DE2347610C3 - Process for cleaning molten aluminum - Google Patents

Description

_met of whether

Impurities such as dissolved gases, Vt tun..B £. _"Withdraw ■ _s.

i _around « _SO || here aluminum and ^ ΐ & Α5 "with -at least 50" / ο or 75 "or more aluminum.

_In aluminum ^^^^
see impurities, im

_the aluminum, dujth Vcrhu. ^. ^^^ Aluminiuinschrotl mainly see Vertmre.mgungui hand It ^ .. ^ ^

^um , ^ ¹ TdTcAaIk- Rammen, us der Schmelz-Kal / .wm up; d.cst JIc _{u odcr also from the}

_aufb crc.lung «.njjji» ^ desired, these

Äcmcn - especially magnesium, that S bc, the dirt preparation on an ante,

of 5% unstciecii can. _{wi || nmz;}

^Wü , ^m Zv mme t cÄ. that magnesium ^ma " ^thC Ι di ii dh

³⁵ ee, want, st its efficiency hmsich.lich t : »Z ί u" 1 "chlorine and its implementation ,,, the exploitation, n * ^l metallic contamination

Γi Ü -.are t. At this considerable

and undesirable

The l.rlintlung concerns a method for cleaning of molten aluminum by means of a gas containing chlorine, tlas at least i'iein under tier Surface animal melt is introduced with stirring, so that the gas bubbles 1 are distributed essentially uniformly over the entire melt.

Hckaunilich one treats aluminum in order to give it it-, ds aluminum chloride to HCI and ΑΙ, Ο, -S.taub, de, - both l'rt.blem der air pollution autwerle ,. In order to resolve these difficulties, numerous ancestors have been suggested. An example has been suggested. Send chlorine through you under a salt cover and adjust the combination of the thickness of the salt cover in such a way that the ammonium chloride gas is formed when the metal and chlorine change slightly is dissolved that Io Safztlcckc dissolved Aluminiumchlond is then de Iiickreaklion with the metallic Venmre.niss κ nts (eg magnesium) at your disposal, the Scr to be l. I-I in such a system may be ve diminished. · vapor development or re . are operated by vaccines and offers some advantages over oil melting, however, but point out that this process / u an effective chlorine utilization in a k η internal process is not in the In order to achieve a high level of chlorine utilization, the system requires a recirculation technique, with de. Tlas, ", c all" s wicdcriu.il through a chlorination chamber, so the chlorination and the back reaction in H.srcichoiulci ,. Dimensions can take place to cmc adequate chlorination to "owahrleiMon.

A method of the type mentioned has become known from the iJS patent specification 16 36 881, according to which _; is stirred into the aluminum melt in chlorine-containing gas. In the known method, however, aluminum chloride is formed during the mixing process, the _a n the surface rises. This formation of aluminum chloride is disadvantageous, inter alia, because it is harmful to health. ^v or all, it reduces the yield of purified aluminum and increases the cost for the provision of chlorine.

Furthermore, a method has become known from French patent specification 10 93 710, according to which the chlorination of metal is carried out in several chambers one after the other. Through the chambers gas bubbles of the gas treating the melt are passed through. Significant mechanical agitation the melt does not take place.

Finally, U.S. Patent J2,27,547 relates to one Process for degassing metal melts in which inert gases are used which are in high volume flows are introduced into the molten metal.

To increase the purity of molten aluminum, the invention is characterized in then stirring and gas injection by means of an impeller known per se takes place in such a way that emulsification occurs the aluminum melt with the chloride reaction products that form is avoided.

The invention makes the highest possible Chlorine utilization rate with very high metal saturation / s achieved, whereby a continuous operation without material return is possible and the degree of chlorine exploitation of 100% or almost 100%. Thereafter, the chlorination takes place under controlled conditions of chlorine-metal contact, which the Efficiency of the conversion between chlorine and the metallic impurities essentially Increase values that were previously not considered achievable for commercial purposes.

The efficiency achieved is not only based on the conversion of the chlorine alone, but, what is more important, on the desired conversion of the chlorine into the chlorine salt and the contamination. Thus, on the basis of a molten aluminum to the magnesium removed from V'crden, a 100% efficiency Jer reaction of chlorine not as important as the fact Dall all of the chlorine with the magnesium (and not with the aluminum) reacts.

Another advantage of the invention is that dall the content of impurities - for example magnesium - ties the treated aluminum very much adjust precisely, and this in itself is a point of utmost importance for commercial implementation. The improved method of treating Aluminum allows the magnesium content to be adjusted to ± 0.02% in a continuous process. This property is very desirable for a furnace operation in which excessive removal of Magnesium can lead to operational disruptions, because the goal of treating ties with aluminum is often not simply lowering the content of a contaminating metal such as I). Magnesium, rather its reduction to a certain value.

Preferred embodiments of the invention are described in more detail with reference to the drawings.

F i g. I am a cut who seliematically maintain ties shows an improved system and an arrangement suitable for carrying out the invention.

F- 'ig. FIG. 2 is a top plan view of the agitator of FIG Fig. 1.

1 to 5 schematically show embodiments of the present invention, tlie of the one shown in FIG. I shown differ.

