JPH0777982B2 - Silica brick for hot repair - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot repair silica stone brick that can be used for hot transshipping repair of a brick wall of a coke oven.

[0002]

2. Description of the Related Art Conventional silica bricks are mainly composed of cristobalite and tridymite, and the microstructure of the bricks does not have a buffer portion for strain caused by expansion and contraction due to crystal transition of constituent minerals. The poling property was extremely poor and it was not suitable for hot repair. That is, tridymite undergoes a crystal transition at 117 ° C. and 163 ° C. and a line change of 0.15% and 0.2% occurs respectively, and cristobalite transitions at 230 to 270 ° C. and a line change of about 0.4% occurs. It is known to occur.
Since conventional silica stone bricks undergo a large volume change due to the transition of these minerals when receiving heat, cracks are easily generated by a heat spall at a relatively low temperature of 200 to 300 ° C.

In order to solve this problem, for example, in Japanese Patent Publication No. 1-38074, 30 to 70% by weight of coarse particles of fused silica having a particle size of 0.7 mm or more is contained, and the surface portion of the fused quartz particles is included. Disclosed is a thermal shock-resistant silica stone brick in which less than 50% of which is transformed into cristobalite and / or tridymite to form a shell, the inside is amorphous, and the portion other than fused quartz is composed of silica stone brick. The thermal shock resistance is imparted by utilizing the low thermal expansion property of the quartz glass remaining inside the fused silica grains.

[0004]

Although the brick described in this publication is certainly improved in spalling resistance, it contains a large amount of fused quartz in the form of coarse particles of 0.7 mm or more, 30 to 70% by weight. Therefore, there is a drawback that the abrasion resistance is significantly inferior to that of conventional bricks.

That is, the fused quartz grains are bonded to the surrounding brick structure through the shell of cristobalite or tridymite on the surface portion thereof, and the bonding force is weak, so that the fused quartz particles are relatively easily separated from the brick structure. Further, since coarse fused silica particles are added, the void structure of the brick structure after the fused silica particles have fallen off is large, which further deteriorates the wear resistance of the brick.
When a brick having such a structure is used for a furnace wall of a coke oven that is in direct contact with coal, the brick is worn due to friction with coal and cannot be used for a long period of time.

The object of the present invention is to eliminate the disadvantages of the conventional silica stone bricks, and even when the bricks are inserted from the normal temperature into the hot atmosphere during hot transshipment repair of the coke oven furnace wall bricks, cracking occurs due to the heat spall. To provide silica brick that has spalling resistance that does not cause cracks or cracks, has excellent wear resistance when used in an actual furnace after repair, and has excellent wear resistance that can withstand long-term use as well as heat spalling resistance. It is in.

[0007]

In the silica stone brick for hot repairing of the present invention, the aggregate is composed of fused silica and calcined silica stone, and the content of fused silica is 35 to 50% by weight. In, the particle size of less than 1 mm is 15 to 30% by weight,
The particle size of 1 mm or more is less than 30% by weight, and in the particle size composition of the remaining calcined silica stone, fine powder of 0.5 mm or less is in the range of 15 to 35% by weight.

[0008]

The fused quartz particles are crystallized into cristobalite or tridymite from the surface portion of the brick during the firing step. Particularly, in the case of coarse particles of fused quartz, the surface portion forms a shell made of cristobalite or tridymite, and the central portion thereof exists in the state of quartz glass.

It is considered that one of the reasons for improving the heat-resistant spalling property by blending fused silica is that the low thermal expansion property of the silica glass contributes. That is, the thermal expansion coefficient of cristobalite and tridymite at 1000 ° C. is 1.5% and 1.0%, respectively, whereas that of quartz glass is about 0.1%, which is due to this extremely small thermal expansion coefficient. The volume change when receiving heat is small and the heat resistant spalling property is improved.

[0010] In the prior art, when blending fused quartz to improve the heat-resistant spalling property, 0.7 m
The reason for using coarse particles of m or more is that if fused silica is added with fine powder of less than 0.7 mm, the inside of the fused quartz particles will be crystallized during the firing of the bricks, and the quartz glass will not remain, or the remaining amount will remain. It was said that the low thermal expansion of the quartz glass could not be exerted because it did not contribute to the improvement of the heat resistant spalling property.

On the other hand, in the case of the present invention, as a result of various studies on the effect of improving the fused silica particle size and the heat-resistant spalling property, the fused silica in the fine powder region, which was conventionally considered unsuitable, was blended. This is based on the new finding that the heat-resistant spalling property is sufficiently improved even when added.

