Control strategy for a multiple hearth furnace in kaolin production

In the face of strong competition, the kaolin calcination industry is aiming at higher profitability through increased productivity and reduction of costs. Specifically, the industry is facing market demands to maintain product quality with the depletion of high-quality ore. Therefore, considerable research is being conducted to enhance existing processes and their operation and control. In this paper, the concept of a mineralogy-driven control strategy for multiple hearth furnaces for kaolin production is presented and discussed. The aim of the advanced control concept is to increase capacity and to reduce energy consumption while maintaining the desired product quality. The control is based on two main soft sensors: the spinel phase reaction rate indicator for energy use reduction and the mullite content indicator for capacity improvement. In this simulation study, the control strategy is tested and compared with an industrial controller based on a proportional-integral scheme as a benchmark. The results show that the capacity of the process is considerably improved and energy use is remarkably reduced.