JP2000171003A - Reheat steam temperature control method of coal- burning thermal power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reheat steam temperature control method of a coal burning thermal power plant, which is capable of regulating a timing for resetting the advance command of a reheater gas damper reference opening degree command in accordance with the kind of coal and capable of improving the controllability of a reheat steam temperature. SOLUTION: The moisture 35 and grindability 36 of coal are estimated in a moisture and grindability estimating device 37 while the outputting amount of coal 38 is estimated in a mill model outputting amount of coal estimating device 39. A coal output delay time constant 40 is obtained in a coal output delay time constant estimating device 41 based on the outputting amount of coal 38, estimated in the mill model outputting amount of coal estimating device 39, while the reset timing 80 of an advance command 74 with respect to a reheater gas damper reference opening degree command 58 is corrected based on the coal output delay time constant 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reheat steam temperature control method for a coal-fired power plant.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a conventional coal-fired power plant. In FIG. 7, 1 is a coal-fired boiler main body, 2 is a furnace of the boiler main body 1, and 3 is a boiler main body 1. Burner for injecting and burning pulverized coal into coal, 4 is a mill for pulverizing coal into pulverized coal, 5 is a coal bunker for storing coal, and 6 is a coal for storing coal stored in a coal bunker 5 to a mill 4. 7 is a driving device of the coal feeder 6, 8 is a primary air supply pipe for supplying primary air to the mill 4, 9 is a guide for pulverized coal pulverized by the mill 4 to the burner 3. The coal stored in the coal bunker 5 is charged into a coal crushing mill 4 by a coal feeder 6 driven by a driving device 7, and the coal is crushed in the mill 4 Primary air is introduced from the primary air supply pipe 8 into the mill 4 The pulverized coal is pulverized by the primary air and the air transported to the burner 3 through a pulverized coal pipe 9, so as to burn in the furnace 2 of the boiler main body 1.

[0003] A coarse powder separator 10 is provided in the mill 4. Generally, as shown in FIG. 7, the coarse powder separator 10 is capable of adjusting the degree of opening of a classification vane 11. A classifying vane 11 is arranged in the circumferential direction so as to change the classifying rate by increasing or decreasing the opening of the classifying vane 11, or a cylindrical shape having slits formed at a required pitch in the circumferential direction. There is a rotor (not shown) in which a rotor is rotatably disposed and the classification rate is changed by increasing or decreasing the rotation speed of the rotor. In FIG. 7, reference numeral 13 denotes a table rotatably provided in the lower portion of the mill 4, reference numeral 14 denotes a roller for coal pulverization provided so as to be pressed onto the table 13, and reference numeral 15 denotes a primary air port.

A reheater 43 and a superheater 44 are disposed in a rear heat transfer section 42 of the boiler main body 1 with a partition wall 45 interposed therebetween, and a fuel in the furnace 2 of the boiler main body 1 is provided. The reheater 43 and the superheater 44 are heated by the combustion gas generated by the combustion of the reheat steam, and the reheat steam and the superheat steam are generated. For controlling the temperature of the reheat steam, the reheater gas damper 46 is used. The reheat steam temperature detector 49 for detecting the reheat steam temperature 48 at the outlet of the reheater 43, and the reheat steam temperature detector 49 for adjusting the opening degree of the superheater gas damper 47. A controller 20 that outputs opening degree commands 50 and 51 to the reheater gas damper 46 and the superheater gas damper 47 based on the reheat steam temperature 48 detected by the hot steam temperature detector 49 is provided.

