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Gas Composition (gas + composition)

Distribution by Scientific Domains

Polymers and Materials Science	28%
Engineering	24%
Chemistry	16%

Distribution within Polymers and Materials Science

Polymer Science & Technology General	42%
General & Introductory Materials Science	28%

Selected Abstracts

Quality changes of treated fresh-cut tropical fruits in rigid modified atmosphere packaging containers

PACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2007
Vanee Chonhenchob
Abstract There has been increasing demand for various fresh-cut tropical fruits. However, their short shelf-life has limited the market increase of this product. Quality changes (firmness, colour, total soluble solids (TSS), titratable acidity (TA), sensory quality and microbial safety) of fresh-cut mangoes, pineapples, melons and mixes of these fruits were evaluated. Chemical treatments to reduce browning, firmness loss and decay of fresh-cut tropical fruits were investigated. The most effective agents for fresh-cut mangoes, pineapples and melons were 0.1m ascorbic acid, 0.2m ascorbic acid and 0.2m ascorbic acid + 0.2m calcium chloride, respectively. Fresh-cut tropical fruits were packaged in various rigid containers (PET, OPS and OPLA). Gas composition in the package headspace and time to reach steady-state condition varied among fresh-cut packaging systems and affected their quality and shelf-life. The effects of package permeability of O2 and CO2 on quality and shelf-life of the fresh-cut products are discussed. Extended shelf-life was observed in fresh-cut mangoes, pineapples and mixes packaged in PET due to reduced O2 and elevated CO2 atmosphere. A modified atmosphere of 6% O2 and 14% CO2 achieved in PET extended the shelf-life of fresh-cut pineapples from 6 to 13 days. Accumulation of CO2 may impart an off-odour of fresh-cut fruits. The results suggested that the shelf-life of fresh-cut fruits could be extended by using proper rigid containers. Suitable mixes to create optimal equilibrium modified atmosphere had a potential to extend shelf-life of short shelf-life fresh-cut tropical fruits. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A Modular Injection System, Multilevel Sampler, and Manifold for Tracer Tests

GROUND WATER, Issue 6 2003
Brian J. Mailloux
Ground water injection and sampling systems were developed for bacterial transport experiments in both homogenous and heterogeneous unconsolidated, surficial aquifers. Two types of injection systems, a large single tank and a dynamic mixing tank, were designed to deliver more than 800 L of amended ground water to the aquifer over 12 hours, without altering the ground water temperature, pH, Eh, or dissolved gas composition. Two types of multilevel samplers (MLSs) were designed and installed. Permanent MLSs performed well for the homogenous surficial aquifer, but their installation procedure promoted vertical mixing, which could obfuscate experimental data obtained from vertically stratified, heterogeneous aquifers. A novel, removable MLS was designed to fit in 2- and 4-inch wells. Expandable O-rings between each sampling port hydraulically isolated each port for sample collection when a nut was tightened at the land surface. A low-cost vacuum manifold system designed to work with both MLS designs used 50 mL centrifuge tubes to efficiently sample 12 MLS ports with one peristaltic pump head. The integrated system was developed and used during four field campaigns over a period of three years. During each campaign, more than 3000 ground water samples were collected in less than one week. This system should prove particularly useful for ground water tracer, injection, and push-pull experiments that require high-frequency and/or high-density sampling. [source]

Modelling of a downdraft biomass gasifier with finite rate kinetics in the reduction zone

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2009
Prokash C. Roy
Abstract A model of a downdraft gasifier has been developed based on chemical equilibrium in the pyro-oxidation zone and finite rate kinetic-controlled chemical reactions in the reduction zone. The char reactivity factor (CRF) in the reduction zone, representing the number of active sites on the char and its degree of burn out, has been optimized by comparing the model predictions against the experimental results from the literature. The model predictions agree well with the temperature distribution and exit gas composition obtained from the experiments at CRF=100. A detailed parametric study has been performed at different equivalence ratios (between 2 and 3.4) and moisture content (in the range of 0,40%) in the fuel to obtain the composition of the producer gas as well as its heating value. It is observed that the heating value of the producer gas increases with the increase in the equivalence ratio and decrease in the biomass moisture content. The effect of divergence angle of the reduction zone geometry (in the range of 30,150°) on the temperature and species concentration distributions in the gasifier has been studied. An optimum divergence angle, giving the best quality of the producer gas, has been identified for a particular height of the reduction zone. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Low-flow anaesthesia at a fixed flow rate

