Gas Composition Research Articles

Techno-economic, energy, and exergy analyses of invasive weed gasification for hydrogen enriched producer gas production

This research work deals with the examination of the techno-economic, exergy, and energy analyses of biomass gasification of the invasive weed Parthenium hysterophorus (PHP) using Steam - Carbon dioxide (CO2) as a gasifying agent with the support of simulation modeling for sustainable energy conversion process. The aim of this work is to simulate the gasification process through consideration of the impacts of various operating factors on gasification. This study attains the gradual increase in hydrogen (H2) concentration from 51% to 63% along with the rise in carbon monoxide (CO) from 14.5% to 19% using Aspen Plus simulation. CO2 falls concurrently from 24% to 13.5%. The findings demonstrate significant advancements over earlier studies in terms of both gas composition and overall system performance. A computational model has been developed for the estimation of energy performance indicators such as total energy input, and energy consumed per mass of biomass gasified, which are used in the determination of the system's energy efficiency. The exergy analysis of the system is performed to assess the system's total losses in terms of efficiency gathered from the system's exergy ratios. The economic analysis evaluates the system's economies of scale by gas production at ₹.15/kg and long-term sustainability. The proposed system has been found with the potential to produce a high yield of alternative energy from PHP with increased economic efficiency and lower environmental impact.

Chemistry, Growth, and Fate of the Unique, Short‐Lived (2019–2020) Water Lake at the Summit of Kīlauea Volcano, Hawaii

AbstractLess than a year after the 2018 Kīlauea caldera collapse and eruption, water appeared in newly deepened Halemaʻumaʻu crater. The lake—unprecedented in the written record—grew to a depth of ∼50 m before lava from the December 2020 eruption boiled it away. Surface water heightened concerns of potential phreatic or phreatomagmatic explosions but also offered a new means of possibly identifying eruption precursors. The U.S. Geological Survey Hawaiian Volcano Observatory (HVO) monitored the lake via direct visual observation, webcams, thermal imaging, colorimetry, and laser rangefinders. HVO also employed uncrewed aircraft systems to sample the water and measure near‐lake gas composition. The lake's δD and δ18O indicate a groundwater source with substantial evaporation. The initial sample had a salinity (total dissolved solids concentration) of 71,000 mg/L and was rich in sulfate (∼53,000 mg/L), iron (∼500 mg/L), and magnesium (∼10,000 mg/L). Subsequent samples were slightly more dilute. The water's pH (∼4), δ34S (+4.3‰), and surface temperatures (up to 85°C) suggest, rather than significant scrubbing of magmatic volatiles, leaching of basalt and reactions with sulfate minerals resulted in high concentrations of sulfate and other solutes. Thermodynamic modeling and precipitate mineralogy indicate that water composition was controlled by iron oxidation and sulfate dissolution. Although the lake exhibited no detectable precursors before the next eruption, and phreatic or phreatomagmatic explosions did not materialize, our multi‐parameter approach to monitoring yielded an enhanced understanding of the hydrologic, geologic, and magmatic conditions that led to the formation of the unique and short‐lived lake.

Real-time experimental investigation of a multi-flow biomass gasifier by using various locally available wood biomass

Biomass gasification is one of the prominent technologies for thermal applications, electricity generation through engines. The present investigation was carried out to obtain behavior of multi-flow gasifier by using locally available wood biomass chips (i.e., Acacia Nilotica & Eucalyptus biomass). Experiments were conducted to examine the variation of gas composition, LHV, cold gasification efficiency, equivalence ratio at different flow rates, and pressure drop with the time in complete operation of gasifier. Result shows that producer gas obtained from this gasifier has maximum lower heating value of 4.39 MJ/kg with hydrogen gas (13.61% vol/vol) and carbon monoxide (15.61% vol/vol). The composition of CH4 in producer gas was less than 2%. The maximum cold gas efficiency of 72.2% was obtained at optimal equivalence ratio of 0.309 with gas flow rate of 5 g s−1 with moisture content of 7.51%. These locally available wood can be appropriate feedstock for gasifiers. The clean and cooled gas can be utilized in internal combustion engines or turbines for clean power production.

