Supercritical CO2 secondary reheating system based on waste gas of steel mill
By combining a supercritical CO2 secondary reheat system with a circulating fluidized bed boiler in a steel plant, the efficient utilization of steel plant waste gas has been achieved, solving the problems of low energy utilization efficiency and hydrocarbon resource emissions, and providing a stable power supply.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- NORTH CHINA POWER ENG
- Filing Date
- 2025-05-19
- Publication Date
- 2026-04-17
AI Technical Summary
In existing technologies, the energy utilization efficiency of by-product gas from the steel industry and circulating fluidized bed boilers needs to be improved, and the hydrocarbon emissions from steel plants are not effectively utilized, resulting in a lack of stable and reliable power sources.
By combining a steel plant with a circulating fluidized bed boiler and employing a supercritical CO2 secondary reheat system, carbon dioxide and hydrogen from the steel plant's waste gas are used in the supercritical CO2 secondary reheat system and the fluidized bed reactor combustion system through gas classification collection, graded purification, and targeted utilization, achieving cogeneration and near-zero emissions.
It has improved energy efficiency, achieved near-zero emissions of hydrocarbon resources from steel plants, and provided steel plants with a stable and reliable power source, reducing dependence on external carbon sources.
Smart Images
Figure CN224135852U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of combustion technology, specifically relating to a supercritical CO2 secondary reheat system based on steel plant exhaust gas. Background Technology
[0002] The steel industry's production process generates byproduct gases such as coke oven gas, converter gas, and blast furnace gas, which require more rational and efficient utilization. On the other hand, circulating fluidized bed boilers contain a large amount of inert, hot bed material, preventing sudden flameouts during operation. Even if a boiler malfunction causes a main fuel trip, the furnace temperature will not drop abruptly. Therefore, circulating fluidized bed boilers have a low low-load stable combustion zone and can operate stably at 30% of rated load or lower, thus showing promising application prospects. Currently, both steel industry byproduct gases and circulating fluidized bed boilers need improvement in energy utilization efficiency. Furthermore, higher requirements are being placed on hydrocarbon emissions from steel plants, and no satisfactory solution yet exists. Utility Model Content
[0003] The technical problem to be solved by this utility model is to provide a supercritical CO2 secondary reheat system based on steel plant exhaust gas, which solves the problem that the energy utilization efficiency of the existing technology needs to be improved. By combining the steel plant with a circulating fluidized bed boiler, it not only realizes cogeneration, but also makes effective use of the steel plant process gas in the gas boiler, which helps the steel plant to achieve near-zero emissions of hydrocarbon resources, and can provide the steel plant with a stable and reliable power source.
[0004] According to the technical solution of this utility model, this utility model provides a supercritical CO2 secondary reheat system based on steel plant exhaust gas, including a steel plant, a fluidized bed reactor, a gas classification and collection unit, and a supercritical carbon dioxide secondary reheat system; the coke oven gas output pipeline, blast furnace gas output pipeline, and converter gas output pipeline of the steel plant are connected to the gas classification and collection unit; the fluidized bed reactor includes a furnace, a cyclone separator, and a tail flue connected in sequence; the furnace is provided with a primary air inlet, a secondary air inlet, a coal feed inlet, a hydrogen inlet, and a carbon monoxide inlet; the primary air inlet is located at the bottom of the furnace, the coal feed inlet is located above the primary air inlet, the secondary air inlet and the hydrogen inlet are located above the coal feed inlet, and the carbon monoxide inlet is located at the top of the furnace; a carbon capture device is provided downstream of the tail flue. The device is connected to a gas sorting and collection unit; the gas sorting and collection unit is connected to a hydrocarbon separation module, which has a carbon monoxide outlet, a carbon dioxide outlet, and a hydrogen outlet; the carbon monoxide outlet is connected to the carbon monoxide inlet, the hydrogen outlet is connected to the hydrogen inlet, the carbon dioxide outlet is connected to the gas storage station, and the gas storage station is connected to a supercritical carbon dioxide secondary reheat system; the supercritical carbon dioxide secondary reheat system includes a high-temperature superheater, a high-pressure cylinder, a high-temperature reheater, a low-pressure cylinder, and a low-temperature superheater connected in sequence, and the outlet of the low-temperature superheater is connected to the low-pressure cylinder; the high-pressure cylinder and the low-pressure cylinder are coaxially connected to the generator; the high-temperature superheater is located inside the furnace, the high-temperature reheater is located outside the fluidized bed reactor and connected to the furnace through a material circulation pipeline, and the low-temperature superheater is located inside the tail flue.
