Hydrofluoric acid waste liquid recycling device for photovoltaic cell BSG and PSG production sections and use method of hydrofluoric acid waste liquid recycling device

Abstract

The invention relates to a photovoltaic cell BSG and PSG production section hydrofluoric acid waste liquid recycling device and a use method, and the device comprises a hydrofluoric acid collection device, a chemical reaction device, a precipitation separation filtering device, a rectification purification device, a hydrofluoric acid recovery storage tank, a pure water recovery storage tank, pipelines connected between the hydrofluoric acid recovery storage tank and the pure water recovery storage tank, and the like. The hydrofluoric acid collecting device is respectively connected with the PSG industrial pickling tank and the BSG industrial pickling tank, the chemical reaction device and the settling separation filtering device are sequentially connected behind the hydrofluoric acid collecting device, and separated liquid enters the rectification purification device to be rectified and purified. The rectified and purified substances respectively enter a hydrofluoric acid recovery storage tank and a pure water recovery storage tank, and the hydrofluoric acid recovery storage tank is respectively connected with the PSG industrial pickling bath and the BSG industrial pickling bath for recycling. The device has the advantages of simple and reasonable structure, economy, environmental protection, stable operation and the like.

Description

Technical Field

[0001] The present invention belongs to the field of waste liquid recovery and environmental protection and resource recycling in the photovoltaic industry, and relates to a hydrofluoric acid waste liquid recycling device and a method for using the same in a photovoltaic cell BSG and PSG production section. Background Art

[0002] The photovoltaic cell industry has a huge demand for chemicals, especially in the cleaning and etching processes, and especially in the demand for hydrofluoric acid.

[0003] Hydrofluoric acid is an aqueous solution of hydrogen fluoride gas. When the temperature is below 20°C, hydrogen fluoride can be miscible with water in any proportion. Hydrofluoric acid is a colorless, fuming, corrosive liquid with a strong irritating odor.

[0004] Hydrofluoric acid is a weak acid but extremely corrosive and can strongly corrode metals, glass, and objects containing silicon.

[0005] When boron diffuses, a very thin layer of borosilicate glass (BSG for short) is formed on the surface of the silicon wafer. Borosilicate glass is conductive. In order to form a good ohmic contact, the borosilicate glass needs to be corroded and removed. The borosilicate glass is cleaned with hydrofluoric acid to remove it.

[0006] When phosphorus diffuses, a phosphosilicate glass layer (PSG) will be formed on the front and edge of the silicon wafer. The presence of phosphosilicate glass makes the surface of the silicon wafer susceptible to moisture, resulting in a decrease in current and power attenuation. Therefore, the phosphosilicate glass layer needs to be corroded and removed, and hydrofluoric acid is used to clean and remove the phosphosilicate glass.

[0007] The chemical reaction process of hydrofluoric acid cleaning of BSG and PSG sections is as follows: SiO2+6HF=H2SiF6+2H2O After a period of use, hydrofluoric acid will be discharged regularly due to high impurity content and gradually reduced concentration. At present, hydrofluoric acid waste liquid is mainly treated by precipitation process, that is, adding lime, calcium chloride, PAC and PAM and other agents to the wastewater containing hydrofluoric acid to make fluoride ions form precipitated compounds to achieve the purpose of removing fluoride. The wastewater treated by this method needs to be sent to the sewage treatment plant for further treatment, which will also increase solid waste pollution. In addition, a large amount of chemical agents are needed to remove fluoride ions, which is not only uneconomical but also not environmentally friendly.

[0008] Therefore, a device and a method for recycling hydrofluoric acid waste liquid in the production section of photovoltaic cell BSG and PSG are designed to overcome the above problems. Summary of the invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a photovoltaic cell BSG and PSG production section hydrofluoric acid waste liquid recycling device and a method of use which has a simple and reasonable structure, is economical and environmentally friendly, has stable operation, a simple process flow, a high waste liquid recycling utilization rate, and has good practical value and economic benefits.

[0010] The present invention is realized through the following technical scheme: a device for recycling hydrofluoric acid waste liquid in the production section of photovoltaic cell BSG and PSG, the device comprising a hydrofluoric acid collecting device, a chemical reaction device, a precipitation separation and filtration device and a distillation and purification device, a hydrofluoric acid recovery storage tank and a pure water recovery storage tank and pipelines connected therebetween, the hydrofluoric acid collecting device is respectively connected to the PSG industrial pickling tank and the BSG industrial pickling tank, the rear of the hydrofluoric acid collecting device is sequentially connected to the chemical reaction device and the sedimentation separation and filtration device, the separated liquid enters the distillation and purification device for distillation and purification, the distilled and purified substances enter the hydrofluoric acid recovery storage tank and the pure water recovery storage tank respectively, the hydrofluoric acid recovery storage tank is respectively connected to the PSG industrial pickling tank and the BSG industrial pickling tank for recycling.

