A model for particle collection in a turbulent bed contactor - New packings

This work presents an investigation of novel packings for collecting particles in a turbulent bed contactor. Perforated spheres, oblate spheroids and the conventional plain spheres, all made of polypropylene material, were tested for collecting particles in a 0.264 m diameter column. Alumina (aerodynamic diameter from 1.5 to 5.5 mu-m) and titanium dioxide (aerodynamic diameter = 0.7 mu-m) were used as test powders. The results show a lower penetration of particles through the fluidized bed of perforated packings in comparison to plain conventional spheres and oblate spheroids. This indicates that perforated packings are suitable as a contacting medium for particle collection in a turbulent bed contactor. A semi-empirical model for predicting particle collection on the gas-liquid interfacial area formed by the packings is presented in this work. The model describes particle penetration through the bed as an exponential function of the expanded bed height (H) and a global coefficient of particle transfer (m), similar to the global molecular mass transfer coefficient. The coefficient (m) was fitted as function of dimensionless numbers, which describe the hydrodynamics of phases contacting, bed structure and the mechanisms involved in particle collection on a TBC. A statistical analysis of the model predictions has confirmed it to be satisfactory for all types of packings investigated.