CN107416838A - The recyclable silicon material regeneration purifying technique of photovoltaic industry chain - Google Patents

Abstract

The invention discloses the recyclable silicon material regeneration purifying technique of photovoltaic industry chain, regeneration purification is carried out to the recyclable silicon material of photovoltaic industry chain, obtains the silicon material for meeting solar level standard, the technique includes：（1）Classification cleaning,（2）Melting cleans,（3）Vacuum, which is overflow, stays removal of impurities,（4）Product classification step.The technique has the characteristics of environmentally friendly, simple, energy-conservation, inexpensive, meets the output capacity ＞ 70% of the silicon material of solar level standard, and purity of silicon is purified to more than 6N from 2 3N.

Description

Photovoltaic industry chain recyclable silicon material regeneration and purification process

technical field

The invention relates to the technical field of photovoltaic silicon material recycling, and specifically relates to a regeneration and purification process of recyclable silicon material in the photovoltaic industry chain.

Background technique

According to the "Thirteenth Five-Year Plan for Solar Energy Development" issued by the National Energy Administration in 2016, the development goal of solar energy: by the end of 2020, the installed capacity of solar power generation will reach more than 110 million kilowatts, of which the installed capacity of photovoltaic power generation will reach more than 105 million kilowatts, and the annual utilization of solar energy The volume reached more than 140 million tons of standard coal. In order to achieve the development goals of the "13th Five-Year Plan", more than 1 million tons of ingot furnace purification and ingot silicon material or single crystal silicon material must be pulled each year, which will generate about 300,000 tons of photovoltaic industry chain scrap and head Recycle silicon material at the end. Such a large amount of recycled silicon material has not yet found relevant technologies reported in domestic and foreign literature that can be processed. In order to reduce costs, some enterprises doped some recycled silicon materials into high-purity silicon for ingot casting, resulting in defects such as cell instability and high attenuation rate, but there are still a large number of recycled silicon materials in the photovoltaic industry chain that cannot be processed.

Contents of the invention

The object of the present invention is to solve the above problems and provide a process for regeneration and purification of recyclable silicon materials in the photovoltaic industry chain.

The purpose of the present invention is specifically achieved through the following technical solutions:

Photovoltaic industry chain recyclable silicon material regeneration and purification process, regenerate and purify recyclable silicon material in the photovoltaic industry chain, and obtain silicon material that meets solar-grade standards. The process includes: (1) classified cleaning, (2) smelting and removing impurities, ( 3) Vacuum overflow and impurity removal, (4) Product classification steps.

Further, it specifically includes the following steps:

(1) Classified cleaning, the specific method is as follows:

Classification: Classify the recovered silicon material according to the resistivity, and divide it into three categories with resistivity <0.5Ω·cm, 0.5~3Ω·cm and >3Ω·cm;

Surface mechanical treatment: mechanically polish and sandblast the surface of the classified silicon material to remove the silicon material skin;

Wet cleaning: use solution immersion method to treat silicon material, the solution includes acid-H ₂ O ₂ aqueous solution, NH ₄ OH-H ₂ O ₂ aqueous solution, H ₂ SO ₄ -H ₂ O ₂ aqueous solution can remove silicon material surface Organic pollutants and metals, NH ₄ OH-H ₂ O ₂ aqueous solution can remove particles on the surface of silicon materials, used alone or in combination according to the pollution of the surface of silicon materials;

Pure water cleaning: the silicon material after wet cleaning is cleaned with pure water by ultrasonic technology, and then dried;

(2) Smelting and removing impurities, the specific method is as follows:

The silicon material that has been sorted and cleaned in step (1) is put into a melting crucible and sent to a vacuum furnace. The temperature in the furnace is controlled at 1500~1700°C. After the silicon material is completely melted, the temperature of the liquid silicon is controlled above 1500°C;

Start the blowing impurity removal system, blow argon into the liquid silicon, and use the argon to bring in the electrophoretic agent particles to remove P, B and other impurities in the silicon material;

(3) Vacuum overflow and impurity removal, the specific method is as follows:

Transfer the liquid silicon after smelting and removing impurities in step (2) to the overflow bag, and argon gas is introduced into the overflow bag before the transfer, and the overflow bag is covered with a cover after the liquid silicon is transferred, so that the overflow bag is in a closed environment middle;