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 10 2009
A. CHERIAN
Aims and Objectives: This study attempts to assess the safety of low-flow anaesthesia (LFA) at fixed flow rates with particular reference to the incidence of a decline in FiO2 below safe levels of 0.3 and to determine whether LFA can be used safely in the absence of an FiO2 monitor. Methods: A total of 100 patients undergoing procedures under general anaesthesia at fresh gas flows of 300 ml/min of O2 and 300 ml/min of N2O were monitored while maintaining the dial setting of isoflurane at 1.5% for 2 h. The changes in gas composition were analysed and even a single recording of FiO2 of <0.3 was considered sufficient to render the technique unsafe in the absence of gas monitors. Results: The lowest recorded value of FiO2 was 31% (v/v%). There was no incidence of adverse events necessitating the conversion from low flows to conventional flows. Conclusions: We conclude that low flows of 300 ml/min of N2O and 300 ml/min of oxygen can be used safely for a period of 2 h without the use of monitors for gas analysis of oxygen and agent in adult patients weighing between 40 and 75 kgs. [source]

Effect of Modified Atmosphere Packaging and Soluble Gas Stabilization on the Shelf Life of Skinless Chicken Breast Fillets

JOURNAL OF FOOD SCIENCE, Issue 2 2006
Bjørn T. Rotabakk
ABSTRACT The suitability of soluble gas stabilization (SGS) to dissolve CO2 into skinless chicken breast fillets before modified atmosphere (MA) packaging (MAP) was investigated. Head space gas composition (%), top web deflation (mm), muscle surface color (Minolta L*a*b*), pH, exudates in the packages (%), microbial characteristics, and off-odor were assessed in the packaged fillets. Increased SGS treatment time (2 versus 12 h) before MA packaging increased the CO2 content in the packaged fillets and counteracted package collapse. High package filling degree (51.8%) (low gas to product volume ratio) gave significantly (P < 0.001) lower CO2 content in head space than normal filling degree (29.7%). Color, pH, and package exudates were not affected by SGS treatment. Aerobic plate count (APC), Enterbacteriaceae count (EC), and lactic acid bacteria (LAB) increased significantly (P < 0.001) at each sampling during storage (5, 11, 17, and 24 d). SGS treatment significantly (P < 0.015) decreased APC, EC, and Pseudomonas spp. counts (PC) compared with no SGS treatment. Filling degree did not have a significant effect on the investigated microbiological characteristics. Off-odor scores correlated highest with EC (r2(adj)= 0.82). Fillets SGS treated in 12 h were the only one not rejected at off-odor evaluation on day 24. The samples stored in air spoiled after 5 d. SGS treatment in combination with MAP can be used successfully on chicken breast fillets to improve the microbiological (APC, EC, and PC) and sensorial characteristics, and in addition reduce package collapse and possibly increase the filling degree. [source]

Overall Quality Throughout Shelf Life of Minimally Fresh Processed Fennel

JOURNAL OF FOOD SCIENCE, Issue 1 2005
Victor H. Escalona
ABSTRACT: The keeping quality of minimally fresh processed fennel up to 14 d at 0 °C under modified atmosphere packaging was studied. Samples of 1 cm3 diced fennel washed for 1 min with chlorinated (100 mg/L) water were placed in 35 ,m oriented polypropylene (PP) bags or in PP baskets heat-sealed with unperforated or perforated (control) PP film. Changes in respiratory activity, ethylene emission, color, sugars content, chemical parameters, browning, decay, microbial growth, and sensory attributes were monitored. Respiratory activity in diced fennel was 1.5,fold higher than that for whole bulbs, and slight differences in ethylene emission between both whole and fresh processed fennel were found. A gas composition within both kinds of unperforated packages of about 11 to 13 kPa O2 and 9 to 12 kPa CO2 was reached. At the end of storage of fennel dices under this atmosphere, total plate counts were lower than legal limit for safe consumption. At any moment, neither physiological disorders nor decay developed. Although after 14 d a slight browning on the dices surface appeared, levels of sensorial attributes higher than acceptable for commercial purposes were reached. [source]

