Influence of transitional and turbulent flow on electrical, optical, morphological and chemical characteristics of a nitrogen rotating gliding arc

Abstract

The work reports the effect of flow regime on plasma characteristics of an atmospheric N2 rotating gliding arc (RGA). When changed from transitional (5 SLPM) to turbulent (50 SLPM) flow, operation mode transitioned from glow to spark discharge due to frequent reignition events; the average reduced electric field (E/N) and electron temperature raised (38→92 Td, 0.84→2.2 eV); and gas temperature (Tg ) slightly cooled (2973→2807 K). Molecules generated for 100 eV of energy input (G–factor) increased by a factor of 20 and 65, for the chemically active singlet and triplet metastable states of N2, respectively—a promising feature for chemical applications. A sudden three fold increase in the energy efficiency, achieving a destruction of 3.0±0.2 g·kWh-1 of dilute toluene (112±10 ppmV) at highly turbulent flow corroborated the enhancement of the G–factor, E/N and Tg ; and indicated the sensitivity of plasma properties to the flow regime. Interestingly, for flows having Reynolds number ≥3×104, the bandhead of N2 + shifted from 0–0 at 391.4 nm to 3–3 at 383.3 nm attributed to higher-level perturbations, showing again the sensitivity. The smallest eddies (η≈6 μm) is less than the discharge diameter (dd≈220±90 μm), and thermal/mass Péclet number>1. The eddies of size < dd advected the plasma species, wrinkled/distorted the discharge, and increased the reignition events, eventually affected the plasma properties including the chemical performance (energy efficiency), which is observed in this work.

Tar Formation in Gasification Systems: A Holistic Review of Remediation Approaches and Removal Methods

“…These species can dissociate and further reform the stable compounds like “tar” generated in gasification. For this reason, plasma technology has recently been explored for generating relatively clean raw gas from gasifiers and also for cleaning the raw impure gas, i.e., tar destruction. ,,− Thermal plasma (TP) is used as a source of heat to provide a very high-temperature environment (>2273 K) inside the gasifier, enabling in situ tar crackingplasma gasification. Nonthermal plasma (NTP) is used as a source of chemically active species by ionizing the compounds present in the gas to be cleaned, thereby enabling compounds of tar to be reformed; this reformation is possible at lower temperatures than that for the catalytic/thermal cracking. …”