JP2002211961A - Cement clinker and method of manufacturing of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide cement clinker which is free of inclusion of solid combustibles in cooling and is decreased in the content of harmful hexad chromium and a hydraulic material using this clinker. SOLUTION: This cement clinker is obtained by supplying the solid combustibles of a grain size over 5 mm and below 100 mm to a region where the temperature of the cement clinker introduced into a clinker cooler attains 850 to 1,000 deg.C. The solid combustibles are supplied through a pipe or trough consisting of refractories or heat resistant metallic material. The reduction atmosphere is adjusted by shutting off or lessening the cooling air supplied into the clinker cooler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement clinker and a hydraulic material manufactured using the same, and more particularly, to a solid combustible material supplied at the time of cooling without mixing without burning. The present invention relates to a cement clinker with reduced hexavalent chromium and a hydraulic material manufactured using the same.

[0002]

2. Description of the Related Art Conventionally, cement clinker (hereinafter also referred to as clinker) is produced by mixing raw materials such as limestone, clay, quartzite, iron sulfide ores and other iron oxide raw materials in a cement kiln and firing at a high temperature. It has been implemented,
In order not to lower the quality of the cement using the obtained clinker, after injecting combustibles into the cement kiln,
It was necessary to completely burn as quickly as possible to avoid the unburned combustibles remaining inside the granulated raw material particles or clinker particles.

[0003]

However, the clinker produced as described above contains a trace amount of harmful hexavalent chromium. Therefore, clinker from concrete or improved soil using such cement can be used. Hexavalent chromium in the solution sometimes eluted, causing a problem. As the amount of hexavalent chromium in the clinker increases, the amount of elution increases, and in recent years when environmental standards are severe, various standard values and regulation values may be exceeded, which has been a problem. Therefore, there has been a strong demand that the amount of hexavalent chromium in the clinker be reduced as much as possible to be below the environmental standard value. Here, the amount of hexavalent chromium was measured by the "Method for Quantifying Water-Soluble Hexavalent Chromium in Cement" of the Cement Institute Standard Test Method.

In response to such a demand, the present inventors have
We tried to stop using chromium-containing raw materials or take measures to reduce the amount, but considering the high cost of alternative raw materials, the cost of cement production will rise significantly, which is undesirable. all right. Therefore, the present inventors have studied variously including this point,
It was previously found that hexavalent chromium could be reduced by supplying combustibles separately from the main fuel into the cement kiln without significantly increasing the production cost of cement, and applied for a patent (Japanese Patent Application No. 9-360105). issue).

Further, in consideration of the fact that hexavalent chromium is generated in a high-temperature oxidizing atmosphere in a clinker production facility, attention has been paid to a clinker cooler as a place where a reducing atmosphere can be formed without affecting clinker quality. However,
The high temperature clinker particles were found to be in a strongly oxidized state when quenched with air in a clinker cooler.

Accordingly, the present inventors have investigated where in the process of cooling a high-temperature clinker in the clinker cooler, a reducing atmosphere is formed to efficiently reduce hexavalent chromium. The temperature of the cement clinker introduced into the cooler is 850 ° C. to 1000
It has been found that a cement clinker in which the amount of hexavalent chromium is greatly reduced can be obtained by supplying a combustible material to the region where the temperature is ℃ and forming a reducing atmosphere.
No. 8048 and patent application.

However, when a combustible material having a particle size of 5 mm or less is supplied to a region where the temperature of the cement clinker introduced into the clinker cooler is 850 ° C. to 1000 ° C., depending on the supply method, the solid combustible material may be unburned. It has been found that it is directly discharged to the cooler outlet as it is, or is contained in dust collected by a dust collector of the cooler, and is mixed into the obtained cement clinker as, for example, pulverized coal. This was unfavorable in terms of product quality, and as a result of further research on preventing the incorporation of unburned pulverized coal into the cement clinker of the product,
By finding that the particle size of the solid combustibles exceeds 5 mm, it has been found that the solid combustibles can be prevented from being mixed into the cement clinker, and the present invention has been made. That is, the problem to be solved by the present invention is to provide a cement clinker in which the content of harmful hexavalent chromium is reduced without mixing solid combustibles supplied during cooling and a hydraulic material using the clinker. It is in.

