Method for extracting aluminum oxide based on solid waste fly ash

Abstract

The invention relates to the technical field of comprehensive utilization of fly ash, and particularly discloses a method for extracting aluminum oxide based on solid waste fly ash. The extraction of the aluminum oxide sequentially comprises the steps of raw material cooking and dissolution, dissolution slurry desilicication treatment, stock solution refining and crystallization, and roasting decomposition; wherein the desilicication treatment of the dissolved slurry comprises the following steps: adding a desilicication agent into the dissolved slurry, carrying out heating treatment, and filtering to obtain a carbon component stock solution; the desiliconizing agent is prepared by mixing the following raw materials in parts by mass: 65-75 parts of deionized water, 30-40 parts of active desiliconizing powder, 0.5-0.8 part of a dispersing agent and 0.2-0.3 part of a stabilizer, wherein the active desiliconizing powder is obtained by intercalating and compounding modified nano sodalite and modified kaolin; when the desiliconizing agent is used for treating the fly ash mixed raw material, the removal rate of silicon dioxide in the dissolved slurry can be greater than or equal to 90.37%, and the purity of aluminum oxide in the product can reach 97.7% or above.

Description

Technical Field

[0001] The present application relates to the technical field of comprehensive utilization of fly ash, and more specifically, to a method for extracting aluminum oxide based on solid waste fly ash. Background Art

[0002] Fly ash, the main solid waste generated by coal-fired power plants, has become an important potential resource for replacing bauxite to extract alumina due to its high aluminum content. However, alumina and silica in fly ash often coexist in amorphous or composite mineral forms, and the aluminum-silicon ratio is generally low, which makes it difficult to meet the raw material requirements of industrial Bayer process refined alumina. In order to optimize the separation and extraction efficiency of alumina, it is usually necessary to add sodium carbonate or lime milk to the clinker after the raw material is calcined to dissolve the insoluble silicon-calcium components. However, even after this step of treatment, a large amount of free silicate ions still remain in the slurry, which will participate in the refining process of alumina, ultimately leading to a reduction in the separation and extraction efficiency of alumina. Therefore, the difficulty of desiliconization has become the core technical bottleneck restricting the large-scale extraction of alumina from fly ash.

[0003] A Chinese patent application document with application publication number CN108622920A discloses a method for extracting alumina from high-alumina fly ash. In the scheme, high-alumina fly ash is sequentially subjected to activation treatment and pre-desiliconization treatment to obtain desiliconized fly ash. Among them, the activation treatment uses acid solutions such as sulfuric acid and hydrochloric acid, and the sodium hydroxide alkaline solution used in the pre-desiliconization treatment can make the initial desiliconization efficiency of the raw material reach 45% to 53%. The fly ash aluminum-silicon ratio can be increased to above 2.6 through the activation treatment step alone, greatly improving the purity of the obtained alumina product.

[0004] In the above scheme, the silicon-aluminum ratio of the raw material can be reduced by staged treatment with acid and alkali, but the amount of acid-alkali treatment liquid used is large, which is difficult to adapt to the needs of industrial production. In addition, since the acid activation treatment and alkali pre-desiliconization treatment steps are connected in the treatment process, it is easy to cause the residual acid in the previous step to be neutralized by the alkali in the next step, reducing the use effect of the alkali and causing waste of the treatment liquid. Therefore, it is necessary to find a scheme to reduce production costs and improve the desiliconization efficiency of raw fly ash. Summary of the invention

[0005] In order to further reduce the cost of alumina extraction and at the same time improve the desiliconization rate of raw fly ash, the present application provides a method for extracting alumina based on solid waste fly ash.

[0006] A method for extracting alumina from solid waste fly ash, using the following technical solution: The extraction of alumina is carried out in sequence through the steps of raw material burning and dissolution, dissolution slurry desiliconization, stock solution refining and crystallization, and roasting and decomposition; wherein the dissolution slurry desiliconization includes the following steps: adding a desiliconizing agent to the dissolution slurry, heating treatment, and filtering to obtain a carbon stock solution; The desiliconizing agent is prepared by mixing the following raw materials in parts by weight: 65-75 parts of deionized water, 30-40 parts of active desiliconizing powder, 0.5-0.8 parts of dispersant, and 0.2-0.3 parts of stabilizer, wherein the active desiliconizing powder is obtained by compounding modified nano-sodalite and modified kaolin through intercalation; The preparation steps of the modified nano-sodalite include the following: (1) Take aluminum chloride, add sodium hydroxide dropwise, put in an ice water bath, then add ethyl orthosilicate, stir, add a crystal promoter, continue stirring, then adjust the pH, heat up and then keep warm, heat up again after dispersion, filter and take the precipitate, wash with alcohol, readjust the pH, then dry and grind to obtain nano sodalite; (2) taking nano-sodalite, dispersing the mixture, adding an organic acid for treatment, adding a silane coupling agent after heating, continuing the treatment, then adding more silane coupling agent, reacting, then standing in an ice water bath, centrifuging to obtain a precipitate, washing with alcohol, drying and grinding, and obtaining modified nano-sodalite; The intercalation compounding steps include the following steps: taking modified kaolin, mixing it with modified nano-sodalite, dispersing it, then centrifuging it at a low speed, heating it, and then filtering it, washing it with alcohol, drying it, and crushing it to obtain it.

