JP3009793B2 - Water level control method for multi-tube once-through boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water level control method for a multi-tube once-through boiler.

[0002]

2. Description of the Related Art As a small-capacity boiler having a steam generation amount of about 0.5 to 5 t / h, there is a once-through boiler as shown in FIG.

In FIG. 4, reference numeral 1 denotes a boiler main body. The boiler main body 1 is vertically erected at predetermined intervals in a circumferential direction and is surrounded by a plurality of heating tubes 2 and the heating tubes 2. A combustion chamber 3 formed in the inner space formed by the heater, an annular lower header 4 connected to a lower portion of the heating tube 2, and an annular upper header 5 connected to an upper portion of the heating tube 2. A vertical burner 6 is mounted in a space surrounded by the upper header 5 so that fuel oil can be injected into the combustion chamber 3.

A water supply pipe 7 is connected to the lower header 4. The water supply pipe 7 has a water supply pump 8 and a lower header which can supply water to the lower header 4 of the boiler body 1. A check valve 9 is provided to prevent water from flowing back from 4 to the water supply pump 8.

[0005] Reference numeral 10 denotes a steam separator. The upper portion of the steam separator 10 and the upper surface of the upper header 5 are connected by a steam pipe 11, and the bottom portion of the steam separator 10 and the lower header 4 are connected. Are connected by a downcomer 12.

Reference numeral 13 denotes a water level detecting container used for detecting the level (water level) of water in the heating pipe 2 of the boiler main body 1. One end is connected to the bottom part and the upper part of the water level detecting container 13. The other ends of the communication pipes 14 and 15 are connected to the lower header 4 or the upper header 5. The water level detecting vessel 13 has three water level detecting electrode rods 16 _-1 , 16 _-2 , 16 having different lengths for detecting the water levels H ₁ , H ₂ , and H _3.
-3 is inserted, and each of the water level detection electrode rods 16 _-1 , 16 _-1
-2 and 16 _-3 have different heights and 1
The lower ends are arranged in the order of 6 ₋₁ , 16 ₋₂ , 16 ₋₃ (H ₁ <H ₂ <H ₃ ). Water detection command W detected by each water level detection electrode rod 16 _-1 , 16 _-2 , 16 _-3
1 , W ₂ and W ₃ can be given to the water level control device 19.

[0007] 17, 18 is a pressure switch connected to the steam pipe 11, when lowered to the pressure P ₁ is the lower limit that the pressure P of the steam flowing through the steam pipe 11 is predetermined (P ≦
P ₁ ), an operation command V ₁ for switching the burner 6 to the high combustion state can be given from the pressure switch 17 to the combustion control device 20, and the pressure P of the steam flowing through the steam pipe 11 is predetermined. When the pressure is lower than the upper limit pressure P _{2 and} higher than the lower limit pressure P ₁ (P ₁ <P <P ₂ ), the operation command for switching the burner 6 to the low combustion state from the pressure switch 18 to the combustion control device 20. so that the can provide a V _2. Also from the combustion control device 20, with which is adapted to be given a valve opening command V ₃ to the valve such as an electromagnetic valve for controlling the flow rate of the fuel injected from the burner 6 (not shown), fuel control The operation commands V ₁ and V ₂ from the pressure switches 17 and 18 can be given from the device 20 to the water level control device 19, and the water supply pump 8 can be supplied from the water level control device 19.
It is adapted to be given a start-up command V ₄ to.

In the multi-tube once-through boiler, water from a water supply pump 8 is supplied to a water supply pipe 7 and is introduced into a lower header 4 of the boiler main body 1 and is introduced from the lower header 4 to the heating pipe 2. In addition, the fuel injected from the burner 6 is heated by the heat generated by the combustion to become steam, and the steam is introduced from the upper header 5 through the steam pipe 11 into the steam separator 10, The steam from which the moisture has been removed by the separator 10 is sent to the steam usage destination and consumed, and the water separated by the steam separator 10 is returned from the downcomer 12 to the lower header 4.

When the pressure P of the steam generated in the boiler main body 1 has decreased to a predetermined lower limit pressure P _1, an operation command for high combustion is sent from the pressure switch 17 to the combustion control device 20. V ₁ is given and the combustion control device 2
All valve opening by 0 to be given the valve opening command V ₃ to all valves that control the flow of fuel from the burner 6 the flow rate of the fuel injected from the burner 6 is increased in a high combustion state, further, when the pressure P of the steam is higher than the lower limit pressure P ₁ of lower than the pressure P ₂ of the predetermined upper limit, the actuation command V ₂ for low combustion from the pressure switch 18 to the combustion control device 20 A valve opening command V ₃ is given to a predetermined valve among the valves that are given and control the fuel flow rate from the combustion control device 20.
Is no longer output, the valve closes, the flow rate of fuel injected from the burner 6 decreases, the burner 6 enters a low combustion state, and when the steam pressure P reaches a predetermined upper limit pressure P ₂ , the pressure Operation commands V ₁ , V ₂ from switches 17 and 18
There is not outputted, therefore, the combustion control unit 20 closes all valves to control the flow rate of the fuel by the valve opening command V ₃ is not output, the fuel is not injected from the burner 6, the burner 6 is stopped I do.

On the other hand, in the multi-tube once-through boiler,
When performing the so-called three-position control of high combustion-low combustion-stop as described above, control of the water level in the heating pipe 2 is performed.

