JP2000237626A - Milling and sieving apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultra fine powder of 25,000 Blaine value or higher by a vertical mill. SOLUTION: This sieving apparatus bits and mills an object matter (a) to be milled between a milling table 3 and a milling roller 4 and sieves the milled matter (b). At the time of milling, flakes (f) are actively generated and the amount of the flakes f is controlled to be 3 wt.% or more to the object to be fed newly or to be 20 wt.% or more to the whole matter dropping out the milling table 3, and the resultant flakes f are turned back to the milling table 3. The flakes f include flakes of a coarse powder (c), a minute powder (d), and a fine powder (e) and subjected to sufficient milling between the milling table 3 and the milling roller 4. Consequently, by milling the flakes f, the minute powder d and the fine powder d are milled together with the coarse powder c to be an ultra fine powder (g). As a result, an ultra fine powder (g) of 25,000 Blaine value or higher can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for crushing and classifying limestone (calcium carbonate), cement raw material, cement clinker, ore, quartzite, etc., using a vertical mill, and more particularly to calcium carbonate (calcium carbonate), talc, and chip. The present invention relates to a pulverizing and classifying apparatus for obtaining ultrafine powder of an inorganic substance such as silicon oxide and slaked lime.

[0002]

2. Description of the Related Art A pulverizing and classifying apparatus using a vertical mill will be described with reference to FIG. 1 showing an embodiment of the present invention. The crushed material a is interposed between the crushing roller 3 and the crushing roller 4 and crushed, and the crushed crushed material b is raised and classified by an ascending air current (primary air) p sent from below the crushing table 3. The trapped material d is returned to the crushing table 3 and the non-trapped fine powder e is collected by a bag filter or the like to obtain a product.

[0003] In this kind of pulverizing and classifying apparatus, there is a problem how to efficiently obtain a product e of a required particle size, and the technique is disclosed in JP-A-62-45354 and JP-A-6-29.
No. 6886, Japanese Patent Application Laid-Open No. 9-117685, and the like. These techniques return the uncrushed crushed material a dropped from the crushing table 3 to the crushing table 3 again, and determine the sum of the returned amount (circulation amount) and the crushed material a newly sent onto the crushing table 3. For example, the powder layer on the pulverizing table 3 is formed to have a predetermined thickness to perform a stable operation.

[0004]

At present, when used as a resin filler or the like in charcoal or the like, finer powders, for example, those having a 20,000 Blaine value (cm ² / g: specific surface area) or more are required. However, due to the structure of the pulverizing action, the vertical mill mainly performs pulverization with a value of about 15,000 Blaine or less, as in the above publications. For this reason, coarse pulverization is mainly performed, and in order to obtain an ultrafine powder having a 20,000 Blaine value or more, the fine powder after the coarse pulverization is further converted into ultrafine powder by grinding using a ball mill or a medium stirring mill. However, providing a grinding and pulverizing apparatus other than the pulverizing and classifying apparatus causes an increase in equipment cost and also deteriorates productivity.

Here, in the pulverizing classification by the pulverizing table 3 and the pulverizing roller 4, in general, in order to increase the Blaine value of the pulverized substance, the supply amount of the pulverized substance and the classification air volume are reduced, or the pulverizing roller 4 is pushed. It is conceivable to increase the pressure and the number of revolutions of the classifier to make the finer and to collect (sort) only finer fine powder.

[0006] However, when the ratio of the fine pulverized material in the powder layer increases, the fine pulverized material easily floats, so that the powder layer itself on the pulverizing table 3 easily flows. For this reason, when the crushing roller 4 tries to crush, the powder layer on the crushing table 3 flows (runs away), and a sufficient powder layer is not formed between the crushing roller 4 and the table 3, so that smooth crushing is performed. No action is taken. The floating of the fine pulverized material means that only the coarse powder remains in the powder layer, and the fine pulverized material is not pulverized and does not become finer. For these reasons, vertical mills cannot produce ultrafine powder and are employed for grinding below about 20,000 Blaine values. On the other hand, vertical mills do not require larger equipment and have lower running costs than grinding and pulverization.

[0007] It is an object of the present invention to obtain an ultrafine powder only by pulverization and classification by a vertical mill.

[0008]

In order to solve the above-mentioned problems, the present invention allows coagulation of coarse powder, fine powder and fine powder,
The agglomerates (flakes) that fell from the crushing table were returned to the crushing table.

