System and method for reasonably treating iron-containing solid waste in iron and steel enterprise

Abstract

The invention discloses a system and method for reasonably treating iron-containing solid waste in an iron and steel enterprise. The system comprises a reaction furnace, a heat exchanger, a dust remover, a dehydrator, a compressor, a CO2 treatment device, a heating furnace and a briquetting system. The furnace top of the reaction furnace is provided with a charging system and a furnace top gas collecting system, and the lower part is provided with a circulating furnace top gas inlet; after a top gas collecting system of the reacting furnace is sequentially communicated with a top gas passage of the heat exchanger, a dust remover and a dehydrator, one path is sequentially communicated with a compressor, a CO2 treatment device, a heating furnace and a circulating top gas inlet of the reacting furnace, and the other path is communicated with a fuel inlet of the heating furnace; and the charging system of the reaction furnace is connected with the briquetting system and the nut coke supply device. CO2 emission is reduced through top gas circulation, residual CO and H2 in the top gas are recycled to enter the lower part of the furnace body and are deeply utilized, the direct reduction efficiency is maximized, and the overall energy consumption of the reactor is reduced; and coke nuts and iron-containing solid waste briquettes of iron and steel enterprises are utilized for production, energy conservation and environmental protection are achieved, and cost is low.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization in the steel industry, and in particular to a system and method for the rational disposal of iron-containing solid waste by steel enterprises. Background Technology

[0002] Iron-containing solid waste from steel plants is diverse and originates widely. The main sources include: fine particles from blast furnace feed screening, iron residue from blast furnace tapping troughs and slag trough maintenance, sintering machine head / tail ash, blast furnace gas ash (gravity ash / baghouse ash), converter LT ash / OG sludge, electric arc furnace dust collector ash, rolling mill scale, converter slag, and electric arc furnace slag. Since the Ministry of Ecology and Environment and other departments issued the "Opinions on Promoting the Implementation of Ultra-Low Emissions in the Steel Industry" in 2020, new standards have been set for waste emissions from the steel industry, indicating that the amount of solid waste emitted by the steel industry will further increase. At the national level, on the one hand, efforts are being made to promote the reduction, resource utilization, and harmless disposal of solid waste from the steel industry at its source; on the other hand, from the perspective of environmental protection, supply-side reform, and promoting high-quality development of the steel industry, ultra-low emissions are being implemented. In 2018, the "Environmental Protection Tax Law of the People's Republic of China" was officially implemented, and the steel industry faced the pressure of an environmental tax of 25 yuan / ton for metallurgical slag emissions. Under this dual policy of blocking at the front and guiding at the back, the comprehensive utilization of solid waste in the steel industry faces even more severe challenges and pressures.

[0003] Because Chinese steel mills lacked sufficient awareness of the hazards of steel solid waste during project approval, they failed to construct corresponding comprehensive solid waste utilization projects. Subsequent solid waste treatment was limited to simple iron recycling, with tailings primarily sold as road paving and cement iron supplements, accounting for less than 10% of the total. The remaining tailings were mostly stockpiled, posing serious environmental risks. In recent years, numerous incidents of haphazard dumping of steel solid waste have been reported. For example, Shanxi Gaoyi Steel was reported for dumping millions of tons of steel slag into surrounding farmland, and Shagang Group was criticized for stockpiling millions of tons of steel slag along the Yangtze River.

[0004] Furthermore, the steel industry and the comprehensive utilization of steel solid waste are cross-industry sectors. Steel solid waste utilization involves a wide range of areas and exhibits significant industry overlap, intersecting with downstream sectors such as building materials, chemicals, non-ferrous metals, and agriculture. However, the comprehensive utilization industry currently suffers from poor upstream and downstream integration, and numerous problems such as technical and qualification barriers exist between industries. Steel companies themselves lack sufficient research on the comprehensive utilization of solid waste, lack mechanisms for technology research and development and promotion, and have weak industry-academia-research collaboration, resulting in lagging development of technical evaluation standards and product standards, hindering the promotion and implementation of advanced equipment and technologies.

