Hybrid Desalination System: Alternative Designs of Thermal and Membrane Processes

MARIAN G. MARCOVECCHIO; MIGUEL C. MUSSATI; NICOLÁS J. SCENNA; PIO A. AGUIRRE

Salvador

Congreso; 10th International Symposium on Process Systems Engineering; 2009

Seawater desalination is one of the main alternatives to overcome the problem of fresh water supply. Thermal and membrane processes are the conventional technologies widely used to obtain potable water from the sea. Hybrid desalination plants integrating reverse osmosis (RO) and multi stage flash (MSF) systems result interesting alternatives. The hybrid systems combine the advantages of the high separation efficiency of thermal processes with the low energy consumption of reverse osmosis. These systems reduce dramatically the final fresh water cost; meanwhile the recovery ratio is increased. In the present work, a mathematical model for MSF and RO hybrid systems is derived on energy, mass and momentum balances meanwhile the most important aspect of the processes are introduced. Precisely, a superstructure is proposed embedding alternative and feasible arrangements for hybrid plants that will be simultaneously optimized. The resulting mathematical model is solved in order to determinate the global optimal plant layout, optimal equipment sizes and operating conditions, minimizing the fresh water cost. The cost equations evaluate accurately the presence or absence of equipments, streams or systems. The model was successfully solved for different seawater conditions (salinity and temperature). The optimal solutions depend strongly on the salt concentration and temperature of the feed water. Due to space limitations only one case study is presented here.