For example, when the operation command V ₁ of the pressure switch 17 is given to the water level control device 19 via the combustion control device 20 while the burner 6 is in the high combustion state, the water level in the water level detection container 13 becomes It is necessary to control so as to be located between H ₁ and H ₂ . Thus, for example, between the water level in the burner 6 is high combustion state of H ₂ and H ₃ in the water level detection chamber 13, the water level detecting electrode bars 16 _-1, 16 _-2 to water detection command W _When W ₁ and W ₂ are given to the water level control device 19, the start command V ₄ is sent from the combustion control device 20 to the water supply pump 8.
Is not given, and the water supply pump 8 is stopped.

[0012] while the burner 6 the water supply pump 8 is stopped to continue the high combustion state, but In its water level extension of the heating pipe 2 decreases water level in the water level detection chamber 13, the water level is slightly above H ₁ lowered, when the water by the water level detecting electrode bars 16 _-1 is not detected, the water detection command W _1, W _2, W ₃ are not given to the level control unit 19, the water supply from this for the water level control device 19 When a start command V ₄ is given to the pump 8, the water supply pump 8 is started, and water is supplied to the lower header 4 by the water supply pump 8. And Thus, the water level in the water level detection container 13 by the water level in the heating pipe 2 is increased rises to H _2, the water level detecting electrode bars 16 _-1 by 16 _-2 When water is detected, Since the water detection commands W ₁ and W ₂ are given to the water level control device 19 and the start-up command V ₄ is no longer given to the water supply pump 8, the water supply pump 8 is stopped again.

When the burner 6 is in a low combustion state, the water level in the water level detecting container 13 must be located between H ₂ and H ₃ , so that the water level reaches H ₃ and the water level is detected. When water is detected by the electrode rods 16 _-1 , 16 _-2 , and 16 _-3 , the water supply pump 8 is stopped, and the water level stops slightly more than H ₂ and the water level detection electrode rods 16. _-2, 16 the water by _-3 is not detected, the start command V ₄ from the level control unit 19 water supply pump 8 is activated, the water level detecting electrode bars 16 _-1 reached H ₃ water level rises, 16 _-2 ,
When the 16 _-3 water is to be detected, the water supply pump 8 for no longer given start command V _4, the water supply pump 8 is stopped again.

The water level in the heating pipe 2 of the boiler body 1 is controlled to a different height depending on the combustion state of the burner 6, that is, the boiler load, for the following reasons. That is,
The water level for obtaining steam with good dryness differs depending on the boiler load, as shown in the area A between the solid lines a and b in FIG. 5, and when the boiler load is high, the water level is high. If the boiler load is low, if the boiler load is low, the temperature of the heating pipe 2 will rise unless the water level is raised. This is because there is a possibility that the heating tube 2 may be burned out due to excessive heating. In FIG. 5, the region B which is above the solid line b is steam the dryness worse region, the region C is located below the solid line b is a metal temperature rise region of the heat pipe, the lower end of the white frame X ₁ is a high combustion state the lower limit level H ₁ of the time, the upper limit of the white frame X ₁ is an upper limit water level of H ₂ during a high combustion state, the lower limit of the white frame X ₂ is the water level of H ₂ the lower limit of the time of low combustion state, the upper limit of the white frame X ₂ is an upper limit water level H ₃ of the time of the low combustion state represents respectively.

When the burner 6 is in a high combustion state, the water level in the heating pipe 2 is lowered because the heating pipe 2 is in a high combustion state.
This is because the vapor pressure in the upper part is low and the proportion of bubbles is large, so that even when the apparent water level is low, the substantial water level is high and the heating pipe 2 can be sufficiently cooled. The reason for raising the water level in the heating pipe 2 in the combustion state is that the apparent water level is low in the low combustion state because the steam pressure above the heating pipe 2 is high and the proportion of bubbles above the heating pipe 2 is small. This is because the substantial water level is low and the heating tube 2 cannot be sufficiently cooled.

[0016]

The range in which the water level is controlled in the above-mentioned multi-tube once-through boiler is changed when the combustion state of the burner 6 is switched to high combustion or low combustion.
By controlling the water level in the heating pipe 2 according to the combustion state as described above, it is possible to obtain steam having a good dryness and to prolong the life of the boiler.

However, for example, a high combustion state or a low
When the steam pressure in the burning state is relatively high overall
Indicates the water level for obtaining steam with good dryness, as shown in FIG.
Frame X ₁, X_TwoAs shown in the figure, the area A between the solid lines A and B
However, if the steam pressure drops overall,
The water level for obtaining steam with good dryness is indicated by the dotted line in FIG.
It moves to the area A 'sandwiched between c and d. In this case,
Has a white frame X₁, X_TwoIn the water level control range shown in
It enters the region B where the steam dryness is deteriorated. Conversely, steam
If the pressure of the whole rises, the area A
White frame X₁, X_TwoWater level control range shown in
In the area, the water level is in the region C where the metal temperature of the heating pipe 2 rises.
Will enter. Further, the steam pressure is such that the burner 6 is highly flammable.
Not constant during burning or low combustion
And the steam pressure changes with time even in the same combustion state.
Become Therefore, the water level set in advance according to the combustion state
Can not be changed, the degree of steam pressure changes
Therefore, the steam may not be dry enough or
There is a possibility that the metal temperature of the heat tube 2 may rise too much.

The present invention has been made in view of the above circumstances, and has as its object to be able to change the water level in the heating pipe 2 according to the pressure when the steam pressure fluctuates in the same combustion state. Things.

