Fuzzy control of heat recovery systems from solid bed cooling

A fuzzy logic controller of the collected air temperature in heat recovery systems from moving solid beds has been presented in this paper. Controller development and tests have been carried out with reference to an actual grate cooler from a sintering plant of the Ilva steel works in Taranto, Italy. Cooling is performed by blowing fresh air underneath the bed and heat recovery is obtained by hoods collecting the permeating hot air. However, nearly continuous fluctuations of both the solid inlet temperature and flow rate, in conjunction with the practical unfeasibility of direct measurements of such parameters, make the attainment of a constant temperature of the recovered air very difficult, this being the only parameter that can be monitored for process control. In this situation fuzzy logic shows advantages over conventional control techniques either in terms of robustness and ease in implementing the control rules. The paper describes development and optimization of the control system along with simulations of its performance resorting to a previously developed unsteady-state real-time heat exchange model of cooling bed operation.