Multicomponent Heterogeneous Systems Research Articles

Құрамында бор бар силикохромды қолдану арқылы төмен көміртекті феррохромды балқыту процесін термодинамикалық модельдеу

The TERRA program for calculating multicomponent heterogeneous systems, based on the principle of maximum entropy, was used to study systems with a complex chemical composition, in which the task of numerical modeling is chemical and phase transformations play an important role. The effect of charge composition and temperature on the chemical and phase composition of melting products was studied, the degree of transition of charge elements into metal was determined, and optimal conditions for obtaining the alloy were found. The thermodynamic analysis of the ferrochromium production process showed that in order to approach the real process of low-carbon ferrochromium smelting, it is necessary to take into account the degree of silicon use by introducing oxygen into the working fluid to oxidize excess silicon according to the calculation. On the basis of the performed thermodynamic analysis, it is also shown that the choice of the process temperature (1750-1800°C and more) is associated with the kinetic conditions of melting, the melting temperature of the formed metal and slag. Therefore, it is expected that the presence of boron oxide, in addition to stabilizing slag from decomposition, will reduce its melting point, and the early appearance of the liquid phase due to low-temperature boron phases will ensure a shift in the reduction reactions of chromium with silicon to the low-temperature region. All these provisions will be implemented during high-temperature experimental work on the development of technological parameters.

Calculation of Complex Chemical Equilibrium Using Optimization Package Ipopt

An approach to the calculation of complex chemical equilibrium using the open-source optimization package Ipopt and the open-source package JuMP is proposed. The code of two procedures written in the open-source Julia programming language for calculating the equilibrium composition and properties of multicomponent heterogeneous thermodynamic systems is presented. The results of the test calculations showed a good performance of the code and a relatively high speed of calculations. Due to the compactness and simplicity of the code, it can be easily integrated into other applications, or used in combination with more complex models.

Reduction of Nitrous Oxide by Light Alcohols Catalysed by a Low-Valent Ruthenium Diazadiene Complex.

Decomposition of the environmentally harmful gas nitrous oxide (N2 O) is usually performed thermally or catalytically. Selective catalytic reduction (SCR) is currently the most promising technology for N2 O mitigation, a multicomponent heterogeneous catalytic system that employs reducing agents such as ammonia, hydrogen, hydrocarbons, or a combination thereof. This study reports the first homogenous catalyst that performs the reduction of nitrous oxide employing readily available and cheap light alcohols such as methanol, ethanol or ethylene glycol derivatives. During the reaction, these alcohols are transformed in a dehydrogenative coupling reaction to carboxylate derivatives, while N2 O is converted to N2 and H2 O, later entering the reaction as substrate. The reaction is catalysed by the low-valent dinuclear ruthenium complex [Ru2 H(μ-H)(Me2 dad)(dbcot)2 ] that carries a diazabutadiene, Me2 dad, and two rigid dienes, dbcot, as ligands. The reduction of nitrous oxide proceeds with low catalyst loadings under relatively mild conditions (65-80 °C, 1.4 bar N2 O) achieving turnover numbers of up to 480 and turnover frequencies of up to 56 h-1 .

Specific features of the use of pulverized coal fuel in combined chemical processing

Expanding the applications of combined thermochemical processing of mineral raw materials is one of the priority development areas in the non-ferrous metals industry. In particular, combined processes involving reduction roasting and the Waelz process are considered very promising, for example, for additional recovery of non-ferrous and accessory metals from metallurgical cakes. The first chemical stage of these reduction processes is the conversion of carbon fuel into carbon monoxide and carbon dioxide in the presence of oxygen and water vapor. The urgency of a detailed study of this stage is due, among other reasons, to the many problems related to CO2 emissions into the environment. Carbon dioxide emissions into the atmosphere are largely associated with the operation of furnace units that consume a significant amount of carbon-containing utility products. Operation of tubular rotary furnaces involves high temperatures, achieved by burning various types of fuels. This article discusses the process of burning pulverized coal fuel that results in an incomplete burnout of coal particles. Subsequent exposure of the unburned solid phase to the combustion products leads to the formation of a multicomponent heterogeneous system that maintains the synthesis reactions for CO and H2. These reactions, occurring at high temperatures, change the equilibrium composition of the combustion products dramatically. An algorithm is proposed for calculating the equilibrium composition by solving a system of nonlinear equations. The calculation was made by the iterative Newton’s method at a constant temperature, assumed on the basis of the calculated theoretical combustion temperature of the fuel of a given composition.

