Formation mechanisms and removal technologies of dioxin and furan

A large number of pollutants are emitted in flue gases from waste incineration plants. Among these compounds, polychlorinated dibenzo-p-dioxins/dibenzofurans are one of the most important environmental pollutants in ecological systems. These chemical substances have a lot of isomers and congeners some of which are extremely toxic. Most dioxins are introduced to the environment through the air. The airborne chemical can attach to small particles that can travel long distances in the atmosphere. They are found in very small amounts in the environment, including air, water and soil. Dioxins and furans are semivolatile compounds and in the atmosphere, can exist is in both the gaseous phase and bound to particles, depending upon the environmental conditions. Dioxins and furans are transported through the atmosphere and deposit to terrestrial surfaces. The distances of travel, before deposition depend upon factors including the height of release, temperature, prevailing meteorological conditions and particle size. The main pathway by which dioxins move from the atmospheric to terrestrial environment is deposition to soil, vegetation and water bodies by wet and dry processes or mist. Among flue gas treatment technologies for post combustion zone emission control, activated carbon adsorption systems are widely employed for removing dioxins/furans and some other toxic substances, such as Hg and other heavy metals from flue gas. Activated carbon adsorption is generally classified into three types: Entrained-flow, fixed-bed and moving-bed. Dioxin and furan are currently effectively controlled around the world using carbon and lime adsorption processes. This technology effectively reduces the concentration of dioxin/furan in a gas stream to a level well below the international limit of 0.1 ng/Nm3 . In thıs work, some applications regarding dioxin/furan removal technologies are investigated, and optimum active carbon dosages for entrained flow adsorption process are determined for two incineration plants in Turkiye, ZAYDAS Hazardous Waste and STAÇ Medical Incineration plant. It was concluded that the entrained flow adsorption system gives the desired dioxin/furan removal and is a suitable technology for the incineration. Keywords: Dioxins, furans, adsorption, dioksin/furan emission control equipment.