Generally, the pulverized material immediately after pulverization has an active force (cohesive force) of a new surface (a newly generated pulverized surface by pulverization).
, And easily agglomerated with nearby pulverized materials. This tendency becomes conspicuous as the pulverized material becomes finer, and when the ascending airflow rises or on a pulverizing table, the powder is agglomerated and coarsened. If the coarse powder is formed, it becomes difficult to pass through the classifier, and the coarse powder has a weak cohesion and has a floating property as a fine pulverized material, so that a smooth pulverizing action is not performed. For this reason, conventionally, the pulverizing action is performed under the condition that the coagulation action does not occur, and the Blaine value of the obtained product is substantially limited to 15,000 to 20,000.

However, if a large amount of coarse powder having a low cohesive force is produced, the ratio of being caught between the pulverizing table and the pulverizing roller increases, and flakes having a high cohesive force are generated due to the pulverizing (compressing) action. . The flakes are agglomerates such as fine powders and fine powders, but have a large cohesive force (specific gravity) and thus have no floating property. Therefore, if the powder layer in which the flakes are mixed is pulverized, the fine powder and the fine powder in the flakes can be further pulverized into ultrafine powder. Thereby, even a vertical mill can produce ultrafine powder.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, a crushing roller is rotatably pressed against the upper surface of a rotating crushing table, and a crushed object is caught between the crushing table and the crushing roller to be crushed. A pulverizing and classifying apparatus that raises and classifies the pulverized pulverized material by an ascending air current sent from below the table, returns the captured substance to the pulverization table, and collects unpulverized fine powder to produce a product. In the above, a configuration may be adopted in which the flakes falling from the crushing table are returned (circulated) on the crushing table by 3% by weight or more with respect to the amount of the new crushed material sent to the crushing table.

The weight ratio of the flakes dropped from the crushing table and returned to the entire fallen object is 20%.
The configuration described above can also be adopted.

Thus, the amount of flakes returned (circulation rate)
By setting, it is possible to obtain an ultrafine powder (product) having a value of 25000 Blaine or more (see experimental examples described later, FIGS. 2 and 3). The conditions of 3% by weight or more and 20% or more can be used in combination.

In these configurations, if the flakes are crushed to a required size and then returned to the crushing table, an appropriate substantially uniform size (bulk) can be obtained for various crushed materials. (Specific gravity) can be returned, the crushing efficiency is made uniform, and continuous stable operation becomes easy.

If secondary air for particle size distribution adjustment is introduced above the pulverizing table, the flow rate of primary air to secondary air can be changed by adjusting the amount of air (flow velocity). The particle size distribution of the product can be adjusted by changing the classification range. When the introduction is in the tangential direction of the swirling flow of the rising airflow, the adjustment is smooth without disturbing the swirling flow.

[0016]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a vertical mill in which a crushing table 3 and a plurality of crushing rollers 4 are provided in a casing 2, and the crushing rollers 4 rotate. It is free and can be pressed in the direction of the crushing table 3 by the pressurizing cylinder 4a. 5
Is a means for supplying crushed material a such as a screw feeder provided through the casing 2; 6 is a tray fixed below the table 3 on the inner surface of the casing 2;
The scraper 8 fixed to the lower surface of the table 3 is an outlet for the crushed material a dropped from the table 3.

Reference numeral 9 denotes an air flow type classifier provided above the casing 2, 10 denotes guide vanes provided in parallel so as to surround the air flow type classifier, and each guide vane 10 The guide vanes 10 are connected to a rotatable pin 10a penetrating through the ceiling, and all the guide vanes 10 can be inclined at the same angle with respect to the radial direction of the classifier 9 via the pin 10a. 11 is a cone provided below the guide vane 10, 12 is a horizontal discharge means comprising a screw feeder provided below the cone 11, 13
Is the crushed material a (fine powder d) discharged from the horizontal discharging means 12
A measuring means 14 such as a load cell type flow meter for measuring the amount of the crushed material a returned from the measuring means 13 and the discharge port 8 to the supply means 5; for example, a pipetted bucket conveyor or the like; It is a means of circulation.

Reference numeral 15 denotes an inlet for the primary air p of the casing 2, and the air p passes through the nozzle 18 and rises in the casing 2 as a swirling flow. Reference numeral 16 denotes an inlet for the secondary air q, which faces a tangential direction around the casing 2. The introduction of the secondary air q is appropriately determined in consideration of the product particle size. Reference numeral 17 denotes a discharge port for the product (finely crushed material) and air provided at the upper portion of the casing 2, and 19 denotes a switching damper for sampling the amount of the crushed material a discharged from the discharge port 8. The measuring means 13 and the switching damper 19 are provided for confirming the circulation amount in an experiment.

