JPH0375219B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a dry tower mill.

The dry tower type crusher is, for example,
This is a known pulverizer also disclosed in No. ``Dry Tower Type Attrition Pulverizer''. As shown in Figures 1 and 2, this crusher has a shaft at the center of a closed circular column 1, and a screw 3 is attached to this shaft, and a geared motor 4 lifts the contents of the screw 3. Rotate it in the same direction. The feed ore is supplied in a constant quantity into the crusher by a rotary valve 5. Although pulverization is sometimes carried out using feed minerals, the pulverizer is usually filled with a pulverizing medium such as steel balls. The supplied material to be crushed is lifted up by the screw 3 together with the material to be crushed and falls along the wall, during which time it is crushed by the grinding action of the grinding medium and the material to be crushed. Hereinafter, this pulverized product will be referred to as powder.

Powder is discharged outside the crusher, but in the crusher shown in FIG.
It is collected in The airflow is circulated from the blower 6 to the crusher again. In the case of the pulverizer shown in Figure 2, the powder is passed through the slit (not shown) from the bottom end of the pulverizer.
It is extracted by the airflow from the blower 6, discharged outside the crusher, and collected by the bag filter 7.

The above-mentioned conventional tower-type crusher had drawbacks such as inconsistent powder output, so the inventors first developed a perforated plate to pass the powder through the bottom of the closed circular column of the tower-type crusher. A proposal was made to provide a powder retention chamber below this perforated plate (patent application 1986-45678).
However, this improved powder discharge and
As a result, it became possible to change and adjust the amount of powder extracted as desired. Apart from this proposal, there is also a proposal to make the downward movement of powder in the retention chamber uniform (Japanese Patent Application No. 58-99094), or a proposal to provide concentric grooves on the upper surface of a perforated plate (Patent Application No. 58-99094). Showa 58
-99093), which have improved grinding efficiency and reduced the amount of grinding media wasted.

In this way, the tower-type pulverizer, which has a perforated plate on the bottom of the closed circular column that allows the powder to pass through, has shown excellent performance, but the controllable range of the amount of powder extracted is at the upper limit of 150 It was up to ~200%. The inventor aims to further increase this limit by
After various studies and repeated experiments, we discovered that the gap between the lower end of the screw blade and the perforated plate is an important factor in further improving the performance of the crusher. In other words, the gap between the lower end of the conventional screw blade and the perforated plate is 5 to 50 mm, which is the thickness of the grinding media (steel balls) layer.
Since it was normal to leave six or more layers open, the movement of the grinding media slowed down in this area, especially closer to the perforated plate, and the powder was filled and compressed between the grinding media.
The amount of powder extracted remains low (small amount) and is easy to stabilize.
This made it difficult to adjust the amount to a high level (large amount). Since the amount of powder extracted greatly affects the circulation rate of the pulverizer, that is, the grinding efficiency of the pulverizer, there has been a strong desire for a system that can easily and significantly adjust the amount of powder extracted.

The present invention relates to the improvement of such a tower-type crusher, and based on the above knowledge, the gap between the lower end of the screw blade and the perforated plate is made as small as possible, and the shape of the lower end of the screw blade is devised to reduce the rotational movement of the crushing media. Research was conducted with the aim of expanding the adjustment range of the amount of powder extracted by extending the grinding over the entire layer of the grinding media as much as possible.

The inventor of the present invention conducted repeated experiments to create products of various sizes with the aim of reducing the above-mentioned gap, and found that the smaller the gap, the better the movement of the grinding media and the extraction of powder. Vibration occurred, which was thought to be caused by the screw getting caught in the lower end of the screw blade, and it was determined that there was a risk of adversely affecting operations. As a result of further study, by changing the shape of the lower end of the screw blade and carving a new wavy cutout with a combination of peaks and valleys on the entire lower end of the screw blade, it was possible to prevent the above vibration and achieve the desired purpose. It became possible.

The present invention will be explained below based on the drawings. FIG. 3 is an explanatory diagram showing the relationship between the blades of the screw 3 and the bottom plate (perforated plate) 8 in a conventional tower type crusher. 9 is a powder retention chamber, and 10 is a screw conveyor for discharging the powder. The lower end of the blade of the screw 3 is horizontally flat, and this screw 3
The gap between the lower end of the blade and the perforated plate 8 below it is provided with 5 to 6 or more layers of grinding media. FIG. 4 is an explanatory diagram when this gap is set to almost 0 (5 mm or less in experiments). In this case, although the powder extraction ability was improved, vibrations occurred, which were thought to be caused by the grinding media (17 mm diameter steel balls) being caught in the grinding medium. It was also found that the minimum value of the gap at which there is no risk of vibration generation is about three layers of the grinding media layer thickness. However, in a gap of three or more layers, the effect of improvements to improve the powder extraction ability is very small, and after further study, we created something that meets our goals and is free from vibration. In other words, the lowermost end of the screw blade is flat in the horizontal direction, but has a shape in which notches made of wavy irregularities are carved. This is an explanatory diagram of the embodiment shown in FIG. FIG. 6 shows an enlarged view of the main parts of this example, and the dimensions of each part shown in the figure are: notch height h ₁ =2 to 2.5D (D is the diameter of the grinding medium)
It is preferable that the pitch of the lower end of the notch p ₁ = 3 to 3.5D, and the gap h ₂ between the lowermost end of the screw and the bottom plate (perforated plate) = 1/3D to 1/2D, and as a result of testing with this, it was found that the powder extraction amount control range was significantly expanded, and it was possible to extract up to about 500% of the steady extraction amount. Regarding the details of the shape of the notch, it has been confirmed that changing the waveform to a combination of straight lines and curves, or edging each corner after forming, has some effect on improving the control range of the amount of powder extracted. However, since this does not change the main idea, the detailed shape of the wavy cutout is not limited.

According to the present invention, since the range in which the amount of powder extracted can be changed is expanded, it is possible to easily change the amount of powder extracted to the optimum state when pulverizing objects with different characteristics, and it is also possible to We were able to further increase efficiency.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams of a known dry tower-type crusher, Figure 3 is an explanatory diagram of a crusher with a perforated plate at the bottom, and Figure 4 is an explanatory diagram of the lower end of the screw and the bottom plate (perforated plate). Figure 5 is an explanatory diagram of an example in which the lower end of the screw is modified into a notch shape and brought close to the bottom plate (perforated plate), and Figure 6 is the relationship between this notch and the bottom plate. FIG. 6 is a partially enlarged view of FIG. 5 showing dimensions; 1... Closed circular tower, 2... Cyclone, 3... Screw, 4... Geared motor, 5... Rotary valve, 6... Blower, 7... Bag filter, 8... Perforated plate, 9... Retention chamber , 10... Screw conveyor, h ₁ ... Notch height, h ₂ ... Gap between the lower end of the screw blade and the bottom plate (perforated plate), p ₁ ...
Pitch at the bottom edge of the notch.

Claims (1)

[Claims] 1 A closed round tower with a screw in its center,
In a tower-type crusher in which the bottom of the closed circular tower is a perforated plate through which the material to be crushed passes, and a retention chamber for the material to be crushed is provided below the perforated plate, the lower end of the screw blade has a
A tower-type crusher characterized in that a wave-like notch is carved and the distance between the lower end of the screw blade and the perforated plate is 1/3 to 1/2 of the diameter of the crushing medium.