CN111842411A - Red mud full-recycling method - Google Patents
Red mud full-recycling method Download PDFInfo
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- CN111842411A CN111842411A CN202010613601.5A CN202010613601A CN111842411A CN 111842411 A CN111842411 A CN 111842411A CN 202010613601 A CN202010613601 A CN 202010613601A CN 111842411 A CN111842411 A CN 111842411A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
- B09B3/80—Destroying solid waste or transforming solid waste into something useful or harmless involving an extraction step
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
- B09B3/20—Agglomeration, binding or encapsulation of solid waste
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
- B09B3/40—Destroying solid waste or transforming solid waste into something useful or harmless involving thermal treatment, e.g. evaporation
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/24—Sulfates of ammonium
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D1/00—Oxides or hydroxides of sodium, potassium or alkali metals in general
- C01D1/04—Hydroxides
- C01D1/42—Concentration; Dehydration
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/10—Preparation or treatment, e.g. separation or purification
- C01F17/13—Preparation or treatment, e.g. separation or purification by using ion exchange resins, e.g. chelate resins
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/10—Preparation or treatment, e.g. separation or purification
- C01F17/17—Preparation or treatment, e.g. separation or purification involving a liquid-liquid extraction
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/20—Compounds containing only rare earth metals as the metal element
- C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
- C01F17/212—Scandium oxides or hydroxides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/68—Aluminium compounds containing sulfur
- C01F7/74—Sulfates
- C01F7/76—Double salts, i.e. compounds containing, besides aluminium and sulfate ions, only other cations, e.g. alums
- C01F7/762—Ammonium or alkali metal aluminium sulfates
- C01F7/765—Ammonium aluminium sulfates
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- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/02—Oxides; Hydroxides
- C01G49/06—Ferric oxide (Fe2O3)
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/04—Waste materials; Refuse
- C04B18/0418—Wet materials, e.g. slurries
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/41—Preparation of salts of carboxylic acids
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C55/00—Saturated compounds having more than one carboxyl group bound to acyclic carbon atoms
- C07C55/02—Dicarboxylic acids
- C07C55/06—Oxalic acid
- C07C55/07—Salts thereof
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Abstract
The invention relates to a method for recycling red mud, which comprises the following steps: 1) washing the red mud to recover sodium hydroxide; 2) stirring and leaching red mud washing slag in a concentrated acid rotary kiln; 3) using the leaching residue obtained in the step 2) for producing water glass and building ceramsite; step 4) adjusting the pH value of the leachate by using liquid ammonia or ammonia water to precipitate aluminum ammonium sulfate; step 5) precipitating aluminum ammonium sulfate, and then producing iron oxide red by using the solution; step 6), carrying out ion exchange to enrich scandium, vanadium, titanium and gallium; step 7), MVR evaporating and crystallizing ammonium sulfate. The invention has the advantages that: the iron oxide red produced by the method can obtain pigment-grade iron oxide red with bright color without calcination, can produce large-particle smelting-grade aluminum oxide and artificial cryolite, can also produce pure oxides of industrial-grade titanium, scandium, vanadium, gallium, rhenium and rare earth, can really realize full-resource recovery of red mud, and has the advantages of simple process, low cost and easy large-scale production.
Description
Technical Field
The invention relates to a method for recovering high-purity aluminum oxide iron oxide scandium, vanadium, titanium, gallium and rare earth elements from red mud.