[0019]

In order to achieve the above object, in a first means, a plurality of heating tubes 2 erected at predetermined intervals in a circumferential direction and a lower end of the heating tubes 2 are connected. A boiler body 1 having an upper header 5 connected to the upper end of the heating pipe 2 and delivering generated steam, and a lower header 4 capable of introducing water from a water supply pump 8; A burner 6 for injecting fuel into a combustion chamber 3 formed in the main body 1 and surrounded by a heating pipe 2; and a water level detecting container 13 having a lower part communicating with the lower header 4 and an upper part communicating with the upper header 5. And the first, second, and second inserted in the water level detection container 13 so that the lower ends thereof are located at different heights .
Third, fourth four water level detection electrode rods _16-4 , 1
6 _-1 , 16 _-2 , _16-3 , and the first,
Second, third, and fourth electrode rods for water level detection _16-4 , 16
_-1, 16 _-2, 16 _-3 by the water level control method of a multi-tube once-through boiler so as to control the water level in the water level detection container 13, the steam in which the burner 6 is and generated by the high combustion state If higher than the pressure P _O of the pressure P becomes the reference has a water level in the water level detection chamber 13, and the lower end of the second water <br/> level detecting electrode bars 16 _-1, the second The lower end of which is higher than the lower end of the water level detection electrode rod _16-1 .
The controlled so as to substantially located between the lower end of the water level detecting electrode bars 16 _-2 when the burner 6 is less than the pressure P _O of the pressure P is the reference of the steam and generated by the high combustion state lower end, the water level in the water level detection chamber 13, the lower end of the second water <br/> level detecting electrode bars 16 _-1 of the lower end and the second water level detecting electrode bars 16 _-1 a first <br/> controlled to substantially located between the water level detecting electrode bars 16 _-4, the pressure P of the steam the burner 6 is and generated in the low combustion state is reference in the low position When the pressure is higher than the predetermined pressure P _O , the water level in the water level detection container 13 is adjusted to the third level whose lower end is higher than the lower end of the second water level detection electrode rod _16-1 .
The lies in the lower end position higher than the lower end and the lower end of the third water level detecting electrode bars 16 _-2 water level detecting electrode bars 16 _-2
4 is controlled so as to substantially located between the lower end of the water level detecting electrode bars 16 _-3, the case burner 6 is less than the pressure P _O of the pressure P of the steam and generated in the low combustion state becomes the reference to the water level of the water level detection chamber 13, the third <br/> water level detecting electrode bars 16 _-2 bottom and said third lower than the lower end of the water level detecting electrode bars 16 _-2 Is lower in the second position
Of which is controlled so as to substantially located between the lower end of the water level detecting electrode bars 16 _-1, in the second means, a plurality of heating tube 2 and the heating erected at required intervals in the circumferential direction It has a lower header 4 connected to the lower end of the pipe 2 and capable of introducing water from the water supply pump 8 and an upper header 5 connected to the upper end of the heating pipe 2 and for delivering generated steam. A boiler main body 1 and a burner 6 for injecting fuel into a combustion chamber 3 formed in the boiler main body 1 and surrounded by a heating tube 2;
A steam-water separator 10 for separating and returning moisture from the steam sent from the upper header 5, and a water level detecting container 13 having a lower part communicating with the lower header 4 and an upper part communicating with the upper header 5. And the first, second, third, and fourth inserted in the water level detection container 13 so that the lower ends thereof are located at different heights .
Four water level detecting electrode rods _16-4 , _16-1 , 1
6 _-2 , _16-3 , and the first, second, third, and
4, the water level detection electrode rods _16-4 , _16-1 , _16-2 ,
By 16 _-3 in water level control method of a multi-tube once-through boiler so as to control the water level in the water level detection container 13,
Wherein when the burner 6 and steam-water separator less than 10 in the electric conductivity K of the separated water is the reference electric conductivity K _O in a high combustion state, the water level in the water level detection container 13 third water level detecting electrode bars 16 lower than the lower end of the second water level detecting electrode bars 16 _-1 of the lower end and said second <br/> water level detecting electrode bars 16 _-1 is in the high position controlled to substantially located between the lower end of _-2 the burner 6 than the electrical conductivity K _O to and electric conductivity K of separated water in steam-water separator 10 is the reference in high combustion state If large, the water level of the water level detection chamber 13, the second water level detecting electrode bars 16 _-1 of the lower end and the second water level detecting electrode bars 16 _-1
Controlled to substantially located between the first water level detecting electrode bars 16 _-4 at the lower end is lower than the lower end of the burner 6 is separated by steam-water separator 10 and at a low combustion state when the electric conductivity K of the water is less than the electrical conductivity K _O as a reference is the water level in the water level detection chamber 13, from the lower end of the lower end second water level detecting electrode bars 16 _-1 third fourth level detecting electrode bars 16 lower end and said third lower than the lower end of the water level detecting electrode bars 16 _-2 water level detecting electrode bars 16 _-2 is in the high position in the even higher position controlled to substantially located between the lower end of _-3, the burner 6 is than the electrical conductivity K _O the electric conductivity K of separated water in steam-water separator 10 and at a low combustion state becomes the reference If larger,
The water level in the water level detection container 13, first the lower end is lower than the lower end of the third water level detecting electrode bars 16 _-2 bottom and the third water level detecting electrode bars 16 _-2 2 Is controlled so as to be located substantially between the lower end of the water level detection electrode rod _16-1 .

