With the intensification of energy crisis, the country attaches more and more importance to clean power. As one of the representatives of clean power, photovoltaic industry occupies the market with agility and is widely praised. With the explosive growth of the global pv market, the polysilicon market as the pv raw material is also busy, and the polysilicon preparation technology is constantly innovating, among which the improvement of Siemens method, silane method and fluidized bed method are the most widely used methods in the market.

For now, successful commercial production of polysilicon fluidized bed devices are using silane fluidized bed, raw materials of silane and hydrogen. Silane is easy to be separated from other chlorosilanes, with low differentiation temperature, high differentiation rate and few side reactions, which give silane fluidized bed method great advantages: rectification and tail gas treatment process is simple, energy consumption and monomer investment can be greatly reduced, the reaction conversion rate is close to 100%, and the power consumption of the fluidized bed is only 10%~20% of that of the improved Simon method. In addition, the reaction system can be completely closed loop due to complete reaction and few side reactions.

The fluidized bed method usually takes silane or chlorosilane as the silicon source gas and hydrogen as the carrier gas, and the gas-phase stacking reaction occurs on the silicon seed crystal placed in the fluidized bed reactor in advance. Following the production process, granular silicon products are continuously discharged from the bottom of the fluidized bed, and appropriate amount of silicon seed crystals are added together from the top.

As we know, polysilicon is divided into metal level, electron level (EG) and solar energy level (SOG) according to the purity requirement. Especially for electron level, the purity of polysilicon is required to be 11N. This raises the difficult problem to the product purity of polysilicon production method.

Because of the strict requirements on product purity, the production process of fluidized bed method is more complicated than other fluidized processes, which also puts forward higher requirements for equipment production.

During the reaction process, the silane gas will be rapidly differentiated after entering the fluidized bed, and some of them will be heterogeneous and accumulate to the surface of silicon particles. The other part produces homogeneous reaction and generates gas-phase micronucleus. The micronucleus generates silicon powder through a series of polymerization growth process. In this polymerization process, a certain share adheres to the surface of silicon particles and becomes part of granular silicon products. This complex process causes some problems in granular silicon production that cannot be prevented.