摘要
戴奧辛呋喃(PCDD/F)污染在最近年來已成為全世界最重要的環境問題之一，尤其戴奧辛之毒性高且最引人注目，因此世界各國均制定更嚴格之排放標準及最佳控制技術來加以限制戴奧辛的排放及生成。本研究以集塵灰高溫冶煉廠(Waelz process)之萃取液(正壬烷溶液)，作為本研究之進流戴奧辛，以模擬Waelz process戴奧辛之排放特性，選擇以球狀活性碳為實驗之床質吸附劑，並結合分層式流體化床反應器評估在不同氣流流量、操作溫度及水氣含量條件下對戴奧辛吸附效能及戴奧辛前驅物質(氯酚)生成戴奧辛之潛勢及影響。 戴奧辛吸附效率方面，研究結果指出不論在氣流流量、操作溫度及水氣含量條件下，戴奧辛氣流通過第3層時，去除率最高達99.99 %，且毒性當量濃度均已降至0.1 ng-TEQ/Nm3以下，可符合世界最嚴格之法規管制標準。在不同氣流流量條件下，研究結果顯示戴奧辛去除率以7 slpm最高，且戴奧辛去除率均隨氣流流量的提升而呈現下降趨勢。在不同操作溫度條件下，戴奧辛去除率隨著溫度的上升而有下降趨勢。在水氣存在條件下，研究結果顯示水氣存在條件下(0 %、 5 %、10 %及15 %)，通過第一層吸附床之戴奧辛濃度皆超過1 ng-TEQ/Nm3，顯示水氣在活性碳吸附戴奧辛上扮演負面的角色。 本研究亦探討戴奧辛前驅物質(氯酚)在未添加水氣及加入水氣後，通過球狀活性碳吸附床之戴奧辛生成潛勢，研究結果顯示在未添加水氣及加入水氣條件下，戴奧辛總生成量隨著操作溫度的上升而增加，氯酚之轉換率亦隨著操作溫度的升高而增加，呋喃(PCDF)之總生成量比戴奧辛(PCDD)高，此外，操作溫度與戴奧辛生成量成正相關，但不影響戴奧辛生成之物種分佈，水氣條件則使戴奧辛生成物種分佈略有不同，另外，脫附至氣流之戴奧辛濃度(氣相)隨著溫度升高而增加，在200 oC時，戴奧辛濃度(氣相)最高，且戴奧辛物種以低氯數之PCDD及PCDF為主，無水氣條件下，脫附至氣流中之戴奧辛物種以PCDF為主，加入水氣後，脫附至氣流中之戴奧辛除了PCDF之外，亦發現PCDD脫附至氣流中。
並列摘要
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.
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