Rotating Gliding Arc Discharge Research Articles

The Influence of Vortex Formation on the Electrical Characteristics of Argon Plasma in a Rotating Gliding Arc Discharge

The Influence of Vortex Formation on the Electrical Characteristics of Argon Plasma in a Rotating Gliding Arc Discharge

Characteristics of rotating gliding arc induced thermal ignition of lean methane-air mixtures

The rotating gliding arc discharge (RGA) induced methane-air ignition process under the lean conditions is investigated by the high-speed videography and the numerical simulation, with the focus on the effects of dynamic discharge characteristics. The experimental and numerical results both indicate that the ignition process in the burner can be divided into two stages, including the waiting stage and the rapid flame propagation stage. The effective ignition time (τburner) including both stages decreases nonlinearly as the effective input ignition power (i.e. Pig/Pcomb) increases, following the exponential law, i.e. τburner=2.98 × 10−9(Pig/Pcomb)−7.299+81.75. It is because of that as the input power is relatively low τburner is governed by the duration of the waiting stage to decrease notably with the increment of the input power. However, as the input power is too large τburner becomes determined by the rapid flame propagation stage to be insensitive to the input power. The rotation frequency of the plasma sources can impact the τburner with that too low or too high frequency is detrimental to the ignition. The flame quenching is less likely to occur with the increase of the plasma volume. Based upon the experimental and numerical results, an RGA-induced ignition mechanism is proposed. It indicates that the two-staged ignition process is largely determined by the waiting stage, where multiple flame kernels are frequently initialized by the RGA to be locally quenched or propagate downstream/upstream with flow. Due to the recirculating flow, the energy released by the plasma and the ignited flame kernels can be accumulated upstream to reduce the local Ka number and enhance the flame propagation at the waiting stage. As Ka is lower than a critical value, the flame kernels can propagate rapidly to complete the ignition.

Rotating gliding arc discharge induced flame oscillation near the lean blowout limit

This work investigates the rotating gliding arc (RGA) assisted swirling methane combustion characteristics near the lean blowout limit by utilizing the high-speed videography. As the flow rate and the global equivalence ratio were varied, four flame modes, namely self-sustained flame, RGA-sustained stable flame, RGA-induced oscillating flame, and RGA anchored flame modes were detected. In particular, the oscillating flame mode with an oscillating frequency of 2∼4 Hz occurs with the air flow rates above 13 L/min and the equivalence ratio between 0.52 and 0.56. It is an RGA-induced low-frequency flame oscillation phenomenon. The RGA discharge characteristics can impact the oscillating behaviors that with the increase of the transformer input voltage, the flame oscillation frequency is enhanced and the averaged flame area becomes larger to result in a higher combustion efficiency. Besides, increasing the wall temperature of the combustion chamber promotes the combustion during the oscillating stage. Based upon the experimental and numerical results this RGA-induced low-frequency oscillating flame are further interpreted by a three-staged mechanism. It implies that the first stage, during which the fuel/oxidant mixture is refreshed in the chamber and the temperature increases through recirculating flow gradually, determines the oscillating frequency. The fast accumulation of released energy from plasma discharge and partial fuel burning by recirculation can accelerate the temperature growth in the recirculation zone to increase the oscillation frequency. In all, this unique oscillating phenomenon and related explanations indeed broaden our knowledge of oscillating combustion behaviors and GA assisted combustion.

(Invited, Digital Presentation) Eco-Friendly and Sustainable Ammonia Production with Atmospheric Pressure Rotating Gliding Arc Discharge

Increasing fossil-free global energy demands have motivated the scientific community to investigate new clean and sustainable techniques that can meet global energy demands. The production of green and sustainable fuel, such as ammonia, from base molecules like water and nitrogen using electricity from renewable sources shows great potential to solve energy issues. Non-thermal atmospheric pressure plasma-based ammonia synthesis has great potential for carbon-free fertilizer production powered by renewable electricity. We developed an atmospheric pressure rotating gliding arc discharge reactor coupled with a catalyst for a higher ammonia production rate. Here we reported two-step ammonia production, including 1) facile production of NOx and hydrogen from nitrogen discharge in water, and 2) highly selective catalytic reduction of NOx to ammonia in the presence of hydrogen. The studied plasma technique offers ~0.84 % ammonia concentration with ~95 % selectivity and a 120 µmol/s production rate by integrating a catalytic reduction system with plasma. Compared with previous studies on ammonia synthesis from nitrogen, the remarkable ammonia yield (300–400-fold higher). These promising results provide a breakthrough in the transition toward sustainable and environmentally friendly ammonia production.

