A method for comprehensive treatment of red mud and integration with alumina production process and step-by-step utilization of energy

Abstract

The application discloses a method for comprehensively treating red mud and integrating with an alumina production process to realize step-by-step energy utilization, and belongs to the technical field of metallurgy and resource recycling. The method specifically comprises the following steps: oxygen, water vapor, coal powder and red mud powder are sprayed into a flash smelting furnace from a burner at the top of a coal gasification flash smelting furnace, high-temperature heat and high-reducing gas generated by coal gasification are utilized to directly smelt and reduce Fe2O3 in the red mud to produce molten iron, and after the red mud and the coal powder liquid slag are tempered, rock wool or other fiberized materials are directly produced, sodium oxide in the red mud is converted into sodium hydroxide for recycling and reuse; after smelting is completed, high-temperature coal gas waste heat is recovered to produce steam for use in an evaporation section of an alumina production process, coal gas is used in a roasting section of the alumina production process, and roasting tail gas is used for red mud drying. The application realizes integration of red mud treatment and the alumina production process and process reengineering, meets the energy needs of two process courses through clean and efficient step-by-step utilization of coal, realizes energy saving and emission reduction, and has no secondary pollution.

Description

Technical Field

[0001] This invention relates to a method for the comprehensive recycling and utilization of alumina red mud, specifically a method for the comprehensive treatment of red mud and its integration with alumina production processes, process reengineering, and cascade utilization of energy, belonging to the field of metallurgy and resource recycling technology. Background Technology

[0002] The comprehensive recycling and utilization of alumina red mud resources is a global challenge. Currently, over 90% of the world's red mud is stockpiled, with less than 10% being recycled using various methods. Scientists worldwide have invented numerous technologies to address this issue. US Patent US20140369907A1 discloses a method for leaching red mud with hydrochloric acid to extract aluminum, iron, nickel, and magnesium from the leachate, and titanium dioxide from the leachate solids. US Patent US20210079488A1 discloses a physical method for extracting iron oxide and alumina from red mud. Russian Patent RU2579843C2 discloses a technique for leaching metallic elements from red mud with hydrochloric acid. Chinese Patent CN110951931A discloses an alumina red mud reduction method and apparatus, which uses coke particles and a binder to pelletize iron-containing red mud powder, and then uses a U-shaped tunnel kiln for direct gas-based reduction of the pellets—a two-stage reduction method for producing sponge iron (similar to a rotary hearth furnace). These existing technologies are either economically unfeasible and lack practical value, or they can only recover certain elements from the red mud, failing to completely solve the red mud pollution problem. The industry urgently needs a new technology to thoroughly address the red mud remediation issue. Summary of the Invention

[0003] The iron content of alumina red mud ranges from 10% to 40% and above, with red mud containing more than 30% iron accounting for over 60% of the total red mud. This invention aims to provide a comprehensive red mud treatment method that integrates high-iron-content red mud with the alumina production process for tiered energy utilization. Firstly, based on the high iron content of alumina red mud, a novel technical approach is adopted to treat it, solving the technical challenges of high-iron-content red mud treatment in a one-step, fully resource-based manner. Secondly, by integrating red mud treatment with the alumina production process, energy is utilized in a tiered manner, achieving efficient energy utilization in both red mud treatment and alumina production processes.

[0004] The method provided by this invention integrates the coal gasification flash smelting process for treating red mud and the alumina production process, realizing the cascade utilization of coal energy. The first stage utilizes coal gasification, the second stage utilizes flash smelting and reduction to produce molten iron and rock wool, the third stage utilizes the waste heat of high-temperature coal gas to produce steam for the evaporation process in alumina production, the fourth stage utilizes cooled coal gas for the roasting process in alumina production, and the fifth stage utilizes the tail gas from alumina roasting to dry red mud.

[0005] This invention provides a method for the comprehensive treatment of red mud and its integration with the alumina production process for tiered energy utilization. This method uses a coal gasification flash smelting furnace to integrate the treatment of red mud with the alumina production process, achieving process reengineering. Specifically, oxygen + steam, pulverized coal, and red mud powder are injected into the flash furnace from the top burner. The high temperature and highly reducing gases generated during the coal gasification process directly melt and reduce Fe2O3 in the red mud to produce molten iron. The basalt-like gangue minerals such as silicon, aluminum, and calcium in the red mud and pulverized coal are smelted into liquid slag, which is then tempered and directly used to produce rock wool or other fibrous materials. After the reduction of sodium oxide in the red mud, the sodium metal volatilizes at high temperature and reacts with the steam in the coal gas to produce sodium hydroxide, which is then recovered and reused. Ultimately, this achieves a one-step, fully resource-based comprehensive utilization of red mud. The high-temperature coal gas waste heat after smelting is recovered to produce steam for the alumina production evaporation section, coal gas for the alumina production roasting section, and roasting tail gas for red mud drying.