[0020]

According to the first means, the burner 6 is in a high combustion state and
The steam pressure P is the standard pressure P₀Higher than the water
The water level in the level detecting container 13 is the water level detecting electrode rod 1.
6_-1, 16_-2Is controlled to be located approximately between the lower ends of the
The pressure 6 is in a high combustion state and the steam pressure P is a reference pressure P.₀
Lower than the water level in the water level detection container 13.
Is a water level detection electrode rod 16_-Four, 16_-1Approximately between the lower ends of
The burner 6 is in a low combustion state and the steam is
Pressure P is the standard pressure P₀If higher than, for water level detection
The water level in the container 13 is equal to the water level detecting electrode rod 16._-2, 16_-3
The burner 6 is controlled to be located almost between the lower ends of the
In a state where the steam pressure P is a reference pressure P₀Lower than
The water level in the water level detection container 13 is
Pole stick 16_-1, 16_-2Controlled to be located approximately between the lower ends of
In the second means, the burner 6 is in a high combustion state and
The electrical resistance K of the water separated from the steam by the separator 10 is
Reference electric conductivity K_OIf less than, water level detection
The water level of the container 13 is determined by the electrode rod 16 for detecting the water level._-1, 16_-2
The burner 6 is controlled so as to be located approximately between the lower ends of the
Of water separated from steam by the steam-water separator 10
Electric conductivity K based on air conductivity K_OGreater than
Is the water level of the water level detection container 13,
6_-2, 16_-3Is controlled to be located approximately between the lower ends of the
The fuel 6 is in a low combustion state and is separated from steam by the steam separator 10.
The electrical conductivity K of the separated water is the standard electrical conductivity K._OYo
When the water level is lower than the water level,
Position detection electrode rod 16_-2, 16_-3It is located almost between the lower ends of
The burner 6 is in a low combustion state and the steam-water separator 1
Electricity based on the electric conductivity K of water separated from steam at 0
Conductivity K _OIs larger than the water level detection container 13.
Of the water level detection electrode rod 16_{- 1}, 16_-2Between the lower ends of
It is controlled to be located approximately.

Therefore, when the combustion state of the burner 6 is a constant combustion state such as a high combustion state or a low combustion state, the pressure P of the generated steam changes or the steam-water separator 10
Even if the electric conductivity K of the water separated in the step changes, steam with good dryness can be obtained, and an excessive rise in the temperature of the heating tube 2 can be prevented.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention. The basic structure is substantially the same as the conventional one shown in FIG. 4, and the same parts as those shown in FIG. .

[0024] 16 _-4 a water level detecting electrode bars for detecting the low water level H ₄ than the water level H _1, the water level detecting electrode bars 16 _-4, the water level detecting electrode bars shown in FIG. 4 16 _-1 , 1
_6-2, 16 similar to _-3, is inserted into the water level detection chamber 13, and so that the common pressure may perform control of the water level even when the drop, the lower end of the water level detecting electrode bars 16 _-4 level detection It is located below the lower end of the electrode bar _16-1 . The water detection command W ₄ detected by the water level detection electrode rod 16 _-4 can be given to the water level control device 19, and the pressure switch 21 connected to the upper part of the steam separator 10 detects the steam pressure P. When the pressure is lower than a predetermined reference pressure P ₀ , an operation command V _O can be given to the water level control device 19. Furthermore, the combustion control device 20
Commands V ₁ , V ₂ given through the pressure switch 2
The operation command V _O given from 1 and the water level detection electrode rod 16
_Based on the water detection commands W ₁ , W ₂ , W ₃ , and W ₄ given from _-1 , 16 _-2 , 16 _-3 , and 16 _-4 , the water level control device 19 issues a start command V to the feed water pump 8 from the water level control device 19. ₄ can be output.

When the burner 6 is in the normal high combustion state and the steam pressure P in the steam separator 10 is higher than the reference pressure P ₀ , the water level in the water level detecting container 13 is between the lower end of the electrode rod 16 _-1 of the bottom and 16 _-2, i.e. controlled to lie between the water level H ₁ and _{H 2 (H 1 <H 2} ) takes place, from the pressure switch 17 is in this case Operation command V ₁
Is given to the water level control device 19 via the combustion control device 20, and an operation command V _O from the pressure switch 21 is given to the water level control device 19. And Thus, the water level is lowered slightly from the lower end of the water level detecting electrode bars 16 _-1 water level detecting electrode bars 16 _- When not detected by _1,
Only the water detection command W ₄ detected by the water level detection electrode rod 16 _-4 is given to the water level control device 19. In this case, the water supply pump 8 is driven by the start command V ₄ from the water level control device 19, The water is supplied from the water supply pipe 7 to the lower header 4 of the boiler body 1 by the water supply pump 8, and the water in the heating pipe 2 rises and the water level in the water level detection container 13 rises via the communication pipe 14. .

When the water level in the water level detection container 13 rises slightly above H ₁ and water is detected by the water level detection electrode rods 16 _-4 and 16 _-1 , the water detection command W ₄ , W ₁ is given to the level control unit 19, the water supply pump 8 by the activation command V ₄ from the level control unit 19 in this case is subsequently driven further water level in the heating tube 2 and the water level detection container 13 is H ₂ The water level detecting electrode rod 16
_-4, 16 _-1, 16 becomes as water is detected by _-2, water detection command W _4, W _1, W ₂ is supplied to the level control unit 19, a start command V ₄ from the level control unit 19 As a result, the water supply pump 8 stops.

When the burner 6 is in a normal low combustion state and the steam pressure P in the steam separator 10 is higher than a reference pressure P ₀ determined by the combustion state, the water level in the water level detecting container 13 becomes , between the water level detecting electrode bars 16 _-2 and 16 _-3, that is, control is performed such that between the water level H ₂ and _{H 3 (H 2 <H 3} ), in this case pressure switch 18 operation command V ₂ from via the combustion control device 20 water level controller 1
9 and an operation command V _O from the pressure switch 21 is provided to the water level control device 19. When Thus to water so slightly lower than a lower end of the water level detecting electrode bars 16 _-2 water not detected by the water level electrode rod 16 _-2,
Water detection commands W ₄ and W ₁ detected by the water level detection electrode rods 16 _-4 and 16 _-1 are given to the water level control device 19, and the water supply pump 8 is driven by a start command V ₄ from the water level control device 19. Then, the water level in the heating pipe 2 of the boiler body 1 and the water level in the water level detecting container 13 rise.

