Method for removing boron and phosphorus and purifying industrial silicon by using metallurgic method
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An industrial silicon and metallurgical technology, applied in chemical instruments and methods, silicon compounds, non-metallic elements, etc., can solve the problems of unfavorable operators, waste of energy, and high smelting temperature of slag-forming agents, and achieve the goal of simplifying the process and reducing costs. Effect
Inactive Publication Date: 2014-08-13
SOUTH CHINA NORMAL UNIVERSITY
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[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
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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 purifying industrial silicon by removing boron and phosphorus by metallurgical method, which comprises the following steps: 1) heating the industrial silicon block in a vacuum environment until the silicon is completely melted, and maintaining the temperature for 40-80 minutes to refine the silicon block ;2) Introduce a protective atmosphere containing oxygen and water vapor in the vacuum environment of step 1) so that the oxygen and water vapor in the protective atmosphere can fully react with the impurities in the silicon block, and the flow rate of the protective atmosphere is 50-100ml / min ; In this step, the industrial silicon block is still in a molten state; 3) The environment in the previous step is cooled until the industrial silicon block is in a solid state to obtain a silicon ingot, and the slag phase layer of the silicon ingot can be removed. This process can purify various types of industrial silicon, and it does not need to pulverize and ball-mill the samples. It only needs simple crushing, and the sample size is relatively wide; this process does not require any pickling steps, and avoids the use of a large amount of strong corrosive acids. , simplifies the process and reduces the cost; this process can remove phosphorus, arsenic, antimony, calcium and other impurities to meet the requirements of solar-grade polysilicon; boron impurities are reduced to 1.5-0.3ppmw, which meets the solar-grade polysilicon standard.
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...
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