JP5867734B2 - Method for producing β-2CaO · SiO 2 - Google Patents

Description

The present invention mainly relates to a method for producing β-2CaO · SiO _{2 that} can be appropriately used as a cement admixture.

As the crystal form of 2CaO.SiO ₂ (dicalcium silicate), α-type, β-type, γ-type and the like are known. Of these, β-type and γ-type are stable at room temperature. The β type is known as one of the ingredients of Portland cement, and it is weak but hydraulic. On the other hand, although the γ type does not have hydraulic properties, it has high carbonation activity and has recently been found to be useful as a cement admixture (see Patent Document 1).

In the pure 2CaO—SiO ₂ system, β-type 2CaO · SiO ₂ is not generated, but becomes γ-type. As factors affecting the crystal form of 2CaO.SiO ₂ , (1) the influence of the third component, (2) the influence of the cooling conditions, (3) the oxidation-reduction atmosphere, and the like are known.

As an influence of the third component, it is known that β-2CaO · SiO ₂ is generated when a certain amount or more of boron, phosphorus, barium, strontium, iron, aluminum, molybdenum, or the like is mixed (Non-patent Document 1). Non-Patent Document 2 and Non-Patent Document 3).

WO03 / 016234 pamphlet

Schwiete et al. , Zem. -Kalk-Gips, Vol. 21, no. 9,359,1968 Jun Shibata et al., Ceramic Association Magazine, Vol. 92, no. 2,71,1984 Niesel et al. Tonind-Ztg. , Vol. 93, no. 6,197,1969

An object of the present invention is to provide a method for producing β-2CaO · SiO _{2 which} has high whiteness, does not contain harmful substances, and does not inhibit the setting and hardening of cement.

As a result of various investigations, the present inventors have selected a specific raw material, granulated one having a specific particle size, and fired with a rotary kiln using a specific brick or specific mortar as a firing zone, It was found that β-2CaO · SiO ₂ was easily generated.
That is, the present invention is mainly composed of CaO and SiO ₂ , the CaO / SiO ₂ molar ratio is 1.8 to 2.2, and after heating at 1000 ° C., the total of Al ₂ O ₃ and Fe ₂ O ₃ A raw material having a content of less than 5% by mass and a total content of boron, phosphorus, barium, strontium, and molybdenum of less than 0.5% by mass in terms of oxide is selected. 90% by mass or more, that is, a granulated raw material having a 150 μm sieve under 90% by mass, and the granulated raw material is 45 to 80% by mass of Al ₂ O _{3 and 20} to 55% of SiO ₂ in the firing zone. weight percent silica - alumina bricks, _Al 2 _{O 3} is 25 to 80 wt%, SiO ₂ of 20 to 75 wt% silica - alumina mortar, MgO is 85 mass% or more of magnesia bricks, and MgO is 85 mass At rotary kiln using at least one or more selected from the group consisting of more than magnesia mortar, a β-2CaO · SiO ₂ of production method and firing at burn point temperature 1350-1600 ° C..
In the present invention, CaO and _SiO 2 in the raw material are preferably 1.9 to 2.1 at CaO / SiO ₂ molar ratio.
Further, raw material after heating 1000 ° C. is to contain 2 wt% less _Fe 2 _{O 3} is preferred.
Furthermore, the particle size of the raw material is preferably 90% by mass or more at a 100 μm passage rate.
The raw material of the present invention is preferably granulated using 10 to 30% by mass of water in a water / raw material ratio.
Moreover, the baking temperature at the time of baking has preferable 1400-1500 degreeC.
Furthermore, the mortar on the brick surface of the firing zone of the rotary kiln is preferably 5 to 10 mm thick.
Β-2CaO · SiO ₂ obtained by the production method of the present invention is suitably used as a cement admixture.

According to β-2CaO · SiO ₂ of the manufacturing method of the present invention, high whiteness, toxic substances not contain, continuously manufactured easily β-2CaO · SiO ₂ nor inhibit also condensation curing of the cement It becomes possible to do.

  In the present invention, “parts” and “%” are shown on a mass basis unless otherwise specified.

Β-2CaO · SiO ₂ referred to in the present invention is a kind of so-called dicalcium silicate (2CaO · SiO ₂ ) among compounds mainly composed of CaO and SiO ₂ . There are α-type, α-prime type, β-type, and γ-type crystal forms of dicalcium silicate, and the present invention relates to β-type dicalcium silicate.

