JPH10203854A - Cement clinker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain plural kinds of cement clinkers having a fixed mineral substance composition, respectively and to secure product qualities and stable operation of production line, by baking clinker having a tinker mineral substance composition changing with a particle diameter in the same production line and classifying. SOLUTION: When a raw material is successively supplied and baked particles corresponding to the amount of the raw material thrown is successively or intermittently taken out in a baking furnace (e. g. baking furnace of fluidized bed type) of a type in which a particle diameter is dependent on a baking time, a nucleus forming rate and a particle growth rate in the furnace are kept constant. Consequently a clinker having approximately the same particle size distribution and the same composition distribution of the discharged clinker can be obtained. The baking temperature is usually about 1,300-1,450 deg.C, preferably about 1,400 deg.C. Discharge of fine particles having <h0.3mm comprising unreacted raw material particle is suppressed by controlling an air flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling the mineral composition of cement clinker.

[0002]

2. Description of the Related Art Usually, in order to produce a cement having a predetermined mineral composition, raw materials corresponding to a required clinker composition are prepared, and calcined by a rotary kiln so that the mineral composition is as uniform as possible. Manufacturing. When clinker is produced by this rotary kiln firing method, a slight composition variation is observed depending on the clinker particle size, but the composition difference does not occur as much as the type of cement is different. Therefore, from one type of clinker,
One type of cement with a stable mineral composition is always obtained.

[0003] Or from another viewpoint, in order to obtain clinkers having different compositions (clinkers for producing cement of different varieties), it is necessary to change the raw material composition.
The entire production line must be washed out when the production type is changed. Therefore, non-standard products are likely to occur at the time of switching. Further, the production line may be temporarily unstable due to a change in the operating conditions.

[0004]

SUMMARY OF THE INVENTION According to the present invention, clinkers of a plurality of product compositions are obtained simultaneously from the same raw material on the same production line, thereby eliminating the need to switch product types, and stabilizing product quality and the production line. Its main purpose is to provide technologies that can ensure safe operations.

[0005]

The present inventor has made intensive studies in view of the above-mentioned problems of the prior art. In the process, when clinker is fired by a fluidized bed method developed recently, the mineral composition is systematically and greatly different according to the particle size of the fired clinker, and by classifying this to an appropriate particle size, It has been found that clinkers with distinctly different components are obtained. More specifically, it has been found that, for example, by sieving clinker fired with a certain raw material composition at a constant particle size, the small-diameter portion becomes a normal cement clinker, and the large-diameter portion becomes an early-strength cement clinker. .

The present invention has been completed on the basis of such novel findings, and provides the following method for controlling the mineral composition of cement clinker: A method for obtaining a plurality of types of cement clinkers each having a predetermined mineral composition by firing and classifying clinker whose clinker mineral composition changes depending on the particle size.

[0007] 2. Item 2. A cement clinker having a predetermined mineral composition obtained by the method according to item 1.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a conventional rotary kiln system, raw materials move from a charging side to a firing side with rotation of the kiln, and reaction, granulation and sintering occur as the temperature rises during the rotation, and clinker is produced. Is done. At this time, all the raw materials stay in the kiln for substantially the same time, undergo substantially the same calcination and reaction process, and have a little difference due to the particle size because they are stirred and homogenized by the rotation of the kiln. Instead, a clinker having a substantially uniform composition is formed.

On the other hand, in a baking furnace of a type in which the particle size depends on the baking time (for example, a baking furnace of a fluidized bed type), small particles have a large amount of interstitial components, belite components, and the like. The alite component increases. This is because each raw material component put into the firing furnace follows a different reaction process. The raw material rich in the Al component and the Fe component, which are components of the melt, easily forms clinker particle nuclei, that is, small particles, and the Si-rich component is also easily incorporated therein. On the other hand, limestone, which is mainly a Ca source, hardly forms a melt, so it adheres around the generated nucleus and grows clinker particles. Therefore, in the early stage of production, that is, in the clinker with a small particle size, the belite component (2CaO.SiO2) with a small amount of calcium is large, and the alite component (3CaO.SiO2) with a large amount of calcium is increased as the granulation proceeds. It is thought to change. According to the present invention, the raw material is continuously supplied to the firing furnace, and when the fired particles corresponding to the raw material input amount are continuously or intermittently extracted, the nucleation rate and the particle growth rate in the furnace are kept constant. The particle size distribution in the furnace is kept constant. Therefore, it is possible to obtain a clinker having substantially the same particle size distribution and composition distribution of the discharged clinker. In extracting the calcined product, so that unreacted raw material particles are not discharged as it is, for example, according to the method disclosed in JP-A-6-281351, JP-A-6-287043, etc. It is preferable to suppress the discharge of fine particles of 0.3 mm or less composed of unreacted raw material particles by airflow or the like. The firing temperature is not particularly limited, but is usually about 1300 to 1450 ° C., preferably 1400 ° C.
It is about ° C.

