Model for Cryogenic Flashing LNG Leak

Boon How Lim,Eddie Yin Kwee Ng

doi:10.3390/app11199312

Abstract

The growth of liquefied natural gas (LNG)’s importance for curbing greenhouse gas emissions has increased the interest in understanding LNG’s risks, particularly regarding small-diameter leaks (<25 mm). Recently, INERIS performed a series of pressurized LNG release experiments for orifice sizes of up to 9 mm. Based on INERIS findings and the Isenthalpic Homogeneous Equilibrium Model (HEM), this paper created a leak model for flashing LNG leak. The leak model consists of nine equations and quantifies leak parameters for risk assessment. One potential use of this leak model is providing an equivalent leak boundary condition for computational fluid dynamic (CFD) simulation to predict gas dispersion. Using the leak model as input, FLACS gas dispersion simulation was carried out for one INERIS experiment leak case. Compared to TR56, the Singapore safety guideline for LNG bunkering, the dispersion result does not contradict the expected plume reach. Further validation with risk analysis tools and actual experiments is needed to confirm that the leak model is fit for use.

Highlights

According to the DNV GL energy outlook 2019, natural gas will become one of the world’s primary energy sources by 2025 [1]
Due to its cryogenic storage temperature, liquefied natural gas (LNG) leaks will continuously vaporize into natural gas (NG), leading to a potential fire that can result in fatality and asset loss
Dorota and colleagues have demonstrated the use of the fuzzy method and Monte Carlo method to improve the accuracy of predicting LNG dispersion [6]

Summary

Introduction

According to the DNV GL energy outlook 2019, natural gas will become one of the world’s primary energy sources by 2025 [1]. Due to its cryogenic storage temperature, LNG leaks will continuously vaporize into natural gas (NG), leading to a potential fire that can result in fatality and asset loss. The factors affecting the source term modeling include the LNG storage condition (pressure and temperature), orifice size and shape, ambient temperature, leak trajectory, atomization of the liquid spray, and the entrainment rate of fresh air. Studies of a non-cryogenic orifice pressurized leak nature have been performed. ΡL and ρg are the respective LNG liquid and gas densities at boiling point temperature in atmospheric pressure. According to the SPARCLING experiment conducted by INERIS, pressurized LNG leak beyond 1.5 bar has zero rainout, implying that all liquid is vaporized in the entrainment zone [16]. By eliminating the expansion and entrainment zone simulation, which is computationally expensive, the model reduces the CFD simulation time [20]

Leak Scenario

Leak parameter before and after

CFD Initial Condition and Output Control