JP6747213B2 - Coal crushing method - Google Patents

Description

The present invention relates to a method for crushing coal used for producing coke with a crusher.

The coke used in the blast furnace steelmaking method is required to have high strength in order to ensure air permeability in the furnace. Therefore, in the production of high-strength coke, to increase the bulk density of the coal to be charged into the coke oven, the contact state between adjacent coal particles, so that strong adhesion occurs between coal particles when coal softens and melts. Is being improved.

As a method of improving the bulk density at the time of charging coal, there is known a method of controlling the particle size distribution of coal to bring it closer to the ideal particle size distribution (furnace distribution). In order to achieve the ideal particle size distribution, it is preferable to also use large-sized coal particles, but large-sized coal particles, especially the presence of inferior non-caking coal large-sized particles, during heat treatment. Due to the difference in shrinkage ratio between adjacent coal particles, cracks occur at the contact interface and the coke strength decreases.

Therefore, in the crushing treatment of coal for coke, by adjusting the coal particle size after crushing to a target particle size range, it is possible to improve the bulk density during coal charging and cracks caused by large particle size during heat treatment. It is required to achieve both suppression and control.

As a method of adjusting the coal particle size, a gap between a hammer and a grinding plate in an impact type crusher, a crushing slit width of a crushing blade in an impeller breaker (see Patent Document 1), or a rotation speed change of a crusher (Patent Document 2). In general, the method of adjusting the particle size of coal after crushing to a target particle size range according to the above method.
The above two patent documents describe a method in which the particle size of coal after crushing is measured and arithmetic processing is performed, and the operating conditions of the crusher are changed so that the crushed particle size of coal matches the set target value.

JP-A-6-212169 JP, 2004-16983, A

The conventional method changes the crushing conditions of coal according to the particle size of the crushed coal, and does not consider the variation in the particle size of the coal before crushing. However, the present inventors have found that, for example, when the coal particle size before pulverization increases, the coal particle size after pulverization generally becomes larger than the target particle size. When the coal particle size before crushing changes greatly, even if the crushing conditions of coal are changed based on the coal particle size after crushing, many crushed coals having a particle size larger than the target particle size will be produced.

Since the particle size of coal before crushing varies from moment to moment due to the convenience of coal storage, when the method described in Patent Documents 1 and 2 is used, the particle size of coal after crushing varies. Therefore, the methods described in Patent Documents 1 and 2 have a problem from the viewpoint of stability of coal particle size after pulverization.
If the coal particle size after crushing varies, the coke strength, which is one of the coke quality, fluctuates, and coke containing low-strength coke is produced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coal crushing method capable of suppressing variations in the particle size of coal after crushing as compared with the conventional method.

In order to achieve the above object, the coal crushing method according to the present invention,
Coal particle size measuring instruments are installed on the inlet side and the outlet side of a coal crusher for crushing coal between the hammer and the crush plate by the impact of the hammer rotating in the casing and the repulsive impact of the crush plate .
With the current value of the motor rotating the hammer as a parameter, the correlation between the coal particle size before crushing and the coal particle size after crushing is measured by the coal particle sizer installed on the inlet side and the outlet side of the coal crusher. Use the results in advance,
The target current value I0(A) of the motor when the coal particle size after crushing is the target particle size is applied by applying the measurement result of the coal particle size measuring device installed on the inlet side of the coal crusher to the correlation. After determining and setting the current value I1(A) flowing through the motor to the target current value I0(A) to crush the coal, the measurement result of the coal particle sizer installed on the outlet side of the coal crusher It is characterized in that the current value I1(A) is corrected according to the deviation between the target grain size and the target grain size.

The crushing power (motor current value) of the coal crusher depends on the coal crushing load. The coal crushing load is determined by the number of revolutions of the hammer (the number of revolutions per unit time), the distance between the hammer and the grinding plate, and the like. The coal crushing load also varies depending on the amount of coal supplied to the coal crusher per unit time. Therefore, the motor current value can be regarded as a physical quantity that reflects particle size variation factors such as the rotational speed of the hammer, the distance between the hammer and the grinding plate, and the amount of coal supplied to the coal crusher.

