Showing papers on "Vapours published in 2017"

Electrospun polypyrrole-polyethylene oxide coated optical fiber sensor probe for detection of volatile compounds

Abstract: In this work, a multimode optical fiber sensor probe coated with polypyrrole-polyethylene oxide (PPO) nanofibrous mat is investigated to detect volatile compounds such as ammonia, triethylamine, methanol, ethanol and acetone vapours. The fibrous mat on the fiber cladding is deposited using electrospinning method followed by vapour phase polymerization. The affinity of PPO towards different volatile compounds changes the effective refractive index of optical fiber cladding, modulating the intensity of the transmitted spectrum. The intensity variation in presence of volatile vapours of different concentration is investigated to determine the responses of the sensor probe. The sensor probe shows different detection limit such as 0.1 ppm, 2 ppm, 2 ppm, and 1 ppm and recovery time of 10 min, 54.4s, 21.06 s and 11.08 s for ammonia, ethanol, methanol and triethylamine vapours respectively. Thus, the electrospinning technique can be used for coating optical fiber cladding with special material such as PPO to develop optical fiber based sensor to detect trace amount of volatile compound.

Sensing of volatile organic compounds by copper phthalocyanine thin films

Abstract: Thin films of copper phthalocyanine have been deposited by thermal evaporation technique. We have subsequently exposed these films to the vapours of methanol, ethanol and propanol. Optical absorption, infrared spectra and electrical conductivities of these films before and after exposure to chemical vapours have been recorded in order to study their sensing mechanisms towards organic vapours. These films exhibit maximum sensing response to methanol while low sensitivities of the films towards ethanol and propanol have been observed. The changes in sensitivities have been correlated with presence of carbon groups in the chemical vapours. The effect of different types of electrodes on response-recovery times of the thin film with organic vapours has been studied and compared. The electrodes gap distance affects the sensitivity as well as response-recovery time values of the thin films.

Hydrocarbon detection with metal oxide semiconducting gas sensors modified by overlayer or admixture of zeolites Na-A, H-Y and H-ZSM-5

Abstract: A control thick-film SnO2 gas sensor was modified with zeolites holding LTA, FAU and MFI frameworks using two different approaches to integrate them into the gas-sensing interface. The objective was to prompt selectivity and sensitivity enhancements that were otherwise unattained with the unmodified material when detecting a range of hydrocarbon vapours with similar molecular structures and kinetic diameters. Molecules with different functional groups were also explored. Overlayers were designed by screen-printing 1 or 3 zeolite depositions on top of the control sensor. Admixtures were prepared by screen-printing composites of the control material with 10% (w/w) and 30% (w/w) of zeolite. Tests were performed against ethane, propane, butane, ethanol, isopropanol, acetone, toluene and carbon monoxide at concentrations in the 2.5–125 ppm range and sensors were heated to temperatures in the 250–500 °C range. Sensors were also exposed to humid air and to a mixture of ethane and humid air to assess the selective capabilities of the sensing materials in mixed-gas environments. Both fabrication methods provided sensor responses that, combined, favoured vapour discrimination in a way unachievable with the control sensor and the presence of zeolite was seen to assist in sensitivity and selectivity enhancements towards vapours, whilst providing stable and repeatable responses over time.

Understanding the gas sensing properties of polypyrrole coated tin oxide nanofiber mats

Abstract: Tin oxide-polypyrrole composites have been widely studied for their enhanced sensing performance towards ammonia vapours, but further investigations are required for an understanding of the interaction mechanisms with different target analytes. In this work, polypyrrole coated tin oxide fibers have been synthesized using a two-step approach of electrospinning and vapour phase polymerization for the sensing of ammonia, ethanol, methanol, 2-propanol and acetone vapours. The resistance variation in the presence of these vapours of different nature and concentration is investigated for the determination of sensor response. A decrease in resistance occurred on interaction of tin oxide-polypyrrole with ammonia, as opposed to previous reported works. Partial reduction of polypyrrole due to interfacial interaction with tin oxide has been proposed to explain this behavior. High sensitivity of 7.45 is achieved for 1 ppm ammonia concentration. Furthermore, the sensor exhibited high sensitivity and a faster response towards ethanol vapours although methanol has the highest electron donating capability. The catalytic mechanism has been discussed to explain this interesting behavior. The results reveal that interaction between tin oxide and polypyrrole is crucial to control the predominant sensing mechanism.

