JP2007061727A - Abnormality diagnosis method of mill operation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormality diagnosis method of the operation of a mill which can quickly inform an operator of an expected generation cause of the abnormality for the abnormality generating at the start up/operation of the mill, and support a treating method. <P>SOLUTION: In the abnormality diagnosis method, a process of directing the removal of the expected cause by an alarm when a table differential pressure exceeds a first predetermined threshold, a process of directing the removal of the expected cause by an alarm when a mill exit/a fire furnace differential pressure exceeds the first predetermined threshold, a process of directing the start of operation of a spare mill 20 when the table differential pressure exceeds a second threshold greater than the first threshold, and a process of directing the start of operation of the spare mill 20 when the mill exit/the fire furnace differential pressure exceeds the second threshold greater than the first threshold are performed in this order. A biting process of confirming the biting of raw fuel is performed when starting the operation of the mill 20 preceding the respective processes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for diagnosing abnormal operation of a mill, and more particularly to a method for diagnosing abnormal operation of a mill that can quickly and accurately cope with an operational abnormality that occurs in a mill for supplying pulverized coal to a boiler.

In a power plant in which a generator is driven using a turbine, steam is generated by burning fuel such as pulverized coal in a boiler, the turbine is rotated by this steam, and the drive shaft is connected to the rotating shaft of the turbine. The connected generator is driven to generate electricity.
In such a power plant, a mill (pulverized coal machine) for pulverizing raw fuel such as coal and supplying it to the furnace together with combustion air is installed in the front stage of the boiler.

The mill is an important device for supplying fuel to the boiler. If the raw fuel such as coal is not normally supplied to the mill, the operation of the boiler will be hindered.
Thus, various techniques for stably supplying pulverized coal to a boiler have been proposed.

  For example, a “pulverized coal combustion device that aims to maintain stable combustion at the start-up of a boiler and during low-load operation, and does not require auxiliary fuel such as oil and gas and responds well to sudden load changes. And operation method "are disclosed (see Patent Document 1).

  According to “Pulverized Coal Combustion Device and Operation Method” described in Patent Document 1, when the mill is started, the pulverized coal fuel supply line is closed using the combustion supply amount adjusting means and the circulation path passes through the separation device. The pulverized coal is circulated by the above, and the fuel supply amount adjustment means is waited until the concentration sufficient for starting the pulverized coal combustion, that is, the mixing weight ratio C / A of the pulverized coal fuel C and the transport air A reaches 0.3 or more It is said that the mill can be started without using auxiliary fuel such as oil or gas by turning to open. Moreover, it is said that it is no longer necessary to provide auxiliary combustion devices such as gas and oil by controlling so as to maintain stable combustion of pulverized coal at all times.

  Further, the “control method and apparatus for a pulverized coal combustion boiler mill” which aims to provide a control apparatus for a pulverized coal combustion mill that enables operation according to a load schedule and can perform pulverized coal injection at an optimal timing. Is disclosed (see Patent Document 2).

  The "control method and apparatus for a pulverized coal combustion boiler mill" described in Patent Document 2 includes a load input unit that inputs a load at each time, and a coal feeder that starts coal output from the mill based on the load schedule. Mill process data includes mill input time calculation unit that calculates automatic time, residual coal amount in the mill before start-up and its particle size distribution, time change of the amount of coal supplied to the mill, coal particle size, friability, etc. A mill simulation model unit that calculates the expected waiting time for coal delivery from the start of coal supply to the mill based on these data, the automatic time of the coal feeder, and waiting for the mill A calculation unit that calculates a coal supply start time to the mill based on the time, and a control unit that controls the mill based on the coal supply start time and the coal feeder automatic time are provided.

  According to the “control method and apparatus for a pulverized coal combustion boiler mill” having such a configuration, the mill coal output time can be accurately predicted and pulverized coal can be charged at a necessary timing with respect to the boiler load. It is said that the plant can be operated without delay with respect to the load schedule of the plant and that the plant can be operated satisfactorily by supplying coal without a shortage of the steam temperature and pressure requirements of the boiler.

JP-A-5-312305 JP-A-9-969

  However, abnormalities that occur during start-up and operation of the mill are related to various factors such as differences in mechanical characteristics in the assembly process performed after the overhaul of the mill, in addition to the characteristics of each coal brand.

In this regard, the “pulverized coal combustion apparatus and operation method” described in Patent Document 1 or the “control method and apparatus for a pulverized coal combustion boiler mill” described in Patent Document 2 is described as starting and operating the mill. It did not take into account all the causes of abnormalities at the time, and it was difficult to say that it was possible to quickly and appropriately cope with the abnormalities that occurred.
For this reason, when an abnormality occurs during start-up and operation of the mill, whether the cause of the abnormality is due to the characteristics of the coal type or the mechanical characteristics of the mill is determined based on the experience of a skilled operator. is the current situation.

