SE123725C1 - - Google Patents

Description

Inventor: P. Gross.

Priority requested from 19 April 1944 (Great Britain).

The present invention relates to a supernatant clestillation process for the production or refining of aluminum.

It has previously been suggested that aluminum, when intimately mixed with a solid halide such as e.g. Aluminum fluoride, magnesium fluoride or cryolite can be distilled at temperatures well below that at which it is practically possible to distill it at nanorvide rate by heat alone, i.e. it is not mixed with a halide.

Based on this assumption, a method for producing or refining aluminum was proposed, which consists in forming an intimate solid mixture containing a halide and aluminum or aluminum-containing material, heating the mixture in an aluminum-neutral atmosphere to evaporate metallic aluminum and the halide, that the vapors are condensed and that the aluminum is separated from the condensate, which consists of a mixture of halide and halogens, which are unstable at any other operating temperature or which evaporate easily at this temperature or lower temperatures and therefore make the reaction zone poorer in halide. the effective reaction is not inconvenient in carrying out this procedure.

Furthermore, it has been found (W. Klemm and E.

Voss, magazine for anorg. and General Chemistry, vol. 251, p. 232-40 / 1943), that from the condensate obtained from the distillation at about 700 ° C ay aluminum mixed with aluminum fluoride, which consists of a very intimate mixture of aluminum and aluminum fluoride, repeatedly subjected to a renewed destination, the final condensate will consist of a molecules mixture of 2A1 on 1A1R. It has been concluded that the volatility of aluminum, when mixed with aluminum fluoride, is based on the formation of an aluminum monofluoride, which is more volatile on any of them.

In contrast to the foregoing, part of the present invention has been found that halides of halides previously introduced into the react phase react with aluminum at temperatures well below the temperatures at which aluminum would distill to follow its vapor pressure to form volatile reaction products, which by cooling lead to condensation of aluminum and the original halide. The aluminum is heated in an atmosphere which either contains only the halide or halides (preferably under reduced pressure) or these compounds mixed with a gas or gases which are neutral to aluminum, such as I. ex. vale. Similarly, volatile aluminum is made from materials that contain available aluminum, & Isom AlFe or aluminum carbide.

According to the present invention and in contrast to what has previously been learned, boiling or subliming halides such as e.g. aluminum chloride (sublimation point at normal pressure 180.2 ° C) or aluminum bromide (boiling point at normal pressure 256.4 ° C) with advantage is used, solid high-boiling or subliming halides such as e.g. Alurinitun fluoride (sublimation point at normal pressure 1260 ° C) has been found to be effective.

Depending on the halide used, depending on the heating and cooling conditions and the pressure maintained in the system, the halide is condensed either together with the aluminum or separated from delta or not.

If the evaporation temperature of the halide yid the pressure maintained in the system is not below or not or well below the practicable reaction temperature, the aluminum condenses together with or partially together with the halide and must subsequently be separated from it. However, if the temperature in the reaction is sufficiently high above the evaporation temperature of the halide below the prevailing conditions in the system, the aluminum condenses at a temperature which is sufficiently high above the condensation temperature of the halide and is therefore completely or largely separated from the halide. in the hottest zone of the condenser, or around the condenser and associated parts of the apparatus is kept between the hot condensation temperatures, the halide is not condensed ails, and thus the halide vapor in the system available is continuously reacted. Completely separate or no condensation ails of the halide can be found with aluminum chloride or bromide. The reaction temperature of these balogenides is much higher than their faranging temperature.

When the halide vapor is passed over the heated aluminum or material containing available aluminum, the velocity () or partial pressure of the halide and the area and temperature of the material can be controlled so that apparently a maximum amount of the aluminum is distilled off relative to the halide used. The rate of evaporation of aluminum within these limits - i.e. as low as it is below the maximum amount in relation to the velocity of the halide current, alias to a high degree, while other conditions remain constant due to the specific area and temperature of the aluminum-containing material. The following explanation is theoretical and the invention is not limited by the assumption that at the temperature of the reaction an equilibrium is established between the aluminum or the available aluminum-containing material, the angles of the original halide and the angles of an Ogre aluminum halide, which upon cooling gradually overgax to the original halide and aluminum metal, although by rapid cooling little was obtained of a condensate together with aluminum, which could not be identified as such and which proved to be unstable and to undergo a change, after which the analysis showed only t aluminum and halide.

Using aluminum chloride, which has been found to be very satisfactory, the reaction would thus proceed as follows: 2A1AlCl3 (anga) -> - 3A1C1 (anga). Using a complex halide, such as cryolite, the reaction would be: 5A1 (3NaF, AlF,) (as indicated) -> - 6AIF (indicated) 3Na (indicated).

