JP2918047B2 - Grindability evaluation device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pulverizability evaluation apparatus for evaluating the pulverizability of solid particles such as solid fuel such as coal or cement raw material.

[Conventional technology]

A solid raw material such as coal, cement raw material, ore, etc. is finely pulverized by a pulverizer in accordance with the intended use.
Hard grove mill (Hardgr
ove Mill), and the test method is defined by Japanese Industrial Standards [JIS M8801 (hardness test method for hard grove)], and the obtained result is indicated by Hardgrove Grindability Index (abbreviation H).
GI).

FIG. 15 shows the structure of this hard glove mill (test apparatus). In this device, the sample to be ground is
The rolling of the plurality of crushing balls 151 on the crushing race 152 provided on the crushing race 152 provided at the inner bottom portion of the 153 causes crushing for a predetermined time set in advance. In this case, the grinding ball 151 is pressed down by the top ring 154 onto the grinding race 152. The top ring 154 is rotationally driven by a motor (omitted) via a transmission (omitted) provided above the mill drive shaft 155. The load 158 is
A total weight of 29 kgf is set using three weights 157 inserted into the mill drive shaft 155 (usually, one of which is often about 8 kgf) in combination with the weight of the mill drive shaft 155 and other parts.

 In the figure, 156 is a mill center axis, and 159 is a powder layer.

The results obtained by the hard glove mill of this configuration show that, although there are differences between the batch type and the continuous type, a ball type ring roller mill (also called a ball race mill or ring ball mill) having almost the same configuration as this mill has
Because of the similar basic form of milling, the results of the above test equipment are also simple methods that have been made directly available, and this is still a common practice today. It is.

[Problems to be solved by the invention]

Until now, the pulverizability of solid raw materials (coal, coke, sintered ore, slag), etc. was tested using a hard glove mill shown in Fig. 15 with a load M of 29 kgf for 4 minutes (total 60 rotations). Has been sought.

In this case, the load σ per unit projected area of the ball on the race surface is much lower than that of a practical machine mill.
Only about 1/4. The experiment with such a low load is almost the same even when using a roller as a crusher, and the load per unit projected area is considerably lower than that of a practical machine mill.

Fig. 14 (a)
As shown in FIG. 14, a coarse-grain environment is obtained, which is significantly different from the fine-powder environment shown in FIG. 14th
In the figure, 1401 is a powder layer composed of coarse particles, 1402 crushing roller, 1403 is a mill container, 1404 is a rotating shaft, 1405 is a crushing roller shaft, 1406 is a mill rotating shaft, 1407 is a roller holder, 1408 is a mill rotating shaft, 1409 Is a powder layer composed of fine powder.

Therefore, it is difficult to accurately predict the pulverization performance of a practical machine simply by following the conventional method without any measures, regardless of how the test is performed under conditions where the pulverizing section of the practical machine and the powder layer environment are significantly different. Incidentally, although it depends on the properties of coal, the conventional grindability test shows that even if the particle size of the crushing part is high, it is at most 200 mesh pass 20%, usually only 10%, while that of a practical machine is 200 mesh pass 30 at the same time. %,
It can even reach 60% under operating conditions that increase crushing and classification capacity. Recently, mills having a built-in rotary classifier for improving the particle size are increasing. In this case, since the amount of circulation in the mill increases, if the separation performance of the classifier is not so good, the particle size of the pulverizing section increases.

In general, in a coarse-grained environment as shown in FIG. 14 (a), the progress of the pulverization is estimated to be too fast, especially for a raw material having good pulverizability. Therefore, as shown in FIG.
Coal with a high grindability index RGI can obtain a much lower grinding capacity than expected on a commercial machine.

