Process for producing high-purity hydrofluoric acid from chip waste acid

Abstract

The invention relates to the technical field of chemical processes, and discloses a process for producing high-purity hydrofluoric acid from chip waste acid. The method comprises the following steps: S1, taking hydrofluoric acid waste liquid, high-quality sulfuric acid and high-purity water as production materials; s2, carrying out evaporation concentration through a fluoroplastic circulating pump, a fluoroplastic vacuum pump and two-stage concentration high-purity PFA equipment; s3, adding a magnetic adsorbent into the concentrated solution in batches, and adsorbing and filtering; s4, transferring into a steel lining tetrafluoro rectifying tower for isostatic mould pressing, carrying out reactive distillation, and carrying out low-temperature condensation through a high-purity tetrafluoro heat exchanger, so as to obtain hydrogen fluoride liquid; and S5, carrying out gasification and high-purity water absorption preparation through a high-purity polytetrafluoroethylene flash tank to obtain 49% high-purity hydrofluoric acid for reuse, and carrying out reduced pressure distillation on 70% dilute sulfuric acid in a tower kettle through an equal-diameter mold pressing polytetrafluoroethylene distiller to obtain 98% superior sulfuric acid for reuse. The process provided by the invention has the advantages of high recovery rate, good recovery effect, low metal ion concentration of the recovered product, high resource recovery rate, reduction of wastewater discharge, low energy consumption and high comprehensive benefit.

Description

Technical Field

[0001] The invention relates to the technical field of chemical processes, in particular to a process for producing high-purity hydrofluoric acid from chip waste acid. Background Art

[0002] Chip production uses a large amount of high-purity hydrofluoric acid with a concentration of 49%-50%. Its main purpose is to wash high-purity silicon wafers. The concentration of the waste acid generated is about 4-10%. The remaining impurities are various metal ion compounds containing fluorine. The waste acid is difficult to treat. The current common method is to use the water-soluble property of calcium fluoride to precipitate the fluoride ions with calcium chloride (or calcium hydroxide), filter, and dilute the filtrate with a large amount of water before discharge. Various solid wastes containing calcium fluoride are collected and landfilled as solid waste (hazardous waste) by professional environmental protection companies.

[0003] The influence of various factors in the process of recycling resources to produce high-purity hydrofluoric acid: First, temperature / pressure: In the processes such as concentration and reactive distillation, most of them are exothermic and heating processes. During the process of concentration increase and phase change, the heating temperature and cooling temperature must be controlled, and the reaction and absorption pressure must be controlled. Second, air: The air contains water and other media that can contaminate high-purity hydrogen fluoride (hydrofluoric acid). Some key processes require nitrogen protection. Third, reactive distillation efficiency: Low-concentration hydrofluoric acid requires a high-efficiency separation device when it crosses the azeotropic composition and when it is separated from other fluorine-containing compounds. Fourth, absorption time: The circulation absorption time of high-purity water absorption to prepare high-purity hydrofluoric acid is the key to achieving the corresponding concentration. Fifth, production materials: The materials and equipment that waste acid and high-purity hydrofluoric acid come into contact with require special production treatment, and most of the materials are high-purity polytetrafluoroethylene.

[0004] After the above treatment, a large amount of waste acid not only consumes a large amount of production water and generates a large amount of solid waste, but also consumes a large amount of fluorine-containing resources. At present, the recovery and treatment methods for hydrofluoric acid (waste acid) are not only chlorine-alkali neutralization treatment, but also diameter distillation method, ion adsorption method, etc. According to comprehensive industrial tests, the method of using reactive distillation and ultrapure water absorption process to produce high-purity hydrofluoric acid for reuse is the best and has the best overall benefits. Summary of the Invention

[0005] (1) Technical problems solved

[0006] In view of the shortcomings of the existing technology, the present invention provides a process for producing high-purity hydrofluoric acid from chip waste acid.

[0007] (2) Technical solution

[0008] To achieve the above object, the present invention provides the following technical solution: a process for producing high-purity hydrofluoric acid from chip waste acid, comprising the following process steps:

[0009] S1. Select hydrofluoric acid waste liquid, high-grade sulfuric acid and high-purity water used in chip silicon wafer production as production materials;

[0010] S2, evaporation and concentration are carried out through fluoroplastic circulation pump, fluoroplastic vacuum pump and two-stage concentrated high-purity PFA equipment, and the temperature is controlled at 100-120℃;

[0011] S3, adding magnetic adsorbent to the concentrate in batches, each time with an interval of 3 minutes, each addition amount is 1-3% of the total volume of the concentrate, stirring and absorbing for 30-60 minutes, and filtering;

[0012] S4, transfer to an isostatically molded steel-lined PTFE distillation tower for reactive distillation, continuously add high-purity sulfuric acid with a concentration of more than 98%, and continuously generate hydrogen fluoride gas at the top of the tower. After low-temperature condensation in a high-purity PTFE heat exchanger, hydrogen fluoride liquid is obtained;

[0013] S5. After gasification in a high-purity PTFE flash tank and absorption in high-purity water, 49% high-purity hydrofluoric acid is obtained for reuse. 70% of the dilute sulfuric acid in the bottom of the tower is vacuum distilled in an equal-diameter molded PTFE distiller to obtain 98% high-grade sulfuric acid for reuse.

