A new method proven under production conditions is proposed for fine cleaning of air in systems of pneumatic transport of loose materials consisting of the use of filters made of porous metals. A production scheme is considered for a test-industrial unit and operating parameters are recommended.Bag filters are used for dust removal from air in pneumatic transport systems. However, these filters have marked disadvantages: the flat walls of the casing are designed for a pressure of 2.5 -3.0 kPa; valves for changing the direction of the air stream do not provide sufficient sealing; switching of the valve position and shaking of filter bags is accomplished from a mechanical drive which leads to rapid wear of the rubbing parts and breakdown of the filter operating regime; the method for feeding the dust and gas stream does not provide preliminary separation and it does not avoid stirring of dust settling in a bunker [1 -3]. The operating efficiency of these filters established, for example, in a pneumatic transporter for alumina from silo towers to a bunker in separate firing of chamotte for high-alumina articles, is 94%. The residual dust content after filters exceeds health standards.Dust removal by a wet method under these conditions is undesirable in view of the development of deposits that are difficult to remove and there is an insufficient degree of cleaning. Therefore there is interest in experimental verification of the possibility of using granular filters with a bonded structure, in particular filters made of porous metals [3] exhibiting high strength, insensitivity to sharp variations in pressure in the network, and high catching capacity [4 -6]. The layout of an experimental device of such a filter in a pneumatic transported for alumina from a silo tower into a bunker of shown in Fig. 1.The dust and gas stream is taken from the industrial gas conduit 1 and it enters cyclone 2 of the TsN-15 type used as the first cleaning stage. Dust captured in the cyclone is removed through bunker 3, and the dust and gas stream containing highly dispersed fractions of alumina enters the cylindrical body of the cermet filter 4 intended for fine gas cleaning. Direct feed of the dust and gas stream is possible from an industrial gas conduit into the filter through a bypass pipe. The filtering elements 5 used are six welded cylinders with a diameter 90 and a height 600 mm with a wall thickness of 5 mm made from nickel powder of the fraction 0.1 -0.2 mm. In order to reduce the degree of pore blockage

Methods are proposed for designing interpolation models for the preliminary determination and subsequent forecasting of general and fractional breakthrough coefficients for dust used with granular filters, as employed in energy-saving and high-performance dust trapping from technological gases and ventilation discharges in refractory production. The models are supplied with nomograms, which makes them widely suitable for experts working in environmental protection at refractory-producing organizations. The main factors are identified that influence the performance. The results are of interest to experts in related areas of industry such as building materials and engineering ceramics and so on.The general and fractional breakthrough coefficients K and K j are major working characteristics of granular dust trapping filters in refractory production. The breakthrough coefficient isin which z i and z f are the dust contents of the gases or ventilation discharges before the trap and after it respectively in g/m 3 . The effects of actual conditions on the values of these quantities are so varied that it is impossible to present a unified and theoretically sound method of determining them. It is best to use interpolation models in the ranges for the actual physicochemical parameters of the flow and the geometrical characteristics of the trap. It has been found [1] that in generalin which w is the linear velocity of the dusty gas flow in m/sec; d e is the equivalent diameter of the pore channels in the filter layer in m; H is the thickness of the filter material in m; t is the filtration time in sec; d m is the mean median diameter of the dust particles in m; and s is the standard deviation of the logarithm for the particle diameters in a log-normal distribution (LND).Under those conditions, it is sound to plan an experiment to construct interpolation models by the Box-Wilson method with successive realization of short series of experiments on varying all the factors simultaneously. This enables one to approach the region of the optimum rapidly. In the experiments, the model dust was a polydisperse aerosol, which was used as two types of quartz dust with the following LND for the particle sizes: d m = 3.7´10 -6 m, s = 0.405, and d m = = 20´10 -6 m, s = 0.280; the factors d m and s are almost uncontrollable separately, so they are combined in a single control factor d m s. Table 1 gives the conditions, the planning matrix, and the results from the first series of experiments.In accordance with (2), we used the natural valuesx for the factors w, d e , Í, t, z i , d m s, which are denoted respectively byx 1 ,x 2 ,x 3 ,x 4 ,x 5 ,x 6 ; the encoded factors, variation levels, regression coefficients b i , and errors in determining them have been calculated by the method of [2]. Table 1 also gives the experimental values of the response function y = lnK -1 . The regression equation after checking the model for fit takes the form It follows from (3) that in these variation intervals for the factors, K increases with w and d e but ...

