JP2013082953A - Method of extending life of converter refractory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique of preventing melting of a converter refractory more effectively at a lower cost relative to a conventional one.SOLUTION: A converter refractory having been used in an inner refractory liner is crushed to produce a crushed product. The crushed product of particles with a diameter of from 10 mm to smaller than 40 mm is used as an agent for adjusting a slag composition to be charged into a converter to protect a refractory therein. The crushed product of particles with a diameter of smaller than 10 mm is used as a raw material of an unshaped refractory to be sprayed onto the surface of a refractory in the converter to repair the surface of the refractory. The converter refractory preferably is a magnesia-carbon brick including MgO and C.

Description

  The present invention relates to a method for extending the life of converter refractories.

  In converters used for metal refining, the inner surface of the iron skin is covered with permanent bricks (perma bricks) in order to increase the durability against high-temperature molten metal and slag, and refractory bricks (wear bricks) are further inside. Is provided with a lining structure. The lining refractories of these converters are worn with use, and after being used a certain number of times, it is necessary to reload the refractories.

  Since steel cannot be manufactured during the refractory transshipment period, it is required to extend the life of the converter refractory and reduce the frequency of transshipment.

  Conventionally, as a method of extending the life of converter refractories, repairing using refractories such as spraying and baking, adding slag ingredients to control slag components, and suppressing dissolution of magnesia-carbon brick MgO A method (for example, Patent Document 1), a method of coating and protecting slag on a brick by performing a converter furnace swing or a splash are known.

  Among these, the method of repairing using a refractory has a problem that the cost is increased although the life extension effect is high. Even in the method of controlling the slag component, there is a problem that the cost of the auxiliary raw material used for controlling the slag component increases. Furthermore, although the dissolution rate of the auxiliary raw material varies depending on the size and properties (porosity, presence or absence of volatile matter, etc.), since it does not exhibit the control effect of the slag component unless dissolved in the slag at the initial stage of blowing, As a dissolution rate adjusting means, a method of subjecting the magnesia source material to various processes such as pulverization, granulation, addition of volatile matter and the like has been adopted, which has a problem that the cost is further increased.

  Further, Patent Document 2 discloses a technology that recycles waste generated when dismantling the refractory lining the converter as an auxiliary material when controlling the slag component by adding the auxiliary material.

  However, in the technique described in Patent Document 2, when the pulverized product is put into the converter, the pulverized product having a particle size of less than 10 mm is sucked into the converter dust collection, and the slag component adjusting function cannot be exhibited. There is a problem that the effect of suppressing the melting loss of brick is not sufficient only by the means for adding the auxiliary material described in Document 2.

Japanese Patent Laid-Open No. 11-323424 JP-A-6-116617

  An object of the present invention is to solve the above-mentioned problems and to provide a technique capable of suppressing the melting loss of the converter refractory at a lower cost and more effectively than the prior art.

  The method for extending the life of a converter refractory according to the present invention made to solve the above problems, pulverizing a used converter refractory that was lined in the converter, A slag component modifier for protecting refractories used in the converter, and pulverized material having a particle size of less than 10 mm is sprayed on the surface of the refractory in the converter to be used as raw materials for irregular refractories. It is characterized by doing.

  The invention according to claim 2 is characterized in that, in the method for extending the life of the converter refractory according to claim 1, the converter refractory is a magnesia carbon brick containing MgO and C. .

  The invention according to claim 3 is the method for extending the life of the converter refractory according to claim 1 or 2, wherein the slag component adjusting agent is introduced at the start of blowing and slag forming is concentrated and generated at the initial stage of blowing. It is characterized by this.

  In the method for extending the life of a converter refractory according to the present invention, a used converter refractory lined in the converter is pulverized, and a pulverized product having a particle size of 10 to less than 40 mm is put into the converter. A slag component modifier for protecting the refractory to be used, and a pulverized product having a particle size of less than 10 mm is used as a raw material for an indeterminate refractory to be used for refractory surface repair in a converter. Conventionally, the pulverized product having a particle size of less than 10 mm is sucked into the converter dust collection, and the slag component adjustment function cannot be exhibited, and there is a problem that the effect of suppressing the melting of brick is not sufficient, In the present invention, the slag component adjustment function is improved as compared with the prior art by setting the particle size of the pulverized product of the used converter refractory to be introduced into the converter to less than 10 to less than 40 mm. Furthermore, in the present invention, a configuration in which a pulverized product having a particle size of less than 10 mm is used as a raw material for an irregular refractory used for spraying and repairing the surface of a refractory in a converter instead of being disposed of. In addition, by adopting the configuration together, it is possible to more effectively suppress the melting loss of the converter refractory. As described above, according to the present invention, the spent converter refractory is pulverized to less than 40 mm and classified into those less than 10 mm and those less than 10 to 40 mm. In addition, it is possible to exhibit a melting damage suppressing effect superior to that of the prior art.

