JPS61195203A - Controller for starting valve in once-through boiler - 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 <Industrial Application Field> The present invention relates to improvement of main steam pressure control characteristics during the pen phenomenon using a start controller and a start valve in a once-through boiler.

<Conventional Technology> An overview of the general instrumentation of once-through boiler equipment will be explained with reference to Fig. 4. 1 is a main pipe through which water W is pumped by a pump PO, water W is vaporized in an evaporation pipe 201 in a once-through boiler 2,
The output steam S is superheated in the superheating pipe 202 and is supplied to a load such as a turbine.

3 is a spray water pipe branched from the input side of boiler 2,
Spray water W is supplied to the superheating tube 202 to adjust the temperature of the output steam S. Reference numeral 4 denotes a discharge pipe which is controlled by the present invention, and water W' which is not vaporized is discharged at the time of startup. 5 is a supply pipe for fuel P, and 6 is a supply pipe for air A.

F1ti is a water supply flow rate sensor to the boiler 2, F2 is a spray water flow rate sensor, F is a main steam flow rate sensor, and F is a fuel flow rate sensor. T□ is an evaporator output temperature sensor, F2 is an output steam temperature sensor, and pl is an output steam pressure sensor.

■□ is a control valve for supply water W, V2 is a control valve for spray water w8, ■ is a start valve that controls discharge water w', and ■ is a control valve for fuel F.

C□ is a water supply flow rate controller that operates the control valve V□, C2゜C
3 is a cascade controller that operates control valve v2 to adjust the output steam temperature to the set value ST; C4 and C5 are control valves v4
to set the output steam temperature of the evaporation tube 201 to the set value ST2.
A cascade controller C6 is an output steam pressure controller, and an adder Σ1 adds the output of the output steam pressure controller and the output of the flow rate sensor F3 to generate a boiler master signal BM. C7 is a startup controller that operates the startup valve v3 to adjust the output steam pressure to a set value sp at startup.

C8 is a ratio controller for keeping the flow rate of spray water W at a constant ratio to the water supply flow rate to the boiler, and the output of the ratio setting device R3, which inputs the output of the boiler water supply flow rate sensor F, is set as the set value. is given to adder Σ2.

FX1, FX2 are function generators which receive the boiler master signal BM as input, and convert the boiler master signal into water supply flow rate and fuel flow rate iK, respectively, and add them to addition means Σ2. Give to Σ3.

Σ2 adds the output of Fxl and the output of the above-mentioned controller 08, and gives the set value of the water supply flow rate controller C□. Σ3 is FX2
The output of the cascade controller C is added to the output of the cascade controller C to give the set value of the cascade controller C that adjusts the fuel flow rate.

The block D indicated by the dotted line is the startup control unit that is the object of the present invention.
In addition to the above-mentioned starting controller 07, a gain switching means 7 is provided which changes the proportional gain K of the starting controller C7 according to the output steam temperature, that is, the output eT□ of the temperature sensor T2.

Next, the operation at startup will be explained. When the once-through boiler is started, the water passing through the boiler 2 has not yet turned into steam, and at this stage, the output steam pressure is controlled by operating the discharge water w1 using the startup valve V. Setting value s at this time
p is set to a value (approximately 9 od) lower than the main steam pressure setting spO value during steady operation. At startup, the boiler master controller c6 is manually operated, and the boiler master signal BM is regulated to a low value.

In the next sequence of start-up, the burner is ignited, and the temperature of the water gradually rises, and when it reaches a certain temperature, the evaporator tube 201
Boiling begins within the tank and evaporation progresses.

Since the target of startup control changes from water to steam before and after the timing of the change from water to steam, which is called the Proppen phenomenon, it is necessary to switch the gain of the startup controller.

FIG. 5 shows a specific configuration example of the gain switching means 7.
1 is a temperature comparator that controls the timing of switching,
Temperature e at which the pen phenomenon occurs corresponding to the set pressure sP2
The output steam temperature "T2" is monitored with T and r as set values, and e
When T□<eTcr, water gain Kp□ (for example, proportional band 400%) given by setting means 703 is applied to starting controller C via switch means 702 to regulate the proportional band to fall. When the temperature rises to eT2-eTct, 7o2 is switched and the setting means 704 gives steam gain Kp□ (for example, proportional band 30%) to the starting controller 07 to increase the proportional gain.

However, in such a two-stage proportional gain switching system, when switching from water gain to steam gain, the pressure set value s
If there is a control deviation between p2 and the main steam pressure, that is, the output of the pressure sensor p□, the operation output after switching will change greatly because the P1 gain will increase rapidly and the integration time setting will be constant, causing a change in the process. There is a risk of causing large pressure fluctuations.

FIG. 6 is an explanatory diagram of the occurrence of fluctuations due to switching, and as shown in (B), the temperature eT2 rises. At the point when Ta (2300℃) is reached, at t□, the proportional band is set to 400' as shown in (C)K.
When narrowing the range from 4% to 30%, if there is a deviation 6 between the measured pressure value ep□ and the set value SP□ as shown in (A), the main steam pressure will increase due to the generation of a large controller output. may fluctuate significantly, and in some cases the safety valve may operate and shut down the entire system. When such a fluctuation occurs, the operator immediately switches the starting controller 07 to manual operation and the measured value 1i! p□ is set value S,
Urgent treatment is required to converge to 2.

