Silica sol type shell ultrasonic synergistic shell removal process and waste liquid closed loop treatment system
Patent Information
- Application Number
- CN202610960203.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-30
- Publication Date
- 2026-09-25
AI Technical Summary
[0004]本发明所要解决的技术问题在于针对上述现有技术的不足，提供一种硅溶胶型壳超声协同脱壳工艺及废液闭环处理系统，通过复合脱壳液配方优化、超声空化强化、腐蚀后精准中和及废液闭环回收，实现脱壳效率、铸件质量与环保效益的协同提升；该系统无需防腐蚀预处理，可解决硅溶胶型壳脱壳效率低、铸件腐蚀、废液处理难的问题
1、本发明针对硅溶胶型壳脱壳效率低、铸件腐蚀、废液处理难的问题，提供一种无需防腐蚀预处理的超声协同脱壳工艺。复合脱壳液中的葡萄糖酸钠通过五元环螯合Na+，提升Na2SiO3解离平衡常数，降低SiO2+2NaOH反应活化能加速NaOH与SiO2的反应。超声振动过程中空化泡在型壳微孔隙表面崩溃时，产生的微射流可穿透SiO2网络，与化学刻蚀形成协同作用。柠檬酸中和NaOH结合PVP氢键成膜提升氧化电位实现防腐蚀。脱壳废液经CO2自发碳化实现SiO2沉淀回收率提升，中和后的废碱液经电渗析回收NaOH溶液，再生电耗低于传统蒸发法，实现能源节约。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of precision casting technology, specifically relating to an ultrasonic-assisted shell removal process for silica sol molds and a closed-loop waste liquid treatment system. Background Technology
[0002] Silica sol shells, with their high high-temperature strength, high dimensional accuracy, and excellent surface quality, have become the preferred shell material for aerospace blades in the precision casting field. However, the dense SiO2 glass phase network formed after sintering makes shell removal significantly more difficult than with water glass shells, resulting in challenging shell removal after melting and casting. Traditional mechanical shell removal typically uses low-cost vibration and hammering, but this process is time-consuming, and the casting may suffer recrystallization, microcracks, and surface roughness deterioration due to the impact. Furthermore, chemical shell removal is also a mainstream method, but using high-concentration, high-temperature NaOH solutions can lead to residual alkali on the casting surface, causing severe intergranular corrosion and defects, and potentially resulting in alkali embrittlement during subsequent heat treatment. The disposal of waste alkali solution generated after shell removal is also a major problem. The processing of silica sol shells produces a large amount of waste alkali solution, which contains significant unused resources, and its treatment requires substantial costs and resources.
[0003] Therefore, there is a need to propose a shelling method that is efficient, clean, environmentally friendly, and cost-effective. Summary of the Invention
[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a silica sol shell ultrasonic synergistic descraping process and a waste liquid closed-loop treatment system. Through the optimization of the composite descraping liquid formula, ultrasonic cavitation enhancement, precise neutralization after corrosion, and closed-loop recycling of waste liquid, the system achieves a synergistic improvement in descraping efficiency, casting quality, and environmental benefits. This system does not require anti-corrosion pretreatment and can solve the problems of low descraping efficiency of silica sol shells, casting corrosion, and difficult waste liquid treatment.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system, which uses a composite deshelling liquid composed of NaOH, sodium gluconate, surfactant and water, combined with ultrasonic-assisted deshelling, the deshelled casting is corroded and neutralized by a neutralizing liquid, the resulting deshelling waste liquid is filtered and then carbonized by CO2 gas to recover SiO2, and the neutralized waste liquid is precipitated by calcium salt and then the NaOH solution is recovered by electrodialysis; The composite desquaming solution contains 8-12% NaOH, 3-5.5% sodium gluconate, and 0.5-0.8% surfactant.
[0006] Preferably, the molar ratio of sodium gluconate to NaOH in the composite dehulling solution is 1:(8-11).
[0007] Preferably, the surfactant is a fatty alcohol polyoxyethylene ether carboxylate or an α-alkenyl sulfonate.
[0008] Preferably, the pH value of the composite desquamation solution is controlled at 13.0-13.5.