  Further, when the particle size is 40 mm or more, not only the dissolution rate becomes slow and the slag component adjusting function is not effective, but particularly when the pulverized material contains carbon as in the invention of claim 2, Although gas was generated at the end, causing slag foaming and hindering the productivity of the furnace, in the present invention, the particle size of the pulverized product of the used converter refractory to be introduced into the converter is 10 to 10. By setting it to less than 40 mm, the problem of slag forming at the end of the blowing can be effectively avoided.

It is the graph which calculated | required the relationship between the gas generation time by a particle size, and gas generation amount based on the calculation formula. It is a figure which shows the effect of the amorphous refractory used for repair of a converter refractory.

  Preferred embodiments of the present invention are shown below.

  Brick scraps generated by the demolition of MgO-C bricks lined in the converter are pulverized to a particle size of less than 40 mm, and then classified into less than 10 mm and less than 10 to 40 mm. In the present invention, a material of less than 10 mm is used as a raw material for an amorphous refractory to be used by spraying on the surface of the refractory in the converter, and a material of less than 10 to 40 mm is put into the converter. It is used as a slag component modifier for protecting refractories. The particle size of the pulverized brick was classified using two types of sieves having a sieve size of 40 mm and 10 mm. The particle size of the crushed brick that passed through the 40 mm eye was less than 40 mm, and the particle size of the brick that passed through the 10 mm eye was less than 10 mm. The particle size of the crushed bricks that passed through 40-mm eyes and impermeable to 10-mm eyes was 10 to less than 40 mm. In addition, when 40-mm eye-impervious brick crushed material was generated, the pulverization treatment was performed again until the crushed material passed through the 40-mm eye.

(Slag component modifier for refractory protection: crushed material of brick scraps of less than 10-40 mm)
Significant cost reductions can be achieved by putting pulverized MgO-C brick scraps of less than 10 to 40 mm into the converter as an alternative to light-burned dolomite.

  However, when the pulverized MgO—C brick is used as an alternative to light-burned dolomite, gas is generated due to the reaction of C + FeO → CO ↑ + Fe and slag forming occurs. When slag foaming occurs during the last stage of blowing and during steel production, problems such as increased steel production time and out-of-component occur, but the present invention adopts a configuration in which the grain size of MgO-C brick is less than 40 mm. By doing so, the problem can be avoided. In addition, the pulverized material having a particle diameter of less than 10 mm is sucked into the converter dust collection, and cannot sufficiently function as a slag component adjusting agent.

  The configuration in which the particle size is less than 40 mm is determined with a focus on the fact that there is a correlation between the particle size of brick and the dissolution time of brick. Specifically, the gas generation amount is estimated and determined based on the following concept.

  The disappearance rate of MgO-C brick scraps charged into the converter is considered to be a variable depending on the temperature of MgO-C brick scraps. Therefore, the amount of gas generated per unit time in the reaction of C + FeO → CO ↑ + Fe can be determined from the disappearance rate of MgO-C brick waste and the amount of carbon contained in the MgO-O brick waste.

For each of the cases where the particle size of the MgO-C brick scraps is 29 mm, 39 mm, 60 mm, and 100 mm, the ambient temperature (molten slag temperature in the converter) is assumed to be 1650 ° C., and the temperature in the MgO—C brick scrap is The rise was estimated by one-dimensional unsteady heat transfer analysis based on (Equation 1).
Here, T temperature, t time, x distance, and a thermal conductivity were used, and the thermal conductivity was 20.0 W / mK, the heat capacity was 1300 J / kgK, and the density was 3000 kg / m ³ .

  Next, the disappearance rate of the MgO-C brick crushed material under the temperature condition of 1650 ° C., which is the knowledge obtained experimentally, was determined by the above-mentioned method. The disappearance rate of the MgO—C brick crushed material under temperature change was determined for each of the particle sizes of 29 mm, 39 mm, 60 mm, and 100 mm of the pulverized material, The result of estimating the gas generation amount based on this is shown in FIG.

  As shown in FIG. 1, when the particle size is 29 mm and 39 mm, the reaction is completed by the early stage of blowing, and gas generation is observed at the end of blowing, and when the particle size is 100 mm, until the end of blowing. The reaction continued and gas evolution was observed. Based on the observation results, the crushed MgO-C brick scraped to less than 40 mm was subjected to an actual converter, and the solubility was confirmed by visual observation of the occurrence of slopping and evaluation of the composition of the sampled slag. .

  MgO-C brick scraps crushed to less than 40mm using an actual converter are stored in a bunker on the converter furnace, and the MgO pure content of light-burned dolomite, which is an auxiliary material for adjusting MgO in slag, which has been conventionally used Was weighed so as to be the same amount as in the above, and was put into the furnace immediately after the start of converter blowing. As a result of confirming the solubility by visual observation of the state of occurrence of slopping and evaluation of the composition of the sampled slag, no occurrence of slopping was observed.

