JP6752027B2 - Chamotte quality brick and its manufacturing method - Google Patents

Description

The present invention relates to alumina-silica refractory bricks used in various kilns and industrial furnaces, that is, chamotte-quality bricks.

Chamotte bricks are bricks made from fire-resistant clay that has been fired and are also called clay bricks. Generally, they contain about 20 to 50% by mass of Al ₂ O ₃ and about 50 to 80% by mass of SiO ₂ as chemical compositions. , Mineral composition is mullite, critobarite and glass phase. Moreover, in JIS R 2304, it is classified into 12 types according to quality.

Since this chamotte brick is inexpensive, it is widely used in various kilns such as hot air furnaces, incinerators, carbon black furnaces, and chloride furnaces, and industrial furnaces. However, while chamotte bricks are inexpensive, they have a high apparent porosity of about 15 to 26%, and because they contain about 50% by mass or more of SiO ₂ , their durability may be low, and improvement is also being considered. ..

For example, Patent Document 1 states that "refractory bricks for the bottom of float baths (chamot quality bricks) used in the float method using a large tin or tin alloy bath, which is one of the methods for producing flat glass, are included in the flat glass. Alkali (Na ₂ O and K ₂ O) act on the refractory bricks for the bottom of the float bath to change the surface of the refractory bricks and reduce the fire resistance, which is one of the performances of the bricks. For improving the quality of glass. The melting damage phenomenon that foams the surface of the refractory brick due to the heat load accompanying the rise in the operating temperature is often observed. Furthermore, the flaking phenomenon that peels off the surface of the refractory brick to a certain thickness is also observed at the same time. (See paragraph 0005 of Patent Document 1). As a means for solving this problem, Patent Document 1 states that "essentially, Al ₂ O ₃ is contained in an amount of 35 to 50% by weight, and the total amount of Na ₂ O and K ₂ O is 1% by weight or less. In a refractory brick for the bottom of a float bath made of a certain SiO _2- Al ₂ O ₃ refractory brick, a compound in which the total amount of Na ₂ O and K ₂ O in a fine powder region having a particle size of 90 μm or less is 1% by weight or less is kneaded. , A refractory brick for the bottom of a float bath, characterized by being molded and fired. " According to this Patent Document 1, since the amount of alkali in the matrix portion is small, when the Na ₂ O component in the glass permeates into the refractory brick, the amount of alkali in the brick is smaller than that in the commonly used brick. It is said to have a function to prevent the erosion phenomenon.

However, although some improvement effect can be obtained by the means of Patent Document 1, the fire-resistant brick (chamotte-quality brick) for the bottom of the float bath of Patent Document 1 has an apparent porosity of about 16 to 20% by mass (Patent Document). (See Table 3 in 1), the melting damage and flaking phenomenon due to the permeation of the alkaline component into the brick tissue remain unsolved, and the actual situation is that it is the main cause of the wear of the brick.

Further, in Patent Document 2, as a conventional technique, chamotte brick or molten silica brick is used in a chlorination furnace, but since the apparent porosity is 10 to 15%, chlorine gas brick is used along the pores. It is stated that it invades the inside and causes tissue weakening, wears the refractory lining and the reaction product in the furnace, and causes great damage to the bricks, resulting in a short life. On the other hand, Patent Document 2 proposes an improvement of SiO ₂ 99.0% or more of molten silica brick, but since molten silica brick is more expensive than chamotte brick in the first place, chamotte brick is used. Improvement is desired.

Chamotte bricks are also used as heat storage bricks in hot air furnaces and coke furnaces. In recent years, there has been a demand for bricks with thin walls for the production of heat storage bricks with a large heat transfer area. Therefore, improvement of chamotte-quality bricks, that is, improvement of durability of chamotte-quality bricks is desired.

Japanese Unexamined Patent Publication No. 2003-277134 Tokusei No. 5-47503

An object to be solved by the present invention is to improve the durability of chamotte bricks.

The present inventors considered that it is effective to densify the structure, that is, reduce the apparent porosity, in order to improve the durability of chamotte bricks. As a result of various studies, mullite and cristobalite in the bricks after firing It was found that the apparent porosity was significantly reduced and the durability was significantly improved by setting the amount ratio of the above to the appropriate range.

