JPH04131602A - Controller of temperature of boiler furnace outlet - Google Patents

Abstract

PURPOSE:To hold the outlet temperature of the furnace at a set temperature by seeking the ratio of the sum of the quantities of heat received by the coal economizer and furnace of a boiler to the quantity of heat received by the boiler as a whole and seeking a set temperature at the furnace outlet based on the ratio of the received quantities of heat to correct the set value for the flow rate of a spray to control a spray flow rate regulating valve. CONSTITUTION:Based on detection signals 40-43 from heat sensors 36-39 that are provided at respective sections of a boiler 1 the ratio of the sum of the quantities of heat received by the coal economizer 7 and furnace 2 of the boiler 1 to the quantity of heat received by the boiler 1 as a whole is sought by a calculator 44. Based on this ratio a set value of the temperature 49 of the furnace outlet is sought by a calculation control device 68. The deviation between the set value of the furnace outlet temperature and temperature signal 42' of the furnace outlet is taken by a subtractor 24 to seek the furnace outlet temperature deviation value 27 and a spray flow rate correction value 29 is sought by a proportional integration controller 28 base on the furnace outlet temperature deviation value 27. A correction spray flow rate set value 31 is sought by multiplying the spray flow rate set value 47 for controlling the spray flow rate regulating valve 18 by the spray flow rate correction value 29 by a multiplier 30. With this arrangement the outlet temperature of the furnace 2 is kept at the furnace outlet temperature set value 49.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a boiler furnace outlet temperature control device.

[Prior Art] In a once-through boiler for variable pressure operation, the outlet temperature of the furnace is one of the important control targets.

Below, the furnace outlet temperature control device of a conventional boiler is shown in Figure 4.
This will be explained using FIG.

In Fig. 4, 1 is a boiler, 2 is a furnace of boiler 1, 3 is a burner provided in furnace 2, 4 is a sub-side wall connected to furnace 2, and 5 is a rear heat transfer section connected to sub-side wall 4. , 6 is an exhaust gas duct connected to the rear heat transfer section 5, 7 is an economizer provided in the rear heat transfer section 5, and 8 is a superheater provided on the sub side wall 4 and the rear heat transfer section 5.

In Fig. 5, 9 is the water/steam flow path of the boiler 1, 1° is the boiler water, 11 is the feed water pump, 12 is the steam flow rate regulating valve, 13 is the turbine, 14 is the generator connected to the turbine 13, 1
5 is a spray channel branched from the water/steam channel 9; 16;
17 is a spray device that sprays water inside the superheater 8;
18 is a spray flow rate meter provided in the middle of the spray channel 15, and 18 is a spray flow rate adjustment valve provided in the middle of the spray channel 15.

19 is a generator output command, 20 is a spray flow rate setting value 21 for controlling the spray flow rate adjustment valve 18, and 20 is a generator output command 19.
It is a function generator that converts .

22 is a function generator that converts the generator output command 19 into a furnace outlet temperature set value 23.

24 is a subtracter that takes the difference between the furnace outlet temperature setting value 23 and the furnace outlet temperature detection value 26 from the temperature detector 25 provided at the outlet of the furnace 2 to obtain the furnace outlet temperature deviation value 27.

28 is based on the furnace outlet temperature deviation value 27, and when the furnace outlet temperature detected value 26 is larger than the furnace outlet temperature set value 23, the spray flow rate is reduced, and the furnace outlet temperature set value 23 is larger than the furnace outlet temperature detected value 26. In this case, it is a proportional-integral control device that determines a spray flow rate correction value 29 to increase the spray flow rate.

A multiplier 30 multiplies the spray flow rate set value 21 by a spray flow rate correction value 29 to obtain a corrected spray flow rate set value 31.

32 is the corrected spray flow rate setting value 31 and spray flow meter 1
This is a subtracter that takes the deviation from the spray flow rate 33 from 7 to obtain a spray flow rate deviation value 34.

35 is a proportional-integral controller for setting the spray flow rate deviation value 34 to the spray flow rate correction value 35.

