JP5852964B2 - 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 advantageously used as a cement material.

2CaO · SiO ₂ has known crystal forms such as α-type, β-type, and γ-type. 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 a high carbonation activity and has recently been found to be useful as a cement admixture. As described above, 2CaO · SiO ₂ has been found to be used by utilizing the characteristics of both β-type and γ-type, so if a method for controlling the crystal form of 2CaO · SiO ₂ can be established, it will be industrially applied. It is beneficial.

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).

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

The present invention provides a method for producing β-2CaO · SiO ₂ that has high whiteness, does not contain harmful substances, does not inhibit the setting and hardening of cement, can reduce energy costs during firing, and has a high yield. To do.

As a result of various studies, the present inventors have found that the slaked lime produced as a by-product after generating acetylene from calcium carbide contains little of the above-mentioned third component, and is conventionally known, β-2CaO · SiO. _In spite of the content required to produce ₂ and the absence of the third component, β-2CaO · SiO ₂ can be easily produced by heat-treating the raw material in which the siliceous material is blended. I found it. Moreover, β-2CaO · SiO ₂ obtained by this method has a high whiteness, does not contain harmful substances, does not inhibit the setting and hardening of cement, can reduce energy costs during firing, and has a high yield. The present inventors have found a production method of -2CaO.SiO ₂ and completed the present invention. It was found useful in industry.

That is, the present invention has the following gist.
(1) Calcium reacting a carbide and water by-product after generating acetylene, 150 [mu] m sieve to have a particle size which passes through more than 90 wt%, and 71-74 wt% of CaO, loss on ignition (LOI 23 to 25% by mass, SiO ₂ to 0.5 to 1.5% by mass, Fe ₂ O ₃ to 0.2 to 0.35% by mass, and Al ₂ O ₃ to 0.3 to 0.7% by mass. Slaked lime containing less than 0.2% by weight of MgO, less than 0.1% by weight of Na ₂ O and K ₂ O, and 1.0 to 1.5% by weight of SO ₃ ;
A siliceous substance comprising a fine particle of silica, silica fume, diatomaceous earth, or fused silica and having a particle size passing through a 150 μm sieve by 90% by mass or more ,
A raw material blended so that the molar ratio of CaO / SiO ₂ is 1.8 to 2.2 is granulated using water at a water / raw material mass ratio of 0.1 / 1 to 30.3 / 1. And
A method for producing β-2CaO · SiO ₂ , characterized in that the resulting granulated material is fired at a baking temperature of 1300 to 1600 ° C. in a rotary kiln .
(2) The production method according to (1), wherein the slaked lime and / or siliceous substance has a particle size that passes through a 100 μm sieve by 90% by mass or more.
(3) The manufacturing method as described in said (1) or (2) which granulates the mix | blended raw material in the particle size which passes 90 mass% or more of 100 micrometers sieve, and feeds the obtained granulated material to a rotary kiln.
(4) The manufacturing method according to any one of (1) to (3), wherein the yield of the heat treatment product is 75% or more based on the raw material.
(5) The process according to any one of the above β-2CaO · SiO ₂ purity in the fired product is 90% or more (1) to (4).

According to the method for producing β-2CaO · SiO ₂ of the present invention, the obtained β-2CaO · SiO ₂ has high whiteness, does not inhibit the setting and hardening of cement, and can reduce the energy cost at the time of firing. , There is an effect such as high yield.

Hereinafter, the present invention will be described in detail.
In the present invention, “parts” and “%” are indicated by “mass standard” unless otherwise specified.

Β-2CaO · SiO ₂ of the present invention is a kind of dicalcium silicate (2CaO · SiO ₂ ) among compounds mainly composed of CaO and SiO ₂ . In dicalcium silicate (2CaO · SiO ₂ ), α-type, α-prime type, β-type, and γ-type crystal forms exist. The present invention relates to β-type dicalcium silicate.

