JPH05146697A - Dry type tube mill - Google Patents

Abstract

PURPOSE:To provide a dry type tube mill capable of increasing pulverizing throughput above a tube mill fitted with a stationary classifier and of being miniaturized in comparison with the same. CONSTITUTION:Grinding material 2 is ground in a mill drum 1 by rotating the mill drum 1 by a motor. The ground material 2 is sent to a rotary classifier 11 from the inner cylinder 4 of a trunnion by carrier air 3. At this time, in the rotary classifier 11, respective classification blades 12 are rotated and moved around a vertical driving shaft 15 by this driving shaft 15. The ground material 2 in carrier air 3 is classified into coarse powder 8 and fine powder 9 by the respective classification blades 12. The coarse powder 8 is scattered to the outer part in the radial direction and allowed to fall along the inner wall surface of the rotary classifier 11 and transferred into the mill drum 1 together with a pulverizing raw material 13 by a ribbon conveyor 10 and reground. On the other hand, fine powder (product) 9 is discharged to the outside of the mill.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry tube mill for crushing coal, cement or the like and classifying it.

[0002]

2. Description of the Related Art A conventional double-suction tube mill with a fixed classifier will be described with reference to FIG. 6, in which 1 is a mill drum, 2 is crushed material, 3 is carrier air, 4 is a trunnion inner cylinder,
5 is a fixed classifier, 6 is a vane, and 7 is an inner corner with the vane 6 mounted on the upper part.
Is a type of cyclone and is built in the fixed classifier 5.

8 is a coarse powder, 9 is a fine powder (product), 10 is a ribbon conveyor of the fixed classifier 5, 14 is a fine powder outlet, and 18 is a fine powder outlet.
Is a girth gear, 19 is a carrier air inlet duct, and 20 is a trunnion bearing. In the double suction type tube mill with a fixed classifying device shown in FIG. 6, a motor (not shown) is used.
The mill drum 1 is rotated by the above to pulverize the pulverized material 2 in the mill drum 1, and the pulverized pulverized material 2 is sent by the carrier air 3 to the trunnion inner cylinder 4 → the fixed classifier 5 and the fixed classifier 5 Put it in the built-in inner cone (inner cone, which is a type of cyclone) 7, classify into coarse powder 8 and fine powder 9, and discharge the fine powder (product) 9 out of the mill, while the coarse powder 8 is fed into the inner cone 7 Then, it is dropped along the inner wall surface of No. 1 and transferred to the inside of the mill drum 1 again by the ribbon conveyor 10 of the fixed classifier 5 to be re-ground.

[0004]

The conventional double classification type tube mill with fixed classifier shown in FIG.
I had the following problem. That is, the Duube mill (vertical mill)
Is used for fine pulverization of high-fuel ratio coals such as anthracite and semi-anthracite that are difficult to pulverize, but these coals have low volatile components and are flame-retardant. In order to reduce the amount of fine powder, it is necessary to increase the fineness and reduce the proportion of coarse powder as much as possible.

In this respect, the conventional double classification type tube mill with a fixed classifier shown in FIG. 6 is provided with a fixed classifier 5, and the fixed classifier 5 has an inner cone (a type of cyclone). Inner cone)
7 is built in. However, since cyclones are centrifugal classification with free and semi-free vortices, they have the drawbacks that precise classification is difficult to obtain (classification sharpness is poor) and that they are not very suitable for classification of high-concentration powder. In general, the fixed classifying device 5 has a poor classifying performance.

That is, the tube mill provided with the fixed classifier 5 has the following drawbacks. (1) Since the accuracy of classification of fine powder to be a product is low, it is necessary to operate the tube mill with a high fineness by reducing the pulverization processing amount in order to reduce the ratio of coarse powder in the product. (2) Since the fine powder 9 is considerably contained in the coarse powder 8 which is classified by the fixed classifying device 5 and returned to the inside of the mill drum 1 to be re-ground, the amount of return (circulation amount) into the mill drum 1 Is poor and the amount of pulverization processing is small.

