Green comprehensive utilization method of red mud

Abstract

The invention relates to the field of solid waste clean utilization, and discloses a red mud green comprehensive utilization method which comprises the following steps: dehydrating and pelletizing red mud to obtain red mud pellets; the red mud pellets are dried at the temperature of 300-400 DEG C; adding the dried red mud pellets into an electric arc furnace, heating to 1550-1600 DEG C for melting to form a molten pool, and introducing reducing gas hydrogen into the molten pool to generate molten iron and slag; the molten iron is used for steelmaking or casting, and the slag is used for separating and extracting Al2O3, TiO2, Fe2O3 and SiO2 after water quenching. The red mud is reduced through hydrogen, CO2 emission is avoided, the method is clean and pollution-free, various substances are extracted from the slag after iron extraction, the recovery rate is high, the cost is low, and the economic benefit is good.

Description

Technical Field

[0001] The present invention belongs to the field of solid waste clean utilization, and particularly relates to a method for green comprehensive utilization of red mud. Background Art

[0002] Red mud is a solid waste generated in the production of alumina. It is called red mud because it is red due to the presence of a lot of Fe2O3. The main components of red mud are Fe2O3, Al2O3, SiO2, TiO2, NaOH, and CaO, and there are also a small amount of oxides such as gallium, germanium, vanadium, scandium, and rare earths. The stacking of red mud not only occupies a large amount of land but also causes environmental pollution.

[0003] In order to solve the problem of red mud polluting the environment, many methods for treating red mud have been studied. However, due to high costs and poor benefits, they have not been applied. Some methods may also cause secondary pollution. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for green comprehensive utilization of red mud that does not cause environmental pollution and has good economic benefits in view of the above problems.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for green comprehensive utilization of red mud, comprising the following steps:

[0006] (1) Dehydrate and pelletize the red mud to obtain red mud pellets;

[0007] (2) Dry the red mud pellets at 300°C to 400°C;

[0008] (3) Add the dried red mud pellets to an electric arc furnace, heat to 1550°C to 1600°C to melt, form a molten pool, and blow hydrogen into the molten pool for smelting to generate molten iron and slag. The amount of hydrogen added is 100% in excess of the amount of hydrogen required to completely reduce the iron oxides in the molten pool;

[0009] (4) Use the molten iron for steelmaking or casting, and after water quenching the slag, use it to separate and extract Al2O3, TiO2, Fe2O3, and SiO2;

[0010] When hydrogen is introduced into the molten pool of the electric arc furnace, the chemical reaction is as follows:

[0011] Fe2O3 + 3H2 = 2Fe + 3H2O

[0012] FeO + H2 = Fe + H2O

[0013] Among them, Al2O3, SiO2, TiO2, and part of FeO form slag, and Na2O in the red mud enters the flue dust;

[0014] (5) The flue gas generated in the electric arc furnace is introduced into the combustion chamber, and air is introduced into the combustion chamber to burn hydrogen in the combustion chamber. The heat of the flue gas and the heat generated by the combustion of H2 are used for power generation; the chemical reaction occurring in the combustion chamber is:

[0015] 2H2 + O2 = 2H2O

[0016] (6) After the dust generated by the reaction in the electric arc furnace is recovered by the dust removal system, it is soaked in water to react Na2O in the dust with water to form NaOH soluble in water. After filtration, solid slag and a filtrate containing NaOH are obtained. The solid slag is returned to step (1) for recycling. After the NaOH content in the filtrate reaches a certain concentration, evaporation and crystallization are carried out to obtain NaOH products.

[0017] Among them, Na2O dissolves in water, and the chemical reaction occurs as:

[0018] Na2O + H2O = 2NaOH

[0019] NaOH is used for subsequent processes.

[0020] Preferably, in step (1), the red mud is dehydrated to a water content of 10%, and the particle size of the pellets is 20 mm to 30 mm.

[0021] Preferably, in step (2), the pellets are dried to a water content of less than 1%.

