A hydrogen-rich carbon cycle blast furnace three-stage waste heat recovery system based on top gas waste heat cascade utilization and energy coupling optimization method

Abstract

The present application belongs to the technical field of blast furnace ironmaking, and specifically discloses a hydrogen-rich carbon cycle blast furnace three-stage waste heat recovery system based on furnace top coal gas waste heat cascade utilization, which comprises a blast furnace, a high-temperature heat exchanger, a medium-temperature heat exchanger and an ORC power generation unit. The high-temperature heat exchanger is connected with the medium-temperature heat exchanger, and the medium-temperature heat exchanger is connected with the ORC power generation unit. In view of the problem that the hydrogen-rich carbon cycle blast furnace top coal gas waste heat utilization is insufficient, the present application builds a multi-stage energy recovery system of high temperature, medium temperature and low temperature, realizes the full temperature range recovery of the furnace top coal gas waste heat from high temperature to low temperature, solves the problem that the traditional waste heat recovery system cannot be adapted due to the change of energy flow structure of the hydrogen-rich carbon cycle blast furnace, and causes the problem of low system energy efficiency.

Description

Technical Field

[0001] This invention relates to the field of blast furnace ironmaking technology, specifically to a three-stage waste heat recovery system for a hydrogen-rich carbon-circulating blast furnace based on the cascade utilization of waste heat from the furnace top gas, and an energy coupling optimization method. Background Technology

[0002] Under the trend of low-carbon transformation in the steel industry, hydrogen-rich carbon-recycled oxygen blast furnaces have become one of the core directions for upgrading blast furnace ironmaking processes due to their significant carbon emission reduction potential. This process reduces the consumption of fossil fuels and direct CO2 emissions from the source by injecting hydrogen-rich gas into the blast furnace and recycling the top gas after CO2 removal back into the furnace to participate in the reaction. It is the core technological path to achieve low-carbon upgrading of blast furnace ironmaking processes.

[0003] However, while achieving carbon emission reduction, the hydrogen-rich carbon-recycled oxygen blast furnace undergoes a fundamental change in its energy flow structure. On the one hand, after CO2 removal treatment, a portion of the top gas is recycled back into the furnace, while the remaining portion still contains a large amount of high-grade sensible heat and chemical energy, becoming an important potential energy source within the blast furnace system. On the other hand, this process significantly increases the demand for high-temperature heat sources. The circulating gas and hydrogen-rich gas need to be heated to above 1200℃ to meet the process requirements of the high-temperature reduction reaction inside the furnace. This process consumes a large amount of high-grade energy, thus becoming the main energy-consuming link in the blast furnace system, resulting in significant differences in energy supply and demand and transfer patterns compared to traditional blast furnaces.

[0004] Traditional blast furnace waste heat recovery and energy utilization systems are designed based on the energy flow characteristics of conventional blast furnaces, such as blast furnace gas pressure recovery turbine power generation units (TRT) and traditional hot blast stoves. Their energy recovery methods and heat source matching logic are not suitable for the energy flow structure of hydrogen-rich carbon cycle blast furnaces. Among them, the problem of insufficient utilization of top gas waste heat is particularly prominent and is a key factor leading to the low overall energy efficiency of the system: traditional waste heat recovery systems lack staged recovery of top gas and can only perform extensive recovery of some high-temperature sensible heat, while a large amount of medium and low-temperature waste heat is not effectively utilized, resulting in direct waste of energy resources; at the same time, there is no precise temperature matching between waste heat recovery and process heat demand, and high-grade waste heat is inefficiently used in low-temperature demand stages, resulting in significant energy loss during energy transfer and further reducing waste heat utilization efficiency. To meet the high-temperature heating requirements of circulating coal gas and hydrogen-rich gas, CO2 capture, and the energy consumption requirements of processes such as heat and electricity in the plant area, a large amount of high-grade energy such as natural gas and electricity needs to be purchased from outside. This not only increases the energy cost per ton of iron production, but also offsets the carbon emission reduction effect to some extent.

