JPS60114610A - Water-level controller - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a water level control device in a boiler.

In a multi-tube once-through boiler, the liquid level inside the boiler can changes depending on the steam load, and since can water has a high steam content, the water level control device is placed outside the boiler can. Therefore, even if the water level in the water level control device does not change, the liquid level in the boiler can fluctuates because the steam content in the liquid changes depending on the steam load, and when the load is high, the liquid level becomes high.

In order to improve the dryness of steam under high load conditions, the operating water level is set at a position of about 60 to % of the water pipe length. If the boiler is operated at this operating water level, the liquid level in the boiler can will not rise when the load is light, and the water pipes, upper header, etc. will overheat.

The present invention measures the drop in the can water level during low steam load in the boiler as described above by measuring the steam load and controlling the can water level to be near the high water level, thereby increasing the water level indicated by the can water level detector. An object of the present invention is to provide a device that can prevent overheating of water pipes, upper headers, etc. by bringing the actual water level in the can closer to the actual water level in the can.

The present invention includes a boiler steam load measuring device and a water level control device that raises the operating canister water level in inverse proportion to the boiler steam load.

Examples of the present invention will be described below.

FIG. 1(A) is a block explanatory diagram showing the configuration of such a boiler system, and a cross section of the boiler I is shown. FIG. 1(B) is a cross-sectional view taken along the line A-A at the 1st@(6)ζ.

In the figure, inside the boiler l, a large number of water pipes /b are installed along the inner peripheral surface of the wall /a, and the water pipes /1) are made of a hollow cylindrical body, and the lower end thereof is an annular lower header 10. (icehouse), and its upper end is also annular upper pipe header/(1
(steam room), and canned water is stored in the lower part of the lower header 10 and the water pipe/1).

In the center of the boiler surrounded by water pipes /b, there is a combustion chamber /f
3 is formed, and an air passage /h communicating with a blower 1g driven by an electric motor /f is provided above the air passage lh, and a nozzle rod 11 and an electrode rod lj are vertically provided in the air passage lh.

The lower end of the combustion chamber te communicates with the flue /k through a hollow space between a number of water pipes /b. From the upper header ld, a communication pipe /J extends outside the wall /a and communicates with the lower header 10.

A water level gauge/m for visually displaying the can water level and a water level detection section λ are installed in the middle of the communication pipe/J. A water supply control section 3 is connected to the water level detection section ko, and its output terminal is connected to an electric motor 4ta that drives a water supply pump. An inlet pipe of the water supply bomber communicates with a water source (not shown), and a discharge pipe thereof communicates with the lower header 10.

Furthermore, the pressure detection section 3 is connected to the upper part of the communication pipe 11, and its output terminal is connected to the heating control section B. A control signal line A'a%4'O extends from the heating control section 6 and is connected to the electric motor /f and the electrode rod t3 fuel pump 61.1, respectively. An inlet pipe of the fuel pump A'd communicates with a fuel tank (not shown), and a discharge pipe thereof communicates with a nozzle rod 11.

A blow pipe/n extends from the lower header 10,
It communicates with a drainage channel (not shown) via a blowcock/p,
A steam pipe /q extends from the upper header /(l) and communicates with a desired steam load (not shown).

In the configuration of the boiler system described above, when generating steam, the blower/g is driven by the electric motor/f to forcefully feed air into the air passage lh, and a high voltage is applied to the electrode rod lj to control the nozzle rod 11. The fuel injected from the tip is ignited and combusted within the combustion chamber le. The high-temperature combustion gas generated by such combustion enters the middle part of the water pipe /1) from the lower end of the combustion chamber lθ, passes through this, reaches the flue /k, and is exhausted. During this time, heat exchange takes place and the canned water in the water pipe /1) is heated and turned into steam, which is accumulated in the upper header /(L) and supplied to the steam load through the steam pipe /q. It is something.

Regarding power and heat control, the steam pressure in the upper header /(1 is extracted through the communication pipe /J and supplied to the pressure detection part 3, and the pressure detection part j extracts the steam pressure in the upper header /(l). When it is detected that the pressure has reached a preset lower limit vapor pressure, a lower limit vapor pressure signal is sent to the heating control unit B; similarly, when it is detected that the upper limit vapor pressure has been reached, an upper limit vapor pressure signal is sent to the heating control unit B. .