[0007] By adopting the above technical scheme, the cooked raw material is dissolved and then desiliconized, and effective desiliconization can be achieved. The desiliconizer used is a dispersion with desiliconization active components. The modified nano-sodalite in the active component can provide growth nuclei for the free silicate ions in the dissolution slurry. In the hot dissolution slurry environment, the free silicate ions participate in crystallization and are continuously precipitated, thereby achieving the desiliconization effect. The kaolin is organically modified to inhibit its sedimentation behavior in the dissolution slurry, and forms a composite structure with the modified nano-sodalite through intercalation combination. When used, the modified kaolin is used as a crystal bed for the crystallization of modified nano-sodalite, and large particles of impurities are effectively filtered through intercalation gaps to avoid impurities from affecting the growth of modified nano-sodalite crystal clusters; at the same time, due to the isolation effect of intercalation, the merging of adjacent crystal clusters and the occurrence of flocculation are inhibited. Through the combined effect of modified nano-sodalite and modified kaolin, the desiliconization effect of the dissolution slurry can be improved.

[0008] Preferably, the preparation steps of the modified kaolin include the following: taking kaolin, mixing and grinding with ammonium carbamate, then placing in a closed reactor for heat treatment, collecting powder material, dispersing, then adding premixed liquid, treating, adding styrene monomer and initiator, adjusting temperature and reaction time, and finally filtering the filtrate, washing with alcohol, and drying to obtain the product; Preferably, the mixing mass ratio of kaolin and ammonium carbamate is (8.5-9): (1.2-1.5); Preferably, the heat treatment conditions are to adjust the temperature to 72-85°C and treat for 10-12 hours.

[0009] By adopting the above technical solution, the small molecules of ammonium carbamate can be intercalated into the interlayers of kaolin with a layered structure through grinding. Under the heat treatment environment, the ammonium carbamate undergoes thermal decomposition to generate ammonia and carbon dioxide gases, so that the interlayers of kaolin are opened, thereby obtaining exfoliated kaolin.

[0010] Preferably, the premixed liquid is obtained by mixing vinyltriethoxysilane, deionized water, and acetic acid in a mass volume ratio of (1-1.5) g:1 ml:(0.2-0.3) ml.

[0011] By adopting the above technical scheme, in the premixed liquid, vinyl triethoxysilane is activated by acetic acid, hydrolyzed in deionized water to expose the silanol group, and dehydrated and condensed with the silanol group on the stripped kaolin to obtain a grafted composite structure. At the same time, the presence of vinyl in the composite structure can provide a polymerization starting point for the subsequent polymerization of styrene monomer, thereby obtaining organic modified kaolin.

[0012] Preferably, the initiator is azobisisobutyronitrile, the temperature is adjusted to 35-40° C., and the reaction is carried out for 20-30 minutes.

[0013] By adopting the above technical solution, using the above initiator and initiation conditions, the obtained oligomeric polystyrene has the best effect.

[0014] Preferably, in step (1), the molar ratio of aluminum chloride, sodium hydroxide and tetraethyl orthosilicate added is 1:(4-4.6):(0.85-1); and the crystal promoter is prepared by mixing sodium pyrophosphate and aluminum isopropoxide in a mass ratio of 0.3:(1-2).

[0015] By adopting the above technical solution, the raw material ratio can be adjusted to obtain sodalite prepolymer. Aluminum chloride, as an aluminum source, can react with excess sodium hydroxide to obtain aluminate, which is then further reacted with ethyl orthosilicate under ice bath conditions to form a sodalite prepolymer with a gel structure. The addition of a crystal promoter helps to improve the crystal quality. After subsequent treatments of heating and pH adjustment, nano-sodalite can be obtained.

[0016] Preferably, in step (2), the mixed liquid is prepared by mixing deionized water, ethylene glycol and polyvinyl alcohol in a volume ratio of 1:(1-1.5):(0.2-0.3); and the organic acid is one of tartaric acid, citric acid and acetic acid.

[0017] In the step (2), the silane coupling agent is one of 1,2-bis(triethoxysilyl)ethane, vinyltrimethoxysilane, γ-aminopropyltriethoxysilane and vinyltriethoxysilane.

[0018] By adopting the above technical scheme, the mixed liquid can evenly disperse the nano-sodalite, and the organic acid can activate the aluminum hydroxyl and silicon hydroxyl structures on the surface of the nano-sodalite, promote the introduction of the silane coupling agent in the subsequent steps, play a role in modifying the nano-sodalite, and improve the effect of the subsequent intercalation combination.

[0019] Preferably, in step (2), the mass ratio of the silane coupling agent added for the first time to the silane coupling agent added is (0.2-0.5): (1-1.5).

[0020] By adopting the above technical scheme, the effect of regularizing the silane chain segments can be achieved by adding the silane coupling agent twice. First, under the activation of organic acid, the aluminum / silanol groups on the nano-sodalite react with the small amount of silane coupling agent added for the first time to complete the grafting and form active grafting sites. The subsequently added silane coupling agent can continue to react at the grafting sites and finally obtain multi-clustered silane chain segments with nano-sodalite as the core. These silane chain segments serve as anchor points for fixing the nano-sodalite in the subsequent intercalation reaction, thereby improving the firmness of the intercalation structure.

[0021] Preferably, in the intercalation composite step, the mass ratio of modified kaolin to modified nano-sodalite is (25-30):(7-8).

[0022] In summary, this application has the following beneficial effects: 1. The present application uses modified nano-sodalite and modified kaolin to treat and disperse to obtain a desiliconizing agent. Among the active components of the desiliconizing agent, the modified nano-sodalite can provide a nucleus for the growth of free silicate ions in the dissolution slurry, and continuously crystallizes in the hot dissolution slurry environment to achieve a desiliconization effect. The kaolin is organically modified to inhibit its sedimentation behavior in the dissolution slurry, and forms a composite structure with the modified nano-sodalite through intercalation combination.

