CN113582184A - Purification method of silicon scrap impurities - Google Patents
Purification method of silicon scrap impurities Download PDFInfo
- Publication number
- CN113582184A CN113582184A CN202110899282.3A CN202110899282A CN113582184A CN 113582184 A CN113582184 A CN 113582184A CN 202110899282 A CN202110899282 A CN 202110899282A CN 113582184 A CN113582184 A CN 113582184A
- Authority
- CN
- China
- Prior art keywords
- silicon
- flotation
- silicon particles
- particles
- water
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/037—Purification
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
The invention discloses a purification method of silicon scrap impurities, which comprises the following purification production procedures: s1, removing organic matters in the crushed silicon materials; s2, removing inorganic substances such as stones and quartz in the crushed silicon material; s3, crushing to a particle size of less than 1 mm; s4, removing silicon carbide impurities by flotation through a phase transfer separation method; s5, acid washing and flotation; s6, carrying out hydrogen flotation on silicon particles; s7, floating by a phase transfer separation method; and S8, mixing, cleaning and drying the silicon particles obtained in the steps S5, S6 and S7, and then using the silicon particles as raw materials for purifying silicon ingots, and after directional solidification and purification, directly using the silicon particles as the raw materials for the polycrystalline silicon ingots. The invention combines the color selection method, the gravity method, the sintering method, the flotation method and the like, and provides a set of complete silicon material purification treatment methods which can be used independently or combined according to the sequence to remove various impurities, thereby reducing the silicon material purification cost and improving the purification efficiency.
Description
Technical Field
The invention relates to a purification method of crushed silicon material impurities, in particular to a purification method of crushed silicon material impurities mixed with inorganic substances such as stones and organic substances such as rubber wires, belonging to the field of mineral separation.
Background
Silicon material is the main raw material for producing polycrystalline silicon wafers, and the purity requirement of the silicon material is more than 6N (99.9999%). The polycrystalline silicon impurities seriously affect the photoelectric conversion efficiency of the solar cell, especially metal elements such as Fe and nonmetal elements such as N, C. The impurities are easy to form hard cores in the production process of the polycrystalline silicon ingot, the polycrystalline silicon ingot cutting lines and the square ingot cutting lines are broken, and the rejection rate of silicon wafer wire cutting production is increased. The purification of silicon materials is one of the main processes in the production of polycrystalline silicon wafers. The recovered silicon scrap is generally mixed with inorganic scraps such as pebbles, quartz, silicon carbide and the like, and organic scraps such as adhesive tape yarns, woven bag yarns, plastic scraps, hair yarns, epoxy resin and the like. These impurities contain elements such as Fe, C, and N, and must be removed before they can be used as a raw material for a polycrystalline silicon ingot.
At present, the purification methods of silicon scraps containing inorganic impurities such as pebbles, quartz, silicon carbide and the like and organic impurities such as colloidal silica and the like include an electromagnetic induction method, a centrifugal method, an electric separation method, a magnetic separation method, an acid washing method, an alkali washing method, a directional solidification method and the like. According to the difference of one or more physical and chemical properties of the silicon particles and the impurities, the silicon crushed materials are purified by one or more methods. For example, chinese patent CN101623672A discloses a method for sorting silicon material mixed with impurities of quartz, adhesive tape, dust and silicon carbide, which separates the impurities from silicon particles by electric sorting method according to the difference of resistivity between the silicon particles and the impurities, and the electric sorting voltage is 10-80 KV. This technique has problems that the silicon particles are very difficult to be charged because of poor conductivity, and the silicon particles are not sufficiently separated from the quartz impurities. In addition, the existing purification method is relatively independent and cannot form a complete purification treatment system.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for purifying impurities in a silicon scrap material, aiming at conveniently and quickly removing inorganic impurities such as pebbles, quartz, silicon carbide and the like mixed in the silicon scrap material and organic impurities such as adhesive tape yarns, plastic broken yarns, epoxy resin and the like, and improving the recovery rate of the silicon material.
The technical scheme of the invention is as follows: a purification method of silicon scrap impurities comprises the following purification production procedures:
s1, removing organic matters such as adhesive tape yarns, woven bag yarns, plastic broken yarns, hair yarns and epoxy resin from the silicon scrap;
s2, removing inorganic substances such as stones and quartz in the crushed silicon material;
s3, cleaning the silicon chip material, and then crushing the silicon chip material to obtain silicon chip particles with the particle size of less than 1 mm;
s4, removing silicon carbide impurities by flotation through a phase transfer separation method: adding the crushed silicon particles crushed in the step S3 into an aqueous solution, adding a collecting agent which has no polarity, low water solubility and density less than that of water, stirring, adsorbing silicon carbide impurities by the collecting agent, floating, depositing the silicon particles with oxide films on the surface of the silicon particles in the water bottom, and collecting the silicon particles deposited in the water bottom;
s5, acid washing flotation: acid-washing the crushed silicon particles collected in step S4 in a hydrofluoric acid solution to remove the surface oxide film thereof while collecting floating silicon particles for the first time;
s6, performing hydrogen flotation on crushed silicon particles: discharging the pickling solution in the step S5 to obtain bottom silicon particles, adding deionized water, adjusting the pH to be more than 8 to obtain an alkaline aqueous solution containing silicon particles, stirring, blowing hydrogen to the bottom of the alkaline aqueous solution, and collecting floating silicon particles for the second time;
s7, flotation by a phase transfer separation method: adding a collecting agent which is non-polar, low in water solubility and lower in density than water into the alkaline aqueous solution without the floating silicon granules in the step S6, stirring, adsorbing the silicon granules by the collecting agent, carrying out phase transfer separation and floating, still settling the stones at the bottom of the water, and collecting the floating silicon granules for the third time; sintering the silicon particles to remove the collector, and carrying out hydrofluoric acid pickling on the silicon particles to remove the surface oxide of the silicon particles;
and S8, mixing, cleaning and drying the silicon particles obtained in the steps S5, S6 and S7, and then using the silicon particles as raw materials for purifying silicon ingots, and after directional solidification and purification, directly using the silicon particles as the raw materials for the polycrystalline silicon ingots.
