A method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid

Abstract

The invention discloses a method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid, comprising the following steps: first, distillation separation is performed to obtain, in sequence, distilled liquid, stable mixed acid, and crystals. Secondly, the distilled liquid is blended and sold as an ultra-high purity electronic grade finished product; the stable mixed acid is dehydrated and separated to obtain high-purity hydrogen chloride and hydrogen fluoride; the crystalline mixture is separated to obtain related industrial materials. The process sequentially adopts distillation, dehydration, concentrated crystallization, rectification, blending and other processes to concentrate, purify and separate the waste liquid step by step, so as to realize the value-added recycling of high-concentration, strongly acidic and highly corrosive waste liquid. It has many advantages such as low energy consumption, good environmental protection benefits, no waste generation, and high social and economic value.

Description

Technical Field

[0001] The invention relates to the technical field of recycling and utilizing hazardous waste resources, and in particular to a method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid. Background Art

[0002] With the rapid development of the electronics industry, semiconductor industry, and lithium battery industry, a large amount of waste acid liquid is generated in the processes of lithium hexafluorophosphate production, solar silicon wafer cleaning, glass thinning, and high-purity quartz sand purification. Usually, the waste liquid contains 1-30% hydrochloric acid, 1-30% hydrofluoric acid, and 10-15% fluorosilicic acid. Because the waste acid contains hydrochloric acid and hydrofluoric acid with similar corrosive, toxic, and volatile properties, it is difficult to completely separate them. Direct treatment and discharge is not conducive to environmental protection and causes waste of resources.

[0003] CN113003545A discloses a method for recycling and treating iron-containing mixed acid waste liquid in the steel industry. First, the mixed acid waste liquid is precipitated and filtered; then, excessive sulfuric acid is replaced, cooled and crystallized, and crystal-liquid is separated to obtain iron sulfate dodecahydrate crude salt and mixed acid filtrate; then the mixed acid filtrate is subjected to reduced pressure distillation, the distillate is recycled, and the residual liquid is cooled and crystallized; finally, the residual liquid crystal is transferred to a filter press, and the filter press is used to filter and separate to obtain iron sulfate dodecahydrate crude salt and high-concentration sulfuric acid, and the high-concentration sulfuric acid is recycled. The present invention uses low-cost sulfuric acid to replace high-value nitric acid and hydrofluoric acid, and the cost is low. The reduced pressure distillation process is used to make the equipment operating temperature lower than 75°C, the equipment has a long service life, and the operation is safe and reliable. The method of the present invention is used to treat pickling waste liquid in the steel industry, and high-concentration iron-containing mixed acid waste liquid can be subjected to reduced pressure distillation. The process is simple, the treated waste acid is fully reused, no alkali neutralization is required, no wastewater is discharged, and the environmental pollution is small.

[0004] In the prior art, the recovery and treatment method for the mixed acid of hydrochloric acid, hydrofluoric acid, fluorosilicic acid and nitric acid includes: adding the mixed acid to a reactor and stirring, adding sodium carbonate at a uniform speed to react completely and then separating the solid and liquid, transferring the obtained supernatant to a synthesis reactor, adding barium carbonate to react completely, and then separating the solid and liquid again, adding sodium carbonate to the obtained supernatant to adjust the pH value to a preset value to obtain a mixed salt solution, adding potassium chloride to the mixed salt solution, evaporating and concentrating to separate sodium chloride crystals, and diluting the mother liquor and cooling to a preset temperature to precipitate potassium nitrate crystals; this method is mainly an operation based on the composition and properties of the acid itself, there are many types of mixed acids, the operation is relatively complicated, the recovery rate of the acid is limited, and the obtained products are all corresponding salts, no usable industrial materials are obtained, and the acid is not recycled for value-added utilization.

[0005] In summary, in order to solve the problems existing in the above-mentioned prior art, the present invention provides a method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid, which involves the production of electronic-grade basic chemical raw materials and chemical high-purity separation technology. Summary of the invention

[0006] The purpose of the present invention is to provide a method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid.

[0007] This method solves the following technical problems of the prior art:

[0008] The operation is relatively complicated, the recovery rate of the acid is limited, and the products obtained are all corresponding salts. No usable industrial materials are obtained, and the acid is not recycled for value-added utilization.

[0009] This method uses hazardous waste containing fluorosilicic acid and fluoride salts, mainly hydrochloric acid and hydrofluoric acid, as raw materials. After separation and recovery treatment, high-value ultra-high-purity electronic-grade hydrochloric acid and hydrofluoric acid can be obtained, and the mass content of metals is less than 1ppt; high-value ultra-high-purity hydrogen chloride and anhydrous hydrogen fluoride with a purity of 6.5N can also be obtained.

[0010] To achieve the above object, the present invention is implemented by the following technical solutions:

[0011] The present invention provides a method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid, which comprises the following steps:

[0012] Step (1) is to pass the waste acid solution containing hydrochloric acid and hydrofluoric acid into a distillation kettle for heating and distillation, control the time and temperature, and take samples for testing, and obtain water, hydrochloric acid, hydrofluoric acid, and a stable mixed acid of hydrochloric acid, hydrofluoric acid, and fluorosilicic acid through condensation and collection; and produce a mixture of one or more of calcium fluoride, sodium fluoride, magnesium fluoride, potassium fluoride, and sodium fluorosilicate at the bottom of the reactor.

