Reverse osmosis and distillation: comparative analysis of their integration in power plants

Abstract

The increasing scarcity of water, world’s overpopulation and the rising demand for electrical demand have given the rise to the need of energy processes to be more efficient. Therefore, this paper presents a comparative analysis of two seawater desalination technologies that provide water and consume large amounts of energy.  The objective of the article, on the one hand, is to carry out an energy comparison of the technologies with the highest global contracting capacity – distillation and reverse osmosis. From the other hand, the paper is aimed to integrate these two technologies into a power block and find out which technology is preferable in terms of its impact on the overall performance of the power cycle.  The study evaluates the energy consumption of distillation and reverse osmosis (RO) taking the feed water as a design parameter.  It is known that as for distillation technology the process is insensitive to salinity, therefore, it does not matter what kind of feed water to use.  In contrast, for the reverse osmosis factors such as temperature and salinity always cause an increase of energy consumption. Besides, it is worth mentioning that there are also evaluated conventional (operating temperature <70 ℃) and unconventional (operating temperature> 70 ℃) distillation technologies that can compete with conventional reverse osmosis (one-step, one-stage) technology with an energy recovery device from the brine. As a result, it has been concluded that, although the thermal efficiency of the distillation process has increased, this technology cannot compete with reverse osmosis, even when it includes a thermo compressor.