Effects of ambient water in the combustion enhancement of heavily chlorinated hydrocarbons: Studies on droplet burning

An experimental and computational investigation has been conducted on the oxidation and combustion of chlorinated hydrocarbon droplets in a hot, oxidizing environment, with emphasis on the effects of ambient water on the droplet burning intensity. The experimental results demonstrated that the presence of a small amount of water in the environment, say 5-10% by volume, can substantially increase the droplet burning rate and reduce the droplet ignition and extinction temperatures of heavily chlorinated, hydrocarbons (HCHCs) and their mixtures whose chlorine-to-hydrogen ratio is close to unity. The computational simulation with detailed chemistry and transport yields good qualitative and quantitative agreement with the experimental results and identifies that this beneficial effect of water arises from its reaction with the Cl atoms, producing the active hydroxyl radicals that subsequently promote the CO to CO₂ conversion and generate the H atoms needed to initiate radical-chain branching. From the practical viewpoints, it is suggested that while the presence of water in combustion environments can potentially enhance the destruction efficiency and combustion stability in halogenated-waste incinerators, it can, however, diminish the effectiveness of halogen-based fire-retarding or fire-suppressing agents.