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Method for directionally solidifying and purifying polycrystalline silicon by adopting ferro-silicon alloy

A technology of directional solidification and ferrosilicon alloy, which is applied in the direction of silicon compounds, chemical instruments and methods, non-metallic elements, etc., can solve the problems of reduction, achieve the effects of cost reduction, low melt temperature, and reduction of silicon loss

Active Publication Date: 2014-03-19
XIAMEN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although this method can effectively remove impurities other than Al and reduce the melting temperature, how to separate Si and Al in the later process and realize industrial production needs further study

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] 1) Soak industrial silicon powder with a purity of 2N in 4mol / L hydrochloric acid for 0.5h at room temperature to remove impurities in the silicon powder, then rinse it with deionized water and dry it.

[0028] 2) Put the silicon powder in 1) and the iron powder with a purity of 2N into the graphite crucible after mixing according to the mass ratio of 9:1, then put the graphite crucible into the directional solidification furnace, close the furnace cover, and evacuate to below 10Pa, Then pass high-purity argon.

[0029] 3) Turn on the induction heating power supply, gradually increase the heating power to make the temperature inside the crucible reach 1600°C, and then keep it warm for 1.5h.

[0030] 4) Set the temperature gradient in the vertical direction of the directional solidification furnace to 10°C / cm, start the directional solidification lifting device, and perform directional solidification at 10 mm / h to remove impurities in the silicon.

[0031] 5) Put the in...

Embodiment 2

[0036] Technological process is with embodiment 1. The addition of iron powder is 15%, and the rest is pretreated silicon powder; the melting temperature is 1590°C, and the holding time after melting is 2h; the temperature gradient in the vertical direction of the directional solidification furnace is 12°C / cm, and the directional solidification The speed is 15mm / h; the annealing temperature after directional solidification is 900°C, and the time is 4.5h. The alloy ingot obtained is cut off 30% of the upper part, and the remaining part is measured by a plasma inductively coupled mass spectrometer (ICP-MS). is 99.99952%. The removed 30% polysilicon can be recycled through the pickling process, and the specific process is the same as that in Example 1.

Embodiment 3

[0038] Technological process is with embodiment 1. Among them, the amount of iron powder added is 20%, and the rest is pretreated silicon powder; the melting temperature is 1650°C, and the holding time after melting is 1.5h; the temperature gradient in the vertical direction of the directional solidification furnace is 15°C / cm, and the directional solidification The speed of the directional solidification is 20mm / h; the annealing temperature after directional solidification is 950°C, and the time is 5h. The obtained alloy ingot cuts off 35% of the upper part, and the remaining part is measured by a plasma inductively coupled mass spectrometer (ICP-MS). is 99.99963%. The removed 35% polysilicon can be recycled through the pickling process, and the specific process is the same as that in Example 1.

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Abstract

The invention provides a method for directionally solidifying and purifying polycrystalline silicon by adopting ferro-silicon alloy and relates to a purifying method of polycrystalline silicon. The method comprises the following steps of putting industrial silicon powder into hydrochloric acid for soaking and then washing with deionized water; putting silicon powder and iron powder into a graphite crucible, putting the graphite crucible into a directional solidification furnace, closing a furnace cover, vacuum-pumping to below 10 Pa and introducing argon; opening an inductive heating power supply and carrying out heat preservation after the temperature in the graphite crucible reaches 1570-1650 DEG C; starting a directional solidifying lifting device for directional solidification and removing impurities in the silicon to obtain a cast ingot; putting the cast ingot into a vacuum annealing furnace for annealing treatment and then cooling the furnace to a room temperature to obtain an alloy cast ingot; and taking out the alloy cast ingot and cutting 20-40 percent of the upper part of the alloy cast ingot and obtaining a remainder, i.e. the polycrystalline silicon directionally solidified and purified by adopting the ferro-silicon alloy. The method has the advantages of low equipment cost, simple and feasible process, good purifying effect and very wide market prospect in the production field of the solar grade polycrystalline silicon.

Description

technical field [0001] The invention relates to a method for purifying polysilicon, in particular to a method for purifying polysilicon by directional solidification of ferrosilicon alloy. Background technique [0002] Since the emergence of human beings, energy has become an important material basis for human life and social development. Before the invention of the steam engine in the 18th century, human beings used carbon as fuel. Since then, their utilization has turned to coal. After the 20th century, human energy utilization has shifted from coal to oil and natural gas. In recent years, with the continuous increase of the world population, the continuous increase of human demand for energy, coupled with the continuous rise of oil prices, and the increasingly serious environmental pollution problems around the world, solar energy, wind energy and other renewable energy sources are increasingly popular. focus on. Solar energy is favored for its wide distribution, clean ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01B33/037
Inventor 罗学涛林彦旭余德钦方明卢成浩李锦堂
Owner XIAMEN UNIV
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