Showing papers on "Vapours published in 2013"

Thermal plasma properties for Ar–Al, Ar–Fe and Ar–Cu mixtures used in welding plasmas processes: I. Net emission coefficients at atmospheric pressure

Abstract: This article is devoted to the calculation of the net emission coefficient (NEC) of Ar?Al, Ar?Fe and Ar?Cu mixtures at atmospheric pressure for arc welding processes. The results are given in data tables for temperatures between 3?kK and 30?kK, for five plasma thicknesses (0, 0.5, 1, 2, 5?mm) and ten concentrations of metallic vapours (pure gas, 0.01%, 0.1%, 1%, 5%, 10%, 25%, 50%, 75% and pure metal vapours in mass proportions). The results are in good agreement with most of the works published on the subject for such mixtures. They highlight the influence of three parameters on the radiation of the plasma: the NEC is directly related to temperature and inversely related to plasma radius and is highly sensitive to the presence of metal vapours. Finally, numerical data are supplied in tables in order to develop accurate computational modelling of welding arc and to estimate both qualitatively and quantitatively the influence of each metallic vapour on the size and on the shape of the weld pool.

Electrochemical gas sensors based on paper-supported room-temperature ionic liquids for improved analysis of acid vapours

Abstract: A prototype of a fast-response task-specific amperometric gas sensor based on paper-supported room-temperature ionic liquids (RTILs) is proposed here for improved analysis of volatile acid species. It consists of a small filter paper foil soaked with a RTIL mixture containing an ionic liquid whose anion (acetate) displays a basic character, upon which three electrodes are screen printed by carbon ink profiting from a suitable mask. It takes advantage of the high electrical conductivity and negligible vapour pressure of RTILs and of their easy immobilization into a porous and inexpensive supporting material such as paper. The performance of this device, used as a wall-jet amperometric detector for flow injection analyses of headspace samples in equilibrium with aqueous solutions at controlled concentrations, was evaluated for phenol and 1-butanethiol vapours which were adopted as model acid gaseous analytes. The results obtained showed that the quite high potentials required for the detection of these analytes are lowered significantly, thanks to the addition of the basic acetate RTIL. In such a way, overlap with the medium discharge is avoided, and the possible adverse effect of interfering species is minimised. The sensor performance was quite satisfactory (detection limits, ca. 0.3 μM; dynamic range, ca. 1–200 μM, both referred to solution concentrations; correlation coefficients in the range 0.993–0.997; repeatability, ± 6 % RSD; long-term stability, 9 %); thus suggesting the possible use of this device for manifold applications.

Polymerized linseed oil coated quartz crystal microbalance for the detection of volatile organic vapours

Abstract: Quartz crystal microbalance (QCM) sensors are developed from polymerized linseed oil and used for the detection of volatile organic compounds (VOCs) such as p-cresol, o-xylene, benzene, and toluene. The polymer film on QCM surface is synthesized from the free radical polymerization of linseed oil in chloroform using benzoyl peroxide as initiator by dip coating method. The sensitivity, stability and selectivity of the sensors are measured by exposing the QCM surface to vapours. The synthesis of films are optimized and is found to have maximum adsorption of vapours when it is polymerized with 1.7% (w/v) of benzoyl peroxide. Among these four types of vapours, the maximum sensitivity is found with p-cresol and frequency shift of 110 Hz is obtained for 250 ppm of p-cresol vapour in nitrogen atmosphere. The sensor responses of concentration ranges from 5 to 250 ppm are found to be linear. The structure of the polymeric films is confirmed by FTIR analysis. Surface morphologies of the films before and after absorption are studied using AFM. The sensors are reactivated by releasing the adsorbed vapour by passing dry nitrogen gas. The sensing responses of VOC are observed to be substantial and reproducible.