This is due to the fact that even after the brick is fired, the quartz glass still remains inside the fine-powder fused silica grains, and its low thermal expansion can be expected sufficiently, and even if it is completely transformed into cristobalite or tridymite. Also,
The particles are present as independent particles without part of the surface of the particles melting and becoming integrated with the matrix like the case of calcined silica stone particles, and the strain caused by crystal transition when the brick receives heat is relaxed in this part. it is conceivable that. That is, since fused silica has a high SiO ₂ purity, it is difficult to generate a melt during the firing of bricks, and since the crystallization of the bricks causes the bricks to crystallize and shrink during firing, the bricks are not integrated with the structure of the bricks, especially the matrix glass. In addition, the effect of alleviating the strain that occurs inside the tissue when the brick receives heat, or even if a crack occurs inside the brick tissue, it exerts the effect of preventing the propagation of cracks and keeps them as micro-cracks of a microcrack level. It is considered to improve the heat-resistant spalling property. Therefore, in order to improve the heat-resistant spalling property, it is not particularly necessary to limit the particle size of fused silica to the coarse particle region as seen in the prior art, and in order to improve the wear resistance of bricks, fused silica is required. On the contrary, the addition in the coarse particle region is extremely disadvantageous, and rather, fused silica should be positively added in the fine powder region having a particle size of less than 1 mm.

The amount of fused quartz added is preferably 35 to 50% by weight. If it is less than 35% by weight, the effect of improving the heat-resistant spalling property is small, and if it exceeds 50% by weight, the strength of the brick is deteriorated and the wear resistance is greatly deteriorated. As a result of a sandblasting test on the relationship between the added fused silica grain size and wear resistance, it was found that the addition of fused silica in the coarse grain region with a grain size of 1 mm or more has a weak bond between the fused silica grain and the brick structure. In addition, since the voids in the defective portion are large when the fused silica particles fall out of the brick, the wear resistance is greatly deteriorated. In particular, if the added amount exceeds 30% by weight, the wear resistance rapidly deteriorates, so the added amount must be 30% by weight or less. For this reason, it is desirable to add fused silica in the form of fine powder having a particle size of less than 1 mm, and the optimum addition amount is in the range of 15 to 30% by weight. If the amount of fused silica having a particle size of less than 1 mm exceeds 30% by weight, the strength of the brick decreases, and if it is less than 15% by weight, the heat spalling resistance is not sufficiently improved.

As the aggregate other than fused quartz, calcined silica stone is used. The mineral composition is preferably one having a small amount of quartz due to the progress of transition to cristobalite and / or tridymite. This is a conventional silica brick 1430 ~ 1500 ℃
In contrast, the hot repair silica stone brick of the present invention has a low firing temperature of 1200 to 1400 ° C., so that the transition of the remaining quartz in the fired silica stone does not progress completely during the brick firing. This is because the quartz remains until after firing. That is, this residual quartz gradually transforms to tridymite or cristobalite after the temperature rise after hot transshipment of the coke oven wall brick or during operation, and at the same time, it expands with the surrounding conventional silica stone brick. It is not preferable because there is a difference and there is a fear of warping or cracking of the furnace wall. This calcined silica stone is an important factor for controlling the strength development and heat resistant spalling resistance of bricks, and it is necessary to strictly adjust particularly the amount of fine powder of 0.5 mm or less. That is, fused quartz is more SiO 2 than calcined silica.
Since ₂ is very high impurity less purity, without generating melt during brick firing, and to shrink by crystallization,
Does not contribute to the strength development of bricks. Therefore, it is difficult to achieve the compressive strength of 200 kg / cm ² , which is the standard for silica coke oven brick, by simply replacing the fine powder portion in the conventional brick composition with the fused silica fine powder. In order to solve this problem, it is necessary to add a fixed amount of fine powder of calcined silica of 0.5 mm or less.
35% by weight. If the amount is less than 15% by weight, the strength of the brick is low, and it is difficult to achieve the compressive strength of 200 kg / cm ² which is the standard of silica brick for coke oven.
When the content is more than wt%, the strength is high, but the heat resistant spalling property is deteriorated.

As the mineralizer, one or more of slaked lime, calcium fluoride, sodium silicofluoride and the like are used. The addition amount is preferably in the range of 0.2 to 3.0% by weight. Generally speaking, increasing the amount of mineralizer added improves the strength of bricks, but it promotes the transition of fused quartz and that the amount of mineralizer strengthens the matrix part, so the heat-resistant spalling property is It tends to deteriorate. Therefore, it is necessary to be careful to add an excessive amount of mineralizing agent. If slaked lime is added, the content is 1 to 3% by weight. Higher is 0.2-1
It should be kept to a small amount, such as weight percent.

