INCREASING THE EFFICIENCY OF DUST-COLLECTING EQUIPMENT Yu. L. Vasil'ev
The increase in the production of iron powder, cermets, and friction-operated products, the intensification of basic production processes, and the introduction of more efficient and productive technologies has changed the quantitative and qualitative composition of the dust ejected into the atmosphere. Most of the solid particles discharged into the air consist of dust from iron and copper powder. Gas is cleaned of dust in cyclone separators designed by NIIOgaz (State Scientific-Research Institute for Gas Purification in Industry and Sanitation) and VTsNIPP. These separators are generally ineffective. The lack of generalized data on the performance of gas-cleaning equipment makes it difficult to optimize their selection when designing new units or reconstructing existing facilities. There is also a lack of standards and recommendations on incorporating different types of dust-collecting equipment in production lines. Based on experience in the operation of gas-cleaning facilities, it is possible to distinguish the following approaches toward improving their efficiency: increase the degree of purification of air with respect to finely dispersed dust in existing units -- without increasing energy cost costs -- by using magnetic systems and devices to coagulate (consolidate) the dust in the gas; develop and introduce new designs of dust collectors operating on the basis of combination methods methods of cleaning. It is evident that the first approach is preferable, since it does not entail large material or energy costs. Considering that the dust generated by iron powder has pronounced magnetic properties at all stages of the production process, the Brovarskii plant introduced a wet magnetic coagulator in one of the aspiration systems in the iron powder shop. The principle of operation of the coagulator can be described as follows: during the motion of the dust-laden air, dust particles from the iron powder are removed from the gas flow by the magnetic field of disks comprising the rings of permanent magnets. Dust particles of up to 1.3-2.8 mm coagulate on the disks. Then the air flow and drops of a liquid sprayed by nozzles in the coagulator send the particles to a scrubber. The latter is basically a cyclone of the TsVP-10 provided with a water spray. The use of this equipment has imporved dust-collecting efficiency. Here, the degree of purification in the wet magnetic coagulator has amounted to 47-49%. To imporve the degree of removal of fine dust aspired from the DS-6N/I steelmaking furnace at the plant, a cylindrical rpagnetic coagulator was designed and introduced (Fig. 1). The coagulator consists of sections of concentric magnetic rings 3 with a nonmagnetic shell 4 and another magnetic ring 5 composed of permanent ferrite-barium magnets. The coagulator also contains the tension member 2. The sections of concentric rings are displaced relative to one another by an amount equal to half the diameter of the rings, while the cross section of the air duct is subdivided into equal areas in order to equalize air velocity over the entire duct. The operation of the coagulator is based on the high degree of magnetic susceptiability of the iron dust and can be described as follows: due to the negative pressure created by the aspirating equipment (fan, flue-gas pump), the particles entering the magnetic field of the permanent magnets are reoriented in accordance with the direction of the lines of force of the field. Here, the magnetic forces cause the dust particles to move toward the closest pole. Overcoming gravity and the resistance of the medium, the particles eventually reach one of the poles and form coarser fractions measuring 1.5-2.9 mm. These fractions are then detached by the dust-laden air flow, which is travelling at a velocity of 13.5-16.5 m/sec. The installation of a cylindrical magnetic coagulator on the horizontal section of the air duct has made it possible to increase the degree of cleaning achieved by the centrifugal scrubber by 5-8% without increasing energy costs. Thus, equipment such as wet magnetic coagulators and cylindrical magnetic coagulators can be installed in existing aspiration systems to increase the degree of purification achieved in dust-collecting facilities and can be used as independant units for gas-cleaning. In particular, these coagulators may find broad use for the industrial and municipal cleaning of gases with respect to dust having ferromagnetic properties. Such dust is contained in semifinished and finished products of metallurgical and mining concerns (from the operation of open-hearth and other
Brovarskii Powder Metallurgy Plant. Translated from Metallurg, No. 5, pp. 23-24, May, 1989. 0026-0894/89/0506-0085512.50
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Plenum Publishing Corporation
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Fig. 1. Cylindrical magnetic eoagulator.
types of steelmaking furnance, blast furnances, sinter plants, and concentration plants). Thus, use of the coagulators will not only reduce the harm done to the environment, but wil also increase production through the utilization of recycled materials.
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