[0005] There is an urgent need to invent a technologically advanced, economically reasonable, energy-saving and emission-reducing system and method for disposing of iron-containing solid waste from steel enterprises, in order to solve the pressure faced by steel enterprises in disposing of iron-containing solid waste. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an economical, reasonable, energy-saving and emission-reducing system for the rational disposal of iron-containing solid waste by steel enterprises; the present invention also provides a method for the rational disposal of iron-containing solid waste by steel enterprises.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the system of the present invention is as follows: it includes a reactor, a heat exchanger, a dust collector, a dehydrator, a compressor, a CO2 treatment device, a heating furnace, and a briquetting system; the reactor has a charging system and a furnace top gas collection system at the top, and a circulating furnace top gas inlet at the bottom; the furnace top gas collection system of the reactor is connected in sequence to the furnace top gas passage of the heat exchanger, the dust collector, and the dehydrator, one path is connected in sequence to the compressor, the CO2 treatment device, the heating furnace, and the circulating furnace top gas inlet of the reactor, and the other path is connected to the fuel inlet of the heating furnace; the charging system of the reactor is connected to the briquetting system and the coke supply device.

[0008] The reactor further includes a furnace body, a hearth air supply device, a slag-forming flux injection device, and a slag and iron discharge device. The furnace body consists of, from top to bottom, a throat, a body, a waist, a belly, and a hearth. A top gas ring channel is provided at the lower part of the furnace body, and a circulating top gas inlet is located on the top gas ring channel. The top gas ring channel is an annular cavity structure with a ring of top gas injection ports evenly distributed on its inner side. The air inlet of the hearth air supply device is connected to an oxygen-enriched hot air source, and the air outlet extends into the hearth. The feed inlet of the slag-forming flux injection device is connected to a slag-forming flux supply device, and the injection port extends into the hearth. The slag and iron discharge device is located at the lower part of the hearth.

[0009] Furthermore, it also includes a combustion air blower; the outlet of the combustion air blower is connected to the combustion air passage of the heat exchanger, and then connected to the combustion air inlet of the heating furnace.

[0010] Furthermore, the dust collector includes a gravity dust collector, a cyclone dust collector, and an electrostatic dust collector connected in sequence.

[0011] To solve the above technical problems, the method of the present invention adopts the above system, and the technical solution adopted includes the following steps: 1) The iron-containing solid waste is briquetized by the briquetting system and then fed into the top of the reactor along with the coke through the charging system; 2) The lumpy iron-containing solid waste is heated and melted into molten iron in the reactor; 3) The furnace top gas of the reactor is collected by the furnace top gas collection system and then successively passes through a heat exchanger for heat exchange and cooling, a dust collector for dust removal, and a dehydrator for dehydration. 4) The dehydrated top gas is divided into two paths. One path is pressurized by a compressor, CO2 is captured by a CO2 treatment device, and heated by a heating furnace. Then, it is sent to the lower part of the reactor through the circulating top gas inlet. 5) The dehydrated top gas is sent to the fuel inlet of the heating furnace as fuel.

[0012] Furthermore, in step 1), oxygen-enriched hot air is sent into the hearth of the reactor by the hearth air supply device, and slag-forming flux is sprayed into the hearth of the reactor by the slag-forming flux injection device; in step 2), as the lumpy iron-containing solid waste and coke move downward in the reactor, they come into countercurrent contact with the upward-moving high-temperature reaction gas, thereby heating and melting the lumpy iron-containing solid waste into molten iron; after the molten iron enters the hearth, it mixes with the slag-forming flux, and a slag-forming reaction occurs. The resulting molten iron and slag are discharged by the slag and iron discharge device.

[0013] Furthermore, in step 5), the combustion air is sent by the combustion air blower into the combustion air passage of the heat exchanger, where it exchanges heat with the furnace top air and is then heated before being sent into the heating furnace as combustion air.

