System and method for recycling waste gas and waste liquid in crystal silicic acid washing

Abstract

The invention belongs to the technical field of semiconductors, and particularly discloses a system and method for recycling waste gas and waste liquid in crystal silicon washing, and the system comprises a photochemical reaction device, a nitrogen oxide absorption device, a first rectification device, a second rectification device and a product tank which are connected in sequence. Therefore, the waste gas and the waste liquid of the whole crystal silicon acid washing can be effectively recycled, and the acid washing cost and the hazardous waste disposal cost of the waste acid and the waste liquid are reduced.

Description

Technical Field

[0001] The present application belongs to the field of semiconductor technology, and specifically relates to a system and method for recycling waste gas and waste liquid in crystalline silicon pickling. Background Art

[0002] The main preparation process of crystalline silicon can be roughly divided into hydrogenation, distillation, reduction, crushing and pickling. Pickling mainly involves etching the silicon surface by mixing a certain ratio of nitric acid (nitric acid content is the main component) and hydrofluoric acid to reduce the surface impurity content of silicon.

[0003] The impurity content in the pickling solution gradually increases with the increase in the number of pickling times. Therefore, after a certain number of pickling times, the quality of the crystalline silicon after pickling cannot reach the level required by the enterprise, so the pickling solution needs to be replaced. The replaced pickling solution belongs to hazardous waste liquid and needs to be treated as hazardous waste. If the waste liquid after pickling is treated as hazardous waste, not only will the cost of hazardous waste disposal be high, but a large amount of nitric acid and hydrofluoric acid will be directly wasted. Therefore, the recycling process of waste gas and waste liquid in crystalline silicon pickling needs to be studied. Summary of the invention

[0004] This application is based on the inventor's discovery and understanding of the following facts and problems:

[0005] The principle of pickling solution etching crystalline silicon is: nitric acid reacts with silicon to form silicon dioxide, and silicon dioxide reacts with hydrofluoric acid to form fluorosilicic acid. The overall chemical reaction equation is: 2HNO 3 +Si+6HF=H 2 SiF 6 +3H 2 O+NO 2 +NO. For pickling as a whole, nitrogen (N) and fluorine (F) are mainly involved in pickling etching. The main reason why pickling waste liquid cannot be used is the high content of water, metal impurities and fluorosilicic acid. Among them, the metal impurities mainly come from the etching of the polysilicon surface by the mixed solution of hydrofluoric acid and nitric acid. By reducing the water content, metal impurities and fluorosilicic acid in the waste liquid, the waste liquid can be effectively recovered and reused, thereby reducing the cost of hazardous waste treatment and improving resource utilization efficiency.

[0006] The present application aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the present application proposes a system and method for recycling waste gas and waste liquid in crystalline silicon pickling with a high recycling rate or low cost.

[0007] In the first aspect of the present application, a system for recycling waste gas and waste liquid in crystalline silicon pickling is proposed. The waste gas in crystalline silicon pickling contains NO 2 and NO, the wastewater from crystalline silicon pickling contains HNO 3 , HF, H 2 SiF 6, water, and metal impurities. The system includes a photochemical reaction device, a nitrogen oxide absorption device, a first distillation device, a second distillation device, and a product tank connected in sequence. The present application recycles and treats the waste gas and waste liquid generated in the pickling of crystalline silicon through the above-mentioned device, thereby achieving effective recycling of the waste gas and waste liquid of the pickling as a whole, reducing the impurity content, reducing the purchase cost of hydrofluoric acid and nitric acid, greatly reducing the cost of pickling, and reducing the cost of hazardous waste disposal of waste acid liquid.

[0008] In some embodiments, the photochemical reaction device comprises: a reaction container, 3 The delivery assembly and UV light source, the O 3 The delivery component is connected to the reaction container and is used to deliver O to the reaction container. 3 The ultraviolet light source is arranged inside the reaction container to provide ultraviolet light. 3 environment and ultraviolet light, thereby converting NO in the waste gas from crystalline silicon pickling into NO 2 .

[0009] In some embodiments, the system for recycling waste gas and waste liquid in the crystalline silicon pickling process further comprises a fluorosilicic acid adsorption device disposed between the nitrogen oxide absorption device and the first distillation device. The device is used to separate H 2 SiF 6 , improve separation efficiency.

