Gas Composition Research Articles

Comparative analysis of gas release from biphasic lithium ceramics pebble beds of various pebbles sizes and content under neutron irradiation conditions

This paper presents the results of 4 reactor campaigns on the irradiation of biphasic lithium ceramics containing different ratios of lithium orthosilicate (LOS) and lithium metatitanate (LMT) components (25 and 35 mol% LMT in LOS). The size distribution of pebbles in pebble beds was 250–1250 μm and 500–710 μm, respectively. The studies were carried out sequentially with each type of ceramics. In experiments carried out using the vacuum extraction method, the composition of gases released from lithium ceramic samples was registered in in-situ mode. The absence of purge gas during the experiments minimized the possibility of T2O and HTO formation, significantly simplifying processing of the results and providing more opportunities for results analysis. The main goal of the present paper was to identify the general patterns of the release of gases with mass numbers M2 (H2), M4 (He + HT), M6 (T2) and M18 (H2O) from ceramic samples throughout the entire irradiation experiment in 4 campaigns. Release trends of main gases with mass numbers M2, M4, M6 and M18 for all four campaigns are presented and their comparative analysis was performed. The average partial pressure of tritium release in the form of T2 and HT molecules for all campaigns was determined as 5.8 × 10-7 Torr. The dependences of formation rates of helium release peaks on the irradiation time were plotted. The nature of peak emissions does not have a monotonic relationship; upon irradiation, both an increase in the frequency of peaks and a decrease in it are observed. During irradiation, the process of peak helium release does not stop.The simulation was carried out by the finite element method, assuming that tritium release from the sample is determined by diffusion and desorption processes from the sample surface. The experimental curves are satisfactorily described by a number of sets of desorption and diffusion parameters. One way or another they lie in the range of specified values. The Arrhenius dependences of the effective diffusion coefficient and desorption coefficient obtained for lithium ceramics 35 LMT are equal to:D=5,2×10-11m2sexp-21kJmoleRT,K=1.21×10-4m2sexp-64kJmoleRT.The values of the effective diffusion coefficient and tritium desorption coefficient in 25 LMT ceramics were 15 and 20% lower than in 35 LMT ceramics.

Screening of ten different plants in the process of supercritical water gasification

It is important to know the limitations of the supercritical water gasification (SCWG) in terms of behavior of different biomasses, especially when determining whether SCWG is a suitable conversion process for a certain biomass. Ten different biomasses (eight different plant species, of which two were grown in two different sites) were processed to evaluate this aspect. Moist and dry, woody and grassy biomasses were gasified in the same experimental setup under similar conditions. Only small differences could be seen in the gasification experiments. The carbon gasification efficiency was 60.3 ± 5.1 %, the gas compositions were very similar. Solid deposits formed in all experiments in the same temperature zone of the reactor containing coke, salt building elements and heavy metals, sometimes leading to plugging. Nevertheless, an experimental duration of 6 h could be achieved for the dry biomasses. The experiment with the moist biomass Reed Canary Grass was ended early due to plugging of the feed tubing which is due to the different size reduction procedure for moist biomasses resulting in bigger biomass particles. This emphasizes the importance of sufficient size reduction prior to the experiment. Potassium addition as a homogeneous catalyst, in form of potassium hydroxide, has proven to be beneficial regarding gasification efficiency, but poses a threat regarding plugging due to salt deposits in the system.

Silicon implantation and annealing in β-Ga2O3: Role of ambient, temperature, and time