[0013] Step (2) passing the stable mixed acid of hydrochloric acid, hydrofluoric acid and fluorosilicic acid into a concentrated sulfuric acid reactor for dehydration to produce hydrogen fluoride, hydrogen chloride, silicon tetrafluoride and fluorine-containing dilute sulfuric acid;

[0014] Step (3) after dehydration, passing the dehydrated gas into a distillation tower for distillation, passing the evaporated gas phase into a rectification tower, collecting hydrogen chloride and anhydrous hydrogen fluoride fractions respectively, and obtaining ultra-high purity hydrogen chloride and hydrogen fluoride products;

[0015] Step (4) passing the fluorine-containing dilute sulfuric acid in step (2) through a white carbon black reaction column and a sulfur trioxide absorption tower in sequence to form silicon tetrafluoride and obtain a 98%-107% concentrated sulfuric acid product;

[0016] Step (5) passing the silicon tetrafluoride in step (4) through an absorption tower to form fluorosilicic acid and white carbon black product;

[0017] Step (6) Repeat steps 2-5 with the fluorosilicic acid formed in step (5) to obtain hydrogen fluoride product and white carbon black.

[0018] Step (7) uses a concentrated crystallization process to separate the crystal mixture from step (1) into insoluble calcium fluoride and magnesium fluoride, which can be used as steel slag-making agents and welding products, slightly soluble sodium fluoride and sodium fluorosilicate, which can be used as UF3 adsorbents and opacifier products, and soluble potassium fluoride, which can be used as a permeability enhancer and polishing agent product, according to their different solubilities.

[0019] In step (8), the hydrochloric acid and hydrofluoric acid produced in step (1) are mixed with hydrogen chloride and hydrogen fluoride produced in step (4) to produce ultra-high purity electronic grade products.

[0020] By adopting the technology of separating and recovering waste acid containing hydrochloric acid and hydrofluoric acid in the present application, hazardous waste containing fluorosilicic acid and fluoride salts, mainly hydrochloric acid and hydrofluoric acid, can be used as raw materials to convert waste acid into ultra-high purity electronic-grade hydrogen chloride, hydrogen fluoride, hydrochloric acid and hydrofluoric acid, thereby promoting the recycling of resources and realizing its value-added benefits.

[0021] According to some specific and preferred embodiments of the present invention, in step (1), the source of the hydrochloric acid and hydrofluoric acid waste liquid raw material is selected from the processes of lithium hexafluorophosphate production, solar silicon wafer cleaning, glass thinning, high-purity quartz sand purification, etc.

[0022] According to some specific and preferred embodiments of the present invention, in step (1), the quality of the hydrochloric acid and hydrofluoric acid waste liquid raw material is a mass concentration of 1%-30% hydrochloric acid, 1%-30% hydrofluoric acid, and 10%-15% fluorosilicic acid.

[0023] Further preferably, the mass concentration of hydrochloric acid is 7%-30%, hydrofluoric acid is 7%-30%, and fluorosilicic acid is 10%-15%.

[0024] According to some specific and preferred embodiments of the present invention, in step (1), the distillation kettle equipment material is selected from ordinary PTFE, ultra-high purity PFA, PVDF, fluorine-lined sintered material, graphite, stainless steel, and PFA.

[0025] According to some specific and preferred embodiments of the present invention, in step (1), the temperature in the distillation kettle containing hydrochloric acid is 80°C-160°C, for example, it can be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, or 160°C.

[0026] According to some specific and preferred embodiments of the present invention, in step (1), the mass concentration of the obtained hydrochloric acid is 1%-35%, for example, it can be 1%, 30%, 31%, 32%, 33%, 34%, 35%.

[0027] According to some specific and preferred embodiments of the present invention, in step (1), the mass concentration of the obtained hydrofluoric acid is 1%-39%, for example, it can be 1%, 30%, 31%, 32%, 33%, 34%, 35%, 39%.

[0028] According to some specific and preferred embodiments of the present invention, in step (2), the concentration of concentrated sulfuric acid used is 98%-107%, for example, it can be 98%, 99%, 99.9%, 100%, 103%, 107%.

[0029] According to some specific and preferred embodiments of the present invention, in step (2), the ratio of hydrochloric acid to hydrofluoric acid in the stable mixed acid of hydrochloric acid, hydrofluoric acid and fluosilicic acid is 0.01-100:1, for example, it can be 0.01:1, 0.1:1, 0.5:1, 2:1, 10:1, 50:1, 70:1, 100:1.

[0030] According to some specific and preferred embodiments of the present invention, in step (2), the material is cooled to 26-32°C using a condensation component.

[0031] According to some specific and preferred embodiments of the present invention, in step (2), the temperature in the concentrated sulfuric acid reactor is controlled to be

[0032] 15°C-25°C, for example, it can be 15°C, 16°C, 17°C, 18°C, 20°C, 22°C, 25°C.

[0033] According to some specific and preferred embodiments of the present invention, in step (2), the amount of silicon tetrafluoride (wt%) in tail gas is 0.1%-17%, for example, 0.1%, 1%, 8%, 10%, 12%, 15%, 17%.

