Operation method and control device of slag grinder

Abstract

To provide an operation method and a control device of a slag grinder capable of suppressing secular change of the quality of treated slag and stabilizing the quality of the treated slag.SOLUTION: An operation method of a slag grinder A is used to perform grinding treatment on molten slag S1 generated in a general waste melting treatment facility to change the molten slag S1 to treated slag S2. The method includes adjusting an operation condition corresponding to fluctuation of a current value of a motor 3 for driving a drive unit 1 for the grinding treatment to stabilize the current value of the motor 3. A control device 6 performs the above-described step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an operating method and control device for a slag grinder that grinds molten slag produced in a municipal waste melting treatment facility and turns the molten slag into treated slag. [Background technology]

[0002] At municipal waste treatment facilities, waste is melted at high temperatures of over 1200℃, and the molten material is rapidly cooled using water or other materials to produce molten slag. Molten slag is made up of silicon dioxide (SiO2), calcium oxide (CaO), aluminum oxide (Al2O3), etc., and is used in a wide range of applications, such as asphalt mixtures, aggregate for secondary concrete products, and backfill materials, as a substitute for natural aggregate. Molten slag has larger angular grains than natural sand, so in order to use it as a substitute for aggregate, it is necessary to round off the sharp grains and improve the grain shape determination actual volume ratio, which is an index of aggregate shape, and satisfy standard values ​​for grain size distribution according to the application, coarse grain ratio, which is an index of aggregate particle size, and fine grain content, which indicates the weight ratio of aggregate grains 75μm or less, while maintaining stable quality with little fluctuation.

[0003] To deal with this, it is common to use a granulator as a processing device for molten slag. There are two types of granulator: the "crushing type" in which the molten slag is crushed with a hammer or the like, and the "friction type" in which the molten slag itself is rubbed together. However, there are more and more cases where the "friction type" granulator, i.e., "slag grinder", is used, which is expected to expand the range of applications in the civil engineering field, such as improving the actual volume rate of particle shape judgment. As an example of such a slag grinder, Patent Document 1 discloses one that includes a rotating drum that rotates at high speed and an annular body arranged on its outer periphery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-182202 Summary of the Invention [Problem to be solved by the invention]

[0005] In the method of operating a slag grinder including a rotating drum as disclosed in Patent Document 1, the rotation speed of the rotating drum was generally set in advance so that the quality of the treated slag, which is the molten slag after grinding, would satisfy a predetermined standard value, and operation would generally be continued at the set rotation speed. In other words, in conventional slag grinders, the operating conditions were generally set in advance so that the quality of the treated slag would satisfy a predetermined standard value, and operation was generally continued basically under those operating conditions.

[0006] However, after the inventors conducted repeated long-term tests with a slag grinder, they found that if the operating conditions set at the start of operation were continued for a long period of time, as in the past, the quality of the treated slag would change over time, raising concerns that the quality of the treated slag might not meet the standards, leading to a situation where this would cause problems with the use of the molten slag.

[0007] The problem to be solved by the present invention is to provide an operating method and control device for a slag grinder that can suppress changes in the quality of the treated slag over time and stabilize the quality of the treated slag. [Means for solving the problem]

[0008] The inventors of the present invention conducted repeated tests and studies on factors that cause the quality of the treated slag to change over time, and as a result, found that the main factor is the change over time in the current value (usually an increase in the current value) of the motor that drives the drive unit (e.g., the above-mentioned rotating drum) for grinding the molten slag in the slag grinder. The current value of this motor is an index that indicates the grinding load, which is the load during the grinding of the molten slag in the slag grinder, and for example, an increase in the current value of the motor indicates an increase in the grinding load. In other words, the change in the current value of the motor indicates that the behavior of the molten slag has changed from the start of operation due to wear and tear of the drive unit (e.g., the above-mentioned rotating drum) and its accessories (e.g., the above-mentioned ring body) for grinding the molten slag in the slag grinder, and therefore the grinding load has also changed from the start of operation. The quality of the treated slag changes over time due to this change in the grinding load.

[0009] Based on this knowledge, the inventors believed that in order to suppress changes in the quality of the treated slag over time and stabilize its quality, it was essential to stabilize the current value of the motor. After further testing and consideration, they came up with the present invention.

