Mass Exchange Processes Research Articles

Optimization of the solution of mass- and heat transfer models in capillary-porous media

Extraction efficiency is determined by mass and heat transfer processes in the liquid-solid system. In order to determine the optimal conditions for the extracting process, it is necessary to make up a mathematical model which reliably describes mass and heat exchange processes. In our study there are equations of mass and heat transfer, which occur during extracting process. They allow to determine numerically the process parameters and describe the resistance shares of external mass transfer much easier than in other methods of calculation. Further development of the outlined ideas leads to a new content of the concepts of kinetic coefficients of mass and heat transfer. To prove the accuracy of the calculation method, the share of external mass transfer resistance was calculated when extracting soybean oil with extraction gasoline and dichloroethane. The described calculation method for extracting process features may be used for designing extraction equipment, technology development and technological characterizing of process. Taking into account the identified system features, it is possible to reduce the solution to a particular form and mathematically describe a specific mass and heat exchange process. This makes it possible to determine the optimal conditions and increase the efficiency of the extracting process.

Ефективність використання сопел типу Вентурі при отриманні водних рослинних екстрактів

Technologies for obtaining extracts from plant raw materials require constant improvement due to the significant variety of species, composition and physical and chemical properties of plant raw materials. The constant increase in the volume of manufacturing products and preparations using plant extracts ma¬keit actual to search for individual approaches. Currently, cavitation technologies are considered to be one of the most effective in the treatment of gaseous, solid, and liquid media and are used in various industries. The transformation and redistribution of energy, which occur during the formation and collapse of steam-gas bubbles due to the creation of a high difference in pressure, temperature, and potential, corre¬spondd to their maximum values and contribute to increasing the active dynamic influence on the complex heterogeneous systems. During extraction, the use of hydrodynamic cavitation is allowed to effectively carry out the process of active destructtion of plant cell walls, increase the contact area between phases and intensify mass exchange processes. The design of the equip¬ment, the performance profile of the working devices, the flow parameters (absolute pressure and velocity), the critical pressure Pcav, as well as the material properties have a significant impact on the hydrodynamic conditions of the cavitation treatment. The results of research on determination the effectiveness of the use of venturi nozzles in the extraction of dry flowers of calendulaare presented in the article. The research was carried out with cavitation reactor nozzle neck with diameters of 0.006 m, 0.008 m, 0.01 m and 0.012 m. The nozzle with the minimum diameter of the neck (0.006 m) corresponds to the lowest cavitation number, which indicate the highest dispersion efficiency, but the high dispersity of the suspension makes it difficult to separate insoluble substances from the extract. In theresearch, it was established that a nozzle with diameters of 0.008 m and 0.01 mm is rational to be used. The duration of processing should be no more than 60 cycles to avoid overheating of the mixture and to prevent a critical dispersity index at which the process of filtering and separating the extract from the exhausted raw materials is significantly complicated.

Resolving the spatial scales of mass and heat transfer in direct plasma sources for activating liquids

When plasma is in direct contact with liquid, an exchange of mass and heat between the two media occurs, manifested in multiple physical processes such as vaporization and multiphase heat transfer. These phenomena significantly influence the conditions at the plasma–liquid interface and interfere with other processes such as the multiphase transport of reactive species across the interface. In this work, an experimentally validated computational model was developed and used to quantify mass and energy exchange processes at a plasma–liquid interface. On the liquid side of the interface, it was shown that a thin film of liquid exists where the temperature is approximately three times higher than the bulk temperature, extending to a depth of 10 μm. As the depth increased, a strongly nonlinear decrease in the temperature was encountered. On the plasma side of the interface, plasma heating caused background gas rarefaction, resulting in a 15% reduction in gas density compared to ambient conditions. The combined effect of gas rarefaction and liquid heating promoted vaporization, which increased liquid vapor density in the plasma phase. When water is the treated liquid, it is shown that water vapor constitutes up to 30% of the total gas composition in the region up to 0.1 mm from the interface, with this percentage approaching 70–80% of the total gas composition when the water’s temperature reaches its boiling point.