[0023] 2. In the present application, the intercalation combination method is preferably used to obtain active desiliconized powder. In the constructed intercalation composite structure, modified kaolin is used as the crystal bed for the crystallization of modified nano-sodalite. Large particle impurities are effectively filtered through the intercalation gaps to avoid the incorporation of impurities affecting the growth of modified nano-sodalite crystals. At the same time, due to the intercalation isolation effect, the merging of adjacent crystal clusters and the occurrence of crystal cluster flocculation are inhibited. The combined effect of modified nano-sodalite and modified kaolin can improve the desiliconization effect of the dissolution slurry.

[0024] 3. The desiliconizing agent of the present application is used to treat the fly ash mixed raw material, and the silicon dioxide removal rate in the dissolution slurry is ≥ 90.37%, and the purity of the aluminum oxide in the product can reach more than 97.7%. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the percentage of aluminum oxide in the products after being treated with the desiliconizing agent of Examples 1-5 and Comparative Examples 1-4 of the present application.

[0026] Figure 2 It is the removal rate of silicon dioxide in the dissolution slurry after being treated with the desiliconizing agent of Examples 1-5 and Comparative Examples 1-4 of the present application. DETAILED DESCRIPTION

[0027] Preparation Example 1 Take 0.28g of aluminum chloride, add 16mL of 0.5mol / L sodium hydroxide solution drop by drop, then add 0.36g of tetraethyl orthosilicate to the system under ice bath conditions, adjust the magnetic stirring speed to 50rpm, stir for 15min, then add 0.2g of crystal promoter, continue to treat for 10min, then add ammonia water, adjust the pH to 8.5, adjust the temperature to 80℃, keep warm for 20min, then add 30ml of n-butanol, adjust the magnetic stirring speed to 100rpm, keep the temperature at 85℃ for 8h, filter the precipitate, then use anhydrous ethanol to ultrasonically wash twice, adjust the pH to 7.5, then place in an oven at 45℃ for drying, and finally grind for 1min to obtain nano sodalite.

[0028] Take 4.2g of nano-sodalite, add it to 30ml of the mixed solution, adjust the magnetic stirring speed to 75rpm, disperse for 5min, add 0.2g of tartaric acid, continue to treat for 20min, then heat to 60℃, add 0.2g of 1,2-bis(triethoxysilyl)ethane, treat for 10min, then add 1g of 1,2-bis(triethoxysilyl)ethane, reduce the magnetic stirring speed to 30rpm, react for 1h, treat the reaction solution for another 10min under ice bath conditions, then high-speed centrifuge at 3000rpm to take the bottom precipitate, wash the precipitate twice with hot anhydrous ethanol, dry and grind for 3min to obtain modified nano-sodalite.

[0029] Take 8.5g of kaolin, mix it with 1.2g of ammonium carbamate, grind it for 10min, then place it in a closed reactor, treat it at 72℃ for 10h, then slowly release the pressure to normal pressure, collect the powder material, place it in 30ml of acetone, ultrasonically treat it at 30℃ for 10min, then add 1.7ml of premixed liquid, treat it for 20min, then add 0.4g of styrene monomer and 0.1g of azobisisobutyronitrile to the system, adjust the temperature to 35℃, react for 20min, then filter the filtrate, wash it with alcohol twice, and obtain modified kaolin after drying.

[0030] Take 25g of modified kaolin, mix it with 7g of modified nano-sodalite, add it to 100ml of n-butanol for ultrasonic dispersion, then place the dispersion in a centrifuge, adjust the speed to 2500rpm and centrifuge it at low speed for 30min, then transfer it to a constant temperature water bath, treat it at 70℃ for 2.5h, then filter out the filter cake, wash it twice with hot anhydrous ethanol and dry it, finally crush it and pass it through a 150-mesh sieve to obtain active desiliconized powder.

[0031] Take 65 g of deionized water, 0.5 g of dispersant polyethylene glycol, 0.2 g of stabilizer sodium carboxymethyl cellulose, and 30 g of active desiliconization powder, adjust the magnetic stirring speed to 100 rpm, and process for 20 minutes to obtain a desiliconization agent.

[0032] The crystal promoter is prepared by mixing sodium pyrophosphate and aluminum isopropoxide in a mass ratio of 0.3:1. The mixed solution is prepared by mixing deionized water, ethylene glycol, and polyvinyl alcohol in a volume ratio of 1:1:0.2. Kaolin (model BR-5, average particle size 4.2 microns) is provided by Shanghai Kaiyin Chemical Co., Ltd. The premix is ​​prepared by mixing vinyl triethoxysilane, deionized water, and acetic acid in a mass volume ratio of 1g:1ml:0.2ml.

[0033] Preparation Example 2 Take 0.28g of aluminum chloride, add 18.1mL of 0.5mol / L sodium hydroxide solution drop by drop, then add 0.4g of tetraethyl orthosilicate to the system under ice bath conditions, adjust the magnetic stirring speed to 50rpm, stir for 15min, then add 0.25g of crystal promoter, continue to treat for 15min, then add ammonia water, adjust the pH to 8.9, adjust the temperature to 82℃, keep warm for 20min, then add 30ml of n-butanol, adjust the magnetic stirring speed to 100rpm, keep the temperature at 87℃ for 8.5h, then use anhydrous ethanol for ultrasonic washing twice, adjust the pH to 7.8, then place in an oven at 45℃ for drying, and finally grind for 2min to obtain nano sodalite.

[0034] Take 4.5g of nano-sodalite, add it to 30ml of the mixed solution, adjust the magnetic stirring speed to 75rpm, disperse for 8min, add 0.3g of citric acid, continue to treat for 20min, then heat to 65℃, add 0.25g of 1,2-bis(triethoxysilyl)ethane, treat for 12min, then add 1.1g of 1,2-bis(triethoxysilyl)ethane, reduce the magnetic stirring speed to 35rpm, react for 1.5h, treat the reaction solution for another 15min under ice bath conditions, then high-speed centrifuge at 3000rpm to take the bottom precipitate, wash the precipitate 3 times with hot anhydrous ethanol, dry and grind for 3min to obtain modified nano-sodalite.