Further, the removal of the organic matter in step S1 is performed by a combination of a gravity method and a sintering method, wherein the gravity method is mainly used for removing the organic matter with density less than that of water, and the sintering method is mainly used for removing the epoxy resin organic matter adhered to the silicon material.
Further, in the step S2, the inorganic matter is removed by crushing the crushed silicon material to 3-5mm, and then finishing the crushed silicon material in a silicon material color sorter by adopting a color sorting method, so that stones and quartz particles can be efficiently, economically and environmentally removed.
Further, the collecting agent in the step S4 and/or the step S7 is one or a mixture of diesel oil and kerosene, and the weight ratio of water to the collecting agent is 7: 1-8: 1.
Further, the collector in the step S4 is methyl isobutyl carbinol; adding an anionic surfactant into an aqueous solution of silicon particles and stirring before adding the methyl isobutyl carbinol collecting agent, wherein the weight ratio of the silicon particles to the surfactant is 1000: and 2, adjusting the pH of the aqueous solution to be =5, adding the collecting agent after 5 minutes, and stirring, wherein the weight ratio of the collecting agent to water is 1: 8.
Further, the collector in the step S7 is methyl isobutyl carbinol; adding an anionic surfactant into an aqueous solution of silicon particles and stirring before adding the methyl isobutyl carbinol collecting agent, wherein the weight ratio of the silicon particles to the surfactant is 1000: and 2, adjusting the pH of the aqueous solution to be =3, adding the collecting agent after 5 minutes, and stirring, wherein the weight ratio of the collecting agent to water is 1: 8.
Further, the removal of organic matters in the step S1, the flotation by phase transfer separation method in S4 and S7, the acid washing flotation in S5, and the hydrogen blowing flotation in S6 are all performed in a silicon flotation machine, the structure of the silicon flotation machine includes a flotation tank, a stirring motor, and a stirring shaft, a baffle is disposed on a side wall of the bottom of the flotation tank, a tank cover is disposed on the flotation tank, the stirring shaft penetrates through the tank cover and extends into the flotation tank, and a stirring blade is disposed at the end of the stirring shaft; an air blowing pipeline is arranged at the bottom of the flotation tank and used for blowing hydrogen into the flotation tank; a lower drainage outlet is arranged on the side surface of the bottom of the flotation tank, a first filter screen is arranged at the lower drainage outlet and used for filtering bottom silicon particles, the lower drainage outlet is communicated with a first liquid storage tank through a valve, the first liquid storage tank is used for storing pickling solution or water, and the first liquid storage tank is communicated with a liquid adding hole in the tank cover through a first liquid adding pipe; the flotation tank is characterized in that an upper liquid discharging port is arranged on the side face of the upper portion of the flotation tank, the upper liquid discharging port is communicated with a second liquid storage tank through an overflow pipe, a second valve is arranged on the overflow pipe, a second filter screen is arranged on the upper portion of the second liquid storage tank, the second liquid storage tank is used for storing a collecting agent or pickling solution, the second filter screen is used for filtering flotation silicon particles or impurity floaters, and the second liquid storage tank is communicated with liquid adding holes in a tank cover through a second liquid adding pipe.
Furthermore, an acid-proof pump is respectively arranged on the first liquid adding pipe and the second liquid adding pipe.
Further, the second liquid storage tank is also communicated with a vacuum pump.
Has the advantages that: the invention combines a color selection method, a gravity method, a sintering method, a flotation method, a phase transfer separation method and the like, provides a set of complete silicon material purification treatment method, can efficiently remove inorganic impurities such as stones, quartz, silicon carbide and the like in the silicon material, and organic impurities such as adhesive tape yarns, woven bag yarns, plastic broken yarns, hair yarns, epoxy resin and the like, and can be used alone to remove one impurity or be combined in sequence to remove a plurality of impurities; specially designed silicon material flotation machines can be adopted in organic matter flotation, hydrofluoric acid pickling flotation, hydrogen blowing flotation and phase transfer flotation, so that the silicon material purification cost is reduced, and the purification efficiency is improved.
Drawings
FIG. 1 is a schematic technical route of a method for purifying impurities in a silicon scrap material.
Fig. 2 is a schematic diagram of the composition structure of the silicon material flotation machine.
The labels in the figure are: 1 agitator motor, 2 (mixing) shafts, 3 stirring vane, 4 flotation cells, 5 capping, 6 first liquid feeding pipe, 7 second liquid feeding pipe, 8 overflow pipes, 9 first liquid reserve tank, 10 second liquid reserve tank, 11 second filter screens, 12 air-blowing pipeline, 41 baffles, 42 drain hole down, 43 first filter screen, 44 first valve, 45 drain hole of going up, 46 second valve, 61 acid-proof pump, 71 acid-proof pump, 101 vacuum pump.
Detailed Description
The invention will be described more fully with reference to the accompanying drawings.
The invention provides a method and a technology for purifying impurities of crushed silicon materials mixed with inorganic substances such as stones and quartz and organic substances such as rubber threads, wherein the production process mainly comprises the following steps: removing organic matters; removing stones and quartz in the crushed silicon material; removing the silicon carbide; removing oxides on the surfaces of the silicon particles; fifthly, flotation of crushed silicon materials; recovery and cyclic utilization of acid washing liquid.
