Discharge Reactor Research Articles

A Comparative Investigation of an Argon Dielectric Barrier Discharge Reactor under the Variation of Plasma Conditions for Optimization of Power Deposition

A Comparative Investigation of an Argon Dielectric Barrier Discharge Reactor under the Variation of Plasma Conditions for Optimization of Power Deposition

Impact of the geometric structure parameter on the performance of dielectric barrier reactor for toluene removal.

The reasonable geometry design of non-thermal plasma (NTP) reactor is significant for its performance. However, optimizing the reactor structure has received insufficient attention in the studies on removing volatile organic compounds by NTP. Several dielectric barrier discharge (DBD) reactors with various barrier thicknesses and discharge gaps were designed, and their discharge characteristics and toluene degradation performance were explored comprehensively. The number and intensity of current pulses, discharge power, emission spectrum intensity and gas temperature of the DBD reactors increased as barrier thickness decreased. The toluene removal efficiency and mineralization rate increased from 23.2-87.1% and 5.3-27.9% to 81.7-100% and 15.9-51.3%, respectively, when the barrier thickness reduced from 3 to 1 mm. With the increase of discharge gap, the breakdown voltage, discharge power, gas temperature and residence time increased, while the discharge intensity decreased. The reactor with the smallest discharge gap (3.5 mm) exhibited the highest toluene removal efficiency (78.4-100%), mineralization rate (15.6-40.9%) and energy yield (8.4-18.7 g/kWh). Finally, the toluene degradation pathways were proposed based on the detected organic intermediates. The findings can provide critical guidance for designing and optimizing of DBD reactor structures.

Insights on dielectric barrier discharge plasma treatment of oil drilling cuttings

Oil drilling cuttings produced during oil exploration and extraction contain a high percentage of crude oil, ranging from 5% to 20% weight ratio (w/w) on a dry basis, and must be managed and treated properly before their release to the environment. In this study, non-thermal plasma (NTP) was investigated as an advanced oxidation process for the efficient, sustainable and cost-effective treatment of oil drilling cuttings. To this end, a plane-to-grid dielectric barrier discharge (DBD) reactor operating at atmospheric pressure was tested under different plasma conditions. The effect of treatment time, DBD power and air flow rate on the total organic carbon (TOC) removal efficiency was assessed and the energy efficiency of the process was determined. Within 10 min of plasma treatment, a very high TOC and total petroleum hydrocarbons (TPH) removal (∼90% and ∼99%, respectively) was achieved, while polycyclic aromatic hydrocarbons (PAHs) were degraded by ∼50% within 2 min of treatment. Depending on the experimental conditions, the energy efficiency of the process varied from 5 to 35 mg/kJ. From GC-MS analysis, several byproducts of the oxidation of oil drilling cuttings were identified, while the analysis of exhaust gases revealed that ∼85.1% of the removed organics from oil drilling cuttings was transformed to CO2 and CO. This study provides critical information on the effectiveness of the NTP process for the treatment of heavily contaminated solid wastes and can be considered as the critical step for its application for the treatment of solid wastes from the oil industry.

Physicochemical Characteristics and Antimicrobial Efficacy of Plasma-Activated Water Produced by an Air-Operated Coaxial Dielectric Barrier Discharge Plasma

In this study, Plasma-Activated Water (PAW) was synthesized using a coaxial Dielectric Barrier Discharge (DBD) reactor, benefiting from the elevated capacity of air-flow-assisted DBD discharges to enhance nitrogen-based species concentration. By manipulating operational parameters, including gas flow rate, activation time, and DI water volume, we achieved significant concentrations of reactive oxygen and nitrogen species (RONS). As a result, the PAW obtained displayed pronounced physicochemical attributes: a pH of 2.06, an ORP of 275 mV, conductivity of 3 mS/cm, and TDS of 1200 mg/L. A pivotal aspect of this research was the evaluation of the reactor’s efficiency, as indicated by metrics like the specific input energy and ozone efficiency yield. The antimicrobial potential of the PAW was also assessed against pathogenic microbes, with remarkable reductions in viability for both Staphylococcus aureus and Escherichia coli (99.99%) and a more moderate decrease for Candida albicans (37%). These findings underscore the capability of coaxial DBD reactors in crafting high-quality PAW with significant antimicrobial properties, necessitating further studies to validate its broad-spectrum and safe applications.