[0034] According to some specific and preferred embodiments of the present invention, in step (3), the temperature of the secondary distillation is 40°C-120°C, for example, 40°C, 60°C, 70°C, 85°C, 95°C, 100°C, 105°C, or 120°C.

[0035] According to some specific and preferred embodiments of the present invention, in step (3), the distillation temperature is -5°C to 120°C. For example, it can be -5°C, 0°C, 15°C, 60°C, 90°C, 100°C, or 120°C.

[0036] According to some specific and preferred embodiments of the present invention, in step (3), in the distillation tower, the reflux ratio is 1:7-20, for example, 1:7, 1:9, 1:10, 1:13, 1:18, 1:20.

[0037] According to some specific and preferred embodiments of the present invention, in step (3), in the distillation tower, the purity of the hydrogen chloride reaches 99.99995%, and the purity of the anhydrous hydrogen fluoride reaches 99.99995%.

[0038] According to some specific and preferred embodiments of the present invention, in step (4), the dilute sulfuric acid is defluorinated by passing through a white carbon reaction column, and the exchange rate is 50 mg / g-100 mg / g, for example, 50 mg / g, 55 mg / g, 70 mg / g, 80 mg / g, 90 mg / g, or 100 mg / g.

[0039] According to some specific and preferred embodiments of the present invention, in step (4), the gas flow rate is 0.001-10000m3 / h, for example, 0.01-5000m3 / h, 0.1-1000m3 / h, 1-2000m3 / h.

[0040] According to some specific and preferred embodiments of the present invention, in step (4), the contact time is 0.1-600 min, for example, 0.1-200 min, 1-500 min, or 10-300 min.

[0041] According to some specific and preferred embodiments of the present invention, in step (4), the defluorinating agent is white carbon black.

[0042] According to some preferred and specific aspects of the present invention, in step (5), the flow rate of silicon tetrafluoride gas is 0.01-1000m3 / h, for example, 0.01-900m3 / h, 0.1-700m3 / h, 1-1000m3 / h.

[0043] According to some specific and preferred embodiments of the present invention, in step (5), the absorbent (water) or fluorosilicic acid can be produced by step (1) with a flow rate of 0.1-2000 kg / h, for example, 0.1-1000 kg / h, 0.5-800 kg / h, 1-2000 kg / h.

[0044] According to some specific and preferred embodiments of the present invention, in step (5), the concentration of the fluorosilicic acid after multi-stage absorption is 15%-65%, for example, 15%, 35%, 40%, 50%, 55%, 60%, 65%.

[0045] According to some specific and preferred embodiments of the present invention, in step (7), the crystalline mixture is concentrated and crystallized, and the solvent selected is water or dilute hydrofluoric acid.

[0046] According to some specific and preferred embodiments of the present invention, in step (7), the crystalline mixture is concentrated and crystallized, and calcium fluoride and magnesium fluoride are precipitated with a solubility of <1 mg / 100 g, which can be used as steel slag-forming agents and welding agents in metal smelting, welding, and other fields.

[0047] According to some specific and preferred embodiments of the present invention, in step (7), the crystalline mixture is concentrated and crystallized to precipitate sodium fluoride and sodium fluorosilicate with a solubility of 1-1000 mg / 100 g, which can be used as UF3 adsorbents and opalescent agents in the nuclear industry, glass and enamel fields.

[0048] According to some specific and preferred embodiments of the present invention, in step (7), the crystalline mixture is concentrated and crystallized, and potassium fluoride is precipitated with a solubility of >1000 mg / 100 g, which can be used as a transmittance enhancer and polishing agent in the field of glass engraving.

[0049] According to some specific and preferred embodiments of the present invention, in step (8), the produced hydrochloric acid is mixed with hydrogen chloride to obtain an ultra-high purity electronic grade product, i.e., electronic grade hydrochloric acid 36%-38%, for example, 36% hydrochloric acid, 37% hydrochloric acid, 37.5% hydrochloric acid, 38% hydrochloric acid.

[0050] According to some specific and preferred embodiments of the present invention, in step (8), the generated hydrofluoric acid is mixed with hydrogen fluoride to obtain an ultra-high purity electronic grade product, i.e., electronic grade hydrofluoric acid 40%-49%, for example, 40% hydrofluoric acid or 49% hydrofluoric acid.

[0051] According to some specific and preferred embodiments of the present invention, in step (8), the metal content of the ultra-high purity electronic grade product is lower than 100 ppb, lower than 10 ppb, lower than 1 ppb, lower than 100 ppt, lower than 10 ppt, or lower than 1 ppt.

