N2 Concentration Research Articles

Small ponds have stronger potential for net nitrogen removal: Insight from direct dissolved N2 measurement

Growing demands for watershed nitrogen (N) removal have called attention to abundant small bodies of water such as ponds, which have long been heralded as efficient storage and processing systems. Although pond conservation, restoration, and creation have been widely implemented to mitigate N pollution, information is limited regarding the impact of size—that is, whether N removal potential and efficiency are dependent upon pond size. We investigated the dynamics of N removal rates in 56 ponds from a hilly watershed by studying their bimonthly N2 concentrations and fluxes. Our results showed that smaller ponds performed better in net N removal. This can be discerned from the areal N2 fluxes, which were the highest in small ponds (< 4, 000 m2). The corresponding N2 fluxes (4.73 ± 4.53 mmol N2 m−2 d−1) were 2 to 14 times greater than those observed in larger ponds. The N removal efficiency, a metric used to describe the portions of the substrates released as N2, was also significantly higher in the small ponds (∼8.7 %) than in the larger ponds (∼5.0 %). Further regression analysis showed that both areal N2 flux and N removal efficiency were negatively correlated with pond area. The underlying mechanisms behind the size effects of N removal could be attributed to small ponds having larger sediment contact area to water volume ratios. Thus, smaller ponds allow more opportunities for N to interact with bioactive sediments than larger ponds. Overall, our findings contribute to the understanding of the distal role of pond size in affecting N removal. This research also provides a strong rationale for considering the effects of system size when implementing management practices dedicated to maximizing N removal.

Влияние колебательно-возбужденного молекулярного азота на инфракрасное свечение газов O3 и N2O на высотах средней атмосферы Земли

The concentrations of N2(X1g+, v' = 1) and the emission intensities of infrared bands of ozone O3 and nitrous oxide N2O are calculated at altitudes of 30–70 km of the Earth's middle atmosphere during precipitation of electrons with energies E = 2, 4, 10 MeV. It is shown that for a given relativistic electron flux of 105 e/cm2·s·ster, the concentrations of vibrationally excited molecular nitrogen N2(X1g+, v' = 1) are about 105–106 cm–3 at altitudes of 50–70 km of the middle atmosphere. The emission profiles of the infrared bands of ozone at 4.7 µm and 9,9 µm, as well as the infrared band of nitrous oxide at 4.5 µm, are calculated for precipitation of high-energy electrons with energies E = 2, 4, 10 MeV. It has been shown for the first time that vibrationally excited nitrogen N2(X1g+, v' = 1) plays an important role in changing the infrared balance of the middle atmosphere as a result of inelastic molecular collisions with O3 and N2O molecules during precipitation of high-energy electrons.

Autonomous observations of biogenic N2 in the Eastern Tropical North Pacific using profiling floats equipped with gas tension devices

