Theoretical Foundations of Chemical Engineering

The First International Scientific and Practical Workshop on Processes and Apparatus of Chemical Technology "PAKhT-2025" was held on April 10-11, 2025 at the D.I. Mendeleev Russian University of Chemical Technology and was dedicated to the 100th anniversary of the birth of the outstanding scientist, Honored Scientist and Technologist of the RSFSR Yuri Iosifovich Dytnersky.

Heat and mass transfer of a wet spherical body with an external gas medium under electromagnetic energy supply in the infrared frequency range is considered. The linear problem (constancy of process parameters) of infrared heating of a body at convective heat and mass exchange of its surface with external gas medium is formulated and analytically solved both for the general case of drying process and for drying in the first period. In formulating the heat conduction problem, it is assumed that the internal heat source caused by absorption of radiant energy is exponentially distributed over the thickness of the ball and that the phase transformations during moisture evaporation occur near the surface of the body. The drying intensity is described on the basis of the analytical solution of the linear (constant mass-conductivity coefficient) mass-conductivity (moisture diffusion) problem for the ball under the boundary condition of mass transfer of the third kind. The solutions of heating problems are obtained with respect to the local and average body volume temperature. On their basis, numerical modeling of the ball heating process with regard to its drying is carried out: the influence of the radiant flux density on the ball heating dynamics is shown. For the first period of drying it is shown that the partial solution of the problem obtained for this case allows to calculate the temperature of the body surface and further the intensity of drying in conditions of infrared energy supply (in which the temperature of the body surface is not equal to the temperature of the wet thermometer). To calculate the body surface temperature in this case, a method of successive approximations is proposed, in which the desired temperature is set first, and then it is calculated using the obtained solution and Antoine's equation expressing the dependence of saturated vapor pressure on temperature. For this case, numerical calculations have been performed, showing the performance of the mathematical model and illustrating the influence of additional (to convective) infrared energy supply on the drying intensity. A zonal piecewise stepwise method is recommended to account for the change of thermophysical characteristics during the process.

The analysis of the results of the stochastic model of mixing of components of the bulk charge at work of block "drum-blades" of the apparatus of continuous action is presented. The obtained distributions of granular particles of the specified components by the angle of ejection from the "drum-blade" unit correspond to the criterion of effective mixing. These distributions take into account the character of motion of flexible blades in continuous mode at given sets of design and mode parameters of mixing process.

For the unit of decomposition of isopropylbenzene hydroperoxide of the process of phenol and acetone production the prototype of the digital twin on the basis of the created neural network model is developed, which allows to calculate online the outputs of main and by-products, energy resources and conditional profit with relative error not more than 0.73%. Formation of a database of values of technological process parameters is carried out with the use of simulation modeling of plant operation and subsequent verification of model adequacy by comparing the obtained calculated results with the actual values of technological parameters. As a prototype of the digital twin, allowing to determine optimal values of the cumene process parameters of isopropylbenzene hydroperoxide decomposition unit in the online mode, it is proposed to apply the microcontroller ESP-8266 with built-in and developed program written in the language C.

Chemical and energy technological processes occurring in phosphorites and phosphorus-containing rocks, their influence on structure and composition at firing are considered. The possibility of application of existing methods of determination of sintering kinetics for modeling the firing of phosphorite pellets is analyzed. The results of studies of chemical and energy technological process of phosphorite pellets firing with coke addition by methods of thermal and structural analysis are given. It is established that the main parameters influencing the interaction of coke with the pellet material are the heating rate up to the firing temperature, the coke concentration in the pellet and the oxidizer concentration in the heating gas-heat carrier. It was found that the sintering process of phosphorite pellets is preceded by significant changes in the chemical composition, structure and properties of the initial components. The intensity of these changes is determined by the temperature, composition and pressure of the gas phase, which can be inhomogeneous at different points of the studied samples.

The structure construction of disperse-filled polymer composites of different types is considered. It is shown that the single monolithic structure of disperse-filled polymer composite material includes: heterogeneous structure built of disperse filler particles, free volume and structure of polymer matrix. Formulas for calculating the content of disperse filler and compositions of disperse-filled polymer composites with different types of lattice, the structure of which depends on the maximum packing of disperse particles and coordination number varying from 8 to 1, are presented.

To increase the number of peptide-based drugs produced, an important task is to reduce time costs for the realization of technological stages. One of the longest, energy- and resource-consuming stages of production is vacuum freeze drying. Therefore, in this work we conducted experimental studies on the selection of temperature and time modes of vacuum freeze drying of peptide-based pharmaceuticals. As a result of the experiments, a mode was selected that provides the residual moisture content in the samples not more than 2.5%, no boiling in the first period of drying and minimal shrinkage. Also in the work mathematical modeling of vacuum freeze drying process was carried out using the software package Comsol Multiphysics (calculation of sublimation front motion in a single H5 vial).