A systematic method for reducing carbon dioxide emissions throughout the entire steelmaking and casting process.

Abstract

This invention discloses a systematic method for reducing carbon dioxide emissions throughout the entire steelmaking and casting process, the method comprising a hydrogen injection step into a blast furnace, the hydrogen gas being supplied from a nuclear hydrogen production system, a water electrolysis hydrogen production system, and a coke oven gas-steam reforming hydrogen production system, the electricity consumed in water electrolysis hydrogen production being supplied from natural gas thermal power generation, steam residual pressure power generation, solar power generation, wind power generation, and nuclear power generation, and the combustible gas used in natural gas thermal power generation being coke oven gas, blast furnace The gas and converter gas are used. The steam used for residual steam power generation is supplied from a sintering waste heat boiler. The steam used for coke oven gas-steam reforming hydrogen production is low-pressure steam after residual steam power generation. The end products are cast steel profiles, casting materials for high-carbon spheroidal graphite cast iron profiles with a carbon content of 2-4% and a silicon content of 2-4%, and casting materials for high-carbon spheroidal graphite cast steel profiles with a carbon content of 1-2% and a silicon content of 1-1.9%. The waste from the end products is recycled and smelted in a converter or electric furnace.

Description

Technical Field

[0001] The present invention relates to steel metallurgy, and particularly to a systematic carbon dioxide reduction method in all processes of steelmaking and casting.

Background Art

[0002] As a response to global climate change, the reduction of CO2 greenhouse gas emissions and low-carbon production have become a focus of social attention. The steel industry, which consumes a very large amount of energy, is one of the industries with the highest carbon emissions among 31 categories in the manufacturing industry. In 2022, China's crude steel production reached 1.013 billion tons, ranking first in the world, and its CO2 emissions were 2.1 billion tons, accounting for about 15-17% of the total national carbon emissions. Steel production by the carbon metallurgy and blast furnace-converter process based on ore accounts for about 90%. Among them, blast furnace ironmaking is the process with the highest CO2 emissions, accounting for about 70%-90% of the total CO2 emissions in the whole steel production. By maximizing the use of hydrogen as a reducing agent and fuel in the ironmaking process, and the product of the hydrogen reaction is water, the CO2 emissions can be significantly reduced, thereby fundamentally realizing the low-carbon smelting of blast furnaces. Using green hydrogen gas for hydrogen-rich low-carbon smelting in blast furnaces has become a hot spot in the research and development of innovative technologies in the steel manufacturing process. At the same time, based on the conventional blast furnace-converter long process, the comprehensive and effective utilization of waste heat and waste energy in the whole process is further realized. In order to minimize the energy consumption of the process and achieve the purpose of further energy conservation and carbon dioxide reduction, it is also necessary to build a new optimization system. In addition, the hydrogen gas currently used in factories mainly comes from by-products separated from coke oven gas. However, in order to obtain hydrogen gas by the electrolysis method of water, a large amount of electric power is required. Therefore, in the non-carbon steel smelting process, if a process of producing sufficient hydrogen gas by using stable green energy is not introduced, the goal of carbon dioxide reduction in the whole process cannot be truly achieved. At the same time, the current perspective of carbon dioxide reduction mainly focuses on the source and process of steel production, but ignores the carbon fixation effect of end products. [Overview of the project]

[0003] To solve the above problems, the present invention provides a systematic method for reducing carbon dioxide emissions throughout the entire steelmaking and casting process, comprising a hydrogen injection step into a blast furnace. Hydrogen gas is supplied from nuclear hydrogen production systems, water electrolysis hydrogen production systems, and coke oven gas-steam reforming hydrogen production systems, and the nuclear hydrogen production system includes a nuclear power generation subsystem, a hydrogen production thermal cycle subsystem, and a hydrogen enrichment blast furnace-converter subsystem. The nuclear power generation subsystem generates electricity using a Brayton / Rankine bottoming cycle with high-temperature helium gas and also sends steam to the hydrogen production thermal cycle subsystem. Thermochemical reactions occur in the nuclear hydrogen production heating cycle system to produce hydrogen gas and oxygen gas. The hydrogen gas is heated in the nuclear heating cycle system, and the oxygen gas is released from heat in the nuclear heating cycle system. After thermal energy conversion, the high-temperature hydrogen gas and low-temperature oxygen gas are sent to the hydrogen enrichment blast reactor-converter subsystem. The electricity consumed in water electrolysis hydrogen production is supplied by natural gas-fired power plants, steam residual pressure power plants, solar power plants, wind power plants, and off-peak electricity from the power grid. The combustible gases used in natural gas-fired power plants are coke oven gas, blast furnace gas, and converter gas, and the steam used in steam residual pressure power plants is supplied from sintered waste heat boilers. The steam used in coke oven gas-steam reforming hydrogen production is low-pressure steam after residual pressure power generation. The end products are cast steel profiles, casting materials for high-carbon spheroidal graphite cast iron profiles with a carbon content of 2-4% and a silicon content of 2-4%, and casting materials for high-carbon spheroidal graphite cast steel profiles with a carbon content of 1-2% and a silicon content of 1-1.9%. This provides a systematic method for reducing carbon dioxide emissions throughout the entire steelmaking and casting process, where end-product waste is entered into a converter or electric furnace for recirculating smelting.

