Dielectric Barrier Discharge Plasma Reactor Research Articles

Effect of atmospheric pressure cold plasma (ACP) treatment on the technological characteristics of quinoa flour

Atmospheric pressure cold plasma (ACP) is considered as non-thermal treatment with potential microbial inactivation efficiencies. This study is aimed to determine the effect of ACP treatment on technological characteristics of quinoa flour using Fourier Transform Infrared Spectroscopy, flour hydration characteristics, thermal properties, rheological measurement and morphological characterization. Whole quinoa grains were subjected to a dielectric barrier discharge plasma reactor for 5 min at 50 kV, 10 min at 50 kV, 5 min at 60 kV and 10 min at 60 kV known as S1, S2, S3 and S4 respectively. Untreated sample is named as control sample. Results indicated the significant impact of ACP treatment on rheological, thermal, hydration and morphological characteristics of quinoa flour depending on the exposed time and voltage. For example, while a voltage dependent decrease (p < 0.05) has been found in enthalpy with values equal to 743.6 ± 0.5, 1395 ± 1, 635.6 ± 0.6 and 804.3 ± 0.9 J/g for S1, S2, S3 and S4 respectively, it is positively influenced by increasing the exposure time at constant voltage. Consequently, it seems that the influence of ACP treatment on technological characteristics which is mainly induced by time- and/or voltage-dependent changes in proteins and starch structures needs to be optimized regarding the desired behavior characteristics.

In Situ Identification of NNH and N2H2 by Using Molecular-Beam Mass Spectrometry in Plasma-Assisted Catalysis for NH3 Synthesis

Ammonia synthesis at 533 K and atmospheric pressure was investigated in a coaxial dielectric barrier discharge (DBD) plasma reactor without packing and with porous γ-Al2O3, 5 wt % Ru/γ-Al2O3, or 5 ...

Plasma-assisted catalysis for ammonia synthesis in a dielectric barrier discharge reactor: key surface reaction steps and potential causes of low energy yield

Ammonia synthesis experiments were carried out in a coaxial dielectric barrier discharge (DBD) reactor packed with several different supports and metal catalysts. There was a marked increase in the reaction rate, over that obtained in an empty DBD plasma reactor, upon introduction of a packed bed of γ-Al2O3, Ru/γ-Al2O3, or SiO2 particles. The difference in the reaction rates over γ-Al2O3 and Ru/γ-Al2O3 was minimal. Complementary zero-dimensional plasma kinetic model analysis was also performed using inputs from experimental data. This kinetic analysis allowed for gas phase reactions, Eley–Rideal (E–R) reactions, and direct adsorption of radical species on the γ-Al2O3 surface. On the metal surface, dissociative adsorption of N2 and H2, and Langmuir–Hinshelwood reactions were also included. This analysis revealed that, under the conditions of our experiments, ammonia synthesis proceeds principally by the formation of reactive radicals in the gas phase, which then adsorb and participate in E–R reactions on both the metal and support material surfaces. This finding illustrates a challenge for substantially increasing the energy yield for plasma-assisted ammonia synthesis in typical DBD reactors containing packed catalyst beads.

Numerical modeling and mechanism investigation of nanosecond-pulsed DBD plasma-catalytic CH4 dry reforming

