JPS63315158A - Method of controlling temperature of outlet for 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 Field of Application] The present invention relates to a method for controlling the outlet temperature of a mill (pulverizer).

[Prior Art] Fig. 2 shows an example of a pulverized coal supply line for a coal-fired boiler, in which coal supplied from a coal bunker 1 to a vertical pulverized coal machine 3 via a coal feeder 2 is turned into pulverized coal. The coal is pulverized by the coal machine 3 and transported while being dried by high-temperature primary air supplied from the secondary air duct 4, and then supplied to the burner 7 of the boiler 6 via the pulverized coal pipe 5 for combustion.

The secondary air duct 4 receives hot air 9 from a hot air pipe 8.
The flow rate of cold air 11 from the cold air pipe 10 is adjusted and supplied by mill inlet temperature adjustment dampers 12 and 13, and the inlet temperature of the pulverized coal pipe 5 (mill outlet temperature) is always maintained. The detected outlet temperature signal 15 from the mill outlet thermometer 14 provided at the mill outlet is introduced into the control device 16 and compared with the set temperature signal 17 so as to be kept constant, and the mill inlet temperature is determined based on the difference. The opening degrees of the adjustment dampers 12 and 13 are controlled.

[Problem to be solved by the invention] However, if the moisture content of the raw coal supplied to the mill changes, the saturation temperature of the steam corresponding to this moisture also changes, so as mentioned above, the pulverized coal pipe inlet temperature must be adjusted. With a constant holding control method, the set value may be too high for this saturation temperature, or
The saturation temperature may not be reached, and as mentioned above, if it is too high, there is a risk of ignition, and if the saturation temperature is not reached, the pulverized coal may have a high moisture content during combustion, causing the combustion to deteriorate and cause the coal to burn out. There were problems such as an increase in the amount of unburned fuel.

The present invention was made by focusing on the above-mentioned conventional problems.
The mill outlet temperature is changed and set according to the moisture content of the raw coal supplied to the mill.

[Means for solving the problems] The present invention attempts to solve the above technical problems, and
In a control method that controls the mill outlet temperature to a predetermined value by adjusting the primary air temperature at the mill inlet, the mill inlet temperature is detected, and the raw coal moisture content is determined from the detected mill inlet temperature and the amount of coal fed to the mill. This invention relates to a mill outlet temperature control method, characterized in that the mill outlet temperature is determined in accordance with the raw coal moisture content.

[Function] Therefore, in the present invention, the raw coal moisture is determined from the mill inlet temperature and the amount of coal fed to the mill, and the mill outlet temperature is set according to the raw coal moisture. The optimum value can be set depending on the moisture content.

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

FIG. 1 shows an example of the present invention applied to the apparatus shown in FIG. 2, and the same reference numerals in the figure represent the same parts.

In the conventional method shown in FIG. 2, for example, when the moisture content of the raw coal supplied to the mill 3 increases, thermal energy is normally consumed due to the moisture content and the mill outlet temperature decreases. The signal 15 detected by the thermometer 14 is input to the control device 16, and the mill inlet temperature regulating damper 12, 13 is automatically adjusted to increase the temperature of the primary air flowing through the primary air duct 4 at the mill inlet. It will be done.

The present invention has been made by focusing on the fact that, in the above-mentioned control, when the moisture content of the raw coal changes, the primary air temperature at the mill inlet is changed accordingly.

That is, as shown in FIG. 1, a mill inlet thermometer 18 for detecting the temperature of the primary air is provided in the secondary air duct 4, and a detected temperature signal 19 from the thermometer 18 is guided to a function generator 20 to generate a function. After conversion, a correction coefficient based on the coal feed amount signal 21 from the coal feeder 2 is multiplied via the multiplier 21° to obtain the coal moisture signal 2.
2 is obtained, and the signal 22 is further guided to a function generator 23, and the obtained correction signal 24 is sent to the set temperature signal 1 via an adder 25.
7 and inputs the obtained mill outlet temperature setting signal 26 to the control device 16, and adjusts the mill inlet temperature so that the outlet temperature signal 15 from the mill outlet thermometer 14 matches the mill outlet temperature setting signal 26. Adjustment dampers 12 and 13 are controlled.

For example, to explain the case where the moisture content of raw coal increases,
The mill outlet temperature decreases, and therefore the decreased outlet temperature signal 15 is input to the control device 16 and compared with the preset set temperature signal 17 or the mill outlet temperature set signal 26, so that the difference disappears. That is, the mill inlet temperature adjustment dampers 12 and 13 are adjusted to increase the mill inlet temperature in order to increase the mill outlet temperature.

As described above, when the mill inlet temperature rises, it is detected by the mill inlet thermometer 18, and the raw coal moisture 22 is determined from the detected mill inlet temperature signal 19 and coal feed amount signal 21.
Further, a correction signal 24 obtained through a function converter 23 is added to the set temperature signal 17 to obtain the mill outlet temperature set signal 2.
6 is changed (increased). As a result, the mill outlet temperature is set higher as the moisture content of the raw coal increases.

Furthermore, when the moisture content of raw coal is low, the mill outlet temperature is set to a low value due to the opposite effect to the above.

As a result of the above, the mill outlet temperature is automatically set to the optimum value according to the moisture content of raw coal supplied to the mill, thereby improving the safety of the pulverized coal supply line and improving the combustibility of pulverized coal. .

It should be noted that the present invention is not limited to the above-mentioned embodiments, but may also be applied to outlet temperature control of horizontal mills other than those shown in the drawings, and various other changes may be made without departing from the gist of the present invention. Of course, you can get it.

[Effects of the Invention] As described above, according to the mill outlet temperature control method of the present invention, the mill outlet temperature is controlled to an optimal value depending on the moisture content of raw coal, thereby reducing the risk of ignition and unburned coal. This can have an excellent effect of preventing the problem of increase in fuel consumption and improving safety and flammability.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the mill outlet temperature control method of the present invention, and FIG. 2 is an explanatory diagram showing an example of a conventional control method. 2 is a coal feeder, 3 is a vertical pulverizer, 4 is a primary air duct,
5 is a pulverized coal pipe, 8 is a hot air pipe, IO is a cold air pipe, 12.
13 is a mill inlet temperature adjustment damper, 14 is a mill outlet thermometer, 16 is a control device, 17 is a set temperature signal, 18 is a mill inlet thermometer, 19 is a detected temperature signal, 20 is a function generator, 2
1 is a coal feeding amount signal, 22 is a coal moisture signal, 23 is a function generator, 24 is a correction signal, 25 is an adder, and 26 is a mill outlet temperature setting signal.

Claims (1)

[Claims] 1) In a control method that controls the mill outlet temperature to a predetermined value by adjusting the primary air temperature at the mill inlet, the mill inlet temperature is detected, and the raw material is determined based on the detected mill inlet temperature and the amount of coal fed to the mill. A method for controlling a temperature at a mill outlet, characterized in that the moisture content of the raw coal is determined and the mill outlet temperature is set according to the moisture content of the raw coal.