As the formation of the aluminum monolialogenide consumes heat and proceeds during volume increase, the reaction will be more complete, the higher the temperature and the lower the pressure Or or, if the halide is mixed rated a neutral gas as vale, the higher its partial pressure (concentration) dr. The absolute amount of monobalogenide per unit volume in the gas mixture (i.e. the concentration of evaporated aluminum) decreases with decreasing concentration of the original halide. A practical lower limit is given by its pressure (concentration) Or given by the too small amounts of aluminum, which are distilled off at too high a halide pressure. The practical lower limit of the temperature depends, in accordance with these equilibrium conditions, on the nature of the halide used and the aluminum-containing material and is further limited by the excessively low reaction rate yid for low temperatures.

When the reaction is nearing completion it thus gives higher effect yid & ad reaction temperature and reduced halide pressure and then. the reaction rate 'Ras with the temperature, Or it radially aft halla the reaction temperature hagre On the evaporation temperature of the halide below the farhalIande radan in the system. This difference between the evaporation temperature and the temperature at which the reaction is suitably carried out, Or siisoni already stated very slur yid aluminum chloride or bromide, but Or Oven well avseviird in other cases, e.g. 300-400 ° C depending on the requirements, for sodium chloride. It Or, however, alone with hansyn to jamweight most economically aft yam. satisfied with an efficiency of less On 90%. If higher efficiency experiments were attempted, a relatively large increase in temperature would result in only a relatively small increase in efficiency. Likewise, the lower practical limit of temperature depends on the nature and part of the halide used, the amount of available aluminum being limited by the excessively low efficiency and the ARM.-Fig. Reaction rate at too high a reaction temperature.

The process for producing or ralfinating aluminum according to the present invention involves reacting heated aluminum-containing materials with a halide which is transferred to the gas before being contacted and reacting with the material, thereby volatilizing the aluminum from the material to form aluminum halide compound vapors. angor is cooled to aft condense the aluminum. It is advantageous to allow the reaction to proceed at temperatures at which the halide vapor is not slowed.

The term «aluminum material» Or is intended to include impure aluminum or aluminum alloys such as I. ex. aluminum silicon, as well as compounds such as ferroaluminum (AlFe) and aluminum carbide and mixtures of these compounds with aluminum and aluminum alloys. It may also comprise pure or crude alumina or other aluminum ore together with suitable reducing agents such as carbon or silicon or mixtures of such aluminum materials as previously mentioned and their mechanical mixtures with other materials.

The term "halide" includes simple or complex aluminum halides, the halides of the alkaline earth metals and of the alkali metals or the compounds which form halides with the aluminum-containing materials, such as chlorine or chlorine, or mixtures of two or more identical materials with each other.

Boiling or subliming halides, such as aluminum bromide and, in particular, lower alumina chloride, have been found to be effective and advantageous, inter alia because, if they are condensed at all, they are condensed from the aluminum. The halide or halides can be evaporated in the chambers containing the aluminum-containing material, or in different chambers, and the evaporation can be carried out under normal, reduced or slightly Okat pressure or by passing an inert gas or gas mixture through or over the halide.

Depending on the nature of the aluminum-containing material and the halide used, the halides of the halide compound will either be the only gaseous reaction products or be formed together with other gases or angles, such as e.g. sodium vapor or carbon monoxide. The method of extracting the aluminum must be chosen in accordance with this.

If the aluminum halide compound vapors are the only gaseous products, or if they are formed together with other gases or vapors which are not potentially reoxidizing, direct and gradual cooling is preferred. If potentially reoxidizing fumes are formed together with the aluminum halide compound fumes (eg carbon monoxide if the aluminum-containing material is a mixture of carbon and aluminum or aluminum-containing material), rapid cooling or alternative absorption due to redistillation and cooling must be chosen in accordance with carbothermic regulations. of magnesium oxide.

In the practice of the invention, the aluminum-containing material is suitably brought into a state in which it offers a large specific surface area of the halide vapor or the halide-containing vapor. In the small state, the part can be taken up in superheated flat containers or dirt or spread over heated, crushed materials, which are placed in chambers, which are filled with halide vapor (preferably under reduced pressure) or with a mixture of halide vapor and inert gases such as irate. , said chambers being precluded with suitable condensers for condensing the aluminum or the aluminum together with the halide. The aluminum may drip through towers filled with crushed material or plates or Dar, which are connected to a condenser, through which towers the halide or gas mixture is passed under normal, slightly elevated or reduced pressure. Halide vapor or such gas containing gas can also be bubbled through the liquid aluminum-containing material, then passing through the condenser to condense the aluminum or aluminum together with halide.

If the aluminum-containing material Or is fixed at the reaction temperature, it is broken into small pieces or crushed into a coarse powder, in which case it is clumsily pressed into porous briquettes and applied to said reaction chamber (or tower), Or it is brought into contact with or flushed with halide vapor or such vapor containing gas.

