Mass transfer in gas fluidized beds: Scaling, modeling, and particle size influence

Experimental and theoretical work on the mass transfer from the bubble phase to the dense phase in a freely bubbling bed is discussed. A chemical reacting system for which the ozone decomposition was chosen as a model reaction is studied and residence time distribution measurements are performed. A numerical method for solving the equations describing the non-steady state is presented. The height of a mass transfer unit can be determined as a function of the average particle size and the superficial gas velocity, but these parameters cannot be varied completely independently of each other because larger particles require a larger flow rate. A lot of other parameters, such as maximum bubble diameter, bubbling point, and hydrodynamic behavior, are also dependent on these and other variables. Therefore, a parameter has to be found which is descriptive for all fluid bed systems with equal particle properties. This parameter can then also be used as a tool in scale up.