Optimal constrained control of an infrared-convective drying of a polymer aqueous solution

This paper deals with the optimization of the infrared-convective drying of an aqueous solution of polyvinyl (alcohol) mixed with a plasticizer. Thanks to a knowledge model giving the temperature and moisture content evolutions during drying, the process control is firstly investigated in proportional close-loop approach. Then, the optimization is performed by minimizing an objective function which takes several criteria on drying time, energy consumption, and constraints on product (temperature and moisture content) into account. Particular attention is brought to the improvement of the final quality of the product by limiting the decreasing of surface moisture content during drying. The principle was to determine off-line the infrared irradiation and then to test it by means of a drying setup. The experimental tests are performed in open-loop. The infrared irradiation calculated by using proportional controller and optimal control is applied by adapting the infrared emitters’ power in real time.