JP2508536B2 - Cement clinker firing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method of firing a cement clinker by a shaft kiln, and more specifically, there is no restriction on the selection of clay used as a raw material, and the miniaturization of an apparatus is possible. The present invention relates to a method capable of reducing the fuel consumption rate, which is possible.

[Conventional technology]

In the conventional cement clinker firing method using a shaft kiln, a coke or anthracite powder and water are added in the granulation step to a powder raw material that is prepared by mixing into predetermined components and crushed, and then a pan-type granulator is used. After granulating to a predetermined size, it is put into a shaft kiln and fired.

This step will be described in detail with reference to FIG. FIG. 2 is a schematic diagram of the firing process.

Powder raw material obtained by crushing limestone, clay, silica stone, etc. by a raw material mill (not shown) and coke or anthracite are weighed by respective weighing machines 1 so as to have a predetermined ratio, and then mixed by the mixing device 2, It is supplied to the pan type granulator 3 via a charging chute. The pan type granulator is provided with a water meter 4 equipped with a flow rate adjusting mechanism, and the water content of the granulated product is 12%.
While adding water so as to be ˜14%, the tilt angle and the rotation number of the pan of the granulator 3 are adjusted to prepare a granulated product (hereinafter referred to as pellet) having a predetermined particle size and properties,
It is distributed and supplied from the upper part of the shaft kiln 5 by the charging chute 8 so as to be uniformly distributed in the kiln 5.

The combustion air is blown from the lower part of the shaft kiln 5 by the suction fan 6 to cool the calcined clinker, and the temperature of the clinker is raised by the heat of the burned clinker, and the fuel in the pellets is heated in the calcining zone formed in the upper part of the kiln. To burn the clinker.

The combustion exhaust gas generated at that time is sucked by the exhaust fan 7, cooled to about 200 ° C. while exchanging heat with the pellets supplied from the top of the kiln 5, and the kiln 5
Is discharged from the top of. The combustion exhaust gas may be collected by the dust collector 9 and then discharged through the chimney 10.

On the other hand, the calcined clinker is the extraction device 11 provided at the bottom of the kiln while being cooled by the combustion air as described above.
Is discharged to the outside.

[Problems to be solved by the invention]

When the clinker is fired in the shaft kiln, the properties that the pellet should have are as follows.

1) The particle size of the pellets should be such that ventilation of the kiln is not obstructed, and that the particle size is uniform enough not to cause insufficient firing or overfiring.

2) After pelletizing, it should have such strength that it will not be damaged during feeding to the kiln and moving to the firing zone.

3) Porosity and strength not to be damaged by gas or steam generated during calcination and evaporation of water.

When pellets having the above properties are granulated by a pan-type granulator, the plasticity of clay in the raw material mixture is one of the factors that most affect granulation properties. The plasticity of clay is a characteristic peculiar to each clay, so there is a problem that it is necessary to use clay having an appropriate plasticity, and further, the supply amount of powder raw material, the rotation number of the bread and the inclination angle,
Since factors such as the amount of water added have an effect, there is also a problem in that these adjustments require careful attention and require manpower.

Further, there is a problem that the amount of heat for evaporating the water added in the granulation step is required, and the fuel consumption rate becomes large.

[Means for solving problems]

The present inventors have studied the means for solving the above problems, and have developed the following means.

The present invention, in a cement clinker firing method using a shaft kiln, mixes limestone and clay in a predetermined ratio to prepare a compounding raw material, pulverizes the compounding raw material into a powdery raw material, and a predetermined amount of the powdery raw material. The present invention provides a cement clinker firing method characterized by mixing crushed coke and / or anthracite as a mixed raw material, and then press-molding the mixed raw material to granulate and fire.

[Action]

The present invention will be described based on the embodiment shown in FIG. FIG. 1 is a schematic diagram of the firing process of the present invention.

A powder raw material obtained by crushing a mixed raw material made of limestone, clay, silica stone, etc. in a raw material mill (not shown) and anthracite or coke powder are weighed by each weighing machine 1 to a predetermined ratio, and screwed. The mixed raw material mixed by the mixing device 2 including a conveyor is forcibly supplied between the press rollers 14 by a screw conveyor 13 with a supply amount adjusting mechanism attached to a pressure molding granulator. A hydraulic pressure adjusting mechanism 15 is attached to the press roller 14, and the material supply amount and the surface pressure of the press roller 14 are hydraulically adjusted so that a granulated material having strength according to the purpose of use can be granulated. Is being adjusted.