Oxygen Deficient Zones (ODZs) of the world’s oceans represent a relatively small fraction of the ocean by volume (&amp;lt;0.05% for suboxic and&amp;lt;5% for hypoxic) yet are receiving increased attention by experimentalists and modelers due to their importance in ocean nutrient cycling and predicted susceptibility to expansion and/or contraction forced by global warming. Conventional methods to study these biogeochemically important regions of the ocean have relied on well-developed but still relatively high cost and labor-intensive shipboard methods that include mass-spectrometric analysis of nitrogen-to-argon ratios (N2/Ar) and nutrient stoichiometry (relative abundance of nitrate, nitrite, and phosphate). Experimental studies of denitrification rates and processes typically involve either in-situ or in-vitro incubations using isotopically labeled nutrients. Over the last several years we have been developing a Gas Tension Device (GTD) to study ODZ denitrification including deployment in the largest ODZ, the Eastern Tropical North Pacific (ETNP). The GTD measures total dissolved gas pressure from which dissolved N2 concentration is calculated. Data from two cruises passing through the core of the ETNP near 17 °N in late 2020 and 2021 are presented, with additional comparisons at 12 °N for GTDs mounted on a rosette/CTD as well as modified profiling Argo-style floats. Gas tension was measured on the float with an accuracy of&amp;lt; 0.1% and relatively low precision (&amp;lt; 0.12%) when shallow (P&amp;lt; 200 dbar) and high precision (&amp;lt; 0.03%) when deep (P &amp;gt; 300 dbar). We discriminate biologically produced N2 (ie., denitrification) from N2 in excess of saturation due to physical processes (e.g., mixing) using a new tracer – ‘preformed excess-N2’. We used inert dissolved argon (Ar) to help test the assumption that preformed excess-N2 is indeed conservative. We used the shipboard measurements to quantify preformed excess-N2 by cross-calibrating the gas tension method to the nutrient-deficit method. At 17 °N preformed excess-N2 decreased from approximately 28 to 12 µmol/kg over σ0 = 24–27 kg/m3 with a resulting precision of ±1 µmol N2/kg; at 12 °N values were similar except in the potential density range of 25.7&amp;lt; σ0&amp;lt; 26.3 where they were lower by 1 µmol N2/kg due likely to being composed of different source waters. We then applied these results to gas tension and O2 (&amp;lt; 3 µmol O2/kg) profiles measured by the nearby float to obtain the first autonomous biogenic N2 profile in the open ocean with an RMSE of ± 0.78 µM N2, or ± 19%. We also assessed the potential of the method to measure denitrification rates directly from the accumulation of biogenic N2 during the float drifts between profiling. The results suggest biogenic N2 rates of ±20 nM N2/day could be detected over &amp;gt;16 days (positive rates would indicate denitrification processes whereas negative rates would indicate predominantly dilution by mixing). These new observations demonstrate the potential of the gas tension method to determine biogenic N2 accurately and precisely in future studies of ODZs.

High pressure ammonia oxidation in a flow reactor

The present work deals with an experimental and modeling analysis of ammonia oxidation at high pressure (up to 40 bar), in the 600–1275 K temperature range using a quartz tubular reactor and argon as diluent. The impact of temperature, pressure, oxygen stoichiometry and presence of NO has been analyzed on the concentrations of NH3 and N2 obtained as main products of ammonia oxidation. The main results obtained indicate that increasing either pressure or stoichiometry results in a shift of NH3 conversion to lower temperatures. The effect of pressure is particularly significant in the low range of pressures studied. The main product of ammonia oxidation is N2, while NO, NO2 and N2O concentrations are below the detection limit for all the conditions considered. The experimental results are simulated and interpreted in terms of a literature detailed chemical kinetic mechanism, which, in general, predicts satisfactorily the experimental results.

Raman Evidence of Multiple Adsorption Sites and Structural Transformation in ZIF-4

The zeolitic imidazolate framework, ZIF-4, exhibits soft porosity and is known to show pore volume changes with temperatures, pressures, and guest adsorption. However, the mechanism and adsorption behavior of ZIF-4 are not completely understood. In this work, we report an open to narrow pore transition in ZIF-4 around T ∼ 253 K upon lowering the temperature under vacuum (10-6 Torr) conditions, facilitated by C-H···π interactions. In the gaseous environment of N2 and CO2 around the framework, characteristic Raman peaks of adsorbed gases were observed under ambient conditions of 293 K and 1 atm. A guest-induced transition at ∼153 K resulting in the opening of new adsorption sites was inferred from the Raman spectral changes in the C-H stretching modes and low-frequency modes (<200 cm-1). In contrast to a single vibrational mode generally reported for entrapped N2, we show three Raman modes of adsorbed N2 in ZIF-4. The adsorption is facilitated by dispersive and quadrupolar interactions. From our temperature-dependent Raman results and theoretical analysis based on the density functional tight-binding approach, we conclude that the C-Hs are the preferred adsorption sites on ZIF-4 in the following order: C4-H, C5-H > C2-H > center of the Im ring (interacting with C-H centers) > center of the cavity. We also show that with an increasing concentration of N2 adsorbed at low temperatures, the ZIF-4 structure undergoes shear distortion of the window formed by 4-imidazole rings and consequent volumetric expansion. Our results have immediate implications in the field of porous materials and could be vital in identifying subtle structural transformations that may favor or hinder guest adsorption.

