Dust separator, applications Table

Dowtherm(R) pressure drop, charts, 94,113 Draft tubes, mixing, 309, 313 Dust clouds, 517 Dust explosions, 513 Calculations, 513 Dust separator, applications, 278 Characteristics, 234 Table, 232... 

The basic operations in dust collection by any device are (1) separation of the gas-borne particles from the gas stream by deposition on a collecting surface (2) retention of the deposit on the surface and (3) removal of the deposit from the surface for recovery or disposal. The separation step requires (1) application of a force that produces a differential motion of a particle relative to the gas and (2) a gas retention time sufficient for the particle to migrate to the coUecting surface. The principal mechanisms of aerosol deposition that are apphed in dust collectors are (1) gravitational deposition, (2) flow-line interception, (3) inertial deposition, (4) diffusional deposition, and (5) electrostatic deposition. Thermal deposition is only a minor factor in practical dust-collectiou equipment because the thermophoretic force is small. Table 17-2 lists these six mechanisms and presents the characteristic... 

Table 4-5 [10] summarizes dry dust particle separators as to general application in industry, and Table 4-6 and Figures 4-4 and 4-5 [42] compare basic collector characteristics. Figure 4-5 presents a typical summary of dust collection equipment efficiencies which have not changed significantly for many years except for specialized equipment to specialized applications. 

Figures 4-65, 4-66, and 4-67 show several units of the bag. The bags may be of cotton, wool, synthetic fiber, and glass or asbestos with temperature limits on such use as 180°F, 200°F, 275°F, 650°F respectively, except for unusual rnaterials. (See Table 4-12A and B.) These units are used exclusively on dry solid particles in a gas stream, not being suitable for wet or moist applications. The gases pass through the woven filter cloth, depositing the dust on the surface. At intervals the unit is subject to a de-dust-ing action such as mechanical scraping, shaking or back-flow of clean air or gas to remove the dust from the cloth. The dust settles to the lower section of the unit and is removed. The separation efficiency may be 99%-i-, but is dependent upon the system and nature of the particles. For extremely fine particles a precoat of dry dust similar to that used in some wet filtrations may be required before re-establishing the pi ocess gas-dust flow.

The adsorbent slurry may be applied to the TLC plates by means of several methods. For analytical work, the plates are best prepared with a special TLC adsorbent applicator which provides uniform layers and can be often adjusted to various thicknesses from 250 pm (normal) up to 500 or 1000 pm for preparative separations. The preparation of plates with a typical applicator is shown in Fig.3.1. These applicators are available from a number of suppliers of TLC equipment including most of those mentioned in Table 3.2. After the slurry has been applied, the plates are dried in air overnight or in a warm oven at 80-90°C for ca. 30 min. The dry plates are stored in a dust-free cupboard for further use. Portable cabinets for plate storage are available from a number of suppliers. 

It is not unlikely that there may be some confusion in the reader s mind, after going through so many ways of area classifications, again, each class further divided according to material types. Also, these are not uniform across standards. For example, in ATEX for dust in mines, and other than mines, have different representations and ignitable fibers mentioned in the United States standard is not separately treated in other standard. In order to circumvent the situation, a small comparative study has been presented after, so the reader can understand the same properly. In order to supplement Table X/3.2.3-3, at this point some detailed comparisons of various standards have been presented in Table APII/2.2-1 and Fig. APII/2.2-1 (mainly for enclosure class) to get a better grasp on the issue about applicability (as per location/ country). 

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