E. N. Selivanov

Forms of Zinc Found in Electric Steel Smelting Furnace Gas Cleaning Dust

Results are provided for a study of the elemental and phase composition of PAO Northern Pipe Plant electric steel smelting furnace gas cleaning dust. Dust particle shape and size are evaluated. X-ray microanalysis is used to determine the elemental composition of dust particles art local sampling points. It is shown that zinc in dust is found predominantly in calcium and magnesium ferrites, and also in spinels.

Forms of Zinc Occurrence in Blast-Furnace Dust

Results are given for a study of the phase and elemental composition of EVRAZ Nizhny Tagil Metallurgical Plant blast-furnace flue dust. An estimate of particle size is performed in a laser analyzer. Dust is represented by a set of particles of calcined charge with sizes from 1.5 to 1170 μm, with a median size of 82.9 μm. The elemental composition of the blast-furnace dust in local sampling points is determined by x-ray microanalysis. The dust consists of large iron oxide particles and fine particles containing MgO, CaO, SiO2, and Al2O3 in the form of complex silicates and ferrites, as well as inclusions of mechanically entrained coke. Zinc is present in form of oxide, sulphide and sulfate compounds as a surface layer on particles with increased thermal conductivity (FeOx). The zinc and sulfur contents in the layer (1–5 μm) reach 45 and 6%, respectively. The data obtained are useful for substantiating dust treatment processes.

Formation of Metallic Phase on Reducing-Gas Injection in Multicomponent Oxide Melt. Part 3. Separation of Ferronickel and Oxide Melt

Using the equations of physicochemical hydrodynamics and experimental results regarding the surface and interphase properties of metallic and oxide melts, the conditions in which metallic phase is formed in the bubbling of carbon monoxide through molten oxidized nickel ore are described. The critical dimensions of the gas bubble (Rb.cr) and the metal droplet (rd.cr) moving in oxide melt without change in size are determined in the range 1550–1750°C. It is found that Rb.cr increases slightly from 6.35 × 10–2 m at 1550°C to 6.58 × 10–2 m at 1750°C. With change in the droplet composition and the temperature, rd.cr varies from 2.1 × 10–3 to 2.9 × 10–3 m. The dimensions of the metal droplet formed at a single bubble during the reduction of nickel and iron from oxide melt are determined. As the content of nickel and iron oxides in the melt decreases with increase in the overall CO consumption, the nickel content in the ferronickel droplets falls from 89 to 18%, while the droplet diameter decreases from 1.4 × 10–3 to 8.0 × 10–4 m. The droplet mass falls correspondingly from 9.4 × 10–5 to 1.6 × 10–5 kg. The conditions in which the bubble–droplet system rises through the melt are determined. Over the whole range of temperature and Ni content, the bubble–droplet system begins to rise through the oxide melt when rd/Rb is less than 0.68–0.78. To assess the stability of the bubble–droplet system, with the given bubble and droplet dimensions, the parameters determining their joint motion are calculated. It is found that breakaway of the metal droplet from the bubble is not possible in pyrometallurgical systems. The formation of metal phase as a result of the bubbling of carbon monoxide through the oxide melt is described. In this process, the interaction of the oxide melt with the gas is accompanied by the formation of metal droplets, which become attached to the surface of gas bubbles and move to the surface of the oxide melt. Metal with 80–90% Ni is formed at first. With decrease in the nickel content in the oxide melt, its content in the metal declines to 20%. At the surface of the oxide melt, the metal droplets coalesce. When their diameter is greater than 5 × 10–3 m, they break away from the surface and fall to the bottom. If the falling drop collides with ascending bubble–droplet systems, they may coalesce with it or flow around it. On coalescence, the small droplets will be assimilated and rise to the surface. The breakaway force of the droplet from the bubble significantly exceeds the gravitational force on the droplet. Therefore, the bubble–droplet system is stable for all the size ratios considered.

Structure and thermal properties of the matte of the autogenous smelting of copper–zinc concentrates

The phase composition and the structure of the solidified mattes of the autogenous smelting of copper–zinc concentrates containing 49.8 and 61.0% Cu in Vanyukov’s furnace are studied. The forms of the main elements (Cu, Ni, Fe, S, O) and the accompanying impurities (Zn, Pb, As, Sb, Co, Sn, Au, Ag) in the rich matte are determined. The phase-transformation temperatures in cooling of the mattes in an inert or oxidizing gas atmosphere are found.