Volatile Aroma Surfactants: The Evaluation of the Adsorption-Evaporation Behavior under Dynamic and Equilibrium Conditions.

Multicomponent heterogeneous systems containing volatile amphiphiles are relevant to the fields ranging from drug delivery to atmospheric science. Research presented here discloses the individual interfacial activity and adsorption-evaporation behavior of amphiphilic aroma molecules at the liquid-vapor interface. The surface tension of solutions of nonmicellar volatile surfactants linalool and benzyl acetate, fragrances as such, was compared with that of the conventional surfactant sodium dodecyl sulfate (SDS) under equilibrium as well as under no instantaneous equilibrium, including a fast-adsorbing regime. In open systems, the increase in the surface tension on a time scale of ∼10 min is evaluated using a phenomenological model. The derived characteristic mass transfer constant is shown to be specific to both the desorption mechanism and the chemistry of the volatile amphiphile. Fast-adsorbing behavior disclosed here, as well as the synergetic effect in the mixtures with conventional micellar surfactants, justifies the advantages of volatile amphiphiles as cosurfactants in dynamic interfacial processes. The demonstrated approach to derive specific material parameters of fragrance molecules can be used for an application-targeted selection of volatile cosurfactants, e.g., in emulsification and foaming, inkjet printing, microfluidics, spraying, and coating technologies.

Компьютерное моделирование физико-химических процессов образования нефти

A multicomponent heterogeneous system was modeled. As a carbon-containing component, the average composition of sapropel organic matter of the Mesozoic deposits of the West Siberian NGP (according to I.I. Nesterov) was introduced into the multisystem. Solid phases of the multisystem are represented by minerals of sandstones, clay rocks, and limestones.

Расчет равновесного состава сложных термодинамических систем с использованием языка Julia и библиотеки Ipopt

The article considers the possibility of using the Ipopt optimization package for the calculating the phase and equilibrium compositions of a multicomponent heterogeneous thermodynamic system. Two functions are presented for calculating the equilibrium composition and properties of complex thermodynamic systems, written in the Julia programming language. These functions are the key ones in the program integrated with the IVTANTERMO database on thermodynamic properties of individual substances and used for conducting test calculations. The test calculations showed that Ipopt package allows determining the phase and chemical compositions of simple and complex thermodynamic systems with a fairly high speed. Using the JuMP modeling language significantly simplifies the preparation of the initial data for the Ipopt package, therefore the functions presented in this article are very compact. It is shown how the Ipopt package can be used when the temperature of the thermodynamic system is unknown. The approach proposed in this work is applicable both for analyzing the equilibrium of individual chemical reactions and for calculating the equilibrium composition of complex chemically reacting systems. The simplicity of the proposed functions allows their easy integrating into application programs, embedding them into more complex applications, using them in combination with more complex models (real gas, nonideal solutions, constrained equilibria), and, if necessary, modifying them. It should be noted that the versatility of the JuMP modeling language makes it possible to replace the Ipopt package with another one without significant modification of the program text

Подходы к формализации понятия транспортного поведения населения городских агломераций

The article deals with the field of knowledge about the transport behavior of passengers in complex transport systems of megacities, large cities and their agglomerations, in which there is a great variety of transport systems. These systems form hierarchies, where each level is described by mathematical models of homogeneous transport systems and serves as a decision-making area for implementing collective transport behavior. A review of the works of foreign and domestic authors dealing with the definition of the concept of “transport behavior”, its semantic content, a new approach to the definition of transport behavior is presented. The functional description of the “transport system of individual behavior” is presented as a collective result of the decisions made on trips that occur at certain time intervals in the transport system of the agglomeration. The mathematical description of the transport system based on the theory of macrosystems is given as a multicomponent heterogeneous open system, in which there are many decisions about the trip and the corresponding set of transport processes that ensure the achievement of the efficiency criterion.

