| Many normally incombustible materials can be ignited when subjected to a certain minimum heat flux, and sustained fire and flame spread can be achieved on these materials. In the present work, this principle is applied to the emulsion combustion problem so that, if successful, the window of opportunity for in-situ combustion of oil spills can be widened. It is proposed that there exists a threshold heat flux level for most of the emulsions such that, when emulsion is exposed to a heat flux equal to or greater than the threshold heat flux, sustained fire and flame spread can be achieved.; Experimental measurements of threshold heat flux values were made for emulsions of diesel, Milne Point crude oil and Alaska North Slope crude oil with water. The water fraction in the emulsion was changed from 0% to 80% by volume. The crude oil samples were also tested for effects of evaporation of the lighter fractions from the crude oil. Laboratory scale experiments clearly verified that there exists a threshold heat flux far each type of emulsion studied.; The data indicate that higher threshold heat flux is required to cause successful burning of emulsions having higher water content or emulsions of more weathered oil. Upon correlating the threshold heat flux data for the crude oils with the density of the crude oil, it was observed that the threshold heat flux values increase with increasing density of the crude oil.; The average oil burning rate, total duration of burn, the volume of the oil residue and the burn efficiency decreased with increasing water content of the emulsion. Average oil burn rate and the overall burn efficiency decreased with increased weathering of the oil whereas the total burn time and the volume of the oil residue increased with increased weathering of the oil. Comparisons of the model predictions with the experimental observations showed that most of the model predictions were found to be within 25% of the observed values. The model has captured the description of significant processes involved in emulsion combustion, and thus is able to describe the experimental observations with sufficient accuracy. (Abstract shortened by UMI.)... |