[0005] In summary, it is necessary to design a three-stage waste heat recovery system for a hydrogen-rich carbon circulating blast furnace based on the cascade utilization of waste heat from the furnace top gas, along with an energy coupling optimization method. This is to address the problem that traditional waste heat recovery systems are not adaptable to hydrogen-rich carbon circulating blast furnaces due to changes in energy flow structure, resulting in insufficient utilization of waste heat from the furnace top gas and consequently low system energy efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a three-stage waste heat recovery system for a hydrogen-rich carbon circulating blast furnace based on the cascade utilization of waste heat from the furnace top gas, and an energy coupling optimization method, in order to solve the problem that traditional waste heat recovery systems cannot be adapted to hydrogen-rich carbon circulating blast furnaces due to changes in energy flow structure, resulting in insufficient utilization of waste heat from the furnace top gas and thus low system energy efficiency.

[0007] To achieve the above objectives, the basic solution provided by this invention is as follows: a three-stage waste heat recovery system for a hydrogen-rich carbon-circulating blast furnace based on the cascade utilization of waste heat from the furnace top gas, comprising a blast furnace, a high-temperature heat exchanger, a medium-temperature heat exchanger, and an ORC power generation unit. A dust collector is connected to the blast furnace gas outlet pipeline, and the flue gas outlet of the dust collector is connected to the inlet of the high-temperature heat exchanger. An oxygen heat exchanger, a CO2 capture and regeneration unit, and a decarbonized gas heat exchanger are connected in parallel to the outlet of the heat transfer medium of the high-temperature heat exchanger. The outlet of the oxygen heat exchanger is connected to the blast furnace tuyeres. The outlet of the high-temperature heat exchanger is connected to the inlet of the medium-temperature heat exchanger. A coke drying unit and a plant heating unit are connected in parallel to the outlet of the heat transfer medium of the medium-temperature heat exchanger. The outlet of the medium-temperature heat exchanger is connected to the ORC power generation unit.

[0008] The beneficial effects of the present invention are as follows: (1) By constructing a multi-level energy recovery system including high temperature, medium temperature and low temperature, the present invention realizes the recovery of waste heat from the top gas of the furnace from high temperature to low temperature in the whole temperature range. At the same time, the waste heat of different grades is accurately matched with the corresponding process requirements, so that the comprehensive utilization rate of waste heat of the top gas of the furnace is increased from the traditional 40-50% to more than 70%, and the system efficiency is also increased from 51.2% to 63.8%; (2) By establishing three complementary heating methods of top gas combustion, hydrogen-rich gas premixed combustion and electric heating, and constructing an optimization selection model with the goal of minimizing the total operating cost, the load distribution of the heating furnace is dynamically adjusted by comprehensively considering factors such as gas price, electricity price, equipment efficiency and CO2 emission cost, so as to realize the priority utilization of self-produced surplus gas and reduce the consumption of external high-grade energy such as natural gas and electricity.

[0009] Option 2, an energy coupling optimization method for a hydrogen-rich carbon cycle blast furnace based on the cascade utilization of waste heat from the furnace top gas, includes the following steps: S1: Construct the energy flow network of the entire blast furnace system: Draw an energy flow diagram with temperature and heat characteristics based on the energy sources and energy sinks of the hydrogen-rich carbon cycle blast furnace system, and clarify the temperature, flow rate, calorific value and available energy of each stream; S2: Three-stage waste heat recovery and utilization: According to the energy flow diagram, the temperature of the furnace top gas is graded into high-temperature, medium-temperature and low-temperature sections for recovery. Then, the heating method of the decarbonized gas is selected according to the gas price, electricity price, equipment efficiency and CO2 emission cost. S3: Then, with the objective function of maximizing the overall system efficiency or minimizing the overall operating cost, establish a mixed integer linear programming model, set decision variables and constraints, and then obtain the optimal operating parameters of each energy unit through the solver CPLEX or Gurobi. S4: Then, the PLC control system collects the top gas flow rate, top gas temperature, decarbonized gas demand, and hydrogen-rich gas flow rate in real time. Then, the model established in S3 is used to perform calculations every 15-30 minutes, and the results are converted into control commands. Finally, the PLC control system adjusts the valve opening of the heat exchange equipment in the high-temperature, medium-temperature, and low-temperature sections, the load distribution of the heating furnace, and the power of the ORC power generation unit.

[0010] By constructing an energy flow network, selecting three-stage waste heat recovery and heating methods, establishing an optimization model for solution, and real-time data acquisition and dynamic control, the coupling optimization of blast furnace energy flow is achieved.