[0005] In some implementations, a reducing agent spray gun is provided at the top inlet of the cyclone separator, and an SCR denitrification catalyst layer is provided in the tail flue.
[0006] In some embodiments, a primary economizer and a secondary economizer are also installed in the tail flue. The low-temperature superheater, the secondary economizer, the SCR denitrification catalyst layer, the primary economizer, and the carbon capture device are arranged sequentially along the flue gas conveying direction.
[0007] In some implementations, the hydrocarbon separation module also has a residual coke oven gas outlet connected to the primary air inlet.
[0008] In some implementations, the top of the furnace is connected to the top of the cyclone separator via an intermediate flue, and the bottom of the cyclone separator is connected to the furnace via a return material device.
[0009] In some implementations, the furnace is also provided with an ash discharge outlet, which is located at a height between the primary air inlet and the coal feed inlet.
[0010] Compared with the prior art, the beneficial technical effects of this utility model are as follows:
[0011] This invention relates to a supercritical CO2 secondary reheat system based on steel plant exhaust gas. Through staged purification and targeted utilization, carbon dioxide, hydrogen, and carbon monoxide from three types of coal gas—coke oven gas, converter gas, and blast furnace gas—are enriched and applied to the working fluid circulation of the supercritical CO2 secondary reheat system and the combustion system of the fluidized bed reactor, achieving near-zero emissions of hydrocarbon resources from steel plant power plants. Furthermore, the carbon dioxide working fluid circulating in the supercritical CO2 secondary reheat system directly originates from steel plant exhaust gas and fluidized bed combustion tail gas, forming a closed loop of "capture-utilization-recapture" and reducing dependence on external carbon sources. Attached Figure Description
[0012] Figure 1 This is a schematic diagram of the system structure provided by this utility model.
[0013] Explanation of reference numerals in the attached figures:
[0014] 1. Gas classification and collection unit; 11. Hydrocarbon separation module; 2. Supercritical carbon dioxide secondary reheat system; 21. High-temperature superheater; 22. High-pressure cylinder; 23. High-temperature reheater; 24. Low-pressure cylinder; 25. Low-temperature superheater; 31. Furnace; 311. Primary air inlet; 312. Secondary air inlet; 313. Coal feed port; 314. Hydrogen inlet; 315. Carbon monoxide inlet; 316. Ash discharge port; 32. Cyclone separator; 321. Reducing agent spray gun; 322. Intermediate flue; 323. Material return device; 33. Tail flue; 331. Primary economizer; 332. Secondary economizer; 333. SCR denitrification catalyst layer; 4. Carbon capture device; 5. Gas storage station. Detailed Implementation
[0015] This invention provides a supercritical CO2 secondary reheat system based on steel plant exhaust gas, mainly involving hydrogen-doped fluidized bed combustion technology and supercritical CO2 secondary reheat technology. It aims to solve the problem that existing technologies need to improve energy utilization efficiency. By combining the steel plant with a circulating fluidized bed boiler, it not only realizes combined heat and power, but also effectively utilizes the steel plant's process gases in the gas-fired boiler, which helps the steel plant achieve near-zero emissions of hydrocarbon resources and can provide the steel plant with a stable and reliable power source.
[0016] Please see Figure 1 The present invention discloses a supercritical CO2 secondary reheat system based on steel plant exhaust gas, comprising a steel plant, a fluidized bed reactor, a gas classification and collection unit 1, and a supercritical carbon dioxide secondary reheat system 2.
[0017] One of the key innovations of this solution is the integration of fluidized bed combustion technology with steel plants, for example, by constructing small power plants within or near the steel plant. The coke oven gas output pipelines, blast furnace gas output pipelines, and converter gas output pipelines of the steel plant are connected to the gas classification and collection unit 1, thereby enabling the gases in these byproducts to be efficiently utilized in the fluidized bed reactor combustion system.
