Hydrogen extraction from a new integrated trigeneration system working with zeotropic mixture, using waste heat of a marine diesel engine

Abstract

Hydrogen can be used for various applications in ships, but two distinctive places are the combustion processes of the marine diesel engine (MDE) or aircrafts fuelled by aircraft carriers (especially, for long-range transportations applications). For this aim, an integrated trigeneration system working with waste heat of the MDE for mainly hydrogen extraction is proposed here. In addition to hydrogen, the devised trigeneration system can produce surplus electricity and cooling at two different temperature levels. Different zeotropic mixtures are used as working fluid and their performance metrics were compared with each other. It is worthy to say that the simulated basic cooling/electricity system is new and is accounted for as another novelty of the present work. A comprehensive modeling of the proposed trigeneration system is achieved from thermodynamics laws viewpoint and results are elaborated in detail. Based upon the results, the maximum refrigeration load and trigeneration energy efficiency are calculated 166.36 kW and 42.46%, respectively, when R142b/Pentane (0.51/0.49) was used. However, to achieve lower overall exergy destruction, Butene/Isopentane (0.35/0.65) was recommended. Also, the highest trigeneration exergy efficiency is associated with Butene/Isopentane (0.35/0.65) by 18.71%, followed by Isobutene/Isopentane (0.34/0.66) by 18.53%. It is found that the auxiliary vapor generator has the highest exergy destruction by 61.5 kW, followed by ejector by 19.5 kW. At last, an intensive parametric study is also presented to propose some solution for performance enhancement of the system based on the thermodynamics parameters.