Experimental Investigation on Kerosene Cracking Driven by Nanosecond Pulsed Rotating Gliding Arc Discharge Plasma

As an advanced technology that could achieve excellent cracking effects, nanosecond pulsed discharge plasma has attracted a lot of interest in recent years. In this article, nanosecond pulsed gliding arc discharge (GAD) plasma was developed for kerosene cracking. The influence of applied voltage, pulse repetition frequency (PRF), pulsewidth, and carrier gas flow rate on the cracking effects of the nanosecond pulse GAD plasma was investigated. Experimental results indicated that C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> had the highest production rate in all experimental conditions. The increase in applied voltage, PRF, and pulsewidth enlarges the SIE, which drops with greater carrier gas flow rate. Higher applied voltage promotes the secondary cracking of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> , C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> , and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> but influences the primary cracking (cracking of macromolecular hydrocarbons) slightly. Higher PRF and longer pulsewidth promote both the primary cracking and the secondary cracking of the gaseous light hydrocarbon. However, higher PRF could intensify the production of coke while longer pulsewidth inhibits it. Greater carrier gas flow rate would suppress the secondary cracking of gaseous light hydrocarbons while promoting the cracking of macromolecular hydrocarbons significantly.

Stability and Emission Characteristics of Ammonia/Air Premixed Swirling Flames with Rotating Gliding Arc Discharge Plasma

Stability and Emission Characteristics of Ammonia/Air Premixed Swirling Flames with Rotating Gliding Arc Discharge Plasma

Effect of gas flow rate on breakdown voltage in a rotating gliding arc reactor

Understanding breakdown phenomena in rotating gliding arc discharge (RGA) is of interest to tailor them for specific applications. This work revealed that the breakdown voltage in a RGA reactor was not dictated by collisional effects i.e., change in flow rate. The observation was consistent for both the discharge gas medium argon and nitrogen. The collisional effect variation was implemented by varying the operating flow rates i.e., 5 SLPM which is transitional in nature, and 50 SLPM which is turbulent in nature having localized micro-eddies. The observation also indicated failure of Paschen law in RGA having shortest gap between the electrodes of order of mm, operated under atmospheric pressure conditions. Collisional ineffectiveness indicates possibility of streamer formation which needs to be further investigated in future. This work marks preliminary and important step towards understanding the breakdown phenomena in atmospheric RGAs operated under different flow regimes such as laminar/transitional and turbulent.

Electrical and optical characterizations of a rotating gliding arc plasma-enhanced combustion dome in an aero-engine combustor

A gliding arc discharge is a typical method of producing non-equilibrium plasma, presenting excellent advantages in the field of enhanced combustion. In this study, a rotating gliding arc (RGA) plasma was combined with an aero-engine combustor dome to develop a RGA plasma-enhanced combustion dome. Experiments were conducted to investigate discharge, spectral, and infrared radiation temperature characteristics in the RGA plasma-enhanced combustion dome. Experimental results showed that two different discharge modes occurred during the RGA discharge process, the breakdown gliding mode and the steady arc gliding mode. The results had major implications for understanding the effects of the airflow rate and input voltage on the arc gliding mode transformation. The breakdown voltage, the average power, and the gliding arc rotational velocity increased with an increase in the airflow rate and a decrease of the input voltage. The spectral emission intensities of OH, O2, and O and vibrational temperature of N2 (C3Πu→B3Πg) were relatively high at a high airflow rate. Additionally, the RGA discharge had a weak temperature rise effect on electrode, which had no obvious impact on the discharge process. These characteristics could be important for future applications for controlling plasma-enhanced combustion process.

