JPH1190255A - Method for manufacturing crushed sand using wet ball mill and wet ball mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently manufacture a large quantity of high-quality crushed sand using crushed stone including a highly hard raw material for the crushed sand by causing a wet ball mill with a cylindrical body which rotates while being pivotal supported on a wheel, to rotate at a specific range of critical velocity. SOLUTION: A raw material for crushed sand is loaded into a charging hopper 2 and then is cut to the optimal feed level using an adjustable feeder. Thus the cuttings are forcibly flown into a forced ore feeder 10 with water and then are loaded into the cylindrical body 13 of a ball mill 1. This ball mill 1 rotates the cylindrical body 13 at 80% or higher to 89% of the critical velocity with the help of a wheel including a drive wheel and thereby, delivers the crushed raw material into a cylindrical sieve 11 attached to a discharge aperture. In addition, the sieved raw material with a diameter of 5 mm or less is sent to a classifier 4 with water and the dust with a size of not more than 0.074 is discharged with an overflow from the classifier 4. Thus it is possible to efficiently manufacture a large quantity of high-quality crushed sand using various kinds of crushed stone including a highly hard raw material for orushed sand.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing a large amount of high-quality crushed sand from crushed stones containing a hard-hard crushed sand material, and a wet ball mill capable of optimally implementing the method.

[0002]

2. Description of the Related Art Gravel and sand, which are used as raw materials for concrete, were originally made of natural materials. However, as it became more difficult to collect natural gravel and sand, crushed sand obtained by diverting mining equipment was used. became. As mining equipment, there are a ball mill and a rod mill. The former is regarded as an over-crushing machine and is not used, and the latter rod mill, particularly a cylindrical wet rod mill, was diverted for sand crushing.

[0003] Among such cylindrical wet rod mills,
Initially, the overflow type rod mill shown in FIG. 3 was diverted, but because of the trunnion discharge structure, the speed at which the material to be crushed passed through the mill was slow, and the processing capacity was not sufficient with this. .

[0004] Therefore, the passing speed of the crushed material is high.
The circumferential discharge (peripheral discharge) type rod mill shown in Fig. 3 was diverted (Fig. 3 (a) is an end peripheral type, and Fig. 3 (b) is a center peripheral type). Since the cylindrical body 20 had a structure in which the cylindrical body was supported via the trunnion part 21, a large number of steps and precision were required for the foundation work of the bearing, the production cost was high, and a high level of maintenance was required. Furthermore, noise generated from a structure in which a metal and a metal such as a chain and a sprocket of a drive transmission system or a roller of a load supporting system and a cylindrical body move in contact with each other is unbearable.

Therefore, as a structure for solving these problems,
Rod mills that rotate while supporting a cylinder with wheels including drive wheels have been used for crushed sand. However, initially, in order to prevent the rod from protruding from the discharge port, a structure in which the discharge port 22 side is inclined high as shown in FIG. 5 or a taper in which the discharge port 22 side is narrowed as shown in FIG. This is a structure using a cylindrical body 20 having a rod 23
Is not horizontal, so that the worn and thinned rod 23 bends and becomes entangled or broken, and the narrowed outlet 22 increases the residence time of the material to be crushed in the mill. . However, as shown in FIG.
The cylindrical body 20 is closed by closing the discharge port 22 with a side plate 24 having a perforated hole.
Horizontal structure (No. 2528938 utility model registration)
Was developed, and according to this, effective discharge and horizontal rolling of the rod near the above-mentioned circumferential discharge type rod mill became possible, so that it was widely used.

[0006]

As described above, a wheel bearing type rod mill, which has been variously improved, has been used for the present crushed sand, but this structure also has disadvantages.

First, there is a problem in the crushing ability of the rod mill itself. In the first place, the crushing mechanism of the rod mill is such that when the rod lifted by the rotation of the cylindrical body falls on the lower rod, it crushes (compresses) and crushes (shears) the crushed object sandwiched between the rods. . One rod is long and very heavy, while its crushing force is small. That is, when one large crushed object is sandwiched, the other part of the rod is in a floating state and the crushing force is reduced, and when two large grains are sandwiched between both ends of the rod, the rod is interposed between the two grains. Almost the entire length is not involved in crushing. In the case of a raw material having uniform grains, the force is dispersed over the entire length of the rod, so that the crushing force is reduced. Due to such capacity problems, 50% or more of 0.074-0.6mm (fine part) is required to make high-quality concrete, but when crushing progresses in a rod mill, crushing of 1.0mm or less becomes difficult. Often the details were below 50%.

