JPH0351604A - Level controller of deaerator - Google Patents

Abstract

PURPOSE:To make it possible to control levels without causing excessive flow by maintaining the opening of a control valve at a smallest opening necessary for prevention of excessive flow when required condensate flow rate is in the region of excessive flow rate of a condensate booster pump and by, at the same time, controlling the number of revolutions of the pump at an excessive flow prevention critical number of revolutions in a deaerator level control device of a steam turbine plant. CONSTITUTION:A dearator level controller 24 judges whether or not required condensate rate is in the region of excessive flow rate of a condensate booster pump 5 when a deaerator level control valve is fully opened based on the pressure of the deaerator and the number of operating condensate booster pump to determine a lowest throttle pressure command signal of a control valve 6 necessary for preventing excessive flow rate when the required condensate flow rate is in said region. And at the time, said control device 24 determines a critical number of revolutions command signal of the pump 5 to prevent excessive flow rate. Based on these signals, the control valve 6 the number of revolutions of the pump 5 are controlled. By this arrangement, excessive flow can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Field of Industrial Application) The present invention relates to a level control device for a deaerator in a steam turbine plant.

(Prior Art) FIG. 7 is a diagram showing a condensation system and a conventional deaerator level control device of a typical steam turbine plant, in which the steam discharged from the steam turbine (not shown) is Condenser 1
It exchanges heat with cooling water and is stored as condensate. The condensate stored in the condenser 1 is pressurized by the condensate pump 2,
The condensate is sent to a condensate booster pump 5 via a condensate desalination device 3 and a gland steam condenser 4. The double water is further pressurized by a water booster pump 5, passed through a control valve 6 for adjusting the deaerator level, a low water feed water heater 7, and then sent to a deaerator water storage tank 8, and then to a boiler feed water pump. 9 and sent to the boiler via a high-pressure feedwater heater 10.

A condensate flow rate detector 11 is installed on the artificial side of the deaerator of the condensate system.
A level detector 12 is provided in the deaerator water storage tank 8.
A water supply personnel detector 13 is further provided in the water supply system to the boiler.

The signals detected by each of the above detectors are manually input to the deaerator level control device 14, where these signals are used to calculate the opening degree of the control valve 6 and the rotation speed of the condensate booster pump by three-element control. The opening degree of the regulating valve 6 is controlled by the regulating valve opening command signal. On the other hand, the variable speed control device 15 controls the rotation speed of the water booster bomb so that the rotation speed matches the pump rotation speed command signal of the glare device level control device 14, and the level of the deaerator is controlled. Ru.

FIG. 8 is a diagram showing a configuration example of the conventional deaerator level control device, in which the level signal from the deaerator 4 level detector 12 and the setting signal from the level setter 16 are connected to the subtracter 17.
The deviation f is input to the adder 18.

On the other hand, the difference in No. 1Z from the boiler feed water flow rate detector 13 and the condensate flow rate detector 11 is obtained by the subtracter 19, and this deviation signal is also manually inputted to the adder 18, and the signal added by this adder 18 is is manually input to the controller 20.

The controller 20 performs proportional + integral type control, and output signals from the controller 20 are input to function generators 21 and 22, respectively.

The function generator 21 outputs an opening command signal for the control valve 6, and in a region where the output signal from the controller 20 is lower than a certain value, the control valve opening signal is increased or decreased according to the output of the controller 20. In a region where the output signal from the controller 20 is higher than a certain value, an opening command signal equivalent to fully opening the valve is output.

On the other hand, the opening generator 22 outputs a rotation speed command signal for the condensate booster pump 5, and outputs a rotation speed command signal with a constant minimum rotation speed in a region where the output signal of the controller 20 is different from a certain value. However, in a region where the output signal of the controller 20 is higher than a certain value, the rotation speed command signal is increased or decreased according to the output of the controller 20.

Therefore, in a region where the output of the controller 20 is lower than a certain value, the opening degree of the control valve 6 is controlled while the condensate booster pump 5 is maintained at the minimum rotation speed.
The level of the deaerator is controlled by controlling the opening of the deaerator.

In a region where the output of the controller 20 is higher than a certain value, the control valve 6 is fully opened, the rotation speed of the condensate booster pump 5 is controlled, and the level of the deaerator is controlled by this rotation speed control.

(Problem to be Solved by the Invention) In FIG. 9, the curve r,. , 1.2 `` are the characteristic curves of the condensate booster pump IaX 5 at each rotational speed, r is the rated rotational speed, 11aX `` . indicates the minimum rotation speed. In addition, the curve Iln line A shown by the solid line is a system head curve in which the system loss of the condensate system plus the pressure of the deaerator corresponding to χ・1 of the condensate flow rate is plotted according to each condensate flow rate. Therefore, in a stable state at each load of the turbine plant: 1}, the state of the condensate system is determined at a certain point on curve A.

