JPH0239681B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiler reheat steam temperature control device that controls the temperature of each steam sent from two reheaters.

In general, a reheater is installed between a high-pressure turbine and a medium-low-pressure turbine to improve the efficiency of the heat cycle by returning steam to the boiler for reheating and making it work again in the medium-low-pressure turbine. . Some large-capacity boilers, such as boilers for thermal power generation, are equipped with two reheaters.

Conventionally, the steam temperature in such a reheater has been adjusted by the amount of heat absorbed by the reheater, but the heat exchange method in the reheater is the double-pipe heat exchange method. There is a heat exchange method. The double-tube heat exchange system is a fluid-fluid heat exchanger consisting of concentric double circular tube sections. For example, the second reheated steam is passed through the annular section between the inner tube and the outer tube, and the first reheated steam is passed through the inner tube. This method reheats the steam by flowing reheated steam, and the surface heat exchange method reheats the steam by fire from the upper part of the furnace or the furnace wall, and by radiant heat transfer of the combustion gas.

However, these were not boilers for intermediate load thermal power operation, but were planned for base load use (constant output operation), and because of their large heat capacity, they could not respond to the high rate of load change in intermediate load thermal power operation. It was not possible to control the reheat steam temperature.

The present invention improves these conventional drawbacks, stably controls the reheat steam temperature of a two-stage reheat boiler for intermediate load thermal power operation, and controls the load change rate (generator output) for intermediate load thermal power operation. The purpose is to improve the rate of change of combustion gas, and the flue through which the combustion gas passes is divided into a flue equipped with a superheater, a flue equipped with a first reheater, and a flue equipped with a second reheater. In the boiler, the boiler is provided with a damper for controlling the flow rate of combustion gas passing through each flue. a steam temperature detector that detects the outlet steam temperature of the heating device; and a steam temperature detector that detects the steam temperature at the outlet of the heating device;
means for calculating an average outlet steam temperature with the reheater;
means for controlling the damper opening degree of the flue in which the superheater is disposed so that the average outlet steam temperature becomes the average temperature set value based on the output of the means for calculating the average outlet steam temperature; and the each steam temperature detection means. means for calculating an outlet steam temperature difference between the first reheater and the second reheater based on each outlet steam temperature detected by the reheater; and based on the output of the means for calculating the outlet steam temperature difference. means for controlling the damper opening degree of the flue in which the first reheater is disposed and the damper opening degree of the flue in which the second reheater is disposed so that the outlet steam temperature difference becomes a temperature difference set value; The present invention relates to a boiler reheat steam temperature control device comprising:

Next, an embodiment of the present invention will be described with reference to FIG. 1. A boiler 1 is provided with a furnace 2, and a flue 4 through which combustion gas passes from the furnace 2 is a flue 4 in which a superheater 3 is disposed. , a flue 6 in which a first reheater 5 is disposed, and a flue 8 in which a second reheater 7 is disposed, and each flue 4, 6, 8 is provided with a damper 9, 10 and 11, the flow rate of the combustion gas passing therethrough can be adjusted, and the steam temperatures of the superheater 3, the first reheater 5, and the second reheater 7 can be controlled.

The superheater 3 further superheats the superheated steam that has passed through the furnace wall and ceiling with the combustion gas that passes through the flue 4, and sends this superheated steam from the outlet 12 through another superheater (not shown) to the ultra-high pressure turbine. Send to.
The first reheater 5 introduces the steam expanded by the ultra-high pressure turbine, reheats it by the combustion gas passing through the flue 6, and sends it out from the outlet 13 to a high pressure turbine (not shown). The second reheater 7 introduces the steam expanded by the high-pressure turbine, superheats it again by the combustion gas passing through the flue 8, and sends it out from the outlet 14 to a medium-low pressure turbine (not shown).

In the boiler 1 shown in FIG. 1, three flues 4, 6, and 8 are provided as flues through which combustion gas passes, but three or more flues may be provided. That is, the flue 4 in which the superheater 3 is arranged
and one flue 6 each having a first reheater 5 arranged therein;
Two flues 8 with second reheater 7 installed, a total of four flues, or one flue 4 with superheater 3 and first reheater 5 installed. A total of four flues, two ducts 6 and one flue 8 provided with the second reheater 7, may be provided in parallel.