The water level in the water level detecting container 13 is H_TwoThan
Rises slightly and the water level detecting electrode rod 16_-Four, 16_-1, 1
6_-2Even if water is detected by the
W_Four, W₁, W_TwoIs supplied to the water level control device 19 to control the water level.
Start command V from control device 19_FourFeed pump 8
The water level in the water level detecting container 13 is H
_ThreeThe water level detecting electrode rod 16_-Four, 16
_-1, 16_-2, 16_-3Allows water to be detected
And the water detection command W_Four, W₁, W_Two, W_ThreeIs the water level control device 19
From the water level control device 19,_FourComes out
As a result, the water supply pump 8 stops.

The burner 6 is in a high combustion state and the steam-water separator 1
When the pressure P of the steam within ₀ is lower than the reference pressure P ₀ determined by the combustion state, the operation command V ₁ from the pressure switch 17 is transmitted to the water level control device 19 via the combustion control device 20.
To the operation command V from the pressure switch 21
_O is given to the water level control device 19 and the water level detection container 13
Water level is between the water level detection electrode rods 16 _-4 and 16 _-1
That is, control is performed so that the water level is between H ₄ and H ₁ (H ₄ <H ₁ ). For this reason, the water level is changed to the water level detection electrode rod _16-4.
The water is slightly lower than the lower end of the
_-4, the water detection commands W ₄ , W ₁ , W ₂ , W ₃ from the water level detection electrode rods 16 _-4 , 16 _-1 , 16 _-2 , 16 _-3 are transmitted to the water level control device 19. In this case, the start command V from the water level control device 19 is not provided.
_The water supply pump 8 is driven by ₄ , and water is supplied to the boiler main body 1 by the water supply pump 8, and the water level of the heating pipe 2 and the water level in the water level detection container 13 rise.

The water level in the water level detecting container 13 is H_FourTo
The electrode rod 16 for detecting the water level which rises slightly more_-FourWater
When it is detected, the water detection command W_FourIs a water level control device
To the water level controller 19 in this case.
Start command V_FourFeed pump 8 is continuously driven by
And the water level in the heating pipe 2 and the water level detecting container 13 is H
₁The water level detecting electrode rod 16_-Four, 16
_-1When water is detected by the
W_Four, W₁Is supplied to the water level control device 19,
Starting command V from 19_FourIs no longer output, resulting in water supply
The pump 8 stops.

The burner 6 is in a low combustion state and the steam-water separator 1
When the pressure P of the steam within ₀ is lower than the reference pressure P ₀ determined by the combustion state, the operation command V ₂ from the pressure switch 18 is transmitted via the combustion control device 20 to the water level control device 19.
To the operation command V from the pressure switch 21
_O is given to the water level control device 19 and the water level detection container 13
Water level of the inner during the water level detecting electrode bars 16 _-1 and 16 _-2, that is controlled to lie between the water level H ₁ and _{H 2 (H 1 <H 2} ) takes place. Therefore, the water level is lowered slightly from the lower end of the water level detecting electrode bars 16 _-1, water level detecting electrode bars 16
_-1 , 16 _-2 , 16 _-3 , but not detected by the water level detection electrode rod 16 _-4 , the water level detection electrode rods 16 _-1 , 16 _-2 , 16 _-3 Water detection command W
_1, W _2, W ₃ are not given to the level control unit 19, will be water detection command W ₄ from the water level detecting electrode bars 16 _-4 given level control device 19, in this case, The water supply pump 8 is driven by a start command V ₄ from the water level control device 19, and water is supplied to the boiler main body 1 by the water supply pump 8 so that the water level in the heating pipe 2 and the water level in the water level detection container 13 are reduced. To rise.

When the water level in the water level detection container 13 rises slightly above H ₁ and water is detected by the water level detection electrode rods 16 _-4 and 16 _-1 , the water detection command W ₄ , W ₁
Although but so applied to level control unit 19, in this case, the water supply pump 8 by the activation command V ₄ from the level control unit 19 is subsequently driven, the water level further inside the heating tube 2 and the water level detection container 13 water level detecting electrode bars 16 _-4 slightly higher than H _2, 16 _-1, 16 becomes as water is detected by _-2, water detection command W _4, W _1, W ₂ water level controller given 19, from the level controller 19 results start command V ₄ is not outputted, the water supply pump 8 is stopped.

As described above, even when the combustion state (burning amount) of the burner 6 is the same, the water level detecting container is different depending on whether the steam pressure P is higher or lower than a predetermined reference pressure P _0. FIG. 3 shows the relationship between the amount of combustion (boiler load) and the water level when changing the water level to be controlled in 13.

[0034] In FIG. 3, the upper and lower inclined curved solid line b, the region A sandwiched Russia, good steam the dryness is higher than the pressure P ₀ the pressure P of the steam is predetermined reference shows the allowable control range of the water level in order to obtain a lower limit water level during the lower limit of the white frame X ₁ in region a and high combustion at higher than the pressure P ₀ of the reference pressure P of the steam is predetermined H
₁ , the upper limit of the white frame X ₁ is when the steam pressure P is higher than a predetermined reference pressure P _O and the upper limit water level H ₂ at the time of high combustion is the upper limit of the white frame X ₂ in the area A. The lower limit is the lower limit water level H ₂ at the time of low combustion when the steam pressure P is higher than the predetermined reference pressure P ₀ , and the upper limit of the white frame X ₂ is the steam pressure P at the predetermined reference pressure. When it is higher than P _O, it indicates the upper limit water level H ₃ at the time of low combustion.