On the other hand, curve B shown by a dotted line shows the overflow limit value at each rotation speed of the condensate booster pump, and the operating point of the condensate booster pump must be controlled to be within this overflow limit value. .

By the way, in the conventional control system, as mentioned above, there is a region where the rotation speed of the condensate booster pump is fixed and the level of the deaerator is controlled by the control valve 6, and a region where the control valve 6 is fully opened and the condensate booster pump 5 is controlled. Since the condensate booster bomb is divided into areas where level control is performed depending on the rotation speed, in order to prevent the condensate booster bomb from entering the overflow area, it must be controlled so that it follows the trajectory of ■, ■, ...■ in Figure 9. I will do it. However, the minimum rotational speed of the salt water booster bomb has to be set to 2 for operational purposes, and as a result, the n1 gear range of the condensate booster bomb is originally +1
J capable r,. ~ “Not Illax, '2~'ia,
will be subject to the JIIJ limit. Therefore, there is a problem in that the low-frequency effect of the in-house power is reduced, and the reduction leads to a reduction in plant efficiency.

In addition, as mentioned above, curve A in Figure 9 is a planned system head curve that takes into account the deaerator pressure corresponding to the condensate flow rate in terms of heat balance. At a certain point, the operating point of the condensate system is determined.

However, in actual operation, the system head curve of the condensate system at each point n and r moves depending on the pressure of the deaerator, and as shown in Fig. 10, for example, the system head curve of the condensate system at each point n and When the control valve is opened from this state, the operating point of the irrigation system moves along the system head curve S corresponding to the deaerator pressure at negative t:I. As a result, when the control valve is fully opened, it is at the operating point (■') in the figure, and the 1 & water booster pump enters the overflow region. Furthermore, even if the rotation speed of the Sansui booster pump is increased, the condensate booster pump will be over-E between the points
It will be operated in the L amount state.

In this way, in the conventional control system, even if the minimum rotational speed for operation is set to r2 as shown in Figure 9, especially in the low load range, the deaerator's superfluous degree I causes level fluctuations. If the control valve is fully opened in response, there are problems such as the salt water booster pump entering the overflow region.

In view of these points, the present invention prevents the overflow state of the condensate booster pump from occurring in each operating state even if the deaerator pressure changes and the system head curve of the condensate system changes depending on the operating state of the plant. A deaerator that can control the level of the deaerator without causing problems, and also allows the ==Ii speed range of the rear water booster pump to be made as large as possible, thereby increasing the effect of reducing in-house power. The purpose is to obtain a level control device.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides deaerator level control that controls the level of a deaerator using a deaerator level control valve opening control device and a condensate booster pump rotation speed control device. In the device, the system head curve of the condensate system at the +tF7 point is determined based on the deaerator pressure, and the bri1+F. Determine the overflow limit curve in the number, determine whether the required condensate 'jlitQ is in the overflow range of the water booster pump when the deaerator level control valve is fully open, and in the overflow range, the overflow limit In addition to providing an overflow suppressing device that outputs the minimum necessary 21-section valve throttle pressure signal to prevent this, the control valve opening degree is calculated based on the output signal from the overflow suppressing device. '
A control valve opening meter that outputs a J-section valve opening command signal p. In addition, a rotation speed command (..j output device) was installed to output a 110 rotation speed command signal for the condensate booster pump at the limit W that can prevent overflow when the control valve is in the throttle state. It is characterized by

(Function) The overflow suppressing device determines whether the required condensate flow rate is in the overflow range of the condensate booster pump when the A section valve is fully open, and prevents the overflow in the overflow range. The minimum necessary for The reduction valve throttle pressure signal is output, and the control valve opening is calculated in the control valve opening calculator based on this signal, and the calculated control valve opening command signal is applied to the control valve for adjustment. The opening degree of the valve is controlled. At the same time, the rotation speed command signal output device outputs a rotation speed command signal for the condensate booster bomb that is at the limit that can prevent excess flow when the control valve is in the throttle state, and this signal causes the condensate booster pump to be activated. The rotation speed is controlled. In this way, by providing a region where control valve control and rotation speed control are performed simultaneously, it is possible to reliably prevent the overflow state of the condensate booster pump from occurring.

