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Vol 57, No 3 (2023)
Articles
Isotope Effects of Water in Liquid–Vapor Equilibria on Passing to Water–Non-Electrolyte Solvent
Abstract
In solutions of non-electrolytes, there is a single network of hydrogen bonds, including molecules of dissolved substances, bound water, bulk water, and hydration shells of molecules in solution. Under certain conditions, there should be correlations between the bulk properties of the liquid mixture and the separation factor of the isotopic forms of water between the liquid and vapor phases. The shift of the isotope equilibrium in the liquid–vapor phase system for water during the transition from water to non-electrolyte solutions is associated with a violation of the degree of bonding and structuredness of the water of the mixed solvent. Using urea solutions as an example, it is shown that this effect can be one of the main ones and can determine the increase in the separation factor of the isotopic forms of water upon passing from water to a solution.
249-251
Calculation of Seawater Density
Abstract
An equation for calculating the density of multicomponent aqueous solutions of electrolytes is proposed and a calculation of the density of seawater is carried out at 20°С. It is established that six salts make the main contribution to the density of the solutions: sodium, magnesium, calcium and potassium chlorides, and sodium sulfate and bicarbonate. The molar volumes of magnesium and calcium chlorides, as well as sodium sulfate and bicarbonate, are determined. Based on these data on molar volumes and the previously found values for sodium and potassium chlorides, we calculate the density of seawater at 20°С. The resulting value is 1023.7 kg/m3, which practically coincides with the value available in the literature of 1023.6 kg/m3, given for 25°С. The applied technique can be used to calculate the density of technological solutions with various salt compositions
252-256
Removal of Tritium from Gas Flows from Working Areas of Nuclear Facilities
Abstract
Some methods were considered to remove tritium-containing hydrogen compounds from various gas flows from scientific and production facilities in the nuclear and thermonuclear power industry. The possibilities of tritium removal from a gas flow in the form of hydrogen were analyzed, and it was concluded that these methods can be applied at low flow rates of the gas being purified. At high gas flow rates, the main detritiation methods are adsorption and water phase isotope exchange. Both these methods include the preliminary catalytic oxidation of tritium-containing molecules to water with the further removal of tritiated water from the gas. The main technological parameters of these methods were compared, and it was inferred that phase isotope exchange has great advantages.
257-265
A Study of the Influence of the Thermal Conductivity Coefficient of Phosphate Ore Raw Materials on the Efficiency of the Chemical–Power Technological Process of Roasting in a Dynamic Dense Multilayered Mass
Abstract
This study proposes physical and mathematical models of the chemical–power technological process of roasting of a dispersed ore phosphate material in a moving dense multilayer mass on a conveyor of a roasting machine with a cross-supply of the heat-carrier gas. A computational model is developed on the basis of the constructed models, on which computational experiments are performed to study the influence of the thermophysical characteristics of ore raw materials on the efficiency of roasting. The extent of the influence of the thermal conductivity coefficient of ore phosphate materials on the energy efficiency and completeness of thermally activated endothermic reactions of carbonate dissociation is established. The method based on using the multilayer polyfractional charge of ore dispersed raw materials on the grate of the roasting machine conveyor for vigorously influencing the efficiency of the chemical–power technological process of roasting is scientifically substantiated and confirmed in computational experiments. It is established that the changes in the temperature of the heat-carrier gas in the dense layer and at the outlet from it, the roasting efficiency, and the uneven decarbonization along the height of the dense layer of the thermally processed ore raw materials depend substantially on the thermophysical characteristics. As found from the results of computational experiments, the use of polyfractional filling of ore phosphate raw materials on the conveyor of the roasting machine under the prescribed roasting conditions leads to a decrease in the temperature of the exhaust gases, and to an increase of average degree of decarbonization of the layers in raw materials. It is found that the use of polyfractional filling changes the dependence of the heat-carrier-gas temperature on the layer height coordinate.