Innovative Curved-Tip Reactor for Non-Thermal Plasma and Plasma-Treated Water Generation: Synergistic Impact Comparison with Sodium Hypochlorite in Dental Root Canal Disinfection.

Non-thermal plasmas (NTPs), known as cold atmospheric plasmas (CAPs), hold great potential for diverse medical applications, including dentistry. However, traditional linear and rigid dielectric barrier discharge reactors used for NTP generation encounter limitations in accessing oral cavities and root canals. To address this issue, we have developed an innovative NTP reactor featuring an angled end for improved accessibility. The central copper electrode, with a 0.59 mm diameter and adjustable length for desired angulation, is coated with zircon powder (ZrSiO4) to ensure stable NTP generation. This central electrode is housed within a stainless steel tube (3 mm internal diameter, 8 mm external diameter, and 100 mm length) with a 27° angle at one end, making it ergonomically suitable for oral applications. NTP generation involves polarizing the reactor electrodes with 13.56 MHz radio frequency signals, using helium gas as a working medium. We introduce plasma-treated water (PTW) as an adjunctive therapy to enhance biofilm eradication within root canals. A synergistic approach combining NTP and PTW is employed and compared to the gold standard (sodium hypochlorite, NaOCl), effectively neutralizing Enterococcus faecalis bacteria, even in scenarios involving biofilms. Moreover, applying NTP in both gaseous and liquid environments successfully achieves bacterial inactivation at varying treatment durations, demonstrating the device's suitability for medical use in treating root canal biofilms. The proposed NTP reactor, characterized by its innovative design, offers a practical and specific approach to plasma treatment in dental applications. It holds promise in combatting bacterial infections in root canals and oral cavities.

Sterilization of Water-Based Cutting Fluids Using Compact Air-Cooled Coaxial Dielectric Barrier Discharge Reactor with Bubbler

Odor and discoloration in water-based cutting fluids are caused by the growth of microorganisms and putrefying bacteria. This significantly reduces cutting performance, prevents rust, and deteriorates the working environment. To overcome these drawbacks, we developed a compact air-cooled coaxial dielectric barrier discharge (DBD) with a bubbler. Bacteria and microorganisms living in waste cutting fluids were sterilized by the high concentration of ozone produced under the optimized conditions of the compact air-cooled coaxial DBD. Moreover, it was confirmed that 99.99% of bacteria and microorganisms were completely removed. Ozone was found to not affect property changes such as the composition, concentration, and pH of the water-based cutting fluids. The chromaticity and complex odor of waste cutting liquids were thus found to have been improved by the effects of microorganism and bacterial sterilization. We conclude that the proposed a compact air-cooled coaxial DBD with a bubbler is an efficient method for sterilizing water-based cutting fluids.

Valorization of glycerol through plasma-induced transformation into formic acid.

To cope with climate change issues, a significant shift is required in worldwide energy sources. Hydrogen and bioenergy are being considered as alternatives toward a carbon neutral society, making formic acid-a hydrogen carrying product of glycerol-of interest for the valorization of glycerol. Here we investigate the plasma-induced transformation of glycerol in an aqueous nanosecond repetitively pulsed discharge reactor. We found that the water content in the aqueous mixture fulfilled a crucial role in both the gas phase (as a source of OH radicals) and the liquid phase (as a promotor of the dissolved OH radical's mobility and reactivity). The formic acid produced was linearly proportional to the specific input energy, and the most cost-effective production of formic acid was found with 10-%v/v glycerol in the aqueous mixture. A plausible reaction pathway was proposed, consisting of the OH radical-driven dehydrogenation and dehydration of glycerol. The results provide a fundamental understanding of plasma-induced transformation of glycerol to formic acid and insights for future practical applications.