A suitable device for carrying out the method according to the invention is shown in FIG. I shown. The system 10 has a first i2 and a second 16 Chlorination or reaction chamber or zone, which are separated from one another by a partition 18.

A further partition 22 separates the second reaction chamber 16 from a settling chamber 24, which in turn is separated by a partition 28 from the outlet chamber 26 with the cleaned metal. The metal flows into the arrangement through the inlet M)

ι.s and through the first reaction zone 12, from tier it under the partition 18 passes through into the second zone 16. In each reaction or chlorination chamber wirtl the aluminum melt by contact with a reactive chlorine-containing gas - preferably Chlorine - chlorinated under carefully controlled conditions to be described below, the very result in high chlorination speeds and efficiencies. The reaction products- animal chlorination, the Chloridsalz.e the metallic impurities, form a salt layer 20 on the aluminum melt.

Glass flows out of the second reaction chamber 16 Metal under the partition wall 22 through into the first settling chamber 24, where the heavier metal from ile salt-like reaction products from chlorination

\ o drops. Movement in tier chamber 24 is through the Base plate) 2 ensures that the metal-salt mixture is directed upwards to the chamber 24 Movement is granted in order to achieve tlie desired separation of the phases and a flow in tlie chamber

VS 26 bypassing tier chamber 24 to prevent. The Metal then flows from the chamber 24 under the partition 28 through into the chamber 26 before it through the Auslall 40 ausl'lielli. An Absireichwaiul 24 Be careful to install an im at Auslall 40

. | o to ensure a substantial salt-free flow. The container II, containing the tier tlas system, is closed by a suitable lid ti in order to achieve a moisture-free atmosphere and prevent the formation of oxides and escape of vapors

.15 Avoid ambient air. _cr

This is the context in which the system is used preferably a substantially constant purging with a dry, non-reactive gas. how Nitrogen or argon or one of the carrying gases or

so carbon dioxide, be careful, you drank through the Hinlal! 70 introduces and withdraws through outlet 72. The dry, inert purging gas has the advantage of being moisture-free Atmosphere above animal salt and animal molten metal and tlas also takes hydrogen gas escaping from the metal with it. Preferably one sees for each Chlorination zone has its own purge gas inlet 70 in front of it (cf. FIG. I). to have the best security against tlas Presence of air above the chlorination zone, because air can cause considerable corrosion problems.

(10 never - especially for tlie rotating I. on rail shafts - raise.

The partition 18 has an opening 14, tlie so It is arranged that the salt phases 20 in both reaction zones 12. 16 are in communication with one another i.s put. There is also tlie (»bet edge tier partition wall 22 so that here too there is a bond between the salt phases / is established. The mutual connection ilei Salt phases in ile reaction and descent zones

prevents excessive sal / accumulation in one specific zone and facilitates the removal of the salt from the zones or chambers of a plant. Of course, there is a connection of the salt phases via the partition wall 28 to the zone 26, which contains the purified metal contains and should be essentially salt-free, undesirable. Which, as will be explained below, from one Suitable heat-resistant material existing container walls are preferably in a water-cooled Sheath arranged, which is suitably made of steel. The cooling of the walls prevents the molten salt from migrating through the refractory material by being in the refractory material provides a freezing clinic. This point is particularly important for the transition of the partition wall 28 to the partition walls of the container 11. The partition wall is let into the side walls; the salt could however, diffuse around the partition into the zone 26 with the pure metal. Such a salt wall is prevented by in front of the extreme lateral expansion of the partition wall 28 for a Freezing Clinic ensures.

In each of the reaction chambers there is an agitator 50 comprising a shaft 52 and a stirring nozzle assembly or an impeller 54 is arranged. The shaft 52 is hollow 56 on the inside; this cavity serves as a conduit for the Chlorine or other chlorine-containing gases emitted from the gas outlet 59 under the impeller 54 into the melt flow in, as indicated by arrows 60. The shaft 52 of the agitator is driven by a drive 62 - for example an electric or air-powered one Motor - turned. The chlorine gas enters through connection 66 and flows in through line 56 below, in order to flow from the gas outlet 59 into the molten metal introduced into the first reaction chamber 12 stream. The same applies to the second zone 16. The IMg. 2 shown impeller 54 has a turbine-like structure with a hub 55 and radially extending blades 57. The chlorine is in the Melt introduced through the gas outlet in the bottom of the impeller and from the rotating impeller in small amounts Vesicles over the entire reaction canimer 12 distributed. The magnesium or other metallic impurities in the melt react with the Chlorine, magnesium chloride or the corresponding metal chloride forming to form the molten salt layer 20.