Vacuum the overflow bag, adjust the argon flow and pressure leading into the overflow bag, and turn on the heating device, which includes an internal heater and a top heater, to heat the top surface of the overflow bag and the liquid silicon inside , the heating device rotates, the temperature of the top heater is always > 1450°C, the temperature of the internal heater drops from 1560°C to 1450°C, and the overflow bag is always filled with argon during the cooling process;

When the heating device of the overflow bag is turned on, the cooling water is also turned on to cool the surrounding surface of the overflow bag and the outer surface of the bottom, and the liquid silicon solidifies from the periphery to the center. The temperature difference is 90~150°C. In the final stage of vacuum overflow and impurity removal, the liquid silicon in the center of the overflow bag is poured into a water tank composed of ingots for cooling, and the solidified silicon material in the overflow bag is cooled to 200°C before unpacking. , take out the silicon material;

(4) Product classification: The silicon material obtained by vacuum overflow and impurity removal in step (3) is classified according to the content of P, B and total metal, and the silicon material meeting the standard of solar-grade polysilicon is sorted out.

Furthermore, in the step (1), the sandblasting treatment of surface mechanical treatment includes high-pressure spraying method, centrifugal spraying method, and fluid mechanics method, and the thickness of the silicon material skin is removed: the surrounding and bottom skins are 0.1-8 mm, The top skin is 0.2~10 mm;

In wet cleaning, the soaking time of the solution is 15~120min, the volume ratio of _acid , H2O2 and water in the _{acid -} H2O2 aqueous solution is ₃ ~10:1:1, and the acid is 25~ 60wt% sulfuric acid or 30~40wt% hydrochloric acid, the volume ratio of _NH4OH , H2O2 and water in the _{NH4OH -} H2O2 aqueous solution is ₂ ~ ₈ : ₁ :1, and the _NH4OH is 20～30wt% ammoniacal liquor, the massfraction of described H ₂ O ₂ is 25～35%;

The drying process is carried out in vacuum.

Furthermore, in the step (2), the vacuum furnace includes a vacuum intermediate frequency furnace and a vacuum melting furnace, and the process of heating and melting the silicon material is carried out under the protection of vacuum or inert gas;

The purity of the argon gas is >99.99%, the pressure of the argon gas is 0.2-1Mpa, the flow rate is 0.05-0.5m ³ /h, and the electrophoretic agent includes calcium-based and/or sodium-based electrophoretic agents;

The melting crucible is made of graphite or corundum;

The smelting impurity removal time and the amount of electrophoretic agent are: for silicon materials with a resistivity of 0.5~3 Ω·cm, the amount of electrophoretic agent added is 1/150~1/300 of the weight of the silicon material, and the treatment time is 5~10 h; For silicon material with resistivity <0.5 Ω·cm, the amount of electrophoretic agent added is 1/50~1/150 of the weight of silicon material, and the treatment time is 10~15h; for silicon material with resistivity>3 Ω·cm, electrophoretic agent is added The amount is 1/300~1/450 of the weight of the silicon material, and the processing time is 3~5 h.

Furthermore, in the step (3), the argon gas passed into the overflow bag is deoiled, degreased and dried, and the argon gas is introduced through the blowing pipe inserted from the upper part of the overflow bag or the bottom of the overflow bag, and the liquid state Before the silicon is poured into the overflow bag, the pressure of argon gas is 0.3~0.6Mpa, and the flow rate is 0.1~0.6 m³/min. The flow rate is 0.05~0.2 m³/min;

After vacuuming the overflow bag, the vacuum degree is maintained at 4000~6000 Pa;

The internal heater is a silicon-molybdenum rod heater or a graphite heater, which is located in the center of the overflow bag, and the top heater is a graphite heater;

The time of the cooling process is: for silicon materials with a resistivity of 0.5~3 Ω cm, the time is 5~10 h; for silicon materials with a resistivity <0.5 Ω cm, the time is >10 h; material, time <5 h;

The temperature of the cooling water is <25°C, the water pressure is 0.2-0.6Mpa, and the flow rate is 30-75 m ³ /h.