[0010] That is, according to one aspect of the present invention, there is provided a method of operating a slag grinder comprising the steps of: A method for operating a slag grinder for grinding molten slag generated in a municipal waste melting treatment facility to produce treated slag, comprising: A method for operating a slag grinding machine, comprising adjusting operating conditions corresponding to fluctuations in the current value of a motor that drives a drive unit for carrying out the grinding process, thereby stabilizing the current value of the motor. According to another aspect of the present invention, there is provided a control device for a slug grinder. A control device for controlling the operation of a slag grinder that grinds molten slag generated in a general waste melting treatment facility and converts the molten slag into treated slag, A control device for a slag grinding machine, characterized in that the control device adjusts operating conditions corresponding to fluctuations in the current value of an electric motor that drives a drive unit for carrying out the grinding process, thereby stabilizing the current value of the electric motor. Effect of the Invention

[0011] According to the present invention, the change in quality of the treated slag over time can be suppressed, and the quality of the treated slag can be stabilized. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is an overall configuration diagram showing an example of a slag grinding machine for implementing an operating method according to the present invention. [Diagram 2] FIG. 2 is an enlarged explanatory diagram of a main part of the slag grinder shown in FIG. 1. [Diagram 3] FIG. 1 is a diagram conceptually showing the changes in the motor current value and the quality of the treated slag when the slag grinder is operated for a long period of time at a constant rotation speed of the rotating drum. [Figure 4] FIG. 13 is a graph showing the changes in the current value of the motor and the quality of the treated slag during the period when the comparative example operating method according to the prior art was used. [Diagram 5] FIG. 2 is a graph showing the changes in the current value of the motor and the quality of the treated slag during the period when the motor was operated according to the operating method of the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Fig. 1 is an overall block diagram showing an example of a slag grinder for carrying out the operating method according to the present invention, and Fig. 2 is an enlarged explanatory diagram of the main parts of the slag grinder shown in Fig. 1. The slag grinder A shown in Fig. 1 and Fig. 2 is equipped with a rotating drum 1 as a drive unit, a ring body 2 as an auxiliary unit, and an electric motor 3 for rotating the rotating drum 1, as well as a hopper 4 for supplying molten slag S1 to the rotating drum 1, a sprinkler 5 arranged above the rotating drum 1, and a control device 6 for controlling the rotation speed of the rotating drum 1, etc.

[0014] The rotating drum 1 rotates at high speed to store the molten slag S1 supplied from the hopper 4 and move it in the centrifugal direction. The rotating drum 1 is a vertical-axis rotating type that rotates around a vertical axis, and is rotated by transmitting the rotation of the electric motor 3 through a belt 31. That is, the rotation speed of the rotating drum 1 can be adjusted by the rotation speed of the electric motor 3. The rotation speed of the electric motor 3 can be automatically controlled by a control device 6 conceptually shown in FIG. 1, or can be manually controlled by an operator. When manually controlled by an operator, for example, the control device 6 has an input receiving unit that receives input operations by the operator, and the rotation speed of the electric motor 3 can be controlled based on the value of the rotation speed input via the input receiving unit. It is preferable that the correspondence relationship (motor characteristics) between the rotation speed of the rotating drum 1 and the rotation speed of the electric motor 3 is stored in the control device 6 in advance.

[0015] The ring-shaped body 2 is fixedly disposed around the drum edge 11, which is the upper outer peripheral edge of the rotating drum 1, with a predetermined gap G therebetween. The ring-shaped body 2 includes a cylindrical portion 21 having a plurality of protrusions 211 on its inner surface, and a plate-shaped portion 22 joined to the lower end of the cylindrical portion 21. There is a gap G between the inner peripheral edge of the plate-shaped portion 22 and the outer peripheral surface of the drum edge 11.