[0014] Furthermore, the flow rate of the fluoroplastic circulation pump is set to 10-30m 3 / h, the lift is set to 10~50m, the speed is set to 1000~3000r / min, and the working temperature is set to 60~80℃.

[0015] Furthermore, the pumping rate of the fluoroplastic vacuum pump is set to 10-100m 3 / h, the ultimate vacuum is set to 10~100Pa, and the operating temperature is set to 20~80℃.

[0016] Furthermore, the processing time in the two-stage concentrated high-purity PFA equipment is 60 to 120 minutes, and the concentration reaches 16%.

[0017] Furthermore, the top temperature of the steel-lined tetrafluoroethylene distillation tower is 19.5-20.5°C, the top pressure is 0.05-0.1 MPa, the bottom temperature is 110-120°C, the bottom pressure is 0.1-0.2 MPa, the reflux ratio is 5-10, and the feed rate is 1-5 m3. 3 / h, the feed temperature is 60-80°C; the treatment time is 8-10h, and the treated concentration reaches 99%.

[0018] Furthermore, in the high-purity PTFE heat exchanger, the hot fluid inlet temperature is 80-120°C, the hot fluid outlet temperature is 40-60°C, the cold fluid inlet temperature is 20-30°C, the cold fluid outlet temperature is 40-50°C, the hot fluid side pressure is 0.2-0.5MPa, the cold fluid side pressure is 0.1-0.3MPa, and the hot fluid flow rate is 5-20m 3 / h, the cold fluid flow rate is 10~30m 3 / h.

[0019] Furthermore, the feed temperature in the high-purity PTFE flash tank is 60-100°C, the temperature inside the tank is 40-60°C, the pressure is 0.05-0.2 MPa, the liquid level is controlled at 30-70% of the tank height, and the feed flow rate is 1-5 m 3 / h.

[0020] Furthermore, the high-purity water absorption preparation is carried out in a high-purity water absorption device, and the reaction absorption time is 8 to 10 hours; the metal ion content of the 49% hydrofluoric acid solution prepared by the high-purity water absorption has reached the EL grade production standard.

[0021] Furthermore, high-purity hydrofluoric acid (49-50%) can be stored for a long time in a high-purity polytetrafluoroethylene container and recycled for use in chip silicon wafer cleaning production conditions.

[0022] Furthermore, the production process of the magnetic adsorbent includes the following steps:

[0023] A1. Tetrabutyl titanate and anhydrous ethanol were mixed in a volume ratio of 1:5-8 and stirred evenly. A nitric acid aqueous solution was slowly added dropwise while stirring. The volume ratio of nitric acid to water was 1:10-15, the addition rate was 1-2 mL / min, and the temperature was 30-40°C. The mixture was stirred for 2-3 hours to obtain a titanium dioxide solution with a concentration of 0.1-1 mol / L. Ferroferric oxide particles with a particle size of 10-20 nm were dispersed in deionized water to prepare a ferroferric oxide suspension with a concentration of 0.2-0.5 mol / L.

[0024] A2. Slowly add a surfactant to the ferroferric oxide suspension in an amount of 1-5% by mass of the suspension, stir and react at 200-300 r / min for 30-60 min, then slowly add the titanium dioxide solution dropwise at a drop rate of 1-2 mL / min, and continue stirring at 300-400 r / min during the addition process. After completion of the addition, adjust the pH to 8-9 with aqueous ammonia in a 40-50 ° C water bath, stir and react for 2-5 h, centrifuge, wash, and dry to obtain titanium dioxide-coated ferroferric oxide particles;

[0025] A3. Add glycidyl methacrylate to a mixed solution of water and isopropyl alcohol in a mass ratio of 1:1.5 to 2:2 to 4 of sodium sulfite, react at 80 to 100° C. for 20 to 30 hours, remove the solvent by distillation under reduced pressure, add to a 0.4 to 0.8 mol / L sulfuric acid solution, react at 70 to 80° C. for 10 to 15 hours, neutralize with sodium hydroxide, filter, and distill under reduced pressure to obtain sulfonated glycidyl methacrylate;

[0026] A4. Place diethylenetriamine in a three-necked flask, cool in an ice-water bath, purge with nitrogen, and slowly dropwise add 3 times its volume of a mixed solution of sulfonated glycidyl methacrylate and methanol in a volume ratio of 1:1.5-2. React at 20-30°C for 2-6 hours. Transfer to an eggplant-shaped flask on a rotary evaporator, remove methanol under reduced pressure, and heat to 120-150°C. Continue the reaction under reduced pressure for 3-6 hours to obtain amino-terminated sulfonated glycidyl methacrylate.

