EP0591052A1 - Method for injecting plugging mud into the tap hole of a metallurgical vessel, such as blast furnace - Google Patents

Abstract

According to this process a first primary plugging mud (4) mixed with a binder, which has a specified composition and physicochemical characteristics, is injected and this primary mud is allowed to solidify thermally; after this mud has baked, a hole (8) of a specified length is drilled through it, thus producing a degassing, and a second plugging mud, known as secondary mud, of suitable composition and physicochemical characteristics, is injected therein, mixed with a binder, more fluid than the primary mud and with a rate of setting which is lower than that of the latter, in order that this secondary mud may diffuse into cracks in the primary mud before solidifying. The secondary mud reinforces the regions of the primary mud which have been embrittled by microfissuring and thus enables a suitable tap hole length to be obtained. <IMAGE>

Description

The present invention relates to a method of injecting a plugging mass into a taphole of a metallurgical reactor, such as a blast furnace, between two consecutive runs of use.

As is known, the tap holes of metallurgical reactors such as blast furnaces must be plugged between two consecutive castings. The taphole of a blast furnace is delimited by carbon refractory blocks, the inlet of which gradually widens from the inside of the blast furnace during its life. To plug the taphole, it is known to inject a mass of determined physicochemical and plasticity characteristics.

Various types of sealing masses are known, with variable compositions of mineral elements, associated with hydrocarbon binders.

During the inter-flow periods, the volatile materials contained in the plugging mass, when they collect, cause cracks and gas pockets to form in the mass. In addition, the cracking of the refractory blocks around the taphole causes the circulation of liquids in the cracks, and these liquids seep into the plugging mass, furthermore causing an erosion of its internal face in the blast furnace. The infiltration of liquid iron into the cracks gradually fill the pockets of gas, which promotes the detachment of the "fungus" outside the blocking mass.

As a result, during the resumption of the taphole, it is no longer possible, practically, to exceed the location of the cast iron which has filled the gas pockets, which results in a significant reduction in the length of the taphole , for example from 3m to 2.20m. Therefore, the cold source is brought closer to the hot source, which accelerates the degradation of the refractory assembly.

Ultimately, the capping methods implemented so far have many operating disadvantages, in particular the following: embrittlement of the mass by cracking, formation of gas pockets subsequently filled with liquid metal, solidification of the mass before capping full of the taphole, lack of homogeneity of the refractory assembly due to cracks in the carbonaceous blocks, shortening of the taphole, spitting during the pouring of liquid metal due to cracks in the refractory blocks (gas flames) , deterioration of the external face of the "cupboard" formed by the refractory assembly.

The object of the invention is therefore to propose a method of plugging the tap hole by which the above drawbacks are practically eliminated.

• a) on injecte une première masse de bouchage primaire, mélangée à un liant, ayant une composition et des caractéristiques physico-chimiques déterminées, et on laisse cette masse primaire se solidifier thermiquement;
• b) après cuisson de cette masse primaire, on y perfore un trou d'une longueur déterminée en réalisant ainsi un dégazage, et on y injecte une deuxième masse de bouchage, dite masse secondaire de composition et de caractères physico-chimiques appropriés, mélangée à un liant, plus fluide que la masse primaire et à vitesse de cuisson inférieure à celle de cette dernière, afin que cette masse secondaire puisse diffuser dans des fissures de la masse primaire avant d'être solidifiée.

According to the invention, the process for injecting a plugging mass into a taphole of a metallurgical reactor is characterized by the succession of the following steps:

• a) injecting a first primary sealing mass, mixed with a binder, having a determined composition and physicochemical characteristics, and allowing this primary mass to thermally solidify;
• b) after baking this primary mass, a hole is drilled therein with a determined length, thereby degassing, and a second sealing mass is injected therein, called secondary mass of suitable composition and physicochemical characters, mixed with a binder, more fluid than the primary mass and at a cooking speed lower than that of the latter, so that this secondary mass can diffuse into cracks in the mass primary before being solidified.

Thanks to its great fluidity, the secondary mass diffuses through the cracks of the monolithic assembly constituted by the solidified primary mass, and thus stops the cracking under development in this primary mass and in the "mushroom" outside the taphole. . As a result, the wear of the plugging mass is practically limited to its outer face.

According to a variant of the process according to the invention, after diffusion and solidification of the secondary mass, a hole of the same length as the previous one is again drilled therein, and a new quantity of secondary mass is injected therein in order to butcher.