[0018] The fluidized bed reactor comprises a furnace 31, a cyclone separator 32, and a tail flue 33 connected in sequence. The furnace 31 is equipped with a primary air inlet 311, a secondary air inlet 312, a coal feed inlet 313, a hydrogen inlet 314, and a carbon monoxide inlet 315. The primary air inlet 311 is located at the bottom of the furnace 31, the coal feed inlet 313 is located above the primary air inlet 311, the secondary air inlet 312 and the hydrogen inlet 314 are located above the coal feed inlet 313, and the carbon monoxide inlet 315 is located at the top of the furnace 31. More specifically, the secondary air inlet 312 and the hydrogen inlet 314 are located on the left and right sides of the cold wall of the furnace 31. Primary and secondary air are supplied in stratified layers to optimize airflow. High-purity hydrogen is injected into the furnace for co-combustion, which helps improve combustion stability. Carbon monoxide is injected into the reduction zone at the top of the furnace 31 through an independent pipe to react with NOx in the combustion flue gas, reducing nitrogen oxide emissions. A carbon capture device 4 is installed on the downstream side of the tail flue 33. The carbon capture device 4 is connected to the gas classification and collection unit 1, so as to recover the carbon dioxide in the tail gas of the fluidized bed reactor to the gas classification and collection unit 1.
[0019] The gas sorting and collection unit 1 is connected to a hydrocarbon separation module 11, which has a carbon monoxide outlet, a carbon dioxide outlet, and a hydrogen outlet. The carbon monoxide outlet is connected to a carbon monoxide inlet 315, the hydrogen outlet is connected to a hydrogen inlet 314, and the carbon dioxide outlet is connected to a gas storage station 5. The gas storage station 5 is connected to a supercritical carbon dioxide secondary reheat system 2.
[0020] The CO2 working fluid of the supercritical carbon dioxide double reheat system 2 comes from the hydrocarbon separation module and the fluidized bed combustion exhaust carbon capture. Structurally, it adopts a high-pressure and low-pressure dual cylinder and improves the work capacity of the CO2 working fluid through two reheats. Figure 1The dashed line represents the flow direction of the CO2 working fluid, encompassing heat transfer and work. Specifically, the supercritical carbon dioxide secondary reheat system 2 includes a high-temperature superheater 21, a high-pressure cylinder 22, a high-temperature reheater 23, a low-pressure cylinder 24, and a low-temperature superheater 25 connected in sequence. The outlet of the low-temperature superheater 25 is then connected to the low-pressure cylinder 24. The high-pressure cylinder 22 and the low-pressure cylinder 24 are coaxially connected to the generator. The high-temperature superheater 21 is located inside the furnace 31, and the high-temperature reheater 23 is located outside the fluidized bed reactor (i.e., arranged in an external bed) and is connected to the furnace 31 through a material circulation pipeline for heat exchange. The low-temperature superheater 25 is located in the tail flue 33, and its temperature is controlled by adjusting the flue baffles and the ash content of the external bed. The high-temperature reheater 23 is designed to be arranged in an external bed, which offers greater flexibility in temperature, combustion, and heat transfer control compared to an internal bed. As a supplementary explanation, the low-pressure cylinder exhaust pipe of the low-pressure cylinder 24 is eventually connected to the gas box, and the outlet of the gas box is then connected to the inlet of the high-temperature superheater 21 to form a circulation of carbon dioxide working fluid; the gas storage station 5 is connected to the gas box so as to be able to adjust the total amount of carbon dioxide working fluid circulation in the supercritical carbon dioxide secondary reheat system 2.
[0021] The composition, yield, and theoretical combustion temperature of various coal gases are shown in Table 1 below.
[0022] Table 1. Composition and characteristics of by-product gases from steelmaking
[0023]
[0024] It is evident that coke oven gas contains a relatively high amount of hydrogen, blast furnace gas contains a relatively high amount of carbon dioxide, and converter gas contains a relatively high amount of carbon monoxide and carbon dioxide, thus enabling its utilization in combustion systems and supercritical carbon dioxide reheat systems.
[0025] Circulating fluidized bed (CFB) boilers contain a large amount of inert, hot bed material, preventing sudden flameout during operation. Even if a main fuel trip occurs due to a boiler malfunction, the furnace temperature will not drop abruptly. Therefore, CFB boilers have a low low-load stable combustion zone and can operate stably even at 30% of rated load or lower. During low-load operation, hydrogen co-firing further improves combustion stability. Based on this, hydrogen contained in coke oven gas can be recovered and utilized, leading to the development of efficient, energy-saving, and environmentally friendly co-firing technology for CFB boilers.
