JPH03186103A - Boiler controller - Google Patents

Abstract

PURPOSE:To stabilize boiler control at the time when the boiler operation is switched from wet operation to dry operation by providing a supply water bias addition circuit which adds to a lowest supply water signal a supply water bias addition signal that is outputted based on the increase in a water-fuel ratio master signal and corrected for gain. CONSTITUTION:When the quantity of required steam increases at the final stage of wet operation, water-fuel ratio signal 28 is increased and the combustion flow rate by a combustion valve 3 is increased in order to prevent a fall in the pressure of main steam. On the other hand supply water bias signal 56 is obtained by inputting the water-fuel ratio master signal 28 into a function generator 57, and by inputting the supply water bias signal 56 to a multiplier 58 to which gain correction signal 59 from a function generator is inputted so as to input power generation requirement signal 22 supply water bias addition signal 61 is obtained with gain correction made, and supply water bias addition signal 61 is added through a variation limitter 63 to a lowest supply signal 38 from a lowest supply water signal generating device 37 by a multiplier 64. With this arrangement the additional increase to boiler is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a boiler control device designed to stabilize boiler control when switching from wet operation to dry operation in a variable pressure once-through boiler.

[Prior art 1] Figure 5 shows an example of the configuration of a variable pressure once-through boiler and a conventional control circuit. In the figure, 1 is the furnace of the boiler, and the furnace I
is supplied with fuel via a fuel pipe 2 and a fuel valve 3, and is also supplied with water from a water supply pump 4, a water supply pipe 5, and an energy saver (E
The steam and water heated in the furnace I are led to a steam separator 7 and separated into steam and hot water, and the steam is passed through a steam pipe 8 to a superheater 9. It is supplied to the turbine 12 which rotates the generator 11 via lO etc. to do work. In the figure, reference numeral 13 indicates an auxiliary steam extraction pipe for extracting auxiliary steam from the steam pipe 8, and 14 indicates an extraction valve.

On the other hand, hot water separated from steam and moisture # in vessel 7 is transferred to separation tank 1.
5, the water is circulated to the water supply pipe 5 through a circulation passage 18 having a circulation pump 16 and a Q valve 17, and the Q valve 17 ensures that the water level in the separation tank 15 is always maintained. It is automatically controlled to maintain within a certain level range.

A portion of the feed water supplied to the furnace 1 becomes steam and is led to a steam-water separator 7 where steam and water are separated, and the steam is transferred to a steam pipe 8.
The hot water is also led to a separation tank 15, and the hot water in the separation tank I5 is circulated to the water supply pipe 5 by a circulation pump 16.

During the required period from boiler startup, the furnace pass flow rate is 25% of the boiler maximum load evaporation amount (furnace pass minimum flow rate).
Heating is performed gradually while the water supply amount is maintained so that the main steam pressure reaches, for example, 75) cg/cj,
After the steam starts flowing into the turbine, the generator 11 is connected to the turbine L2 (referred to as generator connection), and from then on, the main steam pressure is maintained at 75 kg/cj while the minimum passing flow rate of the furnace path is maintained. Wet operation is performed as follows.

At the initial stage of wet operation, the amount of evaporation is small, so the amount of hot water circulated is large, but as the amount of fuel supplied by the fuel valve 3 increases due to the increase in the power generation command, the amount of steam increases, The amount of hot water introduced to the separation tank 15 is correspondingly reduced, and the amount of hot water circulated is reduced.

The amount of hot water from the steam-water separator 7 decreases, and the separation tank 1
When the level of 5 remains below the set value for the required time, or when the Q valve 17 is continuously shut off for the required time, the boiler control is switched from wet operation to dry operation as a dry state. ing.

The steam pipe 8 is provided with a pressure gauge 19 that detects the main steam pressure at the inlet of the turbine 12, and the main steam pressure signal 2o of the pressure jt19 is input to the subtracter 21, and
The main steam pressure command signal 24 obtained by converting the power generation demand signal (MWD) 22 by the function generator 23 is subtracted by inputting it to the subtracter 21, and the subtracted difference signal 25 is obtained.
is input to the PI control roller 27 via the switch 26, and a water-fuel ratio master signal 28 is output.

