JP2007145624A - Method of producing cement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing cement by which the crushing property of cement clinker is enhanced to improve the initial reactivity of cement and a treatment in finish crushing is facilitated to reduce the cost. <P>SOLUTION: The cement clinker containing A-lite and γ-B-lite is manufactured by firing a mixture prepared by mixing raw materials including silica component and calcium component and cooling the resultant fired material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing cement.

  Cement is used as an adhesive for ceramic building materials (for example, fiber-reinforced cement boards, extruded cement boards, and residential roof slate) in addition to buildings and structures. Thus, the cement used for various uses is manufactured by the following manufacturing process.

  First, as a main raw material, a silica component, a calcium component, an alumina component, and an iron component are prepared. After mixing the raw materials, firing is performed to obtain a cement clinker that is an intermediate product of cement that is a lava-like lump (hereinafter referred to as a cement clinker). , Called "cement clinker").

  Next, the obtained cement clinker is physically pulverized with a ball mill or the like to finally obtain a cement product.

Cement clinker, alite: and _{(C 3 S 3CaO · SiO 2} ) belite _{(C 2 S: 2CaO · SiO} 2) was used as a primary mineral, aluminate phase: and _{(C 3 A 3CaO · Al 2} O 3) A ferrite phase (C ₄ AF: 4CaO.Al ₂ O ₃ .Fe ₂ O ₃ ) is formed as a gap phase. Among them, belite (C ₂ S: 2CaO · SiO ₂ ) has polymorphs of α type, α 'type, β type, and γ type, and α type and α' type are high temperature stable type, β type The γ type is a low temperature stable type.

  When obtaining the cement clinker described above, if the mixture of raw materials is fired in the range of 1450 ° C to 1600 ° C, the belite in the cement clinker will change from α type to α 'type and β type in the cooling process after firing. After that, it transitions to γ type and becomes a stable γ type. However, γ-type belite does not exhibit hydraulic properties and is not suitable for cement use. Furthermore, γ-type belite has a small density, and is accompanied by a rapid volume expansion when transitioning from α′-type and β-type to γ-type, causing a pulverization phenomenon called dusting phenomenon, which is hard. Cement clinker shatters in an instant. For this reason, in the cement manufacturing process, it is desirable to suppress the generation of γ-type belite which does not show hydraulic properties and causes a dusting phenomenon.

For example, a cement clinker firing method and a firing apparatus for quenching cement clinker after firing are disclosed (for example, see Patent Document 1). According to this technique, by rapid cooling after firing and cooling at a glance below the transition temperature to γ-type belite, α′-type belite becomes β-type belite showing hydraulic properties, and γ Suppresses the generation of mold belite. In addition, the β-type belite has a small density difference from the α′-type and does not change in volume, so that no crystal breakage occurs during the transition.
JP 2002-29792 A

Ordinary cement is obtained by pulverizing the cement clinker obtained by the above method to a specific surface area of about 3300 cm ² / g. At this time, if the specific surface area is increased, the initial reactivity of the cement is widely increased. Are known.

For example, early-strength cement has been developed as a cement with high initial reactivity. However, early-strength cement increases the ratio of alite (C3S) contained in the cement clinker and increases the specific surface area. However, even in the case of early-strength cement, the specific surface area remained at about 4000 to 5000 cm ² / g. Further, in order to obtain a specific surface area larger than this from a cement clinker mainly composed of alite and belite, special pulverization is required, resulting in problems such as an increase in cost.

  The present invention has been made in order to solve the above-mentioned problems, and does not show hydraulic properties, but daringly produces γ-type belite that causes dusting phenomenon, thereby improving the grindability of cement clinker. It is made high and can be easily pulverized.

  That is, the method for producing a cement according to the present invention includes a cement containing alite (C3S) and γ-belite by cooling a fired product obtained by firing a mixture of raw materials containing a silica component and a calcium component. The main point is to use clinker.

  According to the method for producing a cement of the present invention, since belite (C3S) and γ-belite (C2S) are generated in the cement clinker, the grindability of the cement clinker can be improved. As a result, the specific surface area of the cement clinker is improved and not only the initial reactivity of the cement is improved, but also the processing at the time of finish pulverization is facilitated, and the cost can be reduced.

