Comparative analysis and estimation of amounts of exhaust gas waste heat from the Tier III-compliant dual-fuel low-speed marine main engines

Existing and future IMO restrictions on emission of harmful substances contained in exhaust gas have introduced an obligation to implement technical solutions to reduce NOX, SOX and CO2 emissions. Reduction in NOX and SOX emissions has been achieved by systems (i.e. SCR and EGR) ensuring Tier III-compliant exhaust gas composition. SCR and EGR systems have also affected the amount of exhaust gas waste heat. Therefore reduction in CO2 emissions has mostly been dependent on available amount of exhaust gas waste heat to produce electricity using waste heat recovery generator unit instead of medium-speed diesel generating set. Comparative analysis of amounts of exhaust gas waste heat in LNG and MGO modes under ISO ambient conditions has been carried out with particular emphasis on the impact of different variants of SCR and EGR systems. Formulae to estimate the amounts of exhaust gas waste heat have been determined using least squares method.