Influence of Operating Parameters on Plasma-Assisted Dry Reforming of Methane in a Rotating Gliding Arc Reactor

The environmental impact of greenhouse gases such as carbon dioxide and methane can be reduced if they are used as feedstock to synthesize chemical building blocks such as syngas (CO, H2) via dry reforming. Methane dry reforming is investigated using an Ar/CO2/CH4 rotating gliding arc (RGA) reactor powered by a dual-stage pulsed DC power supply. Tangential gas injection combined with a static magnetic field enabled the rotation and upward displacement of the arc along the conical cathode and the grounded anode, yielding to a larger plasma volume. Different parameters such as peak arc current (0.74 and 1.50 A), total gas flow rate (3.7, 4.7 and 6.7 SLPM), CO2/CH4 ratio (1.0, 1.5, 2.0) and gas inlet preheating (room temperature, 200 °C) were studied to determine the most efficient parameter combination. Gas conversion was measured online using a calibrated mass spectrometer and offline using a gas chromatograph. Noticeable increases in CO2 and CH4 conversions, as well as H2 and CO yields, were obtained when doubling the peak arc current. For the larger peak current, higher H2 yields were obtained at a CO2/CH4 = 1.0, and the best energy efficiencies were obtained at the lowest specific energy input values. No significant effect of the gas inlet temperature on the conversions or yields was found. Trace amounts of acetylene and ethylene, as well as some carbon deposits were observed as by-products of syngas generation. The low amount of by-products obtained implies a good selectivity for CO and H2, i.e., a cleaner syngas when produced with RGA discharge.

Simultaneous Removal of Toluene, Naphthalene, and Phenol as Tar Surrogates in a Rotating Gliding Arc Discharge Reactor

In this study, a rotating gliding arc (RGA) plasma reactor was investigated for the decomposition of gasification derived tar. Toluene, naphthalene, and phenol were selected as tar surrogates to be...

Experimental study on gliding discharge mode of rotating gliding arc discharge plasma

Alternating current rotating gliding arc discharge can produce large-scale, wide-range non-equilibrium plasma at atmospheric pressure. In order to investigate the gliding discharge mode, discharge characteristics and Spectral characteristics of AC rotating gliding arc discharge plasma, high speed camera, oscilloscope and spectrometer are used to collect discharge images and electrical signals of rotating gliding arc synchronously. Thus the dynamic behavior of arc and the characteristics of electric signal in the process of rotating gliding arc can be analyzed. The experimental results show that there are two different discharge modes in the rotating gliding arc discharge process, namely the breakdown gliding discharge mode (B-G mode) and the stable gliding discharge mode (A-G mode). The B-G mode is mainly characterized by high-frequency breakdown phenomenon (breakdown-extinguish-breakdown) during the arc gliding process, while the A-G mode is mainly characterized by stable continuous arc sliding. The paper also discusses the working mechanism in which the working parameters influence the gliding arc discharge characteristics. It is shown that the discharge mode and discharge characteristics of arc are the result of the combined action of excitation voltage and gas flow. When the gas flow is large and the excitation voltage is small, the gliding arc is an unstable discharge dominated by the B-G mode. Conversely, when the excitation voltage is large and the gas flow is small, the gliding arc is a stable gliding discharge dominated by the A-G mode. In addition, in B-G mode, the energy consumption is mainly concentrated in the breakdown moment, and the energy release is mainly pulsed. However, when the gliding arc discharge is in A-G mode, the energy dissipation is mainly used to maintain the continuous existence of the arc without extinguishing, and the energy release is stable and continuous. Affected by the gas flow rate and excitation voltage, the breakdown frequency of the B-G mode is greater than that of the A-G mode. Higher repeat breakdown frequency can cause multiple ionization in the process of gliding arc discharge, which produces more active particles. The research conclusions in this paper provide theoretical support for regulating the operating characteristics of the gliding arc discharge. In engineering application, the discharge mode, breakdown frequency and breakdown current of the gliding arc can be adjusted by changing the working parameters to obtain plasma sources with different characteristics.

