Mathematical Model of the Deaeration of Finely Dispersed Solid Media in a Spherical Matrix of a Roller-Type Apparatus

The additional operation of deaeration (compaction) of powders affects the quality of many products of chemical industries, the conditions for their delivery. Otherwise, energy consumption increases significantly. The aim of this work is the modeling of the deaeration of solid finely dispersed media in a gap with perforated hemispherical shapes on the surfaces of the shaft and conveyor belt within the framework of the mechanics of heterogeneous systems. A plane-deformation model is described, neglecting the forces of interphase interaction and taking into account the compressibility of a solid-particle-gas mixture without elastoplastic deformations. The model assumes consideration of the movement of (1) the components of the solid skeleton together with the carrying phase as a whole; (2) gas in an isothermal state through the pores of a finely dispersed material. This work is devoted to the study of part (a), i.e., behavior of the solid particle-gas system as a whole. The efficiency of the seal-deaerator is estimated using the obtained analytical dependencies for the main strength and speed indicators. The change in the degree of compaction of a spherical granule made of kaolin with given strength characteristics is investigated. It is shown that for the initial time interval up to 3.7⨯10−2 s, the growth of the porosity value relative to the horizontal coordinate along the conveyor belt is exponential and increases by a factor of 1.1. After eight such time intervals, the porosity values stabilize along the indicated coordinate with an increase of more than 1.4 times from the initial value.

Drying Machines with Combined Hydrodynamic Regimes

The article is devoted to the study of multistage dryers with vertical sectioning of the working space. The factors of influence of the design of the shelf contact and the consumption of the drying agent on the mode of movement of monodisperse and polydisperse material are analyzed. The achievement of the required hydrodynamic regime (at a constant consumption of the drying agent) was ensured by changing the length of the shelf contact, the angle of its inclination to the horizon, and the degree of perforation (free area of cross-section). The features of changing the mode of granular material movement at various stages of the gravitational shelf dryer are shown. A technique for the optimization calculation of a gravitational shelf dryer is proposed. As an objective function, the minimum residence time of the dispersed material in the dryer is taken, at which the required amount of moisture is removed. Variants of the designs of the stages of a gravitational shelf dryer are shown and the features of the movement of dispersed material on the steps are described. The results obtained can be used as the basis for the engineering design of gravitational shelf dryers.

Polishing of precision parts of optical-electronic and laser equipment

The mechanism of interaction of the optical surface with the polishing dispersed system during polishing is investigated. It is established that the energy transfer between them is a consequence of the dipole-dipole interaction in the donor-acceptor system and occurs by the Ferster mechanism. It was found that the decrease in the spectral separation between the treated material and the particles of polishing powder causes an increase in the size of sludge particles and wear particles, which leads to an increase in the roughness parameters Ra, Rq, Rmax of optical surfaces during polishing by polishing dispersed sys-tems. It is shown that the polishing productivity of optical surfaces and the wear intensity of polishing powder particles decrease with increasing corresponding transfer energies, which confirms the main pro-visions of the cluster theory of polishing of nonmetallic materials and the validity of quantum mechanical description of resonant energy transfer mechanism between dispersed material and dispersed system.

Preparation of quaternary compounds Cu2ZnSnS4 by using the self-propagating high-temperature synthesis

Possibility to prepare finely dispersed Cu2ZnSnS4 by using the method of self-propagating high-temperature synthesis has been studied in this work. Investigations of Raman scattering and IR-Fourier spectroscopy of the synthesized finely dispersed material have been carried out. The analysis of the Raman and IR-Fourier spectra showed that the synthesized material in the process of preparing is formed with a kesterite structure with the inclusion of a certain amount of secondary phases in the form of sulfides and stannites.

