JPS58205005A - Controller for drum level of waste heat boiler - 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 drum level control device for controlling the drum level (water level) of a waste heat boiler.

[Technical direction of the invention] In general, a waste heat boiler uses the waste heat of power generation plans 1 to 1 to heat water in a drum, boil it, and supply steam.
The amount of steam generated and steam pressure change depending on the plant load situation, and the water supply and steam generation status become unstable at the start and end of heat reception by the boiler, so it is necessary to always control the drum level to a constant value. is needed.

Conventionally, such drum level control has been performed by adjusting the flow rate of water flowing into the drum, as shown in FIG.

That is, water is sent out by a pump group 1, passes through a water supply detector 2 and a flow rate control valve 3, passes through an economizer 4, is supplied into a boiler drum 5, and is then sent from the drum 5 to a steam/water separator 7 by a circulation pump 6. After being deaerated, it is returned to the drum 5.

Further, the steam generated from the drum 5 passes through a steam flow rate detector 8 and is supplied to the plant. A drum level detector 9 such as a liquid level gauge is interposed inside the drum 5, and this detection signal and the signal from the level setter 10, in which the most desirable level value is set, are simultaneously sent to the addition/subtraction calculator 11. After comparing these differences and inputting the output to the control calculator 12, which performs appropriate calculations such as proportional calculation, differentiation, and integration, the opening degree of the flow rate control valve 3 is determined by the control signal output from the calculation unit 12. is configured to control and adjust.

Furthermore, the signals detected by the aforementioned water supply flow rate detector 2 and steam flow rate detector 8 are passed through a range corrector 13 to correct the level difference, and are inputted to the addition/subtraction calculator 11 of this control device. , This signal is also subjected to addition/subtraction calculations and then control calculations, and the water supply flow rate to the drum is controlled. Note that in the drawings, the flow of water and steam is shown by solid lines, and the transmission of signals is shown by broken lines.

(1) The feedwater flow rate detector 2 and steam flow rate detector 8 are both ranged at the rated flow rate, so when the flow rate is extremely low, such as when the boiler starts receiving heat or during low load with Plan 1~, Detector accuracy deteriorates significantly.

(2) At the start and end of boiler heat reception, or when the load of the plant is low, water blows in the drum and changes in the amount of water held occur, resulting in a significant difference between the feed water flow rate and the steam flow rate.

(3) When Firth 1~cutback occurs, the steam flow rate decreases rapidly, but the drum level temporarily decreases due to the reverse response phenomenon. Therefore, at this time, it is dangerous to rapidly reduce the water supply flow rate in response to the reduction in the steam flow rate.

In this way, when the load of Blan 1 is low, including when the boiler starts receiving heat and before and after it ends, the reason for adopting the conventional control method using the three elements of feed water flow rate, steam flow rate, and drum level is to compensate for the difference in each flow rate. This was not a desirable control method because it introduced a large amount of error.

[Objective of the Invention] The present invention has been made to solve the above-mentioned difficulties with conventional control systems and devices, and enables a smooth transition from three-element control to one-element control only at the drum level when the load of the plant is low. It is an object of the present invention to provide a drum level control device for a waste heat boiler that performs desired tall control in all flow ranges.

[Summary of the Invention] That is, the present invention provides a gain adjuster between the range corrector and the addition/subtraction calculator, and adjusts the gain from the range corrector in response to a plant load signal, boiler pressure, boiler exhaust gas meteor, etc. Automatically changes the gain of the output signal,
This is a drum level control device for a waste heat boiler configured to guide this to an addition/subtraction calculator.

[Embodiment 1 of the Invention] The present invention will be described in detail below based on an embodiment shown in the drawings. Components in FIG. 2 that are common to those in FIG. 1 are designated by the same reference numerals and their explanations are omitted.

In FIG. 2, reference numeral 14 indicates a gain adjuster.

Detection signals of the water supply flow rate and evaporation flow rate whose range difference has been corrected by the range corrector 13 and the parameter signal output from the parameter setting device 15 are inputted to this. Further, the parameter setting device 15 is inputted with a load signal to the bran 1 or an external signal such as boiler pressure or hot exhaust gas.

FIG. 3 is a graph for explaining the operating function of the gain adjuster 1/I. In FIG. 3, the horizontal axis indicates parameters such as plant load or boiler pressure. For example, when a load signal of plan 1- is input to the parameter setting device 15, the load becomes higher as it goes to the right. Also,
The vertical axis shows the gain (G) value. The graph in FIG. 3 shows an example in which the value of G is changed such that G changes from O to 1 while parameter 1- is between 1-1 and L2. - The graph of the change in G value can be modified to obtain the most desirable control in the range between the solid line shown as an example and the dotted line.

The gain adjuster 14 that performs such an operation controls lI!
As a result, the detection signal Qs of the water supply flow rate detector 2 and the steam flow rate detector 8 is corrected for the range difference, and then the gain is adjusted as shown in (a) above to perform addition/subtraction calculations. It is output to the device 11.

Since the flow rate detection signal after passing through the gain regulator 14 is expressed as Gx (Q - Qs), if there is a difference between the feed water flow rate and the evaporation flow rate around the boiler, for example, G-1 ( Using the graph in Figure 3, if the plant has a high angle load, the difference will be guided to the 100% addition/subtraction calculator 11 and three-element control will be performed (G = 0.5 (when the load is high).・In the middle of low), only 50% of the difference is output to the control system.

In addition, in Goo (low load ■;'l), the flow rate difference is not output as a signal to the control system, and one element control of only the drum level is performed (j).

[Effects of the Invention] As is clear from the description in section 1-1, the control device of the present invention can smoothly shift to one-element control of only the drum level during low loads, and can respond to any changes in the situation. , the most desirable control can be performed.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional drum level control device for a waste heat boiler, Fig. 2 is a block diagram of an embodiment of the present invention, and Fig. 3 shows the operation of the gain regulator according to the present invention. This is a graph for explanation. 2...Water supply flow rate detector 5...
・・・・・・・・・Boiler drum 8・・・・・・・・・・・・
...Steam flow rate detector 9...Drum level detector 11...Addition/subtraction calculator 13...・・Range corrector □ 14・・・・・・・・・Gain adjuster 15・・・
・・・・・・Parameter setting device Fig. 1 Fig. 2

Claims (1)

[Claims] a feed water raw ore detector that detects the flow rate of water supplied to the drum of the waste heat boiler; a steam flow rate detector that detects the flow rate of steam generated from the drum; a drum level detector that detects the level of the drum; 'A range corrector that corrects the range difference between the signals output from the a quantity detector and the steam flow rate detector, and the signal output from this range corrector and the signal output from the drum level detector are input and adjusted. an addition/subtraction calculator that performs calculations; a control calculator that receives a signal output from the addition/subtraction calculator and outputs a control signal for controlling the opening degree of the water supply flow rate control valve based on the signal;
A drum level control valve consisting of a water supply flow rate control valve whose opening degree is controlled by a control signal output from this control calculator.
In the device, a gain adjuster is disposed between the range corrector and the addition/subtraction calculator to adjust the gain of the signal output from the range corrector according to a parameter set by a plant load signal, etc. Drum level control wave of waste heat boiler characterized by