JPH11182806A - Method and device for monitoring flow rate of auxiliary steam of boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To permit the stabilized auxiliary steam flow rate monitoring by a method wherein the flow rate of the auxiliary steam is measured accurately even when the flow rate of the same is reduced. SOLUTION: The flow rate of steam is monitored by a method wherein a measured steam flow rate 42 is obtained by an orifice pressure difference 18a in a pressure difference meter 18 to output the same amount 42 to a flow rate indicating meter 35 upon normal time while a steam flow rate calculated value 51 is operated based on a Cv value 46 based on the opening degree 37 of a valve for a pressure regulating valve 17, which is detected by a positioner 38 provided in the pressure regulating valve 17, the primary side steam pressure 39 of the pressure regulating valve 17 and a coefficient 50 to output the result into the flow rate indicating meter 35 when the steam flow rate 42, measured by the orifice pressure difference 18a, is reduced to a value lower than a limit point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for monitoring the flow rate of auxiliary steam in a boiler.

[0002]

2. Description of the Related Art Generally, when starting a boiler whose operation is stopped, a deaerator of the boiler itself to be started, a steam trace (for warming oil or the like), an oil spray of a burner, a gas heater, Auxiliary steam required for various devices such as a turbine gland seal must be introduced from a steam source such as another boiler. After the boiler is started, another auxiliary boiler can be supplied when the auxiliary steam becomes self-sufficient. The auxiliary steam from such a steam source is switched to the auxiliary steam from the activated boiler itself.

FIG. 4 shows an example of a conventional method for monitoring the auxiliary steam flow rate of a coal-fired boiler. In the figure, reference numeral 1 denotes a boiler furnace, and 2 denotes a economizer provided in a rear heat transfer section of the furnace 1. ,
3 is a steam separator, 4, 5 and 6 are superheaters, 7 is a steam turbine, 8 is a deaerator for deaeration from water supplied to the furnace 1 of the boiler, and 9 is a deaerator 8 A water supply pump for pressure-feeding degassed water, 10 is a water supply heater, 11 is a deaerator 8 or a steam trace (for warming oil or the like) (not shown), an oil spray of a burner, a gas heater, a turbine gland seal. Auxiliary steam header connected to various devices such as a supply pipe 12 and the like. The auxiliary steam header 11 has a part of the steam from a required position of a superheater communication pipe 13 connecting the superheaters 4 and 5. Auxiliary steam take-out device 30 in which is introduced as auxiliary steam through auxiliary steam take-out pipe 14
And an auxiliary steam introduction device 31 configured to introduce auxiliary steam from the steam source such as another boiler to the auxiliary steam header 11 by the connecting pipe 15. In the middle of the supply pipe 12, an auxiliary steam pressure regulating valve 19 for heating the deaerator is provided.

A superheater connecting pipe 20 connecting the superheaters 5 and 6 is connected to a condenser (not shown) and has a S
A discharge pipe 22 provided with a valve (superheater bypass valve) 21 is connected, and a communication pipe 23 connecting the superheater 6 and the steam turbine 7 is connected to a condenser (not shown) and has a U
Discharge pipe 25 provided with valve (turbine bypass valve) 24
Is connected. 26 is a steam-water separation drain tank, 27
Is a recirculation pump, 28 is a Q valve (recirculation flow control valve), 2
Reference numeral 9 denotes a valve for extracting air to the deaerator 8.

The own auxiliary steam extracting device 30 includes a steam extracting valve (open / close valve) 16 provided in the middle of the auxiliary steam extracting pipe 14.
, A pressure control valve 17, a pressure transmitter PX for detecting the pressure of the auxiliary steam header 11, and an auxiliary for inputting a pressure signal P from the pressure transmitter PX and controlling the pressure control valve 17 by a control signal 32. A steam pressure control device 33 and a differential pressure gauge 1 for measuring and monitoring the auxiliary steam flow rate by the orifice differential pressure
8 and the orifice differential pressure 18a detected by the differential pressure gauge 18.
A function generator 43 for obtaining a measured steam flow rate 42 from the temperature generator TE and a temperature transmitter TE provided in the auxiliary steam header 11 for correcting the measured steam flow rate 42 from the function generator 43 with the steam temperature.
A temperature correction calculator 34 for correcting the measured steam flow rate 42 based on the temperature signal T from the temperature transmitter TE, and a flow indicator 35 for calculating and displaying the calculation result from the temperature correction calculator 34. It has.