[0026] Double reheat technology is currently the main trend in the development of thermal power units. Under frequent load changes, double reheat units have lower economic performance and poorer flexibility. Blast furnace gas and converter gas from steel plants can provide CO2 working fluid for the turbine cycle system, maintaining high unit thermal efficiency under load changes.
[0027] Furthermore, the fluidized bed reactor also includes an SCR denitrification device, which includes a reducing agent spray gun 321. The reducing agent spray gun 321 is located at the top inlet of the cyclone separator 32, and an SCR denitrification catalyst layer 333 is installed inside the tail flue duct 33. More specifically, a primary economizer 331 and a secondary economizer 332 are also installed inside the tail flue duct 33. The low-temperature superheater 25, the secondary economizer 332, the SCR denitrification catalyst layer 333, the primary economizer 331, and the carbon capture device 4 are arranged sequentially along the flue gas conveying direction. In this embodiment, an SCR catalyst layer is added between the secondary economizer 332 and the primary economizer 331 to form the SCR denitrification catalyst layer 333.
[0028] It should be noted that during normal operation of a circulating fluidized bed boiler, the locations that can meet the temperature requirements for the denitrification reduction reaction are the furnace outlet (840℃~870℃), the cyclone separator inlet (960℃~1000℃), and the superheating section from the cyclone separator outlet to the high-temperature superheater (higher than the inlet) (860℃~900℃). Comparative analysis shows that while injecting the reducing agent at the furnace outlet has the longest reaction time, it requires significant modifications to the boiler's water-cooled walls. Injecting the reducing agent at the transition section from the cyclone separator outlet to the high-temperature superheater (higher than the inlet) results in a too-short reaction time, leading to low denitrification efficiency and increased ammonia escape. The cyclone separator inlet, connected by a steel plate and lined with castable refractory, is suitable for injecting the reducing agent through openings. After being disturbed by the cyclone separator, the reactants are evenly mixed, and the longer reaction time at the rear allows the reducing agent to fully react with NOx in the flue gas, minimizing escape. Therefore, in this design, it is preferable to install the reducing agent spray gun 321 at the cyclone separator inlet.
[0029] Preferably, the hydrocarbon separation module 11 also has a residual coke oven gas outlet, which is connected to the primary air inlet 311 to return the coke oven gas after hydrogen extraction to the fluidized bed for combustion, making full use of it.
[0030] More specifically, the top of the furnace 31 is connected to the top of the cyclone separator 32 via an intermediate flue 322, and the bottom of the cyclone separator 32 is connected to the furnace 31 via a return material device 323. The outlet position of the return material device 323 corresponds to that of the coal feed port 313, for example, at similar heights and located on the left and right sides of the cold wall of the furnace 31. The furnace 31 is also provided with an ash discharge port 316 for discharging ash, and the ash discharge port 316 is located between the primary air inlet 311 and the coal feed port 313.
[0031] Understandably, the various pipeline components in this system are also equipped with valves and power systems as needed to control the transport of various substances.
[0032] The working principle of the system in a typical embodiment of this utility model is as follows.
[0033] Hot primary air entering from under the bed of a circulating fluidized bed boiler fully fluidizes the bed material and coal particles with a diameter of less than 8mm. Ignition occurs under the bed, causing intense collisions and heat exchange between the coal particles and the bed material. Larger particles burn within the bed, while finer particles continue burning and exchanging heat in the dilute phase zone at the top of the furnace, carried by the flue gas flow. Some of these fine particles aggregate into large clusters that cannot overcome gravity and move downwards near the furnace wall, while the relatively dilute gas-solid phase in the furnace center continues to move upwards, forming a strong intra-furnace particle circulation. The relatively dilute gas-solid phase, carrying a large amount of unburned particles, leaves the furnace and enters a cyclone separator, where most of the material particles entrained in the flue gas are separated. These particles are then returned to the furnace bed via a return feeder for continued combustion and utilization, forming a large external material circulation. The boiler combustion status is mainly judged by bed temperature and bed pressure.
