Direct Cooldown Method for Flare-Free Gassing Up Operation
Authors: Al Bulushi H. 
Published: April 2024

Abstract
The Paris Agreement has prompted a growing global sense of urgency to mitigate the climate impact of industrialization. Countries and corporations have committed to becoming carbon neutral by 2050, setting short, medium, and long-term targets for achieving this goal. Notably, the LNG industry is shifting as LNG is the transition fuel of decarbonization journey and major energy buyers seek carbon neutral energy sources to reduce emissions. Oman passed a Royal decree that endorsed the year 2050 as the designated target for attaining a state of net zero emissions. Additionally, this decree involved the formulation of a comprehensive national strategy and the establishment of the Oman Sustainability Centre, all aimed at facilitating the realization of this goal. Aligning with this trend and our mission, Oman LNG (OLNG) has undertaken key initiatives to reduce flaring, ensuring the delivery of clean, reliable energy with lower GHG intensity.
OLNG has a well-developed flare abatement strategy and has top quartile Pacesetter of recent benchmarks in the LNG industry. Through a combination of operational best practices and design modifications, OLNG has significantly minimized flaring, ultimately resulting in achieving zero routine flaring as part of its normal operations. Despite the above, Oman LNG continues to pursue further improvements with respect to flaring reduction in safety and non-routine flaring events. An area of focus is on ship gassing up operations.
Part of Oman LNG Annual Delivery Program is to accommodate ships which are scheduled for dry dock and inerted with Carbon Dioxide or Nitrogen. These ships must be purged to the flare to decrease CO2 or Nitrogen content to an acceptable level. This prevents disruptions in the fuel gas system by avoiding freezing at boil of gas demisters due to high CO2 content or discharge temperature rise and compressor trip due to high N2 content.
In close collaboration with our valued customers, we embarked on a concerted effort to significantly reduce flaring during the ship gassing up operations. This endeavor was achieved through the strategic introduction of an innovative methodology known as the Direct Cooldown Method, which circumvents the conventional ship gassing up procedure. This novel approach entails the utilization of LNG dilution, primarily directed at ships that have been inerted with N2. The essence of this procedure lies in the gradual blending of the cargo tank content with vaporized LNG. Once the tank pressures attain a predetermined threshold and the quality of the diluted vapor aligns with Oman LNG specification, the resulting diluted vapor is channeled ashore directly to fuel gas system. Extensive assessments determined the feasibility of this approach, resulting in the modification of operating procedures for safe and reliable implementation. The successful implementation of this method leads to a truly remarkable outcome – the total elimination of flaring from the ship gassing up operation.
Undeniably, this pioneering method aligns with Oman LNG long-term decarbonization plan, supporting the ambitious goal of becoming a carbon-neutral LNG producer.