Combustion of Inert-Gas-Diluted Volatile Organic Compounds Using a Fuel-Rich Pilot Flame and Rotating Arc Plasma

This report proposes a method that uses plasma in combination with combustion to remove very low concentrations of volatile organic compounds (VOCs) that cannot be combusted with conventional burners. A burner with a fuel-rich pilot flame with an equivalence ratio of 1.5, 2, or 2.5 was formed, and a rotating arc plasma with a specific energy input (SEI) of 0–1.2 kJ/L was applied. When the plasma was used in the pilot flame, the temperature of the emitted gas increased, as did the concentration of combustible gas in the emitted gas, such that the selectivity reached a maximum of 0.8 (CO), 0.4 (H2), and 0.06 (C2H2). Lean VOC emission was simulated by preparing a mixture of propane and nitrogen with nitrogen content of 98% or 99% and this mixture was sprayed downstream from the plasma pilot flame to form the main flame. The combustion state of the main flame and exhaust gas was then analyzed to measure the hydrocarbon treatment ratio. The results showed that, when high-SEI plasma was employed in a high-equivalence-ratio pilot flame, NOx emission remained minimal and an HC treatment ratio close to 1 was obtainable. The use of this method for combustion enables the flow rates of treatable VOC mixtures to be specified such that the concentration of CO and NOx in the emitted gases is minimized.