The present invention is proposed in view of the above problems, and the object of the present invention is to increase the amount of pulverization processing as compared with a tube mill with a fixed classifier. Another point is to provide a dry tube mill that can be made smaller than a tube mill with a fixed classifier.

[0008]

In order to achieve the above object, the present invention is a dry tube mill for pulverizing and classifying coal, cement, etc., in which rotary classifiers are provided at both ends of the dry tube mill. There is.

[0009]

The dry tube mill of the present invention is constructed as described above, and the mill drum is rotated to pulverize the pulverized material in the mill drum, and the pulverized pulverized material is sent to the rotary classifier by the carrier air and rotated. The crushed material in the carrier air is classified into coarse powder and fine powder by each classification blade rotating around the central axis.

[0010]

EXAMPLE A dry type tube mill of the present invention is shown in FIGS.
1 is a mill drum, and 2 is a mill drum.
Is crushed material, 3 is carrier air, 4 is a trunnion inner cylinder, 8 is coarse powder, 9 is fine powder (product), 10 is a ribbon conveyor, 13 is a crushing raw material, 14 is a fine powder outlet, 18 is a girth gear, and 19 is carrier air. The inlet duct, 20 is a trunnion bearing.

Reference numeral 11 denotes a rotary classifier provided at both ends of the dry tube mill. The rotary classifier 11 has a plurality of classes vertically mounted on upper and lower support plates 16 and 17 centering on a vertical drive shaft 15. The blade 12 is provided, and each classification blade 12 is rotatably moved around the vertical drive shaft 15 by the vertical drive shaft 15, and the pulverized material 2 in the carrier air 3 is moved by each classification blade 12.
Is classified into coarse powder 8 and fine powder 9.

Next, the operation of the dry tube mill shown in FIGS. 1 to 3 will be specifically described. The mill drum 1 is rotated by a motor (not shown), and the pulverized material 2 in the mill drum 1 is rotated.
Is crushed, and the crushed crushed product 2 is sent to the trunnion inner cylinder 4 → rotary classification device 11 by the carrier air 3. At this time, in the rotary classifier 11, the vertical drive shafts 15 rotate and move the respective classification blades 12 about the vertical drive shafts 15, and the respective classification blades 12 rotate the pulverized material 2 in the carrier air 3 into coarse powders 8. And fine powder 9.

Then, the coarse powder 8 is scattered outward in the radial direction and dropped along the inner wall surface of the rotary classifier 11, and is fed into the mill drum 1 by the ribbon conveyor 10 into a pulverized raw material 13.
At the same time, the fine powder (product) 9 is discharged to the outside of the mill while being transferred and pulverized again. The operation of the rotary classifier 11 will be described more specifically. The rotary classifying device 11 includes the classifying blade 1
Since it is the centrifugal classification of the forced vortex generated by No. 2, precise classification and classification of high-concentration powder can be easily obtained.

The classification principle is based on the following two actions. (A) As shown in FIG. 2, the balance of the forces acting on the particles entering the classification blade 12 is such that the particles in the blade have a fluid resistance R in the centripetal direction due to the air flow and a centrifugal force F due to the rotational movement of the blade. Acts and each force is expressed by the following equation.

[0015]

[Equation 1]

Dp: particle diameter (cm), μg: gas density (pois), Vr: air flow centripetal velocity (cm / se)
c), V ₀ : Blade speed ((cm / sec), r: Blade radius (cm), _CD : Resistance coefficient, that is, F> R when the classifier is operated under certain conditions. The coarse particles are discharged to the outside of the classifier, and the fine particles with F <R flow into the inside of the classifier to be classified into the coarse particles and the fine particles. (B) Repulsion angle α after collision of the particles with the blade Is as follows: The situation where the particles collide with the blade is shown in FIG.
When the repulsion angle α after the particles have collided with the blade is directed to the outside of the tangent line, the particles on the outside of the classifier are easily discharged,
On the contrary, when the repulsion angle α is directed inward of the tangent line, it easily flows into the classification device.