Particle-in-cell/Monte Carlo collision simulation on gap breakdown characteristics of under the conditions of hot-electrode and high-temperature gas medium in low-voltage circuit breaker chamber

The gas composition inside the low-voltage circuit breaker (LVCB) chamber and the residual plasma in the post-arc stage affect the breakdown process, which in turn affects the breaking capacity of LVCBs. In this paper, the back-arc breakdown and post-arc re-breakdown phenomena occurring inside the LVCB chamber are categorized as the breakdown in the case of high-temperature gas gap of hot electrodes, for which a particle-in-cell/Monte Carlo collision simulation model has been established, which takes into account the effects of high-temperature gas components, cathode electron thermal emission, electron collision ionization, and other effects, and simulation studies have been conducted. The simulation results show that the gap breakdown is mainly caused by the high-temperature hot free background gas and the cathode thermal electron emission. A plasma sheath layer is formed at the cathode during the breakdown process, and the electric field strength in the sheath layer is higher than that in other regions. With the development of the streamer to the cathode, the thickness of the sheath layer becomes narrower and the electric field strength increases, and finally, a discharge plasma channel is formed in the gap.

Deciphering cometary outbursts: linking gas composition changes to trigger mechanisms

ABSTRACT Dust and gas outbursts are recurrent cometary phenomena, playing a crucial role in shaping the coma. Proposed outburst trigger mechanisms include cliff collapse, pressure pockets, and amorphous-to-crystalline phase transition of water ice; however, the underlying processes remain inadequately understood. In this study, we analyse Rosetta/ROSINA data from multiple outbursts on comet 67P/Churyumov-Gerasimenko and present the evolution of the gas composition in the comet’s coma during outburst events. We distinguish two distinct categories of cometary outbursts on the comet: water-driven events characterized by rapid (minutes to hours) changes in coma composition, and CO2-driven events displaying a slow, prolonged (hours to days) increase in highly volatile species. We tentatively associate these different gas composition patterns with different trigger mechanisms. Exposure of fresh ice due to cliff collapse leads to a notable water enhancement, while most perihelion outbursts coincide with substantial density increases of CO2. We propose that these CO2-driven events originate from subsurface gas-filled cavities, whose walls are suggested to have been sealed by earlier refreezing of CO2 migrating from warmer spots, hence increasing the cavity pressure required to burst.

Using natural gas content of groundwater to improve the understanding of complex thermo-mineral spring systems

The varied gaseous composition of thermo-mineral waters emerging in a non-active zone reflects the diversity and complexity of groundwater pathways and provides important insights into their hydrogeological behaviours. The investigated geochemical content of complex thermo-mineral springs revealed the need to use dissolved gas contents as part of a multi-tracer approach to discriminate processes, geogenic (water–gas-rock interactions), abiotic (geological confinement, flow paths) and biotic activity influencing geochemical of groundwater along regional pathways. Irrespective of the dissolved element content or the water type, examining the overall concentration of dissolved gases enables an effective delineation of regional groundwater flow paths. Using dissolved gas content further contributed to the circumvention of some analytical challenges associated with conventional isotopic or geochemical techniques, often linked to the high concentration of elements such as iron, sulfate, sulfide or other naturally occurring elements content. The primary objectives are to analyse the gas composition of individual springs, to identify the origin of these gases in the groundwater, and to use this gas composition to improve the understanding of the flow patterns contributing to the geochemical diversity observed at the surface. From field investigations in a geologically and structurally complex area of Eastern Corsica (France), three types of gas contents are identified: (type 1) CH4 & H2S-rich, (type 2) N2-rich and (type 3) CO2-rich. The study of these dissolved gases highlights that the wide geochemical diversity of thermo-mineral waters observed here is not only related to the mineralogical composition of the local aquifer but also involves strong and cumulative interactions along deep regional circulation pathways. This approach also reveals a common deep crustal gaseous influence characterised by N2 production, which interacts during up flow with groundwater and then with the local metamorphic or sedimentary rock matrix. The groundwater’s isotopic and geochemical contents are then altered by local lithologies encountered through both abiotic and biotic interactions. Finally, at shallow depths, phreatic groundwater can add its geochemical and isotopic footprint and dilute this complex mixture before groundwater emerges as mineral spring. This paper answers the primary objectives yet further demonstrates that using dissolved gas as a tracer of groundwater flow paths allows a deeper interpretation of surface geochemical and isotopic observations, distinguishes local from regional flow paths, and provides information about processes at the origin of groundwater diversity.The combination of tools presented in this paper (i.e., geochemical, dissolved gas, and isotopic tools) allows the establishment of a reliable regional groundwater flow scheme for thermo-mineral waters in a non-active zone. This scheme is essential to improve thermo-mineral water management, and protection to ensure their sustainable quality in front of increasing anthropogenic and climatic pressures.