266-272
Kinetics of Ultrasonic Dissolution of Metal Oxide Powder for Different Spatial Combinations of the Cavitation Region and Eckart Acoustic Flow
Abstract
The features of the impact of acoustic flow and cavitation created by a traveling ultrasonic wave, which can be used for efficient dissolution of a metal oxide powder, are considered. On the basis of a simplified scheme, which, nevertheless, takes into account all the essential features of the phenomenon under study, exact expressions are obtained for all parameters of stationary vortex motion and cavitation, which fully meet the requirements for proper control of the reaction course. Equations are derived that describe the dissolution kinetics for two typical regimes: developed cavitation and pre-cavitation state. Expressions are found for the time to completion of the process. On the example of these two most typical types of reaction, the conditions are formulated under which it will be possible to fully satisfy the solution of the technological challenges. The methods for the optimal application of the ultrasonic dissolution scheme are presented and those features of its formation that make it possible to control the process are noted. The performed calculations make it possible to select and accurately implement the scheme of acoustic stimulation of dissolution which best corresponds to the expected output results and other processing features.
273-283
A Fractal Analysis of the Effect of Titanium Dioxides on the Biological Properties of Bioinorganic Composite Materials
Abstract
The study is devoted to the problem of creating environmentally friendly materials by using a new generation of composites based on biodegradable biocompatible polymer matrices with the possibility of long-term controlled targeted release of nutrients and bioprotective substances. A technique and an algorithm for using fractal analysis to assess the biological properties of the chitosan–titanium-dioxide composite, which is a bioinorganic composite material used in agriculture to produce highly effective complex fertilizers, is developed. The developed algorithm differs from analogues in the use of skeletons for calculating the fractal dimension of microphotographs. The fractal and mechanical properties of organic/inorganic films of the bioinorganic chitosan–titanium-dioxide composite material are studied. The obtained results are essential for assessing the characteristics of the bioinorganic composite material, such as the biodegradability, biocompatibility, and environmental safety, which are important for environmental protection. The existence of a relationship between the coefficients of asymmetry and kurtosis of the fractal dimension of the chitosan film microphotographs and the percentage of titanium dioxide in them is established. The results of studying the mechanical properties of the films of the chitosan–titanium-dioxide composite allow one to conclude that titanium dioxide impurities have an effect on the strength of the films.
284-291
Steam Reforming of Ethane in a Membrane Reactor with a Nickel Catalyst at High Temperatures
Abstract
A model of steam reforming of pure ethane in a membrane catalytic reactor is proposed. The working elements of the reactor are cylindrical chambers, between which a hydrogen-selective palladium foil is placed. The upper chamber is vacuumized, and the lower one contains a nickel catalyst. In the case of uniform feed of the feedstock (С2Н6 and Н2О) along the perimeter of the lower chamber, the problem is reduced to finding the average flows of С2Н6, СН4, Н2О, СО, СО2, and Н2 by solving a system of nonlinear ordinary differential equations. The studies are carried out in the temperature range of 700–1000 K at acceptable steam/ethane input flow ratios of more than four. The optimal conditions for the process, at which the hydrogen yield is 100%, are found. It is proved that under these conditions and a fixed temperature, the maximum hydrogen flow through the membrane is observed at the minimum permissible ratio of the steam and ethane input flows, equal to four. Comparison of the calculations with the experimental data confirm the assumption of the existence of two sections in the lower chamber (short initial and main sections).
292-308
Strength Characteristics of Polymer Composites Filled with Coarse and Macro Particles with Different Types of Disperse Structure
Abstract
This paper reports some data on the effect of the type of disperse structure and the sizes of particles (coarse and macro particles) on the strength characteristics of disperse-filled polymer composites (DFPCs) based on polymer matrices of different nature (thermoplastics and thermosets). In this study, the types of disperse structure were calculated using a generalized model of the DFPC structure in terms of generalized (Θ) and reduced (Θ/В, Θ/Sf) parameters, which made it possible to estimate the effect of the parameters and type of disperse structure on the strength properties of DFPCs containing fillers with various particle sizes. It was shown that, when designing the composition of DFPCs with macro and coarse disperse particles for both thermoplastics and thermosets in the region of diluted systems (volume fraction Θ > 0.90), the strength remains almost equal to that of the polymer matrix. When creating low-filled systems (0.90 > Θ > 0.75), the strength decreases by 10–15% in comparison with the polymer matrix at a filler volume fraction φf up to 0.14.
