JPS63159606A - Denitration control device for composite power generation facility - Google Patents

Abstract

PURPOSE:To allow transient increase and decrease in steam quantity being injected into a combustion chamber so that NOX concentration in exhaust gas may be suppressed below a reference value thereof, by controlling in advance a set ratio between steam injection quantity and fuel flow quantity, in accordance with a variation in the output of a power generator during the load change in a plant. CONSTITUTION:A denitration equipment 14 is provided with a means 15 for receiving the input of a power generator output command value b as a physical quantity that changes before a NOX concentration value does, and detecting its load change rate e to output it. Further, a means 16 is provided therein a receive the input of the load change e so as to calculate a correction quantity of S/F ratio (a set ratio between steam injection quantity and fuel flow quantity), and then output S/F ratio correction quantity target value f. In addition, a means 17 is provided to receive the input of the S/F ratio correction quantity target value f and also a S/F ratio a that is to be a reference value so as to output added results as a corrected S/F ratio g. The aforesaid constitution will enable the S/F ratio to be controlled in advance in accordance with a variation in the output of the power generator during the load change in a plant, thereby allowing the steam injection quantity to be increased and decreased transiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a denitrification control device for a combined cycle power generation facility that reduces NOx (nitrogen oxides) in exhaust gas in the combined cycle facility.

(Conventional technology) In combined cycle power generation facilities, gas turbines with high-load combustors generate NOx because nitrogen (N2) in the air and excess oxygen (02) react at high temperatures in the combustor. do.

Therefore, if left as is, a large amount of NOX contained in the exhaust gas will be emitted into the atmosphere, so a denitrification control device is provided to reduce NOX in the exhaust gas.

Here, the configuration of the combined power generation facility will be briefly explained using FIG. 4.

An air compressor 2 is provided on the rotating shaft 1, and compressed air (indicated by AIR in the figure) is sent to a combustor 3 together with fuel (indicated by FUEL in the figure). The combustor 3 burns the sent fuel with compressed air, and sends high-temperature, high-pressure gas to the gas turbine 4 to drive it. The high-temperature, high-pressure gas that drove the gas turbine 4 becomes exhaust gas.

It passes through an exhaust heat recovery steam generator (hereinafter referred to as HR5G) 5.

It is discharged into the atmosphere from the chimney 6. On the other hand, )lR5G5
Water is supplied to the steam piping installed in the steam pipe, and the supplied water is converted into steam by the thermal energy of the exhaust gas. The converted steam is sent to the steam turbine 7, and after driving the steam turbine 7, it passes through the condenser 8 and is discharged as water.The generator 9 is driven by the steam turbine 7 and the aforementioned gas turbine 4. Ru.

In order to reduce NOx in the exhaust gas for the above-mentioned combined power generation equipment, ammonia is injected into the HR5GS to reduce NOx.
A denitrification device 10 for reacting with x is provided.

It is also possible to reduce NOx by injecting steam into the combustor 3 and lowering the combustion temperature.

For this reason, a valve 12 is provided on the pipe 11 from the steam turbine 7 to the combustor 3, and the amount of steam injected into the combustor 3 is determined by the valve opening of the valve 12 at the connection part between the combustor 3 and the pipe 11. A steam injection device 13 is provided, which is controlled by a.

In the operation of this combined power generation facility, a conventional denitrification control device (not shown) uses an external setting device to set the steam to an appropriate value in consideration of the efficiency of the gas turbine, in order to reduce NOx in the exhaust gas. Injection amount (hereinafter abbreviated as S/I amount)
Based on the set ratio of and fuel flow rate (hereinafter abbreviated as S/F ratio) and the actual fuel flow rate, steam injection amount (S/I amount target value) = S/F ratio The S/I amount target value is calculated by the following method, and the S/I amount supplied to the combustor 3 is controlled by operating the valve based on this calculation result. As a result, when the combustion flow rate supplied to the combustor 3 increases, the amount of S/I to the combustor 3 is increased, and
The combustion temperature inside the engine was lowered to suppress the generation of NOx caused by higher combustion temperatures.

However, if this S/I amount is too large, that is, if the S/F ratio is set high, the combustion temperature in the combustor 3 will increase based on the relationship between the NOx reduction efficiency and the S/F ratio shown in Figure 5. Although the NOx in the exhaust gas is reduced, the efficiency and output of the gas turbine 4, which is driven by the combustion gas whose temperature has been lowered by injecting steam, is reduced.