That is, according to the present invention, the following chamotte bricks and a method for producing the same are provided.
1. 1.
It contains 41.7 to 48% by mass of Al ₂ O ₃ and 50 to 58.3 % by mass of SiO _{2, and} has the (110) plane peak intensity of cristobalite with respect to the (210) plane peak intensity of mullite in powder X-ray diffraction. Chamotte bricks with a ratio of 0.01 to 0.8 and an apparent porosity of 10% or less.
2. 2.
It contains 34 to 48 % by mass of Al ₂ O ₃ and 50 to 53.7% by mass of SiO _2, and the ratio of the (110) plane peak intensity of cristobalite to the (210) plane peak intensity of mullite in powder X-ray diffraction is Chamotte bricks with an apparent porosity of 10% or less between 0.01 and 0.8.
3.
A fire-resistant raw material compound containing 85% by mass or more and 97% by mass or less of chamotte and 3% by mass or more and 15% by mass or less of clay is kneaded, and after molding, cristobalite with respect to the (210) plane peak intensity of mullite in powder X-ray diffraction. A method for producing chamotte-quality bricks, which is fired under the condition that the ratio of (110) plane peak intensities is 0.01 to 0.8.
4.
The chamotte is described in 3 above, wherein the total amount of Al ₂ O ₃ and SiO ₂ is 92% by mass or more, and the total amount of Fe ₂ O ₃ , Na ₂ O and K ₂ O is 2% by mass or less. How to make chamotte quality bricks.
5.
The chamotte brick according to 3 or 4 above, wherein the ratio of the (110) plane peak intensity of cristobalite to the (110) plane peak intensity of mullite in powder X-ray diffraction of the fireproof raw material compound is 1.0 or more. Production method.

Hereinafter, the technical features of the present invention will be described in detail.

Chamotte The chamotte, which is the raw material for bricks, is obtained by firing ores such as kaolin, whose main rock-forming mineral is clay mineral. Mullite and cristobalite are the main constituent minerals, and it contains a small amount of glass. .. The present invention is based on a new finding that the cristobalite and the originally contained glass melt during firing to form a glass phase, which seals open pores and densifies bricks.

When cristobalite is vitrified, the peak intensity in powder X-ray diffraction decreases. On the other hand, since the melting point of mullite is as high as about 1850 ° C. and vitrification does not occur in the firing temperature range of chamotte bricks, the peak intensity in powder X-ray diffraction does not change. Therefore, the progress of vitrification of cristobalite can be expressed by the peak intensity ratio of these minerals. Therefore, in the present invention, the peak intensity ratio of the (210) plane of mullite and the (110) plane of cristobalite, which shows the strongest peak intensities in both minerals (“Cristobalite (110) plane peak intensity / mullite (210) plane peak” "Strength") indicates the degree of vitrification of cristobalite.

The ratio of the (110) plane peak intensity of cristobalite to the (210) plane peak intensity of mullite in this powder X-ray diffraction (“Cristobalite (110) plane peak intensity / mullite (210) plane peak intensity”, hereinafter simply The “peak intensity ratio”) needs to be in the range of 0.01 to 0.8 after firing in order to densify the chamotte-quality bricks and improve their durability. That is, when the peak intensity ratio exceeds 0.8, the apparent porosity becomes high and the effect of improving the durability becomes small. On the other hand, when the peak intensity ratio is less than 0.01, the glass phase produced by firing foams, and not only the surface texture of the brick is deteriorated, but also the dimensional accuracy is poor and the product yield is significantly lowered. Furthermore, the apparent porosity also tends to increase. If the peak intensity ratio of the fire-resistant raw material compound before firing is too small for densification by firing, the densification will be insufficient. Therefore, the peak intensity ratio of the fire-resistant raw material compound should be 1.0 or more. Can be done.

Here, as a method for advancing the vitrification of cristobalite, an increase in the calcination temperature or an extension of the calcination time can be considered, but it has been conventionally said that excessive calcination is not desirable because the calcination shrinks. However, in the chamotte brick of the present invention, the phenomenon that the calcination shrinkage progresses more significantly than the present one is not observed, and conversely, the phenomenon that the calcination shrinkage becomes smaller is also observed. It is estimated that this is the effect of melting the mineral phase into a glass phase and increasing the volume. In any case, the phenomenon that the firing shrinkage progresses remarkably due to the rise in the firing temperature or the extension of the firing time is not observed, and conversely, the phenomenon that the firing shrinkage becomes smaller is a phenomenon that cannot be predicted from the conventional common general knowledge. is there.

