Charged Mixtures Research Articles

THERMODYNAMIC AND EXPERIMENTAL STUDIES ON THE INFLUENCE OF HIGH-ASH COAL IN THE PRODUCTION OF HIGH-CARBON FERROCHROME

This paper presents the results of scientific research that served as the foundation for developing a technology for producing high-carbon ferrochrome using a new reducing agent in the charge-high-ash coal from the "Saryadyr" deposit. To analyze the carbothermic reduction of chromium, a method of complete thermodynamic modeling (CTM) of metallurgical processes was employed, implemented using the HSC Chemistry 10.0 software package over a temperature range of 600-2800 K. The thermodynamic analysis demonstrated that the production of carbon ferrochrome using high-ash coal does not lead to sharp technological deviations: the process proceeds stably, ensuring complete reduction of chromium and iron. An analysis of the silica and alumina content in the coal ash indicated that it can replace quartzite in the charge mixture. Based on the thermodynamic data, experimental studies of the high-carbon ferrochrome production process using Saryadyr high-ash coal were conducted in a high-temperature Tammann laboratory furnace. The Tammann resistance furnace is a research facility designed to model metallurgical processes at high temperatures. During the laboratory tests, experimental samples of high-carbon ferrochrome corresponding to grade FeCr800 were obtained.

Ordered assemblies of peptide nanoparticles with only positive charge

Surface charge patchiness of different charge types can influence the solution behaviours of colloidal particles and globular proteins. Herein, coiled-coil ‘bundlemer’ nanoparticles that display only a single type of surface charge (SC) are computationally designed to compare their solution behaviours to mixed charge-type (MC) counterparts with both positively and negatively charged side chains. Nematic and columnar liquid crystal phases are discovered in low concentrations of SC particles, indicative of particle end-to-end stacking into columns combined with lateral electrostatic repulsion between columns, while MC particles with the same net charge and particle shape produced only amorphous, soluble aggregates. Similarly, porous lattices are formed in mixtures of SC/MC particles of opposite charges while MC/MC mixtures of opposite charges produce only amorphous aggregates. The lattice structure is inferred with a machine learning optimization approach. The differences between SC and MC particle behaviours directly show the importance of surface electrostatic patchiness.

A New Approach to the Recycling of Silicon Production Waste (Microsilica) as a Raw Material for Metallurgical Processing

This paper proposes a new approach on the processing of silicon production waste (microsilica) as a raw material for metallurgical processing. It is known from practice that the granulometric composition of microsilica does not allow its use in metallurgical processing. The authors of this work propose its use together with a reductant as part of a briquetted charge. In this work, the optimal composition of the charge mixture for briquetting is determined. The main focus is on assessing the strength characteristics of the briquettes and analyzing their efficiency in the silicon smelting process. The strength of the briquettes was studied by the dropping method. As a result, in terms of strength and other characteristics, it is highly advisable to use briquettes consisting of 65% of microsilica and 35% special coke screenings. The obtained batches of high-strength briquettes were tested for the smelting of metallurgical grade silicon in a large-scale laboratory ore-thermal furnace to replace the traditional charge mixtures (high-quality quartzites, petroleum coke, wood chips, etc.) with briquettes. It was established that the briquetted monocharge ensures more intensive reduction processes and improves melting conditions compared to the traditional charge. This leads to higher silicon recovery rates, which was confirmed by tests, during which the maximum recovery rate reached 83.1% with a 30% replacement of the charge with briquettes. The batch of metallurgical silicon with 95-96% of Si content was obtained.

