Hybrid Desalination Systems: Alternative Designs of Thermal and Membrane Processes.

MARIAN MARCOVECCHIO; SERGIO MUSSATI; NICOLAS SCENNA; PIO AGUIRRE

Salvador - Bahia - Brasil

Simposio; 10th International Symposium on Process Systems Engineering, PSE'09; 2009

University of São Paulo (USP)

In this paper, desalination systems integrating thermal and membrane processes are investigated. Specifically, a hybrid desalination plant integrating reverse osmosis (RO) and multi stage flash (MSF) systems is mathematically modeled. The non linear programming problem is developed in order to optimize the configuration and operating conditions in order to satisfy fresh water demands at minimum costs. Both implementations, with one and two reverse osmosis stages are considered at the particular framework RO-MSF adopted. The system is modeled in such a way that the RO unit receives brine feed from the MSF. In addition, partial extractions of flashing brine stream from flash chambers of MSF can be performed in order to feed the RO system. In fact, the flow-patterns and flow-rates of the brine streams of MSF are optimization variables. Heat transfer areas of pre-heaters and the geometric design of stages are design variables to be optimized. The optimization procedure will also decide between one and two RO stages and the number of modules operating in parallel at each stage. Moreover, all the operative conditions will be optimized. Different case studies considering various seawater conditions were successfully solved without convergence difficulties. It can be concluded that the optimal arrangement of hybrid system depends strongly on the seawater conditions (salinity and temperature) and the fresh water demand as well.