Theoretical Foundations of Chemical Engineering最新文献

The separation of emulsions remains a relevant task in industry, requiring innovative solutions to enhance the efficiency and reliability of the processes. In particular, the separation of emulsions in a centrifugal field is a promising method due to its efficiency and the ability to process large volumes of emulsions in a short time. The aim of the present study is to determine the structural dimensions of the separation zone for the effective removal of phases in the process of emulsion separation using a multi-vortex separator. The research focuses on optimizing the design of the devices and evaluating their operational capability. In this context, a three-dimensional model of a vertical separator is described, which uses the inter-tube space for emulsion separation. The emulsion enters through an inlet nozzle with rectangular openings, creating vortices in the inter-tube space. These vortices facilitate phase separation: the heavy phase is discharged upwards and the light phase downwards. An important aspect is the determination of the geometric parameters of the separator, such as the diameter of the openings for phase discharge. Dependences for determining the diameter of the opening in the bottom of the separation zone and in its upper part, considering the flow rate and concentration of the emulsion in the inter-tube space, are obtained. As the concentration of the light phase in the emulsion increases, the size of the opening required in the bottom of the separation zone of the inter-tube space of the multi-vortex separator decreases. The research results demonstrate that changing the mass fraction of the light phase in the emulsion within the range of 0.15–0.25 does not affect the change in the values of the radius r(H) at a flow velocity into the separation zone of 10 m/s. With an increase in the height of the separation zone due to the deviation of the vortex axis in the inter-tube space from a straight line, it is necessary to limit it by introducing a boundary zone of execution. It is expected that the obtained results will contribute to the development of centrifugal field separation technology in oil fields and increase the economic effect of implementing a multi-vortex separator.

Experimental dependences of the sulfite number on the injection coefficient were obtained for various operating and geometric parameters. To evaluate the efficiency of a gas–liquid reactor with ejection gas dispersion, the ratio of the sulfite number to the injection coefficient was selected as the criterion. Based on the experimental results, the optimal ratio of the ejector and nozzle areas was determined for the gas–liquid apparatus with ejection gas dispersion.

Currently, due to the tightening of environmental standards for enterprises on emissions of harmful substances, the problem of reducing these emissions is topical. A special place is occupied by dust- and gas-cleaning systems and equipment: cyclones, electrofilters, etc. Technology improvement is often not advisable due to the rise in the cost of finished products or the complexity of hardware design. Increasing the tonnage of production requires the creation of promising dust-collection equipment of large unit capacity. The authors of the article propose a solution to the problem, namely, the modernization of a high-performance cyclone of the TSN-15-3750 type, and present the results of numerical modeling of the developed, modernized design in comparison with the standard one. As a result of the numerical simulation, practical recommendations are made on the technical improvement of the cyclone in order to increase its efficiency, while the parameters accompanying the increase in productivity and service life are identified.

A new approach is proposed for analyzing the efficiency of self-recovery in polydimethylsiloxane polymers containing bubble-type defects that appear after low-power electrical breakdown in polydimethylsiloxane samples. The process of bubble defect disappearance is simulated with consideration of gas dissolution in the sample and the effect of surface tension forces at the defect boundary. The results show that only the combined action of these factors ensures effective self-recovery of the polydimethylsiloxane sample. Based on the simulation model, a method is developed for evaluating the efficiency of self-recovery of the material’s structural continuity. The method compares the rate of change in the shape and volume of bubble-type defects after electrical breakdown with the rate of change in mechanically induced defects. The mechanical nature of the defects serves as a reference level against which the effect of electrical breakdown is analyzed. The proposed method is particularly effective for collecting statistical data on the self-recovery of transparent amorphous materials.

The article is devoted to microfluidics (microhydrodynamics), a science that describes the behavior of small (micro- and nanoliter-sized) volumes and flows of liquids. Microfluidic reactors have become widely used in various fields of science: medicine, special chemistry, biochemistry, nuclear chemistry, and many others. They are popular due to the increased mass and heat transfer they provide, better process intensification, and, as a result, high product yield. The most important elements of microreactors are the mixing zone, which ensures destabilization and swirling of flows for the purpose of mixing them, and the reaction zone (serpentine channel), calculated depending on the kinetics of a specific reaction. The work is dedicated to the microfluidic industry and reflects one of its most important aspects, i.e., mixing. Mixing in such reactors occurs in a laminar mode and is carried out exclusively by molecular and convective mass transfer. The main mixers used in microreactors, such as T-shaped and Y-shaped mixers, and typical mixing cells used in a cascade design, are investigated. As a result of the conducted research, the most successful mixer options are identified and the required microchannel length for complete mixing of the initial reagents for each of them is calculated. In order to improve the efficiency of the process, standard micromixers are proposed that allow for a reduction in the channel length required for complete mixing of the reagents. The most successful micromixer is identified and cascade modeling is carried out; the minimum number of cells sufficient for a successful reaction is identified. In this work, the kinetics of a specific process is not considered; the length of the reaction channel directly depends on the specific reaction.