Plasma Synthesis of Tungsten Carbide Nanopowder from Ammonium Paratungstate

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2009
Taegong Ryu
A thermal plasma process has been applied to the synthesis of nanosized tungsten carbide powder with ammonium paratungstate (APT) as the precursor. The reduction and carburization of vaporized APT produced nanosized tungsten carbide (WC1,x) powder, which sometimes contained a small amount of W2C phase. The effects of reactant gas composition, plasma torch power, the flow rate of plasma gas, and the addition of secondary plasma gas (H2) on the product composition and particle size were investigated. The produced tungsten carbide (WC1,x) powder was <20 nm in particle size. The synthesized powders were also subjected to a hydrogen heat treatment to fully carburize the WC1,x and W2C phases to the WC phase as well as to remove excess carbon. Finally, WC powder of particle size <100 nm was obtained. [source]

Emission of Pollutants from Glycine,Nitrate Combustion Synthesis Processes

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007
Thomas Pine
Four ceramic powders were produced using the glycine,nitrate process: lanthanum-doped barium cobaltite, ceria, magnesia, and strontium-doped lanthanum chromite (LSC). Glycine-to-nitrate ratios from 0.25 to 1 were investigated. During the combustion synthesis process, careful collection of process off-gas was followed by detailed gas analyses to determine product gas composition. All of the synthesis processes produced pure phase ceramic powders, but also produced criteria pollutant emissions levels that were significant enough (up to 4500 ppm of NOx and 9000 ppm of carbon monoxide) to warrant consideration. Equilibrium and chemical kinetic computations are used to determine the implications of the current findings. [source]

Heat Transfer in Gas Phase Olefin Polymerisation

MACROMOLECULAR SYMPOSIA, Issue 1 2009
Estevan Tioni
Abstract A fixed bed microreactor has been used to study heat transfer during the initial transient state of gas phase olefin polymerization on a supported catalyst. It has been shown that heat transfer during this stage of the polymerisation is critical, and under conditions found commercially problems can arise with hot spots and polymer melting. It is proven how the thermal properties of the gas mixture flowing on the catalytic bed exert great influence on heat dissipation reducing the sudden increase in temperature by as much as a factor of 5. Flow rate and especially the process gas composition are the key factors in controlling the bed temperature. [source]

Non-mass-dependent oxygen isotopic fractionation in smokes produced in an electrical discharge

METEORITICS & PLANETARY SCIENCE, Issue 7-8 2007
Yuki Kimura
The smokes were formed at the Goddard Space Flight Center (GSFC) at total pressures of just under 100 Torr in an electrical discharge powered by a Tesla coil, were collected from the surfaces of the copper electrodes after each experiment and sent to the University of California at San Diego (UCSD) for oxygen isotopic analysis. Transmission electron microscopy studies of the smokes show that they grew in the gas phase rather than on the surfaces of the electrodes. We hypothesize at least two types of fractionation processes occurred during formation of the solids: a mass-dependent process that made isotopically lighter oxides compared to our initial oxygen gas composition followed by a mass-independent process that produced oxides enriched in 17O and 18O. The maximum ,17O observed is + 4.7, for an iron oxide produced in flowing hydrogen, using O2 as the oxidant. More typical displacements are 1,2, above the equilibrium fractionation line. The chemical reaction mechanisms that yield these smokes are still under investigation. [source]

Noble gas compositions of Antarctic micrometeorites collected at the Dome Fuji Station in 1996 and 1997

