Non-reactive Gas Research Articles

Spatial Mapping of Dissolved Gases in the Danube Delta Reveals Intense Plant-Mediated Gas Transfer

Global estimates see river deltas and estuaries contributing about equally to CO2 and CH4 emissions as lakes and reservoirs, despite a factor 6 smaller surface area. Assessing the horizontal gradients in dissolved gas concentrations from large river reaches to connecting canals and wetland lakes remains a challenge in many deltaic systems. To elucidate the processes affecting local CO2 and CH4 concentrations in the Romanian part of the Danube Delta, we mapped dissolved O2, N2, He and Ar using a portable gas-equilibration membrane-inlet mass spectrometer (GE-MIMS), along with CO2, CH4, water temperature and conductivity. We measured the concentrations along the aquatic continuum from a small houseboat during two campaigns, in spring and autumn, to capture different hydrological and plant growth conditions. Delta-scale concentration patterns were comparably stable across seasons. Small connecting channels were highly influenced by the riparian wetland, which was strongest in the eastern part of the biosphere reserve. These sites represented the delta’s CO2 and CH4 hotspots and showed clear signs of excess air, i.e., supersaturation of dissolved noble gases with respect to air-saturated water. As the adjacent wetland was permanently inundated, this signal was likely caused by root aeration of Phragmites australis, as opposed to traditional excess air formation via water table fluctuations in the unsaturated zone. The special vegetation setting with reed growing on floating peat coincided with the highest CO2 and CH4 concentrations (>700 μmol/L CO2 and 13 μmol/L CH4, respectively) observed in an adjacent channel. Shallow lakes, on the other hand, were major sites of photosynthetic production with O2 oversaturation reaching up to 150% in spring. The observed deficit in non-reactive gases (He, Ar and N2) indicated that the lakes were affected by O2 ebullition from macrophytes. According to our estimations, this ebullitive flux decreased O2 concentrations by up to 2 mg/L. This study highlights the effect of plant-mediated gas transfer on dissolved gas concentrations and supports recent studies stressing the need to account for ebullitive gas exchange when assessing metabolism parameters from O2 in shallow, productive settings.

Laser-induced breakdown spectroscopy for local equivalence ratio measurement in opposed jet methane-air flames

Laser-induced breakdown spectroscopy (LIBS) has been applied to both non-reacting and reacting opposed jet flows to evaluate the measurement accuracy of instantaneous, local air-fuel ratio. However, the LIBS signal is much weaker in flames than in the corresponding non-reacting gases and more work is required to investigate the potential of this technique for instantaneous measurements in reacting flows and quantify measurement uncertainties. The present study reported local equivalence ratio measurements of methane/air flames in an opposed-jet burner, which allowed independent control of flow rate and air-fuel ratio. Images and emission spectra of laser-induced plasma were investigated simultaneously using both an Intensified CCD (ICCD) and a spectrometer with a high degree of spatial and temporal resolution. The influences of the camera delay time, exposure time and laser pulse energy on the LIBS measurements were investigated as well. The dependence of spectral intensity ratios of H/O and C2/CN on air-fuel ratio was quantified over a wide range of conditions extending from pure air to pure fuel. It was found that H/O and C2/CN intensity ratios depend monotonically on the mole fraction of methane in the ranges of 0.0–0.8 and 0.3–1.0 respectively. The presence of a flame within the laser beam led to significant measurement deterioration relative to the corresponding non-reacting flows. This could lead to increased measurement uncertainty, and was therefore corrected by increasing the laser pulse energy and applying a proposed data processing method; the proposed correction method was able to reduce the equivalence ratio measurement uncertainty to be within 10% for mixtures with methane mole fractions lower than 50% and within 15% for mixtures with higher methane mole fraction. The established correlations between the intensity ratios of H/O and C2/CN with local air-fuel ratio allowed measurement of the spatial gradient of air-fuel ratio across opposed jet diffusion flames. The LIBS measurements of air-fuel ratio in non-premixed flames were finally compared successfully with CHEMKIN simulations, which demonstrates the ability of LIBS to accurately measure the spatial gradient of the air-fuel ratio.

