JPS6047509B2 - How to form furnace walls - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a furnace wall that enables a synergistic improvement in durability by combining and laminating two specific types of refractories.

The parts exposed to the harshest conditions in electric furnaces and the like are hot spots and slag lines, and MgO- is a suitable refractory to be used in these parts.
There are A12O and -Cr2Oa-based heat-fused cast refractories.

This refractory has extremely excellent corrosion resistance against electric furnace slag, but on the other hand, hot-melt cast refractories with a dense structure suffer from the problem of spalling resistance, which is an unavoidable drawback. be. In particular, as a recent operational trend, the spalling resistance is weak due to thermal shock due to repeated cooling and heating due to the increase in electric furnaces, intermittent operation, periodic furnace closure, etc. However, the lifespan of a furnace is becoming shorter because its corrosion resistance is not effectively utilized. In contrast, carbon refractories or MgO-C refractories, which do not penetrate slurry and are resistant to spalling, have recently been increasingly used as alternative refractories. However, this type of carbon or MgO-C refractory has an extremely stronger spalling resistance than the hot-fused cast refractory, and has less corrosion against slag, but it is not as strong as the basic hot-fused refractory, and it also has a surface that is damaged by oxidation. For example, one way to do this is to coat the surface of these carbon-based refractories with an iron plate, but even that is not perfect, and the conditions of use must be taken into account. Due to the operation, the refractory materials become firmly integrated with each other through the iron plates, which makes it very difficult to remove the mesh-like iron plates during repair, replacement, and demolition work. As a result of various studies and examinations from these viewpoints, the present invention has found that not only can all of the above-mentioned weaknesses be solved by stacking these two specific types of refractories, but also that only basic heat-fused cast refractories can be used. It has been successfully demonstrated that the life span of the refractory is improved to a greater degree than that of the refractory constructed with the above structure.

That is, the gist of the present invention is a method for forming a furnace wall characterized by zebra stacking or checker stacking a basic heat-melting refractory whose main crystals are periclase and spinel and an MgO-C refractory. be.

In the present invention, heat-melting refractories whose main crystals are periclase and spinel are produced by completely melting necessary raw materials such as MgO raw material, alumina raw material, and chromite in a predetermined combination in an electric furnace, and generally using this hot water in a predetermined amount. Periclese (M
gO) and chromium spinel (MgOCr2O3) or alumina spinel (MfAl.

O3) as the main crystal, and its composition is chemically analyzed as 35-80% MgO and 8-5% Cr2O by weight.
0%, Al2O38-40%, Fe2O3 (including that present as FeO) up to 18%, SiO2 up to 8%
, up to 10% CaO are particularly preferred. In the present invention, MgO- which is a carbon-magnesia composite refractory
C-based refractories are usually unfired refractories obtained by molding and drying a mixture of MgO raw materials and carbon raw materials such as carbon and graphite in a predetermined ratio using a conventional method. If there is too much slag, there will be less slag adhesion and it will be easily oxidized, causing problems in terms of heat resistance. If there is too much carbon, the effect of improving the life of the refractory will not be sufficient when combined with basic heat-melting refractories, so It is preferable to have a composition of 95 to 60% MgO and 5 to 40% C, and in combination with carbon. Mg
Components other than O do not have sufficient corrosion resistance.

In the present invention, the MgO-C refractory may be coated with an iron plate, but may be used without necessarily being coated.

The present invention will be specifically described below with reference to embodiments shown in the drawings.

FIG. 1 is an explanatory diagram of the side wall of one hot spot part of the electric furnace, seen from the inside of the furnace. Column 2
This is the part of the zebra stack consisting of.

In the drawings, 3 and 4 are brick areas around the furnace wall where the method of the present invention is applied; for example, 3 is made of dolomite bricks,
4 is an unfired MgO-Cr2O3 refractory, and 5 is a burner arrangement part.

The present invention thus provides specific heat-melting refractories and MgO-C
A desirable embodiment is the so-called zebra type stacking method in which rows of refractories are alternately formed using refractories, but as shown in Figure 4, two types of refractories of the same thickness are of course alternately stacked. (in a so-called checker-type stacking system).

