WO2012064220A1

WO2012064220A1 - Method for producing aluminium by metallothermic reduction of trichloride with magnesium and apparatus for carrying out said method

Info

Publication number: WO2012064220A1
Application number: PCT/RU2011/000676
Authority: WO
Inventors: Альберт Иванович БЕГУНОВ
Original assignee: Begunov Albert Ivanovich
Priority date: 2010-11-08
Filing date: 2011-09-06
Publication date: 2012-05-18
Also published as: KR20130020675A; KR101491891B1; US20130036869A1; CN102959104A; JP2014502307A; EP2639320A1; AU2011326897A1; EP2639320A4; CA2794546A1; BR112013000737A2

Abstract

A method is proposed for producing aluminium by metallothermic reduction of trichloride with magnesium in a stream of inert gas at a temperature of 900 - 1150°C, an overall pressure of 0.01 to 5 at and a mass ratio of aluminium chloride to magnesium in the starting mixture of 3.69 to 1.00. The process is carried out in a cylindrical reactor (1) with thin-walled ceramic packings (6) arranged on the inside and with a conical lower part (2), and a boiler-evaporator of the magnesium into the stream of inert gas is mounted upstream of the reactor, and an apparatus for separating liquid magnesium from the rest of the mixture thereof with aluminium chloride is mounted downstream of said reactor, wherein all of the components of the apparatus are lined inside with fireproof materials (5). The technical result is an increase in productivity by ensuring continuity of the reduction process, and excellent environmental characteristics.

Description

METHOD OF OBTAINING ALUMINUM BY METALLO-THERMAL RESTORATION OF TRICHLORIDE BY MAGNESIUM AND DEVICE FOR ITS IMPLEMENTATION

The field of technology.

The invention relates to non-ferrous metallurgy, in particular, to the technology of aluminum production.

Prior art.

In the metallurgy of non-ferrous metals for the production of aluminum is used electrolysis of cryolite-alumina melts, called the method of Eru-Hall. It is known that electrochemical devices and, in particular, electrolyzers have very low rates of utilization of the useful volume, since working processes do not proceed in the entire volume of the reactor, but only on the surfaces of the electrode-electrolyte. In the Eru-Hall method, only one electrode, the cathode, performs “useful” work. As a result, electrolyzers have a very small unit capacity, no more than 3-4 tons per day. Aluminum plants are therefore equipped with hundreds and thousands of electrolyzers, they occupy large areas and are distinguished by a high level of capital expenditures during their construction.

Due to their design features, electrolyzers are not hermetic, and the process is accompanied by the emission into the atmosphere of sodium fluorides, aluminum, hydrogen, carcinogenic polyaromatic compounds, large volumes of greenhouse gases and, in particular, carbon dioxide and perfluorocarbons. For the reasons stated, the production of aluminum by the electrolysis of cryolite-alumina melts

SUBSTITUTE SHEET (RULE 26) is archaic and does not correspond to the prevalence of aluminum in the earth's crust (first place among all metals), nor a unique set of its physical and structural properties.

Classical solutions are known for metallothermic methods for producing aluminum by reducing it from potassium aluminum chloride (Wohler, 1828 g) or sodium (CK Deville, 1854 g) by the reaction:

A1С1 ₃ + ЗМ - ЗМС1 + А1 (1),

where M is alkali metal.

However, when using alkali metals by reaction (1), too high consumption of these metals and electricity is required. So in the case of potassium per 1 kg of aluminum it is required to spend ~ 4.33 kg of alkali metal and ~ 35 kWh of energy. For sodium, these figures are 2.555 kg of metal and ~ 25.5 kWh of electricity per 1 kg of aluminum.

Of the other known analogues, the proposal of N.N. Beketov, according to which aluminum is obtained by restoring it from aluminum fluoride, which is part of the Greenland cryolite, with magnesium:

2 (3NaF · A1F ₃ ) + 3Mg = 6NaF + 3MgF ₂ + 2A1 (2).

Fluorides are more refractory compounds and the reduction process, as well as a device for implementing this method are more complex. In addition, the only deposit of Greenland cryolite was practically developed in the 19th century.