Machine Learning-Based Interfacial Tension Equations for (H2 + CO2)-Water/Brine Systems over a Wide Range of Temperature and Pressure.

Large-scale underground hydrogen storage (UHS) plays a vital role in energy transition. H2-brine interfacial tension (IFT) is a crucial parameter in structural trapping in underground geological locations and gas-water two-phase flow in subsurface porous media. On the other hand, cushion gas, such as CO2, is often co-injected with H2 to retain reservoir pressure. Therefore, it is imperative to accurately predict the (H2 + CO2)-water/brine IFT under UHS conditions. While there have been a number of experimental measurements on H2-water/brine and (H2 + CO2)-water/brine IFT, an accurate and efficient (H2 + CO2)-water/brine IFT model under UHS conditions is still lacking. In this work, we use molecular dynamics (MD) simulations to generate an extensive (H2 + CO2)-water/brine IFT databank (840 data points) over a wide range of temperature (from 298 to 373 K), pressure (from 50 to 400 bar), gas composition, and brine salinity (up to 3.15 mol/kg) for typical UHS conditions, which is used to develop an accurate and efficient machine learning (ML)-based IFT equation. Our ML-based IFT equation is validated by comparing to available experimental data and other IFT equations for various systems (H2-brine/water, CO2-brine/water, and (H2 + CO2)-brine/water), rendering generally good performance (with R2 = 0.902 against 601 experimental data points). The developed ML-based IFT equation can be readily applied and implemented in reservoir simulations and other UHS applications.

Multi-physics field modeling and electrochemical performance analysis of medium-temperature methanol-fueled proton-conducting solid oxide fuel cell

ABSTRACT A two-dimensional axisymmetric multi-physics field simulation for a methanol-fueled proton-conducting solid oxide fuel cell (CH3OH-SOFC-H) was created in this work. The influence of structural and operating parameters on the performance of the cell was analyzed. Moreover, the cell performance was compared with that of a methanol-oxygen ion-conducting SOFC (CH3OH-SOFC-O) under the same operating conditions. It was found that the anode support enables CH3OH-SOFC-H to exhibit higher performance, with the highest power density being 1493.3 W‧m−2 at 973 K. As the anode flow rate rises, the current density rises and subsequently falls, with a peak of 7623.6 A‧m−2. Meanwhile, as the methanol content in the gas composition and the cathode flow rate increase, so does the current density. CH3OH-SOFC-H has better electrochemical performance at low and medium temperatures, reaching 562.64 W‧m−2 at 773K (66% higher than that of CH3OH-SOFC-O at the same operating conditions). Meanwhile, CH3OH-SOFC-O has better performance at high temperatures. This study provides a theoretical reference for the subsequent application and promotion of CH3OH-SOFC-H.

Impact of Sweep Gas on the Degradation of an La0.6Sr0.4Co0.8Fe0.8O3 Anode in a Solid Oxide Electrolysis Cell

The degradation of solid oxide electrolysis (SOE) cells with different anode sweep gases was studied in 1000 h-long measurements in order to investigate the impact of sweep gas composition on cell performance. Cathode-supported electrolysis cells with an La0.6Sr0.4Co0.2Fe0.8O3 air electrode (active area of 4 × 4 cm2) were tested under a constant current (−0.25 A/cm2) in the electrolysis mode while supplying the cathode side with 70% H2O–30% H2 mixtures at 800 °C and using oxygen, nitrogen, and steam as sweep gases. It was demonstrated that the degradation of the anode in steam conditions resulted in more than a 2-fold increase in both, polarization and ohmic resistance (from 0.20–0.25 to 0.6–0.65 Ω cm2 compared to relatively stable values of 0.15–0.2 Ω cm2 for N2), as a consequence of the phase decomposition. Strontium played an important role in steam-induced degradation, migrating from the volume of the electrode layer to the surface of the electrolyte. As a result, the Sr-enriched layer demonstrated susceptibility to Cr poisoning. The cell purged with N2 demonstrated enhanced performance, while the use of oxygen led to degradation originating from the well-described delamination process. DRT analysis demonstrated some similarity of the spectra for steam and N2, namely the presence of a slow process at τ≈0.5 s, which might be associated with hindered oxygen transport due to point defect association in the perovskite structure. The results of this study showed that Sr-containing materials likely cannot be used as an SOE anode in high humidity conditions.