An area A 'sandwiched between dotted lines C and D of the upper and lower inclined curves and whose upper part partially overlaps the lower part of the area A is a pressure P _{O at which the} steam pressure P becomes a predetermined reference.
Shows the allowable control range of the water level in order to obtain a good steam dryness fraction is lower than the lower limit of the black frame Y ₁ in the region A ', rather than the pressure P _O of the reference pressure P of the steam is predetermined and the lower limit level H ₄ of the time of high burn if low, the upper limit of the black frame Y ₁ in contact with the lower limit of the white frame X ₁ is and when lower than the pressure P ₀ of the reference pressure P of the steam is predetermined the water level H ₁ of the upper limit during high combustion, the black frame Y ₂ in the region a 'lower limit, the lower limit during and low combustion at lower than the pressure P _O of the reference pressure P of the steam is predetermined the water level H _1, the black border Y ₁ in contact with the lower limit of the white frame X ₂ upper limit, the water level of H ₂ limit during and low combustion at lower than the pressure P _O of the reference pressure P of the steam is predetermined It represents.

Further, the area above the solid line A is
The pressure P is a predetermined reference pressure P_OIf higher than steam
The area where the air dryness deteriorates and the area above the dotted line
Gas pressure P is a predetermined reference pressure P_OLower than
Represents the area where the steam dryness deteriorates, and is below the solid line b.
In the other region, the steam pressure P is a predetermined reference pressure P _O
Above the metal temperature of heating tube 2 (see Fig. 1)
In the region below the dotted line d, the pressure P of the steam
Predetermined reference pressure P_OLower than the heating tube 2
Each of the metal temperature rising regions is shown.

Further, in FIG. 3, the upper ends of the white frames X ₁ and X ₂ project above the curve C, and when the steam pressure P is higher than the reference pressure P _O , the dryness When the pressure P of the steam becomes lower than a predetermined reference pressure P _O , the region where the water level is in the allowable control range for obtaining good steam becomes a region where the steam dryness is deteriorated. It turns out that it is necessary to lower the control range of the water level.

Therefore, in this case, by reducing the control range of the water level as in the present embodiment, the case where the combustion state of the burner 6 (see FIG. 1) is the same as the combustion state is the same as the case where the steam pressure P is the reference. When the pressure is lower than the pressure P _O , the control range of the water level can be reduced to obtain steam with good dryness, and the metal temperature of the heating pipe 2 can be prevented from rising unnecessarily. Can be prevented.

The pressure P _{O based on the} steam pressure P is a reference.
If the water level falls below the control level when the water level falls below this level, the reason is as follows. That is, when the saturated steam pressure in the boiler body 1 or the steam separator 10 is 8 kg / cm ² G, the specific volume of steam is 0.21884 m ³ / kg, whereas, for example, the saturated steam pressure is 5 kg / cm. The specific volume of steam in the case of ² G is 0.32135 m ³ / Kg, and the saturated steam pressure is 5 K
The specific volume of steam in the case of g / cm ² G is a saturated steam pressure of 8
It is 1.47 times the specific volume of steam in the case of Kg / cm ² G. Accordingly, the lower the steam pressure P, the higher the heating pipe 2
Since the number of bubbles in the upper steam increases, even if the apparent water level in the heating pipe 2 as the water level control column is lowered, the substantial water level in the heating pipe 2 does not decrease, and the heating pipe 2 is sufficiently cooled. Cooled,
The metal temperature does not rise excessively. According to the test results, in the case of a boiler having a maximum pressure of 10 Kg / cm ² G, the pressure P _O serving as a reference for changing the water level to be controlled is preferably 5 to 6 Kg / cm ² G.

FIG. 2 shows another embodiment of the present invention. In the above embodiment, the water level to be controlled is changed on the basis of the steam pressure. On the other hand, in this embodiment, a steam-water separator is used. The water level to be controlled is changed based on the electric conductivity (can water concentration) of water (can water) separated at 10 and returned to the lower header 4 of the boiler body 1.

In the figure, reference numeral 22 denotes an electric conductivity detector connected to the downcomer 12, and reference numeral 23 denotes an arithmetic control unit. The electric conductivity K detected by the electric conductivity detector 22 is sent to the arithmetic control unit 23. In the arithmetic and control unit 23, the deviation ΔK between the preset reference electric conductivity K _O and the detected electric conductivity K is obtained by K _O −K and the deviation ΔK <0. water level control device operation command V ₅ If 1
9, the control range of the high water level indicated by the white frames X ₁ and X ₂ in FIG. 3 is selected. When ΔK ≧ 0, the operation command V ₆ is supplied to the water level control device 19. Thus, a control range with a low water level indicated by black frames Y ₁ and Y ₂ in FIG. 3 is selected.

In the case of this embodiment, the region A in FIG. 3 is a steam having a good dryness when the electric conductivity K of the still water is smaller than a predetermined standard electric conductivity K _O. shows the allowable control range of the water level in order to obtain the lower limit of the white frame X ₁ in region a, during and high fire when the electric conductivity K of the boiler water is less than the electrical conductivity of K _O of the reference water level H _1, the water level of H ₂ lower during maximum white frame X ₁ is and high fire when the electric conductivity K of the boiler water is less than the electrical conductivity of K _O of the reference, a region lower limit of the the lower limit of the white frame X ₂ in a is a water level of H ₂ lower during and low fire when the electric conductivity K of the boiler water is less than the electrical conductivity of K _O of the reference, a white frame X ₂ The upper limit is that the electric conductivity K of the canned water is the electric conductivity K of the above standard.
_It represents the upper limit water level H ₃ when the _value is smaller than ₀ and at the time of low combustion.