The heating control unit 6 controls the upper header/(
When the vapor pressure in L drops and a lower limit vapor pressure signal is received, the electric motor /f is started through the control signal line 6 + a, the air passage /h is purged with air using the blower /g, and then the control signal is sent. A high voltage is applied to the electrode rod lj through the lines t and Ib, and the fuel pump 4 (l is started through the control signal line 61C to ignite the fuel injected from the nozzle rod 11 and start combustion, and further, When the generation of steam continues and the steam pressure rises, and an upper limit steam pressure signal is received from the pressure detection part j, the combustion is stopped by stopping the fuel pump &+(l) through the control signal line 6+c At the same time, the electric motor /f is stopped through the control signal lines t and +a after the combustion gas is discharged, and the air blowing from the blower /g is cut off.

Thus, by intermittent control of combustion, the steam pressure in the upper header ld can be set as the upper and lower steam pressure limits, and a pressure value between preset measured pressure values can be maintained.

In addition, in a simple device, electric motor/f, fuel pump A'd
Start/stop control and application of high voltage to electrode rod /j may be performed simultaneously.

Furthermore, regarding the water supply system, the air-water interface in the communication pipe/J,
That is, the change in the can water level in the water pipe /b is transmitted to the water level detection part 1, and when the water level detection part 1 detects that the can water level has reached a preset lower limit water level, it transmits a lower limit water level signal. Similarly, when it is detected that the upper limit water level has been reached, an upper limit water level signal is sent to the water supply control section 3.

When the can water level in the water pipe drops due to steam consumption and a lower limit water level signal is received from the water level detection unit, the water supply control unit 3 starts the electric motor 4ta and uses the water supply bomber to control the water pipe/water through the lower header 10. 1) Start water supply to
When water supply continues and the can water level rises, and an upper limit water level signal is received from the water level detector, the electric motor 4Ia is stopped to cut off the water supply to the water pipe/1).

Thus, by controlling the water supply on and off, the water level of the canned water in the water pipe/1) can be maintained at a water level between the upper and lower limit water levels preset.

The intermittent control of water supply and the intermittent control of combustion are performed separately and independently from each other.

Further, when blowing canned water, by opening the blowing valve /p, part or all of the canned water in the lower header IC and water pipe /1) can be blown out through the drain pipe /n.

In addition, blower/gs airway/h, nozzle rod 11, electrode rod t
The burner made of Any heating device including the above may be used.

Similarly, the heating control section 6 may also be of any type as long as it can turn the heating device on and off.

Next, an example of a steam load measuring device according to the present invention will be described. In the present invention, it is not necessary to measure the amount of evaporation, but it is only necessary to express the steam load as a percentage of the total load.

The state of this change in steam load has already been clarified by the inventors, and the measuring device for heating time and heating stop time is a proposed method, and the steam load can be determined from the ratio thereof. FIG. 1 is a control block diagram showing a heating control section, a heating time measuring section, a heating stop time measuring section, and a water supply control section.

The pressure sensor 3a responds to the steam pressure in the upper header /d guided through the communication pipe /J and outputs a corresponding steam pressure signal Sθ.
) When the vapor pressure is higher than the lower limit vapor pressure PL as shown in a-/, a reference voltage equal to the lower limit set value of the vapor pressure signal Sθ corresponding to the lower limit vapor pressure P supplied from the reference voltage source &d Since the vapor pressure signal BQ becomes larger than V, the first comparator 3b detects this and sets the
) b - Output r/J as shown in t.

Then, as the steam pressure decreases as the steam is consumed or the temperature decreases, and as shown in FIG. 3(B)c-i, when the lower limit steam pressure PL is reached, the steam pressure signal Sθ becomes smaller than the reference voltage VL. Therefore, upon detecting this, the first comparator 3b outputs r7J as shown in FIG. 3(0)+L-t.

