JPH0461241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the flow rate of fuel supplied to a fluidized bed boiler equipped with a reheater or a superheater.

Conventionally, for example, in a fluidized bed boiler equipped with a reheater, the reheat steam temperature is controlled by operating a temperature reducer equipped with a water injection valve, etc., and the flow rate of fuel supplied to the fluidized bed boiler is It is controlled according to the flow rate of thermal steam, that is, the load. In such prior art, although the reheat steam temperature can be controlled by a temperature attenuator if the supplied fuel flow rate is given to balance the steam absorption heat from the reheater, the fuel If the supplied fuel flow rate does not match the required value corresponding to the reheat steam flow rate due to changes in the heating value of There may be cases where it becomes impossible to control the desired value. For example, if the fuel calorific value deviates from the rated design point value and decreases, the fuel flow rate will be insufficient, and therefore the amount of heat absorption in the reheater will decrease, and the water injection valve in the temperature reducer will be completely closed. Even if it becomes closed and the temperature reduction amount becomes zero,
The reheat steam temperature cannot rise to the desired value. Conversely, if the fuel calorific value deviates from the rated design point value and increases, the flow rate of the supplied fuel will be too high and the water injection valve in the temperature attenuator will be fully open. As a result, even if the temperature reducer is set to the maximum, the reheat steam temperature will exceed the desired value. A similar situation occurs in a fluidized bed boiler equipped with a superheater.

An object of the present invention is to correct a fuel flow rate corresponding to a load in a fluidized bed boiler equipped with a reheater or a superheater so that the temperature of reheated steam or superheated steam can be set to a desired value. The goal is to provide the following.

The present invention provides the following features: (a) the first and second reheaters 3 and 5 are provided in this order from the upstream side to the downstream side in the fluidized bed 7 of the fluidized bed boiler 2; An injection chamber 19 is provided between the heating units 3 and 5, and water is injected into this injection chamber 19 by a water injection valve 18 whose opening degree is variable. (c) fuel supply means 8 for supplying fuel to the fluidized bed 7;
(d) a steam load detector 11 that detects the steam loads of the first and second reheaters 3 and 5; and (e) a fuel detector 11 that detects the steam load in response to the output of the steam load detector 11. (f) a steam temperature detector 14 that detects the temperature of the steam supplied from the second reheater 5; (g) a signal from the steam temperature detector 14; temperature deviation calculation means 15 for deriving a signal representing a temperature deviation between the detected steam temperature and a predetermined temperature in response to the output;
(h) a first circuit that responds to the outputs from the temperature deviation calculation means 15 and 16 and applies an operation signal to the water injection valve 18 so that the water injection valve 18 has an opening degree corresponding to the temperature deviation;
a control circuit 17; (i) responsive to the outputs from the temperature deviation calculation means 15, 16; (i2) Deriving a signal that prevents the fuel flow rate from being changed by the temperature deviation signal when the temperature is within the temperature range (t1 to t2); (i2-1) When the detected steam temperature is high, a signal is derived that reduces the fuel flow rate as the detected steam temperature increases, and (i2-2) When the detected steam temperature is low. (j) in response to an operation signal from the first control circuit 17;
The deviation between the operation signal and a predetermined target value is determined, and based on this deviation, when the opening degree of the water injection valve 18 increases, the fuel flow rate decreases, and when the opening degree decreases, the fuel flow rate increases. (k) the output of the first arithmetic circuit 12 and the function generation circuit 2;
3 and the outputs of the correction means 25 and 27, and a second arithmetic circuit 13 which adds the outputs of the correction means 25 and 27 and supplies the sum to the fuel supply means 8.Fuel flow rate restriction of a fluidized bed boiler equipped with a reheater It is a device.

