Hydrodynamic behaviors of an internally circulating fluidized bed with wide-size-distribution particles for preparing polysilicon granules

• A new structure of ICFB reactor is proposed to produce high purity polysilicon.
• Gas bypassing is low enough that deposition on the heating wall is well inhibited.
• The heat transfer between two zones satisfies the actual heat demands.
• Segregation of WSDs is effectively suppressed by the solid circulation.
• Semi-empirical correlations are derived to predict fluidization behaviors.

An internally circulating fluidized bed (ICFB) reactor was proposed for preparing polysilicon granules to prevent silicon deposition on the heating wall. The fluidization behaviors of the ICFB with wide-size-distribution (WSD) particles were studied, with focus on the gas bypassing and solid circulation rate between the riser and downer. The results showed that the segregation of WSD particles was effectively inhibited by the circulation of particles, and the gas bypassing fraction from the riser to downer, γRD, was lower than 4%. Using these experimental results, the concentration of SiHCl3 in the reaction zone was estimated to be 7.3–111.0 times larger than that in the heating zone, thus the silicon deposition on heating walls could be effectively suppressed. At normal operating conditions, the solid circulation rate Gs was larger than the minimum value Gs,min required by heat supply, thus the ICFB is very promising to solve the heat supply problem without significant silicon deposition on the heating walls in a fluidized bed reactor.

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