[0052] The present invention provides a method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid, which has the following beneficial effects:

[0053] 1) The waste acid separation and recovery technology of the present invention has good process tolerance and wide applicability, and can efficiently separate waste acids of different situations, different magnitudes and different concentrations in batches; the recovery technology is highly environmentally friendly, the entire process realizes internal circulation, the products are effectively treated or recycled, and no new waste is generated;

[0054] 2) The recycling technology of the present invention is economical, and the waste acid is reprocessed into ultra-high-purity electronic-grade gas and acid with high economic value. The technology also makes full use of non-renewable fluorine resources, which can reflect its environmental value, economic value, and resource value;

[0055] 3) In the technical solution of the present invention, in S8, the metal content of the ultra-high purity electronic grade product is less than 100 ppb, less than 10 ppb, less than 1 ppb, less than 100 ppt, less than 10 ppt, less than 1 ppt;

[0056] 4) In S3 of the present invention, in the distillation tower, the purity of the hydrogen chloride reaches 99.99995%, and the purity of the anhydrous hydrogen fluoride reaches 99.99995%;

[0057] 5) In S7 of the present invention, the crystalline mixture is concentrated and crystallized, and calcium fluoride and magnesium fluoride are precipitated according to the solubility <1mg / 100g, which can be used as steel slag-making agent and welding agent in metal smelting, welding, and other fields; the crystalline mixture is concentrated and crystallized, and sodium fluoride and sodium fluorosilicate are precipitated according to the solubility 1-1000mg / 100g, which can be used as UF3 adsorbent and opalescent agent in the nuclear industry, glass and enamel fields; the crystalline mixture is concentrated and crystallized, and potassium fluoride is precipitated according to the solubility >1000mg / 100g, which can be used as a transparent agent and polishing agent in the field of glass engraving;

[0058] 6) The present invention provides a method for treating hazardous chemicals with wide applicability for value-added, reduction and internal circulation. The present invention is widely applicable in that it can treat hazardous wastes containing hydrochloric acid, hydrofluoric acid and fluorosilicic acid with different concentrations generated by different industries, which is specifically embodied in S1.

[0059] 7) The value-added concept of the present invention lies in 1: Improvement of product quality: electronic-grade materials that can be used in the semiconductor industry are produced after waste acid treatment, and the treatment cost is changed from several thousand yuan to electronic materials worth thousands of yuan, with a comprehensive value-added of more than 10,000 yuan per ton of hazardous waste; 2: Improvement of product variety: Fluorosilicic acid with a cost of several hundred yuan per ton of waste acid is converted into anhydrous hydrogen fluoride with a cost of tens of thousands of yuan per ton, and hydrogen fluoride is the source of basic raw materials in the fluorine chemical industry; 3: Improvement of product application fields: waste fluoride salts are separated and applied to high-value application fields such as nuclear industry, optics, metal smelting, glass and enamel fields, glass engraving, etc.

[0060] 8) The concept of the present invention is that the present invention adopts processes such as distillation, absorption, crystallization, rectification and preparation. In addition to the consumption of energy, these processes do not introduce water, chemical reagents, resins and other purification treatment methods, and gradually reduce the amount of total hazardous waste, and form relevant high-value products after conversion.

[0061] 9) The concept of the internal circulation of the present invention is that the products of each process in the present invention can be used cross-circulated in the process, which saves the process operation cost and improves the safety factor of the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1The present invention relates to a method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid, and a schematic diagram of the process flow structure of an embodiment;

[0063] Description of reference numerals:

[0064] 1-raw material tank; 2-distillation kettle; 3-crystallization mixture buffer tank; 4-condenser; 5-hydrochloric acid storage tank; 6-hydrofluoric acid storage tank; 7-water storage tank; 8-hydrochloric acid; hydrofluoric acid; fluorosilicic acid mixed liquid buffer tank; 9-concentrated sulfuric acid reactor; 10-distillation tower; 11-rectification tower; 12-hydrogen fluoride storage tank; 13-hydrogen chloride storage tank; 14-white carbon black reaction column; 15-sulfur trioxide absorption tower; 16-dilute sulfuric acid buffer tank; 17-concentrated sulfuric acid storage tank. DETAILED DESCRIPTION

[0065] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following embodiments and the accompanying drawings are combined to illustrate the present invention. Figure 1 The present invention will be further described:

[0066] Step (1): distill the mixed waste liquid at 0.1-200kpa and 80℃-160℃ to obtain a relatively stable mixed liquid mainly composed of hydrofluoric acid, hydrochloric acid and fluorosilicic acid, so as to facilitate the subsequent purification process to be stable and continuous. Depending on the source of the materials, high-purity water, a certain concentration of hydrochloric acid, hydrofluoric acid and a certain proportion of fluoride salt mixture may be produced as by-products.

[0067] Step (2): mixing the mixed solution in step (1) with concentrated sulfuric acid having a concentration of 98% to 107% at a temperature of 15° C. to obtain silicon tetrafluoride and dilute sulfuric acid containing hydrogen fluoride and hydrogen chloride;

[0068] Step (3): dilute sulfuric acid containing hydrogen fluoride and hydrogen chloride is distilled at 40°C to 120°C to obtain hydrogen fluoride and hydrogen chloride gas and dilute sulfuric acid.

[0069] Step (4): distill the mixed gas of hydrogen chloride and hydrogen fluoride at a temperature of -5°C to 120°C to obtain high-purity hydrogen chloride and hydrogen fluoride products.

[0070] Step (5): The high-purity hydrogen chloride gas in step (4) is mixed with hydrochloric acid of a certain concentration in step (1) to obtain an ultra-high-purity electronic-grade hydrochloric acid product with a concentration of 36%-38%.