The closest prototype of the proposed method is to obtain metallic titanium by reducing it from metallic tetrachloride with magnesium (V. A. Garmat and others. Titanium metallurgy. M., Metallurgy, 1968, p. 237-238, p. 241):

SUBSTITUTE SHEET (RULE 26) TiCl ₄ + 2Mg = 2MgCl ₂ + Ti (4).

This process is very difficult, because It involves titanium chlorides of various valences, and the participants in the reaction are in different state of aggregation: titanium chlorides in gaseous form, magnesium and its chloride in liquid phases, and titanium in the solid phase. As a consequence, in the method it is necessary to periodically depressurize the apparatus for extracting titanium, which reduces the productivity of the process and degrades its environmental characteristics.

The technical result is an increase in productivity due to the continuity of the recovery process, and high environmental performance by ensuring the tightness of the equipment.

DISCLOSURE OF INVENTION

The technical result is ensured by the fact that to obtain aluminum using the reaction of metallothermic reduction of aluminum trichloride with magnesium:

2A1C1 ₃ (g) + 3Mg (r) = 3MgCl ₂ (3K) + 2A1 (g) (3), the reduction is carried out in an inert gas flow at a temperature of 900-150 ° C, total pressure from 0.01 to 5 at. the mass ratio of aluminum chloride and magnesium in the original mixture as

3.69 to 1.00.

The consumption of magnesium will be only 1.35 kg per 1 kg of aluminum, and the need for electricity for electrolytic magnesium will be about 17.9 kWh per 1 kg of aluminum.

Even better results are obtained with the use of magnesium obtained by metallothermic. For example, when pre-reducing magnesium from magnesite or dolomite

SUBSTITUTE SHEET (RULE 26) ferro-silicon according to the Pidgen method (V. A. Lebedev, V. I. Sedykh. Metallurgy of magnesium. Irkutsk, 2010, p. 149).

The total energy consumption of the reaction (3) then does not exceed ~ 13 kWh / kg of aluminum, which is comparable with the flow rates in the Eru-Hall method and at the stage of the birth of the magnesium-thermal method of producing aluminum can be considered an excellent indicator.

The reduction of aluminum from trichloride with magnesium according to reaction (3) is, however, an independent scientific and engineering problem. The reaction (3) underlying the invention is much simpler to perform than the reaction (4) of the prototype magnesium thermal reduction of titanium. It is paradoxical that for this, in the method of aluminum production by its reduction with magnesium from trichloride, higher temperatures and pressures are needed.

In fact, magnesium as a reducing agent has a boiling point of ~ 1103 ° - 1 107 ° C (vapor pressure is 1 at) with a melting point of 651 ° C. Of the other participants in the reaction (3), aluminum melts at 660 ° C. It is extremely characteristic a wide range of liquid state with a boiling point of 2497 ° C, i.e. at the boiling points of magnesium (-1107 ° C) aluminum practically does not evaporate at all. Magnesium chloride melts at 708 - 714 ° С and boils only at 1412 - 1417 ° С, i.e. also has a relatively wide temperature range of the liquid state. Finally, aluminum trichloride is sublimated at a temperature of 179.7 ° C and does not have a liquid state at atmospheric pressure. Thus, at temperatures above 1 107 ° C, the raw materials — aluminum trichloride and magnesium — are in a gaseous state, and aluminum metal and magnesium chloride are in liquid, which is convenient for organizing continuous high-performance production.

SUBSTITUTE SHEET (RULE 26) The process according to reaction (3), as shown by the results of thermodynamic calculations, at a temperature of 1300 K (1027 ° C) is characterized by values of enthalpy - 240 kJ and Gibbs energy - 210 kJ, i.e. must proceed spontaneously with the release of a large amount of heat. It should, however, be cautioned against a possible excessively high level of the rate of the reduction process due to the high reactivity of gaseous magnesium and aluminum chloride, which is overheated in the gaseous state by about 900 ° and partially dissociated into monochloride. In addition, reaction (3), where the indices “g” and “g” correspond to the gaseous and liquid state, according to the Le Chatelier rule and II, under the conditions of high pressure, the law of thermodynamics will have an equilibrium significantly shifted to the right. In the kinetic relation, the reaction can proceed with an explosion and for the possibilities of flexible control of its speed, the initial components — aluminum chloride and magnesium — should be supplied in separate streams of inert gas with a temperature lower than that maintained in the reactor.