[0010] When the raw material contains a large amount of lime component or when the raw material particles have a coarse particle size, the reaction may be discharged in an insufficient state. In such a case, it is preferable to complete the reaction by firing in another firing furnace. In the "secondary firing" performed as necessary, it is important to prevent the particles from bonding and growing. When the grain growth is performed, the dependency of the clinker composition on the particle size is impaired, and the object of the present invention cannot be achieved.

In the present invention, the fired product obtained as described above is classified into a desired composition. Classification can be performed by a known method such as a vibration sieve. Next, a predetermined amount of gypsum or the like is added to each classified product according to a conventional method, and the mixture is pulverized by a ball mill or the like, thereby obtaining a plurality of types of cement.

For example, in the case of producing early-strength cement and ordinary Portland cement, the mineral composition (or raw material composition) corresponding to the cement is determined, and the relationship between the mineral composition and the particle size, which has been confirmed experimentally in advance, is determined. Since the particle size (particle size distribution) corresponding to the mineral composition is determined, the particle size (in other words, the diameter of the sieve) of the sieve residue and the passing amount is easily determined. The same applies to other types of cement.

[0013]

In the present invention, the correlation that "the clinker composition changes in accordance with the particle size" is established for all the raw material compositions. Therefore, a plurality of types of cement clinker having a predetermined mineral composition can be easily obtained by previously obtaining the relationship between the clinker particle size and the composition for each raw material composition.

[0014]

EXAMPLES Examples are shown below to further clarify the features of the present invention.

Example 1 Using a fluidized bed type cement clinker manufacturing apparatus based on the disclosure of Japanese Patent Application Laid-Open No. H7-17751 equipped with a rapid heating furnace,
Clinkers having the average composition shown in Table 1 were produced. The temperature during firing was kept at about 1400 ° C. Table 2 shows the particle size distribution of the obtained clinker and the change in the composition corresponding to the particle size distribution.

[0016]

[Table 1]

[0017]

[Table 2]

Further, the clinker obtained above is sieved through a 2 mm sieve, 5% of gypsum is added to the residue on the sieve, and 3% of gypsum is added to the residue passing through the sieve. Each was pulverized by a ball mill to produce an early strength Portland cement and a normal Portland cement. Table 3 shows the composition of each cement.

[0019]

[Table 3]

As is apparent from the results shown in Tables 1 to 3, according to the method of the present invention, a plurality of types of cement clinker having a predetermined mineral composition can be obtained by a single firing step.

Example 2 A clinker having an average composition shown in Table 4 was produced using the same cement clinker production apparatus as in Example 1. The temperature during firing was kept at about 1400 ° C. Table 5 shows the change in the particle size distribution of the obtained clinker and the corresponding composition.

[0022]

[Table 4]

[0023]

[Table 5]

The clinker obtained above is 1.4 mm
And the residue on the sieve was added with 3.5% of gypsum dihydrate, and the amount of gypsum passed through the sieve was added with 4% of gypsum. Each was pulverized by a ball mill and mixed with moderately hot Portland cement. Belite cement was manufactured. Table 6 shows the composition of each cement.

[0025]

[Table 6]

The results shown in Tables 4 to 6 also show that according to the method of the present invention, a plurality of types of cement clinkers having a predetermined mineral composition can be obtained by a single firing step.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Katsuharu Mukai 1 in Kanda Midoshirocho, Chiyoda-ku, Tokyo Sumitomo Osaka Cement Co., Ltd. Cement Concrete Research Laboratory (72) Inventor Toshiyuki Ishibachi No. 1 Daimachi Sumitomo Osaka Cement Co., Ltd. Cement Concrete Research Laboratories (72) Inventor Tatsushi Akiyama 7-55 Minamienkajima, Taisho-ku, Osaka-shi, Osaka Sumitomo Osaka Cement Co., Ltd. Cement Concrete Research Laboratories

Claims (2)

[Claims] 1. A method for obtaining a plurality of types of cement clinkers each having a predetermined mineral composition by firing and classifying clinker whose clinker mineral composition changes depending on the particle size. 2. A cement clinker having a predetermined mineral composition obtained by the method according to claim 1.