309-316
On the Estimates of Convective Heat Transfer Intensification
Abstract
The results of thermal engineering experiments on a water–water tubular heat exchanger of the tube-in-tube type with heat transfer intensified by periodic confuser–diffuser elements arranged along the channel length at a step equal to the doubled inner diameter of the inner tube are compared with the results of experiments on a similar smooth-tube heat exchanger and the results of calculations by the criterial models of B.S. Petukhov, S.S. Kutateladze, W. Nusselt, and M.A. Mikheev. The comparison showed that the ratio of heat transfers in the tube channels of the intensified and smooth-tube heat exchangers, being a function of the Reynolds and Prandtl numbers, depends on the latter to a much higher extent. As a consequence, at least for water as a medium where the Prandtl number depends on temperature, the intensification of heat transfer is determined not only by the profiling parameters, but also by the parameters of the heat transfer process itself. In addition, the comparison demonstrated that the replacement of experimental data on smooth-tube heat exchangers by the results of calculation by the criterial models worsens the accuracy of estimates and leads to an increase in deviations with an increase in the Reynolds number Re.
317-324
Prediction of Nanofiltration Purification of Industrial Solutions from Metal Ions Based on the Theories of Convective Diffusion and Hydrodynamics
Abstract
The paper analyzes the state of the problem of the theoretical prediction of the retention coefficient and specific output flow for purification or concentration of industrial solutions throughout the cycle of nanofiltration separation of industrial solutions containing metal ions. To predict the nanofiltration process, a mathematical model is developed based on solving the equations of convective diffusion, the Navier–Stokes equation, and the flow continuity equation using a polar coordinate system. The theoretical results obtained as a result of solving the system of equations make it possible to evaluate the quality and productivity of nanofiltration separation by calculating the concentrations in the permeate and retentate tracts and the permeate volume. The adequacy of the developed method is assessed by comparing the data calculated using the model with the experimental data obtained on a nanofiltration unit during the separation of solutions containing Cr3+ and Zn2+ cations using semi-permeable membranes OPMN-P and AMN-P.
325-334
Technology of Sintering Phosphorite with KOH
Abstract
The paper shows a new technological approach to the processing of phosphorus-containing raw materials using Syrian phosphorite as an example. Thermodynamic calculations of possible processes of interaction of apatites with KOH and quartz are made, assumptions about the interaction are experimentally verified, and the resulting substances are determined by X-ray phase analysis. The results obtained allow us to recommend the method of sintering followed by leaching with water as a promising technology for the production of fertilizers from phosphorus-containing raw materials, bypassing the stage of production of extractive phosphoric acid.
335-339
Peculiarities of the Kinetics of Composite Material Composition Based on Polytetrafluoroethylene in the Constant Speed Mode of the Press Pluger
Abstract
The work presents a theoretical analysis of the process of one-sided pressing, under conditions of constant speed on the press plunger and taking into account external friction, of powder composite polymer materials based on polytetrafluoroethylene (PTFE) with small additives (less than 5%), such as silicon dioxide SiO2, kaolinite Al4[Si4O10](OH)8, carbon nanotubes, and carbon fiber. The influence on the process of compaction of materials of the speed of the press plunger, the coefficient of external friction, and the composition of the pressed material (depending on its additives) is analyzed. Based on a system of initial equations using Lagrangian variables and averaging over the radius, numerical calculations are carried out of the time dependence of the voltage on the plunger of the press for various values of the friction coefficient, geometric dimensions of the sample, and speeds of the press plunger. New visual representations are provided of the kinetics of compaction of powder materials based on polytetrafluoroethylene under constant speed of the press plunger.
340-345
Inhomogeneity Axiom and Generalized Energy Conservation and Transformation Law
Abstract
The axiom of inhomogeneity in natural objects is formulated so as to enable the energy conservation and transformation law to be expressed in an analytical form suitable for the analysis of real natural and technological processes by combining the methods of mechanics and thermodynamics.
346-357
Памяти профессора Валерьяна Николаевича Блиничева
358-360