Dominant Gaseous Species Research Articles

Active Degassing of Deeply Sourced Fluids in Central Europe: New Evidences From a Geochemical Study in Serbia

AbstractWe report on the results of an extensive geochemical survey of fluids released in the Vardar zone (central‐western Serbia), a mega‐suture zone at the boundary between Eurasia and Africa plates. Thirty‐one bubbling gas samples are investigated for their chemical and isotopic compositions (He, C, Ar) and cluster into three distinct groups (CO2‐dominated, N2‐dominated, and CH4‐dominated) based on the dominant gas species. The measured He isotope ratios range from 0.08 to 1.19 Ra (where Ra is the atmospheric ratio), and reveal for the first time the presence of a minor (<20%) but detectable regional mantle‐derived component in Serbia. δ13C values range from −20.2‰ to −0.1‰ (versus PDB), with the more negative compositions observed in N2‐dominated samples. The carbon‐helium relationship indicates that these negative δ13C compositions could be due to isotopic fractionation processes during CO2 dissolution into groundwater. In contrast, CO2‐rich samples reflect mixing between crustal and mantle‐derived CO2. Our estimated mantle‐derived He flux (9.0 × 109 atoms m−2 s−1) is up to 2 orders of magnitude higher than the typical fluxes in stable continental areas, suggesting a structural/tectonic setting favoring the migration of deep‐mantle fluids through the crust.

Co-pyrolysis of microalgae and municipal solid waste: A thermogravimetric study to discern synergy during co-pyrolysis process

Synergism during the co-pyrolysis of microalgae (CC), municipal solid waste (MSW), and their blends (CC/MSW) (w/w %), 25/75 (CM-1), 50/50 (CM-2), and 75/25 (CM-3), was evaluated based on thermal decomposition pattern, evolved gases, rate and extent of thermal decomposition, and kinetic parameters. Three stages of devolatilization attributed to dehydration, devolatilization of major structural compounds of biomass and decomposition of solid residues were noticed during the co-pyrolysis of biomass samples. The main pyrolysis stages for CC, MSW, CM-1, CM-2 and CM-3 were 175–520, 151-523, 164-504,168-510, 160–501 °C, respectively. Microalgae, CC, appeared to be thermally resistant, while MSW is noticed to be thermally sensitive. The kinetics analysis was studied by deconvoluting the DTG profile into independent stages, followed by application of isoconversional methods to evaluate the activation energy and the pre-exponential factor. Furthermore, the reaction mechanism of each stage was determined by using the master plot method. The semi-quantitative method was used to evaluate the evolved gases and CO, CO2 and H2 were noticed to be the dominant gas species. The obtained thermal and kinetic data for co-pyrolysis of microalgae and MSW can serve are basis for scale-up and reactor design of pyrolysis process for similar kind of waste streams.

Reactive Force-Field Molecular Dynamics Study of SiGe Thin Film Growth in Plasma Enhanced Chemical Vapor Deposition Processes

The SiGe thin films, such as hydrogenated amorphous SiGe (a-SiGe:H) and hydrogenated microcrystalline SiGe (μc-SiGe:H), are known as a potential material. In order to form promising SiGe thin films using chemical vapor deposition, relationship between materials/process and structure/composition should be clarified at the atomic level. We analyzed the influence of the substrate temperature and the ratio of SiH3 and GeH3, which are considered to be the dominant gaseous species on the deposition, on the crystallinity and atomic content in SiGe thin films by reactive force-field molecular dynamics simulations. The crystallinity increases as the substrate temperature increases and reaches its minimum value when the ratio of SiH3 and GeH3 is approximately 0.5. The hydrogen content decreased as the substrate temperature increases, while silicon and germanium content tended to increase as substrate temperature increase. These results were in good agreement with relevant studies.