The controller 20 calculates the difference between the preset reheat steam temperature 52 and the reheat steam temperature 48 detected by the reheat steam temperature detector 49 as shown in FIG. A subtractor 54 for outputting the hot steam temperature deviation 53; and a reheater gas damper 46 for eliminating the reheat steam temperature deviation 53 by performing a proportional integration process on the reheat steam temperature deviation 53 output from the subtractor 54. A proportional-integral controller 56 for outputting a corrected opening command 55; and a first function generator 59 for obtaining and outputting a reheater gas damper reference opening command 58 based on the output command 57.
When the load change signal 60 is “1” during the load change, the input signal 61 of “1” is switched to the output signal 63.
While the load is settled and the load change signal 6
The switch 6 is switched to the b side when 0 becomes “0”, and the input signal 62 of “0” is output as the output signal 63
4 and an output signal 63 output from the switch 64. When the output signal 63 changes, the output signal 63 is subjected to a process of restricting the rate of change to within a set value or less.
5 and a second function generator 68 for obtaining and outputting a correction gain 67 based on an output command 57.
And an output signal 65 output from the change rate limiter 66.
Multiplied by a correction gain 67 output from the second function generator 68 to output an output signal 69;
A third function generator 73 for obtaining and outputting a correction gain 72 based on the load change rate 71; and a correction gain 72 output from the third function generator 73 for an output signal 69 output from the multiplier 70. A multiplier 75 for outputting a preceding command 74 for the reheater gas damper reference opening command 58; and multiplying the reheater gas damper reference opening command 58 output from the first function generator 59 by the multiplication. Adder 77 that outputs a reheater gas damper reference opening command 76 to which a preceding command 74 output from the heater 75 is added, and the adder 77 that outputs the reheater gas damper reference opening command 76 output from the adder 77. An adder 78 for adding a correction opening command 55 output from the integration controller 56 and outputting the opening command 50 to the reheater gas damper 46, and a reheater gas damper 46 output from the adder 78. And a fourth function generator 79 that obtains and outputs an opening command 51 of the superheater gas damper 47 based on the opening command 50.

The opening of the reheater gas damper 46, which serves as a reference, needs to be reduced as the output command 57 increases, so that the first function generator 59 outputs the output as shown in FIG. A function that decreases the reheater gas damper reference opening command 58 as the command 57 increases is input.

The correction gain 67 may be set as a negative value and set closer to 0 as the output command 57 increases, so that the second function generator 68 includes a function as shown in FIG. Is entered.

Since the correction gain 72 may be increased as the load change rate 71 increases, the third function generator 73 includes a load change rate 7 as shown in FIG.
A function for increasing the correction gain 72 with an increase of 1 is input.

Since the opening of the reheater gas damper 46 and the superheater gas damper 47 may be controlled so that the total of both the openings becomes 100%, the fourth function generator 7 is used.
9, a reheater gas damper 46 as shown in FIG.
Is input in such a manner that the opening command 51 of the superheater gas damper 47 is decreased substantially in inverse proportion to the increase in the opening command 50.

During the operation of the boiler body 1 and the mill 4 in the coal-fired power plant as described above, the reheat steam temperature 48 is detected by the reheat steam temperature detector 49 and output to the subtractor 54 of the controller 20. In the subtractor 54, a difference between a preset reheat steam temperature set value 52 and the reheat steam temperature 48 detected by the reheat steam temperature detector 49 is obtained, and the reheat steam temperature deviation 53 is proportional. The reheater is output to an integration controller 56, and in the proportional integration controller 56, the reheat steam temperature deviation 53 output from the subtractor 54 is subjected to a proportional integration process to eliminate the reheat steam temperature deviation 53. The correction opening command 55 of the gas damper 46 is added to the adder 78.
To the reheater gas damper reference opening command 58 based on the output command 57 in the first function generator 59.
Is calculated and output to the adder 77.

Here, when the output command 57 changes as shown in FIG. 13 to change the load, the load change signal 60 changes from "0" to "1". To the a side, and the input signal 61 of “1” is output as an output signal 63 to the change rate limiter 66, where the change rate of the output signal 63 output from the switch 64 is changed. Is performed within a range equal to or less than the set value, and an output signal 65 is output to a multiplier 70. In the multiplier 70, a correction gain 67 output from a second function generator 68 based on an output command 57 is output.
Is the output signal 65 output from the change rate limiter 66.
, And an output signal 69 is output to a multiplier 75, in which a correction gain 72 output from a third function generator 73 based on a load change rate 71 is output from the multiplier 70. The output command 69 is multiplied, and a preceding command 74 for the reheater gas damper reference opening command 58 is output to the adder 77.

