Hydrodynamics of a reactor with updated structure of frame mixing device

This article is devoted to computer simulation of the hydrodynamic situation in a reactor with a standard design and an upgraded design of a frame stirrer. A comparative analysis of the hydrodynamics of fluid flows occurring in the volume due to the use of classical and modernized design was performed. An upgraded design of a frame stirrer for homogenizing the medium in a reactor has been proposed. The aim of this work was to study the influence of the geometry of the stirrer blades and their location in space on the speed and direction of flows in the reactor. The basis for the new design of the mixing device was the standard design of the frame mixer with two horizontal jumpers. Installation of additional blades and their placement at a certain angle to the vertical and horizontal planes and relative to each other was considered as one of the methods of improving the design. For this work, the study was conducted in the universal software system of finite element analysis ANSYS. Computer simulation is used to analyze complex systems and processes based on a computer model. The simulation was performed to analyze the influence of the geometry of the mixing device on the speed and direction of fluid flow in the apparatus. To conduct the study, 3D-models of two different types of geometry of the mixing device were built, physicomechanical parameters of the environment in the reactor were set and on the basis of these data the mixing process in the apparatus was modeled. In this work, the influence of plate geometry and their location in space on hydrodynamics is investigated. The basis of the proposed design of the mixing device is the task of intensifying the mixing process by increasing the mixing efficiency along the height of the apparatus. A comparative analysis of the direction of fluid flow, its velocity and temperature change using a standard and upgraded design of the mixing device was performed. It was found that when installing additional plates that are located at an angle to the horizontal and vertical planes in the reactor there are additional axial and radial fluid flows, which improves homogeneity and increases the intensity of mixing.

Experimental studies of the thermal regime of the room when using heating ceramic panels

The article presents the results of experimental studies of the parameters of ceramic panels. Experimental measurements of air temperature in a room for which an electric ceramic panel is used as heating devices are given. The automatic system of monitoring of temperature in the room is described. During the experiments it was determined that the surface temperature of the ceramic plate of the heater is higher in the center and decreases when approaching the edges. It is proved that the use of constant surface temperature is acceptable in CFD modeling of a room with ceramic electric heaters. The profile of temperature distribution on height of the room at its heating by means of an electric ceramic heater is resulted in work. The air temperature is relatively evenly distributed over the height of the room. In this study, when entering the quasi-stationary mode, the air temperature in the height of the room varied in the range from 24 to 27˚C, which is slightly higher than the norm for the temperature in domestic premises. In order to save energy in this case it is necessary to reduce the service life of ceramic electric heaters. In the future it is necessary to develop a thermophysical numerical model and verify it with the help of the obtained experimental data. In addition, with the help of the model you can conduct research and determine the optimal location of ceramic electric heaters in the space of the room. Key words: radiation ceramic heater, experimental research, temperature monitoring.

Modeling of cooling process of hydroaluminosilicate materials

Porous thermal-insulation materials are widely used in building industry, the advantages of which are cheapness and efficiency. Their commercial appearance is also important in their implementation. Porous thermal-insulation materials to prevent sticking can be packaged only after cooling and after the main thermal processes and classification. The process of cooling porous hydroaluminosilicate materials by the method of modeling with the subsequent check on the laboratory equipment with a fluidized bed is investigated in the work. The main thermal process takes place at a temperature of about 300°C. The cooling time of the porous material to a temperature of 20°C, which is about 20 seconds, is calculated, and the need to ensure this time in its classification is indicated. This model allows you to determine with sufficient accuracy the cooling time for particles of different diameters and temperatures. The process of cooling the obtained thermal insulation material in the production technology occurs simultaneously with its hydrodynamic classification in the cascade classifier of the fluidized bed. It is important to determine the required cooling time of the spherical hydroaluminosilicate material to temperatures close to 20°C and to ensure the presence of particles in the apparatus during this time. Comparison of experimental data with the results of the mathematical model shows the results with an error of 10%. There is a slight increase in the minimum residence time of a single granule obtained experimentally compared with the calculated.

