CN110963493A - Method for preparing super metallurgical grade silicon from crystalline silicon cutting waste - Google Patents
Method for preparing super metallurgical grade silicon from crystalline silicon cutting waste Download PDFInfo
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Abstract
A method for preparing super metallurgical grade silicon from crystalline silicon cutting waste comprises the steps of carrying out primary pretreatment on the crystalline silicon cutting waste to obtain crystalline silicon coarse sizing slurry, and carrying out secondary pretreatment on the coarse sizing slurry to obtain a purified fine sizing material; briquetting the obtained purified and refined material to obtain a first refined material block, and separating slag and silicon after the first refined material block is subjected to oxygen-controlled smelting and refining to obtain first molten silicon and first refined slag; chemically reconstructing impurities of the first molten silicon and/or the first refining slag to obtain first modified solid silicon and/or second modified solid silicon; and removing the reconstructed impurity phase in the obtained first modified solid silicon and/or second modified solid silicon to obtain the super metallurgical grade silicon. The method has the advantages of short flow, cleanness and low cost, and is easy to realize large-scale application of high-valued regeneration cycle of silicon materials cut by crystalline silicon.
Description
Technical Field
The invention belongs to the technical field of secondary resource utilization, and particularly relates to a method for preparing super metallurgical silicon from crystalline silicon cutting waste.
Background
Nearly 40% of silicon in the crystalline silicon cutting process becomes waste, and the demand of recycling low-end silicon materials such as crystalline silicon cutting waste is urgent. The crystalline silicon cutting waste mainly comes from the cutting process of the solar cell, and also comprises leftover materials and the like for cutting silicon ingots. The solar cell is generally cut by matching a multi-wire saw with mortar, and the mortar is usually a mixture of media such as mineral oil or polyethylene glycol (PEG) and SiC (silicon carbide) particles. In the cutting process, nearly 50% of cutting silicon materials enter mortar in the form of fine silicon powder to become waste materials, and cutting liquid, SiC particles and silicon powder in the waste materials have high recycling value. With the expansion of industrial scale and the pressure of cost increase, diamond-plated wire cutting, which has cost and efficiency advantages, is gradually replacing the mortar cutting method. However, it is inevitable that the diamond wire cutting crystalline silicon process also generates a large amount of cutting silicon powder waste. The high-value utilization of the crystalline silicon cutting waste has important practical significance for resource recycling and environmental problem relief, and is also an important problem for restricting the development of the industry.
Aiming at the recovery of silicon powder for cutting crystalline silicon, only substances with larger attribute difference, such as solid-liquid substances, solid particles with larger size difference, particles with electronegativity difference and the like can be separated in the prior art. And good effect is difficult to achieve for substances with small attribute difference, so that a certain amount of resource waste is caused, and comprehensive utilization of all components of the cut silicon powder is difficult to realize. Acid washing is also widely concerned as a common chemical impurity removal method, but wet chemical impurity removal such as acid washing mainly aims at removing metal impurities on the surface layer of cut silicon powder, but has less attention to removing nonmetal impurities and trace impurities in silicon ingots after silicon powder smelting, and the deep removal of the impurities is difficult to realize.
High temperature pyrogenic process decontamination has gained increasing attention as an important method for recovering cutting waste. However, in the prior art, the powder silicon is not directly melted without protection, and the method is difficult to smoothly carry out, and meanwhile, the required melting temperature is high, the melting time is long, and incrustation and silicon loss are easily caused. Compared with the direct melting of cutting silicon powder, the slag agent auxiliary melting can play a role in isolating air and preventing silicon liquid from being oxidized, and can adsorb fine impurities in the silicon liquid so as to purify the silicon liquid. However, in these methods, since the silicon powder is melted and then the slag is formed, the slag formation agent does not promote the melting of the silicon powder, and thus, there are problems of low recovery rate and high post-treatment pressure of the soot, and the requirement for the raw material is high, and for example, it is difficult to select a diamond wire cutting silicon powder having a high silicon content, and it is difficult to perform the method for the mortar waste containing SiC.
The super metallurgical silicon (UMG-Si, 4N) has the advantages of low impurity content, small quantity of impurities, high product cost performance, wide product application range and the like, is widely applied to the fields of photovoltaic industry, organic silicon and high-end alloy, and is a new fulcrum for high-end application of industrial silicon. However, the traditional UMG-Si preparation method depends on the 'concentrate principle' and a multiple directional solidification process too much, and the existing silicon purification method needs to combine multiple metallurgy separation technologies, so that the problems of long flow, high energy consumption, low efficiency and the like are caused.
Therefore, aiming at the problems of the existing wet method and fire method processes, a new process is created for the entry point from the attribute characteristics of the crystalline silicon cutting waste and the impurity occurrence structure, and a new method, a new technology and a new process are developed to solve the problem of high-value utilization of the crystalline silicon cutting waste. Based on the characteristics of UMG-Si and the current state of the prior art, the preparation of UMG-Si by using crystalline silicon cutting waste materials is a new direction for realizing high-value utilization of UMG-Si.
Disclosure of Invention
In view of the above, one of the main objectives of the present invention is to provide a method for preparing super metallurgical grade silicon from crystalline silicon cutting waste and super metallurgical grade silicon, so as to at least partially solve at least one of the above technical problems.
In order to achieve the above object, as one aspect of the present invention, there is provided a method for preparing super metallurgical grade silicon from crystalline silicon cutting scraps, comprising:
(1) carrying out primary pretreatment on the crystalline silicon cutting waste to obtain crystalline silicon roughing material slurry, and carrying out secondary pretreatment on the roughing material slurry to obtain a purified fine material;
(2) briquetting the purified and refined material obtained in the step (1) to obtain a first refined material block, and separating slag and silicon after the first refined material block is subjected to oxygen-controlled smelting and refining to obtain first molten silicon and first refined slag;
(3) chemically reconstructing impurities of the first molten silicon and/or the first refining slag to obtain first modified solid silicon and/or second modified solid silicon;
(4) and (4) removing the reconstructed impurity phase in the first modified solid silicon and/or the second modified solid silicon obtained in the step (3) to obtain the super metallurgical grade silicon.