Plasma-catalytic CH4 dry reforming is an emerging technology that takes advantage of plasma-catalysis interactions to implement the conversion of CH4 and CO2 into syngas and valuable chemicals. In this work, an experiment is conducted to determine the reduced electric field E/N in the numerical modeling. In addition to essential reactor parameters, catalysis characteristics are integrated into the modeling. The 3D geometry of a nanosecond (ns) pulsed DBD plasma reactor for plasma-catalytic CH4 dry reforming is reduced into a 0D kinetics model to investigate the inherent plasma-catalysis mechanisms. The simulation results indicate that C2O4 + and CH4 +, H and O, and CH4(v 13) are the dominant ions, radicals and vibrationally excited species, respectively. Although the reactions related to CH4 and CO2 consume 19.7% and 80.3% of the total electron energy, the electron energy loss caused by the CH4 ionizations (1.3%) is distinctly higher than that caused by the CO2 ionizations (0.4%). Surface reactions can generate a large amount of adsorbed species CH3(s), H(s), CO(s) and O(s). An amount of 77.2% of formaldehyde is produced by the reaction between CH3 and O. In addition, methanol is derived from the reactions between CH3 and OH in the pulsed dielectric barrier discharge (DBD) plasma catalytic reforming CH4/CO2. This numerical modeling reflects the practical plasma-catalysis system and therefore should be a novel tool to further understand the complicated underlying mechanism of the ns-pulsed DBD plasma-catalytic CH4 dry reforming.

Plasma synthesis of ammonia in a tangled wire dielectric barrier discharge reactor: Effect of electrode materials

Plasma synthesis of NH3 from N2 and renewable H2 under mild conditions is very attractive for decentralised sustainable green ammonia production using intermittent renewables. In this study, NH3 synthesis was performed under ambient conditions in a dielectric barrier discharge (DBD) plasma reactor. Different tangled wire internal electrodes were employed to understand the influence of electrode materials on plasma ammonia synthesis. Compared with a rod electrode, a tangled wire electrode substantially enhanced the NH3 concentration and reduced the energy cost for ammonia production, which can be attributed to the expanded surface area and the chemisorption properties of the tangled electrodes. The influence of the N2/H2 molar ratio and total flow rate on the reaction performance was also evaluated. The lowest energy cost (59.0 MJ mol−1) for ammonia production was achieved using a Cu tangled electrode at a total flow rate of 250 ml min−1 and a discharge power of 20 W. The electrical diagnostics of the plasma process showed that the tangled wire electrodes decreased the breakdown voltage of the DBD and enhanced charge deposition, which enhanced the NH3 production. The reaction mechanism was discussed for the process optimisation of ammonia synthesis in a tangled wire DBD system.

PHI-004 - Effectiveness of ozone generated by dielectric barrier discharge plasma reactor against multidrug-resistant bacteria and Clostridium difficile spore

PHI-004 - Effectiveness of ozone generated by dielectric barrier discharge plasma reactor against multidrug-resistant bacteria and Clostridium difficile spore

Plasma catalysis of diesel exhaust for NOX removal: a case study with industrial wastes

ABSTRACT In the current work, a novel combination of discharge plasma and industrial wastes has been proposed to explore the possibility of treating the oxides of nitrogen (NOX) in diesel exhaust through plasma-activation of abundant and freely available industrial wastes. Five industrial wastes have been selected for testing as potential catalysts, namely fly ash, foundry sand, bagasse, mulberry residue, and oyster shells. The diesel exhaust was treated using plasma catalysis, by allowing it to flow through a dielectric barrier discharge plasma reactor packed with industrial waste pellets, at ambient temperature and atmospheric pressure. An increase in NOX removal during plasma catalysis, in comparison to plasma-only treatment, was observed through experiments conducted using the pellets. Maximum removal of NOX (70%) was obtained during plasma catalysis using oyster shell pellets. The results have been discussed in detail along with the possible reaction pathways and explanations for the NOX removal during plasma catalysis.

Elimination of Microcystis aeruginosa in water via dielectric barrier discharge plasma: Efficacy, mechanism and toxin release