Oppositely charged polymer-surfactant nanoparticles stabilized by triblock copolymers for enhanced oil loading

When oppositely charged polymers and surfactants combine, they can form a concentrated phase rich in micelles interconnected by polymer chains. Dispersing this concentrated phase as nanoparticles in an aqueous media can be a way to load and deliver hydrophobic ingredients. This study employed triblock copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), EOxPOyEOx, also known as poloxamers or pluronics, to disperse the concentrated phase, forming nanoparticles of aggregated micelles connected by the polyion chains. We showed that nanoparticles formed by hexadecyltrimethylammonium bromide (CTAB), poly(acrylic acid) (PAA), and different EOxPOyEOx copolymers can enhance the loading of oily ingredients compared to pure surfactant micelles. Dispersions with 1.6 wt% of nanoparticles exhibited water-like viscosity and loaded up to 0.48 wt% of oil. Characterization techniques, including dynamic light scattering (DLS), electrophoretic mobility, small-angle X-ray scattering (SAXS), and cryogenic transmission electronic microscopy (cryo-TEM), revealed positively charged spherical 50–180 nm nanoparticles with a core formed by concentrated micelles, that were stable for at least 4 months. Variations in the EO and PO block lengths did not impact morphology, showing that different EOxPOyEOx copolymers were suitable for dispersing the nanoparticles. Increasing EO block length size decreased the diameter of nanoparticles and enhanced stability, providing a means to control their properties. In conclusion, nanoparticles formed by oppositely charged polymer-surfactant mixtures and stabilized by triblock copolymers showed potential for applications, such as sprays, due to their effective oil loading, high stability, and facile preparation.

Eco-friendly low-carbon manganese ferroalloy production for cleaner steel technologies

Global steel production, a major contributor to anthropogenic carbon dioxide, heavily relies on manganese, a key ingredient that significantly impacts the carbon footprint during the production of high-carbon ferromanganese. A single-step generation of low-carbon ferromanganese (LC-FeMn) from manganese ore in an electric arc furnace (EAF) was investigated. The theoretical and experimental investigations helped to balance the required and supplied energy. The process sustainability was predicted based on the enthalpy of the reaction. Pre-reduction of manganese ore decreased energy consumption in the smelting process and saved raw materials costs. The simulation studies revealed a significant effect of lime and silica on the slag-metal equilibrium. It further confirmed the best-reducing condition with the basicity 1.5–1.77 by smelting tests in EAF. Experimental results showed an optimal charge mixture comprising appropriate ratios of ore:SiMn:lime ratio, producing a standard-grade product. Simultaneous melting and smelting sensibly used the exothermic heat, consuming 410–880 kWh/ton, much lower than the international benchmark, i.e. approximately 2000 kWh/ton. The characterization of resulting slags corroborated the advantages of the manganese ore pre-reduction on the energy and reductant consumption, alloy grade, and slag characteristics. The present study's findings can potentially contribute to the ongoing low-carbon initiatives of steel.

Металлотермиялық тәсілмен орта көміртекті ферромарганецті балқыту процестерінің термиялық қасиеттерін зерттеу

The purpose of this work is to study the phase transformations occurring in the charge mixture during the smelting of medium-carbon ferromanganese. The study of phase transformations occurring in the charge mixture was carried out on a device for synchronous thermal analysis Labsys Evolution TG-DTA/DSC from Setaram in dynamic mode in the tem perature range of 30-1500°С. Derivatograms were obtained for two variants of the charge mixture (Option I – manganese ore, lime, silicomanganese FeSiMn17; Option II – manganese ore, lime, converted silicomanganese) in an inert atmosphere of nitrogen. Calculation of kinet ic parameters – activation energy of endo-exothermic effects occurring at different tempera tures was made. The values of the apparent activation energy determined by the tangent of the slope angle are given.