In the present invention, a CaO raw material and a SiO ₂ raw material are used as main components. The main component preferably means that the total content of CaO and SiO ₂ in the raw material is preferably 80% or more, more preferably 90% or more, and the content of other components is as low as possible. .
As the CaO raw material, calcium carbonate, calcium hydroxide, calcium oxide, or the like can be used.
The SiO ₂ raw material, can be selected quartzite powder, clay, silica fume, fly ash, amorphous silica, etc., and materials of siliceous by-produced from each industry.
However, in the present invention, it is necessary to limit the presence of impurities. Specifically, the total of Al ₂ O ₃ and Fe ₂ O ₃ mixed from the CaO raw material and the SiO ₂ raw material needs to be less than 5% in the raw material after heating at 1000 ° C. The total of Al ₂ O ₃ and Fe ₂ O ₃ is more preferably less than 4%, and most preferably less than 3%.
In particular, the content of Fe ₂ O ₃ is preferably less than 2%, more preferably less than 1.5%, and most preferably less than 1% in the raw material after heating at 1000 ° C. .
Further, as other components, the total content of boron, phosphorus, barium, strontium, and molybdenum is preferably less than 0.5% in terms of oxide, and more preferably 0.3% or less. If it is not within the above range, it may be undesirable from the viewpoint of whiteness, inclusion of harmful substances, and inhibition of cement hardening.

The mixing ratio of the CaO raw material and the SiO ₂ raw material needs to be adjusted so that the CaO / SiO ₂ molar ratio in the raw material is 1.8 to 2.2. When the CaO / SiO ₂ molar ratio of the raw material is less than 1.8, α-type wollastonite is produced as a by-product, and the content of β-2CaO · SiO _{2 in} the product becomes low. If the CaO / SiO ₂ molar ratio of the raw material exceeds 2.2, 3CaO · SiO ₂ and free lime are by-produced, and the content of β-2CaO · SiO _{2 in} the product is also lowered. The raw material CaO / SiO ₂ molar ratio is preferably 1.8 to 2.2, and more preferably 1.9 to 2.1.

The particle size of the CaO raw material and the SiO ₂ raw material needs to be adjusted so that the 150 μm passage rate is 90% or more, that is, the 150 μm sieve is 90% or more, and the 100 μm passage rate is 90% or more, that is, 100 μm. It is more preferable to prepare so that the sieve bottom is 90% or more. If the particle size of the raw material is not fine within the above range, the purity of β-2CaO · SiO ₂ is deteriorated. Specifically, free lime and insoluble residue tend to increase.

In the present invention, it is preferable to granulate the raw material obtained by compounding in order to facilitate the production of β-2CaO · SiO _2. Granulation is an operation of forming the prepared raw material into a dumpling shape. The granulation is performed so that the particle size is preferably 1 to 50 mm, more preferably 10 to 30 mm.
Examples of the granulation method include a method of granulating a raw material and water into a disc-shaped rotary drum, a method of using a so-called pelletizer in which the raw material is placed in a mold and press-molded.
The amount of water used for granulation is preferably (0.1 to 0.3) / 1, more preferably (0.15 to 0.25) / 1 in terms of the mass ratio of water / raw material. If the amount of water used is less than 10%, the granulated raw material tends to collapse, and the firing reaction may not sufficiently proceed during firing in the rotary kiln. Moreover, when the usage-amount of water exceeds 30%, the granulated raw material will become watery, and after all, it will become easy to collapse | crumble and a baking reaction may not fully advance at the time of baking with a rotary kiln. Since the raw material contains a large amount of water, a large amount of firing energy is required to evaporate the raw material, which is uneconomical and undesirably increases the environmental load.

In the present invention, the granulated raw material is fired in a rotary kiln. The temperature needs to be fired at a baking temperature of 1350 to 1600 ° C, preferably 1375 to 1550 ° C, and more preferably 1400 to 1500 ° C. When the burning point temperature is lower than 1350 ° C., the purity of β-2CaO · SiO ₂ is deteriorated. Specifically, free lime and insoluble residue tend to increase. On the other hand, when the baking temperature exceeds 1600 ° C., the coating may melt and the coating will adhere to the kiln, making it difficult to operate, or mixing of β-2CaO · SiO ₂ may be significant. In addition, the firing energy is large and it is uneconomical. In addition, the burning point temperature said by this invention means the highest temperature in a kiln. Usually, the highest temperature in the kiln is near the front of the flame (flame shape) extending from the burner.