SIMULATION OF THERMAL PROCESS FOR ULTRA-LOW CARBON STEEL IN THE CONDITIONS OF SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS

The mathematical modeling of the thermal process of forming the Armko-iron structure with the purpose of increasing the hardness and choosing the optimal charge composition is considered. Investigation of the mechanism of thermal process formation for ultra-low-alloy steel used the method of thermodynamic analysis of possible reactions between system components. For the thermal process, a universal program for the calculation of multicomponent heterogeneous TERRA systems based on the ASTRA-4 program is used. Unlike traditional methods in chemical thermodynamics, methods of calculating the equilibrium parameters using Gibbs energy, equilibrium constants, and Goldberg and Vage law, the universal program of TERRA thermodynamic calculations is based on the maximum entropy principle for isolated thermodynamics.Using the methods of mathematical modeling, a rational charge composition was developed, and the shelf life of arco-iron in the furnace was determined with the aim of increasing hardness and durability.

ИССЛЕДОВАНИЯ ВЫСОКОТЕМПЕРАТУРНОЙ ЯДЕРНОЙ ЭНЕРГОТЕХНОЛОГИИ ДЛЯ ПРОИЗВОДСТВА ВОДОРОДА И ДРУГИХ ИННОВАЦИОННЫХ ПРИМЕНЕНИЙ

The presented results of neutron-physical, thermophysical, and technological studies have shown that it is possible in principle to provide the required parameters of a high-temperature (900-950 °C) reactor installation with a 600 MW reactor (heat) with a sodium coolant for hydrogen production and other innovative applications based on one of thermochemical cycles or high temperature electrolysis with a high coefficient of thermal use of electricity. The relative small size, type of coolant, and the choice of fissile material and structural materials make it possible to create a reactor with intrinsic properties that provide enhanced nuclear and radiation safety. The possibilities of using heatresistant radiation-resistant structural materials and using the proposed technology of hightemperature sodium coolant at a high hydrogen concentration are discussed. The features of the behavior of a high-temperature complex multicomponent heterogeneous system ″sodium coolant - impurities - structural (technological) materials - protective gas″ are analyzed, which are associated with an exponential temperature dependence of constants characterizing heat and mass transfer processes (diffusion, permeability, solubility, absorption rate, equilibrium gas pressures, etc.). It has been shown that the technology system for high-temperature sodium coolant differs significantly from systems at modern nuclear power plants. With an increase in the intensity of hydrogen sources coming from the third circuit to the second, compared with BN-600 NPPs by two to three orders of magnitude, the condition for its implementation is to increase the hydrogen concentration in sodium by two to three orders of magnitude compared to modern nuclear power plants in combination with the removal of hydrogen from sodium by evacuation through membranes from vanadium or niobium.

Сравнительный анализ термохимического активирования молибденитового концентрата с магнезитом и бруситом

The purpose of the paper is to establish physico-chemical regularities and technological parameters of molybdenite concentrate thermochemical decomposition with the use of various magnesium minerals (brucite Mg (OH) 2 , magnesite MgCO 3 ) in the oxidizing medium. The compositions and physico-chemical properties of initial materials and interaction products are studied by atomic absorption spectrometry, photocolorimetry, differential scanning calorimetry and x-ray phase analysis. Physical and chemical modeling of the systems MoS 2 -MgCO 3 -O 2 and MoS 2 -Mg(OH) 2 -O 2 is carried out by means of the universal program for determining the equilibrium parameters of multicomponent heterogeneous systems "Terra" and the Temkin-Schwarzman method. It is shown that magnesium molybdate (MgMoO 4 ) formed in the process of interactions is stable within the range of the studied temperatures from 300 K to 1150 K. We have determined the technological parameters of molybdenite concentrate sintering with each of the additives providing directed transformation of the refractory mineral form into the soluble molybdate phase MgMoO 4 and sulfur oxide into non-volatile magnesium sulfate: temperature 600°C, firing duration 60-90 min, consumption of brucite or magnesite is 100-110% of stoichiometrically required for complete binding of molybdenum and sulfur into a cinder. The developed method of molybdenite concentrate thermochemical activation makes it possible to reduce the cost of the thermochemistry process by using magnesium minerals as a raw material additive and promotes the effective interaction of decomposition products with the formation of soluble compounds MgMoO 4 and MgSO 4 .

