Theoretical Study of Expansion Foam Application on LNG Pool Using Computational Fluid Dynamics

LNG facilities could harm the personnel on site and jeopardize local communities nearby, due to the flammability and dense gas behaviors of LNG. Nowadays, the growing concern with chemical process safety leads to the timely establishment of regulations and standards regarding to consequence mitigation measures, for instance, NFPA 59 A requires that LNG storage tanks should have a dike or impoundment around to constrain the LNG spill and form a LNG pool, and the expansion foam has been one of the proposed safety provisions to minimize the consequence of LNG spill on the ground. However, because of the high cost and potential risk to people of performing field tests to evaluate effectiveness of foam application on LNG pool, just a few of experiments have been conducted, whose results vary as a result of uncertainties in experimental conditions.

In this research, computational fluid dynamics modeling was employed to model LNG spill scenarios on the ground with a dike, and mainly focused on the effect of expansion foam on the LNG vapor dispersion. The effectiveness was evaluated by predicting temperature profiles of methane and foam, LNG vapor concentrations in downwind direction, and vapor exclusion zone with the application of expansion foam. The simulation results were compared with 2009 medium-scale LNG spill field test results conducted by Mary Kay O'Connor Process Safety Center (MKOPSC) for validation. Moreover, a sensitivity analysis was conducted to a number of essential parameters of foam application, such as foam application rate, foam height, position of foam generator. The outcomes of the analysis were used to guide the design of foam mitigation system and application method, which hopefully could be integrated into relevant regulations and standards.