[0010] In some embodiments, the fluorosilicic acid adsorption device includes an adsorption material, and the adsorption material includes polyvinylidene fluoride. This is conducive to more efficient adsorption of H 2 SiF 6 .

[0011] In some embodiments, the adsorption pore size of the adsorption material is ≥ 325 meshes, which is helpful to improve the adsorption efficiency.

[0012] In some embodiments, the first distillation device and the second distillation device are in a negative pressure state; in other embodiments, the pressure in the first distillation device and the second distillation device is ≤ 0.3 bar. This is conducive to recovering the required liquid.

[0013] The second aspect of the present application proposes a method for recycling waste gas and waste liquid in silicon acid washing, comprising:

[0014] Provide waste gas and waste liquid from crystalline silicon pickling, the waste gas contains NO 2 and NO, the waste liquid contains HNO 3 , HF, H 2 SiF 6 , water, metal impurities;

[0015] The NO in the waste gas during the silicon pickling process is converted into NO 2 , to obtain NO 2 , NO, O 3 , O 2 The first gas;

[0016] The first gas is eluted with the waste liquid from the crystalline silicon pickling to remove NO in the first gas. 2 Converted to HNO 3 , to obtain HNO 3 , HF, H 2 SiF 6 , water, a first mixed liquid of metal impurities and a second gas containing NO;

[0017] Separate the H in the first mixed liquid 2 SiF 6 and water to obtain 2 SiF 6 and water, and a second mixed liquid containing HNO 3 , a third mixed liquid of HF, water, and metal impurities;

[0018] Separating HNO from the third mixed liquid 3 , HF, water, to obtain HNO 3 , a fourth mixed liquid of HF and water, and a fifth mixed liquid containing metal impurities.

[0019] The present application recycles and treats the waste gas and waste liquid generated during the pickling of crystalline silicon through the above-mentioned method, thereby achieving effective recycling of the waste gas and waste liquid of the entire pickling process, reducing the impurity content, reducing the procurement cost of hydrofluoric acid and nitric acid, significantly reducing the pickling cost, and reducing the cost of hazardous waste disposal of waste acid liquid.

[0020] In some embodiments, the H in the first mixed liquid is separated 2 SiF 6 and water, further comprising separating H 2 SiF 6 This is helpful to improve the recycling efficiency.

[0021] In some embodiments, the H in the first mixed liquid is separated 2 SiF 6 It is adsorbed by adsorption materials.

[0022] In some embodiments, the NO in the waste gas during the acid washing of the crystalline silicon is converted into NO 2 The process is carried out by introducing ozone and irradiating ultraviolet light to carry out a photochemical reaction.

[0023] In some embodiments, the molar ratio of the waste gas to ozone in the crystalline silicon acid washing is in the range of 4:1 to 6:1. This is conducive to sufficient reaction and improved conversion efficiency.

[0024] In some embodiments, the H in the first mixed liquid is separated 2 SiF 6 The separation of the organic solvent and water is carried out by a first distillation, wherein the distillation temperature of the first distillation is 65° C. to 90° C. This is beneficial to improving the separation efficiency.

[0025] In some embodiments, the HNO in the third mixed liquid is separated 3 , HF and water are separated by a second distillation, and the distillation temperature of the second distillation is 60° C. to 85° C. This is beneficial to improving the separation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of a system for recycling waste gas and waste liquid in crystalline silicon pickling according to an embodiment of the present application.

[0027] Figure 2 This is a schematic diagram of a system for recycling waste gas and waste liquid in crystalline silicon pickling according to an embodiment of the present application.

[0028] Figure 3 It is a schematic diagram of the process flow for recycling waste gas and waste liquid in crystalline silicon pickling according to an embodiment of the present application.

[0029] Figure 4 It is a schematic diagram of the process flow for recycling waste gas and waste liquid in crystalline silicon pickling according to an embodiment of the present application. DETAILED DESCRIPTION

[0030] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, but cannot be understood as limiting the present application.

