Mathematical modelling of fluidised bed dryers with horizontal dispersion

A multiparticle model of a well-mixed fluidised bed was developed in a previous paper [1]. In fluidised beds where the length to width ratio is larger than unity, horizontal dispersion often becomes significant. An attempt is here made to account for this by connecting several well-mixed beds in series. The number of beds that corresponds to a given dispersion coefficient is calculated from dispersion theory. The position of the particles in the vertical direction are randomly interchanged at short time intervals to account for the vertical mixing. One randomly chosen particle is moved towards the outlet at specified time intervals to account for the residence time distribution in a horizontal bed. The statistical behaviour of such a system was studied theoretically and the performance of the code was checked by tracking each individual particle through the bed. The model was validated against experimental data from a pilot-scale fluidised bed. The results were promising in the sense that the longitudinal profiles of temperature and particle moisture content were well predicted by the model.