[0004] Furthermore, the nuclear power generation subsystem includes a reactor, a first steam turbine, a first generator, a steam generator, a first air compressor, a second steam turbine, a second generator, a condenser, a condensate pump, a low-pressure heater, a deoxygenation unit, a feedwater pump, and a high-pressure heater. High-temperature helium gas is supplied from the reactor to the first steam turbine and the hydrogen production thermal cycle subsystem. In the first steam turbine, it expands and performs work, driving the first generator to produce electricity. The first steam turbine then supplies low-pressure helium gas to the steam generator. In the steam generator, the low-pressure helium gas utilizes its thermal energy to convert industrial water into steam through the Rankine bottoming cycle. This steam is then supplied to the second steam turbine, and the low-pressure, low-temperature helium gas is compressed in the first air compressor before being reintroduced into the reactor cycle as a coolant. A portion of the steam from the second steam turbine is introduced into the hydrogen production thermal cycle subsystem. The steam expands in the second steam turbine and performs work, driving the second generator to produce electricity. The steam then enters the condenser, and the electricity generated by the second generator is input to the hydrogen production thermal cycle subsystem. The condensate discharged from the condenser passes through the condensate pump and merges with industrial wastewater supplied from the hydrogen enrichment blast furnace-converter subsystem. It then passes sequentially through the low-pressure heater, deaerator, feedwater pump, and high-pressure heater before entering the pipeline side of the steam generator. After removing oxygen and other gases from the water, it is used as feedwater for part of the steam Rankine cycle.

[0005] Furthermore, the hydrogen production thermal cycle subsystem includes a first pressure reducing valve, a second pressure reducing valve, a hydrogen / oxygen production apparatus using an iodine-sulfur cycle, a gas mixing chamber, a high-temperature low-pressure heater, and a temperature control system. The reactor sends high-temperature helium gas to the second pressure reducing valve, where it reaches the valve along with some steam from the second steam turbine. There, the pressure is simultaneously reduced to the operating pressure of the hydrogen and oxygen production unit using the iodine-sulfur cycle. The sent high-temperature helium gas and high-temperature steam jointly supply thermal energy to the hydrogen and oxygen production unit using the iodine-sulfur cycle. The high-temperature steam replenishes the steam necessary for the thermochemical reaction in the hydrogen and oxygen production unit using the iodine-sulfur cycle, and the thermochemical reaction occurs in the hydrogen and oxygen production unit using the iodine-sulfur cycle, producing high-temperature hydrogen gas. Helium gas is generated, and the generated high-temperature hydrogen gas enters the gas mixing chamber and, together with the coke oven gas and carbon monoxide generated in the hydrogen-enriched blast furnace-converter subsystem, forms a high-temperature reducing atmosphere. The high-temperature helium gas, with stable pressure and temperature, passes through the second pressure reducing valve and temperature control system, and after thermal energy exchange in the high-temperature low-pressure heater, enters the hydrogen-enriched blast furnace-converter subsystem. The high-temperature oxygen gas passes through the low-pressure heater and high-pressure heater to dissipate heat and achieve thermal energy conversion before being supplied to the hydrogen-enriched blast furnace-converter subsystem.