<Problems to be Solved by the Invention> An object of the present invention is to provide a control device that can smoothly change the gain during the block pen phenomenon even when a control deviation exists.

<Means for Solving the Problems> The structural feature of the present invention is that, at the time of startup of the once-through boiler, proportional and integral calculations are performed on the deviation between the main steam pressure signal and the main steam pressure setting signal. A start adjustment means that generates an operation signal, a start valve that releases main steam output to the atmosphere in response to the operation signal, a temperature sensor that detects the main steam temperature, and a proportional band function calculation that inputs the output of this temperature sensor. and an integral time function calculation means which similarly inputs the output of the temperature sensor, the proportional band in the proportional calculation is changed by the output of the proportional band function calculation means, and the proportional band in the proportional calculation is changed by the output of the integral time function calculation means. The point is that the integration time in the above integral calculation is changed.

<Function> Since the proportional band and integral time of the startup controller are changed continuously in a programmatic manner according to the rise in main steam temperature, even if there is a control deviation, it will not cause any fluctuation in the process. can be done.

<Example> The structure and operation of the main parts of the device of the present invention will be explained based on FIGS. 1 and 2. The feature of the present invention is that the element corresponding to the gain switching means 7 in FIG. 5 is replaced with the calculation means 8.

In the calculation means 8, 801 is a proportional band function calculation means,
As shown in FIG. 2(A), based on the main steam temperature signal eT2, the proportional band 5 is programmatically changed from 400 degrees to 30% in the range of 200 DEG C. to 300 DEG C., and is applied to the starting controller 07. 802 is an integral time function calculation means, as shown in FIG. 2(B).
200℃ based on the main steam temperature signal eT2 as shown in
In the range of ~300℃, the integration time T□ is set to 3 from 240sec.
o sec programmatically and applied to the starting controller C7.

In this way, by continuously and programmatically changing the proportional band and integral time to values that are more suitable for steam control than for water control, before and after the temperature at which the Proppen phenomenon occurs, conventional step-like switching can be achieved. It is possible to effectively suppress process fluctuations caused by deviations and realize a smooth transition.

FIG. 3 is an explanatory diagram of switching characteristics by the device of the present invention,
As shown in (R), between time t1 when the main steam temperature is 200°C and the Proppen phenomenon at 300°C (C)
', As shown in (D), the integral time T and the proportional band Kp are changed programmatically in the same way as in FIG. This result (A
), as shown in the waveform of the main steam pressure measurement signal ep1, the control shifts to after the Proppen phenomenon with almost no pressure fluctuation occurring.

In the device of the present invention, the specific numerical values and program waveform of the proportional band and integral time program are selected as appropriate values and optimal waveforms based on the characteristics of the applied once-through boiler, but the waveforms are linear or have simple broken line characteristics. is sufficient, and the configuration of the function calculation means 801 and 802 can be realized extremely simply and at low cost.

Effect> As explained above, according to the present invention, with an extremely simple configuration, the professional
It becomes possible to smoothly shift the proportional band and integral time of the startup controller during the pen phenomenon to new constants without causing any fluctuation in the process, and the startup sequence for mass flow and boilers can be implemented at Nisshin.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the main part of the device of the present invention, Fig. 2 is an explanatory diagram of its operation, Fig. 3 is an explanatory diagram of switching characteristics by the control device of the present invention, and Fig. 4 is a diagram of the once-through boiler device. FIG. 5 is a configuration diagram showing an example of instrumentation, FIG. 5 is a configuration diagram showing an example of a conventional control device, and FIG. 6 is an explanatory diagram of its switching characteristics. DESCRIPTION OF SYMBOLS 1... Main pipe line, 2... Once-through boiler, 4... Discharge pipe line, v4... Starting valve, C7... Starting controller, 8...
- Calculating means, 801... Proportional band function calculating means, 802
...integral time function calculation means, W...water, S...output steam, WI...discharged water, P...output steam pressure sensor, T...output steam temperature. Agent Patent Attorney Makoto Ozawa ゛-゛- Figure 1 7-8 (operation + stage) Figure 2 (B) (A) Figure 3

Claims (1)

[Claims] At the time of startup of the once-through boiler, a startup adjustment means generates an operation signal by performing proportional calculation and integral calculation on the deviation signal between the main steam pressure signal and the main steam pressure setting signal, and a main steam output control means in response to the above operation signal. , a temperature sensor that detects the main steam temperature, a proportional band function calculation stage that inputs the temperature sensor output, and an integral time function calculation means that similarly inputs the temperature sensor output. Start valve control in a once-through boiler, characterized in that the proportional band in the proportional calculation is changed by the output of the proportional band function calculation means, and the integral time in the integral calculation is changed by the output of the integral time function calculation means. Device.