Capture Of Dust Particles Research Articles

Тяжелые металлы в фитосубстратах — индикаторы антропогенного загрязнения воздуха в промышленном регионе

The ecotopic difference in the accumulation of heavy metals (Zn, Cu, Fe, Mn, Ni, Cd, Pb) by botanical objects of indicator significance has been proven. To assess air pollution in Donbass, it is recommended to use the species Ceratodon purpureus (Hedw.) Brid and Bryum argenteum Hedw. to check the accumulation of pollutants in gametophytes and Populus nigra L. on the specific content of the dendroindicator seeds in chalase capillary bristles. The studies were carried out in the the registration sites of the monitoring network in the central Donbass. The plants in the zones of technogenic and particular anthropogenic impacts (industrial enterprises of the metallurgical complex, dumps of coal mines, places of transport load on ecosystems, residential ecotopes) were studied in comparison with the territories of minimal transformation in the zones of the natural reserve fund in the Donetsk region. For the bryophytes of 11 species of the regional natural flora, taxonomic specificity in the accumulation of heavy metals was established, the facts of hyper- and hypoaccumulation in the thalli of bryobionts were noted. Based on the actual accumulation of heavy metals, the facts of the phytogeochemical migration activity of elements in the surface layer of the atmosphere of an industrially intense region were established. Accumulation of heavy metals in bryophytes occurs during precipitation, and in black poplar seeds freely floating in the air, as a result of active capture of dust particles, which causes a difference in accumulation by different phytosubstrates. The facts of the pollen content in other species of poplar fluff have been established, which is also considered in the context of a possible increase in the seasonal allergenic effect in the population. Accumulation of heavy metals in bryophytes occurs with precipitation, and in black poplar seeds freely floating in the air as a result of active capture of dust particles, which causes a difference in accumulation by different phytosubstrates. Pollen content in other species in poplar fluff have been established, which is also considered in the context of a possible increase in the seasonal allergic reactions.

Laboratory Determination of Coal Dust Cleaning Efficacy of a Fibrous Filter for Flooded-Bed Dust Scrubber

Fibrous-type dust filters are used in flooded-bed dust scrubbers to capture dust from underground room and pillar mining atmospheres. They have 10–30 layers of finely woven strands that trap particles through the interception and impaction process. A full-cone water spray is installed upstream of the filter, which floods the screen. A scrubber’s efficacy is usually measured and reported in terms of reduction in gravimetric dust concentration at a known location in a mine. This paper reports the particle-size-dependent dust removal efficiency of a fibrous filter obtained from an instrumented test-set up. A variable frequency drive and an inline flow control knob were used to control the airflow through the filter and water flow onto the filter. Optical particle counting of coal dust particles upstream and downstream was carried out to determine the cleaning efficacy. Experiments showed an increase in cleaning efficiency for all the dust particles with their size. A progressive decrease in dust concentration downstream of the filter with an increase in water flow through the nozzle affirmed the capture of dust particles by water sprays.

Interaction and instability of air films between bituminous coal surfaces and surfactant droplets

While the suppression of airborne coal particulates with water and surfactant sprays has been widely used in underground coal mines, the microscopic mechanism involved during the attachment process between water droplets and dust particles has not been well understood. In this work, both the interaction forces and instability of air films between aqueous droplets and coal surfaces are studied by monitoring the evolution of spatial and temporal thickness profiles of the air films. The measurements are conducted with both non-ionic and anionic surfactants. The results of this work show that the air film between the water droplet and the bituminous coal surface collapses at a critical rupture thickness of 104 nm, which is followed by a rapid spreading of the three-phase contact line. It has been found that both the critical rupture thickness and kinetics of film thinning increase with increasing surfactant concentrations regardless of the types of surfactants. An analysis of the spatiotemporal thickness profiles using the Reynolds equation shows that an attractive force is present across an air film. This force is found to be an electrostatic force. The force becomes more attractive with increasing surfactant concentrations of the aqueous solutions. The present work sheds new light on the capture of dust particles by water and surfactant sprays at a molecular level.

Improvement of the calculation method of cyclone dust collectors

The object of research is a method for calculating the efficiency of cyclones using the magnitude of the velocity of transverse pulsations of a turbulent gas flow in the inlet of the cyclone. One of the most problematic issues when creating a new cyclonic technique for gas dust cleaning is the need to carry out a fairly large amount of work – modeling cyclones in laboratory conditions on model cyclones, taking into account the large-scale transition, etc. Therefore, the development of the most accurate analytical method for calculating the efficiency of cyclones is an important problem since it makes it possible to quickly and accurately determine all the necessary cyclone parameters for specific production conditions.During the study, patterns of dust particle deposition in the approximation of the «diffusion boundary layer» were used, which made it possible to calculate with high accuracy the efficiency of cleaning industrial dust in cyclones of various designs. At the same time, the time and the amount of experimental work are also significantly reduced in the development of new types of cyclones or in their modernization or selection.The most accurate dependencies are obtained for evaluating the most important parameters of dust cleaning efficiency in various cyclones. This is due to the fact that the method for calculating cyclones proposed in the work has a number of features, in particular, the development of new dependences for calculating the cut-off diameter «dh=50», the inertial capture coefficient of dust particles «E», and others. It is also proposed to use the average cross section the inlet pipe of the cyclone of the velocity of transverse pulsations of the turbulent gas flow and the new interpolation dependence of the coefficient of inertial capture of dust particles «E» at the potential flow regime in the inlet pipe of the cyclone x machines. Thanks to this, it is possible to obtain accurate values of the indicators of cleaning efficiency in cyclones of various design parameters. Compared with similar well-known calculation methods, this provides such advantages as accuracy of calculations, speed of execution and reliability of the results.