[0014] Furthermore, in step 3), the furnace top gas is sequentially dusted by a gravity dust collector, a cyclone dust collector, and an electrostatic precipitator.

[0015] The beneficial effects of adopting the above technical solution are as follows: This invention reduces CO2 emissions through top gas circulation, and the residual CO and H2 in the top gas are recycled into the lower part of the furnace body for deep utilization, maximizing direct reduction efficiency and reducing the overall energy consumption of the reactor. This invention utilizes coke and iron-containing solid waste briquettes from steel enterprises for production, which is energy-saving, environmentally friendly, and low-cost, effectively improving enterprise efficiency. Attached Figure Description

[0016] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0017] Figure 1 This is a schematic diagram of the system structure of the present invention; Figure 2 This is a schematic diagram of the structure of the gas ring channel at the top of the reactor described in this invention.

[0018] In the diagram: Reactor 01; Throat 02; Furnace body 03; Furnace waist 04; Furnace belly 05; Hearth 06; Heat exchanger 07; Gravity dust collector 08; Cyclone dust collector 09; Electrostatic precipitator 10; Dehydrator 11; Compressor 12; CO2 treatment device 13; Heating furnace 14; Hearth air supply device 15; Slag-forming flux injection device 16; Slag and iron discharge device 17; Combustion fan 18; Briquetting system 19; Circulating furnace top gas inlet 20; Molten iron transportation system 21; Steelmaking system 22; Furnace top gas injection port 23; Furnace body inner wall 24; Furnace shell side 25; Furnace top gas circulation channel 26. Detailed Implementation

[0019] Figure 1As shown, the system for the rational disposal of iron-containing solid waste in this steel enterprise includes a reactor 01, a heat exchanger 07, a dust collector, a dehydrator 11, a compressor 12, a CO2 treatment device 13, a heating furnace 14, and a briquetting system 19. The reactor 01 is equipped with a charging system and a furnace top gas collection system at the top, and a circulating furnace top gas inlet 20 at the bottom. The charging system of the reactor 01 is connected to the briquetting system 19 and the coke supply device. The dust collector includes a gravity dust collector 08, a cyclone dust collector 09, and an electrostatic precipitator 10. The furnace top gas collection system of the reactor 01 is connected to the inlet of the furnace top gas passage of the heat exchanger 07. The outlet of the furnace top gas passage is connected to the inlet of the gravity dust collector 08. The outlet of the gravity dust collector 08 is connected to the inlet of the cyclone dust collector 09. The outlet of the cyclone dust collector 09 is connected to the inlet of the electrostatic precipitator 10. The outlet of the electrostatic precipitator 10 is connected to the inlet of the dehydrator 11. The outlet of the dehydrator 11 is connected to two paths: one path is connected to the inlet of the compressor 12, the outlet of the compressor 12 is connected to the inlet of the CO2 treatment device 13, the outlet of the CO2 treatment device 13 is connected to the inlet of the inner coil of the heater 14, and the outlet of the inner coil of the heater 14 is connected to the circulating furnace top gas inlet 20 of the reactor 01; the other path of the outlet of the dehydrator 11 is connected to the fuel inlet of the heater 14. It also includes a combustion air blower 18; the outlet of the combustion air blower 18 is connected to the inlet of the combustion air passage of the heat exchanger 07, and the outlet of the combustion air passage is connected to the combustion air inlet of the heater 14. In this way, the furnace top gas, after being cooled by heat exchange, dusted by dust collector, and dehydrated by dehydrator 11, is sent to reactor 01 after being pressurized by compressor 12, CO2 captured by CO2 treatment device 13, and heated by heater 14. Another part is sent to heater 14 as fuel. The combustion air is heated by exchanging heat with the furnace top gas in the furnace top gas passage of heat exchanger 07 and then sent to heater 14 for combustion.