In the present invention, slaked lime (calcium hydroxide) by-produced after the reaction of calcium carbide with water to generate acetylene is used as the CaO raw material. When this is used, β-type 2CaO · SiO ₂ is obtained. Even if calcium hydroxide as a reagent or slaked lime available as other industrial raw materials is used, β-2CaO · SiO ₂ of the present invention cannot be obtained.
The slaked lime used for the CaO raw material in the present invention is a by-product after generating acetylene by reacting calcium carbide and water according to the following reaction formula.
CaC ₂ + 2H ₂ O → C ₂ H ₂ + Ca (OH) ₂

In the present invention, CaO is about 71 to 74%, preferably 72 to 73%, and loss on ignition (LOI) is 23 to 25 as a by-product component after generating acetylene by reacting calcium carbide and water. %, Preferably 23.5 to 24.5%, SiO ₂ is about 0.5 to 1.5%, preferably 0.75 to 1.25%, and Fe ₂ O ₃ is 0.2 to 0.35. %, Preferably 0.25 to 0.3%, Al ₂ O ₃ is about 0.3 to 0.7%, preferably 0.4 to 0.6%, MgO is less than 0.2%, preferably 0 Less than 0.1%, Na ₂ O and K ₂ O are both less than 0.1%, preferably less than 0.05%, and SO ₃ is about 1.0 to 1.5%, preferably 1.2 to 1. About 3% is included.

In general, the content of the third component Fe ₂ O ₃ and Al ₂ O ₃ that stabilizes 2CaO.SiO ₂ as β-type is in the range of 1.05% or less in total even if estimated to be large. The amount does not affect the production of β-2CaO.SiO ₂ (β-C ₂ S).
However, in order to stabilize β-2CaO · SiO ₂ with Fe ₂ O ₃ or Al ₂ O ₃ , it is usually said that the total amount of these contents is preferably 5% or more.
Some commercially available slaked lime has a chemical composition similar to that of slaked lime produced as a by-product after generating acetylene by reacting calcium carbide and water used in the present invention, but the effect of the present invention cannot be obtained. The reason is not clear, but it is assumed that the sulfur component has some influence. As a feature of the slaked lime produced as a by-product after generating acetylene by reacting the calcium carbide and water of the present invention, the sulfur content is about 1.0 to 1.5% in terms of SO ₃ , preferably 1.2 to 1 .3% included.

In the present invention, a siliceous substance (SiO ₂ raw material) is used in addition to slaked lime (CaO raw material) by-produced after the reaction of calcium carbide with water to generate acetylene.

Although the siliceous substance (SiO ₂ raw material) is not particularly limited, silica fine powder, silica fume, diatomaceous earth, fused silica dust, and the like can be used.
For the purpose of obtaining β-2CaO · SiO ₂ , the presence of impurities in the siliceous material (SiO ₂ raw material) may be preferable.

However, in the present invention, even if a high-purity siliceous substance (SiO ₂ raw material) is used, β-2CaO ·· can be obtained by using slaked lime produced as a by-product after generating acetylene by reacting calcium carbide with water. it is possible to obtain SiO _2.

In the production method of β-2CaO · SiO ₂ of the present invention, slaked lime (CaO raw material) by-produced after reacting calcium carbide and water to generate acetylene, and a siliceous material (SiO ₂ raw material) were blended. The raw material is heat-treated.

  The heat treatment method is not particularly limited. A rotary kiln, an electric furnace, a tunnel furnace, a shaft kiln, a fluidized bed incinerator, etc. can be used. Among these, it is preferable to select a rotary kiln from the viewpoints of continuous operation, cost performance, and the like.

  The baking temperature during the heat treatment is preferably 1300 ° C to 1600 ° C, and more preferably 1400 ° C to 1500 ° C. If it is less than 1300 ° C., the efficiency may be deteriorated or it may be burnt. If it exceeds 1600 ° C., it will not only melt and become difficult to operate, but it may be easily coated and the yield may be reduced. . The burning point temperature referred to in the present invention means the maximum temperature in the kiln. Usually, the maximum temperature in the kiln is in the vicinity of 1 to 3 m in front of the flame (flame shape) extending from the burner.