The recovery process can be carried out already at a temperature of 900 ° C, since for these conditions, the elasticity of saturated vapor of magnesium is significant and amounts, for example, to 9 at .9 at. for 927 ° C. At the same time, it is impractical to rise significantly above the boiling point of magnesium (1,103–1107 ° C), since this will be accompanied by unnecessarily high values of the speed of the process and it is possible to set its upper limit to a temperature of 1,150 ° C.

The total pressure of the gas phase in the reactor will be determined in the range from 0.01 at. To 5.0 at at the optimum partial pressures of aluminum and magnesium chloride in the gas phase, determined by experienced

SUBSTITUTE SHEET (RULE 26) by. It is preferable to focus on the upper values of the total pressure, but before reaching the explosive limits.

According to the composition of the gas mixture supplied to the reduction, it is possible to follow the stoichiometric mass ratio of the reaction (3), which should be when the aluminum and magnesium trichloride mass flows are fed to the reactor as 3.69 to 1.

The possibilities of realization of the claimed invention do not cause doubts, since such production of the titanium from its tetrachloride by the thermothermic method exists, and the claimed method of producing aluminum promises to be much simpler. In addition, magnesium is a significantly more electronegative metal than aluminum. Energy costs can be quite small when magnesium is obtained by reducing it from dolomite or magnesite in combination with the traditional method of electrolysis of magnesium chloride. The process is also autogenous.

The method in which gaseous aluminum chloride and magnesium are used as starting materials, and the resulting products — magnesium chloride and aluminum — are liquids, can be implemented in a sealed apparatus. It is easy to automate and does not require manual labor or the use of mechanical devices to service the process. The high level of the environmental characteristics of the invention through the use of sealed apparatus seems obvious. One of the decisive advantages of the proposed method is the possibility of creating equipment with high unit productivity, low capital and production costs.

The possibility of the invention is confirmed by the existence of a powerful and efficient industry

SUBSTITUTE SHEET (RULE 26) magnesium thermal method of producing titanium from tetrachloride, as well as the existence of successfully implemented methods for producing zirconium and hafnium by magnesium thermal reduction from chlorides.

In the magnesium thermal method of producing titanium, cylindrical steel vessels, for example, made of chromium-nickel steel lined with a molybdenum sheet, were originally used as recovery devices. Later, the inner layer was learned to perform from mild steel. The process is carried out at temperatures lower than the melting point of the metal and titanium is obtained in the solid-phase state in the form of a so-called sponge, for the extraction of which the reactor must be cooled, and the process is inevitably realized as periodic. This, in turn, necessitates the use of manual labor, reduces the productivity of the reactor, increases energy consumption and degrades the environmental characteristics of production.

In the claimed invention, the device for metallothermic reduction of aluminum with magnesium is carried out at higher temperatures, reaching 1,100-1,150 ° C, at which both the resulting reduction products-aluminum and magnesium chloride are in liquid form and flow to the bottom of the reactor. (The melting point of aluminum is 660 ° C, and magnesium chloride is -708 - 714 ° C at boiling points, respectively, 2497 ° C and 1412 - 1417 ° C). For this reason, the upper part of the reactor is cylindrical to increase the effective volume of the reactor, and the lower part is tapered to collect liquid aluminum and magnesium chloride.

The main reaction zone is hollow in the area of the introduction of gaseous aluminum chloride and magnesium for better mixing, but the volume attached to the conical part is filled

SUBSTITUTE SHEET (RULE 26) thin-walled hollow ceramics such as nozzles from Raschig rings. The use of nozzles is necessary to accelerate the processes of condensation and coalescence of the resulting aluminum and magnesium chloride droplets.

The reactor is connected by a stream of inert gas with a boiler - magnesium evaporator and with a liquid magnesium separation apparatus from a waste residual mixture of magnesium vapor and aluminum chloride. The boiler - magnesium evaporator and liquid magnesium separation apparatus are an integral part of the device, but are located separately from the reactor, near it.

The reduction of aluminum from its chloride with magnesium in the gas phase is exothermic, proceeds with the release of a large amount of heat, and the process is autogenous. In order to be able to flexibly control the temperature and rate of reduction, the reactor and the magnesium separation apparatus are supplied with an evaporative water cooling system.