As another aspect of the present invention, there is also provided a method for preparing super metallurgical grade silicon from crystalline silicon cutting waste, comprising:
(1) carrying out primary pretreatment on the crystalline silicon cutting waste to obtain crystalline silicon roughing material slurry and inclusion residues, and carrying out secondary pretreatment on the roughing material slurry to obtain a purified fine sizing material;
(2) briquetting the purified and refined material obtained in the step (1) to obtain a first refined material block, and separating slag and silicon after the first refined material block is subjected to oxygen-controlled smelting and refining to obtain first molten silicon and first refined slag;
(3) cooling the second melt silicon obtained in the step (2) at a controlled speed to obtain third modified solid silicon;
(4) and (4) removing the reconstructed impurity phase in the third modified solid silicon obtained in the step (3) to obtain the super metallurgical grade silicon.
As a further aspect of the present invention, there is also provided a method for preparing ultra metallurgical grade silicon from crystalline silicon cutting waste, comprising:
(1) carrying out primary pretreatment on the crystalline silicon cutting waste to obtain crystalline silicon roughing material slurry and inclusion residues, and carrying out secondary pretreatment on the roughing material slurry to obtain a purified fine sizing material;
(2) carrying out chemical impurity removal treatment on the purified and refined material obtained in the step (1) and then briquetting the purified and refined material to obtain a second refined material block, and carrying out oxygen-controlled smelting and refining treatment on the second refined material block to separate slag and silicon to obtain second molten silicon and second refined slag;
(3) performing impurity chemical reconstruction on the second molten silicon and/or the second refining slag to obtain fourth modified solid silicon and/or fifth modified solid silicon;
(4) and (4) removing two ends of the fourth modified solid silicon and/or the fifth modified solid silicon obtained in the step (3) to obtain the super metallurgical grade silicon.
Based on the technical scheme, the method for preparing the super metallurgical silicon by using the crystalline silicon cutting waste and the super metallurgical silicon have at least one of the following advantages compared with the prior art:
1. the invention changes the separation and purification idea of crude products into a short-range purification new method which mainly comprises the steps of reaction transfer regulation and single step separation and mainly comprises the steps of multi-scale structure regulation and grouping synchronous separation. The method is based on basic theoretical research of structure-activity relationship between impurity structure and refining effect, and designs a novel refining slag system to realize synchronous removal of B, P; the method comprises the steps of realizing targeted reconstruction of impurities with different attributes and forming a secondary impurity phase by adopting an impurity reconstruction agent and a phase change control means, realizing efficient corrosion dissociation of the reconstructed impurity phase by evaluating the corrosion resistance of the impurity phase and developing a novel composite acid medium, and finally establishing a novel method for preparing the ultra-metallurgical-grade silicon (UMG-Si) by cutting a silicon material through crystalline silicon through process optimization, process strengthening and system integration;
2. the method has the advantages of short flow, cleanness and low cost, and is easy to realize large-scale application of high-valued regeneration cycle of silicon materials cut by crystalline silicon.
Drawings
FIG. 1 is a flow chart of a method for preparing super metallurgical grade silicon from crystalline silicon cutting waste in example 1 of the invention.
Detailed Description
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
The invention aims to overcome the common problems of difficult impurity separation, low purification efficiency, high environmental cost and low comprehensive recovery rate caused by mismatching of the recovery process in the existing crystalline silicon cutting waste recovery industry, and provides a method for preparing super metallurgical grade silicon from crystalline silicon cutting waste.
The invention discloses a method for preparing super metallurgical grade silicon from crystalline silicon cutting waste, which comprises the following steps:
(1) carrying out primary pretreatment on the crystalline silicon cutting waste to obtain crystalline silicon roughing material slurry, and carrying out secondary pretreatment on the roughing material slurry to obtain a purified fine material;
(2) briquetting the purified and refined material obtained in the step (1) to obtain a first refined material block, and separating slag and silicon after the first refined material block is subjected to oxygen-controlled smelting and refining to obtain first molten silicon and first refined slag;
(3) chemically reconstructing impurities of the first molten silicon and/or the first refining slag to obtain first modified solid silicon and/or second modified solid silicon;
(4) and (4) removing the reconstructed impurity phase in the first modified solid silicon and/or the second modified solid silicon obtained in the step (3) to obtain the super metallurgical grade silicon.
In some embodiments of the invention, the first pretreatment in step (1) comprises at least one of size reduction, slurry formulation, physical centrifugation;
in some embodiments of the present invention, the second pretreatment in step (1) comprises at least one of solid-liquid separation, acid washing for impurity removal, water washing, and drying;
in some embodiments of the invention, the briquetting method in the step (2) comprises mixing the purified beneficiated material with a binder, pressing, and drying;
in some embodiments of the invention, the oxygen-controlled smelting refining process step in step (2) comprises an oxygen-controlled treatment and a slag washing treatment;
in some embodiments of the present invention, the method of oxygen control treatment comprises vacuum oxygen control or inert gas protection oxygen control;
in some embodiments of the invention, the slag washing process includes placing beneficiated lumps multiple times into the molten slag for melt refining at a temperature greater than 1450 ℃.
In some embodiments of the invention, the mass ratio of slag to first beneficiated mass in the oxygen-controlled smelting process step of step (2) is (0.1 to 0.5) to 1.
In some embodiments of the invention, the slag comprises a main agent and an auxiliary agent, wherein the main agent comprises Na2O、SiO2At least one of;
in some embodiments of the invention, the adjuvant comprises CaO, MgO, Al2O3、CaF2、NaF、FeOx、Na3AlF6、BaO、BaF2、TiO2、Cr2O3、B2O3、MnOx、K2O、ZrO2、ZnO、Li2O、SrO、Ce2O3、PbO、CaCl2At least one of NaCl and KCl.