[0009] Preferably, during the ultrasonic-assisted deshelling process, the applied ultrasonic frequency is 40-60 kHz, and the power density is 1.5-2.0 W / cm². 2 The processing temperature is 45-55℃, and the processing time is 30-60 minutes. During the ultrasonic-assisted deshelling process, the average collapse velocity of the cavitation bubbles is ≥150m / s, and the generated local pressure is ≥80MPa, which destroys the SiO2 network structure of the shell.
[0010] Preferably, the neutralization solution used in the neutralization treatment of the casting after corrosion after descaling is a citric acid solution with a mass fraction of 2-4% and 0.1-0.3% polyvinylpyrrolidone added, with a pH value of 3.0-4.5, a neutralization treatment temperature of 35-45℃, and a treatment time of 5-15 minutes.
[0011] Preferably, the dehulling waste liquid is filtered and then subjected to carbonization treatment with CO2 gas, and the reaction pH is controlled to be 8.5-9.5. The generated SiO2 precipitate is recycled after high-temperature calcination. The high-temperature calcination temperature of the SiO2 precipitate is 1100-1300℃, and the calcination time is 1-3h.
[0012] Preferably, the neutralized waste liquid is precipitated with calcium salt and then the NaOH solution is recovered by electrodialysis. The concentration of the regenerated NaOH solution is 6-9%, and the regenerated alkali solution is recycled ≥3 times.
[0013] Compared with the prior art, the present invention has the following significant technical effects: 1. This invention addresses the problems of low decoction efficiency, casting corrosion, and difficult waste liquid treatment associated with silica sol-type shell castings by providing an ultrasonic synergistic decoction process that requires no anti-corrosion pretreatment. Sodium gluconate in the composite decoction solution chelates Na through a five-membered ring. +This process increases the dissociation equilibrium constant of Na2SiO3, lowers the activation energy of the SiO2 + 2NaOH reaction, and accelerates the reaction between NaOH and SiO2. During ultrasonic vibration, the collapse of cavitation bubbles on the microporous surface of the shell generates microjets that can penetrate the SiO2 network, synergizing with chemical etching. Citric acid neutralizes NaOH, forming a PVP hydrogen bond film that enhances the oxidation potential and achieves corrosion protection. The shelling waste liquid undergoes spontaneous carbonization with CO2, improving the SiO2 precipitation recovery rate. The neutralized alkaline waste liquid is then subjected to electrodialysis to recover NaOH solution, with regeneration power consumption lower than traditional evaporation methods, achieving energy savings.
[0014] 2. This invention achieves a synergistic improvement in descraping efficiency, casting quality, and environmental benefits by utilizing the synergistic mechanism of the composite descraping fluid system, optimizing ultrasonic-assisted descraping process parameters, controlling the post-corrosion citric acid-PVP neutralization process, and implementing a closed-loop waste liquid recovery system and process control. This system eliminates the need for anti-corrosion pretreatment and solves the problems of low descraping efficiency, casting corrosion, and difficult waste liquid treatment associated with silica sol molds.
[0015] The present invention will be further described in detail below with reference to the embodiments. Detailed Implementation
[0016] The specifications of the raw materials used in this invention are as follows: NaOH granules: Industrial grade, conforming to standard GB / T 209-2018, purity ≥99.0%, particle size 1-3mm, free of visible mechanical impurities, easily soluble in water and with stable heat of solution.
[0017] Sodium gluconate: Industrial grade, conforming to standard HG / T 3-1074-1977, purity ≥98.5%, white crystalline powder, pH value (1% aqueous solution) 6.0-7.0, easily soluble in water, complexing ability ≥300mg CaCO3 / g.
[0018] The surfactants are fatty alcohol polyoxyethylene ether carboxylates or α-alkenyl sulfonates; fatty alcohol polyoxyethylene ether carboxylates (AEC-9Na): industrial grade, active ingredient content ≥95%, HLB value 12-14, pH value (1% aqueous solution) 6.5-7.5, alkali resistance ≥20% NaOH solution; α-alkenyl sulfonate (AOS-30): industrial grade, active ingredient content ≥30%, inorganic salt content ≤8%, pH value (1% aqueous solution) 7.0-9.0, hard water resistance ≥300mg / L Ca 2+ .
