JP2014058431A - Method for preparing cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing a cement composition in which a large amount of coal gasification slag can be used and the color tone of which is equal to that of portland cement or the like and has a small time-dependent change.SOLUTION: The method for preparing the cement composition comprises: a clinker preparation step of firing a cement clinker containing 20-80% CS, 3-60% CS, 1-16% CA and 6-16% CAF as the cement mineral composition calculated by using Bogue equation to prepare a fired clinker; a slag heat treatment step of throwing 2-100 parts mass of a molten slag of the coal gasification slag having 1 mm or larger particle size in a 710-1,400°C zone of a clinker cooler on the basis of 100 parts mass of the fired clinker to mix the molten slag with the fired clinker so that the fired clinker is cooled and the molten slag is heated to obtain a mixture of the cooled clinker with the heat-treated slag; and a mixing/crushing step of adding gypsum to the obtained mixture and crushing the gypsum-added mixture.

Description

  The present invention relates to a method for producing a cement composition containing coal gasification molten slag by-produced in coal gasification combined power generation (hereinafter referred to as “coal gasification slag”).

Coal gasification combined power generation is a system that generates electricity by using a combustible gas such as CO or H ₂ produced by partially burning coal in a gasification furnace as a fuel and driving a gas turbine and a steam turbine. And from this system, coal gasification slag containing much iron is produced as a by-product in which the ash in the coal is melted and solidified together with the combustible gas.
Since the system has high thermal efficiency and can reduce CO ₂ emissions, it is expected as a means to supplement or substitute for nuclear power generation. Therefore, there is a concern about an increase in coal gasification slag accompanying the spread of the system.

Conventionally, utilization of coal gasification slag has been studied as fine aggregate for concrete (Non-Patent Document 1), artificial lightweight aggregate (Patent Document 1), pozzolan for cement mixture (Patent Document 2), and the like. .
When coal gasification slag is used as a cement mixed material, the color tone of the mixed cement changes according to the mixing amount. For example, as shown in Table 2 below, the whiteness (L value of Hunter color system, L value of 0 is completely black and 100 is completely white) is 70.0 in coal gasification slag. It is as high as (Reference Example 3) and is significantly different from 50.3 (Reference Example 1) of ordinary Portland cement. Therefore, the whiteness of the cement composition in which 67 parts by mass of coal gasification slag is mixed with 100 parts by mass of normal Portland cement is as high as 58.3 (Reference Example 2), which is greatly different from the original tone of cement. . Therefore, when the whiteness and mixing amount of coal gasification slag vary, the color tone of the obtained mixed cement is likely to vary. In addition, the surface of cement concrete containing a large amount of coal gasification slag containing a large amount of iron may change color tone due to the oxidation of iron, resulting in uneven color, which may impair the appearance of the concrete building.
Therefore, there is a demand for a technique that can effectively utilize coal gasification slag as a cement mixture without the above problems.

Masafumi Hojo, “Fundamental study on utilization of coal gasification molten slag as fine aggregate for concrete”, Annual report on concrete engineering, Vol. 28, no. 1, pp. 71-76 (2006)

JP 2002-60257 A JP-A-11-139860

  In view of this situation, the present invention provides a method for producing a cement composition that can use a large amount of coal gasification slag and that has a color tone equivalent to that of Portland cement or the like and that has a small color change over time. Objective.

Therefore, the present inventors have examined a method for producing a cement composition that meets the above-mentioned purpose,
(I) As shown in Reference Examples 3 and 4 in Table 2 below, the whiteness (L value is 49) of slag obtained by heat-treating coal gasification slag (L value is 70.0) at 1000 ° C. for 3 minutes. .7) is equivalent to the whiteness of Portland cement (L value is about 50 to 55), and based on this finding,
(Ii) In a specific temperature range of a clinker cooler (hereinafter referred to as “cooler”), when a coal gasification slag having a specific particle size is introduced into and mixed with a clinker having a specific cement mineral composition, the mixing is performed. In the process, heat exchange takes place between the clinker and the slag, and the clinker is cooled faster than if a cooler is used, and at the same time the slag is heated, the clinker with improved hydraulic properties and the slag with reduced whiteness. That a mixture of
(Ii) By simply adding gypsum to the mixture and pulverizing it, it is possible to easily produce a cement composition that is excellent in strength development, has a color tone equivalent to Portland cement and the like, and has little color change with time,
(Iii) According to this production method, it was found that coal gasification slag can be used in a large amount, and because the remaining heat in the cooler is used, the energy consumption is low, and the production cost can be reduced correspondingly, thereby completing the present invention. .

