A dynamic model for MED-TVC transient operation

The Multi Effect Distillation (MED) process is often proposed as a key technology for the construction of new thermal desalination plants, especially within solar-powered cogeneration schemes. With this respect, the need for transient behaviour analysis requires the development of dynamic models for the MED process. Only a few have been presented so far in the literature, in which, however, several simplifying assumptions and constrains are still limiting their potential use. The model here proposed addresses most of the aspects still limiting previous models formulations. The powerful equation-based process simulator gPROMS® was chosen for the implementation of the model, developed on the basis of available data from a MED-TVC plant located in Trapani, Sicily (Italy). After validation, the model was used for some preliminary analysis of system behaviour under transient conditions, artificially generated starting from steady state by implementing specific disturbances such as the variation in the motive steam pressure, seawater feed flow rate and temperature. This demonstrates the model capability to describe in detail the dynamic response of the system with respect to all its variables, thus representing a useful tool for the prediction of transient operations and control system design purposes of MED-TVC plants.