Combined techniques for revealing the mechanism beneath the inhibition effects of pectin on gluten digestibility using static in vitro gastro-duodenal protocols

In the current study, how pectin retards the digestibility of wheat gluten was investigated using a static in vitro gastric-duodenal model. The degree of protein hydrolysis was estimated using the o-phthaldialdehyde method, while the in vitro digestograms were mathematically fitted using a single first-order kinetics model. Peptides' profile, free amino acids compositions, gluten-pectin interactions and their effects on enzymatic activities of proteolytic enzymes as well as on the gluten secondary structures under digestive conditions were studied using combined techniques. Results showed that pectin could retard gluten digestibility through 1). preferential absorption to insoluble gluten aggregates by electrostatic interactions; 2). increasing the helix and reducing the β-sheet content of the solubilized gluten protein fractions in terms of their secondary molecular structures; 3). reducing pepsin activity by forming negatively charged pectin-gluten mixtures which then interacted with the positively charged pepsin molecules. The deeper insight into gluten-pectin interactions and their influences on gluten digestibility under gastrointestinal conditions provides important clues for developing effective forms of dietary fiber to improve the nutritional benefits of plant protein in individuals.

On the issue of designing and creation of a composite grinding wheels of increased productivity for rails treatment

The article discusses the technological aspects of the development and design of composite modified wheels used in the mechanical treatment of railway rails. It allows to increase the productivity of treatment and tool durability. An increase in the physical and mechanical features of the shard of abrasive wheels can be achieved by modifying the binder component in the composition of the ceramic charge mixture with a nanomodifier such as carbon tubes. As a result of the modification of the abrasive composition of the charge mixture, it was possible to achieve an effective performance of railway rails treatment without a significant loss in the durability of the composite grinding wheel.

One-Step Microwave Synthesis of New Hybrid Phosphor (CSSC) for White Light-Emitting Diodes

The possibility of synthesizing a new hybrid phosphor CSSC (mixture of 0.5 CaSrSiO4:Eu2+: 0.29 Ca6Sr4Si6O21Cl2:Eu2+: 0.21 Ca10Si6O21Cl2:Eu2+) using a one-step microwave synthesis method is demonstrated. The concentrations of europium and calcium in the synthesized phosphors were optimized at 1 and 10 mol. %, respectively, to achieve maximum brightness and color rendering index. The optimal conditions for the synthesis of phosphors in a microwave furnace were determined as 750 °C for 10 min. The resulting phosphor exhibited a wide luminescence spectrum that covered the entire visible region, resulting in a high color rendering index and a warm white luminescence when used as a light source. It is shown that the sol–gel method for preparing the charge mixture for the new phosphor allows for a 35% higher luminescence brightness compared to the solid-phase method, due to a more uniform distribution of the activator.

Charge-induced low-temperature gelation of mixed proteins and the effect of pH on the gelation: A spectroscopic, rheological and coarse-grained molecular dynamics study.

We report the gelation of mixed proteins consisting of oppositely charged lysozyme and serum albumins at various pH. The results from rheological tests showed that at a pH of 7, the gelation temperature (Tgel) of the oppositely charged proteins was lower than the melting temperature (Tm) of the individual protein. To ascertain the conformational state of the proteins at the observed Tgel, the attenuated total-reflectance Fourier-transform infrared (ATR-FTIR) spectra of the proteins were acquired. The recorded spectra showed that the proteins were predominantly alpha helical, suggesting that the observed gelation was electrostatically triggered. However, as the solution pH was changed to acid or alkaline regime, all the proteins became similarly charged and showed Tgel <Tm which was attributed to pH-induced denaturation. Surprisingly, however, the serum albumins were remarkably stable at the alkaline pH of 9 and 10 but very labile at the acidic pH. In contrast, the LYZ was more stable at the acidic than alkaline pH. To understand the role of the opposite charges in the gelation, coarse-grained molecular dynamics (CGMD) simulations revealed an increase in the aggregation of the oppositely charged proteins compared with the pure or similarly charged protein mixture.