  Hereinafter, a method for producing a cement according to the present invention will be described.

  The method for producing a cement according to the present invention comprises cooling a fired product obtained by firing a mixture obtained by mixing a raw material containing a silica component and a calcium component, and adding alite (C3S) and γ-belite (C2S). Including cement clinker. Next, the obtained cement clinker is physically pulverized with a ball mill or the like to finally obtain a cement product.

Here, alite and γ-belite are produced in cement clinker, but alite (C3S) plays a role of strength development, and γ-belite (C2S) is just an admixture in cement clinker. It exists. However, in the cement manufacturing method according to the present invention, γ-C2S is intentionally generated in the cement clinker. this is,
Because γ-C2S, which is present throughout the cement clinker, causes volume expansion at the time of generation and exists in the cement clinker with the stress necessary for crushing, the grindability of the cement clinker is improved. is there. In most cases, the cement clinker containing γ-C2S is naturally crushed into a powder state in the course of cooling. However, when stress is applied, it can be pulverized and the grindability is improved. As a result, a great deal of physical energy required when grinding the cement clinker can be greatly suppressed.

  Moreover, both β-C2S and γ-C2S exist in the cement clinker manufactured by the above-described cement manufacturing method. When XRD analysis of cement clinker is performed, there are characteristic peaks at 2θ = 39.5 ° and 2θ = 20.5 °, and each of these peaks is not the first peak, but the mineral in cement clinker It is located almost alone. For this reason, in this invention, the intensity | strength of the said 2 peak was utilized as a standard of the abundance of (beta) -C2S and (gamma) -C2S which exist in a cement clinker. The intensity ratio with respect to each first peak is I = 22% and 45%.

  The abundance of γ-C2S in the cement clinker is defined by the abundance ratio obtained from Equation 1 below.

(Γ-C2S / β-C2S) = (20.5 ° peak intensity) / (39.5 ° peak intensity) (Equation 1)
Here, the abundance of γ-C2S contained in the cement clinker is preferably (γ-C2S) / (β-C2S) = 1/10 or more, more preferably 1/4 or more in terms of abundance ratio. In this range, γ-C2S is sufficiently present in the cement clinker mineral and the grindability is improved. On the other hand, when the abundance ratio is less than 1/4, the surface of the cement clinker is at a level that is transferred to a minute amount, and sufficient grindability cannot be obtained.

  Moreover, in the manufacturing method of the said cement, when cooling a clinker after a baking process, it is preferable to cool slowly. Usually, rapid cooling is performed from about 1200 ° C. to room temperature, but by slowly cooling to about 600 ° C., α′-C2S in the mineral is transferred to γ-C2S. The temperature drop is preferably 20 ° C./min or less.

Furthermore, in the above-mentioned cement manufacturing method, the weight ratio S / (A + F) of SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ which are components of the cement clinker is preferably 5.0 or more. This is because the cement clinker manufactured in this range is susceptible to dusting due to the formation of γ-C2S even when subjected to a rapid cooling treatment at room temperature. Conversely, when S / (A + F) is less than 5.0, the formation of γ-C2S is difficult to occur and a treatment such as slow cooling is required.

  Moreover, in the said manufacturing method of a cement, it is preferable to use crystalline silica as a silica raw material. Usually, as the silica-based material, an amorphous material such as clay or a weathered material that reacts easily is used, but in this method, silica-based silica such as silica sand or silica stone powder is used. In addition, ceramic-based building waste materials and the like may be formed using a quartz-based material, and this facilitates transfer to γ-C2S even when a rapid cooling treatment is performed.

  In the above method for producing cement, the average particle size of the mixture before firing is preferably 40 μm or more. When the average particle size of the mixture is less than 40 μm, γ-C2S is hardly formed even when crystalline silica (quartz) is used. Conversely, when the average particle size of the mixture exceeds 40 μm, the mixture is gradually reduced after firing. Γ-C2S is generated even when cooling, prescribing the abundance ratio of silica component, alumina component and iron oxide component in the raw material, or even without using crystalline silica as the silica component of the raw material This is because the possibility of dusting is increased.