METEORITICS & PLANETARY SCIENCE, Issue 7 2002
Takahito Osawa
Eleven of the AMMs were collected in 1996 (F96 series) and 16 were collected in 1997 (F97 series). One of the F97 AMMs is a totally melted spherule, whereas all other particles are irregular in shape. Noble gases were extracted using a Nd-YAG continuous wave laser with an output power of 2.5-3.5 W for ,5 min. Most particles released measurable amounts of noble gases. 3He/4He ratios are determined for 26 AMMs ((0.85-9.65) × 10,4). Solar energetic particles (SEP) are the dominant source of helium in most AMMs rather than solar wind (SW) and cosmogenic He. Three samples had higher 3He/4He ratios compared to that of SW, showing the presence of spallogenic 3He. The Ne isotopic composition of most AMMs resembled that of SEP as in the case of helium. Spallogenic 21Ne was detected in three samples, two of which had extremely long cosmic-ray exposure ages (> 100 Ma), calculated by assuming solar cosmic-ray (SCR) + galactic cosmic-ray (GCR) production. These two particles may have come to Earth directly from the Kuiper Belt. Most AMMs had negligible amounts of cosmogenic 21 Ne and exposure ages of <1 Ma. 40Ar/36Ar ratios for all particles (3.9,289) were lower than that of the terrestrial atmosphere (296), indicating an extraterrestrial origin of part of the Ar with a very low 40Ar/36Ar ratio plus some atmospheric contamination. Indeed, 40Ar/36Ar ratios for the AMMs are higher than SW, SEP, and Q-Ar values, which is explained by the presence of atmospheric 40Ar. The average 38Ar/36Ar ratio of 24 AMMs (0.194) is slightly higher than the value of atmospheric or Q-Ar, suggesting the presence of SEP-Ar which has a relatively high 38Ar/36Ar ratio. According to the elemental compositions of the heavy noble gases, Dome Fuji AMMs can be classified into three groups: chondritic (eight particles), air-affected (nine particles), and solar-affected (eight particles). The eight AMMs classified as chondritic preserve the heavy noble gas composition of primordial trapped component due to lack of atmospheric adsorption and solar implantation. The average of 129Xe/132Xe ratio for the 16 AMMs not affected by atmospheric contamination (1.05) corresponds to the values in matrices of carbonaceous chondrites (,1.04). One AMM, F96DK038, has high 129Xe/132Xe in excess of this ratio. Our results imply that most Dome Fuji AMMs originally had chondritic heavy noble gas compositions, and carbonaceous chondrite-like objects are appropriate candidate sources for most AMMs. [source]

PVC and LDPE for packing minimally processed garlic

PACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2002
Nilda de Fátima Ferreira Soares
Abstract Minimum processing associated with an adequate packing system has shown good results in preserving a large group of perishable horticultural produce. The present work was done to determine the effect of the number of layered of low-density polyethylene (LDPE) or polyvinyl chloride (PVC) film on the quality of minimally processed packed garlic (Allium sativum), known for its short shelf-life. Polystyrene trays containing 200,g garlic bulbils were wrapped in one to four layers of PVC or one or two layers of LDPE and stored at room temperature. Changes in weight, bulbil colouration, in-package gas composition and apparent quality were monitored for 14 days. Best results were obtained by wrapping the packages in four layers of PVC film, with insignificant weight loss (5%), changes in colour tone and saturation, and the in-pack atmosphere (O2,=,0.01% and CO2,=,13.5%) inhibited fungal growth, extending shelf-life to 13 days at 25,±,2°C. On the other hand, the high in-package moisture in LDPE wrapping favoured fungal growth, rapidly depreciating bulbil quality. The shelf-life of minimally processed garlic can be increased by maintaining an adequate in-pack atmosphere, which can be achieved by using four layers of PVC or a another film of similar permeability. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Evaluation of plastic packages for guava refrigerated preservation

PACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2001
Angelo Pedro Jacomino
Abstract Guavas cv. ,Kumagai' were packed in several plastic materials and stored at 10°C and 85,90% relative humidity (RH) for 7, 14, 21 and 28 days (+3 days at 25°C). The plastic materials studied were: multilayer co-extruded polyolephine film with selective permeability (PSP), low-density polyethylene film (LDPE), LDPE film with mineral incorporation (LDPEm) and heat-shrinkable polyolephine film (SHR). Guavas not packed were taken as control samples. The physicochemical characteristics of the fruits, O2 and CO2 transmission rates of the packaging materials and gas composition at the package headspace were evaluated. The LDPE film, 69,µm in thickness, with the lowest permeability to both O2 and CO2, led to anaerobiosis and high CO2 concentration inside the packages and promoted physiological disturbances and changes in fruit flavour. The SHR film, 15,µm in thickness, was the most permeable to CO2 and had quite high O2 transmission, which modified the inner atmosphere of the packages slightly. The fruits packed in this film showed a poorer quality than the controls, possibly due to the heat produced during the shrinking of the film. The LDPEm film, 24,µm in thickness, was almost as permeable to CO2 but had reduced O2 transmission, promoting an atmosphere of equilibrium of 3% O2 and 4.5% CO2. Fruits packed in this film kept their skin colour and pulp firmness, suitable for consumption up to 14 days. The PSP film, 35,µm in thickness, had the greatest O2 transmission but just over half of the CO2 transmission of LDPEm, promoting an atmosphere of equilibrium of 0.5% O2 and 4.5% CO2 inside the packages. Fruits packed in such packages kept their physicochemical characteristics up to 21 days. Copyright © 2001 John Wiley & Sons, Ltd. [source]

