Direct reduction system for reducing gas with high hydrogen-carbon ratio

Abstract

The utility model discloses a high-hydrogen-carbon-ratio direct reduction system for reducing gas. The high-hydrogen-carbon-ratio direct reduction system comprises a shaft furnace reactor, a top gas treatment system, a process gas compressor, a CO2 removal system, a humidifier, a heater, an oxygen spraying system, a hydrogen pipeline and a nitrogen pipeline, a furnace top gas outlet of the shaft furnace reactor is sequentially communicated with the furnace top gas treatment system, the process gas compressor, the CO2 removal system and the humidifier, an outlet of the humidifier is communicated with an inlet of the heater through a reducing gas pipeline, an outlet of the heater is communicated with a reducing gas inlet of the shaft furnace reactor through a mixed gas pipeline, and the oxygen spraying system is communicated with the mixed gas pipeline; and the rear end of the hydrogen pipeline is communicated with an inlet of the hydrogen spraying gun. According to the system, the proportion of reducing gas hydrogen in the process of producing direct reduced iron by coke oven gas is increased, pellet reduction expansion is reduced, DRI quality is improved, meanwhile, the direct reduction production efficiency of the reduction shaft furnace is improved, the furnace top temperature is reduced, and energy consumption is reduced.

Description

Technical Field

[0001] This utility model relates to a direct reduction system for a vertical shaft furnace, and more particularly to a direct reduction system for reducing gas with a high hydrogen-to-carbon ratio. Background Technology

[0002] Hydrogen has a thermal conductivity 7 to 10 times greater than other gases, and its density and viscosity are both low, which accelerates heat exchange between gases and solids, thus improving the thermal energy utilization rate in the iron ore reduction process. H2 is a highly efficient reducing agent; its diffusion rate is 3.7 times that of CO, and the diffusion rate of its reduction product, H2O, is 1.6 times that of CO2. H2 can reach the reaction interface through the fine pores of the ore faster than CO, and the H2O generated after reduction also diffuses through the product layer faster than CO2. H2 not only has a reducing effect itself but also catalyzes the reduction of CO.

[0003] Extensive production practice has shown that increasing the H / C ratio in the reducing atmosphere during direct reduction in a shaft furnace not only reduces environmental impact but also accelerates the reduction reaction and reduces pellet expansion. Currently, the production of direct reduced iron using all hydrogen is limited by the scale and cost of hydrogen production, making it difficult to achieve in the short term. Internationally, the mainstream method is to use natural gas for direct reduced iron production, where the H / C ratio after reforming can reach up to 5:1. Due to natural gas scarcity in my country, some steel mills have pioneered the industrial-scale production of direct reduced iron using coke oven gas. In the coke oven gas direct reduced iron production process, after in-situ reforming of the coke oven gas, the H / C ratio can reach up to 8:1, still some distance from pure hydrogen direct reduced iron. How to further increase the hydrogen-to-carbon ratio of the reducing gas in the direct reduction system, bringing it closer to the process state of 100% hydrogen reduction, has become a challenge for direct reduced iron researchers. Utility Model Content

[0004] The technical problem to be solved by this invention is to provide a direct reduction system for reducing gas with a high hydrogen-to-carbon ratio.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: it includes a vertical shaft furnace reactor, a furnace top gas treatment system, a process gas compressor, a CO2 removal system, a humidifier, a heater, an oxygen injection system, a hydrogen pipeline, and a nitrogen pipeline; the furnace top gas outlet of the vertical shaft furnace reactor is sequentially connected to the furnace top gas treatment system, the process gas compressor, the CO2 removal system, and the humidifier; the outlet of the humidifier is connected to the inlet of the heater through a reducing gas pipeline; the outlet of the heater is connected to the reducing gas inlet of the vertical shaft furnace reactor through a mixed gas pipeline; the oxygen injection system is connected to the mixed gas pipeline; the rear end of the hydrogen pipeline is connected to the inlet of the hydrogen injection gun, and the nozzle of the hydrogen injection gun extends into the reducing gas pipeline between the humidifier and the heater; the hydrogen pipeline is sequentially equipped with a #1 check valve, a #1 shut-off valve, a #2 shut-off valve, and a #2 check valve from front to back; the nitrogen pipeline is sequentially equipped with a #4 shut-off valve and a #3 check valve from front to back, and the rear end of the nitrogen pipeline is connected to the hydrogen pipeline between the #1 shut-off valve and the #2 shut-off valve.

