JPS6391402A - Boiler controller - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a boiler control device, and particularly to a boiler control device suitable for a boiler that uses coal, which has a variable calorific value, as fuel.

[Conventional technology]

In boilers that use coal as fuel, the calorific value varies depending on the type of coal, so the amount of coal burned must be corrected according to the change of coal type. As a boiler control device equipped with such a correction function, a system configuration shown in Fig. 3 has been proposed (thermal power generation VoΩ
33, No. 308, p. 73).

The conventional example shown in FIG. 3 is applied to a once-through boiler that co-fires heavy oil and coal, and a fixed rate of correction is performed in accordance with the change of coal type. That is, the advance signal and the water-fuel ratio correction signal are added to the combustion amount command in the adder/subtractor 1, and the water supply amount deviation and the air flow rate deviation are added to this in the adder/subtractor 2 to determine the basic target value of the combustion amount. Furthermore, the deviation from the actual combustion amount is obtained as a feedback signal by the addition/subtraction calculator 3, and the combustion amount is controlled based on this.

Of the actual combustion amount, the coal combustion amount is obtained by taking in the coal feeder speed through the primary lag calculator 11 and adding other coal feeder speeds in the addition/subtraction calculator 12 to obtain the total coal combustion amount. Then, the addition/subtraction calculator 14 adds the flow rate of heavy oil (or light oil) to obtain the actual combustion amount.

Correction based on the calorific value, which varies depending on the type of coal, is performed by a multiplier 13 inserted between the addition/subtraction calculators 12 and 14. That is, correction coefficients for each type of coal are set in advance in each signal generator 21, 22, 23, and one of them is selected by the signal switch 24. The selected correction coefficients are integrated by an integrator 25 and input to the multiplier 13 via an automatic/manual station 26 only in automatic mode. As a result, when in automatic mode, the actual combustion amount of coal is corrected according to the calorific value of the coal type, and when the calorific value is high, the feedback signal is reduced,
In the opposite case, it increases.

In this way, based on the feedback signal of the actual combustion amount corrected by the coal type, the combustion amount is compared with the target value, and the deviation amount is calculated by the multiplier 4. proportional integrator 5,
Via the limiter 6, it is output as a combustion amount control signal.

In FIG. 3, reference numerals 31 and 32 are operation signals (100%, 0%) of the coal feeder, and one of these signals is selected by the signal switch 33, and the addition/subtraction calculator 34 selects one of these signals.
The operation signals of other coal feeders are added at -th lag calculation unit 3.
5 and is input to the multiplier 4 via the program calculator 36.

[Problem that the invention seeks to solve]

According to the conventional example, the amount of heat input to the boiler can be corrected and controlled within a certain range in response to changes in the amount of heat generated due to switching of coal types.

However, this does not take into account the case where the calorific value is not uniform even if the coal type is the same, that is, the calorific value fluctuates from moment to moment. The relationship with the control target combustion amount breaks down, and boiler control becomes unstable.
As a result, there is a problem in that the main steam pressure and temperature fluctuate.

Further, since no consideration is given to disturbances caused to boiler combustion due to coal type switching, problems similar to those described above occur when coal type is switched.

The purpose of the present invention is to solve the above-mentioned conventional problems. In other words, it is an object of the present invention to control the combustion amount not only in response to fluctuations in calorific value due to switching of coal types, but also in quick response to fluctuations in coal calorific value that change from moment to moment. The objective is to provide a boiler control device that can

[Means for solving problems]

In order to achieve the above object, the present invention controls the target combustion amount based on the required heat input amount of the boiler, which is determined in correlation with the load amount, and the predetermined calorific value of the fuel containing coal. The boiler control device is characterized in that it includes a calorific value correction circuit that corrects the target combustion amount in accordance with fluctuations in steam pressure of the boiler.

[Effect]

That is, the present invention has been made by focusing on the fact that when the heat input changes due to a change in the calorific value of coal, this appears as a change in steam pressure (main steam pressure or drum pressure). By doing so, the combustion amount can be corrected and controlled quickly in response to fluctuations in the calorific value of the fuel due to changes in coal type, uneven calorific value, etc., and the combustion amount can be controlled to match the required heat input amount. Become.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

FIG. 1 shows a main system configuration diagram of an embodiment of the present invention.

This embodiment is applied to a natural circulation coal-fired boiler, and as shown in the figure, a boiler master control circuit 110 that performs feedforward control and a feedback circuit 12 are used.
0 and a calorific value correction circuit 130.

The boiler master control circuit 110 determines the required heat input amount by correcting the main steam flow rate (load amount) as a feedforward signal for combustion amount control by the deviation of the main steam pressure, and compares this with the feedback signal of the combustion amount to generate the boiler master signal. It is designed to be output as . That is, in the addition/subtraction calculator 111, the main steam pressure and the pressure setting device 112
The deviation from the main steam pressure set value is determined.

After the gain of this deviation is corrected by the proportional integrator 113, it is added to the main steam flow rate by the addition/subtraction calculator 114, and is used as the basic value of the required heat input amount. This basic value is sent via the automatic/manual station 115 to the high value selection circuit 116 only in automatic mode, where it is compared with the near rich signal and the higher value is selected as the required heat input amount.