On Some Characteristics of Ti Oxynitrides Obtained by Pulsed Magnetron Sputtering

PLASMA PROCESSES AND POLYMERS, Issue S1 2007
Mariana Braic
Abstract TiOxNy coatings were investigated as possible candidates for ion diffusion barrier layers. The elemental and phase composition, texture, hardness, adhesion, and corrosion resistance of the coatings were analyzed. The ion release in Ringer solution for uncoated and coated samples were also determined. The film properties were found to significantly depend on the reactive gas composition (O2/N2 ratio). The coatings proved to enhance the corrosion protection and to reduce the ion release of the uncoated specimens. [source]

Aging of Plasma-Deposited Films Prepared from Organic Monomers

PLASMA PROCESSES AND POLYMERS, Issue S1 2007
Sufal Swaraj
Abstract Plasma-deposited polymer films were prepared from organic molecules and investigated using near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) for aging effects after exposure to air. Results from the investigation of homopolymers are summarized. Primarily the effect of the deposition parameters duty cycle and power are dealt with. The effect of the deposition parameter pressure is briefly discussed. An example to show the effect of feed gas composition on the aging of plasma polymerized ethylene/allyl alcohol and styrene/allyl alcohol copolymer is also given. In general, change in content of unsaturated or aromatic species, change in concentration of monomer functionality, and change in the oxygen content was observed in the plasma polymerized films on aging. [source]

Combustion Measurements of Fuel-Rich Aluminum and Molybdenum Oxide Nano-Composite Mixtures

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 2 2010
Tim Bazyn
Abstract Fuel rich nano-composite powders of aluminum and molybdenum oxide were tested for ignition and combustion behind the incident and reflected shock waves in a shock tube. The powders consisted of approximately 10,,m particles, each of which contained Al and MoO3 mixed by mechanical alloying on the nano-scale. These powders were aluminum rich with composition ratios of 4,:,1, 8,:,1, and 16,:,1 Al,:,MoO3 by mass. Ignition tests were performed behind incident shocks for temperatures in the range of 900 to 1500,K. From these tests, ignition delay times were obtained, and some information on combustion duration was also derived. Samples were tested in air at 0.2,MPa, and compared against nano-Al, 2.7,,m Al, and 10,,m Al baselines. Ignition results for the baseline Al cases were as expected: 10,,m Al not igniting until 2000,K, 2,,m Al igniting down to ,1400,K, and n-Al igniting as low as 1150,K. The thermite samples showed considerable improvement in ignition characteristics. At the lowest temperature tested (900,K), both the 8,:,1 and 4,:,1 samples ignited within 250,,s. The 16,:,1 sample (94% Al) ignited down to 1050,K , which represents an improvement of roughly 1000,K over baseline Al with only a small energetic penalty. In all cases, the ignition delay increased as the amount of MoO3 in the composite was reduced. The 4,:,1 nano-composite material ignited as fast or faster than the n-Al samples. Ignition delay increased with decreasing temperature, as expected. Emission spectra and temperature data were also taken for all samples using high-speed pyrometry and time-integrated spectroscopy. In these cases, measurements were made behind the reflected shock using end-wall loading, though the conditions (temperature, pressure, and gas composition) were identical to the incident shock tests. Spectroscopy showed strong AlO features in all the samples, and the spectra fit well to an equilibrium temperature. Broadband, low resolution spectra were also fit to continuum, gray body temperatures. In general, the observed temperatures were reasonably close to 3500,K, which is similar to the combustion temperatures of pure aluminum under these conditions. [source]