In the case of crushing sand in a rod mill, a product of a first-stage crusher called a crusher run (roadbed material, size 40 mm or less, of which 15 to 30% is 5 mm or less) is passed through a rod mill, and the mill product is sieved by wet milling. It was classified with a mechanical classifier to obtain crushed sand of 0.074 to 5 mm. And from such a rod mill, a large amount of by-products, often referred to as 5 to 13 mm, was generated. Such a bill
Since it is a tough rock core that withstands coarse, medium, and fine crushing and several stages of crushing, it can become high-quality crushed sand.However, current rod mills cannot crush it due to the above characteristics. However, they were piled up in vacant lots as unusable items that could not be sold.

The present invention has been made in view of the above-mentioned problems of the prior art, and aims to provide a technology capable of efficiently producing a large amount of high-quality crushed sand from crushed stone containing a hard crushed sand raw material. Things.

[0010]

As described above, the mill currently used for crushed sand is a rod mill, and a ball mill was not used because it was thought that there was a risk of over-crushing. Therefore, the present inventors have developed the structure shown in FIG. 7, which is now commonly used as a rod mill, by the present inventors themselves. First, in a wet rod mill shown in FIG. And attempted to crush the bill. Operating conditions were within the range of conventional rod mills and ball mills.As a result, crushing was possible, but on the other hand, the tendency of over-crushing was also strong, and high-quality crushing did not reach the desired amount. The product yield was poor.

However, it can be found that using a ball mill having a structure in which a cylindrical body rotates while being supported by a wheel enables at least crushed sand to be obtained from stiffness, and the problem is how to achieve a desired particle size range (particle size 0.074 to 5 mm). I came to the point of getting good. Here, the present inventors have studied the cause of over-pulverization from the operating conditions of the ball mill, the strength and properties of the milling action of the mill depend on the rotation speed of the cylinder,
We paid attention to the rotation speed. Conventionally, the rotation speed in ore crushing of a ball mill is 200 mesh (0.074 mm) for the compression and shearing action of the cascade motion of balls in the mill.
Since it is effective for fine pulverization aiming at the under, the critical speed is set to 60 to 80% of the critical speed in a range in which small waterfall motion is generated, and a low speed level is maintained in that range in order to obtain a scraping action. Here, the critical speed refers to the speed at which the ball rotates while remaining on the inner wall without separating from the inner wall of the rotating cylinder due to the balance of centrifugal force and gravity. Also in the first test example, the rotation speed was in the range of 60 to 80% of the critical speed. Then, the present inventors, as a next test, using other types of rock mixture including the billiards used as a raw material of crushed sand as a sample, using a mill similar to the above test, a rotation speed of 60 to 80% of the critical speed, Two tests with a rotation speed of more than 80% of the critical speed were performed, and the effect of the rotation speed on the crushing state of the crushed sand was examined. As shown in the examples described later, it was not considered under the conventional operating conditions. Good crushed sand was obtained very efficiently in the range of more than 80% of the critical speed. This is because when the rotation speed exceeds 80% of the critical speed, the ball moves in a large waterfall (cataracting) motion in the rotating cylinder, and the impact force of the free fall of the ball exerted by the waterfall motion is the most appropriate under the conditions of crushed sand production. (Note that in the conventional rotation speed range, large grains in the raw material are only slightly thinned and are not crushed, while small grains are excessively crushed to form fine powder, leading to an increase in the amount of sludge. Please note that). However, if the critical velocity exceeds 89% of the critical velocity, the ball collides with the side wall on the opposite side of the rotating cylinder, and since there is no crushed object there, the crushing force becomes zero. That is, the present inventors set the rotation speed of the ball mill to a critical speed exceeding 80 to 89.
%, It has been found that high quality crushed sand can be obtained very efficiently.

