JPS59164822A - Combustion control of coal fired stoker boiler - Google Patents

Abstract

PURPOSE:To make various properties of a load side plant easily controllable by a method wherein the feeding state of coal lumps is monitored and the action to increase the output of a controller is prevented during the period, in which the generation of abnormality contitunes. CONSTITUTION:A judging device 51 receives a signal from an ammeter 50 and a signal inputted to a stoker drive 3 and compares them with each other. If the current lowers and no current corresponding to said signal inputted to the stoker drive 3 is received by the judging device 51, the device 51 decides the generation of abnormality of the feeding state of coal and consequently changes-over the mode of a controller 12 from a proportional plus integral control action to a proportional control action. The controller 12 performs the control action, before an abnormality decision signal arrives, by a proportional plus integral control action and, after the abnormality decision signal is inputted, the control is performed by a proportional control action only because an integral control action is held by the abnormality decision signal. Accordingly, the signal inputted to the stoker drive 3 does not largely differ from the value before the generation of abnormality of feeding state. Thus, various properties of a load side plant are made easily controllable.

Description

[Detailed description of the invention] It is related to.

First, a conventional combustion control method for a coal-fired stoker boiler will be explained with reference to FIG.

Coal lumps for combustion are supplied to hopper 1.

The supplied coal lumps reach a coal feeder 2 provided at the bottom of the hopper 1. This coal feeder 2 is driven and operated by a coal feeder drive device 3 and supplies coal lumps to a spreader 4 . A spreader 4, which has a spreader that rotates at high speed, spreads coal almost uniformly onto a grate 7 (installed at the bottom of the furnace 17), which is moved by a grate drive device 6 and a drive machine 5. Distribute.

Combustion air is introduced from a wind box 8 at the bottom of the grate 7. Combustion air is supplied by a ventilator 16. , the flow rate is adjusted by a damper 15. An actively burning coal seam is formed on the grate 7, and this coal seam is moved from the rear of the furnace (on the side of the grate drive device 6) to the front of the furnace by the grate 7, and is disposed of in the ash pit 18. High-temperature exhaust gas generated by combustion on the grate 7 gives heat to the boiler 9, where it exchanges heat and generates steam, which reaches the outside of the furnace (flue) through the duct 19.

Steam generated in the boiler 9 is supplied to the load-side plant through the steam pipe 10. In this case, the steam flow rate (hereinafter referred to as steam flow rate) sent to the load-side plant (required by the load-side plant) is not constant (it constantly changes).

For this reason, it is necessary to change the supply amount of coal blocks (coal feed amount) and combustion air supply amount in response to changes in the steam flow rate required by the load-side plant, but it is difficult to do this manually. Since this is very difficult, the following control method is adopted.

That is, the steam pressure supplied to the load side (hereinafter referred to as main steam pressure) is detected by the pressure gauge 11 attached to the steam piping 10, and the signal is sent to the controller 12, and the controller 12 detects the detected signal at a predetermined value. (setting value)
and outputs a correction signal to the ratio calculator 13. Ratio calculator 1
3 outputs a value that guarantees the air flow rate necessary for combustion to the drive device 14 that drives the damper 15.

By employing the above method, for example, when the steam flow rate tends to decrease, the main steam pressure increases. This is detected by the pressure gauge 11 and input to the controller 12. - The meter 12 compares this detection signal with a set value. In this case, if the detection signal is lower than the set value, the storage controller 1
2 should correct this (decrease the output signal). The temperature also decreases, and the combustion air flow rate decreases.As a result, combustion is suppressed, the amount of steam generated in the boiler 9 decreases, and the increase in main steam pressure is suppressed, resulting in a level near the set value. It will calm down.

On the other hand, when the steam flow rate tends to increase, the coal feed amount and combustion air flow rate increase due to the same effect, combustion is promoted, and the main steam pressure settles around the set value, making it possible to achieve stable operation.

As described above, by the conventional method, stable operation with little fluctuation in main steam pressure can be achieved even when the steam flow rate fluctuates, and even when the steam flow rate is constant. However, when the properties of the supplied coal lumps are good, stable operation as described above can be achieved, but when the particle size and moisture content of the coal lumps are not uniform (an example of a case where the coal properties are not good, for example, when coal is piled up in the open) (In some cases, the moisture content may fluctuate significantly due to changes in the weather, or the viscosity may be small, etc.), the main steam pressure fluctuates significantly, and various This not only impairs controllability and requires manual intervention on the load side plant, but also requires more labor.
In some cases, the plant may have to be shut down. Furthermore, if a turbine (power generator) is connected as a load-side plant, there is a risk that the turbine may be damaged in the worst case.

As mentioned above, the main reason why the main steam pressure fluctuates significantly is that even if the coal feeder 20 rotation speed is changed (the coal feeder drive device 30 is turned on).
Even if the power signal is changed, the amount of coal fed does not change accordingly. The cause of this is that due to poor coal properties, coal may adhere to the hopper 1, coal feeder 2, etc., or a partial blockage may occur in the hopper 1, which may cause the rotation speed of the coal feeder 2 to decrease. This is because a commensurate amount of coal supply cannot be obtained.

In addition, when such a partial occlusion phenomenon occurs, whether it is left untreated and the partial occlusion phenomenon disappears naturally, or if a person notices it and takes action, the phenomenon will not occur. Due to this occurrence, the amount of coal to be fed decreases, so the main steam pressure rapidly decreases, and the output of the controller 12 rapidly increases (
The number of revolutions of the coal feeder 20 may be close to the maximum. ). If there is no partial blockage in this state, a very large amount of coal lumps will be supplied, which will cause a disturbance to the combustion control system, and the main steam pressure will fluctuate significantly, impairing stable operation.

