JPH0465283B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to improvement of main steam pressure control characteristics during the Protpen phenomenon using a start controller and a start valve in a once-through boiler.

<Prior Art> An overview of general instrumentation of a once-through boiler device will be explained with reference to FIG. 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, becomes output steam S superheated in a superheating pipe 202, and is supplied to a load such as a turbine. be done. 3 is a spray water pipe branched from the input side of the boiler 2, which supplies spray water W _S to the superheating pipe 202 to adjust the temperature of the output steam S. Reference numeral 4 designates a discharge pipe to be controlled by the present invention, through which unvaporized water W' is released at the time of startup; 5 is a supply pipe for fuel F; and 6 is a supply pipe for air A.

F ₁ is the water supply flow rate sensor to boiler 2, F ₂ is the spray water flow rate sensor, F ₃ is the main steam flow rate sensor, F ₄
is the fuel flow sensor. T ₁ is the evaporator output temperature sensor, T ₂ is the output steam temperature sensor, and P ₁ is the output steam pressure sensor.

V ₁ is a control valve for supply water W, V ₂ is a control valve for spray water _WS , V ₃ is a start valve for controlling discharge water W', and V ₄ is a control valve for fuel F.

C ₁ is a water supply flow rate controller that operates control valve V ₁ , C ₂ ,
C ₃ operates control valve V ₂ to set the output steam temperature to the set value.
C ₄ and C ₅ are cascade controllers that adjust the output steam temperature of the evaporation pipe 201 to set value ST ₂ by operating the control valve V ₄ , C ₆ is _an output steam pressure controller Then, add that output and the output of flow sensor F ₃ using adder Σ ₁ to obtain the boiler master signal BM.
to occur. _C7 is a startup controller that operates the startup valve _V3 to adjust the output steam pressure to the set value _SP2 at startup. _C8 is a ratio controller that maintains the flow rate of spray water W _S at a constant ratio to the flow rate of water supplied to the boiler, and the output of the ratio setter RS, which inputs the output of the boiler feed water flow rate sensor _F1 , is used as the set value. , its output is given to adder Σ ₂ .

FX ₁ and FX ₂ are function generators which receive the boiler master signal BM as input, and convert the boiler master signal into a water supply flow rate and a fuel flow rate, respectively, and apply the converted signals to addition means Σ ₂ and Σ ₃ . Σ ₂ adds the output of FX ₁ and the output of the above controller C ₈ to give the set value of the water supply flow rate controller C ₁ .
Σ ₃ is a cascade controller C ₅ that adds the output of FX ₂ and the output of cascade controller C ₄ to adjust the fuel flow rate.
Give the setting value.

Block D indicated by a dotted line is a starting control section to which the present invention is applied.In addition to the above-mentioned starting controller _C7 , the starting controller _C7 is proportionally controlled by the output steam temperature, that is, the output _eT2 of the temperature sensor _T2 . A gain switching means 7 for changing the gain K is provided.

Next, the operation at startup will be explained. When the once-through boiler starts, the water passing through boiler 2 has not yet turned into steam, and at this stage the starting valve V ₃
As a result, the output steam pressure is controlled by manipulating the discharged water W'. The set value SP ₂ at this time is a value lower (90%) than the main steam pressure set value SP ₁ during steady operation.
degree). At startup, the boiler master controller _C6 is in manual mode, and the boiler master signal BM is regulated to a low value.

The next sequence of startup ignites the burner and
The temperature of the water gradually rises, and when it reaches a certain temperature, it starts boiling within the evaporation tube 201 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, called the Prozpen 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, where 701 is a temperature comparator that controls the timing of switching, and outputs the temperature e _T 〓 at which the Protsupen phenomenon occurs corresponding to the set pressure SP ₂ as the set value. The steam temperature e _T2 is monitored, and when e _T2 < e _T 〓, the setting means 703
Water gain K _P1 given by (e.g. proportional band 400%)
is applied to the starting controller _C7 via the switch means 702 to regulate its proportional band to K _P1 . When the temperature rises and becomes e _T2 ≧e _T 〓, switch 702 and set the steam gain K _P2 (for example, proportional band 30
%) to the starting controller C ₇ 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 SP ₂ and the main steam pressure, that is, the pressure sensor P ₁
If there is a control deviation between the output e and _P1 ,
Because the gain increases rapidly and the integration time setting remains constant, the operating output changes significantly after switching, and there is a risk of causing large pressure fluctuations in the process.