Further, the present invention provides the following features: (a) the first and second reheaters 3 and 5 are provided in this order from the upstream side to the downstream side in the fluidized bed 7 of the fluidized bed boiler 2; An injection chamber 19 is provided between the reheaters 3 and 5, and water is injected into this injection chamber 19 by a water injection valve 18 whose opening degree is variable. (c) fuel supply means 8 for supplying fuel to the fluidized bed 7;
(d) a steam load detector 11 that detects the steam loads of the first and second reheaters 3 and 5; and (e) a fuel detector 11 that detects the steam load in response to the output of the steam load detector 11. (f) a steam temperature detector 14 that detects the temperature of the steam supplied from the second reheater 5; (g) a signal from the steam temperature detector 14; temperature deviation calculation means 15 for deriving a signal representing a temperature deviation between the detected steam temperature and a predetermined temperature in response to the output;
(h) a first circuit that responds to the outputs from the temperature deviation calculation means 15 and 16 and applies an operation signal to the water injection valve 18 so that the water injection valve 18 has an opening degree corresponding to the temperature deviation;
a control circuit 17; (i) means for detecting the operation amount of the water injection valve 18 and deriving an operation amount detection signal; (j) responding to the outputs from the temperature deviation calculation means 15 and 16; When the temperature represented by the signal is within a predetermined small temperature range (t1 to t2) that can be controlled by operation of the water injection valve 18, the temperature deviation signal causes a signal to not change the fuel flow rate. Derived, (j2) When the temperature represented by the temperature deviation signal is outside the temperature range (t1 to t2), and (j2-1) When the detected steam temperature is high, the detected steam temperature is high. (j2-2) when the detected steam temperature is low, a function generating circuit 23 that derives a signal that increases the fuel flow rate as the detected steam temperature becomes lower; (k) In response to the manipulated variable detection signal, the deviation between the manipulated variable detection signal and a predetermined target value is determined, and based on this deviation, when the opening degree of the water injection valve 18 increases, the fuel flow rate is adjusted to become smaller. (l) the output of the first arithmetic circuit 12 and the function generating circuit 2;
3 and the outputs of the correction means 25 and 27, and a second arithmetic circuit 13 which adds the outputs of the correction means 25 and 27 and supplies the sum to the fuel supply means 8.Fuel flow rate restriction of a fluidized bed boiler equipped with a reheater It is a device.

FIG. 1 is an overall system diagram of an embodiment of the first invention. Steam passes through a superheater from an evaporator (not shown) and passes through a high-pressure turbine (not shown).
The steam flows from the flow path 1 into a first reheater 3 provided in a fluidized bed boiler 2 and is superheated.The steam from the first reheater 3 is reduced in temperature by a temperature reducer 4, and
After being superheated in the reheater 5, it is sent to an intermediate pressure turbine (not shown) through a flow path 6. In the fluidized bed boiler 2, the fluidized bed 7 is provided with the aforementioned first and second reheaters 3 and 5. Fuel is supplied to the fluidized bed 7 of the fluidized bed boiler 2 from above or below by a fuel supply means 8. Primary air is supplied from below the fluidized bed 7 via a flow path 9. Exhaust gas from the fluidized bed boiler 2 is discharged to the outside through a flow path 10.

For example, the steam flow rate representing the steam load in the flow path 1 or the steam pressure corresponding to the steam flow rate is determined by the detector 1.
Detected by 1. For example, a steam flow rate or a steam pressure corresponding to the steam flow rate representing the detected steam load is provided to the control circuit 12. The control circuit 12 sends, via the arithmetic circuit 13, a signal representing the steam load detected by the detector 11, for example, a steam flow rate or a steam pressure corresponding to the steam flow rate, and thus a fuel flow rate corresponding to the load. The fuel is supplied to the fuel supply means 8. A signal representing the fuel flow rate from the control circuit 12 is corrected by a signal described later in the arithmetic circuit 13. The reheat steam temperature in the flow path 6 is detected by the detector 14. A signal representing the detected reheat steam temperature is given to one input of the arithmetic circuit 15. The other input of the arithmetic circuit 15 is given a signal from a setting circuit 16 that derives a signal representing a predetermined temperature. The arithmetic circuit 15 provides the control circuit 17 with a signal representing the deviation obtained by subtracting the signal from the setting circuit 16 from the signal from the detector 14 . The control circuit 17 is realized by, for example, a so-called PID controller and a sign inverter that perform proportional, integral, and differential operations. Control circuit 17 responds to the temperature deviation signal from arithmetic circuit 15 and derives an operation signal for operating temperature reducer 4 . The temperature reducer 4 includes a water injection valve 18 whose opening degree is variable and an injection chamber 19, and this water injection valve 18 is connected to a control circuit 17.
The opening changes in response to an operation signal from the valve. In this way, the temperature of the steam from the first reheater 3 is reduced by the temperature reducer 4 so that the reheated steam temperature detected by the detector 14 becomes the value set by the setting circuit 16. Ru. The temperature deviation signal from the arithmetic circuit 15 is sent via line 21 and also to the control circuit 17.
An operation signal from the controller is input to the correction control circuit 20 via a line 22. The output from the correction control circuit 20 is given to the arithmetic circuit 13 and then sent to the control circuit 12.
is added to the signal representing the fuel flow rate from the

FIG. 2 is a block diagram showing a specific configuration of the correction control circuit 20. As shown in FIG. The temperature deviation signal via line 21 is input to function generating circuit 23 . The function generating circuit 23 has the characteristics shown in FIG. When the temperature represented by the temperature deviation signal is in the range of t1 to t2, the output level is zero, and in the range below the temperature t1 and above the temperature t2, the output level increases as the absolute value of the temperature represented by the temperature deviation signal increases. rises.