The material of bricks and mortar used for the rotary kiln firing zone is important. In the present invention, at least one brick or mortar selected from the group consisting of the following (1) to (4) is used.
(1) Among the high-alumina refractory bricks defined in JIS R 2305, the content of Al ₂ O ₃ is 45 to 80%, preferably 55 to 70%, the content of SiO ₂ is 20 to 55%, Preferably 30-45% silica-alumina brick.
(2) Among the magnesia bricks defined in JIS R 2302, magnesia bricks having a MgO content of 85% or more, preferably 90% or more.
When bricks other than the above are used, the production rate of β-2CaO · SiO ₂ may be low, or the brick may melt and react with the raw material to generate coating. The shape and thickness of the brick are not particularly limited, and it is desirable to select an appropriate size according to the rotary kiln diameter.
(3) Magnesia refractory mortar with a MgO content of 85% or more, preferably 90% or more.
(4) Among the clay refractory mortar and the high alumina refractory mortar specified in JIS R 2501, the content of Al ₂ O ₃ is 25 to 80%, preferably 35 to 70%, and the content of SiO ₂ is 20-75% silica-alumina mortar, preferably 30-65%.
In the present invention, when the mortar is used for the firing zone, it is preferable that these mortars are applied to the surface of the brick of the firing zone of the rotary kiln.
Although the use conditions of the mortar to apply | coat are not specifically limited, Usually, the thickness of a mortar is 5-10 mm, Preferably it is 6-9 mm. The amount of water used for coating varies depending on the type of mortar, but is preferably 15 to 35% with respect to the mortar component. Among these, the amount of water used for coating is preferably 30 to 35% for silica-alumina mortar, and preferably 15 to 20% for magnesia mortar. Outside the range, the content of β-2CaO · SiO ₂ may be low, or the brick may melt and react with the raw material to generate a coating. Moreover, it is preferable that both bricks and mortar are for a cement rotary kiln and are chromium-free.

  In the present invention, a cooling operation is performed after firing, but the cooling conditions are not particularly limited, and a special rapid cooling operation may be omitted. Specifically, it may be a method according to the general cooling conditions of Portland cement clinker, and after firing with a rotary kiln, it may be cooled through a cooler or the like in an atmospheric environment.

  The heat treatment method is not particularly limited, and a rotary kiln, an electric furnace, a tunnel furnace, a shaft kiln, a fluidized bed incinerator, or the like can be used.

EXAMPLES Next, although an Example and a comparative example demonstrate this invention more concretely, this invention should not be limited and limited to the following Examples.
"Experiment 1"
The following CaO raw material, SiO ₂ raw material, Al ₂ O ₃ component, and Fe ₂ O ₃ component are blended using a vibration pot mill (manufactured by Chuo Kako Co., Ltd.), and the CaO / SiO ₂ molar ratio as shown in Table 1 Of 2.0, and various raw materials having different Al ₂ O ₃ content after heating at 1000 ° C. and Fe ₂ O ₃ content were prepared. These raw materials are granulated with a granulator (apparatus; small bread granulator, manufactured by Mitsui Industry Co., Ltd.) so that the particle size is 10 to 30 mm under the condition that the mass ratio of water / raw material is 0.2 / 1. Then, firing was performed at 1450 ° C. using a rotary kiln in which the material of the inner surface of the firing zone was changed as shown in Table 1. Samples of the resulting product are evaluated and the results are shown in Table 1.

<Rotary kiln>
The rotary kiln used in the experimental example of the present invention has a cylindrical shape with an inner diameter of 1 m and a length of 20 m, and the refractory on the inner surface of the rotary kiln firing zone is brick (thickness 120 mm) or mortar (thickness) on the brick surface. 7 mm).
<Material of firing zone (material of refractory on the inner surface of firing zone>
Firing zone material (1): Silica-alumina brick (commercially available) having an Al ₂ O ₃ content of 60% and an SiO ₂ content of 40%.
Firing zone material (2): Magnesia brick with 91% MgO content (commercially available).
Firing zone material (3): Magnesia refractory mortar (manufactured by Yotai Co., trade name Yotai Heatset M, maximum particle size 0.6 mm) on the inner surface of the brick of (1) above, with a water / mortar mass ratio of 0 .17, applied with a thickness of 7 mm.
Firing zone material (4): Silica-alumina refractory mortar with Al ₂ O ₃ content of 60% and SiO ₂ content of 40% on the inner surface of the brick of (1) above, with a water / mortar mass ratio of 0 .33 and applied with a thickness of 7 mm.

