JP2007070220A - Method of manufacturing basic brick - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance durability greatly by drastically improving the weak point, that is, poor resistance to slag infiltration, of conventional magnesia chrome bricks. <P>SOLUTION: The magnesia chrome bricks with an improved resistance to slag infiltration can be prepared by impregnating magnesia chrome bricks with a solution, which is prepared by dissolving a chrome (III) salt in a state of chrome ions into a solution such as water, in order to impregnate uniformly into small holes inside the bricks and by heating after the above process to decompose chrome (III) salt and to generate chrome oxide (Eskolaite). Namely, by the manufacturing method, magnesia chrome bricks are impregnated with a solution, where chrome (III) salt is dissolved, in order to incorporate a chrome (III) salt in a brick structure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a basic brick used in an incinerator, a cement rotary kiln, a molten metal container or the like.

As basic bricks used for incinerators, waste melting furnaces, etc., magnesia-chromic bricks (hereinafter referred to as “magcro bricks”) are often used. Magchrom bricks are bricks mainly composed of magnesia and chromium ore, and usually contain 10 mass% or more of Cr ₂ O ₃ . The spinel group mineral (MgR ₂ O ₄ ; R = Cr, Fe, Al) containing Cr ₂ O ₃ as a main component is precipitated (secondary spinel) in the matrix during firing of the brick, and is an aggregate mainly composed of magnesia. Combine with. Therefore, the resistance with respect to the slag infiltration of a matrix part becomes high. However, due to the recent severer operating conditions, there is an increasing number of cases where the resistance to slag infiltration is insufficient with conventional magcro bricks.

For this reason, various methods for suppressing slag infiltration of magcro bricks have been studied. For example, chromium oxide (Escolite) powder is blended as a starting material for magchrom bricks to promote sintering and densify (see Patent Document 1), and metallic chrome is blended to utilize volume expansion during firing. Then, a method such as densification has been proposed. However, in fact, these methods are effective for improving the corrosion resistance and hot strength by densification or increasing the purity of the secondary spinel described above (increasing the Cr content), but the spinel mineral is CaO, Since it has poor reactivity with slag mainly composed of SiO ₂ , its effectiveness is limited in suppressing slag infiltration, and structural spalling occurs particularly in kilns that are subjected to a thermal history, resulting in durability. The improvement effect was insufficient.

  Patent Document 2 describes a Fe—Cr alloy-added magcroblende impregnated with fine chromium oxide powder after firing. Specifically, the fired refractory is immersed in an aqueous solution in which chromium oxide fine powder having an average particle size of 0.6 μm is dispersed in ion-exchanged water (pH 7) to which 5 vol% surfactant is added, and this is evacuated to a vacuum. A method of impregnating refractory pores with fine chromium oxide powder is described. It is described that this impregnation makes it possible to make open pores having a radius of 5 μm or more, which serve as a permeation path for molten slag, and to make them discontinuous, thereby suppressing slag permeation. It is also described that chromium oxide filled in the pores reacts with slag to generate a highly viscous liquid phase, so that further slag penetration is prevented.

  However, even if brick is impregnated in an aqueous solution in which fine chromium oxide powder having an average particle size of 0.6 μm is dispersed, it is impossible to impregnate fine chromium oxide powder into the interior. The reason for this is that when an aqueous solution containing fine chromium oxide powder penetrates into the fine pores of the brick, only the moisture brick is instantaneously sucked into the tissue and the concentration of the fine chromium oxide powder rapidly rises, and the aqueous solution becomes a highly viscous slurry. This is because the pores near the surface are clogged. For this reason, the slag permeation suppression effect is hardly obtained in practice.

Japanese Patent Publication No.57-57428 JP-A-9-52755

  An object of the present invention is to significantly improve the slag infiltration resistance, which was a weak point of conventional magcro bricks, and to significantly improve the durability.

As a result of accumulating various researches in order to solve the above-mentioned problems, it is possible to impregnate the inside of the brick by impregnating it into a magchrom brick as a solution in which chromium (III) salt is dissolved in a solution such as water in the form of chromium ions. Chrome (III) salt is uniformly impregnated to the pores, and then heated, the chromium (III) salt is decomposed and Cr ₂ O ₃ (escorite) can be generated, and the slag infiltration resistance is remarkably improved. It was found that magcro brick was obtained.

That is, the present invention is a method for producing a basic brick, characterized in that a mug brick is impregnated with a solution in which a chromium (III) salt is dissolved.
By making Cr ₂ O ₃ (escorite) as a mineral phase present in the brick structure, the slag infiltration resistance is remarkably improved. In other words, since Cr ₂ O ₃ (escolite) is more reactive with slag than secondary spinel, it reacts preferentially with slag and raises the melting point of slag, thereby causing slag infiltration into the brick. Strongly suppressed. Moreover, in the present invention, the chromium (III) salt uniformly penetrates into the brick structure as chromium ions to the inside, so that this Cr ₂ O ₃ (escorite) is also present in fine pores. As a result, an extremely excellent slag infiltration suppressing effect is obtained.

