Model based optimization of emulsification processes

Project members: M. Stork, J. Wieringa, O.H. Bosgra

Sponsored by: EET

Emulsification is a key manufacturing technology in the food industry. Examples of emulsions are mayonnaise and many kinds of dressings. For the manufacturing of these products oil and water (or more general an oily and an aqueous phase), surfactants, ingredients and energy are needed. Equipment as used for the production of oil-in-water (o/w) emulsions is shown in Figure 17. It consists of a stirred vessel in combination with a colloid mill and a recirculation loop. The colloid mill consists of a stator and a rotor. In the narrow gap between these the intensity of the hydrodynamic forces acting on the drops is very high, which causes the breakage of the oil drops. The colloid mill also acts like a pump resulting in a recirculating flow to the vessel. The process is operated fed-batch wise and typical production times are in the order of 10-20 minutes.

Figure 17: Equipment for the production of o/w-emulsions.

In industrial practice the operation procedure is conventional in the sense that the oil flow addition rate and the stirrer and rotor speed (the input variables) have constant values in time. After the oil addition the process is continued for a certain time to ensure a sufficient drop size reduction. For profit maximization it is desirable to decrease the production time while maintaining the product quality specifications. Experiments are expensive and time-consuming; therefore a model-based optimization approach is followed here. The emulsion quality is strongly affected by the drop size distribution (DSD). The desired DSD is often multi-modal and/or asymmetric. This makes the control of the moments of the DSD inadequate and creates the need for the control of the full distribution. The objective of the research is to chose the control inputs such that a certain predefined terminal DSD is reached in minimal time. The research comprises (physical) modeling, parameter estimation, model validation and optimization of the operation procedure.