JPH0227017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method in which a raw material fed onto a grinding table rotating around a vertical axis is sandwiched between the grinding table and a rotatable grinding roller that is pressed toward the top surface of the grinding table. The present invention relates to improvements in roller mills for crushing, and in particular to roller mills aimed at reducing vibration and improving crushing efficiency.

Conventionally, drum mills such as ball mills have been used to crush cement clinker, blast furnace slag, etc., but such drum mills have low efficiency, increase running costs, and are extremely uneconomical.

From this point of view, efforts have been made in recent years to use the above-mentioned relatively efficient roller mills for pulverizing cement clinker, blast furnace slag, and the like.

However, in the case of a roller mill, unlike a drum mill, the raw material is not crushed by the collision and grinding of a crushing medium such as balls with the raw material, but rather between the crushing table supported on the machine base and the crushing roller. Since the crushed raw material is actively crushed by the clamping pressure between the two, vibrations generated in the crushing rollers, etc. are often transmitted to the machine base, so the vibrations are larger than in drum mills. This is an obstacle to using roller mills for grinding cement clinker and blast furnace slag.

Furthermore, although it is known that roller mills have better grinding efficiency than drum mills, the efficiency of current roller mills is not necessarily satisfactory.
It is thought that there is considerable room for improvement.

The causes of vibrations in roller mills as described above, especially those caused by the vibrations of the grinding rollers, can be roughly divided into those caused by the hardness of the raw material or changes in it, and those caused by the slippage of the grinding raw materials. There is so-called self-excited vibration that occurs in the radial direction.
The present invention aims to reduce the latter self-excited vibration and improve grinding efficiency.

First, the cause of the self-excited vibration will be explained with reference to FIGS. 1 to 4.

FIG. 1 is a side sectional view showing the structure of a conventional general roller mill. In the figure, 1 is a crushing table;
It is actively rotated around a vertical shaft 2 by a drive source such as a motor (not shown).

An annular groove 3 centered on the vertical axis 2 is formed on the upper surface of the crushing table 1, and the annular groove 3 has an arcuate cross-sectional shape that is depressed downward as shown in the figure.

In addition, the upper part of the crushing table 1 has an outer circumferential surface 4.
is a set of crushing rollers 5 facing the annular groove 3
a, 5b are attached to the annular groove 3 while being pressed and biased toward the annular groove 3 through a gap 6 between the annular groove 3 and the annular groove 3.

That is, the crushing rollers 5a, 5b are connected to roller shafts 9a, 9 inserted into the crushing chamber 8 from the main casing 7.
b, and the roller shafts 9a, 9b are supported by horizontal shafts 10a, 10 provided outside the main casing 7.
b is fixed to an arm 11a11b swingably attached to the vertical inner surface thereof, and the tip of a bolt 13 screwed to the stopper arm 12 is attached to the arm 11.
a, 11b, the crushing roller 5
A minimum width of the gap 6 between a, 5b and the annular groove 3 is set.

Further, each tip of the pair of arms 11a, 11b is connected to a rod 15a, 15 via a tensioning device 14.
connected by b.

Therefore, the raw material supplied to the center of the top surface of the grinding table 1 moves toward the outer circumference, that is, into the annular groove 3, due to the conical top surface shape of the grinding table 1 and the centrifugal force caused by the rotation of the grinding table 1. It is caught in the gap 6 between the crushing rollers 5a, 5b and the crushing table 1, and crushed under pressure.

However, if the layer of raw material bitten by one of the crushing rollers, for example 5a, is too thick, the crushing roller 5a will resist the rotational biasing force of the tensioning device 14 and rotate in the direction of escaping upward. The rotational force is applied to the arm 11 to which the other crushing roller 5b is attached via the rod 15a, the tension device 14, and the rod 15b.
b, and presses the crushing roller 5b in the direction of the annular groove 3, and the pressing force of the crushing rollers 5a, 5b is automatically adjusted according to changes in the layer thickness of the raw material.

The raw material thus crushed by the crushing rollers 5a and 5b moves to the outer periphery of the crushing table 1 by the centrifugal force of the crushing table 1.
The particles are blown up by an upward air flow flowing out from an upward nozzle 16 that surrounds the outer periphery of the grinding chamber 8, and are sorted by particle size by a sorting device (not shown) installed at the top of the grinding chamber 8. Only the coarse powder is taken out of the grinding chamber 8, and the coarse powder that does not reach a certain particle size is returned to the upper surface of the grinding table 1 and is pulverized.