In order to achieve the chlorination efficiency achievable in accordance with the invention, a number of factors must be carefully controlled. It is essential that the depth </ the metal between the MeLi \ ll-Sal / -. '' ^I nzschicht (ii and the place of introduction ck's C ^{- 1} S IiIoI at least 25.4 cm, preferably at least 38.1 cm cheating where 50.7 or more is desirable This depth c / is the perpendicular distance from the metal salt level / shallow 21 down to the bottom of the impeller, that is, the point of distribution of the deep gas the chamber 11 is designed in such a way that the depth of the impeller 54 allows such a distance (/. The depth (/ of the aluminum melt / .e above the location of the chlorine / utritis has proven to be critical for reaching the gas-metal conflict / eil, which is necessary to ensure the high efficiency according to the invention. One could / was to assume that the stirring of the chlorination / ons is of greater influence than l'ictors such as the melt. Nevertheless, it has been shown that the melt / licfe is of great importance for the improved seduction, since it ensures the appropriate gas pressure retention zc.it in the Rcaktionszonc. As the depth drops below 38.1 cm, the chlorination efficiencies also drop below desirable levels for some applications; accordingly, 38.1 cm is the preferred minimum. If the depth is significantly less than 10 inches, the efficiency will also decrease excessively. As a result of this drop in efficiency, considerable amounts of gas can escape from the metal phase

ίο and thus the direct chlorination reaction are lost, which is so essential to the high chlorination efficiencies of the present invention. This high efficiencies through direct chlorination are extremely important to the success of the continuous process important.

The depth of the molten metal before the system is started up should be considerably greater than that which leads to the desired minimum distance d , since the metal layer 20 becomes constantly thicker during operation and tends to displace metal downwards in the process. While the initial Mclalltiefc can be 61 cm, with several hours of continuous operation a Sal / .sehiehl of 12.7 to 22.9 or 25.7 cm thick, which is the depth of the metal layer

2s reduced from 50.7 to 40.5 cm. Regular removal Lies salt is beneficial and is preferably made to ensure that during continuous A suitable machine is always available. When commissioning, efficiencies are of 100% achieved without adding a layer of saline. In practicing the invention, one will. to the To achieve the best possible efficiency, the SaIzsehichiclicke preferably keep it under control by losing weight regularly - for example on not more than 10.2 cm and preferably no more than 5.1 cm.

Another important factor in the practice of the present invention is the conditions on Check impeller 54. The chlorine gas bubbles must be essentially uniform through the entire melting body in a chlorination chamber or - /. one distributed or dispcrgierl. The impeller must be designed and controlled in such a way that the desired distribution of the chlorine gas bubbles results.

• Is after air-water model study in the chlorination chamber should have at least 80% a diameter of less than 3.175 mm, 40% a diameter of less than 1,587 mm and not more than 10% a diameter of more than 6.35 mm. Off-cut

su borrowed it is practically impossible, the size and that Stressful behavior of chlorine gas bubbles in an aluminum hoop / e to determine. The use of water-to-air models in connection with line-lapse pholography however, it is of great use

ss if you want to determine the operating conditions, dii agree well with those who have proven successful in actual operation. If »Im the size of the vesicles for a given pressure condition gen regarding the impeller and the chamber in

(«1 model results in the stitch pattern described above The conditions should also be sufficient to achieve the required chlorine flower size and distribution in the To achieve aluminum clay. Factors voi Influence on the Blilschengrölk are and vary

(Leave it to get the appropriate flash vision sizes are the type (JKWk and configuration of the impeller (blade size and number), the Tiirbineiidiirchnicssc (especially in relation to the chamber size), di

Running speed, the turbine arrangement and the location of the place where the gas is introduced. the Bubble density naturally depends on these factors and also on the amount of gas supplied.

Another very important point for the system is that it has been found, according to the invention, that the metal must not be substantially sheared into streams or particles. Such a crushing would lead to the formation of a metal-salt emulsion which not only poses problems of separation in the chambers 24 and 26. More seriously, it has been found that when the metal flows or droplets are sheared, the droplets are absorbed by the liquid reaction products. This process prevents the highest possible chlorination efficiency from being achieved and must therefore be avoided. Furthermore, an emulsion acts as continuous salt phase (discontinuous Mctallphasc) and \> \\\ on the gas contact time, the same influence as increased salt phase (decreasing Mctallphasc and depth ti). Similar to vesicle size, but to a lesser extent, water modules can be useful here in determining whether a given set of conditions will distribute the liquid phase such that emulsification may result.

The turbine-like impeller shown in FIG caused by correct analysis and correctness Operation of the desired expansion and distribution of the chlorine bubbles while there is a crushing of the Substantially prevents melt. In a typical system in which the chamber is seen from above a size of about 0.62 0.62 m or one effective diameter of about 0.61 m. has the Impeller hub 55 has a diameter of about 20.32 cm, with 12 radial blades 57 a size of about 5.1 χ 5.1 cm are available. The height of the impeller is then about 5.1 cm: its outer edge has a diameter of about 30.5 cm. Rotating this impeller at speeds of about 150 to 400 I J / niin (i.e. at Circumferential speeds of around S to 2.4 to 6.1 m / s), the desired stirring effect is obtained. The rotational speed of the impeller is preferably about 185 to 275 rpm (circumferential speed from 2.822 to 4.27 m / s). A good nominal speed is about 200 to 220 rpm, 3.05 to 3.36 m / s peripheral speed). Accordingly, the preferably used embodiments of the present invention a (! ^ distribution device with radial blades aiii, which move at a peripheral speed Move through the melt from about 2.4 to 6.1 m / s and preferably 2.74 to 4.27 m / s, For (lic In carrying out the invention, stirring and gas distribution are provided which result from these operating conditions at least one Chloricrkamincr with an effective diameter of 0.46 to 0.61 or up to 0.91 in result, as already unspecified, work if the running speed is too high, the metal seizure counteracts complete chlorination, while running speed that is too low is insufficient Division into vesicles, poor division into blisters and then also causes incomplete chlorination, d. H. so those difficulties which the chlorination according to the prior art was subjected.