Liquid Nanofilms’ Condensation Inside a Heat Exchanger by Mixed Convection

Liquid nanofilm is used in industrial applications, such as heat exchangers, water desalination systems, heat pumps, distillation systems, cooling systems, and complex engineering systems. The present work focuses on the numerical investigation of the condensation of falling liquid film containing different types of nanoparticles with a low-volume fraction. The nanofluid film falls inside a heat exchanger by mixed convection. The heat exchanger is composed of two parallel vertical plates. One of the plates is wetted and heated, while the other plate is isothermal and dry. The effect of the dispersion of the Cu or Al nanoparticles in the liquid on the heat exchange, mass exchange, and condensation process was analysed. The results showed that the heat transfer was enhanced by the dispersion of the nanoparticles in the water. The copper–water nanofluid presented the highest efficiency compared to the aluminium–water nanofluid and to the basic fluid (pure water) in terms of the heat and mass exchange.

STUDY OF THE EFFICIENCY OF SEPARATION BY RECTIFICATION IN A LABORATORY COLUMN

Rectification is one of the most complex energy and metal-intensive chemical and technological processes that have a strong influence on the quality of commodity products, the economy and ecology of production. It is a major process in the petrochemical and oil processing industries and its main apparatuses, rectification columns, are part of common technologies that have many interrelated parameters. The current environmental problems and requirements for the quality of commodity products are increasing and call for improvement of the resolution of rectification installations through their reconstruction by modernizing the basic equipment of the columns. The efficiency of the mass exchange process on the tray is characterized by differential and integral characteristics. The differential (local) characteristic determines the mass transfer in the elementary (local) volume of the gas-liquid system, and the integral one does so on the entire tray. The local efficiency coefficient, ЕOG, (local efficiency) is used as a differential characteristic and the efficiency coefficient of the tray (Murphree efficiency) is used as an integral characteristic. The aim of the present work is to experimentally study the effects of vapour velocity and the concentration of the initial mixture on the local efficiency of rectification and foam height in a glass laboratory column with a single sieve tray.

A clouded bubble-based mass transfer model for the simulation of gas–solid bubbling fluidization

Bubble mesoscale structures play a critical role in the transport process in bubbling fluidization. A bubble-based multiscale method has been developed to modify the conventional model. Whereas the effect of the circulating gas flow features around bubble, called “bubble cloud”, is usually neglected. The bubble cloud is an essential way to transport the reactant species from the bubble phase to the bed. In this work, the impact of the bubble cloud in the mass transfer process is considered. The bubble cloud is taken as the inter-phase based on the multi-scale resolution of the bubbling fluidized bed system and a clouded bubble-based mass transfer model is established. The proposed model is incorporated in the two-fluid model to simulate the ozone decomposition process in 3D bubbling fluidized beds. It is proven that the results using the proposed mass transfer model can give a better agreement with the experimental data than the homogeneous model. The role of the bubble cloud is significant in the mass exchange process.

An enhanced heuristic algorithm with coordination evolution strategy for waste-mass minimization and heat integration network design

The issue of clean production and energy efficiency has become a major concern, especially in the chemical and processing industries. In this paper, an enhanced optimization algorithm satisfying heat-waste minimization and waste-mass minimization is proposed. First, a nodes-based non-structural model and random walk algorithm with compulsive evolution for mass exchanger network synthesis are constructed. The optimization mode of continuous variables is analyzed after analyzing the characteristics of the mass exchange process. To enhance the optimization ability of the heuristic algorithm, a novel coordinated evolution strategy combining the dynamic operations of the walk length optimization and participating evolution probability adjustment is proposed. The proposed strategy can adjust the walk length via an instant objective function change and simultaneously controls the participating evolution of the number of units for effective coupled evolution. The quantified data show that the proposed strategy assists the algorithm in enhancing the local and global optimization abilities, with the final TACs of a benchmark aromatic plant case and phenol absorption process achieved being 125,457 $/yr and 334,696.6 $/yr, respectively. To evaluate the effectiveness of the proposed strategy, it was successfully applied in two industrial-scale cases of heat exchanger network synthesis, where the TAC of the aromatics plant case achieved was 2,892,800 $/yr while the TAC of a gasoline distillation case was 5,089,402.7 $/yr.