[0006] Furthermore, the hydrogen pipeline is also equipped with a No. 1 orifice plate flow meter and a No. 1 Y-type filter at the front end of the No. 1 check valve.

[0007] Furthermore, the hydrogen pipeline is also equipped with a flow regulating valve and a vent pipe between the 2# shut-off valve and the 2# check valve, and the vent pipe is equipped with a vent valve.

[0008] Furthermore, the nitrogen pipeline is equipped with a flow regulating valve, a Y-type filter, and an orifice plate flow meter at the front end of the shut-off valve #4.

[0009] Furthermore, the hydrogen pipeline is equipped with a 3# shut-off valve at the rear end of the 2# check valve; a bypass pipe is also provided, one end of which is connected to the hydrogen pipeline at the front end of the 1# check valve, and the other end is connected to the hydrogen pipeline between the 2# check valve and the 3# shut-off valve, and a bypass valve is provided on the bypass pipe.

[0010] The beneficial effects of adopting the above technical solution are as follows: In the coke oven gas production process, coke oven gas is used as the main raw material gas, supplemented by a certain proportion of pure hydrogen as the reducing gas, with high-grade pellets as the raw material; by increasing the proportion of hydrogen in the reducing gas during the direct reduced iron production process from coke oven gas, the reduction expansion of pellets is reduced, the DRI quality is improved, and the direct reduction production efficiency of the reduction shaft furnace is increased, the furnace top temperature is reduced, and energy consumption is reduced. In this invention, the hydrogen pipeline is connected to the nitrogen pipeline to achieve nitrogen purging. In emergency or maintenance situations, hydrogen injection is stopped, and nitrogen injection is provided to remove hydrogen from the system, ensuring system safety. Attached Figure Description

[0011] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0012] Figure 1 This is a schematic diagram of the structure of this utility model;

[0013] Figure 2 This is a schematic diagram of the structure of the hydrogen pipeline and nitrogen pipeline described in this utility model.

[0014] In the diagram: 1. Hydrogen pipeline; 2. Orifice plate flow meter #1; 3. Y-type filter #1; 4. Check valve #1; 5. Shut-off valve #1; 6. Shut-off valve #2; 7. Bypass valve; 8. Flow regulating valve #1; 9. Vent valve; 10. Check valve #2; 11. Shut-off valve #3; 12. Hydrogen injection gun; 13. Nitrogen pipeline; 14. Flow regulating valve #2; 15. Y-type filter #2; 16. Orifice plate flow meter #2; 17. Shut-off valve #4; 18. Check valve #3; 19. Reducing gas pipeline; 20. Heater; 21. Mixed gas pipeline. Detailed Implementation

[0015] Figure 1 , Figure 2 As shown, this direct reduction system for high hydrogen-to-carbon ratio reducing gas includes a vertical shaft furnace reactor, a top gas treatment system, a process gas compressor, a CO2 removal system, a humidifier, a heater, an oxygen injection system, a coke oven gas compressor, a hydrogen pipeline (1), and a nitrogen pipeline 13. The top gas outlet of the vertical shaft furnace reactor is sequentially connected to the top gas treatment system, the process gas compressor, the CO2 removal system, and the humidifier. The outlet of the humidifier is connected to the inlet of the heater 20 via the reducing gas pipeline 19. The outlet of the heater 20 is connected to the reducing gas inlet of the vertical shaft furnace reactor via the mixed gas pipeline 21. The oxygen injection system is connected to the mixed gas pipeline 21. The coke oven gas pipeline is connected to the coke oven gas inlet of the vertical shaft furnace reactor via the coke oven gas compressor.

