JP3755910B2 - Water injection control device for reheat steam desuperheater - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a water injection control device for a reheat steam system desuperheater that controls the reheat steam temperature by spraying water in a boiler reheater.
[0002]
[Prior art]
In recent years, due to the stable supply of power by nuclear power generation facilities, the operation mode of boilers has increased the intermediate load thermal operation, and with this, both the load change rate and the load change range are large and high. The form of frequency load change has become common. In such a boiler operation mode, the reheat steam temperature is controlled so as to have a predetermined management value for a wide load range in consideration of high-efficiency operation of the plant.
[0003]
As a control for this, means for increasing or decreasing the convective heat transfer coefficient of the heat transfer tube by controlling the amount of exhaust gas discharged from the economizer outlet from the bottom of the furnace, and spraying water to cover the response delay Means are used to bring the reheat steam temperature closer to the control value. These means will be described with reference to FIGS.
[0004]
FIG. 6 is a diagram showing an outline of the boiler configuration. In this figure, 1 is a boiler, 2 is a furnace water wall pipe constituting the furnace of the boiler 1, 3 is a wind box, 4 is a burner, and 5 is a flame. 6 is a high-temperature superheater, 7 is a high-temperature reheater, 8 is a low-temperature reheater, 9 is a low-temperature superheater, and 10 is a economizer, and these are sequentially arranged from upstream to downstream in the furnace. 11 is an air preheater, 12 is a flue for deriving exhaust gas from the economizer 10, and 13 is an airway for introducing air into the wind box 3. 14 is a gas recirculation fan for introducing exhaust gas from the economizer 10 into the furnace hopper, 15 is a recirculation gas control damper for controlling the amount of the exhaust gas introduced, and 16 is for controlling the amount of air mixed with the exhaust gas. A mixed gas amount control damper 17 is a furnace hopper damper that controls the amount of recirculated gas introduced into the hopper. The steam temperature at the outlet of the high-temperature reheater 7 is controlled to a predetermined value by controlling the amount of the recirculation gas by the recirculation gas control damper 15, the mixed gas amount control damper 16, and the furnace hopper damper 17. .
[0005]
FIG. 7 is a system diagram of a boiler water-steam system. In this figure, parts that are the same as or equivalent to the parts shown in FIG. A solid line indicates a water system, and a broken line indicates a steam system. Reference numeral 20 denotes a high-pressure turbine in which steam from the high-temperature superheater 6 is supplied via a high-temperature superheated steam pipe 21 and a main steam shut-off valve 22, and the discharged steam is supplied to the low-temperature reheater 8 via a check valve 23. be introduced. Reference numeral 24 denotes an intermediate pressure turbine, in which steam from the high temperature reheater 7 is supplied via a high temperature reheat steam pipe 25 and a high temperature reheat steam shut-off valve 26, and the steam discharged from this is further supplied to each low pressure turbine 27. be introduced.
[0006]
28 is a condenser for condensing steam discharged from the low-pressure turbine 27, 29 is a low-pressure condensate pump, 30 is a demineralizer, 31 is a low-pressure feed water heater, 32 is a deaerator, and 33 is a deaerator storage. , 34 is a feed water pump, 35 is a high pressure feed water heater, 36 is a feed water flow meter, and 37 is a spray pipe branched from the high pressure feed water heater 35. A temperature reducer 40 is provided at the outlet steam pipe of the low temperature superheater 9, and spray water is supplied from the spray pipe 37 through the superheater spray shut-off valve 41 and the superheater spray flow rate adjustment valve 42. 43 is a temperature reducer provided at the outlet steam pipe of the low-temperature reheater 8, and spray water is supplied from the spray pipe 37 through the reheater spray shut-off valve 44 and the reheater spray flow rate adjustment valve 45. .
[0007]
FIG. 8 is a block diagram of a water injection control device that controls the reheater spray flow rate adjustment valve 45 shown in FIG. In this figure, 51 indicates a generator output command value, and 52 indicates a reheat steam temperature measurement signal. A function generator 53 converts the generator output command value into a reheat steam temperature corresponding to the generator output command value. 54 and 55 are signal generators, and 56 is a signal switcher for switching and selecting either the signal generator 54 or the signal generator 55.