[0006] The aforementioned method for comprehensive red mud treatment and its integration with the alumina production process for cascaded energy utilization includes the following steps:

[0007] (1) Red mud from red mud settling tanks (barrels) or red mud reservoirs is dried and crushed to obtain red mud powder. The total iron content of the red mud powder is more than 30%, the fineness is 200-300 mesh, and the water content is 1-2%.

[0008] (2) The mass ratio of oxygen, water vapor, coal powder and red mud powder is 0.65-0.75:0.1-0.15:0.9-1.1:2-3.7. It is injected into the coal gasification flash smelting furnace. In the coal gasification flash smelting furnace, Fe2O3 in red mud undergoes a melting reduction reaction under the high temperature and high reducing gas conditions of coal powder gasification.

[0009] (3) The lower part of the coal gasification flash smelting furnace is a molten pool. Fe2O3 is reduced to molten iron or ferrous oxide, which enters the lower molten pool along with slag and ungasified coal powder. Ferrous oxide and ungasified coal powder undergo final reduction of ferrous oxide in the molten pool, after which slag and iron are separated. High-temperature coal gas is discharged from the top of the molten pool and enters the waste heat boiler for waste heat recovery to produce steam. Liquid slag is discharged from the slag outlet of the molten pool and is conditioned to produce rock wool or fiber products. Molten iron is discharged from the molten iron outlet of the molten pool and used to produce cast iron or steel.

[0010] (4) The sodium hydroxide produced by the reaction of sodium vapor generated by sodium oxide reduction and water vapor in coal gas is recovered and enters the melting section of alumina production; the steam produced by the waste heat boiler enters the evaporation section of alumina production; the cooled coal gas discharged from the waste heat boiler enters the roasting section of alumina production; the roasting tail gas of the roasting section is used for red mud drying.

[0011] In the above method, the oxygen injected into the coal gasification flash smelting furnace is pure oxygen, the water vapor is saturated steam, the coal powder is 5500-6500 kcal / kg, the fineness is 200-300 mesh, and the water content is 1-2%. The total iron content in the red mud is more than 30%, the fineness is 200-300 mesh, and the water content is 1-2%.

[0012] In the above method, the temperature in the high-temperature zone of the flash furnace is 1500-1700℃, and the CO+H2 content in the highly reducing gas is greater than 90%. The temperature of the high-temperature gas after smelting is 1400-1500℃, and the effective CO+H2 content of the gas is 60-70%.

[0013] In the above method, the steam pressure recovered and produced in the waste heat boiler is 0.6~0.8MPa, and the calorific value of the gas is 1800-2000 kcal / m³. 3 .

[0014] In the above method, the red mud is treated by coal gasification flash smelting and integrated with the alumina production process for cascade energy utilization. The steam produced by the high-temperature coal gas waste heat after the flash smelting is used for the evaporation process in alumina production, the coal gas is used for the alumina roasting process, and the tail gas from the alumina roasting is used for the drying of red mud. The sodium hydroxide recovered during the waste heat recovery process is used in the leaching system of alumina production.

[0015] In the above method, the temperature of the alumina roasting tail gas used for drying red mud is controlled at 180-250℃.

[0016] This invention provides a device for the comprehensive treatment of red mud and its integration with the alumina production process for cascaded energy utilization, comprising a red mud treatment device and an alumina production device; wherein:

[0017] The red mud treatment device includes: a pulverized coal silo, a red mud powder silo, a coal gasification flash smelting furnace, a molten pool, a gravity settling chamber, and a waste heat boiler; the pulverized coal silo is connected to the first pulverized coal injection device and the second pulverized coal injection device respectively, and the red mud powder silo is connected to the red mud powder injection device.