Furthermore, in the step (4), the silicon material with P≤0.5pptWt, B≤0.3pptWt, and total metal content≤1pptWt meets the solar grade polysilicon standard.

The beneficial effects of the present invention are:

(1) This invention is specifically aimed at the repurification production technology of recyclable silicon materials in the photovoltaic industry chain, which has the characteristics of environmental protection, simplicity, energy saving and low cost;

(2) Large-scale production of silicon materials for solar-grade polysilicon ingots that meets the international SEMI PV17-1012 standard, and the output rate of silicon materials that meet the standards is greater than 70%, which greatly improves the quality of ingots for the reproduction of recyclable materials in the photovoltaic industry chain;

(3) The gas blown in during the impurity removal process has a stirring effect on the silicon liquid, continuously allowing mass exchange between the surface silicon liquid and the internal silicon liquid, removing volatile impurities, and blowing air in the overflow bag to quickly diffuse impurities on the solid-liquid surface. In the liquid state, the diffusion of impurities to high-purity solid silicon is reduced;

(4) The low-purity silicon in the overflow and impurity removal is separated in a liquid state, realizing the rapid separation of high-purity silicon and low-purity silicon;

(5) Air blowing keeps the liquid silicon in a dynamic state all the time, realizing dynamic directional solidification;

(6) Heating inside the liquid silicon improves the utilization rate of the heat source;

(7) The purity of silicon material is purified from 2-3N to above 6N.

detailed description

Preferred embodiments of the present invention are described below, and it should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

Photovoltaic industry chain recyclable silicon material regeneration and purification process, regenerate and purify recyclable silicon material in the photovoltaic industry chain, and obtain silicon material that meets solar-grade standards. The process includes: (1) classified cleaning, (2) smelting and removing impurities, ( 3) Vacuum overflow and impurity removal, (4) Product classification steps. Specifically include the following steps:

(1) Classified cleaning

Classification: Recyclable silicon materials in the photovoltaic industry chain are divided into peripheral skins, pot bottom materials, and head and tail materials. According to the resistivity of different parts, the range of impurity content is calculated. Generally, the resistivity of the four sides of purification, the recovery of silicon material at the head, the recovery of silicon material at the head of the ingot, and the bottom material of the monocrystalline silicon pot are relatively small, while the silicon material recovered at the bottom of the purification, the surrounding area of the ingot, and the bottom recovery of silicon material and monocrystalline The resistivity of the silicon rod edge skin silicon material is relatively high. The recyclable silicon material in the photovoltaic industry chain is screened by the resistance tester and manual cooperation, and different purification technology processing times are carried out with reference to different resistance measurement ranges. Silicon materials with a resistivity between 0.5 and 3 Ω·cm are subjected to smelting and vacuum overflow removal of impurities according to the normal purification time, and the time is 10 to 20 h; the resistivity of recovered silicon materials is less than 0.5 Ω·cm. If the impurity content is high, the treatment time for impurity removal and purification is relatively long, generally >20 h; for silicon materials with a resistivity >3Ω·cm, the relative impurity content is low, and the general treatment time is <10 h.

Surface mechanical treatment: In the process of polysilicon photovoltaic industry chain, silicon nitride coating treatment is carried out using quartz crucible. After melting and re-solidification in the ingot furnace, the surrounding and bottom surfaces of the silicon materials are partially polluted. The upper surface of the silicon ingots from the photovoltaic industry chain is the part with the highest impurity content in the silicon ingots. Therefore, it is necessary to mechanically clean the six surfaces of the silicon ingots. Part silicon material is mechanically treated. After the classification of recyclable silicon materials in the photovoltaic industry chain, the surface of the recycled silicon materials is first mechanically treated. The surface of the recovered silicon material is treated by mechanical methods such as mechanical grinding and sandblasting, such as high-pressure injection method, centrifugal injection method, and fluid mechanics method, to reduce the impurity content on the surface of the recovered silicon material. The thickness of the skin around and at the bottom of the mechanical treatment is 0.1-8 mm, and the thickness of the top skin is 0.2-10 mm.

