Analysis of the Reverse Osmosis Process

This paper considers the state of desalination today and explores improvement of the reverse osmosis process via exergy analysis. Various methods of desalination in place today were explored, along with the proportion of each of those methods in use today. From literature reviews, it was found the reverse osmosis (RO) and multi-stage flash (MSF) desalination were the main methods of desalination in use today. Desalination is an energy intensive process and so this paper aimed to address this issue in three ways: by exploring various coupling with renewable energy sources, carrying out an exergy analysis on the MSF and RO processes, and finally exploring conceptual methods of interest. It was found that concentrated solar power was best suited for the MSF process, since the MSF process require direct heat. Wind energy was best suited for the RO process, since RO was less energy intensive and so could account for wind variability. The exergy analysis demonstrated very low second law efficiency for both desalination processes (~4%), with most of the exergy being destroyed in the separation process (~75%). The RO process also demonstrated a higher efficiency and lower exergy destruction, reinforcing the conlcusion that RO is the less energy intensive of the two. Based on the analysis, it was found throttling valves account for the next highest exergy destruction after the separation process. An alternate plant design was proposed to fully utilize wasted pressure, which resulted in less energy consumption. Finally, two conceptual methods, a mobile desalination plant and the Hybrid process, were explored that could potentially make the RO process a more valuable asset to society and more economically viable with a higher yield