[0012] The method for producing crushed sand according to the present invention is based on such new knowledge, and rotates a wet ball mill in which a cylindrical body rotates while being supported by wheels within a range of more than 80 to 89% of a critical speed. It is characterized by the following.

The present inventors further studied the size of a ball as a crushed body as an optimum condition in such a method for producing crushed sand. Generally, large balls are required to crush large grains, and small balls are required to crush small grains. In conventional ball mills, the purpose was to pulverize or finely pulverize a relatively uniform raw material of usually 10 mm or less into a product with a total amount of 0.1 mm or less or 0.074 mm or less, so the ball when filling is also 50 to 60 mm or less. Met. In the case of crushed sand, relatively large raw materials of 5 to 30 mm are targeted, so 90
We selected a ball of ~ 120mm and tried to compare it with a conventional ball of 60mm. As a result of performing a test by rotating the cylinder in a range of more than 80 to 89% of the critical speed which is a condition of the method of the present invention and performing a test, a ball of 90 to 120 mm is different from the operating condition of the conventional ball mill. Found that it could crush raw materials that could not be crushed with a 60 mm ball.
By the way, in the conventional pulverization, a new ball (maximum diameter) is retained at the supply port side in order to more efficiently pulverize the material to be pulverized in the ball mill, which becomes smaller from the supply port side to the discharge port side. In addition, a mill structure in which balls that are more worn toward the discharge port side (the smallest diameter at the discharge port) is arranged, for example, a conical mill or a tricon mill is used. Further, a compartment mill is also used in which a partition is provided in the mill, and a large ball is charged on the supply port side and a small ball is charged on the discharge port side. However, the crushed sand targeted by the present application has a wide particle size range of 0.074 to 5 mm in particle size, and must have a prescribed particle size distribution while appropriate intermediate particles are present in the range. Therefore, in the case of crushed sand, the conventional crushing theory does not apply, and balls having different diameters from the maximum diameter to the minimum diameter may be mixed over the entire area from the supply port side to the discharge port side. On the other hand, since the ball wears with the elapse of the crushing operation time, it is also possible to improve the crushing force by regulating the size of the ball at the time of filling when implementing the method of the present invention. From the results of the above test, it can be said that it is preferable to use one having a diameter of 90 to 120 mm which has a sufficient crushing force in the range of the present invention.

Next, the ball filling amount is conventionally said to be in the range of 35 to 45% of the effective internal volume of the cylindrical body. As a result of conducting a test in that range, the ball becomes slightly over-crushed. Conversely, in the test where the concentration was reduced to less than 35%, crushed sand was obtained efficiently. In general, in a ball mill, the crushing ability is improved as the ball filling amount increases, but in crushed sand to avoid over-crushing, the conventional filling amount for the purpose of fine crushing promotes crushing more than necessary. Therefore, it is considered that over-milling was performed in the conventional range. In the case of crushed sand, it is considered that it is desirable to promote the free fall of the ball with a small number of balls in order to obtain a particle size in a desired range, and in consideration of the test results, it is preferable to reduce the ball filling to less than 35%. Is preferable.

The size of the mill cylinder to be used next is not particularly limited. However, in initially developing the method of the present invention, a rod mill having the structure shown in FIG. 7 was used as described above. Conventional ball mills have a length ratio of 2.
On the other hand, the ratio is 1.6 to 2.2 in the rod mill having the structure shown in FIG. When the ratio of the length to the inner diameter of the cylinder is at least 1.6 to 2.2, it is clear from the above test that the crushing efficiency is good. Therefore, when performing the method of the present invention, the size of the mill is set to the inner diameter of the cylinder. Preferably, the length ratio is between 1.6 and 2.2. In particular, with a cylindrical body of that size, the production method using the ball mill according to the present application can be operated with very little modification using the rod mill shown in FIG.
This is advantageous in manufacturing cost.

