Comparison of Abatement Models for CF4Reacting with Nitrogen Thermal Plasma
Journal
IEEE Transactions on Plasma Science
Journal Volume
49
Journal Issue
1
Pages
120-146
Date Issued
2021
Author(s)
Abstract
This article proposes a numerical model to predict the abatement process of carbon tetrafluoride (CF4) in a reaction chamber with the assistance of nitrogen thermal plasma generated by a nontransferred and direct-current torch. The magneto-hydrodynamic equations, that is, the continuity, momentum, energy, and current continuity equations together with turbulence transport equations, are solved by an in-house parallelized finite volume code to obtain the thermal plasma flow jetting out the plasma torch. The thermal plasma is assumed in local thermal equilibrium, optically thin and electrically neutral. In the reaction chamber, a kinetics model is adopted to describe the transport phenomena as well as the chemical interactions among various species involving in the decomposition process. Fifty-six species and 235 chemical reactions are considered in the proposed full kinetic model. Three different models, namely a full kinetic one, a reduced one, and a simplified one, are compared for the prediction accuracy of the destruction and removal efficiency (DRE) along with the abatement products formed in the decomposition process. With the full kinetic model, the predicted DRE at three CF4 concentration conditions, that is, 7200, 12 600, and 16 000 ppm, has a good agreement with the experimental result indicating a nearly full decomposition except for a very small discrepancy less than 0.5% for the case of 16 000 ppm. The predicted abatement efficiency becomes saturated and approaches to a complete abatement provided the participated H2 O outnumbers CF4 in moles. A dry abatement process is forecast with a destruction rate decline from 97% to 92% as the CF4 concentration grows from 7200 to 16 000 ppm. Although the reduced kinetic model along the simplified model using a compact set of chemical reactions underpredicts the DRE for the investigated CF4 concentration in the range of 1%-2%, they practically deliver an incomplete group of abatement products that might mislead a proper design of the scrubber behind the reaction chamber. The validation with the experimental measurement justifies the employment of the proposed full kinetic model capable of delivering an accurate abatement prediction of the detoxifying process of CF4. ? 1973-2012 IEEE.
Subjects
Decomposition; Forecasting; Kinetic parameters; Kinetic theory; Magnetohydrodynamics; Magnetoplasma; Nitrogen; Product design; Reaction kinetics; Carbon tetrafluoride; Chemical interactions; Decomposition process; Destruction and removal efficiencies (DRE); Detoxifying process; Direct current torch; Local thermal equilibrium; Turbulence transports; Nitrogen plasma
Type
journal article