JPH0626602A - Control device for pressurized fluidized bed type boiler - Google Patents

Abstract

PURPOSE:To prevent a lack of oxygen from occurring and to enable a load to be stably increased by a method wherein a flow rate of air for combustion supplied to a fluidized bed type boiler is increased when a load instruction signal is increased. CONSTITUTION:There is provided a fuel control circuit 27 comprising a variation rate limiter 15 for giving a limitation to a variation of an output instruction 14 by inputting the output instruction 14, an adder 17 for adding a pressure correcting signal P to an output of the variation rate limiter 15 in response to a vapor pressure of a fluidized bed type boiler 2 and a function generator 19 for outputting a fuel instruction signal 20 to a fuel supplying device 8 after converting in a function of an output of the adder 17. Then, there is provided an air control circuit 31 comprising a function generator 29 for inputting the output instruction 14 and outputting an air instruction signal 28 not limiting a variation rate for use in controlling an air supplying device 11, and an adder 30 for adding an oxygen concentration correcting signal 24 to the air instruction signal 28 obtained from the function generator 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for a pressurized fluidized bed boiler.

[0002]

2. Description of the Related Art In a pressurized fluidized bed boiler, a fluidized bed boiler 2 is provided in a pressure vessel 1 as shown in FIG. 3, and combustion air 4 pressurized by a compressor 3 is supplied to the pressure vessel 1.
The combustion air 4 is supplied from the lower part 5 of the fluidized bed boiler 2 to the diffuser plate 6 in the fluidized bed boiler 2 to form the fluidized bed 7 by supplying the combustion air 4 from the lower portion 5 of the fluidized bed boiler 2 to the fuel bed 7. The boiler water supplied to the fluidized bed boiler is heated by fluidly burning the fuel supplied from the fuel supply device 8 such as a pump into the fluidized bed 7. The pressurized fluidized bed boiler prevents combustion gas of the fluidized bed boiler 2 from leaking to the outside by supplying combustion air 4 to the pressure vessel 1 to pressurize the inside of the pressure vessel 1. There is. Further, in the illustrated case, the exhaust gas after combustion of the fluidized bed boiler 2 is supplied to the gas turbine 10 through the inlet guide vane 9 to drive the compressor 3 coaxially connected to the gas turbine 10. An air supply device 11 that supplies the combustion air 4 is configured. Reference numeral 12 in the figure denotes an ash removal pipe provided with a cutoff valve 13 in the middle thereof to cut out ash from the furnace bottom of the fluidized bed boiler 2.

A control device for controlling the fuel supply device 8 and the air supply device 11 of the above-mentioned pressurized fluidized bed boiler will be described with reference to FIGS. 3 and 4, as shown by a solid line in FIG. 4 (A). By introducing the output command (MWD) 14 that rapidly changes to the change rate limiter 15, the pressurized fluidized bed boiler can follow the change of the output command 14 as shown by the broken line in FIG. An adder 17 which gives a limit to change the gradient 16 and adds a pressure correction signal P obtained based on the pressure of steam produced in the fluidized bed boiler 2 to the signal from the change rate limiter 15. Is provided to obtain the boiler master signal 18.

The boiler master signal 18 is generated by the function generator 1
9 by introducing the fuel command signal 20 shown in FIG.
The fuel supply signal 8 is controlled by the fuel command signal 20. Also, the boiler master signal 1
A water supply command signal 21 for water supply is obtained from 8.

Further, the fuel command signal 20 is led to a function generator 22 and converted into a function to obtain an air command signal 25 shown in FIG. 4C, and the oxygen concentration in the exhaust gas of the fluidized bed boiler 2 is detected. The oxygen concentration correction signal 24 obtained based on the detected oxygen concentration from the oxygen concentration meter 23 is introduced to the adder 26 and added to the air command signal 25, and the air command signal 25 thus obtained causes the air to flow. Supply device 1
The inlet guide vane 9 of No. 1 is controlled.

In the above conventional control device, when the output command 14 increases as indicated by the solid line in FIG. 4A, the boiler master signal 18 whose rate of change is limited by the rate of change limiter 15 increases (indicated by a broken line). Based on the indicated gradient 16), each of the fuel command signal 20 and the air command signal 25 is simultaneously increased at a required rate of change.

[0007]

However, in the above-mentioned pressurized fluidized bed, the combustion air 4 from the compressor 3 is once supplied to the pressure vessel 1 and then to the fluidized bed boiler 2. Therefore, the supply amount of air to the fluidized bed boiler 2 is changed only when the pressure in the pressure vessel 1 is changed, and since the capacity of the pressure vessel 1 is large, the combustion air 4 by the compressor 3 is changed.
When the supply amount of is increased or decreased, a large time delay occurs until the supply amount of the combustion air 4 into the fluidized bed boiler 2 actually changes.