[0035] Take 8.7g of kaolin, mix it with 1.3g of ammonium carbamate, grind it for 12min, then place it in a closed reactor, treat it at 74℃ for 10h, then slowly release the pressure to normal pressure, collect the powder material, place it in 32ml of acetone, ultrasonically treat it at 30℃ for 11min, then add 1.8ml of premixed solution, treat it for 20min, then add 0.4g of styrene monomer and 0.15g of azobisisobutyronitrile to the system, adjust the temperature to 35℃, react for 20min, then filter the filtrate, wash it with alcohol twice, and obtain modified kaolin after drying.

[0036] Take 27g of modified kaolin, mix it with 7.2g of modified nano-sodalite, add it to 100ml of n-butanol for ultrasonic dispersion, then place the dispersion in a centrifuge, adjust the speed to 2500rpm and centrifuge it at low speed for 30min, then transfer it to a constant temperature water bath, treat it at 72℃ for 2.5h, then filter out the filter cake, wash it twice with hot anhydrous ethanol and dry it, finally crush it and pass it through a 150-mesh sieve to obtain active desiliconized powder.

[0037] Take 68 g of deionized water, 0.7 g of dispersant polyethylene glycol, 0.2 g of stabilizer sodium carboxymethyl cellulose, and 30 g of active desiliconization powder, adjust the magnetic stirring speed to 100 rpm, and process for 25 minutes to obtain a desiliconization agent.

[0038] The crystal promoter is prepared by mixing sodium pyrophosphate and aluminum isopropoxide in a mass ratio of 0.3:1.2. The mixed solution is prepared by mixing deionized water, ethylene glycol, and polyvinyl alcohol in a volume ratio of 1:1.2:0.2. Kaolin (model BR-5, average particle size 4.2 microns) is provided by Shanghai Kaiyin Chemical Co., Ltd. The premix is ​​prepared by mixing vinyl triethoxysilane, deionized water, and acetic acid in a mass volume ratio of 1.2g:1ml:0.25ml.

[0039] Preparation Example 3 Take 0.28g of aluminum chloride, add 18.5mL of 0.5mol / L sodium hydroxide solution drop by drop, then add 0.43g of tetraethyl orthosilicate to the system under ice bath conditions, adjust the magnetic stirring speed to 50rpm, stir for 15min, then add 0.3g of crystal promoter, continue to treat for 12min, then add ammonia water, adjust the pH to 8.7, adjust the temperature to 83℃, keep warm for 24min, then add 30ml of n-butanol, adjust the magnetic stirring speed to 100rpm, keep the temperature at 87℃ for 9h, then use anhydrous ethanol for ultrasonic washing twice, adjust the pH to 7.6, then place in an oven at 50℃ for drying, and finally grind for 2min to obtain nano sodalite.

[0040] Take 4.2g of nano-sodalite, add it to 35ml of the mixed solution, adjust the magnetic stirring speed to 85rpm, disperse for 10min, add 0.5g of acetic acid, continue to treat for 25min, then heat to 70°C, add 0.3g of vinyltriethoxysilane, treat for 15min, then add 1.4g of vinyltriethoxysilane, reduce the magnetic stirring speed to 35rpm, react for 1.5h, treat the reaction solution for another 15min under ice bath conditions, then high-speed centrifuge at 3000rpm to take the bottom precipitate, wash the precipitate 3 times with hot anhydrous ethanol, dry and grind for 3min to obtain modified nano-sodalite.

[0041] Take 9g of kaolin, mix it with 1.4g of ammonium carbamate, grind it for 10min, then place it in a closed reactor, treat it at 75℃ for 12h, then slowly release the pressure to normal pressure, collect the powder material, place it in 30ml of acetone, ultrasonically treat it at 35℃ for 15min, then add 2.1ml of premixed liquid, treat it for 25min, then add 0.5g of styrene monomer and 0.2g of azobisisobutyronitrile to the system, adjust the temperature to 40℃, react for 30min, then filter the filtrate, wash it with alcohol 3 times, and obtain modified kaolin after drying.

[0042] Take 28g of modified kaolin, mix it with 7.8g of modified nano-sodalite, add it to 120ml of n-butanol for ultrasonic dispersion, then place the dispersion in a centrifuge, adjust the speed to 3000rpm and centrifuge it at low speed for 45min, then transfer it to a constant temperature water bath, treat it at 75℃ for 3h, then filter out the filter cake, wash it with hot anhydrous ethanol 3 times and then dry it, finally crush it and pass it through a 150-mesh sieve to obtain active desiliconized powder.

[0043] Take 72 g of deionized water, 0.55 g of dispersant polyethylene glycol, 0.25 g of stabilizer sodium carboxymethyl cellulose, and 32 g of active desiliconization powder, adjust the magnetic stirring speed to 150 rpm, and process for 20 minutes to obtain a desiliconization agent.

[0044] The crystal promoter is prepared by mixing sodium pyrophosphate and aluminum isopropoxide in a mass ratio of 0.3:1. The mixed solution is prepared by mixing deionized water, ethylene glycol, and polyvinyl alcohol in a volume ratio of 1:1.4:0.25. Kaolin (model BR-5, average particle size 4.2 microns) is provided by Shanghai Kaiyin Chemical Co., Ltd. The premix is ​​prepared by mixing vinyl triethoxysilane, deionized water, and acetic acid in a mass volume ratio of 1g:1ml:0.3ml.