Microcystis aeruginosa (M. aeruginosa), as the representative hazardous algae in cyanobacteria blooms, has long posed a threat to aquatic ecosystems. Here, a self-cooling dielectric barrier discharge plasma (DBDP) reactor was used to eliminate M. aeruginosa in water. The removal efficiency and mechanism of DBDP for M. aeruginosa and its toxin release during the treatment process was investigated. The results showed that over 99% of M. aeruginosa cells were removed by DBDP over 60 min under optimal conditions, and treated M. aeruginosa lost their ability to reproduce entirely. Reactive species generated in the self-cooling DBDP reactor damaged the membrane of M. aeruginosa, leading to leakage and degradation of dissolved organic matter. Increased intracellular reactive oxygen species accelerated the breakdown of protein and enzyme, and causes cell cytolysis. Eventually, M. aeruginosa was mineralized and lost its activity. The ·OH, 1O2 and ·O2- were crucial for inactivating M. aeruginosa. During the treatment process, the toxin microcystin-LR increased in the first 20 min, but declined over time: its concentration fell below 1 μg·mL-1 after 60 min. This study provides insight into M. aeruginosa’ s elimination in water by DBDP and has significant implications for developing a plasma technique to curtail cyanobacteria bloom.

Study of selective hydrogenation of biodiesel in a DBD plasma reactor

In order to achieve the selective hydrogenation of biodiesel at room temperature and under normal pressure, we researched the upgrading of soybean biodiesel using a dielectric-barrier discharge (DBD) reaction system. Using Raney-Ni as the hydrogenation catalyst, the effects of the operating parameters on the hydrogenation depth and the selectivity of biodiesel were systematically analyzed. The results show that the polyunsaturated components in soybean methyl ester were reduced by 57.04%, and that the polyunsaturated components were hydrogenated to monounsaturated components with a selectivity of 77.75%. Based on the gas chromatography and mass spectrometry (GC-MS) test results, we established a kinetic model for biodiesel hydrogenation. A comparison of the calculated and experimental results shows that the hydrogenation of the biodiesel can be described by a quasi first-order reaction model. The calculated reaction rate constants indicate that under DBD plasma reaction conditions, the hydrogenation of biodiesel has high selectivity for the formation of monounsaturated components.

Regeneration of an aged hydrodesulfurization catalyst: Conventional thermal vs non-thermal plasma technology

This study compares the regeneration efficiency of an aged industrial hydrodesulfurization catalyst (CoMoP/Al2O3) by conventional and alternative routes: thermal oxidation versus non-thermal plasma technology (NTP). Spent, partially, and fully regenerated catalysts have been characterized by XRD, XPS, and toluene hydrogenation to measure hydrogenating activity. Complete regeneration of the HDS catalyst via NTP requires the heating of the dielectric barrier discharge plasma reactor. Total removal of coke is obtained from 250 °C by applying only 8.6 W/gcatalyst, against 400 °C by conventional thermal treatment. The hydrogenation activity of the regenerated catalyst by NTP assisted by temperature is higher than that obtained by traditional thermal regeneration practiced industrially. Plasma treatment mitigates the oxide sintering but leads to the formation of cobalt oxide species preventing Co of fully playing its role as MoS2 slabs promoter. HDS catalyst regeneration using non-thermal plasma assisted by low temperature appears as a promising alternative to thermal combustion.

Plasma dielectric barrier discharge for degradation of textile wastewater in a continuous system

Plasma Dielectric Barrier Discharge (DBD) can be applied to degrade textile wastewater. In this study, a DBD plasma reactor was composed of two electrodes of stainless-steel mesh as the outer electrode and Cu wire as the inner electrode with pyrex glass as the dielectric barrier. The electrodes were connected to an AC voltage of 3.07 kV. As much as 1500 ml of textile wastewater has flowed continuously into the system. Variations time of treatment were 0, 30, 60, 90, and 120 minutes. Physical parameters of textile wastewater such as pH, total dissolved solid (TDS), and absorbance were measured before and after treatment to determine the effect of plasma. As a result, the highest degradation efficiency of 54.29% was obtained after treating the textile wastewater for 120 min.