[0022] Preferably, the preparation method for separating and extracting Al2O3, TiO2, Fe2O3, and SiO2 after the slag is water quenched is as follows:

[0023] S1: After the slag is water quenched, it is ground into a powder with a particle size of 80 μm, then dehydrated to a water content of 10%, and ammonium sulfate is added for mixing and pelletizing;

[0024] S2: The pellets prepared in step S1 are heated to 400 °C to 500 °C and roasted for 1 hour; the chemical reactions occurring during the roasting process are:

[0025] Fe2O3 + 3(NH4)2SO4 = Fe2(SO4)3 + 6NH3↑ + 3H2O

[0026] FeO + (NH4)2SO4 = FeSO4 + 2NH3↑ + H2O

[0027] Al2O3 + 3(NH4)2SO4 = Al2(SO4)3 + 6NH3↑ + 3H2O

[0028] TiO2 + (NH4)2SO4 = TiOSO4 + 2NH3↑ + H2O

[0029] SiO2 in the slag does not participate in the reaction, and the NH3 generated by the reaction is recovered for use in subsequent processes;

[0030] S3: Dissolve the clinker produced by roasting in water. The liquid-solid mass ratio of water to the clinker is 3:1, and the dissolution time is 1 hour. Filter and separate the dissolved matter to obtain filter residue SiO2 and filtrate A containing Al2(SO4)3, Fe2(SO4)3, FeSO4, and TiOSO4;

[0031] S4: Add reducing agent iron filings to filtrate A, react for 4 hours, reduce the ferric iron in the filtrate to ferrous iron, remove the iron filings, and obtain a solution; The chemical reaction is:

[0032] Fe 3+ +Fe = 2Fe 2+

[0033] S5: Heat the solution to 110 °C to hydrolyze titanyl sulfate to produce metatitanic acid precipitate. Filter to obtain solid metatitanic acid and filtrate B. Calcinate the solid metatitanic acid at 1000 °C to obtain anatase TiO2 product; The hydrolysis reaction that occurs is:

[0034] TiOSO4 + 2H2O = H2TiO3↓ + H2SO4

[0035] The chemical reaction that occurs during calcination is:

[0036] H2TiO3 = TiO2 + H2O

[0037] S6: Pass ammonia gas into filtrate B, adjust the pH value to 6 to form Al(OH)3 precipitate. Filter to obtain solid Al(OH)3 and filtrate C; The chemical reaction that occurs is:

[0038] Al2(SO4)3 + 6NH3 + 3H2O = 2Al(OH)3↓ + 3(NH4)2SO4

[0039] S7: Continue to pass ammonia gas into filtrate C, adjust the pH value to 7 to form Fe(OH)2 precipitate. Filter to obtain solid Fe(OH)2 and filtrate D. Filtrate D is a solution containing ammonium sulfate. Calcinate the solid Fe(OH)2 in the air at 500 °C to obtain Fe2O3 product; The chemical reactions that occur are:

[0040] FeSO4 + 2NH3 + 2H2O = Fe(OH)2↓ + (NH4)2SO4

[0041] 2Fe(OH)2 + 1 / 2O2 = Fe2O3 + 2H2O

[0042] S8: Add the solid Al(OH)3 obtained in step S6 to a NaOH solution with a concentration of 150 g / L and a temperature of 60 °C to dissolve Al(OH)3 to saturation to form a sodium aluminate solution; The chemical reaction that occurs is:

[0043] Al(OH)3 + NaOH = NaAlO2 + 2H2O

[0044] S9: After the sodium aluminate solution is finely filtered to remove impurities, a small amount of Al(OH)3 is added to the solution as a seed crystal to precipitate pure Al(OH)3, which is then filtered to obtain Al(OH)3 crystals and a mother liquor containing NaOH and NaAlO2. The Al(OH)3 crystals are calcined at 1300 °C to obtain Al2O3 products, and the mother liquor is returned to step S8 for recycling.

[0045] S10: The filtrate D is evaporated to dehydrate to obtain ammonium sulfate crystals, which are returned to step S1 for recycling.

[0046] Preferably, the preparation method for separating and extracting Al2O3, TiO2, Fe2O3, and SiO2 from the slag after water quenching is as follows:

[0047] S1: The slag is water quenched and then ground into a powder with a particle size of 80 μm, and then dehydrated to a moisture content of less than 1%. It is mixed and pelletized with a sulfuric acid solution with a concentration of 80%.