  Further, in the method for producing cement, the firing temperature is preferably 1100 ° C. or higher and 1350 ° C. or lower, more preferably 1300 ° C. or higher and 1350 ° C. or lower. When the firing temperature exceeds 1350 ° C, the transition to γ-C2S is less likely to occur, and conversely, when the firing temperature is less than 1100 ° C, α-C2S is not sufficiently formed and the transition to γ-C2S occurs. Because there is no.

  As described above, according to the method for producing a cement according to the present invention, by generating a cement clinker containing C3S and γ-C2S, the pulverization process at the time of final pulverization is facilitated, and the cost is reduced. Can do.

  In addition, since the cement clinker can be finely pulverized and the specific surface area becomes high, when this cement is used to make a hardened body, the initial reactivity is higher than when using ordinary cement, and early hardening can be expected. .

  Furthermore, when it is used for building materials subjected to hydrothermal treatment such as an autoclave, higher strength may be obtained, and the use value can be increased by using this cement according to applications.

  Hereinafter, more specific description will be given using examples. It goes without saying that the present invention is not limited to the illustrated embodiment.

Examples 1 to 7
In Examples 1 to 7, the cement intermediate (clinker) contains γ-C2S and β-C2S minerals.

Comparative Example In the comparative example, the intermediate product (clinker) of cement does not contain the minerals of γ-C2S and β-C2S.

In each of the above examples and comparative examples, waste glass which is amorphous silica and quartz (silica powder) which is crystalline silica are used as raw materials. In addition to the silica component, carbonic acid is used as a calcium component. Calcium, alumina (Al ₂ O ₃ ) was used as the alumina component, and Fe ₂ O ₃ was used as the iron component.

First, raw materials were blended in the blending ratio (weight ratio) shown in Table 1 based on blending of ordinary cement.

  Next, the blended raw materials were mixed, 200 g of the obtained mixture was put into a container (500 cc), 20 stainless balls were further put, and pulverized for 20 minutes at a rotation speed of 200 rpm. At this time, the mixture was pulverized using a planetary ball mill.

  The average particle size of the mixture after the pulverization treatment was determined by a wet method using a laser type particle size distribution device. This is shown in Table 1 as the average particle size of the mixture before firing.

  Thereafter, the pulverized mixture was put into an electric furnace and baked at the temperature shown in Table 1, and then each sample was held for 60 minutes and further cooled to 1200 ° C. Thereafter, the fired product was taken out from the electric furnace, and the fired product was cooled to obtain a cement intermediate product (clinker). At this time, the fired product was cooled at room temperature, or the fired product was cooled as it was to 600 ° C. in an electric furnace.

The obtained cement intermediate product (clinker) was subjected to XRD analysis to evaluate the physical properties. The evaluation results are shown in Table 2.

  In Table 2, the peak intensity of γ-C2S is shown as X, the peak intensity of β-C2S is shown as Y, and the abundance ratio between them is shown as X / Y. In addition, it means that the ratio with which γ-C2S exists is high, so that the value (X / Y) of this abundance ratio becomes large.

  Next, using a planetary ball mill, 200 g of cement intermediate product (clinker) and 20 stainless balls were placed in a container (500 cc) and pulverized at 200 rpm for 60 minutes.

Thereafter, the specific surface area (cm ² / g) of the powder was measured using a Blaine specific surface area measuring device as the particle size of the powder after the clinker pulverization treatment.

  Finally, the clinker pulverized powder (cement) was used to make a plate, the bending strength of this plate was measured, and the results are shown in Table 2 above.

First, as shown in Table 3 below, 40% powder (cement) after clinker pulverization, 10% pulp that has been defibrated beforehand, 40% fly ash, and 10% silica powder are blended in large amounts. The mixture was uniformly mixed with water and excess water was filtered. After filtration, after pressing and dehydrating under a pressure of 30 kg / cm ² , under conditions shown in Table 3, after wet heat curing (Table 3 (a)), autoclave curing (Table 3 (b)) Then, curing was carried out in two stages to obtain a cured product. The thickness of the obtained cured body was about 12 mm.

