Oxidation Of Impurities Research Articles

ВИЗНАЧЕННЯ РАЦІОНАЛЬНОГО СКЛАДУ РЕАГЕНТІВ ДЛЯ ЗДІЙСНЕННЯ ПРОЦЕСІВ КОМПЛЕКСНОГО РАФІНУВАННЯ РІДКОГО ЧАВУНУ НА ЕТАПІ ПОЗАПІЧНОЇ ОБРОБКИ

The paper is devoted to the issue of complex treatment of cast iron. Possible chemical transformations that can occur when reagents are introduced into liquid cast iron are analyzed, and expressions for calculating the equilibrium constant Kr, depending on temperature, are obtained. Graphical dependences of the equilibrium constants on temperature for these reactions were also constructed. The calculations were performed for desulfurization reactions, carbonate dissociation reactions, oxidation of cast iron impurities due to interaction with carbon dioxide, and for the interaction of liquid cast iron components with iron oxides. Thermodynamic calculations have established that the mixture for the complex refining of liquid cast iron at the out-of-furnace treatment stage should belong to the chemical system CaO - Na2CO3 - FeO(Fe2O3) - Al. The specific ratio of components is determined by the required refining result.

Study of the influence of corona discharge on the efficiency of oxidation of organic impurities using ozone

Purification of air containing volatile organic compounds is an important task in many industries. This article examines the effect of corona discharge on the efficiency of the oxidation of organic mixtures. As a result of our research, we found that the consumption of ozone for the oxidation of various components of the mixture is approximately the same. This means that other particles, including water vapor, also take part in oxidation reactions.

Aqueous electrochemical delithiation of cathode materials as a strategy to selectively recover lithium from waste lithium-ion batteries

Lithium recovery from end-of-life Li-ion batteries (LIBs) through pyro- and hydrometallurgical recycling processes involves several refining stages, with high consumption of reagents and energy. A competitive technological alternative is the electrochemical oxidation of the cathode materials, whereby lithium can be deintercalated and transferred to an electrolyte solution without the aid of chemical extracting compounds. This article investigates the potential to selectively recover Li from LIB cathode materials by direct electrochemical extraction in aqueous solutions. The process allowed to recovering up to 98% of Li from high-purity commercial cathode materials (LiMn2O4, LiCoO2, and LiNi1/3Mn1/3Co1/3O2) with a faradaic efficiency of 98% and negligible co-extraction of Co, Ni, and Mn. The process was then applied to recover Li from the real waste LIBs black mass obtained by the physical treatment of electric vehicle battery packs. This black mass contained graphite, conductive carbon, and metal impurities from current collectors and steel cases, which significantly influenced the evolution and performances of Li electrochemical extraction. Particularly, due to concomitant oxidation of impurities, lithium extraction yields and faradaic efficiencies were lower than those obtained with high-purity cathode materials. Copper oxidation was found to occur within the voltage range investigated, but it could not quantitatively explain the reduced Li extraction performances. In fact, a detailed investigation revealed that above 1.3 V vs. Ag/AgCl, conductive carbon can be oxidized, contributing to the decreased Li extraction. Based on the reported experimental results, guidelines were provided that quantitatively enable the extraction of Li from the black mass, while preventing the simultaneous oxidation of impurities and, consequently, reducing the energy consumption of the proposed Li recovery method.

Effect of oxygen on trace impurities in extremely pure metal ingots used for realising ITS-90 fixed point temperatures

The International Temperature Scale of 1990 (ITS-90) provides a scheme for calibrating thermometers which is largely based on the freezing points of pure metals such as indium, tin, zinc, aluminium and silver. The existence of trace impurities in pure metals results in uncertainties in the realization of these freezing points. Several methods such as the sum of individual estimates (SIE) and overall maximum estimate (OME) are used to assess the uncertainties due to the presence of impurities. However, it is becoming evident that the oxidation of impurities results in their precipitation, which means that these insoluble oxides no longer play a significant role in the elevation or depression of the freezing temperature. Hence the conventional correction techniques may overestimate the magnitude of the effect. In this study, the thermodynamic modelling software MTDATA was used to evaluate the effect of oxygen on selected impurities in In, Sn, Zn, Al and Ag by calculating the binary impurity-metal phase diagram in the presence of specific amounts of oxygen. It was found that oxygen has a significant effect on many of the systems studied. The most significant effect was observed in the Ag system, and then, in decreasing order of significance, In, Sn, Zn and Al.

