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A method for removing impurity iron in polysilicon and single crystal silicon wire cutting waste

A technology for cutting waste and polysilicon, applied in chemical instruments and methods, silicon compounds, inorganic chemistry, etc., can solve problems such as low practicability, high process operation requirements, environmental pollution, etc., achieving low pollution, stable process parameters, The effect of simple process flow

Inactive Publication Date: 2018-06-29
UNIV OF SCI & TECH BEIJING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At the same time, in 2014 alone, the output of polysilicon used in solar cells has reached 240,000 tons, and roughly 400,000 tons of waste is generated. If the iron is directly removed by pickling, the acid used will pollute the environment.
Therefore, although iron can be removed by pickling, the process operation requirements are relatively high and complicated, and the practicability is not very strong.
[0004] In summary, iron is the main metal impurity in polysilicon cutting waste, and currently there is no simple and mature technology that can efficiently remove iron

Method used

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  • A method for removing impurity iron in polysilicon and single crystal silicon wire cutting waste

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0045] Add water to monocrystalline silicon and polycrystalline silicon wire cutting waste slurry, the liquid-solid ratio is 4:1, stir to remove polyethylene glycol, after stirring for 3 hours (this process can be carried out at room temperature), filter (this process It can be repeated 3 times to completely remove the polyethylene glycol), and the filter cake is dried. The dried filter cake was put into a ball mill and ground for 20 minutes to obtain a mixed powder of silicon and silicon carbide.

[0046]Mix silicon, silicon carbide powder and water at a ratio of 5:1, stir for 30 minutes and then let stand for 5 hours, the solution is layered, and the upper layer solution is filtered and dried to obtain a silicon-rich phase powder. Mix the silicon-rich phase powder and water at a ratio of 10:1 and stir evenly, adjust the pH value to 12 with 6% ammonia solution of ammonium tartrate, continue stirring for 10 minutes, and put it into an ultrasonic wave for 40 minutes.

[0047] ...

Embodiment 2

[0049] Add water to monocrystalline silicon and polycrystalline silicon wire cutting waste slurry, the liquid-solid ratio is 5:1, stir to remove polyethylene glycol, after stirring for 3 hours (this process can be carried out at room temperature), filter (this process It can be repeated 3 times to completely remove the polyethylene glycol), and the filter cake is dried. The dried filter cake was put into a ball mill and ground for 20 minutes to obtain a mixed powder of silicon and silicon carbide.

[0050] Mix silicon, silicon carbide powder and water at a ratio of 5:1, stir for 30 minutes and then let stand for 5 hours, the solution is layered, and the upper layer solution is filtered and dried to obtain a silicon-rich phase powder. Mix the silicon-rich phase powder and water at 8:1 and stir evenly, adjust the pH value to 13 with 15% ammonium citrate ammonia solution, continue stirring for 10 minutes, and put it into an ultrasonic wave for 40 minutes.

[0051] The dispersed ...

Embodiment 3

[0053] Add water to monocrystalline silicon and polycrystalline silicon wire cutting waste slurry, the liquid-solid ratio is 5:1, stir to remove polyethylene glycol, after stirring for 3 hours (this process can be carried out at room temperature), filter (this process It can be repeated 3 times to completely remove the polyethylene glycol), and the filter cake is dried. The dried filter cake was put into a ball mill and ground for 20 minutes to obtain a mixed powder of silicon and silicon carbide.

[0054] Mix silicon, silicon carbide powder and water at a ratio of 5:1, stir for 30 minutes and then let stand for 5 hours, the solution is layered, and the upper layer solution is filtered and dried to obtain a silicon-rich phase powder. Mix the silicon-rich phase powder and water at a ratio of 9:1 and stir evenly. Adjust the pH value to 13.5 with a 13% ammonia solution of ammonium malate. After stirring for 10 minutes, put it into an ultrasonic wave for 50 minutes.

[0055] The ...

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Abstract

A method for removing impurity iron in polysilicon and monocrystalline silicon wire cutting waste, the method utilizes alkaline conditions to disperse silicon and silicon carbide particles in polysilicon wire cutting waste, and then removes iron therein by magnetic separation , the steps are: first pretreat the cutting waste, remove the polyethylene glycol solution, and dry to obtain a mixed powder of silicon and silicon carbide; add a certain concentration of weak alkali solution to adjust the pH value to 12-14, stir and react Put it into the ultrasonic wave to make the particles fully dispersed, and then perform repeated magnetic separation to remove more than 90% of the iron. The method has a simple process flow and stable process parameters. The magnetic separation process is used to remove iron, and the operation time is short and the energy consumption is low. , no pollution, high efficiency, less pollution, and after magnetic separation and filtration, the water can be recycled, basically achieving zero discharge.

Description

technical field [0001] The invention relates to a method for removing impurity iron in polycrystalline silicon and monocrystalline silicon wire cutting waste. Background technique [0002] Solar energy is currently the most abundant energy available to human beings. It has many advantages that fossil energy cannot match: clean and pollution-free, unlimited reserves, and universal existence. Therefore, the development of the solar photovoltaic industry has attracted the attention of many countries in recent years, and the output of polycrystalline silicon wafers or monocrystalline silicon wafers, as an important part of solar photovoltaic cell components, is also increasing year by year. The production process of silicon wafers can be roughly divided into five steps: purification process, rod drawing process, slicing process, battery manufacturing process, and packaging process. Among them, the slicing process currently adopts the multi-wire cutting process. This process use...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B33/037
Inventor 朱鸿民刘苏宁黄凯
Owner UNIV OF SCI & TECH BEIJING