- 學位論文
電漿結合觸媒反應器處理含氯有機揮發性廢氣
Plasma combined with catalyst reactor to treat chlorine-containing organic volatile waste gas
摘要
二氯甲烷(DCM)為廣效性溶劑，被工業大量用作有機溶劑，在室溫下具有高揮發性，因而每年有數以千噸的二氯甲烷被排放至大氣中。二氯甲烷易被人類吸收，且被懷疑恐有致癌性，二氯甲烷的化學性質穩定，可以存在大氣中長達130天，導致環境危害，若不在廢氣排放前進行有效處理，一方面有前述之危害性，另一方面也導致氯代烴資源的嚴重浪費。 本研究利用非熱平衡式介電質放電大氣電漿，以交流電場來加速電極周遭的電子，電子會被快速變動的電場游離形成自由電子，而自由電子又會去轟擊載流氣體中的氮、氧、二氯甲烷，生成激發態分子、激發態原子、更多的自由電子、自由基、陰陽離子等，這些粒子具有高度化學反應活性，可將氣流中的二氯甲烷分解。然而在進料DCM濃度933 mg/m3，氣流流速約1 L/min，換算電漿反應器中滯留時間54毫秒的情況下，純利用大氣電漿的DCM分解率僅62.2 %，為了提高電漿的DCM移除能力，故在電漿反應器後方5.8公分處，放置約0.5公克的CeO2/Al2O3、Actived γ-Al2O3、CeO2/ZSM-5、CuO/Mn2O3觸媒進行二氯甲烷的降解實驗，其中CeO2/Al2O3、Actived γ-Al2O3、CeO2/ZSM-5等含有氧化鋁成分之觸媒，會提升氯仿與四氯化碳的選擇率，加速了DCM的分解，可以將平均移除率提升至70%以上。在同樣的電能使用下，添加觸媒可以提升電能使用效率。
並列摘要
Dichloromethane (DCM) is a versatile solvent, which is widely used as an organic solvent in the industry. It has high volatility at room temperature, so thousands of tons of dichloromethane are discharged into the atmosphere every year. DCM is easily absorbed by human being and is suspected to be carcinogenic. The chemical properties of dichloromethane are stable and can stay in the atmosphere up to 130 days, thus cause environmental pollution. If the exhaust gas is not effectively treated before it is discharged, on the one hand, it will cause environmental harm, on the other hand, it will also lead to a serious waste of chlorinated hydrocarbon resources. In this study, non-thermal equilibrium atmospheric plasma by dielectric discharge was used to decompose DCM. The principle of generating plasma is to accelerate the electrons around the electrode by an alternating electric field. The electrons are dissociated by the rapidly changing electric field to form free electrons, which bombard the nitrogen, oxygen, and DCM in the carrier gas. In turn, excited molecules, excited atoms, more free electrons, free radicals, anions and cations are generated. These particles have high chemical reaction activity and can decompose DCM in the gas stream. When the feed DCM concentration is 933 mg/m3, the gas flow rate is about 1 L/min, and the residence time is 54 milliseconds in the plasma reactor, however, the DCM decomposition by sole atmospheric plasma is only 62.2%. In order to improve the DCM removal capability by the plasma, near 0.5 grams of CeO2/Al2O3, Actived γ-Al2O3, CeO2/ZSM-5, or CuO/Mn2O3 catalysts is filled a packed bed, and is connected 5.8 cm behind the plasma reactor in the DCM removal experiment. This study found that catalysts containing alumina, such as CeO2/Al2O3, Actived γ-Al2O3, and CeO2/ZSM-5 would increase the product selectivity of chloroform and carbon tetrachloride, accelerate the decomposition rate of DCM, and increase the average DCM removal over 70%. Under using the same power, additional catalyst can improve the efficiency of electricity.