JPH01107001A - Load response controller for pulverized coal firing boiler - Google Patents

Abstract

PURPOSE: To assure always a high load responding characteristic by a method wherein means for measuring a boiler load responding characteristic is arranged at a fine powder coal combustion boiler for a thermoelectric power plant and a delay in responding operation is adapted by correcting a supplying amount of primary air in respect to a fine powder coal machine. CONSTITUTION: As a major steam pressure, a pressure time constant of a boiler during variation in load is calculated by a pressure time constant measuring device 30. The calculated time constant is stored in an analogue memory 6 in advance. This stored time constant is outputted to a function generating device 7 and a correction characteristic is adjusted in such a way that a supplying amount of primary air is increased in the case that the pressure time constant is increased. A correction signal adjusted in this way is outputted from the function generating device 7 as a primary air flow rate command correcting signal S4 so as to correct a primary air flow rate signal S2. This primary air flow rate is applied as a damper opening degree signal S3 by a subtractor 11, this becomes damper opening degree signals S3a, S3b outputted through a PI adjusting device 12 and a polarity converter 13, a degree of opening of each of the dampers is adjusted to cause the primary air flow rate to be adapted for the signal S2 and then the primary air temperature is adjusted to its set value.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for controlling a system for supplying pulverized coal to a boiler that uses pulverized coal as fuel, and in particular to a device that quickly and appropriately responds to the load on the boiler. The present invention relates to a control device configured as follows.

[Conventional technology]

BACKGROUND OF THE INVENTION Boilers for business use, such as large boilers for thermal power plants, are actively switching the fuel used from petroleum-based fuels to coal. In this case, the coal is pulverized to improve combustibility controllability, but the method of sequentially burning the stored pulverized coal provides good controllability but may cause problems such as ignition of the stored pulverized coal. It is not often implemented because it is necessary to take measures to prevent it, and it is usually carried out using a pulverizer (mill).
A direct combustion method is adopted in which pulverized coal is supplied directly to the boiler. Although this direct combustion method is highly safe, the load response of the pulverized coal supply system, including the pulverizer, directly affects the load response of the boiler, so the load response of the pulverized coal supply system is maintained at a high level. There is a need to.

Figure 5 shows a direct combustion type pulverized coal supply system.

In the figure, coal supplied from a coal feeder 19 is supplied to a pulverizer 18 and pulverized, and is classified by hot air supplied to the pulverizer 19. The fine coal pulverized with predetermined grain scraping is supplied to the burner 26 of the boiler 20 and burned using this hot air as primary air. On the other hand, primary air fan 1
A part of the air supplied by 4 is heated to become heated air in a combustion air preheater 15 whose heat source is combustion exhaust gas from a boiler, and mixed with cold air that has bypassed this combustion air preheater 15. In this case, by adjusting each damper 16 and 17, the hot air (-
The coal flows into the pulverizer 19 as air).

In addition, in the boiler system, steam generated by the combustion heat of pulverized coal is supplied to the turbine 21 to perform work such as power generation, and is then returned to water in the condenser 24 and supplied to the boiler as boiler feed water. The feed water circulates through the boiler. Note that 22 is a main steam pressure gauge, 23 is a turbine control valve, and 25 is a water supply pump.

In the above equipment, the primary air flow rate command for the pulverized coal supply system is programmed in accordance with the coal amount supply command, but since this program is operated fixedly, once it is set, the subsequent situation will be changed. There was a problem with not being able to respond to changes. In other words, the pulverizing capacity of the coal pulverizer gradually decreases as the operating time elapses due to wear of the pulverizing part, etc., and the dynamic characteristics of the coal pulverizer change as the type of coal to be pulverized changes. The crushing capacity also fluctuates. Conventional systems do not take this point into consideration, resulting in poor response to boiler loads and poor controllability.

As a countermeasure to the above problem, a conventional method has been adopted in which advance control is performed by differentiating the load demand signal for the boiler to compensate for the low load response of the pulverized coal supply system. Since the signal that should be used is constantly changing, there is a problem that the differential operation cannot keep up.

Furthermore, there are control problems, such as reacting to linear fluctuations in the target signal in a short period of time and performing unnecessary differential operations, and it has not been possible to fundamentally solve the above-mentioned problems.

[Means for solving problems]

The present invention is configured to solve the above-mentioned problems, and includes means for measuring the load response of the boiler by measuring the boiler time constant for a system that supplies pulverized coal to the boiler; This control device is provided with means for rapidly increasing the supply of pulverized coal by increasing the amount of air, and maintains the amount of pulverized coal supplied appropriately in response to the boiler load.

[Effect]

The primary air flow rate command signal corresponding to the fuel supply command calculated from the load command to the boiler is calculated by using the time constant of steam pressure change of the boiler receiving pulverized coal supply or the deviation of the measured steam pressure from the set steam pressure as the correction value. Correct using the correction value.

That is, by increasing the supply amount of primary air based on this correction value, the supply amount of pulverized coal to the boiler is rapidly increased to compensate for the delay in load response.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the drawings.

In FIG. 1, the main steam pressure of the boiler and the main steam pressure set value are output to a subtracter 1, and the deviation of the actual main steam pressure from the set value is output to the adder 3 via the PI setting device 2, and the boiler main steam pressure is output to the subtracter 1. is added to the load command to obtain the combustion amount command. This combustion amount command and total fuel flow rate are output to the subtractor 4, and the PI
It passes through the regulator 5 and becomes a mill mask signal S1, which is used as a coal feed amount command for each pulverizer.

On the other hand, this mill mask signal S1 is output to the multiplier 8,
Furthermore, a high selector 9 and a signal generator 10 generate a primary air flow rate command signal S2.