Background
The red mud is the extremely fine particle strong alkaline solid waste generated in the process of producing alumina by taking bauxite as a raw material, and 0.8 to 1.5 tons of red mud is generated for each ton of alumina. China is a big country for producing alumina, 2378 million tons of alumina are produced in 2009, which accounts for about 30% of the total world output, and the red mud produced is nearly 3000 million tons. At present, the comprehensive utilization rate of red mud in China is only 4%, and the accumulated stock reaches 2 hundred million tons. With the annual increase of alumina output and gradual reduction of bauxite grade in China, the annual production amount of red mud is continuously increased, and the accumulated stockpiling amount of red mud reaches 3.5 hundred million tons by 2015. The red mud is piled up in large quantity, which not only occupies land and wastes resources, but also easily causes environmental pollution and potential safety hazard. At present, the comprehensive utilization of the red mud still belongs to a worldwide problem, and the red mud is mainly treated by piling and covering soil internationally. The comprehensive utilization work of the red mud in China has gained high attention in all aspects in recent years, and research work of comprehensive utilization technology in multiple fields across subjects is developed, such as extraction of valuable metals from the red mud, production of cement, building bricks, mine cemented filling cementing materials, roadbed consolidation materials, high-performance concrete admixtures, Chemical Bonding Ceramic (CBC) composite materials, heat-insulating refractory materials, environment-friendly materials and the like by using ingredients.
The current comprehensive utilization of red mud has the main problems that: (1) the key technology for largely absorbing the red mud and having industrial competitiveness is lacked. The red mud has the characteristics of strong alkalinity, large specific surface area, mutual wrapping and embedding of various components and the like, so that the comprehensive utilization of the red mud is difficult to refer to mature processes, technologies and equipment in other fields, and a technical support system which is efficiently utilized and suitable for large-scale popularization is not formed in China. (2) The corresponding standard is lacked, and the market acceptance of the product is low. At present, due to the lack of support of national standards or industrial standards, such as the use of red mud as a building material, only by referring to other similar product standards, the developed products for comprehensive utilization of part of red mud have low market acceptance, so that the application of the products is limited, and the products are difficult to popularize on a large scale. (3) There is a lack of targeted support policies. In the current financial and tax preferential policy in China, the comprehensive utilization difficulty caused by strong basicity of the red mud is not fully considered to be far higher than the particularity of other industrial waste residues, the policy of targeted support is lacked, and the enthusiasm of enterprises for utilizing the red mud is not high. (4) The attention degree of the comprehensive utilization of the red mud needs to be improved. The comprehensive utilization of the red mud is a non-main business of alumina enterprises, is at the tail end of the industry, has poor economic benefit, and adopts a certain disposal mode for most enterprises. The environmental risk and the potential safety hazard of red mud stacking have long-term and hidden properties, so that the attention degree of enterprises and related departments is insufficient.
Disclosure of Invention
The invention aims to provide a method for recycling red mud, which aims to solve the problems in the background technology.
In order to solve the technical problems, the technical scheme provided by the invention is as follows: a method for recycling red mud comprises the following steps:
1) washing red mud to recover sodium hydroxide: adding water into the red mud in the slag warehouse, finely crushing the red mud by a dispersion machine, pumping the crushed red mud into a CCD thickener washing system, conveying the washing slag to a red mud concentrated acid leaching and chemical combination section, conveying the washing clear liquid to an MVR evaporation and concentration section, and recovering sodium hydroxide to return to an aluminum factory for use;