[0020] Figure 1 , 2As shown, this steel enterprise has a system for the rational disposal of iron-containing solid waste. The reactor 01 includes a furnace body, a hearth air supply device 15, a slag-forming flux injection device 16, and a slag and iron discharge device 17. The furnace body consists of, from top to bottom, a throat 02, a body 03, a waist 04, a belly 05, and a hearth 06. A furnace top gas ring channel 26 is provided at the lower part of the furnace body 03. The furnace top gas ring channel 26 is an annular cavity structure constructed of refractory material. The outer side of the furnace top gas ring channel 26 is the furnace shell side 25, and the inner side is the furnace body inner wall 24 on the charge side. The circulating top gas inlet 20 connects to the furnace shell side of the top gas ring channel 26, i.e., the outer side; a ring of top gas injection ports 23 is evenly distributed on the charge side, i.e., the inner side, to ensure that the circulating top gas is evenly injected into the reactor 01; there are several top gas injection ports 23, and none of them are located directly opposite the circulating top gas inlet 20. According to the furnace design, the number, size, and injection angle of the top gas injection ports 23 in the top gas ring channel are matched and arranged, with the injection angle of the top gas injection ports 23 preferably tilted downwards at 5°. The refractory materials such as bricks and castables of the top gas ring channel 26 must meet national standards. While ensuring a reasonable structure and meeting support requirements, the furnace body size ratio should be larger than that of a traditional blast furnace to ensure sufficient contact between the gas and the charge, achieving maximum energy efficiency.

[0021] Figure 1 , 2 As shown, this steel enterprise's system for the rational disposal of iron-containing solid waste includes a hearth blower 15 whose inlet is connected to an oxygen-enriched hot air source, and whose outlet extends into the hearth 06. The slag-forming flux injection device 16's inlet is connected to a slag-forming flux supply device, and its nozzle extends into the hearth 06. The slag and iron discharge device 17 is located at the lower part of the hearth 06. The hearth blower 15 discharges air at an angle downwards, and the slag-forming flux injection device 16 sprays air at an angle downwards. The downward tilt angle of the slag-forming flux injection device 16 is greater than that of the hearth blower 15. Both devices possess erosion resistance, corrosion resistance, and high-temperature resistance.

[0022] Figure 1 , 2 As shown, the method for the reasonable disposal of iron-containing solid waste by this steel enterprise includes the following steps: 1) The iron-containing solid waste is sent to the briquetting system 19, where a binder is added and pressed into blocks. The blocky iron-containing solid waste and coke are fed into the charging system, mixed, and then sent to the top of the throat 02 of the reactor 01. The compressive strength of the blocky iron-containing solid waste is controlled at 3000-3500N, and the particle size is controlled at 35±5mm; the particle size of the coke is 10-25mm. Since the cost of coke is lower than that of metallurgical coke, the production cost is significantly reduced. The particle size difference between the blocky iron-containing solid waste and the coke, combined with their own melting characteristics, ensures both the overall permeability of the material column and the deep utilization of coal gas.

[0023] The oxygen-enriched hot air is supplied to the hearth 06 of the reactor 01 by the hearth air supply device 15. The air supply pressure is higher than the injection pressure of the circulating top gas through the top gas ring channel 26 to ensure the upward flow of the gas. The pressure difference is calculated based on the furnace design, the weight of the charge column, etc. The slag-forming flux is injected into the hearth 06 of the reactor 01 in dry powder form by the slag-forming flux injection device 16 in a gas phase conveying manner. The injection volume is calculated based on the basicity required by the reactor 01. The basicity calculation is determined by the basicity of the iron-containing solid waste briquettes, the ash content of coke, and the heat of the hearth, etc., to ensure that the hearth is active and the slag and iron have good fluidity. The treated circulating top gas is injected evenly into the lower part of the furnace body 03 of the reactor 01 through the circulating top gas inlet 20 and the top gas ring channel 26.

