Equilibrium and non-equilibrium states of systems Na 2 O–Al 2 O 3 –H 2 O and K 2 O–Al 2 O 3 –H 2 O are crucial for establishing key technological parameters in alumina production and their optimization. Due to a noticeable discrepancy between experimental results and thermodynamic calculations based on materials of individual researchers the necessity of systematization and statistical processing of equilibrium data in these systems to create a reliable base of their physicochemical state, analysis and mathematical modeling of phase equilibria is substantiated. The tendency to a decrease of the hydration degree of solid sodium aluminates with increasing temperature and the transition of systems from the steady state of gibbsite to equilibrium with boehmite is revealed. The paper contains approximating functions that provide high-precision description of equilibrium isotherms in technologically significant area of Na 2 O–Al 2 O 3 –H 2 O and K 2 O–Al 2 O 3 –H 2 O concentrations. Approximating function can be simplified by dividing the isotherm into two sections with the intervals of alkaline content 0-0.25 and 0.25-0.4 mole/100 g of solution. The differences in solubility isotherms for Na 2 O–Al 2 O 3 –H 2 O and K 2 O–Al 2 O 3 –H 2 O systems provide are associated with changes in the ionic composition solutions that depends on concentration and temperature, as well as differences connecting with alkali cation hydration, which is crucially important for thermodynamic modeling of equilibria under consideration.
The scientific justification and development of the method for industrial synthesis of complex aluminates of alkaline earth metals is an innovative solution that determined several directions in the development of technology for complex processing of nepheline raw materials. It ensures the production of high-quality metallurgical alumina, the effective utilization of nepheline sludge and production of new types of multipurpose by-products. The modern development of these technical solutions is associated with ensuring the energy efficiency of the synthesis of hydrafed calcium carboaluminates (HCCA) and increasing the level of purification of aluminate solutions. The conditions for synthesizing HCCA with the use of calcareous materials of natural and technogenic origin have been experimentally determined, which makes it possible to isolate the average particle diameter as one of the determining factors of this process. The effect of the turnover of the hydrogarnet sludge on the removal of kinetic limitations in the process of deep desalination of aluminous solutions is theoretically justified. The conditions of a two-stage dosage of HCCA are experimentally determined. It is shown that the optimum ratio of the amount of the reagent supplied in the first and second stages is about 3: 2. At the same time, the maximum degree of precipitation of silica provides the production of aluminate solutions with a silicon module at the level of 95,000, which is achieved by using a HCCA synthesized based on chemically precipitated calcium carbonate in the processing of wastes from the production of mineral fertilizers.
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.
Modern metallurgy pays more attention to chemical processes safety of staff and nature environment. One of the most hazardous branches in metallurgy is gold ores cyanidation. Researches on possibility to avoid cyanide leaching are carrying out during last thirty years. Cyanide competitors are thiosulphate and thiourea solvers. Within international cooperation between National Mineral Resources University and Lappeenranta University of Technology researches are devoted to tiosulphate leaching improvement. Main efforts are forwarded on process chemistry, however mass transfer processes of heterogenic systems are important as well. Therefore their optimization is planned to achieve by means of computer modeling based on particle image velocimetry.
Computer based modeling is increasingly strengthening its position in equipment designing, especially unique meeting particular needs of production line or certain plant of metallurgy. There are several reasons for that such as economic benefits, wide range of geometry available to be built and possibility of comprehensive study on materials reliability as well as virtual model testing in working regime. One of the most applied and therefore permanently developed program packages for fluid behavior modeling is Fluent product of ANSYS company. The package is being used for creation first physical and in future chemical model which will be capable to describe and predict process and reactions behavior of high quality taking place in gold leaching gas-liquid reactor with thiosulphate using.
The problem of auto-feeding of aluminum fluoride with high bulk density is discussed. The possibility of reducing the specific consumption of aluminum fluoride in relation to the rational choice of physical and chemical characteristics is studied.
The results of synthesis hydrocarboalyuminates of calcium (GKAK) using carbonate reagents of different nature and size distribution. A high activity of the lime sludge from causticising soda and food processing conversion of phosphogypsum, which allows us to recommend them for use in the process of obtaining GKAK. Installed limiting stage of interaction of internal diffusion of the reactants.
More and more attention is paying to research of feasible cyanide alternative leaching techniques due to increasingly growing concern to Mother Nature. After some serious cyanide accidents some countries have campaigned to ban cyanide in gold mining industry. Political alignments and concern about environmental have been reasons to find good and less-toxic alternatives to cyanide. One of the most promising leach reagents is stated to be thiosulphate because of its benign properties. Moreover it is suitable for sulphide and carbonaceous ores which present a problem for cyanidation. In the present paper number of experiments on research of thiosulphate leaching kinetic study as well as pretreatment of gold concentrate by wet oxidation with following leaching tests is presented.