Furthermore, since the steam injected into the combustor 3 is directly extracted from the steam turbine 7, the extracted amount of steam heat amount becomes a plant loss, which also reduces the efficiency of the steam turbine 7.

Therefore, from the viewpoint of both economics and environmental pollution, the amount of S/I into the combustor 3 is generally set to the minimum necessary, and the amount of S/I into the combustor 3 is generally set to the minimum necessary, and the amount of S/I into the combustor 3 is mainly set to the ammonia into the denitrification device 10 in the HR5GS. By controlling the injection volume.

Measures have been taken to reduce NOx emitted into the atmosphere.

(Problems to be Solved by the Invention) However, according to the above conventional method, since the denitrification control using a catalytic reaction by ammonia injection has a slow reaction, it is not possible to suppress the increase in NOx emissions, especially during load fluctuations, and the exhaust gas There is a problem that the NOx concentration inside exceeds the standard.

Now, as the plant load fluctuates, as shown in Figure 6 (A), the generator output command value, which was constant before time 11, increases from time L1 to L2, and from time L2 Let us consider a case in which the value remains constant until t3, then decreases from time t3 to t4, and then returns to the original state from time t3 onwards.

At this time, the fuel flow rate changes in the same way as the generator output command value, and the amount of ammonia injected into the denitrification device 1fIO, which is the main part of NOx reduction, is increased as shown in FIG. 2(B).

In addition, the S/F ratio, which is the standard S/F ratio, is integrated into the fuel flow rate.
The I amount target value is also increased as shown in FIG.

However, the main reaction rate between ammonia and NOx is slow, and as shown in Figure (D), the NOx concentration increases when the load changes, especially at the time when the fuel flow rate reaches its maximum value.
A problem arises in that the NOx concentration peaks in the vicinity and exceeds the NOx concentration reference value.

Therefore, the present invention can be used even if the plant load fluctuates.

It is an object of the present invention to provide a denitrification control device for a combined power generation facility that can control the NOx concentration in exhaust gas to a reference value or less.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes an output change detection means for detecting a change in the output of a generator, and an output change rate input from the output change detection means into a denitrification control device. , S/F ratio correction amount calculation means for calculating the correction amount for the reference S/F ratio, and this S/F ratio correction amount calculation means.
/F ratio correction amount target value from the S/F ratio correction amount calculation means and the reference S/F ratio are inputted, and these are added.
S/F that outputs the addition result as a corrected S/F ratio
The ratio determining means is provided.

(Function) As a result, when the plant load fluctuates, the amount of S/I injected into the combustor can be increased or decreased during transient periods by proactively controlling the S/F ratio according to changes in the generator output.
It is possible to control the NOx concentration, which cannot be controlled only by increasing the amount of ammonia injection, to below the reference value.

(Embodiment) FIG. 1 shows the configuration of a denitrification control device for a combined power generation facility according to an embodiment of the present invention. In this figure, the denitrification control bag [1
4 inputs the S/F ratio electric motor output command value and the fuel flow rate C, which are the standards per unit weight of fuel, and connects the pipe 11 from the steam turbine 7 to the steam injection bag W113 of the combustor 3. It outputs the operation signal d to the valve 12.

This denitrification control device 14 includes an output change detection means 15 that inputs one generator output command value as a physical quantity that changes in advance of the NOx concentration, detects and outputs a load change rate e that is the rate of change; The load change rate e from this output change detection means 15 is input, the correction amount of the S/F ratio is calculated, and the S/F ratio is calculated.
The S/F ratio correction amount calculation means 16 that serves as the F ratio correction amount target value, and the S/F ratio ratio that serves as the S/F ratio correction amount target value standard from the S/F ratio correction amount calculation means 16. Add these and convert the addition result to the corrected S/
The S/F ratio determining means 17 that outputs the F ratio ratio and the corrected S/F ratio ratio mouth flow rate C from this S/F ratio determining means 17 are input, and this is multiplied to obtain the 1 multiplication result. The S/I amount set value calculation means 18 outputs the S/I amount set value as the S/I amount target value.
It consists of an S/I amount setting means 19 for converting the I amount target value into an operation signal d to the valve 12.