[0016] The grinding process of the molten slag S1 by the slag grinder A is outlined below. The molten slag S1 supplied from the hopper 4 resides on the top of the rotating drum 1 and inside the annular body 2. The residence time of the molten slag S1 is set by the height of the rotating drum 1 and the annular body 2, the rotation speed of the rotating drum 1, the amount of molten slag S1 supplied, etc. During the residence time, the molten slag S1 moves while rotating in the centrifugal direction due to the high speed rotation of the rotating drum 1, and is also pressed against the inner surface of the annular body 2 and flipped over. Due to this centrifugal movement, flipping and rotation of the molten slag S1, the molten slag S1 rubs against each other, the corners of the molten slag S1 become rounded, the granular shape becomes smaller, and it is discharged as treated slag S2. In addition, the slag grinding machine A is equipped with a sprinkler 5 that sprinkles water inside the rotating drum 1 and the annular body 2 to prevent the moisture attached to the surface of the molten slag S1 from evaporating due to frictional heat caused by the molten slag S1 rubbing against each other, thereby reducing the grinding performance.

[0017] Here, the grinding capacity of the slag grinder A, i.e., the quality of the treated slag S2, can be adjusted by the amount of molten slag S1 supplied, the residence time of the molten slag S1, the rotation speed of the rotating drum 1, the amount of water sprayed from the sprinkler 5, etc. However, as described above, in the prior art, it was common to set the rotation speed of the rotating drum 1 in advance so that the quality of the treated slag S2 satisfied a predetermined standard value, and to continue operation at that set rotation speed.

[0018] However, in such a conventional operating method, as described above, the quality of the treated slag S2 changes over time. As an example, Figure 3 conceptually shows the transition of the electric current value of the electric motor 3 and the quality (coarse particle ratio) of the treated slag S2 during long-term operation at a constant rotation speed of the rotating drum 1 of the slag grinder A. As shown in the figure, the electric current value of the electric motor 3 is low and stable at the beginning of operation after replacing the consumables in the rotating drum 1 and the annular body 2, but the electric current value increases after a long period of operation (which varies depending on the supply amount of molten slag S1, but is usually after several months). As the electric current value of the electric motor 3 increases, the coarse particle ratio of the treated slag S2 decreases. As described above, the current value of the motor 3 is an index showing the grinding load, which is the load during the grinding process of the molten slag S1 in the slag grinder A, and an increase in the current value of the motor 3 shows an increase in the grinding load. In other words, the fluctuation in the current value of the motor 3 shows that the behavior of the molten slag has changed from the start of operation due to wear and tear of the rotating drum 1, which is the driving part for grinding the molten slag in the slag grinder A, and its attached ring body 2, and therefore the grinding load has also changed from the start of operation. This fluctuation in the grinding load causes the quality of the treated slag S2 to change over time. This situation further accelerates the wear and tear rate of the consumables in each part of the slag grinder A, especially the rotating drum 1 and ring body 2, and as wear progresses, the thickness of each part becomes thinner, and it becomes necessary to replace the consumables from the viewpoint of maintaining strength, etc. Here, typical examples of consumables in the slag grinder A are the drum edge 11 of the rotating drum 1 and the cylindrical portion 21 and the plate portion 22 of the annular body 2.

[0019] Thus, in the conventional operating method, the quality of the treated slag S2 changes over time. In response to this, in the present invention, the operating conditions are adjusted to correspond to the fluctuations in the current value of the motor 3 that drives the drive unit for performing the grinding process, and the current value of the motor 3 is stabilized. In this embodiment, the rotation speed of the rotating drum 1 is adjusted as an operating condition to correspond to the fluctuations in the current value of the motor 3 that drives the rotating drum 1, which is the drive unit for performing the grinding process, and the current value of the motor 3 is stabilized. The operating method of this embodiment will be described in detail below.