On the other hand, in the grindability test, if a high load, that is, a higher load per unit projected area, is applied, the pulverization proceeds accordingly, and the environment of the pulverizing section can be brought close to the state of a practical machine to some extent. However, this method has a problem peculiar to the batch type, in which the coarse particles are extremely reduced (in a continuous mill, a certain amount of coarse particles always exists because feed coarse particles are always supplied). Due to the cushion effect caused by the accumulation of fine particles, the pulverization efficiency is reduced as shown in FIG. 13, and a deviation from the micro-layer environment of a practical machine to be reproduced occurs.

As described above, the batch type grindability evaluation method has several important problems. As an attempt to solve the above-mentioned problems, as an attempt to solve the problem described above, `` of the pulverized material pulverized by the hard glove mill, the fine powder which was easily pulverized was stopped by removing the mill, and coarse particles which were not easily pulverized were milled. While adding new coarse particles until the predetermined amount is reached, and repeat this operation until the HGI becomes constant. " However, the method of artificially creating a coarse-grained environment as shown in FIG. 14 (a) and pulverizing it for a long time with a low load is intended to bring the situation as close as possible to a practical machine mill as described above. Although the policy is correct for the issues, it is difficult to realize for the following two reasons. The first reason is that a low-load grinding results in a typical coarse-grained environment. The second reason is that since the starting of the mill is repeated frequently, the grinding at the starting causes the grinding of coarse particles to be somewhat faster than in the case of continuous operation.

An object of the present invention is to provide a grindability evaluation device for solving the above-mentioned problems.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a crusher,
In a batch type ring roller mill, in which the load per unit area of the ball or roller projected onto the grinding race (pressing force) is equal to or greater than that of a practical machine, that is, a batch type grinding evaluation device, the bottom of the mill container, that is, the grinding race A large number of sieve holes for discharging the particles pulverized to a predetermined size to the outside of the mill system are formed on the outer peripheral side pulverizing surface of the above, or a sieve having a predetermined opening is arranged. In order to facilitate the discharge of fine particles from the sieve, a scraper is provided on the sieve which rotates in the mill in conjunction with the roller in the roller holder.

According to such an apparatus, the raw material that has been pulverized into fine powder is removed from the mill container, so that the raw material in the mill is reduced, the pulverizing torque is reduced, and the pulverized state is greatly different from the initial state. Therefore, feed back control is performed so that the grinding torque is constant, and a coarse material is supplied.

[Action]

With the device according to the present invention, the disadvantages and problems inherent in the batch type can be eliminated.

First of all, the realization of a powder bed environment close to the state of a practical machine can be mentioned. In order to make the powder layer environment of the pulverizing section a fine powder environment similar to a practical machine, if the load per roller projection area is increased to the equivalent of a practical machine, the fine powder environment is realized as much as possible. However, in the case of a practical machine, a large amount of fine powder to be conveyed to the outside of the mill as product fine powder stays in the pulverizing section, and the pulverizing efficiency is reduced due to the so-called “cushion” action of the fine powder. Therefore, the original purpose of evaluating the pulverizability with the pulverization efficiency almost equal to that of a practical machine has not been achieved by using the conventional batch type test.

In that regard, if the apparatus according to the present invention is used, although it is apparently a fine powder environment, excess fine powder is discharged outside the system of the mill pulverizing unit, and coarse particles feed is also introduced into the mill like a practical machine. The state of the powder layer in the pulverizing section, such as being supplied, is considerably close to the condition of a practical machine. In this way, the result of the crushability (particle size or crushing capacity) estimated by the apparatus according to the present invention makes it possible to satisfactorily predict the crushability characteristics of a practical machine.

According to the present invention, in addition to the particle size and the crushing capacity, crushing power that differs for each raw material (this is indirectly obtained by measuring crushing torque) and the likelihood of mill vibration being predicted are also predicted. Becomes possible. In the latter case, the state of the powder layer that affects the movement of the roller (the particle size of the particles forming the powder layer, the thickness of the powder layer, etc.) is estimated from the magnitude of the fluctuation of the grinding torque. Therefore, raw materials that are likely to cause vibration, dangerous mill operating conditions, and the like can be extracted in advance.

