Gas Composition Research Articles

Thermodynamic and exergy assessment of a biomass oxy-fuel combustion with supercritical carbon dioxide cycle under various recycle flue gas conditions

The ongoing development of second-generation oxy-fuel combustion system with higher oxygen concentration have presented a potential pathway for efficient biomass utilization. It also signified the meticulous role of recycled flue gas in altering the combustion behaviour in the combustor. Accordingly, investigation into different recirculation modes focusing on recycle ratio, wet/dry conditions, and excess oxygen ratio are conducted with an indirect supercritical power cycle integrated biomass oxy-fuel combustion system. Energy and exergy analyses, as well as composition of flue gas produced are presented. Energy and exergy efficiencies increased with reducing recycle ratio, with respective highest efficiency of 31.33% and 44.37% obtained at excess oxygen ratio of 1.01 and recycle ratio of 0.5 under wet condition. Investigation of CO2 and H2O concentration in produced flue gas depicted a separated stage profile under dry recycle condition, different from the slight diverging profile observed under wet condition when the recycle ratio varied. Concentration of NOx and SOx increased with decreasing recycle ratio and are generally higher under dry condition. Selective exergy analyses of the proposed power cycle presented highest exergy loss in the combustor, followed by the air separation unit, heat exchanger, CO2 compression and purification unit, and turbine generator. Based on the obtained result, wet recycle flue gas enhanced the combustion performance in the combustor but slightly impaired the convective heat transfer in the heat exchanger. The performance of proposed biomass power cycle is optimized at low recycle ratio of 0.5 under wet recycle condition.

Energy-efficient scientific-technological approaches to the processing of plastic waste PET, PE, PP, PS to produce hydrogen-containing gas and titanium carbide powder

The paper considers gaseous products, structure and phase composition of hard products resulting from high-temperature exothermic reactions between Ti–PET–(PE, PP, PS) system components, depending on the content of oxygen-free polymers polyethylene (PE), polypropylene (PP), and polystyrene (PS) in the initial blend. It is found that the addition of PE, PP, PS polymers to the Ti–PET system increases the hydrogen content from 45 to 62 vol% and reduces the carbon monoxide content from 38 to 20 vol% in gaseous products. According to calculations, the adiabatic flame temperature of the synthesized gas in air is very close to that of pure hydrogen. The synthesized gas can therefore be used as ecological fuel for energy sources. On the other hand, oxygen-free polymers presenting in the system provide the formation of substoichiometric carbide TiC0.75. Its hardness is not lower than that of stoichiometric TiC and even exceeds widely used carbides and borides of transition metals. In addition, the agglomerate structure of synthesized TiC0.75 allows to apply it as a promising ecological basis for highly-efficient abrasive pastes, in particular for polishing and finishing fabricated metal products.

The Influence of the Composition of Gases in a Modified Atmosphere Packaging on the Storage Capacity of Minced Pork

The Influence of the Composition of Gases in a Modified Atmosphere Packaging on the Storage Capacity of Minced Pork

Photothermal conditions and upwelling enhance very short-lived brominated halocarbons emissions in the western tropical Pacific Ocean

Sea-to-air emissions of very short-lived brominated halocarbons (VSLBrHs) are known to contribute to 30 % of stratospheric and tropospheric ozone depletion. However, empirical data on their occurrence in open ocean are scarce, which makes it difficult to estimate the significant contribution of open ocean releases to the global budget of halocarbons. This study was conducted in 2022 to explore the spatial variations of VSLBrHs and their controlling factors in the western tropical Pacific Ocean (WTPO). The findings highlighted that high biological productivity and the resulting dissolved organic matter (DOM) as well as upwelling dynamics significantly influenced the distribution and production of VSLBrHs in seawater, with atmospheric levels primarily governed by oceanic emissions. Based on the simultaneous observation of seawater and atmospheric concentrations, the mean sea-to-air fluxes of CH2Br2, CHBr3, CHBrCl2, and CHBr2Cl were estimated to be 1.01, 6.65, 9.31, and 7.25 nmol m−2 d−1, respectively. Sea-to-air fluxes of these gases in the upwelling regions were 9.0, 4.6, 2.9, and 6.8 times those in the non-upwelling regions, respectively. Additionally, in-situ incubation experiments revealed that the enzymatic mediated biosynthesis pathways of VSLBrHs were enhanced under temperature and light-induced stress and in waters rich in humus-like substances. Therefore, we tentatively concluded that abundant photothermal conditions and the existence of upwelling in the WTPO made it a potential hotspot for the emission of VSLBrHs. This study offers critical insights into the environmental dynamics of VSLBrHs emissions and underscores the importance of regional oceanic conditions in influencing atmospheric greenhouse gas compositions.

