Improved Process Modeling for a Lime Rotary Kiln Using Equilibrium Chemistry

This article describes an improved process model for simulation of the manufacturing process of lime in a rotary kiln. The model simulates ideal behavior of complex chemical systems with an assumed homogenous mixing without time-dependent factors. It is a totally predictive model that excludes the empirical parameters. The model is a chemical phase equilibrium model that calculates the final product in a non-equilibrium mode, according to established methods. The phase chemistry is among the most complex found in the literature for lime manufacturing. The thermodynamic data used in the model is based on 11 components (Ca, Si, Al, Fe, K, S, Cl, C, H, O and N). The fuel has an important role in the lime manufacturing process. Special attention is required since it is fed directly into the process via the burner and can influence the process and final product. In the model, the fuel is defined in order to have it behave in a realistic way, and operational data from a full scale lime plant verify the simulation results. The simulated amounts of gas and solids correlate well with operational data. The predicting chemical composition of the product needs improvement by adding more system components and their related compounds to the thermodynamic database. Simulation results from co-combustion of coal and processed waste based fuel oil that it is a versatile tool for predicting product quality and amount, temperature profiles of the rotary kiln, and exhaust gas composition and amount.