Computer Simulation and Optimal Control of Continuous Infrared Dryers

This study focuses on Infrared Dryers, which are of great commercial importance in all industrial applications encompassing food, agriculture, mining and manufacturing sectors. An unsteady-state model, and a steady-state model are used to describe the operation of dryers with multiple heating stages, and fresh air injection units. The unsteady-state model is a set of three non-linear partial differential equations, which describe the three state variables: (i) humidity of sheet being dried, (ii) temperature of sheet and, (iii) temperature of air flowing above sheet for the start-up of the drying process as a function of time and dryer length. The steady-state model consists of three non-linear ordinary differential equations, which descrive the three state variables as a function of dryer length. The two sizes of infrared dryers, industrial and lab scale, with a wide range of temperature of the radiants and fresh air injection have been simulated with both models. The optimal control of infrared dryers is considered for the first time in this work. As the next step, radiant temperature has been used as an optimal control function along the length of a dryer to minimize the exit humidity of sheet. A robust optimal control technique based on genetic algorithms is used to achieve the optimal control objective. The results show considerable reduction of the exit humidity of sheet, by 19.5-99.9%, with the application of optimal control.