JPH0550643B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a boiler feed water flow rate control device that improves controllability of a boiler feed water pump and shortens feed water pump switching time. .

[Conventional technology] The conventional control system for the water supply pump to the boiler was replaced with a third control system.
To explain with a diagram, 1 in the diagram is a boiler, 2a, 2
b is a water supply pipe 4 driven by turbines 3a and 3b;
A water supply pump for supplying water to the boiler 1 via a water supply pump, 5 a steam pipe for supplying the steam generated in the boiler 1, 6 and 7 a superheater provided in the steam pipe 5, and 8 a water supply pump for supplying water from the steam pipe 5. A generator 9 is driven by the generated steam.
10 is a fuel supply pipe that supplies fuel to the furnace of the boiler 1; 11a and 11b are flow rate detectors that respectively detect the flow rate of feed water introduced into each feed water pump 2a and 2b; 12 is a water feed pump 2;
a, a flow rate detector for detecting the feed water flow rate discharged from 2b; 13, a load setting device that determines the load of the boiler 1; A control valve 15 that controls the flow rate of fuel supplied to the furnace is a control valve that controls the flow rate of steam introduced from the steam pipe 5 to the turbine 8 based on a setting command from the load setting device 13.

Further, 16 is a subtracter that subtracts the set water supply flow rate in the water supply pipe 4 set by the load setting device 13 and the signal of the supply flow rate detected by the flow rate detector 12, and 17 is a water supply master that adjusts the signal from the subtractor 16. Position adjustment type PI controller that outputs as a command, 18a, 1
8b is a subtractor that subtracts the signal of the water supply flow rate detected by the water supply flow rate detectors 11a, 11b and the signal from the bias operation devices 19a, 19b from the signal from the PI regulator 17; 20a, 20b are the subtractors 18a;
a PI regulator, 22a, for adjusting the signal from 18b;
The opening degree of 22b is adjusted by a command signal applied from the PI regulators 20a, 20b via the manual/automatic switch 21a, 21b, and the water supply pumps 2a, 2b
This is a control valve for controlling the flow rate of steam introduced into the driving turbines 3a and 3b.

When the boiler 1 is started with the above device and shifts to steady operation, the following operation is performed.

For example, the load setting device 13 first has 1/1 of the rated load.
2 loads are set, and a command signal corresponding to the load is given from the setting device 13 to the control valves 14, 15 and the PI regulator 17. Also, bias operation device 19a
The bias value is operated to 0%, and the bias operating device 19b is operated to -100%.

When boiler 1 starts operating in such a state,
The signal from the PI regulator 17 is given to both subtractors 18a and 18b as a water supply master command, but since the bias operator 19b is operated at -100%, no command is output from the subtractor 18b.
Since the bias operating device 19a is operated at 0%, a 100% command signal is output from the subtractor 18a, which is adjusted by the PI regulator 20a, output, and given to the control valve 22a, and the magnitude of the signal is adjusted. In response to this, the control valve 22a opens, steam is supplied to the turbine 3a, and the water pump 2a is driven at a predetermined rotation speed, and water is supplied by the water pump 2a to the boiler 1 through the water supply pipe 4, where it is heated. Steam is generated,
The steam passes through the steam pipe 5, superheaters 6 and 7, and then the turbine 8.
The turbine 8 rotates, and the rotation of the turbine 8 rotates the generator 9 to generate electricity.

The amount of water discharged from the water supply pump 2a is detected by the flow rate detector 12 and given to the subtractor 16,
The subtracter 16 subtracts the signal from the load setter 13, and the subtracted deviation is sent to the PI controller 17 and the subtracter 1.
8a, control valve 22a via PI regulator 20a, etc.
is given, so that the deviation of the subtractor 16 is zero,
That is, control is performed so that the amount of water flowing out from the water supply pump 2a matches the water supply master command. Further, the water supply flow rate detected by the flow rate detector 11a is fed back to the subtractor 18a.

When increasing the load from the above operating state to the rated load, if the load is increased to the rated load using the load setting device 13 while the water supply pump 2b is stopped, the water supply pump 2b is increased to the rated load.
Although the flow rate of feed water discharged from a has a limit and cannot be increased, the opening degree of the control valve 14 increases, so more fuel is injected into the furnace of the boiler 1, and the temperature of the boiler 1 rises. If the temperature is too high, various problems may occur. For this reason, conventionally, when increasing the load, the number of water supply pumps to be operated is increased by first switching the water supply pumps.