[0034] When a circulating fluidized bed boiler operates at, for example, 30% of its rated load or lower, hydrogen recovered from coke oven gas is incorporated to improve combustion stability. The primary air temperature is, for example, 130°C to 150°C. Secondary air in the circulating fluidized bed boiler is used to control the total air volume, providing the oxygen required for combustion of unburned fuel in the upper dilute phase zone of the furnace. The preferred secondary air to primary air ratio is 2.2 to 2.5. A CO inlet is located at the top of the fluidized bed, injecting CO into the reduction zone through an independent pipe to react with NOx in the combustion flue gas, reducing nitrogen oxide emissions. Furthermore, a reducing agent spray gun is added at the flue gas outlet of the cyclone separator, and an SCR catalyst layer is added between the secondary and primary economizers of the circulating fluidized bed boiler. Staged air distribution and SCR denitrification technology together effectively control nitrogen oxide emissions.
[0035] Blast furnace gas and converter gas from the steel plant provide CO2 as the working fluid for the secondary reheat system. First, the CO2 passes through a high-temperature superheater to obtain supercritical CO2. After performing work in a high-pressure cylinder, it reaches the high-temperature reheater, then enters a low-pressure cylinder, performs work there, and finally enters a low-temperature superheater. After performing work in the low-pressure cylinder, it is discharged, completing one cycle. This system maintains high unit thermal efficiency even under varying load conditions, providing the steel plant with a stable and reliable power source.
[0036] Based on the above technical solution of this utility model, this utility model provides a method for combined energy supply, which includes the following preprocessing steps:
[0037] Coke oven gas produced by the steel plant is desulfurized and then fed into hydrocarbon separation module 11;
[0038] The blast furnace gas produced by the steel plant is fed into hydrocarbon separation module 11 after dust removal and residual pressure power generation.
[0039] The converter gas produced by the steel plant is fed into the hydrocarbon separation module 11 after wet dust removal.
[0040] In addition, the combustion exhaust gas from the fluidized bed reactor enters the carbon capture device 4, and the resulting carbon dioxide is input to the hydrocarbon separation module 11.
[0041] Furthermore, following the pretreatment step, the hydrocarbon separation module 11 further includes the following gas separation step:
[0042] The pretreated coke oven gas is used to extract high-purity hydrogen through pressure swing adsorption or membrane separation. The purity of the high-purity hydrogen is >99.9%, and it is transported to the hydrogen outlet. The remaining components of the pretreated coke oven gas are returned to the furnace 31 of the fluidized bed reactor for combustion with the primary air.
[0043] The pretreated converter gas is separated into carbon monoxide by low-temperature distillation, for example, by using a low-temperature distillation column with a temperature of -180℃ to -150℃, and the purity of carbon monoxide is >98%, and then transported to the carbon monoxide outlet.
[0044] The remaining components of the pretreated converter gas (mainly carbon dioxide) and the pretreated blast furnace gas are enriched with carbon dioxide by chemical absorption or low-temperature separation. After the carbon dioxide is purified to more than 95%, it is transported to the carbon dioxide outlet and then pressurized and liquefied for storage in the gas storage station 5.
[0045] Carbon dioxide from carbon capture device 4 is also transported to carbon dioxide outlet, then pressurized, liquefied, and stored in gas storage station 5.
[0046] Preferably, high-purity hydrogen is injected into the furnace 31 through hydrogen inlet 314 only when the fluidized bed reactor is operating at low to medium load (e.g., 30% of rated load or lower). The high-purity hydrogen is injected into the furnace 31 after being heated by waste heat treatment in the steel plant, making full use of the waste heat of the steel plant. The hydrogen blending ratio is 5% to 20% to avoid coking caused by excessively high temperature in the fluidized bed.
[0047] Similarly, the primary and secondary air are preferably heated by waste heat treatment from the steel plant before being injected into the furnace 31. The method of heating by waste heat treatment from the steel plant can be, for example, using only the waste heat system of the steel plant for heating, without installing an air preheater in the fluidized bed reactor, or combining the waste heat system of the steel plant with the air preheater of the fluidized bed reactor to achieve heating together.
