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• Main Authors: Wei-chiao Lo, 羅偉僑
• Other Authors: 張木彬
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/90983466395317446394

碩士 === 國立中央大學 === 環境工程研究所 === 95 === Emission of dioxins has become one of the most important environmental issues in recent years. Due to its high toxicity, the governments worldwide have implemented strict standards to regulate PCDD/F emissions. The objective of this study is to develop a more efficient activated carbon adsorption system. This study employs the bead-shaped activated carbon (BAC) as the adsorbent and combines the laboratory-scale multi-layer fluidized bed reactor to adsorb PCDD/Fs at different operating conditions, including gas flow rates, temperature and water vapor content. For PCDD/F adsorption experiments, the results indicate the removal efficiency of PCDD/Fs is up to 99.99 % as the PCDD/F-containing gas flow passes through the third layer of the adsorption bed and the outlet PCDD/Fs concentrations would meet the 0.1 ng-TEQ/Nm3 emission standard. The influences of operating conditions on removal efficiency of PCDD/F reveal that the PCDD/F removal efficiency decreases as gas flow rates and operating temperature increase. In addition, the water vapor content plays a negative role in PCDD/F adsorption. In the presence of water vapor, as the PCDD/F-containing gas flow passes through the first layer of the adsorption bed, the outlet PCDD/Fs concentration would exceed 1 ng-TEQ/Nm3 . Additionally, this study used chlorophenols as precursor to PCDD/F formation. More PCDD/Fs are formed as the operating temperature is increased from 150 oC to 200 oC. In addition, the conversion of chlorophenols increases with increasing operating temperature and the PCDF/PCDD ratio exceeds 1. The operating temperature has positive influence on PCDD/F formation but does not significantly change seventeen 2,3,7,8-substituted PCDD/Fs congeners distribution. The outlet concentration of PCDD/F (gas phase) also increases as operating temperature is increased and the major PCDD/F congeners are lowly chlorinated PCDD/F. In the absence of water vapor, most of the PCDD/Fs in the gas stream are PCDFs (about 98 %). In the presence of water vapor, some PCDDs would desorb to the gas stream.