Further, the power generation amount request signal 22 is converted into a fuel program signal 30 by leading it to a function generator 29 via an adder 33, which will be described later. 3 to control the fuel supplied to the furnace I, and the water-fuel ratio master signal 2 is added to the fuel program signal 30 via an adder 31.
8 is added, and the main steam pressure is controlled to be constant by the addition signal 31'.

Furthermore, the switching device 2G rejects the difference signal 25 from the subtractor 21 by the switching signal S during dry operation of the boiler,
The temperature deviation signal 32 at the boiler outlet is sent to the PI control roller 27.
It is designed to switch so that it is input to .

Further, the power generation request signal 22 is converted into a water supply program signal 35 by leading it to a function generator 34 via an adder 33, and the water supply program signal 35 is converted to a high signal selector 36.
Enter. The minimum water supply signal 38 from the minimum water supply signal generator 37 is input to the high signal selector 36, and the higher signal is selected and outputted by comparison with the water supply program signal 35. . Normally, during wet operation of the boiler, 25% of the water supply at the maximum load of the furnace 1 is maintained, and the minimum water supply signal generator 3
7 outputs this 25% water supply signal 38.

Water supply command signal 39 selected by the high signal selector 3B
is input to the subtractor 40, and the flow rate signal 42 from the flow meter 41 provided at the outlet of the water supply pump 4 of the water supply pipe 5 and the flow rate signal 43 provided at the outlet of the Q valve 17 of the circulation channel 18 are The flow rate signal 44 is added by an adder 45, the added actual flow rate signal 46 is inputted to the subtracter 40, and the difference signal 47 from the water supply command signal 39 is sent to the water supply flow rate controller 4°.
The water supply pump 4 is outputted to the water supply pump 4 via the flow rate signal 4G, and the operation of the water supply pump 4 is controlled so that the actual flow rate signal 4G matches the water supply command signal 39.

Further, the difference signal 25 from the subtracter 21 is input to the adder 33 via the PI switch roller 48 and the switch 49, and is guided to the function generator 29, 34 to generate the fuel program signal 30 and the water supply program. The power generation request signal 22 from which the signal 35 is obtained is corrected in accordance with fluctuations in the main steam pressure signal 2°. Furthermore, the switching device 49 switches the PI switch roller 48 in response to a switching signal S during wet operation of the boiler.
Switching is performed such that the signal from the zero signal generator 50 is cut off and the zero signal (Ot/h) 51 from the zero signal generator 50 is input to the adder 33.

During wet operation of the boiler, the fuel valve 3 is controlled by the fuel program signal 30 obtained via the adder 33 and the function generator 29 based on the power generation request signal 22, and further,
The main steam pressure signal 20 from the pressure gauge 19 and the constant pressure main steam pressure command signal 24 obtained via the function generator 23 based on the power generation request signal 22 are compared by the subtractor 21, and the difference between them is calculated. PI controller 2 based on signal 25
The water-fuel ratio master signal 28 output from the adder 31
is added to the fuel program signal 30, thereby controlling the fuel flow rate so that the main steam pressure is maintained constant.

On the other hand, the minimum water supply signal 38 from the minimum water supply signal generator 37
and the water supply program signal 35 from the function generator 34 which is output in response to the power generation request signal 22 are input to the high signal selector 36. However, the water supply program signal 35 during wet operation is the lowest water supply. Since it is smaller than the signal 3g (25%), the minimum water supply signal 38 is selected and input to the subtracter 40 as the water supply command signal 39, and the actual flow rate signal 4
6 and the difference signal 47 is input to the feed water pump 4, and the flow rate passing through the furnace path is controlled to maintain the minimum feed water m (25%). Also, during the above wet operation,
The switch 49 is switched by the switching signal S so that the zero signal 51 from the zero signal generator 50 is input to the adder 33, and the signal from the PI controller 48 is cut off.