The output from the function generation circuit 23 is input to the arithmetic circuit 25 via the proportional control circuit 24. The output from the arithmetic circuit 25 is subjected to arithmetic operations such as proportionality, integration, and differentiation by the control circuit 26, and is derived from the line 28.

The operation signal via the line 22 is input to the arithmetic circuit 25, as well as a signal from the setting circuit 27 in which the target value of the operation signal is set. The arithmetic circuit 25 subtracts the operation signal 22 from the target value set by the setting circuit 27. In this way, in the calculation circuit 25, the proportional control circuit 2
4 is subtracted from the difference obtained by subtracting the operation signal via line 22 from the target value setting signal from setting circuit 27.

the reheat steam temperature detected by the detector 14 is in a range that can be controlled by the temperature attenuator 4;
Therefore, when the temperature represented by the temperature deviation signal derived from the arithmetic circuit 15 is in the range of t1 to t2 in FIG. 3, the supplied fuel flow rate is corrected depending on the operation signal for operating the temperature reducer 4. be done. For example, when the amount of temperature reduction to be reduced by the temperature reducer 4 increases, the output level from the arithmetic circuit 25 decreases, thereby suppressing the fuel flow rate to a small value. In this way, the fuel flow rate is controlled by the operation signal set based on the reheat steam temperature.

Assume that the reheat steam temperature detected by the detector 14 has increased, so that the temperature representing the temperature deviation signal derived from the arithmetic circuit 15 has increased beyond the value t2 in FIG. This case occurs because the fuel flow rate supplied by the fuel supply means 8 is too large. The function generating circuit 23 therefore derives a signal with a positive level, whereby the fuel flow rate is corrected to decrease.

On the contrary, assume that the reheated steam temperature detected by the detector 14 decreases and the temperature deviation signal becomes less than the value t1 in FIG. 3. in this case,
This occurs because the supplied fuel flow rate is too low.
The function generating circuit 23 derives a signal having a negative level, whereby the signal from the control circuit 12 is corrected so that the amount of fuel to be supplied is increased.

Assume a case where the operation signal via line 22 increases beyond the target value set by setting circuit 27. This case occurs because the fuel flow rate supplied by the fuel supply means 8 is too large. The output from the arithmetic circuit 25 is slightly changed by the operation signal on the line 22. Therefore, the control circuit 12
is corrected so that the fuel flow rate represented by the signal derived from .

On the contrary, assume that the operation signal from line 22 decreases from the target value. In this case, this is because the supplied fuel flow rate is too small. Therefore, the signal level from the arithmetic circuit 25 changes greatly. As a result, the fuel flow rate represented by the signal derived from the control circuit 12 is corrected to increase.

Although in the embodiments described above the fluidized bed boiler was configured with a reheater, the invention can also be implemented in connection with a fluidized bed boiler with a superheater. The term "reheater" in the claims should be interpreted to include such a superheater.

As an embodiment of the second invention, instead of making the correction based on the operation signal for operating the temperature reducer, the correction may be made based on a detection signal of the operation amount of the temperature reducer based on this operation signal. This detection signal may be, for example, a manipulated variable detection signal representing a flow rate obtained by detecting the flow rate of water used in the temperature reducer.

As described above, in the present invention, the temperature deviation calculation means 1
A major feature is that the superheater outlet temperature deviation signal 21 from 5 and 16 is monitored using nonlinear characteristics by the function generating circuit 23 shown in FIG. In other words, when the temperature control deviation at the exits of the reheaters 3 and 5 is small, the control is achieved by spraying, so the first control circuit 1
The spray signal 22, which is an operation signal from the fuel injection valve 7, is changing, and the fuel is corrected based on this signal. At this time, the magnitude of the reheater outlet temperature control deviation signal 21 falls within the dead zone of the function generating circuit 23 in FIG. 3, that is, within the temperature range t1 to t2.

However, if the reheater outlet temperature control deviation increases beyond the dead zone of the function generation circuit 23 shown in FIG. It's summery.
In this case, the function generating circuit 2 of FIG.
3 makes a correction to the fuel control. This allows continuous correction to be made to the fuel control even when the spray operation signal 22 is saturated at its maximum or minimum. In this case, by changing the output value of the function generating circuit 23, the strength of the correction applied to the fuel control can be arbitrarily changed. With these measures, even if the spray water injection valve 18 is fully closed or fully opened, the temperature of the fluidized bed can be changed as quickly as possible to a range that can be controlled by the spray water injection valve 18.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram of an embodiment of the present invention, and FIG. 2 is a correction control circuit 2 included in the embodiment of FIG.
FIG. 3 is a graph showing the operation of the arithmetic circuit 23. In FIG. 2... Fluidized bed boiler, 3... First reheater, 4...
... Temperature reducer, 5 ... Second reheater, 7 ... Fluidized bed, 8 ... Fuel supply means, 12, 17 ... Control circuit, 13, 15, 25 ... Arithmetic circuit, 14 ... Reheat Steam temperature detector, 20...correction control circuit.