That is, this invention provides the manufacturing method of the cement composition which has the following structures. In addition, unless otherwise indicated,% is the mass%.
[1] A method for producing a cement composition including the following steps (A) to (C).
Cement mineral composition calculated using (A) Borg formula, 20-80% by _{C 3} S, 3 to 60% for _{C 2} S, 1 to 16% in the _{C 3} A, and at _C 4 AF 6 to 16 Clinker preparation step (B) prepared by calcining cement clinker that is 1%, 710 in the cooler at a ratio of 2 to 100 parts by mass of coal gasification slag having a particle size of 1 mm or more with respect to 100 parts by mass of the clinker. ˜1400 ° C. and mixed with clinker, and the clinker is cooled and at the same time the slag is heated to obtain a mixture of the clinker and the slag heat-treated product. (C) Gypsum is added to the mixture. Addition and grinding, mixing and grinding step [2] The amount of gypsum added in the step (C) is 0.5 to 4.0 mass in terms of SO ₃ with respect to 100 parts by mass of the mixture of the clinker and the slag heat-treated product. Part Method for producing a cement composition according to [1].

According to the method for producing a cement composition of the present invention, a large amount of coal gasification slag can be used, and a cement composition can be produced with less energy consumption.
The cement composition produced by the production method of the present invention is excellent in strength development, has the same color tone as Portland cement and the like, and has little color change with time.

It is a schematic diagram which shows an example of the manufacturing apparatus for enforcing the manufacturing method of the cement composition of this invention.

  As described above, the method for producing a cement composition of the present invention includes (A) a clinker preparation step, (B) a slag heat treatment step, and (C) a mixing and pulverizing step as essential steps. (D) The raw material preparation process is included. Hereinafter, the present invention will be described separately for each step.

(A) clinker preparation step the process, cement mineral composition calculated using the Borg type, 20-80% by _{C 3} S, 3 to 60% for _{C 2} S, 1 to 16% in the _{C 3} A, and This is a step of baking and preparing a cement clinker that is 6 to 16% in C ₄ AF. Examples of the clinker having a cement mineral composition within the above range include Portland cement clinker such as ordinary Portland cement clinker and early-strength Portland cement clinker, and eco-cement clinker.
The firing temperature in this step is preferably 1000 to 1500 ° C, more preferably 1200 to 1400 ° C. When the value is in the range of 1000 to 1500 ° C., cement minerals having high hydraulic properties tend to be generated. Moreover, the baking time in this process becomes like this. Preferably it is 30 to 120 minutes, More preferably, it is 40 to 60 minutes. If the time is less than 30 minutes, firing is not sufficient, and if it exceeds 120 minutes, it takes time and productivity is lowered.

In addition, when waste is used as part of the raw material in the production method of the present invention, heavy metals may be mixed in the clinker. When the content of heavy metal in the clinker exceeds a specified value, the content of heavy metal can be adjusted within the range of the specified value by using a chlorination volatilization method or a reduction firing method in the clinker preparation step.
Here, the chlorination volatilization method is a method in which heavy metals contained in the raw material for preparation are volatilized and removed in the form of chlorides having a low boiling point. Specifically, the method is a method in which a chlorine source such as calcium chloride is added to a raw material containing heavy metal, calcined using a calcining furnace such as a rotary kiln, and the generated heavy metal chloride is volatilized and removed. It is.
The reduction firing method is a method in which heavy metals contained in the raw material for preparation are reduced and volatilized and removed in the form of a metal having a low boiling point. Specifically, the method reduces the heavy metal by reducing the heavy metal by reducing the heavy metal containing raw material in a reducing atmosphere and / or adding a reducing agent and using a baking kiln such as a rotary kiln. This is a method of removing heavy metals by volatilization.

In addition, the content rate (composition) of the C ₃ S, C ₂ S, C ₃ A, and C ₄ AF is calculated using the following Borg formulas (1) to (4).
C ₃ S (%) = 4.07 × CaO (%) − 7.60 × SiO ₂ (%) − 6.72 × Al ₂ O ₃ (%) − 1.43 × Fe ₂ O ₃ (%) (1)
C ₂ S (%) = 2.87 × SiO ₂ (%) − 0.754 × C ₃ S (%) (2)
C ₃ A (%) = 2.65 × Al ₂ O ₃ (%) − 1.69 × Fe ₂ O ₃ (%) (3)
C ₄ AF (%) = 3.04 × Fe ₂ O ₃ (%) (4)
However, the chemical formula in the formula represents the content of the compound represented by the chemical formula in the preparation raw material or in the clinker.