[0006] Furthermore, the hydrogen-enriched blast furnace-converter subsystem includes a hydrogen-enriched blast furnace, a converter, a slag waste heat recovery unit, a third generator, and a top gas purification unit, the top gas purification unit including a desulfurization tower, a collection tower, a regeneration tower, a dust collector, a top gas dechlorination / desulfurization wastewater treatment unit, a second air compressor, and a carbon dioxide storage tank. The generated high-temperature reducing atmosphere passes through the hydrogen-enriched blast furnace, where a reduction reaction occurs. The resulting molten iron enters the converter, and the low-temperature oxygen gas enters the hydrogen-enriched blast furnace and converter, where an oxidation reaction occurs to produce steel products. Simultaneously, the waste heat from the slag is utilized and passed through a slag waste heat recovery device. Using a caronar cycle power generation system, thermal energy and electrical energy are converted, driving a third generator to generate electricity, which supplies power to the furnace top gas purification device and the furnace top gas dechlorination / desulfurization wastewater treatment device. The top gas discharged from the hydrogen-enriched blast furnace passes through a dust collector and then enters a top gas purification unit. After sequentially entering the desulfurization tower, collection tower, and regeneration tower, the remaining gas components are discharged into the air. The top gas is fed into the top gas purification unit, and the blast furnace gas washing wastewater discharged from the desulfurization tower enters the condensate pump and is circulated to supply the industrial water necessary for the hydrogen and oxygen production equipment using the iodine-sulfur cycle. The carbon monoxide collected in the collection tower is sent to the gas mixing chamber and circulated to replenish the reducing atmosphere. The carbon dioxide extracted from the regeneration tower is sent to the second air compressor and the carbon dioxide storage tank.

[0007] Furthermore, the CO2 generated after the combustion of coke oven gas, blast furnace gas, and converter gas during natural gas-fired power generation is captured using carbon capture technology and then stored.

[0008] Furthermore, electricity generated from natural gas-fired power plants, steam residual pressure power plants, solar power plants, wind power plants, and nuclear power plants is integrated into the steel plant's internal power grid and then transported to water electrolysis hydrogen production equipment.

[0009] Furthermore, the steam generated in the sintered waste heat boiler is integrated into a high-pressure steam pipeline and transported to the residual pressure power generator. Furthermore, the low-pressure steam remaining after residual pressure power generation is transported via a low-pressure steam pipeline to a reactor for coke oven gas-steam reforming hydrogen production. [Effects of the Invention]

[0010] This invention maximizes the substitution of fossil fuels by injecting hydrogen gas into blast furnaces, thereby reducing the amount of carbon elements entering the steel production process from the source. By replacing carbon with hydrogen, it achieves a reduction of approximately 20% in low-carbon emissions per unit area from the source. Simultaneously, it replaces conventional building and machinery steel materials with high-carbon cast iron profiles and spheroidal graphite cast steel profiles, trapping the carbon elements that entered the steel production process within the end products. These high-carbon end products will eventually be recycled as waste iron and waste steel in electric furnaces and converters during steelmaking, but will not be emitted in the form of carbon dioxide, thereby achieving a carbon fixation rate of over 25% at the end. This invention also incorporates a nuclear hydrogen production system, primarily centered on the main line of the above process. Through nuclear hydrogen production, the carbon footprint is thoroughly eliminated from the source, and waste heat and by-products from all stages of steel production are comprehensively utilized. Sintering waste heat is used to produce steam, and the steam is simultaneously used for reformed hydrogen production and residual pressure power generation. The steam after residual pressure power generation can then be used together with coke oven gas for reformed hydrogen production, etc. This enables systematic integration and maximization of the utilization of various resources in the steel production process, thereby achieving systematic carbon dioxide reduction throughout all stages of the steel and casting process, from source to end.

[0011] In order to fully understand the purpose, features, and effects of the present invention, the concept, specific structure, and resulting technical effects will be further explained below with reference to the drawings. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a flowchart of a systematic carbon dioxide reduction method in all stages of steelmaking and casting according to the present invention. [Figure 2] Figure 2 is a flowchart of the nuclear hydrogen production system according to the method of the present invention. [Modes for carrying out the invention]

[0013] Hereinafter, several preferred embodiments of the present invention will be described with reference to the drawings of the specification in order to make the technical content of the present invention clearer and easier to understand. The present invention can be carried out in various embodiments, and the scope of protection of the present invention is not limited to the embodiments referred to herein.

[0014] As shown in Figure 1, the systematic carbon dioxide reduction method in the entire steelmaking and casting process according to the present invention mainly consists of two parts: carbon dioxide reduction from the source and carbon fixation at the end. Carbon dioxide reduction from the source means reducing the amount of carbon elements that enter the steelmaking process from the source by injecting hydrogen gas into the blast furnace in the blast furnace process, replacing carbon with hydrogen to the greatest extent possible, and using hydrogen as a reducing agent and fuel in the steelmaking process. Carbon fixation at the end means producing steel in an electric furnace and using high-carbon cast iron profiles (carbon content 2-4%) and spheroidal graphite cast steel profiles (silicon content 1-1.9% and carbon content 1-2%) as end products, replacing conventional commonly used building steel (carbon content approximately 0.2%), and fixing more carbon elements in the end products, that is, achieving the goal of low-carbon steel production through carbon fixation at the end.

