Theoretical Foundations of Chemical Engineering

The rate of the unsteady mass-transfer process in horizontal flat channels filled with viscous liquid (water) and in channels filled with gel has been measured experimentally. It has been established that the rate of propagation of a substance through a channel under the unsteady one-dimensional mass transfer conditions depends on its width and exceeds the value corresponding to the rate of diffusion. The measured mass transport rate in an open channel is less than in a closed channel. The reason for the increased mass-transfer rate with regard to the diffusion mechanism is the slow convective flow of liquid caused by the difference between the densities of a diffusing substance and water. The presence of the surface concentration gradient of liquid gives rise to the appearance of surface forces that significantly affect the mass transport rate. The similarity of the mass-transfer behavior in channels filled with pure liquid and gels is found experimentally, which allows one to talk about their presence, as well as of convective transport in them.

Hydrodynamics and mass transfer in regular film apparatuses containing flat irrigated channels with a laminar flow of gas and liquid as the principal element are studied. The problem is solved by the approximate method, which makes it possible to drastically decrease the amount of the required calculations. It is proven that it is sufficient to determine the dimensionless flux as the function of dimensionless length in a restricted domain of parameters. Approximations are permissible outside the bounds of this domain: in some cases the changes of concentrations in phases along the crosswise direction can be neglected and, in other instances, the concentration changes can be neglected in the whole active mass-transfer region; i.e., diffusion layers exist in one or another phase before the estimation of concentration equilibrium in the system. Finally, the mass transfer resistance is concentrated in liquid or gas; there are parameter spaces where the change of concentration in one of the phases in a crosswise direction can be neglected, while another one contains diffusion boundary layers.

Here, we present the results of the study of the interaction in the octamethylcyclotetrasiloxane-aromatic isocyanate-open coupling analogues system of crown ethers containing terminal hydroxyl and potassium alkoxide groups. It was found that the involvement of the organosiloxane cycle in the polymerization process precedes the opening of the isocyanate groups on the carbonyl component. It is shown that the formation of transverse cross-linking bonds in the polymer formation system is caused by the parallel reaction of cyclotrimerization. It is found that the ratio of the reaction rate constants of the copolymerization and the parallel reactions of cyclotrimerization and urethane formation depend on the synthesis temperature.

Problems preparing paraffin wax emulsions stabilized by different types of emulsifiers have been discussed. The effect of the preparation conditions and stabilizers, such as polyethylene glycol and cetyl/oleyl alcohol ether (Eumulgin O10), polyvinyl alcohol, and SiO2@Al2O3 nanoparticles (20 nm in diameter) on the dispersion of paraffin wax emulsions has been demonstrated. It has been noted that, in order to obtain paraffin wax particles with an average diameter of 400–500 nm, the concentration of PVA, Eumulgin O10, and SiO2@Al2O3 nanoparticles must be equal to 0.5, 0.5, and 1.0 wt %, respectively.

A new class of exact solutions of nonlinear and linearized Navier–Stokes equations has been proposed, which generalize the well-known family of exact solutions in which the velocity is linear in some coordinates. The case of the quadratic dependence of the velocities on two horizontal (longitudinal) coordinates with coefficients that are the functions of the vertical (transverse) coordinate and time was considered in detail. The solutions were generalized for rotating liquids. Equations for constructing exact solutions with an arbitrary dependence of velocities on the horizontal coordinates were derived.

Huyền phù nano oxit titan được chế tạo bằng cách thủy phân sulfat titanyl dưới điều kiện thủy nhiệt. Ảnh hưởng của các tham số tổng hợp lên vi hình thái và các đặc tính chức năng của TiO2 thu được đã được nghiên cứu. Các điều kiện tối ưu cho việc tổng hợp các huyền phù với hoạt tính quang xúc tác tối đa đã được xác định.

Based on N.S. Kurnakov’s composition-property conception of physicochemical analysis and on studies by I.V. Tananaev, V.B. Lazarev, A.D. Verkhoturov, and other scientists, we suggest the raw material-technology-composition-structure-particle size-property-application seven-term formula as the methodological basis for mineral processing and for the synthesis of inorganic materials for various purposes. Our systematic studies have resulted in the development of processing technologies for mineral and technogenic calcium- and silicon-containing materials for obtaining synthetic calcium silicates and various related materials.

Direct and differential-invariant methods for processing experimental data are used to analyze Nikuradse’s results for a turbulent flow of a viscous liquid in round smooth tubes for various Reynolds numbers. It is found that direct testing ratios do not make it possible to draw a correct inference about the applicability of the Prandtl logarithmic profile. The explanation of this paradoxical result is given. It is shown that although direct applicability tests for empirical formulas do not generally ensure the necessary conditions of their applicability, they make it possible to draw subtle qualitative inferences that cannot be reached using the least-squares method.

The absorption of methanol from a contact gas in the production of technical formalin has been considered. The model of a conventional process flow sheet for absorbing methanol from a contact gas has been constructed using computer-aided modeling. The empirical coefficients used in the NRTL and Lee–Kesler models were determined. The amount of methanol in the absorption gases utilized by combustion in a conventional process flow sheet has been determined. The amounts of emissions in the case of an additional condensation stage and experimental and calculated data on the process have been compared. A method for minimizing toxic emissions that enables one tom eliminate the environmental load and increase energy and resource conservation has been proposed. The operational conditions of an absorber at a 22% increase in capacity have been considered.

A theory of a condensation method of fine dust collection in a foam bubbler is proposed. It is demonstrated that diffusion plays a decisive role owing to water vapor condensation on the inner surface of bubbles forming on holes in a gas-distributing grid. A calculation formula for evaluating the condensation effect is obtained, which satisfactorily fits available experimental data.