Suitability of binary oxides for molecular-beam epitaxy source materials: A comprehensive thermodynamic analysis

We have conducted a comprehensive thermodynamic analysis of the volatility of 128 binary oxides to evaluate their suitability as source materials for oxide molecular-beam epitaxy (MBE). 16 solid or liquid oxides are identified that evaporate nearly congruently from stable oxide sources to gas species: As2O3, B2O3, BaO, MoO3, OsO4, P2O5, PbO, PuO2, Rb2O, Re2O7, Sb2O3, SeO2, SnO, ThO2, Tl2O, and WO3. An additional 24 oxides could provide molecular beams with dominant gas species of CeO, Cs2O, DyO, ErO, Ga2O, GdO, GeO, HfO, HoO, In2O, LaO, LuO, NdO, PmO, PrO, PuO, ScO, SiO, SmO, TbO, Te2O2, U2O6, VO2, and YO2. The present findings are in close accord with available experimental results in the literature. For example, As2O3, B2O3, BaO, MoO3, PbO, Sb2O3, and WO3 are the only oxides in the ideal category that have been used in MBE. The remaining oxides deemed ideal for MBE awaiting experimental verification. We also consider two-phase mixtures as a route to achieve the desired congruent evaporation characteristic of an ideal MBE source. These include (Ga2O3 + Ga) to produce a molecular beam of Ga2O(g), (GeO2 + Ge) to produce GeO(g), (SiO2 + Si) to produce SiO(g), (SnO2 + Sn) to produce SnO(g), etc.; these suboxide sources enable suboxide MBE. Our analysis provides the vapor pressures of the gas species over the condensed phases of 128 binary oxides, which may be either solid or liquid depending on the melting temperature.

The migration, transformation and control of trace metals during the gasification of rice straw

This research investigates the trace metals speciation, partitioning and removal in rice straw gasification equipped with an integrated hot gas cleaning (HGC) system. The experiments were conducted by fluidized bed gasifier and controlled at 800 °C with equivalence ratio (ER) varied between 0.2 and 0.4. The experimental results indicated that the concerned trace metals Zn, Cr, Cd, and Pb partitioning in the gas phase were increased significantly with an increase in ER. This is because the exothermic reaction could enhance the trace metals reacted with chlorine and/or sulfur as well as correspondingly formed highly volatile metals compounds. However, other tested metals Cu, Na, K, Ca, Mg partitioning was obviously decreased in the gas phase with ER increasing. These tested metals tend to form oxides speciation leading the variation in their partitioning characteristics. The XRD identification and thermodynamic equilibrium simulation results were also confirmed the tested metals speciation and partitioning characteristics. The dominant gaseous species produced from rice straw gasification, such as KCl(g), NaCl(g), KO(g), K2O(g), ZnCl2(g), CrO2Cl2(g), CuCl2(g), PbCl2(g), PbO(g), and Cd(g), were predicted by thermodynamic equilibrium model. The tested metals removal by adsorbents of hot gas cleaning system was found to be adsorbed in decreasing order as: K > Cr > Ca > Pb > Mg > Cd > Na > Zn > Cu. Activated carbon was used in hot gas cleaning system and showed a good performance for adsorbing tested metals, especially for Pb, Cd, Cr, Ca, K, and Mg. In summary, HGC system is proposed as an effective way for improving the syngas quality and reducing trace contaminants emission in rice straw gasification.

Impact of energy production in the Barnett Shale gas region on the measured ambient hydrocarbon concentrations in Denton, Texas