  From the above examples, by using MgO-C brick scraps pulverized to less than 40 mm as a slag component modifier, gas is generated at the end of blowing and slag forming occurs, effectively preventing the furnace productivity. It was confirmed that it can be avoided. Moreover, it was confirmed that the amount of MgO in the slag composition is not different from the conventional slag adjusting agent, and the refractory protection effect is sufficiently exhibited.

(Raw material of amorphous refractory: crushed material of brick waste less than 10 mm)
As described above, the pulverized product having a particle size of 10 mm or less is sucked into the converter dust collection and cannot sufficiently function as a slag component adjusting agent. The crushed material of diameter is also used as a raw material for the irregular refractory material that is sprayed to repair the surface of the refractory inside the converter instead of being disposed of. Therefore, it is possible to more effectively suppress the melting loss of the converter refractory.

Table 1 below is a table summarizing the physical properties of the irregular refractories used for repairing converter refractories.

  The present inventor uses phenol resin as a bond, and uses a crushed material of brick waste of less than 10 mm as an aggregate that is a raw material of the amorphous refractory, so that the MgO—C brick waste occupying the repairable amorphous refractory is reduced. It was newly found that the durability does not decrease even when the proportion of the pulverized product is increased to 70%.

As shown in Table 1, the irregular refractories used for repairing the converter refractories include pitch, phenol resin, magnesia, MgO-C brick waste pulverized to less than 10 mm, and other raw materials, and magnesia and MgO- The ratio of the C brick scrap was changed so that the total mass of the pitch and the phenol resin was 15% by mass, and the blending ratio of the pitch and the phenol resin was mixed in two types A and B. In addition, A set the ratio of pitch and phenol resin to pitch: phenol resin = 1: 1, and B set the ratio of pitch to phenol resin to pitch: phenol resin = 2: 1.
The other raw materials are raw materials containing at least one of a siliceous raw material, an alumina raw material, a dolomite raw material, and a magnesia-lime raw material.

  A 15% moisture was added to the repaired irregular refractory prepared as described above, and the mixture was poured onto a hot plate heated to 1200 ° C. so as to have a uniform thickness, and the strength was measured after curing. The strength evaluation results in Table 1 show that the blending amount of the MgO-C brick crushed material is 0% by mass (the MgO-C brick crushed material is not used as a raw material for the amorphous refractory) (Reference Example 1). The relative values of Examples 1 to 6 are shown in%.

  Although the hardening strength decreases as the proportion of the MgO—C brick crushed material increases, it is considered that there is no problem in practical use. Furthermore, when the blending ratio of pitch and phenol resin was changed to 2: 1 or in Example 6 in which 70% by mass of MgO—C brick waste was used without using magnesia, the pulverized product of MgO—C brick waste was also used. A strength almost equal to that of Reference Example 1 in which no blending was performed was obtained.

  FIG. 2 shows the result of visual observation using a spray repair material made of crushed MgO—C brick as a raw material for repairing the surface of a refractory in an actual converter furnace. As the repair material, a material in which 75% by mass of MgO—C brick crushed material as a raw material was added was used. The surface of the refractory is repaired by transporting the repair material in a gas phase with a hose using compressed air, adding 10 to 15% of water through a nozzle inserted into the converter, and then adding the refractory in the converter. Sprayed on the surface. The durability was determined by visual observation.

  In FIG. 2, the remaining rate determined visually is shown with respect to the number of times of use after spraying. As shown in FIG. 2, it was confirmed that the example of the present invention showed a durability equal to or higher than that of a conventional high durability product. In addition, if the present inventors further consider the selection of the bond (binder), the durability of the indeformed refractory after repair is further improved as compared with the conventional product as in the product of the present invention in FIG. We have also found that it is possible to improve.

  As described above, according to the present invention, the spent converter refractory is pulverized to less than 40 mm and classified into less than 10 mm and less than 10 to 40 mm. It exhibits an excellent melting damage suppression effect than before, and can greatly extend the life of converter refractories.

Claims (3)

Grinding used converter refractories lining the converter,
A pulverized product having a particle size of less than 10 to 40 mm is used as a slag component adjusting agent for protecting a refractory used by being put into a converter.
A method for extending the life of a converter refractory, characterized in that a pulverized product having a particle size of less than 10 mm is used as a raw material for an irregular refractory used by spraying the surface of the refractory in the converter.   2. The method for extending the life of a converter refractory according to claim 1, wherein the converter refractory is a magnesia carbon brick containing MgO and C.   The method for extending the life of a converter refractory according to claim 1 or 2, wherein a slag component adjusting agent is introduced at the start of blowing and slag forming is concentrated and generated in the initial stage of blowing.