Sustainable boil-off gas utilization in liquefied natural gas production: Economic and environmental benefits

Abstract

Boil-off gas (BOG) causes negative environmental impacts related to gas streams flaring in the liquefied natural gas (LNG) industry. This study addresses the resources and energy management and discusses the economic and environmental benefits of recycling the BOG stream in the LNG production process. Three BOG utilization scenarios and strategies are considered. The first scenario is a separate cooling cycle dedicated to re-condensing the BOG before introducing it to the nitrogen rejection unit (NRU). The second strategy is recycling the BOG before the liquefaction section. The third scenario is recycling the compressed BOG directly in the NRU without re-condensation. Three NRU configurations?flash drum, single distillation column, and double distillation column?are analyzed. The assessment is conducted by the steady-state ASPEN HYSYS simulation of an AP-X LNG production flowsheet. In an illustrative case study, various design alternatives are analyzed for recycling 52,000 metric tons of BOG annually while considering and combining economic, energy, and environmental objectives.