2) stirring and leaching the red mud washing slag by a concentrated acid rotary kiln: adding 50-98% of sulfuric acid into a rotary kiln lined with a tile corrosion-resistant tail gas recovery and purification system according to 0.8-1.5 times of the molar weight of chemical elements capable of reacting with sulfuric acid in the red mud, mixing and reacting for 1-3 hours, so that the sulfuric acid and the red mud are uniformly mixed in the rotary kiln, reacting for 1-3 hours, dissolving and reacting the slurry by using water or slag washing liquid after the leaching reaction is finished, and then performing solid-liquid separation by using a deep cone high-efficiency inclined plate thickener;
3) using the leaching residue obtained in the step 2) for producing water glass and building ceramsite: reacting the leached countercurrent washing slag obtained in the step 2) with sodium hydroxide at 180 ℃ for 1-8 hours to obtain water glass slurry, then carrying out solid-liquid separation to obtain industrial water glass and solid slag, washing the solid slag by more than 1 grade of water, and adding a cementing material into the washing slag to produce baking-free bricks or ceramsite;
And 4) regulating the pH value of the leachate with liquid ammonia or ammonia water to precipitate aluminum ammonium sulfate: neutralizing the overflow clear liquid with ammonia gas or ammonia water to pH 1-3 at 10-50 deg.C, and adding ammonium sulfate as required to precipitate aluminum ammonium sulfate; aging for 20-120min, centrifuging, filtering, producing iron oxide red from liquid, washing solid ammonium aluminum sulfate, and delivering to aluminum salt workshop to produce cryolite, crystalline aluminum chloride, ammonium aluminum carbonate and aluminum oxide;
step 5) precipitating aluminum ammonium sulfate, and then producing iron oxide red by using the solution: the liquid after precipitating the aluminum ammonium sulfate is sent to a 10-500m liquid which is added with crystal seeds in advance to adjust the pH and prepare the base material3Simultaneously adding at least one of ammonia gas, liquid ammonia, ammonia water, ammonium carbonate and ammonium bicarbonate into the reaction tank, controlling the temperature to be 40-100 ℃, controlling the PH to be 2.2-5.5, reacting for 30-180min, then carrying out solid-liquid separation, drying and grinding solid iron oxide red to obtain finished iron oxide red, and removing iron from the liquid to the next working section;
step 6) ion exchange enrichment of scandium, vanadium, titanium and gallium: pumping the iron-removed liquid obtained in the step 5) into a reaction tank, introducing ammonia gas or ammonia water to adjust the pH value to 5-5.5, reacting for 120min at the temperature of 10-80 ℃, deeply purifying Fe-Si-Al, and performing solid-liquid separation after the reaction of purifying Fe-Si-Al is finished; after solid-liquid separation, the deeply purified silicon-aluminum liquid is sent into a tank filled with cation exchange resin, elements of scandium, vanadium, titanium and gallium are absorbed by countercurrent exchange, after the resin is saturated by adsorption, at least one of nitric acid, organic acid and ammonium sulfate solution of sulfuric acid and hydrochloric acid is used for backwashing, and rare earth oxalate is recovered by using oxalic acid precipitation for backwashing liquid of backwashing; the hydroxide and carbonate of scandium, vanadium, titanium and gallium are back extracted by sodium hydroxide solution and directly enter an extraction system for separating and purifying scandium, vanadium, titanium and gallium, and liquid after rare earth precipitation is sent to an MVR evaporator for evaporation and crystallization to recover ammonium sulfate;
Step 7), MVR evaporation crystallization of ammonium sulfate: returning one part of the solution after adsorbing the rare earth elements obtained in the step 6) to precipitate ammonium alum, evaporating the other part of the solution by adopting an MVR (mechanical vapor recompression) evaporator crystallizer to recover ammonium sulfate, and washing the solid precipitation slag in a counter-current manner to produce ceramsite or building materials.
The invention has the advantages that: the iron oxide red produced by the method can obtain pigment-grade iron oxide red with bright color without calcination, can produce large-particle smelting-grade aluminum oxide and artificial cryolite, can also produce pure oxides of industrial-grade titanium, scandium, vanadium, gallium, rhenium and rare earth, can really realize full-resource recovery of red mud, and has the advantages of simple process, low cost and easy large-scale production.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The invention is illustrated below by means of specific examples, without being restricted thereto.