[0011] Preferably, the chemical reaction device is further connected to a NaF liquid preparation tank, which is connected to a pure water recovery tank, and the liquid is prepared by using pure water in the pure water recovery tank and externally supplied NaF, and the prepared NaF solution enters the chemical reaction device for chemical reaction.

[0012] Preferably, the pure water recovery tank is provided with a pipeline connected to the PSG industrial pickling tank, a reflux pipeline connected to the hydrofluoric acid recovery tank, and a water replenishment pipeline is provided outside the pure water recovery tank to achieve the functions of recycling and recycling after replenishment.

[0013] Preferably, the hydrofluoric acid recovery tank is provided with a reflux pipeline for reflux to the PSG industrial pickling tank and the BSG industrial pickling tank, and the hydrofluoric acid recovery tank is also provided with an external pipeline for replenishing hydrofluoric acid.

[0014] Preferably, the distillation and purification device includes a dehydration distillation tower and a concentration distillation tower.

[0015] A method for using a hydrofluoric acid waste liquid recycling device in a photovoltaic cell BSG and PSG production section, the method comprising the following steps: 1) The hydrofluoric acid waste liquid from the BSG section and the hydrofluoric acid waste liquid from the PSG section flow into the PSG industrial pickling tank and the BSG industrial pickling tank and then enter the hydrofluoric acid collection device together for mixing; 2) Prepare a 10%-20% concentration NaF solution by mixing the pure water in the pure water recovery tank and the external NaF in the NaF solution tank; 3) The hydrofluoric acid waste liquid and the sodium fluoride solution enter the chemical reaction device at the same volume flow rate, and the reaction residence time is 5-10 minutes; 4) The logistics from the chemical reaction device directly enters the precipitation separation and filtration device, the filtrate at the bottom of the precipitation separation and filtration device is sent to the centrifuge for further dehydration, and the sodium fluorosilicate product is obtained from the centrifuge. The supernatant liquid on the sedimentation tank is sent to the distillation and purification device for distillation operation; 5) The operating pressure of the dehydration distillation tower in the distillation purification device is between 120-200kPa. Pure water is obtained at the top of the distillation tower. The hydrofluoric acid content of the pure water is less than 2000ppm. The pure water is sent to the pure water recovery tank. The hydrofluoric acid solution is enriched at the bottom of the dehydration distillation tower and sent to the hydrofluoric acid concentration tower for further purification; 6) The operating pressure of the hydrofluoric acid concentration tower is between 110-190 kPa. The hydrofluoric acid product with a concentration of 36% at the top of the concentration tower enters the hydrofluoric acid recovery tank, and the hydrofluoric acid coming out of the top of the concentration tower enters the hydrofluoric acid recovery tank for storage; 7) One stream of hydrofluoric acid solution from the hydrofluoric acid recovery tank is directly transported to the BSG industrial pickling tank for use, and the other stream is connected to the PSG industrial pickling tank. According to the cleaning requirements of the PSG section, a stream of pure water is sent from the pure water recovery tank. The hydrofluoric acid recovery rate reaches 97%, and the pure water recovery rate reaches 98%.

[0016] As a preference, the chemical reaction process in the chemical reaction device in step 3) is as follows: H2SiF6+2NaF= Na2SiF6+2HF.