[0018] The gasification flash smelting furnace is equipped with a burner at the top and a molten pool at the bottom. A gravity settling chamber is connected to the upper part of the other side of the molten pool. A copper water jacket and spray gun are installed on the sidewall of the molten pool. The burner is connected to a first pulverized coal injection device, oxygen and steam inlets, a red mud powder injection device, and a burner water cooling device. The copper water jacket and spray gun are connected to a second pulverized coal injection device. The molten pool has an iron outlet and a slag outlet. The iron outlet connects to a casting or steelmaking system, and the slag outlet connects to a rock wool processing system. A high-temperature gas outlet is located at the top of the gravity settling chamber and is connected to a waste heat boiler. The waste heat boiler has a demineralized water inlet, a steam outlet, a gas outlet, and a sodium hydroxide outlet. The steam outlet of the waste heat boiler connects to an alumina production evaporation device, the gas outlet connects to an alumina roasting device, and the sodium hydroxide outlet connects to an alumina leaching device.

[0019] The alumina production unit includes: an alumina production roasting unit, an alumina production evaporation unit, and an alumina production leaching unit; the exhaust gas outlet at the top of the alumina production roasting unit is connected to a red mud drying and pulverizing machine.

[0020] In the above-mentioned device, the red mud drying and pulverizing machine is one of the following: flash dryer, drum dryer + pulverizer, or paddle dryer + pulverizer.

[0021] The beneficial effects of this invention are:

[0022] (1) Using pure oxygen and coal powder gasification to generate high temperature of 1500-1700℃ and reducing gas with more than 90% CO+H2 content, red mud is directly melted and reduced to produce molten iron, rock wool and sodium hydroxide in one step. The technology is simple.

[0023] (2) The red mud treatment and utilization is combined with the alumina production process for process reengineering, and energy is utilized in stages, which has achieved energy conservation and carbon emission reduction;

[0024] (3) Red mud treatment and recycling has no wastewater or waste residue discharge, no secondary pollution, and realizes full resource utilization;

[0025] (4) Red mud treatment directly produces molten iron and rock wool, realizing high-value utilization. Attached Figure Description

[0026] Figure 1 This is a block diagram of the process flow of the present invention.

[0027] Figure 2 This is a schematic diagram of the device for the comprehensive treatment of red mud and its integration with the alumina production process for cascaded energy utilization, as per the present invention.

[0028] In the diagram: 1. Pulverized coal bin, 2. Red mud powder bin, 3. First pulverized coal injection device, 4. Second pulverized coal injection device, 5. Red mud powder injection device, 6. Burner, 7. Coal gasification flash smelting furnace, 8. Molten pool, 9. Copper water jacket and spray gun, 10. Gravity settling chamber, 11. Molten iron outlet, 12. Slag outlet, 13. High-temperature gas outlet, 14. Casting or steelmaking system, 15. Rock wool processing system, 16. Waste heat boiler, 17. Demineralized water inlet, 18. Steam outlet, 19. Gas outlet, 20. Sodium hydroxide outlet, 21. Alumina production roasting device, 22. Alumina production evaporation device, 23. Alumina production leaching device, 24. Drying and pulverizing machine. Detailed Implementation

[0029] The present invention will be further illustrated by the following embodiments, but is not limited to the following embodiments.

[0030] like Figures 1-2 As shown, this invention provides a device for the comprehensive treatment of red mud and its integration with the alumina production process for cascaded energy utilization, comprising a red mud treatment device and an alumina production device; wherein:

[0031] The red mud treatment device includes: a pulverized coal silo 1, a red mud pulverized coal silo 2, a coal gasification flash smelting furnace 7, a molten pool 8, a gravity settling chamber 10, and a waste heat boiler 16; the pulverized coal silo 1 is connected to a first pulverized coal injection device 3 and a second pulverized coal injection device 4, and the red mud pulverized coal silo 2 is connected to a red mud pulverized coal injection device 5; the coal gasification flash smelting furnace is equipped with a burner 6 at the top and a molten pool 8 at the bottom, with the gravity settling chamber 10 connected to the upper part of the other side of the molten pool, and a copper water jacket and spray gun 9 on the side wall of the molten pool 8; the burner 6 is connected to the first pulverized coal injection device, oxygen and steam inlets, a red mud pulverized coal injection device, and a burner water cooling device, and the copper water jacket and spray gun 9 are connected to the second pulverized coal injection device. 4. Oxygen source; the side of the molten pool is provided with molten iron outlet 11 and slag outlet 12. Molten iron outlet 11 is connected to casting or steelmaking system 14, and slag outlet 12 is connected to rock wool processing system 15; the top of gravity settling chamber 10 is provided with high temperature gas outlet 13, which is connected to waste heat boiler 16; waste heat boiler 16 is provided with demineralized water inlet 17, steam outlet 18, gas outlet 19, and sodium hydroxide outlet 20. The steam outlet 18 of waste heat boiler is connected to alumina production evaporation device 22, the gas outlet 19 is connected to alumina production roasting device 21, and the sodium hydroxide outlet 20 is connected to alumina production leaching device 23.

