JPH11325404A - Chemical injection control device for power generation plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control chemical injection amount over a wide range from small to large amount, within a discharge amount range pump control accuracy of which is assured by a single pump. SOLUTION: Between the outlet side of a pump 16 for injecting ammonia and an ammonia injection point P, a bypass valve 45 for returning ammonia to a tank is provided. A minimum discharge amount which is assured for discharge amount control precision with the pump 16 is bypassed to the tank by the bypass valve 45, so that an ammonia equal to or more than the minimum discharge amount is discharged from the pump 16 at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical liquid injection control device of a power plant equipped with a condenser demineralizer (condensate desalination device), and more particularly, to a chemical liquid injection pump having two pumps.
The present invention relates to a chemical liquid injection control device capable of realizing the same chemical liquid injection control as in the case of two units, while reducing the number from one to one.

[0002]

2. Description of the Related Art At present, in a thermal power plant, an alkaline chemical is used as a water quality control agent (chemical solution) for preventing corrosion of a boiler system (that is, steam, condensate, water supply system). NH ₄ OH) is frequently used. The condenser demineralizer installed at the outlet of the condenser uses a cation resin and an anion resin as the ion exchange resin, and the ammonia used for pH adjustment depends on the cation resin. Since the entire amount is adsorbed, a new required amount of ammonia must be injected.

[0003] In order to reduce the amount of ammonia used, thermal power plants employ a system in which the ion-exchange resin does not regenerate even if it adsorbs 100% of ammonia, and continues to use it. For this purpose, a large-capacity pump and a small-capacity pump are equipped as ammonia injection pumps, and when the ion-exchange resin is performing an ion-exchange operation, a relatively large amount of ammonia is injected using a large-capacity pump to perform ion-exchange. When not working, the ammonia returns to the boiler together with the condensate, so the amount of injected ammonia is small. Injecting.

FIG. 3 is a diagram for explaining a control system for this conventional ammonia injection. Reference numeral 1 denotes a condensate pump installed on the outlet side of a condenser (not shown) for condensing boiler steam. 2 is a condenser demineralizer using an anion and cation ion exchange resin, which removes all electrolytes such as ammonia and other cations and anions, silica, etc. in the condensate water, and converts it into pure water (H ₂ O). It works by changing and returning to the boiler system again. 3 is a manual valve for bypassing the condenser demineralizer 2, 4 is a condensate booster pump, 5 is a low-pressure heater for heating condensate, 6 is a deaerator for removing dissolved gas in condensate, and 7 is a feedwater pump. , 8 is a high-pressure heater, 9 is an economizer (conserving device), and 10 is a boiler.

[0005] 11 is a conductivity meter for measuring the conductivity corresponding to the ammonia concentration of the liquid on the outlet side of the condenser demineralizer 2, and 12 is the conductivity corresponding to the ammonia concentration of the liquid on the outlet side of the condensate booster pump 4. Is a conductivity meter that measures. The measured value of the conductivity meter 12 is subtracted by a subtractor 13 from a predetermined set value A, and the deviation obtained therefrom is taken into a PI controller 14, and the output value of the PI controller 14 and the conductivity meter 11 are added by an adder 15 (actually, the measured value of the conductivity meter 11 is input in reverse polarity, and the PI controller 14
The measured value of the conductivity meter 11 is subtracted from the output signal of the pump 16) and input to the servo unit 16a of the large capacity pump 16 and the servo unit 17a of the small capacity pump 17, and the stroke length of the pumps 16 and 17 is adjusted. Is done.

[0006] The motor 16b of the large capacity pump 16 is controlled by an inverter 19 which receives a signal from a function unit 18 for calculating a predetermined function using the condensate flow signal as a parameter. These two pumps 16 and 17 are motors 16b and 1
The discharge amount H is determined by the rotation speed N and the stroke length L of 7b.
(= N · L). The rotation speed of the motor 17b of the small capacity pump 17 is fixed.

Therefore, the rotation speed of the large-capacity pump 16 is controlled in accordance with the condensed water flow rate, and the stroke length is controlled in accordance with the detected ammonia concentration. The amount of injected ammonia is controlled. The former is the main control, and the latter is the sub-control (correction control).
Only the stroke length of the small capacity pump 17 is controlled in accordance with the detected ammonia concentration, and similarly, the amount of ammonia injected into the injection point P is controlled. The large capacity pump 16 and the small capacity pump 17 operate alternatively.