[0045] Preparation Example 4 Take 0.28g of aluminum chloride, add 18.7mL of 0.5mol / L sodium hydroxide solution drop by drop, then add 0.43g of tetraethyl orthosilicate to the system under ice bath conditions, adjust the magnetic stirring speed to 75rpm, stir for 20min, then add 0.3g of crystal promoter, continue to treat for 30min, then add ammonia water, adjust the pH to 8.7, adjust the temperature to 85℃, keep warm for 25min, then add 30ml of n-butanol, adjust the magnetic stirring speed to 100rpm, keep the temperature at 95℃ for 10h, then use anhydrous ethanol for ultrasonic washing 3 times, adjust the pH to 7.8, then place in an oven at 50℃ for drying, and finally grind for 2min to obtain nano sodalite.

[0046] Take 5.5g of nano-sodalite, add it to 35ml of the mixed solution, adjust the magnetic stirring speed to 75rpm, disperse for 10min, add 0.45g of acetic acid, continue to treat for 30min, then heat to 70°C, add 0.5g of vinyltrimethoxysilane, treat for 12min, then add 1.5g of vinyltrimethoxysilane, reduce the magnetic stirring speed to 35rpm, react for 2h, treat the reaction solution under ice bath conditions for another 20min, then high-speed centrifuge at 3500rpm to take the bottom precipitate, wash the precipitate 3 times with hot anhydrous ethanol, dry and grind for 4min to obtain modified nano-sodalite.

[0047] Take 8.9g of kaolin, mix it with 1.5g of ammonium carbamate, grind it for 12min, then place it in a closed reactor, treat it at 85℃ for 12h, then slowly release the pressure to normal pressure, collect the powder material, place it in 40ml of acetone, ultrasonically treat it at 32℃ for 15min, then add 2.3ml of premixed liquid, treat it for 25min, then add 0.5g of styrene monomer and 0.2g of azobisisobutyronitrile to the system, adjust the temperature to 40℃, react for 30min, then filter the filtrate, wash it with alcohol 3 times, and obtain modified kaolin after drying.

[0048] Take 28g of modified kaolin, mix it with 8g of modified nano-sodalite, add it to 120ml of n-butanol for ultrasonic dispersion, then place the dispersion in a centrifuge, adjust the speed to 3000rpm and centrifuge it at low speed for 45min, then transfer it to a constant temperature water bath, treat it at 75℃ for 2.5h, then filter out the filter cake, wash it with hot anhydrous ethanol 3 times and then dry it, finally crush it and pass it through a 150-mesh sieve to obtain active desiliconized powder.

[0049] Take 75 g of deionized water, 0.75 g of dispersant polyethylene glycol, 0.3 g of stabilizer sodium carboxymethyl cellulose, and 37 g of active desiliconization powder, adjust the magnetic stirring speed to 200 rpm, and process for 30 minutes to obtain a desiliconization agent.

[0050] The crystal promoter is prepared by mixing sodium pyrophosphate and aluminum isopropoxide in a mass ratio of 0.3:1. The mixed solution is prepared by mixing deionized water, ethylene glycol, and polyvinyl alcohol in a volume ratio of 1:1.2:0.3. Kaolin (model BR-5, average particle size 4.2 microns) is provided by Shanghai Kaiyin Chemical Co., Ltd. The premix is ​​prepared by mixing vinyl triethoxysilane, deionized water, and acetic acid in a mass volume ratio of 1g:1ml:0.3ml.

[0051] Preparation Example 5 Take 0.28g of aluminum chloride, add 19.2mL of 0.5mol / L sodium hydroxide solution drop by drop, then add 0.43g of tetraethyl orthosilicate to the system under ice bath conditions, adjust the magnetic stirring speed to 75rpm, stir for 20min, then add 0.4g of crystal promoter, continue to treat for 30min, then add ammonia water, adjust the pH to 8.9, adjust the temperature to 85℃, keep warm for 25min, then add 30ml of n-butanol, adjust the magnetic stirring speed to 100rpm, keep constant temperature at 95℃ for 10h, then use anhydrous ethanol for ultrasonic washing 3 times, adjust the pH to 7.8, then place in an oven at 50℃ for drying, and finally grind for 2min to obtain nano sodalite.

[0052] Take 5.5g of nano-sodalite, add it to 35ml of the mixed solution, adjust the magnetic stirring speed to 100rpm, disperse for 10min, add 0.5g of acetic acid, continue to treat for 30min, then heat to 70°C, add 0.45g of γ-aminopropyltriethoxysilane, treat for 10min, then add 1.5g of γ-aminopropyltriethoxysilane, reduce the magnetic stirring speed to 50rpm, react for 2h, treat the reaction solution for another 20min under ice bath conditions, then high-speed centrifuge at 3500rpm to take the bottom precipitate, wash the precipitate 3 times with hot anhydrous ethanol, dry and grind for 5min to obtain modified nano-sodalite.

[0053] Take 9g of kaolin, mix it with 1.5g of ammonium carbamate, grind it for 20min, then place it in a closed reactor, treat it at 85℃ for 12h, then slowly release the pressure to normal pressure, collect the powder material, place it in 40ml of acetone, ultrasonically treat it at 35℃ for 15min, then add 2.3ml of premixed liquid, treat it for 25min, then add 0.5g of styrene monomer and 0.2g of azobisisobutyronitrile to the system, adjust the temperature to 40℃, react for 30min, then filter the filtrate, wash it with alcohol 3 times, and obtain modified kaolin after drying.

[0054] Take 30g of modified kaolin, mix it with 8g of modified nano-sodalite, add it to 120ml of n-butanol for ultrasonic dispersion, then place the dispersion in a centrifuge, adjust the speed to 3000rpm and centrifuge it at low speed for 45min, then transfer it to a constant temperature water bath, treat it at 75℃ for 3h, then filter out the filter cake, wash it with hot anhydrous ethanol 3 times and then dry it, finally crush it and pass it through a 150-mesh sieve to obtain active desiliconized powder.

