Controlling bubble coalescence in a fluidized-bed model using bubble injection

Gas - solids fluidized beds are characterized by the presence of gas voids or bubbles causing a mass-transfer resistance. Enhancing the mass transfer fi om the bubbles to the emulsion phase by reducing the bubble size can be advantageous for the chemical performance (like the conversion and selectiv ity) of the reactor. A model using a 2-D version of the dynamic bubble mode l of Clift and Grace (1970, 1971) where bubble trajectories are predicted b ased on an analytic expression for the flow field around a bubble was studi ed. Bubble coalescence can be reduced by injecting bubbles in certain patte rns which leads to a reduction of the average bubble size higher in the bed . A simple proportional feedback control method to force bubbles on a horiz ontal line made it possible to generate a bubble injection pattern automati cally leading to smaller bubbles than without the feedback control method. The principle of the controlled bubble injection could lead to improved gas distributor designs.