DE1167039B - Process for introducing aluminum oxide in powder form under pressure into the molten bath of an aluminum electrolytic furnace - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C22d

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File number:
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German class: 40 c -3/12

J 167 039

N 17757 VI a / 4Or.
January 14, 1960
April 2, 1964

The invention relates to a method of introducing aluminum oxide into the molten liquid Bath of an aluminum electrolytic furnace under pressure.

It is known to produce aluminum by reducing aluminum oxide in a molten bath of cryolite or fluoride. As a result of the high temperature (approx. 1000 ^° C.) generated by the anode, a thick, hard crust of cryolite forms on the bath surface, which must be pierced in order to introduce the aluminum oxide. Since the removal of the crust by hand is laborious and leads to heat losses because the bath surface comes into contact with the atmosphere when the crust is pressed in, two groups of charging devices have been developed for introducing the aluminum oxide into the bath. The devices of one group act thermally and those of the other group mechanically on the crust.

With the thermally acting charging devices, the heat is dissipated from the charging point so reduced that the crust remains soft, or the charging point are the same for the same purpose hot exhaust gases fed from the furnace. Such devices are only suitable for lumpy loads, the individual pieces must have such a weight that they soften the crust pierce with certainty. Powdery loading material, on the other hand, collects on the surface of the crust until the pile is of sufficient weight to crush the crust. In doing so, they form Lumps that are detrimental to the melting process. Otherwise it requires keeping soft the crust an expense that makes the system considerably more expensive. So is z. B. a furnace known at to which the charging point is still supplied with the heat emanating from the upper part of the anode. to For this purpose, the anode is covered with a stainless steel bell, which is more parabolic Part of the heat radiated from the top of the anode to that in the lower part of the bell Reflecting melt pool. Therefore, an anode must be provided, the upper part of which is considerable Developed amounts of heat. But this is only the case with pre-burned anodes. A self-burning one Anode cannot be used because its upper part has almost normal temperature and therefore does not emit significant amounts of heat. In addition, a stainless steel bell is very expensive.

The second group includes the known charging devices that use the Beschik process for introducing aluminum oxide in powder form under pressure into the molten liquid Bath of an aluminum electrolytic furnace

Applicant:

Nippon Light Metal Co., Ltd., Chuo-ku,
Tokyo (Japan)

Representative:

Dipl.-Ing. M. Bunke, patent attorney,

Stuttgart W, Schloßstr. 73 B

Named as inventor:

Tamiro Hirakawa,

Kosuke Asano,

Shigeki Mukoyama,

Shuichiro Hara, Nügata-Shi (Japan)

Claimed priority:

Japan January 16, 1959 (631)

Kungsgut is pressed into the bath by screws arranged just above the bath. These Devices are complicated and subject to high wear and tear, because the screws through the Heat and the aggressive gases that cause severe corrosion are destroyed in a short time. A Another disadvantage of such systems, which are made more expensive by the worm gear, is that also here the aluminum oxide is compressed into lumps, so that the charge is poorly distributed in the bathroom.

The present invention takes a different approach. She suggests the powdered aluminum oxide to introduce under pressure into the molten bath in such a way that the formation of a crust occurs the charging point is prevented from the start. The charging method according to the invention exists in that a jet of gas is blown onto the bath at the point where the aluminum oxide is supplied which is also used as a means of transport for the aluminum oxide to be introduced into the bath serves, the charging point being set in a wave-like movement that prevents crust formation will.

In addition to this prevention of crust formation, the waves on the bath surface ensure that

409 557/398

the aluminum particles are covered by the melt immediately after they hit the bath, so that even then there cannot be an accumulation with subsequent clumping, if a thin skin should form despite the wave movement. The gas can melt continuously or be supplied intermittently. It can be made from air, a flammable gas, or a Mixture of air and a flammable gas. The flammability of the gas or gas mixture has the advantage that the aluminum oxide powder conveyed by the gas stream is already present when it hits the bath surface, it is heated strongly, preferably up to near the melting temperature.