Now, if the water supply pump 2b is to be driven in addition to the water supply pump 2a, the worker can set the bias operation device 19b to -100% while leaving the load setter 13 at 1/2.
From there, gradually work towards 0%. Therefore, the subtractor 18b also outputs a difference signal between the water supply master command from the PI controller 17 and the signal given from the bias operator 19b, and the difference signal is output from the PI controller 2.
0b, control valve 22 via manual automatic switch 21b
b, and the valve 22b opens in response to the signal, so steam is supplied to the turbine 3b.
b is driven, the water supply pump 2b also starts rotating, and water is supplied from the water supply pump 2b as well. When the bias operating device 19b is operated so that it becomes 0%, the signal output from the subtractor 18b increases, so the opening degree of the control valve 22b increases in proportion to it, and the rotational speed from the turbine 3b increases. Therefore, the water supply flow rate from the water supply pump 2b gradually increases.

On the other hand, since the total water supply flow rate flowing through the water supply pipe 4 is determined by the load, when the water supply flow rate from the water supply pump 2b gradually increases by operating the bias operation device 19b so as to approach 0%, the control valve 22
a is closed accordingly, the rotational speed of the turbine 3a and the water supply pump 2a decreases, and the water supply flow rate gradually decreases. This control is performed by feeding back the signal from the flow rate detector 11a to the subtractor 18a.

When the bias operation device 19b reaches 0%, the water supply pumps 2a and 2b each receive 50% from the water supply master command.
The water supply flow rate corresponding to the command in % units flows into the water supply pipe 4.

The conditions during _{the above} -mentioned control are shown in FIG _. The water supply flow rate gradually increases in the pump 2b, and the water supply flow rate gradually decreases in the water supply pump 2a, and after time _t2 , the water supply pumps 2a and 2b shoulder half the water supply in response to the master command from the load setting device 13. I know what you're doing.

[Problems to be Solved by the Invention] However, in the above-described device, when the water supply pump 2b is additionally operated, for example, the flow rate of water supplied from the water supply pump 2b is determined by the operation of the bias operation device 19b. The total water supply amount needs to be controlled by the remaining water supply pump 2a, and the change in the flow rate of the water supply pump 2a is given to the subtractor 18a for feedback control. Therefore, the change in the water supply flow rate of the additional water supply pump 2a is If it is fast, the total water supply flow rate flowing through the water supply pipe 4 will be curve a in Figure 4 A.
As a result, the steam pressure of boiler 1 fluctuates as shown in Figure 4 E, and the steam temperature of boiler 1 fluctuates as shown in Figure 4 F, which deteriorates the controllability of the total feedwater flow rate. On the other hand, if controllability is emphasized, there is a problem that it takes a long time to switch the water supply pump.

The present invention has been made in view of the above-mentioned circumstances, and is aimed at improving the controllability of a water supply pump that supplies water to a boiler and shortening the pump switching time.

[Means for solving the problem] The present invention is operated by switching between a speed type regulator 17 that outputs a water supply master command and a pump switching command setting device 26, and a water supply flow rate increase command is output from one of them. In this case, a plurality of bias operating devices 19a and 19b output a water supply reduction command whose absolute value is equal to the water supply increase command from the other, and a water supply master command from the regulator 17 or the bias operating device 19.
A plurality of OR circuits 23a, which output a water supply increase command when a water supply increase command is given from a, 19b;
23b, a plurality of OR circuits 24a and 24b that output a water supply increase command when a water supply master command from the regulator 17 or a water supply increase command from the bias operating devices 19a and 19b is given, and an OR circuit 23a. , 24a, 23b, 24b, a memory 25 outputting water supply increase commands or water supply decrease commands from 24b, 24a, 23b, 24b.
a, 25b, flow rate detectors 11a, 11b for detecting the amount of water supplied to the boiler 1 by each water pump 2a, 2b, and the memory 25a,
25b and the outputs from the flow rate detectors 11a, 11b, and the deviation is installed in a pipe that supplies steam from the boiler 1 to the turbines 3a, 3b that drive the water pumps 2a, 2b. Subtractors 18a, 18 output to control valves 22a, 22b
b.

