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Date submitted2023-01-12
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Date accepted2023-06-20
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Date published2023-07-19
Improvement of energy efficiency of ore-thermal furnaces in smelting of alumosilicic raw materials
The issues of energy saving in pyrometallurgical production during processing of mineral raw materials in ore-thermal furnaces are particularly important for the development of new energy-efficient technologies. The reduction of the specific power consumption during melting at different stages of heating and melting of charge materials when modeling is related to obtaining kinetic curves in the process of kyanite concentrate regeneration in polythermal conditions. Based on practical data of carbo-thermal reduction the mathematical modeling of reduction processes from alumosilicic raw materials – kyanite was carried out. In this work, the nonisothermal method based on a constant rate of charge heating (i.e. a linear dependence between time and temperature) was used for the reduction of kyanite charge, which saves electrical energy. The experiments were carried out on a high-temperature unit with a heater placed in a carbon-graphite crucible. Based on the obtained kinetic dependences of nonisothermal heating of enriched kyanite concentrates in plasma heating conditions we obtained a number of kinetic anamorphoses of the linear form which point to the possibility of describing the reaction rate using the modified Kolmogorov – Erofeev equation for given heating conditions and within a narrow temperature range. The complex of mathematical modeling makes it possible to create a control algorithm of technological process of reduction of kyanite concentrate to a metallized state within the specified temperature range for the full flow of reaction exchange and to reduce the specific power consumption by 15-20 %. With the help of the received kinetic dependences, taking into account the thermodynamics of processes and current state of the art it is possible to create a universal thermal unit for the optimal carbothermal reduction of charge to a metallized state (alloy) with minimum power inputs compared to existing technologies.
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Date submitted2020-10-22
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Date accepted2021-03-02
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Date published2021-04-26
Dynamic simulation of industrial-scale gibbsite crystallization circuit
- Authors:
- Vladimir O. Golubev
- Tatyana E. Litvinova
Population balance model is crucial for improving the method of aluminum hydroxide massive crystallization and enhancing the quality of control over industrial precipitation trains. This paper presents the updated population balance model, which can be used for simulation of industrial-scale precipitation. Processes of birth-and-spread and particle breakage are considered integral parts of the precipitation process along with secondary nucleation, growth and agglomeration of particles. The conceptual difference of the proposed system of equations is its ability to reproduce the oscillatory process that occurs in precipitation circuits as a result of cyclic changes in the quality of the seed surface. It is demonstrated that self-oscillations can occur in the system without any external influence. The updated model is adjusted and verified using historical industrial data. The simulation of seed-recycle precipitation circuit showed an exact correspondence between the calculated dynamic pattern of changes in particle size distribution of aluminum hydroxide and the actual data.
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Date submitted2019-04-28
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Date accepted2019-06-28
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Date published2019-10-23
Determination of Optimal Fluorine Leaching Parameters from the Coal Part of the Waste Lining of Dismantled Electrolytic Cells for Aluminum Production
- Authors:
- N. V. Nemchinova
- A. A. Tyutrin
- V. V. Somov
When aluminum is obtained by electrolysis of cryolite-alumina melts when the baths are sent for capital repairs, a solid technogenic product is formed – waste lining of electrolytic cells (WLEC). The volume of formation of WLEC is 30-50 kg per 1 ton of aluminum. Currently, it is mainly stored at landfills near industrial enterprises, causing harm to the environment. However, this technogenic raw material contains valuable components (fluorine, aluminum, sodium) that can be extracted to produce fluoride salts, which are in demand during the electrolytic production of aluminum. The objects of research were samples of the coal part of the waste lining of dismantled S-8BM (E) type electrolytic cells of «RUSAL Krasnoyarsk» JSC (Krasnoyarsk) of RUSAL company. According to the X-ray experiment diffraction analysis (using a Bruker D8 ADVANCE diffractometer) of the phase composition of the samples, it was found that the main fluorine-containing compounds are cryolite, chiolite, sodium and calcium fluorides. The total fluorine content in the studied samples averaged 13.1 %. We conducted studies on the leaching of fluorine from WLEC with a solution of caustic alkali (NaOH concentration – 17.5 g/dm 3 ). The process was carried out in a mechanically agitated reactor using a BIOSAN MM-1000 top drive laboratory stirrer with a two-blade nozzle. By the method of mathematical planning of a three-factor experiment, the mutual influence of three leaching conditions on the optimization parameter was established – the extraction of fluorine in solution (in percent). The maximum recovery of fluorine from WLEC to the leach solution averaged 86.4 % and was achieved with the following indicators:processtemperature–95 ° C, the ratio ofliquidtosolidphase–9:1,duration– 210 min.