[0015] Continuing to refer to Figure 1, it can be seen that in the method of the present invention, the hydrogen gas used for injecting hydrogen gas into the blast furnace mainly comes from two sources: hydroelectrolysis hydrogen production and coke oven gas-steam reforming hydrogen production. The electricity consumed in hydroelectrolysis hydrogen production may be supplied by nuclear power, natural gas thermal power, steam residual pressure power, and off-peak power from the power grid. The combustible gases used in natural gas thermal power are coke oven gas generated during the coking process in the coke oven of a steel plant, blast furnace gas generated during the ironmaking process in a blast furnace, and converter gas generated during the steelmaking process in a converter, respectively. The combustible components of coke oven gas are hydrogen gas (55%~60%), methane gas (23%~27%), and a small amount of carbon monoxide (5%~8%), the combustible component of blast furnace gas is carbon monoxide, with a content of about 25%, and the combustible component of converter gas is carbon monoxide, with a content of 60~80%. CO2 generated after the combustion of coke oven gas, blast furnace gas, and converter gas can be collected using carbon capture technology and then stored. Steam residual pressure power generation refers to the conversion of thermal energy into electrical energy by employing a back pressure unit and utilizing the pressure difference of steam. The steam used for residual pressure power generation is recovered from the high-temperature exhaust gas of the sintering process in a waste heat boiler and transported to the residual pressure power generation equipment via a high-pressure steam pipeline, where it is used to generate electricity. Coke oven gas-steam reforming hydrogen production is a process that generates hydrogen gas and carbon monoxide by reforming coke oven gas with steam, and then obtains hydrogen gas after converting and separating the carbon monoxide. Coke oven gas is a byproduct of the coking process in steel plants, but the steam may be generated directly from a waste heat boiler or from low-pressure steam after residual pressure power generation. The low-pressure steam is transported via a low-pressure steam pipeline to a reactor for coke oven gas-steam reforming hydrogen production. By combining water electrolysis hydrogen production with coke oven gas-steam reforming hydrogen production, and injecting hydrogen gas into a blast furnace, carbon emissions per ton of product can be reduced by 25% from the source.

[0016] In the actual production process, since the required amount of hydrogen injection is huge, in order to obtain hydrogen gas by electrolyzing water, it is necessary to consume a large amount of electric power. If the electric power for electrolyzing water to produce hydrogen is still supplied from coal-fired power generation, green metallurgy cannot be truly realized.

[0017] Therefore, in a further embodiment of the present invention, there is provided a nuclear hydrogen production system including a nuclear power generation subsystem, a hydrogen production heat cycle subsystem, and a hydrogen-enriched blast furnace-converter subsystem. The nuclear power generation subsystem generates electricity by a Brayton / Rankine bottoming cycle using high-temperature helium gas and sends steam to the hydrogen production heat cycle subsystem. A thermochemical reaction occurs in the nuclear hydrogen production heating cycle system to generate hydrogen gas and oxygen gas. The hydrogen gas realizes heating with thermal energy and electrical energy in the nuclear heating cycle system, and the oxygen gas releases waste heat in the nuclear heating cycle system. After realizing thermal energy conversion, the high-temperature hydrogen gas and low-temperature oxygen gas are sent into the hydrogen-enriched blast furnace-converter subsystem and used as a reducing / oxidizing atmosphere.

[0018] As shown in FIG. 2, the nuclear power generation subsystem includes a nuclear reactor 1, a first steam turbine 2, a first generator 3, a steam generator 4, a first air compressor 5, a second steam turbine 7, a second generator 8, a condenser 9, a condensate pump 10, a low-pressure heater 11, a deoxygenation device 12, a feed water pump 13, and a high-pressure heater 14.

[0019] The hydrogen production heat cycle subsystem includes a first pressure reducing valve 6, a second pressure reducing valve 15, a hydrogen / oxygen production device 16 by an iodine-sulfur cycle, a gas mixing chamber 17, a high-temperature low-pressure heater 18, and a temperature control system 19. [[ID=​The nuclear reactor 1 sends out high-temperature helium gas at a temperature of 900 to 1000 °C and a pressure of 7 to 8 MPa. All of the high-temperature helium gas piping materials adopt 310S austenitic stainless steel containing Al, and are respectively fed into the first steam turbine 2 of the nuclear power generation subsystem and the second pressure reducing valve 15 of the hydrogen production heat cycle subsystem.

