The Classic Application of Dry Dedusting in The Polysilicon Industry

At present, the production methods of the polysilicon industry mainly include the silane method and the modified Siemens method. The modified Siemens method and the silane method mainly produce solar-grade/electronic-grade crystalline silicon. The silane method is to pass silane into a fluidized bed with polycrystalline silicon seeds as fluidized particles, so that silane is cracked and deposited on the seeds, thereby obtaining granular polycrystalline silicon. The modified Siemens method is to generate silicon rods by vapor deposition after reduction of trichlorosilane after purification.

The modified Siemens method is the most common and mature method at home and abroad. The modified Siemens method is to use industrial silicon powder and hydrogen chloride to synthesize trichlorosilane, and then rectify and purify the trichlorosilane. The purified trichlorosilane and high-purity hydrogen undergo a reduction reaction in a reduction furnace and vapor deposition to generate high-purity polysilicon. However, during the reduction of trichlorosilane, a large amount of by-product silicon tetrachloride will be produced, and a large amount of amorphous silicon powder will also be produced in the reduction furnace. In the modified Siemens method, the generated silicon tetrachloride and amorphous silicon powder enter the tail gas recovery system, thereby separating the amorphous silicon powder, and the silicon tetrachloride enters the next step of rectification and separation.

The on-line filtration system for exhaust silicon powder developed by Shinkai with metal membrane filter element as the core, including on-line silicon powder filter, silicon powder collection tank and on-line operating system, can completely intercept the amorphous silicon powder through high-precision filter elements, thereby greatly reducing the maintenance frequency of the downstream system equipment, providing guarantee for the stable operation of the downstream system, and improving the efficiency of material utilization.

In addition, the Siemens method is improved to add a cold hydrogenation device to treat the by-product silicon tetrachloride, that is, silicon tetrachloride and hydrogen are mixed and heated, and then passed into a cold hydrogenation fluidized bed reactor to react with the industrial silicon powder added to generate trichlorosilane. Since this process uses a fluidized bed reaction, it is inevitable that a large amount of fine silicon powder will enter the rear system with the reaction gas, and this part of the silicon powder will enter the rear system, which will wear and block the pipeline equipment, and also increase the difficulty of slag slurry recovery, resulting in a decrease in material recovery rate, material loss and increased environmental protection pressure. At present, the above-mentioned fine silicon powder is separated by designing a three-stage cyclone after the cold hydrogenation fluidized bed reactor, but the separation effect of fine silicon powder with fine particles is not good.

The cold hydrogenated silicon powder on-line filtration system developed by Shinkai includes high-temperature silicon powder on-line filter, high-pressure silicon powder hopper, silicon powder collection tank, supporting heat tracing and on-line detection system. With the characteristics of high temperature, thermal shock, precise control of pore size, easy regeneration of components, and low overall pressure difference of the filtration system, the separation of the above-mentioned fine silica powder can achieve excellent separation effect.

At present, the silicon powder filtration system developed and produced by our company has been widely used in the silicon industry and has solved many filtration and separation problems and has been widely praised by customers. The company has developed improved Siemens method, silane method, electronic-grade polysilicon full-process filtration solutions, and developed multiple sets of silicon powder filtration systems in organic silicon, silica and industrial silicon. Many clients’ cases could be found in our page of Partners, if you have any doubts of poly-silicone filtration, please contact we Shinkai.

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