Theoretical and experimental insight into the homogeneous expansion of wet particles in a fluidized bed

Abstract

The presence of liquid in a fluidized bed induces a homogeneous bed expansion at incipient fluidization, which improves the fluidization quality by enhancing the gas-holding capacity of emulsion phase. This paper made an insight into the expansion of wet bed through theoretical and experimental approaches. The bed expansion ratio increases with particle diameter and liquid surface tension, and hardly changes with liquid viscosity due to the absence of viscous term in liquid bridge force. The expansion ends up as the tensile strength of wet bed equals to the shear stress from gas drag force. The superficial gas velocity at this point is the complete fluidization velocity, Ucf. Theoretical calculation shows that Ucf sharply increases then gradually saturates with increasing liquid amount. The tensile strength of wet bed is most sensitive to the superficial gas velocity, followed by the particle diameter. The effect of liquid amount is the smallest. From an optimization perspective, increasing particle diameter and liquid surface tension can enhance the gas-holding capacity of a wet bed during fluidization.