Simulation of the Dust-Air Flow Near a Rotating Disk Cylinder Suction Unit

We study a dust-air flow near a vertical rotating cylinder with suction unit placed on the lateral surface. On the basis of the developed computer model of this suction unit, we determine the influence of the disks mounted on the cylindrical surface on the intake air flow and on the capture of dust particles by the suction unit. We also determine the design and operating parameters of the proposed disk cylindrical suction unit promoting the decrease in the dust loss. The influence of the size of disks, their number, and the aspirated air flow on the dust removal is established. The proposed design of a rotating disk cylinder suction unit can be used in the aspiration shelters equipped with the function of dust-collecting chamber.

Simulation of dust-air flow near a rotating disk cylinder suction unit

A dust-air flow near a vertically located rotating cylinder with a suction unit located on the lateral surface was investigated. A computer model of this suction unit was developed, the effect of disks mounted on a cylindrical surface on the intake air flow and on the capture of dust particles in the suction unit, as well as the design and operating parameters of the proposed disk cylindrical suction (DCC), which reduce the dust loss. The influence of the size and number of discs, aspiration air flow on dust removal has been established. This design of a rotating disk cylinder suction unit can be used in aspiration shelters with the function of a dust-collecting chamber. Ill. 6. Ref. 15.

Studies of mobile dust in scrape-off layer plasmas using silica aerogel collectors

Dust capture with ultralow density silica aerogel collectors is a new method, which allows time resolved in situ capture of dust particles in the scrape-off layers of fusion devices, without substantially damaging the particles. Particle composition and morphology, particle flux densities and particle velocity distributions can be determined through appropriate analysis of the aerogel surfaces after exposure. The method has been applied in comparative studies of intrinsic dust in the TEXTOR tokamak and in the Extrap T2R reversed field pinch. The analysis methods have been mainly optical microscopy and SEM. The method is shown to be applicable in both devices and the results are tentatively compared between the two plasma devices, which are very different in terms of edge plasma conditions, time scale, geometry and wall materials.

First integrals of equations of motion of a droplet in the presence of mass transfer to the carrier medium

Analysis is performed of first integrals in the limiting Stokes and Newtonian modes of motion of a droplet for two cases, namely, that of the droplet moving in its own vapor in the presence of phase transitions and that of the droplet moving in dusty gas without phase transformations but in view of the capture of dust particles. Expressions are found for the lengths over which the processes of condensation, complete evaporation of droplet, and deposition of particles occur. Comparison is made of the lengths and times of complete evaporation of droplet in the Stokes and Newtonian modes of droplet motion. Asymptotic formulas are obtained for these quantities, which correspond to low and high superheating of vapor, as well as formulas for the limiting diameters of droplet in the cases of condensation of vapor or capture of particles.

New physical concept of the formation of dust crystals

A clear physical model is proposed for phase transitions in a dusty plasma. According to this model, the formation of plasma dust crystals is associated with the nonlinear effect of the collective attraction of dust particles. The nonlinear collective attraction between negatively charged dust particles corresponds to large charges of dust particles used in the available experiments. This concept provides a new physical model of crystallization that is attributable to the capture of dust particles in an attractive potential well rather than to the strong interaction between them. Calculation using this model yields the depth of the attractive potential well and the critical coupling constant in good agreement with the available experimental data.

Turbulent coalescence during dust suppression by spraying

The main method of combatting dust in coal mines is spraying the zone of dust evolution with dispersed water. Capture of dust particles is accomplished by droplets moving by inertia whose velocity falls rapidly with an increase in distance from the sprayer, i.e., inertial settling is accomplished only in the active zone of the sprayer plume whose size is small. As a result of this in order to suppress dust formed during operation of a coal shearer a considerable amount of liquid is necessary. It is possible to reduce the amount of sprayed liquid with an increase in the efficiency of dust suppression by using a turbulent coalescence mechanism.

Capture of dust particles in filters by linedipole charged fibres

Fibres carrying a permanent dipole moment are now being used in respirator filters. In this paper expressions are derived for the capture efficiency of such fibres, acting on both charged particles and neutral particles. In the case of charged particle capture, the particle stream line equations and the single fibre efficiencies can be calculated analytically. In the neutral particle case computer calculations are needed, but the radial symmetry of the induction field simplifies the calculation. In each case an approximation for the single fibre efficiency is derived as a power law of a dimensionless parameter. The conditions under which particle interception affects the capture efficiency are specified, and finally the hydrodynamic factor is included in the expressions for the single fibre efficiency.

The Earth's Dust Belt: Fact or fiction?: 2. Gravitational focusing and Jacobi capture

The effectiveness of the gravitational attraction of the earth in increasing the near-earth dust concentration over its interplanetary value is reassessed in this paper. We find that this increase is a maximum for particles entering the earth's sphere of influence with a speed of about 0.1 km/sec. The corresponding near-earth enhancement is of the order of 102 and reaches this maximum at an altitude of about 0.5 earth radii. However, for a realistic distribution of dust-particle speeds at the boundary of the earth's sphere of influence, the enhancement is negligible. In addition to considering purely gravitational focusing, we have also analyzed the restricted three-body problem, including sunlight pressure. The results indicate that the Jacobi capture of dust particles into temporary geocentric orbits is so rare that its effect on the near-earth dust concentration may be neglected.