted into the hot air channel of the tuyere in actual production. In order to avoid the jet of injected gas interfering with the jet of injected coal powder, causing the flow of coal powder particles to be chaotic and the tuyere to be worn, and considering that CH4 in the injected gas is quickly heated and burned by hot air, the outlet position of the gas nozzle is set downstream of the port of the coal powder injection gun 300 (towards the blast furnace), and the distance between the two is controlled at 200-250mm.

[0065] In this technical solution of gas injection mechanism, gas fuel is injected into the hot air channel of the tuyere alone, mixed with the hot air and burned. Not only is the gas injection flow rate of a single tuyere large, but the injection rate per ton of iron in the blast furnace can reach 100Nm 3 / t, and the injection mechanism is well sealed, without the potential safety hazard of hot air and gas leakage. The steel pipe is cast into the rear cavity of the tuyere, which has no effect on the cooling and service life of the tuyere body.

[0066] The smelting operation method of the blast furnace spraying the gas of the present invention is: the blast furnace is shut down, the tuyere gas spraying mechanism (mainly referring to the mixed gas nozzle 200) and the direct blowing pipe 400 are installed successively, and then the gas spraying pipeline at the rear end of the gas spraying mechanism is connected, including the steel pipe and the metal hose of the extended section, and the pulverized coal spray gun 300 is inserted from the direct blowing pipe and fixed. After the blast furnace starts to supply air, the purge gas (N2) is introduced into the inner tube of the coal gun and the gas spraying pipeline through the pulverized coal spraying system and the CH4 gas spraying system respectively to prevent the hot air from flowing back and cooling the steel pipe. After the blast furnace starts to inject fuel, coal injection and gas fuel injection are successively injected. At this time, the gas injection amount is small, and a small flow valve group is used for low-flow gas injection. After the blast furnace restores the normal planned blast parameters and furnace conditions, the pulverized coal injection amount is increased first, and the injection amount of the mixed gas is>10000Nm 3 / h flow rate injection; when the pulverized coal injection volume reaches the acceptable level of the blast furnace and the furnace condition, furnace temperature and airflow distribution are normal and stable, continue to increase the gas injection volume and reduce the pulverized coal injection volume. Gas injection volume <50Nm 3 / t, press 1.1-1.3Nm 3 The principle of replacing 1kg of coal powder with gas reduces the amount of coal injection; gas injection 50-100Nm 3 / t, press 1.3-1.5Nm 3 The principle of replacing 1kg of coal powder with gas is to reduce the amount of coal injection. After each adjustment of the gas injection amount, adjust the coal injection amount accordingly 0.5-1.0 hours later. When the gas injection amount increases to a higher level (50-100Nm 3 / t), for every additional 20Nm 3 / tGas injection volume Theoretical combustion temperature drops by 60-70℃. Theoretical combustion temperature rises by 30℃ for every 1% increase in oxygen enrichment rate. Increase oxygen enrichment rate and take appropriate measures to increase wind temperature and reduce blast humidity to control the theoretical combustion temperature at a level not less than 1980℃. If it is less than 1980℃, increase oxygen by 1000-2000Nm 3 / h. When the gas injection volume increases to 60Nm 3 / t or more, reduce the air volume by 300-500Nm 3 / min, the oxygen enrichment rate is increased to 7-10%, and the gas volume in the furnace is controlled to be no higher than 100-130Nm per ton of iron compared with the original value when coal is injected alone. 3 / t. Every 100Nm reduction in wind speed 3 / min increases by 1000Nm 3 / h oxygen. Bosh gas volume increases by 140Nm 3 / min, the top pressure increases by 5KPa, making the total pressure difference of the blast furnace ≯180-190KPa. By taking the operation of controlling the lower theoretical combustion temperature and the lower amount of furnace gas, the increase in the total pressure difference of the blast furnace can be reduced and the air permeability can be improved. Depending on the changes in the blast furnace gas flow distribution and the heat load of the furnace body, the upper distribution mode can be adjusted to appropriately loosen the edge airflow to stabilize the heat load of the furnace body and the gas utilization rate. If the gas injection volume reaches 80-100Nm 3 / t, when the material speed is faster, the furnace temperature decreases, and the coke ratio increases, the coal ratio should be appropriately increased and the gas fuel injection amount should be reduced.