[0008]

The above object of the present invention is achieved by the following inventions.

(1) It is obtained by supplying a solid combustible material having a particle size of more than 5 mm and 100 mm or less to a region where the temperature of the cement clinker introduced into the clinker cooler is 850 ° C. to 1000 ° C. Cement clinker. (2) The cement clinker according to (1), wherein the solid combustible material is supplied through a pipe or a trough made of a refractory or heat-resistant metal material. (3) The cement clinker according to (1) or (2), wherein the content of hexavalent chromium is 2 ppm or less. (4) The cement clinker according to any one of (1) to (3) above, wherein the cement clinker is manufactured by adjusting a reducing atmosphere by cutting off or reducing cooling air supplied to the clinker cooler. . (5) The above-mentioned items 1 to 4, characterized in that the device is manufactured using a clinker cooler provided with a cooler grate having a structure for reducing the amount of cooling air and / or a means for thickening the cement clinker layer on the cooler grate. The cement clinker according to any one of the above. (6) A hydraulic material manufactured using the cement clinker according to any one of the above items (1) to (5).

[0010] The first aspect of the present invention is that the temperature of the cement clinker introduced into the clinker cooler is 850 ° C to 10 ° C.
The present invention relates to a cement clinker obtained by supplying a solid combustible having a particle size of more than 5 mm and not more than 100 mm to a region where the temperature is 00 ° C. That the hexavalent chromium content is reduced economically and that some of the solid combustible material supplied during cooling is prevented from being mixed as unburned material. Features.

The second item of the present invention is a clay, silica,
Refractories such as alumina, carbon, chromium and silicon carbide; refractories represented by spinel; heat-resistant ceramics; stainless steel; The present invention relates to a cement clinker manufactured by supplying a combustible material to a desired place. At this desired location, the cement clinker is in a fluidized bed at a temperature of 850 ° C. to 1000 ° C. and more than 5 mm and 100 m
The solid combustible material having a particle size of m or less stays and completely burns out while efficiently forming a reducing atmosphere, so that it can be prevented from being mixed into the product clinker. The third item of the present invention is that the content of hexavalent chromium obtained by the present invention is 2%.
It relates to a cement clinker reduced to below ppm. Further, the fourth aspect relates to a cement clinker manufactured under a good reducing atmosphere formed by efficiently adjusting the combustion of combustibles by cutting off or reducing the cooling air supplied to the clinker cooler. Things.

Further, by using the means for thickening the cement clinker layer on the cooler grate and / or the cooler provided with the cooler grate having a structure for reducing the amount of cooling air, the reducing atmosphere can be efficiently produced by the means of the fifth aspect. It can be formed or adjusted. Item 7. In the seventh item, the content of hexavalent chromium produced using the cement clinker according to any one of the first to fifth items is reduced,
A hydraulic material free of unburned solid combustibles is provided.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. In the present invention, "supplying the combustible material to a region where the temperature of the cement clinker introduced into the clinker cooler is 850 ° C. to 1000 ° C." means that the process is performed under cooling by cooling air in the clinker cooler. In Although,
Obviously, the combustible material may be supplied to the region where the temperature of the cement clinker is 850 ° C. to 1000 ° C., and then cooled.

The raw materials for producing the cement clinker used in the present invention may be those usually used in this technical field, and include limestone, clay, quartzite, iron sulfide ore residue, and other iron oxide raw materials.

The solid combustible used in the present invention includes:
Examples include various solid fuels, combustible solid wastes, and mixtures thereof. Specific examples include coke (or petroleum coke), various types of coarse-grained coal, anthracite with low volatile content,
Sub-bituminous coal, solid fuel, solid plastic, municipal solid waste, etc., which are more flame-retardant than bituminous coal. Preferable examples include coke (or petroleum coke), various types of coarse coal, anthracite with low volatility, sub-bituminous coal, and solid fuel which is more flame-retardant than bituminous coal.