Destruction of Toluene, Naphthalene and Phenanthrene as Model Tar Compounds in a Modified Rotating Gliding Arc Discharge Reactor

Tar removal is one of the greatest technical challenges of commercial gasification technologies. To find an efficient way to destroy tar with plasma, a rotating gliding arc (RGA) discharge reactor equipped with a fan-shaped swirling generator was used for model tar destruction in this study. The solution of toluene, naphthalene and phenanthrene is used as a tar surrogate and is destroyed in humid nitrogen. The influence of tar, CO2 and moisture concentrations, and the discharge current on the destruction efficiency is emphasized. In addition, the combination of Ni/γ-Al2O3 catalyst with plasma was tested for plasma catalytic tar destruction. The toluene, naphthalene and phenanthrene destruction efficiency reached up to 95.2%, 88.9%, and 83.9% respectively, with a content of 12 g/Nm3 tar, 12% moisture, 15% CO2, and a flow rate of 6 NL/min, whereas 9.3 g/kW·h energy efficiency was achieved. The increase of discharge current is advantageous in terms of decreasing black carbon production. The participation of Ni/γ-Al2O3 catalyst shows considerable improvement in destruction efficiency, especially at a relatively high flow rate (over 9 NL/min). The major liquid by-products are phenylethyne, indene, acenaphthylene and fluoranthene. The first two are majorly converted from toluene, acenaphthylene is produced by the co-reaction of toluene and naphthalene in the plasma, and fluoranthene is converted by phenanthrene.

Warm plasma activation of CO2 in a rotating gliding arc discharge reactor

Abstract In this study, a rotating gliding arc (RGA) warm plasma has been developed for the conversion of CO2 into CO and O2. The effect of feed flow rate, applied voltage, arc current, and the addition of N2 or Ar on the reaction performance has been investigated. The results show two variation patterns of CO2 conversion and energy efficiency, depending on the specific energy input (SEI): In Pattern A with SEI > 3.5 kJ/L, the CO2 conversion and energy efficiency decrease simultaneously with increasing SEI, while in Pattern B with SEI ≤ 3.5 kJ/L, the energy efficiency and the CO2 conversion show an opposite trend. The recombination of CO and O at high temperatures could be responsible for the decrease of CO2 conversion with rising SEI due to the increased retention time or gas temperature. A CO2 conversion of 4.0-4.4% and energy efficiency of 16-17% can be achieved. Compared to other non-thermal plasmas, the RGA plasma exhibits a lower CO2 conversion but higher energy efficiency, whilst maintaining a flow rate (e.g, 6-7 L/min) that is significantly higher than that of typical non-thermal plasmas (e.g., 20-125 ml/min in dielectric barrier and corona discharges). Increasing the fraction of N2 or Ar promotes the conversion of CO2 but lowers the energy efficiency. N2 is clearly more beneficial for enhancing the CO2 conversion in comparison to Ar. Further enhancement of the reaction performance can be expected by cooling the plasma area to lower the gas temperature, to limit the recombination of CO and O.

Dry reforming of CH4[sbnd]CO2 in AC rotating gliding arc discharge: Effect of electrode structure and gas parameters

Conversion of CH4 and CO2 into synthesis gas has been performed in a rotating gliding arc discharge (RGAD) reactor driven by a high frequency AC power. Influence of electrode structure and gas parameters on RGAD plasma CH4CO2 conversion and energy efficiency of the process was investigated. Summit angle of internal electrode is an important parameter affecting the stability of the reaction. Internal electrode with summit angle of 45° is more favorable for CH4 and CO2 conversions. The energy efficiencies increase by 25% and 22% than those in RGAD involving internal electrode with summit angle of 30° and 60°, respectively. Longer external electrode improves the arc extension leading to an increase of 17% and 25% in CO2 and CH4 conversion at the applied voltage of 11 kV. Feed flow rate has significant impact on the CO2 and CH4 conversion, while low CO2/CH4 ratio inhibits rotating gliding arc extension due to carbon-black deposition. A large number of graphene quantum dots have been observed to generate on the lamellar ley of the carbon-black. Maximum energy efficiency of 3.9 mmol/kJ is achieved at feed flow rate of 3 L/min and CO2/CH4 ratio of 3:2 in this work.