[0016] Figure 1 , Figure 2 As shown, in this direct reduction system with a high hydrogen-to-carbon ratio reducing gas, hydrogen flows from front to back in hydrogen pipeline 1, and nitrogen flows from front to back in nitrogen pipeline 13. Hydrogen pipeline 1 is equipped with, from front to back, a #1 orifice plate flowmeter 2, a #1 Y-type filter 3, a #1 check valve 4, a #1 shut-off valve 5, a #2 shut-off valve 6, a #1 flow regulating valve 8, a vent valve 9, a #2 check valve 10, and a #3 shut-off valve 11. The rear end of hydrogen pipeline 1 is connected to the inlet of hydrogen injection gun 12, and the nozzle of hydrogen injection gun 12 extends into the reducing gas pipeline 19 between the humidifier and the heater 20. The injection angle of hydrogen injection gun 12 into the reducing gas pipeline 19 is 15° to 30°, following the direction of the reducing gas flow. The hydrogen pipeline 1 is also equipped with a bypass pipe. One end of the bypass pipe is connected to the hydrogen pipeline 1 between the #1 Y-type filter 3 and the #1 check valve 4, and the other end is connected to the hydrogen pipeline 1 between the #2 check valve 10 and the #3 shut-off valve 11. A bypass valve 7 is provided on the bypass pipe.

[0017] Figure 1 , Figure 2 As shown, in this direct reduction system with a high hydrogen-to-carbon ratio reducing gas, the nitrogen pipeline 13 is provided with, from front to back, a nitrogen pipeline 13, a flow regulating valve 14 (2#), a Y-type filter 15 (2#), an orifice plate flow meter 16 (2#), a shut-off valve 17 (4#), and a check valve 18 (3#); the rear end of the nitrogen pipeline 13 is connected to the hydrogen pipeline 1 between the shut-off valve 5 (1#) and the shut-off valve 6 (2#).

[0018] Figure 1 , Figure 2 As shown, in this direct reduction system for a high hydrogen-to-carbon ratio reducing gas, the front end of hydrogen pipeline 1 is connected to a hydrogen supply source. The hydrogen supply source includes a water electrolysis hydrogen production system, a hydrogen compressor, and a high-pressure nitrogen storage tank. The water electrolysis hydrogen production system supplies high-pressure nitrogen to the high-pressure nitrogen storage tank via the hydrogen compressor. The outlet of the high-pressure nitrogen storage tank is connected to hydrogen pipeline 1. The water electrolysis hydrogen production system uses alkaline water for electrolysis hydrogen production, and the power source can be wind power and / or photovoltaic power generation.

[0019] Figure 1 , Figure 2 As shown, this direct reduction system with a high hydrogen-to-carbon ratio of reducing gas uses coke oven gas as the main raw material during the coke oven gas production process, and injects a certain proportion of pure hydrogen as the auxiliary reducing gas. High-grade pellets are used as raw materials, and a vertical shaft furnace reactor is used as the main reactor.

[0020] After coke oven gas undergoes in-situ reforming in a vertical shaft furnace reactor, the H / C ratio in the gas can reach up to 8:1. By injecting a certain proportion of hydrogen into the original reducing gas, the proportion of hydrogen in the loop is increased, and the H / C ratio in the reducing gas can reach up to 9:1 or even higher. This accelerates the reduction reaction process in the vertical shaft furnace reactor, improves production efficiency, and also lays the foundation for the future realization of direct reduction in a fully hydrogen-rich vertical shaft furnace.

[0021] The reduction loop consists of a top gas treatment system, a process gas compressor, a CO2 removal system, a humidifier, a heater, etc., which treats the top gas generated by the vertical furnace reactor through heat exchange, cooling, dust removal, and water removal, and then recycles it.

[0022] The oxygen injection system is used to inject a certain proportion of pure oxygen. Through partial combustion and pre-reforming reaction, it increases the temperature and composition of the reducing gas to meet the heat level and temperature required for the reduction and reforming reactions in the vertical shaft furnace.

[0023] Coke oven gas is supplied to the lower part of the vertical shaft furnace reactor via a coke oven gas compressor to replenish the reducing gas required in the entire loop. This supply of coke oven gas to the lower part of the vertical shaft furnace serves two purposes: firstly, it further decomposes impurities such as tar and BTX in the coke oven gas, achieving secondary purification and reducing the number of valves in the process pipelines; secondly, it facilitates the final carburizing and initial cooling of the DRI process.