Therefore, in the above-mentioned conventional control device, as shown in FIG.
As shown in (B), when the fuel command signal 20 introduced to the fuel supply device 8 is increased, the fuel supply amount is immediately increased, but the air command signal 25 introduced to the inlet guide vane 9 is increased. Also, it takes time until the supply amount of the combustion air 4 to the fluidized bed boiler 2 is actually increased. Therefore, as shown in FIG. 4D, the oxygen concentration of the exhaust gas is equal to or less than the target limit value, that is, the fluidized bed. Combustion in the boiler 2 is performed in an air-deficient state, resulting in pollutant generation due to incomplete combustion, adverse effect on gas turbine due to dust, reduction in fuel efficiency, and in some cases, a trip of the entire device. Causes problems such as.

Therefore, conventionally, the oxygen concentration of the exhaust gas is monitored by the oxygen concentration meter 23, and it is detected from the detected value that the above-mentioned inconvenience occurs, and the fuel supply amount by the fuel supply device 8 is detected. Although the worker manually adjusts to narrow down the above, this kind of work is troublesome, and the adjustment operation is delayed and stable oxygen concentration adjustment is not possible, causing the above problems. If the fuel is throttled in order to secure the oxygen concentration in the exhaust gas, there is a command to increase the output command 14 and then the fuel is actually increased to increase the output of the fluidized bed boiler 2. However, there is a problem in that it takes a long time to be able to perform the control, and the control is greatly delayed with respect to the output target value.

The present invention has been made in view of the above-mentioned conventional problems, and prevents the oxygen concentration in the exhaust gas from decreasing when the output command increases and causes a time delay with respect to the increase of the output command. It is an object of the present invention to provide a control device for a pressurized fluidized bed boiler, which is capable of stably increasing the output without being required.

[0011]

The present invention comprises a pressure vessel,
A pressurized fluidized bed boiler equipped with a fluidized bed boiler installed in the pressure vessel, a fuel supply device for supplying fuel to the fluidized bed boiler, and an air supply device for supplying combustion air to the pressure vessel. A controller, which is a change rate limiter for inputting an output command of the pressurized fluidized bed boiler to limit a change in the output command, and a pressure based on the steam pressure of the fluidized bed boiler for the output of the change rate limiter. A fuel control circuit comprising an adder for adding a correction signal and a function generator for converting the output of the adder into a function to output a fuel command signal to the fuel supply device, and inputting the output command, Provided is an air control circuit including a function generator for outputting an air command signal for controlling the air supply device without limiting the rate of change, and an adder for adding an oxygen concentration correction signal to the air command signal from the function generator. Characterized by Control device for a PFBC boiler to, those related to.

[0012]

When the output command is increased, the rate of change of the output command is limited by the change rate limiter, and the pressure correction signal is further added by the adder to obtain the boiler master signal. A fuel command signal is obtained by the function generator, and the fuel supply device is controlled by the fuel command signal.

On the other hand, the output command before being guided to the rate-of-change limiter is guided to the function generator, whereby an air command signal without rate-of-change restriction is obtained, and an oxygen concentration correction signal is added to the air command signal by the adder. The air supply device is controlled by the signal obtained by adding. Therefore, the air supply device is controlled so that a large amount of air is supplied to the fuel in advance by the air command signal whose rate of change is not limited, so that when the output command increases, the pressure rise in the pressure vessel is increased. Therefore, the problem of air shortage due to the time delay caused by the above is reliably prevented, and the control delay when the output is increased is also prevented.

[0014]

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

FIG. 1 shows an embodiment of a control apparatus for a pressurized fluidized bed boiler according to the present invention. In a pressurized fluidized bed boiler similar to that shown in FIG. 3, an output command for controlling the pressurized fluidized bed boiler 2 is output. A rate-of-change limiter 15 that inputs 14 to limit a change in the output command 14, and an adder 17 that adds a pressure correction signal P based on the steam pressure of the fluidized-bed boiler 2 to the output of the rate-of-change limiter 15. , A function generator 1 for converting the output of the adder 17 into a function and outputting a fuel command signal 20 to the fuel supply device 8.
9 is provided.