In the method for producing β-2CaO · SiO ₂ of the present invention, the yield is 75% or more, preferably 80% or more. Here, the yield means the percentage of the heat-treated product obtained with respect to the fed raw material. A higher yield is preferable because it leads to a reduction in manufacturing cost. However, since the theoretical value is about 83%, this is the upper limit. In the method for producing β-2CaO · SiO ₂ of the present invention, a yield of 80% or more can be obtained almost stably.

In the present invention, it is preferable to adjust the CaO / SiO ₂ molar ratio of the raw material to 1.8 to 2.2, 1.9 to 2.2 is more preferable. When the CaO / SiO ₂ molar ratio of the raw material is less than 1.8, α-type wollastonite and lankinite are by-produced, 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. By adjusting the CaO / SiO ₂ molar ratio of the raw material to 1.8 to 2.2, the content of β-2CaO · SiO ₂ can be 90% or more, preferably 95% or more.

The particle sizes of the CaO raw material and the SiO ₂ raw material are preferably adjusted so as to pass 90% by mass or more through a 150 μm sieve, and more preferably adjusted so as to pass 90% by mass or more through a 100 μm sieve. If the particle size of the raw material is not fine within the above range, the purity of β-2CaO · SiO ₂ tends to deteriorate. Specifically, free lime and insoluble residue increase.

In the present invention, it is preferable to granulate the blended raw materials. When the raw material is granulated, the production reaction of β-2CaO · SiO ₂ is likely to proceed, energy costs can be reduced, and purity is increased.
The granulation is an operation of forming the blended raw material into a dumpling shape, and the granulation is performed so that the particle size (diameter) 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 / 1 to 0.3 / 1, more preferably 0.15 / 1 to 0.25 / 1, in terms of the mass ratio of water / raw material. If the amount of water used is less than 0.1, the granulated raw material tends to collapse, the raw material is collected and the yield becomes poor, or the firing reaction may not proceed sufficiently during firing in a rotary kiln. On the other hand, if the amount of water used exceeds 0.3, the granulated raw material becomes watery, and it tends to collapse, and the firing reaction may not sufficiently proceed during firing in the rotary kiln. In addition, 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 the environmental load increases, which is not preferable.

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

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"
Various CaO raw materials and SiO ₂ raw materials were blended so that the CaO / SiO ₂ molar ratio was 2.0. This blended raw material was granulated using a granulator (small bread type, manufactured by Sansho Industry Co., Ltd.). At this time, 20% of water was added to the powder. The granulated material was heat-treated using a rotary kiln. The heat treatment temperature was 1450 ° C. as the burning point temperature of the burner. The samples after firing were evaluated as follows. The evaluation results are also shown in Table 1.

<Materials used>
CaO raw material (1): slaked lime produced as a by-product after the reaction of calcium carbide and water to generate acetylene, CaO 73.1%, MgO 0.07%, Al ₂ O ₃ 0.55% Fe ₂ O ₃ is 0.28%, SiO ₂ is 0.95%, SO ₃ is 1.31%, Na ₂ O is 0.03%, K ₂ O is 0.02%, and ignition loss is 23.80%. The passing rate of the 150 μm sieve is 99.5%, and the passing rate of the 100 μm sieve is 96.9%.
CaO raw material (2): fine limestone powder, CaO 55.4%, MgO 0.37%, Al ₂ O ₃ 0.05%, Fe ₂ O ₃ 0.02%, SiO ₂ 0 .10%, and ignition loss is 43.57%. The passing rate of the 150 μm sieve is 97. %, The passage rate of the 100 μm sieve is 91.9%.
CaO raw material (3): commercially available slaked lime, CaO 74.10%, MgO 0.07%, Al ₂ O ₃ 0.36%, Fe ₂ O ₃ 0.22%, SiO ₂ 0 .90%, SO ₃ is 0.09%, Na ₂ O is 0.13%, K ₂ O is 0.12%, and the ignition loss is 24.00%. The passing rate of the 150 μm sieve is 99.5%, and the passing rate of the 100 μm sieve is 96.9%.
CaO raw material (4): Reagent calcium hydroxide with a purity of 99%.
SiO ₂ raw material: fine silica powder, CaO 0.02%, MgO 0.04%, Al ₂ O ₃ 2.71%, Fe ₂ O ₃ 0.27%, SiO ₂ 95. 83%, TiO ₂ is 0.23%, and ignition loss is 0.51%. The passing rate of the 150 μm sieve is 95.1%, and the passing rate of the 100 μm sieve is 90.3%.
Water: tap water