The auxiliary steam introducing device 31 has the same configuration as that of the auxiliary steam extracting device 30 as shown by adding a dash (') to the reference numeral of the configuration of the auxiliary steam extracting device 30.

[0007] When the boiler is started from the operation stop state, its own steam has not yet been generated, so the steam extraction valve 16 and the pressure regulating valve 17 of the own auxiliary steam extraction device 30 are closed.

Accordingly, when the boiler is started, auxiliary steam from another boiler or the like is supplied via the auxiliary steam header 11 to the deaerator 8, a steam trace (not shown), an oil spray for a burner, a gas heater, a turbine ground seal. Are supplied via the supply pipe 12 and the like.

[0009] The flow rate of the auxiliary steam used at the initial stage when the boiler is started is large, for example, 120 tons / H.

On the other hand, when the boiler is started and the fuel is switched from heavy oil or light oil to coal, and steam is stably generated from its own boiler, the steam extraction valve 16 'is closed by a control command to introduce auxiliary steam. The introduction of auxiliary steam from another steam source such as a boiler by the device 31 is stopped, and at the same time, the steam extraction valve 16 and the pressure regulating valve 17
By opening the auxiliary steam, the own auxiliary steam from the boiler is introduced into the auxiliary steam header 11 by the own auxiliary steam extracting device 30.

As described above, switching is performed by the own auxiliary steam extracting device 30 using the own generated steam from the boiler as the auxiliary steam, and thereafter, when the boiler is operated at the set load, the above-mentioned 120 tons / H is applied. A large amount of auxiliary steam is required to be reduced to about several tens of tons / H, and the amount of auxiliary steam is required to be reduced to several tons / H during steady operation of the boiler, for example, only steam tracing is required. I will be.

At this time, the auxiliary steam extraction pipe 14 and the communication pipe 1
Differential pressure gauge 1 for measuring the flow rate of auxiliary steam flowing through
'As for, the difference pressure gauge 18, 18' 8,18 relationship orifice differential pressure 18a detected by a 18a 'and the measured steam flow 42 is represented by a function Fx ₁ as shown in FIG. 5, the orifice There is a limit point at which the steam flow rate cannot be measured when the differential pressures 18a and 18a 'become extremely small.

That is, as described above, when the steam flow rate is reduced from 120 tons / H to about 1/100 such as several tons / H, the orifice differential pressure having a squared relationship with the steam flow rate is reduced to 1/10000. Since the pressure decreases, an extremely high accuracy is required. However, the orifice differential pressure cannot be detected with such an extremely high accuracy. Exists.

[0014]

Accordingly, when the auxiliary steam is introduced from a steam source such as another boiler through the connecting pipe 15 of the auxiliary steam introduction device 31 as in the initial stage of the above-described boiler startup, , 120 tons / H, the differential pressure gauge 18, 18 '
8a and 18a 'can be detected with high accuracy, and thus the measured steam flow rate 42 can be measured with high accuracy, and the amount of auxiliary steam introduced can be controlled with high accuracy.

However, when the steam of the boiler is introduced as auxiliary steam on its own by the auxiliary steam extracting pipe 14 of the auxiliary steam extracting device 30, the amount of auxiliary steam used gradually decreases, and eventually, The flow rate becomes as small as several tons / H, so that the orifice differential pressure 18a detected by the differential pressure gauge 18 becomes lower than the limit point in FIG. As a result, when the auxiliary steam is controlled to a small value such as several tons / H, there arises a problem that although the auxiliary steam is supposed to be flowing, it is not actually flowing. I was

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides an auxiliary steam flow monitor for a boiler which can accurately measure the flow rate of the auxiliary steam even when the flow rate of the auxiliary steam is small and can stably monitor the flow rate of the auxiliary steam. It is intended to provide a method and apparatus.

[0017]

According to the present invention, in the initial stage of starting a boiler, steam from another steam source is introduced into an auxiliary steam header by an auxiliary steam introduction device. A part of the own steam is supplied to the auxiliary steam header by the own auxiliary steam extraction device equipped with a steam extraction valve, a pressure regulating valve, and a differential pressure gauge for obtaining the measured steam flow rate by the orifice differential pressure and outputting it to the flow indicator. An auxiliary steam flow monitoring method for a boiler in which the auxiliary steam is taken out and supplied by itself, and a pressure regulating valve is controlled by an auxiliary steam pressure control device so that the pressure of the auxiliary steam header becomes constant. When the measured steam flow rate due to the pressure falls below the limit point, the Cv value based on the valve opening of the pressure regulating valve detected by the positioner provided in the pressure regulating valve and the primary steam of the pressure regulating valve. Those of the auxiliary steam flow rate monitoring method, of the boiler, characterized by monitoring the steam flow rate by outputting to the flow indicator by calculating the steam flow rate calculation value based on the force and the coefficient.