Wet cleaning: After prescribing and mechanically removing the surface of the silicon material, a large amount of oily, milky and other dirty substances are left on the surface, which needs further cleaning. The cutting fluid in the prescribing process contains oily and milky substances, mainly composed of polyethylene glycol, chelating agents and organic alcohols. Generally, one or more of particles, metals, organic matter, dust, moisture molecules and natural oxides are deposited on the surface of the silicon material, which must be removed.

Wet cleaning adopts the solution immersion method, through the chemical reaction and dissolution of the solution and the contamination impurities on the surface of the silicon material during the soaking process to achieve the purpose of removing the contamination impurities on the surface of the silicon material. The total soaking time is controlled between 15 and 120 minutes. About 30 minutes. The cleaning solution for the removal of organic matter and metals on the surface of silicon materials is acid-H ₂ O ₂ aqueous solution, the volume ratio of acid, H ₂ O ₂ and water is 3~10:1:1, and the acid is 25~60wt% sulfuric acid or 30~40wt% % hydrochloric acid, the mass fraction of H ₂ O ₂ is 25~35%. This solution has a strong oxidizing ability. It can oxidize metals and dissolve them in the solution, and can oxidize organic matter to generate CO ₂ and water, which can remove silicon materials. Heavy organic contamination and some metals on the surface, but when the organic contamination is heavy, the organic matter will be carbonized and difficult to remove. If sulfuric acid-H ₂ O ₂ aqueous solution is used for cleaning, sulfides will remain on the surface of the silicon material, and these sulfides are difficult to wash off with deionized water. Particle removal on the surface of silicon material is mainly cleaned with NH ₄ OH-H ₂ O ₂ aqueous solution, the volume ratio of NH ₄ OH, H ₂ O ₂ and water is 2~8:1:1, and NH ₄ OH is 20~30wt% ammonia water , the mass fraction of H ₂ O ₂ is 25~35%. In the cleaning solution, due to the action of H ₂ O ₂ , there is a layer of natural oxide film SiO ₂ on the surface of the silicon material, which is hydrophilic, and the surface of the silicon material and between the particles can be soaked with the cleaning solution. Corroded by NH ₄ OH, the particles on the surface of the silicon material fall into the cleaning solution. In the cleaning solution, since the potential on the surface of the silicon material is negative, there is a repulsive force between most of the particles, which prevents the particles from adsorbing to the surface of the silicon material. The above two cleaning methods are used alone or in combination according to the contamination of the surface of the silicon material.

Pure water cleaning: the silicon material is re-cleaned by pure water through ultrasonic cleaning technology, and finally vacuum-dried, and the processed polysilicon photovoltaic industry chain recycled materials are subjected to the next purification process.

(2) Melting and impurity removal

The recovered silicon material after vacuum drying is firstly smelted and impurity-removed. It is heated and melted by vacuum intermediate frequency furnace, vacuum melting furnace or other vacuum furnaces. The heating and melting process can be carried out in a vacuum state or under the protection of inert gas. The melting temperature is controlled at 1500~1700°C. The melting crucible is made of graphite or corundum. After the solid recycled silicon material is completely melted, the temperature of the liquid silicon is controlled above 1500°C. Start the gas blowing impurity removal system, by blowing argon with a purity >99.99%, use the argon to bring in the granular electrophoretic agent, the electrophoretic agent includes one or more of calcium-based, sodium-based or other electrophoretic agents, from the removal The carbon tube or corundum tube in the miscellaneous device enters the liquid silicon, the argon pressure is 0.2~1 Mpa, and the flow rate is 0.05~0.5 m³/h. Through the reaction of electrophoretic agent and liquid silicon, the content of P, B and other impurities is reduced. According to the different classifications of melted and recovered silicon materials, the entire processing time and the amount of electrophoretic agent are different. For silicon materials with a resistivity of 0.5~3 Ω·cm, the amount of electrophoretic agent added is 1/150~1/300 of the weight of the silicon material. The time is 5~10 h; the resistivity of the recovered silicon material is less than 0.5 Ω·cm, the amount of electrophoretic agent added is 1/50~1/150 of the weight of the silicon material, and the treatment time is 10~15 h; the resistivity is greater than 3 Ω·cm cm silicon material, the relative impurity content is relatively low, the amount of electrophoretic agent added is 1/300~1/450 of the weight of the silicon material, and the treatment time is 3~5 h.