(B) Slag heat treatment step In this step, 2 to 100 parts by mass of coal gasification slag having a particle size of 1 mm or more is introduced into an area of 710 to 1400 ° C in the cooler with respect to 100 parts by mass of the clinker. Mixing the clinker and cooling the clinker and simultaneously heating the slag to obtain a mixture of the clinker and a slag heat-treated product having changed whiteness.
In this step, since the clinker is cooled faster than simply cooling the clinker with a cooler, the hydraulic property of the clinker is improved. On the other hand, the iron content in the coal gasification slag is oxidized by the heat treatment, and the whiteness is lowered, and becomes equal to the whiteness of Portland cement or the like.

Moreover, the particle size of coal gasification slag is 1 mm or more. When the value is less than 1 mm, the slag and clinker are likely to react with each other, and the hydraulic property of the clinker may be reduced. The value is preferably 1 to 30 mm in view of strength development of the cement composition.
The temperature of the region where the slag is charged in the cooler is 710 to 1400 ° C. When the value is less than 710 ° C., the clinker hydraulic properties and the blackening of the slag may decrease. When the value exceeds 1400 ° C., the clinker and the slag easily react with each other, and the clinker hydraulic properties may decrease. In addition, this temperature becomes like this. Preferably it is 750-1350 degreeC, More preferably, it is 800-1300 degreeC.

  Moreover, the input amount (usage amount) of coal gasification slag is 2-100 mass parts with respect to 100 mass parts of said clinker. If the value is less than 2 parts by mass, the amount of slag used is small and it is difficult to rapidly cool the clinker, so the hydraulic effect of the clinker is reduced. Moreover, when this value exceeds 100 mass parts, there exists a tendency for the intensity | strength expression property of a cement composition to fall. The lower limit of the value is preferably 5 parts by mass, more preferably 10 parts by mass with respect to 100 parts by mass of the clinker, and the upper limit of the value is preferably 90 parts by mass, more preferably 80 parts by mass.

  In the production method of the present invention, the remarkable point is that, as shown in Example 1 and Example 2 in Table 2 below, the coal gasification slag charge ratio is 20 times in both Examples (5 in Example 1). Despite the difference of 100 parts by mass in Example 2), the whiteness of the cement compositions of both Examples is the same, and the whiteness of Portland cement and the like is also equivalent. . In the case of blast furnace granulated slag and blast furnace slow-cooled slag, as shown in Reference Examples 5 to 8 in Table 2, in light of the fact that there is little or no change in whiteness due to heating, these points are those using coal gasification slag. This is an effect unique to the invention. Therefore, according to this invention, even if it changes the injection | throwing-in ratio of coal gasification slag in the range of 5-100 mass parts, the cement composition which has a color tone equivalent to Portland cement etc. can be manufactured. Thereby, even if this cement composition is added in large quantities to Portland cement or the like, the color tone of cement concrete does not change. Therefore, a large amount of coal gasification slag can be input and a large amount of cement composition containing the slag can be used (combined) as long as a predetermined strength development is ensured.

(C) Mixing and crushing step This step is a step of adding a gypsum to the mixture of the clinker and slag heat-treated product after passing through the cooler and crushing to obtain a cement composition. Since the mixture and gypsum of the mixture and gypsum need only be pulverized once, the production efficiency is high.
However, when the pulverization properties of the mixture and gypsum are greatly different, the mixture and gypsum may be separately pulverized and then mixed in order to suppress excessive expansion of the particle size distribution. In this case, the brane specific surface area of gypsum is preferably 2000 to 5000 cm ² / g, more preferably 3000 to 4000 cm ² / g. When the value is out of the range of 2000 to 5000 cm ² / g, there is a possibility that strength development property is lowered or heat of hydration is increased.