While the operating conditions described above are a preferred embodiment relate to the invention, the invention includes conditions which satisfy the following relationships:

DkIr = 1.5: I to 2: 1 (D drklii = 1.5: 1 (2) tir / Br = 6: I. (3) dr / bi. = 6: 1 (A)

With

D = effective diameter of the chlorine chamber,

dr = outside diameter of the turbine,

you - diameter of the turbine hub,

Br = thickness of the turbine blades,

ι? Bi = length of the turbine blade ^

These relationships seem to run for speed of the impeller between 200 and 400 rpm and an effective diameter of the chloride chamber to be suitable up to 0.91 m. The effective diameter is the length of a side Square or the smaller transverse dimension of a comb cross-section that is rectangular in plan view.

The operating conditions described here are essentially given as guidelines and are intended to Do not necessarily limit the invention. They represent guidelines that come along with water-air modules make it easier for those skilled in the art to carry out the invention.

As already mentioned, the turbine blades should !! and the location of the gas feed as far down in the melt as is practically possible. It has For example, found to be desirable, the blades and the location of the gas inlet about 12.7 to 50.8 mm above the floor of reaction chambers 12 and 16. If you arrange the impeller, for example 25.4 mm above the ground, the gas emerging from the gas outlet 59 forms under the hub 55 of the I .luifrades 54 a large bladder, given by the Sehaul a 56 is thoroughly smashed; this effect occurs essentially without any abrasion. the resulting vesicle dispersion penetrates essentially the entire body within the depth c /, without the Salzschiehl 20 in motion

4.S to put. That means it is sometimes important that the Effect of the impeller the interface 21 between the Melt in chamber 12 and salt layer 2 (1 undisturbed loud and you can get the wheel as close as possible arranges on the ground. If the (ircn / l'läelu

s "one would SaI /. from the reactionories in the Kammci 12, press down into the melt and thus affect the reaction conditions. Additionally / 1 A low left wheel position is a calm borderline favored by a fan wheel construction that does not have a

ss strong upward currents. An impeller mi inclined blades produces such aiifwiirtshewc μιιημ and is preferably avoided against iihc an impeller, the blades of which eizet an essentially horizontal movement of the melt

(in jH'll.

In practicing the invention, di is The length of the metal remains in each region for about 2 to 6 minutes as it passes through the system. D. Mean chlorine rebound time in the system is approximately i's seconds per stage, based on empirical Itc / i hungeii tinter inclusion of the fingangsleisiuu |: tu der Gasslrömuiigsgesclnvindi (: keit. It has heriui put that this Koiitnkt / rush for a full siäiuli

Chlorination, a full utilization of the chlorine or chlorine-containing gas and a thorough and controlled removal of metallic impurities from the melt are extremely advantageous.

The capacity of the system is largely a function of the metal flow rates and desired gradients in the composition of the incoming versus the outgoing melt stream. An essential aspect of the system according to the present invention is that of precise adjustment of the content of metallic impurities in the exiting metal stream. It has been found that the present invention achieves an accuracy of ± 0.02% of the content in any particular metal without difficulty: this factor is often important with impurities such as magnesium, for which a certain defined content is more essential than a complete removal. With regard to the impurities, such as sodium or calcium, which are typically present in untreated aluminum with less than 0.02%, a proportion of 0.0001% or less can be achieved with the present system. Since the system efficiency is essentially 100%, the system can be considered to be essentially stoichiometric even though it is operated continuously; to the knowledge of the Anmeklerin, no commercially implemented system has so far achieved such a performance. In order to achieve a desired level of a metallic impurity such as /. To achieve as magnesium, is switched on a material balance based on the Metallsirömiingsgesehwindigkeit and Magnesiumanteilsgelälles / wipe and placed exiting stream to determine the amount of chlorine on the basis of a stoichiometric operation.

The system shown in the figures works with horizontal melt and execution, what it does with existing aluminum prevention systems makes, which mostly also have horizontal sprues, as this is a small one; Oxide formation than with Systems with considerable differences in price.

The F.inlaß V) may also (and preferably is) located higher in about i \ vr same height as animal outlet 40 and only a few inches to give the melt in the gate - introducing (ilchon conditions in the Keakiionskammer 12, dal. ) the Schmel / mirror is above the highest l'uiiki of the inlet 30: see the figure.

Furthermore / own the figures / ugswoise rings set embodiments in which the melt two or more heakiionskannneni iniclieiiiaiuler, tormented by one or more settling chambers in K ei lit. · switched! runs through, because it hcrausye Mi-Ill, dal) such a system the most effective operation iiiikT the point of view of the highest (hlorausnui / ιιημ and based Ltnlenuiiii ', nit.'iallisi'licr Veiuureiiii Ι'.ιιημί'ΐι jjcsiallei , but can also be a cm / ige "which can be used more than two in rows l'.cschalk'k ¹ (liloricrkiiiimicrn. I.ine i'in / iju ¹ K, always caused / was a lower maximum removal of impurities, Isl but hiiisichllirli the cost effort μiinsIiμer; several chambers are / was cheaper for the Κοίηίμιιιιμ of the MeIaIIs, but I yours.