Highly energy-efficient degradation of antibiotics in soil: Extensive cold plasma discharges generation in soil pores driven by high voltage nanopulses

Cold atmospheric plasma (CAP) is a green and promising soil remediation approach with significant advantages in terms of energy consumption, removal efficiency and treatment time. The most critical factor for exploiting CAP is the accomplishment of very low remediation cost, while in parallel, the limited penetration of plasma species at soil layers holds back its wider implementation. In this study, we developed a novel dielectric barrier discharge plasma reactor driven by high voltage nanosecond pulses (NSP) able to generate micro-discharges within the interconnected soil pores facilitating the effective transport of reactive species within soil layers. Key-role parameters were investigated such as pulse voltage and pulse frequency, soil thickness and air flow rate. The effectiveness of the method was identified against different types of soil (sandy soil and loam soil), both under high and low ciprofloxacin concentration in soil, while soil moisture impact on degradation efficiency was also explored. An energy efficiency of 21.2 mg of pollutant/kJ was accomplished, which is the highest ever reported for CAP-based soil remediation. The most stable intermediate degradants of ciprofloxacin, and the associated degradation pathways were identified in a kinetic point of view, while the elimination of the toxic intermediates after treatment was ensured. The present effort provides a new highly energy efficient perspective for future development of a CAP-based soil remediation technology as it maximizes the transfer and penetration of plasma species in soil layers under very low estimated remediation cost (~0.4-1.2 €/tn of soil).

The chemical kinetics studies of methylene blue degradation treated in dielectric barrier discharge (DBD) plasma with and without TiO2 photocatalyst

The presence of textile industry color-wastewater in a toxic environment needs to be treated to reduce the toxicity. The wastewater treatment can be performed by the combination technique of photocatalysis and plasma ozonation. The kinetics studies of these techniques are interesting to be studied to investigate which process is more dominant when playing a role in pollutant degradation. In this study, the kinetic study of a combination technique of plasma ozonation and photocatalysis using TiO2 was analyzed using a methylene blue (MB) dye pollutant model. The study was compared to the kinetic study of the plasma ozonation alone. The plasma ozonation was generated by a dielectric barrier discharge (DBD) plasma reactor, which used two electrodes separated by a dielectric barrier of quartz glass, which high voltage 5 kV (AC power supply) and an airflow rate of 1 L/min. The results of the experiment show that MB concentration after DBD treatment decreased. The chemical kinetics test is able to determine the reaction order, in which the treatment process using DBD plasma with photocatalyst TiO2 follows the second order. In contrast, those using DBD treatment without TiO2 follows the first order.

Recent Developments in Dielectric Barrier Discharge Plasma-Assisted Catalytic Dry Reforming of Methane over Ni-Based Catalysts

The greenhouse effect is leading to global warming and destruction of the ecological environment. The conversion of carbon dioxide and methane greenhouse gases into valuable substances has attracted scientists’ attentions. Dry reforming of methane (DRM) alleviates environmental problems and converts CO2 and CH4 into valuable chemical substances; however, due to the high energy input to break the strong chemical bonds in CO2 and CH4, non-thermal plasma (NTP) catalyzed DRM has been promising in activating CO2 at ambient conditions, thus greatly lowering the energy input; moreover, the synergistic effect of the catalyst and plasma improves the reaction efficiency. In this review, the recent developments of catalytic DRM in a dielectric barrier discharge (DBD) plasma reactor on Ni-based catalysts are summarized, including the concept, characteristics, generation, and types of NTP used for catalytic DRM and corresponding mechanisms, the synergy and performance of Ni-based catalysts with DBD plasma, the design of DBD reactor and process parameter optimization, and finally current challenges and future prospects are provided.

