Hot-zone boilover suppression using floating objects in crude oil tank fires

Abstract Hot-zone boilover is dangerous in crude oil tank fires. Previous investigations have experimentally shown that floating objects can suppress hot-zone boilover with small scale pool fires, but not indicate a clear suppression mechanism. Thus, this study uses floating perlites (0, 1 and 2 layers) on large scale pool fires to examine the mechanism by performing three series of experiments. The first series applies perlites to 1m-diameter crude oil fires to evaluate the effect of perlites on the hot-zone formation; the second investigates the effect of perlites on heat release rate (HRR) and combustion efficiency, and the third studies the blockage effect of perlites on radiation heat feedback. Experimental results show that the perlites can significantly delay the hot-zone formation, and suppress boilover. Accordingly, this study presents a hypothesis to explain the mechanism of suppressing boilover by floating objects. The perlites form a heat blockage layer decreasing the radiation feedback, and act as a nucleation site, leading to local vigorous boiling. The enhanced local nucleation increases the fuel vapor generation, and further enhances the blockage effect. The perlites consequently raise the fuel regression rate, and decrease the heat transfer to the deep fuel and water, decreasing the hot-zone formation rate.