Advanced thermoconversion technology for municipal solid waste energetic valorization

This paper presents a novel approach to tackle the dual challenges of energy scarcity and municipal solid waste management by exploiting the potential of municipal solid waste gasification. The performance of the modified updraft gasifier is evaluated using computational modeling with Aspen Plus V14 software. The reliability of the gasification model is confirmed by comparing it with experimental data, highlighting its accuracy in estimating key gas composition parameters. A detailed analysis of the percentage error between the gas's experimentally measured lower heating value and the model-estimated value is performed. Results show a 12.2 % error for municipal solid waste gasification, meaning the experimental lower heating value is higher than the model's estimation. On the other hand, a 27,2 % error is observed for pellet gasification, implying a lower experimental lower heating value than the model's estimation. These findings provide useful information for future optimization and improvement of the gasification process, further advancing the field of waste-to-energy conversion and promoting sustainable energy generation.

PSV-11 In vitro screening of selected compounds to reduce ruminal methane production

Abstract Methane is a natural product of rumen fermentation and emissions from ruminant livestock represent a major environmental concern. Methane is not only a potent greenhouse gas but also represents a loss of energy efficiency for the host. The objective of this study was to perform in vitro screening of a range of compounds with potential anti-methanogenic activity, including polyphenols, flavonoids, fatty acids, amino acids, and salts. We aimed to select compounds conferring up to a 20% reduction in CH4 for further investigations. The substances tested included carvacrol, coumaric acid, coumarin, flavanone, gallic acid, glycerol monolaurate (GML), glycine, methylene blue, naringin, quercetin, quinic acid, resorcinol, rutin, tannic acid, vanillic acid, and zinc acetate. These substances varied in their mechanisms of action and were selected based on known antimicrobial or anti-methanogenic properties. The experiment was designed as a randomized block experiment, with treatments tested in triplicates across four batches (n = 228 samples) using the same treatments and experimental conditions. Fresh rumen contents were manually collected from two rumen-fistulated lactating Holstein cows, 3 h after their morning feeding. Rumen contents were blended at a 2:1 ratio, filtered through a four-layered cheesecloth, and added to McDougall’s solution at a 2:1 ratio. Final media (9 mL) was added to a 20 mL Bellco flask containing 150 mg of total mixed ration (TMR) ground to 1 mm. Each batch also had three flasks without TMR and no treatment (blank flasks), three flasks containing only TMR without treatment (negative control), and three flasks containing TMR and treated with chloroform (positive control), resulting in a total of 19 treatments. The end-products of in vitro batch fermentations were assessed after 24 h of incubation, and samples from each flask were collected for gas composition analysis using gas chromatography. Volatile fatty acids were determined using high-performance liquid chromatography (HPLC). The data were analyzed using R Studio, and the following model was applied: yij = µ + treatmenti + batchj + ℇij. Methane production (measured in parts per million, ppm) increased when GML, naringin, and quercetin were added compared with the negative control. In contrast, the addition of carvacrol, glycine, tannic acid, and methylene blue resulted in a decrease of up to 25% in methane production. These compounds show potential to alter ruminal fermentation and mitigate methane production and will be selected for evaluation of synergistic interactions and effects on the rumen microbial communities.