[0016]

EXAMPLES The formulations shown in Tables 1 and 2 were molded into a shape of 300 × 100 × 100 mm by a 250 ton friction press, and fired in a single kiln at 1350 ° C. for 5 hours to obtain test materials, Examined. The conventional bricks shown in each table were separately manufactured and tested.

The heat-resistant spalling resistance in each table is 300 ×
This is an observation of a state in which a 100 × 100 mm brick was inserted into a furnace that was kept at a predetermined temperature from room temperature as it was. In the table, ◯ means that no more bricks were observed, Δ means the occurrence of microcracks, and × means the occurrence of cracks or cracks.

Regarding the evaluation of wear resistance, it is expected that all fused silica of the silica stone for hot repairing will be crystallized during steady operation of the actual furnace after repairing.
It was performed after re-firing at 400 ° C. for a long time to completely crystallize the fused quartz into cristobalite and / or tridymite. Abrasion resistance is an indication of the weight loss of a brick when a predetermined amount of zircon sand is sprayed on the brick with a sandblast tester.

[0019]

[Table 1]

[Table 2] Comparative Example 1 is outside the range specified in the present invention,
35% by weight of fused silica having a particle size of less than 1 mm was added, and the strength was low and the compressive strength of the silica stone for coke ovens did not reach the standard of 200 kg / cm ² . Example 1
No. 3 is within the scope of the claims, and the heat-resistant spalling property is sufficiently improved because conventional bricks are cracked at room temperature to 200 ° C in an atmosphere and cracks are not generated even in an atmosphere at 400 ° C. There is. It has a compressive strength of 200 kg / cm ² or more, which is the standard for silica stone for coke ovens. Although the wear resistance tends to deteriorate as the amount of fused silica increases by 1 mm or more, compared with Comparative Example 3 which is a thermal shock resistant silica brick of the prior art in which fused silica is added only with coarse particles of 1 mm or more. The amount of wear is about 1/2,
The wear resistance is improved about twice. Comparative Example 2 in which coarse fused silica particles were added in an amount of 30% by weight or more, which is outside the scope of claims
In Nos. 3 and 3, the wear resistance is greatly deteriorated. Further, a fused silica fine powder having a particle size of less than 1 mm is out of the scope of claims of 15% by weight.
In Comparative Example 2 in which the heat resistance is less than less than that in Example 3, the heat-resistant spalling property tends to be slightly decreased.

As shown in the table, Examples 1 to 1 according to the present invention
In No. 3, the heat-resistant spalling property is remarkably improved as compared with the conventional brick, and the wear resistance is improved about twice as much as the heat-resistant impact brick which is the conventional technique.

Next, Table 2 shows the influence of the grain size composition of the calcined silica stone on the quality of the brick. The brick strength changes with the addition amount of calcined silica stone having a particle size of 0.5 mm or less, and in Comparative Example 5 in which the addition amount is smaller than the claimed range, the compression strength of 200 kg / cm ² which is the standard of silica stone for coke oven is reached. However, Comparative Example 6, which was added in excess of the scope of the claims,
Although the strength is high, deterioration of the heat-resistant spalling property is recognized. On the other hand, in Examples 4 to 6 in which the calcined silica fine powder was added within the scope of the claims, both the heat spalling resistance and the strength were improved.

[0022]

EFFECTS OF THE INVENTION Since the silica brick for hot repair of the present invention has an extremely excellent heat resistance spalling property, it can be used for hot transshipment repair of coke oven furnace wall bricks, and also has abrasion resistance as compared with the conventional heat resistance. Since it is improved compared to impact brick, it can be used for a long period of time even after repair.

Front Page Continuation (72) Inventor Yuzo Otsuki 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd.Technology Development Division (72) Inventor Keiji Nishimoto 20-1 Shintomi, Futtsu City, Chiba Nippon Steel Co., Ltd. Within the Technology Development Division (56) References JP-A-61-111962 (JP, A)

Claims (1)

[Claims] 1. A silica stone brick whose aggregate is composed of fused silica and calcined silica, and the content of fused silica is 35 to 50% by weight.
In the particle size constitution of fused quartz, the particle size of less than 1 mm is 15 to 30% by weight, and the particle size of 1 mm or more is 30% by weight.
And the rest of the calcined silica has a grain size composition of 0.5
Silica brick for hot repairing in which the fine powder of mm or less is in the range of 15 to 35% by weight.