As shown in fig. 1, a technical scheme of the purification method of impurities in a silicon scrap material of the present invention specifically includes the following steps:
s1, removing organic matters such as adhesive tape yarns, woven bag yarns, plastic broken yarns, hair yarns and epoxy resin in the silicon broken materials by combining a gravity method and a sintering method, wherein the gravity method is mainly used for removing the organic matters with the density smaller than that of water, and the sintering method is mainly used for removing the organic matters such as the epoxy resin and the like adhered to the silicon materials;
s2, removing inorganic substances such as stones and quartz in the crushed silicon materials, namely firstly crushing the crushed silicon materials to 3-5mm, and then finishing the crushing in a silicon material color selector by a color selection method, so that the stones and quartz particles in the silicon materials can be removed efficiently, economically and environmentally;
s3, cleaning the silicon chip material, and then crushing to obtain silicon chip particles with the particle size of less than 1 mm;
s4, removing silicon carbide impurities by flotation through a phase transfer separation method: adding the crushed silicon particles crushed in the step S3 into an aqueous solution, adding a collecting agent which has no polarity, low water solubility and density less than that of water, stirring, adsorbing silicon carbide impurities by the collecting agent, floating, depositing the silicon particles with oxide films on the surface of the silicon particles in the water bottom, and collecting the silicon particles deposited in the water bottom; the collecting agent is one or a mixture of diesel oil and kerosene, and the weight ratio of water to the collecting agent is 7: 1-8: 1.
Or the collecting agent is methyl isobutyl carbinol, the surface modifier of the silicon material is an anionic surfactant, such as sodium dodecyl sulfate and the like, the surfactant is added when the silicon material is stirred, and the weight ratio of the silicon particles to the surfactant is 1000: 2, adding a collecting agent after 5min and stirring, wherein the weight ratio of the collecting agent to water is 1:8, standing, floating silicon carbide impurities, still depositing the silicon carbide particles with oxide films on the surface of the silicon carbide particles in the water, and collecting the silicon carbide particles deposited in the water.
S5, acid washing flotation: acid-washing the crushed silicon particles in step S4 in a hydrofluoric acid solution to remove the surface oxide film thereof while collecting floating silicon particles for the first time;
s6, carrying out hydrogen flotation on silicon particles: discharging the pickling solution in the step S5 to obtain bottom silicon particles, adding deionized water, adjusting the pH to be more than 8 to obtain an alkaline aqueous solution containing silicon particles, stirring, blowing hydrogen to the bottom of the alkaline aqueous solution, and collecting floating silicon particles for the second time;
s7, flotation by a phase transfer separation method: adding a collecting agent which is non-polar, low in water solubility and lower in density than water into the alkaline aqueous solution without the floating silicon granules in the step S6, stirring, adsorbing the silicon granules by the collecting agent, carrying out phase transfer separation and floating, still settling the stones at the bottom of the water, and collecting the floating silicon granules for the third time; sintering the silicon particles to remove the collector, and carrying out hydrofluoric acid pickling on the silicon particles to remove the surface oxide of the silicon particles; the collecting agent is one or a mixture of diesel oil and kerosene, and the ratio of water to the collecting agent is 7: 1-8: 1.
Or the collecting agent is methyl isobutyl carbinol, the surface modifier of the silicon material is an anionic surfactant, such as sodium dodecyl sulfate, the surfactant is added when the silicon material is stirred, and the weight ratio of the silicon particles to the surfactant is 1000: 2, adjusting the pH of the aqueous solution to be =3, adding a collecting agent after 5min, stirring, wherein the weight ratio of the collecting agent to water is 1:8, and adsorbing and floating the silicon chips by the collecting agent after standing.
And S8, mixing, cleaning and drying the silicon particles obtained in the steps S5, S6 and S7, using the silicon particles as raw materials of purified ingots, and performing directional solidification to obtain the purified ingots. 6 percent of the upper end of the purification ingot is cut off (the impurity content is high), 15 percent of the lower end of the purification ingot is cut off (the oxygen, iron and copper contents are high), and the middle part of the purification ingot can be directly used as the raw material of the solar-grade polycrystalline silicon ingot.
The method comprises the following steps of (1) removing organic matters by a gravity method, carrying out hydrofluoric acid pickling flotation, carrying out hydrogen blowing flotation and carrying out phase transfer flotation, wherein a specially designed silicon material flotation machine is adopted, the structure of the silicon material flotation machine is shown in figure 2, the structure of the silicon material flotation machine comprises a flotation tank 4, a stirring motor 1 and a stirring shaft 2, a tank cover 5 is arranged on the flotation tank, a baffle 41 is arranged on the side wall of the bottom of the flotation tank, the stirring shaft 2 penetrates through the tank cover and extends into the flotation tank, and a stirring blade 3 is arranged at the tail end of the stirring shaft and used for stirring a solution in the flotation tank; the flotation tank is provided with a cover to reduce the evaporation and overflow of the pickling solution, and the flotation tank is provided with a baffle to ensure that the pickling solution generates a large speed difference in the rotary flow process and is beneficial to pickling silicon materials. An air blowing pipeline 12 is arranged at the bottom of the flotation tank and used for blowing hydrogen into the flotation tank; a lower liquid discharge port 42 is formed in the side face of the bottom of the flotation tank, a first filter screen 43 is arranged at the lower liquid discharge port 42 and used for filtering bottom-sinking silicon particles, the lower liquid discharge port is communicated with a first liquid storage tank 9 through a first valve 44, the first liquid storage tank 9 is used for storing pickling solution or water, the first liquid storage tank 9 is communicated with a liquid feeding hole in the tank cover through a first liquid feeding pipe 6, and an acid-resistant pump 61 is arranged on the first liquid feeding pipe, so that liquid in the first liquid storage tank can be circularly extracted and utilized; be provided with last drain port 45 in flotation tank upper portion side, last drain port 45 and second stock solution 10 case pass through overflow pipe 8 intercommunication, be equipped with second valve 46 on the overflow pipe 8, be provided with second filter screen 11 on second stock solution case upper portion, second filter screen 11 is used for filtering flotation silicon grain or showy impurity, second stock solution case 10 is used for storing collecting agent or pickle, second stock solution case 10 is through second liquid feeding pipe 7 and the filling hole intercommunication on the capping, be provided with acid-proof pump 71 on the second liquid feeding pipe, thereby can cyclic utilization liquid in the second stock solution case. The second liquid storage tank 10 is also communicated with a vacuum pump 101, an air inlet of the vacuum pump is arranged below the second filter screen and is higher than the liquid level below the second filter screen, and the liquid level in the figure is indicated by a horizontal dotted line; when filtering, start the vacuum pump, second liquid reserve tank below the second filter screen forms a negative pressure, is equivalent to a negative pressure filter, can show improvement filtration efficiency.