At the end of the wet operation, when the hot water level in the separation tank 15 becomes dry for a predetermined period of time, for example, the hot water level in the separation tank 15 remains below the set value for a predetermined period of time, the switch 26 is instantly switched by the switching signal S and the temperature deviation signal at the boiler outlet is changed. 32 is now input to the P summer controller 27, and thereafter the water-fuel ratio master signal 28 is output to the adder 31 so that the boiler outlet steam temperature remains constant.

Furthermore, by the time the above switching is performed, the water supply program signal 35 from the function generator 34 has also become equivalent to the minimum water supply signal 38, and from then on, the increasing water supply program signal 35 is selected by the high signal selector 36. The water supply pump 4 is controlled by a water supply command signal 39 based on a water supply program signal 35.

Further, the switch 49 is switched by the switch signal S caused by the switch to the dry operation, and a signal from the PI control roller 48 based on the difference signal 25 from the subtracter 21 is input to the adder 33. , is added to the power generation request signal 22 input to the function generator 34, and is controlled to correct fluctuations in main steam pressure by adjusting the amount of water supply and fuel.

[Problems to be Solved by the Invention] Figures 6 (e), (B), fc, and (D) show the power generation amount request signal 22, the main steam pressure command signal 24, and the water pressure command signal 22 after the generator is added in the conventional device. This shows the relationship between the fuel ratio master signal 28 and the flow rate passing through the furnace path.
Although the required amount of main steam amount and auxiliary steam amount based on the power generation amount request signal 22 increases as shown by the broken line 52 in FIG. Therefore, the amount of water to be evaporated tends to be insufficient at the end of wet operation when the ratio of water to steam is high, and the amount of evaporation in the furnace 1 is indicated by the solid line 53 in Fig. 6 (C1). As shown, the required amount 52 cannot be satisfied.

Then, as shown in FIG. 6 ([3), the main steam pressure tends to fall as shown by the broken line 54 with respect to the main steam pressure command signal (75 kg/cd) 24, and the pressure drop is compensated for by the compensation IT. : Since the water-fuel ratio master signal 28 is increased and the fuel is controlled to be increased as much as possible, the water/fuel balance is disrupted and the furnace 1. iA heating device9. There were problems such as an increase in temperature of lO, etc.

The purpose of this investigation is to stabilize the boiler control when switching from wet operation to trial operation in the conventional apparatus described above.

[Means for Solving the Problems] The present invention provides a power generation amount request signal 22 during wet operation of a boiler.
is input into the function generator 29 to obtain the fuel program signal 3.
0 to the adder 31 and the power generation request signal 22 to the function generator 23 to obtain the main steam pressure command signal 24.
and the main steam pressure signal 20 from the pressure gauge 19 provided at the inlet of the turbine 12 of the steam pipe 8 are input to the subtracter 21 to obtain the difference between the signals, and the signal 25 of the difference is input to the PI silicon roller 27. The obtained water-fuel ratio master signal 28 is sent to the adder 31.
is input to the fuel program signal 30 and added to the fuel program signal 30, and this addition signal 31' controls the fuel valve 3 so that the main steam pressure is constant (7, furthermore, the power generation request signal 22 is added to the fuel program signal 30). The water supply program signal 35 obtained by inputting the water supply program signal 35 into the water supply unit 34 and the minimum water supply signal 38 from the minimum water supply signal generator 37 are inputted into the high signal selector 36, and the selected water supply command signal 39 and the measured actual flow rate signal are inputted into the high signal selector 36. 46 and subtractor 40
In the boiler control device, the water-fuel ratio master from the PI controller 27 is inputted to determine the difference between the signals, and the water-fuel ratio master from the PI controller 27 is controlled by the difference signal 47 to control the water supply pump 4 so that the water supply amount maintains the minimum water supply amount. A function generator 57 that inputs the signal 28 and outputs the water supply bias signal 56, a function generator 60 that inputs the power generation request signal 22 and outputs the gain correction signal 59, and the water supply bias signal 56 and the gain correction signal. 59 to input the water supply bias addition signal 61
a multiplier 58 that outputs the water supply bias addition signal 61, a change rate limiter 63 that limits the rate of change of the water supply bias addition signal 61, and a change rate limiter 63 that limits the rate of change of the water supply bias addition signal 61; This boiler control device is characterized in that it is equipped with a water supply bias adding circuit 55 having an adder 64 that adds to the signal 38 and outputs it to the high signal selector 3B.