The amount of gypsum added is preferably 0.5 to 4.0 parts by mass, more preferably 1.0 to 3.5 parts by mass in terms of SO ₃ with respect to 100 parts by mass of the mixture of the clinker and the slag heat-treated product, More preferably, it is 1.4-3.0 mass parts. When the value is in the range of 0.5 to 4.0 parts by mass, the cement composition has high strength and good fluidity.
The type of gypsum is not particularly limited, and for example, at least one selected from dihydrate gypsum, flue gas desulfurization gypsum, phosphate gypsum, titanium gypsum, hydrofluoric gypsum, refined gypsum, hemihydrate gypsum, anhydrous gypsum, and the like. The above is mentioned.

  In the pulverization, the mixture of the clinker and the slag heat-treated product may be pulverized as it is, but is preferably pulverized by adding a pulverization aid in order to increase the pulverization efficiency. Examples of the auxiliary agent include one or more selected from diethylene glycol, triethanolamine, triisopropanolamine, and the like. The addition ratio of these grinding aids is preferably 0.01 to 1 part by mass with respect to 100 parts by mass of the mixture. As the pulverizer, a ball mill, a rod mill, or the like can be used.

Fineness of the cement compositions produced according to the present invention, strength development, workability, and in view of manufacturing cost, Blaine specific surface area, preferably 2000~5000cm ² / g, more preferably 2500～4700Cm ² / G, more preferably 3000 to 4000 cm ² / g.
The cement composition may further contain fly ash, coal ash, silica fume, silica powder, limestone powder, and the like as long as the physical properties of the cement composition are not impaired.

(D) Raw material preparation process Furthermore, the manufacturing method of this invention can include the raw material preparation process for preparing a raw material before the said (A) process as arbitrary processes.
In this step, raw materials such as calcium raw material, silicon raw material, aluminum raw material, and iron raw material are prepared so as to be included in the range of the cement mineral composition by using the Borg formulas of the formulas (1) to (4). Prepare the ingredients. Here, limestone, quicklime, slaked lime, and the like are used as the calcium material, silica and clay are used as the silicon material, clay is used as the aluminum material, and iron cake and iron cake are used as the iron material.

  In addition, since the chemical composition of the prepared raw material before firing is often almost the same as the chemical composition of the clinker after firing, in order to obtain a clinker having the cement mineral composition, it is usually calculated based on the Borg equation. It is sufficient to prepare raw materials that satisfy the mineral composition. However, for the sake of accuracy, a part of the raw material is fired in an electric furnace or the like, and the correlation between the raw material and the mineral composition in the clinker obtained by firing is grasped in advance. It is preferable to correct the mixing ratio of the raw materials so that the target mineral composition in the clinker is obtained.

As the raw material, in addition to natural raw materials, industrial waste, general waste, and / or waste such as construction generated soil can be used as part of the raw material.
Examples of the industrial waste include various sludges such as coal ash, ready-mixed concrete sludge, construction sludge, and iron sludge, boring waste soil, various incineration ash, foundry sand, rock wool, blast furnace secondary ash, construction waste, and concrete waste Etc.
Examples of the general waste include purified water sludge, sewage sludge, sewage sludge dry powder, municipal waste incineration ash, shells, and sewage sludge incineration ash.
Examples of the soil generated from construction include soil generated from construction sites and construction sites, residual soil, and the like.
In addition, when it is necessary to adjust the fineness of a preparation raw material, it grind | pulverizes and adjusts to a predetermined fineness with raw material grinders, such as a ball mill.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
1. Production of cement composition Using a rotary kiln 1, ordinary Portland cement clinker (C ₃ S 56%, C ₂ S 20%, C ₃ A 10%, and C ₄ AF 10 in the range of 1200-1500 ° C. The clinker was dropped from the rotary kiln 1 to the cooler 3. Next, coal gasification slag (Examples 1 and 2 and Comparative Example 4) having a character shown in Table 1 and having a particle size in the range of 1 to 10 mm in an area of 1100 ° C. in the cooler 3 and blast furnace water granulation Slag (Comparative Example 1) was blown into the clinker using compressed air at the charging rate shown in Table 2 and charged.
In addition, ig. It is estimated that the loss is negative because the iron content in the slag was oxidized and the mass increased.
Moreover, in order to confirm the effect of cooler temperature, the said spraying was performed also in the 600 degreeC area | region in the cooler 3 (comparative example 3).
The clinker and the slag were mixed while moving in the cooler 3 to obtain a mixture of the clinker and the slag heat-treated product cooled at the outlet of the cooler 3.
Moreover, in order to confirm the cooling effect (hydraulic improvement effect) of the clinker by the coal gasification slag, the slag is mixed with the clinker without being heated without being put into a cooler to prepare a mixture of Comparative Example 2. did.
Next, after adding 1.4 parts by mass of dihydrate gypsum in terms of SO ₃ to 100 parts by mass of the various mixtures, the cement compositions of Examples 1 and 2 and Comparative Examples 1 to 4 were pulverized with a small ball mill. The thing was manufactured.

