Aerodynamic methods for improving the efficiency of dust catchers in the production of refractories. 1. General concepts. Computation models. methods of experiment. Design solutions

The prospects of using aerodynamic methods for improving the efficiency of dust catching in the refractory industry are discussed. The suggested computation models relating the efficiency of dust catchers and the nonuniformity of the distribution of the dust-and-gas flow over the cross section of the device have been tested experimentally. Effective levelling and distributing devices for the dust-and-gas flow have been developed.     

Aerodynamic methods for increasing the efficiency of dust catchers in the production of refractories. 4. Economical and social aspects of the problem

Economical and social aspects of protection of the technosphere and organization of a low-waste production improving the efficiency of dust catchers in the refractory industry are considered. Four groups of parameters are suggested for estimating the results of protection of the ambient from the exhausted dust by aerodynamic methods. Comparative technical and economical parameters of dust catchers under optimum aerodynamic conditions of the distribution of the dust-and-gas flow are introduced for the first time. A method for calculating the main parameters of the economic effectiveness of aerodynamic optimization of dust-catchers in the production of refractories is developed.     

Use of iterative filters for arresting clay dust

The application of iterative filters FTs-2MR for catching clay dust in aspiration of by-products of the refractory industry is considered. The filters are shown to possess a high efficiency and be much more advantageous than bag filters; the performance characteristics of filters produced by the Chelyabtekhstrom IPP JSC are presented.     

复合移动床电石反应器中颗粒运动的离散单元法模拟

针对复合移动床反应器内固体颗粒运动,采用离散单元法模型（DEM）考察布料器分别为扇形开口和矩形开口时,布料器转速和开口对颗粒运动的影响,并基于文献结果论证了本文模型的准确性。模拟结果表明：①对于不同布料器,颗粒在移动床中呈现平推流和汇聚流两种流动形态。②随布料器转速及开口的增加,颗粒质量通量非线性增加。③随布料器转速的增加,下落床径向上颗粒分布更均匀;随布料器开口的增大,下落床径向上颗粒分布范围变大,颗粒分布更均匀;对下落床径向上颗粒分布,布料器扇形开口时分布呈U形、矩形开口时分布呈M形。④沿反应器轴向向下,颗粒分布有均匀化趋势;扇形开口布料器对颗粒分布的离散系数大于1,矩形开口布料器对颗粒分布的离散系数约为0.5。     

Flow in Two-Dimensional Model Filters

Model filters consist of cylindrical collectors of diameter 2a spanning the gap 2s between parallel walls. This paper presents a theoretical flow model based on the unit cell approach of Kuwabara and Happel but accounts for the channel walls in an approximate way. When a/s » 1, as is the case for most model filters, the pressure drop significantly exceeds that due to the channel walls alone, or that due to the cylinders alone in fibrous media. The present calculation is in good agreement with Yoshida and Tien's measurements for filters with hexagonal arrangement of the cylinders of solids fraction 0.675 and a/s = 15.6. Channel walls may also influence capture efficiencies and penetrations for model filters.     

How dust forms on the heating surfaces of waste heat boilers on rotary furnaces firing raw and caustic magnesite

Conclusions The manner in which dust deposits form on the walls of the gas duct and heating surfaces of boiler utilizers attached to rotary furnaces firing magnesite was clarified.It was found that in firing raw and caustic magnesite as a result of dissociation, oxidation, distillation, and evaporation the dust-laden flue gases are enriched with sulfur trioxide, vapors of alkali and fluorine which, being absorbed, are condensed onto the fine particles of dust, and reacting with them and between themselves, form simple and complex sulfates of alkaline and alkaline-earth compounds and magnesium fluoride, causing the formation of a deposit on the walls of the gas duct and surface of the pipes of the boiler until they are completely blocked and stop the furnace.The formation and rate of growth of the bonded strong deposits depend on the amount of active dust entering the furnace from the electric filters and hence on the concentration of sulfates of alkali and alkaline earths and magnesium fluoride, on the dust content, temperature, and flow velocity of the flue gases.Translated from Ogneupory, No. 8, pp. 17–25, August, 1980.     

Detonation-wave structure in RDX dust in vacuum

A mathematical model for detonation of suspensions of volatile secondary explosives in vacuum that takes into account the nonuniform temperature distribution inside the particles in flow of gaseous products is considered. The nonshock structure of stationary detonation, in the RDX dust in vacuum is studied. The parameters of a two-phase flow in the reaction zone and its length are calculated as a function of the mass concentration and sizes of the RDX particles. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 3, pp. 95–103, May–June, 1997.     