The flip-flop 6 receives the inversion of the output signal of the first comparator 3b from r/J to p' at the set terminal.
b is set to r/J, and its positive phase output signal is inverted from "O" to r/J as shown in FIG. 3(D) e-t. Upon receiving this signal, the driver 6C becomes conductive, the relay θ is excited, and the contacts 60', 6e", 6θ
°° is closed and power is supplied to the electric motor /f, electrode rod tj1, and fuel pump AI (l), so that the canned water is heated.

Thus, while the flip-flop 6b is at r/J, heating continues and the vapor pressure continues to rise as shown in FIG. 3(A)f-t.

Eventually, as shown in FIG. 3 (6) g-/, when the vapor pressure reaches the upper limit vapor pressure PH, the vapor pressure signal BQ becomes
Since the reference voltage VH is smaller than the reference voltage VH which is equal to the upper limit setting value of the vapor pressure signal BQ corresponding to the upper limit vapor pressure supplied from the reference voltage source 5e, "θ" The second comparator 3a, which was outputting
As shown in Figure (B) i-t, ζ is performed so as to output r/J.

The inversion of the output signal of the second comparator 3c from "θ" to r/J is performed by the inverter 6a, from r/J to "
The signal is inverted to "0" and supplied to the reset terminal of the flip-flop 6b, resetting it to "θ".

As shown in )j-/ in FIG. 3, the positive phase output signal of the flip-flop 6b becomes "θ", so the relay 6
e becomes de-energized, contact point tθ1゜6θ”6 e I
l+ is opened and heating of the canned water is stopped.

In this way, the time Th1 from when the heating device starts until it stops (hereinafter referred to as heating time) is specified by the time during which the flip-flop 6b is in r/J, and furthermore, the time Th1 from when the heating device starts until it stops is specified by the time when the flip-flop 6b is in r/J, and furthermore, when the heating device stops, Time from start to start Thz
(hereinafter referred to as heating rod time) is the flip-flop 6
It is specified by the time when b is "O".

After heating is stopped, as shown in FIG. 3(A)k-i, the steam pressure decreases again due to steam consumption or temperature drop, and flip-flop Ab remains "until the lower limit steam pressure PL is reached. 0'', a heating stop time Th2 is formed, and then the same operation is repeated to maintain the vapor pressure between the upper limit vapor pressure PH and the lower limit vapor pressure PL.

For example, when the amount of evaporation (steam load) increases in the step of increasing steam pressure, the amount of heat that flows into the boiler system due to the heating of canned water and the amount of heat that flows out from the boiler system due to heating is Although the heating time during steady operation is approximately constant, the amount of heat flowing out from the boiler system due to evaporation of canned water increases in proportion to the amount of evaporation, so more heat is taken away from the boiler system. Figure (5) f
As shown in 1, the upward slope of vapor pressure becomes slower.

Now, hypothetically, at the point in time shown in FIG. 3(A) c -/ζ, at the same time, as shown in FIG. Th+
Assuming that the amount of evaporation increases, the flip-flop changes as shown in FIG. 3(E) j'-t at the time shown in FIG. 3(A) g'-i. Since the value Ab is reversed to "θ", a heating time Th1' is formed which is longer than the heating time Th1 before the amount of evaporation increases.

A quantitative consideration of the change in the heating time Th1 depending on the change in the amount of evaporation is as follows.

In general, changes in internal thermal energy held by a boiler system d
U is dU = ηB - Hu - dt + GP, 6 (11; G,
It is expressed as @techs'at-QR・dt -- (1).

However, η... Boiler efficiency (excluding heat radiation loss) B... Fuel calorific value Hu... Fuel consumption (flow rate) G,... Water supply amount to the boiler (flow rate) 1w1 ”・Enthalpy of water supply G,・・Amount of evaporation (flow rate) 8・・・Enthalpy of steam Qn・・・Amount of heat dissipated from the boiler (heat flow rate).

Regarding the right side of equation (1), the first term is the amount of heat flowing into the boiler system due to the heating of canned water, the second term is the amount of heat flowing into the boiler system due to the supply of canned water, and the third term is the amount of heat flowing into the boiler system due to the supply of canned water. The second term represents the amount of heat flowing out of the boiler system due to evaporation, and the second term represents the amount of heat flowing out of the boiler system due to heat radiation.