[0021] A part of the high-temperature helium gas introduced into the nuclear power generation subsystem expands in the first steam turbine 2 to do work, driving the first generator 3 to generate electricity. The first steam turbine 2 sends low-pressure helium gas to the steam generator 4. The low-pressure helium gas sent out from the first steam turbine 2 is mixed with the low-pressure helium gas circulated by the hydrogen production heat cycle subsystem, and then the temperature of the low-pressure helium gas becomes 600 to 700 °C. The low-pressure helium gas uses thermal energy in the steam generator 4 to convert industrial water into steam by the Rankine bottoming cycle and send it to the second steam turbine 7, and discharges low-temperature and low-pressure helium gas at a temperature of 300 to 400 °C to the first air compressor 5. The low-pressure and low-temperature helium gas passes through the first air compressor 5, and the compressed helium gas at a temperature of 350 to 450 °C is fed into the nuclear reactor 1.

[0022] The industrial water after heat exchange with the low-pressure helium gas is sent to the steam generator 4, heated to become steam, and a part of the steam is introduced into the first pressure reducing valve 6 of the hydrogen production heat cycle subsystem by the second steam turbine 7. After depressurization, it is sent to the hydrogen and oxygen production device 16 by the iodine-sulfur cycle. The remaining steam expands in the second steam turbine 7 to do work, driving the second generator 8 to generate electricity. Then, it enters the condenser 9. The electricity generated by the second generator 8 is input into the temperature control system 19 of the hydrogen production heat cycle subsystem. The condensate sent out from the condenser 9 passes through the condensate pump 10, merges with the industrial wastewater supplied from the hydrogen-enriched blast furnace-converter subsystem, and then sequentially passes through the low-pressure heater 11, deaerator 12, feed water pump 13, and high-pressure heater 14 to enter the pipeline side of the steam generator 4 and become the feed water for the Rankine cycle.

[0023] Reactor 1 sends the remaining high-temperature helium gas to the second pressure reducing valve 15, and after depressurization, supplies the necessary thermal energy to the hydrogen and oxygen production unit 16, which operates on an iodine-sulfur cycle at an operating temperature of 800-900°C and an operating pressure of 4-5 MPa, along with the steam depressurized by the second pressure reducing valve 6. The high-temperature steam simultaneously replenishes the water necessary for the thermochemical reaction in the hydrogen and oxygen production unit 16, and a thermochemical reaction occurs in the hydrogen and oxygen production unit 16 to produce high-temperature hydrogen gas and oxygen gas. This thermochemical reaction is JPEG0007864944000001.jpg30170

[0024] Considering the problems of high temperature and acid corrosion, the hydrogen and oxygen production apparatus 16 using the iodine-sulfur cycle and its piping are both made of Al-containing 310S austenitic stainless steel. The generated high-temperature hydrogen gas enters the gas mixing chamber 17 and, together with coke oven gas and carbon monoxide generated in the top gas purification unit 24 of the hydrogen-enriched blast furnace-converter subsystem, forms a high-temperature reducing atmosphere. The high-temperature helium gas, which has passed through the second pressure reducing valve 15 and been electrically heated by the temperature control system 19, is then heated to 1000-1100°C in the high-temperature low-pressure heater 18, which employs a GH3536 nickel-based alloy, to achieve thermal energy exchange. After being heated to 950-1050°C, the low-temperature helium gas enters the hydrogen-enriched blast reactor-converter subsystem. The low-temperature helium gas, after transferring thermal energy, cools to 750-850°C and merges with the low-temperature helium gas at 300-500°C, which has lost thermal energy in the hydrogen-oxygen production unit 16 via the iodine-sulfur cycle. This ultimately forms helium gas at 600-700°C, which is recycled and enters the nuclear power generation subsystem. The high-temperature oxygen gas passes through the low-pressure heater 11 and high-pressure heater 14 to dissipate heat, achieving thermal energy conversion, and is then sent back to the hydrogen-enriched blast reactor-converter subsystem for recycling.

[0025] The hydrogen-enriched blast furnace-converter subsystem includes a hydrogen-enriched blast furnace 20, a converter 21, a slag waste heat recovery unit 22, a third generator 23, a top gas purification unit 24, a dust collector 25, a top gas dechlorination / desulfurization wastewater treatment unit 26, a second air compressor 27, and a carbon dioxide storage tank 28.