In FIG. 4, the combustion gas generated by the combustion of fuel by the burner 3 passes through the furnace 2, sub-side wall 4, and rear heat transfer section 5 of the boiler 1, and is discharged from the exhaust gas duct 6. The water and steam flowing inside the container 8 and the economizer 7 are heated.

To explain in detail the process of heating the water and steam described above with reference to FIG. , and superheater 8, and are sequentially heated by combustion gas.

On the other hand, the boiler water 10 branched from the water/steam flow path 9 to the spray flow path 15 is injected from the spray device 16 into the superheater 8 and is used to control the temperature of the steam at the outlet of the superheater 8.

A required amount of the steam inside the superheater 8 is finally introduced into the turbine 13 by the steam flow rate regulating valve 12 to drive the turbine 13 and cause the generator 14 coaxial with the turbine 13 to generate electricity.

Control of the spray device 16 is performed as follows.

The generator output command 19 is converted by a function generator 20 into a spray flow rate set value 21 commensurate with the generator output command 19.

Further, the generator output command 19 is converted by a function generator 22 into a furnace outlet temperature set value 23 corresponding to the generator output command 19. The furnace outlet temperature setting value 23 is determined by a subtractor 24 to take the deviation from the furnace outlet temperature detection value 26 from the temperature detector 25 provided at the furnace 2 outlet, and is subjected to feedback control to keep the furnace 2 outlet temperature constant. The furnace outlet temperature deviation value 27 is set as the furnace outlet temperature deviation value 27 necessary for Furnace outlet temperature set value 2 from outlet temperature detection value 26
3 is large, the spray flow rate correction value 29 is set to increase the spray flow rate, and a multiplier 30 adds the spray flow rate correction value 2 to the spray flow rate setting value 2E.
This is used to obtain a corrected spray flow rate set value 31 which is obtained by multiplying the spray flow rate set value 21 by 9 and corrected by the spray flow rate correction value 29.

Then, the correction spray flow rate set value 31 is subtracted by a subtractor 32 from the spray flow rate 33 from the spray flow meter 17, and is set as a spray flow rate deviation value 34 for feedback controlling the spray flow rate. is processed by the proportional-integral controller 35' to become a signal suitable for control, and is used as a spray flow rate correction value 35, which is used to adjust the opening degree of the spray flow rate regulating valve 18 and control the spray flow rate.

In this way, the spray flow rate is controlled based on the corrected spray flow rate set value 31 that is obtained by correcting the spray flow rate set value 21 so that the outlet temperature of the furnace 2 is constant.

[Problems to be Solved by the Invention] However, the conventional boiler furnace outlet temperature control device described above has the following problems.

That is, in the method described above, in which the spray flow rate set value 21 is corrected by the furnace outlet temperature set value 23 determined based on the generator output command 19, control can be performed without any problem when the properties of the fuel are constant. However, when using various types of fuel with different properties, for example, when using different types of coal, the amount of ash adhering to the peripheral wall of the furnace 2 may change depending on the type of coal, and the volatilization in the coal may change depending on the type of coal. As the ratio of carbon and fixed carbon changes, the calorific value changes, and the ratio of the sum of the heat collected from the economizer 7 and the furnace 2 to the total heat collected by the boiler 1 changes. If the ratio of If the outlet temperature of the furnace 2 becomes higher than the furnace outlet temperature setting value 23 and the degree of heating of water or steam on the peripheral wall of the furnace 2 becomes excessive,
There has been a problem in that the temperature of the metal on the peripheral wall of the furnace 2 increases.

In view of the above-mentioned circumstances, the present invention makes it possible to maintain the furnace outlet temperature at a temperature equal to the furnace outlet temperature setting value, regardless of changes in the heat absorption rate of the furnace section due to changes in the properties of the fuel.
The object of the present invention is to provide a boiler furnace outlet temperature control device.

