JPH10286479A - Sample grinding device and grinding method - Google Patents

Abstract

(57) [Problem] To obtain a uniform distribution with a desired particle size when a sample is crushed. SOLUTION: A donut-shaped rotorstone 2 is accommodated in a cylindrical grinding pot 1, and the grinding pot 1 is revolved in an eccentric circle and shaken to move the rotorstone 2 so as to move the circumferential wall 11 and the rotorstone. The sample is ground on the outer peripheral surface of No. 2. By changing the inner diameter of the rotorstone 2, the weight can be adjusted without changing the outer diameter, the average particle size can be changed while maintaining uniformity, and the particle size of the pulverized sample can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for pulverizing a sample to be used for physical property measurement or analysis, and more particularly to a technique for controlling the particle size distribution of a pulverized sample.

[0002]

2. Description of the Related Art When measuring or analyzing physical properties of ore, coal, plastic, or the like, these lumps and grains are often pulverized into powder. In the past, a small rotary mill was used for pulverization, but since the pulverization efficiency was low and the required time was long, it was desired to improve the pulverization efficiency.

[0003] Then, in order to shorten the grinding time and to automate the grinding, a thick disk-shaped rotorstone is put into a short cylindrical grinding pot, and the grinding pot is rotated while continuously loading the massive sample. A method of crushing by shaking vigorously in a shape has been developed. For example, there is a centrifugal pulverizer described in JP-B-6-83794. This will be described with reference to FIG.

FIG. 1 (a) is a longitudinal sectional view of a crushing section, where 1 is a crushing pot, 2 is a rotor stone, and 3 is a screen.
The crushing pot 1 is cylindrical, but its length is short, and its end face is closed by a bottom and a lid. Although not shown, the lid has a charging port for supplying a massive sample and is connected to a flexible charging pipe. A part of the circumferential wall of the crushing pot 1 is a screen 3, and the screen 3 is constituted by a double sieve,
The mesh of the inner sieve is coarse and the mesh of the outer sieve is fine.
The rotorstone 2 has a thickness slightly smaller than the length of the crushing pot 1 and an outer diameter of about half the inner diameter of the crushing pot 1 and can freely move inside the crushing pot 1.

FIG. 1 (b) shows a mechanism for swinging the crushing section. The support shaft 21 of the crushing pot 1 is attached to a swing table 22, and the swing table 22 can swing and rotate. It is pulled right and left downward by a spring 13 so as not to be disturbed.
By the rotation of the cam 14, the swing table 22 swings in an eccentric circle. (A) In the figure, when the crushing pot 1 swings in a circle, the rotor stone 2 is pushed by the inner wall of the crushing pot 1 and given a centrifugal force, revolves in a circle and revolves, and rotates with the inner wall. Crush the massive sample sandwiched between.

A fixed amount of the bulk sample to be pulverized is continuously charged from the charging port 6, and the pulverized sample passes through the screen 3 and is automatically collected by an external sample collector (not shown). Collected in. In this crushing device, power efficiency and crushing efficiency are good, and a lump sample of several mm such as coal, limestone and slag can be crushed to 100 μm or less in a short time of several minutes.

[0007]

However, some pulverized samples not only have an upper limit of particle size, but also have a particle size that must follow a certain distribution. In such a case, it must be ground to a uniform and predetermined particle size. The upper limit of the grain size can be easily controlled by selecting the aperture of the screen, but it is not easy to control the lower limit of the grain size. This is because the sample to be measured must be representative of the original massive sample, and an excessively pulverized fine sample cannot be eliminated by sieving.

In the conventional centrifugal pulverizer, if it is attempted to recover 95% or more of the loaded bulk sample, a large amount of excessively pulverized powder is generated, and it is difficult to control the particle size distribution of the pulverized sample. Met.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an apparatus and a method for controlling the particle size distribution by suppressing the amount of overmilled sample generated.