Optimizing thermal anneals of Si-implanted β-Ga2O3 is critical for low resistance contacts and selective area doping. We report the impact of annealing ambient, temperature, and time on the activation of room temperature ion-implanted Si in β-Ga2O3 at concentrations from 5 × 1018 to 1 × 1020 cm−3, demonstrating full activation (>80% activation, mobilities >70 cm2/V s) with contact resistances below 0.29 Ω mm. Homoepitaxial β-Ga2O3 films, grown by plasma-assisted molecular beam epitaxy on Fe-doped (010) substrates, were implanted at multiple energies to yield 100 nm box profiles of 5 × 1018, 5 × 1019, and 1 × 1020 cm−3. Anneals were performed in an ultra-high vacuum-compatible quartz furnace at 1 bar with well-controlled gas compositions. To maintain β-Ga2O3 stability, pO2 must be greater than 10−9 bar. Anneals up to pO2 = 1 bar achieve full activation at 5 × 1018 cm−3, while 5 × 1019 cm−3 must be annealed with pO2 ≤ 10−4 bar, and 1 × 1020 cm−3 requires pO2 < 10−6 bar. Water vapor prevents activation and must be maintained below 10−8 bar. Activation is achieved for anneal temperatures as low as 850 °C with mobility increasing with anneal temperatures up to 1050 °C, though Si diffusion has been reported above 950 °C. At 950 °C, activation is maximized between 5 and 20 min with longer times resulting in decreased carrier activation (over-annealing). This over-annealing is significant for concentrations above 5 × 1019 cm−3 and occurs rapidly at 1 × 1020 cm−3. Rutherford backscattering spectrometry (channeling) suggests that damage recovery is seeded from remnant aligned β-Ga2O3 that remains after implantation; this conclusion is also supported by scanning transmission electron microscopy showing retention of the β-phase with inclusions that resemble the γ-phase.

Interchangeable effect of polyols-based zeolite on the separation of CO2, CH4, and N2 gases

The adsorptive separation process for CO2/CH4 and CH4/N2 gas separation has commercial potential, in biogas, Coalbed Methane process etc. although it remains to strive due to the absence of effective adsorbents. Zeolite NaY was used in this study due to its uniform pore structures, surface properties, and potential gas separation adsorbent. Zeolite NaY was modified by polyether polyols (PEPO) to get an adsorbent for selective separation of CO2/CH4 and CH4/N2 gas mixtures. The PXRD, FT-IR, GPC, 1H NMR, TEM, and surface area analysis were used to characterize the PEPO and PEPO-modified zeolite. The single component equilibrium adsorption desorption isotherms with PEPO modified NaY zeolites and NaY zeolite for CO2, CH4 and N2 were measured at 298, 313, and 328 K and up to 5 bar pressure. The isotherm data of CO2, CH4 and N2 were fitted in Dual Site Langmuir equations, and adsorption selectivity of CO2/CH4 and CH4/N2 gas mixtures was predicted using Ideal Adsorbed Solution Theory (IAST) method for 90:10, 50:50 (vol/vol) CH4/N2 and 80:20, 50:50 (vol/vol) CO2/CH4 feed gas mixtures representing coal bed methane gas composition and pressure conditions. The high surface area and hydroxyl groups in PEPO-modified NaY enhanced selectivity for CO2/CH4 and CH4/N2 gas separation. The selectivity predicted by the IAST method were 106.12 and 95.34 for 0.5 % PEPO-NaY (80:20 v/v and 50:50 v/v) for CO2/CH4 and 3.95 and 3.52 for 2 % PEPO-NaY (90:10 v/v and 50:50 v/v) for CH4/N2 at 298 K up to 5 bar respectively.

Effects of Gas Composition on the Lipid Oxidation and Fatty Acid Concentration of Tilapia Fillets Treated with In-Package Atmospheric Cold Plasma.

Cold plasma (CP) is a non-thermal preservation technology that has been successfully used to decontaminate and extend the shelf life of aquatic products. However, the preservation effect of CP treatment is determined by several factors, including voltage, time, and gas compositions. Therefore, this study aimed to investigate the effects of gas composition (GasA: 10% O2, 50% N2, 40% CO2; GasB: air; GasC: 30% O2, 30% N2, 40% CO2) on the lipid oxidation of tilapia fillets treated after CP treatment. Changes in the lipid oxidation values, the percentages of fatty acids, and sensory scores were studied during 8 d of refrigerator storage. The results showed that the CP treatment significantly increased all the primary and secondary lipid oxidation values measured in this study, as well as the percentages of saturated fatty acids, but decreased the percentages of unsaturated fatty acids, especially polyunsaturated fatty acids. The lipid oxidation values were significantly increased in the GasC-CP group. After 8 d, clearly increased percentages of saturated fatty acids, a low level of major polyunsaturated fatty acids (especially linoleic (C18:2n-6)), and a decrease in the percentages of eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3) were found in GasC-CP; that is, the serious oxidation of lipids was found in the high O2 concentration group. In addition, the sensory score was also lower than that of the hypoxia CP group. Therefore, high O2 concentrations can enhance lipid oxidation and the changes in the fatty acid concentration. Controlling the O2 concentration is reasonable to limit the degree to which lipids are oxidized in tilapia after the in-package CP treatment.