2. Method for Measuring Whiteness of Cement Composition and Compressive Strength of Mortar The whiteness of the cement composition is determined according to JIS Z 8722 “Color Measurement Method—Reflection and Transmission Object Color”. SE-6000, manufactured by Nippon Denshoku Industries Co., Ltd.). For reference, the whiteness of ordinary Portland cement, a cement composition in which 67 parts by mass of coal gasification slag was mixed with 100 parts by mass of the cement, and coal gasification slag was also measured.
The compressive strength of the mortar using the cement composition was measured in accordance with JIS R 5201 “Physical test method for cement”.
The results are shown in Table 2.

3. Regarding the whiteness of the cement composition As shown in Table 2, the whiteness was 50% in Example 1 in which the charging rate of coal gasification slag was 5 parts by mass, and in Example 2 in which the charging rate was 100 parts by mass. 0.7 and 50.4, and 50.3 for the ordinary Portland cement of Reference Example 1. Therefore, the whiteness of Example 1 and Example 2 is equivalent even if the charging ratio of coal gasification slag is 20 times different, and the whiteness of ordinary Portland cement is also equivalent.
Moreover, the whiteness of the cement composition according to the production method of the present invention did not change over a long period of time. This is presumed that the oxidation of iron in the coal gasification slag has sufficiently progressed in the slag heat treatment step.
On the other hand, the cement of Comparative Example 3 obtained by introducing the coal gasified slag into a region where the whiteness of the cement composition of Comparative Example 2 was simply mixed without heating the coal gasified slag and the cooler temperature was 600 ° C. The whiteness of the composition is 60.2 and 57.5, respectively, which is very different from the whiteness (50.3) of normal Portland cement.

4). About the compressive strength of mortar As shown in Table 2, the compressive strength ratio of the mortar of Example 1 with respect to Comparative Example 1 containing blast furnace granulated slag is equivalent at about 100% in all ages. Moreover, the compressive strength ratio of the mortar of Example 2 with respect to the comparative example 2 which only mixed coal gasification slag without heat processing is about 5 to 7% high. Therefore, the cement composition according to the production method of the present invention is a cement containing a granulated blast furnace slag that is superior in latent hydraulic properties as a result of improved hydraulic properties of the clinker despite including coal gasified slag having poor latent hydraulic properties. It has the same strength development as the composition.
However, the compressive strength of the mortar of Comparative Example 4 having a large proportion of coal gasification slag as high as 150 parts by mass is about 20% lower than that of Example 2.

5. Others The production method of the present invention can effectively utilize the residual heat in the cooler to make the whiteness of coal gasification slag equivalent to the whiteness of Portland cement, etc. Low energy consumption.

  Therefore, according to the production method of the present invention, a large amount of coal gasification slag can be used, and a cement composition can be produced with less energy consumption. Moreover, the cement composition according to the production method of the present invention is excellent in strength development, has a color tone equivalent to Portland cement and the like, and has little change in color tone with time.

1 Rotary kiln 2 Preheater 3 Clinker cooler 4 In front of kiln 5 Main burner 6 Cement clinker

Claims (2)

The manufacturing method of the cement composition including the following (A)-(C) process.
Cement mineral composition calculated using (A) Borg formula, 20-80% by _{C 3} S, 3 to 60% for _{C 2} S, 1 to 16% in the _{C 3} A, and at _C 4 AF 6 to 16 Clinker preparation step (B) prepared by firing cement clinker that is 1% of the clinker in the clinker cooler at a ratio of 2 to 100 parts by mass of coal gasified molten slag having a particle size of 1 mm or more with respect to 100 parts by mass of the clinker. Slag heat treatment step (C) to obtain a mixture of the clinker and the slag heat-treated product, while cooling the clinker and heating the slag at the same time to obtain a mixture of the clinker and the slag heat-treated product. Mixing and grinding process, adding gypsum and crushing The cement composition according to claim 1, wherein the amount of gypsum added in the step (C) is 0.5 to 4.0 parts by mass in terms of SO ₃ with respect to 100 parts by mass of the mixture of the clinker and the slag heat-treated product. Manufacturing method.

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