[Function] When switching between the water supply pumps 2a and 2b, the bias operation device 19 is activated via the pump switching command setting device 26.
Operate a and 19b. Then, the water supply increase command or decrease command from the bias operation devices 19a, 19b is output from the OR circuits 23a, 23b or 24a, 23.
a or 24b, is supplied to subtracters 18a and 18b via memories 25a and 25b, and subtractor 18
In a and 18b, the deviation between the water supply increase command or water supply reduction command and the water supply flow rate detected by the flow rate detectors 11a and 11b is determined, and a command corresponding to the deviation is given to the control valves 22a and 22b, and the control valves 22a,
The opening degree of 22b is adjusted. For this reason, when the water supply flow rate of one water supply pump 2a, 2b increases, the water supply flow rate of the other water supply pump 2a, 2b decreases by the increased amount.

[Examples] Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, and the same parts as those shown in FIG. 1, FIG. 3 are given the same reference numerals.

In the figure, 26 is a pump switching command setting device that operates the bias operating devices 19a and 19b, and 23a and 23b are when either the water supply increase command from the bias operating devices 19a or 19b or the command from the PI regulator 17 is given. 24a and 24b are bias operating devices 19;
an OR circuit 25 that outputs a signal of a water supply flow rate reduction command when either the water supply flow rate reduction command from a or 19b or the command from the PI controller 17 is given;
a, 25b are OR circuits 23a, 23b, 24a,
This is an analog memory that provides the signal from 24b to subtracters 18a and 18b. Further, the PI regulator 17 uses a position adjustment type regulator in the conventional example shown in FIG. 3, but a speed adjustment type regulator is used in this embodiment.

In the above device, for example, if the load set by the load setting device 13 is 1/2 of the rated load and only the water supply pump 2a is driven and the water supply pump 2b is stopped,
The manual automatic switch 21b is switched to manual, and the control valve 22b is manually closed, and the PI controller 1
The water supply pump 2a is activated by the water supply master command from 7.
is being operated. For this reason, the load setting device 13
The deviation between the water supply command set in and the water supply flow rate detected by the flow rate detector 12 is determined by the subtractor 16 and the PI controller 1.
7 to OR circuit 23a, analog memory 25
a, the opening degree of the control valve 22a is adjusted via the subtractor 18a, the PI regulator 20a, and the manual automatic switch 21a, and the opening degree of the control valve 22a is adjusted.
rotates at a predetermined rotational speed, and water is supplied at a predetermined flow rate from the water supply pump 2a. Further, the amount of water sucked into the water supply pump 2a is detected by the flow rate detector 11a and fed back to the subtractor 18a, and the deviation determined by the subtractor 18a is given to the control valve 22a.

For example, when adding and operating the water supply pump 2b while keeping the load from the load setter 13 at 1/2 of the rated load, switch the manual automatic switch 21b to automatic and operate the pump switching command setter 26. do. Therefore, the bias operating device 19a outputs a constant output water supply flow rate reduction command, and the bias operation device 19b outputs a constant output water supply flow rate increase command.

A water supply flow rate reduction command signal supplied from the bias operation device 19a is given to the control valve 22a via the OR circuit 24a, analog memory 25a, subtractor 18a, PI regulator 20a, etc., and the opening degree of the control valve 22a is decreased. Therefore, the amount of steam introduced into the turbine 3a decreases, and the rotational speed of the turbine 3a decreases, so the flow rate of water supplied from the water supply pump 2a decreases.

The signal for increasing the water supply flow rate outputted from the bias operation device 19a is given to the control valve 22b via the OR circuit 23b, analog memory 25b, subtractor 18b, PI regulator 20b, etc., and the control valve 22b opens, so that the steam is introduced into the turbine 3b, the water supply pump 2b is driven, and the water supply pump 2b also starts supplying water.

When the pump switching command setter 26 is operated and a water supply flow rate reduction command is continuously given from the bias manipulator 19a and a water supply flow rate increase command is given from the bias manipulator 19b, the output from the analog memory 25a gradually decreases. Since the output from the analog memory 25b gradually increases, the opening degree of the control valve 22a gradually decreases and the opening degree of the control valve 22b gradually increases. Therefore, the rotation speed of the water supply pump 2a gradually decreases, the water supply flow rate decreases, and the water supply pump 2a gradually decreases.
The rotation speed of b gradually increases and the water supply flow rate increases. Whether or not the water supply flow rates from both water supply pumps 2a and 2b have become equal is determined by the flow rate detectors 11a and 1, for example.
A meter is attached to 1b to visually determine the difference, and when the values are equal, the operation of the pump switching command setting device 26 is stopped. As a result, the bias operating devices 19a, 19b
Since commands for decreasing and increasing the water supply flow rate are no longer output from , the subtractors 16, 18a, and 18b are used from then on.
Control valve 22 only when a deviation signal is output from
a and 22b are controlled.