The Barnett Shale play in North Texas is one of the largest active onshore shale gas regions in the United States. Over the past two decades, unconventional energy production from shale gas in North Texas has grown rapidly. The energy production peaked in 2012 and has declined since. The city of Denton is located at the edge of the Barnett Shale play and is within the Dallas-Fort Worth metropolitan area. In this paper, we describe a long-term trend study of 84 total non-methane organic carbon (TNMOC) species measured at the Denton Airport South monitoring station, an exurban site. The annual mean TNMOC concentrations measured during 2000–2017 increased by +8.03 ± 12.92 ppb-C/year (+12.75%/year). The year-to-year increase in the mean TNMOC concentrations mirrored the energy production volume changes from natural gas wells and liquid condensate facilities within 2-km from the ambient air quality monitoring station. Concentrations of alkanes increased significantly, especially the natural gas species of ethane, propane, n-butane, and isobutane. The annual variations in the ethane concentrations were similar to changes observed in the natural gas and liquid condensate production from nearby wells. High levels of ethane, a dominant natural gas species, were originating from regions with a higher density of gas wells within close proximity of the monitoring site. In contrast, the concentrations of alkene and aromatic species have declined during the study period as a result of decreases from traditional urban emission sources. However, the trend in benzene, a carcinogenic aromatic species found in vehicular and natural gas emissions, and xylene concentrations were similar to the n-alkane trend, suggesting the influence of energy production activities on key ambient aromatic compounds.

Sn isotope fractionation during volatilization of Sn(IV) chloride: Laboratory experiments and quantum mechanical calculations

Volatilization is an important pathway of element transport in nature, and this process may be associated with stable isotope fractionation, which could be used to understand the elemental volatilization mechanisms. In this study, we report that evaporation of Sn(IV) chloride solution under experimental conditions (96 °C, 1 atmospheric pressure) results in significant loss of aqueous Sn(IV) and Sn stable isotope fractionation. The δ122/116Sn of the residue solution can increase by up to 0.50‰ (or a 0.33‰ increase in δ122/118Sn) after repeated evaporation, indicating preferential partitioning of isotopically light Sn species into the vapor phase during evaporation. The observed Sn loss and associated Sn isotope fractionation during the evaporation experiments can be described using a Rayleigh fractionation function, with a best-fitting isotope fractionation factor of −0.36‰ in Δ122/116Snvapor-aq (or −0.24‰ in Δ122/118Snvapor-aq). We also performed quantum mechanical calculations to assess the stability of different potential Sn(IV) species in aqueous and vapor phases, and derived the equilibrium Sn isotope fractionation factors between these Sn(IV) species. The calculation results suggest that the dominant gaseous species of Sn(IV), SnCl4, is isotopically heavier than the aqueous Sn(IV) species by 1.24‰–0.35‰ in δ122/116Sn (or 0.82‰–0.19‰ in δ122/118Sn) under equilibrium at 96 °C, which is opposite to the experimental results. Such contrast in the direction of Sn isotope fractionation implies that kinetic isotope fractionation, rather than thermodynamic equilibrium isotope fractionation, took place for SnCl4 in the evaporation experiments at 96 °C. The observed experimental data can be explained by a kinetic isotope fractionation model involving backward reaction of SnCl4 vaporization at the solution-vapor boundary. This study, in combination with a recent report of positive Δ122/116Snvapor-aq (or Δ122/118Snvapor-aq) factor during evaporation of SnCl4 at 150 °C (Wang et al., 2019a), suggests that Sn(IV) volatilization mechanisms may be different with and without fluid boiling. Combined laboratory experiments and quantum mechanical calculations on the isotopic effects of Sn(IV) chloride solution evaporation provide important constraints for understanding the rapidly accumulating Sn isotopes data from studies on Sn ore-forming processes, bronze metallurgy and archeology, and volatile elements in planetary processes.

Experimental and modeling analysis of Air and CO2 biomass gasification in a reverse lab scale downdraft gasifier

