Reduction in dioxin emissions by the addition of urea as aqueous solution to high-temperature combustion gas

In order to study the effect of urea addition to the waste gas on the dioxin formation, a series of experiments is carried out using the fly ashes sampled from two different types of solid waste incinerators. A remarkable suppression effect is obtained for the dioxin formation, while no clear change is observed for the obtained organic chlorine. Considering these results, the method of urea addition to the water splayed into the cooling tower of waste gas is proposed as an effective measure to suppress the dioxin formation at the cooling stage of the combustion gases. A verification test is carried out using an actual solid waste incinerator. When the concentration of urea in the splayed water is set to 0.1 %, the toxicity concentration of the dioxins in the waste gas is reduced to approximately half that in the case without the addition. Further, the addition of urea does not significantly affect the concentration of NOx in the waste gas.