Investigation on gas generation and corresponding explosion characteristics of lithium-ion batteries during thermal runaway at different charge states

This study investigates the gas generation characteristics and explosion limits of the gas generated by 18650-type LiNi1/3Co1/3Mn1/3O2 (NCM) cells during thermal runaway (TR) at different states of charge (SOCs). An accelerating rate calorimeter is employed to initialize TR, together with an airtight jar for gas measurement. Based on the detected gas composition for NCM cells, the corresponding explosion limits are computed and further compared with those of LiFePO4 (LFP) and LiNi0.80Co0.15Al0.05O2 (NCA) cells. The results reveal that the gas generation rates are slightly higher for NCM cells with lower SOCs prior to the violent TR processes compared to those for high-SOC cells, primarily due to the elevated reaction temperature. Moreover, during violent TR, multiple-peak features are observed for the gas generation rate curves, especially at high-SOC conditions. On the other hand, typical Z-shaped explosion limit curves are observed for all generated mixtures. As the cathode material varies from NCM to LFP and NCA, the explosion limits shift from high-temperature regions to low-temperature regions. In contrast to common beliefs that the generation gas at high SOCs is more explosive, non-monotonic responses of the explosion limit curves are found with respect to cell SOC. The significance of minor components of the generated gas, including ethylene and ethane, in reducing the explosivity of the mixture, is highlighted through sensitivity analyses.

High-efficiency recovery of methane from coal bed gas via hydrate formation in emulsions

Although the hydrate-based coal bed gas (CBG) separations have been investigated, the obtained CH4 recovery ratios were not quite satisfactory. To further improve CH4 extraction, this study developed a high-efficiency CBG recovery method via hydrate formation in emulsions facilitated by an excellent anti-agglomerant. Thermodynamic promoters were introduced to lower operating pressure and the hydrate equilibrium conditions were determined. Then the effect of water-cut (40–100 vol%), initial pressure, experimental temperature, stirring rate and feed gas composition was investigated. The CH4 concentration in equilibrium gas first decreased then increased as the water-cut increased. Specifically, it decreased from 30.16 mol% to 8.23 mol% in the 60 vol% water-cut emulsions and CH4 recovery reached 88.02 % at 274.15 K and an initial pressure of 3.0 MPa, marking the highest CH4 recovery achieved in CBG separation thus far. The CH4 recovery was increased at low temperature while decreased at high pressure conditions. After a second-stage separation, the CH4 concentration in equilibrium gas decreased to 1.64 mol% from 30.16 mol%, signifying a remarkable 94.56 % recovery of CH4 from feed gas. The CH4 contents after a three-stage enrichment exceeded 87 mol%. This study furnishes valuable insights for CH4 recovery from CBG utilizing hydrate-based separation technology.

Techno-economic analysis on the balance of plant (BOP) equipment due to switching fuel from natural gas to hydrogen in gas turbine power plants

<abstract> <p>The concerns over greenhouse gas emissions, environmental impacts, climate change, and sustainability continue to grow. As a result of countermeasures, many modern gas turbine power plants and combined cycle power plants are considering to use hydrogen as a clean fuel alternative to fossil fuels in the power plant industry. We assessed the implications of such transition from natural gas to hydrogen as fuel in a gas turbine power plant's balance of plant (BOP) equipment. Using the DWSIM process simulation software and the methodology of compression power changes against different gas compositions, the impact of blending hydrogen with natural gas on temperature differentials, energy consumption, adiabatic efficiency, compression power, and economic implications in gas turbine power plants were examined in this paper. We discovered, through analysis, that there was not a noticeable boost in compression power or energy consumption when 50% hydrogen and 50% natural gas were blended. Similarly, there was no discernible difference in temperature differentials or adiabatic efficiency when 30% hydrogen and 70% natural gas were blended. Moreover, mixing 50% hydrogen and 50% natural gas did not result in a noticeable cost climb. In addition, the techno-economic analysis presented in this paper offered valuable insights for power plant engineers, power generation companies, investors in energy sectors, and policymakers, highlighting the nature of the fuel shift and its implications on the economy and technology.</p> </abstract>

Nonlinear Seepage Mechanism and Evolution Law of CO2 Enhancing Coalbed Methane Recovery

China’s coal seam permeability is low, and the original coal seam gas extraction is difficult. CO2 displacement of coal seam CH4 technology is an effective gas extraction technology. CO2 is injected into the coal seam under pressure, and competitive adsorption occurs with CH4 in the pores. The gas composition is nonuniformly distributed, and its viscosity μ is the dynamic parameter. As the gas is compressible, the pressure drops, and migration distance does not satisfy a linear relationship. Therefore, the gas transport does not conform to Darcy’s law. The mass transfer process and a multicomponent gas competitive adsorption were investigated theoretically and experimentally. The adsorption characteristics and gas compressibility determine the distribution of the gas components in pores and change the gas dynamic viscosity in different regions. The change in the gas dynamic viscosity in the channel is the direct reason for the nonlinear pressure gradient and gas flow curve. The permeability and gas component affect the degree of nonlinear deviation of the gas flow and pressure gradient curve. This affects the nonlinear deviation degree of the curve by changing the gas dynamic viscosity in the pore channel during displacement. The reasonable displacement pressure is the critical pressure (PO) through experimental and theoretical analysis.

Сухе гасіння коксу: утилізація надлишкового циркулюючого газу

The article is devoted to a practical solution to the problem of improving the environmental safety of a coke dry quenching unit by means of a new technology developed to reduce CO and coke dust emissions by introducing of the utilisation of excess circulating gas using a special utilisation unit, the main element of which is a special utilisation boiler. It is shown that the need to discharge harmful substances into the atmosphere during the operation of the coke dry quenching unit is associated with the fact that during the operation of the unit, repeated circulation of gases through hot coke leads to a change in the gas composition in the direction of increasing the amount of carbon monoxide (CO). This makes the plant explosive and the gas highly toxic. To reduce the explosion hazard of the plant, it is necessary to reduce the concentration of combustible components in the circulating gas. This is done by diluting the mixture with nitrogen. This article discusses the method developed by GIPROKOKS to utilise excess circulating gases by burning CO to CO2 using a special utilisation unit. The equipment of the utilisation unit can be located directly in the boiler house of the coke dry quenching unit or in a separate building near the coke dry quenching unit. The operation of the utilisation unit is controlled by a modern process control system. The concentration and gross carbon monoxide emissions are reduced in a special reactor. In the process of refining the implemented technology, it became necessary to make changes and improve some solutions. In particular, the operation of the gas path of the unit was changed, which increased the potential for receiving excess circulating gas, stabilised the combustion mode and became a key solution to ensure the aerodynamic operation of the coke dry quenching unit. A mixing device was also installed at the circulating gas inlet to the waste heat boiler, which, by controlling the flow rate and composition of the circulating gas, allowed to stabilise the reactor operation and somewhat improve the conditions for the utilisation (combustion) of combustible components when circulating gas of ‘ballasted’ composition is supplied. It is shown that the implementation of this technology by SE “GIPROKOKS” can significantly reduce the concentration of harmful substances and provides additional steam generation, which can be used for the technological needs of the enterprise or for generating electricity. Keywords: coke, dry quenching, afterburning, waste heat boiler, circulating gas, surplus, utilisation, CO content, carbon monoxide, coke quality. Corresponding author: A.A. Kogtin, e-mail: kogtin.giprokoks@gmail.com

Intricacies of CO2 removal from mixed gases and biogas using polysulfone/ZIF-8 mixed matrix membranes - part 1: experimental.

In this work, we explore the potential of polysulfone/ZIF-8 mixed matrix membranes (MMMs) for the enrichment of biogas to biomethane. To this end, we present data for these MMMs on permeability and selectivity as function of pressure and feed composition, at different loadings of ZIF-8. Specifically, we study dense polysulfone membranes prepared by solvent evaporation, with a ZIF-8 loading in the range 0.5-5 wt% for separation of CO2 from artificial mixtures of CO2 and CH4, and also biogas from an operating plant. The MMMs with 1 wt% filler loading gave the highest enhancement in permeability and selectivity, of 56.8% and 41% respectively, as compared to pure PSF membranes. At higher loadings, a tendency for the ZIF-8 particles to agglomerate was seen, which may compromise the ability of the filler to improve membrane performance. With mixed gases, increases in CO2 permeability of about 8 to 34% were observed depending on the gas composition, the enhancement being the higher, the lower the CO2 content. For biogas, permeability and selectivity of the 1% ZIF-8 loaded MMMs were found to be 14.6% and 39.64% lesser respectively than the pure gas values. The study thus throws light on the differences in membrane performance with mixtures as compared to ideal values obtained with pure gases and hence underlines the importance of lab-scale testing of the membranes with actual gas mixtures in the intended applications.

