Gas-dust Flow Research Articles

Numerical study of influencing geometry of separator elements for cleaning dust of food production on its efficiency

At modern food enterprises, the task of providing high-quality air cleaning from dust is relevant. The paper proposes an original dust separator, the peculiarity of which is the presence of structural elements of different shapes, arranged in a chess order. This design solution ensures the formation of a wave-like structure of the gas-dust flow within the device. The separation of solids from air is due to inertial and centrifugal forces. The aim of the work is to evaluate the fractional efficiency of this separator with structural elements of different geometric shape during the dust capture process. The paper considers I-shaped, P-shaped, arc-shaped and V-shaped structural elements. The study is carried out by numerical simulation at a gas dust flow rate of 0.5 to 3 m/s and a particle size of 10 to 200 ?m. During the work it has been found that the shape of the structural elements largely determines the efficiency of separation of dust material from the gas stream. The V-shaped design elements have shown the highest average separation efficiency compared to other shapes under other equal conditions. This is due to the fact that in such a separator the particles are directed to their apex, where the velocity of the particles decreases contributing to their subsequent settling into the bunker. The maximum efficiency for V-shaped elements is on average 80.1 % at a gas dust inlet velocity of 0.5 m/s. The lowest efficiency is observed for I-shaped elements, as particles return to the air stream after rebounding from the walls.

СЕПАРАЦИОННОЕ УСТРОЙСТВО С ДУГООБРАЗНЫМИ ЭЛЕМЕНТАМИ ДЛЯ УЛАВЛИВАНИЯ ЧАСТИЦ КАТАЛИЗАТОРА В РЕАКТОРЕ С ПСЕВДООЖИЖЕННЫМ СЛОЕМ

The reactor with a fluidized bed of catalyst is used in many industries. Most often in oil refining, coal gasification, petrochemistry, etc. It is known that in order to prevent the entrainment of the catalyst, the reactors are equipped with devices of particle capture systems - cyclones. However, there are significant disadvantages - the removal of the catalyst. The paper proposes to reduce catalyst losses in a fluidized bed reactor by replacing cyclones with separation devices with arc-shaped elements. The article presents the design of the proposed separator. The principle of its operation is described. It is shown that under the action of inertial and centrifugal forces, particles are knocked out of the gas-dust flow towards the arc-shaped elements. In the course of numerical studies conducted in the Ansys Fluent software package, it was found that at relatively low speeds up to 1 m/s, a high separator efficiency of more than 69.2% is achieved. At a gas-dust flow velocity of more than 1 m/s, two critical particle sizes were identified, which correspond to maximum and minimum efficiency. At a gas-dust flow velocity of 2 m/s, the value of acr.1 = 52.4 microns (E = 99.9%), acr.2 = 138 microns (E = 63.7%). At a gas-dust flow velocity of 3 m/s, the value of acr.1 = 52.4 microns (E = 99.9 %), acr.2 = 138 microns (E = 25.7%). As the particle size increases to acr.1, the efficiency increases, since the particles can be better knocked out of the structured flow. With a particle size between acr.1 and acr.2 the particles bounce off the arc-shaped elements back into the current and are carried away. When the particle size is more than acr.2, they randomly bounce off different arc-shaped elements and fall into the hopper due to gravity. The pressure loss in the separator is less than 58 Pa at a gas-dust flow rate of less than 1 m/s. The use of separators with arc-shaped elements in fluidized bed reactors to capture catalyst particles as an alternative to cyclone separators is an appropriate measure that significantly reduces its losses.

