Large LNG fire thermal radiation - Modeling issues and hazard criteria revisited

Current models for evaluating the exclusion (hazard) zones around liquefied natural gas (LNG) fires in both U.S. Regulations and NFPA-59A standard are prescriptive and require the consideration of large LNG effects of the releases. These models do not consider the combustion dynamics associated with large-size pool burning. Oxygen starvation in the core of LNG fires oJ' diameters 35 m leads to the formation of nonluminous, cold soot (smoke) resulting in a reduction of thermal energy radiated by the fire to the surroundings, The net effect is smaller (calculated) thermal hazard distances for exposure to people (by factors of 2 or 3 compared to results ignoring this phenomenon). Available large-scale LNG fire test information is reviewed to quantify the effect of this phenomenon. This paper also discusses the common mistakes made in calculating the thermal radiation hazard distances around large fires by using, for the energy radiated from the fire, a constant percentage of energy generated by combustion. The criteria for setting thermal radiation hazard zones around large hydrocarbon fires are also reviewed. (c) 2005 American Institute of Chemical Engineers Process.