[0031] In the first aspect of the present application, a system for recycling waste gas and waste liquid in crystalline silicon pickling is proposed. The waste gas in crystalline silicon pickling contains NO 2 and NO, the wastewater from crystalline silicon pickling contains HNO 3 , HF, H 2 SiF 6 , water, metal impurities, refer to Figure 1 , the system comprises:

[0032] Photochemical reaction device 1, used to convert NO in the waste gas during the silicon pickling process into NO 2 , to obtain NO 2 , NO, O 3 , O 2The first gas;

[0033] The nitrogen oxide absorption device 2 is connected to the photochemical reaction device 1, and uses the waste liquid in the crystalline silicon acid washing to wash the first gas to remove NO in the first gas. 2 Converted to HNO 3 , to obtain HNO 3 , HF, H 2 SiF 6 , water, a first mixed liquid of metal impurities and a second gas containing NO;

[0034] The first rectification device 3 is connected to the nitrogen oxide absorption device 2 and is used to separate the H 2 SiF 6 and water to obtain 2 SiF 6 and water, and a second mixed liquid containing HNO 3 , a third mixed liquid of HF, water, and metal impurities;

[0035] The second distillation device 4 is connected to the first distillation device 3 and is used to separate HNO in the third mixed liquid. 3 , HF, water, to obtain HNO 3 , a fourth mixed liquid of HF and water, and a fifth mixed liquid containing metal impurities;

[0036] The product tank 5 is connected to the second distillation device 4 and is used to collect the HNO 3 The fourth mixed liquid is composed of HF and water.

[0037] The present application recycles and treats the waste gas and waste liquid generated during the pickling of crystalline silicon through the above-mentioned device, thereby achieving effective recycling of the waste gas and waste liquid of the entire pickling process, reducing the impurity content, reducing the procurement cost of hydrofluoric acid and nitric acid, significantly reducing the pickling cost, and reducing the cost of hazardous waste disposal of the waste acid liquid.

[0038] In some embodiments, the photochemical reaction device comprises: a reaction container, 3 The delivery assembly and UV light source, the O 3 The delivery component is connected to the reaction container and is used to deliver O to the reaction container. 3 The ultraviolet light source is arranged inside the reaction container to provide ultraviolet light. Thus, NO in the waste gas during the acid washing of crystalline silicon can be converted into NO 2 .

[0039] In some embodiments, the system for recycling waste gas and waste liquid in crystalline silicon pickling further comprises:

[0040] a first delivery pump, disposed between the nitrogen oxide absorption device and the first distillation device, for delivering the first mixed liquid to the first distillation device;

[0041] The second delivery pump is connected to the first distillation device and is used to discharge the H 2 SiF 6 and a second mixed liquid of water, and the HNO 3 , HF, water, and a third mixed liquid of metal impurities are refluxed to the first rectification device;

[0042] The third delivery pump is arranged between the first distillation device and the second distillation device, and is used to deliver the HNO 3 , HF, water, and a third mixed liquid of metal impurities are transported to the second rectification device;

[0043] A fourth delivery pump is connected to the second distillation device and is used to discharge the HNO 3 , HF, and water, and refluxing the fifth mixed liquid containing metal impurities to the second rectification device;

[0044] A fifth delivery pump is connected to the second distillation device and is used for discharging the fifth mixed liquid containing metal impurities.

[0045] It should be noted that the first distillation device includes a first distillation tower, a first reboiler and a first condenser. The first reboiler is used to heat the first mixed liquid, and the first condenser is used to separate H 2 SiF 6 The second distillation device comprises a second distillation tower, a second reboiler and a second condenser, wherein the second reboiler is used to heat the third mixed liquid, and the second condenser is used to separate the HNO in the third mixed liquid. 3 , HF, water.

[0046] In some embodiments, reference Figure 2 The system for recycling waste gas and waste liquid in the crystalline silicon pickling process further comprises a fluorosilicic acid adsorption device 6, which is arranged between the nitrogen oxide absorption device and the first distillation device, and is used to separate H in the first mixed liquid. 2 SiF 6 , to obtain HNO 3 The sixth mixed liquid of HF, water and metal impurities.

[0047] In some embodiments, the fluorosilicic acid adsorption device includes an adsorption material, and the adsorption material includes polyvinylidene fluoride. This is conducive to more efficient adsorption of H 2 SiF 6 .