Characterization of groundwater recharge through tritium measurements

Abstract. After the nuclear weapons testing in the 1950s and 1960s, the atmospheric tritium levels have almost returned to natural levels (pre-1950 levels), which means that tritium is becoming more effective in determining transit times in hydrological systems. It has also been demonstrated that tritium is a non-reactive noble gas and in water is not subject to chemical reactions, absorption, or dissolution/precipitation processes, so it is conservative of the geochemical fingerprint of the source. In addition, it is used as an effective tracer of water contamination by landfill leachate, allowing to detect mixing percentages of the leachate up to levels not achievable with normal chemical analyses (less than 1 %). The purpose of the present work is to deepen the knowledge of the hydrogeochemical characteristics of the aquifers in the pedemontana area of the Venetian plain, and to formulate a conceptual framework of underground water circulation, aimed at understanding phenomena of contamination by toxic metals, harmful to human health. Tritium concentration analyses were performed on selected samples of groundwater collected in different wells in the south part of Treviso city to correlate the young age of the water recharge. The abundance of young waters, in fact, indicates a vulnerability of the aquifer to climate change with respect to possible contributions of surface waters, in particular to prolonged drought periods which could induce salinization dynamics.

Artificial Neural Network and Regression Models for Predicting Intrusion of Non-Reacting Gases into Production Pipelines

Wax deposition and gelation of waxy crude oil in production pipelines are detrimental to crude oil transportation from offshore fields. A waxy crude oil forms intra-gel voids in pipelines under cooling mode, particularly below the pour point temperature. Consequently, intrusion of non-reacting gas into production pipelines has become a promising method to lessen the restart pressure required and clear the clogged gel. A trial-and-error method is currently employed to determine the required restart pressure and restart time in response to injected gas volume. However, this method is not always accurate and requires expert knowledge. In this study, predictive models based on an Artificial Neural Network (ANN) and multilinear regression are developed to predict restart pressure and time as a function of seabed temperature and non-reacting gas injected volume. The models’ outcomes are compared against experimental results available from the literature. The empirical models predicted the response variables with an absolute error of below 5% compared to the experimental studies. Thus, such models would allow accurate estimation of restart pressure, thereby improving transportation efficiency in offshore fields.

Effect of spilled diluted bitumen on chemical air-water exchange in boreal lake limnocorrals

Following spills into water, petroleum oils can spread widely and produce surface slicks. Resulting slicks may impede volatilization and possibly increase chemical persistence in water. While the influence of oil films on chemical air-water exchange has been examined through theoretical and laboratory studies, field studies have not been conducted to assess the relevance of these effects following actual oil spill events. Here we evaluated the effect of diluted bitumen (dilbit) experimentally spilled in limnocorrals installed in a boreal lake on the volatilization of sulfur hexafluoride (SF6), a non-reactive volatile tracer gas. Dilbit spills were monitored over 70 days and SF6 was introduced twice (after 7 and 48 days) to evaluate the influence of spilled dilbit on the loss of SF6 from water. Volatilization rate constants of SF6 (kVOL) significantly decreased by up to 80% with increasing total dilbit spill cover. Using a theoretical equation, decreases in kVOL were largely explained by a reduction in open water area where chemical exchange across the air-water interface occurs. Apparent effects of the slick on SF6 mass transfer were estimated to be smaller by comparison (20%).To account for this reduction in volatilization, oil spill fate models should include a correction to consider the impact of spill cover on the air-water exchange of organic chemicals.

Stationary BGK Models for Chemically Reacting Gas in a Slab

We study the boundary value problem of two stationary BGK-type models - the BGK model for fast chemical reaction and the BGK model for slow chemical reaction - and provide a unified argument to establish the existence and uniqueness of stationary flows of reactive BGK models in a slab. For both models, the main difficulty arises in the uniform control of the reactive parameters from above and below, since, unlike the BGK models for non-reactive gases, the reactive parameters for the reactive BGK models are defined through highly nonlinear relations. To overcome this difficulty, we introduce several nonlinear functionals that capture essential structures of such nonlinear relations such as the monotonicity in specific variables, that enable one to derive necessary estimates for the reactive equilibrium coefficients.