The lower limit of the black frame Y in the area A 'is the water level for obtaining good dryness steam when the electric conductivity K of the can water is higher than a predetermined standard electric conductivity K _O. shows the allowable control range, the lower limit of the black frame Y ₁ in the region a 'is a lower limit upon and low fire when the electric conductivity K of the boiler water is higher than the electrical conductivity of K _O of the reference water level H _4, the upper limit of the black frame Y ₁ is an electric conductivity K _O of the electrical conductivity K of the boiler water is the reference
Higher and the upper limit water level H ₁ at the time of high combustion,
The lower limit of the black frame Y ₂ in the region A 'is the water level H ₁ of a lower limit at the time of and low fire when the electric conductivity K of the boiler water is higher than the electrical conductivity of K _O reference, the upper limit of the black frame Y ₂ Represents the upper limit water level H ₂ when the electric conductivity K of the can water is higher than the standard electric conductivity K _O and at the time of low combustion.

In this embodiment, the electric conductivity K of the water separated by the steam separator 10 and returned from the downcomer 12 to the lower header 4 is detected by the electric conductivity detector 22 and the arithmetic and control unit 23 is operated. In the arithmetic and control unit 23, the deviation ΔK of the electric conductivity is obtained by ΔK = K _O −K,
When ΔK <0, the operation command V ₅ is given, and when ΔK ≧ 0, the operation command V ₆ is given from the arithmetic control unit 23 to the water level control unit 1.
9

When the operation commands V ₁ and V ₅ are given to the water level control device 19, the burner 6 is in a high combustion state and the water level in the water level detection container 13 is equal to the water level detection electrode rod 16.
Control lower water level between the lower end of the detection electrode rod 16 _-2 i.e. so as to be between the water level H ₁ and H _{2 -1} is performed, operation command V ₂ to the level control unit 19, if V ₅ is given the burner 6 in the low combustion state, the water level in the water level detection container 13, the water level detecting electrode bars 16 _-2 bottom and the water level detecting electrode bars 16 _-3
Controlled to be between between the lower end i.e. the water level H ₂ and H ₃ are performed, and also when the water level control device operation command V ₁ to 19, V ₆ is given, water level detection burner 6 is in a high combustion state the water level in the container 13, is controlled to be between the water level detecting electrode bars 16 _-4 bottom and the water level detecting electrode bars 16 _-1 during i.e. the water level H ₄ of the lower end of the H ₁ is performed, the water level controller When the operation commands V ₂ , V ₆ are given to 19, the water level in the water level detecting container 13 is set to the water level detecting electrode rod 1 when the burner 6 is in the low combustion state.
_6-1 the lower end and between the lower end of the water level detecting electrode bars 16 _-2, that is controlled to be between the water level H ₁ and H ₂ is carried out. The manner of controlling the water level is the same as that of the above-described embodiment, and the description is omitted.

As described above, when the reference electric conductivity K _O is larger than the detected electric conductivity K, the water level to be controlled is raised, and the detected electric conductivity K _O is used as the reference electric conductivity K _O. If it is smaller than that, even if the water level to be controlled is lowered, it is possible to obtain steam with good dryness when the electric conductivity of the can water is large, and an excessive rise in metal temperature of the heating pipe 2. Can be prevented.

The reason that the water level controlled in the water level detecting container 13 can be lowered when the electric conductivity K is small is as follows. That is, when the water evaporates and the concentration of impurities in the still water increases, the electrical conductivity also increases. However, since the number of bubbles at the top of the heating tube 2 also increases, the apparent water level in the heating tube 2 serving as a water level control column is reduced. Even if it is lowered, the substantial water level is not lowered by the amount of bubbles, the cooling effect of the heating tube 2 can be sufficiently expected, and the metal temperature does not rise excessively. According to experiments, it is better to change the water level at which the electric conductivity is controlled at about 500 μs / cm ² .

In the embodiment of the present invention, the case where the controlled water level is switched from a high state to a low state has been described. However, the present invention can be implemented by switching from a low state to a high state. It goes without saying that various changes can be made without departing from the scope of the present invention.

[0049]

According to the water level control method of the multi-tube once-through boiler of the present invention, in any one of the first and second embodiments, when the range in which the steam pressure P fluctuates in the same combustion state is large. Even if it does, it is possible to obtain various excellent effects, such as being able to obtain steam having a good dryness, suppressing an excessive rise in temperature of the heating tube 2 and prolonging the life of the boiler. .

[Brief description of the drawings]

FIG. 1 is a control block diagram of an embodiment of a water level control method for a multi-tube once-through boiler of the present invention.

FIG. 2 is a control block diagram of another embodiment of the water level control method of the multi-tube once-through boiler of the present invention.

FIG. 3 is a graph showing a relationship between a combustion amount (boiler load) and a controlled water level in the water level control method of the multi-tube once-through boiler of the present invention.

FIG. 4 is a control block diagram of an example of a conventional water level control method for a multi-tube once-through boiler.

