Thermal and Economic Analysis of Seawater Desalination Plant (MED-TVC) Using Process Enhancement

The ability to produce potable water economically is the primary focus of seawater desalination researches. There are several methods to desalinate water such as multi-effect desalination, multi-stage flash distillation and reverse osmosis. The desalinated water costs more than potable water produced from natural resources. The present study aims to improving the economy of produced potable water using multi effect desalination with thermal vapor-compression (MED-TVC) with thermal performance enhancements such as feed preheating process using low grade heat and optimizing the distribution of feed flow rate to each effect. Furthermore, the effects of increasing the number of effects with feed preheating on the MED-TVC performance at parallel and parallel cross feed configurations were studied. A mathematical model of the MED-TVC system has been developed. The governing equations based on energy and mass balances of the system components were solved using a computer program to evaluate the MED-TVC system performance. A mathematical model of the steam jet ejector which depends on the mass and energy balances and continuity equations was developed. In addition, an empirical correlation was derived to predict the entrainment ratio of steam jet ejector to simplify the model simulation. This correlation was validated with literature data and it showed good agreement. Increase the feed water temperature using low grade heat source has crucial impact on improving the system performance with low extra initial cost. The energy sources to preheat feed water can be the waste heat of steam-power plants, cogeneration, the exhaust flue gases from the gas-power plants, and the internal combustion engines exhaust hot gases