The proposed invention uses fluid phases (liquids and gases) that react in turbulent flows at high temperatures, which ensures a high unit productivity of the process. In addition, capital costs for the construction of production facilities, as well as equipment maintenance costs, are significantly reduced.

Brief Description of the Drawings

Figure 1 shows a general view of the reactor; in Figure 2, the boiler is an evaporator; in FIG. 3, a separation apparatus in vertical sections.

The reactor (Fig. 1) is made in the form of a steel cylinder 1, passing into the lower conical part 2, designed to collect the products of the reduction - aluminum and magnesium chloride. Between

SUBSTITUTE SHEET (RULE 26) The cylindrical and conical parts have a false bottom 3. The reactor is sealed with a lid 4. All internal surfaces of the reactor are lined with refractory ceramics 5, which can be magnesite, graphite and other resistant materials.

On a false bottom 3, nozzles made of thin-walled ceramics of the Raschig 6 type are used, which are used in chemical absorption technologies. Nozzles are made of refractory materials, for example, magnesite, carbonitrides, etc.

To enter into the reactor the source of gaseous aluminum chloride and magnesium using nozzles or nozzles 7 and 8, installed in the upper hollow part of the reactor tangent to the circumference of the horizontal section of the reaction zone and directed towards each other. The reduced aluminum 9 and magnesium chloride 10 are collected in the conical part 2 of the reactor and after being discharged through a tapping point 11, magnesium chloride 12 and aluminum 13 are collected in a mold 14. To remove an unreacted mixture of aluminum chloride and magnesium chloride, a branch pipe 15 is installed in the reactor cover.

The boiler - evaporator (Figure 2) is a steel hemisphere 16, hermetically closed by a cover 17, lined with the same materials as the reactor. Magnesium is fed to the boiler in liquid form. An electric heater 18, made, for example, in the form of rods of silicon carbide, is lowered into the metal. The heater may be enclosed in a magnesite protective sheath. An inert gas (argon or nitrogen) is fed to the evaporator boiler and the magnesium in the form of steam, together with the inert gas, is sent to the reactor. The boiler - the evaporator can be supplied with a water evaporative cooling system, as well as other elements of the device shown in Fig. 1 and Fig. 3.

SUBSTITUTE SHEET (RULE 26) The separation apparatus (Fig. 3), designed to separate liquid magnesium from its residual gaseous mixture with aluminum chloride, is in the form of a reduced size reactor lined with refractory ceramics 19. The gas mixture is introduced into the apparatus through pipe 20, the magnesium condensate is collected at the bottom apparatus, and not reacted aluminum chloride through the pipe 21 is removed from the apparatus and returned to the reactor. The separation apparatus, like a reactor, is equipped with a shut-off device 22 and an evaporative cooling system 23. Magnesium condensate is returned to the boiler-evaporator and then to the reactor.

The device operates with continuous supply of aluminum chloride and magnesium gas to the reactor, obtained in a single evaporator boiler or in a battery of such evaporators. Aluminum chloride and magnesium gas are transported and fed into the reactor in opposing turbulent flows of an inert carrier gas, which provides ideal contact conditions for the reacting particles, removes diffusion barriers and ensures high speeds of the reduction process. To achieve high rates of exit from the reactor of the final products - aluminum and magnesium chloride, it is necessary to use large surfaces and the number of active centers of the phase formation of the liquid phases. This goal is achieved through the use of the above-noted ceramic thin-walled and rough nozzles such as Raschig rings made of magnesite. The aluminum 13 discharged from the reactor in continuous or batch mode is protected by an upper layer of molten magnesium chloride 12. Separation of the reduction products is not difficult. For example, when the temperature drops to 680 - 700 ° C, the chloride layer

SUBSTITUTE SHEET (RULE 26) magnesium is converted into a solid phase, and liquid aluminum can be easily sent for further technological operations.

A separation apparatus designed to separate aluminum chloride and magnesium in their residual gas mixture works by reducing the pressure in the system and the temperature below the boiling point of magnesium. Liquid magnesium - condensate is sent to the refining or, with its sufficient purity, directly to the recovery process through the boiler - evaporator.

To ensure a high, but adjustable device performance, it provides for a system of evaporative water cooling both in the reactor itself and in the separation apparatus. The principles of operation of such devices in other areas of technology, including metallurgy, are well known and developed. Inert gas circulation systems are also well developed in chemical technologies and in the metallurgy of rare metals.