The principle and method of purifying the silicon material will be described in detail below.
And crushing the silicon material to be selected to 3-5 mm. Because the broken silicon particles are grey brown particles, the color difference between the broken silicon particles and the grey red stone and the white quartz particles is larger, the broken silicon particles are removed by adopting a color selection method, manual selection is replaced, the working efficiency is high, the environment is protected, and the production cost is saved. The method is simple to operate and can be applied industrially.
The silicon material color selector has the function of memorizing the color, silicon particles are placed into the color selector to be photographed, at least three silicon particles are taken, and the silicon material color selector is enabled to memorize the color repeatedly. The flow rate of the silicon material is 1.6 t/h, the silicon material to be selected sequentially passes through the sensor and the background plate, the silicon material color selector removes the material with the color not within the set allowable range, the pressure of the spray valve is 0.8 MPa, and stones and quartz particles with the color not within the allowable range can be conveniently and quickly removed.
Organic matters such as adhesive tape silk, woven bag silk, plastic broken silk, hair silk and the like in the silicon broken materials have density smaller than that of water, can float in the water, and are floated in a silicon material flotation machine through stirring. The silicon particles and crushed stone and quartz particles sink to the bottom of the water.
The most difficult-to-process organic matter in the silicon chip material is epoxy resin sandwiched by two silicon chips, and the silicon chip material can be sintered by a rotary sintering furnace, and a feed inlet and a discharge outlet at two ends of the sintering furnace are not sealed. The feeding rate of the sintering furnace is 0.8 kg/min, the temperature is controlled at 860 ℃ and 900 ℃, the sintering is carried out for 5min, and the rotating speed of the sintering furnace is 0.3 rpm. As the sintering furnace automatically rotates, organic matters (including adhesive tape threads, epoxy resin and the like) in the silicon material fully react with oxygen in the sintering furnace to generate CO2Or CO escapes to obtain the silicon crushed material without organic matters. The feeding and the discharging of the sintering furnace are continuously executed, the electricity is saved, and the sintering efficiency is high.
The mechanism of epoxy resin sintering in the rotary sintering furnace is as follows: the silicon chip mixed with the epoxy resin is heated to 860 ℃ and 900 ℃, and is centrifugally rotated, dropped and collided with the furnace wall through the rotary sintering furnace, the epoxy resin is separated from the silicon chip and fully reacts with oxygen at high temperature to be converted into ash.
The crushed silicon material which is spun out from the rotary sintering furnace is quenched in deionized water at a higher temperature, and then the temperature of the crushed silicon material is reduced to room temperature. The silicon material cracks at the position with higher impurity content, which is beneficial to acid cleaning and crushing of the silicon material.
And (3) washing the silicon crushed material with high-pressure deionized water for 6 min to remove dust, mud, carbon, carbide and the like on the surface of the silicon crushed material, wherein the pressure of the high-pressure deionized water is not lower than 0.2 MPa.
Or pouring the sintered silicon fragments into deionized water, stirring for 6 min at the speed of 168 rpm, and enabling carbides in the silicon fragments to float out of the water surface in a water-repellent manner and be washed away by flowing water. The surface of the crushed silicon particles is provided with an oxide film which has hydrophilicity and is submerged in water. The silicon material loss is less in the rinsing process.
The particle size of the stones remained in the crushed silicon material is the same as or similar to that of the silicon material, and the density of the stones is similar to that of the silicon material.
And crushing the sintered silicon crushed material to the particle size of less than 1 mm.
The surface of the silicon chip material contains an oxide film and has hydrophilicity. The silicon carbide impurities in the silicon material can be removed by flotation by using a silicon material flotation machine designed by the patent: adding the silicon chip material into a flotation tank to prepare 10% aqueous solution, selecting hydrocarbon substances which have no polarity, low water solubility, density less than water and viscosity of about 4.5 mPa & s as collecting agents, for example, selecting diesel oil or kerosene as collecting agents to be added, wherein the ratio of the aqueous solution to the diesel oil or kerosene is 8:1, starting a stirring motor to stir, floating SiC on the water surface after being adsorbed by diesel oil or kerosene, and sinking the silicon fragments with oxidation films on the surface at the water bottom. And then opening a second valve, discharging the diesel oil adsorbing the silicon carbide, recovering the diesel oil or the kerosene serving as a collecting agent after negative pressure filtration by a second filter screen, abandoning the silicon carbide impurities obtained by filtration, and closing the second valve. And opening the first valve, discharging the aqueous solution, allowing the silicon crushed materials to remain at the bottom of the flotation tank under the filtration of the first filter screen, and closing the first valve.
The collector is methyl isobutyl carbinol, the ratio of water to collector is 8:1, and an anionic surfactant, such as sodium dodecyl sulfate (C) is added into the silicon material12H25SO4Na), the pH value of the aqueous solution is approximately equal to 5, the weight ratio of the silicon material to the anionic surfactant is 1000: 2, stirring, and adding the collecting agent after 5 min. The methyl isobutyl carbinol is a hydrocarbon substance which has no polarity, low water solubility, density less than that of water and viscosity of about 5.2 mPa & s, the collecting agent has high viscosity, and the capability of adsorbing silicon carbide particles is strong; sodium dodecyl sulfate ionization in aqueous solution, C12H25SO4Na→C12H25SO4−+ Na+. Isoelectric point of silicon carbide pH =3.7, at pH ≈ 5, C12H25SO4−The chemisorption force with silicon carbide is greater than the electrostatic repulsion force. One end of the sodium dodecyl sulfate is adsorbed by silicon carbide, the other end of the sodium dodecyl sulfate is adsorbed by the collecting agent methyl isobutyl carbinol, and the silicon carbide floats on the water surface. And the silicon particles with the oxide film on the surface are polar molecules, the isoelectric point pH =1.6, when the pH is approximately equal to 5, the zeta potential is greater than-50 mV, the electrostatic repulsive force between the silicon particles with the oxide film and the sodium dodecyl sulfate is greater than the chemical adsorption force, and the sodium dodecyl sulfate hardly adsorbs the silicon particles with the oxide film. The crushed silicon particles containing oxide film have hydrophilicity and are precipitated at the bottom of the aqueous solution.
