A method for recovering and treating pickling waste acid in a photovoltaic industry

Abstract

The application discloses a kind of photovoltaic industry pickling waste acid recovery processing method, belong to wastewater treatment field, steps include: adding potassium salt and first crystallization salt to pickling waste acid, and filter to obtain potassium fluosilicate filter residue and first filtrate;First filtrate is heated, and under negative pressure gas-liquid separation is carried out, obtains first thick liquid and dilute hydrofluoric acid;First thick liquid is concentrated and crystallized, and first crystallization salt is obtained;Vacuum concentration is carried out to dilute hydrofluoric acid, and hydrofluoric acid and low-fluorine acid waste liquid are obtained.The method uses potassium fluoride to maintain pickling waste liquid in acidic state to remove silicon element, obtain high-value potassium fluosilicate, which can be used as an additive in various industries, after removing silicon element, the pickling waste liquid is subjected to gas-liquid separation, the gas component is condensed and then subjected to vacuum concentration, high-concentration purified industrial-grade hydrofluoric acid is obtained, the hydrofluoric acid resource in the pickling waste liquid is effectively utilized, and the first thick liquid after gas-liquid separation is used as a precipitant after crystallization, which is beneficial to save raw materials.

Description

Technical Field

[0001] This invention relates to a method for recovering and treating acid waste from pickling in the photovoltaic industry, belonging to the field of wastewater treatment. Background Technology

[0002] Photovoltaic (PV) power generation is a technology that directly converts solar energy into electricity. Solar energy is a renewable resource, and compared to non-renewable energy sources such as fossil fuels, PV power generation is crucial for a sustainable energy supply. Furthermore, PV power generation does not produce greenhouse gases or other pollutants, resulting in a smaller environmental impact and helping to reduce air and water pollution, thus protecting the health of ecosystems. In addition, PV power generation systems can be distributed and installed in various locations, such as building rooftops, parking lots, and farmland. This distributed energy production model helps improve the reliability and flexibility of energy supply, reduces dependence on centralized energy systems, and enhances energy independence.

[0003] However, the production of photovoltaic power generation equipment is not environmentally friendly. The processing of raw materials for photovoltaic power generation equipment production inevitably involves acid washing, which generates a large amount of wastewater containing hydrofluoric acid. The fluorine element in the acid washing waste is difficult to treat and has become a major bottleneck restricting the development of the photovoltaic industry.

[0004] Currently, the neutralization and precipitation method is generally used to treat waste acid from photovoltaic pickling. First, sodium hydroxide is used to adjust the pH of the waste acid to near neutral. Then, calcium hydroxide and calcium chloride react with the waste acid to form a precipitate, yielding calcium fluoride. However, the neutralization and precipitation method consumes the acid in the wastewater, resulting in the direct waste of hydrofluoric acid. New hydrofluoric acid must be added for the next pickling cycle, which will increase fluoride pollution. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a method for recycling and treating pickling waste acid in the photovoltaic industry, which can recover hydrofluoric acid from the pickling waste acid.

[0006] The technical solution adopted by this invention to solve its technical problem is: A method for recovering and treating acid from pickling waste in the photovoltaic industry includes the following steps: Potassium salt and first crystalline salt were added to the pickling waste acid to react, and the mixture was filtered to obtain potassium fluorosilicate filter residue and first filtrate. The first filtrate is heated and subjected to gas-liquid separation under negative pressure to obtain a first concentrated liquid from the liquid component of the gas-liquid separation. The gas component of the gas-liquid separation is condensed to obtain dilute hydrofluoric acid. The first concentrated liquid is concentrated and crystallized to obtain the first crystalline salt. The dilute hydrofluoric acid is concentrated under vacuum to obtain hydrofluoric acid from the liquid component of the vacuum concentration, and the gaseous component of the vacuum concentration is condensed to become acidic waste liquid.