In the process of using the invention, aluminum chloride is supplied in a gaseous form through nozzles (nozzles) 7 to the upper part of the steel cylinder 1 of the reactor (Figure 1). There also is fed in the counter flow through the nozzles (nozzles) 8 gaseous or vaporous magnesium mixed with an inert gas. This mixture is preliminarily prepared in a boiler-evaporator (Figure 2), into which the initial inert gas (for example, argon) and liquid magnesium are introduced separately, and a two-component stream of magnesium and inert gas is fed to the reactor (Figure 1).

The resulting liquid aluminum and magnesium chloride condense and coalesce on the surfaces of the nozzles 6 (Figure 1), drain into the conical part of the reactor and then through the tap 1 1 the reduction products - aluminum 13 and magnesium chloride 12 enter

SUBSTITUTE SHEET (RULE 26) the mold 14. The residual gaseous mixture is etched through the nozzle 15 (Figure 1). This mixture is fed into the separation apparatus through the pipe 20 (Fig.Z). Next, the magnesium removed from it through the locking device 22 is returned to the boiler-evaporator, and aluminum chloride, removed in gaseous form through the pipe 21, is returned to the reactor through a nozzle - nozzle 7 (Figure 1)

Industrial Applicability

The possibility of implementing the proposed invention is beyond doubt and is confirmed by the fact that a similar, but much more complicated process of magnesium-thermal reduction of titanium from its tetrachloride exists and is successfully used in the United States, the Russian Federation and the CIS countries.

The proposed invention provides the following advantages of new technology and technology for the production of aluminum. This is an unlimited high unit capacity of the device and a low level of capital expenditures during the construction of new capacities. Provided tightness and environmental cleanliness of production. The device eliminates the cost of manual labor and possible full automation of the process. Aluminum recovery in the device occurs with a significant positive thermochemical thermal effect and proceeds in an autogenous mode, with virtually no energy from the outside.

SUBSTITUTE SHEET (RULE 26) Literature:

1. Kroll W.J. Pat USA JV ° 2205854,1940 y.

2. Kroll W.J. Trans. Electrochem. Soc. 1940, v 78, p. 35

3. B.A. Garmata et al. Titanium metallurgy. Moscow, Metallurgy, 1968, 643 p.

4. A.N. Zelikman, G.A. Meerson. Metallurgy of rare metals. Moscow, Metallurgy, 1973, 607 p.

5. Reference chemist. / / Ed. B.P. Nikolsky, t. And, "Chemistry", M., 1964, 1 168 p.

6. M. Jua. History of Chemistry (from Italian), M., 1975, 477 p.

7. Vetiukov MM, Tsyplakov A.M., Shkolnikov S.N.

Electrometallurgy of aluminum and magnesium. M., "Metallurgy", 1987, 320 p.

8. K. Grjotheim, Q. Zhuxian. Molten Salt Technology, v. II, Shenyang, China, 1991, 435 c.

9. B.A. Lebedev, V.I. Gray. Magnesium metallurgy. Irkutsk, 2010, 175 p.

10. A.I. Runners. Problems of modernization of aluminum electrolysis cells. Irkutsk, 2000, 105 p.

1 1. Kroll W.J. Metalls, Trans. Electrochem. Soc, 1947, N 89, p. 41

12. Kroll W.J. Metalls, 1955, v 5, N 9-10, p. 336.

13. V.P. Mashovets. Electrometallurgy of aluminum, ONTI · NKTP · USSR, 1938, 345

SUBSTITUTE SHEET (RULE 26)

Claims

Claim

1. A method of producing aluminum is a metal othermic reduction of trichloride with magnesium, characterized in that the reduction is carried out in an inert gas stream at a temperature of 900-150 ° C, a total pressure of from 0.01 to 5 at and a mass ratio of aluminum chloride and magnesium in the initial mixture as 3.69 to 1, 00.

2. A device for carrying out the method including a cylindrical reactor with thin-walled ceramic nozzles and a conical bottom located inside, characterized in that a magnesium evaporator boiler is installed in the inert gas flow in front of the reactor, followed by a liquid magnesium separation apparatus from its residual mixture aluminum chloride, with all the components of the device are lined from the inside with refractory materials.

SUBSTITUTE SHEET (RULE 26)