The above operating conditions are shown in Figure 2 I to I, and when adding a water supply pump, a command to increase the water supply flow rate is given to one water supply pump 2b, and at the same time, a command is given to the other water supply pump 2a to decrease the water supply flow rate. Since a command can be given, the water supply flow rate of the water supply pumps 2a, 2b changes smoothly, and there is no pulsation in the total water supply flow rate in the water supply pipe 4 (see FIG. 2A). Furthermore, since pulsations do not occur in the total water supply flow rate, the steam pressure and steam temperature of the boiler 1 are also stabilized as shown in FIG.

In this embodiment, the PI regulator 17 is not a position-adjustable type but a speed-adjustable type because in the case of a position-adjustable type, if the bias actuators 19a and 19b are operated in opposite directions at the same time, when the pump switching is completed, both pumps The signals of the bias actuators 19a and 19b remain at a certain value, and if that state continues, when the water supply command changes, the water supply pump command will be limited by the bias value, and the water supply master signal will change from 0 to 100%. However, each water supply pump command becomes the water supply master signal ± bias signal, and there is a problem that the water supply pump command does not fall below the bias value or does not rise by the bias value, but in the case of the speed adjustment type, such a problem occurs. This is because there is no For example, if the bias value given to the subtractor 18b by the bias operation unit 19b is X%, the water supply master command is
Even if it reaches 100%, the command to the water pump is 100-X%.
This is because it cannot increase further.

In addition, in the embodiment of the present invention, the case of adding a water supply pump was explained, but when stopping it, it is sufficient to perform the procedure in the opposite direction to that of the upper air supply, and it is noted that the added water supply pump and other water supply pumps are The difference in water supply flow rate may be determined by calculating the difference between the signals detected by the flow rate detector using a calculator and determining whether the deviation is zero, and various other methods may be used without departing from the gist of the present invention. Of course, changes may be made.

[Effects of the Invention] According to the boiler feed water flow rate control device of the present invention,
Since any of the water supply pumps can be automatically switched when switching the water supply pumps, excellent effects can be achieved in that the controllability of the water supply pumps is improved and the switching time of the water supply pumps can be shortened.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of one embodiment of the present invention, Figures 2-1 are graphs showing the operating state of the present invention, and Figure 3
The figure is an explanatory diagram of the conventional example, and FIGS. 4A to 4F are graphs showing the operating state of the conventional example. In the figure, 1 is a boiler, 2a and 2b are water pumps, and 3
a, 3b are turbines, 4 is water supply pipe, 11a, 11
b is a flow rate detector, 12 is a flow rate detector, 13 is a load setting device, 14 is a control valve, 15 is a control valve, 16 is a subtractor, 17 is a PI regulator, 18a, 18b are subtractors, 19a, 19b are Bias operation device, 20a,
20b is a PI regulator, 23a and 23b are OR circuits,
24a and 24b are OR circuits, 25a and 25b are analog memories, and 26 is a pump switching command setting device.

Claims (1)

[Claims] 1 It is operated by switching between the speed type regulator 17 that outputs the water supply master command and the pump switching command setting device 26, and when a water supply flow rate increase command is output from one, the absolute value from the other is equal to the water supply increase command. Multiple bias operating devices 1 from which water supply reduction commands are output
9a, 19b, and the water supply master command from the regulator 17 or the bias operating device 19a, 19
A plurality of OR circuits 23a and 23b output a water supply increase command when a water supply increase command is given from b.
, a plurality of OR circuits 24a and 24b that output a water supply reduction command when a water supply master command from the regulator 17 or a water supply reduction command from the bias operating devices 19a and 19b is given, and an OR circuit 2.
Memories 25a, 2 that output water supply increase commands or water supply decrease commands from 3a, 24a, 23b, 24b
5b, and the boiler 1 by each water pump 2a, 2b.
flow rate detectors 11a, 11b for detecting the amount of water supplied to the memory 25a, 25b;
The deviation between the command from the flow rate detector 11a and the output from the flow rate detectors 11a and 11b is determined, and the deviation is installed in a pipe line that supplies steam from the boiler 1 to the turbines 3a and 3b that drive the feedwater pumps 2a and 2b. Control valve 22
A boiler feed water flow rate control device characterized in that subtracters 18a and 18b are provided for output to ports a and 22b.