Preparation and characterization of graphene film using biogas derived from oil palm empty fruit bunch (OPEFB) by chemical vapor deposition (CVD) method

This study aims to fabricate graphene films using biogas derived from oil palm empty fruit bunch (OPEFB) as carbon precursors using chemical vapor deposition (CVD) method under various conditions. The fabricated graphene films were deposited on copper substrates at different temperatures and gas compositions. Scanning Electron Microscopy (SEM), Raman Spectroscopy, and the I-V test were used to analyze and characterize the properties of the fabricated film. From the characterization results, SEM images of films grown at 800°C (without additional H2 gas), and 900°C (without additional H2 gas) show a not so well-defined hexagonal domain shape with non-uniform morphology with variations in domain shape and orientation, while Raman spectra show it has only the D band and G band which are attributed to graphene oxide. On the other hand, at 900°C (with additional H2 gas), the SEM image shows more defined hexagonal domain shape and variations in domain shape and orientation, as well as the D, G and 2D band on the Raman spectra, which are like graphene with defects structure. Hence, it is concluded that graphene film was successfully produced at 900°C with additional H2 gas.

Modifiye atmosfer ile paketlemenin etli mantının raf ömrü ve kalite özelliklerine etkisi

This study aimed to evaluate the effects of modified atmosphere packaging on the shelf-life and quality characteristics of mantı (a meat-filled pasta product) stored in refrigerator conditions. In this direction, mantı, whose humidity value is reduced to 34% with the pre-drying process, were packaged with different gas mixtures (ambient air, 80% CO2 + 20% N2, 60% CO2 + 40% N2, 40% CO2 + 60% N2, 20% O2 + 40% CO2 + 40% N2) and kept in cold storage for 90 days. In this process, mantı samples were analysed regarding physico-chemical, microbiological, colour and sensory parameters. According to the findings, Escherichia coli, sulfide-reducing anaerobic bacteria and Salmonella spp. were not detected. While total aerobic mesophilic microorganism and mould yeast counts increased throughout storage, they were lowest in packages containing 80% CO2. The high count of microorganisms in the samples packaged with ambient air also showed parallelism with the lipid oxidation values, causing the products to remain below acceptable sensory levels starting from the 60th day of storage. In the modified atmosphere packaging application, the increased amount of carbon dioxide in the package ensured that the texture and flavour properties of the mantı were preserved close to the first day during their shelf life. As a result, the modified atmosphere packaging application preserved the quality characteristics of mantı for a long time, increased their stay in the aisle and allowed them to be acceptable to consumers. While the protective effect increased, especially with the increasing amount of CO2 in the gas composition, the product's sensory properties were also preserved during storage, and economic losses could be prevented.

Методичний підхід до обґрунтування способу газифікації кам’яного вугілля для виробництва синтетичних моторних палив

The aim of the article is to substantiate the most suitable method of gasification of Ukrainian hard coal for further production of synthetic motor fuel. For this substantiation, a methodical approach has been developed, the use of which has allowed to obtain the following results. As a raw material base, the article recommends long-flame coal of the Western Donbass, located on the territory of the Dnepropetrovsk region, where powerful enterprises for the extraction and enrichment of coal operate. The most common methods of coal gasification in the world are analyzed: Lurgi (counter-current steam-oxygen gasification of large-lump coal (or briquettes) in a stationary bed), Siemens (direct-flow steam-oxygen gasification in the pulverized coal stream), Texaco (direct-flow oxygen gasification in the flow of coal-water pulp). For each of these methods, material balances have been developed; the composition and quality of the generated gas, the possibilities of organizing the production of the necessary energy resources, the level of emissions of harmful substances into the atmosphere and wastewater discharge have been evaluated. A methodology for calculating the composition of generator gas is proposed, which takes into account the composition of the blast (content of oxygen, water vapor or water). All calculations were performed for an enterprise with a coal capacity of 550 thousand tons of working weight per year. Based on the calculations and comparison of their results, the Texaco method is recommended for industrial implementation. The advantages of this method are as follows: the absence of a stage of steam production for gasification, the scarcity of the water cycle, which practically excludes the formation of wastewater, and the possibility of using contaminated water from other sources for gasification; the highest total content of hydrogen and carbon monoxide in the resulting synthesis gas; the maximum assimilated capacity of production reactors and the largest number of capacities created in the world using this technology; utilization of the heat of the resulting gas to obtain a large amount of electric and thermal energy.