Ammonia injection control is performed as follows. (1) When the condenser demineralizer 2 is performing the ammonia adsorption operation, 100% of the ammonia in the condensate is adsorbed there, so a large amount of ammonia needs to be injected. use. The control at this time is to control the rotation speed of the motor 16b in conjunction with the condensate flow rate, and to set the conductivity (measured value μS2 of the conductivity meter 12) on the outlet side of the condensate booster pump 4 and the set value A (= 6.
The stroke is controlled according to the difference of 5 μS). Thus, the ammonia injection control is performed so that the measured value of the conductivity meter 12 becomes μS2 = 6.5 μS. At this time,
Ammonia does not leak from the capacitor demineralizer 2, and the measured value μS1 of the conductivity meter 11 is almost 0.

(2) When the capacitor demineralizer 2 breaks due to the continuation of the above-mentioned adsorption operation (the ammonia adsorption capacity reaches the limit), ammonia gradually leaks out therefrom. Since the amount is measured as μS1 by the conductivity meter 11 and added to the adder 15 with the opposite polarity,
The output of the adder 15 decreases, and the stroke of the large capacity pump 16 decreases first.

That is, the leaked ammonia is eventually included in μS2 by the conductivity meter 12 and measured, and the control system works to reduce the amount of injected ammonia, but is detected as μS1 by the conductivity meter 11 at an earlier timing. Therefore, control is performed such that the injection amount of ammonia is reduced at a timing earlier than the original control performed by comparing μS2 with the set value A, and the control system is brought to the stable region at a faster timing.

(3) Thus, the large capacity pump 16
When the theoretical discharge amount (discharge amount determined solely by the stroke length and the number of revolutions) falls within the performance range of the small capacity pump 17, the control is switched from the large capacity pump 16 to the small capacity pump 17 by switching means (not shown), The pump 17 is operated. The discharge amount control of the small capacity pump 17 is performed solely by the stroke control only by the output signal of the adder 15.

(4) Thereafter, the capacitor demineralizer 2
Is regenerated and the operation is started, that is, when the regenerant (H ₂ SO ₄ and NaOH) is added to the ion exchange resin and the ammonia adsorption operation is started again, the measured value μS1 of the conductivity meter 11 is used.
Is controlled, so that the stroke of the small capacity pump 17 is increased in advance.

(5) Thus, the small capacity pump 17
Is within the performance range of the large capacity pump 16,
Switching from the small capacity pump 17 to the large capacity pump 16 is performed by switching means (not shown).

(6) When the large capacity pump 16 is operated, the condenser demineralizer 2 adsorbs 100% of ammonia.
The stroke length is controlled so that the rotation speed of the motor 16b is controlled in conjunction with the condensate flow rate, and the measured value of the conductivity meter 12 becomes the set value A.

[0015]

However, in the control system described above, two pumps of large capacity and small capacity are required, and four pumps are necessary including a spare. Further, since the ammonia concentration signal (conductivity measurement value μS1) at the outlet of the capacitor demineralizer 2 is added to the adder 15 downstream of the PI controller 14 in advance, quantitative correction cannot be performed.
Each time the value of P or I of the I controller 14 is adjusted, the correction value (the gain of the measured value μS1) must be corrected. Further, since the switching of the pumps 16 and 17 occurs, the bumpless switching measures (both pumps 16 and 17 at the time of switching) are required.
17), which causes a problem that the balance circuit of the control system becomes complicated.

The present invention has been made in view of the above points, and a first object of the present invention is to solve the above-mentioned problems by enabling control with a single pump. It is to improve the control performance.