CFD simulations of turbulent fluid flow and dust dispersion in the 20 liter explosion vessel

A CFD model was developed with the aim at simulating the turbulent flow field induced by dust feeding and dispersion within the 20 L bomb, and the associated effects on the distribution of dust concentration. The model was validated considering a set of data (pressure time histories and root mean square velocity) available in the literature. The time sequences of velocity vector and kinetic energy maps have shown that multiple turbulent vortex structures are established within the sphere. These vortices generate dead volumes for the dust which is pushed toward the walls of the sphere. The obtained results are relevant to the practice of dust explosion testing and the interpretation of test results and, then, they should be taken as reference to improve the conditions for standard tests. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2485–2496, 2013     

不同构形构造分布器的数值研究

Seven distributors with different configurations are designed and optimized by constructal approach. Their flow distribution performance and energy dissipation are investigated and compared by computational fluid dynamics (CFD) simulation. The reliability of CFD simulation is verified by experiments on the distributor that has all distributing rectangle channels on a plate. The results show that the symmetry of the distributing channels has decisive influence on the performance of flow distribution. Increasing the generations of channel branching will improve the flow distribution uniformity, but on the other hand increase the energy dissipation. Among all the seven constructal distributors, the distributor that has dichotomy configuration, Y-type junctions and straight intercon-necting channels, is recommended for its better flow distribution performance and less energy dissipation.     

过滤除尘技术

讲述了空气粉尘、空气过滤器的特性、袋滤机理、袋滤器的性能及过滤材料的开发。     

Modeling instantaneous pressure drop of pleated thin filter media during dust loading

In this paper, we present a modeling methodology for studying the effects of dust loading on the pressure drop across pleated filters. Our simulations demonstrate that there exists an optimum pleat count for clean filters at which pressure drop reaches a minimum regardless of the in-plane or through-plane orientation of the fibers. With the particle deposition included in the analysis, our results indicated that the rate of increase in pressure drop decreases with increase in the pleat count. We demonstrated that a higher pleat count results in a higher flow velocity inside the pleat channels causing more non-uniformity in the dust deposition across the pleat. Especially when particles are sufficiently large, the dust cake tends to form deeper inside the pleated channel when the pleat count is high. This effect is observed to be less pronounced when the pleats have a triangular shape. We also showed that if the dust cake permeability is higher than that of the filters fibrous media, the rate of increase in pressure drop does not always decrease with increase in the pleat count. Finally, by comparing filters having 15 pleats per inch, we observed that rectangular pleats are preferred over the triangular pleats when the particles are highly inertial, i.e., filtering high-speed large particles. When particle's inertia is small, our results indicate that triangular pleats cause less pressure drop, and so are recommended.     

循环流化床锅炉一体化外置式换热器

大型循环流化床锅炉广泛采用各种形式的外置式换热器。传统的换热器只能实现换热器（EHE）和返料机构（loop seal）之间的物料流量的调节,此时进入EHE的物料将会全部顺次流过各个换热仓室,很难对外置床中的各种受热面的传热量进行单独调节。本文首次提出了一种全新的非机械阀式外置式换热器布置方式,通过控制流入各个换热仓室的固体物料流量,从而达到对各换热仓室中布置的受热面的换热情况进行单独调节。同时把EHE和loop seal结合在一起,保证向炉膛的返料。文中对这种一体化外置式换热器及其返料机构中的物料流动特性进行了冷态试验研究。试验结果表明,这种外置式换热器有很好的物料分流和流量控制特性。可以通过调节运行参数和结构参数来控制两个换热室、EHE和loop seal以及两个返料口之间的物料流量和比例。同时还得到了物料在换热室的流动特性。通过对可见输送分离高度的测量,提出了分配室和换热室相对隔板高度的设计方法。     

The Impact of Fluid Dynamics on the Regeneration of Automotive Fiber Coil Filters – Part III. Nonuniform Flow Distribution

A numerical study is performed to demonstrate the influence of a nonuniform fluid distribution on the regeneration behavior of ceramic fiber coil filters of industrial size. A detailed knowledge of the soot distribution inside the filter proves to be a prerequisite for predicting the regeneration behavior adequately. Therefore, a two‐dimensional mathematical model is developed which is able to simulate the filtration as well as the regeneration behavior. For a given soot distribution the inlet mass flow is identified as the important factor determining the overall regeneration behavior. Hints are given to ensure a controlled regeneration in view of a long lifetime of such filters.     

