(515e) Mass Transfer in Tapered Fluidized Beds

Tapered beds can handle fluidization of particles with wide size distribution more effectively. As the area of cross-section increases with height, higher gas velocity at the gas distributor reduces the chances of de-fluidization of larger particles while lower gas velocities at the top ensure less elutriation of fines. Tapered beds can be useful for processes such as combustion of coal, roasting of ores, polymerization, granulation of fines, drying of wet powders in which particle size may change with time. In all these processes gas to particle mass transfer plays a vital role.

Mass transfer rates from naphthalene balls to fluidizing air in tapered beds of inert materials are measured and mass transfer coefficients are estimated. Effect of size and density of the mass transferring particle with respect to properties of bed particles is investigated. A model based correlation is developed to explain the observations