That is, the present invention provides a fine chamotte-quality brick having an apparent porosity of 10% or less, based on a new technical idea of appropriately advancing the vitrification of cristobalite to achieve densification. As a result, the durability of chamotte bricks such as alkali erosion resistance can be significantly improved.

Further, the chamotte brick of the present invention contains 34 to 48% by mass of Al ₂ O ₃ and 50 to 65% by mass of SiO ₂ as a basic chemical composition. If Al ₂ O ₃ is less than 34% by mass, durability such as alkali erosion resistance becomes insufficient, and if it exceeds 48% by mass, the thermal expansion of brick becomes too large. Further, when SiO ₂ is less than 55% by mass, Al ₂ O ₃ is relatively excessive and the thermal expansion of bricks becomes large, and when SiO ₂ exceeds 65% by mass, durability such as alkali erosion resistance is insufficient. Become. The total content of Al ₂ O ₃ and SiO ₂ is preferably 90 to 99% by mass.

Next, the method for producing the chamotte brick of the present invention will be described.

In the method for producing chamotte-quality brick of the present invention, chamotte is used as the main raw material. Specifically, the chamotte can be 85% by mass or more and 97% by mass or less in the fireproof raw material formulation. If it is less than 85% by mass, it becomes difficult to obtain a dense structure, and if it exceeds 97% by mass, the bond becomes insufficient and it becomes difficult to obtain sufficient strength. In order to ensure higher durability such as alkali erosion resistance, the chamotte has a total amount of Al ₂ O ₃ and SiO ₂ of 92% by mass or more, and Fe ₂ O ₃ , Na ₂ O and K ₂ O. It is preferable to use one having a total amount of 2% by mass or less.

Besides this, pyrophyllite, can be used in the under Ryu site, sillimanite, various _SiO 2, such as kyanite _-Al 2 _{O 3} based material and 10 mass% or less (including 0). As the binder, clays such as wood knot clay, serpentine clay, kaolin, pyrophyllite, and talc can be used, and the content can be 3% by mass or more and 15% by mass or less. In addition, a small amount of lignin sulfonate or the like may be used in combination as a thickener. Alkaline oxides and iron in chamotte and clay, which are conventionally regarded as impurities, also have the effect of promoting the above-mentioned glass formation, and therefore, it is not necessary to limit their contents in the present invention.

The chamotte brick of the present invention is produced by adding water to a fire-resistant raw material compound made of the above-mentioned raw materials, kneading the brick, molding the brick, and firing the brick. Kneading and molding may be carried out according to a normal method for producing chamotte bricks, but for firing, the temperature rise rate and firing so that the above-mentioned peak intensity ratio is in the range of 0.01 to 0.8. Control the temperature and firing time. Specifically, the firing temperature can be in the range of 1400 to 1650 ° C., and the firing time can be in the range of 5 to 10 hours.

Since the chamotte brick of the present invention has an apparent porosity of 10% or less, it is possible to improve durability such as alkali erosion resistance. For example, it can contribute to improving the durability of a container such as the above-mentioned float bath, which is required to have alkali erosion resistance. Furthermore, even when erosion due to intrusion of gas or liquid such as a glass melting furnace, an incinerator, a chlorination furnace, etc. is a damage factor, it exhibits high durability in each stage. In addition, since the structure is dense and the strength is high, the durability can be improved even as a heat storage brick in a hot air furnace or a coke oven.

Hereinafter, embodiments of the present invention will be described based on examples. The present invention is not limited to these examples.

An appropriate amount of water is added to the fire-resistant raw material formulation shown in Table 1, kneaded, molded into a shape of 230 mm × 114 mm × 100 mm by an oil press, and then heat-treated (drying) at a maximum temperature of 110 ° C. for 5 hours. , A sample was obtained by firing in a shuttle kiln. From this, a sample for measuring physical properties was cut out and the apparent porosity and compressive strength were measured. Furthermore, the alkali erosion resistance was evaluated. The chemical composition of the raw materials used is shown in Table 2.

The apparent porosity was measured in accordance with JIS R 2205 using a sample having a shape of 50 × 50 × 50 mm and using white kerosene as a solvent. The lower the apparent porosity, the denser the brick, and it is judged that it is effective in improving the durability.

The compressive strength was measured according to JIS R 2206 using a sample having a shape of 50 × 50 × 50 mm. As a tentative guide, we aimed to achieve 100 MPa or more.