Considering the operating conditions of the crushed sand from other viewpoints, in any type of mill, if the residence time in the cylindrical body is too long, the tendency of overmilling becomes strong. Therefore, it is desirable that the setting is such that the residence time is short and rapid discharge is possible. By the way, generally in a wet mill,
The necessary minimum amount of water is added to the raw materials. This is to impart fluidity to the material to be crushed. In the case of the fine grinding operation of a ball mill, water is generally added so that the slurry (mixture of raw material and water) has a concentration of 60 to 70 wt%. ing. The present inventors paid attention to whether or not this water poured into the mill was used as a means for promoting rapid discharge, and examined various optimum conditions thereof,
While the conventional slurry concentration ranged from 60 to 70 wt%, the residence time was prolonged. On the other hand, by pouring a large amount of water so as to be less than 60 wt%, a smooth discharge flow was obtained, and the mud and stone powder in the raw material were removed. I was able to wash off. For this reason, in the present invention, it is preferable to pour water so that the slurry concentration in the cylinder becomes less than 60 wt%.

By the way, in a mill in which a trunnion is provided at the discharge port as shown in FIGS. 3 and 4, the residence time becomes longer due to the presence of the trunnion. This is the same in a conventional ball mill with a trunnion as shown in FIG. That is, in such a mill with the trunnion 21, the material to be crushed is transferred to the trunnion communication section (the discharge port 2
3) Take the step of lifting up and passing the trunnion (the flow of the material to be crushed is indicated by an arrow), and the residence time is required accordingly. However, in the wheel-supporting type mill premised by the method of the present invention, the wheel is rotated while supporting the cylinder with the wheel, and a trunnion serving as a bearing is unnecessary, and there is no need to provide an outlet at the center of the cylinder. Because of the structure, the structure of the mill itself allows for rapid discharge first. On the other hand, in a ball mill, a side plate serving as a baffle plate is disposed on the discharge port side to avoid free discharge of balls from the discharge port side, and through holes of various shapes are formed in the side plate. Since the material to be crushed goes to the discharge port through the through hole, the through hole is an important element in rapid discharge.

From such a viewpoint, the present inventors have examined various shapes of through holes formed in the side plates. As a result, the crushed object is rotated by the rotation of the cylindrical body. If the slit is formed along the direction of rotation of the side plate, the crushed sand and water easily escape from the slit. The effect of discharge was obtained.

Therefore, a mill having such a through hole is defined as the second invention of the present application as a mill capable of efficiently performing the method of the present invention. That is, in the wet ball mill according to the present application, in a wet ball mill in which a cylinder rotates while being supported by wheels, a slit is formed along a rotation direction as a through hole formed in a discharge port side plate of the cylinder. It is characterized by the following. If crushed sand is performed using such a wet ball mill, extremely good rapid discharge can be achieved, and unnecessary over-pulverization can be prevented.

The shape of the slit may be arcuate or linear as long as it is along the rotational direction of the side plate. By the way, such a slit has a function of retaining the ball in the mill cylinder body, and also has a function of discharging the ball whose abrasion force has been reduced due to abrasion to the outside of the mill. This means that by appropriately setting the width of the slit assuming the diameter (abrasion degree) of the ball having a reduced impact force, it is possible to suppress operating costs and efficiently operate. I have. In this regard, in the case of fine crushing by a conventional ball mill, the width of the through hole is usually up to 12 mm, and especially up to 25 mm even for coarse products. In contrast,
In the production of crushed sand, which is the object of the present application, it is preferable to use a large amount of water from the viewpoint of rapid discharge, but that point is also taken into consideration because the hydraulic power also affects the impact force of the ball There is a need. Also, it was found that the crushing force was not sufficient even with a ball worn to a diameter of 35 to 40 mm depending on the amount of water. When the ball was worn to a diameter of 25 mm, there was no crushing force at any amount of water, and the crushing was hindered. From this, the width of the slit is 25-40 mm
It can be said that it is preferable to set it between. With this setting, it is possible to promptly discharge the ball having a diameter of 40 mm or less due to abrasion and a reduced impact force, thereby improving the crushing efficiency.