CO2 conversion promoted by potassium intercalated g-C3N4 catalyst in DBD plasma system

The direct conversion of CO2 to CO and O2 has attracted extensive attention as CO is a key C1 feedstock for chemical synthesis. The CO2 conversion promoted by γ-Al2O3 supported potassium intercalated g-C3N4 (KuCN/AO) catalyst in a packed-bed dielectric barrier discharge (DBD) plasma system was investigated. A coaxial cylinder DBD plasma reactor was used with Cu powder as the high voltage electrode. Reactor temperature showed converse effect on CO2 conversion. As the reactor temperature decreased from 120 ℃ to 50 ℃, CO2 conversion rate and energy efficiency both increased by ca. 50%. After the catalyst was filled into the discharge area, the discharge mode changed from filamentary discharge to the combination of filamentary-surface discharge. The morphology and structure of KuCN was characterized by SEM, XRD, FTIR and XPS. KuCN kept a porous structure and K element distributed uniformly between CN interlayer spacing. In KuCN/AO assisted DBD plasma system, the highest CO2 conversion rate, CO yield and energy efficiency were increased from 11.1%, 10.0% and 9.41% to 19.3%, 18.1% and 20.6% compared with pure DBD/γ-Al2O3 system, respectively. The main mechanism of KuCN assisted enhancing CO2 conversion in packed-bed DBD reactor was analyzed. The larger specific surface area, layers bridging and charge redistribution enabled KuCN/AO to obtain good plasma-catalytic CO2 conversion performance.

Plasma propagation in a single bead DBD reactor at different dielectric constants: insights from fluid modelling

Packed bed dielectric barrier discharge (PB-DBD) plasma reactors are very promising for various plasma catalysis applications, but the exact mechanisms of plasma–catalyst interaction are far from understood, because the plasma discharge and catalyst/packing properties are mutually dependent. To better understand the effect of packing dielectric material on the electrical plasma properties, we study here a single bead DBD plasma reactor operating in dry air, with beads of different dielectric constant and for different applied voltages, by means of fluid modelling validated by optical imaging experiments. Our study reveals that the plasma in the single bead DBD reactor can manifest itself in two different modalities, i.e. (a) polar discharges at the bead poles in contact with the electrodes, and (b) a streamer discharge caused by surface ionization waves, which bridges the gas gap. Beads with high dielectric constant result in localised electric field enhancement and hence yield a reduction of the applied voltage required for plasma production. At low applied voltage, the discharge appears as polar discharges between the bead and the electrodes, and upon higher voltage it undergoes a transition into a bridging streamer discharge. The transition voltage to the streamer mode rises for beads with higher dielectric constant. These observations are important for plasma catalysis applications. A higher dielectric constant yields a higher electric field and thus higher average electron energy and density, giving rise to more reactive species, but it also yields a confined discharge near the contact points of packing beads, limiting the interaction area between the catalyst and the active plasma species. In addition, our model reveals that the dielectric bead behaves as a capacitor and traps charges, which can explain the significant occurrence of partial discharging in PB-DBDs and non-parallelogram shaped Lissajous plots. Hence, equivalent circuit modelling of PB-DBDs should take into account the role of packing beads in charge trapping as a capacitor.

Plasma-activated water from DBD as a source of nitrogen for agriculture: Specific energy and stability studies

Successful application of plasma-activated water (PAW) as an alternate source of nitrogen for agricultural application requires low specific energy consumption. This work reports on a dielectric barrier discharge (DBD) plasma reactor for the generation of PAW having low specific energy (SE) consumption. The SE to produce N in PAW was 3.26 GJ/kg of N, which is 68% lower than the lowest value reported to date for DBD-PAW systems. The PAW generated was characterized for its physico-chemical parameters, most of which showed a linear increase with activation time (ta). The concentration of hydrogen ion and that of the nitrate, which is the desired product for agricultural application, remained stable for four weeks in the PAW. The results indicate that minimal reactive oxygen species was formed in the plasma zone and only reactive nitrogen species (RNS) was formed confirming selectivity toward RNS.