Spray deposited carbon nanotubes for organic vapour sensors

Abstract: In this paper a study of chemiresistor sensors based on Single Wall Carbon Nanotube films deposited at low temperature by means of a spray technique is presented. A nanodispersion of nanotube powder in a non-polar 1,2-Dichloroethane solvent was used as starting solution. Electron Microscopy in Scanning and Transmission mode were used in order to verify the morphological properties of the deposited films. Conductivity of single walled carbon nanotubes (SWNTs) were measured in various organic solvent vapours environments. The solvents used are characterized by different polarities and volume fractions of saturated vapours defined by the vapour pressure. The results show that the electrical resistance of the sensors increases when exposed to solvent vapours. Finally the effect of Teflon-like coating on the sensitivity yield is presented and discussed.

Elimination of Toluene Vapours using Natural Zeolite Treated by Copper Oxide

Abstract: Background: Volatile organic compounds (VOCs) are the most frequent air contaminants which are produced due to industrial processes such as production of chemicals, petrochemical industries and their related industries. These compounds are harmful (even in low concentrations) not only for the environment but also for the human health. One method to control these contaminants is using catalytic beds. In this study we used modified natural Zeolite (Clinoptilolite) to eliminate toluene vapours. Methods: In this study, at first natural Zeolite were modified with cooper ions and calsined thermally. Then, the effect of variables such as toluene concentration, reactor temperature, and flow rate on toluene vapours elimination were surveyed by using a tubular stainless steel reactor and modified. Results: It was found that cooper oxide, as a catalyst, led to the considerable decrease in combustion temperature of toluene vapours. Of course, increasing the space velocity (or flow rate) and toluene concentration led to decreasing Zeolite bed efficiency. Conclusion: Regarding the presence of many natural storage of Clinoptilolite in Iran, it seems that its modification with cooper oxide could be a good catalyst for eliminating of VOCs in air.

TGA-FTIR study of the vapours released by volatile corrosion inhibitor model systems

Abstract: Proprietary mixtures of amines and carboxylic acids are used as volatile corrosion inhibitors (VCIs) for the protection of steel and iron components against atmospheric corrosion during storage and transportation. Interactions between amines and carboxylic acids have been comprehensively reported in the literature. However, little is known about the nature of the vapours these mixtures emit. The present study focused on the development of the evolved gas analysis method which will help in the characterisation of the vapours released by VCIs. In the method, the evaporation of various amine-carboxylic acid binary mixtures was monitored by thermogravimetric analysis (TGA). The nature and the composition of the released vapours was followed by Fourier transform infrared (FTIR) spectroscopy. Mixtures consisting of triethylamine (TEA) and acetic acid were studied as a model compound using TGA-FTIR at 50 °C to validate the TGA-FTIR method. As vaporisation progressed, the composition of the remaining liquid and the emitted vapour converged to a fixed amine content of ca. 27 mol %. This is just above the composition expected for the 1:3 amine: carboxylic acid complex. Mixtures close to this composition also featured the lowest volatility. TGA-FTIR proved to be a convenient method for studying the evaporation of TEA-acetic acid mixtures, and the nature and composition of the released vapours. Amine addition leads to the dissociation of carboxylic acid dimers in favour salt formation. The formation of an ion pair between the amine and carboxylic acid was confirmed by the © University of Pretoria ii FTIR spectra of the liquid phase. The resulting amine-carboxylic acid mixtures showed a slow mass loss rate on TGA when compared with the pure amines and pure carboxylic acids. This indicated that the mixtures have low volatility, hence low vapour pressure compared with the pure components. The low vapour pressure of the mixtures was confirmed by the calculated gas permeability values. These values were much higher for the pure amines and the pure carboxylic acids. However, they dropped significantly on amine addition. The strong amine-carboxylic acid interaction is responsible for the suppressed volatility of the mixtures. No interaction is observed between amine and carboxylic acid molecules in the vapour phase at 230 °C. The method developed was applied to characterise the model compounds simulating the amine-carboxylic acid-based volatile corrosion inhibitors. These model systems contained the primary, secondary and tertiary amines (hexylamine, morpholine and triethylamine), as well as carboxylic acids with different chain lengths (acetic, propanoic, hexanoic and octanoic). These systems are usually employed as equimolar mixtures to protect ferrous metals against atmospheric corrosion. The key finding of the study was that the vapours released by such equimolar mixtures initially contain almost exclusively free amine. After prolonged vaporisation, a steady-state “azeotrope”-like composition is approached. It contains excess acid and features impaired corrosion-inhibition efficiencies according to the Skinner test. In part, this behaviour can be attributed to the mismatch between the volatilities of the amine and carboxylic acid constituents.