By the way, the respective curvature radii r and R when cut along a plane passing through the outer circumferential surface 4 of the crushing rollers 5a, 5b and the roller axis 9a or 9b of the annular groove 3 of the crushing table 1 in a conventional roller mill are conventionally R>r. It is becoming.

In the example shown in Figure 2a, R = R ₁ , r = r ₁ , R ₁ = r ₁ + d ₁ d ₁ = d _p , and the thickness d in the radial direction of the crushing roller in the gap 6 between both curved surfaces is The example shown in Figure _b shows the case of R=R ₁ , r=r ₂ , R ₁ > r ₂ + d _p R ₁ > r ₂ + d ₂ , d ₂ > d _p The thickness d of the gap 6 between both curved surfaces is set so that the thickness d ₂ on the front end side or the rear end side is always larger than the thickness d _p on the central part.

Therefore, in conventional roller mills, for example, Fig. 2b
As shown in the figure, since the raw material G that has entered the gap 6 is crushed between the crushing roller 5 and the annular groove 3, the roller shaft 9 that supports the crushing roller 5 is pressed against the raw material G during the clamping process. A pressing force F ₁ is applied in a direction perpendicular to the pressing force F ₁ , and a shearing force F ₂ is applied in a direction perpendicular to this pressing force F 1 , and the raw material crushed by the shearing force F ₂ is transferred from the gap 6 to the roller shaft 9 The liquid tends to flow in the direction of the axis (i.e. forward or backward).

In the roller mill, the layer thickness of the raw material G, that is, the thickness of the gap 6, changes rapidly due to the forward or backward outflow of the raw material, causing uneven rotation of the crushing roller 5, which causes the crushing roller 5 to vibrate. Such self-excited vibrations occur each time a new raw material is bitten and pulverized, and the finer the raw material is, that is, the smaller the coefficient of friction of the raw material powder is, the more the raw material powder in the axial direction of the roller shaft 9 is The greater the tendency of the flow, the more likely this will occur, and in extreme cases, it will become impossible to operate.

In the case of a roller mill, the raw material is crushed by the crushing roller 5.
As shown in FIG. 3 when viewed from the front, compression is not performed at a point 16 directly below the roll where compression is completed, but at a biting point 17 at the rear of the crushing table 1 in the direction of movement.
(a point l behind the center of the roller), and as shown in FIG. Circumferential speed F ₃
The circumferential speed of the outer circumferential surface of the crushing roller 5 in the rotating direction
F ₄ is deviated by an angle α, and the raw material directly below the biting point 17 corresponds to the roller misalignment angle α.
A shearing force in the direction of F ₅ acts, and this shearing force F ₅ also causes the raw material powder to flow, which is thought to increase the self-excited vibration.

As described above, the cause of the self-excited vibration of the grinding roller 5 is due to the flow of raw material powder in the direction of the roller shaft 9 in the gap 6, but as shown in FIGS. 1 and 2, in the conventional roller mill, Either the thickness of the gap 6 is constant in the direction of the roller axis 9 (Fig. 2a), or it is thicker at the front or rear end than at the center (Fig. 2b); Since the gap 6 is open to the front and rear, the gap 6 does not have a shape that prevents the flow of the raw material, resulting in a structure that is prone to self-excited vibration.

Furthermore, in the conventional roller mill, as described above, the grinding material is structured so that it easily flows out (escapes) from the gap 6 between the grinding roller 5 and the grinding table 1, so the pressing force F ₁ of the grinding roller 5 is The raw material escapes before it can effectively act on the raw material powder, and sufficient compression and crushing is not performed, which is one of the reasons for reducing the crushing efficiency of the roller mill.