Determination of technological parameters of obtaining stevia extract

The prospects for the use of a plant raw material – stevia as a natural sweetener for obtaining sweet extracts have been substantiated. Literary research has been conducted on the expediency of carrying out preparatory operations of stevia-raw material in order to intensify mass exchange processes during extraction; their necessity has been theoretically justified.
 A number of studies have been conducted with the aim of intensifying the process of extracting the dry mass of stevia leaves. Preliminary preparation of stevia was carried out – crushing (using a laboratory crusher – A1-DM2R) and subsequent sieving to the average size of the leaf fraction – 3.9±0.1 mm.
 It is proposed to use whey from the production of sour milk cheese to obtain sweet extracts of stevia for their further use in the food industry.
 It has been established, that the highest efficiency of the extraction process of the prepared dry stevia leaf mass is achieved with a hydromodule – 1:15. Carrying out the process under these conditions allows to achieve the highest degree of extraction of extractive substances – 29.9.
 The results of the experimental studies, obtained and presented in the article, can be used to carry out further physicochemical analyzes of the quality of the obtained stevia extracts and the possibility of combining them with a milk base to obtain a dietary range of food products

Determining the effect of the structural and technological parameters of a gas blower unit on the air flow distribution in a gas generator

The object of this study is the structural and technological parameters of the gas blower unit in the gasification chamber of a gas generator. The task to enable uniform distribution of air masses in the gas generator has been solved using the ANSYS Fluent software. The study is based on a simulation of the movement of air flows in the characteristic cross-sections of the gas generator, in particular the cross-section of the gasification chamber at the border of the oxidation and reduction zones. Seven structures of the gas blower unit were analyzed, the effectiveness of which was determined by the coefficient of variation. The most effective was the design whose value of the coefficient of variation is the smallest and equal to 93 %. At the same time, the total area of zones with no movement of air masses, that is, the absence of a gasification process, does not exceed 12 % of the total cross-sectional area of the gas generator. The speed of air masses at the boundary of the oxidation and reduction zones is aligned in the entire cross-section of the chamber and is V»4.5 m/s. The average value of the vertical component of the speed of air masses in the cross-section at the inlet to the recovery zone of the gasification chamber is V»0.6 m/s. Under such conditions, the production of synthesis gas of high calorific value with the absence of resins, acids, heavy hydrocarbons, and mechanical impurities is ensured. The correspondence of the simulation results with experimental data is confirmed by the coefficient of determination, which amounted to 0.87. The results reported here could be the basis of a modernized methodology for the study of aerodynamic, heat and mass exchange processes that occur during biomass gasification. This would make it possible to define the rational structural and technological parameters of gas generators and improve the efficiency of the gasification process as a whole.

Approaches for the complex assessment of polychemical pollution of permafrost-affected soils and the upper layer of permafrost.