[0032] The alumina production apparatus includes: an alumina production roasting apparatus 21, an alumina production evaporation apparatus 22, an alumina production leaching apparatus 23; the tail gas outlet of the alumina roasting apparatus is connected to the drying and pulverizing machine 24.

[0033] In the above-mentioned device, the drying and pulverizing machine 24 is one of the following: flash dryer, drum dryer + pulverizer, and paddle dryer + pulverizer. Example 1

[0034] Red mud from the red mud settling tank (barrel) or red mud storage is dried in the drying and pulverizing mill 24 (flash dryer) using roasting tail gas from the alumina roasting device 21 at a temperature of 180°C. The dried red mud powder has a total iron content of 30%, a fineness of 200 mesh, and a moisture content of 2%. It is then fed into the red mud powder silo 2. 3.3 tons of red mud powder are injected through the red mud powder injection device 5, along with 1000 kg of pulverized coal (from the pulverized coal silo 1) with a moisture content of 2%. This is then injected through the first pulverized coal injection device 3, along with 650 kg of oxygen and 150 kg of steam, from the burner 6 at the top of the flash furnace into the coal gasification flash smelting furnace 7. The flash furnace temperature is controlled at 1700°C, and the coal gas content is controlled at 90%. Under these conditions, the Fe2O3 in the red mud melts and is reduced to molten iron or ferrous oxide under the high temperature and high reducing gas conditions of the pulverized coal gasification, along with liquid slag and ungasified coal. The pulverized coal falls into the lower molten pool 8; through the second pulverized coal injection device 4, copper water jacket and spray gun 9, 100 kg of pulverized coal and 100 kg of oxygen are injected into the molten pool 8 respectively for the final reduction of ferrous oxide and slag-iron separation; high-temperature coal gas at 1500℃ is discharged from the high-temperature coal gas outlet 13 at the top of the molten pool and enters the waste heat boiler 16 for waste heat recovery to produce steam at a pressure of 0.6 MPa. The steam is discharged from the steam outlet 18 and enters the alumina production evaporation device 22 for the evaporation of intermediate products in alumina production; liquid slag is discharged from the slag outlet 12 and, after conditioning, enters the rock wool processing system 15 to produce rock wool products; molten iron is discharged from the molten iron outlet 11 of the molten pool and enters the casting device to produce cast iron; sodium oxide in the red mud is reduced before Fe2O3, and the resulting sodium vapor and water vapor generate sodium hydroxide, which is discharged from the sodium hydroxide outlet 20 and enters the alumina production melting device 23 for use; the cooled coal gas discharged from the waste heat boiler gas outlet 19 enters the alumina production roasting device 21 for alumina roasting. Example 2

[0035] Red mud from the red mud settling tank (barrel) or red mud storage is dried in a drying and pulverizing mill 24 (paddle dryer + pulverizer) using roasting tail gas from the alumina production roasting unit 21 at a temperature of 250℃. The dried red mud powder has a total iron content of 40%, a fineness of 250 mesh, and a moisture content of 1.5%. It is then fed into the red mud powder silo 2. 2.5 tons of red mud powder are injected through the red mud powder injection device 5, along with 900 kg of pulverized coal (from the pulverized coal silo 1) with a moisture content of 1.5%. This mixture is then injected through the first pulverized coal injection device 3, along with 600 kg of oxygen and 120 kg of steam, from the burner 6 at the top of the flash furnace into the coal gasification flash smelting furnace 7. The flash furnace temperature is controlled at 1600℃, and the coal gas content is controlled at 90%. Under these conditions, the Fe2O3 in the red mud is melted and reduced to molten iron or ferrous oxide under the high temperature and high reducing gas conditions of the pulverized coal gasification, along with liquid slag and no gas. Powdered coal enters the lower molten pool 8; through the second pulverized coal injection device 4, copper water jacket and spray gun, 100 kg of pulverized coal and 100 kg of oxygen are injected into the molten pool 8, where the final reduction of ferrous oxide and slag-iron separation take place; high-temperature coal gas at 1450℃ is discharged from the high-temperature coal gas outlet 13 at the top of the molten pool and enters the waste heat boiler 16 for waste heat recovery to produce steam at a pressure of 0.8 MPa. The steam is discharged from the steam outlet 18 and enters the alumina production evaporation device 22 for evaporation of intermediate products in alumina production; liquid slag is discharged from the slag outlet 12, and after conditioning, it enters the rock wool processing system 15 to produce rock wool products; molten iron is discharged from the molten iron outlet 11 of the molten pool and enters the steelmaking device to produce steel; sodium hydroxide generated by the sodium metal volatiles produced by the reduction of sodium oxide in red mud before Fe2O3 and water vapor is discharged from the sodium hydroxide outlet 20 and enters the alumina production melting device 23 for use; The cooled gas discharged from the waste heat boiler gas outlet 19 enters the alumina production roasting device 21 for alumina roasting. Example 3

