Initiating In Situ Burning of Difficult-to-Ignite Oil Spills via an Aircraft-Deployable Igniter System

Abstract

ABSTRACT Igniting a crude-oil spill in situ is a two-step process. First, the oil must be heated above the fire point such that sufficient flammable vapors are present to allow sustained burning. Second, the flammable vapors must be ignited. Different crude oils have different fire points due to different chemical compositions and the fire point can change over time due to volatilization of the lighter components. Factors such as wind, current, water entrainment, oil spill thickness, and temperature can affect the heat transfer to the oil spill, preventing it from reaching its fire point. As such, a large amount of heat may not ignite an oil spill if it is not of sufficient duration because it does not first heat the oil to its fire point. A light hydrocarbon such as diesel or gasoline is often used as an accelerant to ignite oil spills due to flexibility, low cost, and availability. The ignited accelerant creates a small pool fire in the middle of the larger oil spill that provides a sufficient heating rate over a sufficient duration. The heating rate of the initiating fire is proportional to the surface area of the burning accelerant. The duration of the initiating fire is proportional to the thickness of the burning accelerant. Surface area versus thickness can be controlled by use of a gelling agent. The largest challenge to deploying a liquid-accelerant igniter from an aircraft is safely lighting it in a manner that does not endanger the aircraft and will not extinguish when the igniter impacts the oil spill, especially when the oil spill is over water. A delayed-reaction, chemical ignition system paired with gelled accelerant in a manner that is suitable for deployment from aircraft is described. Test results of this ignition system against a weathered crude-oil surrogate are presented.