The analysis of about 200 samples taken from 42 permafrost-affected soil profiles was carried out on four key sites in different regions of cryolithozone (West Siberia, Central, North, and North-East Yakutia) characterized by different active layer depths and soil lithology. The aim of the study was to determine the influence of different processes of cryogenic mass-exchange on the redistribution and accumulation of major pollutants such as petroleum products, acid-soluble forms of trace elements, polycyclic hydrocarbons, and technogenic radionuclides transferred via atmospheric transport or after the local anthropogenic impact in different soil horizons of Cryosols and in the upper layers of permafrost. Samples were analyzed using modern precise techniques (direct γ-spectrometric measurements with Ge(Li) and NaI(Tl) detectors; fluorometric method; reversed-phase high-performance liquid chromatography; spectrofluorimetric detection; atomic absorption spectrometry with flame atomization). The study has shown that processes (cryoturbations, frost heaving, gelifluction along with fluvial processes) that strongly affect Cryosols' profile structure can also lead to the active migration and accumulation of local and global pollutants in the middle and lowermost suprapermafrost soil horizons. The accumulation of some pollutants in suprapermafrost horizons of cryogenic soils and in the upper layers of permafrost (in particular, petroleum products and mobile forms of trace elements) can be associated with a combination of factors, such as the relatively light particle size distribution, relatively weak manifestation of cryoturbation processes, and low thickness of the active layer (about 40-60cm). The integral calculation of the geoaccumulation index values has shown that all of the groups of human-affected soil horizons are moderately to extremely polluted by petroleum hydrocarbons (and at a relatively lower level by trace elements) and the maximum pollution stands for the suprapermafrost horizons as well as in cryoturbated or buried fragments of organogenic matter in some cases. The maxima of the heavy PAH content in permafrost-affected soils can be confined to horizons enriched with anthropogenic inclusions and artifacts (for example, construction slag, coal) and to individual horizons of soils buried as a result of both cryogenic and alluvial processes. The specific activity of the technogenic radionuclide cesium in cryogenic soils revealed its association mainly with the surface organogenic and organomineral horizons of the studied profiles and rarely observed in the cryoturbated fragments of these horizons in the middle and suprapermafrost layers of soil profiles. The necessity of the complex analytical assessment of the permafrost-affected soils has been revealed especially in case of studying of the ecological state of the anthropogenically affected Cryosols.

The effect of thermal insulation of the lining on the heat exchange of rotating apparatuses

Rotary kilns are used in many industries to process bulk raw materials. In the building materials industry, rotary kilns are widely used for heat treatment. However, the fuel utilization factor in rotary kilns is extremely low. Thus, the bulk of cement clinker is fired in furnaces, the thermal efficiency of which does not exceed 55-60%. Therefore, the task of increasing the efficiency of such units is extremely relevant. In operating furnaces, heat losses to the environment only through the furnace body reach 20-25% of the total heat of combustion. In this case, one of the main factors determining the thermal efficiency of furnace operation is the value of thermal resistance of lining.
 The aim of the work is to study the evolution and temperature changes in the rotary kiln lining made of shaped refractory to reduce heat losses to the environment and improve the efficiency by increasing the thermal resistance of the lining. The increase in thermal resistance is achieved by changing the shape of the refractory by creating appropriate cells and introducing additional fibrous insulating material into them.
 A mathematical model and software have been developed and numerical calculations have been carried out to determine non-stationary temperature fields in the lining with a thermal insulating element and to substantiate the choice of an appropriate thermal insulating fibrous material.
 Analyzing the calculation results, it is possible to conclude about the expediency of using a lining with increased thermal resistance. The use of this technical solution makes it possible to reduce heat losses through the housing by 18-24%, to increase the amount of transferred material in the working zone by 1.5-8% due to the creation of an appropriate temperature field in the working volume, and to reduce the mass of the lining and the furnace as a whole. and increase the energy efficiency of the thermal unit.
 The presence of cells with additional thermal insulation contributes to the emergence of thermal pulsations having oscillatory character and affecting the intensification of heat and mass exchange processes, which in general contributes to the performance of the thermal unit.
 A significant advantage of this method is also the fact that increasing the energy efficiency of the furnace does not require additional fuel consumption, increasing the temperature or increasing the enthalpy of the combustion products.

