Fine dust

CAUTION. The vapour of selenium dioxide is poisonous, and all operations involving the hot material, alone or in solution, should be performed in a fume-cupboard. If lumps of selenium dioxide have to be powdered in a mortar, the latter should also be in a fume-cupboard, with the window lowered as far as possible, to avoid inhaling the fine dust. (cf. p. 191)... 

Activated alumina is a relatively innocuous material from a health and safety standpoint. It is nonflammable and nontoxic. Fine dusts can cause eye irritation and there is some record of lung damage because of inhalation of activated alumina dust mixed with siUca [7631-86-9] and iron oxide [1317-61 -9] (30). Normal precautions associated with handling of nuisance dusts should be taken. Activated alumina is normally shipped in moisture-proof containers (bags, dmms, sling bins) because of its strong desiccating action. 

Inhalation of certain fine dusts may constitute a health hazard. Eor example, exposure to siUca, asbestos, and beryllium oxide dusts over a period of time results ki the potential risk of lung disease. OSHA regulations specify the allowable levels of exposure to kigestible and respkable materials. Material Safety Data Sheets, OSHA form 20, available from manufacturers, provide information about hazards, precautions, and storage pertinent to specific refractory products. 

Plants that bum good quaUty elemental sulfur or H2S gas generally have no faciUties for purifying SO2. Before the advent of relatively pure Frasch or recovered sulfur, however, hot gas purification was frequentiy used in which the SO2 gas stream was passed through beds of granular soHds to filter out fine dust particles just prior to its entering the converter. 

Zinc dust is smaller in particle size and spherical in shape, whereas zinc powder is coarser in size and irregular in shape. The particle size of zinc dust, important in some appHcations, is controUed by adjusting the rate of condensation. Rapid cooling produces fine dust, slower condensation coarse dust. In the case of zinc powder, changes in the atomization parameters can be employed to change particle size to some degree. The particle size distributions for commercial zinc powders range from 44 to 841 p.m (325—20 mesh). The purity of zinc powders is 98—99.6%. 

A. C. Elm, Fine Dust Metal Protective Coatings, The New Jersey Ziac Company, Paknerton, Pa., 1968. 

In humans, inhaled insoluble barium salts are retained in the lung (47,49). Inhalation of high concentrations of the fine dusts of barium sulfate can result in the formation of harmless nodular granules in the lungs, a condition called baritosis (49). Baritosis produces no specific symptoms and no changes in pulmonary function. The nodulates disappear upon cessation of exposure to the barium salt. However, it is possible that barium sulfate may produce benign pneumoconiosis because, unlike barium carbonate, barium sulfate is poorly absorbed (21). 

The spherical packings are too large to serve as effective targets for the deposition of fine dust particles. In dust-coUection service, the packings actually serve as tumulence promoters, while the dust particles are collected primarily by the liquid droplets. 

Because of their inherently high efficiency on dusts in all particle-size ranges, fabric filters have been used for collection of fine dusts and fumes for over 100 years. The greatest limitation on filter application has been imposed by the temperature limits of available fabric materials. The upper limit for natural fibers is about 90°C (200°F). The major new developments in filter technology that have been made since 1945 have followed the development of fabrics made from glass and synthetic fibers, which has extended the temperature limits to about 230 to 260°C (450 to 500°F). The capabihties of available fibers to resist high temperatures are still among the most severe limitations on the possible applications of fabric filters. 

The following diseusses two main eases. Consider, however, that the aetual problem eould be a eombination of exeessive eoneentration of larger partieles (10 p or larger) and exeessive eoneentration of fine dust (smaller than 10 p). 

When mass flow is on the inerease, an exeessive eoneentration of fine dust (smaller than 10 p), eould oeeur and eatalyst deposits may be deteeted. Beeause of the highly sophistieate dust-plugging meeh-anism, there has been no unanimous explanation for this malfunetion. However, field experienee indieates that eatalyst fines settle in lower veloeity areas sueh as stator paths, the trailing edges of rotor blades, and between the rotor disks after dust ingestion events. 

This approach has not been tested for any dusts that burn heterogeneously (A-6-1.2), such as some metal dusts. The equation should not be applied for gas concentrations greater than the LEE [11] otherwise extrapolation might be made into region Q shown on Eigure 6-1.3.1, where the predicted HMIE is greater than the gas MIE. The MIE of dust, D, must be determined by test using a conservatively fine dust sample to represent particles in the hybrid mixture. Values for G and Cg can be found in Appendix B. Where G is not... 

All eombustible solids ean ereate a dust explosion hazard if dispersed in air as a fine dust within eertain eoneentration limits. Refer to Table 6.2. The hazard inereases with deereasing partiele size. 

Tend to be more versatile and cheaper and offer more protection and, according to design, can protect against fine dust, fumes, liquid splashes and impact from flying particles... 

The principal constituents of the paniculate matter are lead/zinc and iron oxides, but oxides of metals such as arsenic, antimony, cadmium, copper, and mercury are also present, along with metallic sulfates. Dust from raw materials handling contains metals, mainly in sulfidic form, although chlorides, fluorides, and metals in other chemical forms may be present. Off-gases contain fine dust panicles and volatile impurities such as arsenic, fluorine, and mercury. 

To stop a fine dust of the salts from being discharged into the conditioned space. This is particularly important in the case of spinning-disk or spray-type humidifiers. 

Peripheral dust captured Fine dust controlled Heovy particles... 

Gases, vapors, and fumes usually do not exhibit significant inertial effects. In addition, some fine dusts, 5 to 10 micrometers or less in diameter, will not exhibit significant inertial effects. These contaminants will be transported with the surrounding air motion such as thermal air current, motion of machinery, movement of operators, and/or other room air currents. In such cases, the exterior hood needs to generate an airflow pattern and capture velocity sufficient to control the motion of the contaminants. However, as the airflow pattern created around a suction opening is not effective over a large distance, it is very difficult to control contaminants emitted from a source located at a di,stance from the exhaust outlet. In such a case, a low-momentum airflow is supplied across the contaminant source and toward the exhaust hood. The... 

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