Characteristics of the formation of particle wall-layers in CFB boilers

Paper in proceeding, 1995

The character of the vertical two-phase flow in circulating fluidized bed (CFB)boiler furnaces is compared with results from small CFB risers presented in literature. The particle flow in furnaces as well as in the smaller risers shows a core/wall-layer structure. In the CFB boilers the particle flow pattern develops up through the furnace with the major back-flow caused by separation to the furnace walls. Both the particle wall-layer thickness and the downward flux within this layer increase downwards along the furnace walls. In the smaller units this downward increase is either absent or much smaller, a consequence of a more developed particle flow profile, which, typically, is parabolic in shape.