Chemical Kinetics Simulation of Toluene Dissociation With Diluted Nitrogen in a Rotating Gliding Arc Discharge: A Simulation Study

The depletion of fossil fuels has driven the development of technologies that utilize biomass or municipal solid waste (MSW) for energy. Gasification is a promising method to convert biomass or MSW into fuel gas or syngas, but tar production is a major challenge, as it can contaminate the gas and damage downstream equipment. Nonthermal plasmas have emerged as an effective solution for efficiently destroying and converting tar during gasification. This study examines how the dissociation of toluene as a tar surrogate from gasification, which is diluted in N<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> plasma, is impacted by a rotating gliding arc (RGA) discharge under different flow regimes. The chemical workbench (CWB) model is utilized to simulate most of the known plasma-chemical kinetic processes of multiple species for this study. For this purpose, a mechanism is formulated, which encompasses over 100 reactions, including a comprehensive range of chemical and electronic processes of N<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>, toluene, and their dissociated species. The simulation in this study was conducted using simulated toluene concentrations of 112 ppm diluted with N<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>. As the flow rate (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i>) transitioned from 5SLPM (TRANS-FLOW) to 50SLPM (HIGH-TURBFLOW), the reduced electric field (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E/N</i>) shifted from 40 Td to 127 Td and gas temperature (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T}_{g}$</tex-math> </inline-formula>) varied from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3339~\pm ~151$</tex-math> </inline-formula> K to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4171~\pm ~147$</tex-math> </inline-formula> K. When <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> rose from 5SLPM to 20 SLPM (LOW-TURBFLOW), destruction efficiency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(\eta _{d})$</tex-math> </inline-formula> dropped from 21% to 4% experimentally and from 25% to 6.3% in simulations, likely due to reduced residence time. However, as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> reached highly turbulent flow, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\eta _{d}$</tex-math> </inline-formula> increased to 12% at 50SLPM experimentally and 17% in simulations. The effect of flow regime on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\eta _{d}$</tex-math> </inline-formula> is studied, and maximum <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\eta _{d}$</tex-math> </inline-formula> is at 5SLPM, which is 25% achieved in this work. This suggests that operating the RGA under TURBFLOW conditions could enhance energy efficiency by generating more energetically active species per unit of energy input compared to TRANSFLOW conditions.