On the development of remote sensing methods and technologies in Ukraine

This article is focused on analyzing the results of scientific researches of the Scientific Centre for Aerospace Research of the Earth of the Institute of Geological Science of the National Academy of Sciences of Ukraine. The article briefly describes the development of aerospace research of the Earth in Ukraine and the role of the Centre in remote sensing research carried out by institutions of the National Academy of Sciences of Ukraine. The history of the Centre, its scientific schools and main areas of research are presented, the prospects for further development are outlined. Data of the organizational structure of the Centre and the achievements of the scientific team are represented. The contribution of employees of the Centre for the development of aerospace research in Ukraine is analyzed. The international activities of the Centre and its employees are presented. Further prospects for the development of research in the field of remote sensing in Ukraine are considered. It is noted that the strategy of research development will be set to implement the basic principles of world community, defined by UN decisions on sustainable development of humanity. It is noted that the development of novel effective methods and technologies based on using aerospace data and computer modeling of energy and mass exchange processes in the Earth geospheres will play a significant role in the solving this problem. The implementation of these methods and technologies will contribute to satisfaction the economic, defense and social needs of Ukraine, taking into account the fundamental program of postwar restoration and reconstruction of the national economy of Ukraine.

Theoretical and numerical assessment of an enhanced Humidification-Dehumidification desalination system based on Indirect Evaporative cooling and Vapour Compression Refrigeration

In this work, a theoretical study and a numerical performance analysis of a novel Humidification-Dehumidification (HDH) desalination system, that simultaneously exploits an Indirect Evaporative Cooling (Maisotsenko cycle, IEC) device and a Vapour Compression Refrigeration cycle (VCR), are proposed. The IEC device is here employed as a very efficient saltwater evaporator-air humidifier, by an optimized mass exchange process between saltwater and working airstream. Both thermal exchanges of the VCR cycle are used: the hot coil pre-heats the inlet air to enhance the effectiveness of the evaporation process, while the cold one provides the cooling capacity to condense freshwater. The numerical model is based on data of actual commercial devices and considers their effective operational mode. The parametric analysis and the yearly simulations in different climatic areas show very promising results (GOR and RWA factor equal to 3.4 and 5.0∙106 in the best operative condition, equal to 3.2 and 4.1∙106 in the best climate situation) that lead to consider this technology as very competitive among HDH desalinations systems.

Experimental simulation of micro-electroosmosis in porous structures of food products

One of the modern directions in the intensification of heat and mass exchange processes widely used in processing of agricultural products is characterized by the use of the electric field in a certain range of its action. A special feature of the electric field impact on agricultural raw materials for food product manufacture is the emergence of micro-electrokinetic phenomena such as micro-electroosmosis. For the effective use of this direction, an experimental study of the character of the electric field interaction with raw materials of biological origin is necessary. The process of micro-electroosmosis in a form of the liquid movement in micro-capillaries depending on the parameters of weak electropulse impacts of a certain frequency is modeling in the study. The obtained experimental results make it possible to trace kinetics of process parameters for the liquid movement in micro-capillaries upon various characteristics of the electric field and understand possibilities of using micro-electroosmosis for intensification of heat and mass exchange processes.

A method for verifying the model of tank operational pressurization process during development of propellant supply system in liquid rocket engines of launch vehicle propulsion systems

During development of propulsion systems for launch vehicles, in order to verify the design results, standalone developmental tests of propellant supply system components were run in specially designed test setups outfitted with the required instrumentation. As an example of such work, this paper describes the experience of standalone developmental testing of operational pressurization of propellant tanks. During tests in the constructed test setups, heat and mass exchange processes were tried out with simulation of design modes of operational pressurization of propellant tanks filled with oxygen and hydrogen. As a result of these tests, a rationale was provided for selection of working mediums as the pressurization gas, design and characteristics of gas injection into propellant tanks, a method for evaluating the efficiency of the pressurization process. Empirical dependences were obtained that were used as the boundary conditions in the models for practical calculations for refining the modes and evaluating the efficiency of the propellant supply subsystem of propulsion systems. The paper calls attention to the need to use for the purpose of development of the propellant supply systems that involves computer simulations the results of such earlier work when designing advanced rocket propulsion systems. Key words: propulsion system, propellant supply system, development of pressurization process, test setup, pressurization gas, propellant components, heat and mass transfer intensity, process efficiency, liquid surface sloshing, computer simulations.