The question of magnesium oxide application for purification of aluminate liquors of aluminous production is in a complex considered. The two-phasic process is offered for providing of magnesium hydrocarbo- and sulfuraluminates formation by interaction of magnesium oxide with aluminate liquors under conditions, corresponding to parameters of aluminous production. High sorption activity of received compounds is defined with reference to organic substances of aluminate liquors.
The possibility of thickening and filtration for separation of heterogeneous disperse systems formed during the chemical conditioning of bauxite was investigated. It is shown that with increasing the ratio between liquid and solid phases of bauxite pulp thickening process indicators are improving. A similar influence provides of temperature increase of the process and the use of flocculants. The obtained results are compared with the indicators of condensation of red mud. The filter cloth was chosen for slurry concentrate bauxite, which provides the most rational regime filtration with the accumulation of sediment.
The statistical analysis has allowed to reveal the additives essentially influencing process of formation of corundum. So, fluoric connections of sodium, calcium, aluminum, oxide of iron and chrome promote formation. Opposite influence is rendered oxide of sodium, by connections of lithium and a dioxide of the titan. Besides, influence of a dioxide of the titan and oxide of chrome is estimated.
Are considered the advantages and disadvantages of complex processing red mud to produce alumina, iron (cast iron) and cement on the area of alumina refineries and way of getting on them only transportable red mud – for shipping and recycling of new marketable products at operating enterprises.
The thermodynamic analysis of aluminium hydroxide dehydration during calcination process at alumina production is carried out. The calcination of aluminium hydroxide is possible at ordinary pressure and temperature value more than 600 K. Diaspor dehydration process is possible by way of freezeout of water as an ice, water rendering or heating till decomposition temperature.
The result of industrial tests of the technology super deep desiliconization of alumina liquors with fractional dose hydrocarboaluminate of calcium 4CaO×Al2O3×0,5CO2×11H2O. Due to this technology solution alumina liquors with higher silicon module (relative weight Al2O3/SiO2) without increasing lime carbonate expenditure.
The results of laboratory studies on super deep desilication of alumina liquors based on hidrocarboalyuminat calcium supplements 4CaO×Al2O3×0,5CO2×11H2O in advance of entering into the process of working hydrogranat sludge. Obtained qualitatively new alumina liquors with a silicon module (weight ratio Al2O3/SiO2) of 50 000 units. Impact of type-ahead hydrogranat sludge to a desilication depth given from the viewpoint of heterogeneous catalysis.
It is well known that lime is an effective additive which allows to increase the depth and speed of the extraction of alumina from bauxite by the Bayer process. The firing is one of the operations in thermochemical conditioning of bauxite, it is rational to enter directly on the lime-stone at firing of bauxite, eliminating the special operation of firing limestone and calcined material damping. In order to test this were carried out research on the firing of bauxite in the presence of calcium oxide, subsequent desiliconization of calcined bauxite and autoclave leaching bauxite concentrate.
All types of raw materials used in aluminum production, are finely dispersed structures, which cause dusting during manufacturing operations, which leads to the formation of substandard raw material deposits. Their turnover in primary production contributes to the deterioration of techno-economic parameters of the process. Alumina dust samples werea collected with a mark of 16,0 meters on aluminum smelters in Russia, in the process of various technologies application. While in the upper layers alumina absorbss moisture, fluorides, and carbon. Penetration of fluoride in the amount of alumina particles depends of the crystallographic characteristics of the grains. At high stratification of the particles, fluorides are evenly distributed on the surface, and in the bulk of the particles. Mostly solid fluorides penetrate into cracks and deformation of the grains of alumina and hydrogen fluoride is adsorbed on the surface with the formation of aluminum fluoride. Alumina dust produced by the company operating for a long time with the cryolite ratio 2,2-2,35, contains a large amount of silicon. Silicon compound coat grain acicular alumina film.
The results of laboratory studies on super deep desilication of alumina liquors based on hidrocarboalyuminat calcium supplements 4CaO×Al2O3×0,5CO2×11H2O in advance of entering into the process of working hydrogranat sludge. Obtained qualitatively new alumina liquors with a silicon module (weight ratio Al2O3 / SiO2) of 50000 units. Impact of type-ahead hydrogranat sludge to a desilication depth given from the viewpoint of heterogeneous catalysis. The results obtained can be used to solve the problem of diversification of production in the complex processing of phosphogypsum in the synthesis calcium hydrocarboaluminates on the basis of fosfomel.