[0067] The calculation of direct CO2 emissions from blast furnaces does not consider changes in other energy consumption of the entire blast furnace system. Only the direct CO2 emissions generated by the complete combustion of blast furnace gas supplied to gas users by the blast furnace itself are calculated, which is equal to (CO+CO2)Nm of blast furnace gas (wet basis). 3 / t*1.429kg / Nm 3 (Unit: kgCO2 / t iron).

[0068] The technical content and specific technical solutions of this application are substantially different from those of existing related patents.

[0069] Compared with the prior art 1, the present application is substantially different in the structural form of the gas blowing from the air port and the requirements for the location of the nozzle in the prior art 1, and the gas types are limited to LNG, LPG, and COG, which are completely different from the gas sources and components of the present application.

[0070] The technical solution of prior art 2 is completely different from that of the present application.

[0071] The spraying method and spraying mechanism of the prior art 3 are completely different from the technical solution of the present application.

[0072] The natural gas injection method and nozzle design of the prior art 4 are completely different from the technical solution of the present application.

[0073] Compared with the prior art 5, the gas and coal powder injection method in the prior art 5 is completely different from the technical solution of the present application.

[0074] The technical solution of prior art 6 is to directly mix coke oven gas and pulverized coal and spray them into the blast furnace, which is completely different from the technical solution of using coke oven gas and pulverized coal in the present application.

[0075] Compared with the present application, the technical solution of prior art 7 is to directly mix the coke oven gas and converter gas after removing CO2, and spray them into the middle of the blast furnace body, which is completely different from the technical solution of using coke oven gas and converter gas in the present application.

[0076] Compared with the present application, the technical solution of prior art 8 is to spray coke oven gas and pulverized coal into the blast furnace tuyere together through a sleeve-type spray gun, which is substantially different from the technical solution of using coke oven gas and pulverized coal in the present application.

[0077] Compared with the present application, the prior art 9 uses coke oven gas and blast furnace gas to extract H2 and CO, and then mixes and sprays them into the blast furnace. This is substantially different from the process of using coke oven gas and converter gas and synthesizing methanogens in the present application.

[0078] Compared with the present application, the prior art 10 is a method of producing natural gas by simply methanating coke oven gas, which is substantially different from the technical content of the present application of using coke oven gas and converter gas for methanation.

[0079] Similarly, compared with the present application, the prior art 11 uses coke oven gas and blast furnace gas to extract H2 and CO, CO2 respectively, and then mixes them as gas raw materials for synthesizing methanol. This is substantially different from the technical content of the present application that uses H2 in coke oven gas and converter gas for methanogenic synthesis.

[0080] That is, compared with the prior art, this application:

[0081] First, the types of gases used are different. This application uses coke oven gas and converter gas as raw materials for producing methane.

[0082] Second, the process routes are different. In this application, hydrogen is extracted from coke oven gas, then mixed with converter gas for methanogenic synthesis, and then the methane is injected into the blast furnace, rather than directly injecting coke oven gas or a mixture of coke oven gas and coal powder into the blast furnace. In addition, in this application, the CH4-rich tail gas after hydrogen extraction from coke oven gas is also mixed with the methanogenic product gas in a suitable proportion before being injected into the blast furnace.

[0083] Third, the method of injecting gas into the blast furnace is different. The present application injects CH4-containing gas by using a gas main pipe-branch pipe-tuyere water jacket built-in nozzle equipment system and mechanism to inject into the blast furnace tuyere channel to mix CH4 with hot air for combustion. The built-in nozzle of the tuyere water jacket is only set in the rear water cavity of the tuyere and does not have any impact on the waterway and water flow in the front cavity of the tuyere.

