Theoretical Foundations of Chemical Engineering最新文献

The oil and gas refining industry in Russia and other countries is faced with the challenge of searching for new highly active catalytic systems and innovative methods for processing various types of petroleum feedstocks, including heavy petroleum feedstocks. One of the main tasks of this industry is to increase the depth of processing of petroleum raw materials to obtain more valuable petrochemical products. The purpose of the work is to study the dependence of the thermal destruction of heavy petroleum feedstock—heavy vacuum gas oil from the AVT-5 unit of PAO Bashneft-Novoil—in the presence of a new metal-complex catalytic system, where the active component is a chlorferrate complex (NaFeCl₄) in an amount of 10%, deposited on a carrier representing a deeply decationized Ymmm zeolite of the acidic form (H-form), when varying process conditions, temperature in the range from 450 to 550°C, and volumetric feed rate of raw materials in the range 1.75–2.50 h^–1. The physicochemical characteristics of the metal complex catalyst—10% NaFeCl₄/HYmmm zeolite—are studied: characteristics of the porous structure, phase composition, and morphology of the surfaces of the catalytic systems. During the experimental studies, it is established that the 10% NaFeCl₄/HYmmm zeolite catalytic system has a highly developed surface with a pore distribution of micro-, meso-, and macropore sizes (total pore volume ~0.64 cm³/g) and preserves the degree of crystallinity of the lattices relative to the original support Ymmm. It is established that the thermocatalytic destruction of heavy vacuum gas oil in the presence of a metal complex catalyst leads to its deep and selective conversion. Data are obtained indicating that in the studied modes of the thermal destruction process, it is possible to achieve the formation of unsaturated olefinic hydrocarbons of the composition C₂–C₄ ~20 wt %, gasoline fraction ~45 wt %, and total light ~68 wt %.

The work is devoted to the study of the topochemical kinetics of solid-phase chemical reactions of ammonium fluoride processing of ash and slag waste from thermal power plants and is carried out with the aim of testing the developed technology on raw materials that are relevant for the Amur region. Previously, the objects of development of this technology were silicate and aluminosilicate raw materials from both the Amur region and the Russian Federation. Calculation of the kinetic parameters (rate constants, shape coefficients of kinetic curves, activation energies) with subsequent determination of zones and reaction equations is carried out using the method of parametric regression and correlation analysis with five parametric functions (power and exponential laws, the Erofeev–Avrami equations, three-dimensional diffusion and compressible volume), the choice between which is carried out based on the minimum approximation errors for each temperature. The calculation is then accompanied by the calculation for a given temperature of the statistical characteristics of the selected regression model and the testing of five statistical hypotheses: Fisher’s hypotheses about the homogeneity of the variance of reproducibility and the adequacy of the regression model, as well as Student’s hypotheses about the significance of the regression coefficients, the practical value of the response function, and the significance of the correlation coefficient. The calculations are performed using a program created by the authors in Visual Basic in the interactive software development environment Visual Studio Community 2019.

Currently, in the chemical, petrochemical, nuclear, and other industries, there is a growing need for fine powders of homogeneous fractional composition. In particular, the task is to obtain a finely dispersed bulk material based on silica gel with a grain size of less than 50 µm. This powder is used for drying and cleaning media that are prone to polymerization and decomposition, etc. To obtain it, it is necessary to carry out fractionation of bulk crushed material based on silica gel after milling. This problem is solved by classifiers, i.e., special separators designed to separate particles into classes by size. The paper presents the design of a developed multi-vortex classifier–separator for solving the problem of fractionation of bulk material based on silica gel with a boundary grain size of less than 50 µm. The principle of operation of the device is described. The aim of the work is a numerical study of the influence of the diameter of the holes in the classifier plate on efficiency at different input velocities of the gas flow. The research is carried out in the Ansys Fluent software product. During the studies, the diameter of the round holes is varied from 5.3 to 11 mm and the inlet velocity of the gas flow from 1 to 16 m/s. The results of numerical studies show that with the diameter of round holes made in the classifier–separator plate equal to 8 mm, a high fractionation efficiency of more than 70–95% is achieved for the size of the boundary grain of 20–50 µm at inlet gas flow velocities from 1 to 16 m/s. The fractionation efficiency and the size of the boundary grain are significantly affected by both the inlet velocity of the gas flow in a wide range from 1 to 16 m/s, and the diameter of the round holes at a certain value, i.e., 8 mm. With other sizes of round holes, the efficiency and size of the boundary grain remains practically unchanged. This is due to the chaotic movement of the circulating flows that destroy the transport channels. The conducted studies show that the use of the developed classifier–separator can become an alternative to many foreign analogues in solving the problem of fractionation of fine bulk material based on silica gel with a grain size of 20–50 µm.