Integrated use of technogenic raw materials in cement technology

This work used a combination of modern physico-chemical research methods with standardized testing of technological and operational properties of raw materials, clinker, cement and compositions with its application. Results over of research of the silicate systems with rice husk and ash-fly as technogenic raw material for making of cement clinker are driven. The features of the chemical-mineralogical composition, phase transformations during burning and astringent properties of material at the use of 42,5-50,5 % industry wastes in composition initial raw material mixtures are shown. The object of the study were raw material mixtures for the production of Portland cement clinker based on the systems of chalk - clay - man-made raw materials and chalk - man-made raw materials. The possibility of replacing exhaustible and non-renewable natural raw materials with a complex of multi-tonnage wastes of agro-industry and heat energy, which meets the objectives of expanding the raw material base of cement production, resource conservation and environmental protection. Peculiarities of phase formation during firing of silicate systems of chalk-polymineral clay and chalk-technogenic raw materials taking into account changes in the quantitative ratio of components, in particular rice husk and ash-removal of thermal power plants are noted.

Adsorption of obsolete silt, peat, sawdust and compositions of them

Environmental security is an important part of Ukraine's national security. It provides for the maintenance and improvement of the environment and should have a set of measures to prevent the danger to the population. It provides for the maintenance and improvement of the environment and should have a set of measures to prevent occurrence the danger to the population. One of the important issues of environmental safety in Ukraine is the accumulation of obsolete sludge after wastewater treatment at aeration stations. Untreated sludge has been merging into overcrowded sludge sites for several decades, which has led to the deterioration of the environment and living conditions in Ukraine. The article presents experimental studies to determine the adsorption properties of granules based on the composition of sludge and peat with the addition of sawdust. Preparation of raw materials, creation of compositions and granulation from obsolete sludge, peat and biomass were covered in previous publications.

Features of heat and mass transfer at drying of ceramic products with overglaze paints

The basic results of researches of process of a heat exchange are instanced and parsed at drying glasour ceramic colors. Character of change of importance number of Rebinder is established at drying colors and dependence of intensity of a heat dissipation on velocity of air is spotted. The main results of researches of heat and mass transfer process at drying of overglaze ceramic paints in a stream of drying agent are resulted and analyzed. The nature of the change in the value of the Rebinder number for drying paints is established and the dependence of the heat transfer intensity on the air velocity is determined. Analysis of the temperature coefficient of drying and Rebinder's number determined the directions of heat consumption in the drying process of overglaze ceramic paints. It is established that the heat flux density depends on the temperature and velocity of the coolant and does not depend on the chemical composition of the paints. It is shown that the heat transfer coefficient depends on the velocity of the coolant. Compared with heat transfer during laminar flow around the plate during drying, the intensity of heat transfer increases by 75%.

Preparation of raw materials, creation of compositions and granulation from obsolete sludge, peat and biomass

The article presents research on the preparation of raw materials, creation and granulation of compositions from obsolete sludge deposits of peat and biomass. Studies of raw material preparation processes have shown that obsolete sludge deposits have excessive ash content. To reduce ash content, it is advisable to add peat and biomass to sludge. During the study of peat, it was determined that peat extracted from the floodplain of Irpen has a high ash content, so for further research used peat from Chernihiv. The created compositions were subjected to granulation in different compositions and ratios. Preliminary dehydration of peat in the drying cabinet and moistening of the sludge were performed to create different sludge-peat mixtures with different moisture content of sludge and peat. When creating two-component compositions to sludge-peat add biomass. Studies have allowed us to choose the optimal ratio for granulation.

Intensification of loosening of asbestos fibers by means of hydromechanical processing

Acceptance of high-quality aqueous suspensions based on chrysotile asbestos is an urgent technical task in a number of industries. Asbestos-cement mortar is used as an asbestos-cement crust for insulation of walls and other building surfaces, due to this composition of the treated surfaces perfectly retain heat, resistant to moisture, and most importantly - asbestos fibers contribute to the smoothness of the surface and crack is not formed. No less popular is the use of asbestos-cement mortar with a high content of asbestos in the insulation of ventilation ducts and pipelines. This composition of asbestos-cement mortar is used to strengthen the joints of asbestos-cement pipes, as well as as a filler in the laying of cast iron pipes to give the joints additional elasticity. Asbestos-cement mortar has plasticity, resistance to stretching and reinforcement of asbestos, as well as strength and versatility in the use of cement. Due to these properties, asbestos and cement perfectly adhere to each other to obtain a durable, strong, frost-resistant, virtually waterproof and fire-resistant building material. The result of the microscopic examination is reason to believe that from the technological process of production of slate can be removed electromechanical mixer for the preparation of a solution of asbestos + water + portland cement. In this case, given the fact of continued loosening of asbestos in the preparation of the mold mixture of asbestos + water + portland cement, it will be sufficient to ensure the degree of loosening of asbestos in the ripper at the minimum required level (for example, not more than 85%). It is assumed to obtain a mold mixture with a high degree of homogeneity of the components with reduced costs of Portland cement due to its physico-chemical activation by hydraulic fluxes.