MODELLING THE PROCESS OF OXIDISING IMPURITIES IN A METAL BATH USING COHERENT NOZZLES

The main task of the oxygen-converter process is to produce a liquid metal semi-product with specified properties. It is directly related to the optimization of the blowing mode and devices responsible for the process and technical and economic parameters of melting. The effectiveness of the organization of the process of introducing oxygen into the melt, and, accordingly, assimilation by the metal bath basically depends on the design of the lance nozzles. In electrometallurgy, coherent nozzles are used to improve bath mixing performance and activate processes (a central nozzle for supplying oxygen and a peripheral one surrounding it for supplying gas as a fuel that forms an enveloping flame). Therefore, the authors conducted a study of the influence of coherent top nozzles on the oxidation of impurities in the metal bath under the conditions of the use for the oxygen-converter process (with oxygen supplied to both parts of the nozzle). A high-temperature simulation of the oxidation process of Si from hot metal was carried out by using a Cu-Zn melt (1%) when comparing blowing through a nozzle of a coherent type with a peripheral part of 75% and a conventional nozzle of the equivalent diameter.

A review of thermal spray coatings for protection of steels from degradation in coal fired power plants

Abstract In coal fired power plants, the metallic surfaces such as boiler tubes, walls of combustion chambers and other parts degrade by corrosion, erosion and abrasion. It happens due to the hot gaseous environment, steam oxidation and presence of hard minerals and impurities in the coal. It is very important to protect these surfaces from material loss, otherwise it would lead to increased repair and maintenance cost along with decreased plant efficiency. In this paper, the role of thermal spray coatings has been studied for the protection of different steel grades exposed to such degrading conditions at high temperatures, in coal-based power plants. A comprehensive study has been done by analysing and comparing the work done by various researchers. Some recent advancements related to coating materials and modification in coating techniques have also been studied. This paper would be helpful for the researchers to get an idea for selecting an appropriate substrate material and coating material for industrial applications.

Pilot tests of processing technologies of process solutions of copper production by ozonation

At the copper-smelting plant of JSC Almalyk MMC, technological solutions are formed containing valuable components in copper production. This article presents the pilot tests of the technology for processing technical solutions of copper production using ozonation. As a result of studies on the oxidation of impurities in wastewater, the process parameters were determined - ozone consumption, process duration, pH, and process temperature, which made it possible to purify and return wastewater to production also receive a sludge of metal compounds. Based on the results obtained, a technology for ozonation of copper production wastewater has been developed. The developed technology was recommended for implementation at JSC Almalyk MMC.

Modeling of hydrogen sulfide removal under biomethane production in the concept of renewable energy potential growth of Ukraine

Today, the global trend in the development of renewable energy sources is the implementation of integrated processing of organic waste with the production of biogenic gases such as biomethane. In this case, an essential focus is the study of biogas purification processes to methane. This paper focuses on the process of modeling biochemical purification of biogas from hydrogen sulfide to develop the direction of biomethane production. Simulation of hydrogen sulfide bio-oxidation process with the use of granulated carrier based on phosphogypsum was conducted using experimental data from previous studies to verify the adequacy of the proposed mathematical model. Thus, to implement the process of phosphogypsum utilization in technological systems of biogas purification, it is important to consider the level of bioactivity in the immobilization of bacteria on the loading surface of phosphogypsum and the degree of biotransformation of phosphogypsum components in the oxidation of carbon dioxide and hydrogen sulfide impurities to achieve the highest ecological effect. Also, the use of overlay visualization allowed to form the main clusters of development of research potential in the field of biogas technologies for Ukraine.

Структура и механизмы образования наноразмерных пленок примесного металла кобальта и никеля в монокристаллах LiF и MgF-=SUB=-2-=/SUB=-

It is investigated the thermal etching of LiF and MgF2 crystals with cobalt and nickel impurities by means of scanning electron microscopy and atomic force microscopy with using decorating. It is shown that impurity inclusions leave the crystal from dislocations. The differences between of thermal etching in vacuum and air atmosphere take place. The crystallographic oriented terraced etch pits are formed after exit of impurities from dislocations. The square thermal etch pits are formed after thermal etching at 750°C in air. The surface impurity nanoscale film is formed at thermal etching. The oxidation of surface impurities observed at thermal etching in air atmosphere or in residual air atmosphere.

