Design and optimization of boil-off gas recondensation process by recovering waste cold energy in LNG regasification terminals

Abstract

In any LNG regasification terminal, boil-off gas (BOG) generation is unavoidable. BOG being predominantly methane, a sustainable and cost-effective BOG management process for any given LNG terminal conditions is of utmost necessary from both economic and environmental perspectives. LNG has substantial amount of cold energy, which is completely wasted when LNG is regassified using air or water at ambient conditions. In this study, we have developed a superstructure encompassing various process integration options to recondense the generated BOG completely using LNG cold energy. The proposed superstructure is optimized using a simulation-based optimization framework to minimize the total annualized cost for the BOG management process. We have performed several case studies to investigate the impact of different LNG terminal conditions on the BOG management process. Results obtained from our proposed framework not only yields the optimal configuration for BOG recondensation process but also provides the optimal operating conditions for any given LNG terminal condition. Our results show that variations in LNG compositions and regasification pressures do not influence the optimal configuration but they do influence the optimal process operating conditions. The amount of BOG to be recondensed strongly influences both optimal BOG management configuration as well as the process operating conditions.