Rapid Phase Transitions between Liquefied Natural Gas and Water

Rapid Phase Transitions between Liquefied Natural Gas and Water 

In certain instances, when LNG contacts ambient water, explosive vaporization occurs with concomitant shock waves both in the air and water. While isolated instances of such events were recorded as early as 1956, it was during the 1968-1969 Bureau of Mines tests that the phenomena first attracted wide interest. In these experiments, three explosive 

These results stimulated a number of studies, both in industry (Conoco, Esso, Shell Pipeline) and in academia (University of Maryland, M.I.T.). The objective was, primarily, to delineate the mechanism that led to these explosive events. The results of many small-scale experiments, primarily conducted by Shell Pipeline Corporation and M.I.T., led to the hypothesis that the apparent explosion was, in fact, a very rapid vaporization of superheated LNG. Contact of LNG, of an appropriate composition, with water led to the heating of a thin film of the LNG well above its expected boiling temperature. If the temperature reached a value where homogeneous nucleation was possible, then prompt, essentially explosive vaporization resulted. This sequence of events has been termed a rapid phase transition (RPT), although in the earlier literature it was often described by the less appropriate title of vapor explosion. 

Pure liquefied propane has a value of around 326 K (53 C). Thus, one must heat water to at least this temperature before an RPT results. When, however, one does use water of this temperature, the probability of attaining an RPT is essentially 100%. 

Some effort has been expended in obtaining RPTs from methane-rich LNG by impacting water on a cryogen surface. The rationale for such tests is to eliminate the vapor film and cause direct liquid-liquid contact. Little success has, however, been achieved for any LNG, but one can 

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III. Rapid Phase Transitions between Liquefied Natural Gas and Water.. .. H3... 

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