Computational fluid dynamics (CFD) modelling was applied to a cement works precalciner with tyre chips used as a support fuel in order to find ways to improve the process. Experimental investigations were performed on tyre chips to provide input data for combustion and aerodynamic behaviour of the tyre chips and to validate the CFD results. Results from the model showed the likely behaviour of the tyre chips in the real vessel where measurements are impracticable. A new feature was added to the vessel in order to prevent tyre chips falling through the bottom-most inlet to the precalciner; this new feature was also modelled. Observation of the plant operation following the modification led to deductions of changes in the tyre chip behaviour that were also demonstrated in the model.