JPH0764604B2 - Cement clinker crushing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for crushing cement clinker, and in particular to an effective crushing of cement clinker by making the most of the respective characteristics of a roller mill and a ball mill.

[Prior Art]

Cement is produced by mixing additives such as gypsum with clinker produced during the firing process and then grinding it.

Fig. 2 is a diagrammatic system diagram showing an example of a conventional crushing process. Cement clinker produced in the preceding processes (burning process, cooling process, etc.) is continuously and quantitatively extracted from a storage bin 31 storing the cement clinker, and mixed with additives such as gypsum and slag extracted from storage bins 32 and 33. The mixture is then transported by a conveyor 34 from a supply port 36 to a crusher 35.
are supplied to.

There are various types and models of cement clinker grinders in use, but this example is a so-called open-circuit ball mill with two chambers separated by a partition plate 38, and air is drawn into the mill by a ventilator 41 to cool the material to be ground and prevent over-grinding. As the material passes through each chamber of the mill 35, it is subjected to the impact force and abrasive action of the falling balls, is ground, and is discharged from the outlet 37. Along with the ventilation within the mill, the material is collected in a dust collector 40 and discharged as product cement 42.

[Problem to be solved by the invention]

Ball mills, which have been used for a long time as a grinding machine for cement clinker, have the advantage that the particle size distribution of the product cement is relatively wide, and in this respect the concrete properties are excellent. However, the grinding power required is large, and the product temperature rises during grinding, which has a negative effect on the product properties.
The water spraying method used to suppress temperature rise has the problem of being troublesome to maintain. Specifically, the clinker supplied to the ball mill from the previous process contains lumps with a maximum particle size of around 40 mm, and the crushing mechanism within the ball mill results in poor crushing efficiency, requiring a large unit of power consumption to crush the material to the specified particle size.

The clinker fed to the ball mill is generally 70 to 100
°C, and most of the power consumed for grinding is converted into heat within the mill body, so the temperature of the material to be ground rises significantly during the grinding process. In order to suppress this temperature rise, a water sprinkler is installed on the casing of the outlet 37 of the ball mill 35.
Although the installation of a water sprinkler system 39 to sprinkle water inside the mill is widely adopted, it does not achieve a sufficient temperature drop, and the sprinkling of water has an adverse effect on the quality of the cement product. At the same time, cement that is not sufficiently cooled is not only difficult to handle, but also deteriorates the quality of the added gypsum and has an adverse effect on the quality of the ready-mixed concrete. Furthermore, not only is the sprinkler system difficult to maintain, but when a large amount of water is sprinkled, water droplets remain in the exhaust, requiring the use of an expensive electrostatic precipitator 40.

In contrast, roller mills, which have recently been trialed for grinding cement clinker, have the advantage of low power consumption as a grinding system, and because a large amount of air passes through the mill, there is little temperature rise within the mill, resulting in the production of relatively low-temperature finished cement.However, because the finished cement has a relatively narrow particle size composition, there are problems with concrete properties in terms of the initial strength of the concrete, the amount of mixing water required, and workability during concrete placement, so they have not yet become widespread.In particular, because their mechanism is to grind a wide range of particle sizes, including the aforementioned lumpy materials, into fine powder in one go, they are not suitable for producing products with fine particle sizes and therefore large specific surface areas, and their uses are limited.

[Means for solving the problem]

The present invention was made in light of these circumstances and aims to provide an effective grinding method that makes use of the grinding characteristics of both roller mills and ball mills. The gist of this invention is that the grinding process for cement clinker is composed of a primary grinding process and a secondary grinding process, viewed in the direction of the clinker flow, in which a roller mill is used in the primary grinding process and a ball mill is used in the secondary grinding process. After the clinker is primarily ground by the roller mill, it is separated into coarse powder and fine powder, and the fine powder is used as a product, while the coarse powder is subjected to secondary grinding by a ball mill.

[Example]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the drawings show one example of a specific implementation, and the present invention is not limited to these illustrated examples. The present invention can be implemented in the same way with other configurations or partial design changes in accordance with the spirit described above and below.

FIG. 1 is a schematic flow diagram showing a cement clinker crushing process which can be used to carry out the method of the present invention, and the same reference numerals are used to designate the equipment having the same functions as those in the conventional crushing process shown in FIG.

In Figure 1, the cement clinker crushing process is composed of a primary crushing process 2 and a secondary crushing process 3, as seen in the direction of the clinker flow. A roller mill 51 is used in the primary crushing process 2, and a ball mill 35 is used in the secondary crushing process 3.
is used.

Therefore, the clinker and gypsum from the storage bins 31, 32 are sent by conveyor 34 to roller mill 51 in primary crushing process 2. Roller mill 51 is equipped with an intake 53 for conveying air connected to forced draft fan 52 at the bottom, a supply port 54 for the material to be crushed at the side, and an outlet 55 for the crushed product and exhaust air at the top, and outlet 55 is connected to an appropriately arranged induced draft fan 58 via a collector 56 such as a cyclone and a bag-type or electric dust collector 57 arranged in series.