Hemispheric Asymmetry of the Annual and Semiannual Variation of Thermospheric Composition

AbstractWe examine hemispheric asymmetry of the annual and semiannual variation of the ratio of O and N2 concentrations (O/N2) using observations by the Global Ultraviolet Imager (GUVI) instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite and compare them with Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension (WACCM‐X) model simulations. We found that in the equatorial region, the “equinox peaks” of the observed O/N2 are near the end of March and October, and the two annual lows are near the beginning of July and January. Compared to the equatorial region, in the northern hemisphere (NH) low latitudes, the first “equinox peak” clearly shifts toward the December solstice, whereas in the southern hemisphere (SH) low latitudes, the “equinox peaks” shift toward the June solstice (JS), forming the hemispheric asymmetry characteristics of the annual and semiannual variation. Seasonal variation of O/N2 shows no apparent phase variation with altitude, and the annual and semiannual pattern is consistent from year to year. WACCM‐X reproduces the observed annual and semiannual pattern in NH but in SH, it simulates an annual variation instead of the observed annual and semiannual variation. The largest discrepancy occurs near JS in the lower and middle thermosphere: the simulated O density has an annual high near JS in SH; the simulated N2 density has an annual high near JS in NH but a predominant annual low near JS in SH. These are not in the GUVI data. A weaker thermospheric meridional circulation in the winter hemisphere, or a reduced summer‐to‐winter latitudinal gradient of neutral temperature in WACCM‐X simulations would make model‐data comparisons more consistent.

Gas dynamics within landfast sea ice of an Arctic fjord (NE Greenland) during the spring–summer transition

Sea ice is an active component of the Earth’s climate system, interacting with both the atmosphere and the ocean. Arctic sea ice is commonly covered by melt ponds during late spring and summer, strongly affecting sea ice physical and optical properties. How melt pond formation affects sea ice gas dynamics and exchanges between sea ice and the atmosphere, with potential feedbacks on climate, is not well known. Here we measured concentrations of N2, O2, and Ar, total alkalinity, and dissolved inorganic carbon within sea ice of Young Sound, NE Greenland, to examine how melt pond formation and meltwater drainage through the ice affect its physical properties and gas composition, including impacts on CO2 exchange with the atmosphere. Sea ice gas composition was controlled mainly by physical processes, with most of the gas initially in gaseous form in the upper ice layer. A minor contribution from biological processes was associated with positive estimates of net community production (up to 2.6 µmol Lice−1 d−1), indicating that the ice was net autotrophic. As the sea ice warmed, the upper ice gas concentrations decreased, suggesting a release of gas bubbles to the atmosphere. However, as melt ponds formed, the ice surface became strongly depleted in gases. Due to melt pond development, meltwater permeated through the ice, resulting in the formation of an underwater ice layer also depleted in gases. Sea ice, including brine, slush, and melt ponds, was undersaturated in CO2 compared to the atmosphere, supporting an uptake of up to −4.26 mmol m−2 d−1 of atmospheric CO2. As melt pond formation progressed, however, this uptake weakened in the strongly altered remaining ice surface (the “white ice”), averaging −0.04 mmol m−2 d−1. This study reveals the importance of melt pond formation and dynamics for sea ice gas composition.

Effect of N2 and CO2 dilution on syngas/air deflagration characteristics in narrow gap disk burner

ABSTRACT This study explored the typical features of flame from syngas/air premixed flame in a narrow gap disk burner based on diluted N2 and CO2. Four concentrations (i.e. 10%, 20%, 30%, and 40%) of CO2 and five concentrations (i.e. 10%, 20%, 30%, 40%, and 50%) of N2 were adopted in this study. The experiment was conducted in a narrow gap disk burner with a clearance of 2 mm. The results showed that the addition of N2 and CO2 significantly reduced the brightness of flame, the flame propagation velocity, and the pressure resulting from the explosion. When the CO2 concentration reached 40%, the maximum pressure was reduced to 60.78 kPa, which was 41.5% lower than that without diluent. When the N2 concentration was increased to 50%, the maximum pressure was reduced to 67.01 kPa, but at this point, the inhibition effect on the maximum pressure was not as good as 40% of CO2. Additionally, the dilution effect of CO2 was more obvious than of N2. An analysis on the dilution mechanism found that reduced moles of critical radicals H, O, and OH were an important reason for the inhibition effect. However, with the increase of N2 and CO2 concentrations, the unstable flame propagation behavior in a later stage was not inhibited, but enhanced. The unstable propagation behavior was related to the flow field disturbance caused by heat loss.