[0019] Citric acid powder: food grade / industrial grade, conforming to standard GB / T 8269-2019, purity ≥99.5%, white crystalline powder, with good water solubility.
[0020] Polyvinylpyrrolidone: Industrial grade, model PVP-K30, standard QB / T 2671-2022, molecular weight 30000-40000, solid content ≥99.0%, pH value (5% aqueous solution) 3.0-7.0, good compatibility with citric acid solution.
[0021] Example 1
[0022] This embodiment describes a silica sol-type shell ultrasonic synergistic deshelling process and a waste liquid closed-loop treatment system, including the following steps: S1. Preparation of peeling solution Add 874L of deionized water to a 1000L stainless steel reactor, start stirring (200rpm), slowly add 80kg of NaOH granules, and after complete dissolution, cool to 40℃; add 40kg of sodium gluconate, stir for 30min until completely dissolved, then add 6kg of fatty alcohol polyoxyethylene ether carboxylate (AEC-9Na), and adjust the pH to 13.2 with a 5% NaOH solution to obtain the composite decapsulation solution.
[0023] In this composite stripping solution, the mass fraction of NaOH is 8%, the mass fraction of sodium gluconate is 4%, and the mass fraction of surfactant is 0.6%. The molar ratio of sodium gluconate to NaOH is 1:10.9, which improves the etching efficiency of NaOH on SiO2 through complexation.
[0024] S2, Dehulling 10 kg of silica sol shell (6 mm thick) sintered at 1150℃ was immersed in the composite shell-removing solution obtained in S1, and ultrasonication was initiated at 50℃ with an ultrasonic frequency of 40 kHz and a power density of 1.8 W / cm². 2 After 45 minutes, the shell completely collapsed, with a collapse rate of 96.2%. After shell removal, the residual Na2O content on the surface of the casting was 0.13%.
[0025] During ultrasonic-assisted shell removal, the average collapse velocity of cavitation bubbles is ≥150m / s, and the generated local pressure is ≥80MPa, which destroys the SiO2 network structure of the shell.
[0026] S3, Neutralization solution preparation Add 485L of deionized water to a 500L plastic tank, add 15kg of citric acid powder, stir until dissolved, and then add 1kg of polyvinylpyrrolidone (PVP-K30). Adjust the pH to 3.8 with 5% sulfuric acid to obtain a neutralized solution (citric acid concentration 3%, PVP concentration 0.2%). The viscosity of the neutralized solution is tested to be 25mPa·s (25℃), and the critical micelle concentration (CMC) of PVP is 0.15%, at which point PVP exists in the solution as a single molecule.
[0027] S4, Neutralization treatment The casting after descrambling in S2 was immersed in the neutralized solution obtained in S3 and stirred at 40°C for 10 min. After washing and drying, the surface pH was 7.1 and the surface roughness Ra of the casting was 3.2 μm.
[0028] S5. Treatment of dehulling waste liquid Processing 1 ton of mold shells generates 5 tons of shell-removing waste liquid. Testing revealed that the NaOH concentration in the waste liquid was 8.5%, and the sodium silicate concentration was 1.8%. After filtering the 5 tons of waste liquid through a ceramic membrane, CO2 gas was introduced at a flow rate of 80 L / min, and the reaction proceeded for 2 hours until the pH reached 9.0. 18 kg of SiO2 precipitate was collected after filtration and calcined at 1200℃ for 2 hours to obtain 16.6 kg of high-purity SiO2. After replacing 35% of the mold shell surface coating, the flexural strength of the mold shell reached 17.8 MPa, meeting the usage requirements.
[0029] S6, Neutralization Waste Liquid Treatment Testing revealed that the citric acid concentration in the neutralized waste liquid was 2.8%, and the pH was 3.8. Ca(OH)₂ powder was added to 5 tons of the neutralized waste liquid until the pH reached 7.5. Filtration yielded 145 kg of calcium citrate precipitate. The supernatant was treated by electrodialysis (30V, 150A) to obtain 4.2 tons of regenerated NaOH solution with a concentration of 7.5%. This regenerated NaOH solution can be used for the next batch of desquamation and can be recycled at least 3 times.
[0030] Comparative Example 1 The following method is used to remove the silica sol-type shell using a high-concentration, high-temperature NaOH solution: S1. Preparation of peeling solution Add 900L of deionized water to a 1000L stainless steel reactor, start stirring at 200rpm, and slowly add 100kg of NaOH granules to obtain the decapsulation solution. S2, Dehulling Take 10 kg of silica sol shell (6 mm thick) sintered at 1150℃, immerse it in the shell removal solution obtained in S1, and treat it at 90℃ for 24 h.
[0031] The results showed that the silica sol shell collapse rate was 82%, the surface roughness of the casting was Ra=8.5μm, and the residual Na2O content was 0.45%.
[0032] Comparative Example 2 The silica sol-type shell is removed using a high-concentration NaOH solution with ultrasonic assistance, as follows: S1. Preparation of peeling solution Add 900L of deionized water to a 1000L stainless steel reactor, start stirring at 200rpm, slowly add 100kg of NaOH granules, and after complete dissolution, cool to 40℃ to obtain the decapsulation solution. S2, Dehulling Take 10 kg of silica sol shell (6 mm thick) sintered at 1150℃, immerse it in the shell-removing solution obtained in S1, and start ultrasonication at 50℃ with an ultrasonic frequency of 40 kHz and a power density of 1.8 W / cm³. 2 Processing time: 90 minutes.
[0033] The results showed that the silica sol-type shell collapse rate was 88%, the lack of sodium gluconate resulted in an effective utilization rate of only 35% for NaOH, and the silicon content in the shelling waste liquid was 65 mg / L.
[0034] Table 1 shows a comparison of the silica sol-type shell removal process and removal effect in Example 1 and Comparative Examples 1-2: Table 1 Comparison between Example 1 and Comparative Examples 1-2
[0035] Example 2
[0036] This embodiment describes a silica sol-type shell ultrasonic synergistic deshelling process and a waste liquid closed-loop treatment system, including the following steps: S1. Preparation of peeling solution Add 860L of deionized water to a 1000L stainless steel reactor, start stirring (200rpm), slowly add 80kg of NaOH granules, and cool to 40℃ after complete dissolution; add 55kg of sodium gluconate, stir for 30min until completely dissolved, then add 5kg of α-olefin sulfonate (AOS-30), and adjust the pH to 13.0 with a 5% NaOH solution to obtain the composite decapsulation solution.
[0037] In this composite stripping solution, the mass fraction of NaOH is 8%, the mass fraction of sodium gluconate is 5.5%, and the mass fraction of surfactant is 0.5%. The molar ratio of sodium gluconate to NaOH is 1:7.9, which improves the etching efficiency of NaOH on SiO2 through complexation.
[0038] S2, Dehulling 10 kg of silica sol shell (6 mm thick) sintered at 1150℃ was immersed in the composite shell-removing solution obtained in S1, and ultrasonication was initiated at 45℃ with an ultrasonic frequency of 60 kHz and a power density of 1.5 W / cm². 2 After 40 minutes, the shell completely collapsed, with a collapse rate of 94.5%, and the residual Na2O content on the surface of the casting was 0.15%.
[0039] During ultrasonic-assisted shell removal, the average collapse velocity of cavitation bubbles is ≥150m / s, and the generated local pressure is ≥80MPa, which destroys the SiO2 network structure of the shell.
[0040] S3, Neutralization solution preparation Add 490L of deionized water to a 500L plastic tank, add 10kg of citric acid powder, stir until dissolved, and then add 0.5kg of polyvinylpyrrolidone (PVP-K30). Adjust the pH to 3.0 with 5% sulfuric acid to obtain a neutralized solution (citric acid concentration 2%, PVP concentration 0.1%). The viscosity of the neutralized solution was tested to be 22 mPa·s (25℃), and the critical micelle concentration (CMC) of PVP was 0.1%, at which point PVP in the solution existed in the form of unimolecular molecules.
[0041] S4, Neutralization treatment The casting after descrambling in S2 was immersed in the neutralized solution obtained in S3 and stirred at 35°C for 15 min. After washing and drying, the surface pH was 7.0 and the surface roughness Ra of the casting was 3.5 μm.
[0042] S5. Treatment of dehulling waste liquid Processing 1 ton of mold shells generates 5 tons of shell-removing waste liquid. Testing revealed that the NaOH concentration in the waste liquid was 6.8%, and the sodium silicate concentration was 1.5%. After filtering the 5 tons of waste liquid through a ceramic membrane, CO2 gas was introduced at a flow rate of 70 L / min, and the reaction proceeded for 2 hours until the pH reached 8.5. 16 kg of SiO2 precipitate was collected after filtration and calcined at 1100℃ for 3 hours to obtain 14.8 kg of high-purity SiO2. After replacing 35% of the mold shell surface coating, the flexural strength of the mold shell reached 16.2 MPa, meeting the usage requirements.
[0043] S6, Neutralization Waste Liquid Treatment Testing revealed that the citric acid concentration in the neutralized waste liquid was 1.9%, and the pH was 3.0. Ca(OH)₂ powder was added to 5 tons of the neutralized waste liquid until the pH reached 7.2. Filtration yielded 132 kg of calcium citrate precipitate. The supernatant was treated by electrodialysis (30V, 150A) to obtain 4 tons of regenerated NaOH solution with a concentration of 6.5%. This regenerated NaOH solution can be used for the next batch of desquamation and can be recycled at least 3 times.
[0044] Example 3
[0045] This embodiment describes a silica sol-type shell ultrasonic synergistic deshelling process and a waste liquid closed-loop treatment system, including the following steps: S1. Preparation of peeling solution Add 852L of deionized water to a 1000L stainless steel reactor, start stirring (200rpm), slowly add 90kg of NaOH granules, and cool to 40℃ after complete dissolution; add 50kg of sodium gluconate, stir for 30min until completely dissolved, then add 8kg of fatty alcohol polyoxyethylene ether carboxylate (AEC-9Na), and adjust the pH to 13.5 with a 5% NaOH solution to obtain the composite decapsulation solution.
[0046] In this composite stripping solution, the mass fraction of NaOH is 9%, the mass fraction of sodium gluconate is 5%, and the mass fraction of surfactant is 0.8%. The molar ratio of sodium gluconate to NaOH is 1:9.81, which improves the etching efficiency of NaOH on SiO2 through complexation.
[0047] S2, Dehulling 10 kg of silica sol shell (6 mm thick) sintered at 1150℃ was immersed in the composite shell-removing solution obtained in S1, and ultrasonication was initiated at 55℃ with an ultrasonic frequency of 50 kHz and a power density of 2.0 W / cm². 2 After 45 minutes, the shell completely collapsed, with a collapse rate of 97.8%, and the residual Na2O content on the surface of the casting was 0.11%.
[0048] During ultrasonic-assisted shell removal, the average collapse velocity of cavitation bubbles is ≥150m / s, and the generated local pressure is ≥80MPa, which destroys the SiO2 network structure of the shell.
[0049] S3, Neutralization solution preparation Add 480L of deionized water to a 500L plastic tank, add 20kg of citric acid powder, stir until dissolved, and then add 1.5kg of polyvinylpyrrolidone (PVP-K30). Adjust the pH to 4.5 with 5% sulfuric acid to obtain a neutralized solution (citric acid concentration 4%, PVP concentration 0.3%). The viscosity of the neutralized solution is tested to be 28 mPa·s (25℃), and the critical micelle concentration (CMC) of PVP is 0.5%, at which point PVP exists in the solution as a single molecule.
[0050] S4, Neutralization treatment The casting after descrambling in S2 was immersed in the neutralized solution obtained in S3 and stirred at 45°C for 15 min. After washing and drying, the surface pH was 7.2 and the surface roughness Ra of the casting was 3.0 μm.
[0051] S5. Treatment of dehulling waste liquid Processing 1 ton of mold shells generates 5 tons of shell-removing waste liquid. Testing revealed that the NaOH concentration in the waste liquid was 10.2%, and the sodium silicate concentration was 2%. After filtering the 5 tons of waste liquid through a ceramic membrane, CO2 gas was introduced at a flow rate of 90 L / min, and the reaction proceeded for 2 hours until the pH reached 9.5. 20 kg of SiO2 precipitate was collected after filtration and calcined at 1300℃ for 1 hour to obtain 18.5 kg of high-purity SiO2. After replacing 35% of the mold shell surface coating, the flexural strength of the mold shell reached 18.5 MPa, meeting the usage requirements.
[0052] S6, Neutralization Waste Liquid Treatment Testing revealed that the citric acid concentration in the neutralized waste liquid was 3.8%, and the pH was 4.5. Ca(OH)₂ powder was added to 5 tons of the neutralized waste liquid until the pH reached 7.8. Filtration yielded 158 kg of calcium citrate precipitate. The supernatant was treated by electrodialysis (30V, 150A) to obtain 4.5 tons of regenerated NaOH solution with a concentration of 8.8%. This regenerated NaOH solution can be used for the next batch of desquamation and can be recycled at least 3 times.
[0053] This invention provides a silica sol-molded shell ultrasonic synergistic descraping process and a waste liquid closed-loop treatment system. Through the optimization of composite descraping liquid formula, ultrasonic cavitation enhancement, precise neutralization after corrosion, and closed-loop recycling of waste liquid, the system achieves a synergistic improvement in descraping efficiency, casting quality, and environmental benefits. This system does not require anti-corrosion pretreatment and can solve the problems of low descraping efficiency of silica sol-molded shells, casting corrosion, and difficult waste liquid treatment.
[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.
Claims
1. A silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system, characterized in that, A composite descraping solution composed of NaOH, sodium gluconate, surfactant and water is used in conjunction with ultrasonic-assisted descraping. The descraped castings are then subjected to corrosion and neutralization treatment in a neutralizing solution. The resulting descraping waste liquid is filtered and then carbonized with CO2 gas to recover SiO2. The neutralized waste liquid is then subjected to calcium salt precipitation and NaOH solution is recovered by electrodialysis. The composite desquaming solution contains 8-12% NaOH, 3-5.5% sodium gluconate, and 0.5-0.8% surfactant.
2. The silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system according to claim 1, characterized in that, The molar ratio of sodium gluconate to NaOH in the composite dehulling solution is 1:(8-11).
3. The silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system according to claim 1, characterized in that, The surfactant is a fatty alcohol polyoxyethylene ether carboxylate or an α-olefin sulfonate.
4. The silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system according to any one of claims 1 to 3, characterized in that, The pH value of the composite dehulling solution is controlled between 13.0 and 13.
5.
5. The silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system according to claim 1, characterized in that, During the ultrasonic-assisted deshelling process, the applied ultrasonic frequency is 40-60 kHz, and the power density is 1.5-2.0 W / cm². 2 The processing temperature is 45-55℃, and the processing time is 30-60 minutes.
6. The silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system according to claim 5, characterized in that, During the ultrasonic-assisted shell removal process, the average collapse velocity of the cavitation bubbles is ≥150m / s, and the generated local pressure is ≥80MPa, which destroys the SiO2 network structure of the shell.
7. The silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system according to claim 1, characterized in that, The neutralization treatment of the casting after descraping involves adding 0.1-0.3% polyvinylpyrrolidone to a 2-4% citric acid solution, with a pH of 3.0-4.
5. The neutralization temperature is 35-45℃, and the treatment time is 5-15 minutes.
8. The silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system according to claim 1, characterized in that, The dehulling waste liquid is filtered and then carbonized by passing CO2 gas through it. The pH value of the reaction is controlled at 8.5-9.
5. The generated SiO2 precipitate is recycled after being calcined at high temperature.
9. The silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system according to claim 8, characterized in that, The SiO2 precipitate is calcined at a temperature of 1100-1300℃ for 1-3 hours.
10. The silica sol-type shell ultrasonic synergistic deshelling process and waste liquid closed-loop treatment system according to claim 1, characterized in that, The neutralized waste liquid is precipitated with calcium salt and then the NaOH solution is recovered by electrodialysis. The concentration of the regenerated NaOH solution is 6-9%, and the regenerated alkali solution is recycled ≥3 times.