This required heat input amount is compared with the actual combustion amount output from the feedback circuit 120 in the addition/subtraction calculator 117, and the deviation becomes the boiler master signal. A heavy oil flow rate (actual heavy oil combustion amount) is added to the coal combustion amount in an addition/subtraction calculator 122 and outputted to the boiler master control circuit 110 via a primary delay circuit 123.

The calorific value correction circuit 130 selectively takes in the main steam pressure deviation or the ground potential by switching the signal switch 131, compares this with the ground potential in the addition/subtraction calculator 132, and sends the deviation to the integrator 133. After being processed, it is output to the multiplier 121 of the feedback circuit 120 via the automatic/manual station 134, thereby correcting the actual amount of coal burned.

With this configuration, when the signal switch 131 is switched and the deviation between the main steam pressure and its set value is input to the calorific value correction circuit 130, the feedback value of the actual coal combustion amount is corrected according to the deviation. will be done. That is, the main steam pressure fluctuates when there is a difference between the heat input and the load of the boiler, and a deviation occurs from the set value. This deviation includes changes in the calorific value of the fuel due to coal type switching and uneven calorific value, and is led to the calorific value correction circuit 130 and boiler master control circuit 110, and is sent to the boiler master signal according to each function. will be controlled.

That is, for changes in vapor pressure other than changes in calorific value of fuel, the required heat input amount is corrected by the boiler master control circuit 110, and the balance between heat input and output is stably controlled.

When the calorific value of the fuel changes, a deviation occurs in the actual heat input from the required heat input, making the control unstable. In this case, the calorific value correction circuit 130 functions to calculate the actual coal combustion amount as a feedback signal. is corrected. As a result, the boiler master signal is controlled according to the calorific value of the fuel, and the balance between heat input and output of the boiler is stably controlled. In particular, such calorific value correction is based on the boiler time constant (
This is suitable when the time from when fuel is introduced until the main steam pressure changes) is several minutes or more.

FIG. 2 shows a system configuration diagram of another embodiment of the present invention. In this embodiment, the calorific value is corrected based on the drum pressure of the steam drum instead of the main steam pressure in the embodiment shown in FIG. In FIG. 2, parts having the same functions and configurations as those in FIG. 1 are given the same reference numerals and explanations are omitted.

The calorific value correction circuit 140 of this embodiment captures the fluctuation in fuel calorific value due to coal type switching etc. by drum pressure, differentiates this drum pressure fluctuation in a differential calculator 141, and then feeds it forward in a multiplier 142. Multiply the main steam flow rate of the signal. Then, the addition integrator 143 calculates the deviation from the actual combustion amount output from the multiplier 126 of the feedback circuit 120, and also corrects the gain. This value is limited to a fixed width (for example, ±20%) by a limiter circuit consisting of a signal switcher 144 and a signal limiter 145, and is input to the multiplier 126 of the feedback control circuit 120 via the automatic/manual station 146, and is then It is designed to correct the combustion amount feedback signal. In addition,
The feedback control circuit 120 calculates the actual combustion amount by adding the weight flow rate in the adder/subtractor 125 to the calculated actual coal burnt amount, and then subtracts the weight flow rate in the adder/subtractor 127, so that the output is The resulting signal becomes the actual coal combustion amount corrected by the calorific value correction circuit 140, and is input to the addition/subtraction calculator 151 as a feedback signal of the coal feeder. on the other hand,
The boiler master signal output from the boiler master control circuit 110 is multiplied by the coal/heavy oil ratio in a multiplier 152 to become a feedforward signal of the required heat input amount by coal, and then compared with the feedback signal in the addition/subtraction calculator 151. , the deviation is output to the coal feeder.

Therefore, according to this embodiment, the same effect as the embodiment of FIG. 1 can be achieved, especially when the coal combustion amount does not match the main steam flow rate of the feedforward signal.
It is characterized by the fact that the amount of coal burned is always corrected and controlled.

〔Effect of the invention〕

As explained above, according to the present invention, since the combustion amount is corrected based on changes in vapor pressure, not only changes in the calorific value due to switching of coal types, but also changes in the calorific value of coal that change from moment to moment can be corrected. The combustion amount can be controlled by taking a long route to fluctuations, and thereby the boiler can be controlled stably.

Further, according to the present invention, there is no need to detect the calorific value of coal, so a calorimeter or the like is not required.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of main parts of an embodiment of the present invention, FIG. 2 is a system diagram of main parts of another embodiment of the invention, and FIG. 3 is a system configuration diagram of a conventional example. 110... Boiler master control circuit. 120...Feedback control circuit. 130.140... Calorific value correction circuit. Figure 1 +10;7;'/77X'l'fE! Figure 3

Claims (1)

[Claims] In a boiler control device that controls a target combustion amount based on a required heat input amount of the boiler that is determined in correlation to a load amount and a predetermined calorific value of a fuel containing coal,
A boiler control device comprising a calorific value correction circuit that corrects the target combustion amount in accordance with fluctuations in steam pressure of the boiler.