[0010]

According to a first aspect of the present invention, a disk-shaped rotorstone is accommodated in a short cylindrical grinding pot, and the rotorstone is shaken in a circle to form the rotorstone. And a sample is crushed between the inner wall surface and a crushed sample, and the crushed sample is sieved through a screen partially provided on the wall surface of the crushing pot, wherein the rotor stone has a donut shape. Wherein the screen comprises an inner reinforcing plate and an outer sieve, and the opening ratio of the reinforcing plate is 50% or more and 75% or less.

The donut shape of the rotorstone is as follows.
This is for adjusting only the weight without changing the outer peripheral surface dimensions. In order to prevent the generation of a large amount of overground sample,
It is only necessary to reduce the weight of the rotorstone or reduce the radius of rotation or the rotation speed of the crushing pot to reduce the motion speed of the rotorstone to reduce the momentum of the rotorstone. However, when the rotation radius or the rotation speed of the grinding pot is reduced, it takes a long time to perform the grinding. Therefore, it is advisable to reduce the momentum by reducing the weight of the rotor stone.

However, if the outer diameter is reduced in order to reduce the weight of the rotorstone, the area of the surface to be pulverized is reduced, so that not only long time is required for pulverization but also uniformity of particle size cannot be expected. For this reason, it is important to adjust only the weight without changing the outer peripheral surface dimension of the rotor stone, and the rotor stone is made into a donut shape.

The finely pulverized sample passes through the screen by centrifugal force, but some fine samples are bounced off the non-opening of the inner reinforcing plate, that is, the mesh line. If the aperture ratio is small, the amount of the rejected fine sample is large, and the pulverization is repeated, which contributes to an increase in the amount of the over-pulverized sample. For this reason, the larger the opening ratio of the reinforcing plate, the smaller the number of over-crushed samples. Therefore, the opening ratio is set to 50% or more. However, if the opening ratio is too large, the strength decreases and the reinforcing effect is lost. The following is assumed.

According to a second aspect of the present invention, a donut-shaped rotor stone is accommodated in a cylindrical grinding pot, and the rotor pot and the inner wall surface are rotated by swinging the grinding pot in a circular shape. The sample is pulverized in between, using a sample pulverizer having a structure in which the pulverized sample is sieved through a screen partially provided on the wall of the pulverization pot, and changing the inner diameter of the rotor stone to obtain a particle size of the pulverized sample. This is a sample grinding method for controlling the distribution.

The sample crushing apparatus used is the above-mentioned crushing apparatus for accommodating a donut-shaped rotor stone. The sample is pulverized by being sandwiched between the inner wall surface of the pulverizing pot and the outer peripheral surface of the rotor stone. This gap is small at the contact point between the inner wall surface and the outer peripheral surface when the diameter of the rotor stone is small, but becomes large as soon as it slightly shifts in the circumferential direction. However, when the diameter of the rotorstone is large, the gap changes slowly, and many samples are pulverized in the gap that does not change much, so that many samples having the same particle size can be obtained. That is, a pulverized sample having a uniform particle size is easily obtained, and the particle size distribution of the pulverized sample becomes uniform.

On the other hand, the average particle size can be changed by changing the weight of the rotorstone, and the average particle size can be increased by reducing the weight. However, when the weight is reduced by reducing the outer diameter of the rotorstone, a ground sample having a uniform particle size cannot be obtained, that is, the uniformity of the particle size decreases. For this reason, using a donut-shaped rotor stone, the average particle size is changed while maintaining uniformity without changing the outer diameter. Thereby, the particle size distribution of the pulverized sample can be controlled.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a sample crushing apparatus, and the embodiment will be described. (A) is a longitudinal sectional view of a grinding pot. Crush pot 1 and rotorstone 2
Manufactured using tool steel. Circumferential wall 11 of crushing pot 1
Have openings 12 at equal intervals, and the screen 3 is provided therein.

The screen 3 has a double structure of a reinforcing plate 5 and a sieve 4, and the inner reinforcing plate 5 is a steel plate having a hole having a diameter considerably larger than the upper limit of the required grain size or a wire mesh having a large opening.
The outer sieve 4 is a wire mesh that meets the upper limit of the required particle size.
A sample collector 7 is arranged surrounding the crushing pot 1, and the crushed sample that has passed through the screen 3 is collected by the sample collector 7 and stored in a sample tray 8.