[0024] 2) The lumpy iron-containing solid waste and coke move downwards in the reactor 01 until the furnace body 03 comes into full counter-current contact with the upward-moving high-temperature reaction gas, thereby heating and melting the lumpy iron-containing solid waste into molten iron; the high-temperature reaction gas includes the circulating furnace top gas injected into the furnace body 03, and the gas generated by the reaction of coke and oxygen-enriched hot air; after the molten iron enters the hearth 06, it mixes with the slag-forming flux and undergoes a slag-forming reaction to generate molten iron and slag; after the molten iron is discharged by the slag and iron discharge device 17, it is transported by the molten iron transportation system 21 to the steelmaking system 22 for steelmaking; the slag is discharged by the slag and iron discharge device 17 and recycled according to its physicochemical properties.

[0025] 3) The top gas from the reactor 01, after being collected by the top gas collection system, first undergoes heat exchange and cooling in heat exchanger 07; then it enters gravity dust collector 08, where gravity removes dust particles from the airflow for primary dust removal. By reducing the airflow velocity and changing the flow direction, particles settle naturally under gravity, removing coarse particles >50μm. The top gas exiting gravity dust collector 08 enters cyclone dust collector 09, where centrifugal force separates dust particles from the airflow, efficiently removing medium and coarse particles larger than 5μm. The top gas exiting the cyclone dust collector enters electrostatic precipitator 10, where physical separation efficiently removes fine particles of 0.01–20μm from the process gas. The clean top gas, now free of dust, is discharged from electrostatic precipitator 10 and enters dehydrator 11 for dehydration.

[0026] 4) The dehydrated top gas is divided into two paths. One path enters compressor 12 for pressurization to maintain circulation power. After pressurization, it enters CO2 treatment device 13 to capture CO2. The CO2 content of the collected circulating top gas is <1 vol%. The high-concentration CO2 is further processed and utilized to increase efficiency. The top gas after CO2 capture enters heating furnace 14 and is heated to 1100℃ or above. After heating in heating furnace 14, the top gas is sent to reactor 01 through furnace body circulating top gas inlet 20 for recycling as high-temperature reaction gas. Since the top gas is rich in CO and has reducing ability after pressurization, heating, dehydration, and dust removal, it is a good reducing agent. Compared with the traditional use of blast furnace gas as fuel, the utilization path is more reasonable.

[0027] 5) The dehydrated top gas is fed into the fuel inlet of the heating furnace 14 via another route and used as fuel. This provides energy value and maximizes energy efficiency throughout the process. Furthermore, it helps maintain N2 balance because the oxygen-enriched hot air supplied by the furnace hearth air supply device 15 contains approximately 78% N2. Recycling the top gas without treatment would lead to nitrogen accumulation. By using it as fuel for the heating furnace 14, the N2 balance of the entire process system can be controlled. The combustion air blower 18 sends combustion air into the combustion air passage of the heat exchanger 07. After exchanging heat with the top gas in the furnace top gas passage of the heat exchanger 07 and being heated, it is then sent into the heating furnace 14 for combustion.

Claims

1. A system for the rational disposal of iron-containing solid waste in steel enterprises, characterized in that: It includes a reactor (01), a heat exchanger (07), a dust collector, a dehydrator (11), a compressor (12), a CO2 treatment device (13), a heating furnace (14), and a briquetting system (19); the reactor (01) is provided with a charging system and a furnace top gas collection system at the top, and a circulating furnace top gas inlet (20) at the bottom; the furnace top gas collection system of the reactor (01) is connected in sequence to the furnace top gas passage of the heat exchanger (07), the dust collector, and the dehydrator (11), and one path is connected in sequence to the compressor (12), the CO2 treatment device (13), the heating furnace (14), and the circulating furnace top gas inlet (20) of the reactor (01), and the other path is connected to the fuel inlet of the heating furnace (14); the charging system of the reactor (01) is connected to the briquetting system (19) and the coke supply device.

