The Dissociation of CO ₂ by Atmospheric Pressure Ar and Ar/He Plasma Jets With Twin-Jet Design

A modified twin-jet plasma system was applied to dissociate carbon dioxide (CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>) using Ar plasma at room temperature and pressure. In the system, two plasma jets were made facing each other in a closed tube. For the first time, the twin-jet plasma system was used to realize the effect of plasma jet collision on the improvement of CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> dissociation rate and efficiency. By using the twin-jet system, the relationship between plasma characteristics and CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> dissociation rate and efficiency under various CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> flow rates, pulse frequencies, and on-time voltage was investigated. Then, the enhanced dissociation mechanism of the twin-jet plasma was verified with a parallel-jet plasma system. In addition, Ar/He mixed gas was used to realize the importance of Penning effects. The plasma spectra were measured by optical emission spectroscopy (OES), with which the electron temperature (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{T}_{\mathrm {e}}$</tex-math> </inline-formula>), electron density (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{n}_{\mathrm {e}}$</tex-math> </inline-formula>), and spectral intensity ratio (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm {CO}}$</tex-math> </inline-formula>/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm {CO2}}$</tex-math> </inline-formula>) were evaluated accordingly. The experimental results show that the highest dissociation efficiency was achieved at 76.02%, and the highest dissociation rate was 0.54 g/h, which is higher than that obtained from parallel jets or single jet. In addition, it is found that by using the twin-jet system, the dissociation rate at higher CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentrations can be maintained. Through the parallel-jet experiment, it can be confirmed that plasma jet collision from the opposite directions would be the main reason for the enhancement of dissociation rate by twin jets. Finally, according to the results obtained from Ar/He plasma, it can be confirmed that the collision cross section of large particles involved in the processes is critical to the dissociation of CO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>. The dissociation process should be dominated by the Penning effect of Ar*, which is enhanced by plasma collision in the twin-jet system.