[0008]
In order to prevent spraying, the signal generator 54 is set to a temperature at which the reheat steam temperature output from the function generator 53 is set to a high value, and the signal generator 55 is set to enable spraying. The temperature at which the reheat steam temperature output from the function generator 53 is set to a low value is set. 57 is an adder for adding the output of the function generator 53 and the output of the signal generator switched by the signal switch 56, and 58 is for calculating the deviation between the output of the adder 57 and the reheat steam temperature measurement signal 52. A subtractor 59 is a proportional integrator.
[0009]
Reference numeral 60 is a signal switcher, 61 is a function generator, and 63 is an automatic / manual switcher. The function generator 61 creates and outputs a reheat steam temperature corresponding to the generator output command value 51 shown above. The signal switcher 60 switches between the proportional integrator 59 and the function generator 61.
[0010]
In the above configuration, the signal switch 56 always connects the signal generator 54 to the adder 57 and connects the signal generator 55 to the adder 57 when the signal A ₁ is input. In addition, the signal switching unit 60 always connects the proportional integrator 59 to the automatic / manual switching unit 63, and connects the function generator 61 to the automatic / manual switching unit 63 when the signal B ₁ is input. The generation conditions of the signals A ₁ and B ₁ , that is, the switching conditions of the signal switchers 56 and 60 are shown in FIGS.
[0011]
FIG. 9 is a diagram showing the switching conditions of the signal switch 56. In this figure, AND is a symbol indicating a logical product. The signal A ₁ is output when “the load is equal to or greater than the predetermined value a” and “the furnace hopper damper is in the lower limit operation (a state in which the steam temperature cannot be lowered by recirculation gas control any more)”.
[0012]
FIG. 10 is a diagram showing the switching conditions of the signal switcher 60. In this figure, AND is a symbol indicating the same logical product as shown in FIG. The signal B ₁ is “starting period elapsed (not during boiler start-up)”, “load increasing”, “reheat steam temperature rise rate is a predetermined value d or more”, “reheat steam temperature deviation is a predetermined value e or more Is output when all the conditions are satisfied. Each condition shown in FIG. 9 and FIG. 10 is a condition obtained in the process of boiler control.
[0013]
In the water injection control device shown in FIG. 8, in the normal state (the state where the reheater steam temperature is controlled by the recirculation gas control), the signal switch 56 selects the signal generator 54 side. The high set temperature is added to the output of the function generator 53 in the device 57, and the deviation obtained by the subtractor 58 is reduced, so that the reheater spray flow rate adjusting valve 45 cannot be operated, and the temperature reducer 43 No spraying is done. However, when the condition shown in FIG. 9 occurs, the signal A ₁ is output, the signal switch 56 is switched to the signal generator 55 side, and a low set temperature is input to the adder 57. In response to this, the reheater spray flow rate adjusting valve 45 is actuated to perform spraying by the temperature reducer 43, and the reheat steam temperature is adjusted.
[0014]
When the conditions shown in FIG. 10 (particularly when the reheat steam temperature rise rate and deviation are extremely large) occur, the signal B ₁ is output and the signal switcher 60 switches from the proportional integrator 59 to the function generator 61. Then, according to the characteristics of the function generator 61, the reheater spray flow rate adjusting valve 45 is operated in advance to perform spraying by the temperature reducer 43.
[0015]
[Problems to be solved by the invention]
In the above conventional apparatus, the spray is exclusively used to keep the reheat steam temperature as constant as possible, and the control is performed along this. By the way, as mentioned above, since the operation form of the boiler has become a high load change rate, a wide load change width, and a high frequency load change in recent years, intermittent spraying has been repeatedly performed. Such sprays cause undesirable problems. This will be described with reference to FIG.