(Example of the invention)

FIG. 1 (a) is a schematic system diagram of a quasi-continuous grindability evaluation apparatus according to the present invention, and FIG. 1 (b) is a BB view of a pressurized portion of the apparatus viewed from above. In this apparatus, it is possible to use a plurality of balls like a hardgrove mill, but in the present invention, the rollers shown in FIGS. 2 and 3 were used.

Three crushing rollers 42 are mounted on the roller holder 41 at equal intervals in the circumferential direction of the crushing race 47 (120 °), and crush the test crushed raw material charged in the lower casing (mill container) 48 of the mill. I do. The roller holder 41 to which the crush roller 42 is attached has a connection portion with the roller holder 41 at the lower end, and is driven by the rotation of the mill shaft 36. The mill shaft 36 rotates at a low speed about the center axis of the mill, but at the base end, the pulleys 2 and 4 and the belt 3 rotate the motor 1.
Driven by A torque meter 8 for measuring torque is provided on the way.

The load required for the pulverization is such that the contraction force of the pressing spring 33 is applied to the pulverizing roller 42 from the mill shaft 36 via the pressing frame 22.
Is transmitted to. The pressurizing frame 22 and the mill shaft 36
The mounting portions of the bearings 24 and 25 of the pressurizing frame 22 are fixed by being locked by a bearing retainer 27, and are configured to move integrally.

As shown in FIG. 1 (b), the pressurizing frame 22 is composed of a portion for supporting the mill shaft 36 and three arms, and a pressurizing spring 33 is attached to the ends of these arms. Arm tip and pressurizing spring 33
Are fixedly supported by the tension rod 30. The pressing frame 22 is held on the mill base 50 by a stopper 58 in order to prevent accidental torsional movement due to rotational driving.

The fine powder crushed in this crushing section is
, I.e., to the outside of the rotation point of the crushing roller 42. Then, the fine particles having a predetermined particle size or less are discharged from a screen 46 provided outside the crushing race 47 to a fine powder receiving container 51 as shown in FIGS.
This discharge is facilitated by a scraper 54 in which a support portion is provided on the roller holder 41 between the rollers, and a toothbrush-shaped tip portion rotates on the screen 46 in conjunction with the rotation (revolution) of the roller on the race. . In the present embodiment, a screen of 200 mesh (opening of 75 μm) was used as the screen 46. The screen 46 can be set by selecting a screen having a different aperture according to the purpose or use.

In the figure, 5 is a speed reducer, 6 is a flexible coupling,
7 is coupling, 8 and 1 are pulse motors, 12 is rotary shaft, 1
3 is a feed brush, 14 is a shot, 14a is a shot 14
Sample shot falling inside, 17a is sample particle, 18 is mill shot, 19 is coupling, 20 is shaft coupling, 21 is shaft coupling stop, 23 is oil seal, 26 is bearing box, 28
Is an oil seal, 29 is a double nut, 31 is a spring seat, 34 is a basement, 36 is a mill drive rotary shaft, 37 is a rotation speed detector, 38 is a sleeve bearing, 39 is an oil hole plug, 40
Is the oil hole. 43 is a roller shaft, 44 is a roller rotating shaft,
45 is a powder layer, 49 is a mill upper casing, 52 is a fine powder falling, 53 is a fine powder collected in a container, 55 is a cutout for a stopper, 56 is a connection groove with a mill drive shaft 36, 57 is a seal plate, 58 Represents stoppers, a represents classified fine particles, and b represents finely pulverized particles.

When the fine powder is discharged out of the system of the pulverizing section in this manner, the hold-up of the pulverized raw material in the pulverizing section gradually decreases, and the pulverizing torque rapidly decreases as shown in FIG. 6 (b). To compensate for this, a crushed sample 16 is newly supplied from the sample hopper 15 to the crushing unit. In the supply, the crushing torque is detected by the torque meter 8 and the crushing torque is set to the sixth.
As shown in FIG. 3A, the feed amount of the sample is controlled by the feedback control using the personal computer 9 and the pulse controller 10 so that the sample supply amount becomes constant after 1 / 8T (T is the total pulverization time) of the coarse particle entrapment period. .