Study of Argon and Xenon gas properties on DC-glow discharge plasma

With the advances in the plasma technology in several fields as waste management, space technology and medical applications, non-thermal plasmas have become popular. They replace the combustion fuels for stationary hall thrusters and require minimal voltage to sustain longer duration. Generally, non-reactive gases such as Xenon, Argon, Krypton in a pure or mixture form is used to generate plasma, in order to have overall better performance of the system. Hence, the study of these gases and its properties becomes very crucial for further improvement in any kind of application. Xenon has proven to be most efficient in Hall thruster as compared to the other gases, but its limited availability and high cost has led to the idea of replacing it with other gases that are in abundant. As the DC glow discharge is considered to be canonical problem of interest, the paper focuses on modelling and simulation of 1-D and 2-D. DC glow discharge tubes using Argon and Xenon as gases to generate plasma and study its properties. The trend in distribution of electron density, electron temperature and electric potential have shown little variation. However, the magnitude on electron density is slightly higher for Argon relative to Xenon for given operating conditions in 1-D simulation and in the case of 2-D simulation the diffusive nature in lateral direction has shown higher peak value for Xenon.

Understanding the transport and break up of reactive ejecta

This manuscript investigates reactive- versus hydrodynamic-breakup processes of ejecta. For this study, the reactive metal is cerium (Ce) and the nonreactive metal is tin (Sn), the nonreactive gas is helium (He) and the reactive gas is deuterium (D2) or hydrogen (H2). Experiments were performed in vacuum and the reactive- and nonreactive-gases at various pressures, where we endeavored to match the post-shock gas densities to differentiate between reactive- versus hydrodynamic-breakup processes. Hydrodynamic breakup sensitively links to the Weber number (gas density, liquid fragment diameter, surface tension, and the square of the relative velocity between the fragment and the gas), whereas reactive breakup links to the reactive dynamics which includes two processes. In one case the reactive metal breaks up into smaller fragments as rapidly as the reaction rate, and in the other a crust grows on the liquid fragments as the reactions occur, a diffusion limited process. In the latter case, the particle diameters increase with time as the crust grows. In this process, which is indicated by the data, particles breakup as the CeD2 loses strength with increasing temperature, leaving an exponentially increasing diameter.

Kinetics of nitrous oxide mass transfer from porewater into root aerenchyma of wetland plants.

The creation and/or restoration of wetlands is an important strategy for controlling the release of reactive nitrogen (N) via denitrification, but there can be tradeoffs between enhanced denitrification and the production of nitrous oxide (N2 O), a potent greenhouse gas. A knowledge gap in current understanding of belowground wetland N dynamics is the role of gas transfer through the root aerenchyma system of wetland plants as a shortcut emission pathway for N2 O in denitrifying wetland soils. This investigation evaluates the significance of mass transfer into gas-filled root aerenchyma for the N2 O budget in wetland mesocosms planted with Sagittaria latifolia Willd. and Schoenoplectus acutus (Muhl. ex Bigelow) Á. Löve & D. Löve. Dissolved gas tracer push-pull tests with N2 O and the nonreactive gas tracers helium, sulfur hexafluoride, and ethane were used to estimate first-order rate constants for gas transfer into roots and microbial N2 O reduction and thereby disentangle the effects of root-mediated gas transport from microbial metabolism on N2 O balances in saturated soils. Root-mediated gas transport was estimated to account for up to 37% of overall N2 O removal from the wetland soils. Rates of microbial N2 O reduction varied widely based on the organic matter content of the soil media and served as a key control on the fraction of N2 O that transferred into roots. This research identifies transport through root aerenchyma as a potential shortcut pathway for N2 O emission from wetland soils and sediments and indicates that this process should be considered in both measurements and mechanistic modeling of belowground wetland N dynamics.

Experimental study on the effects of different fluidic jets on the acceleration of deflagration prior its transition to detonation

Fluidic jet-in-crossflow (JICF) is a reliable technique facilitating the flame acceleration and the transition from deflagration to detonation, most previous investigations on this project have focused on JICF using combustible mixtures but there are relatively few studies explored the mechanism of non-reactive gas JICF in the process of deflagration-to-detonation transition (DDT). In this study, three non-reactive gases (i.e., He, N2 and CO2) are considered as the medium of fluidic jets, the detailed mechanism of JICF enhancing deflagrations in stoichiometric methane-oxygen mixture is discussed. We experimentally demonstrate that JICF prominently enhances the propagation characteristics of deflagration, i.e., the 1st shock wave (1st SW), the 2nd shock wave (2nd SW), the combustion wave (CW) and the formation of precursor shock wave. Non-reactive gas JICF has concurrently positive turbulence-enhancement as well as negative inert gas-inhibition effects, which simultaneously influence the propagation behavior of deflagration. By adjusting the pressure difference (i.e., pJ0/p0) in JICF and test mixture, the performance of non-reactive gas jet on the propagation characteristics of deflagration is varied and mainly dependent on the attributes of the JICF. Our observation sheds light on the competing mechanism of JICF in the acceleration of a deflagration.