Enhanced photocatalytic activities of NiS decorated reduced graphene oxide for hydrogen production and toxic dye degradation under visible light irradiation

Semiconductor nanoparticles have extensively studied for a decade on photocatalytic hydrogen production and remediation of toxic pollutants due to their better activities at nano regime and quantum efficiency. The present study reports on the preparation of NiS nanoparticles decorated reduced-graphene oxide nanocomposite (RGO) as an effective visible photo-catalyst for H2 production and a toxic organic dye degradation. NiS and RGO were synthesized by hydrothermal and modified Hummer's method, respectively. The synthesized nanocomposite was thoroughly investigated for its structural and optical properties by various techniques such as XRD, UV–Vis-DRS, FT-IR, Raman, FE-SEM, HR-TEM, EDAX, XPS, AFM, BET and XPS. The morphology indicates sphere like particles of NiS dispersed on the surface of the RGO layers. Raman spectral analysis of the nanocomposite materials showed the ID/IG intensity ratios in RGO-NiS (1.00) and GO (1.08) which confirmed that the prepared nanocomposite material has lesser defects. The specific surface area of the prepared nanocomposite was found to be 142.68 m2 g-1. Different experimental parameters such as effect of pH, loading of catalyst and kinetics of dye photodegradation and H2 production were optimized to maximize the photocatalytic activities of the nanocomposite materials. It was observed that maximum % of dye degradation occurred at neutral pH with catalyst loading of 10 mg/10 mL of 10 ppm dye and exhibited 99% degradation under visible light irradiation for 6 h. The prepared nanocomposite material was also employed for H2 production from water through photo-splitting method and it resulted in a maximum hydrogen production as 1368 and 2946 μmol g−1h−1 for RGO-NiS and RGO-NiS/Pt respectively with loading of 100 mg catalyst. It was observed that 4.6 and 2.19 fold increase in hydrogen production with pristine NiS and RGO-NiS nanocomposite respectively with good reusability. Hence, the prepared visible active RGO-NiS nanocomposite could be a suitable catalyst for the oxidation of organic impurities and hydrogen generation from water.

Anodic Dissolution of Non-Ferrous Metals in a Glycerate-Alkali Electrolyte

Studies have been conducted to assess the possibility of refining a lead collector containing precious metals, with the aim of obtaining lead using an economically viable and environmentally safe technology. A method of electrochemical selection in an alkaline glycerate electrolyte is proposed. The behavior of lead, silver and “silver crust” during anodic polarization in glycerate electrolyte was studied using the potentiodynamic method. “Silver crust” – type alloy of the following composition were used in this study, (wt.) %: 77.9 Pb, 12.76 Zn, 3.53 Ag, 0.50 Cu, Sb 0.90. The studies were carried out using the method of a rotating disk. Studied the patterns of anodic oxidation of lead and impurities in alkaline-water-glycerate electrolytes, depending on the concentration of sodium hydroxide and glycerol in the electrolyte, the potential sweep rate.

Про механізм окислення домішок металевого розплаву при виплавці конвертерної сталі в великовантажних конвертерах

Про механізм окислення домішок металевого розплаву при виплавці конвертерної сталі в великовантажних конвертерах

Electric resistence hysteresis of platinum filament in chilled air/hydrogen mixtures

Ignition of gaseous combustible mixtures on catalytically active hot solid surfaces has numerous applications in many industrial processes and is a complex process that involves close interaction between surface processes and transfer processes in the gas mixture. In this paper, stable and critical states catalytic oxidation of hydrogen impurities in air on a platinum filament are considered. It is shown that filament temperature and its resistance depending on the mixture temperature and hydrogen concentration are of the hysteresis features. Within this hysteresis region, it is possible to achieve the catalytic combustion mode of hydrogen as a result preheating the catalyst filament above a certain critical value. The dependence of the limiting hydrogen's concentration on catalyst filament's diameter, above which is observed in the cold gas mixture self-sustaining catalytic combustion without electric current.