[0017]

According to a first aspect of the present invention, there is provided a capacitor demineralizer, wherein a chemical is injected into a chemical injection point downstream of an outlet of the capacitor demineralizer. A power generation plant that detects the concentration of a chemical solution at the outlet side of a condensate booster pump or a low-pressure heater provided at a stage subsequent to the chemical solution injection point, compares the concentration with a set value, and controls the injection amount of the chemical solution according to the comparison result. In the chemical liquid injection control device, between the outlet side of the pump for injecting the chemical liquid and the chemical liquid injection point, the chemical liquid for a predetermined discharge amount within a range in which the discharge amount control accuracy of the pump is guaranteed is stored in the tank. A return bypass valve is provided so that the pump always discharges a predetermined amount or more of the liquid medicine from the pump.

According to a second aspect of the present invention, there is provided a condenser demineralizer, wherein a chemical is injected into a chemical injection point downstream of the outlet side of the condenser demineralizer, and a condensate booster pump provided downstream of the chemical injection point. Alternatively, the concentration of the chemical solution at the outlet side of the low-pressure heater is detected and compared with a set value, and the chemical solution injection control device of the power generation plant that controls the injection amount of the chemical solution according to the comparison result. The detection signal of the chemical concentration on the side is delayed by the passage time of the condensate booster pump or by the passage time of this and the low-pressure heater,
A signal obtained by subtracting the delay signal from the detection signal of the chemical concentration at the outlet side of the condensing booster pump or the low-pressure heater, and adding the detection signal of the chemical concentration at the outlet side of the capacitor demineralizer to the subtracted signal, It was configured to compare with the set value.

According to a third aspect, in the first or second aspect, the pump is a reciprocating pump, a stroke of the reciprocating pump is controlled in accordance with the comparison result, and a return flow to the condenser demineralizer is controlled. A chemical solution injection control device for a power plant that controls a rotation speed of the reciprocating pump according to a water flow rate to control an injection amount of the chemical solution, wherein the rotation speed of the reciprocating pump is compared with the condensate flow rate. It was configured to control according to the result.

According to a fourth aspect, in the first or second aspect, the pump is a reciprocating pump, the stroke of the reciprocating pump is controlled according to the comparison result, and the pump flowing into the capacitor demineralizer is controlled. A chemical liquid injection control device for a power plant that controls the rotation speed of the reciprocating pump according to the water flow rate to control the injection amount of the chemical liquid. The control is also performed in accordance with the concentration of the chemical solution on the outlet side of the nebulizer.

According to a fifth aspect of the present invention, in the first or second aspect, the pump is a reciprocating pump, the stroke of the reciprocating pump is controlled in accordance with the result of the comparison, and the pump flowing into the capacitor demineralizer is controlled. Controlling the number of rotations of the reciprocating pump according to the flow rate of water, a chemical solution injection control device for a power plant that controls the amount of the chemical solution injected, the number of rotations of the reciprocating pump, the outlet of the condenser demineralizer When the concentration of the chemical solution on the side exceeds a predetermined value, the rotation speed is switched to a fixed rotation speed.

[0022]

FIG. 1 is a diagram showing the configuration of a control system for ammonia injection according to one embodiment of the present invention.
The same components as those shown in FIG. 3 are denoted by the same reference numerals. In this embodiment, only the large capacity pump 16 is used as the pump. In addition, a condenser (condenser) 31 is provided at a stage preceding the condenser pump 1. Reference numeral 32 denotes a conductivity meter for measuring the conductivity μS3 of the liquid in the condenser 31.

The ammonia type condenser demineralizer 2 allows the ammonia ions in the condensate to pass therethrough, but is about five times (1 times as large as the H type condenser demineralizer).
(For about a month), the number of times of regeneration, the amount of regeneration waste, and the amount of water for regeneration are low, the running cost is low, and the amount of ammonia injection for increasing PH is small.

In the present embodiment, the conductivity μS 3 measured by the conductivity meter 32 and the conductivity μS 1 measured by the conductivity meter 11 are compared and detected by the monitor 33, and the operating state of the capacitor demineralizer 2 is determined. Is determined. That is, μS3 >> μS1... Capacitor demineralizer 2
Is operating μS3> μS1 ... Capacitor demineralizer 2
Is running and a break has begun.

ΜS3 = μS1... The capacitor demineralizer 2 completely breaks. Is determined.