[0024] Green electricity generated by wind power or photovoltaic power can be generated by one of these methods or a combination of both, in order to improve the stability of the green electricity supply system and reduce the cost of hydrogen production by water electrolysis. Hydrogen is produced by electrolyzing alkaline water. The produced hydrogen is pressurized by a hydrogen compressor, stored in a high-pressure hydrogen storage tank, and then injected into the reducing gas pipeline after depressurization.

[0025] The hydrogen injection system consists of a hydrogen pipeline and shut-off valves, flow regulating valves, check valves, venting valves, and measuring instruments. Hydrogen is injected into the reducing gas delivery pipeline through automatic control. The medium in the reducing gas delivery pipeline is vertical furnace top gas and coke oven gas. The injected hydrogen is mixed with the reducing gas in the delivery pipeline, heated by a heater, and then injected into the vertical furnace reactor to participate in the reduction reaction.

[0026] For safety reasons, a nitrogen pipeline is installed in the hydrogen injection system as a purging pipeline. In case of emergency or maintenance, hydrogen injection is stopped and nitrogen is injected to remove hydrogen from the system and ensure system safety.

[0027] Example: The direct reduction system for high hydrogen-to-carbon ratio reducing gas and its production process are described below.

[0028] (1) Green electricity generated by wind power or photovoltaic power generation can be generated by one of these methods or a combination of both, in order to improve the stability of the green electricity supply in the system. Hydrogen is produced by electrolyzing alkaline water. The generated hydrogen is pressurized to 15-20 MPa by a compressor, stored in a high-pressure hydrogen storage tank, and then injected into the reducing gas pipeline 19 after depressurization.

[0029] (2) The top gas of the vertical furnace reactor is heat exchanged, cooled, dust removed and water removed by the top gas treatment system, and then pressurized to 0.7-0.8 MPa by the process gas compressor. After passing through the CO2 removal system, the carbon dioxide in the loop gas is reduced, the reduction performance is improved and the oxidation degree is reduced. Then it is humidified by the humidifier to meet the carburization control requirements in the vertical furnace reactor.

[0030] (3) The humidified process gas is mixed with the injected hydrogen and then enters the heater 20 for heating. The temperature of the mixed gas reaches 950°C. After that, oxygen is injected through the oxygen injection system to form partial combustion with the mixed gas. After partial combustion, the temperature of the mixed gas is increased to more than 1000°C, which meets the temperature and heat level required for the reduction reaction in the vertical furnace reactor.

[0031] (4) The mixed gas is transported through the mixed gas pipeline 21 and injected into the middle of the vertical furnace reactor to carry out a reduction reaction with the pellets; the hydrogen injection must be injected into the system before the reducing gas is heated in order to ensure the temperature level of the mixed gas entering the vertical furnace reactor.

[0032] (5) After depressurization, the hydrogen gas passes through the hydrogen pipeline 1 and passes through the No. 1 orifice plate flow meter 2, No. 1 Y-type filter 3, No. 1 check valve 4, No. 1 shut-off valve 5, No. 2 shut-off valve 6, No. 1 flow regulating valve 8, No. 2 check valve 10, and No. 3 shut-off valve 11 respectively. Then, it is injected into the reducing gas pipeline 19 through the hydrogen injection gun 12 installed on the reducing gas pipeline 19. The hydrogen injection gun 12 is installed at a position of 15° to 30° with the reducing gas pipeline 19 to reduce the resistance to entering the system. The hydrogen injection direction should be consistent with the reducing gas delivery direction.

[0033] (6) The function of the hydrogen jet gun 12 is to guide the hydrogen flow. The hydrogen jet gun 12 is a wear-resistant alloy tube with a nozzle at the end of the wear-resistant alloy tube. The hydrogen is ejected from the nozzle at high speed.

[0034] (7) The flow rate of the jet hydrogen is automatically adjusted by the No. 1 orifice plate flow meter 2 and the No. 1 flow regulating valve 8 system, and high and low pressure alarms of hydrogen are set to ensure the safety of hydrogen use.

[0035] (8) The system is equipped with a nitrogen pipeline 13 for purging and replacing system pipelines. The nitrogen pressure must be 30-50 kPa higher than the hydrogen pressure to ensure safe hydrogen use in the system. When the system is shut down for maintenance, close the #1 shut-off valve 5 to stop hydrogen injection, open the vent valve 9 to release the residual hydrogen in the corresponding pipeline, and then open the #2 flow regulating valve 14, the #4 shut-off valve 17, and the #3 check valve 18 on the nitrogen pipeline 13 in sequence to purge and replace the system with nitrogen. After the inspection is qualified, the pipelines and valves are repaired or replaced.