2. A system for the rational disposal of iron-containing solid waste in steel enterprises according to claim 1, characterized in that: The reactor (01) includes a furnace body, a hearth air supply device (15), a slag-forming flux injection device (16), and a slag and iron discharge device (17). The furnace body consists of a furnace throat (02), a furnace body (03), a furnace waist (04), a furnace belly (05), and a hearth (06) from top to bottom. A furnace top gas ring channel (26) is provided at the lower part of the furnace body (03), and a circulating furnace top gas inlet (20) is located on the furnace top gas ring channel (26). The furnace top gas ring channel (26) is an annular cavity structure with a ring of furnace top gas injection ports (23) evenly distributed on its inner side. The air inlet of the hearth air supply device (15) is connected to an oxygen-enriched hot air source, and the air outlet extends into the hearth (06). The feed inlet of the slag-forming flux injection device (16) is connected to a slag-forming flux supply device, and the injection port extends into the hearth (06). The slag and iron discharge device (17) is located at the lower part of the hearth (06).

3. A system for the rational disposal of iron-containing solid waste in steel enterprises according to claim 1, characterized in that: It also includes a combustion air blower (18); the outlet of the combustion air blower (18) is connected to the combustion air passage of the heat exchanger (07) and then connected to the combustion air inlet of the heating furnace (14).

4. A system for the rational disposal of iron-containing solid waste in steel enterprises according to claim 1, 2 or 3, characterized in that: The dust collector includes a gravity dust collector (08), a cyclone dust collector (09), and an electrostatic dust collector (10) connected in sequence.

5. A method for the rational disposal of iron-containing solid waste by an iron and steel enterprise, employing the system described in any one of claims 1-4, characterized in that, The process includes the following steps: 1) The iron-containing solid waste is briquetized by the briquetting system (19) and then fed into the top of the reactor (01) via the charging system; 2) The lumpy iron-containing solid waste is heated and melted into molten iron in the reactor (01); 3) The furnace top gas of the reactor (01) is collected by the furnace top gas collection system and then passes through the heat exchanger (07) for heat exchange and cooling, the dust collector for dust removal, and the dehydrator (11) for dehydration in sequence; 4) The dehydrated furnace top gas is divided into two paths. One path is pressurized by the compressor (12), CO2 is captured by the CO2 treatment device (13), and heated by the heating furnace (14). Then, it is sent to the lower part of the reactor (01) through the circulating furnace top gas inlet (20). 5) The dehydrated top gas is sent to the fuel inlet of the heating furnace (14) as fuel.

6. A method for the rational disposal of iron-containing solid waste by an iron and steel enterprise according to claim 5, characterized in that: In step 1), oxygen-enriched hot air is sent into the hearth (06) of the reactor (01) by the hearth air supply device (15), and slag-forming flux is injected into the hearth (06) of the reactor (01) by the slag-forming flux injection device (16); in step 2), the lumpy iron-containing solid waste and coke are in reverse contact with the upward-moving high-temperature reaction gas during the downward movement of the lumpy iron-containing solid waste and coke in the reactor (01), thereby heating and melting the lumpy iron-containing solid waste into molten iron; after the molten iron enters the hearth (06), it is mixed with the slag-forming flux and slag-forming reaction occurs. The generated molten iron and slag are discharged by the slag and iron discharge device (17).

7. A method for the rational disposal of iron-containing solid waste by an iron and steel enterprise according to claim 5, characterized in that: In step 5), the combustion air blower (18) sends the combustion air into the combustion air passage of the heat exchanger (07), and after exchanging heat with the furnace top gas and raising the temperature, it is sent into the heating furnace (14) as combustion air.

8. A method for the rational disposal of iron-containing solid waste by an iron and steel enterprise according to claim 5, characterized in that: In step 3), the furnace top gas is sequentially dusted by a gravity dust collector (08), a cyclone dust collector (09), and an electrostatic dust collector (10).

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