A method and example are considered for determining the optimal specific gas loading for a granular filter with connected structure. Calculations are performed on the dependence of the total costs on the specific gas load for the conditions of removing dust from flue gases.Protecting the environment and industrial locations from dust discharges requires efficient trapping of definitive dust products and high-grade cleaning from dust for outgoing technological gases and ventilation discharges [1][2][3][4][5].The commonest method of removing particles from a dusty gas is passage through a granular filter, which enables one to avoid exceeding permissible discharges to the air and to organize waste recycling in some processes [1]. Advantages of Granular Filters:The filter material is readily available and quite cheap; it provides a high degree of cleaning; it has strength and thermal stability in combination with good permeability and capacity to resist sharp changes in pressure; it is stable against corrosion and rusting; there are no electrocapillary phenomena; it can be regenerated by various methods; and individual filter elements are easily combined in a variety of ways.Basic Types of Granular Layer: • immobile freely poured or packed in a certain fashion granulated material; • periodically or continuously mixing of the material; and • material with a connected structure (sintered or pressed metal powders, glass, graphitized carbon, porous ceramics and plastics, and so on). However, granular filters for removing dust from gases are of restricted use because of the high cost of the filters. The surface area of the filter and consequently the cost can be reduced by increasing the specific gas loading q, but then the pressure difference across the filter ∆p and the energy consumption E increase. The optimum value of the specific gas load q opt is determined by the minimal sum of the total costs C 0 for performing the process: the cost C for the content and servicing of the filter, the amortization allowance A, and the energy cost E [8].We consider a method of determining q opt for a granular filter with connected structure (e.g., porous metal), whose total cost usually substantially exceeds the cost of packed filters [1].

Advantages of granular filters with a connected layer structure over alternative means of ultrafine fine removal of mechanical impurities from gaseous process media are examined. Specific structural solutions for these vessels, and their operating parameters in the production of electronic devices, in biotechnology, during the production of electrolytic hydrogen, and in cryogenic engineering are presented. Methods are recommended for regeneration of multilayer filtering structures. Information on commercial and socioeconomic prospects of granular filters with a connected layer structure, which are employed for the fine removal of mechanical impurities from gaseous process media, are presented in the bibliography.Granular filters with a connected layer structure are widely used in various branches of industry; this is dictated by the availability of filtering material, the possibility of operation with marked variation in the physicochemical parameters of the dust-gas flow, entirely adequate efficiency, heat and corrosion resistance, high mechanical strength of the filtering elements, and the possibility of using various means of regeneration [1][2][3][4].These filters are effective for use, for example, in the electronic industry, where the functioning of miniature devices with very small gaps and tolerances may be disrupted when particles of dust, nap, organic substances, and various aggressive gases fall onto critical elements of a device. The reliability of miniature components of electronic devices is ensured by stringent cleanliness of initial materials and gaseous process media, rational structural shaping, and process hygiene [4]. The permissible size of dust particles and their number in an air medium will depend on the character and design of the device, its power parameters, and the distances (gaps, tolerances) between components. If a gap of 1 µm is specified between components of a microcircuit, no particles more than 0.3 µm in size should exist in the air medium. Particles, whose dimensions are smaller than the limiting size also present a risk, since may form conglomerates [5].In fact, the requirements of establishments manufacturing high-precision devices are more stringent, since their operation is disrupted when dust particles 0.3, and even 0.1 µm in size collect on their surfaces. Many production processes

The kinetics of filtering dust-gas flows by rotating self-regenerating filter membranes with decreased hydraulic resistance for energy-saving highly efficient dust collection from process gases and aspiration emissions in the production of refractories is considered. A nomogram is proposed for choosing regeneration parameters for filter membranes, and the advantages and prospects of this dust-collecting method in the production of refractories are formulated.Dust components emitted into the atmosphere in the course of production of refractories contain substantial amounts of materials that have to be recycled in the technological process. The cost of activities intended to protect the atmosphere from dust emissions at refractory works reaches 18% of the total capital investments [1,2]. In this context, it is especially important to develop self-regenerating structures with decreased hydraulic resistance in order to achieve energy-saving highly efficient dust collection from process gases and aspiration emissions. The advantages of cylindrical granular filter layers with a small curvature radius makes them rather promising for dust removal from gases in a centrifugal field [3,4].Theoretical and experimental studies have been carried out to develop a steady hydrodynamic filtering regime, which involves the specifics of resistance of rotating porous bodies, as a dust-gas flow passes through them. We relied on extensive information on separating heterogeneous gaseous systems with a disperse solid phase in a centrifugal field [5 -7].There are known original designs of self-regenerating rotary filters for separating dust-gas flows [8,9]. Therefore, it is interesting to estimate the effect of centrifugal force on pressure difference ÄP in a centripetal motion of a dust-gas flow. To derive a dependence describing the filtering process, we assume here that the pressure difference observed as the flow passes through the filter cake ÄP c.dyn is lower than the pressure difference for a stationary element ÄP c.st by a value ÄP c.cen determined by the effect of the centrifugal force on the cake:(1)The validity of equality (1) is obvious, considering that P c.st and P c.cen are oppositely directed.To determine P c.cen , the elementary pressure developed in the centrifugal field inside a coaxial cake element of a radius R and thickness dR is calculated from the following the formula [10]:where ñ c is the density of the filter cake (dust) on the surface of a rotating filter element; ù is the rotational speed. After integrating equality (2) in the corresponding limits, we obtain ÄP c.dyn = 1/2 ñ c ù 2 (R o.c 2 -R o.m 2 ),where R o.c and R o.m are the outer radii of the filter cake layer and the filter membrane.