In some embodiments of the present invention, the restructuring agent in the chemical restructuring step in step (3) includes at least one of Ca, Al, Ti, Sn, Cu, Ce, La, Pr, Nd;
in some embodiments of the present invention, the process for chemically reconstituting the first silicon melt in step (3) comprises: adding an impurity restructuring agent into the first melt silicon, and performing oxygen control, stirring and speed control cooling treatment to obtain first modified solid silicon;
in some embodiments of the present invention, the chemical restructuring method of the first refining slag in the step (3) includes: adding metal oxide into the first refining slag, performing chemical impurity reconstruction by using a slag-silicon interface redox reaction while controlling oxygen and stirring, and performing slag/silicon separation and speed-controlling cooling treatment to obtain second modified solid silicon.
In some embodiments of the invention, the metal oxide comprises CaO, MgO, Al2O3、TiO2、Cr2O3、MnOx、SrO、Ce2O3At least one of PbO;
in some embodiments of the present invention, the method of controlled cooling comprises uniform cooling, variable cooling or staged cooling, with a cooling rate of 0.1 to 15 ℃/min.
In some embodiments of the invention, the purity of the metallurgical grade silicon in step (4) is greater than 99.99%;
in some embodiments of the present invention, the removing method of the reconstituted impurity phase in step (4) includes subjecting the first modified solid silicon and/or the second modified solid silicon to chemical impurity removal treatment to achieve removal of the reconstituted impurity phase.
In some embodiments of the invention, the chemical impurity removal comprises at least one of physical crushing, chemical crushing, mixed acid medium dissociation strengthening, surfactant interface modification and external field strengthening corrosion treatment;
in some embodiments of the present invention, the particle size of the silicon powder formed by physical crushing or chemical crushing is 50 to 500 micrometers;
in some embodiments of the present invention, the mixed acid medium comprises at least two of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, and aqua regia;
in some embodiments of the invention, the concentration of the mixed acid is 0.1 to 100 wt%, and the weight ratio of the silicon powder to the mixed acid is 1 to (0.1 to 1200);
in some embodiments of the invention, the acid wash temperature is 10 to 100 ℃ and the acid wash time is 0.5 to 25 hours.
The invention also discloses a method for preparing the super metallurgical grade silicon from the crystalline silicon cutting waste, which comprises the following steps:
(1) carrying out primary pretreatment on the crystalline silicon cutting waste to obtain crystalline silicon roughing material slurry and inclusion residues, and carrying out secondary pretreatment on the roughing material slurry to obtain a purified fine sizing material;
(2) briquetting the purified and refined material obtained in the step (1) to obtain a first refined material block, and separating slag and silicon after the first refined material block is subjected to oxygen-controlled smelting and refining to obtain first molten silicon and first refined slag;
(3) cooling the second melt silicon obtained in the step (2) at a controlled speed to obtain third modified solid silicon;
(4) and (4) removing the reconstructed impurity phase in the third modified solid silicon obtained in the step (3) to obtain the super metallurgical grade silicon.
Wherein, the method of the first pretreatment in the step (1) comprises at least one of crushing and grading, slurry preparation and physical centrifugation;
wherein the second pretreatment method in the step (1) comprises at least one of solid-liquid separation, acid washing for impurity removal, water washing and drying;
the briquetting treatment method in the step (2) comprises the steps of mixing the purified and selected material with a binder, pressing and drying;
wherein, the oxygen-controlled smelting and refining treatment step in the step (2) comprises oxygen-controlled treatment and slag washing treatment;
wherein the oxygen control treatment method comprises vacuum oxygen control or inert gas protection oxygen control;
wherein the slag washing treatment comprises the step of putting the selected material blocks into molten slag for smelting and refining for multiple times, and the smelting and refining temperature is higher than 1450 ℃.
Wherein, the mass ratio of the slag to the first selected material block in the oxygen-controlled smelting treatment step in the step (2) is (0.1-0.5) to 1.
The slag comprises a main agent and an auxiliary agent, wherein the main agent comprises at least one of Na2O and SiO 2; the adjuvant comprises CaO, MgO and Al2O3、CaF2、NaF、FeOx、Na3AlF6、BaO、BaF2、TiO2、Cr2O3、B2O3、MnOx、K2O、ZrO2、ZnO、Li2O、SrO、Ce2O3、PbO、CaCl2At least one of NaCl and KCl.
Wherein the speed-controlled cooling method in the step (3) comprises uniform speed cooling, variable speed cooling or staged cooling, and the cooling rate is 0.1-15 ℃/min.
Wherein the purity of the super metallurgical grade silicon in the step (4) is more than 99.99 percent;
and (4) removing the reconstructed impurity phase by using the method for removing the reconstructed impurity phase in the step (4) after chemical impurity removal treatment of the third modified solid silicon.
Wherein the chemical impurity removal comprises at least one of physical crushing, chemical crushing, mixed acid medium dissociation strengthening, surfactant interface modification and external field strengthening corrosion treatment;
wherein the particle size of the silicon powder formed by physical crushing or chemical crushing is 50-500 microns;
wherein the mixed acid medium comprises at least two of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and aqua regia;
wherein the concentration of the mixed acid is 0.1-100 wt%, and the weight ratio of the silicon powder to the mixed acid is 1: (0.1 to 1200);
wherein the pickling temperature is 10 to 100 ℃, and the pickling time is 0.5 to 25 hours.