(3) Vacuum overflow and impurity removal

Using the latent heat energy of liquid silicon itself, the liquid silicon in the smelting vacuum furnace is transferred to the overflow bag for overflow and impurity removal. The liquid silicon is controlled above 1500°C, and the liquid silicon is poured into the overflow bag. Before pouring, argon gas is introduced through the blowing pipe inserted from the upper part of the overflow bag or the bottom of the overflow bag. , degreasing, drying treatment, uninterrupted feeding into the overflow bag, keeping the whole process of leaving the furnace without fluctuations. After the liquid silicon is poured, cover it with a specially designed cover to keep the silicon liquid in a completely closed overflow bag environment to prevent external environmental pollution.

Use a mechanical vacuum pump or a Roots pump to evacuate the overflow bag and keep the vacuum at 4000~6000 Pa. Adjust the argon pressure into the overflow bag to be 0.1~0.3 MPa, and the flow rate to be 0.05~0.2 m³/min. Then turn on the water and electricity, and turn on the heating device. The heating device includes an internal heater and a top heater to heat the top surface and the inside of the liquid silicon in the bag. The heating device rotates during the heating process to make the silicon liquid Radiant heat and conduction heat are stable and consistent. The inner heater is silicon molybdenum rod heater or graphite heater, and the top heater is graphite heater. The temperature of the top heater is always greater than 1450°C, and the temperature of the internal heater is slowly lowered from the initial 1560°C to 1450°C to ensure that the silicon inside the overflow bag is always in a molten state. Depending on the resistivity of the silicon material, the gas blowing and cooling time of this process are different. For silicon materials with a resistivity of 0.5~3 Ω cm, the time for blowing and cooling is 5~10 hours; for silicon materials with a resistivity <0.5 Ω cm, the time for blowing and cooling is >10 hours; for resistivity> 3 Ω · cm silicon material, blowing and cooling treatment time <5h.

While the heating device of the overflow bag is turned on, water is passed around the outer surface of the overflow bag and the outer surface of the bottom for cooling, the water pressure is 0.2~0.6 MPa, and the flow rate is 30~75 m ³ /h. The water temperature is kept below 25°C. During the whole process, the temperature difference between the temperature of the internal heater and the outer wall of the solidified silicon material in the bag is kept between 90 and 150°C. The liquid silicon is directional solidified from the surrounding to the center. Due to the directional solidification, impurity elements are excluded into the liquid silicon, and the purity of the high-purity solidified solid silicon around is much higher than that of liquid silicon. Because the impurity content of the remaining part of liquid silicon after the purification process is completed is extremely high, in order to prevent it from solidifying into a solid state and affecting the solidified high-purity solid silicon, high-purity silicon is separated from low-purity silicon with a very high impurity content. The low-purity liquid silicon with high impurity is poured out of the overflow bag before solidification, realizing the separation of high-purity silicon and low-purity silicon. This part of liquid silicon accounts for 10%-30% of the weight of the entire liquid silicon. Liquid silicon is poured into a water-cooled box made of cast ingots to rapidly cool it into ingots. Turn off the heating device, wait for the temperature of the solidified silicon in the overflow bag to drop to 200°C to unpack, and take out the purified silicon material.

(4) Product classification: The solid silicon material after overflow and removal of impurities is prescribed and tested, and classified according to P, B and total metal content according to the test results. For impurity concentration B≤ 0.3 ppmWt, P≤ 0.5 ppmWt, Σ _metal ≤ 1 ppmWt, it is suitable for polysilicon materials for solar cells; for impurity concentration B>0.3 ppmWt, P>0.5 ppmWt, Σ _metal > 1ppmWt silicon material is re-purified Or sold as low-purity silicon material.

The above method is used to regenerate and purify the reusable silicon material in the photovoltaic industry chain. The obtained high-purity silicon material meets the solar-grade polysilicon standard SEMI PV17-1012 after testing. The silicon material directly enters the ingot furnace, and the finished product is sold directly. Part of the standard low-purity and low-quality silicon materials of solar grade silicon materials are returned to the furnace for further purification, or used in places where the quality of silicon is not high.

