CH657695A5 - OVEN WITH OPEN ROOMS, FOR COOKING CARBON BLOCKS, COMPRISING A BLOWING PIPE. - Google Patents

Description

The invention relates to an oven with open chambers, as indicated in the preamble of claim 1.

The carbon blocks and, in particular, those which form the anodes for the electrolytic production of aluminum by the Hall-Héroult process with "precooked anodes" are obtained by molding a carbonaceous paste essentially consisting of pitch and ground coke and by baking at 1100-1200 ° C in a hundred hours.

Cooking is carried out in so-called “rotating fire” ovens

one of the most used types of which is the open-chamber oven, consisting of successive chambers, bounded longitudinally by transverse walls and divided into cells by heating partitions inside which circulate the air and the combustion gases supplied by liquid or gaseous fuel burners.

At the top of the heating partitions, there are openings called "openings" for the installation of burners and temperature measurement probes.

The cooking anodes are stacked in the cells and completely embedded in a carbon granule, for example: petroleum coke, metallurgical coke or other; they are thus isolated from the walls and sheltered from contact with combustion gases which could cause losses by oxidation, and they can also be separated from one another to avoid the risks of agglomeration or sticking.

During a cooking cycle, the burners are gradually moved (rotating fire), so that each load of anodes, in a given chamber, is successively preheated (in 2 or 3 days), subjected to cooking ( for 2 or 3 days) and cooled.

The combustion fumes are extracted from the oven by a suction pipe connecting, through manholes arranged on the transverse walls, all the cells of the same chamber to the general smoke collector placed along the oven and connected itself to the suction fans. This suction pipe is normally placed on a transverse wall, which makes it necessary to keep a "dead room" downstream of the heating zone and to have the isolation registers between the heating zone and the working zone on the transverse wall downstream of this dead chamber. With this arrangement, a large quantity of cold air is therefore drawn through the dead chamber, which affects the thermal efficiency of the oven.

To remove this inconvenience, the applicant had, in 1979, in its Saint-Jean-de-Maurienne factory, removed the dead chamber by placing the suction pipe on a heating partition in the preheating chamber. Similarly, in patent FR-A-2 488 685, it has been proposed to place the smoke suction pipe no longer on the transverse wall, but on the doors of the heating partitions of the rooms in the preheating zone adjacent to this. transverse wall.

However, this arrangement does not make it possible to modify the constructive arrangements which are capable of improving the mechanical strength, the sealing and the thermal insulation of the transverse walls in their upper part, since it is necessary to maintain manholes on these walls in order to introduce, by the 'Intermediate of a blowing system, the air necessary for cooling the oven after cooking, this air, heated, serving at the same time as combustion air for the fuel in the fire zone. We know, in fact, that the upper part of the transverse walls is a fragile part requiring frequent maintenance of the brickwork and difficult to seal.

The object of the invention is to obviate the drawbacks which have just been mentioned by providing an oven provided with a blowing pipe making it possible to introduce the cooling and combustion air through the openings of the heating partitions.

To this end, the oven according to the invention has the characteristics specified in claim 1. The invention will be better understood thanks to the detailed description which follows of embodiments of the oven, given by way of example, referring to the attached drawing, in which:

Figure 1 shows in plan, schematically, part of an oven with open chambers of conventional type;

Figure 2 shows a cross section, along AA, of a suction pipe according to the prior art;

Figure 3 shows, in partial exploded view, two adjacent chambers, one of which corresponds to the prior art and the other to the invention, and Figure 4 shows, in longitudinal vertical section, a portion of a cooking according to the invention.

The baking oven, which most often consists of two parallel spans, is formed by successions of chambers (1), one of which, for example, is delimited by the dotted line in Figure 1 on the left. Each room is surrounded by transverse walls (2) and divided into cells (3) by hollow heating partitions (4), provided with baffles (5) to ensure a distribution of hot (or cold) gases throughout their volume. The cells communicate with each other by manholes (6) which can be closed by shutters, and open at their upper part. The anodes (7) are stacked in each cell (3) in a coating of carbon granule (8).