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Date submitted2018-05-06
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Date accepted2018-07-17
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Date published2018-10-24
Obtaining intermetallic compounds in Al–Ti–Zn system
- Authors:
- V. V. Kaminskii
- S. Y. Petrovich
- V. A. Lipin
Binary intermetallic compounds – titanium aluminides (TiAl, Ti 3 Al) – when added to the alloys, significantly increase their strength and special properties. The most promising direction to produce intermetallic compounds are mechanochemical technologies, including mechanical alloy building. Mechanical alloying makes it possible to introduce much smaller particles into the metal matrix than can be achieved using standard powder metallurgy technologies. In addition to mechanical synthesis, aluminum-based intermetallic compounds were produced by self-propagating high-temperature synthesis (SHS) of solid chemical compounds. The synthesis was carried out according to a multistage scheme: preparation of titanium and aluminum powder, mixing; synthesis of the Al 3 Ti intermetallic compound by the SHS method in vacuum followed by mechanical activation of stoichiometric charges. The aim of the research was to study the dynamics of the development of nanodispersed phases in the process of synthesis during mechanical alloying. The power absorbed by the unit mass of the material for different processing times of the charge was calculated. When the level of the specific power (dose) of mechanical treatment was 3.5 kJ/g, the maximum content of intermetallic compound in the resulting material was achieved. Based on calculations and the data obtained during X-ray phase analysis, the dependence of the change in the content of ternary intermetallic compounds in the final product on the absorbed power was determined. As a result of the studies using raster electron microscopy and X-ray analysis, it was found that mechanical alloying of nanostructured intermetallic compounds Ti 4 ZnAl 11 and Ti 25 Zn 9 Al 66 with the size of nanodisperse phases less than 12 nm in the Al–Ti–Zn system, the weight ratio of proportion of the latter reaches 74 %.
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Date submitted2017-10-31
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Date accepted2018-01-01
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Date published2018-04-24
Peculiarities of formation and growth of nanodispersed intermetallic strengthening inclusions in rapidly-solidified alloys of Al–Mg–Zr–X-system
- Authors:
- D. I. Budelovskii
- S. Yu. Petrovich
- V. A. Lipin
The paper is devoted to the influence of the fourth element on the microstructure of the rapidly-solidified alloys of the Al–Mg–Zr-system. Alloys were additionally doped with high-melting-point metals Ti, Hf, W, and Nb. In the structure of all samples in the immediate area of the cooled surface, uniformly distributed intermetallic inclusions of several nanometers in size were detected. Such a structure can be represented as a dispersion-strengthened composite. A quantitative metallographic analysis was carried out to quantitatively describe the structure of the obtained particles of the cooled melt. The obtained rapidly-solidified alloys can be described as dispersion-strengthened composite materials with the aluminum-magnesium alloy matrix and the intermetallic particles strengthener. Depending on the alloying component, these particles differ in shape (spheres, plates, agglomerates) and in size (from 200 nm when alloying with Hf and W up to 1.2-1.5 μm with Ti and Nb alloying). The X-ray phase analysis (XPA) showed that in the studied alloys of the Al–5Mg–1.2Zr–(0.5÷2.0)X-system, high cooling rates of melts lead to the formation of new intermetallic compounds that are absent in equilibrium systems. The example of an alloy with hafnium additive shows that an increase in the content of the alloying component (from 0.5 to 2 % by mass) leads to an increase in the volume ratio of intermetallic inclusions (from 5 to 12.8 %). At the same time, their shape and average size remain unchanged. The additional alloying component will improve the mechanical characteristics of aluminum alloys by increasing the recrystallization threshold of a rapidly-solidified alloy.
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Date submitted2017-08-30
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Date accepted2017-11-23
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Date published2018-02-22
Basic provisions and problems of ELW technology for the manufacture of aluminum-magnesium alloys constructions
- Authors:
- E. I. Pryakhin
- N. I. Sharonov
Existing problems of electron beam welding of aluminum alloy constructions are considered. For research purposes, the aluminum-magnesium alloy of grade 1561 up to 60 mm thick was used. The thermal field in the heat influence zone is studied experimentally and analytically on the basis of the finite element method (the «Ansys» program). The effect of electron beam movement (scanning) influence on the quality of welded connections and the surface of the welded parts was studied. On the basis of metallographic studies and mechanical tests of welded metal, it is proved that high quality of welded joints is ensured when the beam moves along a curve of the «compressed brackets» shape. A special generator is designed to control the electron beam, which allows to implement a new type of scanning (compressed brackets). The fundamentals of welding technology for alloy 1561 up to 60 mm thick are outlined. Specific recommendations are given, and two new methods are proposed that will allow the successful use of the developed technology in factories in the production of new products and in the repair processes. Examples and analysis of thermal cycles obtained by calculation and experimental method are given. The patterns of heat distribution along the trajectory of the beam movement for different types of scanning are established. The main types of defects in the formation of the welded joints and those formed in the metal during crystallization are considered. Their interrelation with the parameters of the welding mode is shown.