[0017] The beneficial effects of the present invention are as follows: The present invention recycles the hydrofluoric acid waste liquid in the BSG and PSG production sections of photovoltaic cells. This method greatly reduces sewage discharge, reduces the high-fluorine waste liquid treatment and investment costs, improves the utilization efficiency of hydrofluoric acid and reduces sludge solid waste discharge. The recovery rate of hydrofluoric acid in the present invention can reach more than 95%, the recovery rate of pure water can reach more than 95%, and sodium fluorosilicate products are richly produced, which greatly improves the economic and environmental value of the recycling of hydrofluoric acid cleaning waste liquid in the BSG section and PSG section of photovoltaic cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to more clearly understand the objectives, technical solutions and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0020] In the description of the present invention, it is necessary to understand that the orientation or position relationship indicated by the terms such as "up", "down", "left", "right", "inside", "outside", "horizontal" and "vertical" is based on the orientation or position relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or original referred to must have a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0021] The present invention will be described in detail below with reference to the accompanying drawings: Figure 1 As shown, a hydrofluoric acid waste liquid recycling device for the BSG and PSG production sections of photovoltaic cells, the device comprises a hydrofluoric acid collecting device 1, a chemical reaction device 2, a sedimentation separation and filtration device 3 and a distillation and purification device 4, a hydrofluoric acid recovery tank 5 and a pure water recovery tank 6 and pipelines connected therebetween, the hydrofluoric acid collecting device 1 is respectively connected to the PSG industrial pickling tank 7 and the BSG industrial pickling tank 8, the rear of the hydrofluoric acid collecting device 1 is sequentially connected to the chemical reaction device 2 and the sedimentation separation and filtration device 3, the separated liquid enters the distillation and purification device 4 for distillation and purification, the distilled and purified substances enter the hydrofluoric acid recovery tank 5 and the pure water recovery tank 6 respectively, the hydrofluoric acid recovery tank 5 is respectively connected to the PSG industrial pickling tank 7 and the BSG industrial pickling tank 8 for recycling.

[0022] The chemical reaction device 2 is also connected to a NaF liquid preparation tank 9, which is connected to a pure water recovery tank 6. The pure water in the pure water recovery tank 6 and the externally supplied NaF are used for liquid preparation, and the prepared NaF solution enters the chemical reaction device 2 for chemical reaction.

[0023] The NaF solution preparation tank is used to prepare a certain concentration of NaF solution according to needs, and the raw water is prepared using water from the pure water recovery storage tank 6.

[0024] The pure water recovery storage tank 6 is provided with a pipeline connected to the PSG industrial pickling tank 7, and is also provided with a reflux pipeline connected to the hydrofluoric acid recovery storage tank 5. In addition, a water replenishment pipeline 12 is also opened outside the pure water recovery storage tank 6 to achieve the functions of recycling and recycling after replenishment.

[0025] The hydrofluoric acid recovery storage tank 5 is provided with a reflux pipeline 10 for reflux to the PSG industrial pickling tank 7 and the BSG industrial pickling tank 8, and the hydrofluoric acid recovery storage tank 5 is also provided with an external pipeline 11 for replenishing hydrofluoric acid.

[0026] The distillation and purification device 4 includes a dehydration distillation tower and a concentration distillation tower.

[0027] A method for using a hydrofluoric acid waste liquid recycling device in a photovoltaic cell BSG and PSG production section, the method comprising the following steps: 1) The hydrofluoric acid waste liquid from the BSG section and the hydrofluoric acid waste liquid from the PSG section flow into the PSG industrial pickling tank 7 and the BSG industrial pickling tank 8 and then enter the hydrofluoric acid collection device 1 together for mixing; 2) Prepare a NaF solution with a concentration of 10%-20%, and mix the pure water in the pure water recovery tank 6 and the external NaF in the NaF solution preparation tank; 3) The hydrofluoric acid waste liquid and the sodium fluoride solution enter the chemical reaction device 2 at the same volume flow rate, and the reaction residence time is 5-10 minutes; 4) The logistics from the chemical reaction device 2 directly enters the precipitation separation and filtration device 3, the filtrate at the bottom of the precipitation separation and filtration device 3 is sent to the centrifuge for further dehydration, and the sodium fluorosilicate product is obtained from the centrifuge. The supernatant liquid in the sedimentation tank is sent to the distillation and purification device 4 for distillation operation; 5) The operating pressure of the dehydration distillation tower in the distillation purification device 4 is between 120-200 kPa, and pure water is obtained at the top of the distillation tower. The hydrofluoric acid content of the pure water is less than 2000 ppm. The pure water is sent to the pure water recovery tank 6, and the hydrofluoric acid solution is enriched at the bottom of the dehydration distillation tower and sent to the hydrofluoric acid concentration tower for further purification; 6) The operating pressure of the hydrofluoric acid concentration tower is between 110-190 kPa, the hydrofluoric acid product with a concentration of 36% at the top of the concentration tower enters the hydrofluoric acid recovery tank 5, and the hydrofluoric acid coming out of the top of the concentration tower enters the hydrofluoric acid recovery tank 5 for storage; 7) One stream of hydrofluoric acid solution from the hydrofluoric acid recovery tank 5 is directly transported to the BSG industrial pickling tank 8 for use, and the other stream is connected to the PSG industrial pickling tank 7. According to the cleaning requirements of the PSG section, a stream of pure water is sent from the pure water recovery tank. The hydrofluoric acid recovery rate reaches 97%, and the pure water recovery rate reaches 98%.

