Exergy Analysis of the Optimized MSFD Type of Brackish Water Desalination Process

This paper presents a detailed thermodynamical exergy analysis of an optimized MSF distillation plant based on the latest published thermodynamics properties of water and seawater software of the Massachusetts Institute of Technology by using design and optimized plant operation data. Exergy flow rates are evaluated throughout the plant and the exergy flow diagram is prepared in both cases. The rates of exergy destruction and their percentages are indicated on the diagram so that the locations of each exergy destruction can easily be identified. The study concludes that as a result of an optimization, making the MSFD unit once-through cooling system to recirculating type by using cooling tower system, the unit's exergy destruction pattern changes meaningfully. Besides, in the three exist thermal desalination plants up to ۵۳ percent of feed water, i.e.; ۶۶۷ m۳/h and the same amount of reject water can be conserved. Though, with this modification, the unit steam consumption has been increased up to ۱۳ ton/h, about ۵۰ percent of design. Moreover, the detail of the study showed that the exergy destruction can be reduced more than ۳۹% in the pumps, and ۳۰% in blowdown and around ۲۹% in distillate streams. For brine heater, an enhance as small as ۰.۳۷% is also achieved. In the other hand, the rate of destruction of exergy increased around ۲۵% in the cooling process and above ۵% in the evaporators.

کلیدواژه ها:

Multi-Stage Flash Distillation (MSFD) ، Exergy destruction ، Gain Output Ratio (GOR) ، Heat rejection