[0007] The photovoltaic industry pickling waste acid recovery and treatment method provided in this application uses potassium fluoride to maintain the pickling waste acid in an acidic state to remove silicon elements, obtaining high-value potassium fluorosilicate, which can be used as an additive in various industries. After removing silicon elements, the pickling waste acid undergoes gas-liquid separation, in which the gas components are condensed and further concentrated under vacuum to obtain highly concentrated and purified industrial-grade hydrofluoric acid. This effectively utilizes the hydrofluoric acid resources in the pickling waste acid. Moreover, the first concentrated liquid after gas-liquid separation is reused as a precipitant after crystallization, which helps to save raw materials.

[0008] Furthermore, in the step of adding potassium salt and the first crystalline salt to the pickling waste acid for reaction, the temperature of the reaction system is controlled at 30℃~40℃ and the reaction time is 40min~50min under stirring, which is beneficial to fully remove silicon elements from the pickling waste liquid.

[0009] Furthermore, the step of heating the first filtrate and performing gas-liquid separation under negative pressure includes preheating the first filtrate in a preheating tank, and then introducing it into a gas-liquid separator. The gas-liquid separator is an external circulation vacuum evaporation device, with the temperature controlled at 55℃~65℃ and the negative pressure controlled at -0.05MPa~-0.06MPa. This allows for the separation of dilute hydrofluoric acid with lower evaporation temperature, higher evaporation rate, and lower energy consumption, while also reducing scaling and ensuring normal equipment operation.

[0010] Furthermore, the step of vacuum concentration of the dilute hydrofluoric acid includes: introducing the dilute hydrofluoric acid into a vacuum concentration tower, wherein the negative pressure of the vacuum concentration tower is controlled at -0.05MPa to -0.06MPa, and the temperature at the top of the tower is controlled at 60℃ to 68℃. Under these process conditions, material adhesion to the inner wall of the equipment can be avoided. The top of the tower contains weakly acidic water vapor, which is condensed into acidic waste liquid by a vacuum condenser and collected for treatment. The concentrated and purified hydrofluoric acid obtained at the bottom of the tower can be directly reused in the pickling process of the production line.

[0011] Furthermore, the volume ratio of the potassium salt to the first crystalline salt is 6-7:1, and the ratio of the total mass of the potassium salt and the first crystalline salt to the mass of the pickling waste acid is 9-10:100. Considering the characteristics of pickling waste liquid in the photovoltaic industry, this volume ratio allows for a slight excess of potassium ions relative to fluorosilicic acid, effectively removing silicon from the pickling waste liquid. It also ensures a relatively stable yield of the first crystalline salt and a relatively stable potassium ion content during continuous treatment of the pickling waste liquid, resulting in relatively stable quality of the recovered potassium fluorosilicate. This also avoids the need for repeated sampling and titration of the components of each stage of filtrate or waste liquid.

[0012] Furthermore, the acidic waste liquid undergoes pre-discharge treatment: the acidic waste liquid is mixed and reacted with calcium hydroxide, and filtered to obtain calcium fluoride first filter residue and wastewater, which helps to remove the small amount of fluoride remaining in the acidic waste liquid, so that the fluoride content of the wastewater meets the discharge standards.

[0013] Furthermore, the potassium fluorosilicate filter residue undergoes post-treatment, the post-treatment steps of which include: Hydrolysis: The potassium fluorosilicate filter residue is mixed with potassium hydroxide and reacted, then filtered to obtain silicon-containing filter residue and potassium fluoride filtrate; Conversion: Add calcium hydroxide to the potassium fluoride filtrate and react. After filtration, obtain calcium fluoride second filter residue and potassium hydroxide solution. The potassium hydroxide solution in the conversion step is recycled into the hydrolysis step.

[0014] Potassium fluorosilicate can be converted into calcium fluoride, which can be used as a flux in other fields and as a building material. Potassium hydroxide can be reused, reducing raw material consumption.

[0015] Furthermore, in the hydrolysis step, the temperature of the reaction system is controlled at 42±2℃, and the system is cooled and crystallized after the reaction.

