Volume 52, Nº 3 (2018)

A mathematical model for cyclic binary distillation in a sectioned column with a continuous supply of streams has been proposed. A method has been developed for organizing cyclic modes in a sectioned apparatus with the operation of one of the sections in the liquid flow mode and the other sections in the vapor flow mode. The effect of the parameters of the proposed model on separation in the column has been studied.

The liquid flow pattern of the countercurrent phase water isotope exchange process used for the removal of tritiated water vapor from gases has been studied via the pulse injection of a tracer into a liquid flow. A specific feature of this process is an extremely low water irrigation density in a column. Based on the performed experiments, the liquid holdups have been calculated and the liquid flow pattern has been determined. It has been demonstrated that the standard estimation of the longitudinal mixing effect on the masstransfer characteristics of this process has a limited character and may result in incorrect conclusions at a low irrigation density on packings.

A one-dimensional two-phase mathematical model of an ideal plug-flow reactor for methane air conversion on a Ni–MgO monolith catalyst on porous nickel was proposed. The model describes the methane air conversion as the result of three simultaneous reaction stages: methane deep oxidation, methane steam reforming, and reverse shift reaction. The effect of the external gas–solid mass transfer is taken into account in two variants: (i) independent diffusion and (ii) multicomponent diffusion for all mixture components. The results of modeling were used to analyze the experimental data (obtained in our previous work) on the dependence of the temperature of the front layer of the catalyst on the pressure and excess air coefficient. The best agreement between the calculation and experiment was obtained under conditions of complete external diffusion control of the exothermic stage for oxygen and the transition (between the kinetic and external diffusion) region of the endothermic stage, the kinetic effect of the endothermic stage being further limited by internal pore-diffusion resistance of the rate of this stage for methane.

The recovery of hydrogen from binary gas mixtures with active (deactivating the surface of the membrane) and passive impurities has been studied. Experiments have been carried out on a multifunctional membrane module, the operating area of which consists of gas chambers separated by a thin foil palladium membrane. A dimensionless coefficient of the deactivation of the surface of the membrane has been introduced. An analytical formula has been obtained for the hydrogen flux from binary mixtures at its preset pressures on the opposite sides of the membrane that takes into account adsorption–desorption, breaking to protons on the surface, the diffusion of the latter in the metal lattice, and the recombination of Н⁺. In the case when the condition are fulfilled, the Н₂ flux can be calculated by the modifiable Sieverts equation. This equation and an assumption about the complete mixing of the mixtures in the chambers of the membrane module have made it possible to develop a theoretical model for the recovery of hydrogen from binary mixtures in the membrane module. An analytical dependence for the Н₂ flux as a function of the fluxes of the mixtures at the inlet of the chambers, ratio of the pressures on the opposite sides of the membrane, initial composition of the hydrogen mixture, and the coefficient of deactivation has been found. Utilizing this dependence, a procedure for finding this coefficient using additional experiments has been proposed. As an example, the coefficients of deactivation for the products of steam reforming of methane (CO, СО₂, СН₄, and water vapor) have been calculated for a palladium membrane with a composition Pd–6%Ru. The theoretical model has been subjected to the experimental verification on Н₂–5%CO and Н₂–20%CO binary mixtures.

The flow and mixing modes of non-Newtonian fluids in a T-shaped micromixer were studied by numerical simulation in the range of Reynolds numbers 1–250. The non-Newtonian fluid was described using the power-law model. The exponent n was varied: 0.3, 0.5, and 0.8. The mixing efficiency and pressure drop in the channel were correlated with the exponent n and Reynolds number. The exponent n was shown to significantly affect the flow structure before and especially after the transition from symmetric to asymmetric flow modes.

This review analyzes papers presented at the symposium “Modern Energy- and Resource-Saving Technologies MERST-2017,” which was held within the International Scientific and Technical Forum “First International Kosygin Readings “Current Topics in Engineering Sciences.”” The presented papers have considered the key problems of energy and resource conservation in modern chemical, thermal, and mass-transfer processes, the priority directions of the implementation of energy-efficient and resource-saving environmentally safe technologies, innovations in energy and resource conservation, alternative energy, current topics in import substitution, the quality of the target products, and other issues. The place, role, and tasks of engineering sciences in the modern Russian society have also been discussed.

Against the improvement of science and technology, earthquake is one of natural disasters that human cannot predict. Researchers indicated that there are many earthquake precursors. One of these precursors is a change in radon concentration in thermal waters about of active faults. Most of radon monitors cannot detect radon concentration in water directly, and they can detect radon concentration in air. Therefore, radon molecules should be separated from water and transferred to air. In this study, a bubbling system was used for the transfer of radon from water to air. Mathematical and neural network modeling of this system has been performed. The time constant parameter as an indicator of the separation rate was less than 20 min in most of experimental conditions. After validation of the models with experimental data, the effects of water and air flow rates and water temperature on the speed response of this system have been studied.

This study experimentally investigates velocity evolution for the coalescence of two in-line bubbles rising in non-Newtonian fluids by using a high speed camera. Due to the wake of the leading bubble and the shear-thinning effect of non-Newtonian fluids, the following bubble is accelerated to approach the leading bubble, leading to the coalescence of the two bubbles. Based on the Newton’s second law and Schlichting’s wake theory, a theoretical model was developed to estimate the instantaneous rising velocity of the following bubble in the coalescence process of the two bubbles. The predicted values by the present model showed a good agreement with the experimental data.

The effect of 2-butoxyethanol as an additive on simple gas hydrate formation in the presence of kinetic hydrate inhibitors such as modified starch, polyvinylcaprolactam, and Gaffix VC-713 under various conditions in a flow mini-loop apparatus has been studied. A laboratory flow mini-loop apparatus has been designed and manufactured to measure the induction time of simple gas hydrate formation. Hydrate formers (such as C1, C2, C3, i-C4, and CO₂) are contacted with water containing dissolved inhibitor in the presence of 2-butoxyethanol as an additive at desired temperature and pressure. The effect of 2-butoxyethanol on the induction time during gas hydrate formation was investigated in the presence and absence of modified starch, polyvinylcaprolactam, and Gaffix VC-713 as kinetic inhibitors. Results show that the induction time is prolonged in the presence of Gaffix VC-713 compared to polyvinylcaprolactam and modified starch as inhibitors. Moreover, the induction time in the presence of 2-butoxyethanol is greater than in the absence of this additive for simple gas hydrate formation. As a result, the performance of kinetic hydrate inhibitors was enhanced in the presence of 2-butoxyethanol for natural gas components during gas hydrate formation.