In the adder 77, a preceding command 74 output from the multiplier 75 with respect to the reheater gas damper reference opening command 58 output from the first function generator 59.
Is added, and a reheater gas damper reference opening command 76 is output to the adder 78. In the adder 78, the proportional integration is performed on the reheater gas damper reference opening command 76 output from the adder 77. The correction opening command 55 output from the controller 56 is added, the opening command 50 is output to the reheater gas damper 46, and the reheat output from the adder 78 is output from the fourth function generator 79. Vessel gas damper 4
6, the opening command 51 of the superheater gas damper 47 is obtained and output, whereby the opening of the reheater gas damper 46 and the opening of the superheater gas damper 47 are adjusted, and the reheat steam is adjusted. The temperature 48 is maintained at the reheat steam temperature set value 52.

The output signal 63 of the switch 64 and the output signal 6 of the change rate limiter 66 in response to a change in the output command 57
5, the output signal 69 of the multiplier 70, the preceding command 74 output from the multiplier 75, the reheater gas damper reference opening command 58, and the reheater gas damper reference opening command to which the preceding command 74 is added. The change at 76 is, for example, as shown in FIG.

[0014]

In the case of a coal-fired thermal power plant, the crushability of coal changes depending on the type of coal used as fuel. As a result, the followability of coal decreases.

However, in the conventional coal-fired power plant as described above, as shown in FIG. 8, the reheater gas damper reference opening command 58 based on the output command 57.
On the other hand, the timing of resetting the preceding command 74 applied during the load change after the load is set is set only based on the change of the load change signal 60. Since no consideration is given, the opening degree of the reheater gas damper 46 cannot be adjusted to a situation where the fuel becomes excessive or insufficient after the end of the large load change, and in some cases, the reheat steam temperature 48 becomes the reheat steam temperature. In some cases, it greatly exceeds the set value 52,
There was a disadvantage that the controllability of the reheat steam temperature 48 was reduced.

In view of such circumstances, the present invention makes it possible to adjust the timing of resetting the preceding command of the reheater gas damper reference opening command according to the type of coal, thereby improving controllability of the reheat steam temperature. An object of the present invention is to provide a method for controlling a reheated steam temperature of a coal-fired power plant to be obtained.

[0017]

According to the present invention, a regenerator gas damper reference opening command based on an output command is added with a preceding command during a load change, and after the load is set, the preceding command is reset. In addition to the reheater gas damper reference opening command, a corrected opening command 55 for eliminating a reheat steam temperature deviation 53 between a preset reheat steam temperature set value 52 and the reheat steam temperature 48 is added to the reheater. In the method for controlling the reheat steam temperature of a coal-fired thermal power plant in which an opening command of a gas damper is obtained and the opening of the reheater gas damper is adjusted by the opening command, the amount of coal supplied to the mill and the primary air Estimate the water content and grindability of coal based on flow rate, mill inlet primary air temperature, mill outlet primary air temperature, classification vane opening or classification rotation speed, and / or mill differential pressure And coal output And determining a coal output delay time constant based on the coal output amount, and correcting a reset timing of a preceding command with respect to the reheater gas damper reference opening command based on the coal output delay time constant. The present invention relates to a method for controlling the temperature of reheated steam in a thermal power plant.

According to the above means, the following effects can be obtained.

In the reheat steam temperature control method for a coal-fired power plant according to the present invention, a preceding command is added during the load change to the reheater gas damper reference opening command based on the output command, and after the load is settled. Resets the preceding command,
Further, a correction opening command for eliminating a reheat steam temperature deviation between a preset reheat steam temperature set value and the reheat steam temperature is added to the reheater gas damper reference opening command, and a reheater gas damper is added. The opening command of the reheater gas damper is adjusted by the opening command. At this time, the amount of coal supplied to the mill, the primary air flow rate, the primary air temperature at the mill inlet, the mill Outlet primary air temperature, classification vane opening or classification rotation speed, and / or mill differential pressure, the water content and crushability of the coal are estimated and the coal output is estimated based on either of them. A coal output delay time constant is determined based on the coal output amount, and the reset timing of the preceding command with respect to the reheater gas damper reference opening command is corrected based on the coal output delay time constant.