[Function] When the required amount of steam 52 increases toward the end of wet operation, the water-fuel ratio master signal 28 is increased to prevent the main steam pressure from dropping 54, and the fuel flow rate by the fuel valve 3 is increased. .

On the other hand, the water-fuel ratio master signal 28 is input to a function generator 57 to obtain a water supply bias signal 56, and the water supply bias signal 56 is subjected to gain correction from a function generator 60 to which the power generation amount request signal 22 is input. By inputting the signal 59 to the multiplier 58, gain correction is performed to obtain a water supply bias addition signal 6t, and the water supply bias addition signal 61 is passed through a change rate limiter 63 and an adder 64 to generate a minimum water supply signal. It is added to the minimum water supply signal 38 from the water supply device 37.

As a result, at the end of wet operation, the water supply pump 4 is controlled by the water supply command signal 39 which is obtained by adding the water supply bias addition signal 61 to the minimum water supply signal 38 in response to the increase in the water-fuel ratio master signal 28. , it is possible to eliminate water supply shortages at the end of wet operation, ensure a balanced water-fuel ratio, and stabilize boiler load increases.

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

FIG. 1 shows one embodiment of the present invention, and the parts in the figure with the same reference numerals as in FIG. 5 represent the same parts.

As shown in FIG. 1, the control circuit shown in FIG. 5 is provided with a water supply bias adding circuit 55.

The water supply bias addition circuit 55 is connected to the PI controller 2.
It has a function generator 57 which inputs the water-fuel ratio master signal 28 from the water-fuel ratio master signal 28 and outputs a feed water bias signal 56 as shown in FIG. A water supply bias signal 56 is input to a multiplier 58.

Furthermore, the multiplier 58 is provided with a function that outputs a gain correction signal 59 as shown in FIG. 3 according to the magnitude of the generated RTI amount request signal (load) 22 as input. said gain correction signal 59 from generator 60;
is input, and the gain of the water supply bias signal 56 is corrected.

The water supply bias addition signal 61 whose gain has been corrected by the multiplier 58 is inputted to the adder 64 via a switch 62 and a change rate limiter 63 for making gradual changes, thereby generating the minimum water supply signal. It is added to the minimum water supply signal 38 from the generator 37 and input to the high signal selector 36.

Further, the switch 62 inputs the water supply bias addition signal 61 of the multiplier 58 as it is to the change rate limiter 63 during wet operation, and at the same time inputs the water supply bias addition signal 61 from the zero signal generator 65 using the switch signal S when switching to dry operation. Switching is performed so that the zero signal 6B is input to the rate of change limiter 63.

During wet operation of the boiler, the fuel program signal 3 is obtained by the function generator 29 based on the power generation request signal 22.
0, the fuel valve 3 is controlled by the main steam pressure signal 20 from the pressure gauge 19, and the constant pressure (75) cg/
(4) The main steam pressure command signal 24 is compared with the subtracter 21, and based on the difference signal 25, the water-fuel ratio master signal 28 outputted from the control roller 27 or the fuel program signal 3o is determined by the adder 31. By inputting the addition signal 31' to the fuel valve 3, the fuel flow rate is controlled so that the main steam pressure is maintained constant.