Further, the steam of the boiler is introduced into the auxiliary steam header by itself as auxiliary steam by a self-supporting auxiliary steam extracting device in which a steam extracting valve, a pressure regulating valve, and a differential pressure gauge are arranged in the auxiliary steam extracting pipe. An auxiliary steam flow monitoring device for a boiler comprising an auxiliary steam pressure controller for controlling the pressure regulating valve so as to keep the pressure of a pressure transmitter for detecting the pressure of the header constant, wherein the valve of the pressure regulating valve is provided. A positioner that detects the opening degree, a pressure gauge that detects the primary steam pressure of the pressure regulating valve, a first function generator that outputs a measured steam flow rate based on the orifice differential pressure of the differential pressure gauge to the flow indicator, A second function generator for obtaining a Cv value of the pressure regulating valve based on the valve opening detected by the positioner, and multiplying a Cv value from the second function generator by a primary steam pressure from the pressure gauge; Multiplier A multiplier for obtaining a calculated steam flow value by multiplying a calculation signal from the multiplier by a coefficient, and a switching signal when the measured steam flow is input and the measured steam flow becomes equal to or less than a specified flow value. A switching indicator to be output, the measured steam flow rate and the calculated steam flow rate are input and the measured steam flow rate is output to the flow rate indicator at normal times, and a switching instruction is issued when the measured steam flow rate falls below a specified flow rate value. The present invention relates to an auxiliary steam flow monitoring device for a boiler, comprising: a switching device that switches so as to output a steam flow calculation value to a flow indicator according to a switching signal from a steam generator.

According to the above means, the operation is as follows.

Normally, the flow rate is monitored based on the measured steam flow rate based on the orifice differential pressure of the flow rate transmitter. When the flow rate of the auxiliary steam introduced into the auxiliary steam header decreases, the flow rate is monitored based on the orifice differential pressure of the differential pressure gauge. If the situation cannot be detected with the measured steam flow rate, the flow rate is automatically monitored by the steam flow rate calculated based on the valve opening detected by the positioner and the steam pressure and coefficient from the pressure gauge. Since the switching is performed periodically, even when the flow rate of the auxiliary steam is small, the flow rate of the auxiliary steam can be measured with high accuracy, and thus, the flow rate monitoring with high accuracy can be performed over the entire operation range.

[0021]

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

FIG. 1 shows an example of an embodiment of the present invention. In the figure, portions denoted by the same reference numerals as those in FIG. 4 represent the same components. As shown in FIG. 1, the present embodiment is characterized in that the valve opening 37 of the pressure regulating valve 17 of the auxiliary steam extraction device 30 is detected and the valve opening 37 is used as a flow rate. Arithmetic unit 36
And a pressure gauge 40 for detecting the pressure of the primary side of the pressure regulating valve 17, for example, the gas-water separation drain tank 26, and inputting the primary-side steam pressure 39 to the flow rate calculator 36. ing. Even if the opening of the pressure regulating valve 17 is constant, if the pressure of the auxiliary steam changes, the flow rate of the auxiliary steam changes.
Is input to the flow rate calculator 36. The flow rate calculator 36 has a steam extraction valve 16.
Open / close signal 41 is input.

FIG. 2 shows the flow rate calculator 36 in FIG.
FIG. 3 is a block diagram showing the circuit configuration of the flow rate calculator 36;
Inputs the orifice differential pressure 18a from the differential pressure gauge 18, the provided first function generator 43 which outputs a measured steam flow 42 by the function Fx ₁ in FIG. 5, measuring the steam flow from The function generator 43 Reference numeral 42 is displayed on the flow indicator 35 via the multiplier 44 and the switch 45.

The C of the pressure regulating valve 17 is determined based on the valve opening 37 of the pressure regulating valve 17 detected by the positioner 38.
A second function generator 47 for obtaining the v value 46 is provided. Second
A function Fx ₂ as shown in FIG. 3 is input to the function generator 47, and the function generator 47 can accurately obtain the Cv value 46 of the pressure regulating valve 17 based on the valve opening 37 detected by the positioner 38. it can.

