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Method for carrying out slagging, pickling and boron removal on metal silicon

A metal silicon, pickling technology, applied in the direction of non-metal elements, chemical instruments and methods, silicon compounds, etc., can solve the problems of low operating cost, large processing capacity, boron removal effect is difficult to achieve solar-grade polysilicon, etc., to achieve boron removal high efficiency effect

Inactive Publication Date: 2011-08-17
XIAMEN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0008] The research on slagging method has a long history, but there are still the following problems in its current industrial application: First, the removal effect of boron is still difficult to meet the requirements of solar-grade polysilicon
The above process can be carried out at room temperature, with low operating cost, simple equipment, and large processing capacity. The disadvantage is that qualified solar-grade silicon materials can only be produced by combining with other metallurgical methods, especially for non-metallic impurities such as boron and phosphorus. basically no removal effect

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0024] 1) 2.5kg of slagging agent Al 2 o 3 (20%wt)-MnO(5%wt)-SiO 2(70%wt)-CaF 2 (5%wt) for pre-melting, and the obtained slag is loaded into the feeding bin in the feeding device in equal amounts.

[0025] 2) Put 50kg metal silicon blocks into the melting crucible, turn on the mechanical pump, and when the vacuum reaches 500Pa, close the vacuum valve, turn off the mechanical pump, and fill with argon to 10000Pa.

[0026] 3) Start the intermediate frequency heating to melt the silicon material. After the silicon material is completely melted, rotate the feeding bin, add the pre-melted slagging agent to the silicon liquid, and use the dual colorimetric-infrared thermometer to control the reaction temperature at 1700°C .

[0027] 4) Lower the aeration rod to the surface of the silicon liquid to preheat for 10 minutes, then slowly insert it 10 mm from the bottom of the crucible, start ventilation and stirring, control the gas flow rate to 3L / min, and after aeration for 3 hours...

Embodiment 2

[0035] Process flow is with embodiment 1. The slagging agent is 5kg of Al 2 o 3 (20%wt)-MnO(10%wt)-SiO 2 (65%wt)-CaF 2 (5%wt). The weight ratio of the slagging agent to the silicon material is 1:10 (the slag-silicon ratio is 0.1). After the silicon material is completely melted, rotate the feeding bin, add the pre-melted slagging agent into the silicon liquid, and control the reaction temperature at 1700°C by using a double colorimetric-infrared thermometer. Lower the venting rod to the surface of the silicon liquid to preheat for 10 minutes, then slowly insert it into a place 20mm away from the bottom of the crucible, control the gas flow rate to 3L / min, and after ventilating for 4 hours, pour all the upper silicon liquid in the melting crucible into the graphite crucible mold , lower the temperature to 800°C, keep the temperature for 1h, then cool down, and take out the silicon ingot. Silicon ingots Silicon ingots are crushed, ground, and sieved to obtain 60-100-mesh s...

Embodiment 3

[0039] Process flow is with embodiment 1. The slagging agent is 7.5kg of Al 2 o 3 (30%wt)-MnO(5%wt)-SiO 2 (55%wt)-CaF 2 (10%wt). The weight ratio of slagging agent to silicon material is 1:5 (the ratio of slag to silicon is 02). After the silicon material is completely melted, rotate the feeding bin, add the pre-melted slagging agent into the silicon liquid, and control the reaction temperature at 1600°C by using a double colorimetric-infrared thermometer. Lower the aeration rod to the surface of the silicon liquid to preheat for 10 minutes, then slowly insert it into a place 20mm away from the bottom of the crucible, control the gas flow rate to 2L / min, and after aeration for 3 hours, pour all the upper silicon liquid in the melting crucible into the graphite crucible mold , lower the temperature to 800°C, keep the temperature for 1h, then cool down, and take out the silicon ingot. Silicon ingots Silicon ingots are crushed, ground, and sieved to obtain 60-100-mesh silic...

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Abstract

The invention discloses a method for carrying out slagging, pickling and boron removal on metal silicon, relates to a method for purifying polysilicon and provides the method for carrying out slagging, pickling and boron removal on the metal silicon. The method comprises the following steps of: premelting a slag forming constituent and placing the slag forming constituent into a charging bin; filling a metal silicon material into a smelting crucible; filling argon into the smelting crucible after vacuumizing; heating to melt the metal silicon material; adding the pre-molten slag forming constituent into the molten liquid metal silicon material; after a reaction is completed, pouring the liquid metal silicon material into a die and cooling the die to obtain a silicon ingot; crushing and grinding the obtained silicon ingot; sieving the obtained powder to obtain silicon powder; soaking the silicon powder in ethanol to remove oil; washing the silicon powder with water; soaking and washing the obtained powder at least once by solution of hydrochloric acid, mixed solution of sulphuric acid and nitric acid, mixed solution of hydrofluoric acid and solution of hydrochloric acid sequentially; and flushing the pickled silicon powder with clear water to obtain the metal silicon subjected to boron removal. The efficiency of removing boron is high and can reach over 96 percent. The boron content in the metal silicon is reduced to below 0.3ppmw from 8ppmw. The requirement of solar polysilicon is met.

Description

technical field [0001] The invention relates to a method for purifying polysilicon, in particular to a method for removing boron by slagging and pickling of metal silicon. Background technique [0002] With the development of the world economy and the advancement of industrialization, the human demand for energy is increasing day by day. While satisfying its own rapid development, human beings are also facing the crisis of gradually depleting fossil energy sources such as coal, oil, and natural gas, and cannot avoid the problem of serious environmental pollution. Compared with traditional energy sources, solar power generation has the advantages of cleanness, environmental protection, safety and convenience, and sufficient resources. It is a renewable green energy that can effectively alleviate the problems of energy shortage and environmental pollution. Therefore, photovoltaic energy is considered to be the most important new energy in the 21st century. [0003] Polycryst...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B33/037
Inventor 罗学涛黄平平李锦堂吴浩张蓉傅翠梨
Owner XIAMEN UNIV
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