Exergy Analysis of a Brine Mixing Once - Through MSF-BM Distillation Plant

Abstract

Exergy analysis is a tool that can be used to detect the sites and causes of thermodynamic inefficiencies in a thermal process, as well as to prospect the design performance of any industry plants. The practice of such an analysis in seawater desalination plants is of increasing importance to discover the sites of the biggest irreversible losses. In this paper a full exergy analysis of a brine mixing once through multi stage flash MSF-BM desalination plant was carried out to identify the component that has the largest exergy destruction. The MSF-BM desalination plant is located at 30 km north-west of Tripoli the capital of Libya. Exergy flow rates are estimated all over the plant and exergy flow diagram is prepared. The results of the exergy analysis show that the multi-stage flash unit, pumps and motors are the major sites of highest exergy destruction, where 61.48 % of the entire input exergy took place in the MSF unit, and 19.8 % happens in the pumps and motors. The second law of efficiency was estimated to be 6.24 %, which seems to be low that mean some improvements should be made to improve the plant efficiency and reduce exergy destruction, the improvement can be made to the MSF unit by increasing the number of flashing stages and to the pumps and motors by installing modern pumps with high efficiency.