Mechanistic analysis of acid gas storage and oil recovery in naturally fractured reservoirs using single matrix block approach

AbstractThe objective of this study is to assess the storage of acid gas, containing CO2 and H2S, in a depleted naturally fractured reservoir (NFR) using single matrix block (SMB) approach. The acid gas dissolution in oil is considered by Peng‐Robinson equation of state and compositional simulation. The PHREEQC package is used to determine acid gas solubility in formation brine. Three types of acid gases with different compositions are used for this study and their swelling behavior and miscibility in relation to the reservoir oil are analyzed. An SMB model, with a matrix block surrounded by fractures, is constructed, and validated for simulation of a real experiment. The simulation is conducted for synthetic and real reservoir fluids when the oil is in its residual saturation. A sensitivity analysis is performed to study the effects of key parameters, such as acid gas composition, reservoir pressure, permeability, porosity and matrix height on the storage capacity and oil recovery factor. The matrix has a volume of 27 m3 and about half of acid gas storage is achieved in the first 5 years while the simulations are run for 30 years. The results show that up to 90% of remained oil is recoverable, and more than 0.67 kmol of acid gas per cubic meter of matrix is stored whether matrix contains a real oil or a synthetic one. Higher storage is achieved for higher matrix porosities and heights and large H2S proportion in acid gas. In all cases about 10% of acid gas is trapped in water and the remaining 90% is dissolved in oil. The mineral trapping was more active in CO2‐rich acid gases. While about 10 kg of the matrix rock was dissolved in the acidic brine when the acid gas contained H2S, the amount of the dissolved minerals in acidic brine resulted from the injection of CO2‐rich acid gas was more than 16 kg. Finally, this study gives a comparative analysis of the storage performance of acid gas mixture and pure CO2. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

VALORIZATION OF WASTE FRUIT PEELS: A COMPUTATIONAL STUDY ON PREDICTION OF GASIFICATION PRODUCT COMPOSITION

In this work, a variety of discarded fruit peels are investigated using a computational technique in order to anticipate the products of their gasification when subjected to higher temperatures, namely 800°C and 900 °C. The proximate and ultimate analyses of eight different fruit peels were collected from a variety of published sources, and the composition of gasification was predicted by applying the Gibbs free energy minimization method to each fruit peel individually and to both temperatures using the Solver Tool feature of the Microsoft Excel Spreadsheet. As input for the simulation, the thermodynamic constants for each gaseous component and the elemental analysis of each fruit peel were needed. The predicted gaseous composition was compared with some of the data obtained in the literature, and it was determined to be in a close match based on the root mean square error for each number. This was done while taking into account the fact that the carbon conversion process during gasification was only partially successful. For citation: Khedkar R.S., Khonde R.D., Meshram P. Valorization of waste fruit peels: a computational study on prediction of gasification product composition. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 6. P. 127-134. DOI: 10.6060/ivkkt.20246706.6959. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Performance Evaluation of an Anode-Supported SOFC Short-Stack Operating with Different Fuel Blends as Stationary-CHP System

Abstract In the perspective of the transition of gas grids towards hydrogen/natural gas blends or even pure hydrogen, Solid Oxide Fuel Cells “SOFC” could play a crucial role as efficient and clean stationary Combined Heat and Power systems, flexibly operating on different feedstocks. A solid oxide fuel cell short stack is analyzed experimentally under different fuel gas compositions which emulate different gas grid transition scenarios. The testing campaign is defined with the aid of a preliminary system-level simulation which assesses system architecture and operating strategy (off-gas recirculation, external reforming, etc.). Experimental tests (polarization curves and performance/efficiency maps) are run in different operating conditions in terms of fuel utilization and temperature in three gas composition scenarios. 
To assess the efficiency of the SOFC unit under the different feedstock operation, different formulations of stack and system efficiencies are proposed and analyzed, based on the boundary conditions considered for the input/output energy streams. 
Experimental results were key to evaluate the different efficiency definitions proposed; albeit the highest voltage/power is obtained with the 100% H2 scenario, the efficiency may be higher with 100% NG and blend scenarios, due to the lower energy content of the input fuel.

