Studies on the Electrical Behaviour and Removal of Toluene with a Dielectric Barrier Discharge

Abstract

This contribution attempts to establish an easyto-apply non-thermal plasma reactor for efficient toluene removal. Derived from the already established knowledge of the so called Dielectric Barrier Discharge (DBD) Stack Reactor a new model reactor was used in this work. The DBD Stack Reactor is a multi-elements reactor but in this work only one stack element was used to investigate the efficiency and efficacy of toluene removal. In case of reliable results the scalability process for industrial application is already well known. Therefore, laboratory experiments were conducted in dry and wet synthetic air with an admixture of 50 ppm toluene. Along with the toluene removal process the electrical behaviour of the discharge configuration was investigated. It was found that the electrical capacitance of the dielectric barrier changes with variations of the operating voltage. This could be due to the changes in the area of the dielectric barrier which is covered with plasma. Additionally, it was found that the power input into the plasma, at a fixed operating voltage, is proportional to the frequency, which is in agreement with the literature.Regarding the decomposition process, the total removal of toluene was achieved at specific input energy densities of 55 J L -1 under dry conditions and 110 J L -1 under wet conditions. The toluene removal was accompanied by the production of nitric acid (dry conditions) and formic acid (wet conditions). The latter suggested a combination of the plasma reactor with a water scrubber as an approach for total removal of pollutant molecules.

About the Development and Dynamics of Microdischarges in Toluene-Containing Air

“…Another possibility is Penning ionisation of by-products of toluene decomposition. However, at the low specific input energies (27 J/L) the overall conversion is about 20% [52] and effective lifetimes of the metastable nitrogen molecules are low due to quenching by oxygen (see "Microdischarge Morphology and Development" section).…”

“…The reactor concept has been used to clean air admixed with toluene and other VOCs in the past (e.g. [52]). This work also motivated the study of single MDs in low-level VOC contaminated air.…”

Cold Physical Plasmas in the Field of Hygiene—Relevance, Significance, and Future Applications

“…The detoxification of air pollution caused by volatile organic compounds (VOCs, such as TCE, TCA, toluene, and xylene), acid and greenhouse gases (such as SO x , NO x , HCl, CO x , N x O y , and PFCs), or ozone depletion substances (Freon or Halon) may be assisted by plasma . Generally, a number of pollutants are present in waste air, and plasma decomposes different hazardous air pollutants at the same time . Plasma removes toxic particles in shipping diesel engine exhaust gases, including NO x .…”

Desulfurization of Biogas via Dielectric Barrier Discharges

“…According to Penetrante and co‐workers 29, the depletion of many gaseous pollutants in plasma processes follows an exponential behavior dependent on the amount of energy transferred into the working gas; c.f. also Schmidt et al 31.…”