Interface-Capturing Method for Calculating Transport Equations for a Multicomponent Heterogeneous System on Fixed Eulerian Grids

In this paper, we consider a new numerical method for solving the transport equations for a multicomponent heterogeneous system on fixed Eulerian grids. The system consists of an arbitrary number of components. Any two components are separated by a boundary (interface). Each component is determined by a characteristic function, i.e., a volume fraction that is transported in a specified velocity field and determines the spatial instantaneous component distribution. A feature of this system is that its solution requires two conditions to be met. Firstly, the volume fraction of each component should be in the range [0, 1], and, secondly, any partial sum of volume fractions should not exceed unity. To ensure these conditions, we introduce special characteristic functions instead of volume fractions and propose solving transport equations with respect to them. It is proved that the fulfillment of these conditions is ensured when using this approach. In this case, the method is compatible with various TVD schemes (MINMOD, Van Leer, Van Albada, and Superbee) and interface-sharpening methods (Limited downwind, THINC, Anti-diffusion, and Artificial compression). The method is verified by calculating a number of test problems using all of these schemes. The numerical results show the accuracy and reliability of the proposed method.

ТЕПЛОФИЗИКА ЩЕЛОЧНЫХ ЖИДКИХ МЕТАЛЛОВ. ЧАСТЬ 2: ФИЗХИМИЯ, ТЕХНОЛОГИЯ И ИННОВАЦИОННЫЕ ПРИЛОЖЕНИЯ (РЕТРОСПЕКТИВНО-ПЕРСПЕКТИВНЫЙ ВЗГЛЯД)

The article presents the results of experimental and analytical studies carried out at the SSC RF - IPPE in the field of physical chemistry, mass transfer, technology and innovative applications of alkaline liquid metal coolants. An integrated approach to the study of coolants as a complex multi component heterogeneous system, the state of which is determined by the interaction of coolant - impurities - structural (technological) materials - protective gas, was substantiated. Thermodynamic analysis and experimental studies of the coolants properties and the kinetics of their interaction with air, water, hydrogen, structural and technological materials determined the sources of impurities and their intensity. It is shown that for temperature parameters of modern NPPs, the required concentration of impurities in sodium and sodium-potassium alloy, can be provided by purification the coolants by cold traps. The deeper purification of ciilants required for use in high-temperature installations of niobium, tungsten, vanadium, tantalum is achieved by getters (hot traps). This method can also be applied when limiting the weight and size characteristics, for example, for a space NPP. A fundamentally new combined purification system from impurities was proposed and substantiated for a high-temperature NPP for the production of hydrogen with a sodium coolant temperature of ~900 °C. As a result of the development of alkaline liquid metal coolants, liquid metal technology has been proposed in various technical applications: sodium at nuclear power plants with fast neutron reactors, sodium and sodium potassium in the metallurgical and chemical industries; sodium-potassium, cesium, lithium - in space installations; lithium - in fusion reactors - thermonuclear reactors.

Making Use of the δ Electrons in K4Mo2(SO4)4 for Visible-Light-Induced Photocatalytic Hydrogen Production.

