JPS6344708B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a synthetic raw material containing rankinite (3CaO, _2SiO2 ) as a main constituent. Rankinite is pseudowollastonite (high-temperature CaO,
It is a chemically stable mineral that has low hydration activity and no bound water among minerals that contain CaO as well as SiO ₂ ), and when used as a ceramic raw material, it produces products with little firing shrinkage. and can improve physical properties such as translucency of the product. Although it is known that this mineral occurs naturally, the amount is not large enough to be used industrially. The present inventors attempted to produce a synthetic raw material containing rankinite as a main component from a calcareous raw material and a silicic raw material, and conducted various studies _.
Even if they are mixed at a molar ratio of 3:2 and calcined for a long time at a temperature below the melting point, the reaction will not be completed easily, and the resulting clinker will contain little rankinite, free lime, and silicic acid. Dilime (2CaO・SiO ₂ )
This resulted in clinker containing a large amount of intermediate products with high hydration activity, such as However, the calcareous raw material and the silicic raw material are mixed so that the chemical composition (CaO/SiO ₂ weight ratio) is in a specific ratio, and the alumina raw material is added as a mineralizing agent to this mixture. By pulverizing and adjusting the particle size of the pulverized product with a specific range of powder and sending it to a rotary kiln and firing it, the main constituent minerals of rankinite in the clinker are 50% by weight or more, and free lime is present.
We found that it is possible to synthesize synthetic raw materials with less than 0.1% by weight of bound water and less than 0.4% by weight of bound water. Next, an experimental example will be explained. Experimental Example 1 Limestone, silica stone, and clay having the chemical composition of raw materials as shown in Table 1 are mixed at a CaO/SiO ₂ weight ratio as shown in Table 2, and the clay is mixed with Al ₂ O ₃ in the produced clinker as described below. This mixture was pulverized so that the amount of the pulverized material passing through a 0.044 mm sieve was as shown in Table 2, and the mixture was kneaded with water to make pellets. After drying this pellet at 110℃ for 24 hours,
The resulting fired product (clinker) was fired in an experimental electric furnace for 20 minutes each at the temperatures shown in the table.
The amount of free lime and rankinite in the clinker was determined by crushing the clinker so that it passed through a mm-sized sieve. However, the quantitative determination of rankinite was carried out by X-ray diffraction. Next, the crushed clinker was boiled in boiling water for 48 hours, then dried at 110℃ for 24 hours to obtain dried clinker.
The bound water produced by baking at 1000°C for 1 hour and boiling and curing was determined. The results are shown in Table 2.

【table】

[Table] In Table 2, it is thought that the bound water was generated due to the hydration of free lime and hydraulic dicalcium silicate. The clinker listed in Table 2 has a Blaine specific surface area of approximately
Grind to 5000 cm ² /g, then mix 50 parts by weight of clinker powder, 20 parts by weight of Kibushi clay, and 20 parts by weight of low stone, and mold at a pressure of 300 to a size of 100 x 50 x 7 mm.
A tile base was prepared by pressure molding at Kg/cm ² . The tile base was coated with glaze, dried and then fired at 1030°C for 20 minutes. The fired tiles were autoclaved at 10 atm for 1 hour. When we observed the occurrence of cracks on the tiles after curing using a microscope, we found that experiment number 1,
Cracks were observed in tiles using clinkers 3, 5, 7, 9, and 10. That is, clinker containing 0.5% or more of bound water causes hydration expansion and is found to be unsatisfactory as a tile base material. As is clear from Table 2, 0.044 of the blended raw materials
If the material is pulverized so that 80% or more passes through a mm-sized sieve and then calcined, the blended raw material becomes highly reactive, and the amount of free lime remaining in the clinker is found to be significantly reduced. The amount of lanquinite produced depends on the CaO/SiO ₂ (weight ratio) in the mixed raw materials.
If it is less than 1.05, it will be less and pseudowollastonite will be more abundant.
Furthermore, when the CaO/SiO ₂ (weight ratio) exceeds 1.45, the amount of hydraulic dicalcium silicate produced increases rapidly, the instability of the product increases, and the amount of rankinite produced decreases significantly. Admitted. Experimental example 2 Pellets made in the same manner as experimental example 1 were heated to 110°C.
After drying for 24 hours, each sample was fired in an experimental electric furnace at the temperatures shown in Table 3 for 20 minutes. The obtained clinker was crushed to a size of 0.088 mm or less, boiled and dried in the same manner as in Experimental Example 1, and free lime, rankinite, and bound water were determined, and the results shown in Table 3 were obtained. . The firing temperature level Tmax (℃) in Table 3 is experimental example 1.
It is the same as the firing temperature corresponding to the C/S ratio in Table 2, and is the temperature at which clinker grains begin to fuse. When firing in a rotary kiln, if the temperature exceeds this temperature (Tmax), the clinker will fuse together and grow into a huge lump. Note that Tmax varies depending on the chemical composition and fineness of the raw materials. Therefore, Tmax is the upper limit temperature that can be operated, and Tmax−40℃ is
Indicates that the firing temperature is 40°C lower than Tmax.

