A new standalone single effect thermal vapor compression desalination plant with nano-filtration pretreatment

Abstract

Thermal vapor compression is one of the most efficient techniques used in both small and medium scale desalination systems. However, the system works under vacuum pressure which is complex in design that uses expensive materials. Thus, a new system design is proposed to allow operation at atmospheric pressure to bypass scaling issues involving nano-filtration technology. The nanofiltration membrane is used as a pre-treatment, to rise the top brine temperature to almost 100 °C and operate the plant at atmospheric pressure. The proposed plant uses solar energy as the main source of thermal/electrical energy. To assess the performance of the new system, energy, exergetic, economic and environmental analysis are carried out for 500 m3/day standalone solar-nanofiltration-thermal vapor compression desalination plant (Solar-NF-TVC). In addition, the proposed system is tested under different operating conditions such as feed water temperature, compression ratio, salt rejection, recovery ratio and motive steam pressure. Results indicate that the plant exergetic efficiency is up to 10%, which is higher than the multi-effect desalination system, reverse osmosis, multi-effect evaporation mechanical vapor compression and multi-effect desalination thermal vapor compression. The compression ratio is found to be the most effective control variable that affects the plant performance ratio, and the feed water temperature has the most significant effect on exergetic efficiency. The saved amount of CO2 is equal 13661.2 ton/yr. Finally, the plant unit water price is found to be equal to 0.89 $/m3. Overall, the proposed cost-effective desalination plant is more suitable for remote areas due to its manufacturing from local available materials.