[0016] Furthermore, in terms of molar amount, the amount of potassium hydroxide used in the hydrolysis step is more than four times that of potassium fluorosilicate, and the amount of calcium hydroxide used in the conversion step is 3.0 to 3.3 times that of potassium fluorosilicate in the hydrolysis step. Specifically, the potassium fluorosilicate filter residue can be obtained by pressure filtration. The amount of potassium fluorosilicate in the potassium fluorosilicate filter residue can be easily determined by taking a sample from the potassium fluorosilicate filter residue, weighing it, drying it, weighing it again, calculating the moisture content, and considering all the dried filter residue as potassium fluorosilicate. Thus, the amount of potassium fluorosilicate in the potassium fluorosilicate filter cake can be roughly determined.

[0017] Furthermore, the emission pretreatment step includes: The acidic waste liquid is divided into a base liquid portion and an injection portion; The calcium fluoride second filter residue is added to the bottom liquid portion as seed particles, and the pH of the bottom liquid portion is adjusted to 6.8~7.8 with calcium hydroxide; Calcium hydroxide and the injection portion are added simultaneously to the base solution, and the addition rate is controlled to ensure that the pH change is less than 0.3. The reaction system is filtered to obtain the first filter residue of calcium fluoride and the wastewater. The first filter residue of calcium fluoride is dried to obtain calcium fluoride particles.

[0018] The resulting calcium fluoride particles are larger, making them easier to apply in other fields.

[0019] Furthermore, the volume ratio of the base liquid portion to the injection portion is 1~2:9~8, which is beneficial for obtaining calcium fluoride particles with larger particle size and for further reducing the fluoride content in the wastewater.

[0020] The beneficial effects of this invention are as follows: The photovoltaic industry pickling waste acid recovery and treatment method of this invention uses potassium fluoride to maintain the pickling waste liquid in an acidic state to remove silicon elements, thereby obtaining potassium fluorosilicate, which has high value and can be used as an additive in various industries. After removing silicon elements, the pickling waste liquid undergoes gas-liquid separation, in which the gas components are condensed and further concentrated under vacuum to obtain highly concentrated and purified industrial-grade hydrofluoric acid. This effectively utilizes the hydrofluoric acid resources in the pickling waste liquid. Moreover, the first concentrated liquid after gas-liquid separation is reused as a precipitant after crystallization, which helps to save raw materials.

[0021] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a flowchart of a method for recycling and treating acid waste from acid washing in the photovoltaic industry, provided in Embodiment 1 of this application.

[0023] Figure 2 This is a flowchart of a method for recycling and treating acid waste from acid washing in the photovoltaic industry, provided in Embodiment 2 of this application.

[0024] Figure 3 This is a flowchart of a method for recycling and treating acid waste from acid washing in the photovoltaic industry, provided in Embodiment 3 of this application. Detailed Implementation

[0025] The following disclosure provides many different implementations or examples for carrying out the present invention. To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this invention. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] It should be understood that, without conflict, any and all embodiments of the present invention can be combined with technical features of any other embodiment or multiple other embodiments to obtain other embodiments. The present invention includes such combinations to obtain other embodiments.

[0027] Unless otherwise specified, all technical and scientific terms used herein have the standard meaning in the field to which the claimed subject matter pertains. Where multiple definitions exist for a term, the definition herein shall prevail.

[0028] Existing methods for treating waste acid from pickling processes cannot recover hydrofluoric acid, resulting in resource waste. This application provides a method for recovering and treating waste acid from pickling processes in the photovoltaic industry, comprising the following steps: S10: Potassium salt and first crystalline salt are added to the pickling waste acid for reaction, and the mixture is filtered to obtain potassium fluorosilicate filter residue and first filtrate. Specifically, the potassium salt includes at least one of potassium fluoride, potassium chloride, and potassium nitrate, preferably only potassium fluoride. The main reaction in step S10 is the reaction of potassium ions with fluorosilicic acid to form potassium fluorosilicate precipitate.