Comparative Assessment of Hydrothermal Gasification and Anaerobic Digestion using Aspen Plus and SuperPro

Wet biomass is gaining increasing attention as an energy source globally. Various wet biomass materials like macroalgae, microalgae, sewage sludge, cattle manures, and food waste, are of high moisture contents, typically around 70% or more. There are two routes of high potential for converting these wet biomasss resoures to gaeous fuel, which are biomethanation and supercritical water gasification (SCWG). Biomethanation is conversion of wet-organic residues to biogas using via anaerobic digestion process. SCWG is a thermochemical conversion process, taking place in supercritical water producing enriched CH4 and H2 gases. In this study, the two processes are comperatively investigated using different process simulation softwares. Aspen Plus was employed for SCWG, while the biomethanation process was simulated with SuperPro. Various raw materials were used as input. We calculated the energy efficiency of the biomethanation process using experimental yields from the literature. For the SCWG process, we determined the higher heating value based on the simulated composition of the methane-enriched gas. Additionally, we conducted an economic analysis to compare the two processes, taking into consideration specific criteria relevant to the Norwegian context.

Combustion of waste solids in a fluidized bed to generate sustainable energy

Exploring alternative options to address the impending global energy crisis while taking into account environmental concerns and climate change mitigation and addressing the sky-rocketing energy demand has become urgently essential. This need is further highlighted by the significant reliance of the Republic of Serbia on imported energy sources so that the focus of its energy sector strategy is rational use of energy resources, use of renewable energy sources (RES), and waste management with satisfying environmental regulations. The use of low-calorific and waste materials in conjunction with fluidized bed combustion technology is a method to achieve all the above goals synergistically. This paper presents experimental results of combustion of several solid wastes (coal mining waste from the ?RB Kolubara? complex, Serbia, paper sludge and hazelnut shells), conducted in an industrial prototype and experimental bubbling FB boiler (capacity up to 500 kW). Burning these wastes has a variety of advantages, including recovering substantial energy remaining in the waste and minimizing the overall waste volumes. The work focused on determination of furnace temperature profiles, composition of the flue gas at the furnace outlet as well as fluidization air and fuel flowrates, the minimum fluidization rate, fluidization number, maximum heat output and the transferred heat of the tested fuels. Based on the obtained results, potentials of FBC of waste fuels and the possibility of utilization of their energy potential are evaluated.

Biomass screening for syngas production by flash photopyrolysis.

A few seconds flash photopyrolysis is used as efficient screening tool for the investigation of selected biomass in producing syngas, hydrogen and biochar. This innovative approach allowed rapid pyrolysis of the biomass, which was followed by a precise gas analysis and quantification, using Mass Spectrometry (MS). The analysis of the gas composition from three distinct biomass wastes in this study provides new insights into their thermochemical characteristics, expanding thus our knowledge of the potential of the selected biomass resources for the production of carbon, syngas, and/or hydrogen-rich gas production. This enhanced characterization revealed the potential of biomass transformation in contributing to innovative green energy sustainable solutions.