On the other hand, a function generator 29 for inputting the output command 14 and outputting an air command signal 28 for controlling the air supply device 11, and an oxygen command signal 28 from the function generator 29 have an oxygen concentration. An air control circuit 31 including an adder 30 that adds the correction signal 24 is provided. Since the output command before entering the change rate limiter 15 is introduced into the function generator 29, when the output command 14 increases, the air command signal 28 output from the function generator 29 is as shown in FIG.
As indicated by the solid line in (C), the value becomes large from the beginning in response to the increase in the output command 14.

As shown by the solid line in FIG. 2 (A), the output command 1
When 4 is increased, in the fuel control circuit 27, the change rate limiter 15 limits the output command that increases rapidly as shown by the broken line in FIG. And the pressure correction signal P is added by the adder 17.
Is added to obtain the boiler master signal 18, which is further generated by the function generator 19 in FIG.
The fuel command signal 20 as shown in FIG.
Is input to control the fuel.

On the other hand, in the air control circuit 31, the output command 14 before being guided to the change rate limiter 15 is used as the function generator 2
9 shows an air command signal 28 that is not limited in rate of change and is rapidly increased as shown by the solid line in FIG. 2C. The oxygen command correction signal 2 is added to the air command signal 28 by the adder 30.
The signal obtained by adding 4 is input to the inlet guide vane 9 of the air supply device 11, and the combustion air 4 is controlled.

Therefore, the air supply device 11 is controlled by the air command signal 28 having a large value (air amount after the increase) from the beginning when the rate of change is not limited, so that the air supply device 11 can be controlled with respect to the fuel. A large amount of air is supplied in advance only in the shaded area shown in 2 (C). Therefore, output command 1
As the pressure in the pressure vessel 1 is increased in a short time at the time of increasing 4, the shortage of the combustion air 4 caused by the delay in the pressure increase is prevented, and as shown in FIG. It is possible to automatically and surely prevent the detected oxygen concentration from falling below the target limit value.

In addition, as in the conventional method of preventing the occurrence of air shortage by throttling the fuel, the output command 14
It is also possible to prevent a problem that a control delay occurs with respect to the increase of the output, and the output can be stably increased.

It should be noted that the present invention is not limited to the above-described embodiment, the configuration of the air supply device is not limited to that shown in the drawings, and various modifications may be made without departing from the scope of the present invention. Of course, it can be added.

[0022]

According to the control apparatus for the pressurized fluidized bed boiler of the present invention, the fuel control circuit controls the fuel to increase at a certain rate of change by the rate of change limiter in response to an increase in the output command. On the other hand, since the air control circuit controls the air supply device by the air command signal having a large value from the beginning of the non-change rate limit at the same time when the output command increases, the air control circuit burns when the output command increases. It is possible to easily and reliably prevent the problem that the oxygen concentration in the exhaust gas drops abnormally due to a shortage of air for use, and there is also the problem of the control delay that the conventional method that throttles the fuel when the output command increases. It is possible to obtain an excellent effect that the output can be prevented and the output can be stably increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

2 (A), (B), (C), and (D) are diagrams showing the operation of FIG.

FIG. 3 is a block diagram showing an example of a conventional controller for a pressurized fluidized bed boiler.

4 (A), (B), (C), and (D) are diagrams showing the operation of FIG.

[Explanation of symbols]

 1 Pressure Vessel 2 Fluidized Bed Boiler 4 Combustion Air 8 Fuel Supply Device 11 Air Supply Device 14 Output Command 15 Change Rate Limiter 17 Adder 19 Function Generator 20 Fuel Command Signal 24 Oxygen Concentration Correction Signal 27 Fuel Control Circuit 28 Air Command Signal 29 Function generator 30 Adder 31 Air control circuit P Pressure correction signal

Claims (1)

[Claims] 1. A pressure vessel, a fluidized bed boiler installed in the pressure vessel, a fuel supply device for supplying fuel to the fluidized bed boiler, and an air supply device for supplying combustion air to the pressure vessel. A control device for a pressurized fluidized bed boiler, comprising a change rate limiter for inputting an output command of the pressurized fluidized bed boiler to limit a change in the output command, and an output of the change rate limiter. A fuel control circuit is provided that includes an adder that applies a pressure correction signal based on the steam pressure of the fluidized bed boiler, and a function generator that outputs a fuel command signal to the fuel supply device by function-converting the output of the adder, And a function generator that inputs the output command and outputs an air command signal that does not limit the rate of change for controlling the air supply device; and an addition that adds an oxygen concentration correction signal to the air command signal from the function generator. Pneumatic control consisting of vessels A control device for a pressurized fluidized bed boiler, which is provided with a control circuit.