Effects of pressure and type of gas on particle-particle interaction and the consequences for gas-solid fluidization behaviour

The fluidization behavior of cracking catalyst was studied at pressures of 1-15 bar with different fluidization gases (Ar, N2, H2). A no. of parameters of both the homogeneous and heterogeneous fluidized bed were examd. exptl. The exptl. results reveal that the min. fluidization velocity is independent of the pressure. The bubble point velocity and the max. bed expansion at this velocity increase with increasing pressure. This also holds for the dense phase voidage and the dense phase gas velocity in the bubbling bed. The bubble size decreases drastically with increasing pressure. However, the above-mentioned parameters are also strongly dependent on the type of fluidization gas used. The cohesion const. of the powder was measured, using a tilting bed technique. The results reveal that the cohesion const. increases with increasing pressure. Anal. of the results of adsorption measurements of the different gases on the solid reveals for the adsorption, cohesion, and bed expansion the same pressure dependence. The gas adsorption affects the cohesion between the particles and the elasticity modulus of K. Rietema and S.M.P. Musters (1973, 1977). The increasing elasticity modulus with increasing pressure also explains the increasing bed expansion with pressure