Abstract This research work aims at investigating the effect of carbon dioxide feed in biomass gasification as a possible way to directly exploit the exhaust gas from the engine of combined heat and power systems to convert carbon dioxide to carbon monoxide via Boudouard reaction and consequently increase the carbon conversion and reduce char yield. The effects on biomass gasification using air, and air diluted with carbon dioxide were assessed in a reverse downdraft lab-scale gasifier utilizing 2 kg of pelletized biomass. This reactor is mounted on a digital weighing balance which enables the recording of mass loss during the gasification process. Furthermore, the mixture of air and CO2 is obtained from two mass flow controllers which enable constant and desired flux of gasifying agents across the gasifier. At the same time, an in-house developed thermodynamic equilibrium model was applied to predict the gas composition and char output. Unlike the classical equilibrium strategy that calculates the gasification products using the Gibbs energy minimization method at fixed temperature and pressure, the current approach is based on the enthalpy of the reactants, analogous to the adiabatic combustion temperature. Also, a correction factor accounting for the heat losses, was implemented. The model outcome shows a good agreement with the experimental results, especially in terms of predicted char yields and trends of the dominant producer gas species. The same strategy was used to describe the behavior of the gasification system and estimate the quality of producer gas and the cold gas efficiency of the system.

Origin of Carbon Dioxide Evolved during Cycling of Nickel-Rich Layered NCM Cathodes.

Gas formation caused by parasitic side reactions is one of the fundamental concerns in state-of-the-art lithium-ion batteries because gas bubbles might block local parts of the electrode surface, hindering lithium transport and leading to inhomogeneous current distributions. Here, we elucidate on the origin of CO2, which is the dominant gaseous species associated with the layered lithium nickel cobalt manganese oxide (NCM) cathode, by implementing isotope labeling and electrolyte substitution in differential electrochemical mass spectrometry-differential electrochemical infrared spectroscopy measurements. Li2CO3 on the NCM surface was successfully labeled with 13C via a process that involves its removal followed by intentional growth. In situ gas analytics on such NCM samples with 13C-labeled Li2CO3 clearly indicate that Li2CO3 decomposition contributes to CO2 evolution, especially during the first charge. At the same time, the greater contribution of electrolyte decomposition was indicated by the large amount of 12CO2 observed. Employment of butyronitrile as the electrolyte solvent in further measurements helped determine that the majority of electrolyte decomposition occurs via a reaction that involves the lattice oxygen of NCM.

Effect of Humidity on Wear of TiN Coatings: Role of Capillary Condensation

Coated ball-on-disk wear configuration was used to study the effect of relative humidity, water vapor pressure, and water on wear of TiN coatings in the temperature range of room temperature to 100 °C. Two kinds of experiments were designed: one at constant temperature with varying humidity and the second at constant water vapor pressure with varying temperature. Temperature variation experiments were also conducted in water. The trends in wear volume after a fixed sliding distance were analyzed. At constant temperature, the wear volumes increased with humidity/water vapor pressure. However, at a constant vapor pressure, wear volumes remained roughly invariant with temperature until a critical temperature below which they rose sharply. In contrast, the wear rate increased with temperature for tests in liquid water. Considering calculations based on Kelvin’s equations and further characterization of the wear surfaces using profilometry, XPS and FIB techniques, it has been strongly suggested that the anomalous temperature dependence of wear in humid air might be due to capillary condensation occurring at the contacting asperities. The wear of TiN showed two regimes in the influence of humidity. Where the humidity was below a threshold value of ~ 50 pct relative humidity (RH), there was negligible condensation and wear was low. Above 50 pct RH, the wear rate increased due to the availability of liquid water at asperities. The reason for the difference in the wear rate in vapor and liquid was hypothesized, based on XPS data, to depend on the formation of soft hydroxides in the presence of water, in contrast to the harder barrier oxide formed in the presence of oxygen, the dominant gas species in the vapor phase.

Characterization of pyrolysis products from slow pyrolysis of live and dead vegetation native to the southern United States