By the way, in general, in a boiler system, the variable amount of canned water that is replenished by intermittent control of the water supply system is small compared to the amount of canned water held during operation. Therefore, the amount of water held in the boiler system during operation can be considered to be a constant value unique to each boiler system. thermal energy UL
Furthermore, each of the internal thermal energy UR held by the boiler system at the end of the heating time Th+ corresponding to the upper limit steam pressure PH is specified to a value unique to each boiler system.

Therefore, based on formula (I), the increase in internal thermal energy (Un Ub) generated in the boiler system with the passage of one heating time Th+ is U, -UT-==(η''B''' y ) T h
It is approximated by 1+(G y * engineering,) Th1.

In reality, the difference between the upper and lower vapor pressure limits PH1PL is not large, so for the sake of simplicity, we calculate the average enthalpy stn corresponding to the upper and lower vapor pressure limits.
: Then, formula (2) is -CGge 51n) Th1-Q
, 1@'fh1th-*(3).

Furthermore, considering the heating time Th+, within one heating time T141, water is supplied a number of times according to the amount of evaporation due to intermittent control of water supply, which is performed independently of heating control. The amount of water supplied (flow rate) that exceeds the amount of evaporation (flow rate) flows into the boiler; on the other hand, during the water supply stop period, water is not supplied at all, and the amount of water supplied (flow rate) that flows into the boiler becomes zero.

However, from a long-term perspective over a large number of heating times, in an operating boiler system, the average water supply amount (flow rate) supplied by water supply control is in equilibrium with the evaporation amount (flow rate), so the amount of water held in the boiler is approximately It is kept at a constant value.

Therefore, JGwdt = G B Th 1 proboscis... (41 is established.

Then, from equations (3) and (4), we can calculate the amount of evaporation on day 0.

However, if , and the feed water enthalpy is constant, both are constants unique to each boiler system.

Therefore, in equation (5), a=aB-cR...(6) Then, the evaporation amount G8 is v GB;0-m--11(7) hw It is expressed as

0 represents the amount of evaporation when the heating time Th1 is infinite (continuous heating), that is, the maximum amount of evaporation unique to each boiler system.

In addition, the heating time 'I'to at a8=θ4 becomes v 1o c=a(81), and even if the amount of evaporation (steam load) is zero during this heating time T1a, it mainly flows out due to heat radiation from the boiler. This is the minimum heating time required to supplement thermal energy and maintain the boiler system in operation.

FIG. 1 is a graph illustrating the relationship between the heating time Th+ and the evaporation amount GIi expressed by the equation (7).

In this way, the heating time Th1 of the boiler system is specified to a value unique to each boiler system according to the evaporation amount Gs, so if the heating time Th1 is specified by the needle, the above (5) to (7)
) The evaporation amount GB can be calculated according to the equation.

Next, for example, in the process of lowering the vapor pressure, the amount of evaporation (steam load)
When the amount of heat increases, there is no amount of heat flowing into the boiler system due to the heating of the can water, and furthermore, there is an amount of heat flowing into the boiler system due to the supply of can water, and the amount of heat flowing into the boiler system 7! due to heat radiation. J) The amount of heat flowing out from the boiler system is approximately constant during the heating stop time during steady operation, but the amount of heat flowing out from the boiler system due to evaporation of canned water increases in proportion to the amount of evaporation, so the increase in steam pressure As in the case of Fig. 3, more heat will be taken away from the boiler system.

As shown in FIG. 3(A) k'-i corresponding to , the downward slope of the vapor pressure becomes steeper.

Now, suppose that at the time shown in Fig. 3 (6) g-/, the flip-flop 6b is inverted to "O" at the same time as shown in Fig. S (g) j'-/. Assuming that the heating stop time has started, if the amount of evaporation increases, the
At the time shown in Figure (A) J' -i, Figure S (Hl) m
As shown in '-/, the flip-flop 6b is reversed to r/J, so the heating stop time Th2' is shorter than the heating stop time Thz before the amount of evaporation increases.
is formed.

A quantitative consideration of the change in the heating stop time Th2 depending on the change in the amount of evaporation is as follows.

