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Method for purifying solar grade polysilicon

A solar-grade, polysilicon technology, applied in chemical instruments and methods, silicon compounds, inorganic chemistry, etc., can solve the problems of complex process, high cost, and impermanent purity, and achieve low equipment investment, low cost, and process operation simple effect

Inactive Publication Date: 2012-12-12
叶文胜
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

These methods have different disadvantages, some are too costly, some cannot reach the purity, and some are too complicated to be industrialized, and none of them are suitable for the requirements of low-cost (less than 50,000 yuan / ton) solar-grade polysilicon

Method used

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  • Method for purifying solar grade polysilicon
  • Method for purifying solar grade polysilicon

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0019] Example 1 Add aluminum to silicon containing 99.0% by weight of silicon, the weight ratio of aluminum is 99.5%-99.9%, the content of iron in the mixture is not more than 0.8%, and the weight ratio of raw material silicon to aluminum is: 20-30 : 80-70, at the same time add titanium with a weight ratio not exceeding 0.2% of the total weight, and heat it. When the silicon is completely melted in the aluminum, let it stand for 1-4 hours and separate the precipitated boron, and then place it at the bottom of the melt Introduce chlorine gas, blow from bottom to top for 10-40 minutes, phosphorus will concentrate on the surface of the melt, remove phosphorus with traditional methods, start cooling at a rate of 2 degrees per minute, and cool until aluminum is discharged from the crystallization bed out, keep the temperature of the bed at this temperature, and continue to lower the temperature, which is conducive to the outflow of aluminum, and the aluminum remaining on the crysta...

Embodiment 2

[0021] Example 2, adding aluminum with a weight ratio of 99.9% purity to silicon with a weight ratio of 99.0%, silicon 25% (weight ratio), aluminum 74% (weight ratio), and the rest are impurities. Titanium that exceeds 0.2% of the total weight is heated to 850 degrees, and the silicon is melted in the aluminum. After the silicon is melted, the precipitated boron is separated after standing for 1-4 hours. Chlorine gas is introduced at the bottom of the melt and blown from bottom to top Gas for 10-40 minutes, phosphorus will concentrate on the surface of the melt, remove phosphorus with traditional methods, start to cool at a rate of 2 degrees per minute, and cool to 585 degrees, aluminum is discharged from the crystallization bed, and the bed is The temperature is maintained at 585 degrees, which facilitates the outflow of aluminum, leaving about 49% of the aluminum on the crystallization bed, allowing the remaining material to partially remelt, and then cooling, reducing the am...

Embodiment 3

[0022] Embodiment 3: Operation is the same as example 2 before the discharge of the molten phase, and the crystallization bed is treated with a gas flame after the discharge of the molten phase, so that the remaining material part is re-melted, and the amount of residual aluminum is reduced by 42% on average.

[0023] When the silicon is 99.0% pure by weight, the added aluminum can be commercial grade, ie 99.5% pure by weight. Of course, it is better if the purity of aluminum reaches 99.9%, because there are fewer impurities brought in. Moreover, silicon containing a large amount of impurities has no negative impact on the quality of high-purity silicon purified by this method, but in order to obtain high-purity silicon in an economical manner, the amount of other substances such as impurities should be controlled for silicon a certain range. When using aluminum as a flux, the iron content in the molten alloy must be controlled at such a level that during fractional crystalli...

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Abstract

A method for purifying solar grade polysilicon. The method comprises the key points of: using silicon containing 99 wt% of silicon as a raw material; adding at least one flux selected from tin, zinc, aluminum, silver and lead into the silicon, with a weight ratio of silicon raw material to metal flux being 20-30:80-70; meanwhile adding no more than 0.2 wt% of titanium and heating to prepare a melt containing a large amount of silicon and metal; standing for 1-4 h and separating out boron; introducing chlorine gas to the bottom of the melt and blowing upwards for 10-40 min to concentrate phosphorus on the surface of the melt; removing the phosphorus by a traditional method; cooling to a freezing point of an eutectic, and keeping the temperature at the freezing point to form a solid phase containing crystalline; concentrating impurities in the melt phase; separating the melt phase metal flux with the solid phase; reheating part or all the solid phase to a melting state; and repeating the above cooling step to obtain purer crystalline silicon. The invention has advantages of low cost, low equipment investment, and simple and safe operation process.

Description

technical field [0001] The invention belongs to a method for purifying polysilicon, in particular to a method for purifying solar grade polysilicon. Background technique [0002] The solar-grade polysilicon in the present invention refers to polysilicon with a purity greater than 99.9999%, that is, 6N. [0003] Silicon does not exist in the free element state in nature, but exists in the form of silicon dioxide or silicate. Commercial silicon of general purity, such as used in silicon alloys, can be produced by reducing silicon dioxide with carbon in an electric furnace, but high-purity silicon can only be obtained through a series of more complicated treatment processes. For example, silicon reduced from an electric furnace can only reach general chemical purity, and it is converted into silicon halide or halosilane, and undergoes rectification (to remove impurities such as boron and arsenic). High-purity silicon is then produced by reducing silicon tetrachloride or silic...

Claims

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Application Information

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IPC IPC(8): C01B33/037
Inventor 叶文胜
Owner 叶文胜
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