[0028] The chemical reaction process in the chemical reaction device in step 3) is as follows: H2SiF6+2NaF= Na2SiF6+2HF.

[0029] The working process and working characteristics of the present invention are as follows: The material from the chemical reaction device is sent to the sedimentation separation and filtration device. The reacted material first enters the sedimentation tank for sedimentation separation. The filter material in the sedimentation tank enters the centrifuge for dehydration and separation in the centrifuge to obtain the product sodium fluorosilicate. The filtrate from the sedimentation tank is sent to the distillation and purification device.

[0030] The filtrate from the sedimentation tank is connected to the distillation and purification device. The filtrate first enters the dehydration distillation tower, where hydrofluoric acid and water are separated. A pure water product containing a trace amount of HF is obtained at the top of the tower, and the pure water is sent to the pure water recovery storage tank 6. A high concentration of hydrofluoric acid solution is obtained at the bottom of the tower. The hydrofluoric acid at the bottom of the tower is sent to the concentration distillation tower for further purification. A high concentration hydrofluoric acid product that meets the requirements of the BSG section entrance is obtained at the top of the concentration distillation tower. The COA impurity index of the hydrofluoric acid product meets the EL grade requirements. The hydrofluoric acid product at the top of the tower is sent to the hydrofluoric acid recovery storage tank.

[0031] The hydrofluoric acid recovery tank is equipped with a hydrofluoric acid replenishment and water replenishment pipeline. When the hydrofluoric acid in the hydrofluoric acid recovery tank is insufficient, a certain amount of hydrofluoric acid is replenished from outside the boundary. At the same time, according to the requirements of the BSG section on the cleaning concentration, a certain amount of pure water is added. The water replenishment pipeline is connected to the pure water recovery tank 6.

[0032] The pure water recovery storage tank 6 is provided with a supplementary pure water pipeline, and water is supplied through the supplementary water pipeline only when the device is insufficient in pure water. The pure water recovery tank supplies water to the PSG section, the NaF liquid preparation tank and the hydrofluoric acid recovery storage tank respectively, and they are connected by pipelines.

[0033] Example 1 The hydrofluoric acid waste liquid from the BSG section and the hydrofluoric acid waste liquid from the PSG section enter the hydrofluoric acid waste liquid collection tank together, and are prepared with a 10% concentration of NaF solution. The hydrofluoric acid waste liquid and the sodium fluoride solution enter the chemical reaction device at the same volume flow rate. The reaction residence time is 5 minutes. The logistics coming out of the reaction tank directly enters the sedimentation tank. The filtrate in the lower layer of the sedimentation tank is sent to the centrifuge for further dehydration. The sodium fluorosilicate product is obtained from the centrifuge. The upper clear liquid of the sedimentation tank is sent to the dehydration distillation tower. The operating pressure of the dehydration distillation tower is 124kPa. Pure water (hydrofluoric acid is less than 2000ppm) is obtained at the top of the dehydration distillation tower. The pure water is sent to the pure water recovery tank The hydrofluoric acid solution is enriched at the bottom of the dehydration distillation tower and sent to the hydrofluoric acid concentration tower for further purification. The operating pressure of the concentration distillation tower is 119kPa. The hydrofluoric acid product with a concentration of 36% at the top of the concentration tower enters the hydrofluoric acid recovery tank. The COA impurity index of the hydrofluoric acid product meets the EL grade requirements. The hydrofluoric acid coming out of the top of the concentration tower can be directly used by BSG. One stream of the hydrofluoric acid solution coming out of the hydrofluoric acid recovery tank is directly transported to the BSG industrial pickling tank for use, and the other stream is connected to the PSG industrial pickling tank. According to the cleaning requirements of the PSG section, a stream of pure water is sent from the pure water recovery tank. The hydrofluoric acid recovery rate reaches 97%, and the pure water recovery rate reaches 98%.