Plasma-catalytic removal of toluene over bimetallic M/Mn-BTC catalysts in dielectric barrier discharge reactor

In this study, novel bimetallic metal–organic frameworks (MOFs) catalysts were synthesized using a simple solvothermal method. These catalysts involved the incorporation of transitional metals such as Co, Cu, Ce, and Fe into Mn-BTC, which served as the precursor substrate. This approach was undertaken to address the limitations of catalytic degradation of toluene observed in both plasma-based and traditional catalytic materials. The physicochemical characterization confirmed successful synthesis of the bimetallic MOFs with well-defined crystal shape and structure. In toluene degradation experiments, the DBD-coupled bimetallic MOFs (M/Mn-BTC) presented higher toluene removal efficiency, CO2 selectivity, mineralization degree, and fewer by-products when compared to both DBD-coupled single metal MOFs and the DBD-alone system. Besides, the catalytic activity of the DBD-coupled M/Mn-BTC followed the order: Co/Mn-BTC > Cu/Mn-BTC > Ce/Mn-BTC > Fe/Mn-BTC. Furthermore, it was observed that the Co/Mn molar ratio played a significant role in influencing the properties of MOFs catalysts and subsequently had an impact on their performance. The highest catalytic activity was observed at a Co/Mn molar ratio of 1:1. Under conditions of an energy density of 808.99 J‧L-1 and an oxygen fraction of 4% (v/v), Co/Mn-BTC exhibited a CO2 selectivity of 54.1%, a mineralization degree of 93.9%, and a toluene abatement efficiency of 96.2%. Additionally, an energy efficiency of 8.32 g·kWh−1 was achieved. The mechanism of toluene degradation was analyzed, uncovering a synergistic effect between DBD and Co/Mn-BTC. High-energy electron and adsorbed oxygen (denoted as Oads), along with active oxygen species (O*) from O3 decomposition, played crucial roles in the catalytic oxidation reaction. The interactions between Mn and Co enhanced electron mobility and accelerated the formation of Oads and O*, thereby facilitating toluene oxidation within the hybrid catalytic system.

High-pressure CO2 dissociation with nanosecond pulsed discharges

We investigate the conversion of CO2 into CO and O2 with nanosecond repetitively pulsed (NRP) discharges in a high-pressure batch reactor. Stable discharges are obtained at up to 12 bar. By-products are measured with gas chromatography. The energy efficiency is determined for a range of processing times, pulse energy, and fill pressures. It is only weakly sensitive to the plasma operating parameters, i.e the extent of CO2 conversion is almost linearly-dependent on the specific energy invested. A conversion rate as high as 14% is achieved with an energy efficiency of 23%. For long processing times, saturation in the yield and a drop in efficiency are observed, due to the increasing role of three-body recombination reactions, as described by zero-dimensional detailed kinetic modeling. The modeling reveals the presence of three-stage kinetics between NRP pulses, controlled by electron-impact CO2 dissociation, vibrational relaxation, and neutral elementary kinetics. Transport effects are shown to be important for CO2 conversion at high pressures. For fill pressures beyond 10 bar, CO2 may locally transit into supercritical states. The supercritical plasma kinetics may bypass atomic oxygen pathways and directly convert CO2 into O2. This work provides a detailed analysis of plasma-based high-pressure CO2 conversion, which is of great relevance to future large-scale sustainable carbon capture, utilization, and storage.

H2 Production from NH3 in a BaTiO3 Moderated Ferroelectric Packed-Bed Plasma Reactor

Plasma decomposition reactions are used for various gas phase chemical processes including the decomposition of ammonia. In this work we show that pure ammonia can be effectively decomposed at atmospheric pressure and ambient temperature using a packed-bed plasma reactor moderated with BaTiO3 ferroelectric pellets without catalyst. The decomposition rate and energy efficiency of this ferroelectric barrier discharge reactor have been monitored as a function of applied voltage (up to a maximum value of 2.5 kV) and flow rate. For each operating condition reaction efficiencies have been correlated with the parameters defining the electrical response of the reactor. It is found that plasma current and volume inside the reactor and hence the energy efficiency of the process and the decomposition rate vary with the applied voltage and the flow of ammonia (a maximum decomposition rate of 14% and an energy efficiency of 150 LH2/kWh has been determined under optimized operation conditions). The role of back reactions (i.e. N2 + 3H2 → 2NH3) in decreasing reactor performance is another key effect affecting the overall efficiency for the ammonia decomposition. The possibilities of ferroelectric barrier discharge reactors to induce the decomposition of ammonia and the importance of keeping the operating temperature below the Curie temperature of the ferroelectric material are highlighted.

