Method for eliminating dioxins in flue gas

The invention relates to a method used for eliminating dioxin in fume. The method has the following steps that water solution containing substance of hydrazine type is sprayed into the fume containing dioxin or potentially containing dioxin so that the fume fully touches and reacts with the water solution, and the water in the solution is completely evaporated at the temperature above 160 DEG C. In this way, dioxin in the fume is eliminated. The water solution with hydrazine type substance is fresh solution prepared based on 0.05 percent to 1 percent by weight before use, and is sprayed into the fume with the temperature ranging from 200 DEG C to 600 DEG C, or into the fume with the temperature ranging from 600 DEG C to 850 DEG C. At the temperature ranging from 600 DEG C to 850 DEG C, the water in the water solution containing hydrazine can adopt urea or ammonia. At the temperature ranging from 200 DEG C to 600 DEG C, the water to dissolve hydrazine can adopt alkaline solution or urea solution in combination with purification of other noxious gases such as SOx and NOx by using a prior or a late established purification device or system, so that NOx and acidic gases in the fume are eliminated, and toxicant content in fly ash is reduced. By adopting the method, dioxin in the fume is eliminated without production of noxious byproducts. Throughout the course, no waste water or waste solid is produced; the concentration of dioxin in fly ash is reduced; the treating process is simple, and the cost of disposal is low.