Adding hydrofluoric acid solution into the silicon chip material, stirring and pickling, wherein the concentration of hydrofluoric acid is about 7%, the temperature is 60 ℃, the stirring speed is 168 rpm, and the stirring speed is not too high, fully reacting the silicon chip material with the hydrofluoric acid for 30 min, removing oxide films on the surfaces of the silicon chip particles, floating a part of silicon particles, opening a second valve, and collecting the floating silicon particles for the first time after filtering through a second filter screen; a part of the silicon particles still remain in the solution.
The mechanism of hydrofluoric acid corrosion of the oxide film on the surface of the broken silicon particles is as follows: SiO 22+ 4HF → SiF4↑ + 2H2O, SiF produced4SiF adhered to the surface of the crushed silicon particles4Is colorless gas, and drives silicon particles to float upwards. The silicon particles are nonpolar molecules and have water repellency, and the buoyancy and gravity action of the silicon particles are added, so that part of the silicon particles are suspended in a water body in a macroscopic manner. If the stirring speed is too fast, the pickling solution center forms negative pressure, SiF4Is not easy to be attached to the surface of the silicon particles, and is not beneficial to the floating of the crushed silicon particles on the surface of the pickling solution.
If the concentration of hydrofluoric acid is large, Si + 4HF → SiF4↑ + 2H2And the generated hydrogen is attached to the surface of the crushed silicon particles, so that the crushed silicon particles float upwards.
Suspended particle diameter
Wherein d isbThe diameter of the bubbles to which the particles adhere,ρlis the density of the liquid, paIs the suspended particle density. As the diameter of the bubbles increases, the diameter of the suspended particles also increases. The density of silicon is 2.33 g/cm3The density of the acid wash is 1 g/cm in terms of 7%3The diameter of the air bubbles is measured as 1mm, and the diameter of the silicon particles capable of being suspended is about 0.91 mm, so that it is reasonable to the patent to pulverize the silicon crushed material to a particle size of less than 1 mm.
The remaining quartz particles are dissolved during the pickling of the silica.
The density of the residual stones is greater than that of water, and the stones are polar molecules, have hydrophilicity and are deposited at the bottom of the pickling solution.
Discharging and recovering the pickling solution, and changing the pickling solution into deionized water, wherein the pH value of the deionized water is adjusted to be more than 8, because the surface zeta potential of the crushed silicon particles in the alkaline solution is more than-50 mV, and the electrostatic repulsive force between the silicon particles is favorable for the silicon particles to disperse and float in the aqueous solution; silicon particles and alkaline solution OH-The electrostatic repulsion force is beneficial to the floating of the silicon particles. In an alkaline environment, Si +2 OH- + H2O→SiO3 2-+ 2H2And ×) and the generated hydrogen is attached to the surfaces of the silicon particles, so that the silicon particles float upwards. Hydrogen is blown into the bottom of the flotation tank, the hydrogen flow is 6 ml/h, the hydrogen flow is not easy to be too large, only weak bubbles in the flotation liquid overflow, and the hydrogen is attached to the surface of silicon particles to facilitate the silicon particles to float upwards. Opening a second valve, and collecting the floating silicon particles for the second time; and part of silicon particles still remain in the solution after the hydrogen blowing flotation.
The discharged pickling solution can be recycled, the subsequent wastewater treatment pressure is reduced, the use amount of medicines is saved, and the silicon material treatment cost is reduced.
The crushed silicon material difficult to be subjected to hydrogen blowing flotation can be subjected to flotation by adopting a phase transfer separation method: preparing the silicon scrap soaked in the pickling solution (HF) into an aqueous solution less than 6%, adding nonpolar, low water solubility, hydrocarbon substances with density less than that of water and viscosity of about 4.5 mPa & s as collecting agents, such as diesel oil, kerosene and the like, and taking the ratio of water to the collecting agents as 8:1, using ammonia water (NH)4OH) regulating flotation solution pH more than 8, wherein the pH of the solution needs to be regulated more than 8 when kerosene is used as a collecting agent,in an alkaline solution, the zeta potential of silicon is greater than-50 mV, electrostatic repulsion between silicon surface charges and silicon surface charges is facilitated, silicon particles are favorably dispersed and enter the collecting agent, precipitation is avoided, stirring is carried out for 6 min, the rotating speed is less than 100 rpm, and the silicon particles adsorbed by the collecting agent float. Opening a second valve, collecting the flotation silicon particles for the third time, and recovering the collecting agent; at this time, the flotation of the crushed silicon particles in the solution is basically finished, and most of the remaining crushed silicon particles are impurities such as stones. And sintering the collector adhered to the surface of the silicon particles by using a rotary sintering furnace for the floated silicon particles, and then pickling by using hydrofluoric acid to remove an oxide film generated on the surface of the silicon particles in the sintering process.
Or the collecting agent is methyl isobutyl carbinol, and the ratio of water to the collecting agent is 8:1, adding a surfactant into a silicon particle aqueous solution and stirring, wherein the weight ratio of the silicon particles to the surfactant is 1000: and 2, adjusting the pH of the aqueous solution to be =3, adding the collecting agent after 5min, stirring and standing. The silicon particles without the oxide film are non-polar molecules, the isoelectric point pH =2.5, when the pH is approximately equal to 3, the chemical adsorption force between the silicon particles without the oxide film and sodium dodecyl sulfate is larger than the electrostatic repulsion force, one end of the sodium dodecyl sulfate is adsorbed by the non-polar silicon particles, the other end of the sodium dodecyl sulfate is adsorbed by a collecting agent methyl isobutyl carbinol, the silicon particles float on the water surface, and the stones are hydrophilic and still sink to the water bottom.