Chain scission modification mode in plasma catalytic n-undecane decomposition: In situ probing of intermediates and reaction pathways

To provide insight into the mechanism of plasma-catalytic long-chain alkane oxidation from the aspect of chain scission, n-undecane (C11H24) decomposition over γ-Al2O3 and Ag/γ-Al2O3 were investigated in a coaxial dielectric barrier discharge (DBD) reactor. The highest n-undecane conversion (89.7 %) and CO2 selectivity (SCO2, 40.0 %) were achieved in Plasma + Ag/γ-Al2O3 system. It was found that the simultaneous activation of O3 and C11H24 played a very important role in chain scission, which could be promoted by the formation of Ag-O-Al entity introduced by the strong interaction between Ag and γ-Al2O3. Different chain scission behaviors and reaction pathways were proposed by a combined analysis of GC-MS and in-situ DRIFTS. In Plasma + Ag/γ-Al2O3 system, the reaction of chain scission and oxidation preferred to take place in the middle of the chain, producing the ketone and aldehyde species with low carbon number, which were easy to be converted to CO2 and H2O. Instead, without the highly efficient activation of O3 and C11H24, the oxidation of the C11H24 over the surface of γ-Al2O3 was more likely to take place on the edge of the chain, leading to the accumulation of long-chain aldehyde, which lower values of C11H24 conversion and SCO2 (45.6 % and 21.7 %, respectively) in Plasma + γ-Al2O3 system.

A surface dielectric barrier discharge reactor for biological treatments

Antimicrobial plasma effects are promising for therapeutic applications like wound healing, cancer/tumor treatment, or pathogen-associated skin or dental diseases, but also in hygiene, food, and agriculture processing. Dielectric Barrier Discharge (DBD) reactors are the most widely used systems for antimicrobial purposes because they can use atmospheric air as a gas, do not require a vacuum, and are simple, inexpensive, and easy to use. However, when DBD plasma is applied directly to the biological sample, discharge current may pass through the biological sample, causing the plasma to transit to spark discharge and thus causing damage to the biological sample. Since Surface Dielectric Barrier Discharge (SDBD) plasmas can be generated far from the sample, they offer great advantages in the application of non-thermal plasma in extremely large volumes. While SDBD plasmas are generally generated on the lid of the container in which the sample is placed and the plasma species are expected to reach the sample, in this study, SDBD plasmas were produced on the container itself. A new SDBD reactor that can be applied to samples of various sizes and properties for antimicrobial purposes was manufactured. Gram-negative E. coli, gram-positive S. aureus and E. faecalis planktonic bacteria were placed in the reactor and inactivated for 10 min by exposure to non-thermal plasma. A plasma sterilization unit with 31.4 W power, practical, user-friendly, developed for bio-applications, with a 6.2-liter capacity.

Energetics of reactions in an atmospheric pressure plasma jet with argon carrier gas and hexamethyldisiloxane reagent

AbstractWe report on a methodology for measuring the energy dissipated per AC high voltage cycle in a cold atmospheric pressure plasma jet (CAPJet). This method is adapted from research by Nisol et al. on plasma polymerization of hexamethyldisiloxane (HMDSO) organosilicon vapor in a large area planar dielectric barrier discharge (DBD) reactor. Here too, we measured ΔEg, the energy difference with and without small HMDSO vapor concentrations in the argon carrier gas flow. From ΔEg we then derived Em, the energy per molecule, and compared values with those of Nisol. Good agreements were found, including in film structures determined from attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectra, thus suggesting that realistic Em values can be successfully obtained also for the CAPJet case.