[0048] S2: The pellets prepared in step S1 are heated to 400 °C - 500 °C and roasted for 1 hour. The chemical reactions occurring are as follows:

[0049] Fe2O3 + 3H2SO4 = Fe2(SO4)3 + 3H2O

[0050] FeO + H2SO4 = FeSO4 + H2O

[0051] Al2O3 + 3H2SO4 = Al2(SO4)3 + 3H2O

[0052] TiO2 + H2SO4 = TiOSO4 + H2O

[0053] H2SO4 = H2O + SO3

[0054] SiO2 does not participate in the reaction, and the SO3 generated by the reaction is absorbed with dilute sulfuric acid to generate H2SO4, which is returned to the batching.

[0055] S3: The clinker produced by roasting is leached with water. The liquid-solid mass ratio of water to the clinker is 3:1, and the leaching time is 1 hour. The leached product is filtered and separated to obtain filter residue SiO2 and filtrate A containing Al2(SO4)3, Fe2(SO4)3, FeSO4, TiOSO4, and (NH4)2SO4.

[0056] S4: NaOH is added to filtrate A to adjust the pH value to 3 to form a Fe(OH)3 precipitate, which is then filtered to obtain solid Fe(OH)3 and filtrate B. The chemical reaction occurring is as follows:

[0057] Fe2(SO4)3 + 6NaOH = 2Fe(OH)3↓ + 3Na2SO4

[0058] When Fe(OH)3 is calcined at 600 °C, Fe2O3 is obtained, and the chemical reaction that occurs is:

[0059] 2Fe(OH)3 = Fe2O3 + 3H2O

[0060] S5: Add NaOH to filtrate B, adjust the pH value to 6, generate Al(OH)3 precipitate, and filter to obtain solid Al(OH)3 and filtrate C; the chemical reaction that occurs is:

[0061] Al2(SO4)3 + 6NaOH = 2Al(OH)3↓ + 3Na2SO4

[0062] S6: Continue to add NaOH to filtrate C, adjust the pH value to 7, generate Fe(OH)2 precipitate, filter to obtain solid Fe(OH)2 and filtrate D. Filtrate D is a solution containing titanyl sulfate and sodium sulfate, and the chemical reaction that occurs is:

[0063] FeSO4 + 2NaOH = Fe(OH)2↓ + Na2SO4

[0064] When solid Fe(OH)2 is calcined in air at 500 °C, Fe2O3 product is obtained; the chemical reaction that occurs is:

[0065] 2Fe(OH)2 + 1 / 2O2 = Fe2O3 + 2H2O

[0066] S7: Add NaOH to filtrate D, adjust the pH value to 8.5, generate H2TiO3 precipitate and Na2SO4 solution, filter to obtain solid H2TiO3 and filtrate E. Filtrate E is a sodium sulfate solution, and the chemical reaction that occurs is:

[0067] TiOSO4 + 2NaOH = H2TiO3↓ + Na2SO4

[0068] When solid H2TiO3 is calcined at 1000 °C, the chemical reaction that occurs is:

[0069] H2TiO3 = TiO2 + H2O

[0070] Obtain anatase TiO2 product;

[0071] S8: Add the solid Al(OH)3 obtained in step S5 to a NaOH solution with a concentration of 150 g / L and a temperature of 60 °C to dissolve Al(OH)3 to saturation, generating a sodium aluminate solution; the chemical reaction that occurs is:

[0072] Al(OH)3 + NaOH = NaAlO2 + 2H2O

[0073] S9: After filtering and removing impurities from the sodium aluminate solution, CO2 is introduced into the sodium aluminate solution to adjust the pH value to above 7, obtaining Al(OH)3 precipitate and Na2CO3 solution. After filtration, solid Al(OH)3 and filtrate F containing Na2CO3 are obtained. Adding CaO to filtrate F produces CaCO3 precipitate and NaOH solution. After filtration, light CaCO3 product and NaOH solution are obtained, and the NaOH solution is returned to step S8 for recycling;