This prevents the bath from cooling down during charging. About a spread of the load or to prevent it from splashing back from the bath surface, the aluminum oxide jet can be enclosed by the gas jet will.

Further features of the invention emerge from the following description of exemplary embodiments in conjunction with the claims and the drawings. In the latter shows

1 shows a schematic section through the electrolysis vessel,

F i g. 2 the end of the supply line on an enlarged scale,

F i g. 3 a modification of the execution according to Fig. 2, also shown enlarged, and

F i g. 4 shows an embodiment of a spray nozzle in section.

From Fig. 1 it can be seen that the anode 1 of the aluminum electrolytic furnace in a molten Bath 4 is immersed, which is located in the tub 2 provided with a carbon lining 3. On the A rigid cryolite crust 5 is formed on the surface of the bath 4. The electrolytically obtained molten Aluminum 6 is at the bottom of tub 2. A powdered aluminum oxide Containing container 7 has a conical bottom and is connected to a feed device 8, which is installed in a line 9. The aluminum oxide is continuously fed to the bath via line 9 fed.

Furthermore, a control valve 10 is provided that the gas supply from the line 12 and thus also the Alumina feed to bath 4 controls. The gas z. B. Air for use. The end of Line 9 is designed as a nozzle. A mixture is formed from the aluminum oxide and the air, which is sprayed onto the surface 13 of the bath 4 near the anode. The aluminum oxide is in the Bath dissolved and dispersed.

Due to the flow energy of the jet, the point on the surface 13 that it hits is turned into wave-like movement offset. Part of the carbon anode is also used during the Electrolytic reduction generates CO gas, which burns and thereby an increased temperature generated around the charging point. Since the wave movement of the bath does not create a crust on the Can form the bath surface, the aluminum oxide can be fed to the bath continuously and evenly will. The wave motion of the bath surface also causes the aluminum oxide is easily dispersed and dissolved.

According to FIG. 3 a closure 14 is provided through which the nozzle 11 is guided. This lock is fixedly arranged with respect to the anode 1.

The nozzle 16 according to FIG. 4 has two concentric channels 12 and 15. By the former the air and through the other the aluminum oxide is supplied. The emerging ray thus has a core 17 made of aluminum oxide, which is surrounded by a shell 18 made of air. the The air envelope prevents the aluminum oxide from splashing back from the bath surface. Using In this nozzle, the aluminum oxide does not need to be mixed with air beforehand. A continuous Feeding the gas is not absolutely necessary. With continuous supply of aluminum oxide becomes the gas, ζ. B. air, supplied only in such an amount that prevents the formation of a crust will.

Claims (6)

Patent claims: 1. Method of introducing powdered alumina under pressure into the molten liquid Bath of an aluminum electrolytic furnace, characterized in that the A gas jet is blown up at the point where the aluminum oxide is supplied, which also serves as a means of transport for the aluminum oxide to be introduced into the bath, with the charging point is set in a wave-like movement that prevents crust formation. 2. The method according to claim 1, characterized in that the gas is either continuous or is supplied intermittently. 3. The method according to claims 1 or 2, characterized in that the gas is air combustible gas or a mixture of air and a combustible gas is supplied. 4. The method according to one or more of the preceding claims, characterized in, that the aluminum oxide jet is enclosed by a gas jet. 5. Process according to claims 1 to 3, characterized in that the aluminum oxide first mixed with the gas and the mixture is fed to the bath. 6. The method according to any one of the preceding claims, characterized in that the Space around the anode is enclosed and that the gas is supplied in this space. Considered publications:
German Patent Nos. 816 021, 895 062;
U.S. Patent No. 2,564,837. Legacy Patents Considered:
German Patent No. 1,089,553. 1 sheet of drawings 409 557/398 3. 64 ι Bundesdruckerei Berlin