[0084] Fourth, the operation methods of injecting pulverized coal and CH4-rich gas in blast furnace are different. The present application uses two independent injection systems and independent tuyere injection mechanisms to control the injection separately. The two do not interfere with or affect each other. Each tuyere can inject one fuel alone or two fuels at the same time, and the injection amounts of each can be jointly adjusted according to the requirements of the blast furnace smelting process.

[0085] This application also describes in detail the smelting operation method of simultaneously injecting pulverized coal and CH4-rich gas into a blast furnace, which has no similar technical application content in the prior art.

[0086] further,

[0087] Based on the coke oven gas, converter gas and existing blast furnace production conditions of a steel plant, the implementation method of this technical solution is specifically described. The mixed gas containing CH4, H2 and CO is prepared by the above-mentioned steps 1 and 2, and then injected into the blast furnace to replace coal powder or part of the coke to reduce the CO2 emission of the blast furnace.

[0088] The composition of the steel plant coke oven gas and converter gas used to prepare the mixed gas is shown in Table 1, and the composition of the tail gas after hydrogen is extracted from the coke oven gas by pressure swing adsorption and the tail gas after CO2 is removed by chemical method are shown in Table 2 and Table 3 respectively. The composition of the gas obtained by hydrogenation and methanation of converter gas is shown in Table 4. The two gases in Table 3 and Table 4 are mixed in different proportions to obtain a mixed gas for blast furnace injection.

[0089] Table 1: Chemical composition of coke oven gas and converter gas, %

[0090] Gas source <![CDATA[CO2]]> CO <![CDATA[H2]]> <![CDATA[CH4]]> <![CDATA[N2]]> <![CDATA[O2]]> Cm Coke oven gas 1.5～3.5 5～10 53～60 22～25 4～6 0.6 1.5～3 Converter gas 15～20 57～65 <1.5 0 12～20 <2.0 0

[0091] Table 2: Composition of desorbed gas (tail gas) after hydrogen stripping from coke oven gas, %

[0092] <![CDATA[H2]]> <![CDATA[O2]]> <![CDATA[N2]]> <![CDATA[CH4]]> CO <![CDATA[CO2]]> Cm 20～22 1.0～1.1 12～13 38～40 12.5～13.0 8.5～9.0 3.5～3.8

[0093] Table 3: Composition of tail gas after hydrogen extraction from coke oven gas and removal of CO2, %

[0094] <![CDATA[H2]]> <![CDATA[O2]]> <![CDATA[N2]]> <![CDATA[CH4]]> CO <![CDATA[CO2]]> Cm 20-22.8 1.0 13～15 38～39 21～22.0 0.8 3.4

[0095] Table 4: Composition of converter gas after methanation reforming, %

[0096]

[0097] This embodiment takes the mixing of the two gases at a ratio of 1:1 to 1:3 as an example, focusing on the operation method of injecting mixed gas into a blast furnace and the effect of reducing the coal injection ratio and reducing CO2 emissions. The gas composition after the two gases are mixed at different ratios is shown in Table 5.

[0098] Table 5: Gas composition of two gases mixed in different proportions, %; (converter gas methanation gas: coke oven gas after hydrogen stripping and decarbonization, volume ratio)

[0099] Gas ratio <![CDATA[H2]]> <![CDATA[O2]]> <![CDATA[N2]]> <![CDATA[CH4]]> CO <![CDATA[CO2]]> Cm 1:1 11.0 0.5 14.5 61.5 10.5 0.4 1.6 1:2 7.3 0.3 14.7 69.3 7.0 0.3 1.1 1:3 5.5 0.3 14.7 73.3 5.3 0.2 0.7

[0100] The following are more specific examples.

