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A process for washing and removing boron from polysilicon slag by metallurgical method

A technology of polysilicon and metallurgy, which is applied in the field of polysilicon slag washing and boron removal process, can solve the problem that the purity of polysilicon cannot meet the high purity requirements of solar-grade polysilicon

Active Publication Date: 2011-11-30
宁夏高创特能源科技有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although the above-mentioned foreign patents have achieved good results in the purification of polysilicon by metallurgical methods, the purity of polysilicon still cannot meet the high purity requirements of solar-grade polysilicon

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] 1) Weigh 60Kg of raw industrial silicon with a boron content of about 25ppmw.

[0019] 2) The composite slag agent is composed of 5.5:2.5:0.5 by weight percentage, and two parts of Na 2 SiO 3 -SiO 2 - CaO granular powder is used as slag agent, the mass ratio of each slag agent to raw industrial silicon is 1:2, that is, the composite slag agent is 30Kg. Put the slag agent into a graphite crucible and pre-melt it at 1000°C for 30-40 minutes.

[0020] 3) When the slag agent is melted to form a molten pool, add raw industrial silicon, increase the power of the intermediate frequency induction power supply, and its range is between 140 ~ 220Kw, so that the silicon material can be melted quickly (30 ~ 50min), and the melting temperature is maintained at 1700 ° C ~ 1800°C.

[0021] 4) After the slag washing (10min) is completed, that is, all the slag agent floats on the surface of the silicon liquid, the silicon liquid and the slag liquid are separated by the siphon princi...

Embodiment 2

[0025] Technological process is with embodiment 1. Composition by weight percentage is 7:3:0.8, mix two parts of Na 2 SiO 3 -SiO 2 -CaO granule powder is used as slag agent, the mass ratio of each slag agent to raw material is 1:1 (slag-silicon ratio is 1), that is, both the composite slag agent and the raw material industrial silicon are 60Kg. Two times of slag washing and refining: one slag washing and refining for 15 minutes, and one slag washing and refining for 35 minutes. Pour the silicon liquid into a mold with orientation function, let it stand for 10 minutes, take out the silicon ingot after cooling, and obtain purified refined low-boron polysilicon.

[0026] The center part of the silicon ingot was taken, and the boron content was measured to be 0.15 ppmw by a secondary ion mass spectrometer (SIMS).

Embodiment 3

[0028] Technological process is with embodiment 1. Mix two parts of Na by weight percentage composition 6:2.8:1 2 SiO 3 -SiO 2 -CaO particle powder is used as slag agent, and the mass ratio of each slag agent to raw material is 1:1 (slag-silicon ratio is 1). Two times of slag washing and refining: one slag washing and refining for 10 minutes, and one slag washing and refining for 35 minutes. Pour the silicon liquid into a mold with orientation function, let it stand for 7 minutes, take out the silicon ingot after cooling, and obtain the purified and refined low-boron polysilicon.

[0029] The center part of the silicon ingot was taken, and the B content was measured to be 0.26ppmw by a secondary ion mass spectrometer (SIMS).

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Abstract

The invention relates to the technical field of metallurgical polycrystalline silicon purification, and in particular relates to a slag washing process for removing boron from metallurgical polycrystalline silicon. The technical schemes are as follows: a metallurgical slag-washing boron removing method is adopted, the same two composite slag agents are pre-melted into a slag agent molten pool, then industrial silicon is added for melting, boron (B) in molten silicon performs oxidation reaction with the slag agent so that boron (B) forms a multi-element slag phase, and boron (B) impurities in silicon are removed by slag-metal separation to obtain solar-grade high-purity polycrystalline silicon with a boron content being 0.15 ppmw. The process provided by the invention has the advantages that: the process is simple to operate, the cost is low, the used devices are formed by combination and transformation of traditional medium-frequency furnaces, the used slag agent can be used repeatedly after adding new SiO2 and CaO, and the process is conducive to large-scale industrial promotion.

Description

technical field [0001] The invention relates to the technical field of metallurgical polysilicon purification, in particular to a process for washing and removing boron from polysilicon slag. Background technique [0002] Photovoltaic power generation has become one of the new energy sources encouraged by the state, and polysilicon is the basic material of the solar photovoltaic industry. Metallurgical polysilicon has become the main development direction of solar-grade polysilicon because of its relatively simple purification process, low cost, and low environmental pollution. At present, the domestic metallurgical polysilicon industry is aiming to continuously improve the output and quality of metallurgical polysilicon products and reduce costs. [0003] Industrial silicon is an important raw material for the production of solar-grade polysilicon, but its purity is about 98%, and it needs to be purified to remove impurity elements, such as B, P, C, O, Fe, Al, Ca, etc., es...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B33/037
Inventor 刘应宽盛之林刘永贵范占军纳永清周金刚
Owner 宁夏高创特能源科技有限公司
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