And mixing, cleaning and drying the first flotation silicon particles, the second flotation silicon particles and the third flotation, sintering and acid washing silicon particles to obtain a raw material of a purified ingot, and performing directional solidification to obtain the purified ingot. 6 percent of the upper end of the purification ingot is cut off (the impurity content is high), 15 percent of the lower end of the purification ingot is cut off (the oxygen, iron and copper contents are high), and the middle part of the purification ingot can be directly used as the raw material of the solar-grade polycrystalline silicon ingot.
Examples
The method for purifying the silicon crushed material can be used alone or in combination according to the impurity type in the silicon crushed material.
The first embodiment is as follows: and (3) utilizing a CCD color selector to color-select stones in the silicon material, wherein the particle size of the silicon material is 3-5mm, and the flow rate of the silicon material is 1.6 t/h. The color of the stones is mainly grey white, light gray, gray red and other light colors. The color of the silicon particles is grey brown and is single. And (3) putting the silicon material into a silicon material color selector, and selecting at least three silicon particles for photographing to enable the color selector to memorize repeatedly. And removing the materials with the colors out of the allowable range. The pressure of the spray valve is 0.8 MPa, and the vibration frequency of the feeder is 20 Hz. The test result shows that the silicon material net selection rate is more than 99.99 percent. The method can conveniently and rapidly remove the stones with the grain size of 3-5 mm.
Example two: the silicon material contains inorganic substances such as quartz and organic substances such as rubber filament and epoxy resin. Firstly, a rotary sintering furnace is used for sintering organic matters, the temperature is controlled to be about 860 ℃, the rotating speed of the sintering furnace is 0.5 rpm, the materials are continuously fed, the feeding speed is 1.8 t/h, and after 10 min, the silicon materials are continuously spun out from the rotary sintering furnace. Organic matters in the silicon material fully react with oxygen to generate CO2Or CO escape, and the carbide formed is rinsed in cold water (room temperature). And detecting to obtain the processed silicon material without organic matters. And finally, acid cleaning is carried out by utilizing a designed silicon material flotation machine, after 0.5 h, quartz in the silicon material is completely dissolved by 8% of hydrofluoric acid, and silicon particles float upwards. The recovery rate of the silicon material is more than 96.8 percent and the purification rate of the silicon material is more than 99.99 percent.
Example three: the crushed monocrystalline silicon material has particle size less than 0.25 mm and contains crushed stones. Since the stones are insoluble in strong acids and strong bases, they cannot be removed by acid washing. The silicon material flotation machine designed in the paper is used for flotation, the added medicament is 7% hydrofluoric acid, the stirring is carried out for 0.26 h, the rotating speed is 146 rpm, silicon particles float out of the water surface, and stones are deposited at the bottom of the flotation tank. The test result shows that the recovery rate of the silicon material is more than 96.9 percent and the purity of the silicon material is more than 99.99 percent.
Example four: the crushed polycrystalline crude silicon has particle size of less than 1mm, and contains impurities such as SiC. The surface of the broken polycrystal contains an oxide film and has hydrophilicity. Flotation was carried out using a silicon flotation machine designed herein: preparing a 10% aqueous solution from the silicon material, selecting diesel oil as a collecting agent, wherein the ratio of the aqueous solution to the diesel oil is 8:1, stirring speed 126 rpm, after 10 min, SiC was adsorbed by diesel oil and floated, and silicon material was settled on the water bottom to remove the upper floating matter. The test result shows that the recovery rate of the silicon material is more than 96.6 percent and the purity of the silicon material is more than 99.99 percent.
Example five: the silicon circle is a circular silicon wafer polished by two surfaces, the thickness is less than 1mm, the diameter is more than 8 mm, and part of the surface is oxidized. Pulverizing to particle size of less than 1 mm. The purification was carried out using a flotation machine designed here, with a chemical addition of 5.6% hydrofluoric acid, a stirring speed of 116 rpm and a heating temperature of 58 ℃. After 0.26 h, the silicon material floats upwards. The silicon material is taken out and weighed, the recovery rate of the silicon round crushed material is more than 95.9 percent, and the purity of the silicon particles is more than 99.99 percent.
Example six: the monocrystalline silicon ingot casting crucible bottom material with the particle size larger than 8 mm contains impurities such as pebbles and the like. By ICP-OES test, the content of gallium is more than 3.8 ppm. The particle size is less than 1mm by quenching and crushing. The purification was carried out using a flotation machine designed here, with 5.6% hydrofluoric acid and 9.6% hydrochloric acid added, stirred at 129 rpm, at a temperature of 68 ℃. After 0.36H, the pickle is discharged, deionized water is added, the solution concentration is about 6 percent, the pH value is more than 8, and H is blown into the bottom of the flotation tank2The hydrogen flow rate is less than 6 ml/h, the flotation solution only needs to be slightly bubbled, and the flotation solution is stirred at 9 rpm and is at room temperature. And (3) silicon particles after flotation are collected, and the test shows that the recovery rate of the silicon particles is more than 96.9 percent, the purity is 6N, and the silicon particles can be completely used as the raw materials of the polysilicon cast ingot.