The regeneration and purification process of the reusable silicon material of the present invention purifies the recyclable silicon material in the photovoltaic industry chain, and the output rate of the silicon material conforming to the solar-grade standard is greater than 70%, and the purity of the purified polysilicon reaches 6N (99.9999%) required by the photovoltaic grade. )above.

Example 1

Recyclable silicon material regeneration and purification process includes the following steps:

(1) Classified cleaning

The silicon material recovered from the photovoltaic industry chain was screened with a resistance tester and manual cooperation, and the silicon material with a resistivity between 0.5 and 3Ω·cm was screened out.

The above-mentioned sorted silicon material is opened, and the surface is mechanically polished to remove the surrounding and bottom skin with a thickness of 0.1-8 mm, and the top skin with a thickness of 0.2-10 mm.

Soak the silicon material with a mixture of 30wt% sulfuric acid, 28wt% H ₂ O ₂ and water at a volume ratio of 5:1:1 for 15 minutes, and then use 25wt% ammonia water, 28wt% H ₂ O ₂ and Soak in the water mixture for 15 minutes.

The silicon material is cleaned again by ultrasonic cleaning technology with pure water, and finally vacuum dried, and the treated silicon material is subjected to the next purification process.

(2) Melting and impurity removal

The vacuum-dried silicon material is put into a graphite melting crucible, and then enters a vacuum melting furnace for heating and melting. The heating and melting process is carried out under the protection of argon, and the temperature in the furnace is controlled at 1500~1700°C. After the solid recycled silicon material is completely melted, the temperature of the liquid silicon is controlled above 1500°C. Start the gas blowing impurity removal system, blow in argon with a purity >99.99%, use the argon to bring the calcium-based electrophoretic agent particles into the liquid silicon from the carbon tube or corundum tube in the impurity removal device, and the argon pressure is 0.2~1 Mpa, the flow rate is 0.05~0.5 m³/h. The processing time of the smelting and impurity removal process is 8 hours, and the amount of the electrophoretic agent added is 1/200 of the weight of the silicon material.

(3) Vacuum overflow and impurity removal

Pour the liquid silicon in the vacuum melting furnace into the overflow bag. The liquid silicon is controlled at a temperature above 1500°C. Before pouring, the argon gas that has been deoiled, degreased and dried is introduced through the blowing pipe inserted from the upper part of the overflow bag. The argon gas is fed continuously, the pressure of the argon gas is 0.3~0.6 Mpa, and the flow rate is 0.1~0.6 m³/min. After the liquid silicon is poured, cover it with a specially designed cover.

Vacuum the overflow bag through a mechanical vacuum pump to keep the vacuum at 4000~6000 Pa. Adjust the argon pressure into the overflow bag to be 0.1~0.3 MPa, and the flow rate to be 0.05~0.2 m³/min. Turn on the heating device. The heating device includes an internal heater and a top heater to heat the top surface and the inside of the liquid silicon in the bag. The heating device rotates during the heating process to make the radiation heat and conduction heat of the silicon liquid stable and consistent. . The internal heater is a silicon molybdenum rod heater, and the top heater is a graphite heater. The temperature of the top heater is always greater than 1450°C, and the temperature of the inner heater is slowly decreased from the initial 1560°C to 1450°C. The blowing and cooling treatment time is 8h.

While the heating device of the overflow bag is turned on, water is passed around the outer surface of the overflow bag and the outer surface of the bottom for cooling, the water pressure is 0.2~0.6 MPa, and the flow rate is 30~75 m ³ /h. The water temperature is kept below 25°C. During the whole process, the temperature difference between the temperature of the internal heater and the outer wall of the solidified silicon material in the bag is kept between 90 and 150°C. Liquid silicon solidifies directionally from the periphery to the center. After the blowing and cooling process, the low-purity liquid silicon with high impurity content is poured into the water-cooled box made of ingots before solidification, so that it can be rapidly cooled into ingots. Turn off the heating device, wait for the temperature of the solidified silicon in the overflow bag to drop to 200°C to unpack, and take out the purified silicon material.

(4) Product classification: The solid silicon material after overflow and removal of impurities is prescribed and then tested. According to the test results, the silicon material that meets the solar-grade polysilicon standard is sorted out according to P, B and total metal content.

