Analysis of particle coating by spouted bed process

The coating of nearly spherical porous alumina with a mean diameter, <(d)over bar (p)>, of 3.9 mm, with a suspension of sucrose and talc in water, was carried out in a conical-cylindrical spouted bed. The rate of increase in particle mass, K-1, and the mass fraction of atomized solids incorporated by the particles, eta, were measured as a function of spouting gas temperature, T-gi, mass flow rate of atomized suspension relative to spouting gas, W-s/W-g, and the gas flow rate relative to minimum spouting, Q/Q(ms). The spouting gas temperature was varied between 67 and 83 degrees C, W-s/W-g between 0.00263 to 0.00471, and Q/Q(ms) between 1.5 and 1.7. K-1 and eta were found to be insensitive to T-gi within the studied range; expressions for their dependence on W-s/W-g and Q/Q(ms) were derived. Particle mass increased linearly with the coating time. The final product is uniform in shape and conserves a log-normal particle mass distribution. (C) 1997 Elsevier Science B.V.