Co-generation of hydrogen and carbon aerosol from coalbed methane surrogate using rotating gliding arc plasma

A novel atmospheric pressure non-thermal plasma, i.e., rotating gliding arc (RGA), is developed to upgrade coal bed methane (CBM) into hydrogen and carbon aerosol simultaneously. CH4 is used as a CBM surrogate. In present work, the V-I characteristics of RGA discharge in CH4 conversion are monitored with different gases (N2, Ar and CO2) as carrier gas, while the active species (such as OH, CH, CN, C2, excited molecules and ions) involved in the plasma reactions are identified by optical emission spectroscopy (OES). According to the sensitivity analysis of specific energy density (SED), the importance of operating conditions on SED sensitivity is in a sequence of CH4 concentration>applied voltage>residence time. The performance of CH4 conversions are comparatively evaluated based on the variation of operating conditions. In general, the enhancement of applied voltage and residence time effectively increases the CH4 conversions, selectivity of hydrogen, as well as the energy efficiency, while the augment of CH4 concentration has a negative effect in contrast. The carbon aerosol obtained in CH4/N2 and CH4/Ar discharge are comparatively investigated. Transparent crumped-like graphene sheets and spherical nanostructure carbon are observed in both obtained carbon aerosol, with relative high ID/IG ratios (∼0.62) indicated in Raman spectroscopy. High C/O ratios (>14) are obtained in the XPS survey spectra, with the intensity ratios of sp2 CC/sp3 C-C occupy about 80%. However, the BET surface area of carbon obtained from CH4/N2 is almost 3 times larger than that from CH4/Ar discharge. In addition, super hydrophobic and oleophilic properties are observed in both carbon samples. The contact angles of water droplets are above 130°, while the contact angle of oil is less than 4°.

Destruction of toluene by rotating gliding arc discharge

Non-thermal plasma is considered as an alternative treatment of tar present in the effluent from gasification processes. In this study, a novel rotating gliding arc (RGA) discharge reactor was developed for tar destruction. Toluene in nitrogen flow was used as a tar surrogate. The physical features of RGA discharge and its application to toluene destruction are investigated at different input concentrations and total gas flow rates. As a result, the highest destruction efficiency could exceed 95%, with a toluene concentration of 10g/Nm3 and a total flow rate of 0.24Nm3/h. The two major gaseous products are H2 and C2H2, with maximum selectivity of 39.35% and 27.0%, respectively. A higher input concentration slightly reduces this destruction efficiency but the energy efficiency further expanded, with a highest value of 16.61g of toluene eliminated/kWh. In addition, the liquid and solid byproducts are collected downstream of the RGA reactor and determined qualitatively and semi-quantitatively. The amount and structure of these by-products is instructive for reaching a better comprehension of the chemical consequences of plasma treatment to the model compound and to the carrier gas nitrogen.

Investigation of the Physical Properties in Rotating Gliding Arc Discharge With Rapeseed Oil

With the benefits of the high chemical selectivity and low energy cost, atmospheric rotating gliding arc (RGA) plasma is considered as a promising method in various industrial applications. In this paper, rapeseed oil is first proposed as the raw material to produce high-valued chemical products by RGA plasma. The influences of operating conditions (applied voltage, oil flow rate, and gas flow rate) on RGA discharge with rapeseed oil are focused, in terms of the basic physical properties (V-I characteristics and discharge visualization) investigated using electrical diagnostics and high-speed photography. Blank experiments are conducted by supplying only pure N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas. The visual images presented complex arc dynamic behavior in N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> discharge, with the phenomenon of arc contact spot leap, spatial curl arc, and cracked. Intense purple light emission was observed by adding 3-mL/min oil droplets with four distinguished reaction stages. According to the electrical results, average current and power of arc increased with increasing applied voltage, while the average voltage indicated opposite variation tendency in different feedstocks. The augment of rapeseed oil flow rate decreased the average voltage and power, whereas raised the average current value in contrast.

