Showing papers on "Vapours published in 2000"

Polyaniline and its substituted derivatives as sensor for aliphatic alcohols

Abstract: Polyaniline (PAni) as well as its substituted derivatives such as poly( o -toluidine) (Po-Tol), poly( o -anisidine) (Po-Anis), poly( N -methyl aniline) (PNMA), poly( N -ethyl aniline) (PNEA), poly(2,3 dimethyl aniline) (P2,3-DMA), poly(2,5 dimethyl aniline) (P2,5-DMA) and poly(diphenyl amine) (PDPA) were found to be sensitive to different alcohols such as methanol, ethanol, propanol, butanol and heptanol vapours A negative change in resistance was observed upon exposing the polymers to methanol, ethanol or propanol vapours, whereas, a reverse trend has been observed for butanol and heptanol vapours Although, the magnitude of change in resistance was found to be very high in many cases: poor response time was observed for most of the polymers Rapid responses were exhibited only by P2,3-DMA and PAni for methanol and ethanol, respectively High sensitivity value (>80%) have been obtained for saturated methanol vapours compared to other alcohols in all polymers Further, measurable response (sensitivity ∼60%) has been obtained at lowest alcohol concentration of ∼3000 ppm with extended switching time The results are explained on the basis of vapour induced change in the crystallinity of the polymer The extent of change was found to be governed by the chain length of the alcohol and its chemical nature

Some remarks on the viscosity measurement of pyrolysis liquids

Abstract: Accurate measurement of the viscosity of fuels is essential for the proper operation of fuel supply systems and atomisers. In previous years, the use of fuels derived from the fast pyrolysis of biomass (bio-oils) has been demonstrated in, for example, furnace applications. Unfortunately, these fuels are shown to be unstable and start to polymerise even at ambient conditions. At elevated temperatures, these degradation phenomena become even more significant and complex. For example, vapours will be formed, not only due to the presence of volatiles and water in the oil, but also because of the decomposition of the oil. These vapours make the viscosity measurement troublesome. In the present paper, a procedure is proposed for the determination of the viscosity of such (unstable) bio-oils. First, by varying the sample temperature, the so-called decomposition temperature, at which the formation of vapours starts, should be determined. Below that decomposition temperature, the standard procedure for viscosity measurement can be applied. At temperatures above this temperature, the appearance of vapours results in a significant increase and strong fluctuations in the falling time of the ball due to the formation of bubbles. At these latter temperatures, values for the viscosity should be calculated from the lowest value of the falling time during the so-called heat-up period and the vapour formation delay. The values for the viscosity for five types of bio-oils, derived in this way, were shown to be reliable.

Membrane Techniques in Air Cleaning

Abstract: The state of the art of application of membrane techniques for air cleaning is presented. The most characteristic parameters of membrane separation of gases and vapours are described. Separation of gases and vapours has been applied practically in the industry for the following areas: removal of volatile organics from the air and from industrial waste flows, oxygen enrichment of air and vice versa and the membrane absorption process.

Ion-mobility spectrometer

Abstract: An ion mobility spectrometer system comprising: an ion mobility detector; a gas/vapour circulating system for the ion mobility detector into which samples of gases and vapours of interest may be drawn for detection by the ion mobility spectrometer; the circulating system comprising an ion mobility cell (12), means for drying and/or cleaning (20, 22) the circulating gases/vapours in the circulating system, a dopant source (20, 22), and means for causing circulation (10) of the gases/vapours within the circulating system; in which the dopant source and the means for drying and/or cleaning the circulating gases/vapours are combined (20, 22), whereby the need for a physically separate dopant source for the system is obviated. The dopant source material may be combined with the material for drying and or cleaning the circulating gases/vapours.

Microfibrous solids derived from SiO and from other main group oxide vapours

Abstract: The composition of “Monox”, the microfibrous or particulate solid formed by condensing gaseous silicon monoxide in inert gas streams, has been shown to be close to SiO if the solid was collected and analysed in the total absence of oxygen, but the solid oxidised quickly in air to the previously reported composition, Si4O5. Heating mixtures of Si, SiO2 with lithium or calcium silicates to 1800 °C, allowed co-liberation of SiO with Li or Ca vapours which gave microfibres of high aspect ratio when condensed in argon, an effect believed to be due to promotion of fibre growth by SiO2/Li2SiO3 or SiO2/CaSiO3 eutectics. Novel silicon-free microfibrous solids have been prepared by condensation of the vapours liberated at 1700–1800 °C when calcium gallate is reduced by carbon under argon, or when aluminium and gallium oxides are reduced by boron in hydrogen; in each case fibre growth is thought possible because of the formation of both metal and oxide phases in the hot condensate.

