燃煤電廠固相副產物中重金屬及微量汞之穩定性評估

重金屬是燃煤程序中所產生的污染物，其中又以汞(mecury)的排放最受矚目。由於汞具有於自然界存在時間長、具持久性、生物累積性與生物放大等特性，且汞物質能經由大氣、陸地和海洋環境中進行區域性或全球性之長程傳輸，具跨國傳輸特性，故對於生態環境及人體具極大衝擊。重金屬可存在於燃煤飛灰、石膏、底灰及煙道排氣中，一般而言固化(solidification) 程序對於燃煤電廠副產品之重金屬溶出具有有效之抑制作用，故本研究針對電廠副產品使用固化程序後，進行TCLP、可交換態TCLP等試驗。另外也使用熱脫附(thermal desorption)程序，觀察副產品中汞之熱穩定性。飛灰固化體經TCLP溶出試驗後，Pb、Cr、Cu、As、Cd及Hg之TCLP溶出值均符合法規標準，在Zn、As、Hg、Ni方面，添加水泥有明顯抑制溶出的效果，而添加螯合劑之溶出值卻無明顯之變化趨勢。在可交換TCLP溶出程序方面，未經固化法處理的飛灰中Cu、Cd和As占了總量較高的百分比，分別為40.3%、39.1%和77%。相關研究顯示，除了殘餘態的重金屬難以溶出被生物體所利用外，其餘的相態的重金屬則均可能溶出被生物體所吸收利用，而以水溶態與可交換態這兩個相態中的重金屬最容易溶出。在副產品汞之熱穩定性部份，飛灰中的汞在200 oC時開始明顯脫附，在300 oC達到脫附的高峰值，在約480 oC時汞的脫附量開始趨於減緩，石膏中汞的脫附區段在於150 oC ~450 oC，汞在約244 oC中達到脫附的高峰值，底灰中汞脫在於140 oC時開始脫附，在290 oC達到第一個脫附的高峰值，接著在370 oC時有第二個高峰值出現。

關鍵字

TCLP ；序列萃取；重金屬；固化法；熱脫附

並列摘要

Heavy metals are pollutants derived in coal burning, wherein the emission of mercury is the most notable due to it persistency, bioaccumulability, and bio-magnification ability that cause mercury to globally transport through air and deposit to land and ocean, which greatly impacts the ecological environment and human beings. Heavy metal can exist in several coal-combustion byproducts such as coal fly ash, gypsum, and bottom ash. In general, solidification can effectively inhibit the dissolution of heavy metals from coal-combustion byproducts. Therefore, this research aims at conducting experiments such as traditional TCLP and exchangeable-form TCLP on the coal-combustion byproducts from a given power plant in Taiwan. In addition, thermal desorption was performed to observe the heat stability of mercury in byproduct.s Results showed that after solidification, TCLP dissolution concentrations of Pb, Cr, Cu, As, Cd, and Hg for fly ash were all in compliance with the regulations. For Zn, As, Hg, and Ni, Cement solidification significantly inhibited the TCLP leaching, but the addition of chelating agent did not show significant improvement. Exchangeable TCLP tests showed that Cu, Cd, and As were markedly leached out to 40.3%, 39.1%, and 77% of their total amounts in the raw fly ash, respectively. Previous literatures pertaining to sequence extraction on fly ash showed that those heavy metals can be easily leached out via exchange mechanism can be uptaken by living organism. The heavy metals presenting in dissolve and exchangeable fractions were the easiest types to be leached out. Thermal desorption experiments showed that mercury was significantly desorbed from fly ash at 200 oC, reaching a peak value at 300 oC, and the desorption amount reduced at 480 oC. For gypsum, the mercury desorption range was 150-450 oC with a peak at 244 oC. For bottom ash, mercury started to desorb at 140 oC, reaching the first peak at 290 oC and the second peak at 370 oC.

並列關鍵字

TCLP ； sequential extraction procedure ； heavy metal ； solidification ； thermal desorption

參考文獻

李欣怡，汞與戴奧辛污染土壤熱脫附處理研究，碩士論文，國立台北科技大學環境工程與管理研究所，台北，2012。

周書瑋，汽電共生設施重金屬污染物排放調查及管制策略研究，碩士論文，國立台北科技大學環境工程與管理研究所，台北，2013。

Ayala, J., F. Blanco, P. Garcia, P. Rodriguez, and J. Sancho, “Austrian fly ash as a heavy metals removal material,” Fuel, vol. 77(11), 1998, pp. 1147-1154.

Carey, T. R., O. W. Hargrove, C. F. Richardson, R. Chang, and F.B. Meserole, “Factors affecting mercury control in utility flue gas using activated carbon,” J Air Waste Manage, vol. 48, 1998, pp. 1166-1174.

Cocke, D. L., “The binding chemistry and leaching mechanisms of hazardous substances in cementitious solidification/stabilization systems,” Journal of Hazardous Materials, Vol. 24, 1990, pp. 231-253.

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燃煤電廠固相副產物中重金屬及微量汞之穩定性評估

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