In this embodiment, the yield of silicon material meeting the solar grade polysilicon standard was 74%.

Example 2

This embodiment is basically the same as Embodiment 1, the difference is:

(1) The classification cleaning step screens out silicon materials with a resistivity <0.5 Ω·cm.

(2) The treatment time of the smelting and impurity removal process is 12 hours, and the amount of electrophoretic agent added is 1/100 of the weight of the silicon material.

(3) The time for vacuum overflow, impurity removal, air blowing and cooling treatment is 12 hours.

In this embodiment, the yield of silicon material meeting the solar grade polysilicon standard was 71%.

Example 3

This embodiment is basically the same as Embodiment 1, the difference is:

(1) The classification cleaning step screens out silicon materials with a resistivity > 3 Ω·cm.

(2) The treatment time of the smelting and impurity removal process is 4 hours, and the amount of electrophoretic agent added is 1/400 of the weight of the silicon material.

(3) The time for vacuum overflow, impurity removal, air blowing and cooling treatment is 4 hours.

In this embodiment, the yield of silicon material meeting the solar grade polysilicon standard was 76%.

Table 1 and Table 2 are the contents of impurity elements before and after the purification of the silicon material in Example 2.

Table 1 Content of impurity elements in polysilicon before purification (ppmWt)

Table 2 Content of impurity elements in polysilicon after purification (ppmWt)