Kinetic features of breunnerite decarbonization

The decarbonization of breunnerite from talc waste is analyzed by thermogravimetry. The temperatures of thermal effects are determined, and kinetic models for the process are proposed to describe the mechanism of breunnerite decomposition. The unit cell parameters of breunnerite (MgxFe1–x)CO3 and the product of its decomposition, iron–magnesium oxide (Mg,Fe)O, are calculated. The apparent activation energies Ea of the decomposition are calculated using the Ozawa–Flynn–Wall and Kissenger model-free methods and the Avrami–Erofeev one-step model. Depending on the chosen model, the values of Ea range within 180–185 kJ/mol. The conditions of breunnerite roasting for the subsequent use of the obtained material in metallurgical processes are substantiated.

Magnetic properties of pyrrhotine with the hexagonal structure in the temperature range of 4–300 K

The magnetic properties of a synthetic sample of Fe0.94S pyrrhotine with the hexagonal crystal structure have been studied in the temperature range of 4–300 K. It has been found that the temperature dependence of magnetization has maxima in the temperature ranges of 30–35 and 122–133 K, which are explained by the Verwey-type transitions.

Calculation of the Reduction Rate of Copper, Nickel, and Cobalt from Oxide Melts by Carbon(II) Oxide

The kinetic equation for the calculation of the reduction rate, which takes into account the physicochemical properties of contacting phases, is derived under the assumption of the electrochemical nature of interaction between the reducing gas (CO) and the oxide melt. Satisfactory agreement of calculated and experimental data is shown by the example of the interaction of the oxide melt of the CaO-SiO2-Al2O3 system containing up to 6.0 wt % MenOm (NiO, CoO, Cu2O) blown by the gas phase with partial pressure PCO = (0.4–5.0) × 102 MPa at T = 1623 K.

Anodic behavior of the NiO-Fe2O3-Cr2O3-Cu composite during the low-temperature electrolysis of aluminum

In order to fabricate oxide-metallic composites with the composition 25.3NiO-41.2Fe2O3-13.5Cr2O3-20.0Cu (wt %), the temperature and duration of sintering (1350°C, 30 min) that ensure the formation of the solid solution of chromium oxide in nickel ferrite have been determined. This material is tested as an anode for the electrolysis of the low-temperature solution with the composition 12.0NaF-36.8KF-51.2AlF3 (wt %), which was saturated with Al2O3 (t = 800°C). The amount of gaseous oxygen evolved on the anode was measured. It is shown that the main reaction on an anode at current density i = 0.015–1.0 A cm−2 is the oxidation of oxygen-containing anions from a melt with the formation of gaseous O2 and a substantial increase in the oxidation rate of the composite anode is observed at i > 1.0 A cm−2. The voltage across the electrolyzer (4.5 ± 0.5 V) and the anodic potential (2.43 ± 0.2 relative to the Al reference electrode) during a prolonged experiment (for 89 h, i = 0.4 A cm−2) indicate a stable and acceptable electrical conductivity of the material, while the dissolution rate, which was calculated by the weight loss (0.6 kg/yr) and volume loss (0.7 cm/yr), satisfy the requirements to inert anodes.

Thermodynamic Simulation of the Oxidation Processes of Ag2Se by NaNO2

The thermodynamic simulation of the oxidation processes of silver selenide by reagents such as NaNO2, NaNO3 and NaOH during their heat treatment has been conducted. Gibbs energy of silver selenide oxidation reactions has been estimated. It is shown as a reagent–oxidant of silver selenide it is rationally to use a mixture of sodium nitrite and sodium hydroxide. Oxidation of silver selenide during heat treatment together with sodium nitrite and sodium hydroxide is accompanied by the formation of soluble compounds such as Na2SeO3 and Na2SeO4, silver being passed in the metallic state. Separation coefficients characterizing oxidation efficiency and the level of selenium transfer in soluble compounds were estimated. Using the data the separation method of materials containing selenides by means of their sintering with sodium-containing reagents is proposed. The method is based on the transfer of selenium in the water-soluble compounds followed by leaching, precious metals being the elemental state. The products obtained are suitable for the production of selenium and precious metals by traditional technologies.

Phase Transformation in Granular Alloys of Cu2S-Ni3S2-Na2S System

The effect of Na2S on the phase composition and microstructure of tempered Cu2S-Ni3S2 alloys was studied by X-ray diffraction, optical microscopy and electron probe microanalysis (EPMA). It was found that quick crystallization of the sulfide melt leads to separation into two phases - Ni3S2 and a solid solution of Cu2S with Na2Cu4S5, moreover, nickel is concentrated in large particles and copper – in small ones. In contrast to the fine dendrite solidification of granular Cu2S-Ni3S2 alloys, in the ternary system there is a well-defined two-phase microstructure with rounded borders of the interface. Friability and a low microhardness of Cu2S - Na2Cu4S5 solid solution provide an autodecomposition of the sulfides melt by quenching into water (granulation). The degree of separation of copper and nickel depends on the overheating temperature and a quantity of Na2S in melt. The results can be used to hydrometallurgical processing of copper-nickel convert matt.