Figure 6 is an explanatory diagram of the occurrence of fluctuations due to switching. As shown in B, the temperature e _T2 rises and at the time t ₁ when it reaches e _T 〓 (= 300℃), the proportional band changes from 400% to 30% as shown in C.
When narrowed to %, the measured pressure value as shown in A
e If a deviation ε exists between _P1 and the set value S _P2 , the main steam pressure will fluctuate greatly due to the generation of a large controller output, and in some cases, the safety valve will operate and the entire system will be shut down. Sometimes it happens. When such a fluctuation occurs, the operator must immediately take emergency measures to switch the starting controller _C7 to manual operation to converge the measured value e _P1 to the set value _SP2 .

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

<Means for Solving the Problems> The structural feature of the present invention is that a once-through boiler is provided in which water is pumped into the boiler and heated in a superheating tube to obtain output steam, and the main steam pressure is detected. In the startup valve control device for the once-through boiler, which discharges water that has not turned into steam into the atmosphere during startup by operating the startup valve installed in the discharge pipe on the output side of the once-through boiler, the main steam pressure signal and the main steam are controlled. A starting controller that generates an operation signal obtained by performing proportional and integral calculations on the deviation signal from the pressure setting signal, a temperature sensor that detects the main steam temperature, and the starting adjustment based on the main steam temperature signal from this temperature sensor. proportional band function calculation means for programmatically changing the proportional band in the proportional calculation of the controller; and integral time function calculation means for programmatically changing the integral time in the integral calculation of the starting controller based on the main steam temperature signal of the temperature sensor. The point is that you have the means.

<Function> 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, so even if a control deviation exists, the process can be shifted without causing any fluctuation. be able to.

<Embodiment> The configuration 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 calculating means 8, 801 is a proportional band function calculating means, which calculates the main steam temperature signal as shown in FIG. 2A.
e Based on _T2 , calculate the proportional band K _P in the range of 200°C to 300°C.
Change programmatically from 400% to 30% and apply to start controller _C7 . 802 is an integral time function calculation means, which calculates the main steam temperature signal e _T2 as shown in FIG. 2B.
Based on the integration time T _I in the range of 200℃~300℃
Programmatically change from 240sec to 30sec and apply it to 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 water control over the temperature at which the Protpen phenomenon occurs, it is possible to Process fluctuations associated with switching can be effectively suppressed even in the presence of deviations, and smooth transition can be achieved.

FIG. 3 is an explanatory diagram of the switching characteristics of the device of the present invention. As shown in B, from time t ₀ when the main steam temperature is 200°C to time t ₁ when the main steam temperature is 300°C, the switching characteristics are as shown in C and D. The integration time T _I and the proportional band K _P are changed programmatically in the same way as in FIG. As a result, as shown in A, as shown in the waveform of the main steam pressure measurement signal e _P1 , the control shifts to after the Prozpen 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 to be the optimum values and waveforms depending on the characteristics of the applied once-through boiler, but the waveforms are not linear or have simple broken line characteristics. This is sufficient, and the structure of the function calculation means 801 and 802 can be realized extremely simply and at low cost.

<Effects> As explained above, according to the present invention, with an extremely simple configuration, it is possible to cause fluctuations in the proportional band and integral time of the starting controller at the time of the Protpen phenomenon in a state where a control deviation exists. It is possible to smoothly transition to a new constant without any trouble, and the startup sequence in the once-through boiler can be carried out smoothly.

[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. 1...Main pipe line, 2...Once-through boiler, 4...Discharge pipe line, _V4 ...Start valve, _C7 ...Start controller, 8...
... Calculating means, 801 ... Proportional band function calculating means, 8
02... Integral time function calculation means, W... Water, S...
…output steam, W′…discharge water, P ₁ …output steam pressure sensor, T ₂ …output steam temperature sensor.

Claims (1)

[Claims] 1 Installed in a once-through boiler that pumps water into the boiler and superheats it in a superheating tube to obtain output steam, detects the main steam pressure and operates a startup valve installed in the discharge pipe on the output side of the once-through boiler. Therefore, in the startup valve control device of a once-through boiler that discharges water that has not turned into steam into the atmosphere at startup, an operation that performs proportional and integral calculations on the deviation signal between the main steam pressure signal and the main steam pressure setting signal. A starting controller that generates a signal, a temperature sensor that detects the main steam temperature, and a proportional band function calculation means that programmatically changes the proportional band in the proportional calculation of the starting controller based on the main steam temperature signal of the temperature sensor. and integral time function calculation means for programmatically changing the integration time in the integral calculation of the startup controller based on the main steam temperature signal of the temperature sensor.