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Date submitted2015-08-25
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Date accepted2015-10-24
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Date published2016-04-22
The modern technology of drilling and casing of well during the exploration of gas hydrates
- Authors:
- N. I. Nikolaev
- Lyu Tyanle
In the paper, the perspectives of exploration and completion of gas hydrate fields and the drilling problems in the gas hydrates of the northwest china are studied. It has been established, that the main reasons of complications in the Muli field are the secondary hydrate formation on the walls of the well and drilling assembly and ice formation inside the set cement during the well drilling and completion in permafrost. It has been shown, that in the areas with permafrost during the drilling of the layers containing gas hydrates, temperature and pressure changes can lead to the dissociation of hydrates. At the same time, pressure increase in the annular space due to the gas release, can lead to the secondary formation of gas hydrates, drill string stuck, ceasing of drilling fluid circulation, which is the reason of serious trouble in the wellbore. The results of the research on the development of drilling fluids compositions, which lower the drilling troubles of permafrost, are presented. Comparative experiments have been conducted to evaluate the effectiveness of thermodynamic and kinetic inhibitors, which prevent the repeated hydrate formation. It has been established, that the kinetic inhibitors have the clear advantage: they have good inhibiting effects even with low amounts of additives. In the laboratory conditions, the researches have been conducted to evaluate the phase equilibrium of gas hydrates during their reaction with the water solutions, containing kinetic inhibitor PVP. A thin clay drilling mud has been developed on the water base, providing the holding of the temperature in the level of –2 °С and its effectiveness for the gas hydrate fields in the PRC has been shown. Casing effectiveness of unstable rocks during the drilling in the conditions of negative temperatures inside the well largely depends on their physical-mechanical properties, composition and the technical indicators of cement materials. The authors suggest the composition of quick-setting cements based on aluminum binding materials. It has been established, that the analyzed compositions have the ability to considerably improve the results of cementing.
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Date submitted2015-07-14
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Date accepted2015-09-27
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Date published2016-02-24
Chemical and technological mechanisms of a alkaline aluminum silicates sintering and a hydrochemical sinter processing
- Authors:
- V. M. Sizyakov
Complex mineral raw material, as alkali aluminum silicates, is an interest for aluminum industry, chemical industry and for the production of constructional materials. They are well represented in the earth's crust, characterized by the complexity of material composition and variable content of the main components such as alumina, silica and alkalies. They often occur where due to the geological conditions there is no bauxite, for instance, in the United States, Canada, Venezuela, Mexico, Iran, Egypt, Portugal, Spain, Bulgaria and other countries. At the present time for the Russian economy the nephelines from this list are the most valuable and have the great concern for the raw materials balance of the national aluminum industry. Because of limited reserves the bauxites proportion of alumina produced from nephelines by sintering is 40 % and in time this proportion will increase due to the involvement in the production of new deposits of alkali aluminum silicates. Many of foreign companies have also shown interest to the complex processing of ores. The investigation of technology is based on the method of sintering ore with limestone. As a result, the after-sintering mixture consists of alkali metal aluminates and dicalcium silicate; after-sintering mixture is leached by circulating alkaline aluminate solution, alumina, soda and potash are thrown out from the solution. Dicalcium silicate (nepheline sludge) is processed to Portland. For the investigated after-sintering mixture the tendency shows the increasing of optimum sintering temperature with the lowering Al 2 O 3 content. With the increasing of silicate module (SiO 2 / Al 3 O 3 ) of the initial alkali aluminum silicates charges the temperature of after-sintering mixture formation increases. After-sintering mixtures that are on base of alkali aluminum silicates have different microstructure and the degree of crystallization in which b-С 2 S and sodium aluminate is improved with a decrease of the aluminate phase amount. Results of investigations show a very limited solubility of aluminate phase in dicalcium silicate, which theoretically justifies a sufficiently high level of useful components chemical extraction in the processing of different types of alkali aluminum silicates by sintering.
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Date submitted2009-09-22
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Date accepted2009-11-17
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Date published2010-06-25
Linear ccd-sensors based multiprocessor photometer system for spectral analysis
- Authors:
- A. S. Mustafaev
- A. B. Tsyganov
- B. V. Dobrolezh
There is presented a multiprocessor photometric CCD-system for a wide range of spectrometers and for various spectral analysis methods implementation.