Hydrodynamic behaviors of a spouted fluidized bed with a conical distributor and auxiliary inlets for the production of polysilicon with wide-size-distribution particles

In order to improve the fluidization quality of wide-size-distribution (WSD) particles in a spouted bed reactor for the production of polysilicon, a conical distributor with one central gas inlet and six auxiliary inlets was designed and applied in a cold-model reactor to form a spouted fluidized bed. The effects of the central and auxiliary gas velocities on the solid holdup were studied in the gas distributor region. The hydrodynamic behaviors inside the conical distributor were analyzed by pressure fluctuation in the time domain (standard deviation) and the frequency domain (power spectral density, PSD). The gas distribution was measured by the gas tracing method. It was found that the auxiliary gas feed significantly re-distributed the solid particles and effectively improved the fluidization quality; the dead zone phenomenon was well suppressed even at a low superficial gas velocity. Based on different flow behaviors, a regime map of fluidization was determined for fixed bed, bubbling bed, spouted bed, and spouted fluidized bed regimes. These results provided guidance for the reactor design because the gas and solid distributions would significantly affect the deposition efficiency of polysilicon.