[0029] S20: Heat the first filtrate and perform gas-liquid separation under negative pressure to obtain a first concentrated liquid from the liquid component of the gas-liquid separation. The gas component of the gas-liquid separation is condensed to obtain dilute hydrofluoric acid. The first concentrated liquid is concentrated and crystallized to obtain a first crystalline salt. The first crystalline salt includes potassium fluoride, potassium chloride, and potassium nitrate. If only potassium fluoride is added in step S10, then the main component of the first crystalline salt is potassium fluoride.

[0030] S30: Dilute hydrofluoric acid is concentrated under vacuum to obtain hydrofluoric acid from the liquid component during vacuum concentration. The gaseous component during vacuum concentration is condensed to become acidic waste liquid. At this point, the acidic waste liquid mainly contains trace amounts of hydrofluoric acid.

[0031] In this method, step S10 maintains an acidic state to remove silicon from the pickling waste acid, obtaining potassium fluorosilicate, which has high value and can be used as an additive in various industries. In step S20, the first concentrated liquid after gas-liquid separation crystallizes to obtain the first crystalline salt, which can be reused, thus saving raw materials. Following step S20, step S30 involves condensing the gaseous components from the gas-liquid separation and further concentrating them under vacuum to obtain highly concentrated and purified industrial-grade hydrofluoric acid, effectively utilizing the hydrofluoric acid resources in the pickling waste liquid.

[0032] Example 1 This application provides a method for recycling and treating acid waste from acid washing in the photovoltaic industry, the process of which is as follows: Figure 1 .

[0033] S11: Add potassium fluoride and the first crystallized salt to the pickling waste acid and react them. The volume ratio of potassium fluoride to the first crystallized salt is 7:1, and the ratio of the total mass of potassium fluoride and the first crystallized salt to the mass of the pickling waste acid is 9:100. Under stirring, control the temperature of the reaction system at 30℃~40℃ and the reaction time at 40min~50min. Filter to obtain potassium fluorosilicate filter residue and the first filtrate.

[0034] S21: The first filtrate is preheated in a preheating tank and then enters a gas-liquid separator. The gas-liquid separator is an external circulation vacuum evaporation device. The temperature of the gas-liquid separator is controlled at 55℃~65℃, and the negative pressure is controlled at -0.05MPa~-0.06MPa. The first concentrated liquid is obtained from the liquid component in the gas-liquid separation, and the gas component in the gas-liquid separation is condensed to obtain dilute hydrofluoric acid. The first concentrated liquid is concentrated and crystallized to obtain the first crystalline salt.

[0035] S31: Dilute hydrofluoric acid is introduced into a vacuum concentration tower. The negative pressure of the vacuum concentration tower is controlled at -0.05MPa to -0.06MPa, and the top temperature of the tower is controlled at 60℃ to 68℃. Hydrofluoric acid is obtained from the liquid component in the vacuum concentration. The gaseous component in the vacuum concentration becomes acidic waste liquid after condensation.

[0036] In Example 1, step S21 can separate dilute hydrofluoric acid with low energy consumption using a lower evaporation temperature, a higher evaporation rate, and reduced scaling of materials, ensuring normal equipment operation. Under these conditions, the composition of the first concentrated liquid is stable, and the ratio of potassium fluoride to other impurity salts in the first concentrated liquid fluctuates little. Combined with the addition ratio of potassium fluoride to the first crystalline salt in step S11, it can effectively remove silicon from the pickling waste liquid, ensuring stable yield of the first crystalline salt and potassium ion content in the first crystalline salt during continuous pickling waste liquid treatment. This also ensures stable quality of the obtained potassium fluorosilicate and avoids repeated sampling and titration of the components of each stage of filtrate or waste liquid. Furthermore, the process parameters of step S21, when combined with those of step S31, can obtain high-purity industrial-grade hydrofluoric acid, which can be directly reused in the production line for pickling.

[0037] In Example 1, most of the fluorine was recovered and reused. To further reduce the fluorine content after the acid pickling waste acid treatment and recover the fluorine, Example 1 was improved, as shown in Example 2.

[0038] Example 2 This application provides a method for recycling and treating acid waste from acid washing in the photovoltaic industry, the process of which is as follows: Figure 2 .