Example 1
A method for recycling red mud comprises the following steps:
1) washing red mud to recover sodium hydroxide: adding water into the red mud in the slag warehouse, finely crushing the red mud by a dispersion machine, pumping the crushed red mud into a CCD thickener washing system, conveying the washing slag to a red mud concentrated acid leaching and chemical combination section, conveying the washing clear liquid to an MVR evaporation and concentration section, and recovering sodium hydroxide to return to an aluminum factory for use;
2) Stirring and leaching the red mud washing slag by a concentrated acid rotary kiln: adding 50% sulfuric acid into a rotary kiln lined with a tile corrosion-resistant tail gas recovery and purification system for mixing reaction for 1 hour according to 0.8 time of the molar weight of chemical elements capable of reacting with sulfuric acid in the red mud, so that the sulfuric acid and the red mud are uniformly mixed in the rotary kiln, the reaction time is 1-3 hours, after the leaching reaction is finished, dissolving the reacted slurry by using water or slag washing liquid, and then performing solid-liquid separation by using a deep cone high-efficiency inclined plate thickener;
3) using the leaching residue obtained in the step 2) for producing water glass and building ceramsite: reacting the leached countercurrent washing slag obtained in the step 2) with sodium hydroxide at 180 ℃ for 1 hour to obtain water glass slurry, then carrying out solid-liquid separation to obtain industrial water glass and solid slag, washing the solid slag by more than 1 grade of water, and adding a cementing material into the washing slag to produce baking-free bricks or ceramsite;
and 4) regulating the pH value of the leachate with liquid ammonia or ammonia water to precipitate aluminum ammonium sulfate: neutralizing the overflow clear liquid with ammonia gas or ammonia water until the pH value is 1.8-2.2, at 10-50 deg.C, and simultaneously adding ammonium sulfate as required to precipitate aluminum ammonium sulfate; aging for 20-120min, centrifuging, filtering, producing iron oxide red from liquid, washing solid ammonium aluminum sulfate, and delivering to aluminum salt workshop to produce cryolite, crystalline aluminum chloride, ammonium aluminum carbonate and aluminum oxide;
Step 5) precipitating aluminum ammonium sulfate, and then producing iron oxide red by using the solution: the liquid after precipitating the aluminum ammonium sulfate is sent to a 10-500m liquid which is added with crystal seeds in advance to adjust the pH and prepare the base material3Adding at least one of ammonia gas, liquid ammonia, ammonia water, ammonium carbonate and ammonium bicarbonate into the reaction tank, controlling the temperature at 40 ℃, controlling the pH value at 3-3.2, reacting for 30min, then carrying out solid-liquid separation, drying and grinding solid iron oxide red to obtain finished iron oxide red, and removing iron from the liquid to the next working section;
step 6) ion exchange enrichment of scandium, vanadium, titanium and gallium: pumping the iron-removed liquid obtained in the step 5) into a reaction tank, introducing ammonia gas or ammonia water to adjust the pH value to 5.5, reacting for 120min at the temperature of 10-80 ℃, deeply purifying the Fe-Si-Al, and performing solid-liquid separation after the reaction of purifying the Fe-Si-Al is finished; after solid-liquid separation, the deeply purified silicon-aluminum liquid is sent into a tank filled with cation exchange resin, elements of scandium, vanadium, titanium and gallium are absorbed by countercurrent exchange, after the resin is saturated by adsorption, at least one of nitric acid, organic acid and ammonium sulfate solution of sulfuric acid and hydrochloric acid is used for backwashing, and rare earth oxalate is recovered by using oxalic acid precipitation for backwashing liquid of backwashing; the hydroxides and carbonates of scandium, vanadium, titanium and gallium directly enter an extraction system to separate and purify scandium, vanadium, titanium and gallium, and liquid after rare earth precipitation is sent to an MVR evaporator to be evaporated and crystallized to recover ammonium sulfate;
Step 7), MVR evaporation crystallization of ammonium sulfate: returning one part of the solution after adsorbing the rare earth elements obtained in the step 6) to precipitate ammonium alum, evaporating the other part of the solution by adopting an MVR (mechanical vapor recompression) evaporator crystallizer to recover ammonium sulfate, and washing the solid precipitation slag in a counter-current manner to produce ceramsite or building materials.