[0074] S10: Filtrate E is a solution containing Na2SO4. Adding NH4HCO3 to filtrate E reacts to form NaHCO3 precipitate and a solution containing ammonium sulfate. After filtration, NaHCO3 product and filtrate G containing (NH4)2SO4 are obtained. The filtrate G is dehydrated to obtain ammonium sulfate crystals. The chemical reaction that occurs when adding NH4HCO3 to the Na2SO4 solution is:

[0075] Na2SO4 + 2NH4HCO3 = (NH4)2SO4 + 2NaHCO3↓

[0076] Preferably, the mass ratio of the slag to ammonium sulfate is 1:2.

[0077] Preferably, the mass ratio of the slag to sulfuric acid is 1:1.5.

[0078] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0079] The present invention uses hydrogen to reduce red mud to recover metallic iron, without CO2 emissions and without causing environmental pollution;

[0080] The iron recovery rate of this method reaches 95%, and the prepared iron meets the national standard of the People's Republic of China for the ferrous metallurgy industry YB / T5296 - 2011.

[0081] After iron extraction in the present invention, the slag is used to separate and extract products such as Al2O3, TiO2, Fe2O3, and SiO2. The recovery rate of Al2O3 in the slag reaches 98%, the recovery rate of TiO2 reaches 95%, the recovery rate of SiO2 reaches 99%, the recovery rate of FeO reaches 99%, and the recovery rate of Na2O entering the soot reaches 98%, with high added value.

[0082] The present invention can fully recycle and utilize various elements in red mud, with almost no residue remaining, high recovery rates of each element, high comprehensive utilization degree, low production cost, and low energy consumption. It is a green and high - added - value method for comprehensively utilizing red mud. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1Process flow diagram for the green comprehensive utilization of red mud in the invention;

[0084] Figure 2 Process flow diagram for separating and extracting Al2O3, TiO2, Fe2O 3、 SiO2 after water quenching the slag of Method 1;

[0085] Figure 3 Process flow diagram for separating and extracting Al2O3, TiO2, Fe2O 3、 SiO2 after water quenching the slag of Method 2; Specific implementation mode

[0086] The following further illustrates the specific implementation mode of the present invention in conjunction with embodiments.

[0087] The raw material red mud used in the following embodiments is the solid waste red mud produced by the alumina plant. The composition of the red mud is Fe2O3 56.18%, Al2O3 18.29%, SiO2 7.83%, TiO2 7.31%, Na2O 2.31%, CaO 0.83%, and others 7.25%.

[0088] Example 1

[0089] A method for the green comprehensive utilization of red mud includes the following steps:

[0090] (1) Heat the red mud in a rotary kiln to 200°C for drying, dehydrate it to a water content of 10%, make pellets, and the pellet diameter is 20 mm - 30 mm to obtain red mud pellets;

[0091] (2) Dry the red mud pellets at 300°C until the water content is less than 1%;

[0092] (3) Add the dried red mud pellets to an electric arc furnace, heat to 1550°C to melt, form a molten pool, blow hydrogen into the molten pool for smelting, and the hydrogen input amount is 100% in excess of the hydrogen amount required to completely reduce the iron oxides in the molten pool, generating molten iron and slag. After a certain amount of molten iron and slag are reached, first tap the slag, and then tap the molten iron; pour the slag into a slag ladle and the molten iron into a molten iron ladle;

[0093] (4) Use the molten iron for steelmaking or casting;

[0094] (5) Water quench the slag and grind it into a powder with a particle size of 80 μm, then dehydrate it to a water content of 10%, and add ammonium sulfate for mixing and pelletizing; among them, the pellet size is 20 mm - 30 mm, and the mass ratio of the slag to ammonium sulfate is 1:2;

[0095] (6) Heat the pellets made in step (5) to 500°C and roast for 1 hour;

[0096] (7) The clinker produced by roasting is leached with water. The mass ratio of water to the clinker in the liquid-solid phase is 3:1, and the leaching time is 1 hour. The leached matter is filtered and separated to obtain filter residue SiO2 and filtrate A containing Al2(SO4)3, Fe2(SO4)3, FeSO4, TiOSO4, and (NH4)2SO4;