Effect of Metal Vapours on the Radiation Properties of Thermal Plasmas

Abstract: In metallurgic applications of thermal plasmas the presence of metal vapour, even in small proportion tends to increase the electron number density and to modify some basic properties such as the electrical conductivity and the radiation emission. In this paper we focus on the influence of these vapours on the radiation properties. After the definition of some necessary and basic functions and laws we briefly present the mechanisms responsible for emission and absorption of radiation in thermal plasmas. Then an important section is devoted to the role of metal vapours on the net emission coefficient which is the most popular parameter used to evaluate the radiation power losses in general models. It is shown that metal vapours increase the emission especially at low and intermediate temperatures (T < 12,000 K) and that their relative influence depends on the nature of the initial gas and of the metal itself. We list a rather important number of references presenting calculation of net emission in various gas–metal mixtures. Finally we show in a last section the influence of metal radiation on general plasma properties such as the energy transfer (other methods than the net emission coefficient), the cooling effect, the global energy balance and the heating of particulates injected in the plasma. The most spectacular effects are the increase of radiation losses in the energy balance and the complex role of the metal in the local cooling of the plasma.

Magnesium ferrite nanostructures for detection of ethanol vapours - a first-principles study

Abstract: The adsorption behaviour and electronic properties of ethanol vapour on MgFe2O4 ceramic nanostructures are studied using density functional theory technique. The structural stability of MgFe2O4 nanostructure is determined with the help of formation energy. The adsorption behaviour of ethanol molecules on MgFe2O4 base material is analysed in terms of average energy gap variation, Mulliken charge transfer, band gap and adsorption energy. The most prominent adsorption sites of ethanol vapours on MgFe2O4 nanostructure are investigated at atomistic level. The density of states spectrum reveals the clear picture about the electronic properties of MgFe2O4 nanostructure. The density of states and electronic band gap confirmed the adsorption of ethanol vapours on MgFe2O4 nanostructure. The changes in the energy band gap and density of states are observed upon adsorption of ethanol vapour molecules on MgFe2O4 nanostructure. The density of states spectrum also confirms the changes in peak maxima due to the transfer of electrons between MgFe2O4 nanostructure and ethanol vapours. The adsorption of oxygen atom from ethanol vapour on iron in MgFe2O4 is found to be more prominent rather than other adsorption sites. The findings show that MgFe2O4 nanostructure can be utilized to sense the presence of ethanol vapour in the atmosphere.

BTEX detection with composites of ethylenevinyl acetate and nanostructured carbon.

Abstract: By using a solvent-based method composites of ethylenevinyl acetate copolymer and carbon black (EVA-CB) were synthesized for sensing BTEX (benzene, toluene, ethylbenzene and xylene) vapours. The composites were characterized using atomic force microscopy (AFM) in an electroconductive mode. Gas sensing results show that EVA-CB can reproducibly detect BTEX and that the response increases linearly with vapour concentration. Compared to gas-sensing measurements of gasoline vapours, the responses with toluene and ethylbenzene are different and can be explained by varying side chains of the benzene ring.