[0027] A5. Add amino-terminated sulfonated glycidyl methacrylate to methanol solution and stir evenly. Add titanium dioxide-coated ferrosoferric oxide particles and 1-5% of the mass of the reaction system as an initiator, azobisisobutyronitrile. The mass ratio of amino-terminated sulfonated glycidyl methacrylate to titanium dioxide-coated ferrosoferric oxide particles is 1:0.2-1. Turn on the stirring device and stir evenly. Pass nitrogen to remove oxygen from the reaction system. Set the temperature to 60-80°C and the reaction time to 6-12h. Cool to room temperature, centrifuge at 3000-10000 r / min for 10-30min, wash and dry to obtain a magnetic adsorbent.

[0028] Furthermore, in step A2, the surfactant is one of sodium dodecylbenzenesulfonate, sodium citrate or polyvinylpyrrolidone.

[0029] (3) Beneficial technical effects

[0030] The chemical / physical method of the process of the present invention is to use high-grade sulfuric acid to lock the water content of low-concentration hydrofluoric acid, so that it can cross the azeotropic point for distillation preparation, and react with other fluorine-containing compounds to generate hydrogen fluoride gas and other fluorine-containing gases for distillation separation, and use high-purity water for absorption and preparation to obtain EL-grade finished products.

[0031] The high-purity hydrofluoric acid solution obtained by the present invention after treatments such as waste acid concentration, hydrogen fluoride reactive distillation, and ultrapure water absorption not only enhances resource recovery and recycling, but also reduces the discharge of solid (hazardous) waste and fluorine (chlorine)-containing wastewater. In addition to being applied to the recovery of chip waste acid (hydrofluoric acid), the present invention can also be widely applied to the recovery of mixed acid and the recovery of high-purity waste acid in optoelectronic industries such as chips and panels. The invention has good use effect, high resource utilization, low energy consumption, and high comprehensive benefits.

[0032] The magnetic adsorbent produced by the present invention is composed of titanium dioxide coated with ferrosoferric oxide to form a base particle. Glycidyl methacrylate is first sulfonated and then terminally amino-terminated, and the base particles are surface-crosslinked to obtain the magnetic adsorbent. The magnetic adsorbent has a high adsorption capacity for metal ions and can effectively reduce the metal ion concentration in recovered hydrofluoric acid. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] The components of the magnetic adsorbent formulation of the present invention are all commercially available unless otherwise specified;

[0035] Example 1

[0036] The flow rate of the fluoroplastic circulation pump is set to 10m 3 / h, the lift is set to 10m, the speed is set to 1000r / min, and the operating temperature is set to 60℃.

[0037] The pumping speed of the fluoroplastic vacuum pump is set to 10m 3 / h, the ultimate vacuum is set to 10Pa, and the operating temperature is set to 20℃.

[0038] The processing time in the two-stage concentrated high-purity PFA equipment is 60 minutes, and the concentration reaches 16%.

[0039] The top temperature of the steel-lined PTFE distillation tower is 19.5°C, the top pressure is 0.05MPa, the bottom temperature is 110°C, the bottom pressure is 0.1MPa, the reflux ratio is 5, and the feed volume is 1m 3 / h, the feed temperature is 60℃; the treatment time is 8h, and the treated concentration reaches 99%.

[0040] The hot fluid inlet temperature of the high-purity PTFE heat exchanger is 80°C, the hot fluid outlet temperature is 40°C, the cold fluid inlet temperature is 20°C, the cold fluid outlet temperature is 40°C, the hot fluid side pressure is 0.2MPa, the cold fluid side pressure is 0.1MPa, and the hot fluid flow rate is 5m 3 / h, the cold fluid flow rate is 10m 3 / h.

[0041] The feed temperature in the high-purity PTFE flash tank is 60°C, the temperature inside the tank is 40°C, the pressure is 0.05MPa, the liquid level is controlled at 30% of the tank height, and the feed flow rate is 1m 3 / h.

[0042] The high-purity water absorption preparation is carried out in a high-purity water absorption device, and the reaction absorption time is 8 hours; the metal ion content of the 49% hydrofluoric acid solution prepared by high-purity water absorption has reached the EL grade production standard.

