JPS63178858A - Method of operating pulverized coal mill - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] Even when the load change rate of a boiler or the like is large, the present invention can easily supply pulverized coal from a pulverized coal mill to a combustion device at the load change rate. The present invention also relates to a method of operating a pulverized coal mill that allows quick follow-up.

[Prior Art] Fig. 1 is an explanatory diagram of a system for supplying pulverized coal to a pulverized coal boiler. In the figure, 1 is a coal feeder that cuts out coal stored in a hopper 2, and 3 is a coal feeder from the coal feeder 1. A vertical pulverized coal mill crushes the supplied coal, 4 is a primary air supply pipe, 5 is a fuel pipe that conveys the crushed pulverized coal by primary air, and 6 is a boiler burner.

The details of the pulverized coal mill 3 will be explained with reference to FIGS. 2 and 3. A raw coal supply lower is provided above the center of the mill, and a rotary table 9 driven by a drive device 8 is provided below the center of the mill. A plurality of crushing rollers 10 are disposed on the upper part of the rotary table 9 and are rotated by frictional force between the rotary table 9 and the primary air supply pipe 4 shown in FIG. A coarse powder separator 12 is provided with a connected primary air supply port 11, and around the raw coal supply lower in the upper part of the mill is equipped with a large number of vanes 12a whose opening degree can be adjusted by a drive device (not shown). A pulverized coal discharge port 13 is provided around the raw coal supply lower at the top of the mill to send out the pulverized pulverized coal together with primary air. A chute 14 is provided for returning the separated coarse coal onto the rotary table 9.

In the above device, the raw coal in the hopper 2 is cut out from the coal feeder 1, is supplied from the raw coal supply lower into the pulverized coal mill 3, falls onto the rotary table 9, and is rotated by the drive of the drive device 8. It is crushed between the rotary table 9 and the crushing roller 10,
The crushed pulverized coal is transported by primary air supplied into the mill from the primary air supply port 11 at the bottom of the mill via the primary air supply pipe 4, and enters the coarse powder separator 12 through the wide space above the crushing roller 10. The coarse coal is separated into pulverized coal and coarse coal by the coarse separator 12, and the pulverized coal is sent from the pulverized coal discharge port 13 by primary air through the fuel pipe 5 to the boiler burner 6, where it is combusted. Pass through rotating table 9
It is returned to the top and crushed again together with the raw coal supplied from the raw coal supply lower.

If the load on the pulverized coal mill changes due to a change in the boiler output command, for example, the load on the pulverized coal mill changes from A to B in Figure 4.
Conventionally, as shown by straight line A in FIG. At the same time, the amount of raw coal supplied to the pulverized coal mill 3 via the raw coal supply lower is increased.

Therefore, the amount of pulverized coal supplied from the pulverized coal discharge port I3 to the boiler burner 6 gradually increases, and the amount of coal stored in the mill gradually increases from Ql to Q2 as shown by the straight line C in FIG.

Conversely, even when the load on the pulverized coal mill decreases from B to A in Figure 4, the opening of vane L2a is maintained at a constant opening X1 as shown by straight line A in Figure 4, and the amount of primary air is increased. and reduce the amount of raw coal supplied to the pulverized coal mill 3.
Gradually reduce the amount of pulverized coal supplied to the boiler burner 6, and increase the amount of coal stored in the mill as indicated by straight line C in Figure 5.
Gradually decrease from 2 to Ql.

[Problems to be Solved by the Invention] However, with the above conventional means, the responsiveness of the pulverized coal mill 3 is determined by the mill's own mill time constant, and when the load change rate is smaller than the mill time constant, the pulverized coal mill 3 The amount of pulverized coal supplied to the boiler burner 6 follows the change in boiler output, but if the load change rate is greater than the crushing time constant, the amount of pulverized coal supplied to the boiler burner 6 cannot follow the change in boiler output.

The present invention has been made in view of the above-mentioned circumstances, with the object of making it possible to cope with a large mill load change rate that is greater than the grinding time constant specific to the mill.