  The present invention has been proposed in view of the circumstances described above, and it is possible to promptly notify an operator of a predicted cause of an abnormality that occurs at the time of mill start-up and operation, and to support a coping method. An object of the present invention is to provide a simple mill operation abnormality diagnosis method.

The mill operation abnormality diagnosis method according to the present invention has the following features in order to achieve the above-described object.
That is, the operation abnormality diagnosis method according to the present invention includes a plurality of mills that pulverize raw fuel such as coal supplied between a table and a roller into pulverized coal, and send the pulverized coal together with combustion air to a boiler. In a boiler facility, a method for diagnosing an abnormality of a mill during operation is generated, and an alarm is generated and expected when a differential pressure in the table exceeds a predetermined first threshold value. When the first table differential pressure abnormality diagnosis step for instructing the cause removal and the differential pressure between the mill outlet and the furnace exceeds a predetermined first threshold, an alarm is generated and expected. The first mill outlet / furnace differential pressure abnormality diagnosis step for instructing the removal of the cause of the fault and when the differential pressure in the table exceeds a second threshold value that is larger than the first threshold value, Instruct start of operation The second table differential pressure abnormality diagnosing step and when the differential pressure between the mill outlet and the furnace exceeds a second threshold value that is larger than the first threshold value, a first instruction is given to start the operation of the spare mill. The second mill outlet / furnace differential pressure abnormality diagnosis process is performed in this order.

  Further, it is preferable to instruct the operation stop of the mill in which an abnormality has occurred in the second table differential pressure abnormality diagnosis step and the second mill outlet / furnace differential pressure abnormality diagnosis step.

  In the first table differential pressure abnormality diagnosis step, when the differential pressure in the table exceeds a predetermined first threshold, the load current to the drive unit, the amount of air supplied to the mill, the mill outlet The temperature, the distance between the table and the roller, and the confirmation of the pyrite hopper that collects foreign matter in the raw fuel are instructed, and when any abnormality is recognized, the pressing hydraulic pressure of the roller is increased, or Instructing at least one of the reduction of the rotational speed of the rotary classifier for regulating the particle size of the pulverized coal to eliminate the cause of the abnormal operation, and in the first mill outlet / furnace differential pressure abnormality diagnosis step, the mill outlet When the differential pressure between the furnace and the furnace exceeds a predetermined first threshold, the load current to the drive unit increases, the amount of air supplied to the mill, the mill outlet temperature, the table and the roller Interval If there is an abnormality in any of the items to be confirmed, the reduction of the raw fuel supplied to the mill is instructed to eliminate the cause of the abnormal operation. preferable.

  In addition, it is preferable to carry out a biting abnormality diagnosing step of confirming biting of the raw fuel into the gap between the table and the roller at the start of operation of the mill preceding each step.

  Further, in the biting abnormality diagnosis step, when the load current to the drive unit is equal to or less than a predetermined threshold value, the initial supply of the raw fuel is started, and the raw fuel bites into the gap between the table and the roller. If it is determined that the start-up is complete, and it is not detected that the raw fuel is caught in the gap between the table and the roller, in the first table differential pressure abnormality diagnosis step, the table differential pressure is detected. Can be diagnosed as having a bite in the mill when the value is equal to or less than a predetermined first threshold value.

  In the mill operation abnormality diagnosis method according to the present invention, whether or not the differential pressure in the table exceeds a predetermined threshold value is determined in two stages, and whether or not the differential pressure between the mill outlet and the furnace exceeds a predetermined threshold value. It is possible to promptly notify the operator of the expected cause of the occurrence of an abnormality that occurs during the start-up and operation of the mill by determining whether or not in two steps.

  In addition, when the differential pressure at the table exceeds the second threshold and when the differential pressure between the mill outlet and the furnace exceeds the second threshold, the operation of the mill is instructed by instructing the mill to stop. It is possible to quickly and appropriately deal with abnormalities that occur during startup and operation.

  Also, in the abnormality diagnosis, the operator is instructed with a plurality of confirmation items, and the operator is instructed how to deal with the abnormality that has occurred. Further, it becomes possible to deal with the problem promptly and appropriately.

  In addition, it is possible to respond more quickly and appropriately to abnormalities that occur during the start-up and operation of the mill by performing an abnormality check that checks whether the raw fuel has been caught at the start of mill operation. It becomes.