When μS3 = μS1, since the condenser demineralizer 2 has a 100% break, the control of the motor 16b of the large capacity pump 16 according to the condensed water flow rate is started.
Switch to fixed speed control. That is, the switch setting unit 34 is switched from the path b → c to the path a → c based on the detection result of the monitor 33 at this time, and the fixed rotation speed set value C is input to the adder 35. Thus, when the capacitor demineralizer 2 breaks 100%, the amount of injected ammonia is independent of the condensate flow rate, and is controlled exclusively according to the detected ammonia concentration, as described later.

Further, in the present embodiment, a function unit 36 that takes in the conductivity μS1 measured by the conductivity meter 11 as a parameter and performs a predetermined function operation is installed in the rotation speed control system of the motor of the pump 16; Based on the output of the function unit 36, the output of the function unit 18 that takes in the condensate flow rate as a parameter and performs a predetermined operation is divided by a division circuit 37.

This means that it is necessary to control the rotational speed command signal by the calculator 18 which calculates the condensate flow rate as a parameter in inverse proportion to the value of the conductivity μS 1 on the outlet side of the condenser demineralizer 2. Because.

That is, the capacitor demineralizer 2
When working as an ammonia type, since a large amount of ammonia flows in from the condenser 31, it is necessary to reduce the number of rotations of the pump 16 for injecting the ammonia to reduce the amount of the injection. When this occurs, the ammonia does not flow out much from the condenser demineralizer 2, so the rotational speed of the pump 16 must be increased to increase the ammonia injection amount. Therefore, when the measured value μS1 is small, the motor 16
The control is performed such that the rotation speed of b is increased, and the rotation speed is decreased when the rotation speed is large. This control is performed in advance in accordance with the measurement value μS1, and responds at a timing earlier than the normal control for controlling the stroke length.

In the present embodiment, the measured value μS 1 of the conductivity meter 11 is delayed by the delay circuit 38, added to a subtractor 39 for subtracting the measured value μS 2 of the conductivity meter 12, and further subtracted. The measured value μS1 is added to the output of the calculator 39 by the adder 40.

In this control system, μS2−μS1 + μS1 = μS2 (1) in the static state, which seems to be meaningless, but since the process has a time delay, it is excessively effective as quantitative preliminary control. .

That is, when μS1 increases at a certain point in time, μS1 increases after a time delay t by the condensate booster pump 4.
2 is input. Therefore, the delay circuit 38
If the delay time at is set to the time t described above, μS
Preliminary control by μS1 applied to the adder 40 is performed while minimizing the variation of μS2 due to 1, and the stable region is controlled early. At this time, as is apparent from the above equation (1), the problem of the error described in the conventional example does not occur.

FIG. 2 is a diagram for explaining this. When this control is not performed, as shown in FIG. 2A, the time after the measured value μS1 on the outlet side of the capacitor demineralizer 2 fluctuates. After t, μS2 fluctuates, and this directly becomes a disturbance to be input to the subtractor 13. However, by performing the above-described closed loop control, μS1 increases and the injection amount decreases at the same time. , ΜS2 are suppressed to the minimum fluctuation.

In this embodiment, the large-capacity pump 1
The control range of the small capacity pump is also finely controlled by one of the six units. A multiplier 41 multiplies the stroke length signal ST extracted from the servo unit 16a of the large capacity pump 16 by the rotation speed signal TG extracted from the motor 16b, and a pump discharge amount (ST ·
TG) is the minimum discharge amount set value B of the pump 16 (= 7)
%) Is compared with the subtractor 42, and the difference is input to the PI controller 43. The output of the PI controller 43 is input to a control circuit 44 to control the opening of a bypass valve 45 that returns the ammonia discharged from the pump 16 to an ammonia tank (not shown) again.

The basis for setting the minimum discharge amount of the pump 16 to 7% is that when the pump rotation speed becomes 25% or less and the stroke length becomes 25% or less, the theoretical discharge amount and the actual discharge amount become inconsistent, and the discharge amount becomes small. Since it is difficult to ensure the accuracy within a predetermined range, the value is set to 7% from 0.25 × 0.25 = 0.0625. Theoretically, it may be set to a range where the discharge amount control accuracy can be secured, in this case, 6.25% or more.