An electrical solid-state sulphur dioxide vapour sensor based on a polyvinyl alcohol formaldehyde composite

Abstract: Polyvinyl alcohol formaldehyde (PVF)-based composites are synthesized and applied for rapid detection and quantification of sulphur dioxide (SO2) vapours by electrical impedance measurements. A series of polymeric composites, namely PVF/single-walled carbon nanotubes (PVFCNTs), PVF/carbon nanoparticles (PVFCNPs), PVF–coumarin-6 (PVFCOU), PVF/thiophene (PVFTH) and PVF/cytochrome-6-oxidase (PVFCY), are synthesized in high yields by a simple one-pot approach. These were characterized by FT-IR, AC conductivity and FESEM. The composites were then used for the impedimetric detection of SO2 vapours, and the sensitivity was found to follow the order: PVFCOU > PVFTH > PVF. The current vs. voltage (I–V) curves further demonstrated a second-order decrease in conduction for PVFCOU upon exposure to SO2 vapours. Amongst the synthesized composites, PVFCOU exhibited an excellent response time of 3 s for 400 ppt SO2, with a limit of detection of 1.15 ppb. Our findings demonstrate, for the first time, an AC electrical impedance-based SO2 detection, using the PVFCOU polymeric composite. In addition, this polymeric composite fulfills the dual function of highly efficient sensing and analyte sequestration. Thus, PVFCOU may be an ideal cost-effective solid-state sensor material for onsite vapour sensing applications.

The influence of simultaneous adsorption of potassium and sodium vapours on coke structure and performance

Abstract: Alkali metals are one of the important factors promoting the degradation of coke in blast furnace. Previous studies usually focused on the properties of coke affected, respectively, by K and Na separately, while K and Na will simultaneously affect coke performance in the actual production of blast furnace. Through simulating the actual situation where coke is affected by K and Na vapours simultaneously in blast furnace, the evolution of coke structure and thermal properties (CRI, CSR) after alkalisation with different proportions of K and Na vapours are revealed in this study. Results showed that coke structure was broken when the proportion of alkali vapours reached 3%, and coke fine formation rate increased with the increase of K vapour, indicating that K vapour caused a great damage to coke structure; CRI of coke reached the highest and CSR the lowest when K/Na ratio was 3/7. It was observed with SEM/energy dispersive spectrometer that K and Na existed in both mineral matters and carbon matrix; nepheli...

Use of cement-fly ash-based stabilization techniques for the treatment of waste containing aromatic contaminants

Abstract: Research on evaluation of evaporation rate of volatile organic compounds from soil beds during processing is presented. For the experiment, soil samples were prepared with the same amounts of benzene and stabilized using a mixture of CEMI 42.5R cement and fly ash from pit-coal combustion. Solidification of soils contaminated with BTEX hydrocarbons using hydraulic binders involves a risk of releasing vapours of these compounds during homogenization of waste with stabilizing mixture introduced and its dilution with water. The primary purposes of the research were: analysis of benzene volume emitted from soil during stabilization/solidification process and characterization of factors that may negatively affect the quality of measurements/the course of stabilization process. Analysis of benzene emission intensity during the process was based on concentration (C 6 H 6 ) values, recorded with flame-ionization detector above the surface of reacting mixture. At the same time, gaseous contaminants emitted during waste stabilization were passed through pipes filled with activated carbon (SCK, Anasorb CSC). Benzene vapours adsorbed on activated carbon were subjected to analysis using gas chromatograph Varian 450-GC. Evaporation characteristics of benzene during processing contaminated soils revealed the stages creating the highest danger to workers’ health, as well as a need for actions connected with modification of technological line.

Organic vapours sorption on simply modified bentonites

Abstract: Modified materials based on bentonite (acid-activated bentonite, mineralogically defined clay obtained by sedimentation, and composite material composed of bentonite and humic substances) were prepared in this work and sorption properties of the prepared materials for organic vapours (cyclohexane, toluene, mixture of xylenes and acetone) were determined. The aim of modification was the specific surface area enlargement and reduction of hydrophilic character. Results of the organic vapours adsorption show that the polarity of adsorbate is very important factor. It was found that adsorption of less polar and nonpolar organic vapours on the prepared clay-based materials took place through weak interactions and the specific surface area was key factor influencing adsorption process. Influence of water content in the materials can be considered, too. Adsorbed amounts of weakly polar organics on the clay materials were at most on the half level in comparison with active carbon. In the case of polar acetone the studied bentonites show the comparable adsorbed amounts as active carbon. It was found that acetone replaced water molecules in the solvation shells of interlayer cations, which was proven by infrared spectroscopy. The specific surface area did not play a leading role during adsorption of acetone on the bentonites.