It is known that an air flow is generated between the classifying blades, but fine particles make a motion close to a swirling flow, and coarse particles move away from the swirling flow and make a motion close to a straight line. For this reason, the repulsion height α of the fine particles after colliding with the blades faces the inside, and the coarse particles easily face the outside, so that the classification of the fine particles and the coarse particles is performed. The rotary classifying device 11 of the present invention
FIG. 4 shows the comparison test results of the classification performance of the attached double-suction type tube mill and the conventional double-suction type tube mill with the fixed type classification device 5, and FIG.

FIG. 4 shows an example of classification performance of 75 μm.
The relationship between the passage amount (fine powder amount) and the 149 μm passage amount (coarse powder amount) is shown. The double-suction type tube mill with the fixed classifier 5 requires 95% of the 75 μm passage amount to make the 149 μm passage amount 0%, but the double-suction type tube mill with the rotary classifier 11 has 7
There is a clear difference in classification performance, such as a passing amount of 5 μm of 85% is sufficient, and the greater the passing amount of 75 μm, the greater the difference.

This is because, as can be seen from the classification principle of the rotary classification device 11, the proportion of fine powder increases and the classification accuracy increases as the peripheral speed of the classification blade 12 increases. FIG. 5 shows the comparison test results of the crushing throughput as described above. From this FIG. 5, it can be seen that the double-suction type tube mill with the rotary classifier 11 has a larger crushing treatment amount than the double-suction type tube mill with the fixed type classifier 5, and the difference is that the passing amount is 75 μm. The bigger it gets.

The reason for this is that, as described above, the rotary type classifying device 11 is characterized in that the proportion of the fine powder 9 increases as the peripheral speed of the classifying blade 12 increases, and the classification accuracy increases. Thus, it can be seen that the classification accuracy of the classifier has a great influence on the performance of the tube mill.

[0021]

As described above, in the dry tube mill of the present invention, the mill drum is rotated to pulverize the pulverized material in the mill drum, and the pulverized pulverized material is sent to the rotary classifier by the carrier air, and the rotation center shaft is rotated. The crushed material in the carrier air is classified into coarse powder and fine powder by each classifying blade rotating around the center. The classification accuracy of this rotary classifier is high, the ratio of coarse powder in the fine powder to be the product can be very small, and it is not necessary to operate the tube mill with a small amount of fine powder (it operates at high fineness). (Without need), the amount of crushing can be made larger than that of the tube mill with a fixed classifier.

Further, since the ratio of the fine powder contained in the coarse powder to be re-pulverized by returning it to the mill drum can be reduced, the amount of return (circulation amount) into the mill drum can be reduced, and the pulverization efficiency can be improved. Therefore, the crushing amount can be made larger than that of the tube mill with a fixed classifier. Further, since the crushing amount can be made larger than that of the tube mill with the fixed classifier as described above, there is an effect that the tube mill can be made smaller than the tube mill with the fixed classifier.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of a dry tube mill of the present invention.

2 is a cross-sectional plan view taken along the line AA of FIG.

FIG. 3 is a partially enlarged plan view of FIG.

FIG. 4 is an explanatory diagram showing the results of a comparative test of the classification performance of the dry tube mill with a rotary classifier of the present invention and a conventional dry tube mill with a fixed classifier.

FIG. 5 is an explanatory diagram showing the results of a comparative test of the crushing throughputs of the dry tube mill with a rotary classifier of the present invention and a conventional dry tube mill with a fixed classifier.

FIG. 6 is a vertical cross-sectional side view showing a conventional dry type rotary mill with a fixed classifier.

[Explanation of symbols]

 1 Mill Drum 2 Crushed Material 3 Conveying Air 4 Trunnion Inner Cylinder 8 Coarse Powder 9 Fine Powder (Product) 10 Ribbon Conveyor 11 Rotary Classifier 12 Classification Blade 13 Grinding Raw Material 14 Fine Powder Exit

Claims (1)

[Claims] 1. A dry tube mill for pulverizing and classifying coal, cement or the like, wherein a rotary classifier is provided at both ends of the dry tube mill.