JPS61105001A - Fluidized-bed boiler main steam pressure control system - 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] [Technical Field of the Invention] The present invention relates to a main steam pressure control system for a fluidized bed boiler, and particularly relates to a fluidized bed boiler main steam pressure control system. This invention relates to an improvement for increasing the allowable load fluctuation rate of a blower.

[Technical background of the invention]

Is Figure 2 a conventional fluidized bed? 1 is a system diagram showing a general configuration example of a main steam pressure control system in a steam generator, and includes a main steam pressure quadrature transmitter 1, a proportional-integral calculation circuit 2, an adder 3, a main steam flow rate transmitter 4, and a square root calculation circuit 5. It is configured. A conventional fluidized bed with such a configuration? In the main steam pressure control system, the actual main steam pressure is converted into an electrical signal corresponding to the main steam pressure by the main steam pressure quadrature transmitter 1, and is inputted to the proportional-integral calculation circuit 2 as a main steam pressure signal.

An electrical signal, that is, a main steam pressure setting signal, which is preset corresponding to a desired main steam pressure, is inputted into the proportional-integral calculation circuit 2 from a setting circuit (not shown).

Here, the proportional integral calculation circuit 2 calculates the deviation between the actual main steam pressure input from the main steam pressure quadrature transmitter 1 and the setting signal input from the setting circuit, and calculates the proportional integral calculation for the pressure deviation. The output of the proportional-integral calculation is input to the adder 3.

On the other hand, the main steam flow rate is converted by the main steam flow rate transmitter 4 into an electrical signal corresponding to the main steam flow rate, and is detected as a main steam flow rate signal through the square root calculation circuit 5 and inputted to the adder 3. be done. Here, the adder 3 calculates a square master command signal by adding the proportional integral calculation output signal and the main steam flow rate signal, and sends this gay 2 master command signal to the adjustment system such as the fuel supply system and the air supply system. Send. Each of these adjustment systems controls the amount of fuel supplied,
What about the air supply amount, etc.? The main steam pressure is maintained at the above-mentioned set value by adjusting the level according to the Irama master command signal.

In this advance control method, the main steam pressure is maintained constant according to the mail master command signal calculated based on the two-element addition of the proportional-integral calculation output signal and the main steam flow rate signal performed for the main steam pressure deviation. The adjustment system responds to fluctuations in the main steam pressure deviation with a proportional-integral operation, so in fluidized bed mailers, which are generally used in plants with high load fluctuations, it is possible to increase the responsiveness of main steam pressure control during load fluctuations. is considered useful.

[Problems with background technology]

However, this fluidized bed mailer has the characteristic of having a large heat capacity, and because of this characteristic, it tends to take a long time to eliminate the main steam pressure deviation caused by the above-mentioned load fluctuation. For this reason, in the conventional control system in which the adjustment system is operated proportionally and integrally to eliminate the pressure difference of the main steam, the cumulative increase or decrease in the proportional-integral output accompanying the proportional-integral operation is large. Therefore, this adjustment system is required to have an extremely large amount of overload or amplifier firing. On the other hand, the adjustment system cannot tolerate a firing amount that exceeds a certain value due to constraints such as its capacity, and as a result, there is a problem in that the permissible load fluctuation rate of the fluidized bed mailer is limited to a low value.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances.It reduces the amount of overload or amplifier firing in the adjustment system caused by the cumulative output increase or light decrease of the integral operation when the load fluctuates, and increases the allowable load fluctuation rate. The purpose is to

[Summary of the invention]

Therefore, the present invention includes a main steam flow rate fluctuation rate detection means for detecting a main steam flow rate fluctuation rate from the detected main steam flow rate, and a deviation between the output of the main steam flow rate fluctuation rate detection means and the detected main steam flow rate. a timer circuit for setting a predetermined load fluctuation transient period based on the output of the monitoring means when the deviation exceeds a certain value in response to load fluctuation; The above-mentioned object is achieved by having a configuration that includes means for holding the integral calculation output among the proportional integral calculation outputs during the period.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a system diagram showing an embodiment of the control system related to the fluidized bed mailer main steam pressure control system according to the present invention.
In the present invention, the functional elements of a subtracter 10, a proportional calculation circuit 11, a switching circuit 12, an integral calculation circuit 13, and an adder 14 are provided between the adder 3 and the proportional calculation circuit 2. Arithmetic circuit 11 and integral arithmetic circuit 1
3 and their outputs are added by an adder 14. On the other hand, the main steam flow rate detection and adjustment system includes a main steam flow rate transmitter 4 and a square root calculation circuit 5 as well as a main steam flow rate fluctuation rate detection circuit 15, a main steam flow rate fluctuation rate deviation monitor circuit 16, and an on-delay timer circuit 17. , an off-delay timer circuit 18. The operation will be described below with reference to FIG. First, in the main steam pressure detection and adjustment system, the pressure of the main steam currently flowing is converted into a main steam pressure signal by the main steam pressure quadrature transmitter 1, and the main steam pressure signal is inputted to the subtracter 10 by the subtracter 10. It is compared with the pressure setting signal and calculated as the main steam pressure deviation that needs to be resolved. This main steam pressure deviation is input to the proportional calculation circuit 11, and is also input to the integral calculation circuit 13 through the a terminal of the switching circuit 12, where proportional calculation and integral calculation are performed, respectively. , the respective outputs of the integral calculation circuit 13 are added together by the adder 14 and then input to the adder 3. On the other hand, in the main steam flow rate detection and adjustment system, the main steam flow rate detected by the main steam flow rate transmitter 4 is subjected to a square root calculation in the square root calculation circuit 5 to obtain a main steam flow rate signal. It is input to adder 3.