[0097] (8) An excessive amount of 100% reducing agent iron filings is added to filtrate A, and the reaction is carried out for 4 hours to reduce the trivalent iron in the filtrate to divalent iron. After removing the iron filings, a solution is obtained. The addition amount of the iron filings is such that all the Fe 3+ in the solution can be completely reduced to Fe 2+ , with an excess of 100%;

[0098] (9) The solution is heated to 110 °C to hydrolyze titanyl sulfate to produce metatitanic acid precipitate. The hydrolysis time is 4 hours. After filtration, solid metatitanic acid and filtrate B are obtained. The solid metatitanic acid is calcined at 1000 °C to obtain anatase TiO2 product;

[0099] (10) Ammonia gas is introduced into filtrate B to adjust the pH value to 6, generating Al(OH)3 precipitate. After filtration, solid Al(OH)3 and filtrate C are obtained;

[0100] (11) Ammonia gas is introduced into filtrate C to adjust the pH value to 7, generating Fe(OH)2 precipitate. After filtration, solid Fe(OH)2 and filtrate D are obtained. Filtrate D is a solution containing ammonium sulfate. The solid Fe(OH)2 is calcined in the air at 500 °C to obtain Fe2O3 product;

[0101] (12) The solid Al(OH)3 obtained in step (10) is added to a NaOH solution with a concentration of 150 g / L to dissolve Al(OH)3 to saturation. The reaction time is 1 hour, and the temperature is 60 °C to generate a sodium aluminate solution;

[0102] (13) After the sodium aluminate solution is finely filtered to remove impurities, a small amount of Al(OH)3 is added to the solution as seeds. The addition amount of the seeds is 0.2% of the solution mass, and pure Al(OH)3 is precipitated. After filtration, Al(OH)3 crystals and a mother liquor containing NaOH and NaAlO2 are obtained. The Al(OH)3 crystals are calcined at 1300 °C to obtain Al2O3 product, and the mother liquor is returned to the process of step (12) for recycling;

[0103] (14) Filtrate D is evaporated to remove water to obtain ammonium sulfate crystals, which are returned to the process of step (5) for recycling;

[0104] (15) The flue gas generated in the electric arc furnace is introduced into the combustion chamber, and air is introduced into the combustion chamber to burn hydrogen in the combustion chamber. The heat of the flue gas and the heat generated by the combustion of H2 are used for power generation;

[0105] After the dust generated by the reaction in the electric arc furnace is recovered by the dust removal system, it is soaked in water to make Na₂O in the dust react with water to form NaOH soluble in water. After filtration, solid slag and filtrate containing NaOH are obtained. The solid slag is returned to step (1) for recycling. After the NaOH content in the filtrate reaches a certain concentration, evaporation crystallization is carried out to obtain NaOH products.

[0106] In this method, the iron oxides in the red mud are reduced to metallic iron by hydrogen, and the recovery rate of iron reaches 95%. The prepared iron meets the national black metallurgy industry standard YB / T5296-2011 of the People's Republic of China.

[0107] During the process of reducing and extracting iron from red mud in the electric arc furnace, Na₂O in the red mud enters the soot, and NaOH products are obtained after treatment.

[0108] After water quenching, the slag after iron extraction is separated and extracted to obtain products of Al₂O₃, TiO₂, Fe₂O₃ and SiO₂. The recovery rate of Al₂O₃ in the slag reaches 98%, the recovery rate of TiO₂ reaches 95%, the recovery rate of SiO₂ reaches 99%, and the recovery rates of Fe₂O₃ and FeO reach 99%. The recovery rate of Na₂O entering the soot reaches 98%.

[0109] Example 2

[0110] A comprehensive green utilization method for red mud includes the following steps:

[0111] (1) Heat the red mud in a rotary kiln to 200°C for drying, dehydrate the red mud to a water content of 10%, pelletize it, and the pellet size is 20mm - 30mm to obtain red mud pellets.

[0112] (2) Dry the red mud pellets at 400°C until the water content is less than 1%.