<Materials used>
CaO raw material: Limestone fine powder. CaO is 55.4%, MgO is 0.37%, Al ₂ O ₃ is 0.05%, Fe ₂ O ₃ is 0.02%, and SiO ₂ is 0.10%. C) was 43.57%, and no carbon content was detected. 150 μm passage rate; 97.0%, 100 μm passage rate; 91.9%.
SiO ₂ raw material: silica fine powder. CaO 0.02%, MgO 0.04%, Al ₂ O ₃ 2.71%, Fe ₂ O ₃ 0.27%, SiO ₂ 95.83%, and TiO ₂ 0.23% No carbon content is detected. The ignition loss (1000 ° C.) is 0.51%, 150 μm pass rate; 95.1%, 100 μm pass rate; 90.3%.
Al ₂ O ₃ component: industrial alumina, purity 99% or more.
Fe ₂ O ₃ component: Industrial ferric oxide, purity 99% or more.
Water: tap water.

<Measurement method>
Various characteristics of the product obtained after firing were evaluated as follows.
Identification of compound: The compound was identified by powder X-ray diffractometry (apparatus; powder X-ray diffractometer (Multiflex), manufactured by Rigaku Corporation).
Quantification of chemical components: Al ₂ O ₃ components and Fe ₂ O ₃ components were analyzed and quantified according to JIS R 5202.
Observation of color: The degree of white was visually determined. Observation was performed in a room with an illuminance of 200 lux, and the degree of whiteness of the powder prepared to a brain specific surface area of 3000 ± 100 cm ² / g was observed. In the case of white, ◯, in the case of yellow, Δ, and in the case of brown, X.
Setting time and compressive strength: 10 parts of β-2CaO · SiO ₂ and γ-2CaO · SiO ₂ were added to 90 parts of ordinary Portland cement to obtain a cement composition. Using this cement composition, a mortar was prepared according to JIS R 5201, and the setting completion time was measured. The compressive strength at 1 day of age was also measured.

"Experimental example 2"
The raw material CaO / SiO ₂ molar ratio is fixed at 2.0, the Fe ₂ O ₃ content is fixed at 0.3%, and the Al ₂ O ₃ content is fixed at 1.4%. The procedure was the same as in Experimental Example 1 except that the above was changed. The results are shown in Table 2.

<Material of firing zone>
Firing zone material (5): Silica-alumina brick (commercially available) having an Al ₂ O ₃ content of 45% and an SiO ₂ content of 55%.
Firing zone material (6): Silica-alumina brick (commercially available) having an Al ₂ O ₃ content of 80% and an SiO ₂ content of 20%.
Firing zone material (7): Magnesia brick with 85% MgO content (commercially available).
Firing zone material (8): Magnesia brick with 95% MgO content (commercially available).
Firing zone material (9): High-purity alumina brick (commercially available) having an Al ₂ O ₃ content of 95% and an SiO ₂ content of 5%.
Firing zone material (10): Spinel brick (commercially available).
Firing zone material (11): Magnesia-spinel refractory mortar (manufactured by Yotai Co., Ltd., trade name Yotai Heatset M, maximum particle size 0.6 mm) on the inner surface of the brick of (1) above, water / mortar mass ratio Is 0.17 and applied with a thickness of 7 mm.
Firing zone material (12): 90% or more of high alumina mortar Al ₂ O ₃ (trade name Yotai Heatset M, maximum particle size 0.5 mm) on the inner surface of the brick of (1) above, Applied with a water / mortar mass ratio of 0.17 and a thickness of 7 mm.
Refractory mortar of fired zone (13): Silica-alumina mortar having an Al ₂ O ₃ content of 25% and an SiO ₂ content of 75% on the inner surface of the brick of (1) above, with a water / mortar mass ratio of 0 .33 and applied with a thickness of 7 mm.
Refractory mortar (14) of the firing zone: Silica-alumina mortar having an Al ₂ O ₃ content of 45% and an SiO ₂ content of 55% on the inner surface of the brick of (1) above, and a water / mortar mass ratio of 0 .33 and applied with a thickness of 7 mm.
Refractory mortar (15) of fired zone: Silica-alumina mortar with an Al ₂ O ₃ content of 80% and an SiO ₂ content of 20% on the inner surface of the brick of (1) above, with a water / mortar mass ratio of 0 .33 and applied with a thickness of 7 mm.
Firing refractory mortar (16): High purity alumina refractory mortar with an Al ₂ O ₃ content of 90% and an SiO ₂ content of 10% on the inner surface of the brick of (1) above, with a water / mortar mass ratio of Coated with a thickness of 7 mm at 0.33.
Firing refractory mortar (17): A high-purity alumina refractory mortar with an Al ₂ O ₃ content of 96% and an SiO ₂ content of 4% on the inner surface of the brick of (1) above, with a water / mortar mass ratio of Coated with a thickness of 7 mm at 0.33.