[0036] Red mud from the red mud settling tank (barrel) or red mud storage is dried in a drying and pulverizing mill 24 (drum dryer + pulverizer) using roasting tail gas from the alumina production roasting device 21 at a temperature of 200℃. The dried red mud powder has a total iron content of 45%, a fineness of 250 mesh, and a moisture content of 1%. It is then fed into the red mud powder silo 2. 2.2 tons of red mud powder are injected through the red mud powder injection device 5, along with 800 kg of pulverized coal (from the pulverized coal silo 1) with a moisture content of 1%. This is then injected through the first pulverized coal injection device 3, along with 550 kg of oxygen and 100 kg of steam, from the burner 6 at the top of the flash furnace into the coal gasification flash smelting furnace 7. The flash furnace temperature is controlled at 1700℃, and the coal gas content is controlled at 90%. Under these conditions, the Fe2O3 in the red mud melts and is reduced to molten iron or ferrous oxide under the high temperature and high reducing gas conditions of the pulverized coal gasification. Liquid slag and ungasified coal powder enter the lower molten pool 8; 100 kg of coal powder and 100 kg of oxygen are injected into the molten pool 8 through the second coal powder injection device 4, copper water jacket and spray gun, and the final reduction of ferrous oxide and slag-iron separation are carried out in the molten pool; high-temperature coal gas at 1400℃ is discharged from the high-temperature coal gas outlet 13 at the top of the molten pool and enters the waste heat boiler 16 for waste heat recovery to produce steam at a pressure of 0.7 MPa. The steam is discharged from the steam outlet 18 and enters the alumina production evaporation device 22 for the evaporation of intermediate products in alumina production; liquid slag is discharged from the slag outlet 12, and after conditioning, it enters the rock wool processing system 15 to produce rock wool products; molten iron is discharged from the molten iron outlet 11 of the molten pool and enters the casting device to produce cast iron; sodium hydroxide recovered from sodium oxide in red mud is discharged from the sodium hydroxide outlet 20 and enters the alumina production melting device 23 for use; the cooled coal gas discharged from the waste heat boiler gas outlet 19 enters the alumina production roasting device 21 for alumina roasting.

Claims

1. A method for the comprehensive treatment of red mud and its integration with the alumina production process for cascaded energy utilization, characterized in that: This method utilizes a coal gasification flash smelting furnace, integrating the coal gasification flash smelting process for treating red mud and the alumina production process. Specifically, oxygen + water vapor, pulverized coal, and red mud powder are injected into the flash furnace through burners at the top. The heat and highly reducing gases generated during the coal gasification process are used to directly melt and reduce Fe2O3 in the red mud to produce molten iron. The basaltic gangue in the red mud forms liquid slag, which, after conditioning, is directly used to produce rock wool or other fibrous materials. After sodium oxide in the red mud is reduced, the sodium metal volatilizes at high temperatures and reacts with water vapor in the coal gas to generate sodium hydroxide, which is then recovered and reused. This ultimately achieves a one-step, full-resource recovery and utilization of red mud. The high-temperature coal gas after smelting is used to recover waste heat to produce steam for the alumina production evaporation section, coal gas for the alumina production roasting section, and roasting tail gas for red mud drying.

2. The method for comprehensive red mud treatment and its integration with the alumina production process for cascaded energy utilization as described in claim 1, characterized in that... Includes the following steps: (1) Red mud powder is obtained after drying and crushing. The total iron content of the red mud powder is more than 30%, the fineness is 200-300 mesh, and the water content is 1-2%. (2) The mass ratio of oxygen, water vapor, coal powder and red mud powder injected into the coal gasification flash smelting furnace is 0.65-0.75:0.1-0.15:0.9-1.1:2-3.