In these solid combustibles, unburned solid combustibles are present at least instantaneously outside the clinker particles, and in such a state, carbon and monoxide in the solid combustibles are surrounded by the solid combustibles. It is necessary to have a size such that a reducing atmosphere is formed as the carbon is oxidized and the oxygen partial pressure is reduced, and it depends on the type of solid combustible material.
The particle size is more than 10 mm and 100 mm or less, and more preferably more than 10 mm and 50 mm or less,
Those having a particle size of more than 10 mm and not more than 30 mm are more preferable. In this case, if the particle size is 5 mm or less, it is blown to the cooler outlet or collected by the cooler dust collector and sent to the cement clinker transporter after the cooler,
Unburned substances (solid combustible substances) are likely to remain in the clinker after firing, which has a large possibility of adversely affecting the cement quality, which is not preferable. The particle size of the solid combustible is 10
Even when the thickness exceeds 0 mm, unburned matter tends to remain, and the effect on cement quality is the same as that when the thickness is 5 mm or less.

FIG. 1 is a sectional view showing a kiln having a clinker cooler used in the present invention. In FIG. 1, the present invention has a structure in which a clinker cooler is provided at a cement clinker outlet of the kiln 1. However, the present invention is not particularly limited to this. In the present invention, the temperature of the cement clinker is 850 ° C. to 1000 ° C. The structure may be any as long as it is a clinker cooler in which a region is present. In the clinker cooler 3, a cement clinker 8 moves on the cooler great 7, and has a room 6 (61,..., 69) below this, and the cooling air is supplied from these rooms to the cooler great 7. And cooled through the holes. Here, the region where the temperature of the clinker is 850 ° C. to 1000 ° C. is a certain portion of the room with reference numerals 64 to 66, depending on the temperature of the cooling air.

In the present invention, the place where solid combustibles are charged is a cement clinker layer on at least one of the rooms 64 to 66 of the clinker cooler 3. The charge in the layer depends on the particle size of the solid combustible, but is preferably both the cement clinker layer above the chamber 64 or 64 and 65. In the present invention, the place where the solid combustible material is charged is that the temperature of the cement clinker is 85.
The temperature range is from 0 ° C to 1000 ° C, more preferably from 850 ° C to 950 ° C, most preferably the clinker temperature range around 900 ° C. In this temperature range, decomposition of alite does not occur, and only hexavalent chromium is reduced and reduced. The amount of the free lime (f.CaO) does not change, and the solid combustibles put in are burned out, so that they do not enter the clinker and the quality of the clinker does not deteriorate. Further, in the present invention, as the charging form of the solid combustibles, it is preferable to drop the solid combustibles through a pipe or a tub in order to prevent the solid combustibles from being mixed into the cement clinker.

In the present invention, it is extremely effective to modify the clinker cooler or individually adjust the operating conditions of the clinker cooler in order to increase the efficiency of reduction by solid combustibles. For example, as shown in FIG. 2, a wall-shaped or bank-shaped obstacle 9 is provided on the cooler grate 7 of the clinker cooler 3 to increase the thickness of the layer of cement clinker particles 8 moving on the cooler grate 7, or Cooling air holes 71, 72, 7 provided in the great
It is possible to take measures such as forming a region without air holes by reducing the number of the holes 3 or providing the air holes unevenly. The wall-shaped or bank-shaped obstacles 9 are provided on the left and right sides of the cooler great 7 and are formed so as to become wider toward both front and rear sides.

In FIG. 2A, the clinker cooler 3 has a great 7 in the clinker cooler 3. Further, the great 7 is provided with cooling air holes 71, 72, 73, and a room 61
~ 69. In this clinker cooler 3, the position of the pipe into which the solid combustible material is charged is from room 64 to
On top of these are the cement clinker layers 66, on which the pipes or tubs 10 are placed. One or more pipes or tubs 10 can be provided.
It is preferable to provide a plurality. FIG. 2B is a plan view of the clinker cooler 3 as viewed from above, and FIG. 2C is a front view of the clinker cooler 3 as viewed from the vertical direction. FIG.
In (c), pipes or tubs 10 are provided on both sides of the clinker cooler 3 according to the present invention.