[0048] In some embodiments, the adsorption pore size of the adsorption material is ≥ 325 mesh, for example, it can be 325 mesh, 330 mesh, 335 mesh, 340 mesh, 345 mesh or 350 mesh, etc. This is beneficial to improve the adsorption efficiency.

[0049] In some embodiments, the first rectification device and the second rectification device are in a negative pressure state; in other embodiments, the pressure in the first rectification device and the second rectification device is ≤ 0.3 bar, for example, it can be 0.05 bar, 0.1 bar, 0.15 bar, 0.2 bar, 0.25 bar or 0.3 bar, etc. This is conducive to separating the desired liquid.

[0050] The second aspect of the present application proposes a method for recycling waste gas and waste liquid in crystalline silicon pickling, comprising:

[0051] S1: Provide waste gas and waste liquid from crystalline silicon pickling, the waste gas contains NO 2 and NO, the waste liquid contains HNO 3 , HF, H 2 SiF 6 , water, metal impurities.

[0052] Among them, crystalline silicon can be either single crystal silicon or polycrystalline silicon. The principle of etching silicon with pickling solution is: nitric acid reacts with crystalline silicon to form silicon dioxide, and silicon dioxide reacts with hydrofluoric acid to form fluorosilicic acid. The overall chemical reaction equation is: 2HNO 3 +Si+6HF=H 2 SiF 6 +3H 2 O+NO 2 +NO. The main reason why pickling waste liquid cannot be used is the high content of water, metal impurities and fluorosilicic acid. The present application can achieve effective recovery and reuse of waste liquid by reducing the content of water, metal impurities and fluorosilicic acid in the waste liquid, thereby reducing the cost of hazardous waste treatment and improving resource utilization efficiency.

[0053] S2: Converting NO in the waste gas during the crystalline silicon pickling process into NO 2 , to obtain NO 2 , NO, O 3 , O 2 The first gas.

[0054] In this step, NO is converted to NO 2 The method can be a photochemical reaction, specifically, ozone can be introduced and ultraviolet light can be irradiated to carry out the photochemical reaction. The molar ratio of the waste gas to ozone in the crystalline silicon pickling is in the range of 4:1 to 6:1, for example, 4:1, 5:1 or 6:1. This is conducive to sufficient reaction and improved conversion efficiency.

[0055] During the pickling process, NO is generated in the pickling line. 2 and NO gas, NO 2 After NO and NO enter the photochemical reaction device, NO and O 3 The reaction generates NO 2 and O 2 , NO and O 2 The reaction generates NO 2 Specific chemical reaction equations such as: NO+O 3 =NO 2 +O 2 、2NO+O 2 =2NO 2 It is understandable that in most cases, NO is not completely converted into NO in the photochemical reaction device. 2 , so the first gas contains NO 2 and unreacted NO, O 3 , O 2 .

[0056] S3: eluting the first gas with the waste liquid from the crystalline silicon pickling to remove NO 2 Converted to HNO 3 , to obtain HNO 3 , HF, H 2 SiF 6 , water, a first mixed liquid of metal impurities and a second gas containing NO.

[0057] It is understandable that the NO generated by the photochemical reaction device 2 After entering the nitrogen oxide absorption device, the nitrogen oxides are converted into HNO by spraying 3 , the spray liquid source is waste liquid. NO 2 HNO is formed by spraying 3 and NO. The specific chemical reaction equation is as follows: 2 O+NO 2 =HNO 3 +NO, the generated NO enters the photochemical reaction device to continue to form NO 2 This operation not only keeps the nitrogen content in the pickling process unchanged, but also increases the HNO 3 content, convenient for subsequent operations.

[0058] S4: Separating H from the first mixed liquid 2 SiF 6 and water to obtain 2 SiF 6 and water, and a second mixed liquid containing HNO 3, HF, water, and a third mixed liquid of metal impurities.

[0059] In some embodiments, the H in the first mixed liquid is separated 2 SiF 6 The addition of water is carried out by a first distillation, wherein the distillation temperature of the first distillation is 65°C to 90°C, for example, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C.