Inter- and Intra-Annual Glacier Elevation Change in High Mountain Asia Region Based on ICESat-1&2 Data Using Elevation-Aspect Bin Analysis Method

Glaciers are sensitive indicators of climate change and have a significant influence on regional water cycle, human survival and social development. Global warming has led to great changes in glaciers over the High Mountain Asia (HMA) region. Glacier elevation change is a measure of glacier mass balance driven by the processes of energy and mass exchange between the glacier surface and the atmosphere which are influenced by climatic factors and glacier surface properties. In this study, we estimated the inter-annual and intra-annual elevation changes of glaciers in the HMA region in 2003–2020 using Ice, Cloud and land Elevation Satellite (ICESat) data and Shuttle Radar Terrain Mission (SRTM) digital elevation model (DEM) data by developing an “elevation-aspect bin analysis method” that considered the difference of glacier elevation changes in different elevations and aspects of glacier topography. The results showed that: (1) The inter-annual change of glacier elevation in 2003–2020 had large spatial heterogeneity. Glacier elevation reduction mainly occurred in the marginal region of the HMA with the maximum decline in the Nyainqentanglha region, while glacier elevation showed increase in the West Kunlun of inner HMA regions in 2003–2020. The glacier elevation change rate showed an accelerating reduction trend in most of the HMA regions, except in the west HMA where the glacier elevation reduction rate showed slowdown tendency. Specifically, the glacier elevation change rate in the entire HMA was −0.21 ± 0.12 m/year in 2003–2008 and −0.26 ± 0.11 m/year in 2003–2020, respectively. (2) The intra-annual change of HMA glacier elevation in 2019 and 2020 showed obvious spatiotemporal heterogeneity, and the glacier thickening period was gradually delayed from the marginal area to the inner area of the HMA. The glaciers in the western marginal part of the HMA (the Tienshan Mountains, Pamir and Hindu Kush and Spiti Lahaul) and Karakoram thickened in winter or spring, the glaciers in the Nyainqentanglha Mountains exhibited spring accumulation. The glaciers in West Kunlun accumulated in two time periods, i.e., from March to June and from July to September. The glaciers in the Inner Tibetan Plateau and Bhutan and Nepal areas experienced spring or summer accumulation, especially in June or July. Moreover, we found that the inter-annual and intra-annual change of glacier elevation could be explained by the changes in temperature and precipitation. A similar analysis can be extended to mountain glaciers in other regions of the world, and glacier change trends could be further explored over a longer time span with the continuous operation of ICESat-2.

Possible risks for the functioning of cyclic processes in the experimental model of a closed ecosystem

The purpose of the present study is to consider a number of possible risks that may emerge when processed human wastes are involved into mass exchange processes as fertilizers for plants cultivated in the experimental model of the closed ecosystem (CEEM). The problems relating to the disruption of cycling processes in closed ecosystems can be tentatively divided into two groups: the problems that can be rather easily overcome and the chronic problems. Addition of plant inedible biomass to the soil-like substrate (SLS) can result in a decrease in plant productivity because of allelopathic interactions and enhanced growth of microorganisms. The 30% decrease in wheat productivity by the end of long-duration experiments in the CEEM, with plants grown on quasi-non-renewed solutions based on liquid products prepared by physicochemical mineralization of human wastes, was caused by lower resistance of the plants affected by toxicants accumulated in the solution because of incomplete mineralization of the wastes. The reason for the differences between the macronutrient inflows and outflows was that the donor of human wastes followed a European-type diet while the system produced only part of the plant-based diet. Moreover, macronutrients were partly sorbed in rooting substrates and became unavailable to plants: the substrates in the system retained about 50% of the Ca and 20% ÷ 25% of the Mg, Na, and P inflows over one cycle. These problems are temporary and can be minimized in the foreseeable future.