[0048] In summary, this invention's supercritical CO2 secondary reheat system based on steel plant exhaust gas, through graded purification and targeted utilization, enriches carbon dioxide, hydrogen, and carbon monoxide from three types of coal gas—coke oven gas, converter gas, and blast furnace gas—for use in the working fluid circulation of the supercritical CO2 secondary reheat system and the combustion system of the fluidized bed reactor, achieving near-zero emissions of hydrocarbon resources from steel plant power plants. Furthermore, the carbon dioxide working fluid circulating in the supercritical CO2 secondary reheat system directly originates from steel plant exhaust gas and fluidized bed combustion tail gas, forming a closed loop of "capture-utilization-recapture," reducing dependence on external carbon sources.
[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it; obviously, the described embodiments are some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model; for ease of description, only the parts related to the utility model are shown in the accompanying drawings. In the absence of conflict, the embodiments and features in the embodiments of this utility model can be combined with each other; modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.
Claims
1. A supercritical CO2 double reheat system based on steel plant off-gas, characterized by, It includes a steel plant, a fluidized bed reactor, a gas sorting and collection unit (1) and a supercritical carbon dioxide secondary reheat system (2); The coke oven gas output pipeline, blast furnace gas output pipeline, and converter gas output pipeline of the steel plant are connected to the gas classification and collection unit (1); The fluidized bed reactor includes a furnace (31), a cyclone separator (32), and a tail flue (33) connected in sequence. The furnace (31) is provided with a primary air inlet (311), a secondary air inlet (312), a coal feed inlet (313), a hydrogen inlet (314), and a carbon monoxide inlet (315). The primary air inlet (311) is located at the bottom of the furnace (31), the coal feed inlet (313) is located above the primary air inlet (311), the secondary air inlet (312) and the hydrogen inlet (314) are located above the coal feed inlet (313), and the carbon monoxide inlet (315) is located at the top of the furnace (31). A carbon capture device (4) is provided on the downstream side of the tail flue (33), and the carbon capture device (4) is connected to the gas classification and collection unit (1). The gas classification and collection unit (1) is connected to a hydrocarbon separation module (11), which has a carbon monoxide outlet, a carbon dioxide outlet and a hydrogen outlet; the carbon monoxide outlet is connected to the carbon monoxide inlet (315), the hydrogen outlet is connected to the hydrogen inlet (314), the carbon dioxide outlet is connected to the gas storage station (5), and the gas storage station (5) is connected to the supercritical carbon dioxide secondary reheat system (2). The supercritical carbon dioxide secondary reheat system (2) includes a high-temperature superheater (21), a high-pressure cylinder (22), a high-temperature reheater (23), a low-pressure cylinder (24), and a low-temperature superheater (25) connected in sequence. The outlet of the low-temperature superheater (25) is connected to the low-pressure cylinder (24). The high-pressure cylinder (22) and the low-pressure cylinder (24) are coaxially connected to the generator. The high-temperature superheater (21) is located inside the furnace (31). The high-temperature reheater (23) is located outside the fluidized bed reactor and is connected to the furnace (31) through a material circulation pipeline. The low-temperature superheater (25) is located inside the tail flue (33).
2. The steel mill off-gas based supercritical CO2 double reheat system of claim 1, wherein, A reducing agent spray gun (321) is installed at the top inlet of the cyclone separator (32), and an SCR denitrification catalyst layer (333) is installed in the tail flue (33).
3. The steel mill off-gas based supercritical CO2 double reheat system of claim 2, wherein, The tail flue (33) is also equipped with a primary economizer (331) and a secondary economizer (332). The low temperature superheater (25), the secondary economizer (332), the SCR denitrification catalyst layer (333), the primary economizer (331), and the carbon capture device (4) are arranged in sequence along the flue gas conveying direction.
4. The steel mill off-gas based supercritical CO2 double reheat system of claim 1, wherein, The hydrocarbon separation module (11) also has a residual coke oven gas outlet, which is connected to the primary air inlet (311).
5. The steel mill off-gas based supercritical CO2 double reheat system of claim 1, wherein, The top of the furnace (31) is connected to the top of the cyclone separator (32) through the intermediate flue (322), and the bottom of the cyclone separator (32) is connected to the furnace (31) through the return material device (323).
6. The steel mill off-gas based supercritical CO2 double reheat system of claim 1, wherein, The furnace (31) is further provided with an ash discharge port (316), a height position of the ash discharge port (316) is between the primary air inlet (311) and the coal feeding port (313).