| Summary: | 碩士 === 國立中央大學 === 環境工程研究所 === 88 === Ever since it was reported that toxic organohalogen compounds such as PCDD/Fs were emitted from the municipal solid waste (MSW) incineration facilities, most countries have been issuing strict limits to the permissible emission level of such pollutants. PCDD/Fs emissions levels less than 0.1 ng TEQ/dscm have been demonstrated on many medical waste combustor (MWC), municipal waste incinerator (MWI), and hazardous waste incinerator (HWI) using activated carbon based control techniques. However, the adsorption characteristics of gaseous organics at high temperature (typically larger than 110℃) are rarely investigated. This study looked into the adsorption characteristics and removal efficiency of 1,2,3,4-TCDD and OCDD in the simulated flue gas of MWI by the fixed-bed activated carbon adsorption system. In particular, we are interested in the effects of operating temperature and water vapor content on the dioxin adsorption efficiency. Additionally, the properties of activated carbon on dioxin adsorption capacity and transformation of dioxins on the activated carbon are experimentally investigated. Experimental results indicate that the operating temperature and homologues of dioxins have significant effects on the removal efficiency of dioxins with the activated carbon. Especially, the adsorption capacity of 1,2,3,4-TCDD on activated carbon starts to decrease at a temperature close to the melting point of 1,2,3,4-TCDD (i.e. 185℃). Experimental results also indicate that a higher water vapor content evidently decreases the adsorption capacity. Due to the competition effect, the adsorbed 1,2,3,4-TCDD on activated carbon will be replaced by OCDD which is a stronger adsorbate. In addition, the 1,2,3,4-TCDD and OCDD adsorbed on activated carbon may dechlorinate or decompose if no strong gaseous chlorinating agent is present. Furthermore, when the activated carbon with high heavy metals, contents is used as the adsorbent it can actually serve as the active catalyst for PCDD/F formation.
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