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, gamma(RD), 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 G(s) was larger than the minimum value G(s,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. (C) 2015 Elsevier B.V. All rights reserved.