The invention also discloses a method for preparing the super metallurgical grade silicon from the crystalline silicon cutting waste, which comprises the following steps:
(1) carrying out primary pretreatment on the crystalline silicon cutting waste to obtain crystalline silicon roughing material slurry and inclusion residues, and carrying out secondary pretreatment on the roughing material slurry to obtain a purified fine sizing material;
(2) carrying out chemical impurity removal treatment on the purified and refined material obtained in the step (1) through briquetting, then carrying out briquetting treatment to obtain a second refined material block, and carrying out slag-silicon separation on the second refined material block after oxygen-controlled smelting refining treatment to obtain second molten silicon and second refined slag;
(3) performing impurity chemical reconstruction on the second molten silicon and/or the second refining slag to obtain fourth modified solid silicon and/or fifth modified solid silicon;
(4) and (4) removing two ends of the fourth modified solid silicon and/or the fifth modified solid silicon obtained in the step (3) to obtain the super metallurgical grade silicon.
Wherein, the method of the first pretreatment in the step (1) comprises at least one of crushing and grading, slurry preparation and physical centrifugation;
wherein the second pretreatment method in the step (1) comprises at least one of solid-liquid separation, acid washing for impurity removal, water washing and drying;
wherein, the chemical impurity removal in the step (2) comprises at least one of physical crushing, chemical crushing, mixed acid medium dissociation strengthening, surfactant interface modification and external field strengthening corrosion treatment;
wherein the particle size of the silicon powder formed by physical crushing or chemical crushing is 50-500 microns;
wherein the mixed acid medium comprises at least two of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and aqua regia;
wherein the concentration of the mixed acid is 0.1 to 100 wt%, and the weight ratio of the silicon powder to the mixed acid is 1: 0.1 to 1200;
wherein the pickling temperature is 10 to 100 ℃, and the pickling time is 0.5 to 25 hours.
The briquetting treatment method in the step (2) comprises the steps of mixing the purified and selected material with a binder, pressing and drying;
wherein, the oxygen-controlled smelting and refining treatment step in the step (2) comprises oxygen-controlled treatment and slag washing treatment;
wherein the oxygen control treatment method comprises vacuum oxygen control or inert gas protection oxygen control;
wherein the slag washing treatment comprises the step of putting the selected material blocks into molten slag for smelting and refining for multiple times, and the smelting and refining temperature is higher than 1450 ℃.
Wherein the mass ratio of the slag to the second selected material block in the oxygen-controlled smelting treatment step in the step (2) is (0.1-0.5): 1.
the slag comprises a main agent and an auxiliary agent, wherein the main agent comprises Na2O、SiO2At least one of; the adjuvant comprises CaO, MgO and Al2O3、CaF2、NaF、FeOx、Na3AlF6、BaO、BaF2、TiO2、Cr2O3、B2O3、MnOx、K2O、ZrO2、ZnO、Li2O、SrO、Ce2O3、PbO、CaCl2At least one of NaCl and KCl.
Wherein the reconstruction agent in the chemical reconstruction step in the step (3) comprises at least one of Ca, Al, Ti, Sn, Cu, Ce, La, Pr and Nd;
wherein the chemical reconstitution method of the second silicon melt in step (3) comprises: adding an impurity restructuring agent into the second melt silicon, and performing oxygen control, stirring and speed control cooling treatment to obtain fourth modified solid silicon;
wherein the chemical restructuring method of the second refining slag in the step (3) comprises the following steps: adding metal oxide into the second refining slag, performing chemical impurity reconstruction by using slag-silicon interface redox reaction while controlling oxygen and stirring, and performing slag/silicon separation and speed-controlling cooling treatment to obtain fifth modified solid silicon.
Wherein the metal oxide comprises CaO, MgO, Al2O3、TiO2、Cr2O3、MnOx、SrO、Ce2O3At least one of PbO;
wherein the speed-control cooling method comprises uniform speed cooling, variable speed cooling or staged cooling, and the cooling rate is 0.1-15 ℃/min.
Wherein the purity of the super metallurgical grade silicon in the step (4) is more than 99.99 percent;
in one exemplary embodiment, the method for preparing the super metallurgical grade silicon by using the crystalline silicon cutting waste material comprises the following specific steps: (1) physically/chemically separating and removing impurities and a large amount of metal impurities from the crystalline silicon cutting waste to obtain a fine material and impurity residues; (2) mixing the obtained refined material with a binder, pressing and drying, performing oxygen-controlled smelting refining, and removing non-metallic impurities such as B (boron), P (phosphorus) and the like and trace impurities to obtain pure molten silicon and refined slag; (3) chemically reconstructing impurities in the obtained pure molten silicon, and performing phase change control by speed-controlled cooling to promote the reconstructed impurity phase to be separated out on the interface of the silicon crystal to obtain modified solid silicon; (4) and crushing and grading the obtained modified solid silicon, and corroding and removing the reconstructed impurity phase by adopting wet chemical impurity removal of mixed acid corrosion to obtain the ultra-metallurgical silicon (UMG-Si) with the purity of more than 99.99 percent. Aiming at the problems of difficult separation of uniformly distributed impurities, low purification efficiency and high environmental cost in the crystalline silicon cutting waste, the method changes the separation and purification idea of a crude product, changes the traditional purification method mainly based on 'reaction transfer regulation and control-single step separation' into a short-range purification new method mainly based on 'multi-scale structure regulation and control-group synchronous separation', and is easy to realize the large-scale application of high-valued regeneration cycle of the crystalline silicon cutting waste.
In a second exemplary embodiment, the method for preparing super metallurgical grade silicon from crystalline silicon cutting waste of the present invention comprises the steps of:
(1) the method comprises the following steps of carrying out crushing and grading, slurry preparation and physical centrifugal separation combined treatment on crystalline silicon cutting waste to obtain crystalline silicon roughing slurry and impurity residues, and carrying out solid-liquid separation, acid pickling impurity removal, water washing and drying combined treatment on the roughing slurry to obtain a purified and fine-selected material.
(2) And (2) mixing, pressing and drying the fine selected material obtained in the step (1) by using a binder to obtain a fine selected material block (namely a first fine selected material block). And (3) putting the selected lump materials into high-temperature equipment, carrying out oxygen-control smelting refining impurity removal through combined treatment of oxygen control and slag washing, and separating slag/silicon to obtain pure molten silicon (namely first molten silicon) and refining slag (namely first refining slag).