Geochemistry of Liquid Hydrocarbons and Natural Gases Combined with 1D Basin Modeling of the Oligocene Shale Source Rock System in the Offshore Nile Delta, Egypt.

The current study aims to integrate the geochemical characteristics of the Oligocene shale source rock system, oil, condensate, and natural gas samples in the Oligocene sandstone reservoirs from three exploration wells located in the offshore Nile Delta, East Mediterranean Sea, using organic geochemistry and a 1D basin modeling scheme. The Tineh shales exhibit total organic carbon values ranging between 0.90 and 1.89 wt %, along with hydrogen index values in the range of 54-240 mg hydrocarbon/g rock. The geochemical characterization suggests that the shale intervals of the Oligocene Tineh Formation contain type II-III and type III kerogens and, thereby, could be regarded as promising oil- and gas-prone source rocks with high contributions of gas generation potential. The study also reconstructs the 1D thermal and burial history models, showing that the Oligocene Tineh source rock system is in the main oil and wet gas generation phases from the late Miocene to the present time. The simulated basin models reveal the transformation (TR) of 10-50% kerogen to oil during the late Miocene-early Pliocene period and that the Oligocene Tineh source rock system has larger oil generation and expulsion competency, with a TR value of up to 65% during the early Pliocene-Pleistocene time period. The thermogenic gas was also formed during this time and continued to the present day. This study also investigated the presence of oil and condensate in the Oligocene sandstone reservoir samples and revealed that they were generated from mature source rock, ranging from moderately to highly mature stages. This source rock unit was deposited in fluvial to fluvial-deltaic environments under oxic mixed organic conditions and accumulated during the Tertiary time, as evidenced by the presence of the oleanane biomarker dating indicator. The molecular and isotope compositions of natural gases revealed that most of the natural gases in the Oligocene sandstone reservoir are mainly thermogenic methane gases that were generated from mainly mixed organic matter. The thermogenic methane gases were formed mainly from secondary cracking of oil and gas, with small contributions of primary kerogen cracking. The properties of natural gases together with oil and condensate in the Oligocene reservoir rocks suggest that most of the thermogenic methane gases and associated liquid hydrocarbons are derived primarily from the Oligocene shale source rock system and formed by primary kerogen cracking and secondary oil and oil/gas cracking in different thermal maturity stages. Therefore, the Oligocene Tineh Formation can be regarded as self-source generation and self-reservoir rock; hence, an intensive oil exploration and production program can be recommended whenever the Tineh source rock system is is well developed and deeply buried.

DIFFERENTIATED APPROACH TO ANTIHYPOXIC, ENDOPORTAL AND PHAGE THERAPY FOR ADVANCED PURULENT PERITONITIS

The purpose of this study was to evaluate the results of differentiated use of enteral antihypoxic therapy (EAT), endoportal therapy (EPT), as well as phage therapy (PT) in patients with diffuse purulent peritonitis complicated by acute intestinal failure (AIF). Materials and Methods: 144 patients with diffuse peritonitis and AIF were treated. The patients were divided into two equal comparable groups: main (n=72) and comparison (n=72). In addition, each group was divided into three subgroups (24 patients each) depending on the degree of AIF. The groups were distributed using adaptive randomization. EAT was carried out by introducing oxygenated water through a nasogastrointestinal (NGI) tube. EPT was carried out by introducing an antibiotic, a hepatoprotector and an antihypoxant through a catheter into the portal system. PT was carried out by introducing a polyvalent bacteriophage through a NGI tube. The following were dynamically studied: EMFC, APACHE II, abdominal cavity index (ACI), acid-base status and blood gas composition, integral intestinal pressure (IIP), intra-abdominal pressure (IAP). Comparison of quantitative indicators in the study groups was carried out using the Wilcoxon-Mann-Whitney U test, as well as its multivariate generalization - the Kruskal-Wallis test, for checking the equality of medians of several samples. Results: The dynamic study of IIP and IAP in the study groups on the day 3 of treatment, showed significantly lower values in the main group (p≤0.05). There was a more rapid decrease in the manifestations of hypoxia in the main group, which was confirmed by an increase in the oxygen partial pressure in the blood. The average number of bed days in the intensive care unit was 4.2±0.3 days in the comparison group, and 3.3±0.2 days in the study group. The overall average number of bed-days was 15.8 in the study group, and 18.5 in the comparison group. Mortality was 16.3% in the comparison group, and 11.3% in the study group (a decrease of 30.7%). Thus, when prescribing NGI, EAT, EPT and PT, one should be guided by the severity of organ dysfunction and the AIF stage. With values of ACI <13, APACHE II <10 and EMFC <5, NGI and EAT are indicated. With ACI 14-22, APACHE II 10-15, EMFC 5-25 - NGI and EAT are supplemented with PT. In the most severe cases, with ACI ≥23, APACHE II >16 and EMFC >25 points, EPT must be added to the above treatment methods. Conclusion: The proposed scheme for the differentiated use of EPT, EAT and PT in patients with diffuse peritonitis complicated by AIF allows to relatively quickly stop inflammation and prevent the development of multiple organ failure and sepsis.

