JP5191010B2 - Method for producing cement clinker - Google Patents

Description

The present invention relates to the production how the cement clinker, more particularly without solid combustibles supplied to the cooling is mixed unburned relates to reduced cement clinker production how hexavalent chromium Is.

Conventionally, cement clinker (hereinafter also referred to as clinker) is manufactured by mixing limestone, clay, silica, iron sulfide ore raw materials, and other iron oxide raw materials as raw materials in a cement kiln and firing them at a high temperature. However, in order not to deteriorate the quality of the cement using the obtained clinker, after combustible material is put into the cement kiln, it is completely burned as soon as possible and granulated raw material particles or clinker particles It was necessary to avoid the remaining of unburned combustibles in the interior.

However, the clinker produced as described above contains a trace amount of harmful hexavalent chromium. Therefore, the hexavalent chromium in the clinker is eluted from concrete or improved soil using such cement. There was 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 strict, various standard values and regulatory values may be exceeded. For this reason, there has been a strong demand to reduce the amount of hexavalent chromium in the clinker as much as possible to below the environmental standard value. Here, the amount of hexavalent chromium was measured by the “Method for quantifying water-soluble hexavalent chromium in cement” in the standard test method of the Cement Association.

  In response to such demands, the present inventors tried to suspend the use of chromium-containing raw materials or to take measures to reduce the amount thereof, but considering the high cost of alternative raw materials, As a result, the manufacturing cost increased significantly, which was not preferable. Therefore, the present inventors conducted various studies including this point, and reduced hexavalent chromium without significantly increasing the cement manufacturing cost by supplying combustible materials separately from the main fuel into the cement kiln. The patent application was filed (see Patent Document 1).

Further, in consideration of the fact that hexavalent chromium is generated in a high-temperature oxidizing atmosphere in a clinker manufacturing facility, the clinker cooler was focused on as a place where a reducing atmosphere can be formed without affecting the clinker quality. However, it has been found that hot clinker particles are in a strongly oxidized state when quenched with air in a clinker cooler.

Therefore, the present inventors have investigated where the reducing atmosphere is formed in the process where the high temperature clinker is cooled in the clinker cooler to efficiently reduce the hexavalent chromium, and introduced it into the clinker cooler. And found that a cement clinker with a greatly reduced amount of hexavalent chromium can be obtained by forming a reducing atmosphere by supplying a combustible material of 5 mm or less to a region where the temperature of the cement clinker is 850 ° C. to 1000 ° C. And applied for a patent (see Patent Document 2).

Japanese Patent Laid-Open No. 11-189442 (Claims 2 and 3 and FIG. 1) JP 2000-319050 A (Claims 2 and 3)

However, if 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 remains unburned and the cooler outlet It was found that it was mixed directly into the collected dust of the cooler dust collector and mixed into the resulting cement clinker as, for example, pulverized coal. This is not preferable in terms of product quality, and therefore, further research has been conducted on the prevention of the mixing of unburned pulverized coal into the cement clinker of the product. As a result, the particle size of solid combustibles exceeds 5 mm. Thus, the present inventors have found that mixing into cement clinker can be prevented, and the present invention has been made here. That is, the problem to be solved by the present invention is to provide a method for producing a cement clinker in which the content of harmful hexavalent chromium is reduced without mixing solid combustibles supplied during cooling.

The above-described problems of the present invention are achieved by the following inventions.
(1) In the 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, the temperature in the clinker cooler is 850 ° C to 1000 ° C A method for producing a cement clinker with reduced hexavalent chromium content, characterized in that a solid combustible having a particle size of more than 5 mm and not more than 100 mm is supplied to the place.
(2) The method for producing a cement clinker with reduced hexavalent chromium content according to the above item (1) , wherein the solid combustible material is supplied through a pipe or a firewood made of a refractory material or a heat-resistant metal material. .
(3) Said 1st term | claim characterized by manufacturing using the clinker cooler which provided the cooler grate of the means to thicken the cement clinker layer on the cooler grate of the said clinker cooler, and / or the structure which reduces the amount of cooling air Or the manufacturing method of the cement clinker in which the hexavalent chromium content of 2 item | term was reduced.
(4) The hexavalent chromium content according to any one of (1) to (3) above, wherein the reducing atmosphere is adjusted by blocking or reducing cooling air supplied to the clinker cooler. A method for producing reduced cement clinker.
(5) It has wall-like or bank-like obstacle walls on the left and right sides of the first great at the entrance of the clinker cooler, and these obstacle walls are formed widely toward both the front and rear sides. The manufacturing method of the cement clinker in which the hexavalent chromium content in any one of said 1st thru | or 4 was reduced.