[0055] Take 75 g of deionized water, 0.8 g of dispersant polyethylene glycol, 0.3 g of stabilizer sodium carboxymethyl cellulose, and 40 g of active desiliconization powder, adjust the magnetic stirring speed to 200 rpm, and process for 30 minutes to obtain a desiliconization agent.

[0056] The crystal promoter is prepared by mixing sodium pyrophosphate and aluminum isopropoxide in a mass ratio of 0.3:2. The mixed solution is prepared by mixing deionized water, ethylene glycol, and polyvinyl alcohol in a volume ratio of 1:1.5:0.3. Kaolin (model BR-5, average particle size 4.2 microns) is provided by Shanghai Kaiyin Chemical Co., Ltd. The premix is ​​prepared by mixing vinyl triethoxysilane, deionized water, and acetic acid in a mass volume ratio of 1.5g:1ml:0.3ml.

[0057] Example 1 Take 1000g fly ash, 45g fluorite and 1500g limestone, mix them, grind them and pass them through a 200-mesh sieve, bake them at 50℃ for 6h, then calcine and mature them at 1325℃, slurry the matured material with a mass fraction of 15% sodium carbonate solution, treat the slurry at 100℃ for 3h, and then filter to obtain the dissolved slurry; add desiliconizer to the dissolved slurry at an effective active desiliconization powder content of 35g / L, adjust the temperature to 65℃, treat it for 8h and then slurry it again. Filter to obtain a carbon stock solution; continuously introduce carbon dioxide into the carbon stock solution for 3 hours, filter and re-slurry, keep warm at 145°C for 5 hours, then add aluminum hydroxide seeds to the secondary slurry according to the addition amount of 630g / L pure aluminum hydroxide, treat at 65°C for 12 hours, then flash and filter to obtain aluminum hydroxide slag; take the slag and roast it in a high-temperature air flow at 1075°C for 3 hours, naturally cool it and then crush it through a 100-mesh sieve to obtain an alumina product.

[0058] The above desiliconizing agent is prepared by Preparation Example 1.

[0059] Among them, fly ash (industrial grade, Al2O3wt%: 23.5%) was provided by Hunan Baolong Technology Development Co., Ltd.

[0060] Example 2 Take 1000g fly ash, 45g fluorite and 1500g limestone, mix them, grind them and pass them through a 200 mesh sieve, bake them at 50℃ for 6h, then calcine and mature them at 1350℃, slurry the matured material with a sodium carbonate solution with a mass fraction of 15%, treat the slurry at 135℃ for 4h, and then filter to obtain the dissolved slurry; add desiliconizer to the dissolved slurry in an amount of 40g / L of effective active desiliconized powder, adjust the temperature to 67℃, treat it for 8h, and then slurry it again. Filter to obtain a carbon stock solution; continuously introduce carbon dioxide into the carbon stock solution for 4 hours, filter and re-slurry, keep warm at 145°C for 5 hours, then add aluminum hydroxide seeds to the secondary slurry according to the addition amount of 630g / L pure aluminum hydroxide, treat at 65°C for 12 hours, then flash and filter to obtain aluminum hydroxide slag; take the slag and roast it in a high-temperature air flow at 1075°C for 5 hours, naturally cool it and then crush it through a 100-mesh sieve to obtain an alumina product.

[0061] The above desiliconizing agent is prepared by Preparation Example 2.

[0062] Among them, fly ash (industrial grade, Al2O3wt%: 23.5%) was provided by Hunan Baolong Technology Development Co., Ltd.

[0063] Example 3 Take 1000g fly ash, 45g fluorite and 1500g limestone, mix them, grind them and pass them through a 200 mesh sieve, bake them at 50℃ for 6h, then calcine and mature them at 1375℃, slurry the matured material with a sodium carbonate solution with a mass fraction of 15%, treat the slurry at 135℃ for 4h, and then filter to obtain the dissolved slurry; add desiliconizer to the dissolved slurry at an effective active desiliconization powder content of 30g / L, adjust the temperature to 65℃, treat it for 10h and then re-crystallize it. Filter to obtain a carbon stock solution; continuously introduce carbon dioxide into the carbon stock solution for 4 hours, filter and re-slurry, keep warm at 150°C for 6 hours, then add aluminum hydroxide seeds to the secondary slurry according to the addition amount of 630g / L pure aluminum hydroxide, treat at 70°C for 14 hours, then flash and filter to obtain aluminum hydroxide slag; take the slag and roast it in a high-temperature air flow at 1075°C for 4 hours, naturally cool it and then crush it through a 100-mesh sieve to obtain an alumina product.

[0064] The above desiliconizing agent is prepared by Preparation Example 3.

[0065] Among them, fly ash (industrial grade, Al2O3wt%: 23.5%) was provided by Hunan Baolong Technology Development Co., Ltd.

[0066] Example 4 Take 1000g fly ash, 45g fluorite and 1500g limestone, mix them, grind them and pass them through a 200 mesh sieve, bake them at 50℃ for 6h, then calcine and mature them at 1375℃, slurry the matured material with a sodium carbonate solution with a mass fraction of 15%, treat the slurry at 120℃ for 3.5h, and then filter to obtain the dissolved slurry; add desiliconizer to the dissolved slurry in an amount of 25g / L of effective active desiliconized powder, adjust the temperature to 72℃, and treat it for 10h before weighing. The carbon stock solution is newly filtered; carbon dioxide is continuously introduced into the carbon stock solution for 3 hours, filtered and re-slurried, kept at 150°C for 6 hours, and then aluminum hydroxide seeds are added to the secondary slurry at an addition amount of 630g / L pure aluminum hydroxide, and treated at 70°C for 15 hours, and then aluminum hydroxide slag is obtained after flash evaporation and filtration; the slag is roasted in a high-temperature air flow at 1075°C for 3 hours, and after natural cooling, it is crushed through a 100-mesh sieve to obtain an alumina product.

