阅读说明：本技术 一种金刚石线切割硅废料的脱氧方法 (Deoxidation method for diamond wire cutting silicon waste ) 是由 余文轴 杨帆 陈浩 魏鹏 张生富 党杰 游志雄 吕学伟 扈玫珑 刘许旸 辛云涛 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种金刚石线切割硅废料的脱氧方法,包括以下步骤：(1)对硅废料进行预处理；(2)把镁料和步骤(1)处理后的硅废料放置于反应器内不同位置处,将反应器放置于加热炉中,在真空或保护气氛围条件下加热至650℃~1200℃,保温5~200min,冷却后得到处理后的硅料；(3)将步骤(2)冷却后得到的硅料进行酸洗、过滤、清洗、烘干处理,得到脱氧后的硅。本发明将火法与湿法相结合,火法阶段所需温度较低,远低于与现有技术火法工艺的温度,这就使得本发明所述方法的整体能耗较低,具有回收成本低、工艺流程短、杂质去除率高的优势。(The invention discloses a deoxidation method for silicon waste in diamond wire cutting, which comprises the following steps: (1) pretreating the silicon waste; (2) placing a magnesium material and the silicon waste treated in the step (1) at different positions in a reactor, placing the reactor in a heating furnace, heating to 650-1200 ℃ under a vacuum or protective gas atmosphere, preserving heat for 5-200 min, and cooling to obtain a treated silicon material; (3) and (3) carrying out acid washing, filtering, cleaning and drying on the silicon material obtained after cooling in the step (2) to obtain deoxidized silicon. The method combines the pyrogenic process and the wet process, and the temperature required by the pyrogenic process stage is lower and far lower than that of the pyrogenic process in the prior art, so that the method has the advantages of lower overall energy consumption, low recovery cost, short process flow and high impurity removal rate.)

1. A deoxidation method for silicon waste material of diamond wire cutting is characterized by comprising the following steps:

(1) pretreating the silicon waste;

(2) placing a magnesium material and the silicon waste treated in the step (1) at different positions in a reactor, placing the reactor in a heating furnace, heating to 650-1200 ℃ under a vacuum or protective gas atmosphere, preserving heat for 5-200 min, and cooling to obtain a treated silicon material;

(3) and (3) carrying out acid washing, filtering, cleaning and drying on the silicon material obtained after cooling in the step (2) to obtain deoxidized silicon.

2. The deoxidation method of diamond wire cutting silicon waste material as claimed in claim 1 wherein the acid used for pickling is one or a mixture of hydrochloric acid, sulfuric acid and hydrofluoric acid.

3. The method for deoxidizing silicon scrap for diamond wire cutting according to claim 1, wherein the mass ratio of the acid for pickling to the silicon scrap is 0.5 to 500: 1.

4. The deoxidation method of diamond wire cutting silicon scrap according to claim 1, wherein the acid washing time is 0.5-8 h.

5. The deoxidation method of diamond wire cutting silicon scrap according to claim 1 wherein the magnesium material is magnesium or magnesium alloy or magnesium-containing alloy, the mass fraction of magnesium element in the magnesium material is not less than 1%.

6. The method for deoxidizing silicon scrap for diamond wire cutting according to claim 1, wherein said protective gas is an inert protective gas.

7. The deoxidation method of silicon scrap for diamond wire cutting according to claim 1, wherein the mass ratio of the silicon scrap to magnesium in the magnesium material is 1-100: 1.

8. The deoxidation method of diamond wire cutting silicon scrap according to claim 1, wherein the silicon scrap is silicon scrap after diamond wire cutting of solar grade silicon or silicon scrap after mortar cutting.

Technical Field

The invention relates to the technical field of secondary resource recycling of silicon materials, in particular to a deoxidation method of diamond wire-electrode cutting silicon waste.

Background

Global energy structures are accelerating the transformation from fossil energy to clean energy, and solar energy is a clean and efficient renewable resource. The installed capacity of photovoltaic power generation is increasing year by year, but at the same time, the total amount of photovoltaic power generation accounts for less than 4% of the total amount of power generation in China at present. This is largely due to the high manufacturing cost of the polycrystalline silicon wafers required for photovoltaic cells, making photovoltaic power generation cost difficult to create a strong market competitiveness.

The preparation of the solar-grade silicon wafer firstly needs to cut a solar-grade crystal silicon ingot by using a diamond wire, and due to the limitation of a cutting process, more than 40% of high-purity silicon is produced in the cutting process in the form of cutting waste, so that a large amount of waste is caused. The cutting waste materials are accumulated in a large amount, easily pollute soil, air and water resources, and are one of the reasons for high cost of indirect photovoltaic power generation, so that the popularization of the solar technology is not facilitated.