Claims (9)
1. The purification method of the silicon scrap impurities is characterized in that the purification production process comprises the following steps:
s1, removing organic matters such as adhesive tape yarns, woven bag yarns, plastic broken yarns, hair yarns and epoxy resin from the silicon scrap;
s2, removing inorganic substances such as stones and quartz in the crushed silicon material;
s3, cleaning the silicon chip material, and then crushing the silicon chip material to obtain silicon chip particles with the particle size of less than 1 mm;
s4, removing silicon carbide impurities by flotation through a phase transfer separation method: adding the crushed silicon particles crushed in the step S3 into an aqueous solution, adding a collecting agent which has no polarity, low water solubility and density less than that of water, stirring, adsorbing silicon carbide impurities by the collecting agent, floating, depositing the silicon particles with oxide films on the surface of the silicon particles in the water bottom, and collecting the silicon particles deposited in the water bottom;
s5, acid washing flotation: acid-washing the crushed silicon particles collected in step S4 in a hydrofluoric acid solution to remove the surface oxide film thereof while collecting floating silicon particles for the first time;
s6, performing hydrogen flotation on crushed silicon particles: discharging the pickling solution in the step S5 to obtain bottom silicon particles, adding deionized water, adjusting the pH to be more than 8 to obtain an alkaline aqueous solution containing silicon particles, stirring, blowing hydrogen to the bottom of the alkaline aqueous solution, and collecting floating silicon particles for the second time;
s7, flotation by a phase transfer separation method: adding a collecting agent which is non-polar, low in water solubility and lower in density than water into the alkaline aqueous solution without the floating silicon granules in the step S6, stirring, adsorbing the silicon granules by the collecting agent, carrying out phase transfer separation and floating, still settling the stones at the bottom of the water, and collecting the floating silicon granules for the third time; sintering the silicon particles to remove the collector, and carrying out hydrofluoric acid pickling on the silicon particles to remove the surface oxide of the silicon particles;
and S8, mixing, cleaning and drying the silicon particles obtained in the steps S5, S6 and S7, and then using the silicon particles as raw materials for purifying silicon ingots, and after directional solidification and purification, directly using the silicon particles as the raw materials for the polycrystalline silicon ingots.
2. A method of purifying silicon crushed material impurities as claimed in claim 1, wherein: the removal of the organic matter in the step S1 is performed by combining a gravity method mainly for removing the organic matter having a density less than that of water and a sintering method mainly for removing the epoxy resin organic matter adhered to the silicon material.
3. A method of purifying silicon crushed material impurities as claimed in claim 1, wherein: in the step S2, the removal of inorganic matters is to crush the crushed silicon materials to 3-5mm and then finish the crushing in a silicon material color sorter by adopting a color sorting method, so that stones and quartz particles can be efficiently, economically and environmentally removed.
4. A method of purifying silicon crushed material impurities as claimed in claim 1, wherein: the collecting agent in the step S4 and/or the step S7 is one or a mixture of diesel oil and kerosene, and the weight ratio of water to the collecting agent is 7: 1-8: 1.
5. A method of purifying silicon crushed material impurities as claimed in claim 1, wherein: the collector in the step S4 is methyl isobutyl carbinol; adding an anionic surfactant into an aqueous solution of silicon particles and stirring before adding the methyl isobutyl carbinol collecting agent, wherein the weight ratio of the silicon particles to the surfactant is 1000: and 2, adjusting the pH of the aqueous solution to be =5, adding the collecting agent after 5 minutes, and stirring, wherein the weight ratio of the collecting agent to water is 1: 8.
6. A method of purifying silicon crushed material impurities as claimed in claim 1, wherein: the collector in the step S7 is methyl isobutyl carbinol; adding an anionic surfactant into an aqueous solution of silicon particles and stirring before adding the methyl isobutyl carbinol collecting agent, wherein the weight ratio of the silicon particles to the surfactant is 1000: and 2, adjusting the pH of the aqueous solution to be =3, adding the collecting agent after 5 minutes, and stirring, wherein the weight ratio of the collecting agent to water is 1: 8.
7. A method of purifying silicon crushed material impurities as claimed in claim 1, wherein: the removal of organic matters in the step S1, the flotation of the phase transfer separation method in the steps S4 and S7, the acid washing flotation in the step S5 and the hydrogen blowing flotation in the step S6 are all carried out in a silicon material flotation machine, the structure of the silicon material flotation machine comprises a flotation tank, a stirring motor and a stirring shaft, a baffle is arranged on the side wall of the bottom of the flotation tank, a tank cover is arranged on the flotation tank, the stirring shaft penetrates through the tank cover to extend into the flotation tank, and a stirring blade is arranged at the tail end of the stirring shaft; an air blowing pipeline is arranged at the bottom of the flotation tank and used for blowing hydrogen into the flotation tank; a lower drainage outlet is arranged on the side surface of the bottom of the flotation tank, a first filter screen is arranged at the lower drainage outlet and used for filtering bottom silicon particles, the lower drainage outlet is communicated with a first liquid storage tank through a valve, the first liquid storage tank is used for storing pickling solution or water, and the first liquid storage tank is communicated with a liquid adding hole in the tank cover through a first liquid adding pipe; the flotation tank is characterized in that an upper liquid discharging port is arranged on the side face of the upper portion of the flotation tank, the upper liquid discharging port is communicated with a second liquid storage tank through an overflow pipe, a second valve is arranged on the overflow pipe, a second filter screen is arranged on the upper portion of the second liquid storage tank, the second liquid storage tank is used for storing a collecting agent or pickling solution, the second filter screen is used for filtering flotation silicon particles or impurity floaters, and the second liquid storage tank is communicated with liquid adding holes in a tank cover through a second liquid adding pipe.
8. A method of purifying silicon crushed material impurities as claimed in claim 7, wherein: and the first liquid adding pipe and the second liquid adding pipe are respectively provided with an acid-resistant pump.
