The modern production of aluminum which by its global output ranks first among the non-ferrous metals includes three main stages: ore extraction, its processing into alumina and, finally, the production of primary aluminum. Alumina production from bauxites, being the primary raw material in the alumina industry, is based on two main methods: the Bayer method and the sintering method developed in Russia under the lead of an academician Nikolay Semenovich Kurnakov. Alumina production by the Bayer’s method is more cost effective, but has higher requirements to the quality of the bauxite feedstock. A great deal of research has been carried out on low quality bauxites focusing firstly on finding ways to enrich the feedstock, secondly on improving the combined sequential Bayer-sintering method and thirdly on developing new hydrometallurgical ways for bauxites processing. Mechanical methods of bauxite enrichment have not yet brought any positive outcome, and a development of new hydrometallurgical high alkaline autoclave process faced significant hardware difficulties not addressed so far. For efficient processing of such low quality bauxite feedstock it is suggested to use a universal thermochemistry-Bayer method, which was developed in St. Petersburg Mining University under the lead of Nikolay Ivanovich Eremin, allows to process different substandard bauxite feedstock and has a competitive costing as compared to the sintering method and combined methods. The main stages of thermochemistry-Bayer method are thermal activation of feedstock, its further desiliconization with the alkaline solution and leaching of the resultant bauxite product under Bayer’s method. Despite high energy consumption at the baking stage, it allows to condition the low quality bauxite feedstock by neutralizing a variety of technologically harmful impurities such as organic matter, sulfide sulfur, carbonates, and at the same time to remove crystalline hydrate and free water. Subsequent desiliconization of thermally activated bauxite with an alkaline solution allows to regrade it from low quality bauxites to feedstock suitable for processing by the Bayer method.
Power consumption across the globe is constantly increasing for a variety of reasons: growing population, industrialization and fast economic growth. The most widespread gaseous fuel – natural gas – has the low production cost. It is 2-3 times cheaper than liquid fuel production and 6-12 times cheaper than coal production. When natural gas is transported to distances from 1.5 to 2.5 thousand km by the pipeline, its cost with account of transportation is 1.5-2 times less than the cost of coal and the fuel storage facilities are not needed. Plants powered by natural gas have the higher efficiency as compared to the plants operating on other types of fuel. They are easier and cheaper to maintain and are relatively simple in automation, thus enhancing safety and improving the production process flow, do not require complicated fuel feeding or ash handling systems. Gas is combusted with a minimum amount of polluting emissions, which adds to better sanitary conditions and environment protection. But due to depletion of major energy resources many experts see the future of the global energy industry in opportunities associated with the use of solid energy carriers. From the environmental perspective solid fuel gasification is a preferred technology. The use of synthetic gas was first offered and then put to mass scale by English mechanical engineer William Murdoch. He discovered a possibility to use gas for illumination by destructive distillation of bituminous coal. After invention of the gas burner by Robert Bunsen, the illumination gas began to be used as a household fuel. The invention of an industrial gas generator by Siemens brothers made it possible to produce a cheaper generator gas which became a fuel for industrial furnaces. As the calorific value of generator gas produced through gasification is relatively low compared to natural gas, the Mining University studied possibilities to use different types of low grade process fuel at the Russian alumina refineries as an alternative to natural gas, access to which is restricted for some of the regions.
Once N.V.Lipin, a professor of mathematics at the Leningrad Mining Institute, told N.S.Kurnakov that M.V.Lomonosov had complained about his lack of familiarity with mathematics. The outstanding scientist replied «That’s absolutely true, and I have already told you about it: we all need mathematics, and the more chemistry develops, the more it needs a mathematical justification». According to one scenario of the international nongovernmental organization, the Club of Rome, there will be a three-fold decrease in the world’s raw materials resources and multifold volume reduction in industrial production by the middle of the 21st century. Another scenario claims that raw materials will reduce only by one third, and the volume of industrial production will remain at the level of the beginning of the century. Not only the first scenario, but also the second one forecasts industrial stagnation. It is unacceptable for dynamic and sustainable development of the technological civilization. Intensively developing economies in China, India, Brazil and Russia defy the forecast of the Club of Rome, as it has not taken into account the possibility of scientific and technological progress in reducing energy consumption and using alternative sources, as well as the increased technological potential of the humanity. Due to depletion of the main sources of energy (oil and gas), many experts link the future of the world’s power industry with the possible use of solid energy resources. From the environmental point of view solid fuel gasification technology is the most preferable. As the calorific value of producer gas is relatively low in comparison with natural gas, some research of possible use of producer gas (as an alternative to natural gas which is available not in all regions) at Russian industrial enterprises has been conducted.
Oil supplied for primary processing always undergoes preliminary preparation, the purpose of which is to eliminate the harmful effect of water and salt contained in the oil. It is thought that corrosion of the equipment is connected mainly with chlorides of magnesium and calcium, which are subjected to hydrolysis with the formation of hydrochloric acid. Under the influence of hydrochloric acid the destruction (corrosion) of metal equipment at technological plants occurs (especially refrigerating-condensing and heatexchange equipment, furnaces of rectification units etc.). The authors of the article, on the basis of thermodynamic calculations, provide their point of view on this process and give a methodology by which the process of preliminary oil dehydration and desalting can be controlled. The thermodynamic calculations executed for standard conditions on the basis of refer-enced data confirm a high probability of chemical interaction of iron with hydrogen ions, hy-drogen sulphide and especially with carbonic acid. This testifies to high activity of the carbon dioxide dissolved in water and the impossibility of hydrolysis of ions of magnesium, calcium and iron. The calculations show that only the hydrolysis of magnesium chloride is possible tak-ing into account the ionic composition of the water phase in the oil. It should be noted that the presence of ions of chlorine shifts the iron potential in a nega-tive direction and increases the speed of corrosion of petrochemical equipment. The solution of this problem is in the development of modern methods of crude oil dehydration and desalting. It is also, however, in an intensification of the processes of mixing water-oil emulsions with wash-ing water by using various physical fields (for example, ultrasound) and creating new effective mixing devices on the basis of them.
