Utilizing waste heat from natural gas engine and LNG cold energy to meet heat-electric-cold demands of carbon capture and storage for ship decarbonization: Design, optimization and 4E analysis

Abstract

The MEPC 80 session has adopted the revised IMO GHG Strategy, in which the stricter decarbonizing targets have been proposed. Carbon capture and storage (CCS) technologies show significantly excellent to reduce carbon emissions for maritime application, of which the high energy demands were neglected in the majority of past studies. Therefore, we propose a novel integration of natural gas engine, CCS, organic Rankine cycle (ORC) and power turbine (PT). Exhaust gas bypassing strategy is used to improve performances of engine at low/medium loads, which enters PT to generate power. The waste heat from engine is fully used for CCS by cold, heat and power. The comparison of different absorbents in CCS system is conducted, including monoethanolamine and piperazine solutions, showing that carbon capture rate can be achieved by 61.40–92.95% at engine load of 110-50% for piperazine solution, while that can be achieved by 84.81–97.64% for monoethanolamine solution. Additionally, the CO2 storage conditions are also compared and analyzed. The remaining power output can reach 98 kW and 108 kW at CO2 compression pressure of 12 bar and 23 bar, respectively. Furthermore, we show the CO2 capture costs of 124.03 $/tCO2 can be achieved at CO2 compression pressure of 12 bar and piperazine solution application. The proposed system can also achieve 57.3% of EEDI drop for a general cargo ship.