For alkali erosion resistance, a sample having a shape of 114 × 114 × 65 mm was used, the sample was immersed in an alkaline solution containing 10 mL of a 30% aqueous solution of sodium hydroxide, heated at 1100 ° C. for 24 hours, and then the thickness of the altered layer of the sample. Was measured and evaluated. The results are shown as an index with the reciprocal of the altered layer thickness of "Comparative Example 1" in Table 1 as 100. The larger the value of this index, the better the alkali erosion resistance.

In addition, the bricks of each example after firing were finely pulverized in an appropriate amount, and the (210) plane peak intensity of mullite and the (110) plane peak intensity of cristobalite were measured by powder X-ray diffraction method to calculate the peak intensity ratio. .. CuKα rays were used as the X-ray source, the tube voltage was 45 kV, and the tube current was 200 mA.

In Table 1, Comparative Examples 1 and 2 were fired with the firing temperature (maximum firing temperature) at 1380 ° C. and the firing time (holding time) at 5 hours and 10 hours, with a peak intensity ratio of around 1.3. It showed a high value, and the apparent porosity was as high as 14.8% and 14.1%.

On the other hand, in Examples 1 to 7, the firing temperature and the firing time were changed at the same blending ratio as in Comparative Example 1. In Example 1, the temperature was maintained at 1400 ° C. for 10 hours, but the peak intensity ratio was as low as 0.79, the apparent porosity was significantly reduced, achieved 9.8%, and the alkali erosion resistance was also improved. .. In Examples 2, 3, 5, and 6, the firing temperature was raised and the firing time was set to 5 hours, but the peak intensity ratio showed a smaller value, and the apparent porosity decreased as the firing temperature was raised. It was confirmed that the alkali erosion resistance was also improved.

In Examples 4 and 7, the firing time was set to 10 hours at each firing temperature, but it was confirmed that the peak intensity ratio was smaller and the apparent porosity was reduced as compared with Examples 3 and 6, respectively. .. It is presumed that the effect of densification due to glass formation is further advanced.

Example 8 is a type with a large amount of clay, and Example 9 is a type with a small amount of clay, but each has a dense structure and good alkali erosion resistance.

Example 10 uses a raw material (chamot B) having a low sum of Al ₂ O ₃ content and SiO ₂ content and a _high content of alkali oxide and iron oxide, but the firing conditions are the same. Compared with a certain Example 5, the peak intensity ratio was small, the apparent porosity was low, and the alkali erosion resistance was also improved. From these, it can be said that the effect of the present invention is sufficiently exhibited if the chemical composition is within the range of the present invention.

Comparative Example 3 was fired at 1700 ° C. for 10 hours, but the peak intensity ratio was 0, the glass phase formed during firing was foamed, protrusions were formed on the surface of the brick, and the brick was Inflated. When the peak intensity ratio becomes 0 in this way, the dimensional accuracy is deteriorated and the product yield is significantly lowered, which is not practical. Although the apparent porosity is low, it is higher than that of firing at 1650 ° C. (Example 7).

Claims (5)

It contains 41.7 to 48% by mass of Al ₂ O ₃ and 50 to 58.3 % by mass of SiO _{2, and} has the (110) plane peak intensity of cristobalite with respect to the (210) plane peak intensity of mullite in powder X-ray diffraction. Chamotte bricks with a ratio of 0.01 to 0.8 and an apparent porosity of 10% or less. It contains 34 to 48% by mass of Al ₂ O ₃ and 50 to 53.7 % by mass of SiO _2, and the ratio of the (110) plane peak intensity of cristobalite to the (210) plane peak intensity of mullite in powder X-ray diffraction is Chamotte bricks with an apparent porosity of 10% or less between 0.01 and 0.8. A fire-resistant raw material compound containing 85% by mass or more and 97% by mass or less of chamotte and 3% by mass or more and 15% by mass or less of clay is kneaded, and after molding, cristobalite with respect to the (210) plane peak intensity of mullite in powder X-ray diffraction. A method for producing chamotte-quality bricks, which is fired under the condition that the ratio of (110) plane peak intensities is 0.01 to 0.8. Chamotte is Al _Two O _Three And SiO _Two The total amount of is 92% by mass or more and Fe _Two O _Three , Na _Two O and K _Two The method for producing chamotte brick according to claim 3, wherein a brick having a total amount of O of 2% by mass or less is used. The chamotte brick according to claim 3 or 4, wherein the ratio of the (110) plane peak intensity of cristobalite to the (110) plane peak intensity of mullite in powder X-ray diffraction of the fireproof raw material compound is 1.0 or more. Manufacturing method.