[Table] Due to the instability of the burner flame in rotary kiln firing, stable operation is not possible unless there is a temperature range of ±20°C. Therefore, in this case, it is necessary to set the firing temperature to be about 20°C lower than Tmax. For example experiment number
When firing the raw materials 17 and 18 in a rotary kiln, the firing temperature should be set to about Tmax - 20°C. At this time, even if the flame temperature changes and increases by 20℃, a good clinker can be fired, but when the flame temperature decreases by 20℃, that is, Tmax−40
℃, unstable clinker with a large amount of free lime and bound water is produced. Therefore, rankinite is more than 50% and free lime is 0.1%.
Even with the raw material of experiment number 17, which yields clinker with less than 0.4% of bound water, the amount passing through the sieve has a fineness of 0.44mm.
At 74.0%, good clinker cannot be obtained in a rotary kiln. As is clear from Table 3, the particle size of the blended raw materials
If the material that passes through the 0.044 mm sieve is crushed to 80% or more, the clinker will not fuse at relatively low temperatures, the amount of free lime remaining will be very small, and the content of hydraulic minerals will be very low. Synthetic raw material clinker can be produced. Experimental Example 3 Using the same raw materials as in Experimental Example 1, mixed raw materials with different CaO/SiO ₂ weight ratios and Al ₂ O ₃ % by weight were prepared as shown in Table 4, and this mixture was pulverized to obtain a pulverized product. The amount passing through the 0.044 mm sieve was adjusted to 80 to 81% of the blended raw materials, and the pellets were kneaded with water to make pellets. After drying this pellet at 110℃ for 24 hours,
Each sample was fired in an experimental electric furnace for 20 minutes at the temperatures shown in the table. Free lime, lanquinite, and bound water in the obtained calcined product were determined, and the results shown in Table 4 were obtained. Note that Al ₂ O ₃ % by weight is based on the strength reduction standard of the blended raw material, and the horizontal axis shows the CaO/SiO ₂ weight ratio and the vertical axis shows Al ₂ O ₃ % by weight.
Record the results in Table 4, and attach a document showing the range in which clinker with a rankinite content of 50% by weight or more, free lime of less than 0.1% by weight, and bound water of less than 0.4% by weight can be obtained. This is the area surrounded by ABCD in the drawing.