In the display of the material in Table 2, for example, “Al45” means the material of the fired zone with an Al ₂ O ₃ content of 45%, and “Mg85” means the fired zone with an MgO content of 85%. Means the material. The other examples are similar examples.

"Experiment 3"
Comparison with the prior art was performed. As shown in Table 3, Fe ₂ O ₃ , Al ₂ O ₃ , BO ₃ , BaO, P ₂ O ₅ , SrO, or MoO ₃ conventionally known as elements that stabilize β-2CaO.SiO ₂ The experiment was performed in the same manner as in Experimental Example 1, except that the proportions shown in Table 3 were blended. The results are shown in Table 3.

"Experimental example 4"
Except that the CaO / SiO ₂ molar ratio of the CaO raw material and the SiO ₂ raw material was changed as shown in Table 4, it was carried out in the same manner as in Experimental Example 1. The results are shown in Table 4.

“Experimental Example 5”
The same procedure as in Experimental Example 1 was performed except that the heat treatment temperature was changed as shown in Table 5. The results are shown in Table 5.

"Experimental example 6"
The experiment was performed in the same manner as in Experimental Example 1 except that the water ratio during granulation was changed as shown in Table 6. The results are shown in Table 6.

Β-2CaO · SiO ₂ of the manufacturing method of the present invention, high whiteness, condensation cure of the cement is also possible to produce β-2CaO · SiO ₂ without inhibiting, extensively in such cements art Available.
Japanese Patent Application No. 2011-021614 filed on February 3, 2011, Japanese Patent Application No. 2011-021658 filed on February 3, 2011, Japanese Patent Application filed on June 8, 2011 The entire contents of Japanese Patent Application No. 2011-128708 and Japanese Patent Application No. 2011-172188 filed on August 5, 2011, the claims, and the abstract are hereby incorporated herein by reference. It is incorporated as a disclosure.

Claims (11)

CaO and SiO ₂ as main components, CaO / SiO ₂ molar ratio is 1.8 to 2.2, and after heating at 1000 ° C., the total content of Al ₂ O ₃ and Fe ₂ O ₃ is 5 mass%. A raw material having a total content of boron, phosphorus, barium, strontium, and molybdenum of less than 0.5% by mass in terms of oxide,
Granulate the raw material with a particle size of 90% by mass at 150 μm passage rate,
The granulated material, _Al 2 _{O 3} is 45 to 80 wt%, SiO ₂ 20 to 55% by weight of silica - alumina bricks, _Al 2 _{O 3} is 25 to 80 wt%, SiO ₂ 20 to 75 mass % Of silica-alumina mortar, magnesia brick with MgO of 85% by mass or more, and at least one brick or mortar selected from the group consisting of magnesia mortar with MgO of 85% by mass or more were used for the inner surface of the firing zone. At the rotary kiln,
A method for producing β-2CaO · SiO ₂ , characterized by firing at a baking temperature of 1350 to 1600 ° C. It said rotary kiln is a brick firing zone _Al 2 _{O 3} is 45 to 80 wt%, SiO ₂ 20 to 55 wt% of silica - The method according to claim 1 for use alumina bricks.   The manufacturing method according to claim 1, wherein the rotary kiln applies magnesia mortar containing 85 mass% or more of MgO to the surface of the brick in the fired zone.   The said rotary kiln uses the magnesia brick whose MgO is 85 mass% or more for the brick of a baking zone, The manufacturing method of Claim 1. It said rotary kiln is, the surface of the brick firing zone _Al 2 _{O 3} is 25 to 80 wt%, SiO ₂ 20 to 75 wt% of silica - The method according to claim 1 for coating the alumina mortar. The manufacturing method according to claim 1, wherein the molar ratio of the raw material CaO / SiO ₂ is 1.9 to 2.1. 1000 ° C. material after heating, the production method according to claim 1, containing _Fe 2 _{O 3} less than 2% by weight.   The manufacturing method in any one of Claims 1-7 in which a raw material has a particle size of 90 mass% or more by 100 micrometer passage rate.   The production method according to any one of claims 1 to 8, wherein granulation is performed using water having a water / raw material mass ratio of (0.1 to 0.3) / 1.   The manufacturing method according to any one of claims 1 to 9, wherein the baking is performed at a baking temperature of 1400 to 1500C.   The manufacturing method according to claim 1, wherein the mortar on the brick surface of the rotary kiln firing zone has a thickness of 5 to 10 mm.