Determination of Spectroscopic Temperatures and Electron Density in Rotating Gliding Arc Discharge

The spectroscopic characteristics of rotating gliding arc (RGA) discharge, codriven by a magnetic field and tangential gas flow, have been investigated by optical emission spectroscopy. In argon gas, the electron density of the atmospheric RGA plasma was measured, while the vibrotatinoal temperatures were measured in nitrogen discharge. By simulating the spectral line profile determined by the joint effects of Lorentzian (Stark, van der Waals, and natural) and Gaussian (Doppler and instrumental) broadening, the electron density fluctuated in the range of 1.32×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> -4.56×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> and 4.06×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> -5.74×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> within the variation of argon flow rate and applied voltage, respectively. The rotational temperature in N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> discharge was obtained by comparing the modeled optical emission spectrum with the experimental measurements. The vibrational temperature was derived from a Boltzmann plot by analyzing the spectral bands of the second positive system of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> → B <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ). The vibrational and rotational temperatures varied in the range of 0.1-0.13 eV and 0.42-0.44 eV, respectively, under the same operating condition, indicating that the RGA discharge is a nonequilibrium plasma. By analyzing the fundamental spectroscopic parameters of the discharge, a comprehensive understanding of RGA plasma was achieved, facilitating its application in practical industry processes.

Study of the dry methane reforming process using a rotating gliding arc reactor

Dry methane reforming (DMR) via rotating gliding arc (RGA) discharge, co-driven by a magnetic field and tangential flow, was investigated in this study. Optical emission spectroscopy (OES) was used to characterize the major active species (energetic electrons, radicals, ions, atoms and excited molecules) in the DMR chemical process. The influence of the operational conditions (applied voltage and CH4/CO2 ratio) on the basic spectroscopic parameters (electron excitation temperature, electron density and rotational temperature) was determined by spectroscopic methods. The rotational and electron excitation temperatures were approximately 1100–1200 K and 1.1–1.7 eV, respectively, indicating the non-thermal equilibrium characteristics of the RGA discharge. The electron density was approximately 5–20 × 1021 m−3 by fitting the line shape of Hα at 656 nm. The conversions of the reactants (CH4 and CO2) and the selectivities of the products (H2, CO and C2 hydrocarbon) were analyzed using a gas chromatograph (GC) under different energy inputs or feed gas proportions. The structure and morphology of carbon black produced during the chemical process was characterized by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy, indicating the properties of electrical conductivity and high absorption capacity that can be useful for potential application.

Decomposition of Toluene in a Rotating Glidarc Discharge Reactor

Decomposition of toluene as a typical aromatic volatile organic compound was experimentally investigated in a rotating gliding arc discharge nonthermal plasma reactor. The experiments were conducted at a gas flow rate of 5.4–10.8 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{m}^{3}\hbox{h}^{-1}$</tex></formula> . Important parameters, including applied voltage, gas flow rate, initial concentration, and water vapor concentration, were investigated. The results showed that a higher applied voltage results in higher toluene removal and higher power deposited into a discharge system; the decomposition achieved was highly dependent on the total gas flow rate. Under the fixed specific energy density (SED), both toluene removal efficiency and energy efficiency decrease with the increase in gas flow rate. The removal efficiency of toluene decreased with an increase in the initial concentration, whereas the absolute removal amount and energy efficiency increased. For example, the removal efficiency decreased from 77% to 56% with the initial toluene concentration ranging from 200 to 2000 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{m g}^{-3}$</tex></formula> as the SED was 266 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{J L}^{-1}$</tex></formula> ; the toluene removal efficiency evidently increased as the water vapor concentration increased from 0.5945 to 1708.3435 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{mg m}^{-3}$</tex></formula> . A dynamics model was developed to describe the relation of the removal efficiency with SED and initial concentration.