On the other hand, by inputting the water-fuel ratio master signal 28 to the function generator 57, the water supply bias signal 56, which has been calculated as shown in FIG. A gain correction signal 59 from a function generator 60 that inputs the quantity request signal (load) 22 and performs calculations as shown in FIG. 3 is input to the multiplier 58, and the water supply bias signal 56 is bias-corrected. .

That is, in the case of FIG. 3, the water supply bias signal 56 is held to zero until the load is 0 to 15% (the second half of wet operation), and even if there is a fluctuation in the water supply bias signal 56 during this period, the water supply bias addition signal 61 remains unchanged. Do not output and the load is 15
% (at the final stage of wet operation), gradually increase the ratio of extracting the water supply bias load signal 61 from the water supply bias signal 56 until the load reaches the maximum of 1.0 (at the time of switching) of 25%. In other words, all of the water supply bias signal 5G is outputted as the water supply bias addition signal 61.

The water supply bias addition signal 61 is input to an adder 64 via a switch 62 and a change rate limiter 63, and is added to the minimum water supply amount 38 from the minimum water supply signal generator 37, and is added to the high signal selector 36. is input.

At this time, the water supply program signal 35 from the function generator 34 that is output in response to the power generation request signal 22 is also input to the high signal selector 36, but the water supply program signal 35 during wet operation is Since the bias addition signal 61 is smaller than the minimum water supply signal 38 to which the bias addition signal 61 is added, the minimum water supply signal 3 to which the water supply bias addition signal 61 is added is smaller.
8 is selected and input to the subtracter 40 as the water supply command signal 39, and is subtracted from the actual flow rate signal 46 to obtain the difference signal 4.
7 is input to the water supply pump 4, and the furnace bus passing flow rate is controlled to maintain the minimum water supply signal 38+water supply bias addition signal 61. Further, during the wet operation, the switch 49 is switched so that the zero signal 5t from the zero signal generator 5o is input to the adder 33, and the PI controller 4
The signal from 8 is blocked.

At the end of the wet operation, when the hot water level in the separation tank 15 remains below the set value for a predetermined period of time and becomes dry, the switch 26 is instantly switched by the switching signal S and the boiler outlet temperature deviation signal 32 is switched. is now input to the PI controller 27, and thereafter the water-fuel ratio master signal 28 is output to the adder 31 so that the boiler outlet steam temperature is constant.

Furthermore, by the time the above switching is performed, the water supply program signal 35 from the function generator 34 is also as stuffy as the minimum water supply signal 38, and from now on, either the increasing water supply program signal 35 or the high signal selector 36 is selected. , the water supply pump 4 is controlled by a water supply command signal 39 based on a water supply program signal 35.

In addition, the switch 49 is switched by the above-mentioned switch to dry operation (S), and the signal from the PI controller 48 based on the difference signal 25 from the subtracter 21 is input to the adder 33. The output power is added to the power generation request signal 22 input to the function generator 34, and the main steam pressure is controlled to be corrected by adjusting the amount of water and fuel.

Therefore, in the present invention, as shown in FIG. 4, in the final stage of the boiler's wet operation, as the water-fuel ratio master signal 28 in FIG. 4(C) increases, the water supply bias increases as shown in FIG. By adding the load signal 61 to the minimum water supply signal 38, the balance of the water-fuel ratio at the final stage of wet operation is ensured, and the evaporation 1153 matches the required amount of steam 52 as shown in FIG. 4(D). Therefore, it is possible to prevent the main steam pressure from decreasing due to steam shortage, and also prevent the temperature from increasing in each part of the boiler. Therefore, it becomes possible to stably increase the load on the boiler by -L.

It should be noted that the boiler control device of the present invention is not limited to the above-described embodiments, and the installation positions of each switching device can be selected from various locations, and various changes can be made without departing from the gist of the invention. Of course, you can add more.