[0026] The high-temperature reducing atmosphere generated in the hydrogen production thermal cycle subsystem is blown into the lower or lower part of the furnace body of the hydrogen enrichment blast furnace 20. The gas piping and furnace airflow distribution device use GH3536 nickel-based alloy. A reduction reaction occurs in the hydrogen enrichment blast furnace 20, and the resulting molten iron enters the converter 21. Low-temperature oxygen gas enters the hydrogen enrichment blast furnace 20 and the converter 21, where an oxidation reaction occurs to produce product steel. At the same time, the waste heat from the slag is utilized and passed through the slag waste heat recovery device 22. A carrona cycle power generation system is used to convert thermal energy into electrical energy, and the electricity generated by the third generator 23 is supplied to the furnace top gas purification device 24 and the furnace top gas dechlorination / desulfurization wastewater treatment device 26.

[0027] The top gas generated after the reduction-oxidation reaction in the hydrogen-enriched blast furnace 20 passes sequentially through the dust collector 25 and the top gas purification device 24, and the remaining harmless gas components discharged thereafter enter the air. The furnace top gas is fed into the furnace top gas purification apparatus 24, which includes a desulfurization tower 241, a collection tower 242, and a regeneration tower 243. The desulfurization tower 241 is in communication with the collection tower 242, a dust collector 25, and a furnace top gas dechlorination / desulfurization wastewater treatment apparatus 26. The furnace top gas dechlorination / desulfurization wastewater treatment apparatus 26 is in communication with a condensate pump 10. The collection tower 242 is in communication with the regeneration tower 243 and a gas mixing chamber 17. The regeneration tower 243 is in communication with a second air compressor 27. After passing through the dust collector 25, the furnace top gas passes through the desulfurization tower 241 to remove harmful atmospheres such as hydrogen chloride, carbonyl sulfur, and hydrogen sulfide. The resulting furnace top gas cleaning wastewater is treated in the furnace top gas dechlorination / desulfurization wastewater treatment device 26, then enters the condensate pump 10, where it is used as industrial water for the Rankine cycle, thus achieving recycling. Meanwhile, the initially purified furnace top gas further passes through the collection tower 242 to collect carbon monoxide, which is then sent to the gas mixing chamber 17 for circulation adjustment and replenishment of the reducing atmosphere. Finally, the re-purified furnace top gas passes through the regeneration tower 243 to extract carbon dioxide. The extracted carbon dioxide is sent to the second air compressor 27, compressed, and then stored in the carbon dioxide storage tank 28 for use in other industries. Finally, the harmless furnace top gas that has been purified is discharged.

[0028] This invention maximizes the substitution of fossil fuels by injecting hydrogen gas into blast furnaces, thereby reducing the amount of carbon elements entering the steel production process from the source. By replacing carbon with hydrogen, it achieves a reduction of approximately 20% in carbon emissions per unit area from the source. Simultaneously, it replaces conventional building and machinery steel materials with high-carbon cast iron profiles and spheroidal graphite cast steel profiles, trapping the carbon elements that entered the steel production process within the end products. These high-carbon end products will eventually be recycled as waste iron and waste steel in electric furnaces and converters, but will not be emitted in the form of carbon dioxide, thereby achieving a carbon sequestration rate of over 25% per ton of product at the end. This invention simultaneously introduces a nuclear hydrogen production system, centered on the main line of the above process. Through nuclear hydrogen production, the carbon footprint is thoroughly eliminated from the source, and waste heat and by-products from all stages of steel production are comprehensively utilized. Sintering waste heat is used to produce steam, and the steam is used simultaneously for reformed hydrogen production and residual pressure power generation. The steam after residual pressure power generation can be further used with coke oven gas for reformed hydrogen production, etc. This enables systematic integration and maximization of the utilization of various resources in the steel production process. Furthermore, it proposes adopting nuclear power as the main green energy source for water electrolysis hydrogen production, specifically proposing a nuclear hydrogen production system, thereby achieving a systematic reduction of carbon dioxide in all stages of steelmaking and casting.

[0029] The above has described in detail preferred specific embodiments of the present invention. It should be understood that those skilled in the art can make various modifications and changes based on the concept of the present invention without requiring creative effort. Therefore, any technical solution obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation with the prior art should be included within the scope of protection defined by the claims.