FIG. 2 (b) is a side view, in which a loading port 6 is provided at the end face of the crushing pot 1, and a massive sample is continuously loaded at a constant feed rate from a fixed-rate feeding device 9 having a belt feeder. Is done. The inner diameter of the crushing pot 1 is 100 mm, the length is 30 mm by the inner method, and the thickness of the rotor stone 2 is 25 mm. The revolving radius of the grinding pot is 5mm by replacing the cam
It can be changed in the range of ~ 30mm, and the number of revolutions is also variable. These conditions are selected depending on the type of the sample to be ground and the required particle size.

FIG. 2 is a longitudinal sectional view of the screen. Sieve 4
Since the openings are small and the mesh lines are thin, the strength is supplemented by the reinforcing plate 5. For this reason, the mesh wire 51 of the reinforcing plate 5 is thick and repels a large lump here to protect the sieve. However, the reticulated wire 51 repels the crushed small powder together with the large lump. The powder having a sufficiently fine particle size passing through the sieve is repelled by the mesh wire 51, and when the powder is again pulverized by the rotorstone, it becomes an over-pulverized powder, which hinders the uniformity of the particle size distribution. This excessive pulverization is reduced by increasing the aperture ratio of the reinforcing plate 5.

Next, the action of the donut-shaped rotorstone will be described with reference to an example of a slag sample. Particle size 200μm-5
A slag sample was pulverized to a size of 00 μm, and the relationship between the particle size distribution of the powder passed through the sieve and the rotorstone used was examined. A slag lump crushed to 4 mm or less was charged at a constant feed rate of 3 g / min, pulverized over 26 minutes, and the particle size distribution was examined.

The rotorstones used are of three types, A, B and C. A has a conventional cylindrical shape with an outer diameter of 60 mm and a weight of about 550 g. B is a conventional type in which the outer diameter is reduced to 35 mm and the weight is reduced to about one third in order to reduce the number of over-crushed samples. C is a donut according to the present invention, having an outer diameter of 60 mm and an inner diameter of 25 mm as in A, and having a weight as light as about one third or B. The obtained distribution curve is shown in FIG. Those corresponding to rotorstones A, B, and C are shown as A, B, and C, respectively. In Roterstone A, there are many overground samples, and the particle size is 200 μm to 5 μm.
Only about 70 w% of the sample in the target range of 00 μm is obtained. In B, the average particle size is larger than A,
The sample in the target range shows no improvement effect as in the case of A. On the other hand, when the rotorstone C according to the present invention was used, a remarkable improvement effect was observed.
wt% has been obtained.

When the outer diameter of the rotorstone is reduced, the area where the distance between the outer periphery of the rotorstone and the inner wall is properly maintained is reduced and the uniformity of the crushing conditions is impaired simultaneously with the positive effect of the weight reduction. It is considered that this also had the negative effect. As for incidental conditions at the time of grinding, the revolution radius of the grinding pot is 20 mm, and the rotation speed is 60 mm.
The sieve was made of a wire mesh having an opening of 500 μm, the reinforcing plate was made of steel wire having a thickness of 250 μm and having an opening of 3 mm, and the opening ratio was 55%.

When the rotor stone is formed in a donut shape, as the inner diameter becomes closer to the outer diameter, the thickness becomes thinner, which affects the rigidity. In such a case, the weight may be adjusted by attaching a frame to the inside or as a hollow structure, and if the symmetry is secured with respect to the center point of the disk, it may be substantially donut-shaped regardless of appearance. .

[0025]

EXAMPLE A coal sample to be subjected to a fluidity test was pulverized. The fluidity of coal is an important property as a raw material for iron making, and 5 g of powder is used in one measurement. The measurement is performed by a Giesler plastometer according to JIS M 8808, and the fluidity is detected while heating the sample at a constant speed in an inert gas. At this time, since the oxidation of the sample due to oxygen or the like adsorbed on the sample affects the test value, the ratio of the over-crushed sample is regulated.