In view of the above points, the present invention aims to reduce self-excited vibration and improve grinding efficiency by preventing the flow of raw material in the axial direction of the roller in the gap between the grinding roller and the annular groove of the grinding table. The gist of this is that in a roller mill that grinds raw materials supplied onto a grinding table by pinching them between the grinding table and a grinding roller that is pressed toward the top of the grinding table, An annular groove with an arcuate cross section that is depressed toward the bottom is formed, and an annular recess that is depressed in the direction of the roller shaft that supports the crushing roller is formed on the outer circumferential surface of the crushing roller facing the annular groove. , and by offsetting the center point of the radius of curvature of the outer circumferential surface of the grinding roller outward from the center line of the cross section of the annular groove of the grinding table, the cross section of the gap formed between the annular groove and the outer circumferential surface of the grinding roller is The present invention provides a roller mill in which a crushing roller is supported such that the cross-sectional area of the crushing table decreases toward the outside in the radial direction.

Next, embodiments embodying the present invention will be described with reference to the accompanying drawings starting with FIG. 5 to provide an understanding of the present invention.

Here, FIGS. 5 and 6 are side sectional views of a crushing roller and a crushing table portion of a roller mill according to an embodiment of the present invention. Note that the same reference numerals are used for elements common to those shown in FIGS. 1 and 2.

In FIG. 5, 9 is the roller shaft and the main body 20
The roller shaft 9 is fixed to an arm 11 which is rotatable around a support shaft 10 attached to the roller shaft 9, and a crushing roller 25 rotatably supported by bearings 21a and 21b is attached to the tip of the roller shaft 9. .
However, the crushing roller 25 cannot slide in the axial direction of the roller shaft 9.

In addition, the cross-sectional center line Y of the crushing roller 25 and the cross-sectional center line 23 of the annular groove 3 of the crushing table 1 do not coincide (in conventional roller mills, both center lines coincide), and the angle between them with respect to the vertical line Z is α. ₁ and α ₂ , α ₂
The mounting position of the roller shaft 9 is determined so that >α ₁ .

Therefore, the cross-sectional shape of the gap 26 between the outer circumferential surface 24 of the crushing roller 25 and the annular groove 3 that clamps the raw material, taken along a vertical plane including the roller axis, has an area as shown in the figure. The thickness of the intermediate part 26a of the gap 26 is D _p
The thickness D _a of the outlet portion 26b is further reduced. Further, an annular recess 27 is formed in the center of the outer peripheral surface 24 of the crushing roller 25, and the recess 27 is recessed in the direction of the roller shaft 9. This can be replaced with a square trapezoid, a triangle, a semicircle, or other shapes, and the number of recesses can be not only one as shown in the figure, but also a plurality of recesses.

That is, in this embodiment, the center point X ₄ of the radius of curvature of the outer circumferential surface 24 passing through the cross-sectional center line Y of the crushing roller 25 is eccentric to the outside in the radial direction of the crushing table 1 from the cross-sectional center line 23 of the annular groove 3, and the above-mentioned By setting the relationship between the angles α ₁ and α ₂ of both center lines with respect to the vertical line so that α ₂ > α ₁ , the gap 26
The shape is wedge-shaped.

The gist of the present invention is that the shape of the gap 26 is wedge-shaped, which becomes narrower toward the outside in the radial direction of the grinding table 1, and that an annular recess is formed in the outer circumferential surface 24 of the grinding roller. As shown in FIG _. 5, the center point of the radius of curvature
In addition to making the crushing roller 25 more eccentric to the outside,
In addition, by tilting the grinding table 1 with respect to the grinding table 1,
As shown in FIG. 6, with α ₁ =α ₂ maintained, the crushing roller 25 can be freely rotated with the cross-sectional center line Y in the width direction of the crushing roller 25 being shifted outward from the cross-sectional center line 22a of the annular groove 3. substantially at the center point of the radius of curvature of the outer peripheral surface 24 of the crushing roller 25
It is possible to form the groove in the same manner even if X ₄ is arranged outside the center line 22a of the annular groove 3 in the cross-sectional view (as viewed in the radial direction of the crushing table 1).

Next, regarding the operation when grinding is performed using the grinding roller supported in the above state, Section 6 is explained.
This will be explained with reference to the example shown in the figure.

The raw material supplied to the center of the crushing table 1 is
As described above, the powder moves in the radial direction due to the centrifugal force caused by the rotation of the grinding table 1, and flows into the annular groove 3.

The raw material that has flowed in is caught in the gap 26 between the crushing roller 25 pressed onto the annular groove 3, clamped, and crushed.