In the present invention, the measurement result of the coal particle sizer installed on the inlet side of the coal crusher is applied to the correlation of the coal particle size before and after crushing, and the target of the motor when the coal particle size after crushing becomes the target particle size. By determining the current value, the variation in the coal particle size before crushing is taken into consideration, and the coal particle size after crushing varies depending on the coal strength and the water content of the coal. The motor current value is corrected according to the deviation between the result and the target grain size.

Moreover, in the coal crushing method according to the present invention, it is preferable that the water content of the crushed coal is 7 to 15 mass% in the internal number.

The electric current value of the motor determined based on the correlation of the coal particle size before and after the pulverization may slightly increase or decrease due to the fluctuation of the water content in the pulverized coal.
The present inventors have found that by keeping the water content in the coal to be ground within a predetermined range, it is possible to further suppress the variation in the particle size of the coal after grinding. The predetermined range of the water content is preferably 7 to 15% by mass, and more preferably 9 to 12% by mass.

Further, in the coal crushing method according to the present invention, it is preferable that the crushed coal is stored in a hopper and cut out by a feeder.

When the motor current value of the coal crusher is constant, if the amount of coal supplied to the coal crusher (for example, the amount of coal supplied per unit time) changes, the coal particle size after crushing changes.
With this configuration, by using a feeder that can keep the amount of coal cut out per unit time constant, fluctuations in the amount of coal supplied to the coal crusher are prevented, and variations in coal particle size after crushing are further suppressed. ..

In the coal crushing method according to the present invention, the measurement result of the coal particle size measuring device installed on the inlet side of the coal crusher is applied to the correlation of the coal particle size before and after crushing, and the coal particle size after crushing becomes the target particle size. When the target current value of the motor is determined and the motor current value is corrected according to the deviation between the target particle size and the measurement result of the coal particle size measuring instrument installed on the outlet side, the variation in the coal particle size before crushing is determined. Absorb other particle size fluctuation factors. As a result, it is possible to suppress variation in the particle size of coal after crushing, as compared with the conventional case.

It is a schematic diagram of the coal crushing equipment used for the coal crushing method which concerns on one embodiment of this invention. It is a schematic diagram of the coal crusher which comprises the same coal crushing facility. It is an example of the graph which calculated|required the correlation of the coal particle size before crushing and the coal particle size after crushing using the motor current value of a coal crusher as a parameter.

Next, an embodiment of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.

The particle size of coal after crushing is determined by properties such as the particle size of coal before crushing and the strength of coal, and the particle size of coal before crushing is affected by the storage method at the steel mill.
Coal before crushing is generally stacked and stored in a mountain range in a yard. Coal grain size is different at the top and bottom of the pile, and segregation causes grain size segregation. Specifically, there are many coals with a small grain size at the top of the stacking pile and many coals with a large grain size at the bottom of the stacking pile.
The coal stored in the stacking pile is discharged by a reclaimer etc. and supplied to the coal crusher, but since it is sequentially discharged, the coal collection position (collecting from the top, collecting from the mountain hem, etc.) in the stacking pile changes. To do. As a result, the coal particle size before crushing varies to such an extent that the coal particle size after crushing is affected.

[Conventional coal crushing method]
Measure the particle size of the coal after crushing with a coal crusher and set the crushing conditions (hammer rotation speed, distance between hammer and grinding plate, etc.) according to the difference between the actual value of the measured coal particle size after crushing and the target particle size. A method of changing the particle size to stabilize the coal particle size after crushing is known.
However, if the above method is carried out when the coal particle size before pulverization changes, the result of the coal particle size after pulverization fluctuating (the deviation from the target particle size) until the result of particle size measurement of the coal after pulverization is reflected in the change in the pulverization conditions. In many cases, the coal particle size after crushing will vary. For example, when coal having a content of water of 10% by mass is cut out by a feeder and pulverized by the above method, the actual value of the pulverized coal particle size is 85 with respect to the target particle size of 3% under 89% by mass. It was ˜93% by mass (hereinafter referred to as “conventional example”).