[0039] S12: Add potassium fluoride and the first crystallized salt to the pickling waste acid and react them. The volume ratio of potassium fluoride to the first crystallized salt is 6:1, and the ratio of the total mass of potassium fluoride and the first crystallized salt to the mass of the pickling waste acid is 10:100. Under stirring, control the temperature of the reaction system at 30℃~40℃ and the reaction time at 40min~50min. Filter to obtain potassium fluorosilicate filter residue and the first filtrate.

[0040] S22: The first filtrate is preheated in a preheating tank and then enters a gas-liquid separator. The gas-liquid separator is an external circulation vacuum evaporation device. The temperature of the gas-liquid separator is controlled at 55℃~65℃, and the negative pressure is controlled at -0.05MPa~-0.06MPa. The first concentrated liquid is obtained from the liquid component in the gas-liquid separation, and the gas component in the gas-liquid separation is condensed to obtain dilute hydrofluoric acid. The first concentrated liquid is concentrated and crystallized to obtain the first crystalline salt.

[0041] S32: Dilute hydrofluoric acid is introduced into a vacuum concentration tower. The negative pressure of the vacuum concentration tower is controlled at -0.05MPa to -0.06MPa, and the top temperature of the tower is controlled at 60℃ to 68℃. Hydrofluoric acid is obtained from the liquid component in the vacuum concentration. The gaseous component in the vacuum concentration becomes acidic waste liquid after condensation.

[0042] S42: Acidic waste liquid is mixed with calcium hydroxide and reacted, then filtered to obtain calcium fluoride first filter residue and wastewater.

[0043] Based on Example 1, Example 2 adds step S42, where the added reaction mainly involves calcium ions reacting with residual fluoride ions to form calcium fluoride precipitate, and calcium hydroxide neutralizing the acidic wastewater. Specifically, the endpoint for adding calcium hydroxide can be set when the pH of the acidic wastewater reaches 7.0-7.8. After treatment in step S42, the wastewater becomes neutral, and the fluorine in the acidic wastewater is recovered, making it dischargeable wastewater.

[0044] Calcium fluoride, also known as fluorite, can be used as a flux and building material in other fields. Based on Example 1 or Example 2, there are other ways to obtain calcium fluoride. For example, potassium fluorosilicate filter residue undergoes post-treatment S52, specifically including: S521: Hydrolysis; Potassium fluorosilicate filter residue is mixed with potassium hydroxide and reacted. The amount of potassium hydroxide is 4 times that of potassium fluorosilicate. The temperature of the reaction system is controlled at 42±2℃. After the reaction, the mixture is cooled and crystallized. The mixture is then filtered to obtain silicon-containing filter residue and potassium fluoride filtrate.

[0045] S522: Conversion; Calcium hydroxide is added to the potassium fluoride filtrate to react, and after filtration, a second filter residue of calcium fluoride and a potassium hydroxide solution are obtained. The amount of calcium hydroxide used in the conversion step is 3.1 times that of potassium fluorosilicate in the hydrolysis step, and the potassium hydroxide solution from the conversion step is recycled back to the hydrolysis step.

[0046] In existing photovoltaic pickling waste acid treatment technologies, the pH of the pickling waste acid is first adjusted to near neutral using sodium hydroxide, and then calcium hydroxide and calcium chloride are reacted with the pickling waste acid to mainly obtain calcium fluoride precipitate. However, in existing technologies, the precipitate particles obtained by the neutralization precipitation method are very small, making it difficult to apply industrially. The main component of this precipitate is calcium fluoride, and it also contains a large number of impurities such as calcium fluorosilicate and silicon dioxide. Therefore, this application also provides Example 3.

[0047] Example 3 This application provides a method for recycling and treating acid waste from acid washing in the photovoltaic industry, the process of which is as follows: Figure 3 .

