Abstract: To investigate the LNG vapor mitigation mechanism imposed by the high expansion foam, HYSYS analyses and experimental measurement were employed to verify the existence of the natural gas hydrate in the application of high expansion foam on LNG pool. By Taguchi analyses, the effects of foam property, LNG spill amount and foam submergence height on the vapor emission rate average value and standard deviation were examined. It is discovered that at the initial foam addition the foam properties affect the average value and standard deviation greatly, and standard deviation is greater than 0.2 kg/min, that more stable foam tends to decrease the average value and standard deviation, while the foam with higher expansion ratio tends to reduce the average value but increase the deviation, that the expansion ratio influences the deviation greater than the stability, that the vapor emission does not change monotonously with the LNG spill amount, as the foam generation ceases, the effect of the submergence height becomes greater, that at the earlier stage, the vapor emission increases with better stability and lower expansion ratio, and that the standard deviation changes monotonously with both the LNG spill amount and submergence height.

Key words: vapor emission, foam property, natural gas hydrate(NGH), submergence height, liquefied natural gas(LNG), spill amount