Simultaneous re-design and scheduling of multiple effect evaporator systems

Evaporation is a key operation in many industries and its optimization is required for the efficient management of water and energy within the process. During the operation, dissolved solids settle on the heat exchange surfaces with the consequent increase in the heat transfer resistance. Therefore, periodic shutdowns of the trains of evaporators are required for the cleaning of the units in order to restore acceptable performance. In this work the simultaneous re-design and scheduling of multiple effect evaporation systems is addressed. A mixed integer nonlinear programming model based on a discrete time representation is proposed and applied to a typical evaporation system in the sugar industry with several multiple effect parallel lines and time decaying performance.