Abstract

The purpose of this paper is to share the challenges and engineering solutions in managing risk of using nitrogen as the refrigerant in the LNG (Liquefied Natural Gas) liquefaction process on a Floating LNG (FLNG). In December 2016, the first FLNG started to produce LNG 130 km offshore using Nitrogen Liquefaction Technology, which is also the first in the world. Multi-Component Refrigerant (MCR) is commonly used to liquefy natural gas worldwide in the LNG plants. However, the Nitrogen Liquefaction Technology has been selected in view of its inherently safer non-flammable non-corrosive property, simplified process and reduced refrigerant handling and storage onboard. As compared to MCR, the flammable hazard on the FLNG is reduced by adopting nitrogen as refrigerant. Nevertheless, during the course of engineering design, other risk that could potentially be posed by nitrogen was identified. The main concern is the brittle fracture and anoxia risk in the event of cryogenic nitrogen loss of containment. This leads to engineering challenges in terms of the process containment, structural impact, ability to detect, safe disposal and drain and lifesaving appliances, etc. This sharing can be the pioneer reference for other FLNG designs in particular the refrigerant system, the relevant risk management and the engineering solutions.

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