Numerical Simulation On Thermal Field And Wall Deposition In The Fluidized Bed For Production Of Polysilicon

Polysilicon is the most basic and the most important function material in solar photovoltaic industry, electronic information industry and the semiconductor industry. In recent years the preparation researches of polysilicon are very active which use new technologies and new equipments. These researches obtain a lot of achievements and technological breakthroughs, which indicate that the production technology of polysilicon will usher in a new leap forward in the world. Because the fluidized bed can realize the continuous production. when using SiH4as the raw materialsilane,the productions only have H2, H2has no pollution to the environment, and the energies of production are also greatly reduced compared with Siemens method, so more and more scholars begin to use the fluidized bed method to prepare polysilicon.The research group design a new type of fluidized bed reactor. There are12heating plates in the fluidized bed, the heating plates are not only heating gases and solids in the bed; they still have an important role as the internal components in the bed, they have a positive impact on the fluidization condition of gas and solid.In this paper, the temperature field is investigated in detail.We analyse the temperature distribution within the bed with different molar ratios of silane and hydrogen. The simulation results show that the quantity of silane has little effect on the temperature field, so the quantity of silane can be determined by the reactions’need. Compared the distribution of temperature field between internal heating bed with external heating bed, the gas heating rate in internal heating fluidized bed is much faster than the external heating bed, and the gas temperature reach the appropriate temperature in the internal heating bed. It concludes that the gas temperature rise soon, the gas pressure distribute more uniform in the bed, and large bubbles have not formed in the bed. The uniform distribution of gas and solid is advantage to the reactions. This paper study the temperature and pressure influence on the decomposition reaction of silane. We study when the pressure is0.2MPa, the deposition rates of silicon vary with time on the wall in the temperature of873K,923K and973K; when the temperature is923K, the deposition rates of silicon vary with time on the wall at the pressure of0.16Mpa,0.18Mpa,0.20Mpa.The results show that the new fluidized bed has an excellent performance under the reaction temperature of923K and the reaction pressure of0.18MPa.