MODELING OF SINTERING IN HIGH-TEMPERATURE GAS FLUIDIZATION

An investigation was made of the phenomenon of defluidisation caused b y visco-plastic sintering. This occurs when the fluidised bed is opera ted at a temperature sufficiently high for material at the surface of the particles to flow. Previous theoretical treatments of the problem have employed force and energy balances to express the ability of sint ered aggregates to withstand the hydrodynamic forces imposed by the fl uidised bed. A new conceptual approach is proposed which is based on a comparison of the characteristic times for quiescent motion of partic les in a bed and for the growth of sinter necks. The theory gives a qu antitative relationship between the gas velocity required to maintain fluidisation and the temperature of the bed in terms of the surface vi scosity of the particles. Experimental results are reported on the def luidisation and sintering behaviour of a model material (low density p oly-ethylene). The data are used to test the theory and to evaluate th e potential of the new approach. (C) 1998 Elsevier Science S.A. All ri ghts reserved.