Application of Electrodynamic Catalytic Reactors for Intensification of Heat and Mass Exchange Processes of Heterophase Catalysis

This article discusses a model of an electrodynamic reactor. It is fundamentally different in the way of supplying energy to the reaction zone from the reactors currently in operation in industry. This significantly reduces energy consumption, simplifies process control and increases the efficiency of the reactor. The environmental advantage of the developed reactor is also of great importance. There are no emissions of gases into the atmosphere, which are formed in large quantities during fuel combustion in superheating furnaces, the consumption of water is reduced, which is used only in a closed cycle to cool the microwave generator and circulator as a matching load during its operation. The overall efficiency of the electrodynamic reactor is 1.2 times higher than that of existing industrial ones. A method for calculating thermodynamic processes in electrodynamic reactors is proposed. It allows you to determine the technological parameters of the process to ensure a given temperature distribution and provides the maximum yield of the target reaction products with the minimum possible energy consumption of electromagnetic radiation.

Spatial Flow Pattern, Multi‐Dimensional Vortices, and Junction Momentum Exchange in a Partially Covered Submerged Canopy Flume

AbstractThis study experimentally investigated the influence of a model‐submerged canopy on three‐dimensional hydrodynamic structures in a partially obstructed flume. Canopy density, water discharge, and water depth were varied to achieve generalized conclusions. With tracer experiments, multi‐dimensional (vertical and horizontal) large‐scale coherent vortices arising from both the top and lateral edges of the canopy were visualized. The results of the mean flow and turbulence field show that the hydrodynamic characteristics are highly three‐dimensional, impacted by canopy density and submergence ratio. Typical shear layers are confirmed by scaled velocity distribution with local characteristic velocity and length scales in both vertical and transverse directions along the canopy edges except for the near‐bed region where horizontal vortices are inhibited. Along the canopy edges, the average effect of the vertical coherent vortices overall outweighs that of the horizontal coherent vortices for dense canopies, the ratio of which can be regressed more precisely with the water‐related Reynolds number. The vertical profiles of the longitudinal velocity in the near‐junction region are characterized by near‐bed velocity deflection, strengthened by the increase in canopy density. The negative velocity gradients are found to be more closely related to the drag length‐related Reynolds number. An in‐depth analysis of secondary flows and near‐junction momentum budget has been conducted to show the mass and momentum exchange processes. The results show that multidimensional coherent vortices and turbulence‐induced secondary flows play different roles in mass and momentum exchange, accounting for near‐bed velocity deflections in the junction region.

The changing dynamics of the gas-dust flow in the flash smelter due to addition of a spoiler. Part 2. Pilot tests

The use of man-made deposits and fine ore concentrates in the flash smelter process, as well as the poorer quality of the raw materials observed (due to a higher share of particles smaller than 10 μm) lead to a higher amount of entrained dust and causes accretion in the slag end, uptake shaft and waste heat boiler. A higher dust entrainment is associated with a higher recycle, lower energy capacity of the raw materials and poorer recovery of non-ferrous metals. Numeric modelling of the heat and mass exchange processes in the gas environment of the settler and uptake shaft helped determine how different sizes and locations of the spoiler can change the gas flow parameters of the flash smelter. The modelling study showed that a 500 mm wide (the width of the settler) and 270 mm high spoiler mounted on the fire side of the settler at least 2,000 mm away from the entry to the uptake shaft could help reduce the amount of entrained dust by as much as 20% (relative) depending on the size and density of gas-dust particles. On the basis of the above calculations, a series of pilot tests was conducted on Line 1 of Nadezhda Metallurgical Plant in July 2019. Using various analysis techniques (such as thermal imaging of the surface in the spoiler area, the gas temperature, the gas flow rate, as well as methods used in analytical chemistry, scanning electron microscopy and X-ray spectral microanalysis), the authors of this paper examined the effect produced by the mounted spoiler on the gas flow. The authors would like to thank the leadership and the operations personnel of Nadezhda Metallurgical Plant for their support and great contribution to the pilot tests performed.