Full cycle, self-consistent, two-dimensional analysis of a packed bed DBD reactor for plasma-assisted splitting: spatiotemporal inhomogeneous, glow to streamer to surface discharge transitions

We investigate the full-cycle operation of a coaxial Packed Bed Dielectric Barrier Discharge (PB-DBD) reactor operating in pure . The reactor is packed with high permittivity dielectric rods and is analyzed with a two-dimensional (2D) self-consistent plasma model. We show that the PB-DBD operation is governed by both glow and volume/surface streamer discharges, forming alternatively and non-uniformly inside the gas volume. The presence and surface charging of the dielectric rods and dielectric layer is crucial for the initiation, propagation, annihilation and afterglow of these microdischarges. Our calculations show maximum electron and densities in the order 1020 m−3, an average discharge power of 353.42 W m−1 in the first cycle, microdischarge peak currents in the order of 50–400 A m−1, total half-cycle plasma charge of around 6 µC m−1, which compare well with experimental findings. Dominant negative ions are found to be . CO molecules and O atoms are mainly formed during the MDs development and the streamer-surface ionization waves. Molecular oxygen () is preferentially formed during the glow, current-decaying and afterglow phase of each microdischarge. The spatially average reduced electric field inside the reactor lies in the 20–100 Td range. Each MD, presents distinct non-uniform and non-repeatable glow and volume/streamer discharges owed to the non-uniform surface charging processes which dictate the complex spatial distribution of produced neutral (and ion) species. These detailed results shed light on crucial, largely non-uniform plasma spatiotemporal characteristics that can help design efficient PB-DBD reactors for splitting and beyond, while emphasizing the important insights obtained by 2D simulations which can not be captured with 0D-global or 1D models.

An investigation on the removal of tramadol analgesic in deionized water and final wastewater effluent using a novel continuous flow dielectric barrier discharge reactor

In this study, the degradation of tramadol (TRA) was studied for the first time in deionized water (D·I) and final wastewater effluent (FWWE) using a dielectric barrier discharge reactor operated in a continuous flow mode. Initially, the reactor was optimized for voltage and initial concentration conditions. After 60 min treatment, the degradation efficiency of TRA was 93 % in D·I and only 27 % in FWWE. Also, the pseudo-first-order rate constant in D·I (0.056 min−1) was an order of magnitude higher than the FWWE (0.0056 min−1). To understand the reasons for this disparity, experiments were conducted to investigate the impact of conductivity, pH, and certain natural radical scavengers present in the wastewater. The results revealed that the rate of degradation and kinetics of TRA in the presence of HCO3− was comparable to those observed in FWWE due to the scavenging of the ●OH radicals. Meanwhile, Fenton reaction with TRA was confirmed with the synthetic solution based on the increased production of H2O2. Toxicity tests showed that the treated TRA solution did not inhibit the growth of Escherichia coli as opposed to the untreated solution.

Removal of Volatile Organic Compounds from Coal-Fired Power Plants Using Nonthermal Plasma Generated by a Dielectric Barrier Discharge Reactor: Carbon Yield and Application Feasibility

Removal of Volatile Organic Compounds from Coal-Fired Power Plants Using Nonthermal Plasma Generated by a Dielectric Barrier Discharge Reactor: Carbon Yield and Application Feasibility

Low-Temperature Plasma-Assisted Catalytic Dry Reforming of Methane over CeO2 Nanorod-Supported NiO Catalysts in a Dielectric Barrier Discharge Reactor.

Nonthermal plasma (NTP)-assisted catalytic dry reforming of methane (DRM) is considered a powerful single-stage reaction mechanism because of its ability to activate normally stable CO2 and CH4 at a low temperature under ambient conditions. The thermodynamic barrier of DRM requires a high operating temperature (>700 °C), which can be reduced by nonequilibrium plasma. Herein, we present a method for the wet-impregnation synthesis of CeO2 nanorod (NR)-supported 5 and 15 wt % NiO catalysts for efficient NTP-promoted DRM with an applied power in the range of 24.9-25.8 W (frequency: 20 kHz), a CH4:CO2 feed gas ratio of 100:250 sccm, and a total flow rate of 350 sccm. The presence of NTP dramatically increased the reaction activity, even at 150 °C, which is usually inaccessible for thermally catalyzed DRM. The CH4 and CO2 conversion reaches a maximum of 66 and 48%, respectively, at 500 °C with the 15 wt % NiO/CeO2 NR catalyst, which are much higher than the values obtained for the 5 wt % NiO/CeO2 NR catalyst under the same conditions. According to the X-ray photoelectron spectroscopy profile for 15 wt % NiO/CeO2 NR, a higher concentration of NiO on CeO2 increases the proportion of Ce3+ in the catalyst, suggesting enhanced oxygen vacancy concentration with an increased amount of NiO loading. Additionally, a higher NiO loading promotes a higher rate of replacement of Ce4+ with Ni2+, which generates more oxygen vacancies due to the induced charge imbalance and lattice distortion within the CeO2 lattice. As a result, it can be inferred that the incorporation of Ni ions into the CeO2 structure resulted in inhibited growth of CeO2 crystals due to the creation of a NixCe1-xO2-α solid solution and the production of oxygen vacancies.

