Modeling and control of a leaching unit for sunflower oil extraction

In the leaching process alternative solvents to hexane have been studied to reduce the emissions of volatile organic compounds to the atmosphere. Ethanol is considered as an alternative solvent because it is cheap and it can be produced by fermentation from a large variety of biological materials using simple technology. In this paper a phenomenological-based semi-physical model (PBSM) for ethanolic extraction of oil from sunflower collets in a counter-current flow process is derived. In addition, a Proportional-Integral-Derivative (PID) controller and a Model Predictive Controller (MPC) are tested. The response of the controlled variable in both controllers to disturbance rejection, manipulating the ethanol flow, was compared. It was observed that the PID controller needs more than 1 hour to stabilize the controller response while the MPC does it in some minutes.