[0011] Option 3, an optimal choice of Option 2, defines the energy sources in S1 as follows: The energy sources include the sensible heat of the furnace top gas, the chemical energy of the furnace top gas, the physical heat of the molten iron, and the physical heat of the slag. The energy sinks include the heating requirements of decarbonized gas and hydrogen-rich gas, CO2 capture energy consumption, oxygen heating requirements, and the plant's heat and electricity needs. Clearly defining the energy sources and sinks provides a clear research object for the subsequent establishment of a mixed-integer linear programming model, avoiding model construction errors due to ambiguous definitions of energy sources and sinks, and ensuring the operability of the optimization method.

[0012] Option 4, an optimal choice of Option 2, involves the furnace top gas undergoing dust removal before entering a high-temperature heat exchanger in S2. The furnace top gas temperature in the high-temperature section is 400-600℃, decreasing to 250℃ after heat exchange. The recovered heat is used to heat decarbonized gas, preheat oxygen, and serve as a high-temperature heat source for the CO2 capture system's regeneration. This option clarifies the operational standards and utilization boundaries for high-temperature waste heat recovery, limiting its use to heating decarbonized gas, preheating oxygen, and the high-temperature section of CO2 capture and regeneration. This aligns with the principle of cascaded energy utilization, reduces energy losses at the process level, and improves system energy efficiency.

[0013] Option 5, a preferred option of Option 2, involves the mid-temperature section of the furnace top gas at 250-150℃ in S2. After heat exchange in the high-temperature heat exchanger, the furnace top gas enters the mid-temperature heat exchanger for further heat exchange. The recovered heat is used in the coke drying unit and the plant heating unit. The mid-temperature gas temperature of 250-150℃ is seamlessly integrated with the temperature after heat exchange in the high-temperature section, achieving continuous, uninterrupted, and graded recovery of waste gas heat, avoiding waste. Simultaneously, utilizing the mid-temperature waste heat for coke drying and plant heating creates an internal closed loop between blast furnace waste heat and plant heat consumption, improving energy self-sufficiency.

[0014] Option 6, an optimal choice from the basic option, involves using S2 where the temperature of the top gas in the low-temperature section is <150℃. The recovered heat is used for power generation in the ORC power generation unit. This converts the low-grade waste heat wasted in traditional blast furnaces into electrical energy, significantly improving the overall utilization rate of waste heat.

[0015] Option 7, a preferred option of Option 2, involves heating the decarbonized gas in S2 using three methods: top gas combustion heating, hydrogen-rich gas premixed combustion heating, and electric heating. Top gas combustion heating utilizes the heat generated from burning purified gas (after dust removal, three-stage waste heat recovery, and CO2 removal treatment, which was not recycled back into the blast furnace) to heat the decarbonized gas. Hydrogen-rich gas premixed combustion heating involves premixing a portion of the hydrogen-rich gas to be injected into the heating furnace for combustion, then heating the decarbonized gas. Electric heating is only used during peak gas heating demand or when top gas supply is insufficient. Prioritizing the use of surplus purified gas produced by the blast furnace itself for heating decarbonized gas achieves internal energy utilization, reduces the consumption of external high-grade energy, and lowers system operating costs and carbon emissions.

[0016] Option 8 is the preferred option of Option 2. In S3, the decision variables include the heat exchange capacity of each heat exchanger, the load distribution of the heating furnace, the power generation of the ORC power generation unit, and the amount of purchased energy; the constraints include energy balance, equipment capacity limitations, temperature matching requirements, and safety and environmental protection restrictions. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a three-stage waste heat recovery system for a hydrogen-rich carbon circulating blast furnace based on the cascade utilization of preheated blast furnace top gas, according to the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below through specific embodiments: The reference numerals in the accompanying drawings include: 1. Blast furnace; 2. High-temperature heat exchanger; 3. Medium-temperature heat exchanger; 4. ORC power generation unit; 5. Dust collector; 6. Oxygen heat exchanger; 7. CO2 capture and regeneration unit; 8. Decarbonized gas heat exchanger; 9. Coke drying unit; 10. Plant heating unit.

