JP2009119332A - Mill purge stopping method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform a sure and appropriate purge residual coal purge without needing any troublesome operation when stopping a mill. <P>SOLUTION: The mill purge stopping method comprises: a process (S1) for detecting completion of mill stopping conditions; a process (S2) for automatically closing a coal gate provided at a banker outlet for feeding raw fuel to the mil; a process (S5) for stopping a coal feeder by confirming (S3) no raw fuel present on a coal feeder belt transporting the raw fuel from the coal gate to the mill; a process (S8) for confirming no raw fuel present in the mill; and a process (S10) for stopping the mill. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the boiler equipment having a mill for sending pulverized coal to the boiler together with combustion air, the present invention stops the mill by purging the remaining coal during periodic repair of the mill, periodic inspection, long-term rest, weekend stop, etc. It is about the method.

  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 raw fuel such as coal is not normally supplied to the mill, the boiler cannot be stably operated. In particular, it is necessary to carry out the remaining coal purge during periodic repairs, periodic inspections, long-term rests, and weekend stops of the mill. If the residual coal purging method is not appropriate, raw fuel remains in the mill, causing periodic repairs and periodic inspections. There is a risk that the boiler may not be able to be stably operated after the mill is restarted.

  Therefore, various techniques related to purging of residual coal at the time of periodic repair of the mill, long-term rest, weekend stop, etc. have been proposed. For example, a technique for detecting the completion of the remaining coal purge based on the mill differential pressure is disclosed (see Patent Document 1 and Patent Document 2).

  The technique described in Patent Document 1 detects the mill differential pressure, and uses the fact that the mill differential pressure becomes a constant differential pressure at the completion of the purge regardless of the coal pulverization property by the coal type. Immediately after the completion of the process, the vertical mill is stopped. And, the time of metal touch between the mill roller and the crushing table in the case of coal with high pulverization (soft) coal is shortened, and the problem of explosion due to stop of the mill motor in the state of residual coal in the case of coal with low pulverization (hard) Can be prevented.

  In the technique described in Patent Document 2, the shortest purge time for coal with good grindability and the longest purge time for coal with poor grindability are set in advance. After the coal feeder is stopped, a stop signal is output to the vertical mill drive unit within the range from the shortest purge time to the longest purge time and when the rate of change in the mill differential pressure falls below a specified value. The vertical mill is stopped and the mill purge is completed.

JP-A-9-29130 JP 2001-224972 A

  In the conventional technique described above, the purge stop is determined by detecting the differential pressure. However, it cannot always be said that the amount of residual coal in the mill and the mill differential pressure are linked, and if any situation that affects the differential pressure occurs, the purge stoppage could not be determined accurately. .

  Further, since the mill differential pressure for stopping the purge is set for each coal type, it is necessary to measure the mill differential pressure for stopping the purge in advance. Furthermore, the mill differential pressure for stopping the purge must be set for each coal type based on the measured value, and the setting operation is troublesome.

  The present invention has been proposed in view of the above-described circumstances, and provides a mill purge stop method capable of performing a reliable and appropriate residual coal purge without performing a troublesome operation when stopping the mill. With the goal.

The mill purge stopping method according to the present invention has the following features in order to achieve the above-described object.
That is, the mill purge stopping method according to the present invention includes a boiler having a mill that pulverizes raw fuel such as coal supplied between a table and a roller into pulverized coal and sends the pulverized coal together with combustion air to the boiler. This is a method for stopping the mill by purging residual coal in the facility. This mill purge stop method detects that the stop condition of the mill is in place and automatically closes the coal gate provided at the bunker outlet for supplying the raw fuel to the mill, and the raw fuel from the coal gate to the mill. A step of confirming that no raw fuel is present on the coal feeder belt for transporting the coal, and stopping the coal feeder, and a step of confirming that no raw fuel is present inside the mill and stopping the mill. It is characterized by that.

  The process of stopping the coal feeder is performed when a certain time has elapsed after confirming that no raw fuel is present on the coal feeder belt, and the process of stopping the mill is performed inside the mill. It is preferable to carry out when a certain time has elapsed after confirming that no fuel is present.

  Moreover, it is preferable that the stop condition detection of the mill in the process of automatically closing the call gate is performed based on the amount of coal supply and the outlet temperature of the mill.

  In addition, it is preferable to check the absence of raw fuel in the process of stopping the mill based on the load current to the drive unit of the mill.

  In the mill purge stopping method according to the present invention, after automatically closing the coal gate for supplying raw fuel to the mill, the coal feeder is stopped by confirming that no raw fuel is present on the coal feeder belt, Further, the mill is stopped after confirming that no raw fuel is present inside the mill. Therefore, after confirming the state in which raw fuel is not supplied from the coal feeder to the mill, the multiple confirmation of confirming that there is no raw fuel in the mill is performed, so when stopping the mill, It is possible to perform a reliable and appropriate residual coal purge. Further, even when raw fuels having different coal types are used, the remaining coal purge can be performed without performing a troublesome setting operation.

  Also, after confirming that there is no raw fuel on the coal feeder belt, stop the coal feeder after a certain period of time and confirm that there is no raw fuel inside the mill, then for a certain time In the case where the mill is stopped after the elapse of time, it is possible to perform more reliable and appropriate residual char purge.

  In addition, when detecting that the mill stop condition has been established based on the amount of coal supplied and the outlet temperature of the mill, and having a configuration that automatically closes the coal gate, perform a more reliable and appropriate residual coal purge. Is possible.

  In addition, if the configuration is such that the absence of raw fuel is confirmed based on the load current to the drive unit of the mill, it becomes possible to perform the remaining coal purge more reliably and appropriately.

Hereinafter, an embodiment of a mill purge stopping method according to the present invention will be described with reference to the drawings.
FIG. 1 is a flowchart showing a procedure of a mill purge stopping method according to an embodiment of the present invention. 2 is a schematic configuration diagram showing a part of boiler equipment to which the mill purge stopping method according to the embodiment of the present invention is applied, and FIG. 3 is a coal feeder to which the mill purge stopping method according to the embodiment of the present invention is applied. It is a schematic block diagram which shows.

<Boiler equipment>
The boiler equipment to which the mill purge stopping method according to the embodiment of the present invention is applied includes a mill (pulverized coal machine) 20 for pulverizing and supplying pulverized coal as fuel to the boiler 10, as shown in FIG. Yes.
Above the mill 20, a coal bunker 30 is disposed. In the mill 20, a table 21 and a roller 22 for pulverizing coal, and a rotation for classifying the pulverized coal to obtain 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 coal 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 and burned together with the combustion air supplied from the forced blower 50, and water is heated by the furnace 11, superheater and 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.

  As shown in FIG. 3, a coal feeder 60 is disposed between the coal bunker 30 and the mill 20. This coal feeder 60 is provided with upper and lower three-stage coal feeder belts 61, 62, 63, and the uppermost coal feeder belt 61 has coal on the coal feeder belt 61. A carbonless detector 64 is provided for detecting whether or not. The coal feeder belts 61, 62, 63 are driven by a driving means such as a motor. The carbonless detector 64 may be any known device and may be any device that can detect whether or not coal is present on the coal feeder belt 61.

  A call gate 70 for opening and closing the exit of the call bunker 30 is provided at the lower end of the call bunker 30. The call gate 70 is driven by driving means such as a motor. A shutter 80 for opening and closing the outlet of the coal feeder 60 is provided at the lower end of the coal feeder 60. The shutter 80 is driven by driving means such as a motor. A scraper 100 for scraping off the coal supplied to the mill 20 is provided on the chute 90 that connects the coal feeder 60 and the mill 20 in communication. The scraper 100 is driven by driving means such as a motor.

  In FIG. 2, only one call bunker 30 and mill 20 are shown, but a plurality of sets of call bunker 30 and mill 20 may be provided. In addition, 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. The computer and the display device also function as alarm generation means, and can generate an alarm when various abnormalities occur.

<Mill purge stop method>
The mill purge stopping method according to the embodiment of the present invention can be suitably applied particularly to residual coal purging performed during periodic repair of the mill, long-term rest, and weekend stop.
As shown in FIG. 1, in the mill purge stopping method according to the embodiment of the present invention, the amount of coal supply becomes a predetermined value (for example, 4.5 t / h) or less, and the outlet temperature of the mill 20 has a predetermined value (for example, for example). 65 ° C.) (S1), the call gate 70 is automatically closed because the stop condition of the mill 20 is satisfied (S2).

  Subsequently, it is confirmed whether or not coal is present on the coal feeder belt 61 by the no-carbon detector 64 (S3). And when it will be in the state (coal-on state) where coal no longer exists on coal feeder belt 61, it waits for progress of predetermined time (for example, 70 seconds) (S4), and stops coal feeder 60 ( S5). Subsequently, the shutter 80 provided at the outlet of the coal feeder 60 is closed (S6), and the scraper 100 provided on the chute 90 at the inlet of the mill 20 is stopped (S7).

  In this state, it is confirmed that the load current to the drive unit of the mill 20 has become a predetermined value (for example, 42 A) or less (S8), and further waits for the elapse of a predetermined time (for example, 300 seconds) (S9), The drive of the mill 20 is stopped (S10). Thereafter, an operation similar to a normal mill stop operation may be performed.

  As described above, in the mill purge stopping method according to the embodiment of the present invention, while performing multiple confirmation processing, the call gate 70 is automatically closed, the coal feeder 60 is stopped, and the mill 20 is further stopped. By performing such multiple confirmation processing, coal does not remain inside the mill 20, and appropriate and reliable residual coal at the time of periodic repair, periodic inspection, long-term rest, weekend stop, etc. of the mill 20. Purge can be performed.

The flowchart which shows the procedure of the mill purge stop method which concerns on embodiment of this invention. The schematic block diagram which shows a part of boiler equipment to which the mill purge stop method which concerns on embodiment of this invention is applied. The schematic block diagram which shows the coal feeder which applies the mill purge stop 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 60 Coal feeder 61, 62, 63 Coal feeder belt 64 Carbonless quantity detector 70 Cole gate 80 Shutter 90 Chute 100 Scraper

Claims (4)

In boiler equipment equipped with a mill that pulverizes raw fuel such as coal introduced between the table and rollers into pulverized coal, and sends the pulverized coal together with combustion air to the boiler, the remaining coal purge is performed to remove the mill. A method for stopping,
Detecting that the stop condition of the mill is in place, and automatically closing a call gate provided at a bunker outlet for supplying raw fuel to the mill;
Confirming the absence of raw fuel on the coal feeder belt that transports raw fuel from the coal gate to the mill and stopping the coal feeder;
Confirming the absence of raw fuel inside the mill and stopping the mill;
The mill purge stop method characterized by including. The step of stopping the coal feeder is performed when a certain time has elapsed after confirming that no raw fuel is present on the coal feeder belt,
The step of stopping the mill is performed when a certain time has elapsed after confirming that no raw fuel is present inside the mill.
The mill purge stopping method according to claim 1, wherein:   The mill purge stop method according to claim 1 or 2, wherein the detection of the stop condition of the mill in the step of automatically closing the call gate is performed based on the amount of coal supply and the outlet temperature of the mill.   The mill purge stopping method according to any one of claims 1 to 3, wherein the confirmation of the absence of raw fuel in the step of stopping the mill is performed based on a load current to the drive unit of the mill.

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