In this way, the bypass valve 45 is controlled to return 7% of the discharge amount of the pump 16 to the ammonia tank. As a result, the pump 16
Is controlled so as to be at least 7% or more of the maximum discharge capacity of the pump, and even when the injection amount of ammonia becomes small, the pump 16 operates at a large discharge amount with guaranteed accuracy.

It should be noted that the pump 16 always has the subtractor 13
It is sufficient to perform the stroke control by the output of the PI controller 14 so that the measured value μS2 input to the controller becomes the set value A = 6.5 μS.
In some cases, the fluctuation range of the condensate flow rate may be large due to the level control or manual control.
The output of the arithmetic unit 46 that performs a predetermined operation using the output of the controller 14 as a parameter is added to the output of the
The number of revolutions is also controlled by the signal added in step (1).

In each of the above cases, when the measured value μS2 is larger than the set value A = 6.5 μS, the pump 16
Is controlled so as to decrease the discharge amount of the pump 16. In this case as well, the discharge amount is controlled to be 7% or more of the capacity of the pump 16, and 7% of the discharge amount is returned from the bypass valve 45 to the ammonia tank. The amount obtained by subtracting this is injected into the injection point P. For example, when the ammonia injection amount is 0, the discharge amount of the pump 16 is 7% of the capacity, and the entire amount is returned to the ammonia tank by the bypass valve 45.

In the above description, the measured value μS 2 is a value obtained by measuring the liquid on the outlet side of the condensate booster pump 4, but may be a value obtained by measuring the liquid on the outlet side of the low-pressure heater 5. At this time, the delay time t of the delay circuit 38 is set to the time required for the liquid to pass through the condensate booster pump 4 and the low-pressure heater 5.

In the above, the case where ammonia is used as the chemical has been described. However, it is needless to say that the same control can be performed when other chemicals such as caustic soda water or the like are injected.

[0041]

As described above, according to the first aspect of the present invention, a single pump can control a wide range of chemical injection from a small amount to a large amount within a discharge amount range in which the control accuracy of the pump is guaranteed. As compared with the case of using a large-capacity pump and a small-capacity pump, the cost can be reduced without deteriorating the control performance, and further, a bumpless switching measure is not required.

According to the second aspect of the invention, even if the concentration of the detected chemical solution fluctuates rapidly, the detected chemical solution concentration is followed by
It is possible to smoothly control the injection amount of the chemical solution without involving disturbing behavior, and there is no need for correction.

According to the third aspect of the present invention, the rotation speed of the reciprocating pump is controlled not only by the condensed water flow rate but also by a signal for stroke control. Injection control can be performed on the liquid.

According to the fourth aspect of the present invention, the control of the number of revolutions of the reciprocating pump is controlled not only by the condensate flow rate but also by the concentration of the chemical solution at the outlet side of the condenser demineralizer.

According to the fifth aspect of the present invention, when the concentration of the chemical solution exceeds a predetermined value, the number of revolutions of the reciprocating pump is switched to a fixed value, so that the injection amount of the chemical solution is controlled solely by the chemical concentration alone, not by the condensate flow rate. As a result, the control performance of the fine and small amount of chemical liquid injection amount control is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ammonia injection control system according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram of control at the time of a sudden change in ammonia concentration.

FIG. 3 is a block diagram showing a configuration of a conventional ammonia injection control system.

[Explanation of symbols]

