JPS6025683B2 - steam pressure control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steam pressure control device for a steam generator (so-called boiler) in a power generation facility.

BACKGROUND ART One of the operations during the startup or shutdown process of power generation equipment is to control the steam pressure to a predetermined target value while increasing or decreasing the water supply flow rate of the boiler (and thus the amount of generated electricity). Conventionally, this control uses an analog control device and a digital computer to create a target value of steam pressure as a function of the feed water flow rate or the amount of electricity currently generated (so-called load).
This was done by adjusting the steam pressure by operating a steam control valve so as to meet this target value. however,
In conventional control systems, the function generation function that generates the target value of steam pressure is commonly provided for each startup and shutdown operation. It is difficult to absorb
Eventually, a problem occurred. This will be explained in more detail below with reference to FIGS. 1 and 2.

In the power generation equipment shown in Fig. 1, 1 is a condenser, 2 is a feed water pump, 3 is a feed water flow rate control valve (hereinafter referred to as FWC), 4 is a feed water flow rate detector, 5 is a boiler, and 6 is a boiler pressure control valve. ,
7 is a sub valve, 8 is a heater, 9 is a steam pressure detector, 10 is a steam control valve (hereinafter referred to as CV), 11 is a turbine, 12
is a generator.

Here, steam pressure control of a supercritical pressure once-through boiler with a rated steam pressure of 246 kg/ is explained. The steam pressure is mainly controlled by adjusting the water supply flow rate by the FWC 3 and by adjusting the steam supply flow rate to the turbine through the CVI river. At startup, the feed water pump 2 is activated and the FWC 3 is operated to increase the feed water flow rate (hereinafter referred to as FWF) while controlling the CVIO to increase the main steam pressure (hereinafter referred to as PMS) at the inlet of the turbine 1. Increase the pressure to a predetermined target value.

Target pressure for FWF at this time (hereinafter referred to as PR)
The relationship is set as shown in FIG. Here, CV
If the IO is held at a certain opening and the FWF is gradually increased, the PMS will rise to the rated pressure in a manner similar to the curve shown in Figure 2, but it will not necessarily follow the target curve depending on the steam temperature. On the other hand, when stopping, contrary to starting,
PMS while decreasing FWF by operating FWC3.
CV so that it decreases along the target pressure curve in Figure 2.
Control IO.

In this way, the steam pressure control during shutdown uses the startup curve shown in Figure 2 as is, and in reality, the FW
Even if F starts to drop below point B, PMS does not drop immediately because the boiler retains a large amount of heat and generates a large amount of steam.
At this time, when pressure control is started by CVIO operation, it attempts to lower the PMS to a value commensurate with the gate VF.
The CVIO is opened more than necessary, and as a result, the amount of steam flowing into the turbine 11 increases and the load temporarily increases. In this way, when trying to stop the power generation equipment by decreasing the load while lowering FWF and PMS, the load may increase even temporarily, which is caused by the failure of the auxiliary equipment of the power generation equipment This is not preferable because it may cause disturbance to the operation.

In view of the above points, it is an object of the present invention to provide a steam pressure control device that can stably control the pressure of a boiler without causing any disturbance to the operation of auxiliary equipment, etc. when starting or stopping a power generation facility. The purpose is

The details of the present invention will be explained below with reference to the drawings.

FIG. 3 is a configuration diagram showing an embodiment of the present invention, in which 13 is a steam pipe through which steam 6 passes to the turbine 11, 10 is a CV, and 9
21 is a PMS detector, 21 is a CVIO drive mechanism, 22 is a cam of a link mechanism operated by this drive mechanism 21, 23 is a valve opening degree detector that detects the rotation angle of the cam 22, that is, the valve opening degree, 20 The valve opening is controlled to a predetermined target value from the pressure P which is the output of the PN4S detector 9 and the valve function 0 which is the output of the valve opening detector 23.

FIG. 4 shows the configuration of the control device 20 shown in FIG. 3, where the A side in FIG. 4 is the control device and the B side is the controlled object.

24a is the FWF by the water supply flow rate detector 4 shown in FIG.
A function generator for setting a target pressure curve at start-up as shown in FIG. This is a selector switch that selects the output of the function generator.
This is an automatic switching operation that determines whether the necessary control should be started or stopped by inputting the operator's operation or the plant status.

21 of the controlled object B is the drive mechanism of the CV shown in FIG.
9 is a fluid characteristic in the steam pipe 13, 25 is a comparator that compares the pressure P, which is one of the fluid characteristics, with the target pressure PR to determine the deviation ΔP, and 26 is a comparator that calculates the deviation ΔP based on the deviation ΔP. C
A control calculation circuit 27 calculates the valve opening degree of V and compensates the value calculated by the actual valve function a.
This is a control signal output unit that operates the drive mechanism 21 by the output of 6. In this configuration, the target pressure curve 1 in FIG. 5 (same as that in FIG. 2) is set in the function generator 24a that sets the target pressure curve for startup. On the other hand, the target pressure curve shown in FIG. 5 is set in the function generator 24b which sets the target pressure curve for stopping. That is, the target pressure curve 12 for stopping is the FWF that reaches the rated pressure at startup.
The target pressure curve is such that the rated pressure is maintained up to point C even if the FWF decreases more than the amount (point B), and after passing point C, it reaches point A (the point where the pressure is raised at startup). Set the target pressure to decrease as the pressure increases. The problem with having different target pressure curves for starting and stopping in this way is that even if pressure control is started during stopping, the target pressure does not drop immediately, so it is difficult to forcefully lower the pressure like in the past. Trying to C
It is possible to avoid causing load fluctuations due to excessive opening of the VIO.