Study of On-Site Upgraded Livestock Biogas Production and Carbon Emission Reduction By Substituting Coals For Thermal Power Generation

The objective of this project is to integrate a farm-scale bio-desulfurization facility with a novel biogas hollow fibre adsorption module for biogas desulfurization and bio-natural gas production. In this study, the desulfurization experimental results showed that the bio-desulfurization system can remove 96.7 ± 6% of H2S from the biogas after an approximately two-month enrichment period. The average CH4, N2, and CO2 concentrations in raw biogas were 63.4, 15.2, and 21.1%, respectively. As for biogas upgrading experiments, the inlet biogas flow rates were applied from 5 to 20 L/min. The removal efficiency of CO2 under all biogas flow rates was 100%. Meanwhile, methane was promoted from 60% to nearly 94% (i.e. 57% increase in methane concentration). The replacement of anthracite and coking coal by upgraded biogas might reduce 44.4% and 42.5% of CO2 equivalent, respectively. The achievement of this project pursues the mitigation of carbon dioxide emissions by using upgraded pig biogas which can be enlarged and extended to all decentralized pig farms worldwide.

Study of on-site upgraded livestock biogas production and carbon emission reduction by substituting coals for thermal power generation

The objective of this project is to integrate a farm-scale bio-desulfurization facility with a novel biogas hollow fibre adsorption module for biogas desulfurization and bio-natural gas production. In this study, the desulfurization experimental results showed that the bio-desulfurization system can remove 96.7 ± 6% of H2S from the biogas after an approximately two-month enrichment period. The average CH4, N2, and CO2 concentrations in raw biogas were 63.4, 15.2, and 21.1%, respectively. As for biogas upgrading experiments, the inlet biogas flow rates were applied from 5 to 20 L/min. The removal efficiency of CO2 under all biogas flow rates was 100%. Meanwhile, methane was promoted from 60% to nearly 94% (i.e. 57% increase in methane concentration). The replacement of anthracite and coking coal by upgraded biogas might reduce 44.4% and 42.5% of CO2 equivalent, respectively. The achievement of this project pursues the mitigation of carbon dioxide emissions by using upgraded pig biogas which can be enlarged and extended to all decentralized pig farms worldwide.

Impact of He+N2 concentration on self-modulated laser wakefield acceleration driven by pulses of a few TW

Laser wakefield electron acceleration with ionization injection has rarely been studied in the low-power, self-modulated case. We performed simulations of such regimes using a mixture of He and N2 gases and driven by laser pulses with peak powers around 1 TW. Analyses show the generation of electron bunches with an average energy of up to 70 MeV, an energy spread as low as 18%, and an emittance as good as a fraction of a mm mrad. The obtained electron beam parameters lead to several trade-offs as a function of N2 concentration, allowing for many different designs.

Investigations on tailoring physical properties of RF magnetron sputtered Cadmium Sulphide thin films

The effect of nitrogen (N2) partial pressure on the structure and bandgap tunability of RF magnetron sputtered Cadmium Sulphide (CdS) thin films is investigated by varying N2 partial pressure in Ar/N2 mixture. In presence of N2, films have a polycrystalline structure with (002) preferential orientation, which leads to defect-free, continuous, dense, and fibrous structures with increased roughness. The average optical transmittance increased to > 80 at 500–2500 nm for 30 % N2 partial pressure, whereas the band gap decreases from 2.45 eV to 2.30 eV with increasing N2 concentration. This work shows that the bandgap of sputtered CdS thin films can be tuned with the variation of N2 concentration for customized applications.

