Wet collectors

FIG. 14-130 Calve rt s refined particle ciit-size/power relationship for particle inertial impaction wet collectors. Ref. (R-19) by permission. 

This subsection is concerned with the application of particle mechanics (see Sec. 5, Fluid and Particle Mechanics ) to the design and apphcation of dust-collection systems. It includes wet collectors, or... 

Canada, and Mexico (23). The National Atmospheric Deposition Program has established the nationwide sampling network of —100 stations in the United States. The sampler is shown in Fig. 14-9 with a wet collection container. The wet collection bucket is covered with a lid when it is not raining. A sensor for rain moves the lid to open the wet collector bucket and cover the dry bucket at the beginning of a rainstorm. This process is reversed when the rain stops. 

The second mechanism important in wet collectors is removal of the wetted particles on a collecting surface, followed by their eventual removal from the device. The collecting surface can be in the form of a bed or simply a wetted surface. One common combination follows the wetting section with an inertial collector which then separates the wetted particles from the carrying gas stream. 

The most common equipment for cleaning recirculated air from particles is fabric filters, mechanical collectors, electrostatic precipitators, and cleaners and wet collectors.For cleaning of recirculated air from gases, absorbers and adsorbers such as activated carbon, sometimes with impregnation for specific gases, and impregnated alumina are most common. The performance of different air cleaning equipment is described in many textbooks and handbooks. 

The basic principle of wet collectors is to wet the contaminant particles m order to remove them from the gas stream. There is a wide range in scrubber design, cost, and performance." " " Because of this wide variability, scrubbers must be carefully matched to specific applications. 

Wet collector A gas-cleaning device that uses a fluid for the removal of a pollutant from an air or gas stream. 

A projection of this point of collector effluent vertically downward shows that a second high efficiency centrifugal trill be less than 50% efficient. A wet collector, fabric arrester and electro-static precipitator will be not less than... 

There are two types self-induced spray and pressure spray. Many designs have been developed to suit specific dust or fume problems, and it is now possible to use wet collectors on the treatment of solids and fumes down to very small particle sizes. 

Self-induced spray wet collectors This is the most common type, and relies on its separating action by the induced air from the fan pulling the contaminated air through a curtain of water. It is simple in operation with no pumps or moving parts except for the fan, which is set on the clean side of the collector. The scrubbing action is dependent on the pressure drop across the collector. When set, this is constant and is determined by the water level within the collector. The removal of sludge is either by automatic ejection or manual drag-out. 

The general rule with wet collectors is that the higher the collection efficiency, the greater the pressure drop and hence the power absorbed. 

Sand foundry dusts Self-induced wet collectors ... 

Operation Concen- tration Particle Sizes Cyclone High Eff. Centrifugal Wet Collector Fabric Arrester Hi-Volt Electrostatic See Remark No. 

In building B-46, three separate operations are performed consolidation, demachlnlng, and cone swagglng. A rotary press Is used to consolidate A-5 explosive Into a grenade. To pick up the dust from this pressing operation, flexible rubber hoses (2.0 in.) are used. These lines are then connected to a stainless steel line that runs Into a wet collector. 

Introduction to absorption and adsorption, scrubbing, stripping, membrane separation, incineration, cdalytic reduction, particulate removal using settling chambers, cydones, electrostatic preepilators, filters, and wet collectors. 

Particulate Scrubbers Wet collectors, or scrubbers, form a class of devices in which a liquid (usually water) is used to assist or accomplish the collection of dusts or mists. Such devices have been in use for well over 100 years, and innumerable designs have been or are offered commercially or constructed by users. Wet-film collectors logically form a separate subcategory of devices. They comprise inertial collectors in which a film of liquid flows over the interior surfaces, preventing reentrainment of dust particles and flushing away the deposited dust. Wetted-wall cyclones are an example [Stairmand, Tram. lmt. Chem. Eng., 29,356 (1951)]. Wet-film collectors have not been studied systematically but can probably be expected to perform much as do equivalent dry inertial collectors, except for the benefit of reduced reentrainment. 

Figure 1.55. Typical grade efficiency curves for cyclones and a self-induced spray wet collector 53)...

There are several types of wet collectors including spray towers, packed towers, and wet centrifugal collectors. The spray tower is a cylindrical or rectangular tower into which the incoming air is passed. Highspeed water sprays in the tower impact and remove the dust that is subsequently separated from the droplets by various types of eliminators. Spray towers are effective for all kinds of dust and even moisture-laden gases. 

To be an acceptable substitute for wet collectors and to satisfy the NIOSH criterion for acceptable methods, a sorbent material must have a demonstrated sorption capacity for the analyte that is adequate for sampling a reasonable volume of workplace air at an established rate. Typically, a sample volume of at least 12 L (1 h at 0.2 L/min) is desirable. 

Inputs and outputs to the lake have been measured to calculate net retention for the pre-acidified lake. Precipitation inputs of sulfate were based on data from wet collectors (1980-1983) compiled by the National Atmospheric Deposition Program (NADP). SO2 inputs were calculated from regional ambient air concentrations (22) usinga deposition velocity of 0.5 cm/sec. Aerosol sulfate was estimated from NADP dry bucket measurements and from dry bucket and snow core measurements made in this study (22). Groundwater inputs occur largely at the southeast corner of the lake and were calculated from modeled inseepage (21) and measured sulfate concentrations in a well located in the major inseepage area. Sulfate output was estimated from mean lakewater sulfate concentration and modeled outflows. 

A review of Table 8 and Fig. 3-2 indicates that large-diameter particles can be removed with low-energy devices such as settling chambers, cyclones, and spray chambers. Submicron particles must be removed with high-energy units such as bag filters, electrostatic precipitators, and venturi scrubbers. Intermediate particles can be removed with impingement separators or low-energy wet collectors. Obviously, other equipment performance characteristics as noted in Table 8 will also have their influence on the final equipment... 

Particulate Scrubbers Wet collectors, or scrubbers, form a class of devices in which a liquid (usually water) is used to assist or accomplish the collection of dusts or mists. Such devices have been in use for well over 100 years, and innumerable designs have been or are offered commercially or constructed by users. Wet-film collectors logically... 

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