Fs ^ iI) I emc number of arrangements with multiple chloiier / ons, as they are the Fig. 1 to ^r > / own. In the I 'i L ». i siiul the first and the / while (hltirierkainniei

12 and 16 separated by a partition 18 as in FIG. 1, under which the melt flows. Instead of under the partition 22, which separates the second reaction chamber 16 from the settling chamber 24 as in FIG. I separates, hi-flow takes place in the embodiment of FIG. 3 an overflow of the partition 22 takes place. This embodiment offers the advantage of a longer contact time in zone 16 and, from this point of view, can be compared to the arrangement of FIG

ίο are preferably used. In FIG. 4, the first and second chlorination zones 12 and 1b are the same as in FIG. 3; however, the partition 22 here forms a third chlorination chamber 116, from which the metal passes under the partition 122 into the

is settling zone 24 flows, from which it flows in the manner shown in FIG. 5 shows a separate settling zone for each chlorination zone. In FIG. 5, the treated metal leaves the first chlorination zone 12 by flowing under the dividing wall 18 and flows through a first settling zone 24 before it passes over the dividing wall 118 into the second chlorination chamber 16, from this under the dividing wall 22 into the second settling chamber 124 and from there continues to flow in accordance with the other arrangements. The possible advantage of the arrangement according to FIG. The reason for this is that a metal-salt emulsion which may have formed in the first chlorination zone 12 "has an opportunity to settle before the melt reaches the second chlorination zone 16. Any reasonable number of chlorination and settling chambers can be used in the practice of the present invention. be used; the first and the last partition, el. h. those after the first chlorination zone 12 and before the zone 26 with the cleaned metal, however, must not be exposed to the flow.

II Another key consideration in the Implementation of the present invention is that when the melt is exposed to heat in ilen Reaction and settling chambers have no combustion products be introduced into the system. Indirect heating should therefore be preferred; she Kills itself by reaching immersion tubes, which oiler fires from the inner surface in some other way - for example electrically - be heated.

Since the chlorination of aluminum is exothermic, the main purpose of heating is Keep an eye out during business interruptions or downtime.

From the point of view of building materials, one becomes the l.aul'radwellc and the impeller itself from one

so hoclilemperaiurfesieii material, such as Graphite, produce, which, however, must not be attacked by the aluminum hoop / s. Density iiinl Related graphic types are for this / wake-up, whereby the wave consists of

ss permanent and the impeller made of (light graphite (Resistance to erosion) Should also be ordered in the system preferably germs Use ferrous metals, if one also uses one for the outer surfaces of the walls around

(κ · Siitiilmanlel, which is water-cooled. Dk walls 11 and the floor as well as the partitions can consist of any tempered material such as silicon carbide, alumina or graphite, with an essential point that the material is raised vertically

('s negen the Aliiininiuiusehinel / c, chlorine gas and dk sul / halligcn Ueaklioiispmduklc is constant.

When the system is imported, the container U / Herst to / ti is of a height that is both fun and iiui'l

table

llohuiulliing

covers the outlet, filled with molten aluminum. The depth must of course be so great that the minimum depth d defined for the reaction chambers 12 and 16 results; It is pointed out once again that the depth el becomes smaller in the course of the process due to displacement by the molten salt layer 20. So where a minimum depth d of 38.1 cm above the gas inlet 59 is to be maintained, one will start with a melt depth of at least 55.9 to 60.9 cm. If the salt layer then increases, the salt layer must be removed regularly before the melting depth drops below the desired minimum depth of 38.1 cm.

There is normally no need to apply salt to the melt before running the system; ι ^ such a salt layer brings no significant advantage when carrying out the process, but it does Circumstances the disadvantage of displacing the melt. So you start the process with a layer of salt from 5.1 to 7.6 cm, in some cases there may be the disadvantage that the point in time at which the Salt layer must be removed, occurs too early.

Heat is added to the system in order to maintain the heat content of the aluminum melt, and brings in chlorine as soon as the blades of the impeller begin to move. Because the chlorination reaction is exothermic, you can stop the supply of heat when the reaction has started. Have the If the impeller blades are set in motion and the chlorine supply is started, the melt is let through Unit flow because the chlorination speed and tier operating efficiency are so high that at standstill Tier melt an excessive vapor formation occurs, tla the reactive metallic impurities can be used up very quickly. V>

A few examples will now be given to explain the advantages of the present invention. In every example - except for examples 8 and 10 - If the treated metal was Al-Si scrap, as is typical for secondary Al scrap.) < > is. Unless otherwise noted, in principle the arrangement shown was used, with a Impeller, as described above, preferably with a circumferential diameter of 30.5 cm, a hub gym knife of 20.3 cm and provided with twelve blades of 4s table 5.1 χ 5.1 cm area provided. Both Examples I and 2 were continuous processes involving about 5900 kg / h of aluminum in an arrangement according to Fig. I at a wheel speed of 200 rpm were treated. Table I gives the details of Examples I and 2 w i h e he.