Quadruply bonded dimolybdenum complexes with a σ2π4δ2 electronic configuration for the ground state have rich metal-centered photochemistry. An earlier study showed that stoichiometric or less amount of molecular hydrogen was produced upon irradiation by ultraviolet light (λ = 254 nm) of K4Mo2(SO4)4 in sulfuric acid solution, which was attributed to the reductive capability of the ππ* excited state. To make use of the δ electrons for visible-light-induced photocatalytic hydrogen evolution, a multicomponent heterogeneous photocatalytic system containing K4Mo2(SO4)4 photosensitizer, TiO2 electron relay, and MoS2 cocatalyst is designed and tested. With ascorbic acid added as a sacrificial reagent, irradiation by artificial sunlight (AM 1.5) on the reaction in 5 M H2SO4 has produced 13 400 μmol g-1 of molecular hydrogen (based on the Mo2 complex), which is 30 times higher than the hydrogen yield obtained from the reaction of bare K4Mo2(SO4)4 with H2SO4 under ultraviolet light irradiation. Further improvement of hydrogen evolution is achieved by addition of oxalic acid, along with an electron donor, which gives an additional 50% increase in H2 yield. Spectroscopic analyses indicate that, in this case, a junction between the Mo2 complex and TiO2 is built by the oxalate bridging ligand, which facilitates charge injection and separation from the Mo2 core. This Mo2-TiO2-MoS2 system has achieved a high hydrogen evolution rate up to 4570 μmol g-1 h-1. The efficiency of K4Mo2(SO4)4 as a metal-centered photosensitizer is also proved by parallel experiments with a dye chromophore, fluorescein, which presents comparable H2 yields and hydrogen evolution rates. Most importantly, in this study, detailed analyses illustrate that the photocatalytic cycle with hydrogen gas as an outcome of the reaction is established by involvement of the δδ* excited state generated by visible light irradiation. Therefore, this work shows the potential of quadruply bonded Mo2 complexes as photosensitizers for photocatalytic hydrogen evolution.

Determining the Phase Composition of Complex Thermodynamic Systems

Topical issues related to simulating the equilibrium state of multicomponent heterogeneous systems are addressed. Calculation methods for determining the phase composition of such thermodynamic systems are analyzed. It is shown that the need to determine the coordinates of the conditional extremum of the function, the analytical form of which is usually not known a priori, is one of the main reasons for the difficulty in developing algorithms for the calculation of the equilibrium composition of multicomponent heterogeneous systems.

Thermodynamic Stability Areas of Polyvanadates of Alkaline Earth Metals

A thermodynamic method of the global Gibbs energy variation calculation for describing heterogeneous equilibria of transformations of calcium, strontium, and barium polyvanadates, that occur in systems MeO-V2O5-H2O, where Me is the alkaline earth element, has been developed and used. Its quintessence consists in the thermodynamic analysis of the real conditions of various processes on the basis of their total thermodynamic characteristics. On the basis of the selected thermodynamic data for involved species, the thermodynamic stability areas of solid polyvanadates towards the solution pH and vanadium and alkaline earth metal ion concentrations in heterogeneous mixtures have been established, taking into account the complex formation reactions in multicomponent heterogeneous systems. The existing experimental data confirm the results on the thermodynamic stability of polyvanadates obtained in this paper.

Structure of Equations for Multicomponent Mixtures in Heterogeneous Systems According to Size Fluctuations and the Intermolecular Degrees of Freedom of Components

An approach to calculating the effects of density fluctuations is generalized with allowance for the movement of molecules in small condensed multicomponent heterogeneous systems (e.g., droplets, microcrystals, and adsorption on microcrystal faces). The collective character of statistical sums of vibrational, rotational, and translational motions of separate molecules in dense phases is expressed in dependences of these statistical sums on the local configurations of neighboring molecules. Using the quasi-chemical approximation with allowance for interparticle interactions reflecting the effects of direct short-range correlations, a relationship is derived between the statistical sum of a system consisting of a multicomponent mixture of molecules and the statistical sums of individual components. A structure is formulated for isotherm equations associating the density of mixture components and their chemical potentials in a thermostat, and for pair distribution functions.