[0016]
FIG. 11 is a partial cross-sectional view of the temperature reducer 43 shown in FIG. In this figure, the same parts as those shown in FIG. 46 is a water check valve (not shown in FIG. 7). The temperature reducer 43 is interposed in the low-temperature reheat steam pipe 80, and includes a nozzle 431, an inlet nozzle 432, a spray nozzle 433, and a thermal sleeve 434. When the temperature of the steam passing through the low-temperature reheat steam pipe 80 exceeds a predetermined temperature and the above-mentioned conditions are met, the water injection control device operates, and the reheater spray flow rate adjustment valve 45 is adjusted accordingly, and the steam The water supplied through the spray water pipe 37 is sprayed from the spray nozzle 433 to lower the reheat steam temperature.
[0017]
In such a spraying operation, the surface and the inner surface of the low-temperature reheat steam pipe 80 and the thermal sleeve 434 of the temperature reducer 43 are both in a high temperature state before spraying. Thus, only the surface is kept at a high temperature. Here, the low-temperature reheat steam pipe 80 has a large thickness, and the thermal sleeve 434 of the temperature reducer 43 also has a corresponding thickness, so that a considerable temperature difference occurs between the surface and the inner surface, Repeated sprays create large thermal stresses that accumulate and eventually crack (damage) due to thermal fatigue.
[0018]
The object of the present invention is to solve the above-mentioned problems in the prior art, to suppress spraying, and thus to prevent damage due to thermal fatigue of a low-temperature reheat steam pipe or a desuperheater. It is in providing the water injection control apparatus of a vessel.
[0019]
[Means for Solving the Problems]
In order to solve the above problems, the present invention mainly adopts the following configuration.
The exhaust gas recirculation control means that controls the amount of exhaust gas recirculated from the bottom of the boiler into the furnace with the opening of the damper and the temperature at which the desuperheater that performs water injection through the reheat steam pipe is deactivated are set A first signal generating means for outputting a signal corresponding to the non-operating temperature; a second signal generating means for setting a temperature for operating the temperature reducer and outputting a signal corresponding to the operating temperature; Switching means for switching the output signal of the first signal generating means to the output signal of the second signal generating means on the basis of the above conditions, and the switching means to switch to the reheat steam temperature according to the load request signal. Adding means for adding a signal; computing means for calculating a deviation between the signal from the adding means and the measurement signal of the reheat steam temperature; and an adjustment valve for the temperature reducer whose opening is adjusted in accordance with the deviation; , Water injection control device for reheat steam system desuperheater There is,
The predetermined condition is obtained by calculating a logical product between when the load signal of the boiler is a predetermined value or more and when a difference between the load request signal and the load signal is a predetermined value or more, and the exhaust gas recirculation control means Is a logical sum of when the lower limit operation state is continued for a predetermined time and the output of the logical product,
Further, a change rate limiting means for limiting the change rate of the deviation when the adjusting valve is operating in the closing direction is provided between the calculating means and the adjusting valve.
[0020]
[Action]
In the present invention, the fact that the difference between the load request signal and the current load signal is greater than or equal to a predetermined value is added to the condition of the switching means, thereby suppressing water injection. Further, the condition of the switching means is added that the lower limit operation state (a state in which a decrease in the steam temperature due to recirculation gas control cannot be expected) continues for a predetermined time, so that when the lower limit operation state disappears within the predetermined time, Control steam temperature with recirculation gas to reduce water injection. Further, the rate of change limiting means limits the rate of change of the deviation when the regulating valve is operating in the closing direction, and suppresses repeated repetition of water injection.
Further, according to the present invention, not only the deviation and the reheat steam temperature are not less than a predetermined value by the prior water injection means, but also the steam adjustment is not performed until the difference between the load request signal and the load signal is not less than the predetermined value. Pre-water injection is performed by opening the valve. Further, by combining the change rate limiting means and the preceding water injection means, water injection is more effectively suppressed.
[0021]
【Example】
Hereinafter, the present invention will be described based on illustrated embodiments.