Prescribed (i.e., controlled) burning is a common practice used in many vegetation types in the world to accomplish a wide range of land management objectives including wildfire risk reduction, wildlife habitat improvement, forest regeneration, and land clearing. To properly apply controlled fire and reduce unwanted fire behavior, an improved understanding of fundamental processes related to combustion of live and dead vegetation is needed. Since the combustion process starts with pyrolysis, there is a need for more data and better models of pyrolysis of live and dead fuels. In this study, slow pyrolysis experiments were carried out in a pyrolyzer apparatus under nitrogen atmosphere in two groups of experiments. In the first group, the effects of temperature (400–800 °C), a slow heating rate (5–30 °C min−1), and carrier gas flow rate (50–350 ml min−1) on yields of tar and light gas obtained from pyrolysis of dead longleaf pine litter were investigated to find the optimum condition which results in the maximum tar yield. The results showed that the highest tar yield was obtained at a temperature of 500 °C, heating rate of 30 °C min−1, and sweep gas flow rate of 100 ml min−1. In the second group of experiments, 14 plant species (live and dead) native to forests in the southern United States, were heated in the pyrolyzer apparatus at the optimum condition. A gas chromatograph equipped with a mass spectrometer (GC–MS) and a gas chromatograph equipped with a thermal conductivity detector (GC-TCD) were used to study the speciation of tar and light gases, respectively. The results showed that the tar composition is dominated by oxygenated aromatic compounds consisting mainly of phenols. The light gas analysis showed that CO and CO2 were the dominant light gas species for all plant samples on a dry wt% basis, followed by CH4 and H2.

Application of two contrasting rice-residue-based biochars triggered gaseous loss of nitrogen under denitrification-favoring conditions: A short-term study based on acetylene inhibition technique

Denitrification is the key microbial process that leads to gaseous loss of soil nitrogen in agricultural lands. Most alarmingly, the dominant gas species could be N2O, which is a much stronger greenhouse gas than CO2. In addition to the primary role as tool for soil carbon sequestration, biochar has the potential to suppress N2O emissions. However, the mechanism for the suppression of N2O emissions by biochar remains elusive. To address this, we performed a short-term incubation experiment targeting the impact of two contrasting biochars on gaseous loss of soil N under denitrification-favoring conditions including high load of NO3− (100 µg N/g soil), anoxia and high moisture content (70% WFPS). The acetylene inhibition technique was adopted to differentiate N losses as N2 and N2O. Two biochars produced from rice chaff (600 °C, pH > 10, C:N 70) or rice husk (300 °C, pH < 5, C:N 54) were applied at two rates (5 and 10% w/w). Results exhibited an increase in gaseous loss of N in all biochar treatments compared with an unamended control. The presence of a positive correlation between total denitrification and CO2 emission rates suggested that biochar derived labile carbon played a pivotal role in triggering the loss of N in gaseous forms. Similarly, the abundances of denitrifying genes nosZ and nirS were considerably higher in biochar treatments, indicating denitrifier’s heterotrophic nature. The biochar pyrolysis conditions and application rates played a decisive role in controlling N2O emissions. Rice chaff biochar, primarily characterized by its alkaline pH, significantly suppressed N2O emissions. Taken together, biochar amendment to agricultural soil can trigger N losses via denitrification and only the alkaline biochar suppressed N2O emissions, probably because of the enhanced activity of N2O reductase.

Effluent Gas Flux Characterization during Pyrolysis of Chicken Manure

Pyrolysis is a viable option for the production of renewable energy and agricultural resources from diverted organic waste streams. This high temperature thermochemical process yields material with beneficial reuses, including bio-oil and biochar. Gaseous forms of carbon (C) and nitrogen (N) are also emitted during pyrolysis. The effluent mass emission rates from pyrolysis are not well characterized, thus limiting proper evaluation of the environmental benefits or costs of pyrolysis products. We present the first comprehensive suite of C and N mass emission rate measurements of a biomass pyrolysis process that uses chicken manure as the feedstock to produce biochar and bio-oil. Two chicken manure fast pyrolysis experiments were conducted at controlled temperature ranges of 450–485 °C and 550–585 °C. Mass emission rates of nitrous oxide (N2O), nitric oxide (NO), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and ammonia (NH3) were measured using trace gas analyzers. Based on the system mass balance, 23–25% of the total mass of the manure feedstock was emitted as gas, while 52–55% and 23% were converted to bio-oil and biochar, respectively. CO2 and NH3 were the dominant gaseous species by mass, accounting for 58–65% of total C mass emitted and 99% of total reactive N mass emitted, respectively. Temperature variations within the two set of temperature ranges had a perfunctory effect on bio-oil production and gaseous emissions, but the higher temperature range process produced more bio-oil and slightly less emissions. However, a larger effect on the relative amounts of CO and CO2 produced were observed between the different temperature regimes. These results have important implications for greenhouse gas and reactive N life cycle assessments of biochar and bio-oil.