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still understand the foregoing embodiments The recorded technical solutions are modified, or some of the technical features are equivalently replaced. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. Regeneration and purification process of recyclable silicon materials in the photovoltaic industry chain, which regenerates and purifies recyclable silicon materials in the photovoltaic industry chain to obtain silicon materials that meet solar-grade standards. It is characterized in that the process includes: (1) classified cleaning, (2) ) Smelting to remove impurities, (3) Vacuum overflow to remove impurities, (4) Product classification steps. 2. The regeneration and purification process of recyclable silicon material in the photovoltaic industry chain according to claim 1, characterized in that it specifically comprises the following steps: (1) Classified cleaning, the specific method is as follows: Classification: Classify the recovered silicon material according to the resistivity, and divide it into three categories with resistivity <0.5Ω·cm, 0.5~3Ω·cm and >3Ω·cm; Surface mechanical treatment: mechanically polish and sandblast the surface of the classified silicon material to remove the silicon material skin; Wet cleaning: use solution immersion method to treat silicon material, the solution includes acid-H ₂ O ₂ aqueous solution, NH ₄ OH-H ₂ O ₂ aqueous solution, H ₂ SO ₄ -H ₂ O ₂ aqueous solution can remove silicon material surface Organic pollutants and metals, NH ₄ OH-H ₂ O ₂ aqueous solution can remove particles on the surface of silicon materials, used alone or in combination according to the pollution of the surface of silicon materials; Pure water cleaning: the silicon material after wet cleaning is cleaned with pure water by ultrasonic technology, and then dried; (2) Smelting and removing impurities, the specific method is as follows: The silicon material that has been sorted and cleaned in step (1) is put into a melting crucible and sent to a vacuum furnace. The temperature in the furnace is controlled at 1500~1700°C. After the silicon material is completely melted, the temperature of the liquid silicon is controlled above 1500°C; Start the blowing impurity removal system, blow argon into the liquid silicon, and use the argon to bring in the electrophoretic agent particles to remove P, B and other impurities in the silicon material; (3) Vacuum overflow and impurity removal, the specific method is as follows: Transfer the liquid silicon after smelting and removing impurities in step (2) to the overflow bag, and argon gas is introduced into the overflow bag before the transfer, and the overflow bag is covered with a cover after the liquid silicon is transferred, so that the overflow bag is in a closed environment middle; Vacuum the overflow bag, adjust the argon flow and pressure leading into the overflow bag, and turn on the heating device, which includes an internal heater and a top heater, to heat the top surface of the overflow bag and the liquid silicon inside , the heating device rotates, the temperature of the top heater is always > 1450°C, the temperature of the internal heater drops from 1560°C to 1450°C, and the overflow bag is always filled with argon during the cooling process; When the heating device of the overflow bag is turned on, the cooling water is also turned on to cool the surrounding surface of the overflow bag and the outer surface of the bottom, and the liquid silicon solidifies from the periphery to the center. The temperature difference is 90~150°C. In the final stage of vacuum overflow and impurity removal, the liquid silicon in the center of the overflow bag is poured into a water tank composed of ingots for cooling, and the solidified silicon material in the overflow bag is cooled to 200°C before unpacking. , take out the silicon material; (4) Product classification: The silicon material obtained by vacuum overflow and impurity removal in step (3) is classified according to P, B and total metal content, and the silicon material that meets the solar-grade polysilicon standard is sorted out. 3. The regeneration and purification process of recyclable silicon materials in the photovoltaic industry chain according to claim 2, characterized in that, in the step (1), the sandblasting treatment of surface mechanical treatment includes high-pressure spraying method, centrifugal spraying method, fluid mechanics method, the thickness of the silicon material skin is removed: the surrounding and bottom skins are 0.1~8 mm, and the top skin is 0.2~10 mm; In wet cleaning, the soaking time of the solution is 15~120min, the volume ratio of _acid , H2O2 and water in the _{acid -} H2O2 aqueous solution is ₃ ~10:1:1, and the acid is 25~ 60wt% sulfuric acid or 30~40wt% hydrochloric acid, the volume ratio of _NH4OH , H2O2 and water in the _{NH4OH -} H2O2 aqueous solution is ₂ ~ ₈ : ₁ :1, and the _NH4OH is 20～30wt% ammoniacal liquor, the massfraction of described H ₂ O ₂ is 25～35%; The drying process is carried out in vacuum. 4. The regeneration and purification process of recyclable silicon material in the photovoltaic industry chain according to claim 2, characterized in that in the step (2), the vacuum furnace includes a vacuum intermediate frequency furnace and a vacuum melting furnace, and the process of heating and melting the silicon material Carry out under vacuum or inert gas protection; The purity of the argon gas is >99.99%, the pressure of the argon gas is 0.2-1Mpa, the flow rate is 0.05-0.5m ³ /h, and the electrophoretic agent includes calcium-based and/or sodium-based electrophoretic agents; The melting crucible is made of graphite or corundum; The smelting impurity removal time and the amount of electrophoretic agent are: for silicon materials with a resistivity of 0.5~3 Ω·cm, the amount of electrophoretic agent added is 1/150~1/300 of the weight of the silicon material, and the treatment time is 5~10 h; For silicon material with resistivity <0.5 Ω·cm, the amount of electrophoretic agent added is 1/50~1/150 of the weight of silicon material, and the treatment time is 10~15h; for silicon material with resistivity>3 Ω·cm, electrophoretic agent is added The amount is 1/300~1/450 of the weight of the silicon material, and the processing time is 3~5 h. 5. The regeneration and purification process of recyclable silicon materials in the photovoltaic industry chain according to claim 2, characterized in that, in the step (3), the argon gas passed into the overflow bag is deoiled, degreased and dried, and the argon The gas is introduced through the blowing pipe inserted from the upper part of the overflow bag or the bottom of the overflow bag. Before the liquid silicon is poured into the overflow bag, the pressure of argon gas is 0.3~0.6Mpa, and the flow rate is 0.1~0.6 m³/min. After moving into the overflow bag and capping it, the pressure of argon gas is 0.1~0.3 MPa, and the flow rate is 0.05~0.2 m³/min; After vacuuming the overflow bag, the vacuum degree is maintained at 4000~6000 Pa; The internal heater is a silicon-molybdenum rod heater or a graphite heater, which is located in the center of the overflow bag, and the top heater is a graphite heater; The time of the cooling process is: for silicon materials with a resistivity of 0.5~3 Ω cm, the time is 5~10 h; for silicon materials with a resistivity <0.5 Ω cm, the time is >10 h; material, time <5 h; The temperature of the cooling water is <25°C, the water pressure is 0.2-0.6Mpa, and the flow rate is 30-75 m ³ /h. 6. The regeneration and purification process of recyclable silicon materials in the photovoltaic industry chain according to claim 2, characterized in that in the step (4), silicon materials with P≤0.5pptWt, B≤0.3pptWt, and total metal content≤1pptWt Meets solar grade polysilicon standards.