On the importance of the reaction between OH and RO2 radicals

ATMOSPHERIC SCIENCE LETTERS, Issue 2 2009
A. T. Archibald
Abstract A new model, BAMBO (Bristol's Atmospheric Marine Boundary layer mOdel), was developed in order to investigate the reaction between peroxy radicals (RO2) and the hydroxyl radical (OH) under typical marine boundary layer (MBL) conditions. The results of this work have shown that the inclusion of the title reaction has negligible effects on inorganic species and ozone but can have significant effects on predicted atmospheric mixing ratios of oxygenated volatile organic compounds (OVOCs), which are generally poorly represented in atmospheric models. This work highlights that the title reaction may be important to modelling trace gas composition in the MBL. However, thorough experimental and theoretical studies are needed to clarify many of the assumptions made. Copyright © 2009 Royal Meteorological Society [source]

Metabolic and transcriptional response of recombinant Escherichia coli to elevated dissolved carbon dioxide concentrations

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009
Antonino Baez
Abstract The effect of dissolved carbon dioxide (dCO2) concentration on the stoichiometric and kinetic constants and by-product accumulation was determined for Escherichia coli cells producing recombinant green fluorescent protein (GFP). Constant dCO2, in the range of 20,300,mbar, was maintained during batch cultures by manipulating the inlet gas composition. As dCO2 increased, specific growth rate (µ) decreased, and acetate accumulation and the time for onset of GFP production increased. Maximum biomass yield on glucose and GFP concentration were affected for dCO2 above 70 and 150,mbar, respectively. Expression analysis of 16 representative genes showed that E. coli can respond at the transcriptional level upon exposure to increasing dCO2, and revealed possible mechanisms responsible for the detrimental effects of high dCO2. Genes studied included those involved in decarboxylation reactions (aceF, icdA, lpdA, sucA, sucB), genes from pathways of production and consumption of acetate (ackA, poxB, acs, aceA, fadR), genes from gluconeogenic and anaplerotic metabolism (pckA, ppc), genes from the acid resistance (AR) systems (adiA, gadA, gadC), and the heterologous gene (gfp). The transcription levels of tricarboxylic acid (TCA) cycle genes (icdA, sucA, sucB) and glyoxylate shunt (aceA) decreased as dCO2 increased, whereas fadR (that codes for a negative regulator of the glyoxylate operon) and poxB (that codes for PoxB which is involved in acetate production from pyruvate) were up-regulated as dCO2 increased up to 150,mbar. Furthermore, transcription levels of genes from the AR systems increased as dCO2 increased up to 150,mbar, indicating that elevated dCO2 triggers an acid stress response in E. coli cells. Altogether, such results suggest that the increased acetate accumulation and reduction in µ, biomass yield and maximum GFP concentration under high dCO2 resulted from a lower carbon flux to TCA cycle, the concomitant accumulation of acetyl-CoA or pyruvate, and the acidification of the cytoplasm. Biotechnol. Bioeng. 2009; 104: 102,110 © 2009 Wiley Periodicals, Inc. [source]

Thermodynamic Equilibrium Calculations for the Reforming of Coke Oven Gas with Gasification Gas

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2007
B. Li
Abstract Thermodynamic analyses of the reforming of coke oven gas with gasification gas for syngas were investigated as a function of coke oven gas-to-gasification gas ratio (1,3), oxygen-to-methane ratio (0,1.56), pressure (25,35,bar) and temperature (700,1100,°C). Thermodynamic equilibrium results indicate that the operating temperature should be approximately 1100,°C and the oxygen-to-methane ratio should be approximately 0.39, where about 80,% CH4 and CO2 can be converted at 30,bar. Increasing the operating pressure shifts the equilibrium toward the reactants (CH4 and CO2); increasing the pressure from 25 to 35,bar decreases the conversion of CO2 from 73.7,% to 67.8,%. The conversion ratio of CO2 is less than that in the absence of O2. For a constant feed gas composition (7,% O2, 31,% gasification gas, and 62,% coke oven gas), a H2/CO ratio of about 2 occurs at temperatures of 950,°C and above. Pressure effects on the H2/CO ratio are negligible for temperatures greater than 750,°C. The steam produced has an effect on the hydrogen selectivity, but its mole fraction decreases with temperature; trace amounts of other secondary products are observed. [source]