[0113] (3) Add the dried red mud pellets to an electric arc furnace, heat to 1600°C to melt, form a molten pool, blow hydrogen into the molten pool for smelting, and the hydrogen input amount is 100% in excess of the hydrogen amount required to completely reduce the iron oxides in the molten pool. Molten iron and slag are generated. After the molten iron and slag reach a certain amount, the slag is discharged first, and then the molten iron is discharged; the slag is poured into a slag ladle, and the molten iron is poured into a molten iron ladle.

[0114] (4) Use the molten iron for steelmaking or casting.

[0115] (5) Quench the slag with water and grind it into a powder with a particle size of 80μm, then dehydrate it to a water content of less than 1%, and add a sulfuric acid solution with a concentration of 80% to mix and pelletize.

[0116] (6) Heat the pellets prepared in step (5) to 400°C and roast for 1 hour.

[0117] (7) The clinker produced by roasting is leached with water. The mass ratio of water to the clinker in the liquid-solid phase is 3:1, and the leaching time is 1 hour. The leached product is filtered and separated to obtain filter residue SiO2 and filtrate A containing Al2(SO4)3, Fe2(SO4)3, FeSO4, and TiOSO4;

[0118] (8) NaOH is added to filtrate A to adjust the pH value to 3, generating Fe(OH)3 precipitate. After filtration, solid Fe(OH)3 and filtrate B are obtained. Fe(OH)3 is calcined at 600 °C to obtain Fe2O3 product;

[0119] (9) NaOH is added to filtrate B to adjust the pH value to 6, generating Al(OH)3 precipitate. After filtration, solid Al(OH)3 and filtrate C are obtained;

[0120] (10) NaOH is added to filtrate C to adjust the pH value to 7, generating Fe(OH)2 precipitate. After filtration, solid Fe(OH)2 and filtrate D are obtained. Solid Fe(OH)2 is calcined in air at 500 °C to obtain Fe2O3 product;

[0121] (11) NaOH is added to filtrate D to adjust the pH value to 8.5, generating H2TiO3 precipitate. After filtration, solid H2TiO3 and filtrate E are obtained. Filtrate E is Na2SO4 solution. Solid H2TiO3 is calcined at 1000 °C to obtain anatase TiO2 product;

[0122] (12) The solid Al(OH)3 obtained in step (9) is added to a NaOH solution with a concentration of 150 g / L to dissolve Al(OH)3 to saturation. The reaction time is 1 hour, and the temperature is 60 °C to generate a sodium aluminate solution;

[0123] (13) After the sodium aluminate solution is finely filtered to remove impurities, CO2 is introduced into the solution to adjust the pH value to 7, obtaining Al(OH)3 precipitate and Na2CO3 solution. After filtration, solid Al(OH)3 and filtrate F containing Na2CO3 are obtained. CaO is added to filtrate F to generate CaCO3 precipitate and a NaOH solution. After filtration, light CaCO3 product and NaOH solution are obtained. The NaOH solution is recycled to step (11);

[0124] (14) Filtrate E is Na2SO4 solution. NH4HCO3 is added to filtrate E, and the reaction generates NaHCO3 precipitate and a solution containing ammonium sulfate. After filtration, NaHCO3 product and filtrate G containing (NH4)2SO4 are obtained. Filtrate G is dehydrated to obtain ammonium sulfate crystals.

[0125] (15) The flue gas generated in the electric arc furnace is introduced into the combustion chamber. Air is introduced into the combustion chamber to burn hydrogen in the combustion chamber. The heat of the flue gas and the heat generated by H2 combustion are used for power generation;

[0126] (16) After the dust generated by the reaction in the electric arc furnace is recovered by the dust removal system, it is soaked in water to make Na2O in the dust react with water to generate NaOH soluble in water. After filtration, solid slag and filtrate containing NaOH are obtained. The solid slag is returned to step (1) for recycling. After the NaOH content in the filtrate reaches a certain concentration, evaporation crystallization is carried out to obtain NaOH products.