FIG. 5 is a graph showing a relationship between a combustion amount (boiler load) and a water level to be controlled in a conventional water level control method for a multi-tube once-through boiler.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Boiler main body 2 Heating tube 3 Combustion chamber 4 Lower header 5 Upper header 6 Burner 8 Water supply pump 10 Steam separator 13 Water level detection container _16-1 , _16-2 , _16-3 , _{16-4 For} water level detection Electrode P, P ₀ Pressure K, K _O Electric conductivity

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-236502 (JP, A) JP-A-4-148102 (JP, A) JP-A-61-48208 (JP, U) (58) Survey Field (Int. Cl. ⁷ , DB name) F22D 5/00

Claims (2)

(57) [Claims] 1. A plurality of heating tubes 2 erected at predetermined intervals in a circumferential direction and a lower header 4 connected to a lower end of the heating tubes 2 and capable of introducing water from a water supply pump 8. A boiler body 1 having an upper header 5 connected to the upper end of the heating tube 2 and delivering generated steam, and a combustion chamber 3 formed by being surrounded by the heating tube 2 in the boiler body 1. A burner 6 for injecting fuel, a water level detecting container 13 having a lower part communicating with the lower header 4 and an upper part communicating with the upper header 5, and a lower end located at a different height in the water level detecting container 13; First, second, third, fourth inserted
Of the four water level detection electrode rods _16-4 , _16-1 , 16
_-2 , _16-3 , and the first, second, third,
Fourth water level detection electrode rod 16 _-4 , 16 _-1 , 1
_6-2, the water level control method of the multi-tube once-through boiler which is by 16 _-3 to control the water level in the water level detection chamber 13, the pressure P of the steam the burner 6 is and produced in a high combustion state If higher than the pressure P _O as a reference is,
Wherein the water level of the water level detection chamber 13, and the lower end of the second water level detecting electrode bars 16 _-1, the second water level detecting electrode bars 1
6 lower than the lower end of _-1 is controlled to substantially located between the third lower end of the water level detecting electrode bars 16 _-2 at a high position, steam the burner 6 is and generated by the high combustion state of when the pressure P is lower than the pressure P _O as a reference, the water level of the water level detection chamber 13, for the lower end and said second level detection of the second water level detecting electrode bars 16 _-1 Electrode rod 16
Lower than the lower end of _-1 is controlled to substantially located between the first water level detecting electrode bars 16 _-4 at a low position, the pressure P of the steam the burner 6 is and produced at a low combustion state Is higher than the reference pressure P _O , the water level in the water level detection container 13 is set to a third level whose lower end is higher than the lower end of the second water level detection electrode rod _16-1 . between the lower end of the water level detecting electrode bars 16 _-2 bottom and said third fourth lower end than the lower end of the water level detecting electrode bars 16 _-2 is in the high position of the water level detecting electrode bars 16 _-3 When the burner 6 is in a low combustion state and the pressure P of the generated steam is lower than a reference pressure P _O , the water level in the water level detection container 13 is adjusted to the second level . 3 the lower end and the water level detecting electrode bars 16 _-2 third water level detecting electrode bars 1
Second level control method of a multi-tube once-through boiler, characterized by controlling so as to substantially located between the lower end of the water level detecting electrode bars 16 _-1 in _6-2 lower end position lower than the lower end of the . 2. A plurality of heating pipes 2 erected at predetermined intervals in a circumferential direction, and a lower header 4 connected to a lower end of the heating pipe 2 and capable of introducing water from a water supply pump 8. A boiler body 1 having an upper header 5 connected to the upper end of the heating tube 2 and delivering generated steam, and a combustion chamber 3 formed by being surrounded by the heating tube 2 in the boiler body 1. A burner 6 for injecting fuel, and a steam-water separator 10 for separating and returning moisture from steam supplied from the upper header 5
And a water level detection container 13 having a lower part communicated with the lower header 4 and an upper part communicated with the upper header 5, and inserted into the water level detection container 13 such that lower ends thereof are located at different heights. First, second, third, and fourth four water level detection electrode rods _16-4 , _16-1 , _16-2 , _16-3 ;
And first, second, third, and fourth electrode rods 16 for detecting a water level.
_{-4, 16 -1,} 16 -2, the water level control method of the multi-tube once-through boiler which is by _{16 -3} to control the water level in the water level detection chamber 13, and the burner 6 is in a high combustion state gas when the electric conductivity K of separated water in a water separator 10 is smaller than the electric conductivity K _O as a reference is the water level in the water level detection chamber 13, the second water level detecting electrode bars 16 _-1 lower end and said second water level detecting electrode bars _{16 -1}
The lower end is higher than the lower end of the third electrode rod _16-2 for detecting water level, which is higher than the lower end. The burner 6 is in a high combustion state and separated by the steam separator 10. been if the electric conductivity K of the water is greater than the electrical conductivity K _O as a reference is the water level in the water level detection chamber 13, and the lower end of the second water level detecting electrode bars 16 _-1 the first
The lower end of the second water level detecting electrode bars 16 _-1 to control so as to substantially located between the first water level detecting electrode bars 16 _-4 at the lower end is lower position, the burner 6 is at a low combustion state and air-water when the electrical conductivity K of separated water in separator 10 is smaller than the electric conductivity K _O as a reference is the water level in the water level detection chamber 13, the lower end is the second water level third lower end position higher than the lower end of the water level detecting electrode bars 16 _-2 bottom and the third water level detecting electrode bars 16 _-2 at a position higher than the lower end of the detection electrode rod 16 _-1 controlled to substantially located between one fourth lower water <br/> level detecting electrode bars 16 _-3, air-water the burner 6 and at a low combustion state separator 1
When the electric conductivity K of the water separated at 0 is larger than the electric conductivity K _{O as a} reference, the water level detecting container 13
The water level of the inner, the third second water level detecting electrode bars lower than the lower end of the water level detecting electrode bars 16 _-2 bottom and the third water level detecting electrode bars 16 _-2 is in the low position of the multitubular level control method of once-through boiler, characterized by controlling so as to substantially located between the lower end of the 16 _-1.