In the method for producing a cement clinker according to the present invention, a simple method of 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 the cement clinker introduced into the clinker cooler is 850 ° C. to 1000 ° C. the resulting cement clinker, since without solid combustibles unburned product clinker is mixed, the content of hexavalent chromium is reduced, using the clinker, the risk of chromium contamination It is possible to economically obtain a hydraulic material having excellent quality with no quality. In the clinker cooler, taking into consideration that the clinker particles are in a strong oxidation state upon rapid cooling, the solid combustible material is adjusted while adjusting the amount of cooling air in the clinker temperature range of 850 ° C. to 1000 ° C. By supplying and forming a reducing atmosphere, hexavalent chromium can be reduced to trivalent chromium or the like. Further, by supplying the particle size of the solid combustible material to be introduced within a range of more than 5 mm and not more than 100 mm, it is possible to prevent the unburned solid combustible material from being mixed into the product clinker. Immediate Chi, hexavalent cement clinker chromium content is reduced, the cement clinker of high temperature fired by a cement kiln is introduced into clinker cooler, in the manufacturing method of cement clinker is cooled in the clinker cooler, the clinker cooler A cement clinker obtained by supplying a solid combustible material having a particle size of more than 5 mm and not more than 100 mm to a portion where the temperature is 850 ° C. to 1000 ° C., and the content value of hexavalent chromium is 2 ppm or less In addition, by supplying a solid combustible having a size within this particle size range to a region where the residual carbon amount is 0.01% or less, that is, the introduction clinker temperature is within this range, economically hexavalent chromium. The content is reduced, and a part of the solid combustible material supplied during cooling is prevented from being mixed as unburned material. Ntokurinka in which excellent effects that can be obtained.

Further, according to the method for producing a cement clinker with reduced hexavalent chromium content of the present invention, the solid combustible material is supplied through a pipe or a firewood made of a refractory material or a refractory metal material. The cement clinker is a fluidized bed at a temperature of 850 ° C. to 1000 ° C., and the solid combustible having a particle diameter of more than 5 mm and not more than 100 mm supplied to the fluidized bed stays and efficiently forms a reducing atmosphere. By completely burning out, it can be prevented from mixing into the product clinker.

The method for producing a cement clinker with reduced hexavalent chromium content according to the present invention includes a means for thickening the cement clinker layer on the cooler grate of the clinker cooler and / or a clinker cooler provided with a cooler grate having a structure for reducing the amount of cooling air. By using this, it is possible to efficiently form or adjust a reducing atmosphere. The method for producing a cement clinker with a reduced hexavalent chromium content according to the present invention efficiently burns combustibles by adjusting the reducing atmosphere by blocking or reducing the cooling air supplied to the clinker cooler. A cement clinker produced in a good reducing atmosphere, which is formed in a controlled manner, is obtained. The method for producing a cement clinker with reduced hexavalent chromium content according to the present invention is produced using the cement clinker according to any one of the above, whereby the content of hexavalent chromium is reduced and unburned. A hydraulic material free from solid combustible material is obtained. Furthermore, the clinker cooler for producing a cement clinker for producing a cement clinker having a reduced hexavalent chromium content used in the present invention comprises means for thickening the cement clinker layer on the cooler grate installed in the clinker cooler and / or By providing a cooler grate having a structure that reduces the amount of cooling air, a reducing atmosphere can be efficiently formed or adjusted. The cement clinker manufacturing clinker cooler for manufacturing cement clinker hexavalent chromium content to be used in the present invention is reduced, a reducing atmosphere by or reduced to block the cooling air to be supplied to the clinker cooler As a result, the cement clinker produced under a good reducing atmosphere formed by efficiently adjusting the combustion of the combustible material is obtained. In the method for producing a cement clinker with reduced hexavalent chromium content according to the present invention, the clinker cooler for producing cement clinker has a wall-like or bank-like obstacle wall on the left and right sides of the first great at the inlet of the clinker cooler. These barrier walls are widely formed toward both the front and rear sides, so that the layer of cement clinker particles moving on the cooler grate can be thickened, thereby increasing the reduction efficiency by solid combustibles. be able to.