Study of surface reaction during selective epitaxy growth of silicon by thermodynamic analysis and density functional theory calculation

We modeled and simulated the surface reaction of silicon precursor on different surfaces by thermodynamic analysis and density functional theory calculation. We considered SiH2Cl2 and argon as the silicon precursor and the carrier gas without etchant gas. First, the equilibrium composition of both gaseous and solid species was analyzed as a function of process temperature. SiCl4 is the dominant gaseous species at below 750°C, and SiCl2 and HCl are dominant at higher temperatures, and the yield of silicon decreases with increasing temperature over 700°C due to the etching of silicon by HCl. The yield of silicon for SiO2 substrate is lower than that for silicon substrate, especially at 1000°C or higher. Zero deposition yield and the etching of SiO2 substrate at higher temperatures leads to selective growth on silicon substrate. Next, the adsorption and the reaction of silicon precursor was simulated on H-terminated silicon (100) substrate and on OH-terminated β-cristobalite substrate. The adsorption and reaction of a SiH2Cl2 molecule are spontaneous for both Si and SiO2 substrates. However, the energy barrier for reaction is very small (6×10−4eV) for Si substrate, whereas the energy barrier is high (0.33eV) for SiO2 substrate. This makes the differences in growth rate, which also supports the experimental results in literature.

SrZrO3 Formation at the Interlayer/Electrolyte Interface during (La1-xSrx)1-δCo1-yFeyO3 Cathode Sintering

This work probes the formation of SrZrO3 at the SDC/YSZ interface (Sm doped ceria, SDC; Y stabilized zirconia, YSZ) during (La1-xSrx)1-δCo1-yFeyO3 (LSCF) cathode sintering. SEM/EDS and grazing incidence X-ray diffraction results of annealed LSCF and YSZ samples reveal that even without physical contact between LSCF and YSZ, SrZrO3 was formed on the surface of YSZ, preferentially at the grain boundaries. It was suspected that the SrZrO3 formation is due to the Sr-containing gas species diffused through the pores of the SDC layer and reacted with the YSZ electrolyte. Computational thermodynamics was adopted to predict the gas species formed in air during sintering by using the La-Sr-Co-Fe-O-H thermodynamic database. Sr(OH)2 is identified as the dominant Sr-containing gas species under the experimental conditions. In addition, it was found that A-site deficiency in LSCF could effectively suppress the SrZrO3 formation while a dense and pore-free SDC interlayer is required to totally block the SrZrO3 formation. Cell performance was significantly improved for a cell with a dense SDC interlayer fabricated by pulsed laser deposition, due to elimination of SrZrO3 formation and therefore reduced interfacial resistance.

Behavior of volatile dopants (P, Sb) in Czochralski silicon growth

The evaporation from the silicon melt, during Czochralski process, is an important effect for Phosphorus and Antimony dopants. The evaporation rate γ was deduced from the measured axial profile of the resistivity converted into the concentration. For the heavily doped crystals, the value of γ is very similar for both P and Sb: in the order of 5.5×10−5cm/s (which is significantly lower than the previously reported evaporation rates). It was concluded that the rate-limiting step for the evaporation process is neither the evaporation reaction itself nor the impurity transport through the flowing gas, but rather the transport through the melt that strongly depends on the melt convection. For low Phosphorus concentration, the transport through the gas is severely slowed-down – due to a change in the dominant gaseous species, from P2 to P1 – and becomes a limiting step. The evaporation rate is decreased and, in fact, becomes negligible.

