Showing papers on "Vapours published in 1992"

Gas and vapour detection with poly(pyrrole) gas sensors

Abstract: The response mechanism of the conducting polymer poly(pyrrole) to a selection of gases and vapours was investigated using two techniques: measurement of resistance change and mass changes using a piezoelectric quartz crystal microbalance with the objective of characterizing responses for incorporation in sensor arrays. Bromide-doped films were exposed to methanol, hexane, 2-2-dimethylbutane, ammonia and hydrogen sulfide. Polymers of different thicknesses were also exposed to methanol vapour and the response profiles were studied. The responses were all of a Fickian type except the piezoelectric signal, which exhibited an anomalous non-Fickian response to methanol. This suggests that the poly(pyrrole) resistance changes frequently observed are partly due to one stage in the two-stage sorption perhaps involving the swelling of the polymer. It was concluded that the response mechanism of poly(pyrrole) sensing of different gases and vapours is due to a mixed response involving electronic effects and physical effects.

Thin films of iodine—polyphenylacetylene as starting materials for humidity sensors

Abstract: A humidity sensor has been fabricated by using thin films of iodine-doped polyphenylacetylene. The electrical response of the sensor towards relative humidity variations is fast and reversible during long working periods. The investigated sensor is also sensitive to the vapours of other chemical substances.

A fibre-optic fluorescing sensor for amine vapours

Abstract: A fibre-optic fluorescing sensor based on a film of the pH-sensitive molecule 2-napthol, hydrogen-bonded to a matrix of poly(ethylene oxide), is described. The indicator molecule has well-defined fluorescence peaks, due to protonated and deprotonated forms, and the relative proportions of these change in response to interaction with amine vapours. No significant quenching by oxygen is apparent and water vapour does not influence the behaviour below a relative humidity of 90%. At higher humidities the effect is pronounced. The lower limit for reliable detection of monoethanolamine (MEA), and several other amines, is better than 1 μM (24 ppm). The sensor responds reversibly and the time taken to achieve 90% of full-scale variation is approximately 45 s. Recovery to 90% of initial response takes around 5 min.

Use of organophosphorus vapours as chemical modifiers for the determination of cadmium by electrothermal atomic absorption spectrometry

Abstract: The use of the vapours of several organophosphorus liquids as chemical modifiers for the determination of cadmium by electrothermal atomic absorption spectrometry is described. The best results were obtained when triethyl phosphite was used as the modifier. These vapours were found to stabilize cadmium to the same extent as a more traditional modifier but with a reduced possibility of contamination. The method was validated using certified reference materials (NIES Human Hair and Sargasso).

Condenser for vapours contaminated with gases - passes rising various or gases through descending condensate

Abstract: Condenser, for sepn. of vapours condensing in the cooling zone from vapours or gases not condensing in the zone, has a connection (2) for vapour to be condensed above the condensate sump (1) and the cooling zone (3) above the connection, forming part of a straight tubular heat exchanger (5). Rising vapour is passed through the tubes and is washed by the descending condensate. ADVANTAGE - Dusts are not carried into the system.

Studies of the Interactions between Organic Vapours and Organic Semiconductors. Applications to Chemical Sensing

Abstract: A combination of mass, optical spectroscopy and work function measurements has been used to study the interaction of organic vapours with conducting polymers. These steady-state measurements open the way for a qualitative and quantitative evaluation of the charge transfer and sorption interactions of organic vapours with these “network solids”.

High added value products from difficult wastes

Abstract: The residual fly ash produced by coal combustion in thermoelectric power plants was mixed with vegetation water obtained from an olive mill The aim of this research was to increase the adsorptive capacity of fly ash, by means a new way of aggregation, using residues from the food industry, namely the concentrate of the vegetation water from olive mills In particular we tried up to obtain a solid product with the following characteristics: good mechanical strength; wet strength; high porosity and high specific surface area; good adsorptive properties The product of the aggregation was submitted to a pyrolysis and activation process in order to obtain an adsorbent material The pyrolysis produced an oily liquid fraction, with a good calorific value, a high hydrogen content gaseous fraction and a carbonaceous matrix dry residue As the latter present good microstructural characteristics, it was utilized in adsorption processes, on laboratory apparatus, in order to evaluate its adsorptive capacity for organic vapours The results obtained with gas-solid adsorption experiments in fixed-bed bench scale plant, using toluene vapours as the adsorbed gas, verified the possibility of getting useful products at a high added value from waste materials of difficult disposal qualities

Using barrier materials efficiently

Abstract: In addition to protection against mechanical damage, many food products must be protected from atmospheric environmental influences such as rain, water vapour, oxygen and odours. Barriers are mostly used to provide resistance to the passage of gases, vapours and odours; of the gases, carbon dioxide, oxygen, sulphur dioxide and nitrogen are the principal ones concerned in packaging foods. Water vapour is the most important vapour, while flavourings and essential oils are important odours.