The burners, not shown, are fixed to a mobile gangway (20) which moves progressively during the cooking cycle.

The combustion fumes are extracted from the oven by a suction pipe (9) connecting, through the manholes (6) arranged on the transverse walls (2), the various cells (3) to the general smoke collector (11) disposed along the oven.

In this arrangement, the chamber located downstream of the pipe (9) relative to the direction of progression of the furnace indicated by the arrow in FIG. 1 is a “dead” chamber, as we have seen previously explained.

It is possible to eliminate this drawback by placing the suction pipe on the doors of the heated partitions in the chamber of the preheating zone adjacent to this transverse wall (FR-A-2 448 685 already cited).

The improvement, object of the present invention, consists in having at least one blowing pipe (12A, 12B) allowing the introduction of the cooling and combustion air through the openings (13) of the heating partitions (4), to be removed. the upper opening of the manholes (6), which was a fragile point, and to replace it by a simple slot (15) narrower than the width of the wall (2) at the right of the

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look (6). Through this slot (15), it is possible to introduce or remove the shutters (10) called “registers”, which make it possible to establish or suppress the communication between the adjacent chambers.

Normally, there is a blowing pipe (12A) in the cooling zone and a blowing pipe (12B) in the air preheating zone, which is, at the same time, a cooling zone.

In Figure 3, the two manholes (6) of the wall (2A) are shown in the arrangement of the prior art. The upper part (14) is wide open. This results in a certain fragility and the tightness of this look can only be maintained at the cost of frequent maintenance operations.

As soon as the smoke extraction and, in accordance with the present invention, the supply of cold air are carried out by the openings (13), the upper part (14) can be closed, as can be seen on the left part of FIG. 3, at (2B), and no longer comprises more than a simple slot (15). This seemingly minimal change has important consequences for the life of the oven and maintenance costs. The slot (15), which allows the isolation registers (flaps) (10) to pass between the cells, is sealed by a simple cover. In addition, this arrangement allows precise control of the quantities of air introduced into the fire zone to ensure optimum combustion.

Finally, one can, during construction, reduce the width of the walls (2) which no longer have to support the load of the suction and blowing pipes; it can therefore be reduced to what is strictly necessary for the installation and sliding of the isolation registers (10), which provides a significant gain in investment and maintenance costs and also a reduction in heat losses. which occurred, in the prior art, in line with the walls and, in particular, at the open upper part (14) of the manholes (6).

The implementation of the invention therefore constitutes significant progress in the technique of open chamber furnaces.

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3 sheets of drawings

Claims (4)

657,695 1. Oven with open chambers, for cooking carbonaceous blocks (7) intended in particular for the electrolytic production of aluminum by the Hall-Héroult process, constituted by a succession of chambers delimited by side walls (2) provided, at their upper part, of manholes (6), which put the chambers in communication and which can be closed by isolation registers (10), each chamber being divided into cells (3) by hollow heating partitions (4) in which circulate the air and the combustion gases, each partition comprising, at its upper part, openings (13), the whole of the oven, in operation, comprising in the direction of progression of the fire a cooling zone, a zone preheating and a full fire zone, characterized in that it comprises at least one pipe (12A, 12B) for blowing cooling air disposed on the openings (13) of the partitions (4). 2. Oven according to claim 1, characterized in that it comprises a blowing pipe (12A) disposed in the cooling zone and a blowing pipe (12B) disposed in the air cooling and preheating zone. 2 3. Oven according to claim 1 or 2, characterized in that the manholes (6) of the side walls (2) open to the outside by a narrow slot (15) of width less than the thickness of the wall (2) at right of sight (6) and allowing the introduction or removal of the isolation registers (10). 4. Oven according to one of claims 1 to 3, characterized in that the width of the side walls (2) is reduced to the width strictly necessary to ensure the establishment and sliding of the isolation registers (10) .