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The flow characteristic velocities with respect to flow regime classification have been estimated. Flow characteristics in CFB mainly depend on gas velocity, in which the regimes include bubbling, turbulent, fast and pneumatic fluidization. The flow characteristics depend on particle characteristics, bed geometry and gas velocity. Furthermore, in a CFB, the flow regime depends on gas velocity and solid circulation rate. Circulating fluidized bed operates under fast fluidization regime. A cold model of a CFB with column height of 1200 mm and diameter of 50 mm is operated under wide range of gas velocity and solid concentration. Transport velocity is regarded as the boundary dividing the gas–solids up flow into two states and it is estimated by extrapolation technique. It has been observed that slip velocity attains maximum in fast fluidization and it decreases with increase in bed porosity. In the present work it is observed that the transport velocity for sand is higher than terminal velocity, while the transport velocity is more or less close to the terminal velocity Geldart B materials. A flow regime map has been developed for semolina, poppy seeds and sand.

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