When the temperature of the cement clinker is lower than 850 ° C., the combustion state is poor and the reducing effect is insufficient, so that the proportion of solid combustibles remaining unburned increases, and thus the quality of the clinker may be deteriorated. The temperature is 1
If the temperature exceeds 000 ° C, it becomes an area where solid combustibles are added in a high temperature range, and hexavalent chromium is reduced and reduced in this area, but alite, which is a major clinker mineral, is decomposed and free lime increases. Clinker quality deteriorates.

In the present invention, when the solid combustible is supplied to the region where the temperature of the cement clinker is 850 ° C. to 1000 ° C., the supply amount of the solid combustible is clinker particle size, clinker amount, clinker moving speed, cooling air amount. It is appropriately selected depending on the cooling temperature and the like, but is preferably 0.05 to 3.0% by weight based on the amount of clinker. More preferably, it is in the range of 0.5 to 1.0% by weight. 0.
If it is less than 05% by weight, sufficient reduction does not occur,
Less effective for reducing hexavalent chromium. On the other hand, if the content exceeds 3.0% by weight, the reducing effect becomes insufficient, and the proportion of solid combustibles remaining unburned increases, which is not preferable in terms of the quality of clinker and hydraulic substances produced using the same.

In the present invention, as a method of adjusting the cooling air amount, a method of reducing or cutting off the cooling air supplied from the hole of the cooler grate 7 is adopted. The cement clinker having a low hexavalent chromium content obtained in the present invention can be used as it is as a hydraulic material, but as a hydraulic product which is a final product using this cement clinker, those usually used in this technical field are used. Examples thereof include various cements, a solidifying material for ground improvement, a repair material, and the like.

[Action] In consideration of the fact that the clinker particles are rapidly oxidized in the clinker cooler and become strongly oxidized, the temperature of the clinker in the cooler is 850 ° C.
The hexavalent chromium can be reduced to trivalent chromium or the like by supplying a solid combustible material while adjusting the amount of cooling air in a region of up to 1000 ° C. to form a reducing atmosphere. In addition, by supplying the particle diameter of the solid combustible material to be supplied within a range of more than 5 mm and 100 mm or less, it is possible to prevent unburned solid combustible material from being mixed into the product clinker.

[0025]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Examples 1-4, Comparative Examples 1-4 Normal Portland cement clinker is introduced into a clinker cooler 3 shown in FIG. In this clinker cooler 3,
As a place where the clinker temperature is around 900 ° C., the cement clinker layer above the room (cooling room) 64 is selected,
A solid combustible supply pipe 10 is located above the clinker layer.
Was provided almost vertically to the clinker layer, and from there, lump coke having a particle size of more than 5 mm and 100 mm or less (average particle size of 25 mm) was dropped and supplied at a supply rate of 9 kg / t · clinker. Table 1 shows the results of sampling and analyzing a part of the obtained clinker.

[0027]

[Table 1]

As shown in Table 1, when coke is not supplied, the amount of hexavalent chromium is 12.3 ppm. When lump coke is supplied, the amount of hexavalent chromium decreases at 1200 ° C., but free lime increases. 11
At 00 ° C., the amount of hexavalent chromium is 3.0 ppm, and although the reduction effect by adding coke is recognized, it is insufficient. In the temperature range of 850 ° C. to 1000 ° C. which is the temperature range of the present invention, not only the amount of hexavalent chromium is reduced but also the amount of free lime is not increased. Also, the amount of residual carbon is extremely small. However, at 800 ° C., the amount of hexavalent chromium increases again, and the amount of residual carbon also increases. Therefore, when lump coke having a particle size of more than 5 mm and not more than 100 mm is supplied, 850 ° C. to 1000
It can be seen that in the temperature range of ° C., the amount of hexavalent chromium in the clinker is reduced to the target value of 2 ppm or less, and the amount of unburned solid combustibles in the product clinker is extremely small.

Examples 5 to 8 and Comparative Examples 5 to 8 Clinker under the same conditions as in Examples 1 to 4 and Comparative Examples 1 to 4 except that the particle size of the lump coke was changed from more than 10 mm to 30 mm or less. The production was carried out, and a part of the obtained clinker was sampled and analyzed.