FIG. 1 is a block diagram of a water injection control device for a reheat steam system desuperheater according to an embodiment of the present invention. In the figure, parts that are the same as or equivalent to the parts shown in FIG. 64 is a power generation end output value, 65 is a subtractor, 66 is a function generator, 70 is a change rate limiter, 71 is a differentiator, and 72 and 73 are monitor relays. A ₂ is a switching signal of the signal switching device 56, B ₂ is a switching signal of the signal switching device 60, and C is an operation signal of the change rate limiter 70.
[0022]
Here, the output conditions of the switching signals A ₂ and B ₂ of the signal switching units 56 and 60 and the operation signal C of the change rate limiter 70 are shown in FIGS.
FIG. 2 is a diagram showing the switching conditions of the signal switch 56. In this figure, AND represents a logical product, OR represents a logical sum, and DER represents a time delay. The switching signal A ₂ is output when the following conditions occur. (I) When the load is equal to or greater than a predetermined value a and the difference between the “power generation request output command value” and the “output value requested at the current power generation end” is equal to or greater than the predetermined value b, or ( ii) When the furnace hopper damper lower limit operation is continued for the time set in the DER.
[0023]
The above condition (“power generation required output command value” − “current power generation end required output value” ≧ b) is such that when the change of the generator output command value with respect to the power generation end required command value is small, the change width of the reheat steam temperature is also small. Therefore, in such a case, the condition is such that the spray is not performed. In this embodiment, by adding this condition to the condition in the conventional apparatus, the spray can be further suppressed than in the conventional apparatus. Moreover, even if the furnace Hoppadanpa lower limit operating conditions, i.e., no more even if by recirculation gas control state can not be expected that the steam temperature falls, without immediately outputs a switching signal A _2, a predetermined time (for example, several 10 I have waited seconds) and outputs the signal a ₂ Setsu only when the lower limit operation is continued. Thereby, when recirculation gas control becomes possible within the predetermined time, it is not necessary to perform spraying, and spraying can be suppressed.
[0024]
FIG. 3 is a diagram showing an output condition of the operation signal C of the change rate limiter 70. In this figure, AND indicates a logical product. The operation signal C is output when the following conditions occur. (I) the reheater spray flow rate adjustment valve 45 is in a state of being automatically controlled, (ii) the load is changing, and (iii) the reheater spray flow rate adjustment valve 45 is in the closing direction. And (iv) when the opening degree command of the reheater spray flow rate adjusting valve 45 is less than a predetermined value c%. Of these conditions, (i) and (ii) can be obtained from the boiler controller, (iii) is detected by the differentiator 71 and the monitor relay 73 shown in FIG. 1, and (iv) 1 is detected by the monitor relay 72 shown in FIG. The effect of these conditions will be described later.
[0025]
FIG. 4 is a diagram showing the switching conditions of the signal switcher 60. In this figure, AND indicates a logical product. In addition to the conditions shown in FIG. 10, the switching signal A ₂ is equal to the predetermined value b in the difference between the “generation request output command value” and the “output value required at the current power generation end” as in FIG. Output when the above condition is satisfied. By adding this condition, it is possible to further suppress the advance spraying from the conventional apparatus for the same reason as the switching condition of the signal switch 56.
[0026]
Next, the operation of this embodiment will be described. As a switching condition of the switching signal A ₂ , the difference between the “generation request output command value” and the “output value requested at the current power generation end” is a predetermined value b or more in the conventional switching signal A ₁ switching condition. By adding something, the operation of switching the signal switch 56 to the signal generator 55 side is suppressed, and the spray is correspondingly suppressed as described in the explanation of the conditions shown in FIG. Regardless of the switching state of the signal switch 56, the deviation signal from the subtractor 58 is input to the change rate limiter 70 via the proportional integrator 59.
[0027]
The change rate limiter 70 transmits the signal from the proportional integrator 59 to the signal switch 60 as it is when the operation signal C is not input. Among the output conditions of the operation signal C, the fact that the reheater spray flow rate adjustment valve 45 receives the opening direction command in the closing direction is detected by the differentiator 71 as described above, and this detection signal is sent via the monitor relay 73. Are input to the change rate limiter 70. In addition, it is grasped | ascertained by the boiler control apparatus that the reheater spray flow control valve 45 is operating. The monitor relay 72 detects that the opening command of the reheater spray flow rate adjustment valve 45 is less than a predetermined value c%, and the signal is input to the change rate limiter 70.