A spatio-temporal temperature prediction model for coal spontaneous combustion based on back propagation neural network

Coal spontaneous combustion (CSC) occurs with the change of temperature and gas concentration which is useful for early warning. To explore the intrinsic correlation between temperature evolution and gas distribution, a Back Propagation Neural Network (BPNN) model of coal temperature - gas composition - spatial distance was constructed, which is based on the gas characteristics and spatial distribution of coal temperature in large-scale coal spontaneous combustion experiments. The results showed that the O2 concentration reached the lowest value (8.058%) at 45 cm on Day 52 with the time. CO and CO2 also formed concentration peaks at 45 cm, and the gas distribution continuously moved towards the inlet position. The hydrocarbon gas components showed periodic increases, with values below 100 ppm. When the supply air time increased, the temperature rise rate in the initial stage of oxidation was slow but relatively uniform. Affected by ventilation conditions and coal density, two high-temperature zones were observed at 45 cm and 85 cm in the experimental furnace. With the inclusion of spatial distance parameters in coal temperature prediction, the BPNN model exhibits accurate predictive capability, with a total error of 0.94997. This can provide a method for predicting temperature changes in coal mine.

Condition‐dependent NOx adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study

AbstractPd/BEA is chosen as a model passive NOx adsorber (PNA) to elucidate the effect of the feed gas composition on the NOx adsorption/desorption behavior. The Brønsted acid and the partially hydrolyzed framework Al (P‐HAl(OH)) sites in HBEA adsorb NO and NO2 under dry conditions. Moreover, the performance of HBEA is not affected by CO, while CO inhibits nitrate formation and promotes NO adsorption via the Pd(NO)(CO) complexes formation over Pd/BEA. H2O inhibits NO adsorption over the Brønsted acid and P‐HAl(OH) sites, and ionic Pd is the only active site for NOx adsorption under wet conditions. Furthermore, NO adsorption over hydrated Pd (Pd2+(OH)(NO)(H2O)3) is weaker than NO adsorption over bare ionic Pd (Z2[Pd2+(NO)], Z[Pd2+(OH)(NO)]). Dehydration of Pd2+(OH)(NO)(H2O)3 forms more stable Z[Pd2+(OH)(NO)] during desorption. The NO adsorption capacity of Pd/BEA improves in the presence of CO under both dry and wet conditions by forming a stable carbonyl–nitrosyl complex.

The role of gravity and temperature on hydrogen-containing mixtures in the subsurface

A model for thermal and gravity-induced compositional grading of hydrogen-containing gas mixtures using a cubic equation of state is presented. The theoretical background of compositional gradient modeling is reviewed, and the implementation of a thermal gradient model is used to predict the compositional variation of a hydrogen-natural gas mixture for both depleted gas reservoir and salt cavern applications. We show that near-uniform gas composition versus depth is expected during the storage of hydrogen mixed with natural gas over 100 m of vertical relief. Further study into the calculation and significance of the ideal portion of the component molar enthalpy is needed to increase confidence in model implementation and application.