The precursor shock wave and flame propagation enhancement by CO2 injection in a methane-oxygen mixture

Successful initiation of a detonation in a confined combustor with limited length is a formidable task for designing the detonation-based engines, shortening the length for the run-up distance of a detonation greatly reduces the weight of the detonation engine, rendering the detonation propulsion become possible in the advanced aerospace propulsion systems. In this work, we proposed a new method that using a non-reactive gas jet (CO2) to facilitate the formation of the precursor shock wave and the flame propagation speed in a deflagration wave in a stoichiometric methane-oxygen mixture, by changing a series of the injection parameters, i.e., the initial pressure of mixture, the jet delay time, the jet pressure and its position, the effects of those parameters on the deflagration propagation are systematically investigated. The experimental results show that, the development processes of pressure rise are divided into two stages prior to the DDT: 1) slow deflagration stage, which characterized by two discrete shock waves named as the 1st shock wave and 2nd shock wave; 2) Fast deflagration stage, the two discrete waves merge into a strong precursor shock wave, and the velocities of precursor shock and flame achieve to the “quasi-detonation” state. The experimental results also illustrate that, introducing the CO2 jet in the first stage prior to the DDT promotes the formation of precursor shock wave and accelerates the flame speed, which speeds up the transformation of a detonation in a shorter distance. By comparing different jet parameter combinations, it is found that high jet pressure and long jet time increase the local concentration of CO2, which adversely affect the formation of a detonation. Thereby there exists an optimal condition of injection, whose injection pressure ratio is 15, jet delay time is 20 ms and jet position is found to be 0.6 m, those parameters are verified to have prominent detonation-enhancement effects on DDT, the underlying mechanisms for those optimal conditions are explored and explained in this study. This study provided new experimental evidences supporting the theory of turbulence-enhancement effect on the initiation of a detonation.

Mitigation of disruption on IR-T1 tokamak by means of low-energy neutral beam injection to control runaway electron generation

In a tokamak, the poloidal magnetic field provided by the toroidal plasma current forms an essential part of the magnetic field confining the plasma. However, instabilities of magnetohydrodynamic equilibrium can lead to an uncontrolled sudden loss of plasma current and energy, which is called a disruption. Disruptions are of significant concern to future devices due to the large amount of energy released during the rapid quenching of the plasma. One important consequence of disruption is the generation of significant current carried in multi-MeV runaway electrons that are eventually lost into plasma components. They can damage the tokamak walls and its structure if they are not controlled. Disruption control by neutral beam injection has been performed on IR-T1 to study the effect on runaway electron generated by plasma disruptions. Noble gases are used for injection, pure Hydrogen, Helium and Argon. The use of these non-reactive gases for disruption control ensures they fast removed from the vessel after the termination of a tokamak discharge. A piezo-valve is used for injection which has the precision of 1 ms. The effect of runaway electron generation control during disruption is studied using a comparison between reference disruptive discharge and a discharge into which different impurity species are injected. The data collected can then be used to optimize the performance of these energetic electrons control generated in disruption.

Thermal and clinker‐catalyzed pyrolyses of polystyrene waste using the Portland cement solid‐base catalyst

AbstractPolystyrene is a nondegradable lightweight foamy substance that easily blows from landfills into drains and waterways. This material creates litter and water pollution and harms the wildlife who mistakenly eat it. This study investigated a cost‐effective pyrolysis approach for catalytic conversion of waste polystyrene into useful oil and gas products. The Portland cement was used as a solid base to catalyze the pyrolysis reaction for improving the product yield, lowering the reaction temperature and shortening the reaction time. Optimum reaction conditions were investigated by varying the process temperature, process time, and amount of the catalyst. The catalytic conversion of polystyrene into oil was measured about 94.98% at 400°C. In noncatalytic conversion experiments, same conversion efficiency was achieved at 600°C, which is significantly higher than the catalytic conversion. Catalytic pyrolysis produced oil with major part of volatile fractions and 42.14% styrene. The thermal pyrolysis produced oil with high styrene content (63.17%). Overall, styrene content of oil product was lower than the reported values in the literature. The noncatalytic pyrolysis produced nonreactive gases toward the copper‐I solution while catalytic pyrolysis produced highly reactive gases. The presence of olefins and acetylene in gaseous form confirmed the presence of hydrogen in the product.

Size control of Au nanoparticles from the scalable and solvent-free matrix assembly cluster source

Nanostructured gold is an intriguing system for heterogeneous catalysis at low temperature. Its activity is related to choice of support selection, particle-support interaction, and especially the particle size. Here, we investigate the possibility of controlling the size of Au clusters (nanoparticles) in the novel Matrix Assembly Cluster Source (MACS), a solvent-free nanoparticle source with potential for scale-up to the gram level. The novelty of the MACS is the idea of making clusters by sputtering a pre-condensed matrix of metal atoms embedded in a condensed non-reactive gas, e.g., Ar. This concept, introduced in 2016, has already proved deposition rates several orders of magnitude higher than conventional cluster beam routes. Such scale-up in the cluster production rate is crucial for industrial research on nanocatalysis under realistic reaction condition. Here, we report a systematic study of how Au metal loading in the matrix affects the size distribution of clusters generated. Furthermore, the obtained dependence of cluster size on deposition time provides clear confirmation of cluster formation inside the matrix by ion irradiation, rather than by aggregation of atoms on the TEM support after deposition.

Wide-ranging prediction of phase behavior in complex systems by CP-PC-SAFT with universal kij values. I. Mixtures of non-associating compounds with [C2mim][EtSO4], [C4mim][MeSO4], and [C2mim][MeSO3] ionic liquids

This study shows that the inter-relations between critical constants can explain various phenomena occurring in the ionic liquids (IL) systems, such as the higher solubility of aromatic compounds and the differences between solubilities in the specific ILs. Indeed, as the critical constants get more remote, the systems become more asymmetric, increasing thus the immiscibility gaps. The Critical Point-based Perturbed-Chain Statistical Association Fluid Theory (CP-PC-SAFT) EoS rigorously obeys the Tc and Pc of ordinary substances. Moreover, its high precision in modelling the liquid phase properties yields realistic estimations of the imaginary critical constants of ILs. Such features attach an enhanced predictive capacity to this model, even while neglecting the complex chemical background of ILs. Although the substantial disagreements between different sources allow examining the general truthfulness of predictions rather their quantitative precision, it is demonstrated that using the universal value of k12 = 0.027 obtained for just one of the VLE datasets, CP-PC-SAFT realistically predicts various phase equilibria in mixtures of non-reacting gases, n-alkanes, aromatic hydrocarbons, ethers, ketones and haloalkanes with the considered ILs. The accuracies of these predictions are comparable with the widely implemented COSMO-RS approach. However, unlike it, CP-PC-SAFT can be applied for estimating high-pressure phase equilibria and it provides accurate predictions of volumetric data of mixtures in the particularly wide range of conditions.

Technical note: Determination of binary gas-phase diffusion coefficients of unstable and adsorbing atmospheric trace gases at low temperature – arrested flow and twin tube method

Abstract. Gas-phase diffusion is the first step for all heterogeneous reactions under atmospheric conditions. Knowledge of binary diffusion coefficients is important for the interpretation of laboratory studies regarding heterogeneous trace gas uptake and reactions. Only for stable, nonreactive and nonpolar gases do well-established models for the estimation of diffusion coefficients from viscosity data exist. Therefore, we have used two complementary methods for the measurement of binary diffusion coefficients in the temperature range of 200 to 300 K: the arrested flow method is best suited for unstable gases, and the twin tube method is best suited for stable but adsorbing trace gases. Both methods were validated by the measurement of the diffusion coefficients of methane and ethane in helium and air as well as nitric oxide in helium. Using the arrested flow method the diffusion coefficients of ozone in air, dinitrogen pentoxide and chlorine nitrate in helium, and nitrogen were measured. The twin tube method was used for the measurement of the diffusion coefficient of nitrogen dioxide and dinitrogen tetroxide in helium and nitrogen.

Combined Effects of Cooled EGR and Air Dilution on Butanol-Gasoline TGDI Engine Operation, Efficiency, Gaseous, and PM Emissions.