Alternatively, some of the aluminum-containing material may be blown into the reaction chamber as a foam by means of the halide vapor or the halide vapor containing gas, whereby solid or liquid residues are deposited at the bottom of the reaction chamber or separate chambers kept at suitable temperatures while conducting the reaction vapors. aluminum. NO low-boiling or low-sublime halides are used, the halide vapor does not need to be condensed at all. Since the reaction is in ruins in a static system (preferably under reduced pressure), this can be achieved simply by holding each part of the whole system, including the condenser for the aluminum, above the condensation temperature of the halide. However, a stream of the halide vapor or the halide-containing gas can be passed through the condensers to condense only the aluminum and then recirculated by means of suitable pumping devices over the aluminum-containing material. Low-boiling or subliming halides are used and the halogen sound is condensed during the process. If it is possible to use my two halide condensers, VII-ha could be anylindled alternately as a condenser and as a vapor evaporator. By all at the same time one (or one group) is used as a condenser and the other (or the other group) as an evaporator, a large amount of aluminum can be distilled or can even be added. an uninterrupted distillation of aluminum is carried out with a very limited amount of halide.

In any case, using low-boiling or subliming halides, the heat generated by the condensation of the aluminum can be used to vaporize the halide, if it is condensed, and / or to preheat the halide vapor.

The halide vapors can be preheated by using it as a refrigerant for the aluminum condenser, or also some other refrigerant, for example, on gas, can be caused to circulate the Indian aluminum condenser and the worm wax through which the halide vapor passes. Finally, the residual heat in the refrigerant can be used to reduce the evaporation heat of the halide. Both methods, direct and indirect heating of the balogenide by the condensation heat of the ordinary, can be combined.

An advantage of the present winding is that mechanical processing of the halide such as mining () or pressing into briquettes is unnecessary. In addition, in the case of malignant material, the distillation chamber may be introduced into the distillation chamber in its original form.

Another advantage of the present invention is that it provides a considerable saving in the amount of halide which must be evaporated for each part of aluminum. Mr e.g. number of aluminum fluoride (which IOU can aydunslas yid about 750 'G under reduced pressure) was led Over small drops (trained aluminum, which was in a tower with crystalline initials; clay soil yid at a temperature ay about 1000' C, was the amount of aluminum fluoride, seem was used to distill off one part of aluminum, about 1.6 parts, while, when the reaction was started from a briquette pressed from crude aluminum twit solid fluoride, ten parts of the fluoride were required for each part of aluminum.

Additional advantages of the present invention, when law-boiling or subliming halides are used, are based on the fact that the halide is condensed separately from the aluminum, and these advantages are not separated, mechanical or otherwise, or necessary or the distillation. The waste heat, which is recovered from the aluminate ma condenser, can be used to evaporate any condensed halide and to preheat the vapor. c) The amount of halide present in the system can be slightly reduced in relation to the nhunin evaporated in the course of a work, which results in a reduction in the size of the apparatus for the destination of a given amount of aluminum or to () eh with mojliggiir a continental destination. to repeatedly use a boiling or subliming halide titanium to interrupt the distillation Italics halide either in the angular state or condensation of the aluminum and be repeatedly contacted with the aluminum, containing material or it can be condensed in one, two or more condensers , 'viikaaanvandas som forangare. If the balogenide vapor is not condensed, it can be recirculated to the reaction chamber of the aluminum condenser by means of a circulation pump which adjusts to operate at elevated temperatures, say above 120 ° C, when aluminum chloride is otherwise at 0, about atmospheres, or the circulation of the halogenide vapor can be effected. by convection and diffusion within the reaction chamber. For this purpose, the distillation can be carried out in batches by heating the aluminum-containing material (electrically) within the reaction vessel, the rockers are cooled, but not below the condensation temperature of the halide at a suitable pressure, and which is sealed, after the aluminum-containing material and halide have been applied air and duck! permanent gases have been removed.

The following examples of the embodiment of the Coding Salt are given: Example I.

A tower filled with crystallized clay soil was used as a reaction cannon, the alumina being spun in liquid form or as narrow droplets on the clay soil and slowly moving freely from the top to the bottom. The tower was brought up to the desired temperatures by means of electric currents, which were induced in a jacket fIX carbon-poor jam. The lower spirit of the tower was connected to a halide evaporator, which contained the halide used in the skittle, was electrically heated and the lower spirit was connected to a condenser which was water cooled at its upper spirit and connected to a vacuum pump. The aluminum is condensed. usually in a zone near the reaction chamber at a temperature estimated to be about 700 G, while the halide used is condensed in the water-cooled zone by the condenser.The residual pressure was in any case less On 0.5 inm Figs () eh for the most part considerably The distillation time was between one and four tint-nine.

