Mitigation Effect of High Expansion Foam on LNG Vapor Hazard

The growing production and consumption of natural gas due to the advancement of technology, e.g., hydraulic fracturing, has accelerated the inter-regional trade.  Liquefied Natural Gas (LNG) provides the flexibility of the transportation in the natural industry; however, it causes a safety concern in terms of flammable vapor cloud and fire associated with a potential spill in LNG facilities.  High expansion foam is recommended as a mitigation measure for an LNG incident by NFPA 11 and NFPA 471, and was proved to be effective for the LNG spill emergency response through field tests. The mechanisms of the physical interaction in the high expansion foam and LNG system is essential to develop CFD models, which help assess the risk and provide guidance on emergency response for vapor dispersion and fire scenarios due to an accidental LNG spill.  The LNG vapor hazard, i.e., a huge flammable vapor cloud on the ground, can result in a more hazardous scenario, fire, if it is not properly mitigated. High expansion foam can mitigate LNG vapor hazard through blanketing effect to reduce vaporization rate (source term) and warming effect to enhance vapor buoyance. The blanketing effect was studied through tests conducted in a wind tunnel, in which convection and radiation were provided manually. The reduction of vaporization rate of liquid nitrogen by high expansion foam was determined quantitatively for heat convection and radiation. The warming effect is conducted with a test apparatus and a foam generator, which are newly designed and built with features contributing to the study of warming effect and parametric analysis.