[Means for Solving the Problems] The present invention provides thermal sensors 36 to 39 provided in each part of the boiler 1.
Based on the detection signals 40 to 43 from the respective heat sensors 36 to 39, the total heat absorption amount of the heat absorption amount of the boiler 1's economizer 7 and the heat absorption amount of the furnace 2 with respect to the heat absorption amount of the entire boiler 1 is determined. A calculation device 44 that calculates the ratio, a calculation control device 48 that calculates the furnace outlet temperature setting value 49 based on the signal 46 indicating the rate of heat absorption from the calculation device 44, and the furnace exit temperature setting value 49 and the furnace exit temperature signal 42. A subtractor 24 that calculates the furnace outlet temperature deviation value 27 by calculating the deviation from the furnace outlet temperature deviation value 27, a proportional integral controller 28 that calculates the spray flow rate correction value 29 based on the furnace outlet temperature deviation value 27, and a spray flow rate adjustment valve 18 are controlled. Spray flow rate correction value 2 to spray flow rate setting value 47 for
This invention relates to a boiler furnace outlet temperature control device characterized in that it is equipped with a multiplier 30 for calculating a corrected spray flow rate set value 31 by multiplying by 9.

[Function] According to the present invention, the thermal sensor 36 provided in each part of the boiler 1
Based on the detection signals 40 to 43 from the boiler 1 to 39, the arithmetic unit 44 calculates the
The ratio of the total amount of heat absorbed by the economizer 7 and the furnace 2 is calculated, and the furnace outlet temperature set value 4 is determined by the arithmetic controller 48 based on the signal 46 indicating the ratio of the heat absorbed from the arithmetic device 44.
9 is obtained, and the furnace outlet temperature setting value 4 is determined by the subtractor 24.
9 and the furnace outlet temperature signal 42' is taken to obtain the furnace outlet temperature deviation value 27, and the spray flow rate correction value 2 is determined by the proportional integral controller 28 based on the furnace outlet temperature deviation value 27.
9 is determined, and the spray flow rate setting value 47 for controlling the spray flow rate regulating valve 18 is multiplied by the spray flow rate correction value 29 by the multiplier 30 to obtain a corrected spray flow rate setting value 31.

Thereby, even if the ratio of the heat absorption amount of the economizer 7 and the furnace 2 changes depending on the properties of the fuel, the outlet temperature of the furnace 2 is maintained at a temperature corresponding to the furnace outlet temperature setting value 49.

[Implementation 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 same parts in the figure as in FIG. 5 are given the same reference numerals, so a description thereof will be omitted.

36 is a thermal sensor equipped with a temperature detector and a pressure detector (hereinafter, a combination of a temperature detector and a pressure detector is collectively referred to as 37 is a heat sensor installed between the exit of the economizer 7 in the water/steam flow path 9 and the furnace 2, and 38 is a heat sensor installed at the exit of the furnace 2 in the water/steam flow path 9. Sensor, 39 is a thermal sensor provided at the outlet of superheater 8, 40.41.42.4
3 is a detection signal indicating the temperature and pressure from the thermal sensors 36, 37, 38, and 39, and 42' is a furnace outlet temperature signal forming a part of the detection signal 42 of the thermal sensor 38.

44 is an arithmetic device which inputs the detection signals 40, 41, 42, and 43 and calculates the ratio of the total heat absorption amount of the economizer 7 and the furnace 2 to the heat absorption amount of the boiler 1 as a whole. 45 is an arithmetic and control device that inputs a signal 46 indicating the rate of heat absorption and derives a spray flow rate set value 47 for controlling the spray flow rate regulating valve 18 in accordance with the generator output command 19. 48 is an arithmetic and control device that inputs a signal 46 indicating the rate of heat absorption and derives a furnace outlet temperature setting value 49 according to the generator output command 19.

Next, the operation will be explained.

The boiler water 10 supplied to the water/steam flow path 9 is heated,
The process of generating electricity is similar to that shown in FIG.