Example 2
A method for recycling red mud comprises the following steps:
1) washing red mud to recover sodium hydroxide: adding water into the red mud in the slag warehouse, finely crushing the red mud by a dispersion machine, pumping the crushed red mud into a CCD thickener washing system, conveying the washing slag to a red mud concentrated acid leaching and chemical combination section, conveying the washing clear liquid to an MVR evaporation and concentration section, and recovering sodium hydroxide to return to an aluminum factory for use;
2) stirring and leaching the red mud washing slag by a concentrated acid rotary kiln: according to the molar weight of chemical elements which can react with sulfuric acid in the red mud, 1.5 times, adding 98% sulfuric acid to perform mixed reaction for 3 hours in a rotary kiln which is lined with a tile corrosion-resistant and provided with a tail gas recovery and purification system, so that the sulfuric acid and the red mud are uniformly mixed in the rotary kiln, the reaction time is 3 hours, after the leaching reaction is finished, dissolving the reacted slurry by using water or slag washing liquid, and then performing solid-liquid separation by using a deep-cone high-efficiency inclined plate thickener;
3) using the leaching residue obtained in the step 2) for producing water glass and building ceramsite: reacting the leached countercurrent washing slag obtained in the step 2) with sodium hydroxide at 180 ℃ for 8 hours to obtain water glass slurry, then carrying out solid-liquid separation to obtain industrial water glass and solid slag, washing the solid slag by more than 1 grade of water, and adding a cementing material into the washing slag to produce baking-free bricks or ceramsite;
And 4) regulating the pH value of the leachate with liquid ammonia or ammonia water to precipitate aluminum ammonium sulfate: neutralizing the overflow clear liquid with ammonia gas or ammonia water to pH 3 at 40 deg.c while adding ammonium sulfate to precipitate aluminum ammonium sulfate; aging for 120min, centrifuging, filtering, producing iron oxide red from liquid, washing solid ammonium aluminum sulfate, and delivering to aluminum salt workshop to produce cryolite, aluminum chloride crystal, ammonium aluminum carbonate and aluminum oxide;
step 5) precipitating aluminum sulfateProducing iron oxide red by using the ammonium post-solution: the liquid after precipitating the aluminum ammonium sulfate is sent to 500m with seed crystal added in advance to adjust the pH and prepare the base material3Adding at least one of ammonia gas, liquid ammonia, ammonia water, ammonium carbonate and ammonium bicarbonate into the reaction tank, controlling the temperature to be 100 ℃, controlling the pH to be 5.5, reacting for 150min, then carrying out solid-liquid separation, drying and grinding solid iron oxide red to obtain finished iron oxide red, and removing iron from the liquid to the next working section;
step 6) ion exchange enrichment of scandium, vanadium, titanium and gallium: pumping the iron-removed liquid obtained in the step 5) into a reaction tank, introducing ammonia gas or ammonia water to adjust the pH value to 5.5, reacting for 120min at the temperature of 160 ℃, deeply purifying Fe-Si-Al, and performing solid-liquid separation after the reaction of purifying Fe-Si-Al is finished; after solid-liquid separation, the deeply purified silicon-aluminum liquid is sent into a tank filled with cation exchange resin, elements of scandium, vanadium, titanium and gallium are absorbed by countercurrent exchange, after the resin is saturated by adsorption, at least one of nitric acid, organic acid and ammonium sulfate solution of sulfuric acid and hydrochloric acid is used for backwashing, and rare earth oxalate is recovered by using oxalic acid precipitation for backwashing liquid of backwashing; the hydroxides and carbonates of scandium, vanadium, titanium and gallium directly enter an extraction system to separate and purify scandium, vanadium, titanium and gallium, and liquid after rare earth precipitation is sent to an MVR evaporator to be evaporated and crystallized to recover ammonium sulfate;
Step 7), MVR evaporation crystallization of ammonium sulfate: returning one part of the solution after adsorbing the rare earth elements obtained in the step 6) to precipitate ammonium alum, evaporating the other part of the solution by adopting an MVR (mechanical vapor recompression) evaporator crystallizer to recover ammonium sulfate, and washing the solid precipitation slag in a counter-current manner to produce ceramsite or building materials.
