LU82051A1 - EQUIPMENT AT THE BOTTOM OF A METALLURGICAL CONTAINER FOR GAS INJECTION INTO A METAL BATH - Google Patents

Description

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Equipment at the bottom of a metallurgical container for injecting gas into a metal bath.

The present invention relates to equipment at the bottom 5 of a metallurgical container for injecting gas into a metal bath, in particular in the context of a process for refining retort cast iron by blowing oxygen from above and by inert gas bubbling from below.

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The process that the applicant described in patent application LU 81.207, plans to refine the cast iron by blowing oxygen from above and it is characterized in that on the one hand it causes in the immediate vicinity of the surface of the 15 bath a post-combustion of the CO released during decarburization by distributing oxygen on said surface and that on the other hand the thickness and the consistency of the slag are regulated by acting on the imbalance between it and the bath, by injection of essentially inert gas from the bottom of the bath.

This process makes it possible on the one hand to appreciably increase the rate of cold iron materials, in particular scrap metal, added to the bath and on the other hand to achieve a marked reduction in the phosphorus and sulfur contents in steel.

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It has already been proposed to incorporate porous bricks into the bottom of oxygen refining converters in order to effect, by injecting gases into the bath of molten metal, various treatments thereof . For this purpose, porous bricks of refractory material sheathed on the outside with a metal jacket were used, as they are known for the treatment with inert gas of metals contained in bags. For this use, porous bricks are preferred to nozzles, since the former allow discontinuous work. The same applies to the equipment _ 2 of the converter bottoms when it is a question of injecting into the bath gases other than those of a combustible or oxidizing nature required for the refining proper.

However, the porous bricks mentioned above which have been used up to now to equip converters have only a limited lifespan, far less than that of the lining of these containers. Since it is difficult to change these bricks during a converter campaign, it is hardly possible to treat with gas at most the first third of the charges blown into a converter at the start of the campaign. In addition, it is quite difficult to obtain gas flow rates adapted to the volume of the baths to be treated.

In his patent application LU 81.208 the applicant disclosed a device which is intended to be incorporated into the bottom of a refining container, for the purpose of blowing a treatment gas into a metal bath and which has a significantly improved lifetime vis-à-vis known devices, while allowing to inject the desired amounts of gas.

This device, essentially consisting of a porous refractory material, is characterized in that in the mass of the refractory material are inserted, in axial direction, a plurality of flat, wavy, tubular or filiform metal partitions with thickness of reduced wall.

30 Despite the advanced durability of this device, the behavior of which generally corresponds practically to that of the lining of the bottom of the crucible, it should be noted that logically the physical span of the device is lessened as the thickness of the filling decreases. Thus each device is practically shaved continuously, as is the upholstery, so that the effects of any deterioration occurring at some point during a blowing campaign

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- 3 - läge, are constantly accumulated and multiplied, thus risking the total destruction of the device in question before the end of the campaign.

The object of the invention therefore consists in proposing equipment which no longer exhibits the disadvantages described above.

This object is achieved by the equipment according to the invention 10 which is characterized in that several units consisting essentially of a porous refractory material and having a difference in span, in particular of the height, towards each other, are housed in the bottom of the container so that the tops of the 15 tallest units are flush with the level of new upholstery while those of the lower units are below this level.

The idea on which the present invention is based consists in presenting the units of the bubbling equipment in series, so that, as the lining becomes worn, a first unit or series of units are attacked by liquid metal, while other units hidden at the start only emerge at some point during the blowing campaign of the lining surface in the process of wear and are added and / or replace the units initially in service.

According to a first embodiment of the invention, each unit forming part of the bubbling equipment comprises an independent gas supply circuit, which circuit includes pressure regulation.

Another advantageous embodiment of the equipment according to the invention provides for combining in a few circuits series of units of equal size.

Thus we obtain the means to control not only the state - 4 - * of each individual unit, but also to achieve the possibility of evaluating at any time the degree and uniformity of wear of the lining of the bottom of the crucible . Indeed, it suffices for this to measure the gas pressure on the one hand at the inlet of each unit and on the other hand at the inlet of each assembly forming part of a series of units with equal spans.

Other characteristics and advantages will emerge from the description of the drawings, in which FIG. 1 shows schematically and without limitation a section through a representative sub-assembly of the equipment according to the invention, while FIG. 2 is a view from above of the bottom of a metallurgical crucible and a possibility of arrangement of the different units in said bottom.

We can see in fig. 1 the diagram of the lining of the bottom of a crucible, roughly subdivided into 3 layers (A, B and c).

In this lining are housed units (1,2 and 3) so that their vertices correspond to the respective upper levels of the layers of the lining. It is easily understood that once the layer (A) of the lining has worn out, the units (2) can come into action. The units (1) can then either be stopped by closing the valves (10) or remain active.

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Since each unit has its own circuit, it is also possible, if you wish to keep all the available units in action, to stop only the 30 (1) units which have suffered damage (metal infiltration, etc.). .) during the wear period of the upper layer of the lining (A).

The same remarks apply to the situation which exists when the wear on the lining has progressed until the top of the units (3) is exposed.

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Fi nally?" 2 there is shown a possible embodiment of the equipment at the bottom of the converter, where 3 separate series of 6 units are provided each, the larger units (1) being housed towards the center of the hollow-5 set. This is where the impact zone (I) of the oxygen jet is located, which corresponds to the highest rate of wear. It is therefore near this place that it is necessary to plan to house the units (1) intended to be used in the first place. The units (3) having the smallest span, are usefully housed the furthest away from the critical zone (I).

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Claims (2)

1. Equipment at the bottom of a metallurgical container for injecting gas into a metal bath, in particular in the context of a process for refining retort cast iron by oxygen blowing from above and by barbo- 5 floor with inert gas from the bottom, which equipment comprises several units consisting essentially of porous refractory material characterized in that several units consisting essentially of porous refractory material and having a difference in size, in particular of the height, one against the other, is housed in the lining of the bottom of the container so that the tops of the tallest units are flush with the level of the new lining while those of the shorter units are below 15 said level. 2. Equipment according to reference 1, characterized in that each unit forming part of the bubbling device comprises an independent gas supply circuit, which circuit includes pressure regulation. 1 2 Equipment according to claims 1 and 2, characterized "in that the circuits of series of units of equal span are combined. 25 2 Equipment according to claims 1-3 characterized in that the span of the different series of units decreases as the distance from the center of the container.