Cement manufacturing using alternative fuels and the advantages of process modelling

Energy costs and environmental standards encouraged cement manufacturers world-wide to evaluate to what extent conventional fuels can be replaced by alternative fuels, i.e., processed waste materials. Clinker burning is well suited for various alternative fuels. In order select a suitable alternative fuel, a commercial modelling tool (ASPEN PLUS (R)) is used to model the four-stage pre-heater kiln system of a full-scale cement plant (clinker production similar to2900 tons/day), using petcoke as fuel. The goal is to optimise process control and alternative fuel consumption, while maintaining clinker product quality. Calculations with varying amounts of different fuels are compared with a reference case. The dependence of process performance on the amount of combustion air is clearly demonstrated and the energy demand of the process could be predicted for varying fuel mixes.