Techno-economic evaluation of a multi effect distillation system driven by low-temperature waste heat from exhaust flue gases

In this study, technical and economical evaluation of a multi effect distillation (MED) system is presented which utilizes the vapor produced from waste heat of exhaust flue gases. In order to recover the waste heat of flue gases, a shell and tube heat exchanger was designed with the Polytetrafluoroethylene (PTFE) material in order to resist corrosion as a result of sulfuric acid formation. Recoverable energy, which is obtained from experimental data, serves as the source of energy required to produce water vapor. Due to high fluctuations in the amount of vapor produced, an auxiliary boiler is employed for its compensation. The vapor which has been produced by the heat exchanger and/or auxiliary boiler, is used as the motive steam in the MED distillation. Economic analysis of MED distillation system driven by low-temperature waste heat is carried out and system payback period based on natural gas saving is obtained. Finally, waste-heat-driven MED distillation system is compared to a conventional MED on the basis of the levelized cost of water (LCOW) at different electrical and natural gas tariffs as well as the real interest rates. Economic evaluation shows that the LCOW is about 1.13-2.9 $/m(3).