Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/4936
標題: 以三向觸媒同時處理焚化廢棄中有機污染物、CO 及NOx 之研究
作者: 葉家伶
關鍵字: 三向觸媒
觸媒焚化
溶膠-凝膠法
鈀-銠
PAHs
BTEX
CO
NOx
出版社: 環境工程學系
摘要: 以焚化的方式處理廢棄物,具有去毒性、資源回收、減少體積、技術可行性、較小之土地使用等優點,且焚化產生之熱能可回收產生蒸氣,以利發電等用途,因此對於地狹人稠的台灣而言,焚化是未來處理垃圾的趨勢。 然而,以焚化處理垃圾時,最引人關切的問題是空氣污染,其中最令人擔憂的是PAHs、VOCs、Dioxin等微量有機污染物排放的問題。一般處理方式是以文氏洗滌塔、填充床洗滌塔、乾式洗滌塔等做部分脫除,或以活性碳吸附來濃縮去除,但這些似乎並非最終的處理方式。 三向觸媒在處理汽車排氣上,使用廣泛,此一觸媒單元可同時將碳氫化合物、CO氧化成CO2及H2O,將NOX還原成無害的N2,如此提供了一個最終處理的技術,也可因應未來更嚴苛的空污濃度排放標準;於是乎將此三向觸媒優秀的特性,應用到焚化所產生的廢氣處理上,利用觸媒焚化的方法,除了針對有機污染物的催化氧化去除外,也研究觸媒對CO及NOX的催化去除效果。 本研究選用的三向觸媒為Pd-Rh/CeO2/Al2O3,製備方法:首先以溶膠-凝膠法製備出CeO2/Al2O3擔體,再以含浸法將擔體含浸至含Pd/Rh前驅物的水溶液當中,之後經乾燥、鍛燒,製備出實驗所用的三向觸媒。而製備出的觸媒以流體化床型式來處理焚化廢氣。 操作條件包括不同的廢棄物進料組成、不同之觸媒含量配比和雙層觸媒床之設計,探討三向觸媒應用在焚化後之空氣污染防治設備中,處理焚化廢氣的效果,以及廢氣中含有觸媒的毒化物:Cl、S及重金屬,對三向觸媒催化去除有機物、CO及NOX能力之影響。 結果顯示,三向觸媒以鈀1wt%、銠0.15wt%之配比,對有機污染物、CO及NOX之轉化效果較佳,但三者無法同時兼顧,經雙層觸媒床之設置後,使焚化廢氣先經過鈀觸媒床再經過銠觸媒床,不但可提升對有機污染物、CO及NOX之破壞去除率,也較能達到三污染物種同時處理之目標。而當焚化廢氣中含有重金屬(Pb、Cr、Cd)及酸性氣體(SOX及HCl)時,不但會毒化鈀及銠觸媒,還會造成兩觸媒對各自所扮演的角色產生混淆,破壞其於此系統中之分工,使此雙層觸媒床反應裝置對污染物之破壞去除效率降低。
Incineration is considered to be an effective method to disposing waste, but the emissions of organic compounds in the flue gas have received major attention recently. When trace organic products of incomplete combustion (PICs) contained in flue gas emitted into the atmosphere, it will be harmful to the environmental and human health. The object of this study was to investigate the effect of different operation conditions on the catalytic oxidation of trace organic compounds [i.e., benzene, toluene, ethylbenzene, and xylene (BTEX); and polyaro- matic hydrocarbons (PAHs)] and CO and catalytic decomposition of NOX in incineration flue gas. Three-way Pd-Rh/CeO2/Al2O3 catalysts (TWC), connectedly applied to treat automobile exhaust, were employed in this study. Catalyst supports, CeO2/Al2O3, were prepared using a modified oil- drop sol-gel process for synthesis of mesoporous spherical γ-Al2O3 granu- lation and CeO2-coated γ- Al2O3 granulation particles of 1-2mm in diameter. Bimetallic catalysts were prepared by impregnation of palladium nitrate and rhodium nitrate following successive impregnation procedures. The investigated parameters include (1) effect of different composition of Pd/Rh, (2) contribution of two-stage catalyst beds, (3) effect of heavy metals, (4) effect of acid gas, and (5) effect of water vapor. Experimental results showed that the destruction removal efficiency (DRE) of BTEX, PAHs, CO, and NOX in two-stage TWC reactor was generally greater then 80%. The bimetallic catalyst with a Pd/Rh ratio of 1/0.15 was found to have a best activity for highest destruction removal efficiency. The presence of Pb, Cr and Cd inhibited the oxidation of organic compounds and CO and reduction of NOX. The acid gases SO2 and HCl contained in the flue gas will poison and deactivate the palladium and rhodium catalysts and subsequently reduce the DRE of pollutants. The presence of water vapor was also found to slightly decrease the destruction efficiency of BTEX, PAHs, CO, and NOX.
URI: http://hdl.handle.net/11455/4936
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