Evaluating the Existing Protocol for LNG Bunkering Operations

IMO 2020, a regulation mandated by the International Maritime Organization, demands an 80% reduction in NOx emissions and limits Sulphur to 1000 ppm in fuels used for maritime transportation. This forces the need for a cleaner and sustainable fuel for the ocean-going ships to reduce the emissions generated by the conventional Heavy Fuel Oil (HFO). Liquefied Natural Gas (LNG) turns out to be a promising and long-term solution that complies with the new set of emission standards, but the technology to use LNG for ships is still underdeveloped. The cryogenic nature of LNG demands a special infrastructure and protocol for LNG bunkering operations. However, the procedures suggested in the literature seem to be mere concepts/ideas proposed without detailed quantitative evaluation. In this study, a comprehensive evaluation of the existing LNG bunkering protocol was conducted using a Unisim Dynamic Simulation (DS) model of the LNG bunkering system. The major pitfalls identified in the current protocol are a) the time taken for inerting and purging processes, b) GHG emissions (methane/CO2) released from frequent inerting and purging operations, c) high cost of inerting gas and d) improper pressure management resulting in increased Boil-Off Gas (BOG) generation. These shortcomings will have a major impact on the safety and operating cost of an LNG bunkering system, especially for busy bunkering ports/facilities.