A novel combination of non-thermal plasma process and a heterogenous nanophotocatalyst-sorbent comprising zinc sulfide, graphene oxide and polyaniline as an efficient strategy for treatment of organic-contaminated water

A dielectric barrier discharge (DBD) reactor was designed in the present study to generate non-thermal atmospheric pressure Ar plasma. A heterogeneous p-n-p visible-driven photocatalyst comprising ZnS, Graphene oxide, and Polyaniline (ZGP) was also synthesized via chemical polymerization. A novel combination of photocatalyst and plasma treatment was then developed for the synergetic removal of organic pollutants from aqueous solutions. The addition of the p-n-p photocatalyst (5 mg) to the dye solution (malachite green, 50 mL, 20 mg/L) under plasma radiation resulted in a 97 % removal rate in 12 min. Scavenging studies confirmed a decline in the effectiveness of the reactive species in the following order: OH• > e־ > O2־• > h+. The changes in surface chemistry of the recovered photocatalyst were probed by XPS, and possible involved reactions were suggested. The synergetic factor of 1.53 in this system was a remarkable achievement comparable with the records of air or oxygen plasma reactors. The absence of hazardous by-products was confirmed by GC–MS and AAS techniques. The treated aqueous solution was utilized to evaluate its effect on lentil seed growth and trout blood factors, which led to promising results with several advantages but no negative effects.

Efficient degradation and mineralization of aniline in aqueous solution by new dielectric barrier discharge non-thermal plasma

Aniline is a priority pollutant that is unfavorable to the environment and human health due to its carcinogenic and mutagenic nature. The performance of the dielectric barrier discharge reactor was examined based on the aniline degradation efficiency. Different parameters were studied and optimized to treat various wastewater conditions. Role of active species for aniline degradation was investigated by the addition of inhibitors and promoters. The optimum conditions were 20 mg/L initial concentration, 1.8 kV applied voltage, 4 L/min gas flow rate and a pH of 8.82. It was observed that 87% of aniline was degraded in 60 min of dielectric barrier discharge treatment at optimum conditions. UV–Vis spectra showed gradual increase in the treatment efficiency of aniline with the propagation of treatment time. Mineralization of AN was confirmed by TOC measurement and a decrease in pH during the process. To elicit the aniline degradation route, HPLC and LC-MS techniques were used to detect the intermediates and byproducts. It was identified that aniline degraded into different organic byproducts and was dissociated into carbon dioxide and water. Comparison of the current system with existing advanced oxidation processes showed that DBD has a remarkable potential for the elimination of organic pollutants.

Exsolution Synthesis of Alloyed Nanoparticles from Perovskite Oxide by Plasma

Bimetallic alloy nanoparticles (NPs) exsolved on the surface of perovskite oxides (ABO3) alter the structural and electronic properties of the primarily monometallic counterparts. These synergistic effects make the whole material present superior electrolytic and catalytic performances. The strong bonding interaction between alloy NPs and perovskite substrate enables the stability and durability of the catalysis.However, traditional thermal exsolution requires a long-time treatment at a high temperature. Researchers have been pursuing more time-saving and energy-efficient alternative routes. Herein, a low-temperature and fast pathway based on the dielectric barrier discharge (DBD) reactor is provided to in-situ exsolve alloy NPs. A favorable activity of the catalyst for CO oxidation is demonstrated. Additionally, we conclude that the factor restricts metallic agglomeration is the morphology of the substrate. Even after an overtime plasma treatment, the exsolved alloy NPs are still embedded in the porous structure of perovskite oxides.