Abstract: Effects of two different pre-lifting structures on solid circulation rate in an experimental circulating fluidized bed with a riser of 10.6 m high and inner diameter of 0.1 m and the gas-solid flow behavior were compared macroscopically and microscopically.The results showed that there is a remarkable difference in solids circulation rate between standpipe-type riser and showerhead-type riser.Due to the increased particles flow areas and the reduced entrance resistance，solid circulation rate in standpipe-type riser as a whole is higher than showerhead-type riser，especially in high particle feed rate from storage vessel.Under the same operating conditions，the solid concentration at the bottom in showerhead-type riser is higher than standpipe-type riser because of the strong restraining effect from the showerhead structure-The higher radial non-uniformity index and intermittency index in showerhead-type riser indicates that while showerhead distributor causes a local intense particle turbulence，the interaction distributions between gas and particle as well as particles are even more uneven.The instantaneous solid concentration and probability density distribution reflect that although showerhead distributor at the bottom can partly relieve gas-solid segregations in transition region，no fundamental changes occur in general non-uniform flow structure as a whole.

Key words: circulating fluidized bed, pre-lifting, circulation rate, flow behavior