Analysis of the Impact of Thermochemical Recuperation of Waste Heat on the Energy Efficiency of Gas Carriers

Abstract

Enlarging the fleet of gas carriers would make it possible to respond to the growing demand for hydrocarbon gases, but it will increase carbon dioxide emissions. The International Maritime Organization (IMO) has developed the energy efficiency design index (EEDI) with the objective of carbon emission reduction for new ships. In this paper, thirty gas carriers transporting liquefied natural gas (LNG) and liquefied petroleum gas (LPG) and equipped with various types of main engines are considered. As shown by the calculation of the attained EEDI, 2 of the 13 LPG carriers and 6 of the 17 LNG carriers under study do not comply with the EEDI requirements. To meet the stringent EEDI requirements, applying thermochemical regenerators (TCRs) fed by main engine exhaust gases is suggested. Mathematical modeling is applied to analyze the characteristics of the combined gas-turbine-electric and diesel-electric power plant with thermochemical recuperation of the exhaust gas heat. Utilizing TCR on gas carriers with engines fueled by syngas produced from boil-off gas (BOG) reduces the carbon content by 35% and provides the energy efficiency required by IMO without the use of other technologies.