Lower flammability limit of hydrogen/air mixture under different electrode parameters, initial pressure and diluent gas

The investigation of the lower flammability limit (LFL) is essential to the security application of hydrogen. In the present work, the LFL of hydrogen under a variety of conditions is systematically measured. The effect of electrode gap length (2–4 mm), electrode shape (30°, 90°, and spherical) and initial pressure (40–200 kPa) on the LFL of hydrogen/air mixture are analyzed. It shows that the LFL of hydrogen/air mixture increases with the increase of initial pressure and decreases with the increase of electrode gap length. The LFL of 30° electrodes is higher than that of 90° and spherical electrodes at the initial pressure higher than 80 kPa. Besides, the LFL of hydrogen/air mixture diluted with inert gas (CO2 and N2) at different initial pressure (50 kPa, 100 kPa, and 150 kPa) is investigated. The LFL of H2/air/CO2 mixture increases with increasing CO2 concentration, while the LFL of H2/air/N2 mixture is almost unchanged under different N2 concentration.

Phase 3 Open-Label Clinical Trial of Elexacaftor/Tezacaftor/Ivacaftor in Children Aged 2-5 Years with Cystic Fibrosis and at Least One F508del Allele.

Rationale: Elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) has been shown to be safe and effective in people with cystic fibrosis (CF) aged ⩾6 years with at least one F508del-CFTR allele but has not been studied in younger children. Objectives: To evaluate the safety, pharmacokinetics, pharmacodynamics, and efficacy of ELX/TEZ/IVA in children with CF aged 2-5 years. Methods: In this phase 3, open-label, two-part study (parts A and B), children weighing <14 kg (on Day 1) received ELX 80 mg once daily (qd), TEZ 40 mg qd, and IVA 60 mg each morning and 59.5 mg each evening; children weighing ⩾14 kg received ELX 100 mg qd, TEZ 50 mg qd, and IVA 75 mg every 12 hours. Measurements and Main Results: The primary endpoints for part A (15-d treatment period) were pharmacokinetics and safety and tolerability. For part B (24-wk treatment period), the primary endpoint was safety and tolerability; secondary endpoints included pharmacokinetics and absolute changes from baseline in sweat chloride concentration and lung clearance index2.5 (LCI2.5, defined as the number of lung turnovers required to reduce the end tidal N2 concentration to 2.5% of its starting value) through Week 24. Analysis of pharmacokinetic data from 18 children enrolled in part A confirmed the appropriateness of the part B dosing regimen. In part B, 75 children (F508del/minimal function genotypes, n = 52; F508del/F508del genotype, n = 23) were enrolled and dosed. Seventy-four children (98.7%) had adverse events, which were all mild (62.7%) or moderate (36.0%) in severity. The most common adverse events were cough, fever, and rhinorrhea. Decreases in sweat chloride concentration (-57.9 mmol/L; 95% confidence interval [CI], -61.3 to -54.6; n = 69) and LCI2.5 (-0.83 U; 95% CI, -1.01 to -0.66; n = 50) were observed from baseline through Week 24. Mean body mass index was within the normal range at baseline and remained stable at Week 24. Conclusions: In this open-label study in children 2-5 years of age, ELX/TEZ/IVA treatment was generally safe and well tolerated, with a safety profile consistent with that observed in older age groups, and led to clinically meaningful reductions in sweat chloride concentration and LCI2.5. Clinical trial registered with www.clinicaltrials.gov (NCT04537793).

In Situ Investigation on the Morphology and Formation Kinetics of a CO2/N2 Mixed Hydrate Film

The influence of N2 molecules on the morphology and growth kinetics of CO2 hydrate films under different gas compositions and subcooling degrees (ΔT) was studied using a gas bubble suspended in water and in situ Raman spectroscopy, and some perspectives about the CO2/N2-CH4 replacement were put forth in this work. The evolution morphologies and formation of hydrate films were studied via optical microscopy and in situ Raman spectroscopy, respectively. The results demonstrated that the size of the hydrate single crystal on the hydrate film was related to the N2 concentration and ΔT; the roughness of the hydrate film was inversely proportional to the N2 content and ΔT; and the hydrate formation rate was highest in the 80% CO2 + 20% N2 gas system, in which the function of N2 on the hydrate formation may primarily be to improve the hydrate film’s roughness and enlarge the gas pore size on the film, which makes molecular mass transfer easier to carry out, and to stabilize the CO2 hydrate structure. Raman results showed that the amount of CO2 stored in the hydrate phase was still greater than that of N2 molecules due to CO2 molecules being more stable in the hydrate phase, despite the fact that N2 molecules were more competitive for mass transfer during the evolution of hydrate films because of their smaller size. With an increase in N2 concentration and ΔT, the amount of CO2 molecules trapped in the hydrate phase decreased, which is partly due to the low concentration of CO2 in the gas mixture as well as the fact that the hydrate film was much dense and impeded mass transfer of CO2 molecules. The experimental results implied that the morphology of the hydrate film and the composition of the CO2/N2 mixed gas are important to achieve better replacement efficiency during the exploitation of natural gas hydrates via the CO2/N2-CH4 replacement method.