Egg white proteins/lignin-DAP intumescent multilayer nanocoating for flame retardant cotton fabric

An environmentally benign nanocoating for flame retardant cotton was developed by pairing positively charged egg white proteins (EWP) and a negatively charged mixture of magnesium lignosulfonate (LS)–diammonium phosphate (DAP) solution. Egg white proteins are cheap and easy to prepare nitrogen-containing polyelectrolytes with strong char ability. Five bilayers of 0.5 % EWP3/(1 % LS–10 % DAP)4 add 6.8 % weight gain and impart self-extinguishing behavior to cotton on a vertical and horizontal flame test. This nanocoating, which creates a conformal cover of cotton fibers, reduces peak heat release by 60.1 %, total heat release by 59.3 %, and fire growth capacity up to 81.5 %. The results of this investigation show the potential of EWP to be used as a char-forming material with high nitrogen content in intumescent systems.

Experimental and numerical study of a condensation-driven dilution refrigerator

Dilution refrigerators are widely used in the fields of condensed-matter physics and quantum technology. For small cooling power applications, condensation-driven dilution refrigerator utilizes a condensation pump to achieve 3He cryogenic circulation and has advantages of compact structure, small 3He usage, and convenient operation. Related published research mainly focused on the overall system performances, and in-depth thermodynamics and fluid dynamics analyses are lacking. In this paper, a condensation-driven dilution refrigerator was experimentally studied and corresponding numerical simulations were performed. The results of experiments and simulations were compared and analyzed. In the experiments, lowest no-load temperature was 84.4 mK. The experimental cooling power was 1.91 μW @100 mK with a still heating power of 280 μW and the corresponding COP and second-law efficiency of the dilution cold cycle at 100 mK reached 0.0068 and 2.4% with the high temperature of 452 mK, respectively. The experiments also revealed that the charged mixture amount had a certain influence on the performance. With the help of simulations, the heat leak to the mixing chamber was estimated and certain intrinsic features of the cycle were enlightened. The heat leak and Kapitza resistance in the mixing chamber are possibly the main reasons for the differences between experimental and simulation results. Extended study based on the simulation also showed how flowrate variation changed the liquid column height difference and how the requirement of gas circulation and liquefaction set the limit on the minimum still temperature.

Effect of Chromium Carbide on the Structure and Properties of Weld-Deposited Metal Introduced into the Charge Mixture of a Flux-Cored Wire

Effect of Chromium Carbide on the Structure and Properties of Weld-Deposited Metal Introduced into the Charge Mixture of a Flux-Cored Wire

Regulations of the Influence of External Thermal Influences on Speed and Explosive Safe Combustion Modes of Pyrotechnic Nitrate-Metallized Mixtures with Metal Fluoride

A study was made of the regularities of the influence of the main parameters of external thermal effects (elevated heating temperatures and external pressures) on the rate and explosive modes of combustion development of compacted mixtures of magnesium, aluminum and sodium nitrate with fluoride additives metals for different values of technological parameters (excess ratio of the oxidizing agent, nature and content of the additive, dispersion of the components). The effect of technological parameters (ratio and dispersion of components, compaction coefficient, charge diameter, shell material, etc.) on the dependence of the burning rate of mixtures on elevated heating temperatures and external pressures was established; critical ranges of changes in these parameters are determined, the excess of which leads to premature explosive development of combustion of mixtures and fire hazardous destruction of products. On the basis of the research, methods were developed to prevent these destructions of products by regulating technological parameters at the stage of preparation of charge mixtures, which increases the stability of the combustion process of mixtures to external thermal influences. A database has been obtained on the burning rates of compacted mixtures of metal powders (Mg, Al), nitrate-containing oxidizer (NaNO3 ) and additives of inorganic substances (metal fluorides (LiF, NaF, BaF2 , SiF2 , SrF2 , AlF3 )) under conditions elevated heating temperatures and external pressures for various values of technological parameters, which makes it possible to determine the explosive modes of their combustion.