Theoretical Evaluation of YSZ and Alumina-YSZ Thermal Barrier Coatings in a Hydrogen Enriched Combustion Environment

Abstract Yttria-stabilized zirconia (YSZ) ((ZrO2)0.93(Y2O3)0.07) and alumina-yttria-stabilized zirconia ((Al2O3)0.853 + (ZrO2)0.93(Y2O3)0.07) thermal barrier coatings (TBCs) were modeled in the presence of hydrogen-enriched combustion product gases to evaluate phase composition and thermal expansivity (coefficient of thermal expansion). Thermal equilibrium simulations for various equivalence ratios (0.5–0.75) and hydrogen enrichment percentages (0−50%) were conducted to determine the product gas composition for various combustor operating conditions. The obtained product gases were then used in a second thermal equilibrium simulation to demonstrate their effect on the defined thermal barrier coatings. The modeling predictions showed that hydrogen enrichment percentage and equivalence ratio were positively correlated to thermal expansivity for both the thermal barrier coatings examined. The alumina-YSZ composite coating exhibited a higher CTE, more closely matching the CTE of a metallic bond coat, for the studied conditions. This closer match of thermal expansivity results in less significant thermal stresses than the YSZ thermal barrier coating. An increase in hydrogen enrichment percentage and equivalence ratio yielded increased percentages of phase transitions from tetragonal zirconia (t-ZrO2) to cubic zirconia (c-ZrO2). The YSZ thermal barrier coating had a larger percentage of phase transitions throughout the operating range examined, which renders concerns for potential failure from thermal cycling and creep. Theoretical examination of the phase composition and thermal expansivity provided further insights into the fate and behavior of the thermal barrier coatings.

Temperature and Thermal Diffusivity Diagnostics in Laminar Methane Flames Using Infrared Four-Wave Mixing Techniques.

Four-wave mixing techniques, such as coherent anti-Stokes Raman spectroscopy (CARS), laser-induced grating spectroscopy (LIGS), and degenerate four-wave mixing (DFWM), have been widely used in combustion diagnostics due to their advantages of high signal-to-noise ratio (S/N), coherent signal, and spatial resolution. In this work, a nano-second pulsed laser is utilized to generate mid-infrared (near 3 µm) pump beams, exciting the rovibrational transitions of nascent water in flames. Combined LIGS and DFWM measurements are demonstrated in premixed laminar CH4/O2/N2 flames with equivalence ratios from 0.6 to 1.5, to achieve precise thermometry in a wide range of flame conditions. The flame temperatures were also measured by thermocouple as a reference, and the results from LIGS and DFWM align well with the trends shown in the thermocouple measurements. In fuel-lean flames, where the mass-to-specific-heat ratio variation is minimal, LIGS provides temperature data with a precision better than 16 K (0.8%). In fuel-rich flames, where the increased H2 concentration in the flame introduces uncertainty in gas constants thus affecting the accuracy of LIGS thermometry, DFWM is instead employed for temperature measurement since it is less sensitive to the gas composition within the measured volume. The high-precision LIGS temperatures in lean flames serve as temperature reference during the DFWM calibration of the degree of saturation, and a precision better than 90 K (4.5%) is achieved for DFWM thermometry. In addition to temperature, a theoretical model is employed to fit LIGS signal time waveforms, extracting the local speed of sound and thermal diffusivity with precisions better than 0.5% and 1.3%, respectively. These high-precision measurements contribute additional data for flame research and simulation calculations. This way, the combined use of DFWM and LIGS proves the potential for accurate thermometry and diagnostics of other thermodynamic parameters across a wide range of flame conditions.

Desulfurization performance and mechanism for H2S from blast furnace gas over FAU zeolite sorbent

The desulfurization of blast furnace gas is crucial to meet the strict requirements for clean production of steel industry. However, the composition of blast furnace gas is complicated, and the gases of H2O, CO, CO2, and O2 would significantly affect the desulfurization activity. Therefore, the desulfurization performance for H2S in simulated blast furnace gas by Na-type FAU zeolites with different Si/Al was investigated. The physicochemical properties of zeolite sorbents were measured, and their correlation with desulfurization performance was studied. Moreover, the adsorption mechanism of H2S was investigated. The breakthrough sulfur capacity improved with the increase of relative crystallinity, Na+ content, specific surface area, and the decrease of Si/Al ratio. The adsorption mechanism of H2S on Na-type FAU zeolite was proposed. One is the hydrogen bond interaction between the bridging hydroxyl groups and H2S, and the other one is the base-acid interaction between sodium ion and H2S. In blast furnace gas, when interacting with Na+, H2S would be transformed into S, which further oxidized into thiosulfate and sulfate by O2.

CO2 flux from the French Massif Central groundwaters: Modelling and quantitative estimation of the degassing process

Passive rift systems are often characterized by CO2 degassing, witnessed by the presence of mineral and thermal springs, bubbling pools, mofetes. Despite these field manifestations, the quantitative estimation of the CO2 budget released to the atmosphere from these geodynamic structures is not well constrained. Here, we examine the chemistry of 169 springs, the isotopic composition of the dissolved carbon (δ13CTDIC) of 33 springs and the dissolved gases composition of 6 springs from the French Massif Central, part of the European Cenozoic Rift System (ECRIS), in order to describe the CO2 degassing process and to compute the CO2 emission rate released from groundwaters at regional scale. Water-gas-rock models reveal that the separation of gas from the liquid phase occurs at P-T conditions between 10 bar-180 °C and 1 bar-10 °C. The carbon mass and isotopic balance of spring waters of the French Massif Central allow us to compute a total deeply-sourced CO2 emission rate of 1.52 ± 0.14 × 109 mol yr−1, suggesting that the CO2 release from passive rift systems is significant at global scale and should be considered in the present-day global Earth degassing budget. The comparison of our data to other continental rift systems shows a high variability of CO2 emission rates, highlighting that more detailed studies are needed to constrain the CO2 flux from this geodynamic setting that, at present, is likely underestimated.

Reliability of Domestic Gas Flow Sensors with Hydrogen Admixtures.

Static flow sensors (e.g., thermal gas micro electro-mechanical sensors-MEMS-and ultrasonic time of flight) are becoming the prevailing technology for domestic gas metering and billing since they show advantages in respect to the traditional volumetric ones. However, they are expected to be influenced in-service by changes in gas composition, which in the future could be more frequent due to the spread of hydrogen admixtures in gas networks. In this paper, the authors present the results of an experimental campaign aimed at analyzing the in-service reliability of both static and volumetric gas meters with different hydrogen admixtures. The results show that the accuracy of volumetric and ultrasonic meters is always within the admitted limits for subsequent verification and even within those narrower of the initial verification. On the other hand, the accuracy of the first generation of thermal mass gas flow sensors is within the limits of the verification only when the hydrogen admixture is below 2%vol. At higher hydrogen content, in fact, the absolute weighted mean error ranges between 3.5% (with 5%vol of hydrogen) and 15.8% (with 10%vol of hydrogen).

On the formation of ammonia from the thermal decomposition of hydroxylammonium nitrate vapor

The ionic liquid hydroxylammonium nitrate (HAN) is a promising propellant for various types of spacecraft propulsion systems. With respect to combustion and plasma-based electric propulsion, the thermal decomposition of HAN into gas phase species provides a convenient feed gas supply. While the decomposition of HAN in the liquid phase has been extensively studied, little is known about the decomposition chemistry of HAN vapor interacting with heated surfaces. The ability to decompose HAN vapor on a reactive surface could provide a means to control the feed gas composition and enhance the performance of spacecraft propulsion systems.In this initial qualitative study, HAN was vaporized and thermally decomposed using porous 316-stainless-steel and quartz disks under vacuum conditions. Decomposition products with low vapor pressures would condense on an in-line quartz tube which was subsequently collected and analyzed with Raman spectroscopy, NMR spectroscopy, and FT-IR spectroscopy. At temperatures above 440 K the 316-stainless-steel system produced significant quantities of ammonia which reacted with vaporized nitric acid to form ammonium nitrate. Temperatures below 440 K yielded partial HAN decomposition which resulted in a binary mixture of HAN and ammonium nitrate. The degree to which HAN was consumed was determined by analysis of the 1008 cm−1N-OH asymmetric Raman band of HAN and the 1049 cm−1 symmetric stretching Raman band of the nitrate ion, NO3−. The quartz system yielded significantly different results with no ammonium nitrate detected at temperatures above 440 K. Reformed HAN was the primary product detected at lower temperatures. The difference in reported measurements and visual observations highlights the distinct differences in HAN vapor decomposition chemistry from the two materials examined.