The total area of the slits with respect to the effective sectional area of the cylinder also affects the discharge speed of the crushed material. here,
The effective cross-sectional area of the cylinder refers to the cross-sectional area in the space inside the cylinder in the actual operating state.For example, when a liner is attached to the cylinder, the cross-sectional area of the liner is calculated from the cross-sectional area calculated from the inner diameter of the cylinder. It means the area that was subtracted. As a result of trial operation with a slit having the above preferred conditions, i.e., a ball mill having a side plate provided with a slit having a width of 25 to 40 mm in a circular arc shape along the rotational direction, the total area of the slit with respect to the effective cross-sectional area of the cylinder If it is less than 3%, the passing speed of the slurry will be extremely slow, and the residence time will be long, resulting in unacceptable fine grinding as sand. On the other hand, if it exceeds 12%, the passing speed will be higher than necessary. It was found that the residence time was too short and sufficient crushing was not performed. In addition, if it exceeds 12%, the ball hits the ball directly, or the ball hits the inner wall directly, which causes a problem that the ball is broken, and generates a very loud noise. For this reason,
The total area of the slits with respect to the effective sectional area of the cylindrical body is preferably at least 12% or less, more preferably 3 to 12%.
Should be set to%.

[0022]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a basic apparatus configuration relating to the production of crushed sand. In the figure, 1 is a ball mill, 2 is a charge hopper, 3
Is a feeder, 4 is a classifier, 5 is a magnet separator,
Reference numeral 10 denotes a forced ore feeder connected to the inlet of the mill, 11 denotes a cylindrical sieve, and 13 denotes a cylinder (drum). Here, the ball mill 1 has a structure in which a cylindrical body 13 rotates while being supported by wheels (not shown) including drive wheels. As will be described later, a disc-shaped liner plate 14 serving as a baffle plate is provided on the discharge port 12 side. The cylindrical body 13 is kept horizontal with respect to the ground.

The crushed sand raw material is received by the charge hopper 2, cut out by the adjustable feeder 3 at an optimum supply amount, and is flushed by water into the forced feeder 10, and the mill 1
Into the cylindrical body 13. The product crushed in the cylinder 13 of the mill 1 rides on the cylindrical sieve 11 attached to the discharge port, and
The m-under is sent to the classifier 4 together with the water, and the under-0.074 mm is discharged with the classifier overflow. While 0.074 to 5 mm of the classifier product becomes crushed sand, more than 5 mm is returned to the charge hopper 2 via a return conveyor (not shown),
The raw material is again charged into the cylinder 13 of the mill 1. Note that a magnet separator 5 is disposed on the return conveyor to pick up the balls discharged by abrasion when returned.

FIG. 2 shows a characteristic structure of the ball mill 1 according to the embodiment passing through the above steps. FIG.
Shows a structure on the discharge port 12 side of the ball mill 1, and a disc-shaped liner plate 14 is attached to a side wall of the cylindrical body 13 on the discharge port 12 side. In the center of the liner plate 14, a manhole 15 communicating with the discharge port 12 is formed, and around the manhole 15,
Within a range corresponding to the discharge port 12, an arc-shaped slit 16 is formed concentrically along the rotation direction of the liner plate. Here, the width of the arc-shaped slit 16 is set to be in a range of 25 to 40 mm, and the total area is set to be in a range of 3 to 12% with respect to the effective sectional area of the cylindrical body. The size of the cylindrical body 13 is such that the ratio of the length to the inner diameter of the cylindrical body is 1.6 to 2.2.

[0026]

【Example】

Test Example 1 An example satisfying the conditions of the manufacturing method according to the present application and a comparative example performed under the operating conditions of a conventional ball mill were performed in the apparatus configuration shown in FIG. 1 (however, the slit 16 width of the comparative example is different). Was. The crushed sand raw material is a hard crushed stone of 5 to 13 mm including the bill. Table 1 shows the operating conditions and results.

[0027]

[Table 1]

As is clear from the above table, in the ball mill of the same size, the crushing method under the conditions of the present invention showed a crushing production capacity of 182% compared to the comparative example under the conventional conditions.
Despite the fact that the rotation speed of the cylinder is 81-85% of the critical speed, which is high speed that cannot be considered with a conventional ball mill,
It can be seen that a high production capacity has been obtained.

Test Example 2 An example which satisfies the conditions of the production method according to the present application, as in Test Example 1, using ordinary crushed stone of 5 to 30 mm as a crushed sand raw material,
FIG. 1 shows a comparative example performed under the operating conditions of a conventional ball mill.
(However, the width of the slit 16 in the comparative example is different). Table 2 shows the operating conditions and results.