[Means for Solving the Problems] The present invention involves pulverizing raw coal supplied from above using a rotary table and pulverizing rollers, transporting the obtained pulverized coal upward by primary air, and turning it into pulverized coal in a coarse separator. In a vertical pulverized coal mill, the pulverized coal is separated into coarse and coarse coal, and the pulverized coal is supplied to the burner and the coarse pulverized coal is returned to the rotary table.When the mill load increases, the vanes of the coarse separator are opened and the coal is stored in the mill. The mill is configured to discharge the powdered coal that has been stored in the mill, and to increase the amount of powdered coal stored in the mill by squeezing the vanes of the coarse powder separator when the mill load decreases.

``When the mill load increases, the vanes of the coarse separator open, and the amount of powdered coal stored in the mill is released outside the mill.The released powdered coal is sent to the burner, and when the mill load decreases. Sometimes the vanes are constricted, increasing the amount of pulverized coal stored in the mill and reducing the amount of pulverized coal fed to the burner.

[Example] Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

First, the principle of the present invention will be explained.
In the vertical pulverized coal mill 3 shown in the figure, generally the coarse powder separator 1
When the vane 12a of the second vane 12a is squeezed, the recirculation amount of the powdered coal separated by the coarse separator 2 and returned from the chute 14 to the rotary table 9 increases, and the amount of coal stored in the mill increases. It is known that when opened, the amount of pulverized coal separated by the coarse separator 12 and returned to the rotary table 9 that is recirculated into the mill decreases, and the amount of coal stored in the mill also decreases.

Next, the method of the present invention based on the above method will be explained.

For example, when the load of the pulverized coal mill is low as shown in FIG. 4, in the present invention, the opening degree of the vane 12a is narrowed down to the opening degree Xo, which is smaller than the conventional opening degree X1. In this case, the in-mill coal storage ff1Qo corresponds to the vane opening degree Xo, and is larger than the coal storage amount Q1 in the case of the conventional vane opening degree X1.

When the load on the pulverized coal mill 3 increases from A to B in FIGS. 4 and 5, the vane opening degree is increased from Xo to Xl along the straight line opening in FIG. 4. Therefore, the amount of coal stored in the mill increases along the straight line E in Figure 5 from Qo to Q2, but the increase in the amount of coal stored in the mill at this time is greater than that in the triangle shown in Figure 5 compared to the normal control method. The amount of XYZ parts can be reduced. Therefore, even if the load change rate is large, the power to the boiler burner 6 is
Sufficient pulverized coal is supplied in accordance with the increase in load, and the responsiveness of the pulverized coal mill 3 is improved.

When the load of pulverized coal mill 3 is lowered, the vane opening degree is changed from Xl to X. Narrow it down to For this reason, the amount of coal stored in the mill decreases from Q2 to Qo, but the amount of pulverized coal discharged outside the mill decreases by the amount of triangle X72 in Figure 5 compared to when the vane opening degree remains Xl as in the past. , it is possible to quickly follow a decrease in load.

It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the pulverized coal supply method of the present invention, it is possible to follow up with good responsiveness even when the mill load change rate is larger than the crushing time constant, and therefore, even when the load changes, a predetermined amount of coal can be supplied from the mill. An excellent effect can be achieved in that pulverized coal is reliably fed to the burner.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a boiler equipped with a pulverized coal mill, Figure 2 is a detailed diagram of the pulverized coal mill, Figure 3 is a view from the ■-■ direction of Figure 2, and Figure 4 is the pulverized coal mill load. FIG. 5 is a graph showing the relationship between the pulverized coal mill load and the amount of coal stored in the mill. In the figure, 1 is a coal feeder, 3 is a pulverized coal mill, 4 is a primary air supply pipe, 5 is a fuel pipe, 6 is a boiler burner, 7 is a raw coal supply port, 9
10 is a rotary table, 10 is a crushing roller, 12 is a coarse powder separator, 12a is a vane, 13 is a pulverized coal discharge port, and 14 is a chute. −9=

Claims (1)

[Claims] 1) Raw coal supplied from above is pulverized by a rotating table and pulverizing rollers, the resulting pulverized coal is conveyed upward by primary air, separated into pulverized coal and coarse pulverized coal by a coarse separator, and the pulverized coal is sent to a burner. In a vertical pulverized coal mill that supplies coarse pulverized coal and returns it to a rotary table, when the mill load increases, the vanes of the coarse separator are opened to release the pulverized coal stored in the mill, and the mill load decreases. A method for operating a pulverized coal mill, characterized in that the amount of pulverized coal stored in the mill is increased by occasionally squeezing the vanes of the coarse separator.