9. A method of purifying silicon crushed material impurities as claimed in claim 7, wherein: the second liquid storage tank is also communicated with a vacuum pump.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110899282.3A CN113582184B (en) | 2021-08-06 | 2021-08-06 | Method for purifying crushed silicon material impurities |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110899282.3A CN113582184B (en) | 2021-08-06 | 2021-08-06 | Method for purifying crushed silicon material impurities |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN113582184A true CN113582184A (en) | 2021-11-02 |
| CN113582184B CN113582184B (en) | 2023-09-19 |
Family
ID=78255773
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110899282.3A Active CN113582184B (en) | 2021-08-06 | 2021-08-06 | Method for purifying crushed silicon material impurities |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113582184B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114890429A (en) * | 2022-05-18 | 2022-08-12 | 江苏新效新材料科技有限公司 | Purification method for removing resin impurities from solar silicon wafer cutting waste residues |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004223321A (en) * | 2003-01-20 | 2004-08-12 | Hayaji Shibata | Method and apparatus for separating sio2 particle and sic particle, and separated/recovered sic |
| CN101428252A (en) * | 2008-12-16 | 2009-05-13 | 江西赛维Ldk太阳能高科技有限公司 | Classification method for waste silicon material mixed with foreign matter |
| CN101491888A (en) * | 2009-03-05 | 2009-07-29 | 南昌大学 | Foam flotation method capable of separating silicon powder and carbon silicon powder |
| US20100215561A1 (en) * | 2006-12-29 | 2010-08-26 | Lan C W | Recovery method of silicon slurry |
| US20100278707A1 (en) * | 2007-12-19 | 2010-11-04 | Ecole Polytechnique Federale De Lausanne (Epfl) | Method for recovering silicon from sawing waste |
| CN102205965A (en) * | 2011-05-05 | 2011-10-05 | 王楚雯 | Method for recovering silicon powder |
| CN102247933A (en) * | 2011-03-22 | 2011-11-23 | 江西赛维Ldk太阳能高科技有限公司 | Method for purifying silicon powder |
| WO2013004001A1 (en) * | 2011-07-04 | 2013-01-10 | Rhodia (China) Co., Ltd. | BI-PHASE Si/SIC SEPARATION METHOD |
| CN110240167A (en) * | 2019-07-26 | 2019-09-17 | 苏州中材非金属矿工业设计研究院有限公司 | A kind of extraction process of high purity quartz |
-
2021
- 2021-08-06 CN CN202110899282.3A patent/CN113582184B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004223321A (en) * | 2003-01-20 | 2004-08-12 | Hayaji Shibata | Method and apparatus for separating sio2 particle and sic particle, and separated/recovered sic |
| US20100215561A1 (en) * | 2006-12-29 | 2010-08-26 | Lan C W | Recovery method of silicon slurry |
| US20100278707A1 (en) * | 2007-12-19 | 2010-11-04 | Ecole Polytechnique Federale De Lausanne (Epfl) | Method for recovering silicon from sawing waste |
| CN101428252A (en) * | 2008-12-16 | 2009-05-13 | 江西赛维Ldk太阳能高科技有限公司 | Classification method for waste silicon material mixed with foreign matter |
| CN101491888A (en) * | 2009-03-05 | 2009-07-29 | 南昌大学 | Foam flotation method capable of separating silicon powder and carbon silicon powder |
| CN102247933A (en) * | 2011-03-22 | 2011-11-23 | 江西赛维Ldk太阳能高科技有限公司 | Method for purifying silicon powder |
| CN102205965A (en) * | 2011-05-05 | 2011-10-05 | 王楚雯 | Method for recovering silicon powder |
| WO2013004001A1 (en) * | 2011-07-04 | 2013-01-10 | Rhodia (China) Co., Ltd. | BI-PHASE Si/SIC SEPARATION METHOD |
| CN110240167A (en) * | 2019-07-26 | 2019-09-17 | 苏州中材非金属矿工业设计研究院有限公司 | A kind of extraction process of high purity quartz |
Non-Patent Citations (1)
| Title |
|---|
| 马瑾;: "太阳能级硅料的污染杂质及清洗技术浅谈", 太阳能, no. 03, pages 102 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114890429A (en) * | 2022-05-18 | 2022-08-12 | 江苏新效新材料科技有限公司 | Purification method for removing resin impurities from solar silicon wafer cutting waste residues |
Also Published As
| Publication number | Publication date |
|---|---|
| CN113582184B (en) | 2023-09-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Li et al. | Progress in recovery and recycling of kerf loss silicon waste in photovoltaic industry | |
| US4472271A (en) | Froth flotation apparatus and process | |
| CN104313679A (en) | Method for processing silicon powder to obtain silicon crystals | |
| CN104925818B (en) | High-purity quartz powder producing technology and device utilizing quartz mill tailings | |
| JP2011020070A (en) | Device and method for flotation separation and method for producing product using same | |
| CN102600988A (en) | Foam flotation method for separating silicon powder from silicon carbide powder | |
| CN102247933A (en) | Method for purifying silicon powder | |
| CN101428252B (en) | Classification method for waste silicon material mixed with foreign matter | |
| CN113582184B (en) | Method for purifying crushed silicon material impurities | |
| JP5702567B2 (en) | Method and apparatus for purifying contaminated soil | |
| CN102320701A (en) | Device and method for recycling silicon powder in silicon processing waste water | |
| JP2012115781A (en) | Method of beneficiating copper-containing material containing arsenic | |
| JP4737395B2 (en) | Method for treating fine powder containing calcium component and lead component | |
| CN107758672A (en) | The recovery method of silica flour in crystalline silicon cutting waste material | |
| CN209189015U (en) | A kind of quartz sand automatic impurity removing equipment | |
| CN202030600U (en) | Silica powder and waste water recycling device for silicon cutting waste water | |
| JP4579211B2 (en) | Processing method and processing system for fine powder containing calcium component and lead component | |
| CN102079520A (en) | Recycling method of silicon carbide | |
| JP2006346512A (en) | Treating method of fine powder containing calcium component and lead component | |
| CN102530948A (en) | Method for recycling silicon from filings obtained through silicon wafer cutting | |
| JP2024103899A (en) | Graphite purification method | |
| CN113089076B (en) | Method for preparing calcium sulfate whiskers based on chlor-alkali salt mud | |
| JP2008093510A (en) | Method and system for treating fine powder containig calcium component and lead component | |
| WO2019219822A1 (en) | Silicon and silica production process | |
| CN202164124U (en) | Silica powder recycling device for silicon processing waste water |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |