JPH10288303A - Water-supply flow rate control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time for hot clean-up, and to rapidly start a boiler by providing a high signal selector which outputs the higher command among the water supply flow rate set command from an adder or the water supply flow rate program command to supply water to the boiler. SOLUTION: When the outlet temperature of a furnace nose reaches a prescribed value, hot clean-up is performed. The prescribed value control start command 39 is given to a switching unit 38, and the switching unit 38 is switched to (b) side. The bias command 37 from a signal generator 36 is given to an adder 41 through the switching unit 38 and a change of rate controller 40. In the adder 41, the minimum water supply flow rate set command 28 and the bias command 37 are added to calculate the water supply flow rate set command 42 at the hot clean-up, and the calculated water supply flow rate set command 42 is given to a drive device of a water supply pump 2. The number of revolution of the water supply pump 2 is increased, and the water supply from the water supply pump 2 is increased and the water supply flow speed is increased. As a result, the water circulation time is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed water flow control device capable of rapidly performing hot cleanup for setting the quality of boiler feed water to a specified value.

[0002]

2. Description of the Related Art When a boiler is restarted after being shut down for a long period of time, the water quality of the boiler feed water may be out of a prescribed value. In such a case, the outlet temperature of the furnace nose is reduced to a predetermined temperature (200 ° C.). After the temperature is raised to), hot cleanup is performed to bring the water quality to the specified value.

[0003] An outline of a water supply system of a boiler is shown in FIG. 2. In the figure, reference numeral 1 denotes a water supply pipe to which a water supply pump 2 is connected in an intermediate portion for supplying water W. A coal evaporator 4 connected to the tip of the water supply pipe 1 is a furnace evaporator for heating and evaporating the feed water W heated by the economizer 3 and fed through the pipe 5, and 5 is a furnace evaporator 4. A pipeline for feeding a two-phase fluid in which steam and water generated by heating are mixed, 6 is a pipeline 5
Steam-water separator for separating steam and water from the two-phase fluid sent from the tank, 7 is a drain tank for storing water sent from the steam-water separator 6, 8 is a steam-water separator 6 and a drain tank 7 A steam pipe for feeding the steam V obtained in the above step to a subsequent process for further heating; and 9 a feed pipe for water discharged from the drain tank 7.
This is a drain water supply pipe to which a drain water supply pump 10 is connected in the middle so as to return to.

A drain water discharge pipe 11 is connected to an on-off valve 12 in the middle and drains part of the drain water so that the drain tank 7 does not overflow during hot cleanup. A steam turbine driven by steam supplied through a heat transfer section 14 such as a ceiling wall, a rear transfer section, and a superheater to rotate a generator 15 and generate electric power. A bypass pipe branched from the steam pipe 8 on the side thereof and connected to an on-off valve 17 in the middle thereof, 18 is an extraction pipe for extracting steam from the steam turbine 13, 19 is drain water from the drain water discharge pipe 11 and a bypass pipe 16. A condenser for receiving steam from the bleed pipe 18 and returning the received steam to water.
This is a deaerator installed between the condenser 19 and the water supply pump 2 so as to deaerate the water condensed at 9 and sent to the water supply pump 2.

[0005] Further, reference numeral 21 denotes a temperature detector connected to the pipe line 5 for detecting the outlet temperature of the furnace nose, and 22 denotes an inlet of the economizer 3 connected to the water supply pipe 1 and introduced into the economizer 3. A sampling pipe 24 capable of sampling the supplied water W by opening the on-off valve 23 is a chemical tank 25.
An on-off valve 27 is provided in the middle so that a chemical such as hydrazine in the inside can be injected into the inlet side of the economizer 3 by the chemical injection pump 26.
Is connected to the water supply pipe 1 at the tip.

FIG. 3 shows a feedwater flow control device for performing hot cleanup at the time of starting the boiler.
Is a minimum water supply flow rate setting command at the outlet of the economizer 3, 29 is a rate-of-change limiter that changes the given minimum water supply flow rate setting command 28 without outputting it as it is, and outputs the same. A function generator 3 capable of outputting a feed water flow rate program command 32 corresponding to 31;
3 is a minimum water supply flow rate setting command 28 from the change rate limiter 29.
Or the feed water flow rate program command 32 from the function generator 30
Is a high signal selector which outputs a larger command and supplies it to the drive device of the feedwater pump 2.

The relationship between a generator output command 31 and a feed water flow rate program command 32 as shown by a straight line A in FIG. Thus, if the generator output is high, a large amount of steam is required, and therefore the feedwater flow rate must also be high. Therefore, the generator output command 31 and the feedwater flow program command 32 are in a substantially proportional relationship.

When the boiler is started, the generator output command 31 is low, so that the feed water flow rate program command 32 is lower than the minimum feed water flow rate setting command 28 (see FIG. 4).

Therefore, the minimum water supply flow rate setting command 28 is given to the drive unit of the water supply pump 2 through the change rate limiter 29 and the high signal selector 33, and the water supply pump 2 rotates at a predetermined rotation speed.

The water discharged from the water supply pump 2 and the drain water from the drain water supply pipe 9 in response to the minimum water supply flow rate setting command 28 are supplied to the economizer 3 as water supply W, and after the burner ignition. The fuel gas is heated in the economizer 3 by the combustion gas generated by the combustion of the fuel, and also heated in the furnace evaporator 4 and introduced into the steam-water separator 6 from the pipe 5 as steam and water as a two-phase fluid. The steam separated by the vessel 6 is introduced into a steam pipe 8, the water separated by the steam separator 6 is introduced into a drain tank 7, and the steam generated in the drain tank 7 is introduced into a steam pipe 8.

The water collected in the drain tank 7 is returned to the water supply pipe 1 through the drain water supply pipe 9 by the drain water supply pump 10. At this time, since the on-off valve 12 is open, some water is collected. Water is supplied from a drain water discharge pipe 11 to a condenser 19. A part of the water from the drain tank 7 is supplied to the condenser 19 because the amount of the water stored in the drain tank 7 is larger than the discharge amount of the drain water from the drain water supply pump 10. This is to prevent overflow from occurring.

The steam V in the steam pipe 8 is supplied to the heat transfer section 1 of the boiler.
4, the steam is sent through the steam pipe 8 and a part of the steam passes through the bypass pipe 16 with the open / close valve 17 open.
9, the remaining steam is introduced into the steam turbine 13 and warms the steam turbine 13, is then bled into the bleed pipe 18, is fed from the bleed pipe 18 to the condenser 19, and is thus recovered. In the water dispenser 19, the steam is returned to the water.

The water from the condenser 19 is deaerated by the deaerator 20, introduced into the water supply pump 2, discharged from the water supply pump 2 and merged with the water from the drain water supply pipe 9, It is again introduced into the economizer 3 as feed water W.

The steam pressure (main steam pressure) at the inlet of the steam turbine 13 at this time is substantially constant for a while after the burner ignition as shown by a straight line B in FIG. And gradually begin to rise. In addition, the temperature of the furnace nose exit of water and steam is as shown by the straight line d in FIG.
The temperature gradually starts slightly earlier than the start of the main steam pressure rise. Thus, by performing such an operation, the water supply at the outlet of the economizer 3 is secured to the minimum water supply flow rate.

On the other hand, when the furnace nose outlet temperature detected by the temperature detector 21 reaches a predetermined temperature (200 ° C.), the amount of fuel from the burner is reduced by the furnace nose in order to shift to hot cleanup constant value control. The outlet temperature is decreased so as to maintain the predetermined temperature (see the straight line e in FIG. 5), and the water supply at the outlet of the economizer 3 is continued while maintaining the minimum water supply flow rate as described above. 23 is opened and a part of the feed water at the inlet side of the economizer 3 is sampled, and the water quality of the sampled water is analyzed (pH, O ₂ concentration, Fe concentration, electric conductivity, etc.), and the water quality does not reach the specified value. In this case, the opening / closing valve 27 is opened, the chemical liquid injection pump 26 is driven, and a predetermined amount of the chemical liquid (for example, hydrazine) stored in the chemical liquid tank 25 is introduced into the water supply W flowing through the water supply pipe 1 at the inlet of the economizer 3. You type. While the furnace nose outlet temperature is maintained at 200 ° C., the main steam pressure also maintains a constant value as shown by the straight line in FIG.

Also, a predetermined time (about 30 minutes) after injecting the chemical solution
After the elapse, the water supply W at the inlet side of the economizer 3 is sampled again, the water quality of the sampled water is analyzed, and when the water quality does not reach the specified value, the chemical is again supplied to the water supply pipe 1 at the inlet of the economizer 3. Inject into the flowing feed water W.

The above operation is repeated until the water quality reaches the specified value.
To increase the flow rate of fuel from the burner. For this reason, as shown by straight lines G and H in FIG. 5, the outlet temperature of the furnace nose and the main steam pressure also gradually start to increase again.

On the other hand, the feed water flow rate program command 3 output from the function generator 30 with the rise of the generator output command 31
2 exceeds the minimum water supply flow rate setting command 28, the water supply flow rate program command 32 is given to the driving device of the water supply pump 2 through the high signal selector 33, and the rotation speed of the water supply pump 2 increases, and the water supply flow rate becomes the minimum. The flow rate exceeds the water supply flow rate.

[0019]

As described above, when starting the boiler, once the clean-up constant value control of the boiler is started, the amount of fuel is reduced until the water quality of the feed water reaches a specified value, and the furnace nose is reduced. Since the outlet temperature is held so as not to rise, and the water supply flow rate at the outlet of the economizer is controlled to the minimum necessary, it takes time for the water to circulate in the water supply system, and the hot clean-up time is extended and the boiler There is a problem that the startup time becomes longer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to shorten the time for hot cleanup and, moreover, to quickly start up a boiler.

[0021]

According to the present invention, a 0% command is output from a first signal generator until a hot clean-up constant value control start command is given when a boiler is started, and a hot clean-up constant value control start command is issued. , A switch for outputting a bias command from the second signal generator, a minimum water supply flow rate setting command and 0% from the switch.
An adder for obtaining a water supply flow rate setting command by adding a command or a bias command, and a water supply pump for supplying water to the boiler by outputting a higher water supply flow rate setting command or a given water supply flow rate program command from the adder. And a high signal selector.

In the present invention, a change rate limiter may be provided between at least one of the switch and the adder or between the adder and the high signal selector.

When hot cleanup is performed at the time of starting the boiler, the flow rate of the water supplied from the water supply pump is controlled by the water supply flow rate setting command obtained by adding the bias command to the minimum water supply flow rate setting command. For this reason, the flow rate of the feedwater flowing through the economizer outlet side increases, the feedwater flow velocity in the feedwater system increases, and the time for circulating the feedwater is shortened. As a result, hot cleanup can be performed quickly.

When a change rate limiter is provided between at least one of the switch and the adder or between the adder and the high signal selector, the feed water flow rate setting command is gradually increased. Therefore, the flow rate of water supplied from the water supply pump gradually increases, and stable control can be performed.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. However, in this embodiment, the water supply system of the boiler is the same as that shown in FIG. 2, and the same reference numerals as those shown in FIG. I have.

In FIG. 1, reference numeral 34 denotes a signal generator capable of outputting a 0% command 35 when hot clean-up is not performed.
The signal generator 38 capable of outputting the bias command 37 of about% is switched to the a side when the hot cleanup constant value control start command 39 is not given, and outputs the 0% command 35, When a cleanup constant value control start command 39 is given, the switch is switched to the b side to output the bias command 37, and 40 is a switch 3
A rate-of-change limiter 41 for gradually changing the 0% command 35 or the bias command 37 from 8 without outputting the same, and outputs a minimum water supply flow rate setting command 28 and a 0% command from the rate-of-change limiter 40. This is an adder that obtains a water supply flow rate setting command 42 when hot cleanup is performed by adding 35 or a bias command 37 to the change rate limiter 29.

Next, the operation of the embodiment of the present invention will be described.

At the start of boiler startup, the switch 38 is switched to the a side, so that the 0% command 35 from the signal generator 34
Is supplied to an adder 41 via a switch 38 and a change rate limiter 40. However, since the 0% command 35 is given from the switch 38 to the adder 41, the adder 41 eventually outputs the minimum water supply flow rate setting command 28 as the water supply flow rate setting command 42, and the change rate It is provided to the high signal selector 33 via the limiter 29.