During the heating stop time, the canned water is not heated (, the first term on the right side of equation (1) becomes zero, and the change in internal thermal energy du is clu = = G, * ω W'1t - 08" ω s・dt -Q
*6c'=... (represented by 91, and the decrement (TJr, -ITH) of the internal thermal energy accompanying the elapse of one heating stop time Th2 is UL-UH: (Gs-Eng 51n )Th2-Q, 1Th2
---Q (represented by l).

(In formula 11 Taking that into consideration, 1. Adding the amount of evaporation GB, becomes.

υ1v= =Oy -----(iirie5ln-workW eh5in-〇 # @ @ 11 (//b) and R, and the heating stop time T20 is even if the amount of evaporation (steam load) is zero. , is the maximum heating stop time required from the upper limit steam pressure to the lower limit steam pressure, mainly due to the outflow of thermal energy due to heat radiation from the boiler.

Therefore, even when the steam load is no load, the boiler system heating device has a heating time of T111. Intermittent control will be performed during the heating stop time T20.

FIG. 6 is a graph illustrating the relationship between the heating stop time Th2 and the evaporation amount G8 expressed by the above equation 1.

In this way, the heating stop time Th2- of the boiler system is also specified to a value unique to each boiler system according to the evaporation/emission amount G.
By measuring and specifying the heating stop time Th2, the evaporation amount GB can be calculated according to the above-mentioned formula 1.

Next, return to FIG. 2 and check the heating time meter "j section TH/,
The operation of the heating period calculating section za-7 will be explained as follows.

When controlling the heating device on and off, the flip-flop 6b
The positive phase output signal of, for example, becomes r/J during the heating time Th1, as shown in Figure 3 (D). Upon receiving a positive phase output signal with a power of 1, the ant-game) 71 is activated only during the heating time.
)-/ is opened and the clock pulse from the clock pulse oscillator a-/ is guided to the force counter 70-/ for counting.

Then, as shown in FIG. 3(D) j-/, when the flip-flop 6b is inverted from "/" to "O", the positive phase output signal f"/J is inverted to "Q", and the AND The gate 71)-/ closes and the supply of clock pulses to the counter '70-/ is cut off, and a digital code representing the heating time Th1 is generated in the counter 7Q-/, which is output as the heating time signal 51-1. be done.

At the same time, the arithmetic unit ga-/ receives the inversion of the positive phase output signal of the flip-flop 6b from "1" to "0" at the control terminal, and executes the arithmetic processing described later.

After the arithmetic processing by the arithmetic unit ffa-/ is completed,
r of the positive phase output signal of the above-mentioned −7 flip-flop 6b
The monostable multivibrator 7d-/ which was triggered and transitioned to a metastable state upon reversal from /J to "0"
returns to a stable state and sends a clear pulse to the counter 70-
Since the counter 70-/ is sent to the clear terminal of /, the counter 70-/ is cleared and prepared for the next measurement.

On the other hand, the heating stop time measuring section THJ, which has the same configuration as the heating time measuring section TH/, receives a reset signal from the complementary output terminal of the flip-flop 6b and outputs a signal 52-1 representing the heating stop time 'l''h2. The signal is input to the arithmetic unit ZA-/ via the MTH-.

Before the counter 70-/ is cleared, the arithmetic unit, jja-
/ calculates and outputs a load state signal from the signals 51-1 and 51-2, and sends it to the water supply control section J.

The water level detection unit 2 includes a water level detection box body that guides can water from the inside of the boiler can through a communication pipe 21, a water level detection electrode 2a whose tip always lands within the water level fluctuation range, and 2 ℃ and
Water level detection electrode, underwater electrode fixedly installed away from 2b, 2
C, one terminal of which is connected to the underwater electrode-20, and the other terminal of which is connected to one terminal of the current-voltage converter, 2E1, and the terminal connected to the power source, 2(l). It consists of a current-voltage converter, 2e, whose different terminals are connected to the water level detection electrode λb.