Gasification of ash-free coal prepared with microwave method

The production of ash-free coal as a clean fuel for high temperature fuel cell was investigated. The ash-free coal was made from a bituminous coal. It was prepared by solvent extraction using a microwave. The solvent-to-coal ratio and microwave irradiation time of raw coal were parameters for the extraction yield. The microwave method showed merits in terms of faster extraction and higher extraction yield than conventional heating methods. In addition, gasification behaviors of the ash-free coal were investigated by gas chromatography. Contrary to carbon, ash-free coal showed hydrogen as a dominant gas species in its gasification and did not require carbonate catalyst. The electrical conductivity of ash-free coal was found very low close to zero.

Comparison of Oxidation Behaviors Between Ash Free Coal and Carbon in a Coin Type Direct Carbon Fuel Cell

Ash free coal extracted from a bituminous coal and carbon made from Oak were served as fuels in a direct carbon fuel cell and their oxidation behaviors were compared in terms of temperature, coal to carbonate ratio, and gas compositions in the cell. The ash free coal had much higher OCV and voltage at polarization states than carbon fuel at 650oC. Dominant product gases from the coal were H2and CO, while carbon had carbon monoxide in the tested range. Therefore difference in the oxidation process would be existed between the two fuels.Coal is relatively abundant energy source compared with other fossil fuels. Regardless of its abundance and long history of usage, inconvenience of its use reduces coal consumption at present. Coal as a solid fuel has a big problem of remaining ash in its use. Ash free coal has been attempted to overcome the problem. So far, ash free coal can be produced by two ways; one is removing ash compounds with acids and alkalines in the coal, calling UCC(Ultra Clean Coal), and another one is extracting organic compounds from the coal with organic solvents, named by ash free coal.In this work, ash free coal was produced by a micro-wave method with a polar solvent of NMP. For the comparison of oxidation behavior, carbon made from Oak was employed in this work. The electrochemical oxidation behaviors of coal and carbon were investigated with respect to temperature, coal to carbonate ratio, and gas compositions in a coin type direct carbon fuel cell (DCFC).The raw coal used in this work was Berau bituminous supplied by KEPRI in Korea. Carbon was made in-house, for 2 hrs at 400oC under N2 environment. A coin type direct carbon fuel cell was fabricated by molten carbonate fuel cell technology. The diameter of electrodes was about 3 cm. The anode was porous Ni-Al alloy, and the cathode was porous Ni. The matrix was made of LiAlO2. The long alumina tube at the upside of the cell was installed for the coal supply to the anode. A mixture of 62 mol% Li2CO3 and 38 mol% K2CO3 was served as electrolyte. The cathode gas was 70 % air and 30 % CO2. More details of the DCFC operation was described in a previous work [1]. The normal H2 fuel for the anode was H2:CO2 = 0.125 L/min: 0.025 L/min with ca. 5 % of H2O. Temperature ranged from 923K to 1123K. Coal to carbonate ratios were 3g to 3g, 3g to 1g, and 1g to 3g. Gas compositions in the cell were analyzed with a gas chromatography (HP 5890II).Figures 1 and 2 show OCV behaviors of fuel change from the normal H2 fuel to carbon fuel and ash free coal, respectively at 650oC, 750oC, and 850oC. The carbon fuel was a mixture of 3 g of carbon and 3 g of Li-K carbonates, while the ash free coal was a mixture of 3 g coal and 3 g of Li-K carbonates. Before 0 s the OCV was determined by the H2 fuel. After 0 s the carbon fuel shows only one minimum in the OCV whereas the coal does two minimums. The difference was attributed to the different gas species that carbon produced mostly CO species, while the coal gave H2 and CO as dominant gas species. In particular, very low OCV is observed at carbon fuel of 650oC, which indicates that very small reaction species in the condition. Very low gasification of carbon is the reason at the condition. On the other hand, coal fuel shows much higher OCV at 650oC. Rather easy gasification of ash free coal can be the reason. The main gas species of coal were CO and H2 because the hydrocarbon species in the coal is readily gasified even at 650oC. Similar amounts of CO and H2 were measured at the coal fuel in the anode chamber. The H2gas is generally more active than CO gas in the oxidation. Then the difference in the oxidation process between coal and carbon can be existed. ACKNOWLEDGEMENT This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2011-0009748).