Claims

1. A systematic method for reducing carbon dioxide emissions throughout the entire steelmaking and casting process, This includes a step of injecting hydrogen into the blast furnace, with the hydrogen gas supplied from a nuclear hydrogen production system, a water electrolysis hydrogen production system, and a coke oven gas-steam reforming hydrogen production system. The nuclear hydrogen production system includes a nuclear power generation subsystem, a hydrogen production thermal cycle subsystem, and a hydrogen enrichment blast reactor-converter subsystem. The nuclear power generation subsystem includes a reactor (1), a first steam turbine (2), a first generator (3), a steam generator (4), a first air compressor (5), a second steam turbine (7), a second generator (8), a condenser (9), a condensate pump (10), a low-pressure heater (11), a deoxygenation unit (12), a feedwater pump (13), and a high-pressure heater (14). The hydrogen production thermal cycle subsystem includes a first pressure reducing valve (6), a second pressure reducing valve (15), and an iodine-sulfur cycle. The hydrogen enrichment blast furnace-converter subsystem includes a hydrogen and oxygen production apparatus (16), a gas mixing chamber (17), a high-temperature low-pressure heater (18), and a temperature control system (19), and includes a hydrogen enrichment blast furnace (20), a converter (21), a slag waste heat recovery apparatus (22), a third generator (23), a top gas purification apparatus (24), a dust collector (25), a top gas dechlorination and desulfurization wastewater treatment apparatus (26), a second air compressor (27), and a carbon dioxide storage tank (28). The reactor (1) sends out high-temperature helium gas at a temperature of 900-1000°C and a pressure of 7-8 MPa, which is then supplied to the first steam turbine (2) of the nuclear power generation subsystem and the second pressure reducing valve (15) of the hydrogen production thermal cycle subsystem. The high-temperature helium gas expands in the first steam turbine (2) and performs work, driving the first generator (3) to generate electricity, which is then supplied to the water electrolysis hydrogen production system. The low-pressure helium gas sent out from the first steam turbine (2) and the low-pressure helium gas circulated by the hydrogen production thermal cycle subsystem are mixed, resulting in a mixture at a temperature of 600-700°C, which is then transported to the steam generator (4). In the steam generator (4), the thermal energy of the low-pressure helium gas is used to convert industrial water into steam via the Rankine bottoming cycle, which is then sent to the second steam turbine (7), and low-temperature, low-pressure helium gas at a temperature of 300-400°C is discharged to the first air compressor (5). Low-temperature helium gas passes through the first air compressor (5), and the compressed helium gas at a temperature of 350-450°C returns to the reactor (1). A portion of the steam generated in the steam generator (4) is transported to the first pressure reducing valve (6) of the hydrogen production thermal cycle subsystem, where it is depressurized and then sent to the hydrogen and oxygen production unit (16) using the iodine-sulfur cycle. The remaining steam expands in the second steam turbine (7) and performs work to drive the second generator (8) and generate electricity. Afterward, the condensate enters the condenser (9), and the electricity generated by the second generator (8) is input to the temperature control system (19) of the hydrogen production thermal cycle subsystem. The condensate discharged from the condenser (9) passes through the condensate pump (10), merges with industrial wastewater supplied from the hydrogen enrichment blast furnace-converter subsystem, and then sequentially passes through the low-pressure heater (11), deaerator (12), feedwater pump (13), and high-pressure heater (14) before entering the pipeline side of the steam generator (4), where it serves as feedwater for the Rankine cycle. The high-temperature helium gas from the reactor (1) supplied to the second pressure reducing valve (15) is depressurized and then supplied to the hydrogen and oxygen production unit (16) using the iodine-sulfur cycle. Together with the water vapor that has been depressurized by the first pressure reducing valve (6), it supplies the necessary thermal energy to the hydrogen and oxygen production unit (16) using the iodine-sulfur cycle, which operates at a temperature of 800-900°C and a pressure of 4-5 MPa. The water vapor further contributes to the thermochemical reaction in the hydrogen and oxygen production unit (16) using the iodine-sulfur cycle. It also serves to supply the necessary water. The high-temperature hydrogen gas generated in the hydrogen and oxygen production device (16) using the iodine-sulfur cycle enters the gas mixing chamber (17), where it mixes with coke oven gas and carbon monoxide generated in the top gas purification device (24) of the hydrogen-enriched blast furnace-converter subsystem to form a high-temperature reducing atmosphere. This atmosphere then enters the high-temperature low-pressure heater (18), where it is electrically heated by the second pressure reducing valve (15) and the temperature control system (19). After heating, thermal energy exchange is achieved with high-temperature helium gas at 1000-1100°C, and after heating up to 950-1050°C, it enters the hydrogen enrichment blast furnace-converter subsystem. The low-temperature helium gas, after transferring thermal energy, then cools down to 750-850°C and merges with low-temperature helium gas at 300-500°C after losing thermal energy in the hydrogen / oxygen production device (16) using the iodine-sulfur cycle, finally reaching a temperature of 600-700°C. The helium gas circulates and enters the nuclear power generation subsystem, that is, after mixing with the low-pressure helium gas sent from the first steam turbine (2), it enters the steam generator (4). The high-temperature oxygen gas generated in the hydrogen and oxygen production unit (16) by the iodine-sulfur cycle is dissipated by passing through the high-pressure heater (14) and the low-pressure heater (11), and after thermal energy conversion with the water inlet to the steam generator (4), it is sent to the hydrogen-enriched blast furnace-converter subsystem. The high-temperature reducing atmosphere generated in the hydrogen production thermal cycle subsystem is blown into the lower part or lower part of the furnace body of the hydrogen enrichment blast furnace (20), where a reduction reaction occurs. The resulting molten iron enters the converter (21), and low-temperature oxygen gas enters the hydrogen enrichment blast furnace (20) and converter (21), where an oxidation reaction occurs, producing product steel. At the same time, the waste heat from the slag passes through the slag waste heat recovery unit (22), where a carrona cycle power generation system is used to convert thermal energy into electrical energy, driving the third generator (23) to generate electricity, which in turn powers the top gas purification unit (24) and The top gas dechlorination and desulfurization wastewater treatment system (26) is powered by electricity. The top gas generated after the reduction and oxidation reaction in the hydrogen-enriched blast furnace (20) passes sequentially through the dust collector (25) and the top gas purification system (24), after which the remaining harmless gas components are discharged into the air. After passing through the dust collector (25), the top gas passes through the desulfurization tower (241) of the top gas purification system (24). The resulting top gas washing wastewater is treated in the top gas dechlorination and desulfurization wastewater treatment system (26) and then enters the condensate pump (10) to be used as industrial water in the Rankine cycle, thereby achieving circulation. The electricity consumed in water electrolysis hydrogen production is further supplied by natural gas-fired power plants, steam residual pressure power plants, solar power plants, wind power plants, and off-peak electricity from the power grid. The combustible gases used in natural gas-fired power plants are coke oven gas, blast furnace gas, and converter gas, and the steam used in steam residual pressure power plants is supplied from sintered waste heat boilers. The steam used in coke oven gas-steam reforming hydrogen production is low-pressure steam after residual pressure power generation. The end products are cast steel profiles, casting materials for high-carbon spheroidal graphite cast iron profiles with a carbon content of 2-4% and a silicon content of 2-4%, and casting materials for high-carbon spheroidal graphite cast steel profiles with a carbon content of 1-2% and a silicon content of 1-1.9%. A systematic method for reducing carbon dioxide emissions throughout the entire steelmaking and casting process, characterized in that waste from end products is entered into a converter or electric furnace for recirculating smelting.

