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Treatment of Volatile Organic Compounds Emitted from Opto-electronic Industry by a Trickle-bed Air Biofilter
TSAI, CHANG KUO
|關鍵字:||trickle-bed air biofilter;生物濾床;Opto-electronic industry;volatile organic compounds;isopropyl alcohol;acetone;butyl acetate;toluene;xylene;光電產業;揮發性有機物;異丙醇;丙酮;乙酸丁酯;甲苯;二甲苯||出版社:||環境工程學系||摘要:||
本研究主要是以生物濾床（trickle-bed air biofilter, TBAB）處理光電產業揮發性有機化合物（volatile organic compounds, VOCs）。本研究共分成四大部分，第一部份為處理單一VOC；第二部份為處理混合VOCs；第三部份為理論模式模擬與驗證；第四部份則為光電實場VOCs廢氣之研究。
以TBAB處理異丙醇（isopropyl alcohol, IPA）、丙酮（acetone, ACE）、乙酸丁酯（butyl acetate, BA）及1,1,1-三氯乙烷（1,1,1-trichloroethane, TCA）等四種單一VOC。其中，除三氯乙烷進流濃度範圍為25∼50 ppmv外，其餘三種VOCs進流濃度範圍均為100∼500 ppmv，而停留時間（empty-bed residence time, EBRT）則從90 s逐漸縮短至20 s。由試驗結果中發現，處理異丙醇、丙酮、乙酸丁酯及三氯乙烷的有機碳負荷可以分別達到88.24、88.24、176.47及5.88 g/m3•h。四組TBAB碳平衡均達到95 %以上，顯示本試驗系統操作狀況良好，且試驗數據具有相當高之準確性。
異丙醇及丙酮、乙酸丁酯及二甲苯與甲苯及丙酮三組有機溶劑的組合為半導體及光電產業最常使用的VOCs。本研究即在探討以不同進流濃度及EBRT之下，TBAB處理三組混合VOCs的效率，試驗結果中發現，混合VOCs的去除效率會隨著進流有機碳負荷的增加而降低，而在處理混合VOCs時，異丙醇、乙酸丁酯及甲苯的去除率較丙酮及二甲苯佳。如果異丙醇及丙酮的去除率要高於90 %，則有機碳負荷就必須在80及53 g/m3•h以下；如果乙酸丁酯及二甲苯去除率要高於80 %，則有機碳負荷就必須在150及110 g/m3•h以下；如果甲苯及丙酮的去除率要高於90 %，則有機碳負荷就必須在125及15 g/m3•h以下。由上述結果顯示，TBAB非常適合處理異丙醇及丙酮、乙酸丁酯及二甲苯與甲苯及丙酮三組混合VOCs。
另外，本研究於新竹科學園區某一光電實場設置TBAB來處理所排放出來的VOCs，光電實場所使用的主要VOCs為異丙醇及丙酮，試驗過程中EBRT逐漸由90 s 縮短至20 s，在EBRT = 20 s的試程裡，總碳氫化合物（total hydrocarbon, THC）去除率可維持在95 %以上，因此，TBAB非常適合處理光電實場所排放的VOCs廢氣。
The purpose of this study is to evaluate the performance of trickle-bed air biofilter (TBAB) for treating volatile organic compounds (VOCs) form the Opto-electronic industry. This study contains four parts. The first part focused on the process control of TBAB system to treat single VOC. The second part highlighted on the process control of TBAB system to treat mixed VOCs according to different emission characteristics from the Opto-electronic industry. The third part developed a theoretical model and derived the performance equation.The fourth part concentrated on the process control of TBAB system to treat mixed VOCs from the field Opto-electronic factory.
The performance of TBAB for the removal of pure isopropyl alcohol (IPA), acetone (ACE) and butyl acetate (BA) was evaluated under different influent concentrations of 100 to 500 ppmv, and 1,1,1-trichloroethane (TCA) was evaluated in concentrations varying from 25 to 50 ppmv. The empty-bed residence time (EBRT) is from 20 to 90 s. Nearly complete IPA, ACE, BA and TCA removal could be achieved for influent carbon loading between 5.88 to 88.24 g/m3•h, 5.88 to 88.24 g/m3•h, 11.76 to 176.47 g/m3•h and 0.98 to 5.88 g/m3•h, respectively. The TBAB appears high efficiency for controlling IPA, ACE and BA emission under low-to-high carbon loading and TCA emission under low carbon loading conditions. Greater than 95 % carbon recoveries were achieved demonstrating the accuracy of test results.
IPA and ACE, BA and xylene (X), toluene (T) and ACE mixtures are commonly encountered from the manufacture of Opto-electronic. The removal of these mixtures by TBABs were evaluated under different gas flow rates and influent concentrations. In the pseudo-steady-states, the elimination capacities of IPA and ACE, BA and X, T and ACE increased but the removal efficiencies decreased with the increase of influent carbon loading. The removal efficiencies of IPA, BA and T were higher than those of ACE and X, indicating that IPA, BA and T are a preferred substrate in the mixtures. Greater than 90 % removal efficiencies were achieved with influent carbon loadings of IPA and ACE below 80 and 53 g/m3•h, respectively. Greater than 80 % removal efficiencies were achieved with influent carbon loadings of BA and X below 150 and 110 g/m3•h, respectively. Greater than 90 % removal efficiencies were achieved with influent carbon loadings of T and ACE below 125 and 15 g/m3•h, respectively. The TBAB appears efficient for controlling mixed IPA and ACE, BA and X, T and ACE emissions with low-to-medium carbon loadings. Applicable operating conditions of TBAB for treating mixed IPA and ACE, BA and X, T and ACE emission were suggested.
A mathematic model that incorporates mass transfer process and biofilm reactions is presented to predict the performance of a TBAB for treating IPA and ACE, BA and X, T and ACE mixtures. The model consists of a set of mass balance equations for IPA, ACE and oxygen; BA, X and oxygen; T, ACE and oxygen in the bulk gas phase and within the biofilm. The effluent gas phase IPA and ACE, BA and X, T and ACE concentrations predicted by the present model were in good agreement with the measured data available in a previous study. The important parameters were evaluated in the sensitivity analysis to determine their respective effects on the model performance. Four parameters were identified to strongly influence the model performance: surface area of the biofilm per unit volume of packing material (As), EBRT, maximum specific growth rate of microorganism (μm), and microbial yield coefficient (Y). Practical applications of the model to derive the performance equation of TBAB for treating different inlet IPA and ACE, BA and X, T and ACE concentrations are also demonstrated.
Finally, this study evaluated the TBAB performance for the removal of VOCs emitted from an Opto-electronic manufacturer. The major emitted VOCs are IPA and ACE. Different EBRTs of 90, 60, 30 and 20 s were evaluated to establish the optimum operating condition. Nearly complete VOC removal could be achieved at the end of each run. The TBAB appeared efficient for controlling VOC emission from an Opto-electronic manufacturer.
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