As typically occurs in the pulverization of the batch type operation shown in FIG. 6 (c), about 1 to 8 of the total pulverization time T (4 minutes in this embodiment) from the start-up is a period required for coarse-grained pulverization. And the crushing torque drops rapidly. afterwards,
The rate of decrease decreases, and the grinding torque gradually decreases. The method according to the invention compensates for the reduction in grinding torque during this grinding period of 7 / 8T. Although it greatly depends on the applied load and the pulverizability of the sample (physical conditions), fine powder of 75 μm or less in 4 minutes
Generate ~ 40g. Therefore from feeder 0.08-0.16g
The sample is supplied to the pulverizing unit at a rate of / sec. Recently, a variety of manufacturers have been developing feeds for small amounts of powder,
These can also be applied.

In this embodiment, a feeder having a structure in which a screen and a brush are combined is supplied into the pulverizing section via a shot 14. In order to prevent blockage, the chute 14 is made as thick as possible (in this embodiment, the inside diameter is about 12 mm and the size of the feed is 590 to 1190 μm, so that there is no problem of blocking), and it is set up as vertically as possible. Is considered. The crushed sample 16 that has entered the mill falls into the crushing section and is crushed by the crushing roller 42 one after another.

According to the quasi-continuous pulverization method, a sample amount of 70 g to 90 g is used for a sample amount of 50 g according to the conventional pulverizability test method (JIS M8801). According to the method of the present invention, it is possible to evaluate the pulverizability while keeping the pulverization torque almost constant during the pulverization period, and it is possible to evaluate the pulverizability under conditions that are quite close to the operation of a practical mill. In the present embodiment, unlike the continuous operation in which a fixed amount of sample is continuously supplied from the feeder, the mill is operated continuously by controlling the milling torque to be substantially constant. However, the supply amount is almost constant during the period of about 1/4 from the end of the pulverization period).

Prior to the quasi-continuous crushing experiment using the apparatus according to the present invention, a batch-type experiment is performed in advance under a condition in which a predetermined amount of a sample is charged, and this is set as a reference crushing torque in crushing torque control. In the case of a pulverized raw material having extremely good pulverizability, the fine powder is generated quickly and the pulverization torque is rapidly reduced, so that the additional supply amount is naturally reduced. Therefore, the amount of pulverization treatment for each raw material in a practical machine can be roughly estimated, though only as a relative comparison amount. Also, depending on the characteristics of the raw material, the grinding torque may decrease significantly more rapidly than other raw materials as the grinding proceeds. For example, the smaller the broken particles, the thinner (flakes)
There are special coals that tend to form. Even if the coal is pulverized, the roller easily slides on the powder layer, and the pulverization torque is extremely reduced. Since the grinding torque is small, there is a certain degree of prospect, but the amount of generated fine powder is also small. The use of the quasi-continuous type pulverization evaluation device according to the present invention enables more accurate evaluation of the pulverization characteristics of a coal type having the above-described unique properties.

Here, useful experimental results obtained using the quasi-continuous grindability evaluation apparatus according to the present invention will be described.

FIG. 7 shows the change of the effective grinding torque with respect to the load. The load on the horizontal axis is expressed as a load per roller projected area equivalent to a practical machine of 1.0, and the vertical axis is expressed as dimensionless, with the effective grinding torque at that time being 1.0.

The effective crushing torque increases substantially linearly with respect to the load except for very light load conditions. This suggests that the crushing efficiency is almost constant, and indicates that these can be directly used as scale-up data of the mill crushing section within these load ranges.

By the way, if the pulverization is carried out completely by changing the load M, the pulverization efficiency is reduced under the high load pulverization condition as shown in FIG. Therefore, since the efficiency changes, the data for scale-up of the mill pulverizing section cannot be used as it is.