(3) Chemically reconstructing impurities of the refining slag and the pure silicon melt obtained in the step (2), wherein the method specifically comprises the following steps:
impurity chemical reconstitution of the clean melt silicon: and (3) adding an impurity restructuring agent into the pure melt silicon obtained after the slag/silicon separation in the step (2), and carrying out impurity chemical restructuring while carrying out combined treatment of oxygen control, stirring and speed control cooling to obtain the first modified solid silicon.
Chemically reconstructing impurities in the refining slag: and (3) adding metal oxide into the refining slag at the later stage of oxygen-controlled smelting refining in the step (2), performing impurity chemical reconstruction by utilizing slag-silicon interface redox reaction while performing oxygen-controlled and stirring combined treatment, and performing slag/silicon separation and speed-controlled cooling combined treatment to obtain second modified solid silicon.
(4) And (4) respectively carrying out physical crushing, chemical crushing, mixed acid medium dissociation strengthening, surfactant interface modification and external field strengthening corrosion combined treatment on the first modified solid silicon and the second modified solid silicon obtained in the step (3) to realize chemical impurity removal, and carrying out water washing and drying treatment to obtain UMG-Si with the purity of more than 99.99%.
As a further improvement of the present invention, in the step (2)The method for controlling oxygen in oxygen-controlled smelting refining is one of vacuum treatment and inert gas protection, wherein the vacuum degree of the vacuum treatment is less than 1000Pa, and the inert gas is O2、H2O, Ar and H2One or more combinations thereof.
As a further improvement of the invention, the slag washing in the step (2) is that the selected material blocks are put into the slag in a small quantity and multiple times mode for oxygen-controlled smelting refining, the temperature of the oxygen-controlled smelting refining is higher than 1450 ℃, and the mass ratio of slag to silicon (namely the mass ratio of the slag to the selected material blocks) is 0.1: 1-0.5: 1.
Furthermore, the slag agent used by the slag is Na2O and SiO2The auxiliary slag agent mainly comprises CaO, MgO and Al2O3、CaF2、NaF、FeOx、Na3AlF6、BaO、BaF2、TiO2、Cr2O3、B2O3、MnOx、K2O、ZrO2、ZnO、Li2O、SrO、Ce2O3、PbO、CaCl2One or more of NaCl and KCl, and one or more of slag agents.
As a further improvement of the present invention, in the step (3), the metal oxide in the route 1 is CaO, MgO, Al2O3、TiO2、Cr2O3、MnOx、SrO、Ce2O3And PbO. The impurity restructuring agent in route 2 is one or a combination of more of Ca, Al, Ti, Sn, Cu, Ce, La, Pr, and Nd, and the addition manner of the impurity restructuring agent includes feeding a metal/alloy wire, adding a metal/alloy lump material, and melting liquid silicon.
As a further improvement of the invention, the speed-controlled cooling in the step (3) is uniform speed cooling, variable speed cooling or staged cooling, and the cooling rate is 0.1-15 ℃/min.
As a further improvement of the invention, the physical crushing in the step (4) adopts mechanical grinding and chemical crushing adopts an acid leaching way to crush the solid silicon into silicon powder, and the granularity of the silicon powder is 50-500 μm.
Further, in the chemical crushing, the acid adopted in the acid leaching is one or a combination of more than two of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and aqua regia, the concentration of the acid is 0.1-100 wt.%, and the weight ratio of silicon to the acid is 1: 0.1-1: 1200.
As a further improvement of the invention, the mixed acid medium in the step (4) is a combination of two or more of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and aqua regia, the dissociation strengthening mode of the mixed acid medium is a single acid concentration or a combination of two or more acid concentrations, the acid concentration is 0.1-100 wt.%, the weight ratio of silicon to acid is 1: 0.1-1: 1200, the acid pickling temperature is 10-100 ℃, and the acid pickling time is 0.5-25 h.
In some other embodiments of the present invention, the steps (1), (2), (3) and (4) may not be limited to be performed in sequence, and the following two process routes are also included:
route 1: and (3) cooling the pure silicon melt obtained in the step (2) at a controlled speed to obtain third modified solid silicon, and after the chemical impurity removal treatment in the step (4), washing and drying to obtain UMG-Si with the purity of more than 99.99%.
Route 2: and (3) carrying out chemical impurity removal treatment on the purified and selected material obtained in the step (1) in the same way as in the step (4), then carrying out combined treatment in the step (2) and the step (3), separating slag/silicon to obtain pure molten silicon, cooling at a controlled speed to obtain modified solid silicon (namely fourth modified silicon and fifth modified solid silicon), and cutting off two ends to obtain UMG-Si with the purity of more than 99.99% in the remaining middle part.
The basic processing steps in different embodiments are the prior art, and may be the same or different, and may all meet the requirements, for example, the speed-controlled cooling processing and chemical impurity removal processing in route 1 and route 2 may be the same as the chemical impurity removal processing method in the second exemplary embodiment, and are not described again here.
The technical solution of the present invention is further illustrated by the following specific embodiments in conjunction with the accompanying drawings. It should be noted that the following specific examples are given by way of illustration only and the scope of the present invention is not limited thereto.
The chemicals and raw materials used in the following examples were either commercially available or self-prepared by a known preparation method.
Example 1
The method for preparing the super metallurgical grade silicon by using the crystalline silicon cutting waste material is shown in fig. 1, and specifically comprises the following steps:
(1) after crushing and grading treatment, the crystalline silicon mortar cutting waste is mixed with a water medium to form slurry, and a hydrocyclone is used for separating and removing SiC, Fe, Al and other inclusions to obtain crystalline silicon roughing slurry and inclusion residues. And performing solid-liquid separation on the coarse material slurry by using a filter press, and performing combined treatment of acid washing for impurity removal, water washing and drying to obtain the purified and fine selected material.