Evaluation of plasma parameters’ impact on MRR and surface roughness in plasma polishing of fused silica: An investigation of surface characterization

Advanced fabrication methods with high efficiency are needed to meet the rising demand for precision optical components. This study proposes a plasma-based isotropic polishing method to remove fused silica's surface defects and subsurface damaged layers. Hence, a medium-pressure plasma process is developed to serve this purpose. The qualitative analysis of the plasma and atom emission spectrum explores the plasma generation and scattering of the activated fluorine (F*) radicals inside the plasma chamber. Material removal rate (MRR) and surface roughness variations with different total pressures of 5–30 mbar and substrate dimensions (i.e., varying length between 5 and 45 mm with fixed width and thickness of 5 and 2 mm) at fixed process parameters, i.e., radio-frequency power of 80 W, pressure ratio of 1:1, gas composition of 90:10, have been investigated. The highest and lowest MRR, i.e., 0.039 mm3/min and 0.0061 mm3/min, are achieved at 5 and 30 mbar total pressures on substrates having lengths 45 and 5 mm, respectively. The highest and lowest percentage change in surface roughness observed are 86.4 % and 17.1 % at 5 mbar and 30 mbar for substrates with 5 and 45 mm lengths, respectively. Surface morphology analysis shows the micro-cracks are reduced after plasma processing. The presence of elements, i.e., F and C, through EDX analysis, confirms the reactions on the plasma processed surface. Moreover, The XPS findings demonstrated that minimal radicals could be incorporated onto the fused silica surface during He/O2/SF6 plasma processing. At lower pressure, the surface roughness value increases due to the increased excitation and ionization rate caused by more interaction between the fluorine and surface atoms. The MRR increases with substrate dimension with constant pressure. Larger substrate dimensions result in increased MRR at lower pressure.

Utilization and Experimental Use of Stainless Steel Metal Scrap Machinery Waste, St-40 Iron, Copper and Aluminum to Reduce Co, Hc, Co2 Elements in Vehicle Exhaust

Air pollution due to motor vehicle exhaust emissions is increased. Polluted air harms human health dan the environment. Consequently, it is essential to make a sustained effort to reduce air pollution. The purpose of this research is to investigate the effect of adding aluminum scrap to the exhaust system of a motor vehicle on gas emissions composition. The motor vehicle exhaust system was modified to accommodate aluminum scrap placement. A gas analyzer was utilized to observe exhaust gas composition, such as carbon dioxide, hydrocarbon, and carbon monoxide. Aluminum scrap with different masses was wrapped around the exhaust's inner tube in 50 gr, 70 gr and 90 gr. The engine speed was maintained at 500 rpm throughout the testing process. It was found that the temperature of the outer exhaust tube is in a range of 40 degrees Celsius to 50 degrees Celsius. The results revealed that the most appropriate amount of aluminum scrap was 90 gr n to reduce carbon monoxide, hydrocarbon, and carbon dioxide in an exhausts gas. The surprising outcome was 76.78 % of carbon monoxide content declined, and furthermore hydrocarbon, and carbon dioxide content were deteriorated by 61.63% and 78.37%, respectively.

Impact of processing gas composition on process stability and properties of PBF-LB/M processed alloy 718

The almost unlimited design freedom of the laser-based powder bed fusion of metals (PBF-LB/M) makes this technology very attractive for industry. However, as a developing technology, it still faces some challenges when it comes to productivity and robustness, to name some. Whereas numerous studies covered the impact of laser-based parameters on material properties and robustness, the effect of the processing gas received limited attention. The objective of this study was to evaluate the effect of processing gas composition, containing helium (He) and hydrogen (H2), compared to conventionally used argon (Ar), during PBF-LB/M processing of virgin alloy 718 powder, on printing behavior and part properties. The four gases studied were Ar, Ar +30%He, Ar +30%He +2%H2, and Ar +70%He. Optical Tomography (OT) was used to monitor process stability, which unveiled a significant decrease in process-by products (spatters) between 51 % and 89 % using He and H2-containing gases. It was also found that the process gas decreased the bulk porosity from an average value of 0.08 % when processed with Ar to 0.04 % when using Ar + 70%He. The oxygen pickup by the spatter particles was reduced from 630 ppm (Ar) to 331 ppm (Ar +70%He). EBSD analysis revealed that there were no evident changes in microstructure with the processing gas. The samples processed also had similar tensile properties with yield and ultimate tensile strength of 1180 MPa and 1395 MPa, respectively. However, there was a slight increase in ductility from 16.5 % to 17.2 %, when processed with pure Ar and Ar + 70%He, respectively. This study shows that utilizing standard Ar processing atmosphere with He addition leads to a more stable process with reduced spatter, porosity and a marginal increase in ductility for Alloy 718.