The Cv value 4 from the second function generator 47
6 and a primary steam pressure 39 from the pressure gauge 40, a multiplier 48 is provided, and a calculation signal 49 from the multiplier 48 is multiplied by a coefficient 50 to obtain a steam flow calculation value 51. The multiplier 52 is provided.
The calculation value 51 of the steam flow from 2 is input to the switch 45 via the multiplier 53 and the switch 54. Reference numeral 54 denotes a switch which outputs the calculated steam flow value 51 as a signal of "0" when the open / close signal 41 of the steam extraction valve 16 is closed.

Since the apparent flow rate increases due to the increase in volume of the steam when the temperature rises, a function for generating a gain G by inputting a temperature signal T from the temperature transmitter TE in order to correct the flow rate. A generator 55 is provided, and the gain G from the function generator 55 is input to the multipliers 44 and 53 to be multiplied to thereby correct the temperature of the measured steam flow rate 42 and the calculated steam flow rate 51. .

Further, the measured steam flow rate 42 from the multiplier 44 is input, and the measured steam flow rate 42
A switching indicator 56 for outputting a switching signal 56a when the switching signal 56a falls below is provided.
According to a, the switch 45 is switched so as to output the calculated steam flow value 51 to the flow indicator 35.

Next, the operation of the above embodiment will be described.

The auxiliary steam pressure control device 33 controls the opening of the pressure regulating valve 17 by the control signal 32 so that the pressure signal P from the pressure transmitter PX becomes a set constant pressure.

On the other hand, by the orifice differential pressure 18a detected by the differential pressure gauge 18 is input to the first function generator 43, is measured steam flow 42 by the function Fx ₁ in FIG. 5 is determined.

Further, the valve opening 37 of the pressure regulating valve 17 detected by the positioner 38, by being input to the second function generator 47, Cv by the function Fx ₂ in FIG. 3
A value 46 is obtained, and the Cv value 46 and the primary steam pressure 39 from the pressure gauge 40 are multiplied by a multiplier 48 to obtain an operation signal 49. Further, the operation signal 49 is multiplied by a multiplier 52 by a multiplier 52. Is multiplied to obtain a steam flow rate calculation value 51. At this time, the Cv value 46 is Cv,
If the primary steam pressure 39 is P ₁ , the coefficient is K, and the calculated steam flow value 51 is F, the calculated steam flow value 51 can be obtained from F = Cv × P ₁ × K. The calculated steam flow value 51 thus obtained has high accuracy and reliability.

Further, at this time, since the temperature signal T from the temperature transmitter TE is input to the function generator 55,
The gain G from the function generator 55 is multiplied by the measured steam flow rate 42 and the calculated steam flow rate 51 via the multipliers 44 and 53, and the temperature of the measured steam flow rate 42 and the calculated steam flow rate 51 is corrected. A more accurate steam flow calculation value 51 can be obtained.

At the normal time when the flow rate of the auxiliary steam introduced into the auxiliary steam header 11 is relatively large, the switch 45 is switched to the a side, and the measured steam flow rate 42 from the first function generator 43 remains unchanged. The flow rate is output and displayed on the flow rate indicator 35, and the flow rate can be monitored based on the measured steam flow rate 42.

On the other hand, when the boiler enters a steady operation state, the flow rate of the auxiliary steam introduced into the auxiliary steam header 11 decreases, for example, to several tons / H, and the flow rate of the measured steam from the first function generator 43 is reduced. When 42 becomes smaller than the specified flow rate value S set in the switching indicator 56, the switching device 45
6 is switched to the b-side by a switching signal 56a, whereby the calculated steam flow value 51 from the multiplier 52 is output to and displayed on the flow indicator 35 so that the flow rate is monitored based on the calculated steam flow value 51. Become.

As described above, normally, the flow rate is monitored by the measured steam flow rate 42 based on the orifice differential pressure 18a of the differential pressure gauge 18, and the flow rate of the auxiliary steam introduced into the auxiliary steam header 11 is reduced. If a situation cannot be detected with the measured steam flow rate 42 based on the orifice differential pressure 18 a of the differential pressure gauge 18, the valve opening 37 detected by the positioner 38 and the primary steam pressure 39 from the pressure gauge 40.
Steam flow rate calculation value 51 calculated based on and coefficient 50
Automatic switching is performed so that the flow rate of the auxiliary steam can be accurately measured even when the flow rate of the auxiliary steam is low, and thus the flow rate can be monitored with high accuracy. Becomes possible over the entire operation area.