Propane combustion in non-adiabatic microreactors: 2. Flow configuration in posted microreactors

The aim of this paper is to analyze cross-flow operation in a microreactor with posted catalytic inserts for Pt-catalyzed propane combustion under fuel-lean conditions. The insert consists of 150 posts arranged in-line in six rows. The posts are static pillar-like structures in the flow channel, which act as static mixers and provide higher catalytic surface area. Computational Fluid Dynamics (CFD) simulations are used to compare the post microreactors for axial- and cross-flow configurations. In cross-flow case, where the bulk flow is in transverse direction across the six rows of posts, significant flow mal-distribution is observed. Tapering of the inner walls of the microreactor solid structure, at an angle of 5.766°, is proposed for obtaining more uniform flow distribution. For the cross-flow microreactors with tapered inner walls (referred to as “tapered-post”), the flow distribution becomes more uniform as the flow rate is decreased. The axial- and tapered-post microreactors show similar propane conversion for a wide range of operating conditions. Tapered-post microreactors have lower pressure drop and more uniform wall temperatures because the reaction zone is spread over the entire length of the catalytic insert. We also show that tapered-post microreactors have lower heat losses, and therefore are more stable towards device extinction. Consequently, the primary advantages of tapered-post microreactors are better thermal management and ability to operate at more fuel-lean conditions.     

A network flow analysis of extrusion dies and other flow systems

A method is presented to calculate the slow viscous flow distribution in systems of passages, for which the major velocity components are substantially parallel to the axes of those passages. That condition is generally satisfied in flat extrusion dies, disc filters, in-line filters, and other now devices. A finite difference matrix method is initially used to determine the flow distribution for an assumed viscosity distribution. That flow distribution is next used to determine a new distribution of resistances, now based on a specified rheological equation. This process is iterated until there is no significant change in the flow distribution. The passages are subdivided in this method and replaced by a network of resistances. A few unknowns are introduced at one end of the network, which are solved at the other end, using a matrix marching routine. The method is described for newtonian flow through a flat die with equalizing channel, for which the analytic solution is known. Results are shown for that die for flow of power law liquids.     

板翘式换热器物流分配特性的实验研究

The flow maldistribution and the effect of different inlet configuration on the flow distribution in platefin heat exchangers were studied experimentally. It is found that the flow maldistribution is serious because of the defects of inlet configurations, while the inlet configuration and Reynolds number are the main factors affecting the flow distribution. The improved inlet configurations, which are the header with a two-stage distributing configuration and the guide vane with a fluid complementary cavity were proposed and tested in this paper. The experimental results show that the improved inlet configurations can effectively improve the performance of flow distribution in heat exchangers.     

Die Abscheidung von Partikeln aus Gasen in Faserfiltern

Particle collection by fibrous filters . Technically employed fibre filters can be classified according to their construction and application in two major groups: deep bed filters and fabric filters. Approaches to the calculation of the collection efficiency for both types of filters start from a clean nondusted filter layer. From this one examines only the initial state, which is especially critical, while the degree of collection as a rule becomes better with increasing dust accumulation. Various models are available for the calculation of the pressure drop. The initial pressure drop for deep bed filters can be calculated with the help of the resistance model. Especially important are those estimates, which for purification filters describe the pressure drop or the gas flow with increasing dust accumulation, because these equations can serve directly for the dimensioning of filter plants. Of courese, characteristic permeability values for filter fabric and dust layer must be determined beforehand. The possibilities and problems of these calculations, as well as open questions, will be discussed.     

Effect of Aspect Ratio and Viscosity Gradients on Flow Through Open Channels

The effect of aspect (height to half width) ratio on flow through open channels is considered by evaluation of St. Venant's solution. Near the center line, flow through moderately wide channels is unatrected by the side walls. Therefore, analytical solutions for the single-dimension case of flow above a flat plate are determined. They reveal that until viscosity differentials are extreme, the velocity distribution is relatively insensitive to viscosity gradients. With several simplifying assumptions the temperature distribution and the corresponding viscosity field in a cross section of the melting end of a glass tank can be calculated. This permits a numerical solution of open-channel flow for conditions appropriate to a glass tank. Calculated temperature and velocity distributions are presented for three values of the ratio of effective thermal conductivity of glass to thermal conductivity of refractory. Applications of this type of information to glass-tank technology are briefly discussed.     

Influence of filtration conditions evaluated by X-ray computerized tomography

This research article investigates the effect of flow rate conditions on particle distribution within cartridge filters using X-Ray computerized tomography. Graphical analysis and an image reconstruction technique show that particle distribution and particle capture efficiency are significantly different for each flow condition.     

Mathematical modeling of detonation of an aluminum dust in oxygen with allowance for velocity nonequilibrium of the particles

The problem of propagation of a plane detonation wave is studied on the basis of a mathematical model for the detonation of aluminum particles in oxygen with allowance for the difference in velocities and temperatures of components. A qualitative analysis of the final steady state is performed. The domains of existence of steady solutions and the manifold of solutions of various types are determined. Various types of flows are illustrated numerically. The special features of the flow structure behind the front are analyzed, depending on relaxation parameters. We have performed flow calculations taking into account the characteristic times versus the parameters behind the front and have shown agreement between the data obtained and the frozen and variable relaxation parameters. The data obtained are found to correspond to the known experimental results concerning the widths of the ignition and combustion zones. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 6, pp. 80–91, November–December, 1997.