Collection Equipment

In wetted-wall units, the walls of a tall circular, slightly tapered combustion chamber are protected by a high volume curtain of cooled acid flowing down inside the wall. Phosphoms is atomized by compressed air or steam into the top of the chamber and burned in additional combustion air suppHed by a forced or induced draft fan. Wetted-waU. plants use 25—50% excess combustion air to reduce the tail-gas volume, resulting in flame temperatures in excess of 2000°C. The combustion chamber maybe refractory lined or made of stainless steel. Acid sprays at the bottom of the chamber or in a subsequent, separate spraying chamber complete the hydration of phosphoms pentoxide. The sprays also cool the gas stream to below 100°C, thereby minimising corrosion to the mist-collecting equipment (typically type 316 stainless steel). 

Environmental Pollution Control. The cement iadustry has had an iatensive program of capital expenditure to iastaH dust collection equipment on kilns and coolers siace the 1970s (60). Modem equipment collects dust at 99.8% efficiency. Many smaller dust collectors are iastaHed ia aew plants (61). 

FIG. 14-105 Particle classification and useful collection equipment versus partiele size. 

Most forms of dust-collection equipment use more than one of the collection mechanisms, and in some instances the controlhng mechanism may change when the collec tor is operated over a wide range of conditions. Consequently, collectors are most conveniently classified by type rather than according to the underlying mechanisms that may be operating. 

Evidence of spills or overflow of particle collection equipment (for example, hoppers)... 

The usual estimating technique is to collect equipment pricing information from other projects and correlate this data by size, weight, pressure rating, and/or materials of construction. Each piece must be adjusted for inflation to bring all costs to one base time. Adjusting costs for inflation is discussed later under the heading, " Construction Cost Indexes. ... 

Good housekeeping practices are key to minimizing losses and preventing fugitive emissions. Losses and emissions are minimized by enclosed buildings, covered conveyors and transfer points, and dust collection equipment. Yards should be paved and runoff water routed to settling ponds. 

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. 

Figure 4-5. Efficiency curves for various types of dust collection equipment as of 1969. Only marginal improvements have been made since then. By permission, Sargent, G. D., Chemical Engineering, Jan. 27,1969, p. 130.

Collection equipment expensive but public nuisance complaints becoming more frequent. 

Collection equipment installed primarily to prevent public nuisance. 

Often no collection equipment is used where dispersion from exhaust stack is good and stack location favorable. 

By permission, John M. Kane, Operation, Application and Effectiveness of Dust Collection Equipment, Heating and Ventilating. Aug. 1952, Ref. (10)... 

Kane, John M., Guideposts Tell Flow To Select Dust Collecting Equipment," Plant Engineering, November 1954. 

A widely used type of dust-collection equipment is the cyclone separator. A cyclone is essentially a settling chamber in which gravitational acceleration is replaced by centrifugal acceleration. Dust-laden air or gas enters a cylindrical or conical chamber tangentially at one or more points and leaves through a central opening. The dust particles, by virtue of their inertia, tend to move toward the outside separator wall from where they are... 

Querying the adequacy of chimneys and stacks, scrubbers and particulates collection equipment (e.g. filters, cyclones). 

Selection of collection location Selection of collection equipment and materials Collection and acquisition Interim transport and storage I... 

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