Dynamic modelling for optimisation of pellet softening

Abstract

Mathematical models for the crystallisation process in pellet reactors have been developed during recent decades. In this paper, these models are extended with new insights in the pellet softening process. The diffusion of the supersaturated water to the pellet surface is included in the model and the fluidisation model of the bed is modified. The new model is calibrated in a pilot plant setup. Calibration results are validated in two different full-scale plants. The validation process shows that, even under basic process operation, the model can be used to identify a malfunctioning apparatus and identify undesired process conditions. For the normal situation the model gives satisfactory results in predicting fluidised bed porosity and water quality parameters such as calcium, pH, conductivity and m-alkalinity.