As a result, the timing of resetting the preceding command applied during the load change with respect to the reheater gas damper reference opening command based on the output command after the load stabilization is determined by the time required in accordance with the coal output delay of the mill by the type of coal. In the case of coal with poor pulverizability, the ability of coal as fuel to comply with the output command is reduced, and the situation in which the fuel becomes excessive after the end of a large load change occurs Also,
In such a situation, it is possible to adjust the opening degree of the reheater gas damper to prevent the reheat steam temperature from greatly exceeding the reheat steam temperature set value, and to control the reheat steam temperature. Will be improved.

[0021]

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

FIGS. 1 and 2 show an example of an embodiment of the present invention. In the drawings, the portions denoted by the same reference numerals as those in FIGS. 7 and 8 represent the same components, and the basic configuration is as follows. 7 and FIG. 8, but the feature of the illustrated example is that, as shown in FIG. 1 and FIG. A primary air supply pipe 8 for detecting a primary air flow rate 26 introduced into the mill 4, a primary air flow detector 27 for detecting a primary air flow rate 26 introduced into the mill 4, Inlet primary air temperature 2
And a mill inlet primary air temperature detector 31 for detecting the mill outlet primary air temperature 30 in the pulverized coal pipe 9 and a mill 4 for the mill 4.
A mill differential pressure detector 33 for detecting a mill differential pressure 32 is provided. Further, in the controller 20, the amount of coal 16 supplied to the mill 4, a primary air flow rate 26, a primary air temperature 28 at a mill inlet, and a mill outlet A moisture content / grindability estimator 37 for estimating the moisture content 35 and the grindability 36 of the coal based on all or any of the primary air temperature 30, the opening degree 34 of the classification vane 11, and the mill differential pressure 32. The amount of coal 16 supplied to the mill 4, the primary air flow rate 26, the primary air temperature 28 at the mill inlet, the primary air temperature 30 at the mill outlet, the opening 34 of the classification vane 11, the differential pressure 32 of the mill, And a mill model coal output estimator 39 for estimating the coal output 38 based on all or any of the water content 35 and the grindability 36 of the mill. Calculate coal output delay time constant 40 based on coal quantity 38 and output The reset timing 80 of the preceding command 74 of the reheater gas damper reference opening command 58 is determined based on the coal output delay time constant estimator 41 and the coal output delay time constant 40 obtained by the coal output delay time constant estimator 41. A fifth function generator 81 for calculating and outputting the output from the fifth function generator 81 when the load is settled from a state during the load change and the load change signal 60 changes from “1” to “0”; And an off-delay timer 82 for outputting a delay signal 60 'that changes from "1" to "0" to the switch 64 by causing a time delay D (see FIG. 6) corresponding to the reset timing 80 to be performed. On the point.

In the mill model coal output estimation unit 39, as shown in FIG. 3, a region where coal is supplied inside the mill 4 and falls on the table 13 A region where coal moves by centrifugal force caused by rotation of the table 13 (The part of coarse coal in the transport area is added) where the coal moves due to the centrifugal force due to the rotation of the table 13 Coal supply area to the grinding area (part of the coal in the grinding area is added) (Return to coal supply area) Area where pulverized pulverized coal is transported by primary air (part of coarse coal falls and returns to area) Coarse powder separation area (part of coarse coal is separated and returns to area) ) Is virtually divided into seven regions, and the movement route of the coal is grasped as shown in FIG.
The coal output 38 is calculated in consideration of the crushability 36 and the crushability.

In the coal output delay time constant estimator 41, the coal output 38 estimated by the mill model coal output estimator 39 and the normal primary delay, ie, K / (1 + T _S )
(Where T _s is an operator of Laplace transform) and the amount of coal output determined at each time, t is determined by the least squares method to minimize the deviation, and this t is output. The delay time constant 40 is output. Here, a function representing the coal output 38 is y (t),
Assuming that a function representing the coal output determined by the first-order lag is y ′ (t), ∫ (y (t) −y ′ (t)) ² d
It is in a form to find t that minimizes t.

The load is settled from the reset timing 80 of the preceding command 74 of the reheater gas damper reference opening command 58, that is, the load changing state, and the load change signal 60 becomes "1".
When the switch 64 changes from "a" to "0",
It is necessary to delay the timing of switching to the side and resetting as the coal removal delay time constant 40 is larger. Therefore, the fifth function generator 81 includes, as shown in FIG. A function that increases the reset timing 80 is input.