Claims (1)

[Claims] 1 (a) The first and second reheaters 3 and 5 are provided in this order from the upstream side to the downstream side in the fluidized bed 7 of the fluidized bed boiler 2, (b) The first and second reheaters 3 and 5 are provided in this order from the upstream side to the downstream side. An injection chamber 19 is provided between the second reheaters 3 and 5, and water is injected into this injection chamber 19 by a water injection valve 18 whose opening degree is variable. (c) Fuel supply means 8 which reduces the temperature of the steam from the heater 3 and guides it to the second reheater 5, and (c) supplies fuel to the fluidized bed 7.
(d) a steam load detector 11 that detects the steam loads of the first and second reheaters 3 and 5; and (e) a fuel detector 11 that detects the steam load in response to the output of the steam load detector 11. (f) a steam temperature detector 14 that detects the temperature of the steam supplied from the second reheater 5; (g) a signal from the steam temperature detector 14; temperature deviation calculation means 15 for deriving a signal representing a temperature deviation between the detected steam temperature and a predetermined temperature in response to the output;
(h) a first circuit that responds to the outputs from the temperature deviation calculation means 15 and 16 and applies an operation signal to the water injection valve 18 so that the water injection valve 18 has an opening degree corresponding to the temperature deviation;
a control circuit 17; (i) responsive to the outputs from the temperature deviation calculation means 15, 16; (i2) Deriving a signal that prevents the fuel flow rate from being changed by the temperature deviation signal when the temperature is within the temperature range (t1 to t2); (i2-1) When the detected steam temperature is high, a signal is derived that reduces the fuel flow rate as the detected steam temperature increases, and (i2-2) When the detected steam temperature is low. (j) in response to an operation signal from the first control circuit 17;
The deviation between the operation signal and a predetermined target value is determined, and based on this deviation, when the opening degree of the water injection valve 18 increases, the fuel flow rate decreases, and when the opening degree decreases, the fuel flow rate increases. (k) the output of the first arithmetic circuit 12 and the function generation circuit 2;
Fuel flow rate control of a fluidized bed boiler equipped with a reheater, characterized in that the second calculation circuit 13 adds the outputs of 3 and the outputs of the correction means 25 and 27 and supplies the sum to the fuel supply means 8. Device. 2 (a) The first and second reheaters 3 and 5 are provided in this order from the upstream side to the downstream side in the fluidized bed 7 of the fluidized bed boiler 2, (b) The first and second reheaters 3 , 5, an injection chamber 19 is provided between the injection chamber 19 and the injection chamber 19. Water is injected into the injection chamber 19 by a water injection valve 18 whose opening degree is variable. (c) Fuel supply means 8 for reducing the temperature and guiding the fuel to the second reheater 5, and (c) supplying the fuel to the fluidized bed 7.
(d) a steam load detector 11 that detects the steam loads of the first and second reheaters 3 and 5; and (e) a fuel detector 11 that detects the steam load in response to the output of the steam load detector 11. (f) a steam temperature detector 14 that detects the temperature of the steam supplied from the second reheater 5; (g) a signal from the steam temperature detector 14; temperature deviation calculation means 15 for deriving a signal representing a temperature deviation between the detected steam temperature and a predetermined temperature in response to the output;
(h) a first circuit that responds to the outputs from the temperature deviation calculation means 15 and 16 and applies an operation signal to the water injection valve 18 so that the water injection valve 18 has an opening degree corresponding to the temperature deviation;
a control circuit 17; (i) means for detecting the operation amount of the water injection valve 18 and deriving an operation amount detection signal; (j) responding to the outputs from the temperature deviation calculation means 15 and 16; When the temperature represented by the signal is within a predetermined small temperature range (t1 to t2) that can be controlled by operation of the water injection valve 18, the temperature deviation signal causes a signal to not change the fuel flow rate. Derived, (j2) When the temperature represented by the temperature deviation signal is outside the temperature range (t1 to t2), and (j2-1) When the detected steam temperature is high, the detected steam temperature is high. (j2-2) when the detected steam temperature is low, a function generating circuit 23 that derives a signal that increases the fuel flow rate as the detected steam temperature becomes lower; (k) In response to the manipulated variable detection signal, the deviation between the manipulated variable detection signal and a predetermined target value is determined, and based on this deviation, when the opening degree of the water injection valve 18 increases, the fuel flow rate is adjusted to become smaller. (l) the output of the first arithmetic circuit 12 and the function generating circuit 2;
Fuel flow rate control of a fluidized bed boiler equipped with a reheater, characterized in that the second calculation circuit 13 adds the outputs of 3 and the outputs of the correction means 25 and 27 and supplies the sum to the fuel supply means 8. Device.