[0060] It can be understood that after the first mixed liquid enters the first distillation device through the first delivery pump, the first mixed liquid is heated by the first reboiler, and the top gas is condensed by the first condenser to form H 2 SiF 6 and water, and then discharged through the second delivery pump, and the remaining liquid (i.e., the third mixed liquid) flows back to the first distillation device.

[0061] S5: Separating HNO from the third mixed liquid 3 , HF, water, to obtain HNO 3 , a fourth mixed liquid of HF and water, and a fifth mixed liquid containing metal impurities.

[0062] In some embodiments, the HNO in the third mixed liquid is separated 3 , HF and water are removed by a second distillation, and the distillation temperature of the second distillation is 60°C to 85°C, for example, 65°C, 70°C, 75°C, 80°C or 85°C.

[0063] It can be understood that the third mixed liquid in the bottom of the first distillation unit enters the second distillation unit through the third delivery pump, is first heated by the second reboiler, and the top gas is condensed by the second condenser to form HNO 3 , HF, water, and then enter the product tank through the fourth delivery pump. The metal impurities in the tower bottom are discharged through the fifth delivery pump. The metal impurities include B, Na, Mg, Al, K, Ca, P, Cr, Fe, Ni, Cu, Zn and other elements, which exist in the form of ions.

[0064] The above-mentioned recycling method of the present application has at least the following beneficial effects:

[0065] (1) The effective recycling of waste gas and waste liquid from pickling is achieved, and the impurity content is reduced to the pptw level, which reduces the purchase cost of nitric acid and hydrofluoric acid and significantly reduces the pickling cost of the enterprise;

[0066] (2) Reduce the cost of hazardous waste disposal of waste acid liquid.

[0067] In some embodiments, the H in the first mixed liquid is separated 2 SiF 6and water, further comprising separating H 2 SiF 6 For example, it can be carried out through a fluorosilicic acid adsorption device, and the adsorbed fluorosilicic acid has high purity and can be used as a raw material for producing white carbon black and hydrofluoric acid. This is conducive to improving the recovery efficiency.

[0068] According to the embodiments of the present application, referring to Figure 3 The method for recycling the waste gas and waste liquid generated in the pickling of crystalline silicon specifically includes:

[0069] (1) NO is generated in the pickling line 2 and NO gas enter the photochemical reaction device, under the influence of ultraviolet light and O 3 In the environment, NO 2 Convert to NO, NO 2 Enter the nitrogen oxide absorption device;

[0070] (2) NO 2 HNO is formed by spraying the waste acid raw material 3 and NO, the generated NO enters the photochemical reaction device to continue to form NO 2 , at this time, the liquid in the nitrogen oxide device is a No. 0 mixed liquid;

[0071] (3) Mixed liquid No. 0 enters distillation tower 1 through pump 0A, and the first mixed liquid is heated through reboiler 1. The top gas passes through condenser 1 to form mixed liquid No. 1, and part of H is removed through pump 1B. 2 O and H 2 SiF 6 , the remaining liquid is refluxed to tower 1;

[0072] (4) The remaining liquid in the bottom of tower 1 enters tower 2 through pump 1A. The gas at the top of tower 2 passes through condenser 2 to form mixed liquid No. 2, which is then pumped through pump 2B to remove part of the H 2 O、HNO 3 and HF products, part of which is refluxed to tower 2. The metal impurities in the kettle of tower 2 are removed by pump 2A.

[0073] According to the embodiments of the present application, referring to Figure 4 The method for recycling the waste gas and waste liquid generated in the pickling of crystalline silicon specifically includes:

[0074] (1) NO is generated in the pickling line 2 and NO gas enter the photochemical reaction device, under the influence of ultraviolet light and O 3 In the environment, NO 2 Convert to NO, NO 2 Enter the nitrogen oxide absorption device;

[0075] (2) NO 2 HNO is formed by spraying the waste acid raw material3 and NO, the generated NO enters the photochemical reaction device to continue to form NO 2 , at this time, the liquid in the nitrogen oxide device is a No. 0 mixed liquid;

[0076] (3) The No. 0 mixed liquid enters the fluorosilicic acid adsorption device to remove H 2 SiF 6 At this time, the remaining liquid in the fluorosilicic acid adsorption device is mixed liquid No. 1;