1: condensate pump, 2: condenser demineralizer, 3: manual valve, 4: condensate booster pump, 5: low pressure heater, 6:
Deaerator, 7: Feed water pump, 8: High pressure heater, 9: Economizer, 10: Boiler, 11, 12: Conductivity meter, 13:
Subtractor, 14: PI controller, 15: adder, 16: large capacity reciprocating pump, 16a: servo unit, 16b:
Motor, 17: small capacity reciprocating pump, 17a: servo unit, 17b: motor, 18: function unit, 19: inverter, 31: condenser, 32: conductivity meter, 33: monitor, 34: switching controller, 35 : Adder, 36: function unit,
37: divider, 38: delay circuit, 39: subtractor, 40:
Adder, 41: multiplier, 42: subtractor, 43: PI controller, 44: control circuit, 45: bypass valve, 46: function unit.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryuzo Yabe 3-3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Inside Kansai Electric Power Company (72) Inventor Tetsuro Iwamoto 3-chome Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture 22 Kansai Electric Power Co., Inc. (72) Hiroteru Kamata 3-2-2 Nakanoshima, Kita-ku, Osaka, Osaka Prefecture Kansai Electric Power Co., Inc. (72) Kazuo Nishida 3-chome, Nakanoshima, Kita-ku, Osaka, Osaka No.3-22 Kansai Electric Power Co., Inc. (72) Genhisa Kitazawa 4-1-1, Kitahama, Chuo-ku, Osaka-shi, Osaka Prefecture Inside Nikkiso Co., Ltd.Osaka Branch (72) Masahiro Suzuki Kitahama, Chuo-ku, Osaka-shi 4-1-2-1, Nikkiso Co., Ltd. Osaka Branch (72) Inventor Tsutomu Kaneko 4-1-1, Kitahama, Chuo-ku, Osaka-shi, Osaka Nikkiso Co., Ltd. Osaka Branch

Claims (5)

[Claims] A condenser demineralizer, wherein a chemical is injected into a chemical injection point downstream of an outlet side of the condenser demineralizer, and a condensate booster pump or a low-pressure heater provided downstream of the chemical injection point. In a chemical liquid injection control device of a power generation plant, which detects the concentration of the liquid chemical at the outlet side and compares it with a set value, and controls the injection amount of the liquid chemical according to the comparison result, the outlet side of a pump for injecting the liquid chemical A bypass valve is provided between the pump and the chemical solution injection point to return a predetermined amount of the chemical solution to the tank within a range in which the discharge amount control accuracy of the pump is guaranteed. A chemical liquid injection control device for a power plant, wherein a chemical liquid is discharged. 2. A condenser demineralizer, wherein a chemical is injected into a chemical injection point downstream of an outlet side of the condenser demineralizer, and a condensate booster pump or a low-pressure heater provided downstream of the chemical injection point is provided. In the chemical liquid injection control device of the power generation plant, which detects the concentration of the liquid chemical at the outlet side and compares it with a set value, and controls the injection amount of the liquid chemical according to the comparison result, the concentration of the liquid chemical at the outlet side of the condenser demineralizer The detection signal is delayed by the passage time of the condensing booster pump or by the passage time of the low pressure heater, and the delay signal is subtracted from the detection signal of the chemical concentration at the outlet side of the condensing booster pump or the low pressure heater. A signal obtained by adding a detection signal of the concentration of the chemical solution at the outlet side of the capacitor demineralizer to the subtracted signal is compared with the set value. Liquid injection control device. 3. A reciprocating pump, wherein a stroke of the reciprocating pump is controlled in accordance with the comparison result, and a rotation speed of the reciprocating pump is controlled in accordance with a condensate flow rate flowing into the condenser demineralizer. do it,
A chemical solution injection control device for a power plant that controls an injection amount of the chemical solution, wherein a rotation speed of the reciprocating pump is controlled in accordance with the comparison result together with the condensate flow rate. Item 3. The chemical liquid injection control device for a power plant according to Item 1 or 2. 4. A reciprocating pump, wherein a stroke of the reciprocating pump is controlled according to the comparison result, and a rotation speed of the reciprocating pump is controlled according to a condensate flow rate flowing into the condenser demineralizer. do it,
A chemical injection control device for a power plant that controls an injection amount of the chemical, wherein the number of rotations of the reciprocating pump is controlled in accordance with the chemical concentration at the outlet side of the condenser demineralizer together with the condensate flow rate. 3. The method according to claim 1, wherein
3. The chemical injection control device for a power plant according to claim 1. 5. A reciprocating pump, wherein a stroke of the reciprocating pump is controlled according to the comparison result, and a rotation speed of the reciprocating pump is controlled according to a condensate flow rate flowing into the condenser demineralizer. do it,
A chemical solution injection control device for a power plant that controls the injection amount of the chemical solution, wherein the number of rotations of the reciprocating pump is changed to a fixed number of rotations when the concentration of the chemical solution on the outlet side of the condenser demineralizer exceeds a predetermined value. The chemical liquid injection control device for a power plant according to claim 1 or 2, wherein the control is performed.