Results of investigations of the conversion methods of processing of large-scale fertilizer production of waste – phosphogypsum to ammonium sulfate and calcium carbonate (phosphomel). It is shown that, based on fosfomel can be synthesized by an innovative product multi-purpose – hydrocarboaluminates calcium 4CaO×Al2O3×nCO2×11H2O; the ways of effective use of hydrocarboaluminates calcium in the various sectors of the economy.
The theoretical basis of the synthesis of calcium hydrocarboaluminates 4CaO×Al2O3×mCO2×11H2O based on the CaCO3 in the aluminate-base system. We construct the isotherm of metastable equilibria in the system CaCO3 – 4CaO×Al2O3×mCO2×11H2O – 3CaO×Al2O3×6H2O – NaAl(OH)4 – NaOH – H2O at 50, 70 and 90°C.
Calcium hydrosulfasaluminates (GSAK) is a component of cement. They are slowly formed together with the forming of the structure of cement in water solution at measurable temperatures (0-25 °C) during about 4-6 months. Slow rate of crystallization of GSAK wasn`t allowed to treat them as self-autonomy objects for use in various technological applications. The possibility of formation of GSAK (4CaO×Al 2 O 3 ×mSO 3 ×nH 2 O) is proved in an environment of saturated electrolytes – aluminates solutions of alumina production. They crystallize in a short time about 1-2 hours and retain their stability in long time about 24-36 hours. This allowed for us to identify ways of their industrial use.
Описана математическая модель процесса сверхглубокого обескремнивания алюминатных растворов с предварительным вводом оборотного гидрогранатового шлама, которая может быть использована для создания АСУТП процесса в технологической схеме комплексной переработки нефелинового концентрата на глинозем и попутные продукты.
The main directions of improvement of complex processing of nepheline for alumina and passive products are considered. The estimation of promising "dry" method of alumina and portland cement production, problems of aluminum and silicon separation and obtaining coarse-grained alumina of higher qualities, the prospect of expanding the range of products is shown, the comparative analysis of cost characteristics of apatite and nepheline concentrates is given, indicating a higher potential of nepheline raw materials.
Industrial tests on the improvement of coarse-grained alumina at the PAR-SUAL Branch are conducted during the period of stable operation of the enterprise. Hydrate hydro classification was included in the apparatus-technological scheme of aluminate solutions processing on special hydro classifiers (HC) of VAMI design. The unbalanced part of fine fractions was eliminated in production.
The issues of optimization of nepheline-limestone charge preparation processes based on the principle of independence of grindability of individual components are considered. Recommendations are given for improving the efficiency of grinding equipment at the PAR-SUAL Branch.
The influence of nepheline and limestone dispersibility in nepheline-limestone charge on the quality of aluminate sinter is considered, the optimum ratio of the size of these components is revealed.
The state-of-the-art of the aluminum industry in Russia is shown. The ways of raw material base development, creation of complex waste-free technologies of aluminum production are proposed.
The variants of rational processing of industrial products of titanium-magnesium production are considered. The technology of obtaining vanadium metal using spent magnesium electrolyte and vanadium oxychloride has been tested. During magnesium- and sodium-thermal reduction of vanadium chloride the metal was obtained in the form of powder, crystals and spongy mass.
Expansion of the product range will always be one of the urgent tasks of increasing the efficiency of complex processing of nepheline. At present, the most prepared for industrial implementation are the technologies for processing of ultra-deep desilting hydrogranate slurries into foundry cements and obtaining dry calcium hydrocarboamminates for use in various sectors of the economy (production of quick-hardening shrinkage-free cements, waterproofing materials, sealants, cement slurries, coagulants, etc.). For theoretical justification of the mentioned technologies the parameters of thermal decomposition of weakly saturated calcium hydrogranates (constituting the basis of ultra-deep desilting slimes) and calcium hydrocarboaluminates were investigated. According to the results of the studies technological regulations were developed and pilot batches of new products were produced.
This article considers the main directions of improving the technology of complex processing of nepheline into alumina and related products. A promising "dry" method of alumina and Portland cement production is evaluated. The problem of separation and Si(IV) and obtaining coarse-grained alumina of maximum grades is considered. Prospects for expanding the range of products are shown.
The issues of improving the technology of complex processing of non-auxite aluminum raw materials - nepheline; synthesis of refractory titanium compounds; technology for the extraction of platinum and its companions; improvement of apparatuses for autogenous melting of sulfide materials are considered. The research was supported by the RFBR (Russian Foundation for Basic Research). (The Programme of the Leading Scientific Schools Support - Project 00-15-99070).
Review of alumina and aluminum production in Russia is given in this paper. The paper contains an analysis of raw material problems, the ways of plants modernization and reconstruction, the problems of aluminium plants development in the North-West region. The conception of "North-West Aluminium" holding company foundation is offered.