Energy and exergy analysis of the different configurations of a reverse osmosis desalination plant in Gran Canaria

Abstract

This work deals with the exergetic analysis of a seawater reverse osmosis (RO) desalination plant in Gran Canaria (Canary Islands, Spain). The thermodynamic analysis was performed using actual plant operation data. The plant has a nominal capacity of 82 000 m3/day and consists of ten lines. Different configurations are possible depending on the energy recovery procedure (Pelton turbine or pressure exchanger devices), the reverse osmosis stages (double or single), the filtration technology or the feed water pressurization procedure (high pressure pump, pressure exchanger, booster pump). The primary locations of exergy destruction were the membrane modules in which the seawater is separated into permeate (product) and brine (reject). The use of two stages highly increases the flow of produced water and does not affect significantly to the exergetic efficiency of the global separation process. The use of a pressure exchanger device saves 23.5 % electricity by reducing the pumping power of the feed water and increases the exergetic efficiency. A sensitivity analysis taking into account the influence of the seawater inlet temperature on the most important process parameters during a year of operation of the plant is also carried out.