[Coal crushing method according to the present embodiment]
FIG. 1 shows a coal crushing facility used in a coal crushing method according to an embodiment of the present invention.
The present coal crushing facility is provided with a coal crusher 10 for crushing coal, a hopper 11 for storing coal, and a feeder 12 for cutting out the coal in the hopper 11, at the upstream portion, and the coal cut out by the feeder 12 is used for the coal crusher 10. It is provided with a conveyor 13 for carrying the coal and a conveyor 14 for carrying the coal crushed by the coal crusher 10.
Coal particle size measuring devices 15 and 16 for measuring the particle size of the conveyed coal are installed at the downstream part of the conveyor 13 and the upstream part of the conveyor 14, respectively. In order to prevent the coal particle size measuring devices 15 and 16 from being contaminated by the dust, the coal particle size measuring devices 15 and 16 are installed at a position apart from the coal crusher 10 by 5 m or more in the horizontal direction.

FIG. 2 shows a schematic diagram of the coal crusher 10.
The coal crusher 10 is an impact crusher, and includes a box-shaped casing 23, a rotor 25 arranged in a horizontal direction and rotating about a horizontal axis, and a plurality of hammers 24 radially extending from an outer peripheral surface of the rotor 25. It is provided with a pair of grinding plates 26 arranged on the left and right with the rotor 25 interposed therebetween. A charging port 21 for charging coal is provided on the upper surface of the casing 23, and a discharging port 22 for discharging the crushed coal is provided on the bottom surface of the casing 23.

A motor (not shown) for rotating the rotor 25 is connected to the rotor 25. By controlling the current value of this motor, the particle size of the crushed coal can be adjusted.
The hammer 24 includes a hammer arm 24a whose base end is connected to the rotor 25 and extends radially from the outer peripheral surface of the rotor 25, and a hammer head 24b which is connected to the tip end of the hammer arm 24a.
The grinding plate 26 is formed in an arc shape so as to enclose the plurality of hammers 24, and a mountain-shaped grinding plate liner 26a effective for grinding and impact is attached to the inner peripheral surface of the grinding plate 26. .. Further, the grinding plate 26 is movable in the horizontal direction (direction orthogonal to the horizontal axis of the rotor 25) by the cylinder 27, and the distance between the hammer 24 and the grinding plate 26 can be adjusted.

When the motor is operated to rotate the rotor 25 in one direction and coal is charged from the charging port 21, the coal is hit by a number of hammers 24 provided on the outer periphery of the rotor 25 and the grinding plate liner of the grinding plate 26. Due to the repulsive impact at 26 a, the hammer 24 and the grinding plate 26 are repeatedly ground and impacted, and are effectively crushed and discharged from the discharge port 22.

Optical measuring devices may be used for the coal particle size measuring devices 15 and 16, for example.
As a method of optically measuring the particle size of the coal, a method of measuring the particle size of the coal before and after being conveyed by crushing the coal, and a method of measuring the particle size of the coal before and after being collected (for example, automatic collection) However, there is a method of measuring the particle size of coal falling in a liquid using light that passes through (for example, laser light).

In addition, the particle size to measure refers to the content (mass %) calculated for each particle size by measuring the particle size of each coal particle. Alternatively, in a simplified manner, the content (mass %) of particles having a specific size is indicated (for example, 3 mm under is 85 mass %).

Next, a method for crushing coal using the coal crushing equipment having the above configuration will be described.
(1) STEP-1
Using the current value of the motor that rotates the hammer 24 as a parameter, the correlation between the coal particle size before crushing and the coal particle size after crushing is determined by the coal particle size measuring devices 15, 16 installed on the inlet side and the outlet side of the coal crusher 10. It is obtained in advance using the measurement result of.
The particle size of the coal to be crushed is about 20 to 70% by mass when 3 mm under.

FIG. 3 shows an example of the correlation between the particle size of coal before crushing and the particle size of coal after crushing. This figure is the result of a preliminary investigation at the time of coal crushing operation, and shows the correlation of the coal particle size before and after crushing according to the motor current value (Iγ>Iβ>Iα). The plot points that are the basis of the graph are omitted.

(2) STEP-2
The coal particle size before crushing is measured using the coal particle size measuring device 15 installed on the inlet side of the coal crusher 10.
(3) STEP-3
Determine the target granularity.
In the example of FIG. 3, the target particle size is 89% by mass when 3 mm under.
When deciding the target particle size, it is advisable to produce coke using the crushed coal and determine the target grain size according to the strength of the produced coke.

(4) STEP-4
The target grain size I0(A) of the motor when the coal grain size after crushing becomes the target grain size is determined by applying the coal grain size before crushing determined in STEP-2 to the correlation determined in STEP-1.
The target particle size and the coal particle size before crushing are plotted in the correlation obtained in STEP-1, and the target current value I0(A) of the motor is set. In the example of FIG. 3, if the coal particle size before crushing to obtain the target particle size (89% by mass of 3 mm under) (mass ratio of 3 mm under) is 40% by mass, the target current value I0 of the motor is set as the current value Iβ, If the coal grain size before crushing, which is the target grain size, is 48 mass %, the target current value I0 of the motor is set as the current value Iα.

If the coal particle size before crushing, which is the target particle size, is 44% by mass, it is an intermediate value between 40% by mass and 48% by mass. It is preferable to set the current value I0. Alternatively, the current value of the motor is set in small increments without using proportional distribution (for example, not the two types of the current value Iα and the current value Iβ, but the ten types of current values between the current value Iα and the current value Iβ). , The closest current value may be the target current value I0 of the motor.

(5) STEP-5
The current value I1(A) flowing through the motor is set to the target current value I0(A) to crush the coal, and the particle size measurement result of the crushed coal is measured by the coal particle sizer 16 installed on the outlet side of the coal crusher 10. To get
In the example of FIG. 3, the coal is crushed with the current value I1 flowing through the motor as the current value Iβ based on the target particle size (89% by mass of 3 mm under) and the coal particle size before crushing (40% by mass of 3 mm under).
The particle size of the coal crushed by the current value I1 flowing through the motor is fixed for a certain period of time after the motor is operated (the time during which the coal passes through the coal crusher 10 and the coal after crushing is measured by the coal particle sizer 16 on the outgoing side). It is obtained by the coal particle size measuring device 16 on the outlet side of the coal crusher 10 after the passage (sum of transportation time).

(6) STEP-6
The current value I1(A) is corrected according to the deviation between the measurement result of the coal particle size measuring device 16 installed on the outlet side of the coal crusher 10 and the target particle size.
If the particle size measurement result of the crushed coal with the current value I1 flowing through the motor as the current value Iβ is less than the target particle size (◆ plot in FIG. 3), the coal particle size before crushing is regarded as a ● plot, and Coal grain size ● Select a motor current value Iγ (graph passing through ▲) that can crush the plot to the target grain size, and correct the current value I1 from the current value Iβ to the current value Iγ.

The current value Iγ (graph passing through ▲) of the motor may be determined by using the procedure such as the proportional distribution described above.
Further, in the above-described example, the current value I1 passed through the motor is corrected from the current value Iβ to the current value Iγ, but the current value I1 is changed to an intermediate value between the current value Iβ and the current value Iγ (for example, (Iβ+Iγ)/2). Then, the correction value of the current value I1 may be determined again by the above procedure.

Coal having a water content of 6 to 16% by mass is cut out by the feeder 12 and the target particle size of 3 mm under is set to 89% by mass, and the above procedure is carried out. As a result, the particle size of the coal after grinding is 86% by mass. ˜92% by mass (hereinafter referred to as “Example 1”). Compared with the conventional example, although the water content of the crushed coal varied, the coal particle size after crushing could be improved.

On the other hand, when the particle size measurement result of the crushed coal exceeds the target particle size (for example, the particle size of the crushed coal is 90% by mass), the current value I1(A) flowing through the motor can be corrected by the same procedure as above. Good.

Furthermore, in the example of FIG. 3, the target particle size was set to 89% by mass for 3 mm under, but the target particle size is in the numerical range (for example, 89% by mass or more for 3 mm under, or 87% by mass or more and 91% by mass or less for 3 mm under). Etc.).