Next, the operation of the illustrated example will be described.

During operation of the boiler body 1 and the mill 4 in the coal-fired power plant, during a load change,
Basically, as in the conventional case, the re-heater gas damper reference opening command 58 based on the output command 57 is replaced by the preceding command 74.
Is added, and a correction opening command 55 for eliminating a reheat steam temperature deviation 53 between the preset reheat steam temperature set value 52 and the reheat steam temperature 48 is added, and the reheater gas damper 46 is opened. Degree command 50 is obtained, and the opening degree command 50
The opening degree of the reheater gas damper 46 is adjusted by
At the same time, the coal feed amount 16 supplied to the mill 4 is detected by the coal feed detector 17 and the primary air flow detector 27 is detected.
The primary air flow 26 introduced into the mill 4 is detected by the above, the primary air temperature at the mill inlet 28 is detected by the primary air temperature detector 29 at the mill inlet, and the primary air temperature 30 at the mill outlet is detected by the primary air temperature detector 31 at the mill outlet. The mill differential pressure detector 33 detects the mill differential pressure 32, and further detects the opening degree 34 of the classification vane 11, the coal supply 16, the primary air flow 26, and the mill inlet primary air temperature 2.
8, the mill outlet primary air temperature 30, the opening degree 34 of the classification vane 11, and the mill differential pressure 32 are input to the water content / crushability estimator 37 and the mill model coal output estimator 39 of the controller 20.

In the water content / crushability estimator 37, the amount of coal 16 supplied to the mill 4, the primary air flow rate 26, the primary air temperature 28 at the mill inlet, and the primary air temperature 30 at the mill outlet 30
And / or the opening degree 34 of the classification vane 11 and / or the mill differential pressure 32, the water content 35 of the coal
The mill model coal output estimator 39 estimates the amount of coal 16 supplied to the mill 4, the primary air flow 26, the primary air temperature 28 at the mill inlet, and the primary air temperature 30 at the mill outlet. And the opening degree 34 of the classification vane 11, the mill differential pressure 32, the coal water content 35 and / or the crushability 36, or the coal output 38 is estimated based on all or any of them.
The output is output to a coal output delay time constant estimator 41, and the mill model output amount estimator 39 is output from the coal output delay time constant estimator 41.
A coal removal delay time constant 40 is obtained based on the coal removal amount 38 estimated in the above.
And the fifth function generator 81 outputs the coal removal delay time constant 40 obtained by the coal removal delay time constant estimator 41.
, The reset timing 80 of the preceding command 74 of the reheater gas damper reference opening command 58 is obtained and output to the off-delay timer 82.

Thereafter, when the load is settled from the state during the load change and the load change signal 60 changes from "1" to "0", it corresponds to the reset timing 80 output from the fifth function generator 81. A delay signal 60 ′ that changes from “1” to “0” with a time delay D (see FIG. 6) is output from the off-delay timer 82 to the switch 64, and output from the off-delay timer 82 to the switch 64. When the delayed signal 60 ′ becomes “0”, the switch 64 is switched from the “a” side to the “b” side, and the input signal 62 of “0” is output as the output signal 63 to the change rate limiter 66.
Preceding command 7 for reheater gas damper reference opening command 58
4 is reset.

The output signal 63 of the switch 64 and the output signal 6 of the change rate limiter 66 in response to the change of the output command 57
5, the output signal 69 of the multiplier 70, the preceding command 74 output from the multiplier 75, the reheater gas damper reference opening command 58, and the reheater gas damper reference opening command to which the preceding command 74 is added. The change at 76 is, for example, as shown in FIG.

As a result, the timing at which the preceding command 74 applied during the load change to the reheater gas damper reference opening command 58 based on the output command 57 is reset after the load stabilization is reset to the coal output delay of the mill 4 due to the type of coal. Accordingly, in the case of coal having poor pulverizability, the followability of coal as fuel to the output command 57 is reduced, and the fuel becomes excessive after the end of a large load change. Even if a situation arises, the opening degree of the reheater gas damper 46 can be adjusted to such a situation, and the reheat steam temperature 48 greatly exceeds the reheat steam temperature set value 52. Thus, the controllability of the reheat steam temperature 48 is improved.