Experimental Characterization and Simulation of a Dipole Plasma Antenna for VHF Band and Effect of Ar–Ne Gas Composition

Experimental Characterization and Simulation of a Dipole Plasma Antenna for VHF Band and Effect of Ar–Ne Gas Composition

Genesis of sediment‐hosted copper and silver mineralization at the Omatapati prospect, Kaoko Belt, Opuwo district, Kunene region, Namibia

AbstractThe Omatapati copper and silver prospect within the Kaoko Belt is located in the Opuwo district, Kunene region, Namibia. The prospect is hosted by dolomite and interbedded argillites of the Neoproterozoic Devede Formation, the Ombombo Subgroup. An ore body is exposed in shallow artisanal mining pits and drill‐cores of the prospect have grades of 0.4 to 5.2 wt% Cu, and 23 to 312 g/t Ag. The prospect was formed by both hypogene and supergene mineralization processes. The hypogene mineralization occurred in three stages. Stage 1 is represented by calcite veins containing chalcopyrite, bornite, sphalerite and galena. Stage 2 consists of quartz and calcite veins with chalcopyrite and bornite. Stage 3 consists of quartz‐calcite‐barite veins with chalcopyrite. The veins of stages 1 and 2 are subparallel or discordant to the foliation of argillites, and those of Stage 3 are NE‐striking and steeply dipping in the brecciated dolostone and argillite. The mineralization stages 1, 2, and 3 are overprinted by supergene chalcocite, digenite, annite, covellite, malachite, delafossite, hematite, and goethite. The supergene process forms a semi‐massive chalcocite‐covellite zone, which extends from the surface to ~50 m depth. The veins show average concentrations of 2.1 wt% Cu, 80 ppm Ag, and 532 ppm Pb for the stage 1, 3.1 wt% Cu, 118 ppm Ag, and 66 ppm Pb for the stage 2, and 18.6 wt% Cu, 675 ppm Ag, and 565 ppm Pb for the Stage 3 with supergene overprinting. Silver occurs as impurity in supergene chalcocite (6303 ppm Ag), digenite (4425 ppm Ag), and covellite (3060 ppm Ag). Fluid inclusions in quartz and calcite revealed that the hypogene mineralization occurred under a pressure >7–8 MPa. Temperatures of ore formation of the stages 1, 2, and 3 were >145–155 °C, >290–300 °C, and >190–230 °C, respectively. Large variation of salinities in each fluid inclusion assemblage suggests fluid mixing and dilution processes. Fluid inclusion gas compositions in the Stage 3 have weighted means of 98.98 mol% H2O, 0.75 mol% N2, 0.52 mol% CO2, 0.02 mol% CH4, 0.0021 mol% Ar, 0.0009 mol% H2S, and 0.00006 mol% He and indicate a signature of magmatic fluids mixed with meteoric waters or seawater. δ34SCDT values of sulfides in the stages 1, 2, and 3 in the prospect have three data clusters, (1) near 0 ‰ of chalcopyrite in the stages 1 and 2, (2) near −11 ‰ of bornite in the stage 2, and (3) +5 to +11 ‰ of the supergene chalcocite and covellite. Modes of occurrence of ores, fluid inclusions and sulfur isotope data show that the prospect is likely the same type as sediment‐hosted copper‐silver deposits with veining found in the Central African Copperbelt.

Effect of TIG welding parameters on 316 L stainless steel joints using taguchi L27 approach

The AISI 316 L stainless steel was welded using Tungsten Inert Gas (TIG) welding, utilizing ternary shielding gases Argon (Ar), Helium (He), and Nitrogen (N2). This study aimed to assess the effects of these ternary shielding gases on the microstructure, bead profile, and bead appearance. It provides a comprehensive grasp of welding parameters’ interplay with shielding gas compositions, enabling engineers to make informed choices that significantly influence the excellence, productivity, and lastingness of the welding process. The Taguchi L-27 approach was employed, incorporating different contents of N2 (2.5 vol. % to 7.5 vol. %) and He (10 vol. % to 30 vol. %) within the Ar shielding gas composition. Additionally, welding current intensities, ranging from 120 A to 180 A, were also used in the experiment. The results demonstrated that higher content of He and N2 resulted in elevated levels of austenite-forming elements. Therefore, for TIG welding at the arc current intensity of 150 A, it is recommended to utilize the shielding gas mixtures (2.5 vol. % N2 + 10 vol. % He + 87.5 vol. % Ar). Furthermore, by augmenting the content of both N2 and He within the Ar shielding gas mixture, in addition to adjusting the arc current, a notable expansion in both the width and depth of the weld profile was achieved. This achievement, in turn, played a pivotal role in securing comprehensive fusion throughout the welding process.