FIG. 8 summarizes the change in the fine powder generation rate with respect to the load. Along with the horizontal and vertical axes, the dimensions are made dimensionless based on the load per roller projection area equivalent to a practical machine and the fine powder generation speed at that time.

It can be seen that the fine powder generation rate does not reach a peak even under a high load and increases in a substantially proportional state with the increase in the load. When this result is combined with the result of the effective pulverization torque in FIG. 7, it can be seen that in the quasi-continuous pulverization evaluation apparatus according to the present invention, even if the load is increased, the generation of fine powder is almost the same. In this way, the condition of constant grinding torque is realized, and the grinding characteristics obtained by the grinding evaluation apparatus according to the present invention can be effectively used as data for scale-up.

FIG. 9 summarizes the actual value of the grinding capacity with respect to the modified grindability index MRGI in the roller mill. Horizontal axis
The MRGI is obtained by deriving a result obtained in a grindability test based on JIS M8801 using the same definition formula as the hard-groove grindability index HGI. Modification symbol M
(Acronym for Modified) indicates that this is not a complete batch grindability test. The RGI value of the coal used as the standard is set at 1.0, and the RGI value of other coals is used.
Is expressed as a ratio to it. The grinding capacity on the vertical axis is
This is a dimensionless value obtained by dividing the pulverization capacity of a practical-use roller mill or a pilot-scale roller mill equivalent thereto by the pulverization capacity when using standard charcoal.

It has been found that the crushing capacity of a practical machine roller mill can be predicted well by using the crushing property evaluation device according to the present invention. RG
In the case of coal with high I, the problem of the conventional method that the rate of fine powder generation tends to plateau (Fig. 12) is largely solved.

FIG. 10 summarizes changes in the effective friction coefficient with respect to the modified grindability index MRGI. The horizontal axis indicates the relative grindability based on the MRGI of the standard coal. On the other hand, the vertical axis represents the effective friction coefficient μe of the reference coal as 1.0. Concentrated parts of the plot are hatched to avoid clutter. When pulverizing coal with low MRGI, the effective coefficient of friction is small but increases rapidly, and tends to be almost constant when MRGI> 130. It can also be seen that there are several types of coal that deviate from the hatched values. These characteristics are very useful in predicting the pulverizing power when using coal having different pulverizability in a practical machine.

FIG. 11 summarizes the fluctuation of the grinding torque with respect to the modified grindability index MRGI. From this result, it can be seen that as the crushability of the coal increases, the variation increases, but the variation increases. It is considered that such a torque fluctuation is caused by the movement of the roller on the powder layer. That is, it is estimated that the roller becomes slippery on the thin and soft powder layer, and irregular vibrations are caused accordingly.

As described above, by using the quasi-continuous grindability evaluation device according to the present invention, various grinding characteristics that cannot be found with high accuracy using a conventional device can be grasped more accurately for many ground materials. It becomes possible.

The pulverizability evaluation method according to the present invention is not limited to the roller mill in which the rollers and the lace are metal-touched when the pulverized raw material is not charged as shown in the examples, but a supporting method in which a time is previously provided between both the pulverization surfaces of the roller and the lace. The present invention can also be directly applied to a roller mill to be employed, a roller mill having a trapezoidal cross-sectional shape, or a ring ball mill using balls whose structure is shown in FIG.

〔The invention's effect〕

The effects obtained by evaluating the pulverizability of the solid raw material using the apparatus according to the present invention are summarized as follows.

(1) Since the environment of the powder layer portion equivalent to that of a practical machine mill is realized, that is, a test in which the particle size of the pulverizing section is equivalent to that of a practical machine can be performed, and the pulverizing ability of the practical machine mill can be more accurately and highly accurately. To be able to predict.

(2) Although related to the above-mentioned effect (1), it is possible to select a roller shape that optimizes the pulverizing ability, and the roller shape can be directly applied to a practical machine.