(2) And (2) mixing the purified and selected material obtained in the step (1) by using a binder, pressing and drying to obtain a selected material block. Adding Na into the intermediate frequency furnace2O-SiO2The slag agent is melted into a slag pool, and the selected material block is put into the slag pool for smelting for a plurality of times in a small amount under the condition of argon protection. After the silicon blocks are completely melted, the first slag skimming is carried out, and Na is added2O-SiO2Refining and impurity removal are carried out on the slag agent, and the smelting and refining temperature is 1550 ℃. And obtaining pure molten silicon after the secondary slagging-off treatment.
(3) And (3) feeding a calcium-titanium wire with the total amount of 0.2 wt.% into the pure molten silicon obtained in the step (2) for impurity chemical reconstruction, uniformly stirring for 10min, and uniformly cooling to room temperature at a cooling speed of 10 ℃/min to obtain the modified solid silicon.
(4) And (4) crushing and grading the modified solid silicon obtained in the step (3) to obtain silicon powder with the particle size (namely the particle size) of 150 nm. Preparing a mixed acid solution with the acid concentration of 15% by using HF and HCl, and pickling silicon powder for 2 hours at the temperature of 60 ℃ and the weight ratio of silicon to acid of 1: 10 to obtain UMG-Si with the purity of 99.995%.
Example 2
The method for preparing the super metallurgical grade silicon from the crystalline silicon cutting waste comprises the following steps:
(1) after crushing and grading treatment, the crystalline silicon mortar cutting waste is mixed with a water medium to form slurry, and a hydrocyclone is used for separating and removing SiC, Fe, Al and other inclusions to obtain crystalline silicon roughing slurry and inclusion residues. And performing solid-liquid separation on the coarse material slurry by using a filter press, and performing combined treatment of acid washing for impurity removal, water washing and drying to obtain the purified and fine selected material.
(2) And (2) mixing the purified and selected material obtained in the step (1) by using a binder, pressing and drying to obtain a selected material block. Adding Na into the intermediate frequency furnace2O-SiO2The slag agent is melted into a slag pool, and the selected material block is put into the slag pool for smelting for a plurality of times in a small amount under the condition of argon protection. After the silicon blocks are completely melted, the first slag skimming is carried out, and Na is added2O-SiO2-CaF2Refining and impurity removal are carried out on the slag agent, and the smelting and refining temperature is 1650 ℃. And obtaining pure molten silicon after the secondary slagging-off treatment.
(3) And (3) adding aluminum-silicon alloy blocks with the total amount of 0.2 wt.% into the pure melt silicon obtained in the step (2) for impurity chemical reconstruction, uniformly stirring for 10min, and uniformly cooling to room temperature at a constant speed of 1 ℃/min to obtain the modified solid silicon.
(4) And (4) crushing and grading the modified homogeneous silicon obtained in the step (3) to obtain silicon powder with the particle size of 50 nm. Preparing a mixed acid solution with the acid concentration of 5% by using HF and HCl, and pickling silicon powder for 4 hours at the temperature of 90 ℃ and the weight ratio of silicon to acid of 1: 100 to obtain UMG-Si with the purity of 99.998%.
Example 3
The method for preparing the super metallurgical grade silicon from the crystalline silicon cutting waste comprises the following steps:
(1) after the crystalline silicon diamond wire cutting waste is subjected to crushing and grading treatment, the purified and selected material is obtained after combined treatment of acid washing, impurity removal, water washing and drying.
(2) And (2) mixing the purified and selected material obtained in the step (1) by using a binder, pressing and drying to obtain a selected material block. Adding Na into the intermediate frequency furnace2O-SiO2-CaF2The slag agent is melted into a slag pool, and the selected material block is put into the slag pool for smelting for a plurality of times in a small amount under the condition of argon protection. After the silicon blocks are completely melted, the first slag skimming is carried out, and Na is added2O-SiO2-CaF2The slag agent is refined and the impurities are removed,the smelting and refining temperature is 1500 ℃.
(3) In the later stage of refining and impurity removal in the step (2), 1 wt.% of Al is added into the refining slag2O3And TiO2And chemically reconstructing impurities of the metal oxide, electromagnetically stirring uniformly for 10min, then obtaining pure molten silicon through slagging-off treatment, and then uniformly cooling the pure molten silicon to room temperature at a cooling speed of 10 ℃/min to obtain the modified solid silicon.
(4) And (4) crushing and grading the modified solid silicon obtained in the step (3) to obtain coarse silicon powder with the particle size of 500 nm. Aqua regia with an acid concentration of 20% is utilized, and the silicon/acid weight ratio is 1: and chemically crushing the coarse silicon powder under the condition of 200 ℃ to obtain fine silicon powder with the particle size of 100 nm. Preparing a mixed acid solution with the acid concentration of 20% by adopting HF and HCl, wherein the weight ratio of silicon to acid is 1: acid washing is carried out on the fine silicon powder for 4 hours under the condition of 100, and UMG-Si with the purity of 99.996 percent is obtained.
Example 4
The method for preparing the super metallurgical grade silicon from the crystalline silicon cutting waste comprises the following steps:
(1) after the crystalline silicon diamond wire cutting waste is subjected to crushing and grading treatment, the purified and selected material is obtained after combined treatment of acid washing, impurity removal, water washing and drying.
(2) And (2) mixing the purified and selected material obtained in the step (1) by using a binder, pressing and drying to obtain a selected material block. Adding Na into the intermediate frequency furnace2O-SiO2The slag agent is melted into a slag pool, and the selected material block is put into the slag pool for melting for a plurality of times in a small amount under the condition that the vacuum degree is 1000 pa. After the silicon blocks are completely melted, the first slag skimming is carried out, and Na is added2O-SiO2-Al2O3And refining and impurity removal are carried out on the-FeO slag agent, and the smelting and refining temperature is 1650 ℃.