Effects of oxidant composition on premixed propane flames in a narrow-gap disk burner at elevated pressures

The effects of length-scale and oxidant composition on the propagation characteristics of premixed propane flames were investigated in a narrow-gap disk burner with a constant volume process (NGDB-CV). First, the oxidant was diluted with N2, and the disk gap was varied. Overall, flame propagation velocity decreased, and flame oscillation became weaker as the N2 concentration increased. In particular, the effect of the increasing N2 concentration on the weakening flame propagation velocity was clearer when the disk gap was sufficiently larger than the quenching distance. The trends in pressure increase varied with the disk gap and could be explained based on the flame propagation velocity and the heat transfer in the burned gas region. In addition, post-combustion with luminosity in the burned gas region was observed within larger disk gaps, and its mechanism was explained. Finally, the effects of oxidant composition on flame oscillation were examined by controlling the concentrations of N2, CO2, and He. It was found that the Lewis number plays an important role in flame oscillation. The ratio of the laminar burning velocity to the Lewis number dominated the oscillation frequency, and the oscillation amplitude was additionally affected by the variation in momentum across the flame. Finally, the mechanism of the flame oscillation was refined.

Assessing the calculation of conductive and acinar ventilatory heterogeneity indices Scond and Sacin from multiple-breath washout data.

Sensor errors resulting in elevated values of N2 concentration [N2] in commercial multiple-breath washout (MBW) devices have been shown to prolong the washout and result in erroneously high functional residual capacity (FRC) and lung clearance index (LCI) values. The errors also affect the indices of conductive and acinar ventilatory heterogeneity (Scond and Sacin) although the mechanism by which this change in values occurs remains unclear. Exploring these effects also provides a timely opportunity to examine the appropriateness of the algorithm used to calculate these indices. Using a two-compartment model with differing specific ventilation (SV) such that the lower SV unit empties late, noise-free MBW were simulated both corrected and uncorrected for the recent sensor error. Scond was calculated using regression of normalized phase III slope (SnIII) against lung turnover (TO) from a TO range starting at 1.5 and ending at an upper turnover (TOupper) between 4 and 8 (default 6) over a range of simulated values. The principal effect of the sensor error was that as the MBW proceeded the phase III slope of successive breaths was normalized by an increasingly overestimated [N2], resulting in SnIII values that fell precipitously at high TO, greatly reducing Scond. Reanalysis of previously published data and of simulated data showed a large proportional bias in Scond, whereas Sacin was only minimally affected. In adult subject data, reducing TOupper below 5.5 was associated with a large drop of up to ∼60% in Scond calculated from data corrected for sensor error. Raising the upper TO limit elevated Scond by ∼20% but with a large concomitant increase in variability. In contrast to Scond, Sacin was relatively unaffected by changes in TOupper with changes of <3%. This work serves to emphasize that the upper limit of TO of 6 represents an appropriate upper limit for the calculation of Scond.NEW & NOTEWORTHY Sensor errors that elevated values of N2 concentration in commercial multiple-breath washout (MBW) devices resulted in errors in calculated parameters including Scond and Sacin. We examined the mechanism of the change in values produced by these errors and explored the appropriateness of the calculation of Scond and Sacin. This work serves to emphasize that the current algorithm in use is appropriate for the calculation of Scond and Sacin.

