Numerical Simulation of Leakage and Diffusion Process of LNG Storage Tanks

Abstract

To investigate the evolution process of LNG (Liquefied Natural Gas) liquid pool and gas cloud diffusion, the Realizable k-ε model and Eluerian model were used to numerically simulate the liquid phase leakage and diffusion process of LNG storage tanks. The experimental results showed that some LNG flashed and vaporized rapidly to form a combustible cloud during the continuous leakage. The diffusion of the explosive cloud was divided into heavy gas accumulation, entrainment heat transfer, and light gas drift. The vapor cloud gradually separated into two parts from the whole “fan leaf shape”. One part was a heavy gas cloud; the other part was a light gas cloud that spread with the wind in the downwind direction. The change of leakage aperture had a greater impact on the whole spill and dispersion process of the storage tank. The increasing leakage aperture would lead to 10.3 times increase in liquid pool area, 78.5% increase in downwind dispersion of methane concentration at 0.5 LFL, 22.6% increase in crosswind dispersion of methane concentration at 0.5 LFL, and 249% increase in flammable vapor cloud volume. Within the variation range of the leakage aperture, the trend of the gas cloud diffusion remained consistent, but the time for the liquid pool to keep stable and the gas cloud to enter the next diffusion stage was delayed. The low-pressure cavity area within 200 m of the leeward surface of the storage tank would accumulate heavy gas for a long time, forming a local high concentration area, which should be an area of focus for alert prediction.

Keywords

• LNG leakage and diffusion
• combustible cloud
• phase change
• plume flow
• leakage aperture