Design of an Optimum Compact EGR Cooler in a Heavy-Duty Diesel Engine towards Meeting Euro 7 Emission Regulations

Exhaust gas recirculation (EGR) has been an efficient emission treatment strategy employed in internal combustion engines (ICEs) to cope with NOx emission limits since the introduction of Euro 4 regulations for heavy-duty commercial vehicles. A portion of the exhaust gas is fed back into the intake port, replacing O2 in the fresh air with inert CO2 from the exhaust gas, resulting in a reduction in the combustion temperature and, hence, a reduction in NOx emissions. Considering the high exhaust temperature, this process increases the charge mixture temperature and degrades the volumetric efficiency of the engine. EGR coolers have been introduced as vital parts of EGR exhaust treatment systems with the aim of reducing the intake port temperature to increase volumetric efficiency and further reduce combustion temperatures. EGR coolers are heat exchangers (HXs) that generally employ engine coolant to reduce the EGR temperature with effectiveness values around 0.7~0.85 and downgrade with engine usage owing to soot deposition. Increasing the effectiveness of the EGR cooler has a positive effect on engine volumetric efficiency and reduces NOx, particulate matter (PM), and fuel consumption. The current study involved the design of a microchannel HX for a 500 PS heavy-duty Euro 6 diesel engine EGR cooler. The mechanical and thermal-hydraulic design calculations of the proposed HX were performed using Mathematica software. The optimum HX dimensions for the required boundary conditions were determined, and the performance of the EGR cooler was analyzed for the current and proposed options. Furthermore, Diesel-RK software was used to model the engine performance with NOx, PM, CO2 emissions, and fuel consumption predictions. The results show that the newly proposed microchannel HX design improves NOx, PM, and specific fuel consumption by 6.75%, 11.30%, and 0.65%, respectively.

Production of Zirconium-Niobium Alloys for Nuclear Reactors Fuel Rods via SHS Process

This article presents the results of studies of the self-propagating high-temperature synthesis (SHS) for obtaining zirconium alloys with niobium by the method of calcium-thermal reduction of nuclear-grade zirconium tetrafluoride in the presence of niobium powder. The optimal heating temperature of the initial charge and the methods of charge mixture with different calcium content were determined. The safety of the SHS process is ensured by the formation of an optimal combustion front of the mixture to remove the released high-pressure gases. A setup for the furnace reduction of zirconium alloys with charge preheating, discharge of molten products into molds of various designs, and control of the time and rate of slag and alloy crystallization has been tested. The required performance of the installation, the degree of transition of zirconium from salt into the alloy, and the purity, structure, and uniformity of the alloy were achieved.

Dilution-Induced Deposition of Concentrated Binary Mixtures of Cationic Polysaccharides and Surfactants.

This work investigates the effect of dilution on the phase separation process of binary charged polysaccharide-surfactant mixtures formed by two cationic polysaccharides and up to four surfactants of different nature (anionic, zwitterionic, and neutral), as well as the potential impact of dilution-induced phase separation on the formation of conditioning deposits on charged surfaces, mimicking the negative charge and wettability of damaged hair fibers. The results obtained showed that the dilution behavior of model washing formulations (concentrated polysaccharide-surfactant mixtures) cannot be described in terms of a classical complex precipitation framework, as phase separation phenomena occur even when the aggregates are far from the equilibrium phase separation composition. Therefore, dilution-enhanced deposition cannot be predicted in terms of the worsening of colloidal stability due to the charge neutralization phenomena, as common phase separation and, hence, enhanced deposition occurs even for highly charged complexes.

Experimental Investigation of Spark-Assisted Compression-Ignition with Ammonia-Hydrogen Blends