[0071] Step (6): The high-purity hydrogen fluoride gas in step (4) is mixed with the hydrofluoric acid of a certain concentration in step (1) to obtain an ultra-high-purity electronic-grade hydrofluoric acid product with a concentration of 40%-49%.

[0072] Step (7): The silicon tetrafluoride in step (2) is subjected to multi-stage circulation absorption to obtain 15%-65% fluorosilicic acid and white carbon black products, and the fluorosilicic acid product is sent to step (1) for circulation treatment.

[0073] Step (8): Controlling the temperature and concentration of the saturated fluoride salt mixture in step (1) to crystallize into different fluoride salt products.

[0074] Step (9): The dilute sulfuric acid in step (3) is passed through the white carbon black reaction column in step (7) to fully convert the hydrogen fluoride in the dilute sulfuric acid into silicon tetrafluoride, and the generated silicon tetrafluoride gas is collected and sent to step (7) for complete treatment.

[0075] Step (10): The dilute sulfuric acid in step (9) is recycled to absorb sulfur trioxide to obtain an industrial grade concentrated sulfuric acid product of 98%-107%.

[0076] Combine the following Figure 1 The above-mentioned technology for separation and recovery of waste liquid containing hydrochloric acid and hydrofluoric acid is further described. Figure 1 The process flow shown is batch processing, and can also be continuous processing. The following is an example of continuous processing.

[0077] The raw material tank 1 can be used to cache the waste acid raw materials containing hydrochloric acid and hydrofluoric acid, and can also be used as a transfer tank for fluorosilicic acid. It is connected to the distillation kettle 2 to introduce the raw waste acid into the distillation kettle 2, and the distillation kettle 2 is controlled to be under the processing pressure (0.1-200kpa) and the processing temperature (80℃-160℃). After condensation sampling and detection by the condenser 4, a mixed liquid mainly composed of hydrofluoric acid, hydrochloric acid and fluorosilicic acid can be obtained and collected in the hydrochloric acid, hydrofluoric acid and fluorosilicic acid mixed liquid buffer tank 8. The by-products of hydrochloric acid, hydrofluoric acid and high-purity water with a certain concentration are collected in the hydrochloric acid storage tank 5, the hydrofluoric acid storage tank 6 and the water storage tank 7 respectively, as well as a fluoride salt mixture of a certain proportion.

[0078] Further, the hydrochloric acid, hydrofluoric acid, and fluorosilicic acid mixed solution in the buffer tank 8 are transported by a transmission pump in a ratio (0.01-100:1) and mixed with concentrated sulfuric acid (98%-107%) in the concentrated sulfuric acid reactor 9 at a temperature (15° C.-25° C.) to obtain silicon tetrafluoride and dilute sulfuric acid containing hydrogen fluoride and hydrogen chloride;

[0079] Further, the dilute sulfuric acid containing hydrogen fluoride and hydrogen chloride is connected to the distillation tower 10, and the distillation tower 10 is controlled to distill at a processing temperature (40°C-120°C). The gas from which hydrogen fluoride and hydrogen chloride are evaporated is connected to the distillation tower 11 through the distillation tower 10, and the distillation tower 11 is controlled to distill at a processing temperature (-5°C-120°C), and the reflux ratio is 1:7-20. After sampling and testing, high-purity hydrogen fluoride and hydrogen chloride are respectively obtained and passed into the hydrogen fluoride storage tank 12 and the hydrogen chloride storage tank 13 for storage.

[0080] Furthermore, the hydrochloric acid (1%-35%) in the hydrochloric acid storage tank 5 is mixed with the hydrogen chloride (6.5N) in the hydrogen chloride storage tank 13 to obtain an ultra-high purity electronic grade hydrochloric acid product with a concentration of 36%-38%. The hydrofluoric acid (1%-39%) in the hydrofluoric acid storage tank 6 is mixed with the hydrogen fluoride (6.5N) in the hydrogen fluoride storage tank 12 to obtain an ultra-high purity electronic grade hydrofluoric acid product with a concentration of 40%-49%.

[0081] Further, the silicon tetrafluoride in the concentrated sulfuric acid reactor 9 is connected to the absorption tower 15, and the absorbent is selected to be water or fluorosilicic acid (which can be water in the storage tank 7). The silicon tetrafluoride gas flow rate of the absorption tower 15 at normal temperature and pressure is 0.01-1000m 3 / h, the absorbent flow rate is 0.1-2000kg / h, and fluorosilicic acid (15%-65%) is formed and buffered in the raw material tank 1, and white carbon black product, and then after repeated multi-stage circulation absorption, hydrogen fluoride is obtained and passed into the hydrogen fluoride storage tank 12 for storage.

[0082] Furthermore, the fluorine-containing dilute sulfuric acid in the distillation tower 10 is passed through the white carbon reaction column 14 in which the defluorinating agent is white carbon black, and the contact time (0.1-600 min), exchange rate (50 mg / g-100 mg / g), silicon tetrafluoride gas flow rate (0.01-1000 m 3 / h)

[0083] The obtained dilute sulfuric acid is passed into the dilute sulfuric acid buffer tank 16, and sulfur trioxide is absorbed by circulation to obtain (98%-107%) industrial grade concentrated sulfuric acid which is stored in the concentrated sulfuric acid storage tank 17.