Adsorption of hexane and cyclohexane vapours at the water drop surface

Abstract: The dependence of the dynamic surface tension of water at the interface with saturated hexane and cyclohexane vapours was measured by the drop profile analysis method. The surface tension for the adsorption layers of cyclohexane at different temperatures was compared with the results reported earlier for the adsorption of hexane and other alkanes from the vapour phase on water drops. It is shown that cyclohexane is adsorbed significantly slower than the adsorption of hexane occurs, and is characterised by a much larger induction time. The error in the drop radius measurements at 40 oC attains 45 m. The experimental rheologic characteristics of the adsorbed layers are studied and the results are compared with the model developed to describe an adsorption process governed by a kinetic mechanism.

Thermal stability of γ-Fe2O3 nanoparticles and their employment for sensing of acetone vapours

Abstract: Stability of γ-Fe2O3 nanoparticles-based films upon an isochronal annealing in air was investigated by x-ray diffraction, differential scanning calorimetry, and thermogravimetry. The γ-α transformation temperature increased owing to the nanoscaling of Fe2O3; the higher stability of the γ phase was explained on the ground of the surface free energy of nanoparticles (with the size of about 6.4 nm). Further, chemiresistors based on the Fe2O3 nanoparticle bilayer prepared by the Langmuir-Schaefer method were fabricated and examined in terms of their sensitivity to acetone vapours down to 500 ppb concentration in air.

Amines vapour sensing kinetics and electrical properties of synthetic Polyaniline-titanium(IV)sulphosalicylophosphate cation exchange nanocomposite

Abstract: A novel electrically conductive Polyaniline-titanium(IV)sulphosalicylophosphate (Pani-TSP) cation exchange nanocomposite has been synthesized by in-situ chemical oxidative polymerization of aniline in the presence of Titanium(IV)sulphosalicylophosphate (TSP) nanoparticles. Pani-TSP was characterized by various instrumentation techniques like FTIR, FE-SEM, XRD, TGA, DTA, DTG and EDX. Characterization results confirms that synthesis of Pani-TSP was successfully achieved. Pani-TSP shows good ion-exchange capacity (IEC) (2.15 meqg−1) as well as electrical conductivity (1.531 S/cm) and isothermal stability in terms of DC electrical conductivity retention under ambient condition up to 110 °C. Pani-TSP cation exchange nanocomposite based sensor was fabricated for the detection of methylamine and ethylamine vapours at room temperature. Sensing performance of nanocomposite was checked over the concentration range from 0.1 M (vapour concentration 3.20%) to 0.7 M (vapour concentration 4.65%) aqueous amine. The rate of reaction of amines vapour sensing on Pani-TSP was determined as first order for methylamine and ethylamine vapours which suggest that rate of change in resistivity response is mainly due to amine vapours.

Nanostructured Sensors for Detection of Hydrogen Peroxide Vapours

Abstract: Solid-state sensors made from doped metal oxide ZnO and SnO2 were prepared for detection of hydrogen peroxide vapours. Gas sensitive nanostructured films were manufactured by the high-frequency magnetron sputtering method. Thicknesses of deposited semiconductor nanostructured films were measured and its morphology was investigated. The average size of nanoparticles was equal to 18.7 nm for deposited films. The response of the prepared sensors was measured at different temperatures of the sensor work body and different concentrations of hydrogen peroxide vapours. It was found that both La-doped ZnO and Co-doped SnO2 sensors exhibit a sufficient sensitivity to 10 ppm of hydrogen peroxide vapours at the operating temperature 220 °C and 200 °C, respectively. It was established that the dependencies of the sensor sensitivity on hydrogen peroxide vapours concentration at the work body temperature 150 °C have a linear characteristic for both prepared structures and can be used for determination of hydrogen peroxide vapours concentration.

Thermodynamics of irreversible adsorption of water vapours by montmorillonite

Abstract: The adsorption–desorption of water vapours on swelling layer silicate is considered in the framework of the Brunauer-Emmett-Teller (BET) and Frenkel-Halsey-Hill (FHH) formalisms. The theoretical dependencies calculated with reasonable and consistent values of model parameters are shown to agree quite satisfactorily with the experimental data. Based on these equations, the description of the adsorption hysteresis related to Type III adsorption isotherms is proposed, which also yields a good reproduction of the experimentally observed values.

High voltage AC plasma torch operating on vapours of organic substances

Abstract: In most cases, waste from production of chlorine-containing substances have high toxicity and thermal stability. Traditional combustion is impossible due to the formation of dioxins. There are a number of methods for processing chlorinecontaining substances: catalytic reduction, fusion with alkalis, destruction by thermal air plasma [1, 2]. Plasma torch with separate feeding of plasma-forming media into the near-electrode zone and into the arc combustion zone has been developed in IEE RAS [3, 4]. The shielding gas (carbon dioxide) is supplied into the near-electrode zone, and other gases and vapors of organic and inorganic liquids may be fed into the arc zone. Operation of the plasma torch on a mixture of carbon dioxide (2.9 g/s), steam (2.9 g/s), methane (0.3 g/s) and chlorobenzene vapor (0-3.56 g/s) is discussed in the paper. Short-circuit current of the source is 55A. No load voltage is 10 kV. As can be seen from the figure, the electric arc voltage drop of plasma torch increases with increasing of C6H5Cl flow rate. This is due to increase in the thermal heat losses of the arc (proportion of hydrogen in the mixture increases).

Method for activating aluminium nano-powder

Abstract: FIELD: metallurgySUBSTANCE: passivation of aluminium nano-powder with air containing water vapours, then, the passivated aluminium nano-powder is heated to 300-400°C in air atmosphere at a heating rate of 10 to 30°C/min and kept at this temperature for 30 minutesEFFECT: increase of thermal oxidation effect3 dwg, 1 tbl

Method for treating plant products using alcohol vapours

Abstract: The invention relates to a method comprising the treatment of fruits and vegetables by applying a C3-C9 alcohol in the form of vapour.

Method for cleaning from oil or petroleum vapours of vapour-gas medium which is produced during storage of oil or petroleum, or when filling tank with oil or petroleum and plant for its implementation (options)

Abstract: FIELD: oil and gas industry.SUBSTANCE: method of cleaning from oil and petroleum vapours of vapour-gas medium, produced during the storage of oil or petroleum in a collector or when filling a tank with oil or petroleum, includes pumping absorbent into a jet liquid-gas apparatus, pumping the vapour-gas medium by the jet liquid-gas apparatus out of the oil or petroleum filled tank or oil or petroleum collector, compression of the vapour-gas medium with the absorbent absorbing the oil or petroleum vapours from it, supply of the two-phase mixture obtained in the outlet of the jet liquid-gas apparatus into a separator, separation of the two-phase mixture into a gaseous phase, partially cleaned from the oil or petroleum vapours, and saturated absorbent containing dissolved oil or petroleum vapours, supply of the saturated absorbent from the separator into a vacuum stripper an the gaseous phase into the second jet liquid-gas apparatus, supply of the absorbent by the second pump into the second jet liquid-gas apparatus and compression of the gaseous phase in it with the absorbent absorbing the oil or petroleum vapours in the gaseous phase, supply of the two-phase mixture obtained in the outlet of the second jet liquid-gas apparatus into the second separator, separation of the two-phase mixture in the second separator into a gaseous medium, cleaned from the oil and petroleum vapours, and into saturated absorbent containing dissolved oil or petroleum vapours, supply of the saturated absorbent from the second separator into the vacuum stripper and extraction of the gaseous medium into the atmosphere, isolation of the dissolved oil or petroleum vapours from the saturated absorbent in the vacuum stripper by keeping the pressure below the atmospheric pressure in the vacuum stripper, supply of the absorbent from the vacuum stripper to the pump inlet and the inlet of the second pump and of the oil or petroleum vapours into the vacuum production device of the vacuum stripper.EFFECT: increased cleaning degree.23 cl, 3 dwg