Table 1

Examples 1 and 2 demonstrate the high efficiencies that can be achieved by the present invention. The MgCI_> produced is anhydrous and has a purity of 95 to 98% or better and is therefore a valuable by-product.

Examples 3 and 4 compare the method of the present invention with a conventional one Furnace melting process; the details can be found in Table 2.

example

Diirchlaufverf.

n. ti. invention

Oven mason / seduce

Mg removal above, 2% 0.2%

Weight of the melt 20 000 20 650

(kg)

Cl 2- consumption 117 16 6b2

(kg)

No service life, as the diameter is 1.72 h
running procedure

Cl. 'Conversion to MgCL- 99.92% 80%

Exhaust:

free chlorine (mg / m ') 8.3 670

ppm 2.7 224

Chloride (mg / m ¹ ) 7.4 13 800

It is clear from Table 2 that this was improved Process compared to the Ol'enschmelzverfahren with regard to the chlorine Ausnmzung and the prevention of Air pollution has significant benefits.

In Examples 5 to 7, the present system was used in the return process to / peculiar that, while it can be carried out continuously, a block return drive is also possible which the metal leaving the system is guided into the healing process. Table 3 shows the results of Examples 5 to 7.

Ik'example

Melallethrough (kg / h) 52 20 5970 5-50 Aniangs-Mg-Gchali (%) 0.9 !, I 1.0 I nd Μμ-Gchali (%) 0, 'Ih 0.29 0.1 I. (! ■ • feed (k |, '/ h) Ί4, ^Γ > dl, 8 hlj Μμ distance (kg / h) I 'ι ,! 21.2 21, J. ('1,' - Un) SHtZ / u MgCI- ("M 100 100 100 Uüi-kliHil '/ eit (h) 1 ■ 1 •1 SlulVn / ahl I.

Μμ-ΚοΜ / enlraiiuM at the entrance,
Μμ concentration at the exit,

('!.! ■ / .iil'uhr

Μμ-ΕηΐΙ'ΐΜΊΐιιιιμ (kg / h)

Π 'conversion, to MgCb (%)

MgCL 'produced (kg / h)

Milll. Keaktiousieiuperaliir ((')

H- (IeIiIiIl des l'rnduktes (ml / 100 μ) ', 0.12

0.51
0.18

58.1
19.9
100
78.1
7 yl

(MiO
0.17

tiO.I
20, (i
100
80.8
750
■ = ■ 0.12 Example 8 proves it! the ability of the present invention to reduce the magnitude of the magnesia very quickly and quickly in a high (.'hloiausnutzuiigsgnule hci / ubeiiiilteii) iodileistiingsdiiiThlaiifsyslem. The details of Example H are as follows:

('S Metallduivl'sal / (kg / h)
Anlangs-Mg-content C '/ n)
EiI (I-Mu- (IeIIaIl (%)

"'(From left I M)

0.029

0.00b

CI ₂ feed (kg / h)
Mg removal (kg / h)
CIr conversion to MgCl ₂ (%)
Emission of free Cl ₂

18.1

6.0

97.0

1.7 ppm

4.8 mg / m ¹

While the degree of chlorine utilization in example 8 is lower than in the previous examples, muli it should be noted that the Mg is removed here to a very low level at which a decrease in the Efficiency must be expected. Nevertheless, the utilization rate of 97% is impressive.

From the above examples it can be seen that the process of the present invention is capable of accommodating a variety of input contaminant levels and consistently achieves chlorine utilization levels of up to 100%. More importantly, almost all of the chlorine is converted to the metal salt of the contaminant. The method of the present invention has been shown to be capable. Remove magnesium to a level of 0.05% and less; in fact it has been found to be able to reduce the Mg content to 0.005%, although the efficiency decreases somewhat if the content of the impurity in the metal being treated falls below 0.05%. In addition to removing magnesium and other metallic contaminants, the method shown has proven its ability. Push gas contaminants down to 0.15 ml per 100 g or less - e.g. 0.10 ml / 100 g or less. Furthermore, the oxide content can also be substantially reduced, as has been shown in vacuum sealing materials, which typically ^{indicated an increase in metal density from 2.4 g / cm 3} at the inlet to 2.7 g / cm ³ at the outlet.

The invention so far has essentially been from the point of view of reducing the content of Magnesium, sodium, and calcium have been described. In a broader sense, however, the invention encompasses also the removal of other elements that can be chlorinated in an aluminum melt in the the sturgeon reacts with the chlorine to form the corresponding chloride. For such a Element is the negative ratio of the free chloride formation energy, divided by the valency, higher than that of aluminum in a chloride system. These elements are next to Magnesium, Sodium and Calcium to Strontium, Lithium and Potassium.

Where the invention is particularly useful for removing elements such as sodium, calcium or strontium, is used, which are usually present in a low concentration of 0.002% in the untreated metal should be reduced to 0.0002% or 0.0001% or even less, one of the looks at the present Invention encompassed procedures before that, in addition to the chlorine-containing gas, a non-reactive gas introduces. Since the chlorine-containing gas is introduced in amounts that are in stoichiometric proportion to the Contaminant element of the treated gas or the amount of element to be removed. and there, as described above, certain vesicle distributions in the practice of the invention are preferably used, it can be understood that the for generating this vesicle distribution required amount of gas can be greater than the very small amount of chlorine-containing gas that stoichiometrically corresponds to an extremely low proportion of an interfering element. The unresponsive Gas now serves the purpose of facilitating the formation of the desired distribution of bubbles without having to use excessive amounts of the chlorine-containing gas, which leads to air pollution problems would lead. Gecignelc non-reactive gases are the so-called carry gases like Helium, neon, argon, krypton and xenon as well as their mixtures and also nitrogen and, but less desirable carbon dioxide. In the case of nitrogen and carbon dioxide, precautions must be taken graze to avoid the formation of nitrides, oxides, carbides or their complexes. argon does the task at hand quite well and is preferred because it is effective and easy is available.

The amounts of chlorine-containing and inert inert gas used in performing the present Invention can be used, depending on the proportion of impurities in the starting material and the desired final state vary considerably. Where the starting material is significant amounts of magnesium contains and large quantities of the chlorine-containing gas must be used to reduce the magnesium content To reduce this significantly, the joint use of an inert gas can only do little or none at all Bring advantage, since the removal of the magnesium as well as considerable amounts of the gaseous and oxide forms Contamination already takes place directly through the chlorine-containing gas, although a small proportion an inert gas can also be advantageous here for the removal of gaseous impurities. However, if you want to remove sodium or calcium, their concentrations even in the untreated metal does not exceed a value of 0.002%, or if you want to work with very low levels of magnesium, the amount of chlorine-containing gas to be introduced increases compared to the presence of larger proportions of magnesium strong.

However, in order to achieve the bubble distribution desired for the present invention, more gas than the very small amount of chlorine-containing gas must be present; this deficiency is made up by argon or another inert gas, so that, for example, 141.5 cm ³ or more (chlorine-containing and inert gas combined) per 0.454 kg of molten metal are introduced into the system. Where the stoichiometric amount of chlorine-containing gas exceeds this amount or a preferably used amount of 284 cm ³ or more of gas per 0.454 kg of melt in the system, it is not necessary to supplement the chlorine-containing gas with an inert or non-reactive gas.

However, where the stoichiometric amount of the chlorine-containing gas to achieve the specified amount is not sufficient, it is advantageously supplemented with a non-reactive gas in order to ensure that this is the case the desired distribution of bubbles is achieved unc oxidic and gaseous as well as metallic! Impurities are bound. When treating an aluminum melt, use less sodium or calcium concentration would be the relative amounts of chlorine-containing and inert gas of less than al 1% up to 20% (typically 1 to 5%) for those containing chlorine and 99 or more up to 80% (typically se 99 to 95%) for the inert gas, although these figures are only guidelines and the invention in its

I.

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In the broadest sense, it also includes significant other proportions of the two gases - such as, for example as little as 0.5 or 0.25% or less (e.g. 0.1%) or as much as 60%, 80% or more chlorine.

So as far as the ratio of one gas to the other is concerned, it can obviously be greater or less than To be one.

The amount of chlorine or other chlorine-containing gas approximates that which reacts with the metallic impurities to form their chlorides. The amount of such elements and the extent to which it is desired to remove them can vary within a wide range; accordingly, the amount of chlorine is also different. If one considers z. B. the treatment of aluminum with a small proportion - for example 0.0015% - sodium, the required amount of chlorine is also very low. If the chlorinatable element is present in very small amounts - for example less than 0.03% and especially less than 0.005% - the amount of chlorine used can be greater than the exact stoichiometric amount, since the reaction conditions make an excess appear advisable when treating extremely low concentrations of impurities to make the chlorination as complete as possible. Even if one uses three or four times the stoichiometric amount of 0.0015% Na, the amount of Cl ₂ is still extremely small; the excess is readily absorbed by other reactive elements - such as Mg, which is often also present. For very small proportions of impurities, the amount of chlorine-containing gas can therefore be a multiple of the theoretical exact stoichiometric value.

However, if there is a significant amount of a chlorinable interfering element such as magnesium in Proportions of, for example, 0.05 or 0.5% or more, the usable amount of the chlorine-containing Gases closer to the theoretical value, since the considerably larger amount of the melt hardly can be absorbed or even released into the air. The same applies if the proportion of an element should be reduced to a certain value - for example from 3.5% Mg to 2.5% Mg. The stoichiometrically usable amount is essentially that one percent magnesium that is removed should, equivalent. A stoichiometrically usable amount of chlorine-containing gas is therefore theoretical equivalent value in relation; however, the accuracy of the relationship can vary with the amount of chlorinable element fluctuate. Is the amount reacted less than about 0.03% and particularly less than 0.01% or even 0.005% or less, the amount of chlorine or chlorine-containing gas can be the significantly exceed the theoretical equivalent of this element. Where the proportion of the to be chlorinated Element is about 0.03% or higher, you bring chlorine or the chlorine-containing gas in an amount that corresponds approximately to the theoretical equivalent.

Since, as shown above, the amount of chlorine-containing gas can fluctuate within a wide range, this is true same for the relative proportions of the chlorine-containing and inert gas ·, this fact is responsible for the very broad range given above (0.1% Cb versus 80% or more in one Ch-A mixture).