[0084] Furthermore, the crystallization mixture in the crystallization mixture buffer tank 3 is separated by a concentrated crystallization process, and calcium fluoride and magnesium fluoride are precipitated according to the solubility <1mg / 100g, which can be used as steel slag-forming agent products; sodium fluoride and sodium fluorosilicate are precipitated according to the solubility 1-1000mg / 100g, which can be used as UF3 adsorbent and opalescent agent products; potassium fluoride is precipitated according to the solubility >1000mg / 100g, which can be used as a permeability enhancer and polishing agent product.

[0085] The present invention is a technology for separating and recycling waste liquid containing hydrochloric acid and hydrofluoric acid. It solves the above-mentioned problem of waste of resources and inability to fully recycle waste liquid containing hydrochloric acid and hydrofluoric acid. It achieves separation effect, and converts waste into industrial production materials to obtain ultra-high purity hydrofluoric acid and ultra-high purity hydrochloric acid of a certain concentration, achieving a treatment effect of dangerous chemicals with wide applicability of value-added, reduction and internal circulation.

[0086] Compared with traditional technologies, the technology of the present invention has the advantages of low energy consumption, good environmental benefits, high separation efficiency, and can obtain ultra-high purity electronic-grade products for sale and related industrial materials, achieve internal recycling of materials, and no new waste is generated.

[0087] The above scheme is further described below in conjunction with specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0088] Unless otherwise specified in the following embodiments, all waste liquids are derived from factory production lines such as lithium hexafluorophosphate production, solar silicon wafer cleaning, glass thinning, and high-purity quartz sand purification. In this field, the temperature values ​​at various locations may fluctuate under normal circumstances, generally fluctuating around ±10 degrees Celsius, preferably controlled at around ±5 degrees Celsius. In the following embodiments, the temperature value is limited to "about", indicating that it may exist within the above-mentioned reasonable temperature fluctuation range in the field.

[0089] The contents of hydrochloric acid, hydrofluoric acid or hydrogen chloride and hydrogen fluoride of the invention are analyzed by sodium hydroxide titration method, the metal ion content is detected by inductively coupled plasma mass spectrometer (ICP-MS, Thermo X-7 series), the anion is detected by liquid ion chromatograph (equipment Dionex Aquion IC), and the high-purity hydrogen chloride and hydrogen fluoride are detected by gas chromatograph (equipment American GOW-MAC, GM 1900PDHID-C42).

[0090] Concentrated sulfuric acid has a concentration reaching GB / T534-2002, and sulfur trioxide has a concentration reaching GB / T23855-2018, both of which are commercially available.

[0091] Examples 1-6

[0092] Comparative Example 1

[0093] The method is basically the same as Example 1, except that the first step of distillation for separation of gas, liquid and solid is not performed, and subsequent related processes such as sulfuric acid dehydration cannot be performed.

[0094] Comparative Example 2

[0095] The method is basically the same as Example 2, except that concentrated sulfuric acid dehydration is not performed, and the subsequent value-added process cannot be performed, and only low-value industrial products and a small amount of low-concentration, low-value acid (with no market sales value) are produced.

[0096] The implementation conditions of each step of Examples 1-6 and Comparative Examples 1-2 are shown in Table 1.

[0097] Table 1

[0098]

[0099]

[0100]

[0101]

[0102] Table 2 Test results of electronic grade hydrochloric acid

[0103] project unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Anions ppb <50 <50 <50 <50 <50 <50 Sodium(Na) ppb 6.000 0.300 0.000 0.000 0.001 0.001 Magnesium (Mg) ppb 34.000 4.800 0.180 0.003 0.001 0.000 Aluminum (Al) ppb 89.000 2.000 0.090 0.006 0.000 0.000 Potassium (K) ppb 1.000 0.000 0.000 0.000 0.000 0.000 Calcium (Ca) ppb 62.000 9.000 0.640 0.057 0.004 0.001 Titanium (Ti) ppb 54.000 5.700 0.600 0.058 0.001 0.000 Vanadium (V) ppb 0.000 0.400 0.010 0.001 0.004 0.000 Chromium (Cr) ppb 0.000 0.400 0.020 0.000 0.002 0.001 Manganese (Mn) ppb 1.000 0.300 0.020 0.001 0.002 0.000 Iron (Fe) ppb 40.000 3.800 0.420 0.032 0.005 0.000 Cobalt (Co) ppb 0.000 0.000 0.000 0.000 0.001 0.001 Nickel (Ni) ppb 1.000 0.300 0.020 0.000 0.004 0.000 Copper (Cu) ppb 5.000 0.200 0.000 0.001 0.001 0.000 Zinc (Zn) ppb 10.000 0.800 0.110 0.010 0.001 0.000 Gallium (Ga) ppb 0.000 0.000 0.000 0.000 0.002 0.000 Germanium (Ge) ppb 0.000 0.000 0.000 0.000 0.001 0.000 Arsenic (As) ppb 10.000 0.000 0.000 0.000 0.000 0.000 Strontium (Sr) ppb 1.000 0.100 0.100 0.001 0.000 0.000 Zirconium (Zr) ppb 0.000 0.000 0.000 0.000 0.000 0.000 Niobium (Nb) ppb 0.000 0.000 0.000 0.000 0.000 0.000 Molybdenum (Mo) ppb 0.000 0.000 0.000 0.000 0.000 0.000 Silver (Ag) ppb 0.000 0.000 0.000 0.000 0.000 0.000 Cadmium (Cd) ppb 0.000 0.000 0.500 0.003 0.005 0.000 Tin (Sn) ppb 0.000 0.000 0.000 0.000 0.000 0.000 Antimony (Sb) ppb 0.000 0.000 0.000 0.003 0.000 0.000 Barium (Ba) ppb 2.000 0.100 0.050 0.002 0.000 0.000 Thallium (Tl) ppb 0.000 0.000 0.000 0.000 0.000 0.000 Lead (Pb) ppb 3.000 0.300 0.000 0.003 0.001 0.000

