US1958323A - Manufacture of aluminium in high power tanks - Google Patents

Description

May 8, 934 P J, M TORCHE-- 3,958,323

MANUFACTURE OF ALUMINIUM IN HIGH POWER TANKS Filed NOV. 19, 1931 Patented Moy 8, 1934 UNITED VSTATES PATENT OFFICE et Electrometallurgiques Olais, Froges et Camargue, Paris, France, a corporation o! France Application November 19, 1931, Serial No. 576,153 In France October 21, 1931 s claims. (c1. zei-2o) Aluminium is generally manufactured, through electrolysis, in rectangular or round vessels, the bottom of which forms the cathode, and which comprise a plurality of blocks of coal previously baked which serve as anodes and are usually from 10 to 14 in number and even more.

The use of multiple anodes of the usual type involves diiliculties concerning their good adjustment, which is necessary in order to insure a good distribution of the current, and consequently a satisfactory output. Moreover, mounting said previously baked anodes involves a large consumption thereof, as considerable waste results from that operation.

It has been endeavoured to reduce that consumption by the use of continuous electrodes (that is to say of vertically mounted electrodes the lower ends of which are immersed in the electrolytic bath, while their upper ends are lengthened as their lower ends are wearing oi) of any type whatever, notably the so-called Soderberg electrode, which is of the self -baking type, and of circular transverse section, in circular tanks. A considerable advantage of said continuous electrodes islthat the tank, comprising only one anode, is much easier to manage than tanks containing a plurality of anodes. However, two considerations, one of which is technical and the other economical, prevent the use of said continuous electrodes from spreading rapidly. From a technical point of view, as lsoon as great intensities of current are used, and even for an intensity as low as 18,000 amperes, the large diameter which the electrode must be given prevents the easy evacuation of the gases produced by the electrolysis, and the satisfactory working of the apparatus. It further causes overheating of the central part of the bath, below said electrode of large diameter, and this is prejudicial to a good output.' Various means for obviating such drawbacks have been suggested, for instance providing channels inside the electrodes or giving an annular shape to the latter, or again, sepa-` rating said electrodes into two parts with a space between them, but such arrangements are, in certain instances, complicated and expensive, and in other cases, inefcacious.

From an economical point of view, the necessity of replacing the usual rectangular shaped tanks by round shaped tanks involves discarding a considerable equipment. This is obviously a great obstacle to the prompt adoption of continuous electrodes having circular transverse sections, of any type whatever.

My invention makes it possible to obviate the above mentioned drawbacks by the use, in electrolytick apparatus of great power, and in fact of unlimited power, and more particularly in apparatus comprising a rectangular tank, of a continuous anode or of a limited number of continuous anodes, preferably of rectangular, or substantially rectangular, section, one of the dimensions of which is substantially smaller than the other dimension. In order to avoid the above mentioned drawbacks, it is suiiicient that the transverse section of the electrode should not exceed a certain limit in one of its dimensions. The useful surface which is necessary for the electrode may be maintained by increasing the other dimension.

In the Figs. l and 2 of the drawing I have 70 diagrammatically shown in plan view an electrolytic apparatus according to my invention. The outer vessel, whose bottom forms the cathode, is shown at 2, while the continuous anode or anodes of elongated rectangular shape is or are shown at 1.

Owing to the rectangular or elongated shape of the electrodes, the gases produced during the electrolytic` process find a short way of escape and the overheating of the central part of the bath is either wholly done away with or so reduced that any detrimental action is no longer to be feared in this respect. 'Ihe rectangular tanks already in use can be employed as in the past and it is no longer necessary to e'ect any alteration of the 85 plant beyond that of the anodic apparatus.

Lastly, and this constitutes a highly important advantage, there is now nothing to prevent the increase, in large proportions, of the power or output of the apparatus, which in fact becomes practically unlimited, as it sufces to increase the length of the tanks by increasing the number of continuous anodes with which they are provided.

On the other hand, such an electrode is readily handled and adjusted, and, on account of the great intensity of the current which flows through it, it may be provided, quite economically, with electric controllingY instruments, whereas such an expense would be absolutely prohibitive in the case of multiple electrodes Working under low amperage, such as are used at the present time. Under these conditions, it is easy to control a small number of continuous electrodes of that type, and the eventual use of two such electrodes instead of 10, 14, or even 20 of the electrodes previously employed may be considered with the tanks of the largest type actually utilized for practical purposes. The output thus obtained and the ease with which the apparatus may be controlled are notably superior to the results obtained either with a single continuous electrode of cylindrical shape or with multiple electrodes working under low arnperage.

Experience has proved that the above mentioned results can be easily improved upon and that the power may be increased while allowing the apparatus to be run with the greatest facility. Thus a three electrode tank, adapted to be used with a current of 45,000 amperes has been constructed, the output of which, from all points o! view, was clearly superior to that of all of the apparatus for manufacturing aluminium that are now in use, not only as regards the consumption of current, but also as regards the consumption of electrode paste and the hired labor that is required. These experiments prove that apparatus of high power are quite advantageous for practical purposes, while, up to the present time, the use of such apparatus had met with working diilculties which had not yet been overcome.

What I claim is:

1. A high power electrolytic furnace for the production of aluminium, which comprises in combination, a tank of substantially rectangular horizontal section, the bottom of which acts as a cathode, and a continuous anode of elongated horizontal section placed in said tank, one of the horizontal sectional dimensions of said anode being at the most equal to the maximum dimension permitting the disengagement of gases from beneath the active surface of the anode and preventing superheating of the aluminium beneath the active surface of said anode.

2. A high power electrolytic furnace for the production of aluminium, which comprises in combination, a tank of substantially rectangular horizontal section the bottom of which acts as a cathode, and a continuous anode of elongated horizontal section placed in said tank, said anode having the shorter one of its horizontal dimensions at the most equal to the maximum dimension permitting the disengagement of gases from beneath the active surface of said anode.

3. A high power electrolytic furnace for the production of aluminium, which comprises in combination, a tank of substantially rectangular horizontal section the bottom of which acts as a cathode, and a lcontinuous anode of elongated horizontal section placed in said tank, said anode having the shorter one of its horizontal dimensionsV at the most equal to the maximum dimension preventing superheating of the aluminium beneath the active surface of said anode.

PIERRE JEAN MICHEL TORCHET.

Images