As the chromium (III) salt, one or more of chromium (III) acetate, chromium (III) sulfate, chromium (III) nitrate and chromium (III) chloride can be used. The reason why these compounds are suitable is that they are relatively easily available among chromium (III) salts, have high solubility in solvents such as water, and yield of Cr ₂ O ₃ (escorite) after pyrolysis. Is high.

Further, it is preferable that the impregnation amount of the chromium (III) salt is 0.3% by mass or more and 3% by mass or less in the magchrom brick in terms of Cr ₂ O ₃ (escolite). If it is less than 0.3% by mass, the effect of preventing slag infiltration is insufficient, and if it exceeds 3% by mass, the brick structure becomes too dense and the heat spalling property is lowered.

  According to the present invention, it is possible to remarkably reduce the slag infiltration of magchrom bricks and the accompanying structural spalling, and it is possible to dramatically improve the durability.

  In the present invention, the magcro brick can be used without any problem if it is a general baked magcro brick. For example, a direct bond type, a ribbon type, or a semi-ribbon type can be used.

As the chromium (III) salt, one or more of chromium (III) acetate, chromium (III) sulfate, chromium (III) nitrate and chromium (III) chloride can be used. Specifically, chromium acetate (III) hexahydrate, chromium sulfate (III) 18 hydrate, chromium nitrate (III) 9 hydrate, chromium chloride (III) hexahydrate, and the like. Among these chromium (III) salts, chromium (III) hexahydrate is more preferable because of its high solubility and easy control of the amount of impregnation.
A chromium ion-containing solution in which the chromium (III) salt is dissolved as a chromium ion in a liquid such as water is prepared, and magcro brick is immersed in the chromium ion-containing solution.

The brick taken out from the solution is dried to volatilize the solvent, if necessary. At this time, or as a subsequent process, heat treatment for thermally decomposing the chromium (III) salt can be performed. When chromium (III) salt is pyrolyzed, Cr ₂ O ₃ (escorite) is obtained. However, since chromium (III) salt is also pyrolyzed by heating at the time of use of the brick, only drying for volatilizing the solvent is necessary. There is no particular problem. Furthermore, the impregnation amount of chromium (III) salt can be increased by repeating the impregnation and drying steps.

  As a main raw material, magnesia clinker 30% by mass, chromium ore 20% by mass, and electrofused magcro clinker 50% by mass were blended, and chrome baked bricks manufactured by a known method were prepared as shown in Table 1 as a chromium (III) salt solution. Impregnated. The bulk specific gravity of this magcro brick was 3.24, the apparent porosity was 14%, and the bending strength at 1400 ° C. was 12.0 MPa. The impregnation conditions are room temperature and normal pressure for 30 minutes. Thereafter, the brick was taken out and dried at 110 ° C. for 24 hours. Thereafter, a part of the brick was heat-treated in an oxidizing atmosphere at 1200 ° C. for 3 hours.

The “impregnation amount” shown in Table 1 was determined by measuring the mass of the sample before and after the impregnation / 110 ° C. drying treatment. Incidentally, with the various chromium (III) wherein the ratio of the amount of salt and _Cr 2 _{O 3,} was converted displayed on _Cr 2 _{O 3} amount.

  The mineral phase in these bricks was identified and subjected to a corrosion resistance test.

X-ray diffraction was used to identify the mineral phase. Further, the corrosion resistance test was carried out by the rotary erosion method. The conditions were 1700 ° C. × 4 hours, the slag used was a synthetic slag with a CaO / SiO ₂ ratio = 1.5, and the slag was changed every 30 minutes. The sample dimensions before and after the test and the slag infiltration thickness after the test were measured, and the reduction and the slag infiltration thickness were displayed as an index with the value of the sample “A” being 100.

As a result, (1) in the sample subjected to the impregnation treatment, chromium (III) salt and / or Cr ₂ O ₃ (escorite) is detected as a mineral phase, and (2) the sample subjected to the impregnation treatment is The slag infiltration thickness was greatly reduced as compared with the untreated sample “A”, and two points were revealed that there was a remarkable effect on the slag infiltration resistance.

Comparative Example H is a suspension prepared by kneading 100 parts by mass of chromium oxide fine powder having an average particle size of 0.5 μm, Cr ₂ O ₃ purity of 99% by mass, 0.3 parts by mass of a dispersant, and 60 parts by mass of water. The suspension is impregnated with magcro brick. When the results of the corrosion resistance test are compared with the magcro bricks of the examples, the slag infiltration thickness is particularly large and is almost the same as that of the unimpregnated one (sample “A”). This is presumably because the impregnation effect of chromium oxide is limited to the vicinity of the surface as described above, and the bricks are not impregnated in the pores.

Claims (3)

  A method for producing a basic brick, characterized by impregnating a magnesia-chromic brick with a solution in which a chromium (III) salt is dissolved.   The method for producing a basic brick according to claim 1, wherein at least one of chromium (III) acetate, chromium (III) sulfate, chromium (III) nitrate and chromium (III) chloride is used as the chromium (III) salt. . The impregnation amount of chromium (III) salt is 0.3 mass% or more and 3 mass% or less in magnesia-chromic brick in terms of Cr ₂ O ₃ (escolite). 2. A method for producing a basic brick according to 2.