Collection Of Fine Particles Research Articles

The graphite filter furnace: a new atomization concept for atomic spectroscopy

A new atomization concept for electrothermal atomic absorption spectroscopy (ETAAS) is proposed and discussed. The basic idea is to form within part of an atomizer a large surface over which the collection of fine particles of the sample is to be distributed, and to constrain the vapor exit from that part to the analytical zone. For the amounts of analyte which are in the range of ordinary ETAAS, these techniques do not affect the character of atomic vapor release because the surface area for the analyte is smaller than that of the vapor passage. However, when there is an excess of matrix, this technique creates the conditions for matrix vapor saturation which impedes the evaporation. This in turn restricts the concentration of matrix vapor in the analytical zone and, respectively, limits spectral background and gas-phase chemical interferences. The concept is realized in the design of a graphite filter furnace. The principle of operation of the atomizer and practical methods to obtain analytical advantages are discussed and compared, using experimental data.

Capture of fine particles on charged moving spheres: a new electrostatic precipitator

A study of a novel electrostatic approach to fine-particle collection was carried out on a specially designed test apparatus. Copper spheres were first electrostatically and then dynamically suspended between two horizontal parallel plates using an applied DC electric field. The sizes studied were 74-88, 102-25, and 125-47 mu m. The charged spheres, which were larger by a factor of 10 to 100 than the dust captured (mean diameter 2.4 mu m), were then electrostatically propelled into an adjacent duct where they scrubbed a crossflowing dust-laden gas by the processes of impaction and electrostatic attraction. The total collection efficiency of the device and the target collection efficiency of the charged copper spheres were studied. Both were found to increase with the charging electric field strength, the target particle diameter, and the duct air velocity. This research suggests that electrostatic precipitation based on the scrubbing action of charged solid particles is possible, and that total collection efficiencies of up to 99% cleanup (or greater) should be attainable. Fly-ash collection performance exceeding that based on theory with regard to the particle target efficiency was observed. >

Dispersion model for interceptional and diffusional collection of fine particles in fibrous beds. A comparison with experiments

Characteristic filtration lengths of fibrous filters collecting spherical submicrometer aerosol particles are calculated over a wide range of particle sizes and filtration operating parameters. The calculations were based upon the dispersion/reaction model for aerosol transport and filtration in porous filters, and were performed for spatially periodic models of fibrous arrays of circular cylinders in square arrays. Several orientations of the direction of mean air flow relative to the lattice axes were investigated. A comparison between our theoretical results, available experimental data, and the results of competitive filtration models, demonstrated the greater accuracy of our dispersion/reaction model in correlating characteristic filtration lengths of submicrometer particles possessing diameters less than 0.3–0.5 μm. The filtration rate of larger particles, governed primarily by the interception mechanism, is shown to be sensitive to the choice of the direction of the mean air flow relative to the axes of the periodic array.

Sampling of airborne particles for biological testing within the Swedish urban air project

Within the Swedish Urban Air Projects two methods have been used for sampling of airborne particulate matter for biological testing: high volume sampler (HVS) and an electrostatic precipitator (ESP). The HVS was commercially available while two ESPs had to be constructed. The ESP samplers use impactors for collection of large particles and Teflon-coated collection electrodes for collection of fine particles. The ESP sampler used only one impaction stage, designed for a 15-μm cut-off. Its flow rate was about 4000 m 3/h. The ESP sampler was prepared for the use of adsorbents for gas phase sampling, but this sampling has not been carried out. The collection efficiency of the ESP was normally better than 90% for particles less than 15 μm. Thirteen reference samples, containing several grams of particles, have been collected in different environments such as non-urban, urban-roof, urban-street, and traffic-tunnel environments representing both summer and winter conditions. Several 1-h samples were also collected.

An automated tape-collection system for precise aerosol analysis

A continuously operating device for fine particle collection and particlebound radioactivity detection has been developed. The device consists of a control unit, a drive mechanism and a cassette unit. The sampling is performed by using a low pressure capillary impaction on an aluminum-coated mylar tape. The alpha activity and the thickness of the sample are measured by a semiconductor detector. Also elemental analysis of the collected sample may be performed.

Application and modeling of high gradient magnetic filtration in a particulate/gas system

A theoretical and experimental investigation was conducted to assess the potential use of high gradient magnetic filtration as a method of collecting particulate matter from industrial stack gases. Preliminary calculations and bench-scale experiments were utilized to demonstrate the ability of HGMS to collect fine gas-borne particles and to provide guidelines for the design of a pilot-scale unit. An experimental program was then conducted in the pilot plant using dispersed dusts obtained from two steel industry processes. A theoretical particle trajectory model was used to analyze the results and to study the effects of particle characteristics and system operating parameters. The results indicate that high-efficiency collection of fine particles can be achieved with operating conditions that project to reasonable full-scale capital costs and power requirements.

Fine particle control using sulfur oxide scrubbers.

Compliance with sulfur oxides standards will in many cases result in the installation of scrubbing devices. If these devices operate on an effluent gas stream containing particulate as well as sulfur oxides, simultaneous removal would be expected. Since effective simultaneous removal of particulate matter and sulfur oxides is economically desirable, it is of considerable import to characterize scrubber designs being considered as sulfur oxide absorbers as particulate control devices; especially, for fine particulate control. Data on the fine particle collection efficiency of sulfur oxides scrubbers at two power generating stations is presented. At the first, a venturi and a turbulent contacting absorber (TCA) both with capacities of 30,000 cfm were tested. At the second, a venturi with 600,000 scfm capacity was tested. Fine particle collection efficiency was determined at three pressure drops for the TCA using a cascade impactor. Results for the TCA show high removal efficiencies. It collected more than 9...

Fine Particle Collection Efficiency Related to Pressure Drop, Scrubbant and Particle Properties, and Contact Mechanism

Collection efficiencies are shown for control of fine particles in venturi scrubbers (1) as a function of pressure drop, and (2) as a function of throat area and liquid to gas ratio. A relationship of pressure drop to throat area, gas density, throat velocity, and liquid to gas ratio is given and is used to provide a method for estimating efficiency knowing only these scrubber design parameters. The effect of charged particles and of surface active agents on collection efficiency are discussed briefly.

Filtration of a Dilute Suspension of Fine Particles Using Glass-Fiber Papers

Several qnantitative experiments were carried out on the filtration of fine particles of polystylene in dilute suspension using various glass-fiber paper filters. Each experimental run was performed at constant filtration rate by forcing the suspension through the filter using a syringe-type micro-injection pump. From the experiments, the following results were obtained within the range of experimental conditions.1) The so called log-penetration law is applicable to the thickness of paper filters. The basic equation for filtration could be expressed as eq. (3).2) The collection efficiency of a single fiber with the interference effect is given by eq. (13). The effect of direct interception seems to be the predominant mechanism for the collection of fine particles in dilute suspension in pure water by the glass fibers.Further studies are necessary on the effect of both the fibrous solid fraction in a paper filter and electrostatic forces on the collection efficiency in order to elucidate the proportionality constant in eq. (13).