This embodiment is configured as described above. Next, the operation method will be described. The crushed material a supplied from the supply means 5 onto the crushing table 3 is
Due to the rotation of, it moves toward the outer periphery of the crushing table 3 while drawing a radial trajectory, and is caught between the crushing table 3 and the crushing roller 4 on the way to be crushed.
In the pulverizing operation, at the beginning of the operation, a powder layer is formed on the pulverizing table 3 by the newly supplied crushed material a and pulverized with the pulverizing roller 4. At this time, since the crushed material a is large, it is difficult to be crushed finely,
The coarse powder c rises with the airflow and then falls again on the crushing table 3. Further, the fine powder d rises with the airflow and is classified by the guide vanes 10 and the classifier 9,
Collected in the cone 11, the horizontal discharging means 12, the measuring means 1
3, crushing table 3 via circulation means 14 and supply means 5
Returned to the top. In addition, guide vane 10, cone 1
1. The horizontal discharging means 12 and the measuring means 13 are omitted, and the classifier 9
, Which are not able to pass through the classifier 9, are directly dropped by the free fall.
You can put it back on.

On the other hand, the fine powder e passes through the air classifier 9 and is discharged as a product from the discharge port 17 to the outside of the system and is collected by a bag filter or the like. However, the average Blaine value of the fine powder e is still low, and the fine powder e has not been pulverized to the ultrafine powder g. The crushed material a (excreted stone) that has not been crushed or has not been crushed is moved from the outer peripheral edge of the crushing table 3 to the receiving tray 6.
Is returned to the crushing table 3 by the circulation means 14 via the supply means 5.

The air-flow classifier 9 is rotating at a high speed to obtain the ultrafine powder g, and the fine powder d is considerably finer than usual. For this reason, the fine powder d (in the case of a single particle) tends to float, and if a large amount of the fine powder d is included, the powder layer itself on the crushing table 3 is also likely to be fluidized. Can not be crushed by biting between.

As the operation time elapses, the newly supplied crushed material a, the coarse powder c that has risen with the air current and then falls on the crushing table 3,
A powder layer made of the fine powder d collected at 1 and returned to the pulverizing table 3 via the circulation means 14 is formed. Then, the powder in the powder layer gradually becomes finer, and the fresh surface immediately after being pulverized has a large activity, so that the powders adhere to each other to generate an initial aggregate. This initial aggregate is
Since the cohesive force is weak and has buoyancy as a fine pulverized product, a smooth pulverizing action cannot be performed.

Further, when the operation is continued, the amount of the initial aggregates increases, and accordingly, the pulverizing table 3 and the pulverizing roller 4
In the meantime, the amount of the initial aggregates to be caught also increases, and the flakes f are subjected to a pulverizing (compression) action and have a large cohesive force. The flake f is an aggregate of the fine powder d and the fine powder e. However, when the flake f has a size of, for example, about 1 to 30 mm lump, the flake f loses the floating property. Further, the flakes f or the flakes f and the coarse powder c, the fine powder d, and the fine powder e aggregate to form larger flakes f.

When the amount of the flakes f increases, the powder layer does not flow, a sufficient powder layer can be formed between the crushing roller 4 and the crushing table 3, and crushing is performed to obtain ultra fine powder. Will be able to

When this powder layer is sandwiched between the crushing roller 4 and the crushing table 3 and subjected to a compressive / shear crushing action, the newly supplied crushed material is crushed and the coarse powder c in the flake f, Fine powder d and fine powder e are further pulverized. The flakes f are broken into small flakes and single particles by the compression and shearing action. Along with the crushing, single particles (coarse powder c, fine powder d, and fine powder e) are entrained in the rising airflow and are separated. When compressed and crushed, the flakes f combine with other flakes f to form larger flakes f.

The flakes f crushed by the crushing roller 4 gradually move to the outer edge of the crushing table 3 and are opposed to the airflow p which is blown up from a nozzle 18 provided outside the crushing table 3. Fall on. The flakes f are collected by the scraper 7, discharged out of the casing 2 through the discharge port 8, and returned to the supply means 5 by the circulation means 14. The flakes f
4, the number of flakes f in the powder layer is increased by circulating many times, and the stable operation of the vertical mill can be performed. In addition, as shown in the experimental results described later, all of the flakes f fall from the crushing table 3 and all of the flakes f (non-crushed or crushed material a that has not been crushed) fall. If you are biased to either. However, there are some cases where the flakes f and the waste rock are mixed and fall. This means that once flake f is formed,
It is thought that the amount will surely increase.