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

[0037]

As described above, according to the method and apparatus for monitoring the auxiliary steam flow rate of the boiler according to the present invention, the flow rate is normally monitored by the measured steam flow rate based on the orifice differential pressure of the flow rate transmitter. When the flow rate of the auxiliary steam introduced into the steam header decreases and the steam flow rate cannot be detected by the measured steam flow rate based on the orifice differential pressure of the differential pressure gauge, the valve opening detected by the positioner and the steam from the pressure gauge are detected. Automatic switching is performed so that the flow rate is monitored based on the calculated steam flow rate calculated based on the pressure and the coefficient. It is possible to obtain an excellent effect that the measurement can be performed well, and the flow rate can be monitored with high accuracy over the entire operation range.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of an embodiment of the present invention.

FIG. 2 is a block diagram of a self-supporting auxiliary steam extracting device in FIG.

FIG. 3 is a function diagram showing a relationship between a valve opening and a Cv value.

FIG. 4 is a block diagram illustrating an example of a conventional device.

FIG. 5 is a function diagram showing a relationship between a measured steam flow rate and an orifice differential pressure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Auxiliary steam header 14 Auxiliary steam extraction pipe 16 Steam extraction valve 17 Pressure regulation valve 18 Differential pressure gauge 18a Orifice differential pressure 30 Own auxiliary steam extraction device 31 Auxiliary steam introduction device 33 Auxiliary steam pressure control device 35 Flow rate indicator 37 Valve opening 38 Positioner 39 Primary steam pressure 40 Pressure gauge 42 Measured steam flow rate 43 First function generator 45 Switch 46 Cv value 47 Second function generator 48 Multiplier 49 Calculation signal 50 Coefficient 51 Steam flow calculation value 52 Multiplier 56 Switching indicator 56a Switching signal PX Pressure transmitter P Pressure signal S Specified flow value

Claims (2)

[Claims] At the initial stage of starting the boiler, steam from another steam source is introduced into an auxiliary steam header by an auxiliary steam introduction device. When the boiler generates steam, a part of its own steam is removed. Auxiliary steam extractor equipped with a steam extractor valve, a pressure regulating valve, and a differential pressure gauge for obtaining a measured steam flow rate based on the orifice differential pressure and outputting the measured steam flow rate to a flow indicator, takes out to the auxiliary steam header and supplies the auxiliary steam by itself. And controlling the pressure regulating valve so that the pressure of the auxiliary steam header is kept constant by the auxiliary steam pressure control device, wherein the measured steam flow rate by the orifice differential pressure is a critical point. When the pressure drops below, the steam is generated based on the Cv value based on the valve opening of the pressure regulating valve detected by the positioner provided in the pressure regulating valve and the primary steam pressure and coefficient of the pressure regulating valve. A method for monitoring a steam flow rate of a boiler, wherein a steam flow rate is monitored by calculating a flow rate calculation value and outputting the calculated value to a flow rate indicator. 2. An auxiliary steam extraction device in which a steam extraction valve, a pressure regulating valve, and a differential pressure gauge are disposed in an auxiliary steam extraction pipe, independently introduces steam from a boiler as auxiliary steam into an auxiliary steam header, and An auxiliary steam flow monitoring device for a boiler comprising an auxiliary steam pressure controller for controlling the pressure regulating valve so as to keep the pressure of a pressure transmitter for detecting the pressure of the header constant, wherein the valve of the pressure regulating valve is provided. A positioner that detects the opening degree, a pressure gauge that detects the primary steam pressure of the pressure regulating valve, a first function generator that outputs a measured steam flow rate based on the orifice differential pressure of the differential pressure gauge to the flow indicator, A second function generator for obtaining a Cv value of the pressure regulating valve based on the valve opening detected by the positioner, and multiplying a Cv value from the second function generator by a primary steam pressure from the pressure gauge; Multiplier, A multiplier for calculating a steam flow rate calculation value by multiplying a calculation signal from the multiplier by a coefficient; and a switching signal is output when the measured steam flow rate is input and the measured steam flow rate becomes equal to or less than a specified flow rate value. A switching indicator, the measured steam flow rate and the calculated steam flow rate are input and the measured steam flow rate is output to the flow indicator during normal times, and when the measured steam flow rate falls below the specified flow rate value, the switching indicator is used. An auxiliary steam flow monitoring device for a boiler, comprising a switch for switching a steam flow calculation value to be output to a flow indicator in response to the switching signal.