[0101] Embodiment 1:

[0102] Blast furnace (content 4800-5000m 3 ) Stop the wind, replace all the tuyere (38-40) with the tuyere for spraying gas fuel as described in this application, and connect the connecting pipe (a section of hard pipe and a section of soft pipe) of each tuyere for spraying gas fuel to the corresponding delivery branch pipe arranged above the tuyere platform. Install the straight blowing pipe and insert the coal gun. After the blast furnace is supplied with air, nitrogen is introduced into the pipeline for spraying gas fuel, and air or nitrogen is introduced into the coal injection pipeline, and a certain flow rate is maintained, and the outlet pressure exceeds the blast pressure by more than 0.1MPa. The blast furnace restores the air volume to 3000Nm 3 / min, and when the furnace top pressure is 0.1MPa, pulverized coal injection is started until the blast furnace resumes normal production. 3 / min, coal ratio 180kg / t), the furnace condition is running smoothly and steadily, and the furnace heat is normal. At this time, the blast furnace is still only injecting pulverized coal. When the gas fuel injection system equipment and the two gases to be injected have sufficient reserves, the mixed gas can be started to be injected into the blast furnace. The gas compressor works normally, with an outlet pressure of 0.8-1.0MPa, and the flow regulating valves of the 2-way gas pipelines are opened according to the set mixing ratio of the two gases (for example 1:1) to allow the mixed gas to reach the mixed gas injection station. First open the shut-off valve and regulating valve on the small flow main pipe, and then open half of the branch pipe shut-off valves, and inject the mixed gas into 50% of the tuyere of the blast furnace. The total gas injection volume is controlled at 30Nm 3 / t or less. According to 1.1-1.3Nm 3 The principle of replacing 1kg of coal powder with gas is to reduce the amount of coal injection, and after the blast furnace temperature (molten iron temperature) is kept stable for at least 1 hour, the injection amount of the mixed gas can be increased. Open the shut-off valve and regulating valve on the large-flow gas pipeline, and then open the other half of the branch pipe shut-off valves to inject the mixed gas into all the tuyere of the blast furnace. When the mixed gas injection amount is gradually increased to 50Nm 3 / t or above, according to the calculated theoretical combustion temperature, the change of the value of the furnace gas volume, and the comprehensive observation of the blast furnace pressure difference, permeability index, furnace heat trend, etc., the blast parameters and coal injection amount are adjusted, that is, the blast volume is reduced by 100-200Nm 3 / min, the oxygen enrichment rate is increased to about 6%, according to 1.2-1.4Nm 3 The replacement principle of gas replacing 1kg of coal powder is to reduce the amount of coal injection, control the theoretical combustion temperature to be no less than 2050℃, and the amount of gas in the furnace is <1320Nm 3 / t, blast furnace pressure difference <180KPa, molten iron temperature stabilized at 1500℃ after 4-6 hours. At this time, the amount of coal injection in the blast furnace is reduced by about 40kg / t compared with the case of only coal injection, and the coke ratio remains at the original level. Due to the reduction in the volume of CO+CO2 per ton of iron generated by the blast furnace top gas, the direct CO2 emissions generated by the blast furnace gas are reduced by about 8-10kg / t.

[0103] If the 50Nm is maintained 3 / t of mixed gas injection volume remains unchanged, and the mixing ratio of the two gases is adjusted, for example, from 1:1 to 1:2 or 1:3. The operation of blast furnace mixed gas injection and the method of blast furnace production control operation are similar to the method described above, and the basic principles and requirements of the operation are the same. However, due to the change in the composition of the mixed gas and the increase in the CH4 content, the theoretical combustion temperature in front of the tuyere decreases and the amount of furnace gas increases due to the increase in the amount of CH4 decomposition and combustion in front of the blast furnace tuyere. Therefore, it is necessary to take appropriate measures such as increasing the oxygen enrichment rate and reducing the blast humidity. With the adjustment of the ratio of the two gases and the increase in the CH4 content, the heat release of gas combustion increases, the ability to replace coal powder increases, and the coal ratio is further reduced. The total volume fraction of CO and CO2 in the top gas decreases, and the direct CO2 emissions of the blast furnace are reduced.

[0104] The control range of blast furnace operating parameters in Example 1 and the effects of reducing the coal ratio and reducing direct CO2 emissions are shown in Table 6.