Corrosion of Mild Steel by Acid Vapours and its Prevention by Vapors of VCIs at different RH (80% to 100%)

Abstract: Corrosion of mild steel panels is caused by various environmental factors like different gaseous materials humidity required oxygen for oxidation. Maximum corrosion have been reported from the range of RH is 80% to 100%.Metal is deteriorated and form corrosion is the form of rusted materials. Most of electronic assemblies are packed in wooden boxes which produced acidic vapor which increased rate of corrosion formation corrosion product will increase. Humid atmosphere that causes rusting. It may be brown or black depends on oxygen supply in closed boxes .If the materials are wrapped with VC is soaked paper it can be protect by the vapors’ of anthraquinone, m-dinitrobenzene, alaninetheorem and some other related amino acids.

Method of capturing acrylonitrile vapours

Abstract: FIELD: physics.SUBSTANCE: method involves absorbing the acrylonitrile vapours from a gas mixture in an absorber column cooled by a refrigeration machine with acrylonitrile, the flow rate of which is set so that the concentration of water vapour in the liquid in the absorber is less than its solubility in acrylonitrile.EFFECT: effective capturing acrylonitrile vapours, reducing the power inputs and eliminating the restriction on the consumption of the gas mixture.3 cl, 1 dwg

Process for the conversion of biomass-derived vapours and process for the conversion of a solid biomass material

Abstract: This invention relates to a process for the conversion of biomass-derived vapours, comprising: - a catalytic step, wherein at least part of the biomass-derived vapours are contacted with a catalyst at a temperature in the range from equal to or more than 350°C to equal to or less than 550°C, thereby producing a product mixture; and - a condensing step, wherein part of the product mixture is condensed in one or more condensers, thereby forming a condensed product fraction and a gaseous product fraction; wherein at least part of the gaseous product fraction is recycled to the catalytic step and combined with the biomass-derived vapours. The present invention also relates a process for the conversion of a solid biomass material, comprising: - a pyrolysis step, wherein at least part of the solid biomass material is pyrolysed, thereby producing biomass-derived vapours; - a catalytic step, wherein at least part of the biomass-derived vapours are contacted with a catalyst at a temperature in the range from equal to or more than 350°C to equal to or less than 550°C, thereby producing a product mixture; and - a condensing step, wherein part of the product mixture is condensed in one or more condensers, thereby forming a condensed product fraction and a gaseous product fraction; wherein at least part of the gaseous product fraction is recycled to the catalytic step and combined with the biomass-derived vapours.

Hydrogen Peroxide Vapours Sensors Made From ZnO and SnO2 Films

Abstract: Thin film hydrogen peroxide vapours sensors made from ZnO and SnO2 were manufactured by the high-frequency magnetron sputtering method. Response of the prepared sensors was investigated at different concentrations of hydrogen peroxide vapours and temperatures of the sensor work body. It was found that the La-doped ZnO sensors exhibit a sufficient response at 10 ppm of hydrogen peroxide vapours at the operating temperature of 220 °C. Good response to 100 ppm of hydrogen peroxide vapours at the work body temperature of 150 °C was shown for Co-doped SnO2 sensors.