The gasification of a fuel or biomass is an industrial process that is utilized for synthesis gas (syngas) production. The syngas can be used to generate electricity, but after gasification it is often polluted with tars and various other pollutants. Therefore, the syngas must be cleaned before further use. The objective of this paper was to investigate the potential of removing the tars by non-thermal plasma generated by atmospheric pressure dielectric barrier discharge in combination with various packing materials (TiO ₂ , Pt/ γ -Al ₂ O ₃ , γ -Al ₂ O ₃ , glass beads). Naphthalene was used as a model polyaromatic tar compound. The effect of discharge power, carrier gas and packing material on naphthalene removal was investigated and gaseous and solid by-products were analysed by means of FTIR spectrometry. In ambient air, a naphthalene removal efficiency of 88% and 40% was achieved for 320 J l ^−l with and without the catalyst, respectively. The maximum removal efficiency of almost 100% was observed with a TiO ₂ catalyst and oxygen carrier gas. CO, CO ₂ , H ₂ O and HCOOH were identified among the products, as well as more complex compounds, such as 1,4-naphthoquinone and phthalic anhydride.

An evaluation of the gaseous species production by the discharge, i.e., discharge chemical activity, is very important for determining its potential for practical applications. In this work, production of gaseous species by the multi-hollow surface dielectric barrier discharge generated in a perforated ceramic substrate with the air-exposed electrode is investigated under conditions of various discharge powers (1–5 W), air flow rates (0.25–2.4 L/min) and air relative humidities (0–80%). Production of ozone O₃, nitrous oxide N₂O, nitric oxide NO, nitrogen dioxide NO₂, dinitrogen pentoxide N₂O₅ and nitric acid HNO₃ is evaluated in terms of concentration (ppm), production yield (g/kWh) and production rate (mg/h). The work demonstrates a critical impact of both air flow rate and relative humidity on prevailing discharge mode (“O₃ mode” vs. “NO_x mode”) and, thus, on overall composition and concentration of produced gaseous species. For low discharge power, the discharge operates in the “O₃ mode”, when O₃, N₂O, N₂O₅ and HNO₃ are dominant gaseous products. With the increasing power, the discharge transfers into the “NO_x mode”, when N₂O and HNO₃ along with NO and NO₂ are mostly produced. In dry air, transition from “O₃ mode” to “NO_x mode” is found for the specific input energy of 1000–1100 J/L. With an increase of air relative humidity from 20 to 80%, the transition gradually decreases from approximately 600 to 450 J/L, respectively.

Surface dielectric barrier discharge (SDBD) ignited directly from the liquid electrodes at the 3-phase gas/liquid/solid interface represents a novel approach in both water and polymer surface treatment methods. This study investigates the gaseous and liquid-phase reactive oxygen and nitrogen species (RONS) generated by this discharge. The impact of the discharge power and treatment duration on the concentration of these species in both gas and liquid is explored. The spatial development of ozone, the prevailing molecule produced by air dielectric barrier discharge, is studied. The production yields of plasma-generated species in the gas are described. Additionally, the electrical measurements of the SBDB with liquid electrode are presented and its characteristics are discussed. The combined investigation of RONS production yields, electrical discharge characterization, and in-situ ozone evolution provides important information regarding the presence of the reactive species in the vicinity of the plasma discharge, supporting further development and targeted applications of this technology.

In this paper, multi-hollow surface dielectric barrier discharge generated by a perforated ceramic substrate in a configuration with the air-exposed electrode was investigated. The electrical characteristics (discharge power, peak, and average amplitude of current pulses) and optical characteristics (emission intensity) of the discharge were evaluated under various conditions of applied voltage (peak voltage 3–6 kV, frequency 200–2000 Hz), air flow rate (0.5–2.4 L/min), and air relative humidity (0%–80%). Temperature of ceramic substrate was also monitored. Statistical analysis of current pulses was also performed, and histograms of amplitudes of current pulses were calculated. The results showed that discharge characteristics strictly depend on given working conditions. The analysis of current pulses showed opposite trends in average overall number of positive and negative pulses with an increase of discharge power: number of positive current pulses gradually increased, while number of negative current pulses slightly decreased. The highest peak currents were found at 4 kV (1.8 W). With further increase of peak voltage, peak current decreased and beginning of detection of current pulses upon a rising (declining) slope of applied voltage was slightly shifted toward earlier times. At the highest applied peak voltage, pulses appeared even before polarity of applied voltage reversed. Therefore, we suppose that a residual charge accumulated on dielectric surface plays a crucial role in characteristics of the current pulses. Significant influence on current pulses and discharge emission intensity was also found with a change of air relative humidity, while the effect of air flow rate was found weaker.

Plasma catalysis has been utilized in many environmental applications for removal of various hydrocarbons including tars. The aim of this work was to study the tars removal process by atmospheric pressure DBD non-thermal plasma generated in combination with packing materials of various composition and catalytic activity (TiO₂, Pt/γAl₂O₃, BaTiO₃, γAl₂O₃, ZrO₂, glass beads), dielectric constant (5–4000), shape (spherical and cylindrical pellets and beads), size (3–5 mm in diameter, 3–8 mm in length), and specific surface area (37–150 m²/g). Naphthalene was chosen as a model tar compound. The experiments were performed at a temperature of 100 °C and a naphthalene initial concentration of approx. 3000 ppm, i.e., under conditions that are usually less favorable to achieve high removal efficiencies. For a given specific input energy of 320 J/L, naphthalene removal efficiency followed a sequence: TiO₂ > Pt/γAl₂O₃ > ZrO₂ > γAl₂O₃ > glass beads > BaTiO₃ > plasma only. The efficiency increased with the increasing specific surface area of a given packing material, while its shape and size were also found to be important. By-products of naphthalene decomposition were analyzed by means of FTIR spectrometry and surface of packing materials by SEM analysis.

The research was focused on oxygen nonthermal plasma regeneration of coke‐deactivated catalysts used for plasma‐catalytic toluene removal from air. The nonthermal plasma was generated in a packed‐bed dielectric barrier discharge reactor at atmospheric pressure using pellet‐shaped catalysts (TiO₂, γ‐Al₂O₃, Pt/γ‐Al₂O₃, Pd/γ‐Al₂O₃). Gaseous products of experiments were continuously analyzed by infrared spectroscopy. Plasma regeneration was compared with ozone and thermal regeneration. The results indicated that the plasma regeneration exhibited the highest coke removal efficiency; however, the regeneration was spatially non‐uniform, as confirmed by SEM and TGA. The effect of ozone and heat (100°C) was negligible. GC–MS analysis revealed that coke composed of long‐chain alkanes and oxygen‐ or nitrogen‐substituted aromatics was significantly reduced after plasma regeneration, unlike other regeneration techniques.