When using fuels with different properties as the fuel to be burned in the burner 3, for example when using various types of coal, the amount of ash adhering to the peripheral wall of the furnace 2 may change depending on the type of coal, Since the ratio of volatile matter and fixed carbon in the boiler changes, and the amount of heat generated changes, the ratio of the total amount of heat received by the economizer 7 and the furnace 2 to the amount of heat received by the boiler 1 as a whole changes.

Therefore, the thermal sensors 36, 37, 38, and 39 detect the temperature between the 7th population of the economizer, the 7th exit of the economizer and the 2nd population of the furnace 2, and the 2nd population of the furnace 2, respectively.
The temperature and pressure at the outlet and the outlet of the water/steam flow path 9 are detected, and the detection signals 40, 41, 42, 43 are input to the calculation device 44, which calculates the amount of heat at each position. Then, the amount of heat obtained by the detection signal 40 is subtracted from the amount of heat obtained by the detection signal 43, and the boiler 1
In addition to finding the overall heat absorption amount, the heat amount obtained by the detection signal 40 is subtracted from the heat amount obtained by the detection signal 41 to find the heat absorption amount of the economizer 7, and 41 is subtracted from one detection signal 42. Calculate the heat absorption amount of furnace 2. Furthermore, economizer 7
The total heat loss obtained by adding the heat loss of the furnace 2 and the heat loss of the furnace 2 is divided by the heat loss of the entire boiler 1 to calculate the heat loss of the economizer 7 and the heat loss of the furnace 2 relative to the heat loss of the entire boiler 1. Calculate the percentage of total heat loss.

Once the heat absorption rate is calculated by the arithmetic unit 44, a signal 46 indicating the heat absorption rate is input to the arithmetic control unit 45. The arithmetic and control unit 45 is equipped with a plurality of functions that express the relationship between the rate of heat absorption and the spray flow rate as shown in FIG. 2 according to the magnitude of the generator output command 19. A spray flow rate corresponding to the rate of heat absorption is derived based on a function corresponding to the magnitude of the generator output command 19.

The function shown in FIG. 2 indicates that when the ratio of the total heat absorption amount of the energy saver 7 and the furnace 2 is small, the amount of water flowing to the spray channel 15 side is increased and the amount of water that is absorbed by the energy saver 7 and the furnace 2 is increased by that amount. By reducing the amount of water flowing to the furnace 2 side, the heating degree of water and steam in the economizer 7 and the furnace 2 is controlled to increase to a predetermined value, and conversely, the heating degree of the water and steam in the economizer 7 and the furnace 2 is increased to a predetermined value. When the proportion of the heat absorption amount is large, the amount of water flowing to the spray channel 15 side is reduced and the amount of water flowing to the economizer 7 and furnace 2 side is increased by that amount. Since it is necessary to control the heating degree of water and steam in the furnace 2 to lower it to a predetermined value, the spray flow rate decreases as the rate of heat absorption increases, and the specific function is determined by the generator. The output command 190 is determined in advance by calculation or experiment for each magnitude and is input to the arithmetic unit 44.

Once the spray flow rate corresponding to the rate of heat absorption is derived by the arithmetic and control unit 45, the spray flow rate is set as the spray flow rate set value 47 and the spray flow rate adjustment valve 18 is operated in the same manner as in FIG.
It should be used for control.

As a result, the spray flow rate adjustment valve 18 increases the spray flow rate when the ratio of the total heat absorption amount of the economizer 7 and the furnace 2 is low, based on the spray flow rate set value 47.
On the contrary, when the ratio of the total amount of heat absorbed by the economizer 7 and the furnace 2 is high, the spray flow rate is controlled to be small.

At the same time, a signal 46 indicating the rate of heat absorption is sent to the arithmetic and control unit 4.
Enter 8. The arithmetic and control unit 48 outputs a generator output command 19
As shown in Figure 3, there are multiple functions that express the relationship between the rate of heat absorption and the furnace outlet temperature, depending on the size of the furnace.
The arithmetic and control device 48 derives the furnace outlet temperature corresponding to the rate of heat absorption based on a function corresponding to the current magnitude of the generator output command 19.