[0020] In this embodiment, after replacing the above-mentioned consumables, the current value of the motor 3 is set to a predetermined value and operation is started. When the moving average value of the current value of the motor 3 increases by a predetermined amount after the start of operation, the rotation speed of the rotating drum 1 is reduced by a predetermined amount to stabilize the current value of the motor 3. That is, for example, in the control device 6, when the consumables are not consumed during the first operation or after replacing the consumables, the current value of the motor 3 is set to a predetermined reference value (set value) corresponding to the rotation speed (target rotation speed) of the rotating drum 1 such that the quality of the treated slag S2 satisfies a predetermined reference value and operation is started. Then, when the moving average value of the current value of the motor 3 increases by a predetermined amount after the start of operation, the control device 6 sets the current value of the motor 3 again (updates the set value) so as to reduce the rotation speed of the rotating drum 1 (or the set value of the rotation speed of the motor 3) by a predetermined amount, and performs control to stabilize the current value of the motor 3. When the moving average value of the current value of the motor 3 increases by a predetermined amount again as the operation time elapses, the same response is repeated. It should be noted that such a series of steps can all be performed manually by an operator, or some of them can be performed manually by an operator and the rest can be performed automatically by the control device 6. Of course, all of them can also be performed automatically by the control device 6. Here, the rotation speed of the rotating drum 1 depends on the quality of the molten slag S1 and the required quality level of the treated slag S2, but from the viewpoint of ensuring the grinding processing capacity of the slag grinder A, the range of 1000 to 2500 rpm is a guideline. If the rotation speed of the rotating drum 1 is less than 1000 rpm, the centrifugal force on the molten slag S1 is reduced, and the grinding processing capacity of the slag grinder A tends to decrease. If the rotation speed of the rotating drum 1 exceeds 2500 rpm, the centrifugal force on the molten slag S1 becomes excessive, and the residence time of the molten slag S1 is shortened, and as a result, the grinding processing capacity of the slag grinder A tends to decrease. From the above, in this embodiment, the rotation speed of the rotating drum 1 is adjusted in the range of 1000 to 2500 rpm, and when the rotation speed of the rotating drum 1 reaches a predetermined lower limit value (for example, 1200 rpm), a measure is taken to replace the consumables.

[0021] As described above, in this embodiment, the rotation speed of the rotating drum 1 is adjusted as an operating condition corresponding to the fluctuation of the current value of the electric motor 3, and the current value of the electric motor 3 is stabilized, so that the fluctuation of the grinding load in the slag grinder A over time can be suppressed, and the quality of the treated slag S2 can be stabilized. In addition, in this embodiment, the grinding capacity of the slag grinder A can be maintained and secured within an appropriate range by adjusting the rotation speed of the rotating drum 1 within the range of 1000 to 2500 rpm, so that the quality of the treated slag S2 can be further stabilized and the life of the consumables can be extended. Furthermore, in this embodiment, when the rotation speed of the rotating drum 1 reaches a predetermined lower limit (for example, 1200 rpm), the consumables are replaced, so that the quality of the treated slag S2 over time can be suppressed due to wear and tear of the consumables, and the quality of the treated slag S2 can be further stabilized.

[0022] In the above embodiment, the rotation speed of the rotating drum 1 is adjusted as an operating condition corresponding to fluctuations in the current value of the electric motor 3. However, the operating conditions to be adjusted in the present invention are not limited to the rotation speed of the rotating drum 1 alone. For example, other operating conditions such as the amount of molten slag S1 supplied from the hopper 4 and the amount of water sprayed from the sprinkler 5 can also be adjusted alone or in combination with the rotation speed of the rotating drum 1. EXAMPLES

[0023] In a general waste melting treatment facility (hereinafter referred to as "Facility A") having the slag grinder A of Figure 1, an operating method was implemented as an embodiment of the present invention in which the rotation speed of the rotating drum 1 was adjusted in accordance with the moving average of the current value of the electric motor 3, and as a comparative example, an operating method was implemented in which the rotation speed of the rotating drum 1 was kept constant regardless of fluctuations in the current value of the electric motor 3, and the change in the coarse particle ratio was evaluated as the quality of the treated slag S2 obtained in each case. Here, in the operating method of the embodiment, the rotation speed of the rotating drum 1 at the start of operation after replacing the consumables was set to 2000 rpm, and the reference value of the current value of the electric motor 3 was set to 22 A. When the moving average value of the electric motor current over three days after the start of operation increased by 0.3 A, the rotation speed of the rotating drum 1 was reduced by 100 rpm to stabilize the electric motor current value. In addition, when the rotation speed of the rotating drum 1 reached a predetermined lower limit (1200 rpm), the consumables were replaced. On the other hand, in the operating method of the comparative example, the rotation speed of the rotating drum 1 was kept constant (2000 rpm) regardless of fluctuations in the electric motor current value. Table 1 shows the evaluation results of the coarse particle ratio of the treated slag S2 during the period of operation according to the comparative example and the period of operation according to the embodiment. Figure 4 shows the transition of the current value of the motor 3 and the coarse particle ratio of the treated slag S2 during the period of operation according to the comparative example, and Figure 5 shows the transition of the current value of the motor 3 and the coarse particle ratio of the treated slag S2 during the period of operation according to the embodiment.

[0024] [Table 1]

[0025] The standard value of the coarse particle ratio in facility A is 2.8±0.2, but in the comparative example, the coarse particle ratio was 2.6 on average, fluctuated between a maximum of 2.8 and a minimum of 2.2, with a standard deviation of 0.3. In the comparative example, as shown in Fig. 4, the current value of the motor 3 increased significantly and the coarse particle ratio decreased with the passage of operating time, and then, when the consumables were replaced, the current value of the motor 3 decreased and the coarse particle ratio increased. In contrast, in the case of the embodiment, the coarse particle ratio was 2.7 on average, fluctuated between a maximum of 2.9 and a minimum of 2.6, and the standard deviation was 0.1, which was more stable than the comparative example, and the effect of stabilizing the quality of the treated slag was confirmed. Specifically, as shown in FIG. 5, the increase in the current value of the motor 3 with the passage of operation time was suppressed, and the decrease in the current value of the motor 3 immediately after replacing the consumables was also suppressed, and the current value of the motor 3 was stabilized, so that the stabilization of the coarse particle ratio could be satisfied for a long time. Furthermore, by reducing the increase control value of the moving average value of the current value of the motor 3 and automating the response to the change in the moving average value and the fluctuation in the rotation speed of the rotating drum 1 (for example, by storing in advance in the control device 6 the correspondence relationship between the change in the moving average value and the change in the rotation speed of the rotating drum 1, and the control device 6 automatically controls the rotation speed of the rotating drum 1 based on the change in the moving average value), the standard deviation of the coarse particle ratio can be expected to be further reduced.

[0026] In this way, the operating method of the present invention can stably ensure the quality of the treated slag according to its intended use by stabilizing the current value of the motor. In addition, by reducing the rotation speed of the rotating drum as in the above-mentioned embodiment, the wear and tear rate of consumables caused by molten slag can be reduced, and the replacement time / replacement life of consumables can be extended. [Explanation of symbols]

[0027] A Slag grinder G Gap S1 Molten slag S2 Processed slag 1 Rotating drum (drive unit) 11 Drum Edge 2. Ring-shaped body (appendage) 21 Cylindrical part 211 Projections 22 Plate-shaped part 3 Electric motor 31 Belt 4 Hopper 5. Sprinkler 6. Control device

Claims

1. A method for operating a slag grinder for grinding molten slag generated in a municipal waste melting treatment facility to produce treated slag, comprising: A method for operating a slag grinding machine, comprising adjusting operating conditions corresponding to fluctuations in the current value of a motor that drives a drive unit for carrying out the grinding process, thereby stabilizing the current value of the motor.

2. 2. The method for operating a slag grinder according to claim 1, wherein the driving unit includes a rotating drum, and the operating condition is set by adjusting a rotation speed of the rotating drum.

3. The method for operating a slag grinder according to claim 2, wherein the rotation speed of the rotating drum is adjusted in the range of 1000 to 2500 rpm.

4. 4. The method for operating a slag grinding machine according to claim 2 or 3, wherein the current value of the motor is set to a predetermined value after replacing consumables in the driving unit and its auxiliary units, and operation is started; and when the moving average value of the current value of the motor increases by a predetermined amount after operation is started, the rotation speed of the rotating drum is reduced by a predetermined amount to stabilize the current value of the motor.

5. 5. The method for operating a slag grinder according to claim 4, further comprising replacing the consumables when the number of revolutions of the rotating drum reaches a predetermined lower limit value.

6. A control device for controlling the operation of a slag grinder that grinds molten slag generated in a general waste melting treatment facility and converts the molten slag into treated slag, A control device for a slag grinding machine, characterized in that the control device adjusts operating conditions corresponding to fluctuations in the current value of an electric motor that drives a drive unit for carrying out the grinding process, thereby stabilizing the current value of the electric motor.

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