| 摘要: | 本研究係利用熱脫附與電漿熔融設備處理汞污染之土壤，主要考量輸入必v與時間(能量)及添加劑等參數對處理效率、廢氣特性與熔渣資源化之影響。實驗結果顯示，必v為影響汞去除率、廢氣分佈與產物型態之主要因素。在去除率方面，電漿熔融時間控制於5 min時，必v低於2.8 kW，去除率低於90 %，但必v高於2.8 kW時，去除率可達到96.6 %；熱脫附處理之持溫時間控制於60 min時，去除率於低必v(3.8 kW)為62.6 %，高必v(4.8 kW)為82.1 %，顯示電漿處理有較高之效益。在電漿熔融與熱脫附廢氣分析方面，汞主要分佈於蒸氣相，由於汞有低沸點之特性，導致高能量處理時，汞容易存在於氣相中。經分析氣相中元素汞與氧化態汞型態得知，兩種熱處理系統皆以元素汞的型態佔優勢(> 50 %)。此外，在TCLP試驗結果得知，汞污染土壤經由電漿熔融或熱脫附處理後，其熔渣或是熱脫附後土壤均能符合中華民國毒性特性溶出標準(Hg< 0.2 mg/L)，且電漿熔渣如達到完全熔融時，也可合乎日本法規限值(Hg< 0.005 mg/L)，因此，兩種熱處理方式皆能達到無害化之效果。
由於電漿熔融與熱脫附處理技術所耗費之能量與成本較高，為提升熱處理效益，本研究也分析添加不同比例之氧化鋁時，熱處理產物之減重比、體密度、孔隙率、BET及表面結構等物理特性，作為產物資源化評估之依據。
A thermal desorption and a plasma torch were chosen to treat the mercury contaminated soil. The main target of this work is to evaluate the removal efficiency, effluent gases characteristics, and slag recycling value of these two thermal technologies under the parameters of power/duration (energy) and additive. The results indicated that power input is the main parameter affecting the removal efficiency, gas/particle phase distribution, and slag characteristics.
The removal percentage of mercury contaminated soil was lower than 90%, as the power input less than 2.8 kW in plasma torch treatment of 5 min; however, the removal percentage increased to 96.6% when the power input higher than 2.8 kW. For thermal desorption, the removal percentage of mercury contaminated soil was 62.6% under power input of 3.8 kW and duration of 60 min; however, the removal percentage was 82.1% under power input of 4.8 kW. That indicated the plasma torch has higher efficiency than thermal desorption.
In effluent gas of these two treatment systems, the results indicated that mercury distributed mainly in the gas-phase. It may be due to the high temperature supplying enough energy for low boiling point mercury to convert from particle-phase to gas-phase. Elemental mercury and mercuric oxide are the major two constitution of gas-phase mercury. Analysis results indicated that elemental mercury (> 50 %) is the dominant species in the two treatment systems. The TCLP concentration of slag or desorption soil was under the regulation standard of Taiwan. Meanwhile, the TCLP concentration of fully molten slag can even fulfill the stringent regulation of Japan (> 50 %).
In order to compensate high treatment cost of the two thermal technologies, aluminum oxide, as an additive, was added in contaminated soil to evaluate the slag recycling value by analyzing the physical characteristics of weight loss ratio, volume reduction ratio, volume density, viscosity, BET, and surface structure. |
