Relationship between apparent bed viscosity and fluidization quality in a fluidized bed with fine particles.

The apparent viscosity was measured in a fluidized bed with fine particles. The measurement was performed in the bed expanded uniformly at gas velocities between minimum fluidizing velocity and minimum bubbling velocity by means of the falling-sphere method. As the apparent viscosity obtained decreased with the diameter of the falling spheres, the viscosity value was determined by extrapolation. The apparent viscosity obtained was correlated with particle diameter, density and bed voidage. An equation for predicting the apparent viscosity in the emulsion phase in a bubbling fluidized bed was introduced by combination with the correlation of the voidage of the emulsion phase. Comparison of the values predicted from this equation with the data in the literature shows good agreement. To investigate the influence of the apparent viscosity on the fluidization quality, deviations of pressure fluctuations and bubble diameter were correlated with the apparent viscosity. It was shown that the proposed correlation for the apparent viscosity was useful for predicting the fluidization quality.