Modelling and simulation of fluidized bed steam-oxygen gasification of sewage sludge using thermochemical equilibrium and experimental data

This paper presents a gasifier model to describe steam-oxygen gasification of sewage sludge, as well as simulations to assess the process performance. The gasifier model was set up in the Aspen Plus® software and uses a combined equilibrium and empirical approach. A comparison of the model’s predictions with experimental data showed sufficient accuracy to describe the process The oxygen demand (oxygen ratio) of the gasifier and the cold gas efficiency were found to be highly dependent on various operation parameters, thus a comprehensive sensitivity study was presented. To obtain the relevant gasifier temperature of 850 °C using dried sewage sludge, an oxygen ratio of 0.33 and a cold gas efficiency of 0.65 was calculated. Syngas stoichiometry described by the H2/CO-ratio was found to be adjustable by altering the steam to carbon ratio nSC, which enables to tailor the syngas composition to suit the desired downstream application. The simulations predicted that the water-free syngas has a N2 concentration of 0.04 m3m−3 that originated from fuel-bound nitrogen, which needs to be considered for downstream syngas application. A limestone addition of 0.03 kg limestone per kg fuel was calculated to be the optimum in terms of high cold gas efficiency as well as tar and sulfur reduction. Overall, steam-oxygen gasification was characterized as a promising conversion process.

Experimental investigation for comparative effectiveness of CO2+N2 and CO2+N2+H2 on integrated methane production and carbon storage from natural hydrate media

CH4 hydrates have recently been hailed as a promising new sustainable energy source. The replacement of CO2 within natural gas hydrates is a method that may be used for simultaneous energy production and carbon dioxide storage. In the marine settings of Krishna Godavari basin, pressure and temperature circumstances prevent the faster replacement of hydrate reservoirs by injected CO2. In this work, using a depressurization method and CO2-N2 gas (as a standing for flue gas exhaust) injection, it was tested whether it was technically feasible to recover CH4 while ensuring long term CO2 storage. The presented experiments have demonstrated that injecting gas with a low N2 concentration (up to 40%) happens to cause a significant co-growth in hydrates of mixed nature, as indicated by observed data, along with recovery of CH4. While the results showed that gas injection synthesis of CH4 and its replacement by CO2 was feasible in marine settings, careful attention was required to the proportions of the injected mixed gases. Herein, the role of hydrogen in low concentration is essential; thus, its role as a diluent must be explored separately. Beyond a certain threshold of N2 in the mixed gas, low CH4 recovery (i.e. less than 10 mol% was observed). Alternatively, when a higher concentration of N2 was injected along with H2, it was possible to see a continuous dissociation of CH4 hydrate, even at 45% N2. Beyond 40 mol% N2, low CH4 recovery (i.e., less than 10 mol%) was observed due to a replacement ratio of less than 0.27. Alternatively, when a higher concentration of N2 (45 mol%) was injected along with 1 mol% H2, it was possible to notice a continuous dissociation of CH4 hydrate. The findings of this study, indicate the feasibility of injecting mixed flue gas compositions (CO2 +N2) along with low concentration of H2, as a diluent, for recovery of CH4 from a natural gas hydrate reservoir.

Sustainable Strategies to Counteract Mycotoxins Contamination and Cowpea Weevil in Chickpea Seeds during Post-Harvest.

Mycotoxins contamination and pest infestation of foods and feeds represent a pivotal threat for food safety and security worldwide, with crucial implications for human and animal health. Controlled atmosphere could be a sustainable strategy to reduce mycotoxins content and counteract the vitality of deleterious organisms in foodstuff. Ozone treatment (O3, 500 ppb for 30, 60 or 90 min) and high nitrogen concentration (N2, 99% for 21 consecutive days) were tested in the post-harvest management of four batches of Cicer arietinum grains to control the presence of mycotoxigenic fungi and their secondary metabolites, as well as pest (i.e., Callosobruchus maculatus) infestation. At the end of the treatment, O3 significantly decreased the incidence of Penicillium spp. (by an average of -50%, independently to the time of exposure) and reduced the patulin and aflatoxins content after 30 min (-85 and -100%, respectively). High N2 concentrations remarkably reduced mycotoxins contamination (by an average of -94%) and induced pest mortality (at 100% after 5 days of exposure). These results confirm the promising potential of O3 and N2 in post-harvest conservation strategies, leading to further investigations to evaluate the effects on the qualitative characteristics of grains.