[0067] The above desiliconizing agent is prepared by Preparation Example 4.

[0068] Among them, fly ash (industrial grade, Al2O3wt%: 23.5%) was provided by Hunan Baolong Technology Development Co., Ltd.

[0069] Example 5 Take 1000g fly ash, 45g fluorite and 1500g limestone, mix them, grind them and pass them through a 200 mesh sieve, bake them at 50℃ for 6h, then calcine and mature them at 1375℃, slurry the matured material with a sodium carbonate solution with a mass fraction of 15%, treat the slurry at 135℃ for 4h, and then filter to obtain the dissolved slurry; add desiliconizer to the dissolved slurry in an amount of 24g / L of effective active desiliconized powder, adjust the temperature to 72℃, treat it for 10h and then re-crystallize it. Filter to obtain a carbon stock solution; continuously introduce carbon dioxide into the carbon stock solution for 4 hours, filter and re-slurry, keep warm at 150°C for 6 hours, then add aluminum hydroxide seeds to the secondary slurry according to the addition amount of 630g / L pure aluminum hydroxide, treat at 65°C for 15 hours, then flash and filter to obtain aluminum hydroxide slag; take the slag and roast it in a high-temperature air flow at 1075°C for 5 hours, naturally cool it and then crush it through a 100-mesh sieve to obtain an alumina product.

[0070] The above desiliconizing agent is prepared by Preparation Example 5.

[0071] Among them, fly ash (industrial grade, Al2O3wt%: 23.5%) was provided by Hunan Baolong Technology Development Co., Ltd.

[0072] Comparative Example 1 The difference between this comparative example and Example 1 is that the preparation steps of the desiliconizing agent are as follows: Take 25g of modified kaolin, mix it with 15g of modified nano-sodalite, add it to 100ml of n-butanol for ultrasonic dispersion, then place the dispersion in a centrifuge, adjust the speed to 2500rpm and centrifuge it at low speed for 30min, then transfer it to a constant temperature water bath, treat it at 70℃ for 2.5h, then filter out the filter cake, wash it twice with hot anhydrous ethanol and dry it, finally crush it and pass it through a 150-mesh sieve to obtain active desiliconized powder.

[0073] Take 65 g of deionized water, 0.5 g of dispersant polyethylene glycol, 0.2 g of stabilizer sodium carboxymethyl cellulose, and 20 g of active desiliconization powder, adjust the magnetic stirring speed to 100 rpm, and process for 20 minutes to obtain a desiliconization agent.

[0074] The remaining steps are the same as those in Example 1.

[0075] Comparative Example 2 The only difference between this comparative example and Example 1 is that the desiliconizing agent is lime milk with a calcium oxide content of 180 g / L.

[0076] The remaining steps are the same as those in Example 1.

[0077] Comparative Example 3 The difference between this comparative example and Example 1 is that in the desiliconizing agent component, the preparation steps of the modified kaolin are as follows: 8.5 g of kaolin is taken, mixed with 1.2 g of ammonium carbamate, ground for 10 min, and then placed in a closed reactor, treated at 75° C. for 10 h, then slowly released the pressure to normal pressure, collected the powder material, placed in 40 ml of acetone, ultrasonically treated at 35° C. for 15 min, then 2.3 ml of the premixed solution was added, treated for 25 min, then the filtrate was filtered, washed with alcohol 3 times, and dried to obtain the modified kaolin.

[0078] The remaining steps are the same as those in Example 1.

[0079] Comparative Example 4 The difference between this comparative example and Example 1 is that, in the desiliconizing agent component, the active desiliconizing powder is obtained by directly mixing modified nano-sodalite with untreated kaolin.

[0080] The remaining steps are the same as those in Example 1.

[0081] Performance testing Alumina content detection Referring to the national standards GB / T39201-2020 and GB / T6609.3-2004, take 2g of the alumina products obtained in Examples 1-5 and Comparative Examples 1-4 as test samples. Add them to 500mL conical flasks containing EDTA standard solution, add 15ml of hydrochloric acid standard solution, heat water to a volume of about 80ml, then heat and boil for 2min, add 8 drops of phenolphthalein indicator, and titrate with sodium hydroxide standard solution until it turns slightly red. Then add 10ml of acetic acid-sodium acetate buffer and 0.03g of xylenol orange indicator, and titrate with zinc acetate standard solution until it turns purple-red, which is the end point. Finally, calculate the percentage of alumina in the test sample based on the volume of zinc acetate standard solution used. Take three groups as the average value, and the test results are as follows: Figure 1 shown.

[0082] Silica removal rate detection Referring to the national standards GB / T39201-2020 and GB / T6609.3-2004, 10 ml of each of the dissolution slurry and carbon stock solution obtained in Examples 1-5 and Comparative Examples 1-2 were taken, water was added to make the volume 100 ml, and then 5 ml of ammonium molybdate solution with a mass fraction of 5% was added, shaken well, and left to develop color. Then, 20 ml of sulfuric acid-oxalic acid-ammonium ferrous sulfate mixed solution was added, diluted with water, shaken well, and left for 5 minutes. At a wavelength of 700 nm in the spectrophotometer, a 1 cm colorimetric dish was used, and air was used as a reference to zero, and the absorbance was measured. The silicon dioxide content x1 in the dissolution slurry and the silicon dioxide content x2 in the carbon stock solution were calculated from the standard curve, according to the formula: Silica removal rate = [(x1-x2) / x1] × 100% The silica removal rate was calculated and the test results were as follows: Figure 2 shown.