Removal of benzene as a tar model compound from a gas mixture using non-thermal plasma dielectric barrier discharge reactor

In the present work, the decomposition of benzene as a tar model compound was studied in a gas mixture (CO2, H2, CO, and CH4) using a dielectric barrier discharge (DBD) non-thermal plasma reactor. The combined effect of temperature and power was studied to investigate the performance of the DBD reactor. The decomposition of tar compound increased from 49.9 to 96% with increasing specific input energy (SIE) from 2.05 to 16.4 kWh/m3. The major products were lower hydrocarbons (C2–C5) and solid residues. The higher temperature (400 °C) in the presence of plasma (40 W), decreased the conversion of tar compound from 96 to 78%. However, the selectivity of lower hydrocarbons increases substantially to 52%, and the formation of solid residues is significantly reduced. Hence, the problematic solid residues formation can be controlled at a higher temperature during the treatment of gasifier product gas using non-thermal plasma.

Probing the impact of material properties of core-shell SiO2@TiO2 spheres on the plasma-catalytic CO2 dissociation using a packed bed DBD plasma reactor

Plasma catalysis, a promising technology for conversion of CO2 into value-added chemicals near room temperature, is gaining increasing interest. A dielectric barrier discharge (DBD) plasma has attracted attention due to its simple design and operation at near ambient conditions, ease to implement catalysts in the plasma zone and upscaling ability to industrial applications. To improve its main drawbacks, being relatively low conversion and energy efficiency, a packing material is used in the plasma discharge zone of the reactor, sometimes decorated by a catalytic material. Nevertheless, the extent to which different properties of the packing material influence plasma performance is still largely unexplored and unknown. In this study, the particular effect of synthesis induced differences in the morphology of a TiO2 shell covering a SiO2 core packing material on the plasma conversion of CO2 is studied. TiO2 has been successfully deposited around 1.6–1.8 mm sized SiO2 spheres by means of spray coating, starting from aqueous citratoperoxotitanate(IV) precursors. Parameters such as concentration of the Ti(IV) precursor solutions and addition of a binder were found to affect the shells’ properties and surface morphology and to have a major impact on the CO2 conversion in a packed bed DBD plasma reactor. Core-shell SiO2@TiO2 obtained from 0.25 M citratoperoxotitante(IV) precursors with the addition of a LUDOX binder showed the highest CO2 conversion 37.7% (at a space time of 70 s corresponding to an energy efficiency of 2%) and the highest energy efficiency of 4.8% (at a space time of 2.5 s corresponding to a conversion of 3%).

Advanced nanoscale characterization of aluminum nanoparticles with modified surface morphology via atmospheric helium and carbon monoxide plasmas

Aluminum nanoparticles (nAl) have the potential as energetic additives in explosive/propellant formulations. Scalable methodologies must be pursued to mitigate the inactive amorphous alumina shell surrounding the active aluminum (Al) core with modified surface morphology and chemistry for increased combustion effects. This paper explores the feasibility of making reactive core/shell nAl with thinned oxide shells and modified surface coatings via a two-step atmospheric plasma surface treatment process in a custom dielectric barrier discharge plasma reactor. The commercial nAl of nominal average size ∼40–60 nm was first treated with helium (He) followed by He/carbon monoxide (CO) plasmas for different durations. The resultant samples were characterized via high-resolution transmission electron microscopy (HRTEM) and Fourier transform IR (FTIR) spectra. HRTEM images revealed sporadic patchy γ-alumina deposits on particle surfaces and in gaps among particles for all samples, suggesting the non-uniform plasma effects of the He/CO glow. Nanoscale chemical analyses via scanning transmission electron microscopy elemental mapping and x-ray energy dispersive spectroscopy were further performed. Although no carbon-associated structure appeared in electron energy loss spectroscopy (EELS) spectra, the presence of carbonaceous materials was confirmed as a thin dispersive layer evenly distributed on the nAl surface suggesting either its amorphous nature or is present at a level insufficient to generate satisfactory EELS spectra. The trend of intensity profiles for key elements acquired by drawing lines across a single particle on the elemental maps confirmed that carbonaceous materials only existed on the surface and they were most likely carboxylates that increased with increased He/CO treatment duration, as evident by FTIR results. This work demonstrated the success of atmospheric plasma-treated reactive nAl with comprehensively characterized surface features via advanced microscopy and spectroscopy.