[0104] Table 3 Test results of electronic grade hydrofluoric acid

[0105]

[0106]

[0107] Table 4 Hydrogen Chloride Test Results

[0108] project unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 <![CDATA[H2]]> ppmvol / vol 0.030 0.050 0.020 0.070 0.004 0.020 <![CDATA[N2]]> ppmvol / vol 0.140 0.180 0.140 0.150 0.130 0.160 <![CDATA[O2+Ar]]> ppmvol / vol 0.060 0.050 0.090 0.060 0.040 0.050 CO ppmvol / vol 0.030 0.030 0.020 0.050 0.080 0.070 <![CDATA[CO2]]> ppmvol / vol 0.180 0.180 0.130 0.120 0.130 0.190 <![CDATA[THC(CH4)]]> ppmvol / vol 0.040 0.008 0.100 0.090 0.007 0.100 <![CDATA[H2O]]> ppmvol / vol 0.100 0.060 0.080 0.070 0.100 0.090 Fe ppmwht / vol 0.070 0.020 0.060 0.030 0.072 0.080 Cr ppmwht / vol 0.001 0.100 0.100 0.100 0.007 0.007 Ni ppmwht / vol 0.010 0.008 0.010 0.010 0.009 0.006 Cu ppmwht / vol 0.009 0.010 0.010 0.008 0.009 0.010 Co ppmwht / vol 0.010 0.007 0.006 0.010 0.010 0.009

[0109] Table 5 Hydrogen fluoride test results

[0110]

[0111]

[0112] By comparing Examples 1 to 6 with Comparative Examples 1 to 2, it can be seen that:

[0113] The value-added concept of the present invention lies in 1): Improved product quality: electronic-grade materials that can be used in the semiconductor industry are produced after waste acid treatment, and the treatment cost is changed from several thousand yuan to electronic materials worth thousands of yuan, with a comprehensive value-added of more than 10,000 yuan per ton of hazardous waste; 2): Improved product variety: Fluorosilicic acid worth hundreds of yuan per ton of waste acid is converted into anhydrous hydrogen fluoride worth tens of thousands of yuan per ton, and hydrogen fluoride is the source of basic raw materials in the fluorine chemical industry; 3): Improved product application fields: After separation, waste fluoride salts are applied to high-value application fields such as nuclear industry, optics, metal smelting, glass and enamel fields, glass engraving, etc.

[0114] The present invention embodies the concept of reducing the amount of waste in that the present invention adopts processes such as distillation, absorption, crystallization, rectification and blending. In addition to the consumption of energy, these processes do not introduce water, chemical reagents, resins and other purification treatment methods, and gradually reduce the amount of total hazardous waste, and form relevant high-value products after conversion.

[0115] The present invention embodies the concept of internal circulation in that the products of each process in the present invention can be used cross-circulated in the process, thereby saving process operation costs and improving the safety factor of the process.

[0116] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent changes made using the present invention are within the patent protection scope of the present invention.