(Embodiment) The fourth embodiment of the present invention will be described below with reference to FIGS. 1 to 6. In the figure, the same parts as in FIGS. 7 and 8 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 2 is a diagram showing a condensing system of a steam turbine plant equipped with the deaerator level control device of the present invention, and the deaerator is equipped with a deaerator pressure detector 23. The pressure signal detected from the gas pressure detector 23 is manually input to the deaerator level control device 24 together with the condensate flow rate signal, the deaerator level signal, and the boiler feed water flow rate No. t3, and this deaerator level control is performed. The opening degree of the control valve 6 and the rotation speed of the condensate booster bomb 5 are controlled by the output signal from the device 24.

FIG. 1 is a diagram showing the purchase of the deaerator level control device 24, in which the required condensate flow rate signal q from the controller 20 is manually input to the overflow suppressor 25. The overflow suppressor 25 is also manually inputted with a pressure signal from a deaerator pressure regulator 23 and an operating number signal from a double water booster pump operating number detector 26 .

In the overflow suppressor 25, the system head curve of the condensate system corresponding to the pressure is determined by the pressure signal of the deaerator, and the overflow amount at each rotation speed is determined by the operating number signal of the condensate booster pump. A limit curve is determined. FIG. 3 is a diagram showing the system head curve and overflow restriction curve, in which the flow rate is thicker than the condensate flow rate Q corresponding to the area where the system head curve is above the overflow restriction curve, that is, the intersection of both curves. 0 is the non-overflow area, and the area smaller than Q is the overflow area, which determines whether or not the condensate booster bomb 6 will have an overflow when the required condensate flow rate is taken with the control valve fully open. It is possible to judge.

Therefore, in the above-mentioned overflow suppressor 25, when the required condensate flow rate is in the overflow range, the restriction valve is adjusted to the minimum necessary level to suppress the overflow of the condensate pump at the required condensate flow rate. The pressure loss ΔP1, that is, the pressure difference between the overflow limit curve at the position corresponding to the above-mentioned required condensate flow rate and the system head curve is determined, and the double water booster pump is rotated at the minimum rotation speed ``. In the case of 11n, the throttling pressure loss ΔP2 in the control valve necessary to ensure the condensate flow rate, that is, the pressure ■ line at the lowest rotation speed at the position corresponding to the above required salt water flow rate and the system head curve. The positive force difference between is found. And the above ΔP1
Overflow prevention control valve throttle pressure signals P1 and Δ corresponding to
Control valve throttle pressure signal P2 at the lowest rotation speed corresponding to P2
is manually input to the high value priority circuit 27. This high-fiff priority four-way 27 has 0 signals in addition to the above-mentioned signals P r and P 2.
(No. 4 P3 is also manually generated, and among these 1 items, the high r (=) or throttle pressure signal P is used as the control valve opening calculator
8 is input.

The control valve opening calculator 28 receives the required condensate flow rate signal q.
The control valve opening that produces the required throttle pressure loss at the required condensate flow rate is determined, and the control valve opening command signal V is applied to the control valve 6 to control the control valve. The opening degree of the valve 6 is controlled.

That is, in FIG. 3, when the required condensate flow rate is Q3, it is the lowest rotational speed range of the condensate booster bomb, and Δ
Control valve throttle pressure signal P at the lowest rotation speed corresponding to P2
2 is manually entered into the control valve opening degree calculation 2X28, and the control valve 6 is throttle-controlled accordingly. When the required condensate flow rate reaches Q2, the overflow prevention IL control valve throttle pressure (.7 P1) corresponding to ΔP1 is manually input to the control valve opening calculator 28, and the opening of the control valve 6 is controlled. Further, when the required condensate flow E becomes Q1, a 0 signal is manually input to the control valve opening degree calculator 28, and a throttle 0, that is, a full open signal is applied to the control valve 6, so that it is fully opened.

On the other hand, the required condensate flow rate signal q is determined by the first rotation speed calculator 2.
The second rotation speed calculator 30 is also manually operated.

The first rotation speed calculator 29 has a deaerator 23.
The pressure signal from the control valve is also input manually, and the rotation speed r (Fig. The number is input to the high value priority circuit 31. That is, in FIG. 3, the pump rotational speed r I:H1 corresponds to the pump rotation speed r I:H1 at a position corresponding to the required condensate drop of the system head curve by χ1 (number 20 is input to the high value priority circuit 31).

In addition, a signal for the number of operating rear water booster pumps is inputted to the second rotation speed calculator 30, and the rotation speed of the 1h water booster pump corresponding to the overflow limit value at each required water flow rate is rks, that is, as shown in FIG. Corresponds to the required salt water flow rate of the overflow limit curve in! The pump rotation speed rk at the pump is determined, and the rotation speed command signal is manually input to the high value priority circuit 31.