Biobutanol is a promising alternative fuel for spark-ignition engines. Exhaust gas recirculation (EGR) and air dilution were evaluated on a TGDI engine fueled with butanol–gasoline (B20) in view of engine operation, efficiency, gaseous emissions, and PM emissions. For the B20 engine, EGR affected combustion more strongly than excess air dilution; the brake thermal efficiency (BTE) under excess air dilution was much higher than that with EGR. The oxygen concentration in the cylinder was also markedly reduced with EGR relative to air dilution, as the partial fresh charge was substituted with nonreactive gas. A reduced oxygen concentration contributed to differences in combustion between excess air dilution and EGR. Higher BTE was observed during combined EGR and excess air dilution operation, though it was slightly lower than that under excess air dilution alone. NOx was also markedly reduced by the combination of EGR and excess air dilution, but was slightly higher than that with EGR alone. Under combined dilution conditions, the particle number (PN) emissions from the B20 engine were reduced significantly, particle sizes decreased, and the nucleate PN significantly decreased.

Study of the transition from self-organised to homogeneous plasma distribution in chromium HiPIMS discharge

The self-organised plasma patterns, known as spokes or ionisation zones in magnetron sputtering discharges, were observed in a wide range of power densities, from low power direct current magnetron sputtering (dcMS) discharge to high power impulse magnetron sputtering (HiPIMS) discharge. For some target materials and non-reactive gases, it was observed that at very high power densities (>) the plasma exhibits a transition from a regime where spokes are observed to a homogeneous plasma regime. In this contribution, we present a comparison of plasma properties: plasma emission (optical emission spectroscopy) and flux of argon and chromium ions (mass spectrometry), measured both in the spoke regime and in the homogeneous plasma regime, aimed to expand the understanding of the plasma transition between the two modes. A simple biased flat probe was used to distinguish between the spoke regime and the homogeneous plasma regime. It was found that the flux of multiply charged ions (Ar2+ , Cr2+ , Cr3+ , Cr4+) increases abruptly at the transition between the spoke regime and the homogeneous plasma regime. Similarly, the emission from Cr+ ions exhibits a strong increase of about 50% when the plasma torus becomes homogeneous. These observations are interpreted as an increase in electron temperature and a change in the electron heating mode, from a combination of secondary electron heating and Ohmic heating towards pure Ohmic heating. The transition to the homogeneous plasma regime and pure Ohmic heating is only observed in non-reactive HiPIMS discharges for target atoms with the second ionisation potential higher than the first ionisation potential of Ar (15.76 eV), and a self-sputter yield larger than 1.

Shock tube evaluation on C2H4 ignition delay differences among N2, Ar, He, CO2 diluent gases

To reveal the fuel ignition delay differences among diluent gases, non-reactive gas Ar, He, N2 and reactive gas CO2 four gases were selected to compare the ethylene ignition delay difference on a shock tube rig. The tested condition temperature and pressure range is 1074–1832 K and 2 atm. Comparison results show that the ethylene ignition delay discrepancy was not pronounced among Ar, He and N2 these non-reactive dilution gases. In terms of CO2 dilution, a critical CO2 concentration was observed. When the CO2 concentration was lower than this critical value, no distinguished ignition delay difference was found. Conversely, the ignition delay difference was pronounced once the CO2 concentration was above this critical value. Particularly, the difference was specially apparent in low temperature conditions. Reaction dynamic analysis shows that the heat effect is predominant in low temperature while the chemical effect is predominant in high temperature in the reaction of CO2 participation. Additionally, the CH* and OH* radical emission signal intensity turns smaller and profile curve turns irregular as the CO2 ratio increases. The CO2 shows a strong inhibition effect which is closely related with H radical consumption reaction CO2+HCO + OH.

Atomistic Simulation of Coal Char Oxy-Fuel Combustion: Quantifying the Influences of CO2 to Char Reactivity

Coal oxy-fuel combustion requires CO2 dilution (recycling) to reduce the furnace temperature for material protection. This enhanced CO2 concentration reduces the O2 reaction rate while CO2 gasification contributes to the char reactivity. These conflicting influences together with a competitive behavior between O2 and CO2 complicate char O2/CO2 combustion behavior. Individually quantifying the influences accompanying the replacement of N2 with CO2 and clarifying the competitive behavior are essential for predicting the char O2/CO2 combustion rate, but this is difficult to obtain via experimental approaches. Here, a simplistic atomistic simulation investigated the char oxy-fuel combustion behavior. In simulations, the reactants (O2 and CO2) were either permitted to both react with char or permitted to have only one reactive gas with the other being a passive (nonreactive) gas to explore reactivity for individual gases in a O2/CO2 atmosphere. Thus, gasification contribution to char reactivity was isolated an...