Clinker is supplied to the roller mill 51 through the supply port 54 by the conveyor 34 and is subjected to primary crushing in the roller mill 51. The primary crushed product is discharged from the discharge port 55 accompanied by conveying air supplied by the forced draft fan 52 through the air intake port 53.
The material is sucked into an induced draft fan 58 and guided to a collector 56. The primary crushed product is separated into coarse and fine powder by the collector 56, and the fine powder is collected by a dust collector 57 and immediately removed as the cement product 42. Meanwhile, the coarse powder in the primary crushed product separated by the collector 56 is supplied to the ball mill 35 in the secondary crushing process 3, where it is crushed to a predetermined particle size and then removed as the cement product 42.

According to the configuration of the present invention, the roller mill 51 is a facility that consumes little power for grinding, so it is not necessary to use a ball mill for secondary grinding.
The power consumption of the entire grinding process is reduced by the ratio of the grinding work in the roller mill 51 to that in the roller mill 35. In particular, the fine powder in the clinker that is primarily ground by the roller mill 51 is collected by the collector.
Since the cement is separated at 56 and immediately extracted as product cement, the grinding power consumption at the ball mill 35 is reduced.
In this case, the coarse particles in the clinker that have been primarily crushed by the roller mill 51 are separated by the collector 56 and then crushed by the ball mill 35 for the second time, so that the particle size composition of the product cement does not cause any problems with the concrete properties.

Furthermore, in the roller mill 51, the finely crushed clinker is blown by the forced draft fan 52 and is subjected to heat exchange in a state where it is suspended at a high concentration in the large amount of conveying air rising inside the mill 51, so it is cooled extremely quickly, uniformly and efficiently to the inside of the particles. As a result, low-temperature clinker with a uniform particle size is supplied to the secondary crushing process 3, so the water sprinkler
Even when using 39, temperature control of the crushed product becomes extremely easy, making it possible to easily produce cement at a relatively low temperature, and avoiding adverse effects on the quality of the cement product.

In addition, when the primary crushing work amount in the roller mill 51 is selected to be greater than the secondary crushing work amount in the ball mill 35,
Since the cement product from the roller mill 51 is already quite fine, the grinding efficiency can be further improved by using a single-chamber ball mill 35 as shown in the figure and employing small-diameter balls suitable for grinding fine particles. In addition, since the amount of heat generated within the ball mill 35 is small, the temperature of the material being ground can be kept low without the need for a water sprinkler system.

Therefore, there is no need to bother with the maintenance of a water sprinkler system, and furthermore, since the exhaust gas from the ball mill 35 does not contain water droplets, a bag-type dust collector, which requires low installation costs, can be used as the dust collector 40 without any problems.

In these methods, there are of course no limitations on the type or model of the primary grinding roller mill and the secondary grinding ball mill, the ratio of the grinding work shared between the primary grinding step and the secondary grinding step, the type of additive, or its blending position, etc. Furthermore, by installing an additional roller mill in addition to an existing ball mill, the method of the present invention can be easily carried out, and the processing capacity of the ball mill can also be increased.

The present invention is configured as described above and is extremely advantageous in terms of power consumption, product quality, operation, maintenance, etc. in the cement clinker crushing process.

[Effects of the Invention]

According to the present invention, the crushing process of cement clinker is composed of a primary crushing process and a secondary crushing process when viewed in the direction of clinker flow, and by using a roller mill in the primary crushing process and a ball mill in the secondary crushing process, the power consumption of the entire crushing process is reduced by a ratio of the crushing work by the roller mill to that by the secondary crushing ball mill.

Furthermore, the clinker that has been finely crushed in the roller mill is cooled sufficiently before being fed to the ball mill (secondary crushing step), making it easy to produce relatively low-temperature cement.

Furthermore, the fine powder in the clinker that has been primarily crushed in the roller mill is immediately extracted as product cement, and only the coarse powder is supplied to the ball mill, so the power consumed for crushing in the ball mill can be reduced.

[Brief explanation of the drawings]

Fig. 1 is a schematic system diagram showing a cement clinker crushing process that can be used in carrying out the method of the present invention, and Fig. 2 is a diagram of a conventional method equivalent to Fig. 1. [Explanation of symbols] 2... primary crushing process, 3... secondary crushing process, 31... clinker storage bin, 32... gypsum storage bin, 33... additive storage bin, 35... ball mill, 39... sprinkler system, 40, 57... dust collector, 41, 58... induced draft fan, 42... product cement, 51... roller mill, 52... forced draft fan, 56... dust collector.

Claims (1)

[Claims] Claim 1: The crushing process of cement clinker is composed of a primary crushing process and a secondary crushing process when viewed in the direction of the flow of the clinker, and the primary crushing process uses a roller mill, and the secondary crushing process uses a roller mill.
A method for crushing cement clinker, characterized in that a ball mill is used in the secondary crushing process, and the clinker crushed primarily by the roller mill is separated into coarse powder and fine powder, and the fine powder is used as a product, while the coarse powder is crushed secondarily by the ball mill.