On the Time to Flaming of Flammable Liquids

Abstract

Flammable liquids typically adopted in chemical and industrial processes can be subjected to intense heat radiation due to nearby hot surfaces or fires. A second cascading event is then likely because the flash point can be easily reached and the surrounding environment can provide sufficient energy for ignition. Nevertheless, the flaming condition is not necessarily reached instantaneously if no direct (e.g., spark) ignition is present. Hence, a time to flaming, i.e., in the absence of an ignition source, is extremely relevant for the active and passive fire protection of flammable liquid, as the minimum time for intervention can be defined before developing a pool fire and for the correct evaluation of domino effects, in analogy with gas fires. In addition, a complete characterization of liquid behaviour under radiant heating is essential to guarantee safe operations, prevention measures, robust databases and optimized design. Therefore, this work reports the results for three liquid solvent representative classes of substances: i) hexane, ii) ethyl acetate, and iii) ethanol. A bench scale facility was adopted for the characterization of mass and energy aspects involving a pool fire of the investigated substances. Among the others, the ignitability and the intensity of the generated pool fires were evaluated experimentally in terms of mass burning rate, heat release rate, and combustion efficiency. Different boundary conditions were tested to identify the optimized set of conditions for a robust evaluation of the safety aspects of liquid. Results showed the most relevant trends in terms of ignitability of liquid species and combustion intensity during the pseudo-steady state regime of a pool fire. In addition, indications on the boundary conditions to be considered for a robust and consistent dataset were provided in this work.