It is sectional drawing which shows the kiln used for this invention. It is sectional drawing which shows the clinker cooler used for this invention.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto. In the present invention, “supplying a 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 clinker cooler is cooled under cooling air. However, it is obvious that 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 cement clinker used in the present invention may be those usually used in this technical field, and examples thereof include limestone, clay, silica stone, iron sulfide ore residue, and other iron oxide raw materials.

  Examples of solid combustibles used in the present invention include various solid fuels, combustible solid wastes, and mixtures thereof. Specifically, coke (may be petroleum coke), various types of coarse coal, volatile Anthracite coal, subbituminous coal, or solid fuel, solid plastic, municipal waste solids, etc. that are more flame retardant than bituminous coal. Preferred are coke (which may be petroleum coke), coarse-grained coal, anthracite coal with less volatile content, subbituminous coal, solid fuel that is more flame retardant than bituminous coal, and the like.

  In these solid combustibles, unburned solid combustible materials exist at least instantaneously outside the clinker particles, and in this state, the oxidation of carbon and carbon monoxide in the solid combustible materials is performed around the solid combustible materials. In addition, it is necessary to have a size in which a reducing atmosphere is formed with a decrease in oxygen partial pressure, but it varies depending on the type of solid combustible material, and has a particle diameter of more than 5 mm and not more than 100 mm. Those having a particle size of more than 10 mm and 50 mm or less are preferred, and those having a particle size of more than 10 mm and 30 mm or less are more preferred. In this case, when the particle size is 5 mm or less, it is blown to the cooler outlet, collected in the cooler dust collector, and sent to the cement clinker transporter after the cooler, so that unburned matter (solid combustible) in the clinker after firing. This is not preferable because it is likely to be left behind and adversely affects cement quality. Further, when the particle size of the solid combustible material exceeds 100 mm, unburned material tends to remain, and the influence on the cement quality is the same as in the case of 5 mm or less.

  FIG. 1 is a cross-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 the cement clinker discharge port of the kiln 1, but the present invention is not particularly limited thereto. In the present invention, the temperature of the cement clinker is 850 ° C. to 1000 ° C. Any structure may be used as long as the clinker cooler in which the region to be present exists. The clinker cooler 3 has a cement clinker 8 moving on the cooler great 7, and has a room 6 (61,... 69) at the lower part thereof. Supplied through the holes and cooled. Here, the region where the temperature of the clinker is 850 ° C. to 1000 ° C. is a portion having a room of 64 to 66, although it depends on the temperature of the cooling air.

  In the present invention, the place where the solid combustible material is charged is the cement clinker layer on at least one of the rooms 64 to 66 of the clinker cooler 3, but the solid flammable material is charged in the cement clinker layer above any of these rooms. Depending on the particle size of the solid combustible material, it is preferably the chamber 64 or both cement clinker layers on the 64 and 65. In the present invention, the place where the solid combustible material is charged is a region where the temperature of the cement clinker is 850 ° C. to 1000 ° C., more preferably a region of 850 ° C. to 950 ° C., and most preferably around 900 ° C. The clinker temperature range. In this temperature range, no decomposition of alite occurs and only hexavalent chromium is reduced and reduced. In addition, the amount of free lime (f · CaO) does not change, and the injected solid combustibles are also burned out, so that they are not mixed into the clinker and the quality of the clinker does not deteriorate. In the present invention, the solid combustible material is preferably introduced by dropping the solid combustible material through either a pipe or a firewood in order to prevent entry into the cement clinker. Made of refractories such as clay, silicic acid, alumina, carbon, chromium and silicon carbide, refractories such as spinel, heat resistant ceramics, or stainless steel, austenitic heat resistant metal materials It is preferable to introduce the solid combustible material through a pipe or a firewood.

