An improved multi-evaporator adsorption desalination cycle

In GCC countries, almost 25% of the total annual energy consumption is utilized hitherto for seawater desalination in cogeneration plants and its consumption rate is increasing at 2.2% annually. The high demand for potable water is attributed to high double digit GDP growth rate of 24% and the high water languishes at more than 10%. Over the past two decades, GCC countries have spent tens of billions of dollars to expand their present and planned desalination capacities. As the Arabian Gulf has only a narrow opening to the Indian Ocean, high brine concentrations and chemicals rejection from all desalination facilities, sited on its shores, pose great environmental risks. From an environmental sustainability view point, designers and planners of desalination plants face many challenges both to improve energy efficiency of desalination methods as well as to tackle environmental pollution. It is foreseeable that a business-as-usual scenario for growth of power and water production in KSA may increase to an extent that the domestic oil consumption for these productions exceeds that for oil export. Innovative solutions to water production are needed urgently to address these trends. In this paper, a hybrid desalination cycle is proposed by integrating multi-evaporators (ME) with an adsorption cycle (AD): vapour recovered from the AD desorption process is supplied to the ME, exploiting the synergetic effect of latent energy of condensing vapour with the stages arranged to cascade both in pressures-temperatures and thereby improves the performance ratio (PR) of the cycle. This concept is demonstrated in a laboratory pilot plant using a 3-stage ME-AD design and the results are presented for assorted temperatures, pressures and distillate water profiles.