Modelling solids transport in an industrial flighted rotary dryer

Flighted rotary dryers are used in a wide range of applications, including drying mineral ores and raw sugar. One such example of their application is a large flighted rotary dryer that is used to dry and granulate spherical zinc sulphide particles as part of the Zinifex Century Ltd Karumba zinc processing facility in far North Queensland, Australia. A series of residence time distribution (RTD) pulse tracer tests were performed using lithium chloride as tracer . Tests were undertaken both before and after a significant scheduled cleaning operation to remove significant internal built up scale. This paper describes the RTD collection methodology. The residence time distributions were used to fit a pseudo-physical compartment model to the Zinifex dryer. The model structure, compartment numbers and some of the model transport coefficients were derived through geometric modelling, based on flight and dryer geometry and solids physical properties. Simulations and parameter fitting were undertaken using gProms process modeling software. Fitted parameters include transport coefficients which were used to estimate the effects of air drag on particle movement as well as estimate the rate of kilning or particle rolling along the base of the dryer. Compartment model parameters and derivation of the required compartment model structure are described in this paper. The RTD was found to be able to be reasonably well reproduced by the compartment model