[0030]

[Table 2]

As is clear from the above table, in a ball mill of the same size, the crushing method under the conditions of the present invention showed a crushing production capacity of 169% as compared with the comparative example under the conventional conditions.
In particular, in Comparative Examples, large grains could not be crushed, and small grains tended to be excessively crushed. Also, as in Test Example 1, it can be seen that a high production capacity is obtained despite the extremely high rotational speed of the cylinder of 86 to 89% of the critical speed.

[0032]

As described above, according to the method for producing crushed sand according to the present invention, a large amount of high-quality crushed sand can be efficiently produced not only from hard crushed sand raw materials but also from other types of crushed stone.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an example of a basic apparatus configuration relating to the production of crushed sand of the present application.

FIGS. 2A and 2B show a preferred example of the structure of a wet ball mill according to the present application, in which FIG. 2A is a sectional side view of a cylindrical discharge port side, and FIG. 2B is a front view of a side plate.

FIG. 3 shows an example of a conventional rod mill and is a side view of an overflow type.

4A and 4B show another example of a conventional rod mill, wherein FIG. 4A is an explanatory diagram of an end peripheral type, and FIG. 4B is an explanatory diagram of a center peripheral type.

FIG. 5 shows another example of the conventional rod mill, and is a side view of an inclined rod mill.

FIG. 6 shows another example of a conventional rod mill, and is an explanatory view of a tapered rod mill.

FIG. 7 shows another example of the conventional rod mill, and shows a 252nd rod mill.
It is explanatory drawing of the rod mill which concerns on 8938 utility model registration. (a) is a cross-sectional side view of the cylinder outlet side, (b) is A- in (a)
It is A sectional drawing.

FIG. 8 shows an example of a conventional ball mill, and is an explanatory view of a ball mill with a trunnion.

[Explanation of symbols]

 1 Ball Mill 2 Charge Hopper 3 Feeder 4 Classifier 5 Magnet Separator 12 Outlet 14 Side Plate (Disc-shaped Liner Plate) 16 Slit

Claims (9)

[Claims] 1. A method for producing crushed sand using a wet ball mill, comprising rotating a wet ball mill in which a cylindrical body rotates while being supported by wheels in a range of more than 80 to 89% of a critical speed. 2. The method for producing crushed sand using a wet ball mill according to claim 1, wherein the operation is performed using balls having a diameter of 90 to 120 mm at the time of filling. 3. The method for producing crushed sand using a wet ball mill according to claim 1, wherein the operation is performed with the ball filling rate in the cylinder set to less than 35% of the volume in the cylinder. 4. The ratio of the length to the inner diameter of the cylinder is 1.6 to 2.2.
The method for producing crushed sand using a wet ball mill according to claim 1, wherein the ball mill is used. 5. The method for producing crushed sand using a wet ball mill according to claim 1, wherein the operation is performed while pouring water so that the slurry concentration in the cylinder becomes 60 wt% or less. 6. In a wet ball mill in which a cylindrical body rotates while being supported by wheels, and a side plate having a through hole is disposed on a discharge port side in the cylindrical body, a rotation direction of the side plate is used as the through hole. Wet ball mill, characterized by a slit formed along it. 7. The width of a slit formed in the side plate is 25.
7. The wet ball mill according to claim 6, wherein the diameter is set to about 40 mm. 8. The wet ball mill according to claim 6, wherein the total area of the slits formed in the side plate is set to be 3 to 12% with respect to the effective sectional area of the cylindrical body of the ball mill. 9. A cylinder having a ratio of length to inner diameter of 1.6 to 2.2 is rotated while being supported by wheels, and a side plate is arranged on a discharge port side in the cylinder, and the side plate is disposed along the rotation direction. Width 25
A method for producing crushed sand using a wet ball mill, which is a slit having a diameter of about 40 mm and a total area of the slit is 3 to 12% with respect to the effective sectional area of the cylindrical body. The ball filling rate is set to less than 35% of the cylinder volume,
And a method for producing crushed sand using a wet ball mill, wherein the operation is performed by rotating water within a range of more than 80 to 89% of a critical speed while pouring water so that the slurry concentration in the cylinder becomes 60 wt% or less. .