Techno-Economic-Environmental Study for Recovery of Novel Water Source within a Power Plant - Desalination Complex

Abstract

The global water supply is at an already critical level; around 3.9 billion people (47% of the world population) will be subject to water stress in 2050, according to the Organization for Economic Co-operation and Development (OECD). Unless advanced and alternative technology solutions are applied, construction of desalination facilities will continue to rise, leading to higher CO2 emissions. While desalination allows for the production of water from highly saline sources, it is considered an energy intensive process that is largely powered by fossil fuel sources. The natural interconnections between water and energy known as water-energy nexus has been widely recognized for desalination facilities; yet, there are tremendous amounts of cooling water that are still needed for condensing steam in the thermoelectric Rankine cycle to produce electricity; and large amounts of energy are typically required to transport and treat the water. For example, over 45 thousand cubic meter per hour of water are required to run a 500 MW power plant, for cooling and other process requirements. Moreover, large amounts of water vapour exit in the effluent flue gas from the combustion process. The amount of water that can be recovered from the flue gas is sufficient to substantially reduce the need for freshwater make-up. This represents a promising opportunity to exploit synergies among water and energy systems specifically for arid regions. In this paper, the aim is to identify suitable water recovery (dehydration hybrid) technologies that are capable of maximizing the recovery of water from flue gas in gas fired power plant-desalination plant coupled system. Specifically, compression and cooling, quenching, membrane separation and absorption alternatives are studied. The capacity of the power plant, the capacity of the desalination plant, fuel consumption of the power plant and energy requirement of the desalination facility are known. This work studies the technical, environmental and economic competing objectives when integrating the dehydration hybrid technology within the desalination-power plant complex. In this paper, the results for all the considered alternatives will be presented in terms of water recovery, energy savings, emissions reduction and economic indicators. The integrated low pressure quenching water recovery alternative has shown promising results, with up to 42% water recovery, while the integrated low pressure absorption alternative has demonstrated the highest figure in energy savings and emissions reduction with around 37%. These results can aid the decision on the suitable water recovery alternative to be used in the integrated energy-water complex.