In this paper, an estimated method for determining the cooling capacity of a closed-type nitrogen-helium cryostat is proposed. This problem is solved as a problem of finding the extremum of the calculated values of the heat flow from each stage in each time block under consideration, while minimizing the root-mean-square error between the expected dynamics of the cooling of the stages over the time period under consideration and the calculated dynamics of the cooling. To do this, it is first necessary to solve the “direct” problem of heat transfer of the structure, then find the optimum from the chosen regularization method, iteratively refining the parameters under study. The method of conjugate directions was chosen as the optimization method, as the most accurate method of the first order of convergence. And as a regularization method to overcome the incorrectness in the source data, the iterative regularization method was chosen, where the regularizing parameter is the iteration number.

The paper deals with solution of the numerical simulation problem on the stress and strain concentration tensor components in mesoporous silicon-based structures with adsorbed water frozen under spatial constraints. The constructed model takes into account the presence of a natural layer of silicon dioxide on the surface of the pores in the studied materials, the structure of the inhomogeneous medium (the ratio of the oxide layer thickness to the radius of the filamentous pore, as well as the orientation of the pores in the space of the silicon membrane), and the volume content of the components.

Conducted studies of the statistical distribution of secondary mineral contents in sandy rocks reveal the following pattern: the distribution forms of these contents are polymodal. The purpose of the presented work is to prove the following hypothesis: when unifying the polymodal statistical distribution of the intensity of an established geochemical process, each sample of intensity value within a separate mode will be characterized by a predictable implementation principle interpreted by a specific chemical reaction. The intensity of the geochemical reactions caused by superimposed epigenesis is determined using the method of statistical correlation interpretation of geophysical research materials of a well. The statistical intensities of the secondary processes of kaolinitization, carbonatization, and pelitization of sand deposits are calculated based on the patterns of geochemical dominance of covariance effects on the recorded parameters of geophysical well surveys. As a result, the dependence of the intensity of the rock transformation process on the product of the statistical correlation parameters of the geophysical data is obtained, specifically, the correlation coefficient and the interval parameter. Using the universal equation of modes of unified polymodal probability density distributions for transformation processes of any open systems, the unification of the intensity modes of secondary processes is conducted and the principles of the transformation process states within each calculated mode are determined. The secondary transformations of the sand deposits of the Tambey oil and gas fields are studied. The correlations between the samples of the process intensities under consideration within each manifested mode are investigated. Conclusions.It is confirmed that each intensity mode of the geochemical process under consideration is due to the manifestation of a specific geochemical reaction. The conducted comparisons of the descriptions of the process state principles with the studied states of geochemical transformations prove the equality of their dynamic transformation modes. Knowing the intensity of the secondary process as an attribute of the calculated mode, it is possible to determine the geochemical state mode of the open reservoir system.

The issues related to the need to improve the environmental safety of internal combustion engines and the use of alternative fuels in them are considered. A method has been proposed to reliably reduce the content of toxic components in the exhaust gases of a diesel engine by replacing standard diesel fuel with methanol and methyl ester of rapeseed oil. The results of experimental studies of the environmental parameters of a diesel engine running on methanol and methyl ether of rapeseed oil are presented, the dependences of the influence of load and speed modes of its operation on them are established, and their numerical characteristics are determined. Based on experimental data, concentrations of toxic components in the exhaust gases of a diesel engine are presented, the process of formation of total hydrocarbons CH_x, carbon dioxide CO₂, nitrogen oxides NO_x, carbon monoxide CO, soot C in the combustion chamber is considered and analyzed in detail, and the causal relationship between the formation of toxic components in the cylinder of a diesel engine is considered., powered by methanol and methyl ester of rapeseed oil, and indicators of its workflow.

The relevance of this study is determined by the need to improve the efficiency of classification processes in the chemical industry, which utilizes powdered catalysts and adsorbents in the particle size range of 10–60 μm. Existing separation methods, including mechanical sieving, gravitational and inertial devices, cyclones, and rotary classifiers, are limited in terms of selectivity, reliability, and operational complexity. As an alternative, a multi-vortex classifier design with coaxially arranged tubes is proposed. A multi-vortex system is formed in the annular channel of the device, where solid particles are separated from the gas flow under the action of inertial forces and settle in the classifier’s collection bin. The aim of the study is to perform numerical modeling of particle fractionation in the classifier and to evaluate fractional efficiency and hydraulic resistance under varying geometric parameters. The simulation is conducted in the ANSYS Fluent software environment using a steady-state three-dimensional approach, the k-ω SST turbulence model, and the Discrete Phase Model. The study investigates the effects of vortex diameter and slit opening ratio, which are varied in the ranges of 17.5–29 mm and 0–1, respectively. The inlet gas velocity is set to 12 m/s and particle size ranges from 1 to 200 μm. To evaluate fractional efficiency, a particle trap condition is applied to the walls of the collection bin. It is found that increasing the vortex diameter enhances separation efficiency. A decrease in the slit opening ratio leads to a weakened vortex structure, reduced tangential gas velocity, and increased hydraulic resistance. The best performance is observed at vortex diameters of 27.5–29 mm and slit opening ratios of 0.4–1. The fractional separation efficiency for particles sized 20–25 μm exceeds 95%.