(3) Unlike other devices that have been proposed so far, it is possible to conduct experiments continuously, although it is basically a batch type device. That is, frequent starting and stopping of the mill can be avoided, so that an error associated therewith does not occur. By the way, since strong crushing force is added at startup,
The more times the start-up is repeated, the better the crushability is determined.

(4) Since the experiment is performed in a powder layer environment equivalent to that of a practical machine, it is possible to know the wear state of the crushed surface or the race surface of the roller. Therefore, the device according to the present invention is also applied as a reliability measure (e.g., prediction of durability and life) of a device crushing unit, that is, a wear tester.

[Brief description of the drawings]

FIG. 1 (a) is a schematic configuration diagram of the entire grindability evaluation apparatus according to an embodiment of the present invention, FIG. 1 (b) is a plan view near the stopper in the evaluation apparatus, and FIG. FIG. 3 is a plan view of the vicinity of the scraper in the evaluation device, FIG. 3 is a front view of the vicinity of the pulverizing roller in the evaluation device, FIG. 4 is an explanatory view showing the flow of particles in the evaluation device, and FIG. 6, (a), (b) and (c) show the case where the grinding evaluation device of the present invention was used, the case where the feed was not corrected, and the case where the grinding was performed by a complete batch type. FIG. 7 is a relationship characteristic diagram between the grinding time and the grinding torque in the case, FIG. 7 is a relationship characteristic diagram between the load and the effective grinding torque, FIG. 8 is a relationship characteristic diagram between the load and the fine powder generation speed, and FIG. Characteristic diagram of the relationship between the modified grinding index and the actual grinding capacity, FIG. 10 is a graph showing the relationship between the modified grindability index and the effective friction coefficient, FIG. 11 is a graph showing the relationship between the modified grindability index and the torque fluctuation, and FIG. 12 is RGI / RGI (base coal). 13 is a characteristic diagram showing the relationship between the load per unit projected area and the crushing efficiency, and FIGS. 14 (a) and 14 (b) show the state of the coarse-grain environment and the fine-powder environment. FIG. 15 is an explanatory view of a conventional grindability evaluation apparatus. 16… crushed sample, 22… pressurized frame, 33… pressurized spring, 35… mill rotating shaft, 42… crushed roller,
45 ... powder layer, 46 ... screen, 47 ... grinding race, 54
... Scraper.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroaki Kanemoto 6-9 Takaracho, Kure-shi, Hiroshima Babkotsuk Kure Factory (72) Inventor Yoshinori Taoka 6-9 Takaracho, Kure-shi, Hiroshima Babukotsuk (72) Inventor Tadashi Hasegawa 6-9 Takara-cho, Kure-shi, Hiroshima Prefecture Babkotsukitsu Kure Factory (56) References JP-A-54-26535 (JP, A) JP-A-64 -34448 (JP, A) JP-A-62-87260 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 33/00

Claims (2)

(57) [Claims] 1. A race surface, a member for crushing a sample in contact with the race surface, means for pressing the sample crushing member, and means for rotating one of the race surface and the sample crushing member. In a grindability evaluation apparatus having means for supplying a pulverized sample between the race surface and the sample pulverizing member in a batch manner, the outer periphery of the sample pulverizing member on the race surface is in contact with the outer peripheral portion, A classifying member having a predetermined opening for discharging small particles generated by crushing the crushed sample supplied between the race surface and the sample crushing member is provided, and the power required for the crushing is directly or indirectly provided. Means for supplying the ground sample to the grinding unit so that the level of the ground power is substantially constant in accordance with the reduction of the ground power accompanying the discharge of small particles from the classifying member. A crushability evaluation device characterized by having a feedback control function for feeding. 2. A crushability evaluation apparatus according to claim 1, wherein a scraper for facilitating discharge of small particles from said classifying member is provided on a member indicating said sample crushing member. Grindability evaluation device.