[0019] like Figure 1 The diagram shows a three-stage waste heat recovery system for a hydrogen-rich carbon-cycle blast furnace based on the preheating and cascade utilization of top gas. The system includes a blast furnace 1, a high-temperature heat exchanger 2, a medium-temperature heat exchanger 3, and an ORC power generation unit 4. A dust collector 5 is connected to the gas outlet pipeline of the blast furnace 1. The flue gas outlet of the dust collector 5 is connected to the inlet of the high-temperature heat exchanger 2. An oxygen heat exchanger 6, a CO2 capture and regeneration unit 7, and a decarbonized gas heat exchanger 8 are connected in parallel to the outlet of the heat transfer medium of the high-temperature heat exchanger 2. The outlet of the oxygen heat exchanger 6 is connected to the tuyeres of the blast furnace 1. The outlet of the high-temperature heat exchanger 2 is connected to the inlet of the medium-temperature heat exchanger 3. A coke drying unit 9 and a plant heating unit 10 are connected in parallel to the outlet of the heat transfer medium of the medium-temperature heat exchanger 3. The outlet of the medium-temperature heat exchanger 3 is connected to the ORC power generation unit 4.

[0020] Example 1 An energy coupling optimization method for a hydrogen-rich carbon cycle blast furnace based on the cascade utilization of waste heat from the furnace top gas includes the following steps: S1: Constructing the energy flow network of the entire blast furnace system: Based on the energy sources and energy sinks of the hydrogen-rich carbon cycle blast furnace system, draw an energy flow diagram with temperature and heat characteristics, and clarify the temperature, flow rate, calorific value, and available energy of each stream. Among them, the energy sources include the physical sensible heat of the top gas, the chemical energy of the top gas, the physical heat of molten iron, and the physical heat of slag; the energy sinks include the heating requirements of decarbonized gas and hydrogen-rich gas, CO2 capture energy consumption, oxygen heating requirements, and the plant's heat and electricity requirements. S2: Three-stage waste heat recovery and utilization: According to the energy flow diagram, the temperature of the furnace top gas is graded into high-temperature section, medium-temperature section and low-temperature section for recovery. The temperature of the furnace top gas in the high-temperature section is 400-600℃. It needs to be dusted by dust collector 5 and then enter the high-temperature heat exchanger 2 for heat exchange. The temperature after heat exchange is 250℃. The recovered heat is transported to oxygen heat exchanger 6, CO2 capture and regeneration unit 7 and decarbonized gas heat exchanger 8, which are used to preheat oxygen, regenerate heat source for CO2 capture system and heat decarbonized gas, respectively. There are three methods for heating decarbonized gas: top gas combustion heating, hydrogen-rich gas premixed combustion heating, and electric heating. Top gas combustion heating refers to heating the decarbonized gas with the heat generated from the combustion of purified gas that has not been circulated back into the blast furnace after dust removal, three-stage waste heat recovery, and CO2 removal. Hydrogen-rich gas premixed combustion heating refers to partially premixing the hydrogen-rich gas to be injected into the heating furnace for combustion, and then heating the decarbonized gas. Electric heating is only used when the gas heating demand is at its peak or when the top gas supply is insufficient. After heat exchange in the high-temperature heat exchanger 2, the top gas from the furnace enters the medium-temperature heat exchanger 3 for another heat exchange. The temperature of the top gas in the medium-temperature section is 250-150℃. The recovered heat is transferred to the coke drying unit 9 and the plant heating unit 10. Finally, after two heat exchanges, the top gas with a temperature of <150℃ enters the organic working fluid evaporator of the ORC power generation unit 4 for heat exchange and is then used for power generation. Then, the heating method of the decarbonized gas is selected according to the gas price, electricity price, equipment efficiency and CO2 emission cost. S3: Then, with the objective function of maximizing the overall system efficiency or minimizing the overall operating cost, a mixed integer linear programming model is established, and decision variables and constraints are set. The decision variables include the heat exchange of each heat exchanger, the load distribution of the heating furnace, the power generation of ORC power generation unit 4, and the amount of purchased energy. The constraints include energy balance, equipment capacity limitations, temperature matching requirements, and safety and environmental protection limitations. Then, the optimal operating parameters of each energy unit are obtained through the solver CPLEX or Gurobi. S4: Then, the PLC control system collects the top gas flow rate, top gas temperature, decarbonized gas demand, and hydrogen-rich gas flow rate in real time. Next, the model established in S3 is used to perform calculations every 15-30 minutes, and the results are converted into control commands. Finally, the PLC control system adjusts the valve opening of the heat exchange equipment in the high-temperature, medium-temperature, and low-temperature sections, the load distribution of the heating furnace, and the power of ORC power generation unit 4.