Bioethanol burner operating parameters optimization: Effects of burner opening area modulation on heat output and flue gas composition

Bioethanol burners are significantly expanding devices in Europe, still considered preferably as the design element while its possible importance in the energy system of the household used to be neglected. The aim of this study was to determine the operating techno-environmental parameters as the heat output and the flue gas composition of the bioethanol fireplace with vortex flame. The measurement methodology was based on actual valid standard EN 16647 Fireplaces for Liquid Fuel. In general, three ethanol-based fuels were tested in combination with one bioethanol burner equipped with different regulation rings changing burner opening area. The average reached heat energy output ranged between 3.97 and 2.22 kW with maximal burner opening area (without the usage of regulation rings) for different fuels. By usage of the regulation rings, the heat energy output was reduced to 35 – 40 % of the nominal average heat output. Simultaneously the time of the burning of one fuel dose can be increased by regulation ring usage up to 195 % of the combustion time without the regulation ring. By placing the regulation rings on the burner bowl opening area, the flue gas composition was affected positively in terms of CO and negatively in terms of NOx.

Nondestructive internal disorders detection of ‘Braeburn’ apple fruit by X-ray dark-field imaging and machine learning

'Braeburn' apples are susceptible to internal browning disorders when stored under controlled atmosphere (CA) conditions with unfavorable gas compositions. The progression of CA-related disorders in apple tissues is dynamic, noting a decrease in porosity during early storage due to cellular breakdown and pore flooding, and an increase in porosity in later stages due to structural collapse and cavity formation. Utilizing grating-based X-ray dark-field radiography, which leverages X-ray small-angle scattering to detect microstructural changes below the pixel scale, this study assesses the technique's efficacy in identifying internal disorders in 'Braeburn' apples at both early and later stages. A machine learning approach was applied to compare the diagnostic capabilities of dark-field imaging with those of X-ray absorption radiography at identical image resolutions. Results indicate that for early-stage disordered fruit detection, X-ray dark field radiography is 10 % more accurate than absorption radiography, regardless of the machine learning classifiers that were applied. In the later stage of browning, dark-field imaging performs similarly to absorption imaging. High-resolution micro-computed tomography scans suggested that the distinct detection performance of dark-field imaging may be attributed to the more pronounced microstructural differences between healthy and early-stage defective tissues than those between healthy and later-stage defective tissues. The insights from this work will guide the application of X-ray dark-field systems in fruit quality assurance, particularly in detecting internal disorders.

High performance Ce0.8Nd0.2O2-δ-carbonate hollow fiber membrane for high-temperature CO2 separation

Ceramic-carbonate dual phase (CCDP) membrane consisting of oxygen ionic conductor and molten carbonate has potential applications in clean energy delivery as it enabling the direct CO2 separation or capture at the elevated temperatures. The performance of previous CCDP membranes is not ideal either with a low CO2 flux or with a poor operational stability. In the present work, we looked at the CeO2-based oxygen ionic conductor (neodymium doped cerium (NDC)) as the porous ceramic hollow fiber support to form NDC-carbonate hollow fiber membranes. The NDC hollow fiber was fabricated by the combined phase inversion and sintering techniques and the preparation conditions were optimized to better accommodate the carbonate phase and maintain the mechanical stability. The NDC hollow fibers possessed good bending strength, reaching 91.5 MPa upon sintering at 1500 °C. The effects of feed gas composition and sweep flow rates on the CO2 separation performance were carefully investigated. The resultant dual phase hollow fiber membranes exhibited appreciably high CO2 permeation fluxes at temperatures exceeding 800 °C, which was required to activate both conductions of oxygen and carbonate ions. The achieved maximum CO2 flux of the optimized NDC-carbonate hollow fiber membranes was up to 5.08 mL min−1 cm−2 with 50%CO2–50%N2 as the feed gas at 900 °C. At 700 °C, the membrane exhibited a relatively stable CO2 permeation behavior over 120 h and the spent membrane maintained a stable structure. The high flux and good operational stability of the developed membrane make a huge step towards practical applications.

On the inaccuracies of point-particle approach for char conversion modeling

Char conversion is a complex phenomenon that involves not only heterogeneous reactions but also external and internal heat and mass transfer. Reactor-scale simulations often use a point-particle approach (PP approach) as sub-models for char conversion because of its low computational cost. Despite a number of simplifications involved in the PP approach, there are very few studies that systematically investigate the inaccuracies of the PP approach. This study aims to compare and identify when and why the PP approach deviates from resolved-particle simulations (RP approach). Simulations have been carried out for CO2 gasification of a char particle under zone II conditions (i.e., pore diffusion control) using both PP and RP approaches. Results showed significant deviations between the two approaches for the effectiveness factor, gas compositions, particle temperature, and particle diameter. The most significant sources of inaccuracies in the PP approach are negligence of the non-uniform temperature inside the particle and the inability to accurately model external heat transfer. Under the conditions with low effectiveness factors, the errors of intra-particle processes were dominant while the errors of external processes became dominant when effectiveness factors were close to unity. Because it assumes uniform internal temperature, the models applying the PP approach always predict higher effectiveness factors than the RP approach, despite its accurate estimation of intra-particle mass diffusion effects. As a consequence, the PP approach failed to predict the particle size changes accurately. Meanwhile, no conventional term for external heat transfer could explain the inaccuracy, indicating the importance of other sources of errors such as 2D/3D asymmetry or penetration of external flows inside the particles.

Role of gas composition in weakened nonlinear standing wave excitation and improved plasma radial uniformity in very-high-frequency asymmetric capacitive Ar/CF4 discharges

The higher harmonics generated by nonlinear sheath motion would enhance the standing wave effect, and thus lead to center-peaked plasma density profile in very-high-frequency (VHF) capacitive discharges. In this work, a nonlinear transmission line (NTL) model introduced in Zhou et al (2021 Plasma Sources Sci. Technol. 30 125017) has been extended, with radial transport of various particles and nonlinear sheath motion into account, to investigate the effects of CF4 fraction α on the nonlinear standing wave excitation and plasma radial uniformity in VHF (60 MHz) capacitively coupled Ar/CF4 plasmas at 3 Pa. The results indicate that for pure Ar discharges (i.e. α= 0%), the nonlinearly excited harmonics with short wavelength significantly enhance the electron power absorption at the radial center, resulting in a pronounced central-high plasma density profile. As α increases, the high-order harmonics are gradually damped due to the increase of resistance, as well as the longer wavelength caused by thicker sheath thickness. Thus, the radial profile of the electron absorbed power density shifts from center-peak to edge-high. Besides, at the radial center, the electron density and Ar+ ion density decrease with α , CF3 + ion density shows an increasing trend, while F− ion density initially rises and then decreases. Moreover, the density profiles of all the species become more uniform at higher CF4 fraction, due to the suppressed nonlinear standing wave excitation and the longer wavelength of the nonlinear harmonics.

Co-gasification of lignite and spent tea waste for the generation of hydrogen-rich syngas in a fluidized bed gasifier