[0028]
When the output conditions of the operation signal C are met, the change rate limiter 70 functions to suppress a change in the closing direction of the signal from the proportional integrator 59. This is shown in FIG. FIG. 5 is a diagram for explaining the operation of the change rate limiter 70. In this figure, the horizontal axis represents time, the vertical axis represents the opening of the reheater spray flow rate adjustment valve 45, and spraying is continued three times at intervals of time t ₁ and t ₂ (for example, several minutes each). The case where it was implemented is shown. The solid line in the figure shows the operation of the reheater spray flow rate adjustment valve 45 in the conventional apparatus in which the change rate limiter 70 is not provided.
[0029]
When the opening degree of the reheater spray flow rate adjustment valve 45 is less than c% and the reheater spray flow rate adjustment valve 45 is operating in the closing direction, the operation signal C is output and the change rate limiter 70 is output. As a result, the change in the signal from the proportional integrator 59 is alleviated, and the opening degree of the reheater spray flow rate adjustment valve 45 changes as shown by the broken line in FIG. It will be done only once. In this case, the opening degree of the reheater spray flow rate adjustment valve 45 is fully closed twice (in a state where the reheat steam pipe and the desuperheater become high temperature) in the conventional apparatus, and the reheat steam pipe and the desuperheater. In this embodiment, the two fully closed states do not exist. Therefore, the repetition of the state in which the temperature difference increases is alleviated, and accordingly, the low temperature reheating is repeated. This can greatly contribute to the prevention of damage due to thermal fatigue of steam pipes and desuperheaters.
[0030]
Next, the prior spraying by the signal switcher 60 and the function generator 66 will be described. As the switching condition of the switching signal B ₂ , the difference between the “generation request output command value” and the “output value requested at the current power generation end” is a predetermined value b or more in the conventional switching signal B ₁ switching condition. By adding something, the operation of switching the signal switcher 60 to the function generator 55 side is suppressed, and spraying is suppressed accordingly, as in the case of the signal switcher 56 described above. Further, in this embodiment, the characteristic of the function generator 66 is determined according to the deviation between the generator output command value 51 and the power generation end output value 64, whereby the spray characteristic corresponding to the magnitude of the load change. Can be easily obtained.
[0031]
Thus, in the present embodiment, the difference between the “power generation request output command value” and the “output value required at the current power generation end” is greater than or equal to the predetermined value b as the switching condition of the signal switchers 56 and 60. As a result, spraying can be further suppressed compared to the conventional apparatus, and since the change rate limiter 70 is provided, the temperature difference caused by the reheat steam pipe or the temperature reducer due to the spraying. In this way, it is possible to prevent the damage due to thermal fatigue of the low-temperature reheat steam pipe and the temperature reducer.
[0032]
In the description of the above embodiment, (I) the switching condition of the signal switch 56 is such that the difference between the “power generation request output command value” and the “output value required at the current power generation end” is a predetermined value b or more. (II) means for delaying the signal that has become the furnace hopper damper lower limit operation in the switching condition of the signal switcher 56, (III) means for providing the change rate limiter 70, and (IV) signal An example will be described in which all the means for adding that the difference between the “power generation request output command value” and the “output value required at the current power generation end” is equal to or greater than the predetermined value b is included in the switching condition of the switch 60. However, it is not necessary to provide all of them, and they may be provided alone, that is, any one of (I), (II), (III), (IV) may be provided, or all of them may be provided. Combinations, ie (I) and (II), (I) and (III), (I) and (IV), (II) and (III), (II) and (IV), (III) and (IV), (I) and (II) and (III), (I) and (II) and (IV), (II ), (III), and (IV), the desired effect can be obtained by any combination.
