Three kinds of riser inlet distributors were designed to investigate their effects on particle flow characteristics in a CFB riser with 18 m in height and 80 mm in diameter. The results show that inlet distributors have significant impact on particle hydrodynamics at the bottom region of the riser and different inlet distributors have different effects as indicated by characteristic length of the developing section. At the same operating condition

multiple tube inlet had uniform radial distribution of solid holdup and particle movement reached fully-developed state at about 9 m in axial direction

whereas perforated plate inlet had large concentration difference at bottom and particle movement developed slowly in axial direction requiring about 11 m in length to reach fully-developed state. On the other hand

single tube inlet had radial solid holdup and axial development region somewhere between those of the other two inlets. The single tube inlet had non-uniform radial solid holdup distribution of dilute center and dense side at the bottom of the riser and required 10 m axial length to reach fully-development state.