On the high-temperature degradation mechanism of ZnO-based thermoelectrics

The stability and reproducibility of the electric properties in n-type doped ZnO represent known bottlenecks towards potential thermoelectric applications. The degradation is promoted by the vanishing of the electronic defects on oxidation and irreversible exsolution of the phase impurities. This work proposes a microstructural mechanism showing that these processes take place mainly in the pores and highlighting the necessity for high densification of ZnO-based thermoelectrics to ensure more stable operation. The electrical performance was monitored at various temperatures, followed by a detailed microstructural analysis. The evolution of the electrical conductivity and Seebeck coefficient confirm that the degradation is related to a gradual decrease in the charge carrier concentration rather than to the effects suppressing their mobility. The results suggest that the donor exsolution may promote an increase or decrease of the power factor, guided by the self-optimization of the charge carrier concentration.

Low-Temperature Oxidation of Hydrogen Sulfide and Formaldehyde Pollutants in Humid Air by UV Radiation at 184.95 and 253.65 nm.

An experimental study of the oxidation of hydrogen sulfide and formaldehyde impurities in humid air by ultraviolet radiation at wavelengths of 184.95 and 253.65 nm has been carried out at a pressure of 1 atm, an initial temperature of 20 °C, a relative humidity of 90%, and a flow rate of the gas mixture of 4920 m3/h. The initial concentrations of hydrogen sulfide and formaldehyde in air ranged from 8 to 20 and from 2.9 to 7.2 mg/m3, respectively. The photochemical kinetic mechanism was proposed for a numerical simulation of the low-temperature photooxidation of hydrogen sulfide and formaldehyde pollutants as well as the formation of ozone in humid air. The mechanism consists of 7 and 4 photochemical reactions initiated by UV radiation at wavelengths of 184.95 and 253.65 nm, respectively, and 62 reversible individual chemical reactions involving 32 chemical species (radicals, atoms, and molecules). The obtained results of numerical simulation are in good agreement with experimental data.

Spinel cobalt(II) ferrite-chromites as catalysts for H2O2 decomposition: Synthesis, morphology, cation distribution and antistructure model of active centers formation

Cobalt (II) ferrite-chromites CoCr2-xFexO4 (x = 0.0 ÷ 2.0, step is 0.2) with spinel structure have been synthesized using sol-gel method with citrate metal-polymer precursor. The relations between structural, morphological and catalytic properties of the mixed spinels have been studied. The CoCr2-xFexO4 powders were analyzed using X-ray diffraction analysis, Mössbauer spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive analysis and Brunauer–Emmett–Teller (BET) methods. The average crystallite size was calculated using the Williamson-Hall and size-strain plot methods. Increase of Fe content resulted in increase of the crystallite size from 10 nm (CoCr2O4) to 35 nm (CoFe2O4). Chromium ions were located mainly in octahedral sites, whereas the cobalt and ferric ions were distributed between the octahedral and tetrahedral sites. The lattice parameter was dependent mostly on the octahedral site radius. Superparamagnetic properties of the nanoparticles were described by two-level relaxation model. The samples with a high content of chromium (III) have highly porous structure. Porosity of the samples was decreased with increasing the Fe content. IR spectra contain two peaks corresponding to two characteristic sites in the cubic spinel structure. The mixed ferrite-chromite spinels have catalytic activity in decomposition of hydrogen peroxide. Rate of H2O2 decomposition in the presence of cobalt (II) ferrite-chromite NPs corresponds to the first-order kinetic model. Within 25 min, the decomposition degree is 76.6% with the most active CoFe2O4 sample. Catalytic activity of the samples depends on two factors: the specific surface area and the surface active sites. Antistructure modeling revealed that the tetrahedral Fe(III) sites have electron acceptor properties. The formed Fe(II) ions are active centers in the Fenton-like processes. Probably, the red-ox pairs Co2+/Co3+ in the spinel lattice promote catalytic activity due to acceleration of electron transfer. The spinel cobalt (II) ferrite-chromites are promising catalysts for oxidation of toxic organic impurities in wastewaters with using H2O2.

Anodic Dissolution of Non-Ferrous Metals in a Glycerate-Alkali Electrolyte

Studies have been conducted to assess the possibility of refining a lead collector containing precious metals, with the aim of obtaining lead using an economically viable technology. Studied the patterns of anodic oxidation of lead and impurities in alkaline-water-glycerate electrolytes, depending on the concentration of sodium hydroxide and glycerol in the electrolyte, the potential sweep rate.

МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ КОНВЕРТЕРНОЇ ПЛАВКИ З УРАХУВАННЯМ ДИНАМІКИ ПРОЦЕСУ ЗНЕВУГЛЕЦЮВАННЯ

The oxygen converter is one of the most important metallurgical objects of automation. Improvement of its control is necessary to obtain steel with a given temperature and composition at maximum efficiency of the heat. However, the task of fully automating the process is extremelycomplex and requires knowledge of the laws governing the influence of many factors on the technological process: physicochemical, gas–hydrodynamic, and others that have not been sufficiently studied to date. The physicochemical basis of steel production in the converter is formed by the processes of oxidation of pig iron impurities, and primarily carbon oxidation. Despite the large amount of research devoted to the problem of metal carbon oxidation, a significant number of questions in this area remain little studied. The well–known scientific theory that decarburization at a low carbon content is controlled mainly by its mass transfer does not fully explain all the features of the process. In this regard, the problem arose of conducting additional scientific studies of the dynamics of carbon oxidation, especially at its low concentration.The work describes the techniques that describe the decarburization process of converter steel. A model for calculating the decarburization rate and the dynamics of the carbon content in the converter bath during purging was built. It has been established that the developed dynamicmodel of carbon oxidation is adequate to the processes occurring in the converter bath. The model allows continuous monitoring and regulation of the most important parameters of the metal by means of controlling an oxygen lance, determining the rates of decarburization, changes intemperature and oxidation of iron in the bath, as well as the degree of afterburning of CO in CO2 in the converter cavity.

The Behavior of Low Molecular Weight Organic Carbon-14 Containing Compounds in Contaminated Groundwater During Denitrification and Iron-Reduction

Aqueous low molecular weight organic carbon-14 (14C) substances can be formed by the oxidation of carbide and impurities within nuclear fuel cladding. During reprocessing and interim storage 14C-labeled organic compounds may leak to the shallow subsurface environments at nuclear facilities where denitrifying and iron reducing zones can exist. 14C-labeled organic compounds (acetate, formate, formaldehyde and methanol) were used as electron donors in microcosm experiments, under both denitrification and iron reduction, using glacial outwash sediments and groundwater composition representative of the Sellafield nuclear reprocessing site, UK. In denitrifying microcosms, <6% of the initial 14C-DOC remained 15 days after injection into the microcosm irrespective of the electron donor; with concurrent 14CO2 (g) production. Lack of removal in sterile controls suggests that 14C-organics were metabolized by microorganisms. Under iron-reducing conditions both 14C-carboxylates were removed from solution rapidly, but some formaldehyde and methanol remained in solution 32 days after injection into the microcosm so there is potential that a proportion of 14C-formaldehyde and 14C-methanol may persist for longer in subsurface environments.

Diffusive Steel Scrap Melting in Carbon-Saturated Hot Metal-Phenomenological Investigation at the Solid⁻Liquid Interface.

The oxygen steelmaking process in a Linz-Donawitz (LD) converter is responsible for more than 70% of annual crude steel production. Optimization of the process control and numerical simulation of the LD converter are some of the current challenges in ferrous metallurgical research. Because of the process conditions and oxidation of impurities of the hot metal, a lot of chemical heat is generated. Therefore, steel scrap is charged as a coolant with the economical side aspect of its recycling. One of the more complex aspects is, among others, the dissolution and melting behaviour of the scrap in carbon-saturated hot metal. Heat and mass transfer act simultaneously, which has already been investigated by several researchers using different experimental approaches. The appearances at the interface between solid steel and liquid hot metal during diffusive scrap melting have been described theoretically but never investigated in detail. After an experimental investigation under natural and forced convective conditions, the samples were further investigated with optical microscopy and electron probe microanalysis (EPMA). A steep carbon concentration gradient in the liquid appeared, which started at an interface carbon concentration equal to the concentration on the solid side of the interface. Moreover, the boundary layer thickness moved towards zero, which symbolized that the boundary layer theory based on thermodynamic equilibrium was not valid. This fact was concluded through the prevailing dynamic conditions formed by natural and forced convection.