Effects of organic vapour adsorption on the photoelectron emission from Au thin films in atmospheric air

Abstract: Photoelectron emission from Au thin films was measured in ambient atmosphere with the presence of various kinds of organic vapours under irradiation of ultaviolet light (254 nm) The photoelectron emission was greatly influenced by the introduction of certain vapours The observed effects were classified into three types (i) Alkenes such as cyclohexene gave a large increase of photoelectron current with O2 in the atmosphere (ii) Ethanol and water showed moderate and quick increases of the current irrespective of the presence of oxygen (iii) Acetone reduced the photoelectron current irreversibly to near zero The work function of Au thin films changed considerably upon the introduction of vapours: a decrease with cyclohexene and an increase with acetone X-ray photoelectron spectroscopy (XPS) analysis demonstrated that molecular oxygen reacted with cyclohexene to form an oxygenated species on the Au thin films under the irradiation of UV light, which appeared to induce the decrease of the work function of the films

A device for recovery and control of the fuel vapours in a tank of a vehicle

Abstract: A device (6) for recovery and control of the fuel vapours in a tank (2) of a vehicle has a single case (8) which is produced in a single piece, and is provided with two portions (12, 13), of which one (12) accommodates a vapour separator (15), which can be connected to the tank (2) in order to condense part of the vapours output from the tank (2) itself, and to separate the liquid fuel from the gaseous fuel, whereas the other (13) accommodates a device (20) for accumulation of activated carbon vapours, through which the remaining part of the fuel vapours passes.

Development of a Piezoelectric Crystal Sorption Detector for Monitoring of Total Organic Compounds in Air

Abstract: A light and portable organic vapours monitor has been developed using piezoelectric (P/Z) quartz crystal to determine Volatile Organic Compounds (VOCs) commonly found in workplace air. Out of the eight coating material studied, High Vacuum Grease (HVG) was found to be the best for determining commonly encountered organic vapours such as 1,1,1-Trichloroethane, Chloroform, Benzene and Toluene in room air. The optimised coating weight was 23 μg HVG at a flow rate of 200 mL/min. Moisture was found to interfere and the use of a Nafion gas dryer was found to reduce the relative humidity to a constant 37 % for room air with 43–81 % relative humidity. Under optimised conditions, a mean sensitivity of 1.9 × 1−2 Hz/ppm was obtained for total VOCs with 17.2% RSD variation towards different VOCs. Excellent linear working ranges were obtained from 40 to 2400 ppm (v/v), with response time and recovery time within one minute up to 500 ppm (v/v) of analyte. High and relatively constant response factors were obta...

Application of polydimethylsiloxane as adsorbent for detection of aliphatic hydrocarbon compounds vapours using quartz crystal microbalance (qcm)

Abstract: Polydimethylsiloxane (PDMS) was used as adsorbent for detection and determination of some allphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and cyclohexane . The contamination of environment by these volatile organic compounds is a seriousproblemdue to theirpotentialhuman toxicity . Therefore, analysis of these compounds has become more and more important and various techniques have been developed to target this aim . A thin layer of PDMS was coated at the surface of an AT-cut gold-coated quartz crystal electrodes and a sensor based on the technique of quartz crystal microbalance has been developed for the detection of these organic vapours. Detection wasbasedon the measurement of the frequencyshiftsdue to the adsorption of the organic compounds on the polymer film . Calibration graphs were constructed by plotting the frequency changes (AFIHz) against the concentration of organic compounds . Using this method, the detection of these organic vapours was successfully carried out at parts per million concentrations.

Effect of Different Chemical Environment on Porous Silicon

Abstract: Properties of porous silicon (PS) are found to be sensitive towards different chemical environment. Because of its large surface area, it is highly reactive and can adsorb chemical vapours. The present study shows that photoconductivity and photoluminescence (PL) properties are changed significantly in the presence ofacetone, ammonia and steam vapours and can be used to identify and sense these chemical environment. These results also suggest that the molecules adsorbed on the pores change the transport mechanism of carriers in PS, leading to increase or decrease in conductivity. On the other hand, surface states on the enormous PS surface are modified under different chemical environment, leading to change in visible PL.

Combustible gas detection

Abstract: A method for detecting combustible gases or vapours using a combustible gas sensor or pellistors includes the steps of keeping the combustible gas sensor or the pellistor beads inactive until an oxygen sensor indicates a variation from a reference level of oxygen, such variation representing the potential presence of combustible gases or vapours.

Method for removing vapours from fabric

Abstract: The method involves removing the vapours from a run of fabric (4) and separating the vapours into a gas component and a liquid component. The run of fabric is guided by one or more rotating rollers arranged in the running direction of the fabric. The vapours are removed by a vacuum generator and separated and the gas component is returned to the treatment housing (1) in the outlet area of the run of fabric of the last rotating roller. A liquid component from the vapour can be supplied to an additional user and - returned to the treatment housing.