15D-14 |
Design of a supervision and control system applied to a drum dryer for milk |
G. C. RODRIGUEZ1, F. Hernandez, M. A. Garcia, and M. A. Salgado. (1) Food Engineering Department, Instituto Tecnológico de Veracruz, P.O. Box 1420, Veracruz, Ver., 91860, Mexico Dried products using drum dryers present a great variation in final content producing therefore quality variation and reduced productivity. The aim of this work was to develop a Supervision and Control System (SCS) to maintain final moisture product by means of a classic controller PID (proportional-integral-derivative) acting on the drum rotation speed (Vrc) and the heating steam pressure (Pv). The instrumentation of the dryer consisted of an electroneumatic valve, a variator of speed and an infrared thermometer. The communication of the sensors with the program was carried out by means of external cards. The SCS allowed to change on-line setpoints in order to control the process in automatic or manual. In automatic mode it was possible to act over Vrc or Pv or over both of them simultaneously. The controller's parameters could also be changed. This kind of software allowed to visualize in real time the input and output variables and storage the experimental data. Results showed that it was possible to control the system acting on the two control variables in independent form, however when they were tested simultaneously, the controller was not able to absorb the non lineality of the system. The fastest response of the system was obtained with drum rotation speed. It was of 75 seconds in the presence of set-point changes and 135 seconds in the presence of perturbations in the Pv. The SCS allowed to maintain in a given set-point the final moisture of the product and it can also be used to develop advanced control on this and other processes carrying out slight modifications.
Session 15D, Food Engineering: Processing Technologies
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