[0127] This method reduces iron oxides in red mud to metallic iron with hydrogen, and the iron recovery rate reaches 95%. The prepared iron meets the national standard of the People's Republic of China for the ferrous metallurgy industry YB / T5296-2011;

[0128] After the iron-extracted slag is crushed and water-quenched, Al2O3, TiO2, Fe2O3 and SiO2 products are separated and extracted. The recovery rate of Al2O3 in the slag reaches 98%, the recovery rate of TiO2 reaches 95%, the recovery rate of SiO2 reaches 99%, and the recovery rates of Fe2O3 and FeO reach 99%. The recovery rate of Na2O entering the smoke and dust reaches 98%.

[0129] The above description is a detailed description of the preferred and feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications completed under the prompt of the present invention shall fall within the scope of the patent covered by the present invention.

Claims

1. A comprehensive utilization method for greening red mud, characterized in that, It includes the following steps: (1) Dehydrate and pelletize the red mud to obtain red mud pellets; (2) Dry the red mud pellets at 300°C - 400°C; (3) Add the dried red mud pellets to an electric arc furnace, heat to 1550°C - 1600°C to melt, form a molten pool, introduce the reducing gas hydrogen into the molten pool, generate molten iron and slag, and the hydrogen addition amount is 100% in excess of the hydrogen amount required to completely reduce the iron oxides, etc. in the molten pool; (4) Use the molten iron for steelmaking or casting, and after water quenching the slag, use it to separate and extract Al2O3, TiO2, Fe2O3, and SiO2; (5) The flue gas generated in the electric arc furnace is introduced into a combustion chamber, air is introduced into the combustion chamber, so that hydrogen burns in the combustion chamber, and the heat of the flue gas and the heat generated by H2 combustion are used for power generation; (6) After the dust generated in the electric arc furnace reaction is recovered by a dust removal system, soak it in water to make Na2O in the dust react with water to form water-soluble NaOH, filter to obtain solid slag and NaOH-containing filtrate, return the solid slag to step (1) for recycling, and after the NaOH content in the filtrate reaches a certain concentration, evaporate and crystallize to obtain NaOH products.

2. The comprehensive utilization method for greening red mud according to claim 1, characterized in that In step (1), the red mud is dehydrated to a moisture content of 10%, and the particle size of the pellets is 20mm - 30mm.

3. A method for comprehensive green utilization of red mud according to claim 1, characterized in that, In step (2), the pellets are dried to a water content of less than 1%.

4. A comprehensive utilization method for greening red mud according to claim 1, characterized in that, The preparation method for separating and extracting Al2O3, TiO2, Fe2O3, and SiO2 after water quenching the slag is as follows: S1: Grind the water-quenched slag to a powder with a particle size of 80μm, then dehydrate to a water content of 10%, and add ammonium sulfate to mix and pelletize; S2: Heat the pellets prepared in step S1 to 400°C - 500°C and roast for 1 hour; S3: Dissolve the roasted clinker in water, the liquid-solid mass ratio of water to clinker is 3:1, the dissolution time is 1 hour, filter and separate the dissolved matter to obtain filter residue SiO2 and filtrate A containing Al2(SO4)3, Fe2(SO4)3, FeSO4, TiOSO4, and (NH4)2SO4; S4: Add reducing agent iron filings to filtrate A, react for 4 hours, reduce the trivalent iron in the filtrate to divalent iron, remove the iron filings, and obtain a solution; S5: Heat the solution to 110°C to hydrolyze titanyl sulfate to produce metatitanic acid precipitate, filter to obtain solid metatitanic acid and filtrate B, and calcine the solid metatitanic acid at 1000°C to obtain anatase TiO2 product; S6: Introduce ammonia into filtrate B, adjust the PH value to 6 to generate Al(OH)3 precipitate, filter to obtain solid Al(OH)3 and filtrate C; S7: Continue to introduce ammonia into filtrate C, adjust the PH value to 7 to generate Fe(OH)2 precipitate, filter to obtain solid Fe(OH)2 and filtrate D, filtrate D is a solution containing ammonium sulfate, and calcine the solid Fe(OH)2 in the air at 500°C to obtain Fe2O3 product; S8: Add the solid Al(OH)3 obtained in step S6 to a NaOH solution with a concentration of 150g / L, react for 1 hour at a temperature of 60°C to dissolve Al(OH)3 to saturation, and react to generate a sodium aluminate solution; S9: After the sodium aluminate solution is finely filtered to remove impurities, a small amount of Al(OH)₃ is added to the solution as seeds to precipitate pure Al(OH)₃. After filtration, Al(OH)₃ crystals and mother liquor are obtained. The Al(OH)₃ crystals are calcined at 1300 °C to obtain Al₂O₃ products, and the mother liquor is returned to step S8 for recycling. S10: The filtrate D is dehydrated by evaporation to obtain ammonium sulfate crystals, which are returned to step S1 for recycling.

