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  • Study on dioxin emission rule and deep control technology of waste incineration

    With the acceleration of urbanization, the amount of Municipal solid waste (MSW) is increasing year by year, and waste disposal has become an important environmental problem faced by all countries. Waste incineration, as a reduction and resource treatment method, has been widely used in the world. However, the emission of pollutants such as dioxins generated during waste incineration has aroused the concern of the public and environmental protection organizations.

     

    Due to its complex formation mechanism and numerous influencing factors, how to effectively control dioxin emission in the process of waste incineration has always been a difficult and hot research topic in the field of environmental protection.

     

    In order to reduce the dioxin emission in the process of waste incineration and promote the sustainable development of the waste incineration industry, this paper aims to systematically summarize the generation mechanism, discharge law and in-depth control technology of dioxin in the process of waste incineration, and provide theoretical support and technical guidance for the control of dioxin emission in waste incineration plants.

     

    The flue gas purification process of the waste incinerator selected in this study includes: the flue gas is cooled by the superheater and then enters the economizer. The large ash particles are separated by collision with the superheater and economizer, and then collected in the four ash buckets under the vertical superheater and economizer. The flue gas then passes through a semi-dry reactor where most of the acid gas is removed by reacting with the hydrated lime slurry. Then, by adding activated carbon to adsorb the dioxins, the flue gas other fine ash and activated carbon are removed by a cloth bag dust collector. The flue gas nitrogen oxides are then removed by selective catalytic reduction (SCR). In order to achieve ultra-low emission of nitrogen oxides, non-selective catalytic reduction is also applied. The results show that chimney dioxin emission is 0.0064 ng I-TEQ/Nm3, which is much lower than the Chinese and European standards (0.1 ng I-TEQ/Nm3). The combination of vertical economizer and ash hopper is beneficial to the removal of dioxins in flue gas, and the removal efficiency reaches 59.83%. Due to the memory effect, the content of dioxin in flue gas is much higher than that in economizer separated ash. In the chimney, the proportion of dioxins in the liquid phase is 53.67%, and the estimated content of dioxins in the liquid phase is about 16.20 ng I-TEQ/t MSW. Therefore, dioxin emission limits should take into account dioxins in the liquid phase. In addition, chlorination levels affect dioxin allocation. The chlorine level of dioxins in liquid phase is lower than that in solid phase, but higher than that in gas phase. Dioxins in liquid phase mainly come from fine particles, and the characteristics of fine particles can change the emission of dioxins in liquid phase. In the whole incineration process, the memory effect mainly occurs in the vertical economizer, followed by the semi-dry reactor and SCR.

     

    Source: https://mp.weixin.qq.com/s/q5be8UPqG5hfVEZ6ebhuMw


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