The process of trichlorosilane synthesis in fluidized bed reactor (FBR), via hydrochlorination of metallurgical-grade silicon, is usually accompanied with the side-reaction to produce tetrachloride. Many efforts have been devoted to increase the selectivity of desired product (SiHCl₃) and reduce the formation of tetrachloride (SiCl₄)....[ Read more ]

The process of trichlorosilane synthesis in fluidized bed reactor (FBR), via hydrochlorination of metallurgical-grade silicon, is usually accompanied with the side-reaction to produce tetrachloride. Many efforts have been devoted to increase the selectivity of desired product (SiHCl₃) and reduce the formation of tetrachloride (SiCl₄).

The two primary reactions involved are both highly exothermic and temperature-sensitive, and the composition of products depends largely on the temperature. However, the temperature distribution during the reaction is often neglected, as FBR is generally considered as temperature homogeneous due to the intense solids mixing and good heat transfer between gas and solids. Actually, for highly exothermic reactions, such as the reaction between metallurgical silicon and hydrogen chloride, the temperature gradient will occur, especially in large-scale reactor. In this case, to further optimize the operation condition and maximize the yield of SiHCl₃, the analysis of temperature distribution throughout the reactor is necessary and meaningful for trichlorosilane synthesis.

In this study, a two-dimensional temperature model is proposed for synthesizing trichlorosilane in the process of solar-grade polycrystalline silicon production. Based on the mechanisms of non-catalytic gas-solid reactions, the kinetic expression is given to investigate the overall reaction rate of silicon to producing SiHCl₃ and SiCl₄. Meanwhile, by combing the heat transferred between packed coolant tube and reactants with the heat released by chemical reaction, the temperature profile is deduced in radial and vertical directions. The simulation and parameter sensitivity analysis are conducted at different conditions, and the result shows the model is reasonable and reliable.