[0043] A process for producing high-purity hydrofluoric acid from chip waste acid comprises the following steps:

[0044] S1. Select hydrofluoric acid waste liquid, high-grade sulfuric acid and high-purity water used in chip silicon wafer production as production materials;

[0045] S2, evaporation and concentration are carried out through fluoroplastic circulation pump, fluoroplastic vacuum pump and two-stage high-purity PFA concentration equipment, and the temperature is controlled at 100°C;

[0046] S3, adding magnetic adsorbent to the concentrate in batches, each time with an interval of 3 minutes, each addition amount is 1% of the total volume of the concentrate, stirring and absorbing for 30 minutes, and filtering;

[0047] S4, transfer to an isostatically molded steel-lined PTFE distillation tower for reactive distillation, continuously add high-purity sulfuric acid with a concentration of more than 98%, and continuously generate hydrogen fluoride gas at the top of the tower. After low-temperature condensation in a high-purity PTFE heat exchanger, hydrogen fluoride liquid is obtained;

[0048] S5. After gasification in a high-purity PTFE flash tank and absorption in high-purity water, 49% high-purity hydrofluoric acid is obtained for reuse. 70% of the dilute sulfuric acid in the bottom of the tower is vacuum distilled in an equal-diameter molded PTFE distiller to obtain 98% high-grade sulfuric acid for reuse.

[0049] The production process of magnetic adsorbent includes the following steps:

[0050] A1. Tetrabutyl titanate and anhydrous ethanol were mixed in a volume ratio of 1:5 and stirred evenly. A nitric acid aqueous solution was slowly added dropwise while stirring. The volume ratio of nitric acid to water was 1:10, the addition rate was 1 mL / min, and the temperature was 30°C. Stirring was carried out for 2 h to obtain a titanium dioxide solution with a concentration of 0.1 mol / L. Ferroferric oxide particles with a particle size of 10-20 nm were dispersed in deionized water to prepare a ferroferric oxide suspension with a concentration of 0.2 mol / L.

[0051] A2. Slowly add a surfactant, sodium dodecylbenzenesulfonate, sodium citrate or polyvinylpyrrolidone, to the ferroferric oxide suspension in an amount of 1% by mass of the suspension, stir and react at 200 r / min for 30 min, then slowly add titanium dioxide solution dropwise at a drop rate of 1 mL / min, and stir continuously at 300 r / min during the addition process. After completion of the addition, adjust the pH to 8 with aqueous ammonia in a 40°C water bath, stir and react for 2 h, centrifuge, wash, and dry to obtain titanium dioxide-coated ferroferric oxide particles;

[0052] A3. Add glycidyl methacrylate to a mixed solution of sodium sulfite in water and isopropyl alcohol in a mass ratio of 1:1.5:2, react at 80°C for 20 hours, remove the solvent by distillation under reduced pressure, add to a 0.4 mol / L sulfuric acid solution, react at 70°C for 10 hours, neutralize with sodium hydroxide, filter and distill under reduced pressure to obtain sulfonated glycidyl methacrylate;

[0053] A4. Place diethylenetriamine in a three-necked flask, cool in an ice-water bath, purge with nitrogen, and slowly dropwise add 3 times the volume of a mixed solution of sulfonated glycidyl methacrylate and methanol in a volume ratio of 1:1.5. React at 20°C for 2 hours. Transfer to an eggplant-shaped flask on a rotary evaporator, remove methanol under reduced pressure, and heat to 120°C and continue the reaction under reduced pressure for 3 hours to obtain amino-terminated sulfonated glycidyl methacrylate.

[0054] A5. Add amino-terminated sulfonated glycidyl methacrylate to methanol solution and stir evenly. Add titanium dioxide-coated ferrosoferric oxide particles and 1% of the mass of the reaction system as the initiator azobisisobutyronitrile. The mass ratio of amino-terminated sulfonated glycidyl methacrylate to titanium dioxide-coated ferrosoferric oxide particles is 1:0.2. Turn on the stirring device and stir evenly. Pass nitrogen to remove oxygen from the reaction system. Set the temperature to 60°C and the reaction time to 6 hours. Cool to room temperature, centrifuge at 3000 r / min for 10 minutes, wash and dry to obtain a magnetic adsorbent.

[0055] Example 2

[0056] The flow rate of the fluoroplastic circulation pump is set to 20m 3 / h, the lift is set to 30m, the speed is set to 2000r / min, and the operating temperature is set to 70℃.

[0057] The pumping speed of the fluoroplastic vacuum pump is set to 50m 3 / h, the ultimate vacuum is set to 50Pa, and the operating temperature is set to 50℃.

[0058] The processing time in the two-stage concentrated high-purity PFA equipment is 90 minutes, and the concentration reaches 16%.

[0059] The top temperature of the steel-lined PTFE distillation tower is 20°C, the top pressure is 0.08MPa, the bottom temperature is 115°C, the bottom pressure is 0.15MPa, the reflux ratio is 8, and the feed volume is 3m 3 / h, the feed temperature is 70℃; the treatment time is 9h, and the treated concentration reaches 99%.

[0060] In the high-purity PTFE heat exchanger, the hot fluid inlet temperature is 100°C, the hot fluid outlet temperature is 50°C, the cold fluid inlet temperature is 25°C, the cold fluid outlet temperature is 45°C, the hot fluid side pressure is 0.3MPa, the cold fluid side pressure is 0.2MPa, and the hot fluid flow rate is 10m 3 / h, the cold fluid flow rate is 20m 3 / h.

[0061] The feed temperature in the high-purity PTFE flash tank is 80°C, the temperature inside the tank is 50°C, the pressure is 0.1MPa, the liquid level is controlled at 50% of the tank height, and the feed flow rate is 3m3 / h.

[0062] The high-purity water absorption preparation is carried out in a high-purity water absorption device, and the reaction absorption time is 9 hours; the metal ion content of the 49% hydrofluoric acid solution prepared by high-purity water absorption has reached the EL grade production standard.

[0063] A process for producing high-purity hydrofluoric acid from chip waste acid comprises the following steps:

[0064] S1. Select hydrofluoric acid waste liquid, high-grade sulfuric acid and high-purity water used in chip silicon wafer production as production materials;

[0065] S2, evaporation and concentration are carried out through fluoroplastic circulation pump, fluoroplastic vacuum pump and two-stage high-purity PFA concentration equipment, and the temperature is controlled at 110℃;

[0066] S3, adding magnetic adsorbent to the concentrate in batches, each time with an interval of 3 minutes, each addition amount is 2% of the total volume of the concentrate, stirring and absorbing for 45 minutes, and filtering;

[0067] S4, transfer to an isostatically molded steel-lined PTFE distillation tower for reactive distillation, continuously add high-purity sulfuric acid with a concentration of more than 98%, and continuously generate hydrogen fluoride gas at the top of the tower. After low-temperature condensation in a high-purity PTFE heat exchanger, hydrogen fluoride liquid is obtained;

[0068] S5. After gasification in a high-purity PTFE flash tank and absorption in high-purity water, 49% high-purity hydrofluoric acid is obtained for reuse. 70% of the dilute sulfuric acid in the bottom of the tower is vacuum distilled in an equal-diameter molded PTFE distiller to obtain 98% high-grade sulfuric acid for reuse.

[0069] The production process of magnetic adsorbent includes the following steps:

[0070] A1. Mix tetrabutyl titanate and anhydrous ethanol in a volume ratio of 1:6 and stir evenly. Slowly add aqueous nitric acid dropwise while stirring. The volume ratio of nitric acid to water is 1:12, the addition rate is 1.5 mL / min, the temperature is 35°C, and stirring is continued for 2.5 h to obtain a titanium dioxide solution with a concentration of 0.5 mol / L. Disperse ferroferric oxide particles with a particle size of 10-20 nm in deionized water to prepare a ferroferric oxide suspension with a concentration of 0.3 mol / L.

[0071] A2. Sodium dodecylbenzenesulfonate, sodium citrate or polyvinylpyrrolidone, a surfactant, was slowly added to the ferroferric oxide suspension in an amount of 3% by mass of the suspension. The mixture was stirred at 250 r / min for 45 min, and then the titanium dioxide solution was slowly added dropwise at a dropping rate of 1.5 mL / min. The addition process was continued with stirring at 350 r / min. After completion of the dropwise addition, the pH was adjusted to 9 with aqueous ammonia in a 45°C water bath, and the mixture was stirred for 4 h. The mixture was centrifuged, washed and dried to obtain titanium dioxide-coated ferroferric oxide particles.

[0072] A3. Add glycidyl methacrylate to a mixed solution of water and isopropyl alcohol with a mass ratio of 1:1.8:3 of sodium sulfite, react at 90°C for 25 hours, remove the solvent by distillation under reduced pressure, add to a 0.6 mol / L sulfuric acid solution, react at 75°C for 12 hours, neutralize with sodium hydroxide, filter and distill under reduced pressure to obtain sulfonated glycidyl methacrylate;

[0073] A4. Place diethylenetriamine in a three-necked flask, cool in an ice-water bath, purge with nitrogen, and slowly dropwise add 3 times the volume of a mixed solution of sulfonated glycidyl methacrylate and methanol in a volume ratio of 1:1.8. React at 25°C for 4 hours. Transfer to an eggplant-shaped flask on a rotary evaporator, remove methanol under reduced pressure, and heat to 130°C and continue the reaction under reduced pressure for 5 hours to obtain amino-terminated sulfonated glycidyl methacrylate.

[0074] A5. Add amino-terminated sulfonated glycidyl methacrylate to methanol solution and stir evenly. Add titanium dioxide-coated ferrosoferric oxide particles and 3% of the mass of the reaction system as the initiator azobisisobutyronitrile. The mass ratio of amino-terminated sulfonated glycidyl methacrylate to titanium dioxide-coated ferrosoferric oxide particles is 1:0.6. Turn on the stirring device and stir evenly. Pass nitrogen to remove oxygen from the reaction system. Set the temperature to 70°C and the reaction time to 9 hours. Cool to room temperature, centrifuge at 6000 r / min for 20 minutes, wash and dry to obtain a magnetic adsorbent.

[0075] Example 3

[0076] The flow rate of the fluoroplastic circulation pump is set to 30m 3 / h, the lift is set to 50m, the speed is set to 3000r / min, and the operating temperature is set to 80℃.

[0077] The pumping speed of the fluoroplastic vacuum pump is set to 100m 3 / h, the ultimate vacuum is set to 100Pa, and the operating temperature is set to 80℃.

[0078] The processing time in the two-stage concentrated high-purity PFA equipment is 120 minutes, and the concentration reaches 16%.

[0079] The top temperature of the steel-lined PTFE distillation tower is 20.5°C, the top pressure is 0.1MPa, the bottom temperature is 120°C, the bottom pressure is 0.2MPa, the reflux ratio is 10, and the feed volume is 5m 3 / h, the feed temperature is 80℃; the treatment time is 10h, and the treated concentration reaches 99%.

[0080] The hot fluid inlet temperature of the high-purity PTFE heat exchanger is 120℃, the hot fluid outlet temperature is 60℃, the cold fluid inlet temperature is 30℃, the cold fluid outlet temperature is 50℃, the hot fluid side pressure is 0.5MPa, the cold fluid side pressure is 0.3MPa, and the hot fluid flow rate is 20m 3 / h, the cold fluid flow rate is 30m 3 / h.

[0081] The feed temperature in the high-purity PTFE flash tank is 100°C, the temperature inside the tank is 60°C, the pressure is 0.2MPa, the liquid level is controlled at 70% of the tank height, and the feed flow rate is 5m 3 / h.

[0082] The high-purity water absorption preparation is carried out in a high-purity water absorption device, and the reaction absorption time is 10 hours; the metal ion content of the 49% hydrofluoric acid solution prepared by high-purity water absorption has reached the EL grade production standard.

[0083] A process for producing high-purity hydrofluoric acid from chip waste acid comprises the following steps:

[0084] S1. Select hydrofluoric acid waste liquid, high-grade sulfuric acid and high-purity water used in chip silicon wafer production as production materials;

[0085] S2, evaporation and concentration are carried out through fluoroplastic circulation pump, fluoroplastic vacuum pump and two-stage concentrated high-purity PFA equipment, and the temperature is controlled at 120℃;

[0086] S3, adding magnetic adsorbent to the concentrate in batches, each time with an interval of 3 minutes, each addition amount is 3% of the total volume of the concentrate, stirring and absorbing for 60 minutes, and filtering;

[0087] S4, transfer to an isostatically molded steel-lined PTFE distillation tower for reactive distillation, continuously add high-purity sulfuric acid with a concentration of more than 98%, and continuously generate hydrogen fluoride gas at the top of the tower. After low-temperature condensation in a high-purity PTFE heat exchanger, hydrogen fluoride liquid is obtained;

[0088] S5. After gasification in a high-purity PTFE flash tank and absorption in high-purity water, 49% high-purity hydrofluoric acid is obtained for reuse. 70% of the dilute sulfuric acid in the bottom of the tower is vacuum distilled in an equal-diameter molded PTFE distiller to obtain 98% high-grade sulfuric acid for reuse.

[0089] The production process of magnetic adsorbent includes the following steps:

[0090] A1. Mix tetrabutyl titanate and anhydrous ethanol in a volume ratio of 1:8 and stir evenly. Slowly add nitric acid aqueous solution dropwise while stirring. The volume ratio of nitric acid to water is 1:15, the addition rate is 2 mL / min, and the temperature is 40°C. Stir for 3 h to obtain a titanium dioxide solution with a concentration of 1 mol / L. Disperse ferroferric oxide particles with a particle size of 20 nm in deionized water to prepare a ferroferric oxide suspension with a concentration of 0.5 mol / L.

[0091] A2. Slowly add a surfactant, sodium dodecylbenzenesulfonate, sodium citrate or polyvinylpyrrolidone, to the ferroferric oxide suspension in an amount of 5% by mass of the suspension, stir and react at 300 r / min for 60 min, then slowly add the titanium dioxide solution dropwise at a drop rate of 2 mL / min, and stir continuously at 400 r / min during the addition process. After completion of the addition, adjust the pH to 9 with aqueous ammonia in a 50°C water bath, stir and react for 5 h, centrifuge, wash, and dry to obtain titanium dioxide-coated ferroferric oxide particles;

[0092] A3. Add glycidyl methacrylate to a mixed solution of water and isopropanol with a mass ratio of 1:2:4 of sodium sulfite, react at 100°C for 30 hours, remove the solvent by distillation under reduced pressure, add to a 0.8 mol / L sulfuric acid solution, react at 80°C for 15 hours, neutralize with sodium hydroxide, filter and distill under reduced pressure to obtain sulfonated glycidyl methacrylate;

[0093] A4. Place diethylenetriamine in a three-necked flask, cool in an ice-water bath, purge with nitrogen, and slowly dropwise add 3 volumes of a mixed solution of sulfonated glycidyl methacrylate and methanol in a volume ratio of 1:2. React at 30°C for 6 h. Transfer to an eggplant-shaped flask on a rotary evaporator, remove methanol under reduced pressure, and heat to 150°C and continue the reaction under reduced pressure for 6 h to obtain amino-terminated sulfonated glycidyl methacrylate.

[0094] A5. Add amino-terminated sulfonated glycidyl methacrylate to methanol solution and stir evenly. Add titanium dioxide-coated ferrosoferric oxide particles and 5% of the mass of the reaction system as an initiator, azobisisobutyronitrile. The mass ratio of amino-terminated sulfonated glycidyl methacrylate to titanium dioxide-coated ferrosoferric oxide particles is 1:1. Turn on the stirring device and stir evenly. Pass nitrogen to remove oxygen from the reaction system. Set the temperature to 80°C and the reaction time to 12 hours. Cool to room temperature, centrifuge at 10,000 r / min for 30 minutes, wash, and dry to obtain a magnetic adsorbent.

[0095] Comparative Example 1: Step S3 was not performed, and the remaining processes were the same as in Example 1.

[0096] Comparative Example 2: The magnetic adsorbent is titanium dioxide-coated ferrosoferric oxide particles, and the rest of the process is the same as in Example 1.

[0097] Test example:

[0098] The metal ion removal rates of Examples 1 to 3 and Comparative Examples 1 to 2 were tested, and the results are shown in Table 1.

[0099] Table 1

[0100] Group Iron removal rate / % Nickel removal rate / % Cobalt removal rate / % Lithium removal rate / % Example 1 92.35 82.38 84.59 65.42 Example 2 93.54 82.51 85.35 66.53 Example 3 92.86 82.55 85.26 66.89 Comparative Example 1 75.68 62.42 58.24 45.64 Comparative Example 2 88.65 68.36 72.53 53.42

[0101] As can be seen from Table 1, compared with the embodiment, the metal ion removal rate of the comparative example is lower, and the comparative example 1 is lower than the comparative example 2, indicating that the magnetic adsorbent can effectively adsorb metal ions, and the adsorption capacity of the modified magnetic adsorbent for metal ions is improved.

[0102] The hydrofluoric acid recovery rates of Examples 1 to 3 were tested, and the results are shown in Table 2.

[0103] Table 2

[0104] Group Hydrofluoric acid recovery rate / % Example 1 96.6 Example 2 95.1 Example 3 96.5

[0105] As can be seen from Table 2, the hydrogen fluoride recovery rates of Examples 1 to 3 reached over 95%, and the hydrofluoric acid recovery efficiency was high.

[0106] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for producing high-purity hydrofluoric acid from chip waste acid, characterized in that: The process steps include: S1. Select hydrofluoric acid waste liquid, high-grade sulfuric acid and high-purity water used in chip silicon wafer production as production materials; S2, evaporation and concentration are carried out through fluoroplastic circulation pump, fluoroplastic vacuum pump and two-stage concentrated high-purity PFA equipment, and the temperature is controlled at 100-120℃; S3, adding magnetic adsorbent to the concentrate in batches, each time with an interval of 3 minutes, each addition amount is 1-3% of the total volume of the concentrate, stirring and absorbing for 30-60 minutes, and filtering; S4, transfer to an isostatically molded steel-lined PTFE distillation tower for reactive distillation, continuously add high-purity sulfuric acid with a concentration of more than 98%, and continuously generate hydrogen fluoride gas at the top of the tower. After low-temperature condensation in a high-purity PTFE heat exchanger, hydrogen fluoride liquid is obtained; S5. After gasification in a high-purity PTFE flash tank and absorption in high-purity water, 49% high-purity hydrofluoric acid is obtained for reuse. 70% of the dilute sulfuric acid in the bottom of the tower is vacuum distilled in an equal-diameter molded PTFE distiller to obtain 98% high-grade sulfuric acid for reuse.

2. A process for producing high-purity hydrofluoric acid from chip waste acid according to claim 1, characterized in that: The flow rate of the fluoroplastic circulation pump is set to 10~30m 3 / h, the lift is set to 10~50m, the speed is set to 1000~3000r / min, and the working temperature is set to 60~80℃.

3. A process for producing high-purity hydrofluoric acid from chip waste acid according to claim 1, characterized in that: The pumping speed of the fluoroplastic vacuum pump is set to 10~100m 3 / h, the ultimate vacuum is set to 10~100Pa, and the operating temperature is set to 20~80℃.

4. A process for producing high-purity hydrofluoric acid from chip waste acid according to claim 1, characterized in that: The processing time in the two-stage concentrated high-purity PFA equipment is 60 to 120 minutes, and the concentration reaches 16%.

5. A process for producing high-purity hydrofluoric acid from chip waste acid according to claim 1, characterized in that: The top temperature of the steel-lined PTFE distillation tower is 19.5-20.5°C, the top pressure is 0.05-0.1 MPa, the bottom temperature is 110-120°C, the bottom pressure is 0.1-0.2 MPa, the reflux ratio is 5-10, and the feed rate is 1-5 m3. 3 / h, the feed temperature is 60-80°C; the treatment time is 8-10h, and the treated concentration reaches 99%.

6. A process for producing high-purity hydrofluoric acid from chip waste acid according to claim 1, characterized in that: The hot fluid inlet temperature of the high-purity PTFE heat exchanger is 80-120°C, the hot fluid outlet temperature is 40-60°C, the cold fluid inlet temperature is 20-30°C, the cold fluid outlet temperature is 40-50°C, the hot fluid side pressure is 0.2-0.5MPa, the cold fluid side pressure is 0.1-0.3MPa, and the hot fluid flow rate is 5-20m 3 / h, the cold fluid flow rate is 10~30m 3 / h.

7. A process for producing high-purity hydrofluoric acid from chip waste acid according to claim 1, characterized in that: The feed temperature in the high-purity PTFE flash tank is 60-100°C, the temperature inside the tank is 40-60°C, the pressure is 0.05-0.2MPa, the liquid level is controlled at 30-70% of the tank height, and the feed flow rate is 1-5m 3 / h.

8. A process for producing high-purity hydrofluoric acid from chip waste acid according to claim 1, characterized in that: The high-purity water absorption preparation is carried out in a high-purity water absorption device, and the reaction absorption time is 8 to 10 hours; the metal ion content of the 49% hydrofluoric acid solution prepared by high-purity water absorption has reached the EL grade production standard.

9. A process for producing high-purity hydrofluoric acid from chip waste acid according to claim 1, characterized in that: The production process of magnetic adsorbent includes the following steps: A1. Tetrabutyl titanate and anhydrous ethanol were mixed in a volume ratio of 1:5-8 and stirred evenly. A nitric acid aqueous solution was slowly added dropwise while stirring. The volume ratio of nitric acid to water was 1:10-15, the addition rate was 1-2 mL / min, and the temperature was 30-40°C. The mixture was stirred for 2-3 hours to obtain a titanium dioxide solution with a concentration of 0.1-1 mol / L. Ferroferric oxide particles with a particle size of 10-20 nm were dispersed in deionized water to prepare a ferroferric oxide suspension with a concentration of 0.2-0.5 mol / L. A2. Slowly add a surfactant to the ferroferric oxide suspension in an amount of 1-5% by mass of the suspension, stir and react at 200-300 r / min for 30-60 min, then slowly add the titanium dioxide solution dropwise at a drop rate of 1-2 mL / min, and continue stirring at 300-400 r / min during the addition process. After completion of the addition, adjust the pH to 8-9 with aqueous ammonia in a 40-50 ° C water bath, stir and react for 2-5 h, centrifuge, wash, and dry to obtain titanium dioxide-coated ferroferric oxide particles; A3. Add glycidyl methacrylate to a mixed solution of water and isopropyl alcohol in a mass ratio of 1:1.5 to 2:2 to 4 of sodium sulfite, react at 80 to 100° C. for 20 to 30 hours, remove the solvent by distillation under reduced pressure, add to a 0.4 to 0.8 mol / L sulfuric acid solution, react at 70 to 80° C. for 10 to 15 hours, neutralize with sodium hydroxide, filter, and distill under reduced pressure to obtain sulfonated glycidyl methacrylate; A4. Place diethylenetriamine in a three-necked flask, cool in an ice-water bath, purge with nitrogen, and slowly dropwise add 3 times its volume of a mixed solution of sulfonated glycidyl methacrylate and methanol in a volume ratio of 1:1.5-2. React at 20-30°C for 2-6 hours. Transfer to an eggplant-shaped flask on a rotary evaporator, remove methanol under reduced pressure, and heat to 120-150°C. Continue the reaction under reduced pressure for 3-6 hours to obtain amino-terminated sulfonated glycidyl methacrylate. A5. Add amino-terminated sulfonated glycidyl methacrylate to methanol solution and stir evenly. Add titanium dioxide-coated ferrosoferric oxide particles and 1-5% of the mass of the reaction system as an initiator, azobisisobutyronitrile. The mass ratio of amino-terminated sulfonated glycidyl methacrylate to titanium dioxide-coated ferrosoferric oxide particles is 1:0.2-1. Turn on the stirring device and stir evenly. Pass nitrogen to remove oxygen from the reaction system. Set the temperature to 60-80°C and the reaction time to 6-12h. Cool to room temperature, centrifuge at 3000-10000 r / min for 10-30min, wash and dry to obtain a magnetic adsorbent.

10. The process for producing high-purity hydrofluoric acid from chip waste acid according to claim 1, characterized in that: The surfactant in step A2 is one of sodium dodecylbenzenesulfonate, sodium citrate or polyvinylpyrrolidone.