  In the present invention, in order to increase the reduction efficiency by the solid combustible material, remodeling the clinker cooler or individually adjusting the operating conditions of the clinker cooler is an extremely effective means. For example, as shown in FIG. 2, a wall-like or bank-like obstacle 9 is provided on the cooler great 7 of the clinker cooler 3 to thicken the layer of cement clinker particles 8 moving on the cooler great 7, or It is possible to take measures such as reducing the number of cooling air holes 71, 72, 73 provided in the great or forming a region without air holes by unevenly providing the air holes. The wall-like or bank-like obstacle 9 is provided on both the left and right sides of the cooler great 7 and is formed so as to become wider toward the front and rear sides.

  In FIG. 2 a, the clinker cooler 3 has a grate 7, and the grate 7 is provided with cooling air holes 71, 72, 73, and chambers 61 to 69 are provided in the lower part thereof. Yes. In this clinker cooler 3, the position of the pipe into which the solid combustible material is charged is the cement clinker layer above the chambers 64 to 66, and the pipe or ridge 10 is installed on the upper part thereof. One or more pipes or tubs 10 can be provided, but one or two are preferably provided. 2b is a plan view of the clinker cooler 3 seen from above, and FIG. 2c is a front view of the clinker cooler 3 seen from the vertical direction. In FIG. 2c, pipes or scissors 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 reduction effect is insufficient, and the proportion of the solid combustible material remaining unburned increases, so that the quality of the clinker may be deteriorated. When the temperature exceeds 1000 ° C, it becomes a region where solid combustibles are added in the high temperature range. In this region, hexavalent chromium is reduced and reduced, but the main clinker mineral, alite, decomposes and free lime increases. As a result, the quality of the clinker deteriorates.

  In the present invention, when supplying the solid combustible material in the region where the temperature of the cement clinker is 850 ° C to 1000 ° C, the supply amount of the solid combustible material is the clinker particle size, the clinker amount, the clinker moving speed, the cooling air amount, and the cooling temperature. Although it is appropriately selected depending on the amount of clinker, it is preferably 0.05 to 3.0% by weight with respect to the clinker amount. A more preferred range is 0.5 to 1.0% by weight. When it is less than 0.05% by weight, sufficient reduction does not occur and the effect of reducing hexavalent chromium is small. On the other hand, if it exceeds 3.0% by weight, the reduction effect becomes insufficient and the ratio of the solid combustibles remaining unburned increases, which is not preferable in terms of the quality of the clinker and the hydraulic substance produced using the clinker.

In the method for producing a cement clinker according to the present invention , as a method of adjusting the amount of cooling air, a method of reducing or blocking the cooling air supplied from the holes of the cooler grate 7 is employed. The cement clinker having a low hexavalent chromium content obtained by the production method of the present invention can be used as it is as a hydraulic material. However, as a hydraulic material as a final product using this cement clinker, it is usually used in this technical field. What is used, for example, various cements, solidifying materials for ground improvement, repair materials, and the like can be mentioned.

Hereinafter, the method for producing a cement clinker of the present invention will be described with reference to examples, but the present invention is not limited thereto.

[Examples 1-4, Comparative Examples 1-4] Ordinary Portland cement clinker is introduced into a clinker cooler 3 shown in FIG. In this clinker cooler 3, the cement clinker layer above the room (cooling chamber) 64 is selected as the place where the clinker temperature is around 900 ° C., and the solid combustible material supply pipe 10 is placed above the clinker layer as the clinker layer. Lump coke having a particle size exceeding 5 mm and having a particle size of 100 mm or less (average particle size 25 mm) was dropped into it at a supply rate of 9 kg / t · clinker. Table 1 shows the results of sampling and analyzing a part of the obtained clinker.

  As shown in Table 1, when no coke is 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. At 1100 ° C., the amount of hexavalent chromium is 3.0 ppm, and although a reduction effect by adding coke is recognized, it is insufficient. In the temperature range of 850 ° C. to 1000 ° C. of the present invention, not only the amount of hexavalent chromium is decreased but also the amount of free lime is not increased. Also, the amount of residual carbon is extremely small. However, it can be seen that at 800 ° C., the amount of hexavalent chromium again increases and the amount of residual carbon also increases. Accordingly, when supplying coke with a particle size exceeding 5 mm and not exceeding 100 mm, the hexavalent chromium content in the clinker is reduced to the target value of 2 ppm or less in the temperature range of 850 ° C. to 1000 ° C., and the product It can be seen that the unburned solid combustible material is very little mixed into the clinker.