Further, a feed water flow rate program command 32 corresponding to the generator output command 31 is output from the function generator 30 and given to the high signal selector 33.

At the start of boiler startup, the minimum water supply flow rate setting command 28 is higher than the water supply flow rate program command 32, so the high signal selector 33 sends the minimum water supply flow rate setting command 28 to the water supply flow rate setting command 42. As water supply pump 2
The driving of the water supply pump 2 is performed so that the water supply flow rate from the water supply pump 2 is secured at the outlet of the economizer 3 in the same manner as in the conventional case.

When the furnace nose outlet temperature detected by the temperature detector 21 reaches a predetermined temperature (200 ° C.), hot cleanup is performed as in the conventional case. In this case, the hot cleanup constant value control is started. Command 39 is given to switch 38, and switch 38 switches to the b side. Therefore, the bias command 37 from the signal generator 36 is given to the adder 41 via the switch 38 and the rate-of-change limiter 40, and the adder 41 adds the minimum water supply flow rate setting command 28 and the bias command 37, and A water supply flow rate setting command 42 at the time of cleanup is obtained, and the obtained water supply flow rate setting command 42 is given to the driving device of the water supply pump 2.

As a result, the rotation speed of the feed water pump 2 increases, the flow rate of the feed water discharged from the feed water pump 2 increases, and the flow rate of the feed water increases. As a result, the feed pipe 1 → the economizer 3 → the steam separator 6 → Drain tank 7 → Drain water supply pipe 9 → Water supply pipe 1 also in the system, water supply pipe 1 → economizer 3 → steam-water separator 6 →
Also in the system of the drain tank 7 → the drain water discharge pipe 11 → the condenser 19 → the water supply pipe 1, the time required for one circulation of water is reduced.

Therefore, when hot cleanup for injecting a chemical solution is performed when the water quality of the sampled water has not reached the specified value, the water quality of the water supply system can be set to the specified value more quickly than in the past. The cleanup time can be shortened, and as a result, the boiler can be started more quickly than before.

After the water quality reaches the specified value and the hot cleanup is completed, the generator output command is increased to increase the amount of fuel injected from the burner into the furnace as in the conventional case. For this reason, the outlet temperature of the furnace nose and the main steam pressure also gradually increase again.

In this case, when the feed water flow rate program command 32 output from the function generator 30 exceeds the feed water flow rate setting command 42, the command 42 is passed through the high signal selector 33 to drive the feed water pump 2. And the rotation speed of the water supply pump 2 increases, and the water supply flow rate becomes a flow rate exceeding the water supply flow rate in consideration of the bias command.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the spirit of the present invention.

[0037]

According to the present invention, the time required for hot cleanup can be shortened, so that an excellent effect that the boiler can be started quickly can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a feedwater flow control device of the present invention.

FIG. 2 is a schematic diagram of a boiler water supply system.

FIG. 3 is a block diagram of a conventional feedwater flow control device.

FIG. 4 is a graph showing a relationship between a generator output command and a feedwater flow rate program command.

FIG. 5 is a graph showing a relationship between a time at the time of starting a boiler, a steam pressure, and an outlet temperature of a furnace nose.

[Explanation of symbols]

 2 Feedwater pump 28 Minimum feedwater flow rate setting command 29 Rate-of-change limiter 32 Feedwater flow rate program command 33 High signal selector 34 Signal generator (first signal generator) 350 0% command 36 Signal generator (second signal generator) 37) Bias command 38 Switch 39 Hot cleanup constant value control start command 40 Rate-of-change limiter 41 Adder 42 Water supply flow rate setting command

Claims (2)

[Claims] 1. A 0% command is output from a first signal generator until a hot clean-up constant value control start command is given at the time of starting the boiler. A switch for outputting a bias command from the signal generator of No. 2; an adder for adding a minimum water supply flow rate setting command and a 0% command or a bias command from the switch to obtain a water supply flow rate setting command; And a high-signal selector for supplying a water supply pump for supplying water to the boiler by outputting a higher command out of a water supply flow rate setting command or a supplied water supply flow program command. 2. The water supply flow rate according to claim 1, wherein a change rate limiter is provided between at least one of the switch and the adder or between the adder and the high signal selector. Control device.