If the overmilled sample is removed by sieving in order to adjust the particle size, the easily crushable portion has been artificially removed from the bulk sample, and the test sample no longer represents the bulk sample. For this reason, extreme care must be taken so that over-crushed samples do not occur during grinding. That is, the particle size of the powder sample is 4
25 μm or less, but 40% of all samples have a particle size of 425 μm.
It is required to be in the range of m to 250 μm, with an acceptable range of only 3%.

Using the apparatus shown in FIG. 1, a lump of coal crushed to 3 mm or less was charged at a constant feed rate of 2 g per minute over 30 minutes. The sieve was a wire mesh having a mesh size of 425 μm, the reinforcing plate was formed with a hole having a diameter of 2 mm and the opening ratio was 50% to 70%, and the material was SUS304 in each case. The revolution radius of the grinding pot was 20 mm, and the rotation speed was 600 times / minute.

By changing the outer diameter and inner diameter of the rotorstone,
Table 1 shows the result of examining the particle size distribution of the collected sample. The target range compatibility is the percentage of powder within the range of 425 μm to 250 μm.

[0029]

[Table 1]

In an embodiment of the invention, the outer diameter of the rotor stone is 45 mm to 55 mm, that is, 45 to 55% of the inner diameter of the grinding pot.
The weight was adjusted to about 140 g to 160 g by changing the inner diameter of the donut-shaped rotor stone.
As a result, the recovery was 97 wt% to 99 wt%, and the target particle size range was good, with 40 wt% to 42 wt%.

On the other hand, in the comparative examples, there was no example in which a sample having a target particle size range of 40 wt% or more was obtained.

[0032]

According to the present invention, the sample is pulverized by shaking the cylindrical pulverization pot accommodating a rotorstone having a circular outer periphery in a circular manner, and a double structure provided on the pulverization pot circumferential surface. In a sample crusher for collecting a crushed sample through a screen, the rotor ston is made to have a donut shape, and the opening ratio of the reinforcing plate inside the screen is set to 50% or more and 75% or less. By increasing the opening ratio of the reinforcing plate and adjusting its weight by changing the inner diameter of the donut-shaped rotor stone, the amount of over-ground sample can be controlled, and the regulated particle size distribution can be obtained with good reproducibility. . As described above, the effect of the present invention, which makes it possible to control the particle size distribution, which is difficult in the related art, is great.

[Brief description of the drawings]

FIG. 1 is a view showing a pulverizing section of a sample pulverizing apparatus used in an embodiment of the present invention, where (a) is a longitudinal sectional view and (b) is a side view.

FIG. 2 is a longitudinal sectional view of a screen.

FIG. 3 is a diagram showing a particle size distribution of a pulverized sample.

4A and 4B are views showing a conventional sample crusher, wherein FIG. 4A is a longitudinal sectional view of a crusher, and FIG. 4B is a front view of the sample crusher.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crushing pot 2 Rotorstone 3 Screen 4 Sieve 5 Reinforcement plate 6 Loading port 7 Sample collector 8 Sample tray 9 Quantitative feeder 11 Circular wall 12 Opening 51 Netting

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yutaka Yoshioka 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (2)

[Claims] 1. A disk-shaped rotorstone is accommodated inside a cylindrical grinding pot, and the sample is moved between the rotorstone and the inner wall surface by swinging the grinding pot in a circular shape. In a sample crushing apparatus having a structure in which a crushed and crushed sample is sieved through a screen partially provided on a wall surface of the crushing pot, the rotor stone has a donut shape, and the screen has an inner reinforcing plate and an outer reinforcing plate. A crusher, wherein the opening ratio of the reinforcing plate is 50% or more and 75% or less. 2. A donut-shaped rotorstone is housed inside a cylindrical grinding pot, and the sample is moved between the rotorstone and the inner wall surface by swinging the grinding pot in a circular shape. Using a sample crusher having a structure in which the crushed and crushed sample is sieved through a screen partially provided on the wall surface of the crushing pot, the particle size distribution of the crushed sample is controlled by changing the inner diameter of the rotor stone. A sample grinding method characterized by the above-mentioned.