[0030]

[Table 2]

[Comparative Examples 9 to 16] Fine solid coke having an average particle size of 90 µm (maximum 200 µm) was used as solid combustible material.
Room (cooling room) with supply rate of 0kg / t-clinker
Table 3 shows the results of sampling and analyzing a part of the clinker obtained at the position No. 64.
Example 1 of 128048).

[0032]

[Table 3]

As shown in Comparative Examples 1, 5 and 9 in Tables 1 to 3, when coke was not supplied, the amount of hexavalent chromium was 12.3 ppm, 12.1 ppm and 11.1 ppm, respectively.
It is 0 ppm, which shows that there is almost no change. In addition, when lump coke and fine coke were supplied as solid combustibles, the clinker temperature was 1200 ° C. and 1100 ° C. in any of the examples shown in Tables 1 to 3.
In the case of, the amount of hexavalent chromium decreases, but the amount of free lime (f. CaO) increases. On the other hand, in the temperature range of 850 ° C. to 1000 ° C. used in the present invention, the amount of hexavalent chromium decreases but the amount of free lime does not increase. However, at 800 ° C. or lower, it can be seen that the amount of hexavalent chromium increases again.

Regarding the residual carbon contained in the clinker, the temperature range used in the present invention is 850 when the fine coke which is out of the range of the present invention is supplied.
Significant amounts are detected from all clinkers obtained at temperatures between 100 ° C and 1000 ° C.
In the case of lump coke with the following particle size,
In the case where lump coke having a particle size exceeding 30 mm and not exceeding 30 mm was used, it was hardly detected. From these results, 85
5 mm for clinker in the temperature range of 0 ° C. to 1000 ° C.
The method of the present invention for supplying lump coke having a particle size of more than 100 mm and less than 100 mm is the target value of hexavalent chromium without increasing the amount of free lime contained in the product clinker.
It can be seen that not only can the amount be reduced to ppm or less, but also an excellent effect that there is no mixing of unburned solid combustibles is exhibited.

[0035]

The present invention obtained by a simple method of supplying a solid combustible having a particle size of more than 5 mm and less than 100 mm to a region where the temperature of the cement clinker introduced into the clinker cooler is 850 ° C. to 1000 ° C. In the cement clinker, since unburned solid combustibles are not mixed into the product clinker and the content of hexavalent chromium is reduced, the clinker is used to obtain a quality free from the possibility of chromium contamination. An excellent hydraulic material can be obtained economically.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a kiln used in the present invention.

FIG. 2 is a sectional view showing a clinker cooler used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary kiln 2 Preheater 3 Clinker cooler 4 Kiln bottom 5 Burner 6 Room (cooling room) 7 Cooler great 8 Cement clinker 9 Obstacles such as walls 10 Pipe 11 Meter

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tetsuo Saito 1-297 Kitabukuro-cho, Omiya-shi, Saitama F-term in Ube-Mitsubishi Cement Research Institute Co., Ltd. 4G012 KD01

Claims (7)

[Claims] 1. A cement obtained by supplying a solid combustible having a particle size of more than 5 mm and not more than 100 mm to a region where the temperature of a cement clinker introduced into a clinker cooler is 850 ° C. to 1000 ° C. Clinker. 2. The cement clinker according to claim 1, wherein the solid combustible is supplied through a pipe or a trough made of a refractory or a heat-resistant metal material. 3. The cement clinker according to claim 1, wherein the content of hexavalent chromium is 2 ppm or less. 4. The cement according to claim 1, wherein the reducing air is adjusted by shutting off or reducing cooling air supplied to the clinker cooler. Clinker. 5. A manufacturing method using a clinker cooler provided with a cooler grate having a structure for reducing the amount of cooling air and / or a means for thickening a cement clinker layer on the cooler grate. 4. The cement clinker according to any one of 4. 6. A method for producing a cement clinker in which a high-temperature cement clinker fired by a cement kiln is introduced into a clinker cooler and cooled in the clinker cooler, wherein the temperature in the clinker cooler is:
In a place where the temperature is 850 ° C to 1000 ° C, more than 5 mm and 10
A method for producing a cement clinker, comprising supplying a solid combustible having a particle size of 0 mm or less. 7. A hydraulic material produced by using the cement clinker according to claim 1. Description: