熱電漿輔助四氟化碳裂解模擬

Modeling of Thermal Plasma Assisted Carbon Tetrafluoride Abatement

簡聖偉(Sheng-Wei Chien)

指導教授 ： 趙修武

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202100896

摘要

本研究提出預測以水蒸氣與氬氣熱電漿裂解四氟化碳的數值模型，與實驗對比不同流量四氟化碳混合氣體在不同功率條件下的裂解效率以及產物評估。本研究在氣體物種達到熱平衡的假設下以有限體積法聯立求解二維軸對稱穩態連續方程式、動量方程式、能量方程式、K-ε紊流模型和電漿物種傳輸反應方程組，使用物種的碰撞參數計算混合氣體的傳輸特性。本研究比較兩套電漿反應機制Model A和Model B在三組電漿功率(20、27、40 kW)的四氟化碳裂解效率。計算結果顯示，兩套反應機制在處理純四氟化碳條件下均得到與實驗匹配的裂解趨勢，與實驗比對誤差約落在在6%以內，其中Model B預測出的出口物種分布較符合文獻結果。Model B在處理與氬氣輔助四氟化碳裂解模擬中獲得與實驗結果相同的裂解趨勢，裂解率誤差隨著四氟化碳增大而成長，然而Model B在氫氣輔助的四氟化碳裂解模擬具有超過20%的誤差，同時也無法預測實驗獲得15 slm氫氣流量的最佳裂解率反應條件。本研究所提出的數值模型可有效預測以水蒸氣與氬氣熱電漿裂解四氟化碳的分解率，發現三氟化碳、二氟化碳與醛基的生成可能有助於提升裂解率，而二氟甲烷、三氟甲烷與氟甲烷的生成則可能導致裂解率下降。

關鍵字

熱電漿 ； 四氟化碳 ； 裂解數值模擬 ； 廢氣處理 ； 水 ； 氬 ； 氫

並列摘要

This study proposes a numerical approach to predict the decomposition and removal efficiency rate in a thermal plasma assisted carbon tetrafluoride abatement process. Three working conditions of plasma torch (20, 27, 40 kW) treating pure CF4, CF4-Ar mixture and CF4-H2 mixture were simulated. A two-dimensional axisymmetric model considering mass, momentum, energy, and species conservation considering turbulence effects was implemented to solve the species distribution under the assumption of steady flow in thermal equilibrium. In order to couple the plasma flow and species transport model, physical properties were calculated based on collision parameters in a simplified way. Finally, two different reaction sets, i.e., Model A and Model B, were applied to investigate the species distribution for a CF4 abatement processes. The predicted DRE of CF4 is compared with the experimental data where a prediction error within 6% was obtained for processing pure CF4 by both kinetic models. Model B delivered more realistic species profiles at the outlet when compared to Model A. In treating a CF4-Ar mixture, the underestimation in DRE over 10% was shown in 10 slm CF4 cases by Model B where the predicted results were still comparable to the experimental ones. Higher DRE errors with maxima over 20% compared to the experiments were shown in the CF4-H2 cases. The present numerical model successfully predicted the DRE in processing pure CF4 and acceptable outcomes for treating CF4-Ar mixture but seemed to fail in predicting a comparable DRE behavior with the experiments in the CF4-H2 cases. The results of Model B suggest several important mid-products in the CF4 decomposition process. The presence of CF3, CF2 and CHO leads to improved DRE performance while the occurrence of CH2F2, CHF3 and CH3F results in a low DRE value.

並列關鍵字

Thermal Plasma ； Carbon Tetrafluoride ； Abatement Modeling ； Gas Treatment ； Water ； Argon ； Hydrogen

參考文獻

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