This additional step provides greater safety in plugging the tap hole.

Other features and advantages of the invention will become apparent during the description which follows, given with reference to the appended drawing, of an embodiment of the process according to the invention given by way of nonlimiting example.

The single figure is a half-vertical, half-elevation view with cutaway, of the wall of a metallurgical reactor surrounding its taphole and of the plugging mass thereof.

The metallurgical reactor, such as a blast furnace, a wall 1 delimiting its tap hole 2 is partially shown in the drawing, comprises a set of refractory blocks 3 juxtaposed around the tap hole 2.

Between two reactor operating flows, the hole 2 is normally blocked by a mass 4 which ends, on the interior side of the reactor, by an enlarged part 5 called "mushroom" filling the end 2a flared from hole 2.

According to the state of the art prior to the invention, cracks such as 6 appear in the plugging mass 4 and especially in its fungus 5. The cracks 6 result in pockets of gas such as 7, formed during the solidification of the plugging mass 4, and which are gradually filled with liquid metal (cast iron in the case of a blast furnace), as has been explained above.

le reste étant constitué par des éléments résiduels. MASSE DE BOUCHAGE PRIMAIRE Constituant de base BAUXITE Nature de liaison ORGANIQUE Dimension maximum des grains en mm 3 Masse volumique apparente en kg/m³ 2210 PROPRIETES PHYSIQUES : mesurées sur éprouvettes cylindriques ⌀ 50x50 EN VALEUR MOYENNES Après cuisson à ... °C 800 Masse volumique apparente Kg/m³ 1930 Résistance à la compression MPa 5,4 Porosité ouverte % 32
Cette masse primaire de bouchage possède un coefficient de plasticité adapté aux conditions d'utilisation et à la puissance des "boucheuses".
Au cours de sa solidification, les matières volatiles de cette masse de bouchage primaire se rassemblent pour former des poches de gaz telles que 7, après avoir cheminé dans la masse par des microfissures telles que 6.
b) Après cuisson de la masse primaire, on y perfore un trou 8 d'une longueur déterminée, depuis l'extérieur du réacteur, jusqu'à une poche de gaz 7, ce qui provoque le dégazage de celle-ci.According to the invention, the plugging mass 4 is injected into the taphole 2 as follows:
a) a first primary sealing mass is injected, having a determined chemical composition and physico-chemical characteristics, adapted to the operating conditions of the blast furnace. This primary mass is intimately mixed with an appropriate organic binder chosen from phenolic resins, tars, petroleum or vegetable oils, for example a phenolic resin, and is allowed to solidify thermally.
The chemical analysis of the so-called primary mass on calcined product has for example the following general weight composition: Al₂O₃ 8 to 65% SiO₂ + Si₃N₄ 8 to 62% SiC 5 to 35% Fe₂O₃ 0.1 to 5% MgO 0.1 to 4.5% and more precisely the following composition:

the rest being made up of residual elements. PRIMARY CAPPING MASS Basic constituent BAUXITE Type of connection ORGANIC Maximum grain size in mm 3 Bulk density in kg / m³ 2210 PHYSICAL PROPERTIES: measured on cylindrical specimens ⌀ 50x50 IN AVERAGE VALUE After cooking at ... ° C 800 Bulk density Kg / m³ 1930 Compressive strength MPa 5.4 Open porosity% 32
This primary capping mass has a plasticity coefficient adapted to the conditions of use and to the power of the "cappers".
During its solidification, the volatiles of this primary plugging mass come together to form gas pockets such as 7, after having passed through the mass by microcracks such as 6.
b) After the primary mass has been cooked, a hole 8 of a determined length is drilled therein, from outside the reactor, to a gas pocket 7, which causes the latter to be degassed.

A second sealing mass, called secondary mass, the composition of which is then injected into hole 8. chemical and physicochemical characteristics are those mentioned in Table 2 below, within the approximate limits of the ranges mentioned in this table.