Furthermore, target pressure curves can be set separately for startup and shutdown based on the actual boiler characteristics, making it easy to achieve good pressure control without wasting CV operations. becomes possible.

For example, as shown in 13, as a target pressure curve for stopping, PR can be suddenly lowered from point C to point D, and below point D, PR can be gradually lowered toward point A. FIG. 6 shows another embodiment of the present invention, in which the control calculation circuit 26 shown in FIG.
, a selector switch 32 that selects the output of either of these comparators depending on the starting or stopping state, and the output of the control calculation circuit 26 when the valve function 8 is within the set range as shown in FIG. A gate 33 for sending data to the output section 27 shown is added.

The other configurations are the same as those shown in FIG. 4, but are not shown. The comparators 31a and 31b are equipped with a function generator using the FWF as a parameter, and as shown in FIG. The upper limit OU and lower limit 8 of the opening degree are set, and the actual CV opening degree a is compared with these upper and lower limit values corresponding to each FWF value, and the valve opening degree a is determined to be the upper limit value 8U.
By sending a signal to the gate 33 such that the output of the control calculation circuit 26 is satisfied if it is smaller than the lower limit value OL, that is, if it is within the shaded area in FIG.
To prevent the opening degree from deviating from a predetermined limit value.

By providing such a comparator and gate 33,
When the plant condition exhibits characteristics different from normal, C
It is possible to prevent the power generation equipment from falling into an unstable state by blocking the V opening so that it cannot be operated above or below a preset limit opening. That is, when a disturbance to the plant occurs, for example, when the feed water flow rate decreases and the boiler pressure control valve 6 shown in Fig. 1 suddenly closes, the PMS decreases rapidly and the CV is opened more than necessary, causing the CV to open more than necessary. As a result, the boiler outlet pressure increased rapidly, and there was a risk that the boiler outlet pressure and turbine inlet pressure would hunt, putting the plant in a dangerous situation. If you set a CV opening limit value that is
This is effective in preventing dangers caused by V operation. As explained above, according to the present invention, the target value of steam pressure and CV valve opening degree that match the characteristics of the boiler are set and selected exclusively for startup and shutdown, so that the steam pressure is applied to the power generation plant. Good pressure control can be achieved by minimizing fluctuations in load, etc., and without causing any disturbance to the operation of auxiliary equipment.

Further, by setting the valve opening operation range for starting and stopping as shown in the embodiment, hunting of the boiler outlet pressure etc. can be prevented and more stable control can be performed.

[Brief Description of the Drawings] Fig. 1 is a steam pressure control system diagram of power generation equipment, Fig. 2 is a pressure target curve diagram at startup of power generation equipment, and Fig. 3 is a schematic configuration example of a steam pressure control device according to the present invention. FIG. 4 is a block diagram showing an embodiment of the steam pressure control device according to the present invention, FIG. 5 is a pressure target curve diagram according to the present invention, and FIG. 6 is a block diagram showing another embodiment of the present invention. Block diagram of control calculation circuit,
FIG. 7 is a control valve opening degree upper and lower limit setting curve diagram in the embodiment of FIG. 6. 1...Condenser, 2...Water pump, 3...
...Water supply flow rate control valve, 4...Water supply flow rate detector,
5... Boiler, 6... Boiler pressure control valve, 9...
... Steam pressure detector, 10 ... Steam control valve, 11 ... Turbine, 12 ... Generator, 13 ... Steam pipe, 20 ...Control device, 21...Valve drive mechanism, 22...Cam, 23...Control valve opening detector, 24a...
...Target pressure function generator for starting, 24b...Target pressure function generator for stopping, 25...Comparison circuit, 26
... Control calculation circuit, 27 ... Control signal output section, 30, 32 ... Changeover switch, 31a
...Comparator for setting valve operation range at startup, 31b.
...Comparator for setting valve operation range at stop, 33...
·Gate. Multi-Z drawing Multi-Z drawing Multi-fig. 4th prisoner brother 5 Ward g Multi-6 drawing Multi-f drawing

Claims (1)

[Claims] 1. When operating a steam generator in a power generation facility, as a function of process quantities such as water supply flow rate or amount of generated electricity,
A function that sets different target pressure values for starting and stopping power generation equipment in a steam pressure control device that includes means for creating a pressure target value to be controlled and a control calculation circuit for driving a steam control valve as an operation target. 1. A steam pressure control device comprising a generator and a switching device that selects the output of the corresponding function generator depending on the process state at startup and shutdown.