THE DICHOTOMY OF THE MECHANISMS OF DECAMETER RADIO EMISSION FROM JUPITER: THE INFLUENCE OF STREAMER INHOMOGENEITIES AND MHD PERTURBATIONS IN THE SOURCE

There are analyzed a model of the source of DAM radiation bursts which are activated under the MHD waves excitation in the Jupiter lower magnetosphere in a presence of ionized streamer-like inhomogeneities of limited thickness (1-100 km). There was studied the formation of an anisotropic kinetic distribution of electrons, which leads to the generation of Jupiter DAM radiation bursts under the various scenarios. It was investigated the influence of gas-dust flows in the Io-Jupiter tube, the ionization processes and the diffusion effects in the streamer plasma to the creation the cone-type kinetic distribution of electrons. On the other hand, it has been shown that Alfven waves, due to the fluctuations of electric fields, are to form of both cone-like electron distribution (primarily on the streamer periphery) and beam-like distribution with the beams of accelerated electrons (primarily inside the streamer), which further run along the streamers at speeds of about 0.1c and have been modulated by a "longitudinal" MHD wave with a length of about 1000 km and a period of about 1 second. The streamer oscillations in the direction tangential to the magnetic field lines lead to the excitation the fast magneto-sonic waves (at about the ion cyclotron resonance frequencies). The beams of accelerated electrons of along the magnetic field lines generate the plasma waves in the same direction (at about the electron cyclotron resonance frequency). At the same time, plasma perturbations create a stratification of the steamer-tube structure into ultrafine threads of ionized plasma, and they contribute to the ultrafine modulation of bursts of DAM radiation with millisecond periods. Finally, it is shown in detail how all these processes lead to activate the Jupiter DAM radiation bursts in that source at the frequency of electron cyclotron resonance by different generation mechanisms, such as the Maser Cyclotron or Cherenkov mechanisms of generation, and with different burst’s properties.

Influence research of electrostatic environment on dispersion and explosion characteristics of typical biomass organic dust clouds

In order to explore the explosion characteristics of dust cloud under the coupling condition of electrostatic field, flow field and particle motion field, based on the theoretical analysis of the charging mechanism of dust particles in the electrostatic field, the motion mechanism and explosion behavior of three typical biomass dust were studied by means of experiment and simulation. The research results were presented in the electrostatic field to evaluate the dispersion effect and explosion hazard of dust clouds. It was found that when the dust concentration is less than 500 g/m3, both the peak explosion overpressure and the rate of explosion overpressure rise of dust increase with the increase of dust concentration under the loading of electrostatic field. Compared with the case without electrostatic field, the maximum explosion overpressure of three typical organic dusts are increased by 2.6%, 5% and 12.1% respectively. Moreover, a multi-field coupling mathematical model of particle charge and motion was established, which not only studied the influence law of electrostatic field on particle charging and gas-dust flow characteristics, but also discussed the influence mechanism of electrostatic field on dust cloud explosion intensity from the perspectives of particle concentration distribution, particle velocity distribution and turbulence intensity parameters.

The changing dynamics of the gas-dust flow in the flash smelter due to addition of a spoiler. Part 2. Pilot tests

The use of man-made deposits and fine ore concentrates in the flash smelter process, as well as the poorer quality of the raw materials observed (due to a higher share of particles smaller than 10 μm) lead to a higher amount of entrained dust and causes accretion in the slag end, uptake shaft and waste heat boiler. A higher dust entrainment is associated with a higher recycle, lower energy capacity of the raw materials and poorer recovery of non-ferrous metals. Numeric modelling of the heat and mass exchange processes in the gas environment of the settler and uptake shaft helped determine how different sizes and locations of the spoiler can change the gas flow parameters of the flash smelter. The modelling study showed that a 500 mm wide (the width of the settler) and 270 mm high spoiler mounted on the fire side of the settler at least 2,000 mm away from the entry to the uptake shaft could help reduce the amount of entrained dust by as much as 20% (relative) depending on the size and density of gas-dust particles. On the basis of the above calculations, a series of pilot tests was conducted on Line 1 of Nadezhda Metallurgical Plant in July 2019. Using various analysis techniques (such as thermal imaging of the surface in the spoiler area, the gas temperature, the gas flow rate, as well as methods used in analytical chemistry, scanning electron microscopy and X-ray spectral microanalysis), the authors of this paper examined the effect produced by the mounted spoiler on the gas flow. The authors would like to thank the leadership and the operations personnel of Nadezhda Metallurgical Plant for their support and great contribution to the pilot tests performed.