2. A systematic method for reducing carbon dioxide emissions in the entire steelmaking and casting process according to claim 1, wherein top gas is fed into a top gas purification device (24), the top gas purification device (24) includes a desulfurization tower (241), a collection tower (242), and a regeneration tower (243), the desulfurization tower (241) is in communication with a collection tower (242), a dust collector (25), and a top gas dechlorination / desulfurization wastewater treatment device (26), the top gas dechlorination / desulfurization wastewater treatment device (26) is in communication with a condensate pump (10), the collection tower (242) is in communication with a regeneration tower (243) and a gas mixing chamber (17), and the regeneration tower (243) is in communication with a second air compressor (27).

3. A systematic method for reducing carbon dioxide in the entire steelmaking and casting process according to claim 2, wherein the furnace top gas passes through a regeneration tower (243) to extract carbon dioxide, the extracted carbon dioxide is sent to a second air compressor (27) and compressed, and then stored in a carbon dioxide storage tank (28).

4. A systematic method for reducing carbon dioxide emissions throughout the entire steelmaking and casting process according to claim 1, wherein electricity generated by natural gas-fired power generation, steam residual pressure power generation, solar power generation, and wind power generation is integrated into the internal power grid of the steelworks and transported to a water electrolysis hydrogen production apparatus.

5. A systematic method for reducing carbon dioxide emissions in the entire steelmaking and casting process according to claim 1, wherein steam generated in a sintering waste heat boiler is integrated into a high-pressure steam pipeline and transported to a residual pressure power generator.

6. A systematic method for reducing carbon dioxide emissions throughout the entire steelmaking and casting process according to claim 1, wherein the low-pressure steam after residual pressure power generation is transported through a low-pressure steam pipeline to a reactor for coke oven gas-steam reforming hydrogen production.

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