Sulfur degassing at Erta Ale (Ethiopia) and Masaya (Nicaragua) volcanoes: Implications for degassing processes and oxygen fugacities of basaltic systems

We investigate the relationship between sulfur and oxygen fugacity at Erta Ale and Masaya volcanoes. Oxygen fugacity was assessed utilizing Fe3+/∑Fe and major element compositions measured in olivine‐hosted melt inclusions and matrix glasses. Erta Ale melts have Fe3+/∑Fe of 0.15–0.16, reflecting fO2 of ΔQFM 0.0 ± 0.3, which is indistinguishable from fO2 calculated from CO2/CO ratios in high‐temperature gases. Masaya is more oxidized at ΔQFM +1.7 ± 0.4, typical of arc settings. Sulfur isotope compositions of gases and scoria at Erta Ale (δ34Sgas − 0.5‰; δ34Sscoria + 0.9‰) and Masaya (δ34Sgas + 4.8‰; δ34Sscoria + 7.4‰) reflect distinct sulfur sources, as well as isotopic fractionation during degassing (equilibrium and kinetic fractionation effects). Sulfur speciation in melts plays an important role in isotope fractionation during degassing and S6+/∑S is &lt;0.07 in Erta Ale melt inclusions compared to &gt;0.67 in Masaya melt inclusions. No change is observed in Fe3+/∑Fe or S6+/∑S with extent of S degassing at Erta Ale, indicating negligible effect on fO2, and further suggesting that H2S is the dominant gas species exsolved from the S2−‐rich melt (i.e., no redistribution of electrons). High SO2/H2S observed in Erta Ale gas emissions is due to gas re‐equilibration at low pressure and fixed fO2. Sulfur budget considerations indicate that the majority of S injected into the systems is emitted as gas, which is therefore representative of the magmatic S isotope composition. The composition of the Masaya gas plume (+4.8‰) cannot be explained by fractionation effects but rather reflects recycling of high δ34S oxidized sulfur through the subduction zone.

An experimental study of the solubility of Gallium(III) oxide in HCl-bearing water vapour

The solubility of β-Ga2O3(s) in HCl-bearing water vapour was measured at temperatures between 150 and 400°C and pressures up to 257bar. These measurements indicate that Ga(III) oxide dissolves in significant concentrations in water vapour, and that its solubility depends on fHCl and fH2O. At low fHCl, the dominant gallium gas species is Ga(OH)3(g), whereas at high fHCl, Ga(OH)Cl2(g) predominates. Gallium(III) oxide solubility increases exponentially with increasing pressure at 350 and 400°C due to the formation of the hydrated clusters, GaOHCl2(H2O)n(g), where n=1–7. The logarithms of the dissolution constants for the reaction, 0.5Ga2O3(s)+1.5H2O(g)=Ga(OH)3(g), are −7.70±0.30 and −7.93±0.30 at 350 and 400°C, respectively, and for the reaction, 0.5Ga2O3(s)+2HCl(g)=GaOHCl2(g)+0.5H2O(g), are −0.32±0.29, 0.03±0.20, and −2.59±0.15 at 150, 200, and 400°C, respectively.The data obtained in this study were used to determine the partitioning of Ga between vapour and liquid at temperatures between 150 and 350°C, and a pH for the liquid ranging from 0 to 10. The estimated partition coefficient (Kd) decreases with increasing temperature, and reaches a maximum value of ∼100 at 150°C and ∼25 at 200°C at a pH of ∼4. The values are very similar to those estimated from data for geothermal wells in Iceland and hot springs in the Kamchatka Peninsula.