[About water content of crushed coal]
The target current value of the motor, which is obtained in advance using the correlation between the coal particle sizes before and after crushing, may increase or decrease due to fluctuations in the water content.
The present inventors have found that stabilizing the water content within a predetermined range can suppress variations in coal particle size after crushing. According to the knowledge of the inventors, when the water content is 7 to 15% by mass in the above-mentioned Example 1, the actual value of the coal particle size after crushing is 87 to 91% by mass (hereinafter, " It is referred to as "Example 2"), and the variation in the particle size of coal after pulverization is improved as compared with Example 1. In addition, it is more preferable that the contained water content is 9 to 12% by mass.

[About means for supplying coal to be crushed to a coal crusher]
When the motor current value of the coal crusher 10 is constant and the amount of coal supplied to the coal crusher 10 changes, the particle size of the crushed coal changes. Therefore, in the present embodiment, the coal cut out by the feeder 12 is supplied to the coal crusher 10.

Even if the motor current value of the coal crusher is changed according to the change in the amount of coal supplied to the coal crusher, it is possible to suppress the variation in the coal particle size after crushing, but the amount of coal can be reduced in a short time. It is not realistic because it may fluctuate.
For example, the coal is conveyed on the conveyor A, and at the end of the conveyor A, a damper is applied to the falling coal to take out a certain amount of the coal, and the coal is placed on the conveyor B and supplied to the coal crusher B. A method of placing it on the conveyor C and supplying it to the coal crusher C can be considered.
However, in this method, the amount of coal taken out by the damper and the amount of remaining coal vary depending on the water content of the coal. Further, when the coal taken out by the damper is placed on the conveyor B, the height of the coal stacked on the conveyor B may vary, and the amount of coal supplied to the coal crusher by the conveyor varies. It also causes

According to the knowledge of the present inventors, when the coal of Example 1 having a water content of 10% by mass is crushed using a feeder, the coal of 3 mm under is 89% by mass (corresponding to the target particle size). The range was 88.5 to 89.5% by mass), while the amount of coal cut out by the damper was about 88 to 90% by mass. Although the variation in the particle size of the coal after crushing was improved compared to the conventional example, the effect of improving the variation in the particle size of the coal after crushing was inferior to that obtained by cutting with a feeder.

Although one embodiment of the present invention has been described above, the present invention is not limited to the configuration described in the above-mentioned embodiment at all, and within the scope of matters described in the claims. It also includes other possible embodiments and modifications. For example, the order of STEP-1 to STEP-3 in the above embodiment is not fixed and may be changed freely.

10: Coal crusher, 11: Hopper, 12: Feeder, 13, 14: Conveyor, 15, 16: Coal particle sizer, 21: Input port, 22: Discharge port, 23: Casing, 24: Hammer, 24a: Hammer Arm, 24b: Hammer head, 25: Rotor, 26: Grinding plate, 26a: Grinding plate liner, 27: Cylinder

Claims (3)

Coal particle size measuring devices are installed on the inlet side and the outlet side of a coal crusher for crushing coal between the hammer and the crush plate by the impact of a hammer rotating in the casing and the repulsive impact of the crush plate .
With the current value of the motor rotating the hammer as a parameter, the correlation between the coal particle size before crushing and the coal particle size after crushing, the measurement of the coal particle sizer installed on the inlet side and the outlet side of the coal crusher Use the results in advance,
The target current value I0(A) of the motor when the coal particle size after crushing reaches the target particle size is applied by applying the measurement result of the coal particle size measuring device installed on the inlet side of the coal crusher to the correlation. After determining and setting the current value I1(A) flowing through the motor to the target current value I0(A) to crush the coal, the measurement result of the coal particle sizer installed on the outlet side of the coal crusher And the current value I1(A) is corrected according to the deviation between the target grain size and the target grain size. The coal crushing method according to claim 1, wherein the content of water contained in the crushed coal is 7 to 15 mass% in the internal number. The coal crushing method according to claim 1 or 2, wherein the crushed coal is stored in a hopper and cut out by a feeder.

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