The steam temperature sent out from the outlet 13 of the first reheater 5 is detected by the steam temperature detector 15, and
The temperature of the steam delivered from the outlet 14 of the reheater 7 is detected by a steam temperature detector 16. The temperature of each steam detected by the steam temperature detectors 15 and 16 is used to calculate an average outlet steam temperature by an average temperature calculator 17, and a difference in outlet steam temperature by a temperature difference calculator 18. Calculated.

On the other hand, an output command 19 that instructs the thermal power plant (boiler, turbine, etc.) to set the amount of electric power according to the electric power demand at that time is sent to the average temperature setting function generator 2.
0, gain correction function generator 21, superheater gas damper reference opening command setter 22, differential preceding command generation circuit 23, temperature difference setting function generator 24, gain correction function setting device 25, differential preceding command It is adapted to be applied to the generating circuit 26 and the damper total opening function generator 27, respectively.

The average temperature setting function generator 20 outputs an output command 1
9, the gain correction function generator 21 outputs a gain correction value corresponding to the supply command 19, and the superheater gas damper reference opening command setting. The device 22 outputs a superheater gas damper reference opening command 29 corresponding to the output command 19, and the differential preceding command generation circuits 23 and 26 output a superheater gas damper reference opening command 29 corresponding to the output command 19.
1, the effect on the steam temperature is delayed (there is a response delay), so in order to improve this delay, the change in the output command 19 is taken into account and a differential preceding command or A differential advance command is output when the output command decreases, and is preceded by control corresponding to the actually detected temperature, which will be described in detail later.

The temperature difference setting function generator 24 outputs an output command 19
The gain correction function setter 25 outputs the temperature set value 30 corresponding to the output command 19.
The damper total opening function generator 27 outputs a gain correction value that corrects the nonlinearity of the boiler so that it becomes a control system signal corresponding to the output command 1.
The damper total opening command corresponding to No. 9 is output.

The temperature signal of the average outlet steam temperature calculated by the average temperature calculator 17 is compared with the average temperature set value 28 in a subtracter 31, and is further compared with the gain output from the gain correction function generator 21 in a multiplier 32. After the gain is corrected by the correction value, it is input to the adder 34 via the proportional + integral regulator 33, and is added to the superheater gas damper reference opening command 29 from the superheater gas damper reference opening command setter 22. Ru. Then, a differential advance command from a differential advance command generation circuit 23, which will be described later, is added by an adder 35 and inputted to a superheater gas damper control drive 36 and a subtractor 37, which will be described later. The superheater gas damper control drive 36 controls the opening degree of the damper 9 according to the output of the adder 35.

On the other hand, the signal of the outlet steam temperature difference calculated by the temperature difference calculation unit 18 is compared with the temperature set value 30 by a subtracter 38, and further by a multiplier 39, the signal of the outlet steam temperature difference calculated by the temperature difference calculation unit 18 is After the gain is corrected by the correction value, the proportional + integral adjuster 4
0 to an adder 41, which adds a differential leading command from a differential leading command generating circuit 26, which will be described later, and inputs the result to an adder 42 and a subtracter 43.

These adders 42 and subtracters 43 receive a reheater gas damper average reference opening signal 44 from a subtracter 37.
is also entered. This reheater gas damper average reference opening signal 44 is derived from the damper total opening command output from the damper total opening function generator 27 in response to the output command 19, and is derived from the superheater gas damper control output from the adder 35. - The signal sent to the drive 36 is subtracted by the subtracter 37.

The adder 42 adds the signal from the adder 41 and the reheater gas damper average reference opening signal 44 and sets it as the opening command for the first reheater gas damper control drive 45. Adder 4 from reheater gas damper average reference opening signal 44
The signal obtained by subtracting the signal 1 is used as the opening command for the second reheater gas damper control drive 46.