[0034] The specific embodiments described herein are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A device for recycling hydrofluoric acid waste liquid in the production section of photovoltaic cell BSG and PSG, characterized by: The device comprises a hydrofluoric acid collecting device, a chemical reaction device, a sedimentation separation and filtration device, a distillation and purification device, a hydrofluoric acid recovery tank and a pure water recovery tank and pipelines connected therebetween; the hydrofluoric acid collecting device is respectively connected to a PSG industrial pickling tank and a BSG industrial pickling tank; the rear of the hydrofluoric acid collecting device is sequentially connected to a chemical reaction device and a sedimentation separation and filtration device; the separated liquid enters the distillation and purification device for distillation and purification; the distilled and purified substances enter the hydrofluoric acid recovery tank and the pure water recovery tank respectively; the hydrofluoric acid recovery tank is respectively connected to the PSG industrial pickling tank and the BSG industrial pickling tank for cyclic use.

2. The photovoltaic cell BSG and PSG production section hydrofluoric acid waste liquid recycling device according to claim 1, characterized in that: The chemical reaction device is also connected to a NaF liquid preparation tank, which is connected to a pure water recovery tank. The pure water in the pure water recovery tank and the externally supplied NaF are used for liquid preparation, and the prepared NaF solution enters the chemical reaction device for chemical reaction.

3. The photovoltaic cell BSG and PSG production section hydrofluoric acid waste liquid recycling device according to claim 1, characterized in that: The pure water recovery storage tank is provided with a pipeline connected to the PSG industrial pickling tank, and is also provided with a reflux pipeline connected to the hydrofluoric acid recovery storage tank. In addition, a water replenishment pipeline is also opened outside the pure water recovery storage tank to achieve the functions of recycling and recycling after replenishment.

4. The photovoltaic cell BSG and PSG production section hydrofluoric acid waste liquid recycling device according to claim 1, characterized in that: The hydrofluoric acid recovery storage tank is provided with a reflux pipeline for reflux to the PSG industrial pickling tank and the BSG industrial pickling tank, and the hydrofluoric acid recovery storage tank is also provided with an external pipeline for replenishing hydrofluoric acid, which is used for replenishing hydrofluoric acid.

5. The photovoltaic cell BSG and PSG production section hydrofluoric acid waste liquid recycling device according to claim 1, characterized in that: The distillation and purification device comprises a dehydration distillation tower and a concentration distillation tower.

6. The method for using the photovoltaic cell BSG and PSG production section hydrofluoric acid waste liquid recycling device according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: 1) The hydrofluoric acid waste liquid from the BSG section and the hydrofluoric acid waste liquid from the PSG section flow into the PSG industrial pickling tank and the BSG industrial pickling tank and then enter the hydrofluoric acid collection device together for mixing; 2) Prepare a 10%-20% concentration NaF solution by mixing the pure water in the pure water recovery tank and the external NaF in the NaF solution tank; 3) The hydrofluoric acid waste liquid and the sodium fluoride solution enter the chemical reaction device at the same volume flow rate, and the reaction residence time is 5-10 minutes; 4) The logistics from the chemical reaction device directly enters the precipitation separation and filtration device, the filtrate at the bottom of the precipitation separation and filtration device is sent to the centrifuge for further dehydration, and the sodium fluorosilicate product is obtained from the centrifuge. The supernatant liquid on the sedimentation tank is sent to the distillation and purification device for distillation operation; 5) The operating pressure of the dehydration distillation tower in the distillation purification device is between 120-200kPa. Pure water is obtained at the top of the distillation tower. The hydrofluoric acid content of the pure water is less than 2000ppm. The pure water is sent to the pure water recovery tank. The hydrofluoric acid solution is enriched at the bottom of the dehydration distillation tower and sent to the hydrofluoric acid concentration tower for further purification; 6) The operating pressure of the hydrofluoric acid concentration tower is between 110-190 kPa. The hydrofluoric acid product with a concentration of 36% at the top of the concentration tower enters the hydrofluoric acid recovery tank, and the hydrofluoric acid coming out of the top of the concentration tower enters the hydrofluoric acid recovery tank for storage; 7) One stream of hydrofluoric acid solution from the hydrofluoric acid recovery tank is directly transported to the BSG industrial pickling tank for use, and the other stream is connected to the PSG industrial pickling tank. According to the cleaning requirements of the PSG section, a stream of pure water is sent from the pure water recovery tank. The hydrofluoric acid recovery rate reaches 97%, and the pure water recovery rate reaches 98%.

7. The method for using the device for recycling hydrofluoric acid waste liquid in the production section of photovoltaic cell BSG and PSG according to claim 6, characterized in that: The chemical reaction process in the chemical reaction device in step 3) is as follows: H2SiF6+2NaF= Na2SiF6+2HF.

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