Study the Sensitivity of Quartz Crystal Microbalance (QCM) Sensor Coated with Different Thickness of Polyaniline for Determination Vapours of Ethanol, Propanol, Hexane and Benzene

Abstract: A quartz crystal microbalance (QCM) sensor coated with a thin film of polyaniline was used as a sensitivemethod for the determination of a number of following vapours: ethanol, propanol, hexane and benzene. Thedetection was based on the absorption of the vapours of these organic compounds into the film by using gas cellchamber. The detection of these vapours can be obtained in part per million (ppm). The work includes the use ofpolyaniline films with different thickness (70, 93, 118 and 176) nm where thickness of the PANI films wascontrolled by the spin coating process. Results show that increasing of sensitivity with increase of theconcentration of injected analyte when the PANI-film-coated QCM was exposed to the vapours of ethanol,propanol hexane and benzene. Best sensitivity to ethanol and hexane were obtained with film thicknesses 93nmwhile in the case of propanol best results were obtained with thickness of 118 and 93 nm. Thickness of 93 and176 nm gave good sensitivity to benzene.Keywords: quartz crystal microbalance, polyaniline, film thickness, ethanol, propanol, hexane, benzene.

Bimetallic nanoparticles as a novel chemiresistor coating

Abstract: Here, we describe the chemiresistive sensing of some volatile organic compounds with a novel film of chemically synthesized Au–Pt bimetallic nanoparticles (NPs) stabilized with 11-mercaptoundecanoic acid. The chemiresistive sensing properties were measured over a concentration range of 1.4–250 mg L−1 for methanol, ethanol, ethyl acetate and acetone vapours and the responses were compared with Au and Pt monometallic nanoparticles. It is observed that the sensitivity of bimetallic nanoparticles is increased about 60 % in exposure to methanol and ethanol vapours, but there are no changes in the sensitivity to the other tested vapours. In addition, the detection limit is improved about 80–100 % for all tested vapours in bimetallic nanoparticles compared to AuNPs and 20–30 % compared to PtNPs.

Hydrothermal decomposition method and apparatus for making pyrolysis liquid in the range of diesel fuel

Abstract: Conversion of organic matter to higher value hydrocarbon products comprises the step of decomposing the organic matter into liquid, char and gas in a fast catalytic hydrothermal method that has improved efficiency due to a high local energy transfer through a cavitational effect Organic matter and catalysts are feed to a hydrothermal decomposition reactor to decompose the organic matter into gas, vapours and char that utilizes the high local energy transfer through a cavitational effect The reactor operates at temperatures from about 200°C to 380°C with a residence time of about 1 to 60 minutes The product is separated into a heavy slurry of char and oil, vapours and gas where the vapours are then condensed and separated into an aqueous fraction and an hydrocarbon fraction Part of the char slurry is recycled to a cavitation chamber and excess char is outputted from the decomposition chamber

Method and device for deposition reactors

Abstract: FIELD: process engineeringSUBSTANCE: precursor vapours 101 are fed through reaction chamber cover in feed line 141, 142 into deposition reactor reaction chamber 110 Vertical flow of precursor vapours is set and forced vertically from top to bottom in spacing between vertical substrates 170 Material is deposited on surfaces of substrates 170 mounted verticallyEFFECT: higher efficiency, reduced mean time interval between servicing jobs13 cl, 15 dwg

System for automatic control and regulation of industrial and environmental safety of emissions of harmful vapours and gases of acidic and alkaline nature after safety valves in emergency situation