Aiming at the recovery of crystalline silicon wire-electrode cutting waste materials, the prior art mainly comprises two processes, namely a fire process and a wet process, and both the two processes show certain limitations. In patent CN109052407, an induction furnace slagging smelting is carried out on silicon cutting waste materials through an all-fire process, then the obtained fusion cakes are cut and separated to obtain high-purity silicon, and the required temperature reaches above 1450 ℃; in patent CN110217797, a vacuum intermediate frequency induction furnace smelting method is adopted, and the smelted silicon liquid is cast in a mold to obtain high-purity industrial silicon, wherein the required smelting temperature reaches more than 1500 ℃; in patent CN111646476, the silicon waste is cleaned by acetone and ethanol, then is pickled by hydrochloric acid solution, and is recovered by air separation after being dried, thereby realizing the fractional recovery of high-purity silicon. Among the methods, the pyrogenic process aims at silicon cutting waste powder with oxidized surface, and the required melting temperature is high, the melting time is long, so that the recovery cost is high, and the large-scale industrial application is difficult to realize. The all-wet process has the problems of long process flow, low production capacity, low purity of recycled silicon and the like in production, and the two processes have not ideal removal effect on oxygen. Whether pyrogenic or wet, there are very strict requirements on the purity of solar-grade crystalline silicon. Therefore, how to remove oxygen impurities in the diamond wire-cutting silicon waste material has become a technical problem to be solved by those skilled in the art.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a deoxidation method for silicon waste materials of diamond wire cutting, so as to solve the problems that the recovery cost of the silicon waste materials of crystal silicon wire cutting is high and the removal effect of oxygen element is not good in the prior art.

In order to solve the technical problems, the invention adopts the following technical scheme:

a deoxidation method of silicon waste materials of diamond wire cutting comprises the following steps:

(1) the silicon waste is pretreated.

(2) And (2) placing the magnesium material and the silicon waste material treated in the step (1) at different positions in a reactor, placing the reactor in a heating furnace, heating to 650-1200 ℃ under the vacuum or protective gas atmosphere, preserving heat for 5-200 min, and cooling to obtain the treated silicon material.

(3) And (3) carrying out acid washing, filtering, cleaning and drying on the silicon material obtained after cooling in the step (2) to obtain deoxidized silicon.

Wherein, the silicon waste can be pretreated by selecting the processes of crushing, pelletizing, tabletting and the like so as to be fully contacted with magnesium vapor. The magnesium material and the silicon scrap may be mixed and placed in the reactor, or may be placed separately in the same reactor.

Preferably, the acid for acid washing is one or a mixture of hydrochloric acid, sulfuric acid and hydrofluoric acid.

Preferably, the mass ratio of the acid for acid washing to the silicon waste is 0.5-500: 1.

Preferably, the pickling time is 0.5-8 h.

Preferably, the magnesium material is magnesium or a magnesium alloy or a magnesium-containing alloy, and the mass fraction of magnesium element in the magnesium material is not less than 1%.

Preferably, the shielding gas is an inert shielding gas.

Preferably, the mass ratio of the silicon waste to the magnesium element in the magnesium material is 1-100: 1.

Preferably, the silicon waste is silicon waste obtained after solar-grade silicon is subjected to diamond wire cutting or silicon waste obtained after mortar cutting. The method has low requirements on silicon waste, and the silicon waste generated in the preparation process of the solar-grade silicon wafer can be deoxidized by the method.

Compared with the prior art, the invention has the following beneficial effects:

1. according to the invention, by virtue of the magnesium steam thermal reduction and acid pickling process technology, the pyrometallurgical process and the wet process are combined, the temperature required by the pyrometallurgical process is not high and is far lower than that of the pyrometallurgical process in the prior art, the problems of overhigh temperature and overlarge energy consumption required by the traditional pyrometallurgical process are solved, meanwhile, the problem of poor impurity oxygen removal effect of the wet process technology in the prior art is also solved, and oxygen impurities in the diamond wire-electrode cutting silicon waste are effectively removed by a low-cost method.

2. The method comprises the steps of heating a magnesium material to form magnesium vapor, reacting the magnesium vapor with silicon waste, reducing oxides in the silicon waste by the magnesium vapor to generate magnesium oxide, and dissolving the magnesium oxide in acid through the reaction of the acid and the magnesium oxide, so that oxygen is removed from the silicon waste; the method has excellent effect of removing oxygen, and can greatly reduce the content of oxygen in the silicon waste, so that the silicon waste meets the strict requirement on the content of oxygen in relevant national standards.

3. The method has low requirements on silicon waste materials, is suitable for the deoxidization process of most silicon waste materials, and the magnesium salt obtained after acid washing also has industrial value.

Detailed Description

The present invention will be further described with reference to the following examples.

The following examples used diamond wire cut silicon scrap and mortar cut silicon scrap, each having a mass fraction of oxygen of 10% or more.

Example 1:

(1) cutting silicon waste materials by diamond wires, crushing and grinding to obtain massive and granular silicon waste materials.

(2) Adding magnesium particles (the mass fraction of magnesium is more than 99%) into a graphite crucible, tabletting the silicon waste by using a tabletting machine to obtain silicon waste pieces, wherein the mass ratio of the magnesium particles to the silicon waste is 1:5, the silicon waste pieces are fixed in the middle of the crucible by a fine iron wire net, putting the crucible into a medium-frequency induction furnace, vacuumizing, introducing argon, heating to 950 ℃ under the argon atmosphere, preserving the temperature for 120min, and cooling to obtain the silicon wafer subjected to magnesium thermal reduction.

(3) And (3) crushing and grinding the silicon wafer subjected to the magnesiothermic reduction in the step (2) to obtain silicon powder subjected to the magnesiothermic reduction.

(4) And (3) adding the prepared HCl with the concentration of 2mol/L into the silicon powder in the step (3) at the liquid-solid ratio of 100:1, pickling for 5 hours at normal temperature, and then filtering, cleaning and drying to obtain the silicon powder subjected to deoxidation treatment.

Through detection, the mass fraction of the oxygen element in the silicon powder obtained in the embodiment is 0.9643%.

Example 2:

(1) and cutting the silicon waste material by the diamond wire, crushing and grinding to obtain the massive silicon waste material.

(2) Placing magnesium-containing aluminum alloy (the mass fraction of magnesium is more than 1%) and silicon waste in parallel in a boat-shaped crucible, wherein the mass ratio of the alloy to the silicon waste is 20:1, placing the crucible in a tubular resistance furnace, vacuumizing, introducing argon, heating to 1200 ℃ under the argon atmosphere, preserving heat for 5min, and cooling to obtain a silicon block subjected to magnesium thermal reduction.

(3) And (3) crushing and grinding the silicon briquette subjected to the magnesiothermic reduction in the step (2) to obtain the silicon powder subjected to the magnesiothermic reduction.

(4) Preparing 1mol/L HCl, adding the HCl into the silicon powder obtained in the step (3) at a liquid-solid ratio of 500:1, pickling for 8 hours at normal temperature, and then filtering, cleaning and drying to obtain the silicon powder subjected to deoxidation treatment.

Through detection, the mass fraction of the oxygen element in the silicon powder obtained in the embodiment is 0.9527%.

Example 3:

(1) and cutting the silicon waste material by the diamond wire, crushing and grinding to obtain powdery silicon waste material.

(2) And (3) layering AZ91D magnesium alloy particles (the mass fraction of magnesium is more than 88%) and the silicon waste powder in a crucible, wherein the mass ratio of the alloy to the silicon waste is 1:10, putting the crucible into a medium-frequency induction furnace, vacuumizing, heating to 1000 ℃, preserving heat for 120min, and cooling to obtain the silicon material subjected to magnesium thermal reduction.

(3) And (3) crushing and grinding the silicon material subjected to the magnesiothermic reduction in the step (2) to obtain the silicon powder subjected to the magnesiothermic reduction.

(4) Preparing mixed acid containing 2mol/L HCl and 0.5mol/L HF, adding the mixed acid into the silicon powder obtained in the step (3), carrying out acid washing at normal temperature for 5 hours, and then filtering, cleaning and drying to obtain silicon powder subjected to deoxidation treatment.

Through detection, the mass fraction of the oxygen element in the silicon powder obtained in the embodiment is 0.6908%.

Example 4:

(1) cutting silicon waste materials by diamond wires, crushing and grinding to obtain massive and granular silicon waste materials.

(2) Putting magnesium particles (the mass fraction of magnesium is more than 99%) into a crucible, fixing a silicon waste material block in the middle of the crucible by a fine wire netting, wherein the mass ratio of the magnesium particles to the silicon waste material is 1:20, putting the crucible into a medium-frequency induction furnace, vacuumizing, heating to 950 ℃, preserving heat for 150min, and cooling to obtain the silicon block subjected to magnesium thermal reduction.

(3) And (3) crushing and grinding the silicon briquette subjected to the magnesiothermic reduction in the step (2) to obtain the silicon powder subjected to the magnesiothermic reduction.

(4) Preparation of a 1mol/L H solution containing 4mol/L HCl₂SO₄And 0.5mol/L of HF, to the step(3) And (3) pickling the silicon powder at normal temperature for 6 hours at a liquid-solid ratio of 0.5:1, and then filtering, cleaning and drying to obtain the silicon powder subjected to deoxidation treatment.

Through detection, the mass fraction of the oxygen element in the silicon powder obtained in the embodiment is 1.1326%.

Example 5:

(1) cutting silicon waste materials by diamond wires, crushing and grinding to obtain massive and granular silicon waste materials.

(2) Adding magnesium blocks (the mass fraction of magnesium is more than 90%) into a crucible, tabletting the silicon waste material by using a tabletting machine to obtain a silicon waste material sheet, wherein the mass ratio of the magnesium blocks to the silicon blocks is 1:5, the silicon waste material sheet is fixed in the middle of the crucible by a fine iron wire net, putting the crucible into a resistance furnace, vacuumizing, introducing argon, heating to 650 ℃ under the condition of argon atmosphere, preserving the temperature for 180min, and cooling to obtain the silicon wafer subjected to magnesium thermal reduction.

(3) And (3) crushing and grinding the silicon wafer subjected to the magnesiothermic reduction in the step (2) to obtain silicon powder subjected to the magnesiothermic reduction.

(4) And (3) adding HCl with the preparation concentration of 2mol/L into the silicon powder obtained in the step (3), carrying out acid washing at normal temperature for 5 hours at the liquid-solid ratio of 50:1, and then filtering, cleaning and drying to obtain the silicon powder subjected to deoxidation treatment.

Through detection, the mass fraction of the oxygen element in the silicon powder obtained in the embodiment is 0.8665%.

Example 6:

(1) cutting silicon waste materials by diamond wires, crushing and grinding to obtain massive and granular silicon waste materials.

(2) And (3) putting magnesium powder (the mass fraction of magnesium is more than 95%) and the silicon waste blocks into a crucible in a layered mode, wherein the mass ratio of the magnesium powder to the silicon waste is 1:3, putting the crucible into a medium-frequency induction furnace, vacuumizing, heating to 850 ℃, preserving heat for 120min, and cooling to obtain the silicon material subjected to magnesiothermic reduction.

(3) And (3) crushing and grinding the silicon material subjected to the magnesiothermic reduction in the step (2) to obtain the silicon powder subjected to the magnesiothermic reduction.

(4) And (3) preparing mixed acid containing 2mol/L HCl and 0.5mol/L HF, adding the mixed acid into the silicon powder in the step (3), carrying out acid washing at normal temperature for 3 hours at a liquid-solid ratio of 10:1, and then filtering, cleaning and drying to obtain silicon powder subjected to deoxidation treatment.

Through detection, the mass fraction of the oxygen element in the silicon powder obtained in the embodiment is 0.8236%.

Example 7:

(1) cutting the mortar into silicon waste, crushing and grinding to obtain massive and granular silicon waste.

(2) Adding magnesium particles (the mass fraction of magnesium is more than 99%) into a graphite crucible, tabletting the silicon waste by using a tabletting machine to obtain silicon waste pieces, wherein the mass ratio of the magnesium particles to the silicon waste is 1:2, the silicon waste pieces are fixed in the middle of the crucible by a fine iron wire mesh, putting the crucible into a medium-frequency induction furnace, vacuumizing, introducing argon, heating to 750 ℃ under the argon atmosphere condition, preserving the temperature for 180min, and cooling to obtain the silicon wafer subjected to magnesium thermal reduction.

(3) And (3) crushing and grinding the silicon wafer subjected to the magnesiothermic reduction in the step (2) to obtain silicon powder subjected to the magnesiothermic reduction.

(4) Adding HCl with the preparation concentration of 4mol/L into the silicon powder in the step (3) at the liquid-solid ratio of 100:1, pickling for 6 hours at normal temperature, and then filtering, cleaning and drying to obtain the silicon powder subjected to deoxidation treatment.

Through detection, the mass fraction of the oxygen element in the silicon powder obtained in the embodiment is 0.7917%.

As can be seen from the above examples:

(1) according to the invention, the impurity oxygen in the silicon waste is removed by using a magnesium steam thermal reduction and acid pickling method, the temperature required in the pyrogenic process stage is lower, the energy consumption in the silicon waste recovery process can be effectively reduced, the oxygen element is well removed, and the deoxidation and purification treatment of the diamond wire-electrode cutting silicon waste is realized.

(2) The method has low requirement on silicon waste, can not only deoxidize the cutting waste of the solar-grade silicon wafer, but also deoxidize the silicon waste obtained by other processes, has no pollution to the environment, has low recovery cost, short process flow and high impurity oxygen removal rate, and is easy to realize large-scale industrial application of crystal silicon wire cutting waste recovery.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the technical solutions, and those skilled in the art should understand that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all that should be covered by the claims of the present invention.