(3) In the later stage of refining and impurity removal in the step (2), 1 wt.% of Ce is added into the refining slag2O3Chemically reconstructing impurities with SrO metal oxide, electromagnetically stirring for 10min, removing slag to obtain pure molten silicon, cooling to 1200 deg.C at 10 deg.C/min, and cooling to 900 deg.C at 5 deg.CAnd finally, uniformly cooling to room temperature at the cooling speed of 1 ℃ to obtain the modified solid silicon.
(4) And (4) crushing and grading the modified solid silicon obtained in the step (3) to obtain coarse silicon powder with the particle size of 500 nm. And chemically crushing the crude silicon powder by using aqua regia with acid concentration of 50% at the temperature of 60 ℃ under the condition that the weight ratio of silicon to acid is 1: 300 to obtain fine silicon powder with the particle size of 80 nm. HF and HCl are prepared into mixed acid solution with the acid concentration of 10%, and the fine silicon powder is pickled for 2 hours at the temperature of 80 ℃ and the weight ratio of silicon to acid of 1: 150 to obtain UMG-Si with the purity of 99.996%.
Example 5
The method for preparing the super metallurgical grade silicon from the crystalline silicon cutting waste comprises the following steps:
(1) after crushing and grading treatment, the crystalline silicon mortar cutting waste is mixed with a water medium to form slurry, and a hydrocyclone is used for separating and removing SiC, Fe, Al and other inclusions to obtain crystalline silicon roughing slurry and inclusion residues. And performing solid-liquid separation on the coarse material slurry by using a filter press, and performing combined treatment of acid washing for impurity removal, water washing and drying to obtain the purified and fine selected material.
(2) And (2) mixing the purified and selected material obtained in the step (1) by using a binder, pressing and drying to obtain a selected material block. Adding Na into the intermediate frequency furnace2O-SiO2The slag agent is melted into a slag pool, and the selected material block is put into the slag pool for smelting for a plurality of times in a small amount under the condition of argon protection. After the silicon blocks are completely melted, the first slag skimming is carried out, and Na is added2O-SiO2-CaF2Refining and impurity removal are carried out on the slag agent, and the smelting and refining temperature is 1600 ℃. And after the secondary slagging-off treatment, obtaining pure molten silicon, and then uniformly cooling to room temperature at a cooling speed of 10 ℃/min to obtain solid silicon.
(4) And (3) crushing and grading the solid silicon obtained in the step (2) to obtain silicon powder with the particle size of 150 nm. Using HF and HNO3Preparing mixed acid solution with acid concentration of 25%, and pickling silicon powder for 4h at 60 deg.C and silicon/acid weight ratio of 1: 100 to obtain UMG-Si with purity of 99.993%.
Example 6
The method for preparing the super metallurgical grade silicon from the crystalline silicon cutting waste comprises the following steps:
(1) after the crystalline silicon diamond wire cutting waste is subjected to crushing and grading treatment, the purified and selected material is obtained after combined treatment of acid washing, impurity removal, water washing and drying.
(2) And (2) mixing the purified and selected material obtained in the step (1) by using a binder, pressing and drying to obtain a selected material block. Adding Na into the intermediate frequency furnace2O-SiO2-CaF2The slag agent is melted into a slag pool, and the selected material block is put into the slag pool for smelting for a plurality of times in a small amount under the condition of argon protection. After the silicon blocks are completely melted, the first slag skimming is carried out, and Na is added2O-SiO2-CaF2Refining the slag agent to remove impurities, then slagging off for the second time, and adding Na again2O-SiO2-Al2O3Refining and impurity removal are carried out on the slag agent to obtain pure silicon melt, and the smelting and refining temperature is 1500 ℃. And then cooling the pure molten silicon to room temperature at a constant speed of 10 ℃/min to obtain the modified solid silicon.
(3) And (3) crushing and grading the modified solid silicon obtained in the step (2) to obtain coarse silicon powder with the particle size of 500 nm. And chemically crushing the crude silicon powder by using aqua regia with the acid concentration of 10% under the conditions that the temperature is 60 ℃ and the weight ratio of silicon to acid is 1: 400 to obtain fine silicon powder with the particle size of 100 nm. HF and HCl are prepared into mixed acid solution with the acid concentration of 50%, and fine silicon powder is subjected to acid cleaning for 4 hours at the temperature of 60 ℃ and the weight ratio of silicon to acid of 1: 150, so that UMG-Si with the purity of 99.995% is obtained.
Example 7
The method for preparing the super metallurgical grade silicon from the crystalline silicon cutting waste comprises the following steps:
(1) and crushing and grading the crystalline silicon diamond wire cutting waste to obtain silicon powder with the particle size of 100 nm. With HF and H2SO4Preparing mixed acid solution with acid concentration of 40%, and pickling silicon powder at 70 deg.c and silicon/acid weight ratio of 1 to 100 for 8 hr to obtain purified material.
(2) The purified and selected material obtained in the step (1) is subjected to chemical impurity removal treatment and then is subjected to chemical impurity removal treatmentAnd mixing, pressing and drying the binder to obtain a selected material block. Adding Na into the intermediate frequency furnace2O-SiO2The slag agent is melted into a slag pool, and the selected material block is put into the slag pool for smelting for a plurality of times in a small amount under the condition of argon protection. After the silicon blocks are completely melted, the first slag skimming is carried out, and Na is added2O-SiO2-CaF2-FeOxRefining and impurity removal are carried out on the slag agent, and the smelting and refining temperature is 1650 ℃. And obtaining pure molten silicon after the secondary slagging-off treatment.
