Energy and exergy analysis of three major recirculating multi-stage flashing desalination plants in Kuwait

This study compares the thermal performance of three Multi-Stage Flashing (MSF) desalination plants constructed at various dates over 30 years. The MSF desalination plants considered in this study are Al-Doha East, Al-Zour, and Al-Sobia, built in 1978, 2001, and 2007, respectively. Using actual operating data, analyses based on the first and second laws of thermodynamics were conducted to study the three MSF desalination plants. The thermal performance comparisons included energy consumption, exergy consumption, second law efficiency, and exergy destruction in different components. The results showed that the Al-Sobia MSF desalination plant yielded 17% lower energy consumption and 21% lower exergy consumption than Al-Doha East and Al-Zour. The results also showed that the Al-Sobia desalination plant had the highest second-law efficiency of 6.9%, compared to 5.4% and 5.5% for the Al-Doha East and Al-Zour. The Al-Sobia desalination plant also had less thermal and electrical energy consumption, which can be explained by the high-performance ratio, high heat exchanger effectiveness, high recovery ratio, and high Top-Brine Temperature (TBT). On the other hand, the low exergy consumption of the Al-Sobia desalination plant is due to the low exergy destruction in the de-superheater and ejectors. Compared to the Al-Doha East and Al-Zour plants, the Al-Sobia de-superheater had lower exergy destruction because of less steam extraction and higher exit flow exergy from the high TBT and pressure.