It should be noted that whether the falling object from the crushing table 3 is a flake f or a quarry is checked by sampling by switching the switching damper 19. That is, the flakes f are crushed by rubbing with hand, but the flakes are not crushed. In general, the flakes f are oval and have a length of 20 to
The thickness is about 30 mm and the thickness is about 1 to 3 mm. In some cases, the length is as small as about 1 mm or as large as about several tens mm.

As described above, by making the fine powder into the flakes f, the floating thereof is prevented, and the flakes f are formed.
Is pulverized, so that the average Blaine value of the obtained fine powder e is as high as 25,000 to 46000, which is pulverized to ultra fine powder g.

Incidentally, since the fine powder d is surely returned to the center of the crushing table 3 without drifting in the casing 2, the chance of crushing the fine powder d increases. Further, since the fine powder d is forcibly discharged from the inside of the casing 2, the powder density in the casing 2 is reduced, and the classification performance of the airflow classifier 9 is improved.

Since the fine powder e obtained in the early stage of the operation is not pulverized to the ultrafine powder g, it is preferable to separate the fine powder e from the ultrafine powder g obtained in the steady operation. For example, it may be temporarily stored and supplied to the vertical mill 1 when the operation becomes a steady operation in which the ultrafine powder g is obtained.

In the initial stage of operation, the air passing through the airflow classifier 9 is extremely reduced, and
Stopping the supply of the crushed material a newly supplied after the thickness of the upper powder layer reaches a predetermined value, and circulating and crushing the crushed material a (the crushed material b) to generate flakes f early. Is also possible.

In the embodiment, the crushed material circulated by the circulating means 14 is sent to the pulverizing table 3 via the supply means 5 so that the supply amount thereof can be adjusted. Means 14 may be sent directly to the crushing table 3. Further, if the crusher 20 is provided to return the flakes f in a uniform required size, the crushing efficiency is stabilized. Further, by crushing the flakes f, the surface area ratio of the flakes f is increased, and simple particles such as the ultrafine powder g are easily separated from the flakes f. Further, the fine powder d that has reached the upper part of the casing 2 is transferred to the corn 1
By collecting them at 1 and discharging them by the horizontal discharge means 12, it is possible to reliably prevent the fine powder d from being discharged from the outlet 17, and to increase the Blaine value of the product g.

[0033]

[Experimental example] The experiment was performed by changing the conditions such as the amount of raw material supplied, the amount of air introduced, the number of revolutions of the airflow classifier, and the pressing force of the crushing roller. Weight ratio of flakes to be supplied), circulation ratio (weight ratio of flake circulation amount to new supply amount (product amount)), and the like. Then, when it was determined that the operation had reached a steady state, the product was sampled. The steady state was determined by examining changes in the product amount, the power, and the amount of the fine powder d by the weighing means 13. If these were stabilized, it was determined that the steady state had been reached. To reach the steady state, about one hour after the start of operation,
In some cases, two hours were required. After the sampling, the experiment was stopped, and the secondary air q was not introduced.

FIGS. 2 to 9 show the experimental results.
Is a relationship diagram between the Brain value and the falling ratio, in which the amount of flake f is 0.2 (20%) among the falling objects from the crushing table.
Exceeds 25,000 Brain values,
In many cases, the entire amount of the falling object becomes the flake f. This suggests that if a small amount of flake f is formed, the ratio of flake f sharply increases from a certain point in time. FIG. 3 is a graph showing the relationship between the Blaine value and the circulation ratio. The Brain value increases with the circulation ratio.
When it exceeds 03 (3% by weight), the value is 25,000 Blaine or more. FIG. 4 is a diagram showing the relationship between the Blaine value and the air volume. By reducing the air volume, a product having a high Brain value can be obtained. FIG. 5 is a diagram showing the relationship between the air volume and the falling ratio. FIG. 6 is a diagram showing the relationship between the average particle diameter of the product and the circulation ratio. Fine powder can be obtained by increasing the circulation ratio. FIG. 7 is a diagram showing the relationship between the average particle diameter of the product and the falling ratio. As the falling ratio increases, fine powder is obtained. FIG. 8 is a diagram showing the relationship between the Brain value and the new supply amount (product amount). In order to obtain a product g having a high Brain value, the production amount must be reduced. FIG. 9 is a graph showing the relationship between the air flow rate and the circulation rate. When the air flow rate is reduced, the powder cannot ride on the rising airflow and the flake circulation rate ratio increases. FIG. 10 is a graph showing the relationship between the average particle diameter of the product and the Blaine value. The average particle diameter decreases as the Blaine value increases. Products of 1 μm or less, which were possible, have been obtained.