The minimum rotation speed signal of the condensate booster pump is also input to the high value priority circuit 31, and the high IirL priority circuit 31
From there, the high value signal among the above-mentioned rotational speed command signals and minimum rotational speed signals is outputted and manually inputted to the variable speed control device 15 of the double water booster bomb, and the rotational speed of the condensate booster pump is controlled by the variable speed control device. controlled.

By the way, in Fig. 3, the water flow rate is Q. Q
In the case of ``. . In the non-overflow area, a command signal corresponding to is output.

According to this embodiment, in a region where an overflow does not occur when the control valve is fully open (non-overflow region), the control valve is fully opened as the throttle differential pressure of the control valve is 0, and the condensate booster bomb is The required salt water flow rate is ensured by the rotation speed.

In addition, in the area where the flow rate is flowing when the control valve is fully open (overflow area), the control valve is designed to maintain the minimum pressure loss Δ necessary to prevent the salt water booster bomb from entering the overflow area.
The opening degree is set to P1, and the condensate booster bomb is operated at a rotational speed of eye W that can avoid excess flow due to the pressure loss ΔP1 caused by this control valve.

Further, in a flow rate range equal to or lower than the minimum rotation speed of the condensate booster pump, the condensate booster pump is operated by setting the rotation speed to a minimum of 1'i11 and throttling the control valve.

Therefore, the operating point of the condensate booster pump will be on the solid line in Figure 4, and as can be seen from Figure 4, the condensate booster pump will prevent overflow while preventing overflow. This is an operation method that maintains the minimum pressure loss necessary to achieve this on the control valve side, making it possible to control the level of the deaerator while preventing overflow over the entire variable speed range of the condensate pump. In addition, the pressure of the deaerator is detected and the system head curve of the condensate system at that point is determined.Based on this, the overflow area is determined and the control valve is throttled to prevent overflow. Since the differential pressure is calculated, the above function can always be performed e(H!j) even if the system head curve of the condensate system changes due to a change in the pressure of the deaerator.

FIG. 5 is a diagram showing another embodiment of the present invention, in which the first rotation speed calculator 29 of the first embodiment (FIG. 1) is replaced with the minimum rotation speed in the non-overflow region=1. A nasal organ 32 and a rotation speed bias calculator 33 are provided.

Minimum rotation speed in non-overflow region = 1 The calculator 32 indicates the minimum rotation speed of the salt water booster pump that can be operated with the control valve fully open in the non-overflow region, i.e., the rotation speed r in FIG. 3.

It determines the minimum number of rotations in the non-overflow area ``
The signal is manually input to an adder 34.

0 Further, the rotation speed bias calculator 33 calculates the increase in the rotation speed command due to the level of the required condensate flow rate signal q with respect to the minimum rotation speed in the non-overflow area, and this bias signal is applied to the adder 34 to Added to the minimum rotation speed in the non-overflow area. Then, the output signal from the adder 34 and the output signal from the second rotation speed calculator 30 are selectively switched by a switch 36 operated by the detection from the overflow area detector 35 (= sign). The high price priority circuit 31 is manually operated.

The overflow area detector 35 has an overflow limit +I-J! corresponding to the minimum throttle pressure loss ΔP1 in the four-node valve, which is essential for suppressing the overflow in response to the variable condensate flow rate. The J control valve throttle pressure signal P1 is manually input, and the overflow area detector 35 detects the control valve throttle pressure loss ΔP,> (if 1, the overflow area, Δ
If P,<O, it is determined as a non-overflow area and it is detected whether the overflow area is present. If the flow rate is in the overflow region, the switching valve 36 is operated to the illustrated position by the detection signal, and the output signal from the second rotary speed 51 controller 30, that is, the rotation speed corresponding to the pump rotation speed rk in FIG. A command signal is manually input to the high value priority circuit 31, and the rotation speed of the double water booster pump is controlled by the command signal.

On the other hand, when the overflow area detector 35 detects that the non-overflow area is present, the switch 36 is switched by the detection signal, and the minimum rotational speed of the non-overflow area is biased (a) corresponding to the required condensate flow rate. The output signal from the adder 34 is sent to the high value priority circuit 3 via the switch 36.
1, and the rotation speed of the condensate booster pump is controlled by that signal.

FIG. 6 is a diagram showing still another embodiment of the present invention.

