Abstract
Rotary dryers are very versatile process equipment as it can accommodate a large variety of products over a wide range of flow rates. To obtain a uniform product quality and to operate the dryer economically with minimal environmental impact, it is necessary to use efficient control strategies. In this article, two simple control strategies are proposed to improve the feedback-only controller that is normally used. One strategy is a partial feedforward control loop addition to the feedback loop and the second is a moisture predictor that allows taking control actions on the estimates of the discharge moisture content rather than waiting to measure its value at the discharge. The performance of these two strategies was compared with the performance of a feedback-only controller and an ideal feedback-feedforward controller. It is shown that the two proposed control strategies significantly improve the performance of a feedback-only control strategy without having to install new sensors.