[0077] (4) Mixed liquid No. 1 enters distillation tower 1 through pump 0A, and the first mixed liquid is heated through reboiler 1. The top gas passes through condenser 1 to form mixed liquid No. 2, which is then pumped through pump 1B to remove some H 2 O, the rest of the liquid is refluxed to tower 1;

[0078] (5) The remaining liquid in the bottom of tower 1 enters tower 2 through pump 1A. The gas at the top of tower 2 passes through condenser 2 to form mixed liquid No. 3, which is then pumped through pump 2B to remove some H 2 O、HNO 3 and HF products, part of which is refluxed to tower 2. The metal impurities in the kettle of tower 2 are removed by pump 2A.

[0079] The embodiments of the present application are described in detail below.

[0080] Example 1

[0081] (1) Provide waste gas and waste liquid from crystalline silicon pickling. The waste gas contains NO 2 and NO, the waste liquid contains HNO 3 , HF, H 2 SiF 6 , water, metal impurities;

[0082] (2) the waste gas from the crystalline silicon pickling enters the photochemical reaction device and provides ozone and ultraviolet light sources, wherein the molar ratio of the waste gas to the ozone is 4:1;

[0083] (3) using the waste liquid from the acid washing of crystalline silicon to elute the gas generated by the reaction in step (2) in a nitrogen oxide absorption device;

[0084] (4) The mixed liquid generated in step (3) enters the first distillation device for distillation at a distillation temperature of 65° C. and a distillation pressure of 0.05 bar, and discharges fluorosilicic acid and part of the water;

[0085] (5) The remaining liquid from the first distillation unit enters the second distillation unit for further distillation at a distillation temperature of 60°C and a distillation pressure of 0.05 bar. The distilled liquid enters the product tank.

[0086] Example 2

[0087] (1) Provide waste gas and waste liquid from crystalline silicon pickling. The waste gas contains NO 2 and NO, the waste liquid contains HNO 3 , HF, H 2 SiF 6 , water, metal impurities;

[0088] (2) the waste gas from the crystalline silicon pickling enters the photochemical reaction device and provides ozone and ultraviolet light sources, wherein the molar ratio of the waste gas to the ozone is 5:1;

[0089] (3) using the waste liquid from the acid washing of crystalline silicon to elute the gas generated by the reaction in step (2) in a nitrogen oxide absorption device;

[0090] (4) The mixed liquid generated in step (3) enters the first distillation device for distillation at a distillation temperature of 75° C. and a distillation pressure of 0.15 bar, and discharges fluorosilicic acid and part of the water;

[0091] (5) The remaining liquid in the first distillation device enters the second distillation device for further distillation at a distillation temperature of 70°C and a distillation pressure of 0.15 bar. The distilled liquid enters the product tank.

[0092] Example 3

[0093] (1) Provide waste gas and waste liquid from crystalline silicon pickling. The waste gas contains NO 2 and NO, the waste liquid contains HNO 3 , HF, H 2 SiF 6 , water, metal impurities;

[0094] (2) The waste gas from the crystalline silicon pickling enters the photochemical reaction device and provides ozone and ultraviolet light sources, wherein the molar ratio of the waste gas to the ozone is 6:1;

[0095] (3) using the waste liquid from the acid washing of crystalline silicon to elute the gas generated by the reaction in step (2) in a nitrogen oxide absorption device;

[0096] (4) the mixed liquid generated in step (3) enters a fluorosilicic acid adsorption device, the material of the fluorosilicic acid adsorption device is polyvinylidene fluoride, and the adsorption pore size is 325 meshes. This step can discharge fluorosilicic acid;

[0097] (5) The remaining liquid in step (4) enters the first distillation device for distillation at a distillation temperature of 85° C. and a distillation pressure of 0.25 bar, and discharges fluorosilicic acid and part of the water;

[0098] (6) The remaining liquid in the first distillation device enters the second distillation device for further distillation at a distillation temperature of 80°C and a distillation pressure of 0.25 bar. The distilled liquid enters the product tank.

[0099] The recovery system and method described in this application are used to recycle the waste gas and waste liquid after polysilicon pickling. ICP-MS is used to detect the impurity content of the product in the product tank. The test results are shown in the following table.

