Experimental investigation and correlation of the Bodenstein number in horizontal fluidized beds with internal baffles

Abstract

In many branches of industry, there is a high demand for the formation or the conditioning of particulate products. In many cases the fluidized bed technology is applied due to its robustness and intensity of heat and mass transfer. Furthermore, many producers look for a continuous process for economic reasons instead of a batch process with high labor and dead-time. These continuous processes, however, hold the disadvantage of a particle residence time distribution (RTD) and therefore a distribution of particle properties. To minimize the spread of the RTD vertical baffles can be installed into the system, causing an influence on the particle transport behavior. To investigate this influence several experiments have been conducted, varying relevant parameters, such as superficial gas velocity, particle diameter, the kind and placement as well as the number of internal baffles, the height of the exit weir and the apparatus itself (pilot and lab-scale plant). From the experiments different influences of the varied parameters on the Bodenstein number, as a measure of convective to dispersive transport, are shown. Based on these trends an empirical correlation for the Bodenstein number is developed and compared to the experimentally determined Bodenstein numbers. Furthermore a correlation for apparent bed porosity is proposed, which uses the set exit weir height instead of the unknown bed height to predict the particle holdup mass and thus the particle mean residence time. It is shown, that both correlations fit well with the experimentally determined values. Finally a prediction of the RTD is shown from the correlated Bodenstein number and the mean particle residence time.