Numerical Study on Physical Mechanisms of Forced Dispersion for an Effective LNG Spill Mitigation

Abstract

Mitigation techniques for liquefied natural gas (LNG) facilities require further investigation to minimize the uncertainty in determining the impact and consequence of an LNG spill on public safety and security. Water curtain systems have been proven to reduce the hazard zone by diluting the vapor concentration below the flammability limits when directly applied to LNG vapors. Currently, no definitive engineering criteria for designing effective water curtains applicable to LNG facilities are available, mainly due to a lack of understanding of the complex interaction between the droplets and LNG vapor. This work applies LNG forced dispersion modeling to study the physical mechanisms involved in enhancing vapor dispersion. Computational fluid dynamics (CFD) codes have been utilized to examine the effects of momentum imparting from the droplets to the air–vapor mixture, the thermal transfer between the two phases (droplet/vapor), and various air entrainment rates on the behavior of the LNG vapor. This work aims to investigate the complex interaction of the water droplet–LNG vapor system, which will provide guidelines in developing and establishing engineering criteria for site-specific LNG mitigation systems.

Influence of active mitigation barriers on LNG dispersion

“…A series of experimental and modeling studies to analyze the behavior of LNG have been carried out to collect an archive of evaporation, dispersion and combustion information (Britter & Griffiths, 1982;Ermak, Chan, Morgan, & Morris, 1982;Koopman et al, 1982;Luketa-Hanlin, 2006;Puttock, Blackmore, & Colenbrander, 1982). Based on this information, several modeling based works have been developed to represent LNG dispersion in realistic environments (Blocken, van der Hout, Dekker, & Weiler, 2015;Koopman, Ermak, & Chan, 1989; Luketa-Hanlin, Schleder, Pastor, Planas, & Martins, 2015;Zhang, Li, Zhu, & Qiu, 2015); these models can be used both to estimate the hazardous area in case of an accidental release of LNG, as well as to investigate the efficiency of potential mitigation measures (Busini, Lino, & Rota, 2012;Derudi, Bovolenta, Busini, & Rota, 2014;Kim, Mentzer, & Mannan, 2014). Recently, the effect of mitigation barriers with different shapes has been investigated, resulting in the conclusion that passive barriers act only as a physical hindrance without enhancing the mixing rate between cloud and air due to the remarkable inertia of large LNG releases .…”