That is, in FIG. 5, the throttle differential pressure ΔP of the control valve is determined in the high value priority circuit 27 based on the signal from the overflow suppressor 25, but if ΔP-0, that is, in the non-overflow region, the control valve is Calculation is performed using the control valve opening factor 28 so that the valve opening becomes 100%.

On the other hand, in the embodiment shown in FIG. 6, a switch 37 is provided on the output side of the control valve opening calculator 28 and is operated by a detection signal from an overflow area detector 35. There is.

When the overflow range detector 35 determines that the overflow is within the range, the control valve opening signal calculated by the control valve opening calculator 28 based on the throttle differential pressure ΔP is transmitted to the switch 37.
is applied to the control valve 6 through the control valve 6, and the degree thereof is controlled.

On the other hand, if it is determined that the flow is in the non-overflow region, the switch 37 is switched, and the 100% opening command signal set by the full opening setting device 38 is applied to the control valve via the switch 37.

Therefore, the two-length embodiments shown in FIGS. 5 and 6 also provide the same effects as the first embodiment.

〔Effect of the invention〕

Since the present invention is configured as described above,? h The level of the deaerator can be controlled without overflowing the condensate booster pump over the entire variable speed range of the water booster bomb. In addition, the amount of throttling loss of the control valve for preventing excess flow is reduced to the required minimum level, and in addition to being able to operate the condensate booster pump over the entire variable speed range, it is possible to reduce the in-house power by eight. Further, even if the system head curve of the condensate system changes due to a change in the pressure of the deaerator, it is possible to reliably prevent the condensate booster pump from entering the overflow region.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the purchase of the deaerator level control device of the present invention, Fig. 2 is a diagram showing the salt water system of a steam turbine plant using the deaerator level control device of the present invention, and Fig. 3 is a diagram showing the purchase of the deaerator level control device of the present invention. is an explanatory diagram showing the relationship between the system head curve, excessive flow restriction curve, etc., and FIG. 4 is an IS! operated by the control device according to the present invention! FIG. 5 and FIG. 6 are diagrams showing other embodiments of the present invention, respectively, and FIG. 7 is a diagram showing the condensing system and deaerator of a typical steam turbine plant. Figure 8 shows the configuration of a conventional deaerator level control device, and Figure 9 shows the operating point and variable speed of the condensate booster pump when operated by the conventional control device. FIG. 10 is an explanatory diagram showing the range restriction, and is an explanatory diagram of changes in the overflow area due to pressure fluctuations in the deaerator. 5... Condensate booster pump, 6... Control valve, 8...
・Deaerator water storage tank, 11...double water flow rate detector, 12
・・Level detector, 13・・Water supply flow rate indicator, 23・
... Deaerator pressure detector, 24 ... Deaerator level control device, 25 ... Overflow suppressor, 26 ... Operation number alarm device, 27.31 ... High value priority circuit, 28. ...Control valve opening calculator, 2...First rotation speed calculator, 30...
2nd rotational speed calculator, '32...Non-overflow area An (four-turn-kei 61 calculator, 33...rotational speed bias Ni 1 calculator, 3
5. Overflow area detector.

Claims (1)

[Scope of Claims] 1. A deaerator level control device that controls the level of a deaerator by a deaerator level control valve opening control device and a condensate booster pump rotation speed control device; The system head curve of the condensate system at that point is determined by the pressure of the deaerator, and the overflow limit curve at each rotation speed is determined by the number of condensate booster pumps in operation. An overflow suppressing device that determines whether the water flow rate is in the overflow range of the condensate booster pump and outputs the minimum necessary control valve throttle pressure signal in the overflow range to prevent the overflow. , the control valve opening degree is calculated based on the output signal from the overflow suppression device,
A control valve opening calculator that outputs a control valve opening command signal, and a rotation speed command signal output device that outputs a limit condensate booster pump rotation speed command signal that can prevent overflow when the control valve is in the throttle state. A deaerator level control device comprising: 2. When the condensate booster pump enters the overflow range, the overflow suppression device controls the minimum throttling pressure loss in the control valve necessary to prevent overflow and the minimum rotation speed of the condensate booster pump. It consists of an overflow suppressor that calculates the amount of throttle pressure loss in the control valve when The deaerator level control device according to claim 1, characterized in that: 3. The rotation speed command signal output device is a first controller that calculates the pump rotation speed corresponding to the excess flow limit value at the time of the requested condensate flow rate.
a pump rotation speed calculator, a second pump rotation speed calculator that calculates the pump rotation speed when securing the required condensate flow rate with the control valve fully open, and output signals from both pump rotation speed calculators. A deaerator level control device characterized by having a pump minimum rotation speed signal and a high value priority circuit that outputs a high value signal.