[0100] Table 1 Impurity content of products in product tanks (unit: pptw (ng / Kg))

[0101] element B Na Mg Al K Ca P Cr Fe Ni Cu Zn Example 1 36 69 153 128 14 51 12 8 259 7 7 75 Example 2 15 25 73 63 34 128 1 5 126 1 2 32 Example 3 13 32 72 25 58 171 12 2 247 2 4 7

[0102] By testing the product in the product tank, the total nitrogen content in the product tank is balanced with the total nitrogen content of the original pickling. The process achieves effective recycling of waste gas and waste liquid in the pickling system. In addition, the metal impurity content of the recovered acid product is tested, and the main impurity content reaches the pptw level, which has met the requirements for polysilicon pickling, and the product can be recycled and reused.

[0103] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0104] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0105] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0106] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A system for recycling waste gas and waste liquid in crystalline silicon pickling, characterized in that: The waste gas from crystalline silicon pickling contains NO2 and NO, and the waste liquid from crystalline silicon pickling contains HNO3, HF, H2SiF6, water, and metal impurities. The system includes a photochemical reaction device, a nitrogen oxide absorption device, a first distillation device, a second distillation device, and a product tank connected in sequence.

2. The system according to claim 1, characterized in that The photochemical reaction device comprises: a reaction container, an O3 transport component and an ultraviolet light source. The O3 transport component is connected to the reaction container and is used to transport O3 into the reaction container. The ultraviolet light source is arranged inside the reaction container and is used to provide ultraviolet light.

3. The system according to claim 1, characterized in that The system for recycling waste gas and waste liquid in crystalline silicon pickling also includes a fluorosilicic acid adsorption device, which is arranged between the nitrogen oxide absorption device and the first distillation device.

4. The system according to claim 3, characterized in that The fluorosilicic acid adsorption device comprises an adsorption material, and the adsorption material comprises polyvinylidene fluoride.

5. The system according to claim 4, characterized in that The adsorption pore size of the adsorption material is ≥325 meshes.

6. The system according to claim 1, characterized in that The first distillation device and the second distillation device are in a negative pressure state, preferably with a pressure of ≤0.3 bar.

7. A method for recycling waste gas and waste liquid in crystalline silicon pickling, characterized in that: include: Providing waste gas and waste liquid from crystalline silicon pickling, wherein the waste gas contains NO2 and NO, and the waste liquid contains HNO3, HF, H2SiF6, water, and metal impurities; Converting NO in the waste gas during the acid washing of the crystalline silicon into NO2 to obtain a first gas containing NO2, NO, O3, and O2; The first gas is eluted with the waste liquid in the crystalline silicon pickling to convert NO2 in the first gas into HNO3, thereby obtaining a first mixed liquid containing HNO3, HF, H2SiF6, water, and metal impurities and a second gas containing NO; Separating H2SiF6 and water in the first mixed liquid to obtain a second mixed liquid containing H2SiF6 and water, and a third mixed liquid containing HNO3, HF, water, and metal impurities; The HNO 3 , HF and water in the third mixed liquid are separated to obtain a fourth mixed liquid containing HNO 3 , HF and water, and a fifth mixed liquid containing metal impurities.

8. The method according to claim 7, characterized in that Before separating H2SiF6 and water in the first mixed liquid, the method further includes separating H2SiF6 in the first mixed liquid.

9. The method according to claim 8, characterized in that The H2SiF6 in the first mixed liquid is separated by adsorption by an adsorption material.

10. The method according to claim 7, characterized in that The NO in the waste gas during the acid washing of the crystalline silicon is converted into NO2 by introducing ozone and simultaneously irradiating with ultraviolet light to carry out a photochemical reaction.

11. The method according to claim 10, characterized in that The molar ratio of the waste gas to ozone in the crystalline silicon pickling is in the range of 4:1 to 6:

1.

12. The method according to claim 7, characterized in that Separating H2SiF6 and water in the first mixed liquid is performed by a first distillation, and the distillation temperature of the first distillation is 65°C to 90°C.

13. The method according to claim 7, characterized in that The separation of HNO3, HF and water in the third mixed liquid is carried out by a second distillation, and the distillation temperature of the second distillation is 60°C to 85°C.

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