土壤中苯、甲苯、乙苯、二甲苯之熱脫附

Thermal Desorption of Benzene, Toluene, Ethylbenzene and Xylene Contaminated Soils

黃文聖(Wen S. Huang)

指導教授 ： 林勝雄

元智大學/工程學院/化學工程與材料科學學系/碩士(2000年)

摘要

石油及其產品是人類生活上所需之主要來源，常因為人為疏失而造成各種土壤或地下水污染事件。因土壤成分較為複雜，要分離土壤中有機物頗為不易。本論文即利用熱脫附之方法去除土壤中的有機化合物(BTEX：苯、甲苯、乙苯、二甲苯)。
在批式實驗中，所選用的三種溫度為各有機物沸點及其上下各20℃為實驗條件，來探討等溫去除實驗及質傳模式。在等溫去除實驗方面，Modified-Langmuir Model比Langmuir、Freundlich和Jossens et al.三種等溫式更能適切的描述其等溫熱脫附的平衡關係。在質傳模式的探討上，以兩段指數型模式即可表達本實驗之質傳現象。
連續式熱脫附實驗是將受污染土壤經過螺桿式加熱床，達到將有機物與土壤分離的效果。測試此實驗的效能如何，以探討其實用性。本實驗係採桃園縣中壢市內壢里土壤添加有機化合物，針對系統溫度、通氣量、處理時間、污染濃度及土壤量對熱脫附處理效果之影響進行討論。由實驗結果顯示，影響熱脫附效果最大的變因是系統溫度、處理時間以及污染濃度。而通氣量和土壤量這兩組變因，必須在長時間不斷進料，效果才會有較為明顯的變化。
由批式和連續式實驗中發現，BTEX四種有機化合物中，以苯最容易脫附，其次為甲苯，而最不易脫附的是乙苯和二甲苯。由現階段實驗模擬處理成效證明熱脫附系統對於受BTEX污染土壤具有良好之處理能力，對於實際應用於污染現址復育具有相當的可行性與開發潛力。

關鍵字

土壤 ； 苯 ； 甲苯 ； 乙苯 ； 二甲苯 ； 熱脫附

並列摘要

Petrochemical and other chemical products are important parts of mainstay requires in our life. However, manufacturing of these products very often can cause severe soil or groundwater pollution problems. Due to its complex structure, remediation of soil contaminated by organic compounds has never been easy. In the present experimental research, thermal desorption is considered as a means for remediating soil contaminated by benzene, toluene, ethylbenzene and xylene (BTEX) which are common organic compounds found in the petrochemical industries.
In the batch experimental tests, the desorption temperature were chosen to be around respective boiling points of BTEX. Based on the chosen temperature, experimental tests were conducted to gather data for establish the desorption isothermal Langmuir model was found to describe quiet well the observed data. On the mass transfer aspect, a power type mass transfer model was proposed to represent the mass transfer process.
In the continuous desorption tests, the contaminated soil was transported in a screw heating bed to achieve thermal detachment of organic compounds from soil. Test runs were conducted to investigate the thermal desorption efficiencies of contaminated soil under various operating conditions of temperature, gas flow rate, soil loading and initial organic concentration. Proper conditions were indentified for efficient operation of the thermal desorption process.
The test results idicated that among the four compounds tested, benzene is the easiest to remove from the contaminated soil by xylene, ethylbenzene and toluene. Thermal desorption was found to be a highly efficient process for removal of BTEX or similar compounds.

並列關鍵字

soil ； Benzene ； Toluene ； Ethylbenzene ； Xylene ； BTEX ； Desorption ； Thermal Desorption

參考文獻

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Atalay, A. and Hwang, K. J., " Extraction of Light Hydrocarbons from Soil", Water, Air, and Soil Pollution, 90, pp. 451-468, 1996.

Batterman, S., Kulshrestha, A. and Cheng, H. Y., " Hydrocarbon Vapor Transport in Low Moisture Soils", Environmental Science & Technology, 29, pp. 171-180, 1995.