In a series of tests carried out on this apparatus, the aluminum-containing material consisted of crude aluminum containing 8.86 Cu, 0.75 t of Ni, lenFe, 1, n cn ', Si and 0, Mn, but the impurities in the distillate were averages less On 0n-, 3% Cu, less On 00.3 Fe, less On 0.61 t Si and saves up to 0, o5 c ;, manganese. The halide used was aluminum chloride, which was evaporated at about 120 ° C.

At the temperature of the reaction tower bOils yid 900 to 1000 ° C, the ratio of the median weight of aluminum dichloride, soni bath passed through the aluminum-containing material and the weight of distilled aluminum was about 2.3 to 2.6 oeh, rose to about 2.8 to 3, o, when the realmillion temperature dropped. to about 800 ° C and became more unfavorable with the value between 4 and 7, when the reaction temperature was reduced to about 700 ° C or when the precipitation temperature of the aluminum chloride was raised to 130 ° C or more.

Using A1Br3 in the same apparatus, aluminum was distilled with the halide evaporator in the hall at a temperature of about 100 ° C and the reaction tower at about 1000 ° C.

Example II.

In another series of experiments in a similar apparatus, aluminum silicon containing 46% Si was used as the aluminum-containing material. It was introduced into the reaction chamber as a coarse powder, and no supporting material was used. AlCL evaporated to about 120 ° C was used as halide. The distillate contained in all cases less. 0.03% silicon. The ratio between the weight of the aluminum chloride and the weight of the distilled aluminum was on average 2.7 at reaction temperatures of about 930 ° C and rose to the value of about 7 and higher - at temperatures of 8 ° C and lower.

Example In a third series of experiments, ferroaluminum of different compositions was used. These materials were introduced into the reaction chamber as a coarse powder, without the use of any underlying material. The results given below were obtained using aluminum chloride as halide and an evaporation temperature of 120 ° C.

When ferro-aluminum containing 45.2% of iron and consisting essentially of the compound ALFe 2 or the compounds ALFe 2 and Al 2 Fe 4 was reacted with the aluminum chloride vapor at about 9 ° C, about 2.5 to 2.7 parts of aluminum chloride must be passed through. the ferro-aluminum to distill off one part of aluminum, while at about 8 ° C approximately 8 parts of AICI must be distilled for each part of aluminum under the given conditions. The iron content of the distillate was of the order of 0.1 or less.

When ferro-aluminum containing 71.4% iron and consisting mainly of the compound AlFe was introduced into the reaction chamber at about 1000 ° C, the ratio of distilled aluminum to aluminum chloride was about 2.5 to 2.7. At about 950 ° C the ratio between 3 and 8 became dependent on and decreasing with height of the ferroaluminum charge. A temperature of 800 ° C (with this aluminum-containing material) was found to be too low for a satisfactory distillation.

Claims (8)

Patentanspra.k: A process for the production or refining of aluminum, characterized in that heated aluminum-containing material is reacted with a halide which is transferred to the mold before it is brought into contact and reaction with the material, whereby the aluminum is volatilized from the material to form aluminum halide and compound compounds. these indicate are cooled to condense the aluminum. A process according to claim 1, characterized in that the halide vapor used is amnionized under the given conditions for its reaction with the aluminum-containing material. 3. A process according to claim 1 or 2, characterized in that the reaction temperature is higher than the evaporation temperature of the halide under the conditions prevailing in the said apparatus. 4. A process according to any one of claims 1-3, characterized in that the reaction is carried out under reduced pressure and / or in the presence of cotton or other neutral gas relative to aluminum. A method according to any one of claims 1-4, characterized in that low-boiling or subliming halides such as aluminum chloride (AICL) are used. Process according to Claims 1 to 5, characterized in that the aluminum and the halide are condensed in separate zones. 7. A method according to claim 6, characterized in that at least two halide condensers are used and used alternately as a halide condenser and as a halide evaporator, the same amount of halide being used repeatedly with the aluminum-containing material essentially without interruption. 8. A process according to claim 5, characterized in that the temperature of the aluminum condenser is kept between the condensation temperatures of the aluminum and the halide, so that the halide is kept in the angular Mom reaction chamber or in circulation therethrough. 9. A process according to claims 5-8, characterized in that the heat generated by the condensation of the aluminum is used to evaporate the halide in which it is condensed, and / or to preheat the halogen vapor. Procedure according to any one of the preceding claims, characterized in that the aluminum-containing material is brought into a dispersed state, i.e. in the form of powders or droplets, which offer a hog specific. area. Stockholm 194 8. Kungl. Boktr, P. A. Norstedt & Miler 4.80089