On the other hand, as shown in FIG. 6, an annular groove 3 having an arcuate cross section
and the outer peripheral surface 24 of the crushing roller 25.
As described above, the crushing roller 25 is formed into a wedge shape whose cross-sectional area decreases toward the outside.
Since an annular recess 27 is formed in the outer circumferential surface 24 of the gap 26, the cross-sectional area of the gap 26 increases to the maximum at the recess 27, and then rapidly decreases at the wedge-shaped portion as it moves outward.

Therefore, the raw material that is about to flow outward is accumulated between the recess 27 and the annular groove 3, and the outlet portion 26b is clogged, preventing the raw material from flowing outward. Only the crushed raw material passes through the outlet portion 26b to the crushing table 1.
As a result, the thickness of the gap 26 is kept constant and self-excited vibration is reduced.

Furthermore, as a result of blocking the outward flow of the raw material as described above, the inconvenience of unpulverized raw material flowing outward from the crushing table 1 is eliminated, and only the sufficiently crushed raw material flows out in the direction of the nozzle 16. Therefore, the crushing efficiency increases dramatically.

For example, Figure 7 shows the relationship between the Blaine value (representing particle size and unit: cm ² /g) versus throughput using a conventional roller mill (○ represents experimental values) and a roller mill according to the present invention (represented by ●). was determined by experiment, but as is clear from the figure, when the same amount of raw material is processed per unit time, the present invention can yield a product with a much finer particle size. It is understood that the grinding efficiency of such roller mills has been dramatically improved.

Furthermore, in the same graph, the "slight vibration region" refers to the region where slight vibrations occur that do not interfere with operation at all, and the "weak vibration region" refers to the region where vibrations exceeding this range may hinder long-term operation. This is a part that generates vibrations larger than the micro-vibration range, and the difference between the present invention and the conventional roller mill can be clearly understood.

As described above, the present invention provides a roller mill in which a raw material supplied onto a grinding table is crushed by being pinched between the grinding table and a grinding roller that is pressed toward the top surface of the grinding table. An annular groove with an arcuate cross section that is depressed toward the bottom is formed, and an annular recess that is depressed in the direction of the roller shaft that supports the crushing roller is formed on the outer circumferential surface of the crushing roller facing the annular groove. , and by offsetting the center point of the radius of curvature of the outer circumferential surface of the grinding roller outward from the center line of the cross section of the annular groove of the grinding table, the cross section of the gap formed between the annular groove and the outer circumferential surface of the grinding roller is This roller mill is characterized by supporting a crushing roller so that the cross-sectional area decreases toward the outside in the radial direction of the crushing table. This prevents the raw material from escaping (flowing) in the direction of the roller axis, suppressing vibration of the crushing roller, and improving crushing efficiency.

[Brief explanation of drawings]

Figure 1 is a side sectional view of a conventional roller mill, Figures 2a and b are side sectional views showing the relationship between the shapes of the crushing roller and the crushing table of the same roller mill, and Figure 3 is for explaining the crushing state. 4 is a plan view of the same crushing roller, and FIGS. 5 and 6 are side sectional views showing the relationship between the crushing roller and the crushing table of the roller mill according to the embodiment of the present invention, respectively. FIG. 7 is a graph showing the effects of the present invention. Explanation of symbols, 1... Grinding table, 3... Annular groove,
9...Roller shaft, 24...Outer peripheral surface, 25...Crushing roller, 26...Gap, 26a...Inlet part, 26b...Outlet part, 27...Recessed part.

Claims (1)

[Claims] 1. In a roller mill that crushes raw material supplied onto a crushing table by pinching it between the crushing table and a crushing roller that is pressed toward the top surface of the crushing table, a cross-sectional arc that concaves downward on the top surface of the crushing table. While forming the upper annular groove,
An annular recess is formed on the outer circumferential surface of the crushing roller facing the annular groove, and the center point of the radius of curvature of the crushing roller is set on the crushing table. By eccentrically moving the annular groove outward from the cross-sectional center line, the cross-sectional shape of the gap formed between the annular groove and the outer peripheral surface of the crushing roller becomes such that the cross-sectional area decreases toward the outside in the radial direction of the crushing table. A roller mill characterized by supporting a crushing roller as shown in FIG.