Size classification screens

Other Classifiers.— These include the Ovoca, using a continuous double helix the Esperanza, using a continuously moving belt or chain equipped with rakes or paddles, and various other combinations of rakes and paddles, screws, etc. all based on the same principle. For definite particle-size classifications screens are more efficient than classifiers. 

The production of aluminum begins with the mining and beneficiation of bauxite. At the mine (usually of the surface type), bauxite ore is removed to a crusher. The crushed ore is then screened and stockpiled, ready for delivery to an alumina plant. In some cases, ore is upgraded by beneficiation (washing, size classification, and separation of liquids and solids) to remove unwanted materials such as clay and silica. 

Air classification Is preferred for fine sizes because screens of 150 mesh and finer are fragile and slow. 

Fig. 3.9. Schematic diagram of an inclined disc agglomerator. (In many applications, subsequent screening is not required because of size classification on the disc see Fig. 3.10.)...

The Chatfield comparator [93] was devised for the size classification of sub-10 pm particles from 35 mm film records and was based on the projection of a photograph on to a translucent screen which was back illuminated by a variable size light spot. When a match was made the operator used a foot switch to record the size. 

In addition to the two major categories of LEVS approaches, similarity searching and compound classification, database filtering techniques should also be added to the virtual screening spectrum. Rule-based filters that screen databases for compounds with desired (e.g., drug- or leadlike) or undesired (toxicity and instability) molecular properties are widely used, not to identify individual active compounds but rather to reduce the size of screening databases as much as possible for further studies using more sophisticated methods. 

Vibration The vibratory grid, or screen equipment, is the most widely used technique for primary reclamation purposes. The sieved sand is removed for subsequent treatment, e.g. for cooling, size classification, and thermal reclamation, and the residual material is collected for disposal... 

Screen. An industrial-scale unit for size classification (a sieve (q.v.) is for laboratory use). A screen consists of a wire mesh or a perforated metal plate the usual types are revolving screens (q.v.) and vibrating screens (q.v.). Screen Printing. A decorating method that can be applied to pottery, glassware or vitreous enamelware. The simplest... 

In the cement industry, particle size classification by screening as part of the production operations is of less importance than, say, in the lime industry or in coal and ore preparation. Indeed, true classification procedures in the primary size reduction stage do not occur in cement manufacture, since the aim of the crushing treatment is to produce a feed material suitable for grinding to a fine powder, not the production of size fractions as required for crushed stone used in road construction, concrete production, etc. 

Industrial processes for size separation are screening and classification. Screening is carried out by vibrating sieves for coarse particles with sizes... 

Within a given catalyst size classification, differences in particle size distribution and in equivalent particle diameter are possible, particularly for wide classification ranges. This is shown in Table 6.3, which collates values obtained by application of Eq. (6.29) to the screen analysis of two catalyst samples, both classified in the range 6-10 mm. When particle size-distribution data are not available, bed parameters for the most commonly used catalyst sizes can be taken from Table 6.4, where ranges of values are given and which allow a satisfactory approximation for use in pressure-drop calculations in industrial converters. 

Classification of nanofiber length has proven to be more difficult than diameter and therefore has been the main focus of online size classification research. The principle method of classifying nanoflbers by length is electrostatic classification. Other methods include wire screen penetration [20] and gravitational settling [21] but these will not be discussed. The electrostatic classification method can be further divided into two categories dielectrophoretic and electrophoretic classification. 

Sizing of the cmshed and ground product is a necessary step prior to any mineral processing operation, and in the production of a product having a specific size. Controlling the size of material fed to other equipment is important. AH equipment has an optimum size range of material that it can handle most efficiently. Size separation can be achieved either by screening (for coarser particles) or by classification (for fines) (see also Separation, size). 

Classification of screening operations and the range of separations that can be attained with various screens were given in concise form by Matthews (op. cit., 1971). See Table 19-5. Further details are given under Equipment. Figure 19-14 indicates the size-range applicability of various screen types. 

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