| 摘要: | C3F8為全氟化物之一，近年來已逐漸取代CF4與C2F6成為高科技產業CVD腔體清洗之主要製程氣體。由於全氟化物具長生命週期與強活外線吸收能力，致使其全球暖化潛勢極高，乃京都議定書明訂管制之溫室效應氣體。 就全氟化物破壞削減技術而言，目前仍以高溫技術為主流，如燃燒法與觸媒法，然高科技產業機檯尾氣排放屬間歇式，上述技術為確保全氟化物去除效率能符合標準，即使於非排放期間亦需維持於一定溫度，因此能量利用效率相對不佳。不同於上述技術，非熱電漿具可間歇操作、快速啟動及反應溫度接近室溫等優點，然若欲將此技術大規模實場化，去除污染物之能量效率與產物選擇性尚有待改善。為克服上述瓶頸，本研究嘗試以非熱電漿同時結合觸媒與吸附劑(combining the nonthermal plasma, adsorption and catalysis, CPAC)去除全氟化物，此技術立論基礎為吸附作用與催化作用可改善非熱電漿破壞污染物之能量效率與產物選擇性。本研究最主要的目的為評估CPAC方法破壞PFCs之可行性，此外，為釐清CPAC內觸媒和吸附劑之填充方式是否會影響C3F8去除效能，本研究亦使用不同組合方式，包括分層或混合填充；再者，為驗證CPAC是否可有效提升C3F8之去除效能，本研究亦使用非熱電漿結合觸媒(combinations of plasma with catalysis, CPC)與非熱電漿結合吸附劑(combinations of plasma with adsorption, CPA)進行對照組實驗。 結果顯示，當比能量為34.8 kJ/L時，C3F8去除效率由高至低分別為分層CPAC (85.9%) > CPA (85%) > CPC (74.1%) > 混合CPAC (71.8%)；CPAC、CPA及CPC之以CO2、CO、N2O與CF4為主，並且沒有C2F6產生，這是一件好事，其暖化潛勢遠高於C3F8 （C2F6與C3F8之GWP100分別為12,200與8,300），若C3F8經處理之後產生大量的C2F6，對全球暖化之貢獻反而有增無減。當比能量為34.8 kJ/L時，CO2產物選擇率由高至低分別為分層CPAC (82.5%)、CPA (81.1%)、CPC (73.5%)及混合CPAC (68.6%)。綜觀C3F8去除效率與CO2產物選擇率可知，分層CPAC技術優於CPA、CPC及混合CPAC。 With the characteristics of extremely long lifetimes and high GWPs (global warming potentials), PFCs are regulated as one of the GHGs (greenhouse gases) in Kyoto Protocol. In recent years, C3F8, one of the perfluorocompounds (PFCs), has been gradually replacing CF4 and C2F6 as the CVD (chemical vapor deposition) chamber cleaning gas used in high-tech industry. In terms of PFC abatement, the high temperature-based technologies, such as catalytic oxidation and thermal decomposition, are still the mainstream. Although acceptable removal efficiency could be achieved, these equipments have to be maintained at a certain temperature even during the period without PFC emission. Unlike the above-mentioned technologies, nonthermal plasma can be ignited and operated at room temperature, making it a potentially viable technique for PFC abatement. However, prior to further industrial application, the energy efficiency and the products’ selectivities still need to be improved. To resolve these challenges, a novel technique, combining the nonthermal plasma, adsorption and catalysis (CPAC) simultaneously, is developed in this study. This technique is proposed based on the concept that adsorption and catalysis could enhance the energy efficiency and products’ selectivities theoretically. The main purpose of this study is to demonstrate the feasibility of abating PFC via CPAC. The CPAC was constructed by introducing almost the same volumes of both packed-bed materials either as single-component layers or as a mechanical mixture. In addition to CPAC, the combinations of plasma with catalysis or adsorption alone, which are termed as CPC and CPA, are used as control as well. The experimental results indicate that the C3F8 removal efficiencies obtained by different reactors are in the order as: single-component layers of CPAC (85.9%) > CPA (85%) > CPC (74.1%) > mechanical mixture of CPAC (71.8%), as the specific input energy (SIE, the ratio of discharge power to gas flow rate) is fixed at 34.8 kJ/L. For the different reactors tested in this study, the products detected after plasma treatment include CO2, CO, N2O and CF4. The formation of C2F6 is not observed in this study. The CO2 selectivity obtained at 34.8 kJ/L is in the sequence of single-component layers of CPAC (82.5%) > CPA (81.1%) > CPC (73.5%) > mechanical mixture of CPAC (68.6%). In summary, the removal efficiency of C3F8 and CO2 selectivity achieved with single-component layers of CPAC is greater than CPA, CPC, and mechanical mixture of CPAC. |