Claims

1. A method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid, wherein high-value ultra-high-purity electronic-grade hydrochloric acid and hydrofluoric acid are obtained from waste acid containing hydrochloric acid and hydrofluoric acid, and the mass content of metal is below 100 ppb; and ultra-high-purity hydrogen chloride and anhydrous hydrogen fluoride with a purity of 6.5N are obtained, characterized in that: The method uses hazardous waste containing fluorosilicic acid and fluoride salts, mainly hydrochloric acid and hydrofluoric acid, as raw materials, and includes the following preparation steps: Step (1) passing the waste acid solution of hydrochloric acid and hydrofluoric acid into a distillation kettle for heating and distillation, controlling the time and temperature, and taking samples for testing, and obtaining water, hydrochloric acid and hydrofluoric acid through condensation and collection; A stable mixed acid of hydrochloric acid, hydrofluoric acid and fluorosilicic acid; a mixture of one or more of calcium fluoride, aluminum fluoride, sodium fluoride, magnesium fluoride, sodium chloride and sodium fluorosilicate is produced at the bottom of the distillation kettle; Step (2) passing the stable mixed acid of hydrochloric acid, hydrofluoric acid and fluorosilicic acid into a concentrated sulfuric acid reactor for dehydration to produce silicon tetrafluoride, hydrogen fluoride, hydrogen chloride and fluorine-containing dilute sulfuric acid; Step (3) after dehydration, passing the dehydrated gas into a distillation tower for distillation, passing the evaporated gaseous phase into a rectification tower, collecting hydrogen chloride and anhydrous hydrogen fluoride fractions respectively, and obtaining ultra-high purity hydrogen chloride and hydrogen fluoride products; Step (4) passing the fluorine-containing dilute sulfuric acid in step (2) through a white carbon black reaction column and a sulfur trioxide absorption tower in sequence to form silicon tetrafluoride and obtain a 98%-107% concentrated sulfuric acid product; Step (5) passing the silicon tetrafluoride in step (4) through an absorption tower to form fluorosilicic acid and white carbon black product; Step (6) Repeating the processes of steps 2-5 with the fluorosilicic acid formed in step (5) to obtain a hydrogen fluoride product and a white carbon black product; Step (7) using a concentrated crystallization process to separate the crystals of step (1) into insoluble calcium fluoride, magnesium fluoride steel slag-making agent, welding agent products, slightly soluble sodium fluoride, sodium fluorosilicate UF3 adsorbent, opalescent agent, and soluble potassium fluoride permeability enhancer, polishing agent products according to their different solubilities; Step (8) mixing the hydrochloric acid and hydrofluoric acid produced in step (1) with the hydrogen chloride and hydrogen fluoride produced in step (4) to produce an ultra-high purity electronic grade product; In step (1), the waste acid is derived from lithium hexafluorophosphate production, solar silicon wafer cleaning, glass thinning, and high-purity quartz sand purification processes; In step (1), the mass concentration of hydrochloric acid in the waste acid is 1%-30%, hydrofluoric acid is 1%-30%, and fluorosilicic acid is 10%-15%; In step (1), the temperature of the distillation kettle is controlled at 80°C-160°C; In step (1), the distillation kettle equipment material is selected from any one or more of ordinary PTFE, ultra-high purity PFA, PVDF, fluorine-lined sintered material, graphite, stainless steel, and PFA; In the step (1), during the primary distillation of the waste acid, sampling is performed to detect the gas phase components of different fractions, and the gas phase components are condensed and collected to obtain water, hydrochloric acid, hydrofluoric acid, and mixtures thereof; In the step (2), the ratio of hydrochloric acid to hydrofluoric acid in the stable mixed acid of hydrochloric acid, hydrofluoric acid and fluosilicic acid is 0.01-100:1; In the step (2), the stable mixed acid is dehydrated with concentrated sulfuric acid, which becomes a green process route, achieves the dehydration effect without introducing new impurities, and the concentrated sulfuric acid concentration used in the concentrated sulfuric acid reactor is 98%-107%; In the step (3), secondary distillation is performed after dehydration for further separation, and the distillation temperature of the distillation tower is controlled at 40°C-120°C; Fluorosilicic acid is formed in step (6), and processes 2-5 are repeated to achieve an internal circulation effect; In the step (7), the crystal mixture is concentrated and crystallized to separate the solubility. <1mg / 100g->1000mg / 100g respectively crystallizes calcium fluoride and magnesium fluoride as steel slag-making agent and welding agent products, sodium fluoride and sodium fluorosilicate as UF3 adsorbent and opalescent agent products, and potassium fluoride as transparent enhancer and polishing agent products; in the step (8), the obtained hydrogen chloride is mixed with hydrochloric acid to obtain electronic grade hydrochloric acid with a concentration of 36%-38%, and the anhydrous hydrogen fluoride is mixed with hydrofluoric acid to obtain electronic grade hydrofluoric acid with a concentration of 40%-49%, and the metal content is less than 100ppb, less than 10ppb, less than 1ppb, less than 100ppt, less than 10ppt, and less than 1ppt.

2. The method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid according to claim 1, characterized in that: In step (1), the hydrochloric acid and hydrofluoric acid form fluoride salts and chloride salts with metal ions in the waste acid, and a mixture of one or more of calcium fluoride, sodium fluoride, magnesium fluoride, sodium fluorosilicate and potassium fluoride is produced at the bottom of the distillation kettle, so that no new waste is generated.

3. A method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid according to claim 1, characterized in that: In the step (3), the vaporized gas phase is distilled by controlling the temperature of the distillation tower to -5°C-120°C and the reflux ratio to 1:7-20, and the hydrogen chloride and anhydrous hydrogen fluoride fractions are collected respectively to obtain ultra-high purity hydrogen chloride and hydrogen fluoride products; in the step (3), the purity of hydrogen chloride reaches 99.99995%, and the purity of anhydrous hydrogen fluoride reaches 99.99995%.

4. The method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid according to claim 1, characterized in that: In the step (4), in the defluorination of dilute sulfuric acid through a white carbon black reaction column, white carbon black is selected as a defluorination agent, the exchange ratio is 50 mg / g-100 mg / g, the silicon tetrafluoride gas flow rate is 0.01-1000 m3 / h, and the contact time is 0.1-600 min.

5. The method for separating and recovering waste liquid containing hydrochloric acid and hydrofluoric acid according to claim 1, characterized in that: In the step (5), silicon tetrafluoride is absorbed in an absorption tower using absorbent water or fluorosilicic acid, with a gas flow rate of 0.01-1000m3 / h and an absorbent flow rate of 0.1-2000kg / h.

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