[0021] Example 2 An energy coupling optimization method for a hydrogen-rich carbon circulating blast furnace based on the cascade utilization of waste heat from the furnace top gas is proposed. The steps are identical to those in Example 1, except that: S1: Constructing the energy flow network of the entire blast furnace system: First, based on the parameters of the top gas: the flow rate is 180,000 Nm³. 3 / h, temperature 400℃, calorific value approximately 3.5 MJ / Nm 3 Decarbonized gas heating requirement: 100,000 Nm³ 3 Heating from room temperature to 1200℃ requires approximately 130MW of heat and CO2 capture energy consumption of approximately 1.0 GJ / t-CO2, of which regeneration heat consumption accounts for 70%. Draw an energy flow diagram with temperature and heat characteristics. S2: Three-stage waste heat recovery and utilization: Based on the energy flow diagram, the temperature of the top gas is recovered in stages according to high-temperature, medium-temperature, and low-temperature sections. Specifically: First, the top gas generated by the blast furnace passes through dust collector 5 for dust removal and then enters high-temperature heat exchanger 2 to exchange heat with the heat transfer medium. The temperature of the top gas is 400℃, and the temperature after heat exchange is 250℃, obtaining approximately 45MW of heat. Of this, 10MW of heat is transferred to oxygen heat exchanger 6 for preheating oxygen, and 35MW of heat is used for preheating the combustion air in the gas heater. Then, the top gas after the first heat exchange is transferred to medium-temperature heat exchanger 3 to exchange heat with the heat transfer medium in medium-temperature heat exchanger 3. The medium undergoes secondary heat exchange, reducing the temperature of the top gas from 250°C to 80°C, yielding approximately 35MW of heat. Of this, 15MW of heat is transferred to the coke drying unit 9 for coke drying within the plant area, and 20MW of heat is transferred to the CO2 capture and regeneration unit 7. The top gas, after undergoing two heat exchanges, is then transferred to the organic working fluid evaporator in the ORC power generation unit 4 to recover low-temperature waste heat for power generation, reducing the top gas temperature from 80°C to 40°C. The remaining top gas is then burned, generating 100MW of heat energy, which is used to heat the decarbonized gas. If the remaining gas is insufficient, it is premixed with natural gas and then used to heat the decarbonized gas.

[0022] In summary, by constructing a blast furnace system-wide energy flow network, a three-stage waste heat recovery and utilization system, and establishing a multi-source complementary heating system, not only is the precise energy supply for each process stage under the new energy flow structure of the hydrogen-rich carbon cycle blast furnace guaranteed, but the full-grade cascade recovery of top gas waste heat from high temperature to low temperature is also achieved, significantly reducing energy loss. By constructing a mixed integer linear programming optimization model, the dynamic optimal allocation of energy units such as furnace load, heat exchanger heat exchange, and ORC power generation is realized. Ultimately, the comprehensive utilization rate of top gas waste heat is increased from 40-50% in the traditional method to over 70%, reducing the energy consumption cost per ton of iron by 10-20%, increasing the system efficiency from 51.2% to 63.8%, increasing the self-sufficiency rate of waste heat power generation from 8% to 15%, and reducing CO2 capture energy consumption by 12%. This achieves global optimization of the hydrogen-rich carbon cycle blast furnace energy system, significantly improving the economic and environmental benefits of the process.

[0023] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A three-stage waste heat recovery system for a hydrogen-rich carbon circulating blast furnace based on the cascade utilization of waste heat from the furnace top gas, characterized in that, The system includes a blast furnace (1), a high-temperature heat exchanger (2), a medium-temperature heat exchanger (3), and an ORC power generation unit (4). A dust collector (5) is connected to the gas outlet pipeline of the blast furnace (1). The flue gas outlet of the dust collector (5) is connected to the air inlet of the high-temperature heat exchanger (2). An oxygen heat exchanger (6), a CO2 capture and regeneration unit (7), and a decarbonized gas heat exchanger (8) are connected in parallel to the outlet of the heat transfer medium of the high-temperature heat exchanger (2). The outlet of the oxygen heat exchanger (6) is connected to the tuyeres of the blast furnace (1). The outlet of the high-temperature heat exchanger (2) is connected to the air inlet of the medium-temperature heat exchanger (3). A coke drying unit (9) and a plant heating unit (10) are connected in parallel to the outlet of the heat transfer medium of the medium-temperature heat exchanger (3). The outlet of the medium-temperature heat exchanger (3) is connected to the ORC power generation unit (4).

