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Numerical analysis of thermal plasma scrubber for CF4 decomposition

CF4 gas emitted in the semiconductor and display manufacturing process is a very harmful greenhouse gas. It must be removed or converted safely due to its extreme toxicity. Although a CF4 decomposition system using a thermal plasma scrubber was commercialized, its removal efficiency is limited. In this work, a numerical analysis of CF4 decomposition in the thermal plasma scrubber was carried out in order to propose an efficient decomposition environment. The decomposition and recombination temperatures of CF4 were analyzed using thermodynamic equilibrium calculations. The chemical reaction of CF4 decomposition into carbon and fluorine gas was considered in this numerical analysis. The injection position and angle of the CF4 were controlled in order to enhance the decomposition rate. The vertical injection of CF4 near the torch exit improved the mixing of the CF4 with the thermal plasma flame. In addition, it was confirmed that the high temperature region expanded due to a vortex generated by strong turbulence in the bottleneck-shaped reactor. As a result, it is revealed that the CF4 injection location and the reactor configuration are the most important factors in improving the decomposition rate.