The co-gasification of high moisture and high volatile content low-rank lignite (LG) coal and a common waste generated from the brewed tea leaves was studied in a fluidized bed gasification unit. Multiple experiments were conducted at different temperatures, ranging from 800 °C to 900 °C, at fixed operating parameters to elucidate the catalytic thermo-chemical impact on the gasifier performance parameters. The catalytic effect of alkali and alkaline earth metals (AAEMs), especially CaO, K2O, and Na2O present in the spent tea waste (STW) sample, on the product gas composition and performance parameters during the co-gasification experiments with LG was demonstrated. Mixed blends of LG and STW showed enhancement in the overall reactivity of the steam gasification runs, compared to the LG-only feed, primarily due to the change in the surface morphology, textures, and pore structures of the solid product ash samples, as identified with the electron spectroscopy analysis. Liquid and product samples were analyzed using characterization techniques such as Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) analytical techniques, along with the proximate, ultimate, and X-ray fluorescence (XRF) analysis of the gasification feed samples. An optimized blend ratio of 20 wt % of STW with LG sample enhanced the volumetric gas composition of H2 and CH4 gases from 52.03 % to 61.32 % and 3.98 %–5.45 % (on a dry-N2-free basis) with a relatively constant CO gas composition. It showed a reduced CO2 composition from 28.64 % to 18.25 % (on a dry-N2-free basis) for the gasification temperature of 900 °C. Even at the lower gasification temperatures of 800 °C and 850 °C with LG + STW feed, steam gasification experiments showed relatively comparable or superior performance to gasification experiments at 900 °C with LG-only feed. The present study indicated a holistic way to utilize the spent tea waste generated from millions of homes and commercial establishments in various parts of the world with potential application towards synergistic gasification process with other conventional carbon-source materials.

Repetitively pulsed streamer discharge with laser-induced surface trapped electron desorption to exploit residual charges in situ

Positive streamer behaviors under repetitive pulses are predominantly dependent on the availability of free electrons. If surface residual electrons stored from previous discharges could be intentionally released and involved into the next discharge, an alternative control freedom is provided apart from voltage waveform tailoring methods that mainly attract or repel gaseous residual charges. Evolutions of repetitively pulsed surface streamers in compressed (0.2 MPa) air were investigated after low-photon-energy pulsed visible (532 nm) and infrared (1064 nm) laser irradiations. Pulse-sequence and temporally resolved diagnostics were implemented to investigate effects of laser parameters (irradiation moment, wavelength, energy) and gas composition. A 2D surface streamer fluid simulation was performed to qualitatively unveil impacts of localized plasma patches. The surface streamer morphology and emission light are significantly and repeatably affected by the laser irradiation before the streamer inception, while, variations totally disappear without the solid surface. The secondary streamer is prolonged accompanied by a higher flashover probability after the pulsed laser irradiation in compressed air. Intriguingly, influences of the infrared laser persist for tens of microseconds before the next voltage pulse. Residual charge dynamics under the laser irradiation are analyzed, where the additional increase of O2− of low electron bound energy is emphasized. The laser induced surface trapped electron desorption is achieved through the direct or the step-wise process, dependent on the laser energy and the surface trap state distribution.

Nitrogen fixation and H2O2 production by an atmospheric pressure plasma jet operated in He–H20–N2–O2 gas mixtures

AbstractAtmospheric pressure plasmas are widely used for nitrogen fixation processes to produce ammonia NH3 or nitrogen oxides NOx, including, for example, nitrite NO2− or nitrate NO3−. Small‐scale atmospheric pressure plasma jets (APPJs) can provide the production of these species on demand at the site of consumption. The species of interest are generated by the plasma and can be dissolved in liquids, for example, to use them. In this work, liquid treatments were performed by an APPJ operated in a He––– gas composition to investigate the influence of the gas composition on the production of hydrogen peroxide , and . A validation of two diagnostics showed that the spectrophotometric approach using ammonium metavanadate was interfered by other species when was added to the system. Thus, electrochemical sensing of was performed. The concentrations of and were measured by commercially available test kits based on the o‐phythalaldehyde method and the Griess reagent, respectively. At low admixtures, the dominant species was with a maximum concentration of 0.9 mM, while became dominant at admixtures of 0.5% and higher with concentrations of up to 1.5 mM. was also present in the system and could be measured at low concentrations of less than 0.2 mM in the liquid. By varying the treatment distance and the gas flow rate, insights into the transport phenomena of the species and their dissolution into the liquid could be gained. Low‐frequency pulsing of the radio frequency (RF) jet led to an accumulating effect on , a reduced production of and a switch from ‐dominated production to ‐dominated production.