Method for purifying silicon through removing boron

A purification method and technology of silicon liquid, applied in chemical instruments and methods, silicon compounds, inorganic chemistry, etc., can solve the problems of large loss of silicon raw materials, poor boron removal efficiency, high cost, etc., and achieve increased yield, improved purity, The effect of simple equipment

Active Publication Date: 2012-02-08
BYD CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] The technical problem to be solved by the present invention is: in the method for removing boron from silicon in the prior art, the silicon raw material loss is large, the energy consumptio

Method used

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Examples

Experimental program
Comparison scheme
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Example Embodiment

[0049] Example 1

[0050] Add 20Kg of industrial silicon powder (with a B content of 15.2 ppmw) into an induction furnace with a graphite crucible, and heat to melt it. Then, the molten silicon liquid is transferred into an induction furnace with a high-purity quartz crucible through a tundish, heated to 1750°C with electricity, and evacuated to a pressure of 5000 Pa.

[0051] When the above conditions are reached, the porous rotating nozzle with mixed gas (60 parts by volume of argon + 10 parts by volume of oxygen + 30 parts by volume of water vapor) is lowered to the surface of the silicon liquid and preheated for 5 minutes. Then insert the porous rotating nozzle down into the silicon liquid, and stop inserting it 15mm away from the bottom of the high-purity quartz crucible. Pass in the mixed gas, control the gas flow to 400L / h, and the rotating speed of the porous rotating nozzle to 400rad / min. At the same time, 4Kg slagging agent (industrial grade Na with an average particle ...

Example Embodiment

[0054] Example 2

[0055] Add 20Kg of industrial silicon powder (with a B content of 15.2 ppmw) into an induction furnace with a graphite crucible, and heat to melt it. Then, the molten silicon liquid is transferred to an induction furnace with a high-purity quartz crucible through the tundish, and heated to 1700°C with electricity, and evacuated to a pressure of 5000 Pa.

[0056] When the above conditions are reached, the porous rotating nozzle with mixed gas (65 parts by volume of argon + 5 parts by volume of oxygen + 30 parts by volume of water vapor) is lowered to the surface of the silicon liquid and preheated for 5 minutes. Then insert the porous rotating nozzle down into the silicon liquid, and stop inserting it 15mm away from the bottom of the high-purity quartz crucible. Pass in the mixed gas, control the gas flow to 400L / h, and the rotating speed of the porous rotating nozzle to 500rad / min. At the same time, 4Kg slagging agent (industrial grade Na with an average partic...

Example Embodiment

[0059] Example 3

[0060] Add 20Kg of industrial silicon powder (with a B content of 15.2 ppmw) into an induction furnace with a graphite crucible, and heat to melt it. Then, the molten silicon liquid is transferred to an induction furnace with a high-purity quartz crucible through the tundish, and heated to 1700°C with electricity, and evacuated to a pressure of 5000 Pa.

[0061] When the above conditions are reached, the porous rotating nozzle with mixed gas (70 parts by volume of argon + 10 parts by volume of oxygen + 20 parts by volume of water vapor) is lowered to the surface of the silicon liquid and preheated for 5 minutes. Then insert the porous rotating nozzle down into the silicon liquid, and stop inserting it 15mm away from the bottom of the high-purity quartz crucible. Pass in the mixed gas, control the gas flow to 400L / h, and the rotating speed of the porous rotating nozzle to 400rad / min. At the same time, 1Kg of slagging agent (industrial grade Na with an average pa...

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Abstract

The invention which belongs to the technical field of silicon purification concretely discloses a method for purifying silicon through removing boron. The method comprises the following steps: 1, heating and melting silicon to form a silicon liquid, keeping the temperature of the silicon liquid at 1600-1800DEG C, accessing a mixed gas to the silicon liquid and simultaneously adding a slag former sodium metasilicate, and smelting the silicon liquid, wherein the mixed gas comprises a carrier gas, oxygen and water vapor; and 2, cooling and ingoting the smelted silicon liquid, and cutting off an impurity enrichment part. According to the method of the invention, the smelting time is substantially shortened, the loss of a silicon raw material is substantially reduced, and the yield of silicon purification is improved; the content of boron in purified silicon is low, and the boron removal efficiency is high; and no new impurities are introduced, and there is a certain removal effect on metal impurities, so the purity of silicon can be further improved. The method of the present invention has the advantages of simple required equipment, no need of high energy equipment of plasma equipment and the like, and low energy consumption.

Description

Technical field [0001] The invention belongs to the technical field of silicon purification, and in particular relates to a silicon purification method for removing boron in silicon. Background technique [0002] In order to meet the needs of solar cells, the boron content in solar-grade silicon must be less than 0.3 ppmw. [0003] Industrial silicon is an important raw material for solar-grade silicon production, but it contains a lot of impurity elements, such as Al, Ca, Fe, C, P, B, etc. Among them, P and B are particularly difficult to remove, because the segregation coefficients of P and B in silicon are 0.35 and 0.8, which are much higher than metal elements. For P impurity, the most effective method is to use the characteristic that the vapor pressure of P under vacuum increases rapidly with the increase of temperature, and to remove phosphorus by vacuum smelting. The vacuum smelting method has basically no effect on the B impurity. [0004] The main methods of removing bor...

Claims

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Application Information

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IPC IPC(8): C01B33/037
Inventor 吴志能司雷沈益顺彭少波
Owner BYD CO LTD
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