[0036] (9) A wall-mounted single-point toxic gas detector, model VTD110, is installed near the hydrogen injection pipeline and hydrogen storage tank for safety protection during maintenance operations and personnel inspections.

[0037] (10) In case of valve failure in the hydrogen injection system or under special circumstances, hydrogen can be injected through the bypass valve 7 to ensure that the hydrogen supply for system production is uninterrupted.

[0038] After its implementation, this direct reduction system with a high hydrogen-to-carbon ratio in the reducing gas became the highest-ratio direct reduction iron production example to date, bringing it closer to a 100% hydrogen reduction process, accelerating the reduction reaction in the reactor, and improving production efficiency. Simultaneously, the project uses green electricity generated from wind or solar power for hydrogen electrolysis, reducing carbon dioxide emissions and lowering hydrogen production costs. The produced hydrogen is used immediately, reducing the long-term storage and transportation safety risks and costs associated with hydrogen production. Furthermore, the hydrogen injection rate can be adjusted according to process and production requirements, greatly improving the system's flexibility.

Claims

1. A direct reduction system for reducing a gas having a high hydrogen to carbon ratio, characterized by: It includes a vertical shaft furnace reactor, a top gas treatment system, a process gas compressor, a CO2 removal system, a humidifier, a heater, an oxygen injection system, a hydrogen pipeline (1), and a nitrogen pipeline (13); the top gas outlet of the vertical shaft furnace reactor is sequentially connected to the top gas treatment system, the process gas compressor, the CO2 removal system, and the humidifier; the outlet of the humidifier is connected to the inlet of the heater (20) via the reducing gas pipeline (19); the outlet of the heater (20) is connected to the reducing gas inlet of the vertical shaft furnace reactor via the mixed gas pipeline (21); the oxygen injection system is connected to the mixed gas pipeline (21); the hydrogen pipeline ( The rear end of 1) is connected to the inlet of the hydrogen injection gun (12), and the nozzle of the hydrogen injection gun (12) extends into the reducing gas pipeline (19) between the humidifier and the heater (20); the hydrogen pipeline (1) is provided with a 1# check valve (4), a 1# shut-off valve (5), a 2# shut-off valve (6) and a 2# check valve (10) in sequence from front to back; the nitrogen pipeline (13) is provided with a 4# shut-off valve (17) and a 3# check valve (18) in sequence from front to back, and the rear end of the nitrogen pipeline (13) is connected to the hydrogen pipeline (1) between the 1# shut-off valve (5) and the 2# shut-off valve (6).

2. A direct reduction system for reducing a gas having a high hydrogen to carbon ratio as claimed in claim 1, characterized in that: The hydrogen pipeline (1) is also equipped with a No. 1 orifice plate flow meter (2) and a No. 1 Y-type filter (3) at the front end of the No. 1 check valve (4).

3. The direct reduction system of reduced gas with high hydrogen to carbon ratio according to claim 1, characterized in that: The hydrogen pipeline (1) is further equipped with a flow regulating valve (8) and a vent pipe between the 2# shut-off valve (6) and the 2# check valve (10), and the vent pipe is equipped with a vent valve (9).

4. The direct reduction system of reduced gas with high hydrogen to carbon ratio according to claim 1, characterized in that: The nitrogen pipeline (13) is also equipped with a flow regulating valve (14), a Y-type filter (15), and an orifice plate flow meter (16) at the front end of the shut-off valve (17) (4).

5. The direct reduction system of reduced gas with high hydrogen to carbon ratio according to any one of claims 1-4, characterized in that: The hydrogen pipeline (1) is also equipped with a 3# shut-off valve (11) at the rear end of the 2# check valve (10); a bypass pipe is also provided, one end of which is connected to the hydrogen pipeline (1) at the front end of the 1# check valve (4), and the other end is connected to the hydrogen pipeline (1) between the 2# check valve (10) and the 3# shut-off valve (11). A bypass valve (7) is provided on the bypass pipe.

Images