[0083] Among them, the steps for drawing the standard curve are: respectively transfer 0.00ml, 1.00ml, 2.00ml, 3.00ml, 4.00ml, 5.00ml, and 6.00ml of the silica standard solution (0.10mg / mL) into a 100ml volumetric flask, accurately add water to the volume of 60ml, and measure according to the above steps to establish a standard curve.

[0084] Analyze Examples 1-5 and Comparative Examples 1-4 and combine Figure 1-2 It can be seen that the extraction rate of aluminum oxide and the removal rate of silicon dioxide in the embodiment scheme are higher than those in the comparative example scheme. Among them, the product obtained by the embodiment 2 scheme has the highest aluminum oxide purity and the highest silicon dioxide removal rate, while the two data of the comparative example 2 scheme are at the lowest level in the embodiment and comparative example groups.

[0085] Analyze Example 2 and Comparative Examples 1-4 and combine Figure 1-2It can be seen that the scheme of comparative example 3 does not carry out styrene grafting treatment on kaolin, which reduces the effect of desiliconization agent. This may be because, as the desiliconization process progresses, the growth of sodalite nuclei in the desiliconization agent solution causes the kaolin to settle faster. The rapid sedimentation causes the active components of the desiliconization agent to leave the dissolution slurry before they are fully saturated, and ultimately leads to a reduction in the desiliconization effect of the scheme. At the same time, it can be seen that the conventional lime milk used in the scheme of comparative example 2 is not as good as the combined effect of modified nano-sodalite and modified kaolin.

[0086] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for extracting aluminum oxide from solid waste fly ash, characterized in that: The extraction of alumina is carried out in sequence through the steps of raw material burning and dissolution, dissolution slurry desiliconization, stock solution refining and crystallization, and roasting and decomposition; wherein the dissolution slurry desiliconization includes the following steps: adding a desiliconizing agent to the dissolution slurry, heating treatment, and filtering to obtain a carbon stock solution; The desiliconizing agent is prepared by mixing the following raw materials in parts by weight: 65-75 parts of deionized water, 30-40 parts of active desiliconizing powder, 0.5-0.8 parts of dispersant, and 0.2-0.3 parts of stabilizer, wherein the active desiliconizing powder is obtained by compounding modified nano-sodalite and modified kaolin through intercalation; The preparation steps of the modified nano-sodalite include the following: (1) Take aluminum chloride, add sodium hydroxide dropwise, put in an ice water bath, then add ethyl orthosilicate, stir, add a crystal promoter, continue stirring, then adjust the pH, heat up and then keep warm, heat up again after dispersion, filter and take the precipitate, wash with alcohol, readjust the pH, then dry and grind to obtain nano sodalite; (2) Take nano-sodalite, disperse it in a mixed solution, add an organic acid for treatment, add a silane coupling agent after heating, continue the treatment, then add more silane coupling agent, react, then let it stand in an ice water bath, centrifuge to obtain a precipitate, wash it with alcohol, dry it, and grind it to obtain modified nano-sodalite.

2. The method for extracting alumina from solid waste fly ash according to claim 1, characterized in that: The intercalation compounding step comprises the following steps: taking modified kaolin, mixing with modified nano-sodalite, dispersing, then centrifuging at a low speed, heating, filtering, washing with alcohol, drying, and crushing to obtain; The preparation steps of the modified kaolin include the following: taking kaolin, mixing and grinding with ammonium carbamate, then placing in a closed reactor for heat treatment, collecting powder material, dispersing, then adding premixed liquid, treating, adding styrene monomer and initiator, adjusting temperature and reaction time, and finally filtering the filtrate, washing with alcohol, and drying to obtain the modified kaolin.

3. The method for extracting aluminum oxide from solid waste fly ash according to claim 2, characterized in that: The mixing mass ratio of kaolin and ammonium carbamate is (8.5-9): (1.2-1.5); the heat treatment conditions are to adjust the temperature to 72-85° C. and treat for 10-12 hours.

4. The method for extracting aluminum oxide from solid waste fly ash according to claim 2, characterized in that: The premixed liquid is obtained by mixing vinyl triethoxysilane, deionized water and acetic acid in a mass volume ratio of (1-1.5) g:1 ml:(0.2-0.3) ml; the initiator is azobisisobutyronitrile, the temperature is adjusted to 35-40° C., and the reaction time is 20-30 min.

5. The method for extracting alumina from solid waste fly ash according to claim 1, characterized in that: In the step (1), the molar ratio of aluminum chloride, sodium hydroxide and tetraethyl orthosilicate added is 1:(4-4.6):(0.85-1).

6. The method for extracting aluminum oxide from solid waste fly ash according to claim 1, characterized in that: In the step (1), the crystal-growing agent is prepared by mixing sodium pyrophosphate and aluminum isopropoxide in a mass ratio of 0.3:(1-2).

7. The method for extracting aluminum oxide from solid waste fly ash according to claim 1, characterized in that: In the step (2), the mixed liquid is prepared by mixing deionized water, ethylene glycol and polyvinyl alcohol in a volume ratio of 1:(1-1.5):(0.2-0.3); the organic acid is one of tartaric acid, citric acid and acetic acid.

8. The method for extracting aluminum oxide from solid waste fly ash according to claim 1, characterized in that: In the step (2), the silane coupling agent is one of 1,2-bis(triethoxysilyl)ethane, vinyltrimethoxysilane, γ-aminopropyltriethoxysilane and vinyltriethoxysilane.

9. The method for extracting aluminum oxide from solid waste fly ash according to claim 1, characterized in that: In the step (2), the mass ratio of the first added silane coupling agent to the additional added silane coupling agent is (0.2-0.5): (1-1.5).

10. The method for extracting aluminum oxide from solid waste fly ash according to claim 2, characterized in that: In the intercalation composite step, the mass ratio of modified kaolin to modified nano-sodalite is (25-30): (7-8).

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