A study on burning of crude oil in ice cavities

In situ burning is a practical means of oil spill cleanup in icy conditions. This study considers one example of oil spill scenario: burning oil in an ice cavity. A new set of parameters to the classical problem of confined pool fires in vessels arises under these unique conditions. The icy walls of the cavity create a significant heat sink causing considerable lateral heat losses, especially for the small cavity sizes (5-10 cm). The melting of ice due to the heat from the flame causes the cavity geometry to change. Specifically, the diameter of the pool fire increases as the burning proceeds. This widening causes the fuel to stretch laterally thereby reducing its thickness at a faster rate. The melted ice water causes the oil layer to rise up, which causes the ullage (the distance from the oil surface to the top surface of ice block) to decrease. The reduction in the ullage and increase in the diameter counter-act the reduction in oil thickness due to the widening. This results in a strong coupling between the mass loss rate and the geometry change of the pool and cavity. To systematically explore this process, experiments were performed in cylindrical ice cavities of varying diameters. It was found that due to the cavity expansion the average mass loss rate of crude oil in the ice cavity is greater than the mass loss rate in a pan. For example, the mass loss rate of crude oil burning in a pan found to be 50% less than that of an ice cavity with similar initial diameter. A model was developed to estimate mass loss rates and efficiencies which are in reasonable agreement with the experimental results. Extension of the model to larger sizes, comparable to realistic situation in the Arctic is discussed. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.