The pressing pressure at the time of granulation needs to be adjusted so as to have porosity, tackiness and strength that are not damaged by the gas generated during calcination.

In addition, the surface of the press roller 14 is provided with innumerable recesses so that a granulated product having a shape suitable for the usage situation can be manufactured. Therefore, the diameter of the granulated pellets is preferably about 15 to 25 mm in width and about 10 to 15 mm in thickness in consideration of ventilation resistance when supplied to the shaft kiln 5 and the difficulty of firing.

Since the mixed raw material is pressure-molded, it can be granulated using any clay.

As the press-molding granulator, other types than the above can be used.

The granulated material granulated as described above is removed by a sieving device 16 to remove the incompletely shaped granulated material, and then is uniformly distributed in the kiln from the top of the shaft kiln 5 by the charging chute 8. As distributed. As described above, the combustion air blown from the bottom of the shaft kiln 5 by the blower fan 6 cools the calcined clinker and burns the fuel in the granulated material in the calcining zone to calcine the clinker. The cooled clinker is discharged to the outside of the kiln 5 by the clinker discharging device 10. Further, the combustion exhaust gas generated in the firing zone is sucked by the exhaust fan 7 while exchanging heat with the supplied granules and discharged from the top of the kiln 5, or the dust collector 9 and the chimney 10 are passed through the system. It is discharged outside.

〔Example〕

In the process outlined in Fig. 1 and using the equipment used in Table 1, coke was used as fuel and clinker firing was performed at a mixed raw material supply rate of 75 kg / h, and the shaft kiln at that time was used. The heat balance of is shown in Table 2.

As a comparative example, baking was performed using this mixed raw material using a pan-type granulator instead of the pressure-molding granulator, but the baking could not be performed due to destruction of pellets. Also, instead of the clay used in the examples, clay capable of being baked by a baking method using a pan-type granulator was used, and the heat balance when baking was performed using the pan-type granulator is also shown in Table 2. .

As a result, clay that could not be used when using a conventional bread granulator can be used, the firing efficiency can be improved by 6%, the fuel consumption rate can be reduced by 17%, and the specific firing capacity can be reduced. Could be as large as 15 kg-cl / m ³ h.

〔The invention's effect〕

It was found that the use of the cement clinker burning method of the present invention has the following excellent effects.

(1) By using a pressure molding granulator, there is no restriction on the selection of a clay raw material that has a large amount of use next to limestone among firing raw materials, and it is possible to use clay near the firing location. It has also become possible to reduce raw material transportation costs.

(2) It becomes possible to omit or simplify the steps of adjusting the amount of water added and the granulator due to changes in raw material properties,
Labor saving or process automation has become easier.

(3) Since the granulated product itself is a dry product, the amount of heat required to evaporate water is unnecessary, and the fuel consumption rate is reduced by 17%.
Furthermore, since the specific firing capacity is increased by about 15 kg-cl / m ³ h,
It has become possible to reduce manufacturing costs.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a clinker firing process according to the method of the present invention, and FIG. 2 is a schematic diagram of a conventional clinker firing process. 1 ... Weighing machine, 2 ... Mixing device 3 ... Pan-type granulator, 4 ... Water meter 5 ... Shaft kiln, 6 ... Blow fan 7 ... Exhaust fan, 8 ... Input chute 9 ... … Dust collector, 10 …… Chimney 11 …… Extractor, 12 …… Supply tank 13 …… Screw conveyor 14 …… Press roller, 15 …… Pressure adjusting mechanism 16 …… Sieving device

Front page continued (72) Inventor Yoshiyuki Tamura 1-5-1, Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Mining Cement Co., Ltd.

Claims (1)

(57) [Claims] 1. A cement clinker firing method using a shaft kiln, wherein limestone and clay are mixed in a predetermined ratio to prepare a compounding raw material, and the compounding raw material is pulverized into a powdery raw material, and a predetermined amount of the powdery raw material is prepared. The cement clinker firing method, which comprises mixing the crushed coke and / or anthracite as a mixed raw material, and granulating and firing the mixed raw material by pressure molding.