JPH02253861A - Controlling method for fineness of pulverized coal in vertical mill - Google Patents

Abstract

PURPOSE:To hold the fineness of pulverized coal conducted out from a fuel pipe constant and to prevent the characteristics of pulverized coal delivered from a mill from being changed by regulating either the opening degree of the separation vane of a separator for coarse powder or number of revolution of the separation vane according to the change in a load command of the mill. CONSTITUTION:A raw material coal introduced according to a load command 22 of a mill is ground by both a grinding table 8 and the grinding rollers 9. The ground coal is carried by primary air 12 supplied according to the load command of the mill and separated into pulverized coal 18 and coarse powder 17 by a separator 16 for coarse powder. Pulverized coal 18 is delivered and also coarse powder 17 is returned to the grinding table 8. Either the opening degree of the separation vane 13 of the separator 16 or number of revolution of the separation vane 13 is regulated according to the change in the load command 22 of the mill. As a result, even when the load of the mill is changed, fineness of pulverized coal conducted out from a coal pipe is held constant and thereby the characteristics of pulverized coal delivered from the mill are prevented from being changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for controlling the fineness of pulverized coal in a vertical mill.

[Prior Art] Fig. 6 shows an example of a vertical mill, in which raw coal 8 cut out from a coal bunker by a coal feeder 2 driven by a drive device l such as a motor is fed to the main body of the vertical mill 4. The coal is introduced into a coal input pipe B provided at the upper center of the casing 5, and is rotated from the coal input pipe 6 by a drive device 7 such as a motor. The pulverized coal is supplied between the rollers 9 and pulverized, and the pulverized coal produced by the pulverization floats inside the main body casing 5 by the primary air 12 introduced from below through the primary air supply port 10 and the air port 11. After the coarse powder 17 is separated into pulverized coal 18 of the required fineness by a coarse powder separator 16 consisting of a separation vane 13 provided at the upper part, an eject chute 14 and a discharge pipe 15, the fuel pipe 19 It is supplied to a burner such as a pulverized coal combustion boiler via a pulverized coal combustion boiler.

Note that the separation vane 13 is connected to the drive shaft 21 by operating the handle 20. The angle in the circumferential direction, that is, the degree of opening can be adjusted via a conventionally known link mechanism.

Moreover, as the coarse powder separator 1B used in the vertical mill 4,
In addition to the above-described type in which the opening degree of the separation vane 13 can be adjusted, a separation vane is provided at the axial center of the coarse powder separator and rotated by a drive device to perform coarse powder separation. There is also a rotary coarse separator.

In the case of the coarse separator 18 shown in FIG. 6, the separation vanes 13 are manually adjusted during trial operation so that the pulverized coal supplied to the boiler burner has a predetermined fineness when the mill load is the rated load. Once the opening degree is adjusted, the opening degree of the separation vane 13 is maintained constant even if the mill load changes, and operation is continued, and even in the case of a rotary coarse powder separator, the fine powder is supplied to the boiler burner at the rated load. The rotation speed of the separation vane is selected so that the charcoal reaches a predetermined fineness, and the mill is operated at a constant rotation speed even when the mill load changes.

On the other hand, when the mill load changes, the mill load command 22 is given to the drive device 1 of the coal feeder 2, and the primary air supply port IO
The amount of raw coal 3 and the primary air supplied into the vertical mill by adjusting the rotation speed of the drive device 1 etc. By adjusting the amount, the amount of pulverized coal 18 drawn out from the fuel pipe 19 is adjusted. The reason why the amount of pulverized coal produced and the amount of primary air change as the mill load changes is because the amount of primary air is a function of the mill load.

[Problems to be Solved by the Invention] However, for example, when the mill load decreases below the rated load, the input amount of coking coal 3 is reduced and the amount of primary air 12 is also reduced in response to the decrease in mill load. If you decrease it,
The flow rate of the primary air 12 decreases and the pulverized coal L8 is transferred to the fuel pipe 19.
The flame may not be transferred from the boiler to the boiler burner, or the flame may come from the boiler furnace into the vertical mill.

Therefore, in order to ensure the conveyance of the pulverized coal 18 or to prevent the flame from entering the vertical mill, the minimum flow rate of the primary air 12 is determined, and the primary air 12 is adjusted as the mill load decreases. cannot be reduced. For this reason, when the mill load becomes as low as possible, the proportion of pulverized coal 18 in the primary air flowing into the fuel pipe 19 decreases compared to when the load is rated or when the load is relatively high. Pulverized coal 18 from which coarser coarse powder 17 is led out from fuel pipe 19
The fineness of the pulverized coal 18 changes.

Therefore, when the fineness changes, the amount of raw coal 3 introduced from the coal input pipe 6 per unit time and the amount of pulverized coal 1B derived from the fuel pipe 19 per unit time become equal in balance. There is a problem in that the mill coal output characteristics, which are determined by the time required, change, and when the mill coal output characteristics change, it becomes difficult to accurately control the temperature and pressure of the boiler.

In view of the above-mentioned circumstances, the present invention maintains the fineness of the pulverized coal led out from the fuel pipe constant even when the mill load changes, so that the mill coal output characteristics do not change. This was done for that purpose.

[Means for Solving the Problems] The present invention crushes raw coal input in response to a mill load command using a crushing table and a crushing roller, and transports it by primary air supplied in response to a mill load command. , in a vertical mill that separates pulverized coal and coarse powder with a coarse powder separator, outputs the pulverized coal, and returns the coarse powder to the grinding table.
The separation vane opening degree or separation vane rotation speed of the coarse powder separator is adjusted in response to changes in the mill load command.