Experimental study of convective dryer with centrifugal fluidized bed

Nowadays, the units with a fluidized bed hold a special place among all heat-mass transfer plants currently used in industry. First of all, it is due to the highly developed surface of interaction between the fluidizing agent (air) and dispersed materials in such units, their low hydraulic resistance, relatively simple design and small sizes. At the same time, the units with a centrifugal fluidized bed, which is formed in an annular channel of the working chamber when a fluidizing agent is added under the fixed angle, are of particular interest. Currently, a limited number of experimental and theoretical studies of hydrodynamics and heat-mass transfer in a fluidized bed are known. Besides, these studies were carried out mainly in respect to regenerative heat exchangers and absorbers. In this regard, such studies in respect to the devices for other purposes, such as dryers, seem to be relevant. The results of these studies are the scientific backgrpund for development of an engineering calculation methodology of such units and their design. The study has been carried out based on an experimental plant using means for measuring temperature, relative air humidity, differential pressure, air velocity, and moisture content of solids. A TPM 148 PID controller has been used as a secondary device. Experimental data have been recorded in MasterSCADA SCADA system. Data processing has been carried out using interpolation by cubic splines. The article describes in detail an experimental plant that allows carrying out a full factor experiment to study the hydrodynamic and thermal parameters of a convective dryer with a centrifugal fluidized bed. The article presents the results of a preliminary series of experiments in which silica gel is used as a dispersed material. As a result of visual observations over the dispersed material in the working chamber, the values of the minimum and maximum speed of the drying agent have been determined. The grafic relationship of the hydraulic resistance of the working chamber and the height of the material layer are obtained depending on the speed of the drying agent and the mass of the material, as well as the temperature and moisture content of the material and the drying agent depending on the drying time. The results obtained make it possible to determine the design and operational parameters of the centrifugal fluidized bed drying plant and select a fan to supply the drying agent.

STUDY OF EFFICIENCY OF DRUM DRYERS OF METALLURGICAL PRODUCTIONS USING PERFORATED PIPES WITH LOCALIZATION OF HEAT FLOWS

The article presents the design of a drum furnace, providing for the provision of differentiated heat flows through the use of an internal perforated pipe. The design of the presented horizontal drum dryer with a perforated tube having openings is designed to eliminate such technological risk factors as the ignition of the oil component of the processed material, and the metal dispersed material itself having pyrophoric properties. As a result of the numerical simulation using the LS–DYNA program, the temperature and heat fluxes in the quasi-boiling zone of the drained oil-containing dispersed material were determined. The calculations made it possible to establish the dependence of the temperature in the quasi-boiling zone on the number of holes of the perforated pipe. Analysis of the obtained graphs allows us to conclude that the gradient of temperature (heat) flows in fixed sections of the furnace of the quasi-boiling zone.

Interaction of Mixing Water with Superlasticizers and Hyperplasticizers Additives in Concrete Mixture

The article deals with the mechanism of interaction of super-plasticizers and hyper-plasticizers additives with mixing water, the formation of micelles and organized water. The interaction of mixing water and additives with Portland cement particles, surface tension, specific surface of bindings and their significance in setting and hardening processes are considered. It is shown that a local effect plays a decisive role in micro-heterogeneous organized media associated with the dissolution of hydrophilic and hydrophobic molecules in the volume of the micellar system or the receptor molecule cavity. In this case, the change of dissolved substances properties is due to the change of the medium state only in the microenvironment, and not in the whole solvent - water. The surface energy of the dispersed material and the degree of dispersion are very important for the concrete technology. All dispersed materials of the system are unstable. The aggregation of powder particles of building materials spontaneously takes place in highly dispersed powders and if such powders get pressure, it is possible to get a hard and strong material without water and additives.

MÉTODO ALTERNATIVO PARA LA EVALUACIÓN DE LA POLUCIÓN ATMOSFÉRICA CAUSADA POR LA QUEMA DE BIOMASA EN PLANTACIONES DE CAÑA DE AZUCAR

This paper describes an alternative method to assess atmospheric pollution levels caused by the burning of sugar cane fields during the harvest, affecting visibility in nearby residential areas. The samples of atmospheric dispersed material were taken on glass slides exposed to the environment on different periods of time. The scattered light by these samples is measured using a digital goniometric device that moves a CCD around each sample with 2,0 arc min resolution. Scattering measurements reveals that it is possible to differentiate between the samples of 12, 24, 36 and 48 hours of integration. This method is more sensitive because it integrates through time, even when the concentrations of contaminants are low. Based on Beer-Lambert scattering model, the scattered light on the samples is related to the atmospheric extinction coefficient and the meteorological visibility measured in the same days. A good linear correlation for the different time periods (R2 > 0.94)was obtained. Finally, measured scattering levels were compared to the intraocular scattering ones calculated from CIE equation, obtaining similar values to eyes of 80 years old people