If very small amounts of the chlorine-containing gas are used, there is less need (cf.

Fig. 1) to ensure that the reaction products of the Separate aluminum melt, since the amount of the reaction product is extremely small. In such cases it is usually also possible to use only a single instead of the two reaction zones of FIG. 1, for the same reason, namely the small amounts of reactive substances with who have to be touched. In the system of FIG. So 1 is for treating a Aluminum melt for removing a small amount of sodium of about 0.001% only a single one Reaction or chlorination chamber 12 required. The metal flowing through under the partition 18 can then pass directly into the last chamber 26, the second chlorination chamber 16 and a separate one Settling chamber 24 can be omitted. The amount of salty product resulting from the reaction would be extremely small and would not pose any problems under normal conditions even if considerable parts of the same flow out with the melt. Example 9 shows the operation of the system according to de present invention using a chlorine-argon mixture for treating an aluminum melt with 0.053% Mg. The details are as follows:

Metal throughput (kg / h) 17270

Initial Mg content (%) 0.053

Final Mg content (%) 0.013

Initial H _{2 level} (ml / 100 g) 0.41

Final Hr percentage (ml / 100 g) 0.10

Gas to Metal Ratio (cnWkg) 0.013 total

The gas used in Example 9 consisted of 56% CI2 and 44% A, the amount of chlorine being about that Mg amount to be removed and the chlorine utilization rate was about 100%. The argon was added to the gas-metal ratio to a preferably used value of more than 0.01 bring and thus improve the removal of gaseous components; this is expressed at a very low level Hydrogen content of the treated metal.

Example 10 shows the use of the improved method according to the invention for removing metallic contaminants from sodium and calcium and hydrogen gas and oxide inclusions from an aluminum alloy of the type 1100 using a chlorine-argon mixture of 0.8 to 1.7 % Cl ₂ . The details are as follows:

Metal throughput (kg / h) 9090 Initial Na content (%) 0.0011 End-N a-share (%) <0.0002 Initial Ca content (%) 0.0006 End Ca content 0.0001 Initial H ₂ content (ml / 100 g) 0.37 Final H ₂ content (ml / 100 g) 0.125 Vacuum gas density (g / cm ³ ) before treatment 2.59 Vacuum gas density (g / cm ³ ) after treatment 2.70 Gas throughput A. 6509 [l / h] Cl ₂ 56.6-U 3.2 [l / h]

The measured values are determined under normal conditions (° C, 760 mm Hg).

As can be seen immediately, the improved process turned the aluminum smelt into good quality by significantly reducing the proportion of metallic, oxidic and gaseous impurities remarkably improved.

Similar results were obtained with Al alloys containing significant amounts of Mg, where with the method Na and Ca were selectively removed without substantial loss of Mg.

For this purpose 2 sheets of drawings

Claims (1)

" ^{Λ V} "'»" ¹¹¹ V ^ Xi "the clekVropositive sintl, himself 3 method according to one of the preceding, 0 ¹ Y ';; ^^ _tsscn ; _int | _cm one the molten aluminum read molten aluminum tMiiltintii ^ ^L reactive chloride vapor 1 Patent claims: 1, Method of purifying molten aluminum by means of a chlorine-containing gas, which is introduced at least 25 cm below the surface of the melt with stirring, so that the Gas bubbles are distributed essentially evenly over the entire melt, thereby g e k o η η ζ e i c h η e t that stirring and gas blowing by means of an impeller known per se takes place in such a way that emulsification of the aluminum sea salt with the chloride salt reaction products that form is avoided. 2. The method according to claim I, characterized in that the stirring with an impeller it is carried out that chlorine is used as the chlorine-containing gas and the chlorine in the center of the pressure is introduced. hren nacu l-mh-u. ^ _ " Claims in which the molten aluminum is passed through a first chlorination chamber in when it comes into contact with the chlorine-containing gas, the molten metal from the chlorination chamber into a settling chamber to separate the trapped salt from the molten metal is passed, characterized in that the stirring is essentially at the On of the chlorine content in the way is effected that an air-water mixture Corresponding gas vesicle distribution is generated, in animal at least 60% of the cias vesicles have a diameter of not more than 3.2 mm, and all scatter and shear octo on the metal can be essentially avoided. 4. The method according to claim 5, characterized in that tlas chlorine is supplied in an amount which is in siochiomctrischem ratio / w of the amount of animal / u removing impurity. 1 Process according to claim 3 or 4, characterized in that the gas additionally contains / M chlorine a proportion of a non-convertible gas. b. Method according to claim 3, characterized in that at least SlOcniVkp gas. is introduced based on the treated melt. 7. The method according to claim b, characterized in that that the relative amount of the chlorine-containing gas compared to the unreactive gas is low. K. 1 lügelratl for the implementation of the method according to claims I -7. Characterized in that! the diameter of which is JO, ". tin and tlas has twelve lines, the approximately"> χ 1 cm groll sintl unit tlas rotates at a speed of I8 ^r > to revolutions per minute and is arranged at a distance of ηίιι from the motion of the chloride chambers . different
Oxides and