Abstract: FIELD: chemistry.SUBSTANCE: system for automatic control and regulation of industrial and environmental safety of emissions of harmful vapours and gases of acidic and alkaline nature after safety valves in an emergency situation has a device for collecting and condensing the gas-vapour phase, which has a vapour ejector and a container with a central perforated tube. The system further includes: a unit for monitoring emergency situations, having a chromatograph and a device for automatic sampling of gas from a receiving tube, a valve for feeding water vapour into the vapour ejector, for intake of harmful vapours and gases from the receiving tube into a device for neutralising harmful vapours and gases. The device for neutralising harmful vapours and gases is in form of a container with nominal diameter (Du) 400 mm with a central perforated tube with Du 250 mm with openings F 2-3 mm. The container has an elliptical bottom and three nozzles: an upper nozzle for an air vent with a flame arrester at the end; a middle nozzle for periodically feeding aqueous solution of the neutralising substance into the device for neutralising harmful vapours and gases; a lower nozzle for releasing the reacted neutralisation product through a control valve into the intermediate vessel of a water-contaminant separator, where there is a level metre, from which said mixture is periodically pumped for recycling by a pump.EFFECT: reduced environmental pollution by emissions of harmful gases and vapours of acidic or alkaline nature after safety valves in emergency situations through neutralisation thereof.7 cl, 1 dwg

Device for multi-component gas and/or vapour sorption

Abstract: The invention relates to a devices for multi-component gas and/or vapour sorption analysis, which device can be used to measure the sorption isotherms of multi-component gases and/or vapours, simultaneously obtaining the total adsorption isotherm and each of the isotherms of the different compounds that form the gas and/or vapour to be analysed. The device comprises an extraction system (19) which can be used to extract part of the gas to be analysed for the analysis thereof and to obtain said sorption isotherms.

Method for formation of ultrathin film

Abstract: FIELD: metallurgy.SUBSTANCE: method includes deposition of adsorbate vapours onto a substrate in vacuum and growing of a film from single layers. Deposition is carried out at minimum possible kinetic energy of adsorbate atoms, and also under thermal capacity of vapours and substrate temperature providing for absence of adsorbate atoms mixing with the substrate and formation of island aggregates of the adsorbate in the film. Density of adsorbate vapours simultaneously and in the entire length along the section parallel to the surface of the substrate is maintained identical.EFFECT: increased quality of a produced ultrathin film.7 cl, 17 dwg

The Test of Organic Solvents Vapours Based on Commercial Tin Dioxide Gas Sensors

Abstract: This article describes the experiments carried out with the system of three tin dioxide gas sensors MQR 1003, TGS 822 and TGS 813, as well as the achieved results Vapours of five industrial organic solvents were tested The measurement values were processed by a cluster analysis The programmes STATGRAPHIC 50 Plus and MATLAB 711 were used for data processing The achieved results show, that the used commercial sensors are able to successfuly distinguish chosen industrial solvents and the results can be used for discrimination of organic solvents vapours in air

Extraction method of molybdenum trioxide from tailings

Abstract: FIELD: metallurgy.SUBSTANCE: method involves distillation of vapours of molybdenum trioxide in vacuum at residual pressure of 1-15 mm Hg and condensation of formed vapours of molybdenum trioxide. Besides, initial tailings are dissolved in molten boron oxide. Distillation of vapours is performed from molten metal at temperature of more than 1350°C, and condensation of vapours is performed at temperature of 800-820°C.EFFECT: simplifying the technology; improving the quality of trioxide owing to its obtaining in compact state; reducing the cost owing to reducing labour costs and power consumption; improving environmental conditions.1 tbl, 2 ex

Plant for de-alcoholizing a product containing alcohol, particularly ethanol

Abstract: The invention relates to a plant for de-alcoholizing a product containing ethanol, for example beer or wine, which plant comprises a preheating stage (5) for heating up the product and an evaporator arrangement (1) drawing product vapours from the product heated up in the preheating stage (5) and discharging the de-alcoholized product. A mechanical vapour compressor (33) compresses the product vapours from the evaporator arrangement (1) and supplies the compressed product vapours to the evaporator arrangement (1) for the heating thereof. In order to heat the preheating stage (5), product vapours from the evaporator arrangement (1) are supplied to the preheating stage (5) through a bypass route (37, 39) to the mechanical vapour compressor (33), at least a part of the product vapours being condensed by means of the preheating stage (5). The bypass route preferably includes a thermal vapour compressor (39).