Further, as shown in FIG. 2, the S/F ratio correction amount calculation means 16 in the denitrification control device 14 inputs the load change rate e from the output change detection means 15, and calculates the input load change rate e. A gain selection means 20 for selecting a corresponding gain from a memory table (not shown) created in advance according to the positive/negative sign and the magnitude of its absolute value, and a load change to the gain selected by this gain selection means 20. Multiply by the rate e, S
/F ratio correction amount - input S/F ratio correction amount calculation means 21 and input S/F ratio correction amount target value of S/F ratio correction amount to follow within a constant change rate range It consists of a limiting means 22.

With the above configuration, if there is no load fluctuation in the plant, the generator output is constant, and the generator output command value does not change,
The output change detection means 15 outputs "0" as the load change rate e. As a result, the S/F ratio correction amount target value from the S/F ratio correction amount calculating means 16 is set to 0'', and the S/F ratio determining means 17 uses the corrected S/F ratio ratio as a reference. The S/F ratio ratio is output as it is above the S/F ratio ratio.The S/F ratio upstream flow rate C, which is the standard output from the S/F ratio determination means 17, is inputted into the S/I amount setting value calculation means 18. The S/I amount target value that does not fluctuate is output by performing multiplication.The S/I amount setting means 19 inputs this S/I amount target value, outputs a constant operation signal d, and outputs the S/I amount target value that does not fluctuate. The plant is controlled stably by keeping the opening degree constant.

From this state, load fluctuations occur in the plant.

When the generator output command value S fluctuates, the output change detection means 15 first calculates the load change rate e using the following formula.

(Load change rate e) = d (generator output command value b)/dt・
(1) Next, the gain selection means 20 in the S/F ratio correction amount calculation means 16 shown in FIG. Based on the absolute value of the load change rate e, a corresponding gain is selected from the aforementioned memory table (not shown).

The reason why different gains are selected depending on whether the load change rate e is positive or negative even if the absolute value is the same is because the operating tendency of NOx emissions is different when the generator output increases and when it decreases. . The S/F ratio correction amount calculation means 21 calculates the S/F ratio correction amount using the following formula based on the gain selected by the gain selection means 20 and the load change rate e.

(S/F ratio correction amount 1) = (gain) x (load change rate e
)...(2) The change rate limiting means 22 adds a change rate limit to the S/F ratio correction amount from the S/F ratio correction amount calculation means 21 to correct the S/F ratio ratio. Quantity target value basis.

The S/F ratio determining means 17 in FIG. The S/F ratio correction amount target value is calculated based on a, and the corrected S/F ratio ratio twisting force is applied.

(Corrected S/F ratio twist (standard S/F ratio a) + (S/F ratio correction amount target value base)
......(3) However, (when the corrected S/F ratio twist α (corrected S/F ratio twist α) (when the corrected S/F ratio twist β) (Corrected S/F ratio twist β α: Upper limit value β: Lower limit value The reason for setting the upper limit value α and lower limit value β is 1.
When the generator output increases, a sudden increase in the S/I amount may cause a misfire in the combustor 3, and when the generator output decreases, the ammonia reaction is slow, resulting in a sudden S/I increase.
Due to the inability to reduce the amount.

Next, the corrected S/F ratio twisting material flow rate C from this S/F ratio determining means 17 is inputted to the S/I amount set value calculation means 18, and the S/I amount target value is determined by the following formula. Calculate the difference.

(S/I quantity target value h) = (Fuel flow rate c) S/I amount target value h) = r r: Lower limit value This lower limit value r is set when the S/I amount decreases.
The amount of steam flowing to the combustor 3 decreases, the temperature of the pipe 11 decreases, and even if the S/I amount is increased in this state, an appropriate amount of S/I may not be supplied to the combustor 3.
This setting is for warming up the steam injection device 1 and the steam injection device 13, etc.

In this way, S/
The I amount target value is output to the valve 12 via the S/I amount setting means 19 as an operation signal d.

Next, FIG. 3 shows the NOx reduction effect using the denitrification control bag @14 of this embodiment and the operating characteristics of each plant amount with respect to actual plant load fluctuations. The timing is the same as in FIG. 6 above. When the generator output command value changes as shown in FIG. 3(A) due to load fluctuations in the plant, the gain selection means 201 in the S/F ratio correction amount calculation means 16 adjusts the change in the generator output command value. The corresponding gain is selected, and the S/F ratio correction amount calculation means 21 calculates the S/F ratio that does not become "0" while the generator output is changing, as shown in FIG. Enter the F ratio ratio correction amount. The rate-of-change limiting means 22 adds a predetermined rate-of-change limit to this to set the S/F ratio correction amount target value as a base value.

