Dust collection applications

As in the production of the fabrics for dust collection applications, heat is again instrumental in inducing the necessary fabric stability, which, on this occasion, may be achieved through hot aqueous treatment, heat setting, or a combination of both. In the case of aqueous treatmeuts, these may also include surfactants to remove unwanted fibre and yam processing aids. Once again, media manufacturers will be aware of the machine speeds and tanperatures that will be necessary in these processes in order to achieve the maximum effect... 

The shrinkage tests take one of several forms, depending on whether the application is wet or dry. For dust collection applications, measurement of the fabric s free shrinkage in an air circulating oven is the standard practice, the time of exposure, and temperature varying according to the specific test procedure. 

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... 

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... 

Typical applications in the chemical field (Beaver, op. cit.) include detarring of manufactured gas, removal of acid mist and impurities in contact sulfuric acid plants, recovery of phosphoric acid mists, removal of dusts in gases from roasters, sintering machines, calciners, cement and lime Idlns, blast furnaces, carbon-black furnaces, regenerators on fluid-catalyst units, chemical-recoveiy furnaces in soda and sulfate pulp mills, and gypsum kettles. Figure 17-74 shows a vertical-flow steel-plate-type precipitator similar to a type used for catalyst-dust collection in certain fluid-catalyst plants. 

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. 

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

The separation step requires (1) application of a force that produces a differential motion of the particles relative to the gas, and (2) sufficient gas-retention time for the particles to migrate to the collecting surface. Most dust-collections systems are comprised of a pneumatic-conveying system and some device that separates suspended particulate matter from the conveyed air stream. The more common systems use either filter media (e.g., fabric bags) or cyclonic separators to separate the particulate matter from air. 

Design and configuration of the dust-collection system varies with the vendor and the specific application. Generally, a system consists of either a single large hopper-like vessel or a series of hoppers with a fan or blower affixed... 

Typical application nuisance dust collection, non-abrasive materials multiple source/multiple destination systems abrasive or fragile materials... 

Plate Towers Plate (tray) towers are countercurrent gas-atomized spray scrubbers using one or more plates for gas-liquid contacting. They are essentially the same as, if not identical to, the devices used for gas absorption and are frequently employed in applications in which gases are to be absorbed simultaneously with the removal of dust. Except possibly in cases in which condensation effects are involved, countercurrent operation is not significantly beneficial in dust collection. 

The first step of the process is performed in a separate, dedicated building. The drums of arsenic trioxide are opened in an air-evacuated chamber and automatically dumped into 50% caustic soda. A dust collection system is used. The drums are carefully washed with water, the washwater is added to the reaction mixture, and the dmms are crushed and sold as scrap metal. The intermediate sodium arsenite is obtained as a 25% solution and is stored in large tanks prior to further reaction. In the next step, the 25% sodium arsenite is treated with methyl chloride to produce the disodium salt DSMA (disodium methanearsenate, hexahydrate). This DSMA can be sold as a herbicide however, it is more generally converted to MSMA, which has more favorable application properties [8]. 

Separation based on rotating flow principles is one of the most common operations involved in gas-solid flows. This section describes the fundamental rotating flow principles and their applications to cyclone operation. The efficiency of dust collection in cyclones is also described. 

Newer, more effective control equipment has led to more efficient designs and simultaneously to lower operating expenses. This section describes various dust collection equipment, ranging from the simple to the more sophisticated. Design equations for this equipment are proprietary when contacting equipment manufacturers, they will require certain information so that they can design or recommend the proper equipment applications. 

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