A Nonequilibrium, Atmospheric-Pressure Argon Plasma Torch for Deposition of Thin Silicon Dioxide Films

CHEMICAL VAPOR DEPOSITION, Issue 4 2007
P. Kasih
Abstract A nonequilibrium, atmospheric-pressure plasma torch that can be generated either in He or Ar gas by using a pulsed high-voltage power supply with the discharge temperature in the range 22,35,°C has been developed. This system is used to deposit silicon dioxide films from a hexamethyldisiloxane (HMDSO) precursor diluted in an oxygen carrier gas. It is concluded that, in terms of both quality and deposition rate at the same applied power, frequency, and gas composition, Ar plasma is more powerful than He plasma for depositing SiO2 -like films. The maximum feed rate of HMDSO/O2 injected into the Ar plasma torch is limited to 100,mL,min,1 to ensure inorganic coatings are deposited. In order to improve the visual quality, without adversely affecting the inorganic features of the film, a small amount of nitrogen (N2) can be added to the Ar as a working gas. When the ratio of Ar to N2 in the flow gas is 30:1, the discharge behavior is transformed from filamentary to glowlike as a result of the quenching effect of admixed N2 on Ar plasma. [source]

The Fate of Lead in MSWI-Fly Ash During Heat Treatment: An X-Ray Absorption Spectroscopy Study,

ADVANCED ENGINEERING MATERIALS, Issue 6 2009
Rudolf Paul Wilhelm Jozef Struis
The study focuses on the potential of removing toxifying Pb from a certified, multi-element fly ash (BCR176) by thermal treatment between 300 and 950,°C under different carrier gas compositions (Ar or Ar,+,O2). The treatment was studied by in situ monitoring the evaporation rate of Pb, C, S, Na, and K during heating and by synchrotron X-ray absorption spectroscopy of selected samples collected during vaporization at the Pb L3 -edge. [source]

Fundamental study on biomass-fuelled ceramic fuel cell

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2002
B. Zhu
Abstract Recent development in the advanced intermediate temperature (400 to 700°C) ceramic fuel cell (CFC) research brings up feasibility and new opportunity to develop innovative biomass-fuelled CFC technology. This work focuses on fundamentals of the biomass-fuelled CFCs based on available biofuel resources through thermochemical conversion technologies. Both real producer gas from biomass gasification and imitative compounded gas were used as the fuel to operate the CFCs in the biomass CFC testing station. The composition of the fuel gas was varied in a wide range of practices of the present conversion technology both in KTH and Shandong Institute of Technology (SDIT). CFC performances were achieved between 100 and 700 mW cm,2 at 600,800°C corresponding to various gas compositions. A high performance close to 400 mW cm,2 was obtained at 600°C for the gas with the composition of H2 (50 per cent)+CO (15 per cent)+CO2 (15 per cent)+N2 (20 per cent) and more than 600 mW cm,2 for the H2 (55 per cent)+CO (28 per cent)+CO2 (17 per cent) at 700°C. This paper presents the experimental results and discusses the fundamentals and future potentiality on the biomass fuelled CFCs. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Cosmic-ray exposure age and heliocentric distance of the parent bodies of enstatite chondrites ALH 85119 and MAC 88136

METEORITICS & PLANETARY SCIENCE, Issue 6 2006
D. Nakashima
These two meteorites contain solar and cosmogenic noble gases. Based on the solar and cosmogenic noble gas compositions, we calculated heliocentric distances, parent body exposure ages, and space exposure ages of the two meteorites. The parent body exposure ages are longer than 6.7 Ma for ALH 85119 and longer than 8.7 Ma for MAC 88136. The space exposure ages are shorter than 2.2 Ma for ALH 85119 and shorter than 3.9 Ma for MAC 88136. The estimated heliocentric distances are more than 1.1 AU for ALH 85119 and 1.3 AU for MAC 88136. Derived heliocentric distances indicate the locations of parent bodies in the past when constituents of the meteorites were exposed to the Sun. From the mineralogy and chemistry of E chondrites, it is believed that E chondrites formed in regions within 1.4 AU from the Sun. The heliocentric distances of the two E chondrite parent bodies are not different from the formation regions of E chondrites. This may imply that heliocentric distances of E chondrites have been relatively constant from their formation stage to the stage of exposure to the solar wind. [source]