  The obtained cured body was cut into a size of 150 mm long × 40 mm wide × 12 mm thick to prepare a test sample. This test sample was stored for 72 hours in a thermo-hygrostat (60 ° C., 20% RH) to adjust the moisture content. Thereafter, a three-point bending test was performed for each test sample of the example and the comparative example, and the three-point bending strength was measured.

  As test conditions at this time, the span was set to 100 mm, the test speed was set to 2 mm / min, and the value of the three-point bending strength was calculated based on the following formula 2. In Equation 2, k is the bending strength [MPa], s is the span [mm], m is the bending fracture load [N], h is the width (lateral dimension) [mm], and w is the thickness [mm]. Show.

k = 3 × s × m / (2 × h × w ² )… (Formula 2)
As shown in Table 2, Example 1 was at a level intended to produce ordinary ordinary cement, and the amount of γ-C2S produced in the clinker was slight. In Examples 2 and 3, since the clinker was gradually cooled when it was cooled, the firing temperatures were 1300 ° C and 1350 ° C, respectively, but by slowly cooling, the amount of γ-C2S present in the clinker was reliably increased. Turned out to be. Furthermore, when Examples 2 and 3 were compared, it was found that the amount of γ-C2S produced decreased as the firing temperature increased. In Example 4, the value of S / (A + F) is increased as compared with the other examples, that is, the amounts of A (alumina) and F (iron oxide) with respect to the amount of S (silica). Although decreased, the amount of γ-C2S produced in Example 4 was increased compared to Example 1. Example 5 uses quartz as the silica component. When Example 5 is compared with Example 1, the other conditions are the same, but the amount of γ-C2S produced in the clinker increases. Turned out to be. Furthermore, Example 6 is based on Example 1, and the particle size of the mixture before firing is coarsened. By making the particle size of the mixture coarse, the amount of γ-C2S produced in the clinker may increase. found.

  Furthermore, when each example is compared, when the value of the abundance ratio of X / Y is set to 0.25 or more and the clinker contains a large amount of γ-C2S (Examples 2 to 6), the dusting phenomenon is confirmed. In any case, the pulverization property is improved, and even when pulverized under the same conditions, the specific surface area is larger than that of Example 1, and at the same time, alite (C3S), which is a hydraulic substance, is included. It became clear that it became a cement with good reactivity and became hard after making the plate.

  Further, in Example 7, the calcination temperature was processed at a high temperature of 1400 ° C. based on the conditions when the crystalline silica of Example 5 was used. In this case, almost γ-C 2 S is generated in the clinker. The pulverizability was also reduced.

In contrast, since the comparative example was fired at a low temperature of 1050 ° C., the generation of belite (C2S), which is a hydraulic mineral present in the clinker, was not sufficient, γ-C2S was not generated, and the clinker Alite (C3S), which is essential for the development of strength, was not generated. As a result, the strength after the plate-making of the comparative example was significantly reduced as compared with the example.

Claims (7)

  A method for producing a cement, comprising cooling a fired product obtained by firing a mixture of raw materials containing a silica component and a calcium component to obtain a cement clinker containing alite and γ-belite.   The cement clinker contains β-belite, and an abundance ratio of γ-belite to β-belite having a peak intensity by XRD observation of the cement clinker is 0.25 or more. Cement manufacturing method.   The method for producing a cement according to claim 1 or 2, wherein the fired product is gradually cooled.   The abundance ratio (S / (A + F)) of the silica component (S) contained in the raw material with respect to the alumina component (A) and the iron oxide component (F) contained in the raw material is 5.0 or more by weight. The method for producing a cement according to any one of claims 1 to 3, wherein:   The said silica component contains crystalline silica, The manufacturing method of the cement of any one of the Claims 1 thru | or 4 characterized by the above-mentioned.   The method for producing a cement according to any one of claims 1 to 5, wherein an average particle size of the mixture is 40 µm or more. The method for producing a cement according to any one of claims 1 to 6, wherein the mixture is fired at 1100 ° C to 1350 ° C.