Electrodialysis is one of the most popular methods of electrochemical purification using membranes, and the scope of its application is constantly expanding. The aim of the work is to study the kinetic characteristics of multicomponent solution electrodialysis purification of electroplating plants from Mn²⁺, Fe (common), ({text{SO}}_{4}^{{2 - }}) and Cl^– ions. To achieve this aim, a number of applied tasks are solved. Measures are taken for the preparation and conditioning of membranes and experimental studies are carried out on electrodialysis purification of several series of model solutions. These solutions contain MnSO₄·5H₂O and FeCl₃ in various concentrations up to 0.4 kg/m³ and are similar to wastewater from a some segments of the electroplating industry. Analysis of the results obtained on changes in kinetic characteristics in the purification process depending on the time and initial concentration of the solutions is carried out. The separation process is carried out on a laboratory electrodialysis plant using a package of alternating MK-40L and MA-41P ion-exchange membranes manufactured by IP Shchekinoazot LLC, Russia. The plant consists of an electrodialysis cell and three independent circulation lines, each of which is designed for desalinated, concentrated, and near-electrode solutions. The solutions are purified with a current density of 20 A/m². As a result of the work, it is found that a change in the initial concentration of substances in the multicomponent solutions under consideration has a different effect on the electrodialysis purification process, depending on the removal of a specific type of ions. For example, at initially low ion concentrations, high purification rates are observed, that reach values of 99.5%. However, as the concentration increases, for most of the studied solutions of the “M,” “ZH,” and “ZHM” series, a significant decrease in purification efficiency occurs when a certain threshold value of the initial concentration is reached. It is important to note that this threshold value can vary significantly depending on the type of ion.

Composite materials play a key role in modern technologies, providing lightness, strength, and corrosion resistance. They are used in various industries, including aviation, the automotive industry, construction, oil and gas processing, petrochemistry, etc. In this paper, it is proposed to study the production of aluminum oxide/iron oxide composite particles in sub- and supercritical water environment. The high heat- and mass-transfer characteristics inherent in supercritical water ensure the implementation of chemical reactions in this environment at a high rate. The studies in this paper are carried out in the temperature range T = 350–410°C and reaction time τ = 180–420 min. The volume of loaded water corresponds to the critical value at the critical point (in our case, V = 326 mL). Composite particles obtained in the processes of sub- and supercritical water oxidation are analyzed using a Nova 2200e analytical analyzer for changes in the specific surface area and pore size. The analysis results show that an increase in the process temperature leads to a decrease in the specific surface area and the specific surface area of the micropores of the samples. Changing the time of sample treatment in supercritical water did not lead to significant changes in the surface of composite particles. The results of X-ray quantitative phase analysis showed that during sub- and supercritical water oxidation, metallic aluminum can transform into various phases of aluminum oxide: ({{gamma - A}}{{{text{l}}}_{2}}{{{text{O}}}_{3}}); ({{chi - A}}{{{text{l}}}_{2}}{{{text{O}}}_{3}};) and α({text{ - A}}{{{text{l}}}_{2}}{{{text{O}}}_{3}}). An increase in the temperature of the sub- and supercritical water oxidation process leads to a decrease in the formation of the ({{gamma - A}}{{{text{l}}}_{2}}{{{text{O}}}_{3}}) phase, and the amount of the α({text{ - A}}{{{text{l}}}_{2}}{{{text{O}}}_{3}}) phase increases. With an increase in the time of supercritical water oxidation, the amount of the α({text{ - A}}{{{text{l}}}_{2}}{{{text{O}}}_{3}}) phase increases. Photographs obtained using a scanning electron microscope with an energy-dispersive spectrometer identify the formation of micron-sized porous aluminum oxide particles and nanosized iron oxide particles deposited on their surfaces.

Currently, the technology of producing composite hydrogel materials in the form of an aqueous suspension is used in various industries. The issue of grinding a hydrogel material in an aqueous medium to obtain an aqueous suspension of particles with a target particle size distribution is considered. In the work, polyacrylamide polymer is chosen as a composite hydrogel material, and anti-Stokes phosphors of various brands are used as a filler. A method for producing a composite hydrogel material is developed, as well as a complex installation for its implementation. The unit includes a reactor with a set of mixing devices, high-speed toothed and knife cutters, as well as a special dispersion unit, including a pump and a two-zone disperser. Data on the study of the influence of the technological and operating parameters of the equipment used on the granulometric composition of the resulting hydrogel material are presented. The influence of the quality of the obtained hydrogels on the rotation frequency of the disperser, the dispersion time, and the ratio of hydrogel to water are revealed. Suspensions with a narrow granulometric composition with particle diameters from 1300 to 200 µm are obtained. Micrographs of a composite material based on polyacrylamide hydrogel and inorganic phosphor are presented. The authenticity of the obtained security paper is visually confirmed by clearly visible luminescent greenish-yellow dots. When examining the paper through the light and in reflected rays, particles of the polymer network of the material are not visually detectable. The mechanism for introducing composite material into paper on a paper-making machine is described. A description of the technology for obtaining a suspension of hydrogel material in a single technological cycle is given.

The current level of technological development of the automotive industry imposes demands on the quality of commercial gasoline. The degree of engine boost and the improvement of its design significantly affect the requirements for the detonation resistance of gasoline, which is determined by the octane rating. However, the race for high octane values sometimes contradicts the solution of environmental problems. Thus, along with ensuring that the engine operates at the declared power and efficiency, the fuel must comply with the EURO environmental standards for emissions of harmful substances into the atmosphere. It is this quality system that limits the content of aromatic hydrocarbons in gasoline (the transition from 50 to 25%), which for many years have been solving the issue of increasing the octane number. Currently, isomerization and sulfuric acid alkylation processes are used to produce high-octane gasoline. To increase the efficiency of a sulfuric acid alkylation reactor, the authors of the article conduct numerical modeling of a new design of a feed collector with V-shaped nozzles.

The article presents a method for calculating the interphase surface area in a gas–liquid apparatus with ejection gas dispersion. The apparatus is divided into three phase contact zones: the injection zone (free torch zone), the ejection zone (constrained torch), and the working volume. The geometric surface area of phase contact is calculated for all zones of the gas–liquid apparatus with ejection gas dispersion. The specific surface area of phase contact is calculated for each zone and compared. Based on experimental data, the geometric surface area of phase contact is determined for the working volume and the effective area for the entire gas–liquid apparatus. The calculated and experimental values of the surface areas of phase contact are compared.