In addition, if the coal seam on the grate is thick (and draft is not sufficient and combustion efficiency decreases), black smoke and tarinka will occur.

In order to achieve stable operation, the feeding state of the coal lumps is monitored and the output of the controller 12 is prevented from increasing while an abnormality is occurring. That is, it is sufficient to maintain the integral control operation output (integral calculation output) included in the output of the moderator 12 near the value before the occurrence of the abnormality, and prevent the output of the controller 12 from increasing during the abnormal period.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a combustion control method for a coal-fired stoker boiler that eliminates the conventional drawbacks.

According to the present invention, the coal lumps are supplied so as to maintain the pressure of the steam supplied to the load side at a predetermined value from the coal-fired stoker boiler that obtains steam by burning the coal lumps spread on a moving grate. In a control system that operates the amount and flow rate of combustion air, the supply state of the coal block is monitored, and during a period when an abnormality in the supply state occurs, the control system controls the difference between the pressure of the steam and a predetermined value. The supply amount of the coal lump and the flow rate of combustion air are changed in accordance with a signal obtained by performing a proportional calculation on the deviation, and during a period in which the supply state is normal, in accordance with a signal obtained by performing a proportional integral calculation on the control deviation. A combustion control method for a coal-fired stoker boiler is provided, the method comprising changing the amount of coal block supplied and the flow rate of combustion air.

Since the present invention employs the above-mentioned method, even if the coal lump supply status becomes abnormal due to poor properties of the coal lumps, there is no possibility that a larger amount of coal lumps than necessary will be supplied, and the main steam Pressure fluctuations are smaller than before, no black smoke is generated, and stable operation can be achieved.

A preferred embodiment of the present invention, illustrated in FIG. 2, will be described in detail below.

In FIG. 2, reference numerals 1 to 19 indicate the same elements as in the conventional example, and numerals 50 to 52 indicate newly added elements for carrying out the present invention. Reference numeral 50 is an ammeter that measures the current of the coal feeder drive device (motor) 3. The output of this ammeter 50 is sent to a supply state monitoring and determining device 51 (hereinafter referred to as a determining device). The judgment device 51 outputs the output to the controller 12.
The signal is sent to the controller 12 for use as a mode (proportional operation/proportional integral calculation) switching signal. In addition, the determination device 51
outputs an alarm signal to the alarm device 52 to notify the operator when the supply condition is abnormal.

The judgment device 51 receives the ammeter 50 and the input signal of the coal feeder drive device 3, compares them, and determines whether the current decreases and a current (output signal of the ammeter 50) corresponding to the input signal is obtained. If not, it is determined that the supply status is abnormal, and the mode of the controller 12 is switched from proportional + integral movement to proportional operation. The controller 12 is held in the abnormal-0 range and performs control operation only by proportional operation.

Therefore, the input signal of the coal feeder drive device 3 will not deviate greatly from the value before the supply state abnormality.

Further, when the determining device 51 determines that the coal block partial blockage phenomenon has disappeared and the supply state has become normal due to the output recovery of the ammeter 50, the control operation of the controller 12 is made to be a proportional-integral calculation. Due to this, the input signal of the coal feeder drive device 30 has the value before returning to normal as its initial value, and a signal that has been subjected to proportional operation and integral operation calculations is now output from the controller 12. The combustion control system returns to the control method used before the abnormality occurred.

If an abnormality occurs in the supply state in a stable operating state in which the steam flow rate is stable and the combustion control system is operating well, the judgment device 51 determines that there is an abnormality, and during the abnormal period, the The increase in the input signal to the coal machine drive device 30 is reduced, so that a large amount of coal lumps is not supplied onto the grate 7 as in the past, and even when the coal lump properties are poor, the main steam pressure can be increased significantly unlike in the past. This is a coal-fired boiler that does not fluctuate and maintains a stable combustion state.

Therefore, various controllability of the load-side plant can be facilitated, the labor of those operating the coal-fired boiler and the load-side plant can be reduced, and plant stoppage and damage to the plant can be prevented.

The present invention has been described above with reference to the embodiments illustrated in the drawings, but of course the present invention is by no means limited to these specific embodiments, and various modifications can be made without departing from the spirit of the invention. It's something you get.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a conventional combustion control method for a coal-fired stoker boiler, and Fig. 2 is an explanatory diagram showing an example of a combustion control method for a coal-fired stoker boiler according to the present invention.
．． #l□'@, 30. #U, i1 Drive device, 4... Spreader, 5... Drive machine, 6... Grate drive device, 7... Grate, 8... Wind box, 9... Boiler, 10... Steam piping, 11...・Pressure gauge, 12...Controller, 13...Ratio calculator, 14-O damper drive device, 1
5. Cloud/damper, 16.. Ventilator, 17.. Furnace, 18.
-ash bottle), 19... duct, 50... ammeter, 51...
- Judgment device, 52... Alarm device. Figure 1

Claims (1)

[Claims] The supply amount of coal lumps and the amount of combustion air are adjusted so as to maintain the pressure of the steam fed to the load side from a coal-fired stoker boiler, which obtains steam by burning coal lumps spread on a moving grate, at a predetermined value. In the control system that operates the flow rate, the supply state of the coal block is monitored, and during a period when an abnormality in the supply state occurs, a proportional calculation is performed on the control deviation, which is the difference between the steam pressure and a predetermined value. 1. changing the supply amount of the coal lump and the flow rate of combustion air in accordance with the signal; Combustion of a coal-fired stoker boiler, characterized in that during a period when the supply state is normal, the supply amount of the coal lump and the flow rate of the combustion air are changed in accordance with a signal obtained by performing proportional integral calculation on the control deviation. Control method.