Abstract: Device for discharging a fluid (5) fed into a reaction chamber (1) containing solid particles fluidized by said fluid, through a rotary chamber (100) provided with a finned wheel (13) having fins (14), which may deliver into said reaction chamber the solid particles that are concentrated along the rotary circular wall (8) of said rotary chamber under the effect of the centrifugal force, and processes for the catalytic polymerization, combustion, gasification, drying, impregnation, coating or other treatments of solid particles in suspension in a fluid or for the cracking, dehydrogenation or other catalytic conversions of a fluid using this device.