<Measurement method>
Identification of compound: Compound was identified by powder X-ray diffraction method (Multiflex, manufactured by Rigaku Corporation).
Quantification of chemical components: Al ₂ O ₃ components and Fe ₂ O ₃ components were quantitatively 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.
Firing energy: The total energy of the amount of heavy oil used and the amount of power used when limestone corresponding to the prior art is used as a CaO raw material is defined as 100 and expressed as a relative value.
Yield: The ratio of the mass of the fired product obtained when the mass of the raw material fed to the rotary kiln was taken as 100 was expressed as a percentage.
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"
Comparison with the prior art was performed. As shown in Table 2, Fe ₂ O ₃ , Al ₂ O ₃ , BO ₃ , BaO, P ₂ O ₅ , or SrO, which is conventionally known as an oxide of an element that stabilizes β-2CaO · SiO ₂ , Experiment No. The test was performed in the same manner as in Experimental Example 1 except that it was added to the raw material 1-2 in an external split. The results are shown in Table 2.
Here, “outside split” means that the ratio of the additive component is relative to the entire component to be added excluding the additive component.

"Experiment 3"
The experiment was performed in the same manner as in Experimental Example 1 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 3. The results are shown in Table 3.

"Experimental example 4"
The test was performed in the same manner as in Experimental Example 1 except that the burn point temperature of the burner as the heat treatment temperature was changed as shown in Table 4. The results are shown in Table 4.

“Experimental Example 5”
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 5. The results are shown in Table 5.

Β-2CaO · SiO ₂ of the manufacturing method of the present invention, high whiteness, it without inhibiting even condensation curing of the cement, energy costs during firing can also be reduced, the yield is also high β-2CaO · SiO ₂ It is a manufacturing method and can be widely used in the cement field.
The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2010-253174 filed on November 11, 2010 are incorporated herein as the disclosure of the specification of the present invention. Is.

Claims (5)

Calcium carbide and water are reacted to by-product after generating acetylene, 150 [mu] m sieve to have a particle size which passes through more than 90 wt%, and 71-74 wt% of CaO, loss on ignition and (LOI) 23 25 wt%, a SiO ₂ 0.5 to 1.5 wt%, from 0.2 to .35% by weight of _{Fe 2 O 3, Al 2 O} 3 0.3 to 0.7 wt%, the MgO Slaked lime containing less than 0.2% by mass, Na ₂ O, K ₂ O each less than 0.1% by mass, and SO ₃ in an amount of 1.0 to 1.5% by mass ;
A siliceous substance comprising a fine particle of silica, silica fume, diatomaceous earth, or fused silica and having a particle size passing through a 150 μm sieve by 90% by mass or more ,
A raw material blended so that the molar ratio of CaO / SiO ₂ is 1.8 to 2.2 is granulated using water at a water / raw material mass ratio of 0.1 / 1 to 30.3 / 1. And
A method for producing β-2CaO · SiO ₂ , characterized in that the resulting granulated material is fired at a baking temperature of 1300 to 1600 ° C. in a rotary kiln . The slaked lime and / or siliceous material, β-2CaO · SiO ₂ of the manufacturing method according to claim 1 having a particle size which passes through 100μm sieve of 90 mass% or more. The compounded material, 100 [mu] m sieve was granulated particle size which passes through more than 90 wt%, granulation product beta-2CaO · SiO ₂ of the manufacturing method according to claim 1 or 2 feeds the rotary kiln obtained. The method for producing β-2CaO · SiO _{2 according to} any one of claims 1 to 3, wherein the yield of the heat treatment product is 75% or more based on the raw material. The method for producing β-2CaO · SiO _{2 according to} any one of claims 1 to 4, wherein the purity of β-2CaO · SiO _{2 in} the fired product is 90% or more.