[0105] Embodiment 2:

[0106] This embodiment specifically describes a method for adjusting the furnace conditions of a blast furnace to increase the amount of mixed gas injection and further reduce the amount of coal injection under the condition of a certain mixing ratio of the two gases. The ratio of the two gases in the mixed gas is set to 1:3. When the mixed gas injection amount is increased from 50Nm 3 / t increased to 70Nm 3 / t or 90Nm 3 / t, the blast volume is reduced by 300-500Nm compared with the base period (only coal injection). 3 / min, the oxygen enrichment rate is increased to 7-10% to suppress the significant decrease in theoretical combustion temperature and the significant increase in the amount of furnace gas. When the mixed gas injection volume reaches 90-100Nm 3 / t, the reduction of coal injection volume should not be too large to prevent the furnace temperature from falling and the coke ratio from increasing significantly. Through the comprehensive adjustment of air volume, oxygen enrichment rate, gas injection volume, and coal powder injection volume, the gas volume of the furnace belly per ton of iron can be controlled at 1400Nm 3 / t or less, the theoretical combustion temperature is not less than 1980℃, and the blast furnace pressure difference is <190KPa. The charge descent speed and molten iron temperature are controlled by adjusting the hourly coal injection rate to prevent insufficient furnace temperature due to high oxygen enrichment rate.

[0107] When the injection volume of the mixed gas increases to 70Nm 3 / t or 90Nm 3 / t, the coal injection ratio is reduced to about 100kg / t, and the total solid fuel ratio (coke + coal powder) of the blast furnace is reduced by 65-75kg / t. Since the mixed gas is rich in CH4 and hydrogen, the coal ratio is greatly reduced, the carbon consumption of the blast furnace and the tons of iron generated by the top gas CO+CO2 are reduced, and the direct CO2 emissions of the blast furnace gas are reduced by 25-35kg / t. The control range of the blast furnace operating parameters of Example 2 and the effects of reducing the coal ratio and reducing the direct CO2 emissions are shown in Table 7.

[0108] Therefore, the present invention utilizes the byproduct coal gas of the steel plant to prepare the coal gas rich in CH4, and injects it into the blast furnace to replace the coal powder or part of the coke in the ironmaking method, utilizes the converter gas methanation process and the smelting method of simultaneously injecting coal gas and coal powder into the blast furnace, and the converter gas is hydrogenated and catalytically reacted in the methanation conversion system to synthesize methane (CH4), and the required hydrogen comes from the coke oven gas; the prepared methane is sprayed into the blast furnace from a tuyere mechanism for injecting gas fuel through a pressurization and injection system, and mixed with oxygen-rich hot air before the tuyere for combustion. By controlling the blast conditions of the blast furnace and adjusting the injection amount of coal gas and coal powder per ton of iron, the theoretical combustion temperature of the blast furnace, the amount of coal gas per ton of iron in the furnace and the coke ratio are maintained within an appropriate range. By minimizing the consumption of coal powder or coke, the amount of CO+CO2 per ton of iron in the blast furnace top gas is reduced to the minimum level, thereby reducing the CO2 emissions generated by the blast furnace gas user in the process of using it as a gas combustion.

[0109]