The changing dynamics of the gas-dust flow in the flash smelter at Nadezhda metallurgical plant due to addition of a shield. Part 1. Model calculations

A poorer quality of the raw materials that go in the flash smelter operated by Nadezhda Metallurgical Plant, as well as the use of man-made deposits and fine ore concentrates with high concentrations of particles smaller than 10 μm, leads to a higher amount of entrained dust. Dust entrained by the gas flow leads to the formation of accretion in the slag end, uptake shaft and waste heat boiler. A higher dust entrainment is associated with higher loads on the gas duct, higher material turnover, decreased performance and recovery of non-ferrous metals. Fitting the furnace crown with a shield avoiding any major changes to the furnace design or the smelting process helps change the dynamics of the gas flow and lower dust entrainment. This paper defines the optimum location and dimensions of such shield. Depending on the particle size and the density of the gas-dust flow, with the shield installed, the estimated reduction in the amount of dust getting in the dust treatment system may reach 20%. 

COMPUTER SIMULATION OF PARTICLE VELOCITY IN A CYCLONE

The article sets the goal of determining and calculating the speed of accelerated movement of particles in the gas-dust flow of an air cyclone, depending on the size of the cyclone, the physical properties of the particle and the gas-dust flow. A method for constructing a computer model of the motion of a particle in a roaring gas-dust flow of a cyclone is presented. The sequence of formalization of the computer model of the process of sedimentation of particles of a gas-dust flow of a cyclone unit is based on the theoretical foundations of aerodynamics and touches on the most significant aspects of the development of a cyclone. Attention paid to the analysis of the dynamics of particle motion in a centrifugal field, accelerated motion and a realistic estimate of the particle velocity. The mutual influences of five forces are considered. This is the centrifugal force, the force of resistance of the gas-dust flow, the forces of gravity, the Archimedean force and the force of inertia, acting on the accelerating motion of the particle in the flow. On the basis of the block principle, a general computer model of the cycloning process is built, which makes it possible to calculate the uneven velocity of a particle in a gas-dust flow. Analytical methods for evaluating the acceleration parameters and the main methods of numerical analysis of the dynamics of particle motion, shows that the main advantage of up to 0.8 seconds is the accelerated motion of a particle in a gas-dust flow under the given conditions. During this time, most of the particles reach the cyclone wall. This shows that the determination of the accelerating motion of a particle plays an important role in cyclones.

Innovation comprehensive solutions for off-gases cleaning in steel industry. Technical solutions for dusty gas flows cleaning

Metallurgical production associates with such processes as crushing, drying and pneumatic transportation of raw materials, roasting, melting etc., in the process of which hard particles and harmful gaseous components are emitted into atmosphere. At pneumatic transportation of raw materials and sand, their concentration in the atmosphere as a rule exceeds maximum permissible concentrations. Existing facilities of dusty flows cleaning in some cases don’t ensure sanitary norms ГН 2.1.6.3492‒17. Technical solutions proposed to clean gases in a centrifugal filter, a facility of complex gas cleaning – cyclo-filter and two-stage system of high-concentrated gas-dust flows cleaning. Description of the centrifugal filter, cyclo-filter, two-stage facility of gas cleaning design presented. The facility comprises centrifugal filter and ceramic pulse filter. Industrial tests of the centrifugal filter ЦФ2-6-1 under conditions of a system of pneumatic transportation of sand established, that efficiency of gas-dust flows cleaning of sand particles in a six-channel filter can reach 98.65%. Application of two-stage system of gas cleaning comprising centrifugal filter and ceramic pulse filter ФКИ enables to reach residual hard particles concentration at the exit of such a facility of 5 mg/m3, having initial dust level of 127878 mg/m3. Application of such a complex two-stage cleaning facility allows to reach values of 0.1 of maximum permissible concentrations near the source of emissions.

