Currently, the two dominant desalination methods are reverse osmosis (RO) andmulti-stage flash (MSF). RO requires large capital investment and maintenance, whereasMSF is too energy intensive.An innovative vapor-compression desalination system is developed in this study. Acomprehensive mathematical model for the heat exchanger/evaporator is described. Theliterature indicates that extraordinarily high overall heat transfer coefficients for theevaporator are possible at selected operating conditions that employ dropwisecondensation in the steam side and pool boiling in the liquid side. A smooth titaniumsurface is chosen to promote dropwise condensation and to resist corrosion.To maximize energy efficiency, a combined-cycle cogeneration scheme isemployed composed of a gas turbine, a heat recovery boiler, and a steam turbine thatdrive a compressor. The combined-cycle power source is oversized relative to the needsof the compressor. The excess power is converted to electricity and sold to the openmarket. A three-effect evaporator is employed. It is fed with seawater, assumed to be3.5% salt. Boiling brine (7% salt) is in the low pressure side of the heat exchanger and condensing steam is in the high-pressure side of the heat exchanger. The condensingsteam flows at 1.52 m/s (5 ft/s), which maximizes the heat transfer coefficient. The plantis sized to produce 37,854 m3/d (10 mill gal/day) and is assumed to be financed with a5%, 30-yr municipal bond.Two economic cases were emphasized: the United States and the Middle East.For the United States, the fuel costs $5/GJ ($5.27/mill Btu) with the latent heatexchanger at ( ) 1.11 K 2.00 F T ?? = ?? . The required compressor energy is 14 MJ/m3 (14.7kW h/thous gal). The capital cost for the U.S. is $884 d/m3 ($3,342/thous gal) and thedelivered water selling price is $0.47/m3 ($1.79/thous/gal).For the Middle East, the fuel costs $0.5/GJ ($0.53/mill Btu) with the latent heatexchanger at K T 33 . 3 = ?? ( ) F 00 . 6 ?? . The required compressor energy is 26 MJ/m3 (27.3kW h/thous gal). ). The capital cost for the Middle East is $620 d/m3 ($2,344/thous gal),and the delivered water selling price is $0.25/m3 ($0.95/thous/gal).In all cases, the water selling price is attractive relative to competing technologies.
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