Carbon-free emissions and stable operation of ammonia-fueled internal combustion engines have been demonstrated in recent studies through combustion strategies suited to the fuel’s unique properties. High ignition energy and slow flame speed of ammonia are typically compensated for by hydrogen addition and/or enhanced ignition systems while the high octane rating of ammonia allows high compression ratio. The experimental study in this work investigates the performance of ammonia in spark-assisted compression-ignition (SACI) mode, where the cylinder charge is spark ignited and a subsequent auto-ignition event results in a faster burn and more ideal combustion phasing. The high-compression ratio engine was fueled by 100% anhydrous ammonia or blends with small quantities of hydrogen (2.5% and 5% by volume). Fuels were port-injected for a homogeneous intake charge mixture at stoichiometric equivalence ratio. Two different engine speeds were tested at several intake temperatures and spark timings. All cases showed an inflection point in the apparent heat release rate (AHRR) followed by more rapid rate of heat release, signaling the onset of auto-ignition. Blending hydrogen in the fuel benefited gross indicated mean effective pressure (gIMEP) at maximum brake torque (MBT) timing, but pure ammonia fuel was more stable across a wide range of spark timings and intake temperatures. Burn durations in the present study were similar to those of conventional SI engines fueled by gasoline indicating that the combustion enhancement of SACI compensated for the lower flame speed of ammonia. The control of SI percent, defined as the fraction of heat release before auto-ignition compared to the total heat release, is shown to be strongly related to the sensitivity of auto-ignition timing to spark timing. Unburned ammonia emissions are hypothesized to be primarily driven by unburned gases trapped in the crevices and are mitigated slightly through blending hydrogen in the fuel or by increasing intake temperature. However, the addition of hydrogen and increasing intake temperature led to increased nitric oxide (NO) emissions. Of primary concern because of its potent global warming potential, nitrous oxide (N2O) did not show a clear trend with fuel hydrogen content or intake temperature, but definitively increased for the higher engine speed.

Experimental study on startup characteristics of R290 air conditioner with low lubricant charge

As an A3 refrigerant, the charge of the natural refrigerant R290 in the refrigeration system is limited. The use of partially miscible lubricants and a reduction of the lubricant charge can effectively decrease the refrigerant charge. These two measures affect the startup dynamic characteristics of the compressor and the air conditioner. In this paper, variations in system temperature, pressure, and oil sump parameters during the cold startup process of a 1.5P R290 split inverter room air conditioner with different charges of PAG VG40 were experimentally measured under the rated cooling and low-temperature heating condition. The experimental results showed that the viscosity of the refrigerant/lubricant mixture of low lubricant charge (LLC) was lower than that of the normal lubricant charge (NLC), and the duration of low viscosity with LLC was longer. The low viscosity during startup is mainly due to the insufficient amount of lubricant in the oil sump. Three measures were proposed to alleviate the problem of low startup viscosity. Among them, the modification of the bearing cover effectively improved the viscosity of the LLC mixture, and the minimum viscosity of the bearing cover with LLC was even higher than that of the prototype with NLC. Furthermore, the bearing cover modification allows using a lower viscosity grade of lubricant for R290 rotary compressors.

Studying the mechanical properties of iron ore concentrate briquettes

This paper studies the properties of metallurgical briquettes of iron ore concentrate with coke screenings and liquid glass as a binder. The briquettes are produced by one-sided pressing in a closed die mounted on the plates of a vertical press with a force of 100 kN. The studies were carried out in the laboratory of Spidermash LLC. The following properties of briquettes were determined: density, impact strength and compressive strength (for green and dry briquettes). The functional dependences of the mechanical properties on 4 parameters are plotted, namely on charge mixture composition (the content of iron ore concentrate and coke), binder (liquid glass) percentage in the mixture, moisture content in the mixture, and charge mixture compacting pressure. The obtained experimental data are approximated with the use of a multiplicative model, with the application of the least squares method. Various analytical models for describing the behavior of the material to be briquetted are studied. It is concluded that the multiplicative model provides a more adequate description of the mechanical properties. The quality of the multiple regression model is assessed by the adjusted coefficient of determination. The significance of the regression equation is evaluated by the Fisher criterion, and the significance of the regression coefficients is evaluated according to Student. The mechanical properties of briquettes from iron ore concentrate with coke screenings, presented in the form of analytical dependencies, are necessary to assess the strength of the briquettes when designing the briquetting process. For example, it is necessary to take into account the change in yield during briquette transportation after briquetting. These dependences are also necessary for formulating and solving problems of pressing/briquetting of finely dispersed materials, including iron ore concentrate with coke screenings.