Solubility, liquid-liquid equilibrium and critical states for quaternary system acetic acid – n-amyl alcohol – n-amyl acetate – water at 303.15 K and atmospheric pressure

The object of this study is multicomponent heterogeneous liquid-liquid system with n-amyl acetate synthesis reaction. New experimental data on solubility, liquid-liquid equilibrium (LLE) and critical compositions for acetic acid – n-amyl alcohol – n-amyl acetate – water at 303.15 K and atmospheric pressure are presented. Solubility and critical states were investigated by “cloud-point technique” and pale opalescence blue methods accordingly. LLE compositions were determined by gas chromatography and correlated by NRTL model. Results calculated using NRTL modeling are in sufficient agreement with experimental data. Standard deviations for binary, ternary subsystems do not exceed 0.45% and for quaternary system investigated – 0.53%.

Resource-saving direct alloying of steel

The development of the alloying and modification of steel by oxides, including natural materials, is very promising. Potential materials include barium–strontium carbonate ores, nickel concentrates, and vanadium converter slag, which may be used to produce steel with improved properties, without the expensive process of producing ferroalloys and intermediate alloys. Considerable research is required to improve steel-making processes. Thermodynamic modeling may be used for that purpose. In the present work, thermodynamic modeling is used for elementary systems involved in the extraction of barium, strontium, vanadium, and nickel from their oxides by means of different reducing agents. The results indicate that microalloying and modification of steel by inexpensive materials is possible; and permit the determination of the type of reducing agent and the optimal quantities employed. The Terra software used in thermodynamic modeling permits the determination of the equilibrium composition of the multicomponent heterogeneous system for high-temperature conditions, on the basis of the maximum-entropy principle. The reducing agents considered are carbon, silicon, and aluminum. The influence of the temperature and reducing-agent consumption on the reduction processes is investigated. The results regarding the reduction of barium and strontium show that silicon or aluminum is the best reducing agent when barium-bearing oxide materials are employed. The optimal reducing-agent consumption corresponding to maximum reduction of the barium and strontium is determined. The possibility of reducing nickel by carbon is confirmed. It is found that vanadium may be reduced by silicon or carbon or a complex process in which carbon is the predominant reducing agent. The results permit the development of a resource-saving technology based on oxides for the alloying, microalloying, and modification of Fe–C systems.

DEVELOPMENT OF RESOURCE-SAVING TECHNOLOGIES OF STEEL DIRECT ALLOYING ON THE BASIS OF THERMODYNAMIC MODELING OF METALS RECOVERY PROCESSES IN ELEMENTARY SYSTEMS

One of the promising trends of the perfection of the existing technologies is the development of the technologies of alloying and modification of steel oxide, including natural materials. Such materials are the bariumstrontiumcontaining carbonate ores, the nickel concentrates and converter vanadium slag, whose use makes it possible to obtain metal with the improved properties, at the same time from the process is excluded the stage of obtaining ferroalloys and masteralloys, which is characterized by significant expenditures. For improving the existing metallurgical processes the significant studies are required, which can be accomplished with the use of methods of thermodynamic simulation. In the article the results of thermodynamic simulation in the elementary systems of the reduction processes of barium, strontium, vanadium and nickel from their oxides from different restorers are given. The obtained results made it possible to explain the possibility in principle of the realization of the processes of microalloying and modification of steel by inexpensive materials and to determine type and optimum expenditures of restorer. As the tool with the thermodynamic simulation was used the program set “TERRA”, which allows on the basis of the principle of the entropy maximum defining equilibrium classification of multicomponent heterogeneous system for the high-temperature conditions. As the restorers were examined carbon, silicon and aluminum. Studies of the effect of temperature and expenditures of restorers for conditions and regimes of the reduction processes of metals were carried out. The results of investigating the reduction processes of barium and strontium have shown that as the restorer during the application of the oxide barium-containing materials for the treatment of steels is more preferably to use silicon or aluminum. The optimum expenditures of restorers were determined, which ensure the maximum degree of the reduction of barium and strontium. The studies were carried out and the possibility of nickel restoring by carbon was confirmed. The results of investigating the process of vanadium reduction confirmed the realizability of process both separately by silicon and by carbon and by the joint carbon-thermal reduction, during which carbon is the predominant restorer. The use of obtained results will make it possible to develop the new resource-saving technologies with the use of oxide materials for the alloying, microalloying and modifications of the fusions of the system Fe – C.