The S/F ratio determination means 17 adds this S/F ratio correction amount target value standard S/F ratio a, and twists the corrected S/F ratio ratio as shown in FIG. . The product obtained by multiplying this corrected S/F ratio ratio by the fuel flow rate C that changes as shown in Figure 6 (A) is the S/I amount set value calculation means 18 force shown in Figure 3 (D). /I amount is at target value.

S/I amount setting means 19 into which this S/I amount target value is input
The result of controlling the NOx concentration by operating the valve 12 is shown in the same figure (E). As can be seen from the comparison with the prior art example shown in FIG. 6, the NOx concentration is significantly reduced near time L2, where in the past, the NOx concentration had peaked and exceeded the reference value.

In this way, by increasing or decreasing the amount of S/I injected into the combustor 3 instead of ammonia, which reacts slowly, in response to changes in the generator output, the amount of S/I can be increased or decreased when the plant load fluctuates.

In particular, the NOx concentration, which exceeds the reference value when the load increases, can be controlled to within the reference value.

In the above embodiment, the S/F ratio correction amount is calculated based on the rate of change in one generator output as a physical quantity that changes prior to the NOx concentration, but the S/F ratio is adjusted based on the rate of change in the fuel flow rate C. A similar effect can be obtained by using means for correcting the F ratio ratio.

[Effects of the Invention] As described above, according to the present invention, even when a large amount of NOx is generated, such as when the plant load fluctuates, the NOx concentration contained in the exhaust gas discharged into the atmosphere can be kept below the standard value. can be controlled.

Moreover, the S/I amount is only injected transiently.

Since steady operation without load fluctuation is performed at an S/I amount that takes economic aspects into account, an efficient denitrification control device for combined power generation equipment can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a denitrification control device for a combined cycle power generation facility according to an embodiment of the present invention, FIG. 2 is an internal block diagram of the S/F ratio correction amount calculation means of FIG. 1, and FIG. Fig. 4 is a configuration diagram of a combined power generation facility, Fig. 5 is a characteristic diagram of the NOx reduction coefficient versus S/F ratio, Fig. 6 The figure is an explanatory diagram of changes in main state quantities during load fluctuations when a conventional denitrification control device is used. 1...Rotating shaft, 2...Air compressor, 3...Combustor. 4...Gas turbine, 5...Exhaust heat recovery steam generator (
HR5G), 6...Chimney, 7...Steam turbine. 8... Capacitor, 9... Generator, 10... Denitrification device, 11... Piping, 12... Valve, 13...
Steam injection device, 14... Denitration control device, 15... Output change detection means. 16...S/F ratio correction amount calculation means, 17...S/
F ratio determining means, 18...S/I amount setting value calculation means 9...S/I amount setting means, 20...gain selection means, 21...S/F ratio correction amount calculation means, 22...
Rate of change limiting means. Figure 2 Figure 5 Figure 6

Claims (1)

[Scope of Claims] Steam that controls the amount of ammonia injected into the intermediate part of the exhaust heat recovery steam generator of a combined power generation facility consisting of a gas turbine and a steam turbine, and also sets the amount of steam injection to the combustor in advance. In a denitrification control device for a combined cycle power generation facility that suppresses NO_x concentration in exhaust gas by controlling according to the set ratio of injection amount/fuel flow rate and the fuel flow rate at that time,
A denitrification control device for a combined power generation facility, comprising means for detecting a rate of change in a physical quantity that changes in advance of O_x concentration, and means for correcting the set ratio according to the detected rate of change. (2) In claim 1, the means for correcting the set ratio adjusts a predetermined rate of change to the product of a gain and a rate of change selected in accordance with a rate of change of a physical quantity that changes prior to the NO_x concentration. A denitrification control device for a combined power generation facility, comprising: a ratio correction amount calculation means for adding a limit and outputting it as a correction amount; and a ratio determination means for adding the correction amount from the ratio correction amount calculation means to the set ratio. . (3) A denitrification control device for a combined power generation facility according to claims 1 and 2, wherein the physical quantity that changes prior to the NO_x concentration is a generator output or a fuel flow rate.