  In addition, when performing the biting abnormality diagnosis, the initial supply of the raw fuel is started based on the load current to the driving unit, and thereafter, if the table differential pressure is equal to or less than a predetermined threshold, the mill biting abnormality is detected. By diagnosing, it becomes possible to quickly and appropriately diagnose a mill biting abnormality.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a mill operation abnormality diagnosis method according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a part of boiler equipment to which a mill operation abnormality diagnosis method according to an embodiment of the present invention is applied. In FIG. 1, only the mill and the boiler that are particularly necessary for the description of the present embodiment are shown among the devices constituting the boiler facility.

  As shown in FIG. 1, a boiler facility to which a mill operation abnormality diagnosis method according to an embodiment of the present invention includes a mill (pulverized coal machine) 20 for pulverizing and supplying pulverized coal as fuel to a boiler 10. I have.

  A bunker 30 is disposed above the mill 20, and in the mill 20, a table 21 and a roller 22 for pulverizing coal, and a rotation for classifying the pulverized coal into a desired particle size. A type classifier 23 is provided. The mill 20 is connected to a pyrite hopper 40 for collecting foreign matter mixed in the coal as raw fuel and a pusher blower 50 for transferring pulverized coal into the furnace 11 of the boiler 10.

  The mill 20 receives supply of coal as raw fuel from the bunker 30, bites the coal between the table 21 and the roller 22, and rotates the table 21 while pressing the roller 22 against the table 21. Coal is pulverized to produce pulverized coal. Moreover, by adjusting the rotational speed of the rotary classifier 23, the pulverized coal can have a desired particle size.

  The pulverized coal produced in the mill 20 is supplied to the furnace 11 of the boiler 10 together with the combustion air supplied from the forced blower 50 and combusts, and water is heated by the furnace 11, the superheater and the reheater to generate steam. Let The generated steam is sent to the turbine to rotate the turbine, and power is generated by driving a generator connected coaxially with the turbine. The steam after rotating the turbine is returned to water by the condenser and supplied to the superheater again.

In the mill 20 having such a configuration, a pressure difference is generated from the raw material inlet side toward the outlet of the mill 20 by the combustion air supplied from the forced blower 50.
Although only one bunker 30 and mill 20 are shown in FIG. 1, the boiler facility according to this embodiment includes a total of six bunkers 30 and mills 20. In a normal operation state, the five mills 20 are operated to generate power, and when the inspection or abnormality occurs, the spare mill 20 is operated to generate power.

  Equipment for monitoring the operation status of the mill 20 is attached to the mill 20 and its attached equipment. Although not shown, the equipment includes an ammeter for measuring the load current to the drive unit for driving the table 21 and the roller 22 and the like, a flow meter for measuring the amount of air supplied to the mill 20, and a mill. A thermometer for measuring the outlet temperature of 20, a position measuring device for measuring the vertical position of the table 21, a hydraulic meter for measuring the pressing hydraulic pressure of the roller 22, and the rotational speed of the rotary classifier 23 are measured. It consists of a tachometer for the purpose.

  Although not shown, these devices are connected to a computer provided in the central control room, and the measured values in each device are displayed on a display device such as a panel display or a liquid crystal display. Yes. Further, the computer and the display device also function as an alarm generation means, and can generate an alarm when various abnormalities occur.

  Next, the procedure of the mill operation abnormality diagnosis method according to the embodiment of the present invention will be described. 2 to 4 are flowcharts showing the procedure of the mill operation abnormality diagnosis method according to the embodiment of the present invention.

  In the mill operation abnormality diagnosis method according to the embodiment of the present invention, as shown in FIGS. 2 and 3, the biting abnormality diagnosis step (S1), the first table differential pressure abnormality diagnosis step (S2-1 to S2-3). ), First mill outlet / furnace differential pressure abnormality diagnosis step (S3-1 to S3-3), second table differential pressure abnormality diagnosis step (S4-1 to S4-3), second mill outlet / furnace The differential pressure abnormality diagnosis process (S5-1 to S5-3) is performed in this order.

In the biting abnormality diagnosing step (S1), it is confirmed whether or not the raw fuel has bitten into the interval between the table 21 and the roller 22.
In this biting abnormality diagnosing step (S1), as shown in FIG. 4, the mill 20 is started (S1-1), and at the time of starting the mill 20, the load current to the drive unit is greater than or equal to a predetermined threshold value. If the load current to the drive unit is greater than or equal to a predetermined threshold value, there are conditions for detecting the biting of raw fuel, such as remaining charcoal in the mill 20 or the like. Since it is not ready, processing for coping with this is performed (S1-3). Here, the predetermined threshold is 57A, for example.

  On the other hand, when the load current to the drive unit is less than 57 A, for example, initial coal supply is started at 45 t / h (S1-4), and whether the raw fuel is caught is determined (S1-5). In this biting determination, for example, if the state where the load current to the drive unit is 57 A or more continues for 3 seconds or longer, it is determined that the raw fuel has been bitten and the activation is completed.

  On the other hand, when the raw fuel bite is not detected, the process proceeds to the first table differential pressure abnormality diagnosis step (S2-1 to S2-3).

  In the first table differential pressure abnormality diagnosis step, as shown in FIG. 2, it is determined whether or not the table differential pressure exceeds a predetermined first threshold (S2-1), and the table differential pressure is determined in advance. When the first threshold value is exceeded, an alarm is generated (S2-2), and the removal of the expected cause is instructed (S2-3). Here, the first threshold is, for example, 3.8 KPa.

  In the first table differential pressure abnormality diagnosis step, when the table differential pressure exceeds the first threshold value, the load current to the drive unit, the amount of air supplied to the mill 20, the mill outlet temperature, the table 21 and the roller 22 And the confirmation of the pyrite hopper 40 that collects foreign matter in the raw fuel. And when abnormality is recognized about any confirmation matter, at least one of the increase in the pressing hydraulic pressure of the roller 22 or the decrease in the rotational speed of the rotary classifier 23 for regulating the particle size of the pulverized coal is instructed. . The operator can remove the cause of the abnormal operation by adjusting the operation state of the device according to the instruction.

  Further, in the case where the biting abnormality diagnosis step (S1) does not detect the biting of the raw fuel, and the table differential pressure is equal to or less than a predetermined first threshold value, it is diagnosed that the biting abnormality is in the mill. To do.

  In the first mill outlet / furnace differential pressure abnormality diagnosis step, as shown in FIG. 2, it is determined whether or not the mill outlet / furnace differential pressure exceeds a predetermined first threshold (S3-1). When the outlet / furnace differential pressure exceeds a predetermined first threshold value, an alarm is generated (S3-2), and removal of an expected cause is instructed (S3-3). Here, the first threshold value is variably set according to the operation status of the mill 20 and the boiler equipment for diagnosing operation abnormality. For example, a value lower than 1.35 KPa, which is the second threshold value, is set. The

  In this first mill outlet / furnace differential pressure abnormality diagnosis step, when the mill outlet / furnace differential pressure exceeds a predetermined first threshold, the load current increases to the drive unit, and the air supplied to the mill 20 The amount, the mill outlet temperature, the distance between the table 21 and the roller 22, and the confirmation of the pyrite hopper 40 that collects foreign matter in the raw fuel are instructed. And when abnormality is recognized about any confirmation matter, the reduction | decrease of the raw fuel supplied to the mill 20 is instruct | indicated. The operator can remove the cause of the abnormal operation by adjusting the operation state of the device according to the instruction.

  In the second table differential pressure abnormality diagnosing step, as shown in FIG. 3, it is determined whether or not the table differential pressure exceeds a second threshold value that is larger than the first threshold value (S4-1), and the table differential pressure is determined. When the value exceeds a second threshold value that is greater than the first threshold value, the raw fuel supplied to the mill 20 is reduced (S4-2), and the removal of an expected cause is instructed (S4-3). . Here, the second threshold value is, for example, 4.78 KPa.

  In the second table differential pressure abnormality diagnosis step, when the table differential pressure exceeds the first threshold value, the raw fuel supplied to the mill 20 is forcibly reduced to, for example, 30 t / h, and the operation status of other mills 20 The operation status of the boiler 10, the load current to the drive unit, the amount of air supplied to the mill 20, the temperature at the exit of the mill, the distance between the table 21 and the roller 22, and the confirmation of the pyrite hopper 40 that collects foreign matter in the raw fuel Instruct. When an abnormality is recognized for any of the confirmation items, the operator activates the preliminary mill 20 and stops the operation of the mill 20 in which the abnormality has occurred after the activation of the preliminary mill 20 is completed. The cause can be removed.

  In the second mill outlet / furnace differential pressure abnormality diagnosis step, as shown in FIG. 3, it is determined whether the mill outlet / furnace differential pressure has exceeded a second threshold value that is larger than the first threshold value (S5- 1) The operation of the mill 20 in which an abnormality has occurred is stopped, a run-back operation is performed (S5-2), and an expected cause removal is instructed (S5-3). Here, the second threshold is set to 1.35 KPa, for example. A predetermined confirmation operation is performed during the runback.

  In this second mill outlet / furnace differential pressure abnormality diagnosis process, after performing the run-back operation, the operator starts the preliminary mill 20 and increases the load after the start of the preliminary mill 20 is completed. The cause of the abnormality can be removed.

  As described above, in the mill operation abnormality diagnosis method according to the embodiment of the present invention, the abnormality that occurs during the start-up / operation of the mill 20 is quickly and reliably grasped by a predetermined logic, and the predicted cause of occurrence is determined to the operator. And can cope with it.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, A predetermined | prescribed threshold value is suitably changed according to the scale of the boiler 10, an operating condition, etc. Of course, various changes can be made without departing from the scope of the invention.

  The mill operation abnormality diagnosis method of the present invention can be used mainly when diagnosing operation abnormality of a roller mill, which is a component of a power plant, but is a roller mill in which the boiler 10 is operated by supplying pulverized coal. Any mill 20 can be applied.

It is a schematic block diagram which shows a part of boiler equipment to which the mill driving | operation abnormality diagnosis method which concerns on embodiment of this invention is applied. It is a flowchart which shows the procedure of the mill driving | running | working abnormality diagnosis method which concerns on embodiment of this invention. It is a flowchart which shows the procedure of the mill driving | running | working abnormality diagnosis method which concerns on embodiment of this invention. It is a flowchart which shows the procedure (Mill biting abnormality diagnostic process) of the mill driving | operation abnormality diagnostic method which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Boiler 11 Furnace 20 Mill 21 Table 22 Roller 23 Rotary classifier 30 Bunker 40 Pyrite hopper 50 Pushing blower

Claims (5)

In a boiler facility equipped with a plurality of mills that pulverize raw fuel such as coal introduced between the table and rollers into pulverized coal and send the pulverized coal together with combustion air to the boiler, abnormalities in the mill during operation A method for diagnosing comprising:
A first table differential pressure abnormality diagnosing step for generating an alarm and instructing removal of an expected cause when the differential pressure in the table exceeds a predetermined first threshold;
The first mill outlet / furnace differential pressure abnormality that generates an alarm and instructs the removal of an expected cause when the differential pressure between the mill outlet and the furnace exceeds a predetermined first threshold. Diagnostic process;
A second table differential pressure abnormality diagnosing step for instructing the start of operation of a spare mill when the differential pressure in the table exceeds a second threshold value that is greater than the first threshold value;
When the differential pressure between the mill outlet and the furnace exceeds a second threshold value that is larger than the first threshold value, a second mill outlet / furnace differential pressure abnormality diagnosis that instructs the start of operation of the spare mill And a method for diagnosing abnormal operation of a mill, wherein the steps are performed in this order.   2. The mill operation according to claim 1, wherein in the second table differential pressure abnormality diagnosis step and the second mill outlet / furnace differential pressure abnormality diagnosis step, the operation of the mill in which an abnormality has occurred is instructed. Abnormal diagnosis method. In the first table differential pressure abnormality diagnosis step, when the differential pressure in the table exceeds a predetermined first threshold, the load current to the drive unit, the amount of air supplied to the mill, the mill outlet temperature, Instructing confirmation of the distance between the table and the roller and the pyrite hopper that collects foreign matter in the raw fuel, and if any of the items to be confirmed is abnormal, increase in the pressing hydraulic pressure of the roller or pulverized coal Instruct at least one of the reduction of the rotational speed of the rotary classifier to regulate the particle size of the
In the first mill outlet / furnace differential pressure abnormality diagnosis step, when the differential pressure between the mill outlet and the furnace exceeds a predetermined first threshold, the load current increases to the drive unit, and the mill Instructed to confirm the amount of air to be supplied, the mill outlet temperature, the distance between the table and the roller, and the pyrite hopper that collects foreign matter in the raw fuel. The method for diagnosing abnormal operation of a mill according to claim 1 or 2, wherein the cause of abnormal operation is eliminated by instructing a decrease in raw fuel to be supplied to the vehicle.   4. The biting abnormality diagnosing step of confirming biting of raw fuel into the gap between the table and the roller at the start of operation of the mill preceding each of the steps is performed. The method for diagnosing abnormal operation of a mill according to claim 1. In the biting abnormality diagnosing step, when the load current to the drive unit is equal to or less than a predetermined threshold value, the initial supply of the raw fuel is started, and the biting of the raw fuel into the interval between the table and the roller is detected. It is determined that the startup is complete,
When it is not detected that the raw fuel is caught in the gap between the table and the roller, in the first table differential pressure abnormality diagnosis step, when the table differential pressure is equal to or less than a predetermined first threshold value. The method for diagnosing a mill operation abnormality according to claim 4, wherein the diagnosis is a mill biting abnormality.

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