Example 3
A method for recycling red mud comprises the following steps:
1) washing red mud to recover sodium hydroxide: adding water into the red mud in the slag warehouse, finely crushing the red mud by a dispersion machine, pumping the crushed red mud into a CCD thickener washing system, conveying the washing slag to a red mud concentrated acid leaching and chemical combination section, conveying the washing clear liquid to an MVR evaporation and concentration section, and recovering sodium hydroxide to return to an aluminum factory for use;
2) stirring and leaching the red mud washing slag by a concentrated acid rotary kiln: according to the molar weight of chemical elements which can react with sulfuric acid in the red mud, 1.2 times, 80% of sulfuric acid is added to be mixed and reacted for 2 hours in a rotary kiln which is lined with a tile corrosion-resistant and provided with a tail gas recovery and purification system, so that the sulfuric acid and the red mud are uniformly mixed in the rotary kiln, the reaction time is 2 hours, water or slag washing liquid is used for dissolving reacted slurry after the leaching reaction is finished, and then a deep-cone high-efficiency inclined plate thickener is used for solid-liquid separation;
3) using the leaching residue obtained in the step 2) for producing water glass and building ceramsite: reacting the leached countercurrent washing slag obtained in the step 2) with sodium hydroxide at 180 ℃ for 4 hours to obtain water glass slurry, then carrying out solid-liquid separation to obtain industrial water glass and solid slag, washing the solid slag by more than 1 grade of water, and adding a cementing material into the washing slag to produce baking-free bricks or ceramsite;
And 4) regulating the pH value of the leachate with liquid ammonia or ammonia water to precipitate aluminum ammonium sulfate: neutralizing the overflow clear liquid with ammonia gas or ammonia water to pH 2 at 25 deg.c while adding ammonium sulfate to precipitate aluminum ammonium sulfate; aging for 70min, centrifuging, filtering, washing liquid to obtain iron oxide red, and washing solid ammonium aluminum sulfate in aluminum salt workshop to obtain cryolite, aluminum chloride crystal, ammonium aluminum carbonate and aluminum oxide;
step 5) precipitating aluminum ammonium sulfate, and then producing iron oxide red by using the solution: the liquid after precipitating the aluminum ammonium sulfate is sent to a 10-300m liquid which is added with seed crystals in advance to adjust the pH and prepare the base material3Simultaneously adding at least one of ammonia gas, liquid ammonia, ammonia water, ammonium carbonate and ammonium bicarbonate into the reaction tank, controlling the temperature at 70 ℃ and the pH at 3.2, reacting for 90-180min, then carrying out solid-liquid separation, drying and grinding solid iron oxide red to obtain finished iron oxide red, and removing iron from the liquid to the next working section;
step 6) ion exchange enrichment of scandium, vanadium, titanium and gallium: pumping the iron-removed liquid obtained in the step 5) into a reaction tank, introducing ammonia gas or ammonia water to adjust the pH value to 5, reacting for 120min at 35 ℃, deeply purifying Fe-Si-Al, and performing solid-liquid separation after the reaction of purifying Fe-Si-Al is finished; after solid-liquid separation, the deeply purified silicon-aluminum liquid is sent into a tank filled with cation exchange resin, elements of scandium, vanadium, titanium and gallium are absorbed by countercurrent exchange, after the resin is saturated by adsorption, at least one of nitric acid, organic acid and ammonium sulfate solution of sulfuric acid and hydrochloric acid is used for backwashing, and rare earth oxalate is recovered by using oxalic acid precipitation for backwashing liquid of backwashing; the hydroxides and carbonates of scandium, vanadium, titanium and gallium directly enter an extraction system to separate and purify scandium, vanadium, titanium and gallium, and liquid after rare earth precipitation is sent to an MVR evaporator to be evaporated and crystallized to recover ammonium sulfate;
Step 7), MVR evaporation crystallization of ammonium sulfate: returning one part of the solution after adsorbing the rare earth elements obtained in the step 6) to precipitate ammonium alum, evaporating the other part of the solution by adopting an MVR (mechanical vapor recompression) evaporator crystallizer to recover ammonium sulfate, and washing the solid precipitation slag in a counter-current manner to produce ceramsite or building materials.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (1)
1. A method for recycling red mud is characterized by comprising the following steps:
1) washing red mud to recover sodium hydroxide: adding water into the red mud in the slag warehouse, finely crushing the red mud by a dispersion machine, pumping the crushed red mud into a CCD thickener washing system, conveying the washing slag to a red mud concentrated acid leaching and chemical combination section, conveying the washing clear liquid to an MVR evaporation and concentration section, and recovering sodium hydroxide to return to an aluminum factory for use;
2) stirring and leaching the red mud washing slag by a concentrated acid rotary kiln: adding 50-98% of sulfuric acid into a rotary kiln lined with a tile corrosion-resistant tail gas recovery and purification system according to 0.8-1.5 times of the molar weight of chemical elements capable of reacting with sulfuric acid in the red mud, mixing and reacting for 1-3 hours, so that the sulfuric acid and the red mud are uniformly mixed in the rotary kiln, reacting for 1-3 hours, dissolving and reacting the slurry by using water or slag washing liquid after the leaching reaction is finished, and then performing solid-liquid separation by using a deep cone high-efficiency inclined plate thickener;
3) Using the leaching residue obtained in the step 2) for producing water glass and building ceramsite: reacting the leached countercurrent washing slag obtained in the step 2) with sodium hydroxide at 180 ℃ for 1-8 hours to obtain water glass slurry, then carrying out solid-liquid separation to obtain industrial water glass and solid slag, washing the solid slag by more than 1 grade of water, and adding a cementing material into the washing slag to produce baking-free bricks or ceramsite;
and 4) regulating the pH value of the leachate with liquid ammonia or ammonia water to precipitate aluminum ammonium sulfate: neutralizing the overflow clear liquid with ammonia gas or ammonia water to pH 1-3 at 10-50 deg.C, and adding ammonium sulfate as required to precipitate aluminum ammonium sulfate; aging for 20-120min, centrifuging, filtering, producing iron oxide red from liquid, washing solid ammonium aluminum sulfate, and delivering to aluminum salt workshop to produce cryolite, crystalline aluminum chloride, ammonium aluminum carbonate and aluminum oxide;
step 5) precipitating aluminum ammonium sulfate, and then producing iron oxide red by using the solution: the liquid after precipitating the aluminum ammonium sulfate is sent to a 10-500m liquid which is added with crystal seeds in advance to adjust the pH and prepare the base material3Simultaneously adding at least one of ammonia gas, liquid ammonia, ammonia water, ammonium carbonate and ammonium bicarbonate into the reaction tank, controlling the temperature to be 40-100 ℃, controlling the PH to be 2.2-5.5, reacting for 30-180min, then carrying out solid-liquid separation, drying and grinding solid iron oxide red to obtain finished iron oxide red, and removing iron from the liquid to the next working section;
Step 6) ion exchange enrichment of scandium, vanadium, titanium and gallium: pumping the iron-removed liquid obtained in the step 5) into a reaction tank, introducing ammonia gas or ammonia water to adjust the pH value to 5-5.5, reacting for 120min at the temperature of 10-80 ℃, deeply purifying Fe-Si-Al, and performing solid-liquid separation after the reaction of purifying Fe-Si-Al is finished; after solid-liquid separation, the deeply purified silicon-aluminum liquid is sent into a tank filled with cation exchange resin, elements of scandium, vanadium, titanium and gallium are absorbed by countercurrent exchange, after the resin is saturated by adsorption, at least one of nitric acid, organic acid and ammonium sulfate solution of sulfuric acid and hydrochloric acid is used for backwashing, and rare earth oxalate is recovered by using oxalic acid precipitation for backwashing liquid of backwashing; the hydroxide and carbonate of scandium, vanadium, titanium and gallium are back extracted by sodium hydroxide solution and directly enter an extraction system for separating and purifying scandium, vanadium, titanium and gallium, and liquid after rare earth precipitation is sent to an MVR evaporator for evaporation and crystallization to recover ammonium sulfate;
step 7), MVR evaporation crystallization of ammonium sulfate: returning one part of the solution after adsorbing the rare earth elements obtained in the step 6) to precipitate ammonium alum, evaporating the other part of the solution by adopting an MVR (mechanical vapor recompression) evaporator crystallizer to recover ammonium sulfate, and washing the solid precipitation slag in a counter-current manner to produce ceramsite or building materials.
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