The opening degree of the damper 9 of the flue 4 in which the superheater 3 is disposed in this way is controlled in relation to the average outlet steam temperature of the first reheater 5 and the second reheater 7. The opening degree of the damper 10 of the flue 6 in which the heating device 5 is disposed and the opening degree of the damper 11 in the flue 8 in which the second reheater 7 is disposed are determined based on the first reheater 5 and the second reheater 7. It will be controlled in relation to the outlet steam temperature difference between

Next, details of the differential advance command generation circuits 23 and 26 will be explained with reference to FIG.

In the present invention, a differential advance command generation circuit 23 that applies a differential advance command to an adder 35 that outputs an opening command for the superheater gas damper control drive 36, a first reheater 5, a second reheat A differential preceding command generating circuit 2 adds a differential preceding command to an adder 41 as the difference in opening between the dampers 10 and 11 of the damper 7.
6, all of which are constructed as shown in FIG.

In FIG. 2, a signal obtained by differentiating the output command 19 is generated by a differential signal generator 47, and is limited to a predetermined amplitude by an upper/lower limit limiter 48. When the value of the output command 19 is increasing, the positive differential signal is selected by the positive signal selector 49, passes through the change rate limiter 50, and is waveform-shaped by the multiplier 51.
52 is a function generator which outputs a signal for waveform shaping when the output command 19 is rising. The signal whose waveform has been shaped by the multiplier 51 is sent to the adder 54 as a differential leading command 53 when the output command rises.
added to. At this time, the differential preceding command 59 when the output command falls is zero.

On the other hand, when the value of the output command 19 is decreasing, the negative side differential signal is selected by the negative side signal selector 55, passed through the rate of change limiter 56, and waveform-shaped by the multiplier 57. 58 is a function generator which outputs a signal for waveform shaping when the output command 19 is falling. The signal waveform-shaped by the multiplier 57 is added to the adder 54 as a differential preceding command 59 when the output command falls. At this time, the differential preceding command 53 when the output command rises is zero. By adding the differential advance command 53 when the output increases and the differential advance command 59 when the output decreases, either signal becomes the differential advance command (signal for correcting response delay) 60 depending on the increase or decrease of the output. It is output from the differential advance command generation circuits 23 and 26. By using this differential advance command 60, it is possible to improve the steam temperature control characteristics that have dead time (response delay time) and a large time constant in the apparatus shown in FIG.

The present invention can stably control the steam temperature at the outlet of the first reheater and the steam temperature at the outlet of the second reheater, and the steam temperature control characteristics can suppress the lifetime consumption of the turbine even in intermediate load thermal power operation. can.

In addition, if the outlet steam temperature characteristics of the first reheater and the second reheater are similar, the flow rate of the combustion gas passing through the flue in which the first reheater and the second reheater are installed, respectively. is maintained at approximately the required amount, so disturbances in the control signal to the superheater side can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of a differential advance command generation circuit. 1... Boiler, 3... Superheater, 4, 6, 8...
flue, 5...first reheater, 7...second reheater,
9, 10, 11... damper, 17... average temperature calculator, 18... temperature difference calculator, 36... superheater gas damper control drive, 45... first reheater gas damper control drive,
46...Second reheater gas damper control
drive.

Claims (1)

[Claims] 1 The flue through which the combustion gas passes is divided into a flue equipped with a superheater, a flue equipped with a first reheater, and a flue equipped with a second reheater, and each flue is divided into a steam temperature detector for detecting the outlet steam temperature of the first reheater; and a steam temperature detector for detecting the outlet steam temperature of the second reheater; a temperature detector; means for calculating an average outlet steam temperature of the first reheater and the second reheater based on each outlet steam temperature detected by each of the steam temperature detectors; means for controlling the damper opening degree of the flue in which the superheater is disposed so that the average outlet steam temperature becomes the average temperature set value based on the output of the means for calculating the steam temperature; means for calculating an outlet steam temperature difference between the first reheater and the second reheater based on each outlet steam temperature detected by the method; and an outlet based on the output of the means for calculating the outlet steam temperature difference. means for controlling the damper opening degree of the flue in which the first reheater is disposed and the damper opening degree of the flue in which the second reheater is disposed so that the steam temperature difference becomes a temperature difference set value; A boiler reheat steam temperature control device characterized by comprising: