Numerical Study on LNG Carrier Releasing Underwater and Emergency Treatments

This paper is concerned about building up a model to simulate the LNG carrier releasing underwater process and assess the influence of emergency treatments. As a result, a model is proposed for simulating the process of LNG releasing underwater. It included releasing rate, spreading on water, heat & mass transferring and vapor cloud dispersion. Calculations have been performed whereby the releasing rate, liquid pool radius and vapor cloud size of LNG releasing underwater with explosive boiling triggering by thermodynamics instability, which have been compared to without explosive boiling in the releasing process, respectively, under the same initial conditions. The results suggest that treating LNG releasing underwater with explosive boiling triggering by thermodynamics instability results in overestimation of the pool during time of the order of ~10% and the flammable cloud size of order of ~5%. Furthermore, the model is also used to examine the influence of emergency treatments on the LNG releasing process. A comparison with the results generated by starting ejection system, spreading foam on liquid poo and spraying water mist into vapor cloud shows that the former two respectively play a major role on LNG releasing and spreading on water, and the last one can be considered as the most effective means to reduce dense gas dispersion scope and flammable cloud size.

I. Introduction

Demand for Natural Gas (NG) as a clean fuel and as a petrochemical feedstock has been on the increase in resent yeas. Trade around world requires long distance marine transportation and for economic reasons NG is cooled and transported in the liquid state, that is Liquefied Natural Gas (LNG), and vessel is called LNG carrier. Such an increase will bring renewed pressures on improved quantification of the risk and emergency treatments associated with LNG carriers.