5. A comprehensive utilization method for greening red mud according to claim 1, characterized in that, The preparation method for separating and extracting Al₂O₃, TiO₂, Fe₂O₃, and SiO₂ from the slag after water quenching is as follows: S1: The slag is water quenched and then ground into a powder with a particle size of 80 μm, and then dehydrated to a moisture content of less than 1%. It is mixed and pelletized with a sulfuric acid solution with a concentration of 80%. S2: The pellets prepared in step S1 are heated to 400 °C - 500 °C and roasted for 1 hour. S3: The roasted clinker is leached with water. The mass ratio of water to the clinker liquid-solid is 3:1, and the leaching time is 1 hour. The leached product is filtered and separated to obtain filter residue SiO₂ and filtrate A containing Al₂(SO₄)₃, Fe₂(SO₄)₃, FeSO₄, and TiOSO₄. S4: NaOH is added to filtrate A to adjust the pH value to 3 to form a Fe(OH)₃ precipitate. After filtration, solid Fe(OH)₃ and filtrate B are obtained. The Fe(OH)₃ is calcined at 600 °C to obtain Fe₂O₃. S5: NaOH is added to filtrate B to adjust the pH value to 6 to form an Al(OH)₃ precipitate. After filtration, solid Al(OH)₃ and filtrate C are obtained. S6: NaOH is added to filtrate C to adjust the pH value to 7 to form a Fe(OH)₂ precipitate. After filtration, solid Fe(OH)₂ and filtrate D are obtained. The solid Fe(OH)₂ is roasted in air at 500 °C to obtain Fe₂O₃ products. S7: NaOH is added to filtrate D to adjust the pH value of filtrate D to 8.5 to form a H₂TiO₃ precipitate. After filtration, solid H₂TiO₃ and filtrate E are obtained. Filtrate E is a Na₂SO₄ solution. The solid H₂TiO₃ is calcined at 1000 °C to obtain anatase TiO₂ products. S8: The solid Al(OH)₃ obtained in step S5 is added to a NaOH solution with a concentration of 150 g / L at a temperature of 60 °C for 1 hour to dissolve Al(OH)₃ to saturation, and a sodium aluminate solution is formed by reaction. S9: After the sodium aluminate solution is finely filtered to remove impurities, CO₂ is introduced into the sodium aluminate solution to adjust the pH value above 7 to obtain an Al(OH)₃ precipitate and a Na₂CO₃ solution. After filtration, solid Al(OH)₃ and filtrate F containing Na₂CO₃ are obtained. CaO is added to filtrate F to produce a CaCO₃ precipitate and a NaOH solution. After filtration, light CaCO₃ products and a NaOH solution are obtained. The NaOH solution is returned to step S8 for recycling. S10: The filtrate E is a Na2SO4 solution. Add NH4HCO3 to the filtrate E, and a reaction occurs to form a NaHCO3 precipitate and a solution containing ammonium sulfate. Filter to obtain the NaHCO3 product and the filtrate G containing (NH4)2SO4. Dehydrate the filtrate G to obtain ammonium sulfate crystals.

6. The comprehensive utilization method for greening red mud according to claim 4, wherein, The mass ratio of the slag to ammonium sulfate is 1:

2.

7. A comprehensive utilization method for greening red mud according to claim 5, characterized in that, The mass ratio of the slag to sulfuric acid is 1:1.5.

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