PROPRIETES PHYSIQUES : mesurées sur éprouvettes cylindriques ⌀ 50x50 EN VALEURS MOYENNES Après cuisson à ..........°C 800 Masse volumique apparente Kg/m³ 1750 Résistance à la compression MPa 2,8 Porosité ouverte % 38,5 The chemical analysis of the so-called secondary mass on calcined product has the following general weight composition: Al₂O₃ 35 to 65% SiO₂ + Si₃N₄ 20 to 40% SiC 0.1 to 30% Fe₂O₃ 0.2 to 4.5% MgO 0.1 to 3.5%
preferably Al₂O₃ 40 to 58% SiO₂ + Si₃N₄ 20 to 35% SiC 0.1 to 30% Fe₂O₃ 0.2 to 4.5% MgO 0.1 to 3.5%
and for example Al₂O₃ 52% SiO₂ + Si₃N₄ 29% SiC 16% Fe₂O₃ 2.6% MgO 0.2%

PHYSICAL PROPERTIES: measured on cylindrical specimens ⌀ 50x50 IN AVERAGE VALUES After cooking at .......... ° C 800 Bulk density Kg / m³ 1750 Compressive strength MPa 2.8 Open porosity% 38.5

The secondary mass comprises more than 95% of grains whose size is less than 500 μm. These grains are mixed with one or more organic binders, the amount of which represents more than 10% of the weight of the total mixture, a binder whose residue after coking according to, for example, standard ASTM D 2416 is greater than 5%. This finer particle size gives the secondary mass a greater fluidity than that of the primary mass; this fluidity is characterized by a workability index greater than 20% at 20 ° C measured according to, for example, standard ASTM C181. The secondary mass has a cooking speed lower than that of the primary mass, through which it diffuses by seeping into the cracks during formation and development in the primary mass 4 and in its fungus 5, until its complete solidification. All of the cracks are then filled and the gas expelled from them.

In other words, the injection of a secondary mass which is more fluid than the primary mass strengthens the zones of the latter which are weakened by microfissuring, the secondary mass having time to infiltrate the microcracks in the primary mass thanks to its low curing speed and greater fluidity.

Therefore, the plugging mass is no longer degraded by cracks, and the fungus 5, which no longer undergoes degradation in its mass, therefore remains in place, only its outer face still undergoing erosion.

After injection of the secondary mass, the plugging of the tap hole 2 is in principle finished. However for safety it is possible to proceed to a new drilling of a hole 8, on the same length as the previous one, and to inject again an appropriate quantity of secondary mass, which completes if necessary the action of the secondary mass former.

Claims (9)

Process for injecting a plugging mass into a taphole of a metallurgical reactor such as a blast furnace, between two consecutive pourings for the use of the latter, characterized by the succession of the following steps: a) a first mass (4) of primary plugging, mixed with a binder, having a determined composition and physicochemical characteristics, is injected and this primary mass is allowed to solidify thermally; b) after baking this primary mass, a hole (8) of a determined length is drilled therein, thereby degassing, and a second sealing mass is injected therein, called secondary mass of suitable composition and physicochemical characters , mixed with a binder, more fluid than the primary mass and at a curing speed lower than that of the latter, so that this secondary mass can diffuse into cracks in the primary mass before being solidified. Method according to claim 1, characterized in that, after diffusion and baking of the secondary mass, a hole is again drilled in the latter of the same length as the previous one (8), and a new quantity of secondary mass is injected into it in order to plug it. Primary sealing mass used in the process according to claims 1 or 2, characterized in that it has the composition below: Al₂O₃ 8 to 65% SiO₂ + Si₃N₄ 8 to 62% SiC 5 to 35% Fe₂O₃ 0.1 to 5% MgO 0.1 to 4.5% the rest being made up of residual elements. Secondary sealing mass used in the process according to claims 1 or 2, characterized in that it comprises grains, the majority of which have a size of less than 500 µm, which are mixed with one or more organic binders, the residue of which after cokefaction is greater than 5%. Secondary sealing mass according to claim 4, characterized in that the binders are organic binders such as phenolic resins, tars, petroleum or vegetable oils. Secondary capping mass according to claim 5, characterized in that it has a fluidity greater than that of the primary mass, resulting in a workability index greater than 20% at 20 ° C. Secondary capping mass according to claim 6, characterized in that it has the following general composition: Al₂O₃ 35 to 65% SiO₂ + Si₃N₄ 20 to 40% SiC 0.1 to 30% Fe₂O₃ 0.2 to 4.5% MgO 0.1 to 3.5% the rest being made up of residual elements. Secondary capping mass according to claim 7, characterized in that its composition is as follows: Al₂O₃ 40 to 58% SiO₂ + Si₃N₄ 20 to 35% SiC 0.1 to 30% Fe₂O₃ 0.2 to 4.5% MgO 0.1 to 3.5% the rest being made up of residual elements. Clogging mass of the tap hole of a metallurgical reactor, obtained by the process according to any one of Claims 1 to 8.

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