Preface

XIII International Conference on Applied Mathematics and Mechanics in the Aerospace Industry (AMMAI’2020) http://www.npnj.ru/index_e.htm 6-13 September 2020 Alushta, Russia The Thirteenth International Conference on Applied Mathematics and Mechanics in the Aerospace Industry (AMMAI’2020) will be held on 6-13 September 2020 at Alushta Health and Educational Center, Russia. AMMAI’2020 is dedicated to the 90th anniversary of Moscow Aviation Institute and the 100th anniversary of the birth of academician I.F. Obraztsov.The conference deals with the topical issues of the aerospace industry, including methods of applied mathematics and mechanics, as well as computer modeling. The conference focuses on solving the problems associated with modeling the flows of liquid, gas and plasma in combustion chambers, nozzles, jets and flow paths of power plants, as well as the interaction of gas and gas-dust flows with the aircraft surface. The participants of AMMAI’2020 will discuss the numerical methods, computational algorithms and software systems that allow solving problems of general mechanics, mechanics of continuous media and deformable solids, tribology in application to aviation, rocketry and astronautics. Information systems and technologies, in particular, high-performance computing technologies, will be also discussed at the conference.This year the conference was planned to be held on 24-31 May 2020, but due to COVID-19 it was put forward to September 2020. The conference will be organized partially by personal attendance of participants as well as virtually using Internet communication technologies (Zoom, Skype). The conference attendance will be organized in compliance with all sanitary standards and safety requirements. The majority of participants will take part in the Conference virtually. It is worth noting that the option of virtual participation allows expanding significantly the geography and increasing the number of participants. More than 320 participants from different regions of Russian Federation as well as from Asia and Europe will present their reports during the Conference sessions.The conference has already received 194 submissions that were reviewed. Finally, 85 papers were accepted for publication in IOP Conference Series: Materials Science and Engineering. The papers cover the conference topics; they present results of theoretical and experimental studies in such areas as hypersonic aerothermodynamics, combustion, detonation, multiphase flows and heat and mass transfer processes, nonequilibrium processes in nozzles and jets, plasma aerodynamics, rarefied gas flows, interaction of flows with the surface, solid mechanics, tribology. Among the accepted papers, there are some devoted to modern methods of numerical modeling, high performance computing, artificial intelligence algorithms, machine learning and big data processing.The Organizing Committee of AMMAI’2020 acknowledges the financial support from Russian Foundation for Basic Research and the technical support from Moscow Aviation Institute.We would like to thank reviewers for their time and effort in reviewing the papers, as well as authors, which took into account the reviewers recommendations and improved their papers to insure high quality of the AMMAI’2020 Proceedings.Chair of the AMMAI’2020 Technical Programs Committee: Dr. Natalia SeverinaEditor of AMAI’2020 Conference Proceedings: Anna Bogdan

Fragments of the Moon Formation: Geophysical Consequences of the Giant Impact

The most likely scenario for the Moon formation is given by calculations of the Giant Impact (GI) of the ProtoEarth with a protoplanet with a mass close to Mars. During the GI, gases and silicate fragments with a total mass of about 55 to 70% of the mass of the Moon go to infinity, but infinity for the runaway particles is infinity in the terrestrial reference frame. In the Solar System, these fragments go into finite orbits with periods both less and more than a year. The most important feature of their orbits is that they all pass through the region of the Earth’s orbit where the GI occurred. A concentrated gas–dust flow was formed there with a fading intensity; it existed for about a million years. Numerically solving the three-body problem yields numerous fragment trajectories. The probabilities of fragments colliding with the Earth and the Moon are estimated as a function of time after the GI. The scenario of fragments falling into the L4 and L5 triangular Lagrange points and the trajectories of their evolution is considered. The most important geophysical consequence of these collisions was the formation of the terrestrial atmosphere and ocean from the concentrated gas–dust flow.

Tricolor Technique for Visualization of Spatial Variations of Polydisperse Dust in Gas-Dust Flows

The aim of this work is to construct an algorithm for visualizing a polydisperse phase of solid particles (dust) in an inhomogeneous flow of a two-phase gas-dust mixture that would allow us to see, within one plot, the degree of polydispersity of the dust phase and the difference in the spatial distributions of individual fractions of dust particles in the computational domain. The developed technique allows us to reproduce concentrations from one to three fractions of dust particles in each cell in the computational domain. Each of the three fractions of dust particles is mapped to one of the main channels of the RGB palette. The intensity of the color shade is set to be proportional to the relative concentration of dust particles in this fraction. The final image for a polydisperse mixture is obtained by adding images in each of the three color channels. To visualize the degree of polydispersity, we propose depicting the spatial distribution of the entropy of the dust mixture. The definition of the entropy of a mixture is generalized to take into account the states of a mixture with zero number of particles in the mixture. They correspond to dust-free sections of the computational domain (voids). The proposed method for visualizing the polydispersity of a mixture of particles is demonstrated using the example of dynamic numerical modeling of the spatial features of dust structures formed in turbulent gas-dust flows and in flows with shock waves.

