Methods of dust removal from process gases by granular filter baffles are reviewed. The process flow diagram of the pilot plant is described. Areas of application of filter elements for high-temperature cleaning are indicated. Key words: high-temperature dust cleaning (removal), pilot plant, filter elements.With increase in heat loads and temperature of gaseous media entrainment of dust in the working space of apparatuses increases dramatically, reaching, for example in calcination of pyrite in KS-type kilns, 7000-7400 kg/day. Dusts exceeding 20 wt.% collect onto heat using surfaces and then to the atmosphere. Dust of volatilization (dry distillation) origin is highly disperse -90 wt.% of solid particles is finer than 2 μm [1].The dust sticks to steam superheater tubes, evaporators, and economizers, reducing thereby the steam output of boiler units that utilize the heat of waste gases. In this case, the hydraulic resistance in the dust-gas flow channel rises, and draft potentials of exhaust fans and operational efficiency of the chief process equipment decrease. Furthermore, in the area of location of the enterprise and the residential district, the concentration of toxic dust emissions exceeds the allowable sanitary standards manifold.A similar situation is observed in the case of high-temperature gasification of high-sulfur residual fuel oils under pressure, fluidized-bed catalytic cracking, and thermooxidative pyrolysis of methane. In these situations, electrofilters (electrostatic precipitators), turbulent Venturi scrubbers (washers), and cloth filters do not provide the required degree of cleaning of the dust-gas stream. Granular filters can be used to solve this problem [2][3][4].The schematic diagram of the specially designed plant for high-temperature cleaning of flue gases is shown in Fig. 1. This plant can clean dust-gas streams having various physicochemical parameters with vertical, horizontal, successive and parallel positions of the granular bed.In experiments with real dust-gas stream, the size of quartz sand granules was varied between 0.5 and 5 mm, the bed thickness (height), 20 and 150 mm, and the filtration rate (speed) between 0.2 and 0.7 m/sec. The cleaning efficiency increased under these conditions because of accelerated formation of autofilter (mobile filter) and increased role of inertial precipitation of the particles. The obtained data support the conclusions drawn earlier by analysis and prognostication of effectiveness of granular beds and interpolation models of aerosol filtration process [5][6][7].The efficiency was the maximum when 0.5-1.0 mm sand fraction was used. A bed composed of such a fraction, however, offers high hydraulic resistance and therefore must be of small thickness, which complicates design of the appara-
The mechanism of flow is considered for a dusty gas in distribution devices in dust traps in the production of building materials. Studies have been made on thin-walled grids and various cases of their use. Particular attention is given to several successively placed distribution grids, each of which has a hydraulic resistance coefficient less than the necessary coefficient for one grid. The results can be used in the chemical industry and also in the production of building and refractory materials, as it meets the standards for the limiting permissible discharges and the utilization of the trapped dust by returning it to the technological process.In building-material production, dust trapping is an essential part of the process, since raw materials processed in the suspended state must be maximally extracted from the air not only for health reasons but also for technological considerations.For most dust traps used in making building materials [1], importance attaches to the calculation and choice of devices for providing the best aerodynamic conditions in cleaning the gases [2].Current trends [1] lead to the development of methods of optimizing the aerodynamic conditions in dust trapping as important for filtering equipment and other plant of Polotsk type with layers of granular (lumpy) bodies, and for apparatus of radial type, in which the dusty gas passes through the lateral permeable surface of the filtering material: the surface of a layer of granular material or cemented bodies, cloth, various fibers, grids, and so on in collector systems with uniform flow of the dusty gas in the distributors, and also for electrical filters with their exceptional variety of conditions in handling the dusty gas flow in the trap.Particular interest attaches to the mechanism of dusty gas flow over the distribution devices. A uniform distribution can be used by the employment of hydraulic resistances distributed over the cross section of the working layer. As such resistances one can use grids of various types and pack layers of lumpy or granular material. Granular beds are very promising ways of dust trapping in making building materials [1], and we consider the flow of the dusty gas through such beds (Fig. 1).For a bed thickness corresponding to the optimal hydraulic resistance coefficient ζ opt (Fig. 1a), there is a dusty flow incident as a narrow jet that spreads out gradually in the section from one section to another and beyond the layer establish-
Mechanisms and appropriate engineering solutions are considered for improving various methods for regenerating granular dust collectors. Model interpolation calculations for evaluating the efficiency of the recommendations developed are proposed and tested in practice.Use of granular filters is promising for removing dust from gases at high temperature. In addition, it is economically beneficial to remove dust from gases using charge materials in a layer. This makes it possible to capture effectively sticking, lumpy, and abrasive dust from moist gases, i.e., in those cases when use of other dust removal methods is inexpedient.Granular filters are used in removing dust from high-temperature gases in the cement industry, and preparation of rare and expensive metals. Apart from filtration, granules may fulfill the function of a heat carrier and absorbent or catalyst in combination with filtration with an absorption or catalytic process.Due to the continuous improvement of regeneration methods, granular filters are used throughout the world for cement, lime, gypsum plants, chemical enterprises, in electrical instrument manufacture, radio engineering, atomic power generation, etc. Structurally this equipment is simple, has low operational consumption, is reliable in operation and provides quite a high degree of gas cleaning.The efficiency of using granular filters in industry is governed to a considerable extent by the choice of granular layer regeneration method.Filters are shown in Fig. 1 with different methods of loose material granular regeneration. A filter with regeneration by vibration shaking and back flushing (see Fig. 1a) has a holder installed on a spring and joined to the body by means of a flexible seal. The lower part of the holder is filled with metal turnings or coarse fraction loose material granules. This part of the layer is intended for capturing the coarsest dust fractions. The upper half of the holder is filled with granules with a size of 1.5-6 mm.The thickness of the layer is normally 100-250 mm. In order to reduce loose material movement, the holder is separated into small compartments.During filtration, dusty gas passes from the bottom upwards, and during regeneration from the top downwards. Simultaneously with flushing there is vibration. During vibration, intense granule movement commences when acceleration of the induced vibrations exceeds free fall acceleration taking account of the frictional force of granules between each other and over a holder wall.Vibrators have a shaft rotation frequency of 2800 rpm and power up to 3 kW.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.