Method for purifying silicon through semi-continuous crystallization in silicon alloy melt

Abstract

The invention discloses a method for purifying silicon through semi-continuous crystallization in silicon alloy melt. The method comprises the steps of heating and melting silicon and Al or Al alloy to form an Al-Si base alloy melt, inserting an air-cooled revolving crystallizing rod in the melt so that silicon crystal is separated out of the alloy melt while such major impurities as B and P are kept in the alloy melt, thus achieving an effect of removing impurities. The air-cooled continuous rotating crystallizing rod is inserted in the melt and relatively high cooling speed is adopted to improve crystal growth speed, so as to realize semi-continuous crystallizing growth in the silicon alloy melt. The method disclosed by the invention has the advantages of being low in energy consumption, free from pollution, high in production efficiency, capable of realizing semi-continuous production, small in investment scale, and simple in production process and equipment operation.

Description

technical field [0001] The invention relates to the field of silicon purification, in particular to a method for semi-continuous crystallization and purification of silicon from a silicon alloy melt. Background technique [0002] Traditional energy sources such as oil and coal are showing signs of depletion and serious pollution. For example, currently 50% of China's "haze" PM2.5 emissions come from fuel combustion. Photovoltaic power generation has many advantages such as cleanness, safety, and sustainable use, and has become one of the main new energy sources. In recent years, it has been vigorously supported by many governments around the world. The output and market of solar cells have shown rapid growth, with an average annual growth rate of Above 30%. Due to the mature technology of silicon materials, abundant raw materials, relatively low price, and no toxic and side effects to the environment, silicon materials occupy an important position in solar cells. The main ...

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Problems solved by technology

[0005] In U.S. Patent US42567117A (R.K.Dawless, Silicon purification method), after Si and Al are alloyed, the temperature is lowered to grow Si sheets, and then a pressing plate is used to press the grown Si sheets to the bottom of the crucible, and then the excess alloy melt is poured Take out the crucible, collect the remaining Si flakes, and realize discontinuous Si flake crystal growth, but this method has slow growth rate, low production efficiency, complicated separation method of Si flakes and melt, and difficult operation

[0006] In the world patent WO2010098676A1 (H.Tathgar, Method for the production of solar grade silicon), two furnaces for melting Si alloys are used, one furnace with a higher temperature is used to add and melt Si raw materials, and then high-temperature Si alloy melt After filtering, it is pumped to a second furnace with a lower temperature, where Si grows into larger crystals and is periodically removed, and the remaining Al-Si melt is pumped back to the first furnace through a filter screen. In the furnace, the continuous purification of Si has been realized, but the growth rate of Si crystals in this method is slow, the equipment and operation process are very complicated, and it is difficult to achieve precise control

[0007] In the U.S. Patent US3933981 (G.F.Wakefield, H.S.Nagaraja Setty, Tin-Lead purification of silicon), a crucible is divided into two parts with high temperature and low temperature by a heat shield, and the raw material Si is melted in the high temperature part, and in the low temperature part, a The Si seed rod is pulled up to grow the Si rod, realizing the continuous purification and growth of Si, but the Si crystal growth speed is slow in this method, the equipment and operation process are very complicated, and it is difficult to achieve precise control

[0008] In the Chinese patent CN101798705A (Jiang Junxiang, Hu Jianfeng, Xu Jingyu, Dai Ning, Chu Junhao, a method and special device for continuous crystallization and purification from low-temperature melt), the above-mentioned method has been improved. In the low-temperature part, a water-cooled crystallization head is used upward Pulling and growing Si rods realizes the continuous purification of Si, and its growth and pulling speed is higher than that of Si seed rods, but the equipment and operation process are still very complicated, and it is difficult to achieve precise control

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