Dust collectors, cost

Electrical precipitators are probably the most versatile of all types of dust collectors. Veiy high collection efficiencies can be obtained regardless of the fineness of the dust, provided that the precipitators are given proper maintenance. The chief disadvantages are the high initial cost and, in some cases, high maintenance costs. Furthermore, caution must be exercised with dusts that are combustible in the carrier gas. 

The details of specifications for bag filter dust collectors are important to a proper and operable design selection. There are many variables which must be furnished by the manufacturer so that the user can understand how the unit operates mechanically and the unit s dust loading capabilities. The larger the air/cloth ratio for the unit, the smaller will be its physical dimensions and generally, cost however, the higher will be the frequency of cleaning. This can be quite troublesome, therefore low values of this ratio are preferable, consistent with the analysis of overall performance. 

Cost data for blenders and mixers, kneaders, centrifugal separators, crystallizers, crushing and grinding equipment, dust collectors, electrostatic precipitators, and screens are presented in Figs. 14-66 through 14-88. 

Cost of dry, mechanical dust collectors, high-voltage electrostatic precipit ators. and fabric-filter dust collectors. 

Consideration must also be given to ancillary requirements that will be necessary to support the milling process. Such equipment could include cooling systems, dust collectors. special electrics and conveying mechanisms which will affect capital requirements and day to day operating costs. Dust-free manufacturing capability is a very important requirement in current industry standards. 

Airflow, thousonds of cfm Fig. -4. Installed cost of dust collectors (ENR = 750). 

These solvents, due to their high cost and detrimental influence on the environment, may not be disposed off into atmosphere even at very low concentrations. In vacuum dryers solvent vapors after Altering in dust collectors undergo condensation in single or multistage condensers. In convective drying the presence of solvents and powders can produce an explosive mixture with air, which calls for inert gas as the heat carrier. It is then necessary to close the drying cycle. 

Many types of particulate collection devices are available commercially (see Table 53.2). Each operates on a different principle for accomplishing removal of particulates from the gas stream. Four basic types are common in drying systems (1) the drying vessel itself (in the case of vessel dryers), (2) cyclones, (3) bag filters, and (4) wet scrubbers. Electrostatic precipitators (ESPs) are not used widely in drying installations in spite of their low-pressure drop and high collection performance. The initial cost of purchase and construction is high. For this reason, the emphasis in Section 53.3 will be on the three most widely used devices, e.g., cyclones, fabric filters, and wet scrubbers. For a concise discussion of various types of solid-gas separation equipment and guidelines for selection of dust collectors,... 

C is the installed cost (US in the year of the M S Index) covering the dryer and auxiliaries, including foundations and erection, but no secondary dust collectors or building... 

Equations for estimating the f.o.b. purchase costs of dust collectors are given in Table 16.32, where the size factor is the actual gas flow rate. All collectors are of mild steel construction. For relatively large dust particles, cyclones are adequate and are the least expensive alternative. For gases containing a wide range of particle sizes, a cyclone followed by an electrostatic precipitator is a common combination. 

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