Innovative directions of development of ceramic materials for dentistry

The need to improve the level of dental health of the population of Ukraine was identified. The prospects for the use of ceramic prostheses to provide quality medical care in dentistry have been established. An analytical review of various types of ceramic and glass-ceramic materials used as dental prostheses for tooth replacement: porcelain, alumina, zirconium oxide, glass-ceramics based on leucite and lithium disilicate and mica with the addition of fluorides. Peculiarities of the structure and operational properties of ceramic and glass-ceramic materials for dentistry have been identified, their advantages and disadvantages have been established. The effectiveness of the use of glass-ceramic materials based on lithium disilicate for dental prosthetics is substantiated. The basic lithium silicate system was selected and glasses for obtaining glass-ceramic crowns based on lithium disilicate by the method of high-temperature pressing and calcium phosphate-silicate system for obtaining glass-ceramic coatings were synthesized. The methodological approach to the development of glass-ceramic prostheses based on lithium disilicate is determined. The limits of the compositions of oxide components are determined and raw materials for the synthesis of the glass matrix are selected. The technological parameters of melting (T = 1350 – 1400ºС) and heat treatment with simultaneous formation of products (stage of nucleation T = 600 – 650ºС, τ = 30 – 60 min; stages of formation T = 900ºС, τ ≈ 20 min) are selected. The composition of fluoroapatite glass-ceramic coating for glazing of glass-ceramics and the mode of its firing (T = 800 – 850ºС, τ ≈ 1,0 – 1,5 min) were determined. The serviceability of the developed glass-ceramic samples DL st.glass, which were obtained by the technology of high-temperature pressing, are determined. The comparative analysis of glass-ceramic prostheses for dentistry allowed to establish that the operational properties of the developed glass-ceramic prostheses according to ISO 6872:2015 are at the level of world analogues. This will allow them to successfully compete in the Ukrainian market with well-known foreign counterparts and help ensure the social priorities of the state in the field of health care.

Structure, thermophysical properties and electrical conductivity of nanocomposites based on epoxy polymer and carbon tubes

The aim of this work was to find the optimal conditions for the formation of nanocomposites, study their structure and properties and conditions for the formation of multicomponent materials based on epoxy polymers and carbon nanotubes with predetermined performance properties. The basis for the formation of epoxy polymers was an epoxydian oligomer (EDO) based on bisphenol A. Polypox H354 was used as a hardener for EDO. Carbon nanotubes (CNT) were used as a nanofiller for the preparation of nanocomposites. The research methods were a diffractometer for measuring the intensity of X-ray scattering in the region of small angles and a differential scanning calorimeter for obtaining heating thermograms. The electrical conductivity of the samples at a temperature of 293 K was measured at direct current according to the two-electrode scheme. In this work the structure, thermophysical properties and electrical conductivity of nanocomposites based epoxy polymers and carbon nanotubes have been studied. It was found that at low CNT content the formation of nanocomposites occurs by the mechanism of epoxy network growth, which is accompanied by the displacement of CNT particles to the periphery of the epoxy matrix. This process is accompanied by an increase in the scattering intensity of the SAXS, a rapid increase in the glass transition temperature and the degree of crosslinking of the epoxy polymer. When the critical concentration is reached, CNT particles form a continuous cluster, which leads to occurrence percolation threshold, reducing the glass transition temperature, expanding the glass transition range, occurrence of pores and reducing the degree of completion of the crosslinking reaction in nanocomposites relative to the epoxy polymer. It is established that the improvement of nanocomposite properties and the occurrence of the percolation threshold is due to the maximum specific energy of ER-CNT interaction and is achieved at a critical mass concentration of nanofiller from 0,1% to 0,4%.