Influence of the inlet flow swirler construction on hydrodynamics and efficiency of work

The object of research is construction of a vortex dust collector. To solve the problem of increasing the efficiency of dust cleaning in a vortex apparatus with revealing the features of the mechanism and the destructive forces of the process, the features of the hydrodynamic regime of rotation of the gas-dust flow in the zone of the swirler and immediately after it are used. The influence of the swirler construction and the location of its installation in the gas duct for feeding the gas-dust flow on the efficiency of the vortex apparatus is studied. It is shown that the aerodynamic processes that determine the nature of the flow rotation and its flow in the flue after the swirler reach the maximum possible angular velocity of the gas flow rotation in the separation chamber for this construction. It is proved that the swirler construction under the appropriate conditions allows a swirling flow leaving the duct to the separation chamber to reach the maximum possible angular velocity of the gas flow rotation for the given construction. The characteristic regimes of the gas-dust flow in the duct are established immediately after the swirler from its construction. It is shown that for a traditional vane swirler with a swirling flow in one direction, the most effective blade inclination angle corresponds to 45°. Its installation must be carried out in the duct from the end outlet to the separation chamber below by 1 . 4 ¸ 1 . 6 of the swirler diameter. Before the gas-dust flow flows into the separator, the flow is agglomerated with dust particles. At the exit of the gas-dust flow from the end of the flue to the separation space, the maximum value of the angular velocity of the flow in the separator is ensured. It is established that the blade vortex, which provides for the organization of coaxial turbulent flows in the flue, twisted in opposite directions, will allow more efficient agglomeration of dust particles. A basic construction of the vortex dust collector is developed, which makes it possible to increase the cleaning efficiency with a vortex device to 98–99 %.

Numerical Simulation Research on Gas-Dust Flow Field of Forced-Exhausted Hybrid Ventilation in Whole Rock Mechanized Heading Face

Euler-Euler two-fluid model was used to construct control equations of gas-solid two-phase flow, based on SIMPLE algorithm of collocated grid and FLUENT software, the pressure distribution of air-flowing field and dust field diffusion in fully-mechanized excavation face with different air-draft volume were simulated. The results show that with the increase of exhausted dust ability, diffusion intensity of producing dust pollution in driving head constantly decreases. Compared to air-draft volume of 320m3/min, when it is 600m3/min, the average dust concentration at the driver and whole section positions respectively decrease 51.28% and 56.51%, and high-concentration dust diffusion distance of the other workers position section decrease from 13.6m to 8.5m. Engineering Application indicates that the measured dust concentration is basically anastomosed with simulation result. When air-draft volume of dedusting fan is 600m3/min and dust control system with air curtain formed by forced fan drum is used, the dedusting rates of total coal dust and respirable dust on spot are respectively 95.1% and 96.1%, which achieves a great dedusting effect.

Systems evaluation of the factors that affect the efficiency of an electrostatic precipitator used to clean waste gases

This article examines the cleaning of waste gases formed in steel production. As an effective tool for improving dust-cleaning processes, mathematical modeling requires analytical description of the structural components of the given process and the completion of a systems analysis. The article examines an integrated furnace–smokestack gas-cleaning system which in the general case includes the furnace proper, flues and by-pass channels, waste-heat boiler, electrostatic precipitator, flue-gas pump, and smokestack. Approximate relations are presented to describe theoretical and experimental data on cleaning efficiency. The indices that determine the efficiency of an electrostatic precipitator are divided into two large groups: the properties and parameters of the gas-dust flow; the parameters of the precipitator. The factors that have the greatest effect on the residual dust content of the gas being cleaned are identified.