The resistance value between the underwater electrode 2C and the water level detection electrode 21) is a function of the length 1 of the water level detection electrode 2b in the liquid, assuming that the specific resistance of the canned water is constant. Underwater electrode, 2c-power supply, 2d-
The current flowing through the load circuit consisting of the current-voltage converter - water level detection electrode, 2b - can water - submersible electrode, 20 increases or decreases according to the length 1 of the water level detection electrode λb in the liquid, and converts the current to voltage. The water level signal S/ output from the device C changes in proportion to the value of the current flowing through the load circuit.

The water supply control unit 3 has one input terminal connected to the output terminal of the current/voltage detector koe, and a comparator whose reference voltage input terminal is connected to the output terminal of the arithmetic unit ga-/ via the DA converter 30. One input terminal is connected to the output terminal of the current/voltage detector 2e, and the arithmetic unit zaa-/
A DA converter 3e and a grounded variable resistor 3 are connected to the output terminal of
a comparator 3b connected to its reference voltage input terminal via f, and a flip-flop 3d whose set terminal is connected to the output terminal of comparator 3b and whose reset terminal is connected to the output terminal of comparator 3a through inverter 3C; , and a relay 3h, one end of which is connected to the positive phase output terminal of the flip-flop 3a through a driver 3g, and the other end of which is connected to the power supply 31, and the contacts of the relay 3h, ? h-/ is inserted into the power supply line 4tb to the drive motor 4<a of the water supply pump.

The comparator 3a outputs the water level signal S/ and the analog load state signal SL' converted by the digital load state signal 5Lt-DA converter 3e from the arithmetic unit fa-/ to the variable resistor 3f. When the signal SL'/ generated by the grounding resistance is SL'/>El/, it operates and "θ"
Output. The comparator 3b outputs a signal SL'2 obtained by subtracting the signal voltage drop supplied through the variable resistor 3f from the water level signal S/ and the analog load state signal SL', and the crab SL'! (It operates when 8/ and outputs r/J.

Therefore, when the water level of the current water level detection part reaches the set lower limit water level, the comparator 3b outputs "O", the set input of the flip-flop 3d changes from r/J to "O", and the flip-flop 3d is in positive phase. Output r/J and energize relay 7h through driver 3g. Relay contact 3h
-/ is opened, the electric motor pa rotates, the water supply pump is operated, and canned water is supplied. The water level rises due to the supply of canned water, and when it reaches the upper limit water level H, the output of the converter 3a changes from "O" to "L", and the output becomes 3C overnight.
r/J is converted to “0” at flip-flop 3
is added to the reset terminal of a, and the flip-flop 3d
is reset, relay 3h is deenergized, and water supply is stopped.

Since the supply of canned water is sufficiently larger than the steam load, the water supply is carried out intermittently, and the water level in the water level detection section changes by reciprocating between the upper and lower limit water levels.

FIG. 7 is a time chart showing the operation of FIG. 2. In the figure, FIG. 7 (5) shows the state of steam load. In this example, the steam load decreases linearly with time.

This is the load status signal SI.

The reason why is expressed as a continuous quantity is as follows. Even if the steam load is actually a continuous amount, the load status signal SL
does not become linear due to intermittent combustion. However, it is well known that the difference between the intermittent combustion and the trend line is small, and that such an intermittent line can be smoothed as a trend line by the calculator ffa-/.

The load status signal SL is converted into an analog load status signal 8L', and since a difference is provided between the reference voltage of the comparator 3a and the reference voltage of the comparator 3b using variable resistors 3f, the comparator 7a is not connected to the load status signal 8L'. B) cs
As shown in FIG. 7(B)d, the reference voltage lines connected to the comparator 3b are provided at equal intervals at each time in proportion to the load state signal SL. As shown in FIG. 7(C), by setting the reference voltages of the comparators JIL and jb, the upper limit water level H1 and the lower limit water level detected by the water level detection electrode 2b change according to the reference voltage line C2d of the comparators 3a and Jb, respectively. .

