Optimal operating conditions for a batch fluidised bed dryer

In this study, operating conditions for a batch fluidised bed dryer are found that achieve the specifications on the final moisture level, while minimising the energy consumption. The operating conditions are obtained by solving an optimisation problem, where the specification for the final moisture content of the bed is included as a constraint. The optimisation is based on a lumped mechanistic model that describes the heat and mass transfer between solid, gas and bubble phases in the bed. Experimental validation of this model shows that it can be used to predict the particle moisture content and temperature profiles during the drying process and it is shown that the wall temperature has a major effect on the predictions. Compared to the standard approach of maintaining the inlet air temperature and flow rate at constant values, the optimal operating conditions for a lab-scale bed dryer reduce the energy consumption by 26% and shorten the duration of a batch by 20%min.