Inert gas desorption of single organic vapours from activated carbon

Abstract: Inert gas desorption of three single organic vapours from a highly activated carbon into a finite volume is investigated theoretically and experimentally. A model is proposed, which takes into account the internal as well as the external mass transport resistance. Inside the pellet two mechanisms, surface flow and gas-phase diffusion, contribute to the total desorption flux. In most experiments suface flow was found to be the dominant transport phenomenon. The analytical solution presented relates the desorption conversion rate to four dimensionless parameters, which can be calculated a priori. For all sorptives, the fitting parameters tortuosity μ and ratio of surface to molecular diffusivity Ds/Dog were found to be identical. Moreover, Ds/Dog does not depend on the desorption conditions, such as total pressure, temperature, concentration range and amount adsorbed.

Series conversion technology of hydrocarbon vapours

Abstract: This invention relates to the conversion of hydrocarbon vapours by using seriesly-connected heat-exchange type conversion furnace and intermediate conversion furnace of heat supply by burning out of tubes. It utilizes efficiently two-stage conversed gas to conduct indirect heat-exchange with technological gas in heat-exchange type conversion furnace, and reserves the existing heat-exchange furnace of medium and low temperature type with the addition of necessary heat recovery facilities.

Electron drift in alkali-metal vapours

Abstract: Electron drift velocities in sodium, potassium, rubidium and caesium vapours are calculated using theoretical momentum-transfer cross sections for electron-atom scattering. The results strongly disagree with experimental data for saturated vapours at low values of E/N (ratio of electric field to vapour number density). The author shows using the case of sodium as an example, that the disagreement could be explained by the presence of alkali dimers in saturated vapours which lead to the processes of electron-impact vibrational excitation and deexcitation and dissociative attachment. These processes strongly affect the electron energy distribution function and reduce drift velocities. Results of model calculations show that inclusion of inelastic processes involving the dimers leads to a better agreement with the experiment.

Condensing ammonia, natural gas and fluoro-chloro-hydrocarbon(s) - in simple washing-condenser plant, including prepn. for storage and transportation

Abstract: This is a method of condensing vapour from industrial process. By material exchange processes in a washing condenser where it is washed in counterflow with a fluid having a higher boiling points. the cold vapour is converted to the higher b.pt. vapour of the washing fluid. The cold vapour becomes liquified, and the vapour from the higher b.pt. fluid is liquefied in a heat exchanger. The heat exchanger can be installed in the vapour outlet pipe from the condenser. USE/ADVANTAGE - Used for the liquefaction of cold vapours such as ammonia, natural gas, and FCKW, and includes the cooling of pressing vessels in which the cold vapours are stored and transported, and also the evacuation of parts of the plant that contain these gases. The complications of earlier methods of condensing these vapours are avoided.

Use of DCI-platine coupled to gas chromatography for measuring the transfer of organic vapours through packaging materials

Abstract: A new technique uses DCI-Platine coupled to gas chromatography in order to measure the transfer rate of organic vapours through packaging materials. Experimental results are presented for ethyl acetate vapour through two polymer films, a vegetable parchment paper, and a coated paperboard. The films allow vapour mass transfer even at low vapour feed concentrations (i.e. the concentration expected in the package) whereas the paper and, especially, the paperboard, need higher feed concentrations.

Process and plant for recovering heavy metals from waste

Abstract: A process is disclosed for recovering heavy metals, according to which adsorbants or waste are heated under depression in an inert gas within a processing chamber. The gasses containing heavy metal vapours produced in the processing chamber are led to a post-combustion chamber and the heavy metals are recovered by condensation from the exhaust gas that comes out of the latter chamber.