Study on Boil-off Gas (BOG) Minimization and Recovery Strategies from Actual Baseload LNG Export Terminal: Towards Sustainable LNG Chains

Abstract

Boil-off Gas (BOG) generated at the liquefied natural gas (LNG) export terminal causes negative economic and environmental impacts. Thus, the objective of this study is to develop and evaluate various handling schemes to minimize and/or recover the generated BOG from an actual baseload LNG export terminal with a capacity of 554 million standard cubic feet per day (MMSCFD) of natural gas feed. The following three main scenarios were assessed: JBOG re-liquefaction, LNG sub-cooling, and lean fuel gas (LFG) reflux. For the LNG subcooling, two sub-cases were considered; standalone subcooling before LNG storage and subcooling in the prevailing liquefaction cycle. Steady-state models for these scenarios were simulated using Aspen Plus® based on a shortcut approach to quickly evaluate the proposed scenarios and determine the promising options that should be considered for further rigorous analysis. Results indicated that the flow of attainable excess LNG is 0.07, 0.03, and 0.022 million metric tons per annum (MTA) for the standalone LNG sub-cooling, LNG sub-cooling in the main cryogenic heat exchanger (MCHE), and both LFG-refluxing and jetty boil-off gas (JBOG) liquefaction, respectively. This in turn results in a profit of 24.58, 12.24, 8.14, and 7.63 million $/year for the LNG price of 7$ per Metric Million British Thermal Unit (MMBtu) of LNG.

Liquefied Petroleum Gas (LPG) Storage Tanks Boil-off Gas Generation and Management– Review

“…Bouabidiet al, [26] presented a study on analysis of the processes in the components of the LPG (propane/ butane) re-liquefaction plant under the conditions of co-mingling in tanks when transporting by sea. In the analysis, energy analysis of the mixture-based reliquefaction plant has been performed using the monitoring data of an LPG cargo operation.…”

“…While the growing LPG adoption rate undoubtedly holds huge promise for Nigeria's clean energy agenda (due to LPG's low carbon intensity) Nigeria does not appear to be ready for large-scale LPG adoption in its domestic market. This un-readiness is due to a number of bottlenecks including a low level of regulation of the LPG retail market, shortage of LPG facilities, an unresolved tank crisis in the country, and BOG generation in the LPG storage tank [26].…”

Reducing Power Use in the Cold Section of LNG Plants

“…Even though BOG reliquefication increases LNG output, it needs power. While the industry has long been using the NG feed as a fuel, systematic integration of all fuel gases including BOG (e.g., tank and jetty) is useful to reduce power consumption. − Hence, as argued by Bouabidi et al, balancing BOG and other gas generation with a plant’s FG needs is important to ensure that the LNG plant is sustainable in terms of energy requirements and emissions . Second, the present literature ignores key process/equipment/product specifications, such as the high heating value (HHV) of the LNG product, the NGL Reid vapor pressure (RVP), and the WI/pressure of FG.…”

“…16−18 Hence, as argued by Bouabidi et al, balancing BOG and other gas generation with a plant's FG needs is important to ensure that the LNG plant is sustainable in terms of energy requirements and emissions. 19 Second, the present literature ignores key process/equipment/product specifications, such as the high heating value (HHV) of the LNG product, the NGL Reid vapor pressure (RVP), and the WI/pressure of FG. Most gas turbines mandate a certain minimum pressure and WI of FG.…”

Managing Jetty Boil-Off Gas for More Sustainable LNG Export Terminals

“…Results indicated that the attainable excess LNG flow ranged from 0.02 to 0.07 million tonne per annum (MTA). The preliminary economic assessment revealed profits ranging from $7.63 to $24.58 million …”