2. An energy coupling optimization method for a hydrogen-rich carbon cycle blast furnace based on the cascade utilization of waste heat from the furnace top gas, characterized in that, Includes the following steps: S1: Construct the energy flow network of the entire blast furnace system: Draw an energy flow diagram with temperature and heat characteristics based on the energy sources and energy sinks of the hydrogen-rich carbon cycle blast furnace system, and clarify the temperature, flow rate, calorific value and available energy of each stream; S2: Three-stage waste heat recovery and utilization: According to the energy flow diagram, the temperature of the furnace top gas is graded into high-temperature, medium-temperature and low-temperature sections for recovery. Then, the heating method of the decarbonized gas is selected according to the gas price, electricity price, equipment efficiency and CO2 emission cost. S3: Then, with the objective function of maximizing the overall system efficiency or minimizing the overall operating cost, establish a mixed integer linear programming model, set decision variables and constraints, and then obtain the optimal operating parameters of each energy unit through the solver CPLEX or Gurobi. S4: Then, the PLC control system collects the top gas flow rate, top gas temperature, decarbonized gas demand and hydrogen-rich gas flow rate in real time. Then, the model established in S3 is used to perform calculations every 15-30 minutes, and the results are converted into control commands. Finally, the valve opening of the heat exchange equipment in the high temperature section, medium temperature section and low temperature section, the load distribution of the heating furnace and the power of the ORC power generation unit (4) are adjusted through the PLC control system.

3. The energy coupling optimization method for a hydrogen-rich carbon cycle blast furnace based on the cascade utilization of waste heat from the furnace top gas, as described in claim 2, is characterized in that... In S1, the energy sources include the physical sensible heat of the furnace top gas, the chemical energy of the furnace top gas, the physical heat of molten iron, and the physical heat of slag; the energy sinks include the heating demand of decarbonized gas and hydrogen-rich gas, the energy consumption of CO2 capture, the heating demand of oxygen, and the heat and electricity demand of the plant area.

4. The energy coupling optimization method for a hydrogen-rich carbon cycle blast furnace based on the cascade utilization of waste heat from the furnace top gas, as described in claim 2, is characterized in that... In S2, the top gas needs to be dusted before entering the high-temperature heat exchanger (2) for heat exchange. The temperature of the top gas in the high-temperature section is 400-600℃, and the temperature after heat exchange is 250℃. The recovered heat is used to heat the decarbonized gas, preheat oxygen, and serve as the high-temperature part of the CO2 capture system as a regeneration heat source.

5. The energy coupling optimization method for a hydrogen-rich carbon cycle blast furnace based on the cascade utilization of waste heat from the furnace top gas, as described in claim 2, is characterized in that... In S2, the temperature of the gas at the top of the furnace in the medium temperature section is 250-150℃. After being heated by the high temperature heat exchanger (2), the gas at the top of the furnace enters the medium temperature heat exchanger (3) for heat exchange again. The recovered heat is used for the coke drying unit (9) and the plant heating unit (10).

6. The energy coupling optimization method for a hydrogen-rich carbon cycle blast furnace based on the cascade utilization of waste heat from the furnace top gas, as described in claim 2, is characterized in that... In S2, the temperature of the gas at the top of the furnace in the low-temperature section is <150℃, and the recovered heat is used for power generation in the ORC power generation unit.

7. The energy coupling optimization method for a hydrogen-rich carbon cycle blast furnace based on the cascade utilization of waste heat from the furnace top gas, as described in claim 2, is characterized in that... In S2, the decarbonized gas is heated in three ways: top gas combustion heating, hydrogen-rich gas premixed combustion heating, and electric heating. Top gas combustion heating refers to heating the decarbonized gas with the heat generated from the combustion of purified gas that has not been circulated back into the blast furnace after dust removal, three-stage waste heat recovery, and CO2 removal. Hydrogen-rich gas premixed combustion heating refers to partially premixing the hydrogen-rich gas to be injected into the heating furnace for combustion, and then heating the decarbonized gas. Electric heating is only used when the gas heating demand is at its peak or when the top gas is insufficient.

8. The energy coupling optimization method for a hydrogen-rich carbon cycle blast furnace based on the cascade utilization of waste heat from the furnace top gas, as described in claim 2, is characterized in that... In S3, the decision variables include the heat exchange capacity of each heat exchanger, the load distribution of the heating furnace, the power generation of the ORC power generation unit (4), and the amount of purchased energy; the constraints include energy balance, equipment capacity limitations, temperature matching requirements, and safety and environmental protection restrictions.

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