[0033]
【The invention's effect】
As described above, in the present invention, the difference between the “power generation request output command value” and the “output value required at the current power generation end” is greater than or equal to the predetermined value b in the switching condition of the signal switch. To the switching condition of the signal switcher, the means for delaying the signal that became the furnace hopper damper lower limit operation, the means for providing the change rate limiter 70, and the switching condition of the signal switcher for selecting the prior water injection , Any one of the means for adding that the difference between the “power generation request output command value” and the “output value required at the current power generation end” is equal to or greater than the predetermined value b, or any combination thereof. Therefore, the water injection by the reheat steam desuperheater can be suppressed, or the temperature difference due to the spray can be suppressed, and as a result, the low temperature reheat steam pipe and the desuperheater Prevent damage from thermal fatigue Door can be.
[Brief description of the drawings]
FIG. 1 is a block diagram of a water injection control device for a reheat steam system desuperheater according to an embodiment of the present invention.
FIG. 2 is a diagram showing switching conditions of the signal switcher 56 shown in FIG.
FIG. 3 is a diagram showing a switching condition of an operation signal output of the change rate limiter shown in FIG. 1;
4 is a diagram showing switching conditions of the signal switcher 60 shown in FIG. 1. FIG.
FIG. 5 is a diagram illustrating the operation of a change rate limiter.
FIG. 6 is a diagram showing an outline of a boiler configuration.
FIG. 7 is a system diagram of a boiler water-steam system.
8 is a block diagram of a water injection control device that controls the reheater spray flow rate adjustment valve shown in FIG. 7. FIG.
9 is a diagram showing switching conditions of the signal switcher 56 shown in FIG. 8. FIG.
10 is a diagram showing switching conditions of the signal switcher 60 shown in FIG. 8. FIG.
11 is a partial cross-sectional view of the temperature reducer 43 shown in FIG. 7;
[Explanation of symbols]
51 Generator output command value 52 Reheat steam temperature measurement signal 53, 66 Function generator 54, 55 Signal generator 56, 60 Signal switch 64 Power generation end output value 70 Change rate limiter 71 Differentiator 72, 73 Monitor relay

Claims (3)

The exhaust gas recirculation control means that controls the amount of exhaust gas recirculated from the bottom of the boiler into the furnace with the opening of the damper and the temperature at which the desuperheater that performs water injection through the reheat steam pipe is deactivated are set a first signal generating means for outputting a signal corresponding to the non-operating temperature is, the second signal generating means for temperature for actuating the desuperheater is set to output a signal corresponding to the operating temperature, a predetermined Switching means for switching the output signal of the first signal generating means to the output signal of the second signal generating means on the basis of the above conditions, and the switching means to switch to the reheat steam temperature according to the load request signal. adding means for adding signals, calculating means for calculating a deviation between the signal and the reheat steam temperature measurement signal of the adding means, the desuperheater of the adjustment valve opening degree in response to the deviation is adjusted , Water injection control device for reheat steam system desuperheater There is,
The predetermined condition is obtained by calculating a logical product between when the load signal of the boiler is a predetermined value or more and when a difference between the load request signal and the load signal is a predetermined value or more, and the exhaust gas recirculation control means Is a logical sum of when the lower limit operation state is continued for a predetermined time and the output of the logical product,
Further, a reheat steam system reduction means is provided between the computing means and the regulating valve, wherein a rate of change limiting means for limiting the rate of change of the deviation when the regulating valve is operating in the closing direction. Water heater control device. In claim 1,
The activation signal for activating the rate-of-change limiting means operates when the regulating valve is in a state of being automatically controlled, the load is changing, and the regulating valve receives an opening degree command in the closing direction. And when the condition that the opening command of the regulating valve is less than a predetermined value occurs,
The water injection control device for a reheat steam system desuperheater , wherein the change rate limiting means operates so as to limit the change rate of the deviation by the output . In claim 1 or 2,
The adjustment is performed in advance on condition that the deviation is equal to or greater than a predetermined value, the reheat steam temperature increase rate is equal to or greater than a predetermined value, and a difference between the load request signal and the load signal is equal to or greater than a predetermined value. A water injection control device for a reheat steam system desuperheater , wherein a prior water injection means for opening the valve is provided between the change rate limiting means and the regulating valve .

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