[0048] S13: Add potassium fluoride and the first crystallized salt to the pickling waste acid and react them. The volume ratio of potassium fluoride to the first crystallized salt is 6:1, and the ratio of the total mass of potassium fluoride and the first crystallized salt to the mass of the pickling waste acid is 10:100. Under stirring, control the temperature of the reaction system at 30℃~40℃ and the reaction time at 40min~50min. Filter to obtain potassium fluorosilicate filter residue and the first filtrate.

[0049] S23: The first filtrate is preheated in a preheating tank and then enters a gas-liquid separator. The gas-liquid separator is an external circulation vacuum evaporation device. The temperature of the gas-liquid separator is controlled at 55℃~65℃, and the negative pressure is controlled at -0.05MPa~-0.06MPa. The first concentrated liquid is obtained from the liquid component in the gas-liquid separation, and the gas component in the gas-liquid separation is condensed to obtain dilute hydrofluoric acid. The first concentrated liquid is concentrated and crystallized to obtain the first crystalline salt.

[0050] S33: Dilute hydrofluoric acid is introduced into a vacuum concentration tower. The negative pressure of the vacuum concentration tower is controlled at -0.05MPa to -0.06MPa, and the top temperature of the tower is controlled at 60℃ to 68℃. Hydrofluoric acid is obtained from the liquid component in the vacuum concentration. The gaseous component in the vacuum concentration becomes acidic waste liquid after condensation.

[0051] S43: Divide the acidic waste liquid into a bottom liquid portion and an injection portion; the volume ratio of the bottom liquid portion to the injection portion is 1~2:9~8.

[0052] S531: Hydrolysis; Potassium fluorosilicate filter residue is mixed with potassium hydroxide and reacted. The amount of potassium hydroxide is 4 times that of potassium fluorosilicate. The temperature of the reaction system is controlled at 42±2℃. After the reaction, the mixture is cooled and crystallized. Filtration yields silicon-containing filter residue and potassium fluoride filtrate. The silicon-containing filter residue obtained at this time mainly contains silicon dioxide and potassium silicate.

[0053] S532: Conversion; Calcium hydroxide is added to the potassium fluoride filtrate to react, and after filtration, a second filter residue of calcium fluoride and a potassium hydroxide solution are obtained. The amount of calcium hydroxide used in the conversion step is 3.2 times that of potassium fluorosilicate in the hydrolysis step, and the potassium hydroxide solution from the conversion step is recycled to the hydrolysis step.

[0054] S631: Add calcium fluoride second filter residue to the bottom liquid as seed particles, and use calcium hydroxide to adjust the pH of the bottom liquid to 6.8~7.8.

[0055] S632: Simultaneously add calcium hydroxide to both the base solution and the injection solution, controlling the addition rate to ensure that the pH change is less than 0.3. For example, if the pH of the base solution in step S631 is 7.2, then in step S632, the feeding rate needs to be monitored and controlled to keep the pH consistently between 6.9 and 7.5. This prevents either calcium hydroxide or the injection solution from suddenly becoming excessive, avoiding the formation of small calcium fluoride particles and promoting the continuous growth of calcium fluoride particles.

[0056] S633: The filtration reaction system yields the first filter residue of calcium fluoride and wastewater. The first filter residue of calcium fluoride is dried to obtain calcium fluoride granules.