7. In the coal gasification flash smelting furnace, Fe2O3 in red mud undergoes a melting reduction reaction under the high temperature and high reducing gas conditions of coal powder gasification. (3) The lower part of the coal gasification flash smelting furnace is a molten pool. Fe2O3 is reduced to molten iron or ferrous oxide, which enters the lower molten pool with the molten slag. Ferrous oxide and ungasified coal slag fall into the molten pool for final reduction of ferrous oxide, and then the slag and iron are separated. High-temperature coal gas is discharged from the top of the molten pool and enters the waste heat boiler for waste heat recovery to produce steam. Liquid slag is discharged from the slag outlet of the molten pool and conditioned to produce rock wool or fiber products. Molten iron is discharged from the molten iron outlet of the molten pool and used to produce cast iron or steel. (4) Sodium vapor and water vapor generated by sodium oxide reduction react to form sodium hydroxide, which is then recovered and enters the alumina production leaching system; steam generated by the waste heat boiler enters the alumina production evaporation section; cooled coal gas discharged from the waste heat boiler enters the alumina production roasting section. The roasting exhaust gas from the roasting section is used to dry red mud.

3. The method for comprehensive red mud treatment and its integration with the alumina production process for cascaded energy utilization as described in claim 2, characterized in that: The oxygen injected into the coal gasification flash smelting furnace is pure oxygen, the water vapor is saturated steam, the calorific value of the pulverized coal is 5500-6500 kcal / kg, the fineness is 200-300 mesh, and the moisture content is 1-2%.

4. The method for comprehensive red mud treatment and its integration with the alumina production process for cascaded energy utilization as described in claim 2, characterized in that: The high-temperature zone of the flash furnace has a temperature of 1500-1700℃, and the carbon monoxide and hydrogen content in the highly reducing gas is greater than 90%; the high-temperature gas temperature after smelting is 1400-1500℃, and the effective CO+H2 content of the gas is 60-70%.

5. The method for comprehensive red mud treatment and its integration with the alumina production process for cascaded energy utilization as described in claim 2, characterized in that: The steam recovered from the waste heat boiler has a pressure of 0.6~0.8MPa, and the calorific value of the discharged gas is 1800-2000 kcal / m³. 3 .

6. The method for comprehensive red mud treatment and its integration with the alumina production process for cascaded energy utilization according to claim 2, characterized in that: The temperature of the alumina roasting tail gas used for drying red mud is controlled at 180-250℃.

7. An apparatus for the comprehensive treatment of red mud and its integration with the alumina production process for the cascaded utilization of energy, used to implement the method for the comprehensive treatment of red mud and its integration with the alumina production process for the cascaded utilization of energy as described in any one of claims 1 to 6, characterized in that: It consists of a red mud treatment unit and an alumina production unit; wherein: The red mud treatment device includes: a pulverized coal silo, a red mud powder silo, a coal gasification flash smelting furnace, a molten pool, a gravity settling chamber, and a waste heat boiler; the pulverized coal silo is connected to the first pulverized coal injection device and the second pulverized coal injection device, and the red mud powder silo is connected to the red mud powder injection device. The gasification flash smelting furnace is equipped with a burner at the top and a molten pool at the bottom. A gravity settling chamber is connected to the upper part of the other side of the molten pool. A copper water jacket and spray gun are installed on the sidewall of the molten pool. The burner is connected to a first pulverized coal injection device, oxygen and steam inlets, a red mud powder injection device, and a water cooling device. The copper water jacket and spray gun are connected to a second pulverized coal injection device. The molten pool has an iron outlet and a slag outlet. The iron outlet is connected to a casting or steelmaking system, and the slag outlet is connected to a rock wool processing system. A high-temperature gas outlet is located at the top of the gravity settling chamber and is connected to a waste heat boiler. The waste heat boiler has a demineralized water inlet, a steam outlet, a gas outlet, and a sodium hydroxide outlet. The steam outlet of the waste heat boiler is connected to an alumina production evaporation device, the sodium hydroxide recovery outlet is connected to an alumina production leaching device, and the gas outlet is connected to an alumina roasting device. The alumina production unit includes: an alumina production roasting unit, an alumina production evaporation unit, and an alumina production leaching unit; the roasting exhaust gas outlet at the top of the alumina production roasting unit is connected to a red mud drying and pulverizing machine.

8. The device for comprehensive red mud treatment and integrated energy utilization in a cascade manner with alumina production as described in claim 7, characterized in that: The red mud drying and pulverizing machine is one of the following: flash dryer, drum dryer + pulverizer, or paddle dryer + pulverizer.

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