Large and small particles in CFB combustors

The behaviour of coarse particles was studied in a fluidized bed rig and in a 12 MW CFB boiler. Minimum fluidization velocity and the entrainment rate of course particles from a bed with and without fine sand were measured in the cold rig. A series of solid samples were talen from the boiler furnace in different points with suction probes under various test conditions. The amount of coarse particles was analysed. Bulk densities at different heights with and without coarse particles were compared. It was found that both the minimum fluidisation and terminal velocities were influenced by the flux of fine particles