Onboard CO 2 Capture From Ship Engines

An early phase feasibility study has been carried out for offshore CO2 capture from ship engines of a CO2 transport ship. Capture of CO2 from ship engines is a challenging task, especially considered the limited space and energy available onboard, and the logistics involved in bringing the captured CO2 to permanent storage. In this relation, CO2 transport ships could be a special case that is viable, since the capture plant would be located next to dedicated tanks already heading for a storage site. The aim of the current work was to explore the possibility of capturing CO2 from the exhaust gas emitted by the engines of CO2 transporting ships as part of CO2LOS II (CO2 Logistics by Ship Phase II) project. A flexible in-house process simulator was applied in the assessments. Parametric studies were enabled by a fast data-driven capture plant model derived from a large dataset of rigorous simulations. The results show, based on the given models and assumptions, that the thermal energy coming from the ship engine exhaust gas is not sufficient alone to cover the thermal energy demand of an absorption-based CO2 capture unit operating above 50 % capture rate using 30wt% MEA (monoethanolamine) as solvent. The thermal energy demand can be met using a fuel afterburner as heat source. The added fuel consumption is estimated to increase the fuel consumption by 6-9 % when operating with liquefied natural gas (LNG) as fuel source, while an increase of 8-12 % is expected with diesel as fuel source. The effect of absorber height on energy consumption at a given CO2 capture rate is limited, especially for lower capture rates, and may be an important degree of freedom for optimizing the CAPEX/OPEX trade-offs. Use of state-of-the art solvents with lower specific energy consumptions will shift the results towards higher capture rates before a fuel afterburner is required to meet the thermal energy demands.