(3) And (3) adding silicon liquid containing higher titanium and calcium concentrations into the pure molten silicon obtained in the step (2) for impurity chemical reconstruction, wherein the total amount of calcium and titanium in the molten pure silicon is less than 2 wt%, uniformly cooling to room temperature at a cooling speed of 0.5 ℃/min after uniformly stirring for 10min by electromagnetic stirring to obtain a silicon ingot of the modified solid silicon, and cutting off two sections to obtain UMG-Si with the purity of 99.995% in the remaining middle part.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for preparing super metallurgical grade silicon from crystalline silicon cutting waste is characterized by comprising the following steps:
(1) carrying out primary pretreatment on the crystalline silicon cutting waste to obtain crystalline silicon roughing material slurry, and carrying out secondary pretreatment on the roughing material slurry to obtain a purified fine material;
(2) briquetting the purified and refined material obtained in the step (1) to obtain a first refined material block, and separating slag and silicon after the first refined material block is subjected to oxygen-controlled smelting and refining to obtain first molten silicon and first refined slag;
(3) chemically reconstructing impurities of the first molten silicon and/or the first refining slag to obtain first modified solid silicon and/or second modified solid silicon;
(4) and (4) removing the reconstructed impurity phase in the first modified solid silicon and/or the second modified solid silicon obtained in the step (3) to obtain the super metallurgical grade silicon.
2. The method of claim 1,
the first pretreatment method in the step (1) comprises at least one of crushing and grading, slurry preparation and physical centrifugation;
the second pretreatment method in the step (1) comprises at least one of solid-liquid separation, acid washing for impurity removal, water washing and drying;
the briquetting treatment method in the step (2) comprises the steps of mixing the purified and selected material with a binder, pressing and drying;
the oxygen-controlled smelting and refining treatment step in the step (2) comprises oxygen-controlled treatment and slag washing treatment;
wherein the oxygen control treatment method comprises vacuum oxygen control or inert gas protection oxygen control;
wherein the slag washing treatment comprises the step of putting the selected material blocks into molten slag for smelting and refining for multiple times, and the smelting and refining temperature is higher than 1450 ℃.
3. The method of claim 1,
in the step (2), the mass ratio of the slag to the first selected material block in the step of oxygen-controlled smelting and refining treatment is (0.1-0.5) to 1.
4. The method of claim 3,
the slag comprises a main agent and an auxiliary agent, wherein the main agent comprises Na2O、SiO2At least one of; the adjuvant comprises CaO, MgO and Al2O3、CaF2、NaF、FeOx、Na3AlF6、BaO、BaF2、TiO2、Cr2O3、B2O3、MnOx、K2O、ZrO2、ZnO、Li2O、SrO、Ce2O3、PbO、CaCl2In NaCl, KClAt least one of them.
5. The method of claim 1,
the reconstruction agent in the chemical reconstruction step in the step (3) comprises at least one of Ca, Al, Ti, Sn, Cu, Ce, La, Pr and Nd;
the chemical reconstitution method of the first silicon melt in the step (3) comprises: adding an impurity restructuring agent into the first melt silicon, and performing oxygen control, stirring and speed control cooling treatment to obtain first modified solid silicon;
the chemical restructuring method of the first refining slag in the step (3) comprises the following steps: adding metal oxide into the first refining slag, performing chemical impurity reconstruction by using a slag-silicon interface redox reaction while controlling oxygen and stirring, and performing slag/silicon separation and speed-controlling cooling treatment to obtain second modified solid silicon.
6. The method of claim 5,
the metal oxide comprises CaO, MgO and Al2O3、TiO2、Cr2O3、MnOx、SrO、Ce2O3At least one of PbO;
the speed-controlled cooling method comprises uniform speed cooling, variable speed cooling or staged cooling, wherein the cooling rate is 0.1-15 ℃/min.
7. The method of claim 1,
the purity of the super metallurgical grade silicon in the step (4) is more than 99.99 percent;
and (4) removing the reconstructed impurity phase by carrying out chemical impurity removal treatment on the first modified solid silicon and/or the second modified solid silicon.
8. The method of claim 7,
the chemical impurity removal comprises at least one of physical crushing, chemical crushing, mixed acid medium dissociation strengthening, surfactant interface modification and external field strengthening corrosion treatment;
wherein the particle size of the silicon powder formed by physical crushing or chemical crushing is 50-500 microns;
wherein the mixed acid medium comprises at least two of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and aqua regia;
wherein the concentration of the mixed acid is 0.1 to 100 wt%, and the weight ratio of the silicon powder to the mixed acid is 1: 0.1 to 1200;
wherein the pickling temperature is 10 to 100 ℃, and the pickling time is 0.5 to 25 hours.
9. A method for preparing super metallurgical grade silicon from crystalline silicon cutting waste is characterized by comprising the following steps:
(1) carrying out primary pretreatment on the crystalline silicon cutting waste to obtain crystalline silicon roughing material slurry and inclusion residues, and carrying out secondary pretreatment on the roughing material slurry to obtain a purified fine sizing material;
(2) briquetting the purified and refined material obtained in the step (1) to obtain a first refined material block, and separating slag and silicon after the first refined material block is subjected to oxygen-controlled smelting and refining to obtain first molten silicon and first refined slag;
(3) cooling the second melt silicon obtained in the step (2) at a controlled speed to obtain third modified solid silicon;
(4) and (4) removing the reconstructed impurity phase in the third modified solid silicon obtained in the step (3) to obtain the super metallurgical grade silicon.
10. A method for preparing super metallurgical grade silicon from crystalline silicon cutting waste is characterized by comprising the following steps:
(1) carrying out primary pretreatment on the crystalline silicon cutting waste to obtain crystalline silicon roughing material slurry and inclusion residues, and carrying out secondary pretreatment on the roughing material slurry to obtain a purified fine sizing material;
(2) carrying out chemical impurity removal treatment on the purified and refined material obtained in the step (1) through briquetting, then carrying out briquetting treatment to obtain a second refined material block, and carrying out slag-silicon separation on the second refined material block after oxygen-controlled smelting refining treatment to obtain second molten silicon and second refined slag;
(3) performing impurity chemical reconstruction on the second molten silicon and/or the second refining slag to obtain fourth modified solid silicon and/or fifth modified solid silicon;
(4) and (4) removing two ends of the fourth modified solid silicon and/or the fifth modified solid silicon obtained in the step (3) to obtain the super metallurgical grade silicon.
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