Here, this adder 3 adds the proportional + integral calculation output inputted from the adder 14 in the previous stage and the main steam flow rate signal inputted from the square root calculation unit circuit 5 to calculate the gay 2 master command signal. The engine gives an Iramamaster command to a combustion control system (not shown) to maintain the pressure of the main steam at the above-mentioned set value.

By the way, in the switching circuit 12 of the present invention, when the main steam flow rate is under a constant condition, the υ switching is switched to the b terminal side by a hold command signal input from the main steam flow rate fluctuation rate deviation monitor circuit 6. Alternatively, at this time, the main steam pressure deviation to be input from the subtracter 10 to the integral calculation circuit 13 is cut in accordance with the signal input from the signal generator 19 through the corresponding terminal. A function is added to hold the integral operation of the main steam pressure adjustment system that is operated based on the Irama Master command signal. The conditions for holding this integral operation are determined and executed as shown below. That is, the square root calculation circuit 5
The detected main steam flow rate signal is input to the adder 3 and also to the main steam flow rate fluctuation rate detection circuit 15 and the main steam flow rate fluctuation rate deviation monitor circuit 16. Based on this main steam flow rate signal, the fluctuation rate detection circuit 1
At step 5, the fluctuation rate is detected and inputted to the deviation monitor circuit 16. On the other hand, the deviation monitor circuit 16 determines the input/output deviation of the fluctuation rate detection circuit 15 from this main steam flow rate fluctuation rate and the above-mentioned main steam flow rate signal, and monitors this.

When this input/output deviation exceeds a certain value, a hold command signal is sent to the switching circuit 12 as a hold condition for the above-mentioned integral operation, and the sending is stopped when the input/output deviation becomes below a certain value. Incidentally, as described above, an on-delay timer 17 and an off-delay timer 18 are provided between the deviation monitor circuit 16 and the switching circuit 12, and the hold command signal is used to accurately set the hold condition period. T1 and T from the start and end of transmission, respectively.
It has a time delay function of 2.

Therefore, as described above, the cut time of the main steam pressure deviation from the subtracter 10 to the integral calculation circuit 13 by the switching circuit 12 in a load fluctuation transient state where the input/output deviation of the fluctuation rate detection circuit 150 exceeds a certain value. is determined by the time T shown in FIG. 3, and during this time T, the main steam pressure regulating system described above is operated only by proportional operation. This makes it possible to significantly reduce the above-mentioned over- or under-firing amount of the main steam pressure regulating system in the load fluctuation transient state as compared to the conventional system.

〔Effect of the invention〕

As explained above, according to the main steam pressure control method for a fluidized bed boiler of the present invention, in a transient state of load fluctuation that occurs with a rate of fluctuation above a certain value, the integral operation of the adjustment system is stopped and the main steam pressure is operated only in proportional operation. Since the steam pressure is maintained constant, the amount of overfire or underfiring of the adjustment system in the transient state can be suppressed, and as a result, the allowable load fluctuation rate of the fluidized bed mailer can be increased, which is an excellent effect. play.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an example of a control system according to the fluidized bed boiler main steam pressure control method of the present invention, and Fig. 2 is a system diagram showing an example of a control system according to this type of conventional control system. , FIG. 3 is a relationship diagram between the amount of load fluctuation and time shown to explain the hold function of the integral operation according to the present invention. DESCRIPTION OF SYMBOLS 1... Main steam pressure quadrature transmitter, 2... Proportional integral calculation circuit, 3... Adder, 4... Main steam flow rate transmitter, 5...-square root calculation circuit, 1o... Subtractor, 1
1... Proportional calculation circuit, 12... Switching circuit,
13... Integral operation circuit, 14... Adder, 15...
・Main steam flow rate fluctuation rate detection circuit, 16... Main steam flow rate fluctuation rate deviation monitor circuit, 17... On-delay timer circuit, 18... Off-delay timer circuit, 19... Signal generator'! lN Asazuka

Claims (1)

[Claims] A fluidized bed boiler that controls the main steam pressure to be maintained at the preset value by using the sum of the proportional integral calculation output of the pressure deviation of the detected main steam pressure with respect to the preset main steam pressure and the detected main steam flow rate as a boiler master command signal. In the main steam pressure control system, a main steam flow rate fluctuation rate detection means detects a main steam flow rate fluctuation rate from the detected main steam flow rate, and a deviation between the output of the main steam flow rate fluctuation rate detection means and the detected main steam flow rate is determined. means for detecting and monitoring this; and a timer circuit for setting a predetermined load fluctuation transient period based on the output of the monitoring means when the deviation exceeds a certain value in response to load fluctuation;
A main steam pressure control system for a fluidized bed boiler, comprising means for holding an integral calculation output among the proportional integral calculation outputs during the period set by the timer circuit.