Waste heat recovery from ship diesel generators for water-energy dual purpose plants

• Published in: Desalination and water treatment 2017-03, Vol.69, p.322-327
• Main Authors: Capocelli, M., Moliterni, E., Bello, A., Piemonte, V., Di Paola, L., De Falco, M.
• Format: Article
• Language: English
• Subjects: Diesel engine; MED; MSF; Process analysis; Waste heat
• ISSN: 1944-3986
• DOI: 10.5004/dwt.2017.0717

Although, the recent efforts in the field of sustainable shipping, the energy efficiency is still limited at a half of the fuel calorific value, whereas the spare input energy is discharged in the environment as exhausted gas and jacket water. It is possible to increase the overall engine efficiency virtually up to 80% by introducing a Combined Rankine cycle to recover the enthalpy of the exhausted gases, and Multi-Stage Flash (MSF) or Multiple-Effect Distillation (MED) to recover the waste heat from the hot temperature cooling water system. In this paper we propose the process analysis of dual purpose plants for the on-ship desalination and compare different alternatives with respect to the process energy duty. In the proposed solution, an additional 1–2 MW of electrical power and around 1,400 m3/d of freshwater can be produced by recovering the waste heat of a 19 MW diesel engine (at 85% load). MSF allows to recover a higher percentage of waste heat, highly increasing the HTW efficiency. On the other hand, when compared to MED, the distillate production by MSF is lower at the same number of stages/effects and, due of the higher quality of the steam, the MSF integration reduces the additional production of electrical energy.