In FIG. 4 as well, 1 indicates a hot melt refractory and 2 indicates a MgO-C refractory. As described above, the furnace wall of the present invention may be of either the zebra or checker type, or a combination of these types, and various applications are possible as the embodiment thereof.

For example, in Fig. 1, each row is made of one heat-melting refractory and one MgO-C refractory of different thickness, and two MgO-C refractories are placed in the width of one heat-melting refractory. Figure 2 shows an example in which the joints are arranged in a continuous manner, Figure 2 shows an example that is similar to Figure 1, but the joints are staggered, and Figure 3 shows an example in which MgO-C refractories are arranged in two rows and An example in which the arrangement ratio with the molten refractories is 1:1. In Fig. 4, the arrangement ratio is the same as in Fig. 3 and is 1:1, but the refractories are close to each other between each row. An example is shown in which the contact area is halved.

As described above, various construction methods are possible with the present invention, but
In any case, as a preferred embodiment, the arrangement ratio of the basic heat-melting refractory and the MgO-C refractory as seen from the inside of the furnace is 4.
:1 to 1:2.

As a demonstration of the effects of the present invention, as a result of forming a furnace wall in the hot spot part of a 40-ton electric furnace by the construction method shown in Figs. 1 and 2, the service life of the hot spot part was as follows.
Even after three weeks (approximately 210 charges), the remaining thickness of the refractory was sufficient, indicating that it could continue to be used safely.

In addition, the service life when the entire furnace wall is made of MgO-C refractory is conventionally only 200 charges, and similarly, the service life when the entire furnace wall is made of basic heat-melting refractory is the same as that of MgO-C refractory. It was inferior to the case of , and it was often about 150 charges.

Furthermore, if the entire furnace wall is made of dolomite bricks, the durability is about 140 charges at most. The reason why the furnace wall according to the present invention exhibits excellent durability is considered to be due to the following reasons.

First, the thermal conductivity of basic heat-melting refractories, such as Asahi Glass Co., Ltd.'s MAC Upper C, is 3 to 4 Kca117n-Hr・℃, while that of MgO-C bricks is 10KcaIIm-H.
By skillfully combining MgO-C bricks, which are more than r・0C and thermally follow temperature changes sensitively, MAC
As for the upper part C, the temperature difference between the operating surface (inside) and the rear surface of the furnace is eliminated, and the durability can be improved by alleviating the sudden change in temperature that occurs when heating up the electric furnace.

In addition, as a furnace material to be combined with MAC upper C, the combination with MgO-C brick is currently considered to be the best, as conventional basic bricks wear out quickly and cannot prevent the spalling tendency of MAC upper C. . Even when looking at the C residue on the MAC after dismantling, it is clear that although internal cracks have occurred, the original slag corrosion resistance has been exhibited without any chipping. Furthermore, a protective layer was formed on the surface of the MAC top C, which is thought to be due to the glazing of some components in the MgO-C brick.
It is thought that it acts as a buffer layer for thermal expansion and contraction of C on AC. By skillfully combining two specific types of refractories, the present invention achieves effects such as improved durability, repairability, and ease of furnace construction that would be unimaginable if they were used alone. It has been successfully applied to not only electric furnaces but also degassing furnaces, converters, etc., and has great practical value.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a side wall of an electric furnace hot spot section showing one embodiment of the present invention, seen from the inside, and FIGS.
The figures each show explanatory diagrams showing the manner in which the refractories of the present invention are stacked. In the drawings, 1 indicates a basic heat-melting refractory series or refractory whose main crystal is periclase spinel, and 2 indicates an MgO-C refractory series or refractory.

Claims (1)

[Claims] 1. A method for forming a furnace wall, characterized in that a basic heat-melting refractory whose main crystals are periclase and spinel and an MgO-C-based refractory are stacked in zepra or checkered stacks. 2. The method for forming a furnace wall according to claim 1, wherein the arrangement ratio of the basic heat-melting refractory and the MgO-C refractory as seen from the inside of the furnace is 4:1 to 1:2. 3 The basic heat-melting refractory contains MgO35 to 8 in weight%.
0%, Cr_2O_38~50%, Al_2O_38~
40%, Fe_2O_3 max. 18%, SiO_2 max. 8
%, and a chemical composition of at most 10% CaO. 4 MgO-C refractory is MgO95-60 in weight%
%, C5 to 40%.