A simplified physical model of turbulence in a circulating fluidized bed (CFB) combustor is presented. The existence of a dense bubbling bottom bed, a splash zone with pronounced clustering effects and a transport zone with predominantly disperse solids flow in the core is accounted for. The energy dissipation rate evaluated from the total energy supply and the macro-scale of the bubble-induced turbulence are used as defining parameters for order of magnitude estimates of turbulence effects in a 0.7 m wide cold rig and a 12 MW CFB boiler. The results obtained show a reasonable agreement with available experimental data