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.
In Russia and some other countries proposed various ways to the chemical enrichment of bauxite, which usually does not affect the question of regeneration of an alkaline solution of silica, or reduce it to the release of silica in the form of calcium silicate. While the technological circuits of the chemical enrichment of the return should include an alkaline solution, after regeneration, the following parties desiliconization bauxite. It is known that the chemical enrichment is accompanied by a secondary process – the formation of hydroaluminosilicates sodium, the rate of which depends on the concentration in the alkaline solution as aluminum oxide and silicon dioxide. This paper presents data a two-stage osazhdniya silica from an alkaline solution. In the first stage in the form of sodium hydro-aluminosilicates and second in the form of calcium silicate.
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.
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 analysis shows a sharp aggravation of resource replenishment problem on the mining enterprises of the country. The share explored to date active bauxite stocks is 60-68 %. Provision of proven bauxite reserves has reached a critically low level, and a strategic reserve for existing fields is insufficient. The situation is aggravated by the lack of new mining facilities and the discontinuance of exploration. While the resource base preparation in the volume, cost-effective for industrial development, requires 10-15 years with a concentration of significant resources. Unfortunately, in Russia there is no high quality bauxite, which is global alumina industry based on. One solution to this problem is to engage in the Bayer process production the low-quality bauxite with thermochemical pre-conditioning. Despite high energy costs, calcinations condition allows bauxite materials for a variety of technologically harmful contaminants such as organics, sulfide sulfur, carbonates, and post-treatment circulating alkaline solutions to improve the silicon module of bauxite concentrate. On the example of high-silicon chromium Severoonezhsk bauxite shows the positive role of calcinations in their processing and increase the possibility of multiple silicon module of bauxite ore, successfully processed by the Bayer method. Laboratory tests confirmed by the experimental-industrial tests.
The corrosion stability of some pure metals and alloys in the titanium (II) and (III) chloride melts was investigated. It was demonstrated, that the rate and specific features of the process depend upon the chemical composition of metals. Under these conditions chrome-containing alloys are most influenced to the corrosion. Data of the relative corrosion stability of some materials were obtained.
Results of desalination thermoactivated siliceous minerals alkali-containing are presented by solutions. Testify that at desilication bauxite it is observed gradual braking dissolution of a dioxide of silicon and alumina oxide at the expense of formation of a shielding layer. The increase in temperatures desalination roasting and the silicon module of initial bauxite leads to increase of factor of braking.
Results of desalination extraction chamoisite minerals alkali-containing are presented by solutions. It is shown that the behavior chamoisite at interaction with alkaline solutions depends on a parity orthogonal and monoclinic updatings and degree oxidation. However, prebaking in oxidizing medium these distinctions at the expense of almost complete decomposition chamoisite with formation amorphous aluminum and silicon oxides.
Results of desalination siliceous minerals alkali-containing are presented by solutions. Testify that that decomposition kaolin occurs in thickness of the firm phase covered with crust hydroalumosilicate of sodium, without breaking its basic structure and without surplus of solvent. The dissolved surface remains to a constant that is one of conditions of applicability of the equation of Drozdova – Rotinjana.
A new energy-saving technology for the production of dead-burnt alumina has been studied, which differs from the existing ones in that the introduction of boric acid mineralizer simultaneously neutralizes the residual content of alkali. This makes it possible to carry out roasting in one stage. A method of chemical control over the content of α-modification of aluminum oxide during calcination of alumina has been proposed and tested. The method allows to monitor not only the quality of the obtained product, but also to quantify the content of corundum in alumina. The experimental results were confirmed by crystal-optical and X-ray diffraction studies.
A brief summary of the research and engineering work performed by professors, graduate students, and students of the Department of Furnaces, Control and Automation of Metallurgical Processes in 2000 is given. Two main directions of research activities were modeling of technological equipment for metal production and modeling of control systems for industrial metallurgical furnaces. In the first direction of research the following mathematical models were developed: converter conversion of smelting shop of Pechenganickel metallurgical plant; ore thermal smelting process; dissolution and liquation processes; waste water treatment using calcium hydrocarboaluminate. The technology of zinc-tin iron dust processing in a rotary kiln was also developed. A method of separating suspensions using LAROX PF press-filters was introduced. The second area of research includes works on development of spectral density method for synthesis of control systems with intermittent lag and on improvement of efficiency of manipulation of gas regimes in converters.
Расплавы, содержащие хлориды титана и циркония, применяют при производстве тугоплавких металлов и их сплавов. В частности, был исследован электролитический процесс получения титанциркониевых порошков. В качестве электролита использовали эквимолекулярный расплав солей NaCl и КС1, содержащий дву- и треххлористый титан и четыреххлористый цирконий. Содержание в электролите растворенного циркония не превышало 0,8% ...