[Function] When the mill load command changes, the separation vane opening degree or separation vane rotation speed is adjusted in accordance with the change in the mill load command, so the fineness of the pulverized coal produced remains constant. Retained.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 5 show one embodiment of the present invention, and the parts designated by the same reference numerals as in FIG. 6 represent the same parts.

As shown in the figure, a drive shaft 21 for adjusting the opening degree of the separation vane 13 is rotated by a drive device 23 such as a motor, and a mill load command 22 is sent to the drive device l of the coal feeder 2. Function generator 24
The function generator 24 is configured to send an opening adjustment command 25 to the drive device 23.

FIG. 2 shows details of the coarse powder separator 1, in which separation vanes 13 are rotatably attached to a fixing ring 26 provided at the upper part of the eject chute 14 at a required interval in the circumferential direction.
The vane arms 27 formed integrally with each separation vane 13 are sequentially connected to each other by connecting rods 28, and the drive shaft 21
The lever 29 fixed to the lever 29 and one of the vane arms 27 are connected to the connecting rod 30.

3 and 4 show examples of a drive device 23 for adjusting the opening degree of the separation vane 13, and the device in FIG.
The worm of a worm shaft 32 connected to the rotating shaft of the cylinder 1 is engaged with a worm wheel 33 so that the drive shaft 21 is driven by the drive of the motor 31, and FIG. The drive shaft 21 is connected to a lever 35 fixed to the shaft 21, and the drive shaft 21 is rotated by the operation of a cylinder 34.

When the mill load changes, the mill load command 22 is given to the drive device I of the coal feeder 2, and the rotation speed of the drive device I changes.
For this reason, 3 coking coals cut from coal bunkers
The amount of primary air supplied from the primary air supply port IO is also adjusted according to the load by giving the mill load command 22 to the blower drive device, and the mill load command 22 is also adjusted according to the load. 22 is given to the function generator 24, and from the function generator 24 is given to the drive device 23 as an opening adjustment command 25, which determines the separation vane opening θ of the separation vane 13 (see FIG. 2).
is also adjusted according to the mill load.

Therefore, the amount of pulverized coal 18 that is pulverized by the vertical mill 4 and discharged from the fuel pipe 19 corresponds to the mill load, and the fineness of the pulverized coal 18 corresponds to the mill load. Therefore, even if the mill load changes, the mill coal output characteristics do not change, and the pressure and temperature of the boiler can be easily and accurately controlled.

The relationship between the mill load, the primary air amount, and the separation vane opening degree θ is shown in the graph of FIG. 5. The primary air amount is controlled so that the mill load is on the graph of FIG. By adjusting the degree θ, the fineness of the pulverized coal 18 led out to the fuel pipe 19 can be kept constant. The primary air amount and separation vane opening degree θ corresponding to the mill load are determined by collecting data during a trial run.

In addition, in the embodiment of the present invention, the case where the separation vane opening degree θ is adjusted in order to maintain the fineness constant has been explained, but in the case of a rotary coarse powder separator, the separation vane opening degree θ is adjusted as shown in FIG. It goes without saying that the separation vane rotational speed n may be adjusted as shown in FIG.

[Effects of the Invention] As explained above, according to the method for controlling the fineness of pulverized coal in a vertical mill of the present invention, even when the mill load changes, the fineness of the pulverized coal produced changes. Since there is no heat exchanger, it is possible to keep the mill coal output characteristics constant, and therefore the temperature and pressure of the boiler can be controlled easily and accurately, and other excellent effects can be achieved.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of an embodiment of the method for controlling the fineness of pulverized coal in a vertical mill of the present invention, and Fig. 2 is a detail showing the left half of the separation vane portion of the coarse separator shown in Fig. 1. 3 is a front view of the drive device portion of the separation vane shown in FIG. 2, FIG. 4 is a front view showing another example of the drive device portion of the separation vane, and FIG. 5 is a front view of the drive device portion of the separation vane shown in FIG. Mill load in method and 1
Graph showing the relationship between air amount and separation vane opening, No. 6
The figure is a conceptual diagram of conventional means for controlling the amount of pulverized coal produced from a vertical mill. In the figure, 2 is a coal feeder, 3 is raw coal, 4 is a vertical mill, 6 is a coal input pipe, 8 is a crushing table, 9 is 1 crushing roller, 12
is primary air, 13 is separation vane, 1B is coarse powder separator,
17 is coarse powder, 18 is pulverized coal, 19 is a fuel pipe, 22 is a mill load command, 23 is a drive device, 24 is a function generator, 25
is the opening adjustment command, θ is the separation vane opening, and n is the separation vane rotation speed. Patent applicant Ishikawajima Harima Heavy Industries Co., Ltd.

Claims (1)

[Claims] 1) Raw coal input in response to the mill load command is crushed by a crushing table and crushing rollers, transported by primary air supplied in response to the mill load command, and is separated into pulverized coal and coarse coal by a coarse powder separator. In a vertical mill that separates the coal into powder and outputs pulverized coal while returning the coarse powder to the crushing table, the opening degree of the separation vane or the rotation speed of the separation vane of the coarse powder separator is adjusted in response to changes in the mill load command. A method for controlling fineness of pulverized coal in a vertical mill, characterized by adjusting the fineness of pulverized coal.