Claims

1. A method for reducing CO2 emissions in a blast furnace ironmaking process, characterized in that: The steps include: (1). Hydrogen is produced using coke oven gas as the raw material, and CO2 is removed from the tail gas to obtain methane-rich gas; The hydrogen is produced by purifying coke oven gas to meet the standards and then entering a pressure swing adsorption hydrogen extraction system to extract hydrogen. The purification includes the removal of benzene, naphthalene, tar and sulfur. The removal condition is that naphthalene is reduced to 50 mg / Nm 3 Below, tar drops to 10mg / Nm 3 Below, and the organic sulfur in coke oven gas is reduced to 10mg / Nm 3 Below, the olefin component is reduced to <0.5%; the hydrogen pressure of the obtained product is ≥ 0.8MPa; (2) Using converter gas as a gas source, the hydrogen obtained in step (1) is hydrogenated and converted into methane to obtain a gas containing a high concentration of methane; When the converter gas is hydrogenated to synthesize methane, the converter gas is mixed with the produced hydrogen at a molar ratio of (CO+CO2) / H2 of 2:7.2 to 2:7.6 as the raw gas for the methanation reaction; and water vapor is added at a water / gas ratio of 2-3% by volume; (3) The methane-rich gas obtained in step (1) is used as the tail gas after the treatment of coke oven gas, and the gas containing high concentration of methane obtained in step (2) is used as the methanogenic product gas, and the mixture is mixed in a volume ratio of methanogenic product gas: tail gas after the treatment of coke oven gas = (1-3): 1 to obtain a mixed gas containing methane, hydrogen and CO; (4) The mixed gas obtained in step (3) is injected into the blast furnace through the injection system to replace coal powder or part of the coke.

2. The method for reducing CO2 emissions in a blast furnace ironmaking process according to claim 1, characterized in that: In step (1), the CO2 is removed by the alcohol amine method; after the CO2 is removed, the CO volume concentration is 21-22%.

3. The method for reducing CO2 emissions in a blast furnace ironmaking process according to claim 1, characterized in that: A 2-3 stage series fixed bed reactor is used to carry out hydrogenation and methanation of converter gas.

4. The method for reducing CO2 emissions in a blast furnace ironmaking process according to claim 1, characterized in that: The medium-pressure superheated steam generated during the methanation reaction is used as a heat source for heating the regeneration towers of various adsorbents and catalysts in the coke oven gas pressure swing adsorption hydrogen extraction system and the converter gas methanation synthesis system.

5. The method for reducing CO2 emissions in a blast furnace ironmaking process according to claim 1, characterized in that: The mixed gas is injected from the blast furnace tuyere, and the outlet position of the nozzle port in the blast furnace tuyere is set downstream of the pulverized coal injection gun port, and the distance between the two is controlled at 200-250mm.

6. The method for reducing CO2 emissions in a blast furnace ironmaking process according to claim 1 or 5, characterized in that: After the blast furnace starts to supply air, purge gas is introduced into the inner tube of the coal gun and the gas injection pipeline through the pulverized coal injection system and the mixed gas injection system respectively to prevent the hot air from flowing back and cool the steel pipe; After the blast furnace starts to inject fuel, coal injection and mixed gas injection are started successively. The mixed gas is injected at a speed of <10000Nm 3 / h low flow rate spraying; After the blast furnace returns to normal planned blast parameters and furnace conditions, priority will be given to increasing the amount of pulverized coal injection, and the amount of mixed gas injection should be >10000Nm 3 / h flow rate spray; When the pulverized coal injection volume reaches an acceptable level for the blast furnace and the furnace conditions, furnace temperature, and airflow distribution are normal and stable, continue to increase the mixed gas injection volume and reduce the pulverized coal injection volume; the mixed gas injection volume <50Nm 3 / t, press 1.1-1.3Nm 3 The principle of using mixed gas to replace 1kg of coal powder is to reduce the amount of coal injection; the injection amount of mixed gas is 50-100Nm 3 / t, press 1.3-1.5Nm 3 The principle of using mixed gas to replace 1kg of coal powder is used to reduce the amount of coal injection.

7. A tuyere blowing structure for implementing the method described in any one of claims 1 to 6, comprising a blast furnace tuyere and a straight blowing pipe matching the blast furnace tuyere, characterized in that: It comprises a nozzle for spraying the mixed gas, a part of which is buried in the rear water cavity of the blast furnace tuyere, and an air inlet end is used to connect to an external mixed gas source pipeline; a port of the nozzle jet end is flush with the inner wall of the straight blowing pipe, and a pipe opening of the nozzle air inlet end forms an angle of 35-40° with the center line of the blast furnace tuyere.

8. The tuyere blowing structure according to claim 7, characterized in that: The blast furnace tuyere is a cross-flow tuyere.

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