[Effects of the Invention] As explained above, according to the boiler control device of the present invention, in the final stage of wet operation, the water-fuel ratio master signal 2
Since the water supply bias addition circuit 55 is provided which adds the water supply bias addition signal 61 which is output based on the increase of 8 and has been gain corrected to the minimum water supply signal 38, the shortage of water supply at the end of the wet operation can be resolved. It is possible to achieve an excellent effect of ensuring a balance in the water-fuel ratio and achieving a stable load increase in the boiler.

Furthermore, by achieving a smooth temperature rise in each part of the boiler when transitioning from wet operation to dry operation, there is also the effect of reducing boiler life consumption.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of the relationship between the water-fuel ratio master signal 28 and the water supply bias signal 56 in the function generator 57, and FIG. 3 is a diagram showing the function generator 57. A diagram showing an example of the relationship between the power generation request signal (load) 22 and the gain correction signal 59 in the generator 60, FIG. 4 (4) (B) (C) E) shows the power generation command signal and the main steam pressure. A diagram showing the relationship between the command signal, the water-fuel ratio master signal, and the flow rate passing through the furnace bus. Figure 5 is a block diagram showing the configuration of the boiler and an example of a conventional control circuit. Figure 6 (4) (B
) (C1(D) is a diagram showing the same relationship as in FIG. 4 in a conventional control circuit. 1 is a furnace, 3 is a fuel valve, 4 is a water pump, 8 is a steam pipe,
12 is a turbine, 19 is a pressure gauge, 20 is a main steam pressure signal, 21 is a subtracter, 22 is a power generation request signal, 23 is a function generator, 24 is a main steam pressure command signal, 25 is a difference signal, 2
7 is the PI control roller, 28 is the water-fuel ratio master signal, 2
9 is a function generator, 30 is a fuel program signal, 31 is an adder, 31' is an addition signal, 34 is a function generator, 35 is a water supply program signal, 36 is a high signal selector, 37 is a minimum water supply signal generator, 38 is a minimum water supply signal, 39 is a water supply command signal, 40 is a subtracter, 46 is an actual flow rate signal, 47 is a difference signal, 55 is a water supply bias addition circuit, 56 is a water supply bias signal, 57 is a function generator, 58 is a multiplier, 59 is a gain correction signal, 60 is a function generator, 61 is a water supply bias addition signal, 63 is a rate of change limiter, and 64 is an adder. Patent applicant Ishikawajima Harima Heavy Industries Co., Ltd.

Claims (1)

[Claims] 1) During wet operation of the boiler, the fuel program signal 30 obtained by inputting the power generation amount request signal 22 to the function generator 29 is inputted to the adder 31, and the power generation amount request signal 22 is inputted to the function generator 23. The main steam pressure command signal 24 obtained by The water-fuel ratio master signal 28 obtained by inputting the signal 25 to the PI controller 27 is inputted to the adder 31 and added to the fuel program signal 30, and this added signal 31' keeps the main steam pressure constant. The fuel valve 3 is controlled, and the power generation amount request signal 22 is
Water supply program signal 3 obtained by inputting to the function generator 34
5 and the minimum water supply signal 38 from the minimum water supply signal generator 37 are input to the high signal selector 36, and the selected water supply command signal 39 and the measured actual flow rate signal 46 are input to the subtracter 40. In the boiler control device, the water-fuel ratio master signal 28 from the PI controller 27 is inputted in a boiler control device that calculates the difference between the signals and controls the water supply pump 4 so that the water supply amount maintains the minimum water supply amount using the signal 47 of the difference. a function generator 57 that inputs the power generation amount request signal 22 and outputs a gain correction signal 59; a multiplier 58 that outputs a water supply bias addition signal 61; a rate of change limiter 63 that limits the rate of change of the water supply bias addition signal 61; and a rate of change limiter 63 that limits the rate of change of the water supply bias addition signal 61; Vessel 3
7. A boiler control device characterized by comprising a water supply bias adding circuit 55 having an adder 64 which adds the lowest water supply signal 38 from 7 and outputs the signal to the high signal selector 36.