Further, for the main steam pressure, the pressure time constant of the boiler during load fluctuation is determined using a pressure time constant measuring device 30 (details of its function will be described later), and the determined time constant is stored in the analog memory 6. Further, this time constant is updated as appropriate to match the current state of boiler operation. The time constant stored in the analog memory 6 is output to the function generator 7, and as shown in FIG. 3, when the pressure time constant increases, the correction characteristic is adjusted so that the primary air supply amount (gain) also increases. Ru. The correction signal whose correction characteristics are adjusted in this way is output from the function generator 7 as the primary air flow rate command correction signal S4, and the -order air flow rate signal S2 is outputted from the function generator 7 as the primary air flow rate command correction signal S4.
Correct. Further, the primary air flow rate adjusted based on this flow rate signal is determined by the primary air flow rate signal S in the subtracter 11.
2 is used as the damper opening signal S3, and the PI controller 12
The hot air damper opening signal S3a that adjusts the opening of the hot air damper is output through the polarity converter 13, and the cold air damper opening signal S3b is outputted through the polarity converter 13. By adjusting the opening of each damper, the primary The air flow rate is made to correspond to the primary air flow rate command signal S2, and the secondary air temperature is adjusted to a set value.

Here, the pulverized coal supply capacity of the pulverized coal combustion boiler changes due to changes in the characteristics of the pulverized coal machine (changes in pressurizing force in the pulverizer, wear of the pulverizer such as pulverizer balls), differences in coal type, etc.

For this reason, the responsiveness of the main steam pressure of a boiler that uses this pulverized coal as fuel changes, causing a drop in followability to the boiler load. As a solution to this problem, it is determined whether or not the responsiveness of the boiler's main steam pressure (the rate of change in the main steam pressure in response to the load demand for the boiler) is changing, and based on this result, the pulverized Adjust primary air flow to the machine. FIG. 4 shows the concept of this primary air flow rate correction, and when the pressure time constant becomes large, the previously set primary air flow rate control model F1 is changed to F2. As a result, the primary air flow rate to the pulverized coal machine is increased, and the amount of pulverized coal supplied to the boiler is increased in a short time, thereby compensating for the decrease in the load response of the boiler.

Next, the functions and configuration of the pressure time constant measuring device described above will be specifically explained.

Figure 2 shows the results of measuring the main steam pressure response to a step increase in the amount of coal fed. When the amount of coal fed to the boiler is increased, the time it takes for this increased amount to reach the burner section of the boiler, the time for the amount of combustion heat to increase due to the increased pulverized coal,
There is a time t1 in which the main steam pressure hardly increases even if the amount of coal feed is increased due to the time for the heat absorbing surface of the boiler to absorb the increased heat amount, and then there is a time t2 in which the pressure rises to the specified level due to the increased heat amount. There is. The boiler time constant T is the sum of these times t and t2.

In other words, the larger the time constant T of the boiler, the lower the load response of the boiler. That is, the pressure time constant measuring device 30 shown in FIG. The time t and t2 are determined, and the time constant T is determined from these. This is used as a primary air increase amount signal by a function generator, and this -order air increase signal is used as a correction value S4 of the primary air amount command signal S2. .

FIG. 7 shows another embodiment of the invention.

In this embodiment, the function generator 7 is used to calculate the coal supply amount to correct the delay (deviation) of the measurement time constant with respect to the set time constant, and the primary air increase amount corresponding to this corrected coal supply amount. This primary air increase amount is further used as a correction signal for the primary air supply command signal. Note that the reference numeral 27 in the figure is an adder. In this embodiment, since the main steam pressure deviation is used as a parameter, the correction amount corresponds to the pressure deviation, and therefore the correction amount can be easily set automatically.

〔effect〕

As the configuration of the present invention has been specifically explained above, a means for measuring the boiler load response is arranged, and the load response delay is dealt with by correcting the primary air supply amount to the pulverizer. Therefore, the amount of pulverized coal supplied to the boiler can be changed in a short time by adjusting the amount of primary air based on the accurately measured load response of the boiler.

For this reason, high constant load responsiveness can be ensured regardless of the deterioration of the crushing capacity due to aging of the pulverized coal or changes in the type of coal.

[Brief explanation of the drawing]

Fig. 1 is a control system diagram of a load response control device showing the first embodiment of the present invention, Fig. 2 is a diagram showing the relationship between the boiler main steam pressure time constant and the coal feed amount, and Fig. 3 is a diagram showing the relationship between the main steam pressure time constant and the main steam Diagram showing the relationship between pressure time constant and primary air increase amount (gain), 4th
The figure is a diagram showing the relationship between the coal feed amount command and the primary air amount when the pressure time constants are different. Figure 5 is a fuel supply and steam circulation system diagram of a pulverized coal combustion boiler. Figure 6 is a conventional diagram. FIG. 7 is a control system diagram of a load response control device showing another embodiment of the present invention. 7...Function generator 10...Signal generator 11...
・Subtractor 18...Pulverized coal machine 19...Coal feeding machine
20...Boiler 26...Burner Sl...Milmask signal S2...Next air amount command signal S3...Damper opening signal S4...Next air amount correction signal

Claims (1)

[Claims] A device for controlling the amount of pulverized coal supplied from a pulverizer to a boiler based on a load command signal to the boiler and a steam pressure signal of the boiler, which includes a means for measuring the pressure time constant of the boiler and a means for controlling the amount of primary air to the pulverizer. The primary air flow rate for rapidly increasing the pulverized coal is corrected in response to the measured boiler pressure time constant, and the primary air flow rate is corrected in response to the boiler load command. A load response control device for a pulverized coal combustion boiler, characterized in that it is configured to be used as a value.