Modeling, optimization and control of a ceramic tunnel kiln for consistent product quality under changing production demands

This study presents a detailed physics-based model focusing on an industrial tunnel kiln under feedback control. Initially, an empirical sintering model is integrated into the kiln model to accurately predict the product outlet density, a quality-defining parameter reflecting firing process efficacy. Afterwards, the initial steady-state burner valve positions are determined using industrial temperature data. Subsequently, the interactions between gas temperatures and burner valve positions are quantified through the investigation of the Relative Gain Array. A systematic derivation of optimal set-points for different production rates is then carried out, aiming at minimizing energy consumption while meeting end-product quality specifications. The PID controllers are tuned using a dynamic optimization approach, which involves the minimization of integral criteria. Finally, a case study is conducted to evaluate the efficacy of the optimal set-points under varying production rates. The results demonstrate exceptional system response, thus indicating that firing curves should adapt to production rates for consistently producing quality products.