Control of the rotary calciner for soda ash production

The paper presents the dynamic simulation results obtained by modelling and control of the rotary calciner for sodium carbonate production by the endothermic decomposition of sodium sesquicarbonate. The calciner model with distributed parameters consists of three zones, each described by sets of PDE's: the combustion zone, the reaction zone and the disengaging zone. Dynamic responses to typical disturbances are presented and compared with industrial and literature data. As main target variable, the sodium sesquicarbonate content control at the discharge end of the calciner is investigated using different control approaches. The classical PID control and the Nonlinear Model Predictive Control (NMPC) algorithms are compared in mixed feedforward and feeback schemes. Incentives are revealed for particular control structures using feedforward NMPC, becoming also a feasible approach for the control of similar processes taking place in rotary calciners.