The classifying vane 1 is used as the coarse powder separator 10.
Instead of changing the classifying rate by increasing or decreasing the opening degree of 1, a cylindrical rotor having slits formed at a required pitch in the circumferential direction is rotatably disposed,
In the case where the classification rate is changed by increasing or decreasing the rotation speed of the rotor, the classification rotation speed of the rotor is detected in place of the opening degree 34 of the classification vane 11 to determine the water content. What is necessary is just to input to the grindability estimator 37 and the mill model coal output estimator 39.

Thus, the timing for resetting the preceding command 74 of the reheater gas damper reference opening command 58 can be adjusted according to the type of coal, and controllability of the reheat steam temperature 48 can be improved.

The method of controlling the reheated steam temperature of the coal-fired power plant according to the present invention is not limited to the above-described example, and various changes can be made without departing from the gist of the present invention. Of course.

[0035]

As described above, according to the method for controlling reheat steam temperature of a coal-fired power plant according to the present invention, the timing for resetting the preceding command of the reheater gas damper reference opening command in accordance with the type of coal is described. Can be adjusted, and an excellent effect that the controllability of the reheat steam temperature can be improved can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an embodiment of the present invention.

FIG. 2 is a block diagram of a controller according to an example of an embodiment of the present invention.

FIG. 3 is a schematic diagram showing seven regions inside the mill virtually divided by a mill model coal output estimator in an example of an embodiment of the present invention.

FIG. 4 is a block diagram illustrating a coal movement path inside a mill in an example of an embodiment of the present invention.

FIG. 5 is a diagram showing a function input to a fifth function generator shown in FIG. 2;

FIG. 6 is a diagram showing a change between various output signals and a reheater gas damper reference opening command with respect to a change in an output command in an example of an embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a conventional example.

FIG. 8 is a block diagram of a controller in a conventional example.

FIG. 9 is a diagram showing a function input to the first function generator shown in FIGS. 2 and 8;

FIG. 10 is a diagram showing a function input to the second function generator shown in FIGS. 2 and 8;

FIG. 11 is a diagram showing functions input to the third function generator shown in FIGS. 2 and 8;

FIG. 12 is a diagram illustrating a function input to a fourth function generator illustrated in FIGS. 2 and 8;

FIG. 13 is a diagram showing a change in various output signals and a reheater gas damper reference opening command with respect to a change in an output command in a conventional example.

[Explanation of symbols]

 4 Mill 11 Classification Vane 16 Coal Supply 20 Controller 26 Primary Air Flow Rate 28 Mill Inlet Primary Air Temperature 30 Mill Outlet Primary Air Temperature 32 Mill Differential Pressure 34 Opening 35 Water Content 36 Crushability 37 Moisture / Crushability Estimator 38 Coal output 39 Mill model output of coal estimator 40 Coal output delay time constant 41 Coal output delay time constant estimator 43 Reheater 46 Reheater gas damper 48 Reheat steam temperature 50 Opening command 52 Reheat steam temperature set value 53 Reheat steam temperature deviation 55 Correction opening command 57 Output command 58 Reheater gas damper reference opening command 60 Load change signal 60 'Delay signal 74 Advance command 80 Reset timing 82 Off delay timer

Claims (1)

[Claims] 1. A re-heater gas damper reference opening command based on an output command, a preceding command is added during a load change, the preceding command is reset after the load is set, and a preset reheat steam temperature is set. A corrected opening command for eliminating the reheat steam temperature deviation between the set value and the reheat steam temperature is added to the reheater gas damper reference opening command to obtain a reheater gas damper opening command. In the method for controlling the reheat steam temperature of a coal-fired power plant in which the opening degree of the reheater gas damper is adjusted by the method, the amount of coal supplied to the mill, the primary air flow rate, the primary air temperature at the mill inlet, and the mill outlet Based on the primary air temperature, the classification vane opening or the classification rotation speed, and / or any of the mill differential pressures, the water content and the crushability of the coal are estimated, and the coal output is also estimated. Coal delay time constant based on quantity A method for controlling a reheat steam temperature of a coal-fired thermal power plant, wherein the reset timing of a preceding command with respect to a reheater gas damper reference opening command is determined based on the coal removal delay time constant.