The function in Figure 3 is a curve that slopes upward to the right because the furnace outlet temperature increases as the rate of heat absorption increases, and the specific function is calculated in advance or experimentally determined for each magnitude of the generator output command 19. It is input to the control device 48.

Once the arithmetic and control unit 48 derives the furnace outlet temperature corresponding to the rate of heat absorption, the furnace outlet temperature is set as the furnace outlet temperature set value 49 and the spray flow rate set value 4 is set as in FIG.
It should be used for the correction of 7.

By determining the furnace outlet temperature setting value 49 and correcting the spray flow rate setting value 47 for controlling the spray flow rate adjustment valve 18 based on the heat absorption rate, it is possible to adjust the spray flow rate setting value 47 for controlling the spray flow rate adjustment valve 18. Even when different types of coal are used as fuel, the outlet temperature of the furnace 2 can always be maintained at a temperature corresponding to the furnace outlet temperature setting value 49.

It should be noted that the boiler furnace outlet temperature control device of the present invention is not limited to the above-described embodiments, the fuel is not limited to coal, and various other changes may be made without departing from the gist of the present invention. Of course, you can add more.

[Effects of the Invention] As explained above, according to the boiler furnace outlet temperature control device of the present invention, the ratio of the total heat absorption amount of the economizer 7 and the furnace 2 to the heat absorption amount of the entire boiler 1 is determined, Since the furnace outlet temperature set value 49 is determined based on the ratio of the heat absorption amount, and the spray flow rate set value 47 for controlling the spray flow rate adjustment valve 18 is corrected based on the furnace outlet temperature set value 49, Even when fuels with different properties are used, an excellent effect can be achieved in that the outlet temperature of the furnace 2 can always be maintained at a temperature corresponding to the furnace outlet temperature set value 49.

[Brief explanation of the drawing]

Fig. 1 is a water/steam system diagram showing one embodiment of the present invention;
The figure is a diagram showing the relationship between the heat absorption rate and the spray flow rate when the generator output command is constant, and Figure 3 shows the relationship between the heat absorption rate and the furnace outlet temperature when the generator output command is constant. Figure 4 is a schematic overall side view of a general boiler to explain the conventional example, and Figure 5 is a diagram of the conventional boiler.
It is a steam system diagram. In the figure, 1 is the boiler, 2 is the furnace, 7 is the economizer, 18 is the spray flow rate adjustment valve, 24 is the subtractor, 27 is the furnace outlet temperature deviation value, 28 is the proportional integral controller, and 29 is the spray flow rate correction value , 30 is a multiplier, 31 is a correction spray flow rate setting value,
36-39 are thermal sensors, 40-43 are each thermal sensors 36-
Detection signal from 39, 42° is furnace outlet temperature signal, 44
46 is a calculation device for calculating the rate of heat absorption, and 44 is a calculation device.
47 is a spray flow rate set value, 48 is an arithmetic and control device, and 49 is a furnace outlet temperature set value.

Claims (1)

[Claims] 1) Based on the thermal sensors 36 to 39 provided in each part of the boiler 1 and the detection signals 40 to 43 from each of the thermal sensors 36 to 39, the energy consumption of the energy saver 7 of the boiler 1 is determined relative to the total heat absorption amount of the boiler 1. An arithmetic device 44 calculates the ratio of the total amount of heat and the amount of heat absorbed by the furnace 2, and a furnace outlet temperature set value 49 is calculated based on a signal 46 indicating the ratio of the amount of heat received from the arithmetic device 44.
an arithmetic and control unit 48 for determining the furnace outlet temperature set value 49;
a subtractor 24 that calculates the furnace exit temperature deviation value 27 by taking the deviation between the furnace exit temperature signal 42' and the furnace exit temperature signal 42'; a proportional integral controller 28 that calculates the spray flow rate correction value 29 based on the furnace exit temperature deviation value 27; A multiplier 30 that calculates a corrected spray flow rate set value 31 by multiplying a spray flow rate set value 47 for controlling the regulating valve 18 by a spray flow rate correction value 29.
A boiler furnace outlet temperature control device comprising: