Model Evaluation of a Steam Distillation Process for Steam Temperature Regulation

Steam temperature of a steam distillation process possessed variable process gain and a significant dead-time when operating from 27oC to its saturation point. Model accuracy is an important factor when tuning a PID for temperature regulation using model-based method such as open-loop Ziegler-Nichols. This study will evaluate the adequacy of two models; each estimated at different operating range using first-order plus dead-time structure. PID controllers derived using both models were evaluated experimentally for its regulating performance and robustness against set point change. The results show that PID controller derived within the linear operating range performed better for all cases. During the operation, the PID controller will be activated once the controlled variable exceeds the threshold limit. Otherwise, the actuator will be operating at its full-range.