[Examples 5 to 8, Comparative Examples 5 to 8] The clinker was produced 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. Table 2 shows the results of sampling and analyzing a part of the obtained clinker.

[Comparative Examples 9 to 16] Clinker obtained by supplying fine coke having an average particle size of 90 μm (maximum 200 μm) as a solid combustible material to the position of the room (cooling chamber) 64 at a supply rate of 10 kg / t · clinker. Table 3 shows the result of sampling and analyzing a part of the sample (Example 1 of JP 2000-319050 A).

  As shown in Comparative Examples 1, 5, and 9 in Tables 1 to 3, when coke is not supplied, the amount of hexavalent chromium is 12.3 ppm, 12.1 ppm, and 11.0 ppm, respectively, which is almost unchanged. I understand that. In addition, when coking coke and fine coke are supplied as solid combustibles, the amount of hexavalent chromium decreases when the temperature of the clinker is 1200 ° C. and 1100 ° C. in any of the examples shown in Tables 1 to 3. On the other hand, the amount of free lime (f. CaO) is increasing. 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 no increase in the amount of free lime is observed. However, it can be seen that the hexavalent chromium content increases again at 800 ° C. or lower.

  Further, with respect to residual carbon contained in the clinker, when supplying fine coke outside the scope of the present invention, a considerable amount is obtained from all the clinker obtained in the temperature range of 850 ° C. to 1000 ° C. used in the present invention. However, in the present invention, the coke having a particle size of more than 5 mm and not more than 100 mm is extremely small, and hardly detected when the coke having a particle size of more than 10 mm and not more than 30 mm is used. From these results, the method of the present invention for supplying a lump coke having a particle size of more than 5 mm and not more than 100 mm to the clinker in the temperature range of 850 ° C. to 1000 ° C. increases the amount of free lime contained in the product clinker. It can be seen that not only the amount of hexavalent chromium can be reduced to the target value of 2 ppm or less, but also an excellent effect that there is no mixing of unburned solid combustibles is obtained.

In recent years when environmental standards are strict, there is a strong demand to reduce the amount of hexavalent chromium in the cement clinker as much as possible to less than the environmental standard value, that is, 2 ppm or less, so as not to exceed various standard values and regulatory values. A method for producing a cement clinker that solves this problem and does not adversely affect the quality was obtained. The hydraulic material using the cement clinker has extremely high industrial applicability as a product that satisfies environmental standards.

1 Rotary kiln 2 Preheater 3 Clinker cooler 4 Kiln bottom 5 Burner 6 Room (cooling room)
7 Cooler Great 8 Cement Clinker 9 Wall Obstacle 10 Pipe 11 Meter

Claims (5)

In the method for producing a cement clinker in which a high-temperature cement clinker fired by a cement kiln is introduced into the clinker cooler and cooled in the clinker cooler, the temperature in the clinker cooler is 850 ° C to 1000 ° C. A method for producing a cement clinker with reduced hexavalent chromium content, characterized by supplying a solid combustible material having a particle size of more than 5 mm and not more than 100 mm. The method for producing a cement clinker with reduced hexavalent chromium content according to claim 1 , wherein the solid combustible material is supplied through a pipe or a firewood made of a refractory material or a refractory metal material. Claim 1 or claim 2, characterized in that it is manufactured using a clinker cooler provided with a cooler Great structure reducing means and / or the amount of cooling air to increase the cement clinker layer on the cooler Great of the clinker cooler A method for producing a cement clinker having a reduced hexavalent chromium content described in 1. The cement with reduced hexavalent chromium content according to any one of claims 1 to 3 , wherein the reducing atmosphere is adjusted by blocking or reducing cooling air supplied to the clinker cooler. A method for producing clinker. Claim 1, characterized in that said has a clinker cooler wall-like right and left sides of the first Great at the entrance or bank-shaped disorders wall, these disorders walls are wider toward both sides before and after The manufacturing method of the cement clinker in which the hexavalent chromium content in any one of Claim 4 thru | or 4 was reduced.

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