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Method for removing boron and phosphorus and purifying industrial silicon by using metallurgic method

A metallurgical and industrial silicon technology, applied in chemical instruments and methods, silicon compounds, non-metallic elements, etc., can solve the problems of wasting energy, unfavorable operators, and excessive impurities introduced by slag-forming agents, and achieve cost reduction and simplification. The effect of craftsmanship

Inactive Publication Date: 2012-10-03
SOUTH CHINA NORMAL UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0015] The above-mentioned processes mostly involve silicon powder, but silicon powder is very easy to oxidize, the loss is relatively large in the process of slagging and pickling, and the product recovery rate is low; combined with the pickling process involves highly corrosive nitric acid, sulfuric acid, hydrofluoric acid etc., which is unfavorable to operators; in addition, the melting temperature of some slagging agents is too high, which wastes energy; the use of slagging agents artificially introduces too many impurities, which brings burdens to post-processing

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0042] The industrial silicon processed is 3303# industrial silicon, and the actual analysis and detection of the impurity contents are: B (14 ppmw), P (61 ppmw), As (7.5 ppmw), Sb (9 ppmw), Fe (2640 ppmw), Al (1640 ppmw), Ca (290 ppmw), Ti (711 ppmw), Cr (11.75 ppmw), Mn (271.5 ppmw), Ni (254 ppmw).

[0043] The steps to take are as follows:

[0044] 1) Weigh 1000 g of the above-mentioned silicon block and break it into small pieces of 10-50 mm, wash off the surface oil with distilled water, ethanol or acetone, 100 o Put into a quartz crucible after vacuum drying for 12 h; put the silicon block together with the quartz crucible into the graphite crucible of the electromagnetic induction furnace, and seal the furnace;

[0045] 2) Use a vacuum device to control the pressure in the furnace at 10 -2 Pa, and heat the induction furnace until the furnace temperature rises to 1550°C until the silicon is completely melted, continue to maintain the vacuum, and melt at this temperatu...

Embodiment 2

[0052] The processed industrial silicon is 441# industrial silicon, and the actual analysis and detection of the impurity contents are: B (71ppmw), P (84ppmw), As (11.5 ppmw), Sb (14 ppmw), Fe (4333 ppmw), Al ( 3853 ppmw), Ca (601 ppmw), Ti (375 ppmw), Cr (25 ppmw), Mn (426 ppmw), Ni (121 ppmw).

[0053] The steps to take are as follows:

[0054] 1) Weigh 1000 g of the above-mentioned silicon block and break it into small pieces of 10-50 mm, wash off the surface oil with distilled water, ethanol or acetone, 100 o Put into quartz crucible after vacuum drying for 12 h; put into the graphite crucible of electromagnetic induction furnace, and seal the furnace;

[0055] 2) Use a vacuum device to control the pressure in the furnace at 10 -2 Pa, heat the induction furnace until the furnace temperature rises to 1550 °C until the silicon is completely melted, continue to maintain the vacuum degree, and melt at this temperature for 40 minutes;

[0056] 3) Close the vacuum device and...

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Abstract

The invention discloses a method for removing boron and phosphorus and purifying industrial silicon by using a metallurgic method. The method comprises the steps: (1) placing industrial silicon blocks in the vacuum environment to be heated till the silicon blocks are melted, keeping the temperature for 40-80 minutes so as to refine the silicon blocks; (2) leading protective atmosphere containing oxygen and steam to in the vacuum environment in the step (1) to enable the oxygen and the steam in the protective atmosphere to be fully reacted with impurities in the silicon blocks; and (3) reducing the temperature of the environment in the step (2) till the silicon blocks are in a solid state to obtain silicon ingots, and cutting off slag layers of the silicon ingots. By means of the method, various models of industrial silicon can be purified, samples are not required to be subjected to crushing and ball milling, only simple crushing is required, and the requirement for sample size is low. The method does not comprise any acid-washing steps, usage of a great quantity of strong corrosive acid is avoided, the process if simplified, and the cost is reduced. The impurities including phosphorus, arsenic, antimony, calcium and the like can be removed so as to meet the requirements of solar grade silicon by means of the process. The boron is reduced to be 1.5-0.3 ppmw, and the standard of the solar grade silicon is met.

Description

technical field [0001] The invention relates to a method for purifying industrial silicon by removing boron and phosphorus through a metallurgical method. Background technique [0002] With the increasing shortage of energy in the world and the improvement of environmental protection awareness, the demand for solar photovoltaic conversion cells and their main materials is increasing. The purification technology of high-purity polysilicon (solar-grade silicon 6N), which is used as a solar photovoltaic material, has also attracted worldwide attention. The cost of polysilicon accounts for 60% of the cost of solar cells. The vast majority of domestic enterprises still produce polysilicon by the Siemens method with high energy consumption and high pollution. Although the Siemens method has high product purity (11N), the production equipment is complicated, the efficiency is low, and the investment is huge, the energy consumption is high, and the release of chlorine gas endangers...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B33/037
Inventor 孙艳辉陈红雨刘玉
Owner SOUTH CHINA NORMAL UNIVERSITY
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