Experimental study of the dynamics and macrostructure of laser-induced high-pressure dust gas-plasma flows

We propose and for the first time experimentally carry out a method of laser-induced generation of high-pressure dust gas-plasma flows with complex chemical and ionization composition under UV laser ablation of a polymer matrix containing the dust component. The method uses the difference in the spectral-energy threshold of laser ablation and optical properties of polymer materials and dust components in the short-wavelength region of the spectrum. We present the results of an experimental study of the dynamics and macrostructure of laser-induced high-pressure dust gas-plasma flows under UV (λ1 = 213 nm, λ2 = 266 nm, λ3 = 355 nm) laser ablation of condensed targets based on a (C2F4)n polymer matrix with a dust component (SiO2, Al2O3, CeO2). Using laser interferometry and shadowgraphy, we determined the spectral-energy thresholds and conditions for generating dust structures in ionized pairs of the target matrix and their spatiotemporal localization in a gas-dust flow up to spatial division of the evaporated substance of the target matrix and the dust-component cloud. We determine the lifetimes of heterophase flows as a function of the parameters of laser action on a condensed target and the charge of dust particles.

Development and introduction of new designs for gas-dust flow mixing distribution systems at thermal power plants

The successful introduction and setup of new designs for dust separators in Russian and foreign 200–800 MW coal-fired power production units is described. Results from mathematical and physical modelling of these designs, as well as data on their operation in test stands, are presented. Recommendations are given for the most suitable equipment and configurations of new dust distribution systems in dust preparation systems.

Synthesis of perfluoroalkanes by fluorination of graphite with elementary fluorine in a vertical ascending gas-dust flow

Synthesis of lower pefluoroalkanes, tetrafluoromethane, hexafluoroethane, octafluoropropane, and decafluorobutane, in a high-temperature reaction of graphite with fluorine in a reactor with a vertical ascending gas-dust flow was studied.

Determination of the characteristics of gas-dust flow of exhaust gases from the gas-turbine plant to the reconstructed boilers of the Bereza State District Power Station

Flow of the exhaust gases in intricately shaped gas ducts between the gas-turbine unit and the steam boiler in the steam-gas plant of the Bereza State District Power Station has been investigated. The distribution of the gasdynamic parameters of three-dimensional turbulent flow of exhaust gases in channels of different geometries has been studied. The influence of certain structural elements of the gas duct on the hydrodynamic characteristics of flow has been considered. The amplitude-frequency analysis of the natural oscillations of the gasdynamic parameters in different cross sections of the channel has been performed using fast Fourier transformation.

Estimation of the sampling error in the determination of benzo[a]pyrene in organized gas-dust air emissions

The components and the total error of the determination of benzo[a]pyrene in gas–dust flows from organized sources of various technological processes of heat-and-power, aluminum, and building-material production; petroleum chemistry; and heating systems using low-temperature luminescence were studied. The dependences of the sampling errors on the factors of their formation (flow temperature; rate, time, and volume of the sampled material; the type of sorbent; and filtration method) were determined. The conditions favorable to the improvement of the sampling precision were found.

Dissipative-free Models for Wave Dynamics of Interstellar Gas-dust Medium in Galactic Magnetic Fields

Current study of interstellar gas dynamics leads to the conclusion that large scale motions are dominated by strong coupling between gas-dust flows and Galactic magnetic fields; the widths of molecular lines is a direct evidence for such motions. However the absence of reliable information regarding microscopic composition and electrodynamical properties of interstellar matter can cause serious difficulties for an unambiguous theoretical interpretation of observable motions. We accentuate this uncertainty by three alternative models of dissipative-free wave motions owing their origin to the presence of uniform magnetic field. To wit, (i) the hydromagnetic waves in a non-magnetic perfectly conducting medium, (ii) the magneto-elastic waves in a non-conducting highly paramagnetic medium and (iii) whistlers - spiral magneto-electron waves. Emphasis is laid on two last wave processes, fairly fresh to interstellar gas dynamics, which are discussed in juxtaposition with well-studied hydromagnetic Alfvénic waves.