PURPOSE: To prevent the deposition of a powder in the pipe guiding a mixed stream of a powder and gas from a reaction fluidized bed to a solid-gas separator by setting the angle formed by the feed direction of the powder and a horizontal surface in the conduit guiding the mixed stream of the powder and the gas from the reaction fluidized bed to the solid-gas, separator to the angle of repose of the powder or more.

CONSTITUTION: The powder discharged from a reaction fluidized bed 1 along with gas is separated from the gas in a solid-gas separator 2 and the separated powder is again circulated to the reaction fluidized bed 1. In this circulation fluidized apparatus, the angle formed by the feed direction of the powder and a horizontal surface in the conduit 7 guiding the mixed stream of the powder and the gas from the reaction fluidized bed 1 to the solid-gas separator 2 is set to the angle of repose of the powder passing through the guide pipe. As a result, the accumulation of the powder in the pipe guiding the mixed stream of the powder and the gas from the reaction fluidized bed 1 to the solid-gas separator 2 can be prevented and stable operation can be kept over a long period of time without generating clogging trouble.