[0035]

As described above, according to the present invention, even in the pulverization and classification by the vertical mill, the flakes are positively generated and returned to the pulverization table, so that the flakes are reduced to 250.
It is possible to obtain an ultrafine powder having a value of 00 Blaine or more.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of one embodiment.

FIG. 2 is a diagram showing a relationship between a brain value and a falling ratio according to the embodiment.

FIG. 3 is a diagram showing a relationship between a brane value and a circulation ratio according to the embodiment.

FIG. 4 is a diagram showing a relationship between a brane value and an air flow according to the embodiment.

FIG. 5 is a diagram showing a relationship between an air volume and a drop rate according to the embodiment.

FIG. 6 is a diagram showing the relationship between the average particle size of the product and the circulation ratio according to the example.

FIG. 7 is a diagram showing the relationship between the average particle diameter of the product according to the example and the falling ratio.

FIG. 8 is a diagram showing the relationship between the Blaine value and the product quantity according to the embodiment.

FIG. 9 is a diagram showing the relationship between the air volume and the circulation ratio according to the embodiment.

FIG. 10 is a diagram showing the relationship between the average particle size and the Blaine value of the product according to the example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vertical mill 2 Casing 3 Grinding table 4 Grinding roller 5 Supply means (screw feeder) 6 Receiving tray 7 Scraper 8 Discharge port 9 Air flow classifier 10 Guide vane 11 Cone 12 Horizontal discharge means 13 Measuring means 14 Circulation means 15 Primary air introduction Mouth 16 Secondary air inlet 17 Outlet 18 Nozzle 19 Switching damper a Crushed material b Crushed material c Coarse powder d Fine powder e Fine powder f Flake (aggregate) g Ultra fine powder

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Shinichi Shimamura, Inventor 3-8-1, Nishikanda, Chiyoda-ku, Tokyo Inside Noda Engineering Co., Ltd. (72) Fumio Kawano 3--8, Nishikanda, Chiyoda-ku, Tokyo No. 1 Onoda Engineering Co., Ltd. (72) Inventor Masaru Ogata 1-12-19 Kitahorie, Nishi-ku, Osaka City Inside Kurimoto Iron Works Co., Ltd. (72) Inventor Kantaro Kango 1-112-19, Kitahorie, Nishi-ku, Osaka City No. Inside Kurimoto Iron Works Co., Ltd. (72) Inventor Yuki Bando 1-12-19 Kitahorie, Nishi-ku, Osaka City Inside Kurimoto Iron Works Co., Ltd. (72) Inventor Mutsuyasu Kawashima 1-112 Kitahorie, Nishi-ku, Osaka City No. 19 F-term in Kurimoto Iron Works, Ltd. (reference) 4D063 EE03 EE12 GA05 GA06 GA07 GA10 GC02 GC08 GC12 GC14 GC19 GC32 GC36 GD02 GD15 GD17 GD24 4D067 EE05 EE07 EE 23 EE50 GA01 GA05 GA07 GA20 GB02

Claims (5)

[Claims] 1. A crushing roller 4 is rotatably pressed against an upper surface of a rotating crushing table 3, and a crushed object a is bitten between the crushing table 3 and the crushing roller 4 to be crushed and fed from below the crushing table 3. The pulverized material b is raised and classified by the ascending airflow p, and the captured material d
Is returned to the pulverizing table 3 and the flakes f falling from the pulverizing table 3 are returned to the pulverizing table 3 to obtain 25,000 A pulverizing and classifying apparatus characterized in that a product g having a Blaine value or more is obtained. 2. The crushing and classifying apparatus according to claim 1, wherein the flakes f are returned to the crushing table 3 after being crushed. 3. The amount of the returned flakes f is 3 to the amount of new crushed material a sent to the crushing table 3.
2. The method according to claim 1, wherein the weight of the product is not less than 25,000, and the weight of the product is more than 25,000.
Or the pulverizing and classifying apparatus according to 2. 4. The method according to claim 1, wherein the weight ratio of the flakes f falling from the crushing table 3 to the whole falling object is 20% or more to obtain a product g exceeding the 25,000 Blaine value or more. 3. The pulverizing and classifying apparatus according to 2. 5. The pulverizing and classifying apparatus according to claim 1, wherein secondary air q for adjusting particle size distribution is introduced above the pulverizing table 3.