[Table] The present invention is based on these findings, and in producing a synthetic raw material containing rankinite as a main constituent mineral by firing a mixture of a calcareous raw material and a silicic acid raw material in a rotary kiln, the calcareous raw material and the silicic acid raw material are used. An alumina raw material is further added to the mixture with a silicic acid raw material, and the CaO/SiO ₂ (weight ratio) in the combined mixture is
The ratio with Al ₂ O ₃ is based on the ignition loss standard as shown in the attached drawing.
The combined raw material mixture is mixed so as to be in the range surrounded by ABCD, and is pulverized so that at least 80% of the particle size of the combined raw material mixture passes through a 0.044 mm sieve, and then sent to a rotary kiln and fired. This is a method for producing a synthetic raw material containing rankinite as a main constituent mineral. In the present invention, the calcareous raw materials include limestone,
Quicklime, slaked lime, etc. are used, silicic acid raw materials include silica stone, silica sand, by-product silica, clay, etc., and alumina raw materials include clay, Bayer process alumina, etc. In the present invention, the alumina raw material acts as a mineralizing agent in the reaction between the calcareous raw material and the silicic acid raw material, and iron oxide, fluorine compounds, etc. can also be used. In this case, if the amount of Fe ₂ O ₃ in the raw material exceeds 0.5% by weight, the clinker obtained will turn brown, which is not preferable. The form of the combined raw material used in the present invention is at least 80%
Particles having a particle size of 0.044 sieve or less may be fed into the rotary kiln as they are, or pellets or compression-molded particles may be fed into the rotary kiln. According to the present invention, a synthetic raw material with a high rankinite content can be produced by adding a specific mineralizer to a mixture of calcareous raw material powder and silicic raw material powder and firing it in a rotary kiln.
Its industrial value is great. Example 1 The same raw materials used in Experimental Example 1 (CaO/
SiO ₂ =1.05 and 1.2) were mixed and pulverized to prepare two types of mixed raw materials. The proportion of the blended raw materials that passed through the 0.044 mm sieve was 80.5%. Half of this mixed raw material was granulated using a pan pelletizer, and after granulation, it was dried. The pellets thus produced and the blended raw material powder were put into a small rotary kiln (diameter 0.5 m length 10 m) and fired at the temperature listed in Table 5 (raw material passing time was approximately
1.5 hours) Made clinker. The obtained clinker was analyzed and the results shown in Table 5 were obtained.

[Table] The firing temperature of the rotary kiln in the table is 20°C or 40°C lower than the firing temperature Tmax of the electric furnace. Rotary kiln firing temperature
Even at temperatures 20°C or 40°C lower than Tmax, the kiln operation was stable regardless of the form of the raw material, and clinker with favorable properties was obtained. Example 2 Quicklime, by-product amorphous silica, and Bayer process alumina listed in Table 6 were mixed and ground.
A blended raw material with 92% passing through a 0.044 mm sieve was prepared and then pressed to produce a molded product with a thickness of 10 to 15 mm. This molded product was fired in the same small rotary kiln as used in Example 1 at the temperatures listed in Table 7 to produce clinker. The obtained clinker was analyzed and the results shown in Table 7 were obtained.

【table】

[Table] The firing temperature of the rotary kiln was 1310℃, that is, the firing temperature Tmax of the electric furnace was 1330℃, but good quality clinker was obtained at a temperature 20℃ lower than that. 60 higher than Tmax due to the use of by-product amorphous silica as a raw material.
Even at a low temperature of 1270°C, the quality of clinker was not significantly affected and high quality clinker was obtained.

[Brief explanation of the drawing]

The drawing shows the C/S ratio (weight) and Al ₂ O ₃ in the blended raw material that yields clinker with a lanquinite content of 50% by weight, free lime of less than 0.1% by weight, and bound water of less than 0.4% by weight. % and the range is shown in ABCD.

Claims (1)

[Claims] 1. When producing a synthetic raw material containing rankinite as a main constituent mineral by firing a mixture of calcareous raw materials and silicic raw materials in a rotary kiln, an alumina raw material is further added to the mixture of calcareous raw materials and silicic raw materials. In addition, CaO/
Mix so that the ratio of SiO ₂ (weight ratio) and Al ₂ O ₃ falls within the range surrounded by ABCD in the attached drawing based on ignited raw materials, and the particle size of the combined raw material mixture is
A method for producing a synthetic raw material containing rankinite as a main constituent mineral, which comprises pulverizing the material so that at least 80% of the material passes through a 0.044 mm sieve and sending the material to a rotary kiln for firing.