[0057] In Example 3, step S531 first hydrolyzes potassium fluorosilicate into potassium fluoride and silicon dioxide. Cooling and crystallization removes most of the silicon. Then, in step S532, the potassium fluoride filtrate reacts with calcium hydroxide to generate calcium fluoride with a low silicon dioxide content. This calcium fluoride serves as a seed to continue absorbing fluoride from the acidic wastewater and growing. Since the acidic wastewater is almost devoid of silicon, this process reduces the fluoride content in the effluent and allows the calcium fluoride seed to continue growing with a lower silicon dioxide content. The final obtained calcium fluoride particles have a particle size D50 of 0.83 mm and a silicon dioxide content of 5%. The particle size is sufficiently large, and the impurity content is low, making it easily applicable to other industrial sectors.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0059] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for recovering and treating acid waste from pickling in the photovoltaic industry, characterized in that, Includes the following steps: Potassium salt and first crystalline salt were added to the pickling waste acid to react, and the mixture was filtered to obtain potassium fluorosilicate filter residue and first filtrate. The first filtrate is heated and subjected to gas-liquid separation under negative pressure to obtain a first concentrated liquid from the liquid component of the gas-liquid separation. The gas component of the gas-liquid separation is condensed to obtain dilute hydrofluoric acid. The first concentrated liquid is concentrated and crystallized to obtain the first crystalline salt. The dilute hydrofluoric acid is concentrated under vacuum to obtain hydrofluoric acid from the liquid component in the vacuum concentration, and the gaseous component in the vacuum concentration becomes acidic waste liquid after condensation. The acidic waste liquid also undergoes pre-discharge treatment: the acidic waste liquid is mixed and reacted with calcium hydroxide, and then filtered to obtain calcium fluoride first filter residue and wastewater; The potassium fluorosilicate filter residue also undergoes post-treatment, the steps of which include: Hydrolysis: The potassium fluorosilicate filter residue is mixed with potassium hydroxide and reacted, then filtered to obtain silicon-containing filter residue and potassium fluoride filtrate; Conversion: Add calcium hydroxide to the potassium fluoride filtrate and react. After filtration, obtain calcium fluoride second filter residue and potassium hydroxide solution. The potassium hydroxide solution in the conversion step is recycled back into the hydrolysis step; The pretreatment steps for emissions include: The acidic waste liquid is divided into a base liquid portion and an injection portion; The calcium fluoride second filter residue is added to the bottom liquid portion as seed particles, and the pH of the bottom liquid portion is adjusted to 6.8~7.8 with calcium hydroxide; Calcium hydroxide and the injection portion are added simultaneously to the base solution, and the addition rate is controlled to ensure that the pH change is less than 0.

3. The reaction system is filtered to obtain the first filter residue of calcium fluoride and the wastewater. The first filter residue of calcium fluoride is dried to obtain calcium fluoride particles.

2. The method for recovering and treating acidic waste from pickling in the photovoltaic industry according to claim 1, characterized in that, In the step of adding potassium salt and first crystalline salt to the pickling waste acid for reaction, the temperature of the reaction system is controlled at 30℃~40℃ and the reaction time is 40min~50min under stirring.

3. The method for recovering and treating acidic waste from pickling in the photovoltaic industry according to claim 1, characterized in that, The step of heating the first filtrate and performing gas-liquid separation under negative pressure includes preheating the first filtrate in a preheating tank, and then introducing it into a gas-liquid separator. The gas-liquid separator is an external circulation vacuum evaporation device. The temperature of the gas-liquid separator is controlled at 55℃~65℃, and the negative pressure is controlled at -0.05MPa~-0.06MPa.

4. The method for recovering and treating acidic waste from pickling in the photovoltaic industry according to claim 3, characterized in that, The step of vacuum concentration of the dilute hydrofluoric acid includes: introducing the dilute hydrofluoric acid into a vacuum concentration tower, wherein the negative pressure of the vacuum concentration tower is controlled at -0.05MPa to -0.06MPa, and the temperature at the top of the tower is controlled at 60℃ to 68℃.

5. The method for recovering and treating acidic waste from pickling in the photovoltaic industry according to claim 3, characterized in that, The volume ratio of the potassium salt to the first crystalline salt is 6-7:1, and the ratio of the total mass of the potassium salt and the first crystalline salt to the mass of the pickling waste acid is 9-10:

100.

6. The method for recovering and treating acidic waste from pickling in the photovoltaic industry according to claim 1, characterized in that, In terms of molar amount, the amount of potassium hydroxide used in the hydrolysis step is more than 4 times that of the potassium fluorosilicate filter residue, and the amount of calcium hydroxide used in the conversion step is 3.0 to 3.3 times that of the potassium fluorosilicate filter residue in the hydrolysis step.

7. The method for recovering and treating acidic waste from pickling in the photovoltaic industry according to claim 1, characterized in that, The volume ratio of the base liquid portion to the injection portion is 1~2:9~8.

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