The water level, which has been decreasing as shown in Figure 7 (0) (!-/) due to the steam load until time T/, reaches the lower limit water level as shown in Figure 7 (0) c-co at time T/. , the comparator 3b as shown in FIG.
outputs rOJ, the flip-flop 3d is set, and the water supply pump is operated as shown in FIG. 7(F) fl to start water supply, so the water level is as shown in FIG. 0)c-,? rise as shown in . Then, at time T2, the output of the comparator 3a at the upper limit water level H, which is higher than the upper limit water level H when the steam load is constant, as shown by c-e in FIG. The signal changes from "O" to r/J, and is converted from r/J to "θj" through the inverter Ja, the flip-flop 3d is reset, and the water supply is stopped as shown in Fig. 7 (F) f-1. From time 'IJ to T3, the water level decreases as shown in Figure 7 ((3) a-6) due to the steam load, and at time T3, the water level decreases as shown in Figure 7 (0) Q-7. (0) At the lower limit water level that is higher than the lower limit water level shown in c-2, the comparator Jb changes from "/" to [θ-ko, and the flip-flop 3d is set as shown in FIG. 7 (7) θ-ko. Then, water supply is started as shown in FIG. 7 CF) f-3.

Thereafter, water is supplied in the same manner from time T3 to 'l, and time T
From II to T5, there was no water supply and the water level decreased due to steam load.
Water supply from time Tj- to T6, no water supply from time T6 to T-ri, water supply from time T7 to Tj, time Tf to T9'
No water supply until, water supply from time T9 to T10, time T10
No water is supplied from time T// to time T//, water is supplied from time // to time/2, and so on. As the steam load decreases, the water supply time increases (T/))(TJ-TJ))...>(
Ti cole/)〉・-11, and the non-water supply time decreases as the steam load decreases (TJ-T
,2)〈(TJ-TII)＜...(TII-T/
θ)〈ψ■”・ .

Since the upper limit water level H1 and the lower limit water level rise in inverse proportion to the steam load, the can water level in the water level detection section is both low when the steam load is large, and high when the steam load is small. change as it becomes.

The example in Figure 7 shows a case where the steam load gradually decreases, but generally the upper and lower limit water levels HL change in inverse proportion to the steam load, so the variation in steam load is limited to the example in Figure 7. isn't it.

In the above explanation, the load status signal was calculated from the heating time and the heating stop time, but it can also be similarly calculated from the operation of the water supply device during the water supply period and the water supply stop period.
No. 1079.70) Therefore, the calculation of the steam load is not limited to calculation based on the intermittent operation of the heating device, but may be calculated as long as it can be calculated during continuous operation.

As described above, the present invention enables the control reference position of the can water level to be raised or lowered depending on the steam load in a boiler in which the can water level is intermittently controlled by a water supply device, and increases the upper and lower limits of the can water level when the steam load is small. By controlling the water level to lower the upper and lower limit water levels when the steam load is large, overheating of water pipes, upper headers, etc. is eliminated.

Although the embodiment has been described with respect to a boiler with intermittent control, this water level control device can also be applied as is to a boiler with proportional combustion control. In that case, a signal from a pressure transmitter or the like may be used as the load status signal. (If the signal is an analog quantity, you only need to perform voltage conversion without DA conversion.)

[Brief explanation of drawings]

FIG. 1(A) is a block diagram showing the configuration of a small boiler system to which the configuration of the present invention can be attached, FIG. 1(b) is a sectional view taken along line AA in FIG. 1(A), and FIG. is a control diagram of the embodiment of the present invention, FIG. 3 and FIG. S are waveform diagrams of the main parts of the heating control section in FIG. 1, and FIG.
FIG. 6 is a graph showing the relationship between heating stop time Th2 and evaporation amount G. FIG. 7 is a time chart of the embodiment. , 21)...Water level detection electrode, 3a, 3b...Comparator 3d...Flip-flop 5L--Load status signal. Patent Applicant Ebara Corporation Agent Arai - Department Figure 1fA) Figure 1CB)

Claims (1)

[Claims] / A water level detection means that detects the canned water level and outputs a lower limit/upper limit water level signal, starts a water feed pump that supplies water to the boiler in response to the lower limit water level signal, and stops the water feed pump in response to the upper limit water level signal. In a boiler system water level control device equipped with an intermittent control water supply control means, the means for calculating the steam load factor and the signal from the means for calculating the steam load factor are received, and the upper and lower limit water levels are adjusted in the opposite direction to the change in the steam load. A water level control device in a boiler system, comprising means for controlling the water level so as to change the water level.