JPH0544537B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a gas turbine, and in particular, to reducing the amount of NOx (nitrogen oxides) and CO (carbon monoxide) generated in turbine exhaust gas by a premixed fuel method. This invention relates to a gas turbine with an improved method for reducing

[Technical background of the invention and its problems]

Conventionally, the basic configuration of this type of gas turbine is as shown in FIG. Enter. The high-pressure air 3 introduced into this annular space 5 flows around the outer periphery of the combustor inner cylinder 6, and while cooling the combustor inner cylinder 6 through forced convection, it burns through the air holes 7, swirler 8, etc. It flows into the internal cylinder 6. On the other hand, fuel is connected to a fuel supply source (not shown), and a fuel supply system 10 is provided with a regulating valve 9 for appropriately controlling the amount of fuel supplied.
is supplied to the combustor 4 via the combustor 4. The fuel supplied to the combustor 4 is injected from the fuel nozzle 11 to the vicinity 12 of the backflow region inside the combustor inner cylinder 6, and then the igniter 1
3 gives ignition energy to ignite and burn. The high-temperature gas 14 generated through constant volume and constant pressure combustion is introduced into the turbine 15 and does work.
A portion of the driving force of the turbine 15 is consumed as power for the air compressor 2, and most of the power is consumed as power for a driven machine 16 such as a generator (not shown). The opening degree of the regulating valve 9 of the fuel supply system 10 is controlled according to the load of the driven machine 16 to control the amount of fuel supplied.

Incidentally, even when the combustor 4 has one or more fuel nozzles 11, a large amount of NOx, so-called thermal NOx, is generated in the high-temperature gas 14. This NOx can be reduced slightly by increasing the number of fuel nozzles 11 and using air holes 7, etc., to promote a slight decrease in flame temperature in a local area, but it is impossible to significantly reduce NOx. It is.

However, by locally lowering the flame temperature, NOx
The premix combustion method is more effective as a method for reducing NOx emissions, and FIG. 8 shows the effect of reducing the amount of NOx generated by increasing the premix ratio. That is, when premix combustion is not performed, the amount of NOx generated in the high-temperature gas 14 increases exponentially as the fuel-air ratio increases, as shown by the characteristic curve 20.

On the other hand, when premix combustion is performed, even if the fuel-air ratio increases, as shown in characteristic curves 21a to 21d,
There is almost no increase in NOx, and a remarkable NOx reduction effect can be observed. Moreover, this NOx reduction effect reduces the premixing rate by, for example, 50% to 80% (21a to 21
It shows that it becomes more noticeable as the value is gradually increased to d).

A conventional gas turbine that employs such a premix combustion method is configured as shown in FIG. are doing. The A fuel supply system 30 is connected to the fuel nozzle 11 and supplies fuel directly into the combustor inner cylinder 6. In FIG. 9, the same parts as in FIG. 7 are given the same reference numerals, and their explanations are omitted.

On the other hand, the B fuel supply system 31 supplies fuel to the combustor inner cylinder 6.
Before being introduced into the combustor inner cylinder 6, the high pressure air 3 is supplied to the premixing chamber 32, where it is mixed with the high pressure air 3 in advance, and then passed through the air hole 7 and supplied into the combustor inner cylinder 6. There is. This mixed fuel 36 is supplied to the combustor inner cylinder 6 by the fuel supplied from the A fuel supply system 30.
The ignition energy is given by the high-temperature gas generated by combustion inside, and it burns at a low temperature. This reduces the amount of NOx generated. The graph of FIG. 10 shows the amount of NOx and CO generated by the gas turbine configured in this way in relation to the turbine load. In other words, when the turbine load is the rated load (100%), it indicates the amount of NOx generated.
The NOx characteristic curve 37 and the CO characteristic curve 38 indicating the amount of CO generated are NOx regulation value 39 and CO regulation value 40.
have been cleared respectively. However, during partial load operation where the turbine load is in the middle of the rated load, for example near switching point C, the amounts of both NOx and CO generated significantly exceed the respective regulation values 39 and 40. In particular, since the amount of CO generated increases rapidly, the combustion efficiency of the combustor 4 decreases, resulting in a disadvantage that the plant efficiency is greatly reduced. Also,
In a partial load operating state, combustion efficiency is reduced and combustion vibrations are more likely to occur, resulting in a disadvantage that the reliability of the gas turbine is significantly reduced.

Furthermore, depending on the type of fuel, operating method, change in turbine shape, etc., both A and B fuel supply systems 3
Since it is not possible to automatically control the switching point C of 0 and 31 and the fuel supply distribution of both AB systems 30 and 31, it is necessary to prevent fuel vibration and reduce the NOx and CO regulation values 32 during partial load operation. , 33 could not be cleared.

Therefore, such conventional gas turbines
As shown in the figure, an air bypass 34 and an air regulating valve 35 were provided in the middle of the air bypass 34, respectively. That is, by controlling the opening degree of the air adjustment valve 35, the amount of high-pressure air 3 supplied to the combustor inner cylinder 6 is controlled, and the fuel-air ratio of the high-temperature gas 14 is kept as constant as possible. NOx
and controlled CO generation.

However, in such conventional gas turbines, the maximum values of NOx and CO are set to the respective regulation values of 39 and 4.
Although it can be suppressed to 0 or less, high-temperature gas 14
Since the low-temperature, high-pressure air 3 is blown into the vicinity of the flow, the temperature distribution is not favorable, and there is a risk that new problems may occur regarding the gas turbine structure.

[Purpose of the invention]

The present invention was made in view of the above-mentioned circumstances, and
It is an object of the present invention to provide a gas turbine that reduces NOx and CO concentrations in exhaust gas and reduces combustion oscillations, particularly during partial load operation.

[Summary of the invention]

The present invention provides multiple premixed fuel supply systems,
A computer is programmed with a fuel supply pattern that is set for each system by making each fuel supply start by these premixed fuel supply systems and the amount of fuel supplied at or after this start correspond to the turbine load.
The calculator calculates the turbine load and controls the fuel supply operation of each premix fuel supply system based on this fuel supply pattern to reduce the amount of water in the turbine exhaust gas.
The fuel supply pattern is changed as appropriate depending on the detected values of NOx and CO concentrations, air column vibrations, and combustion vibrations.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 6.

Note that in FIGS. 1 to 6, the same parts are given the same reference numerals, and the explanation of the overlapping parts will be omitted.

FIG. 1 is a system diagram showing a main part of an embodiment of a gas turbine according to the present invention, in which an air compressor 50 compresses atmospheric air 51 and sends high-pressure air 53 to a combustor 52. This combustor 52 has a structure to which a premix combustion method is applied, and the required type of fuel is fed to the combustor 52.
It has multiple premixed fuel supply systems, for example, three systems FA, FB, and FC. These premixed fuel supply systems FA, FB, and FC each have regulating valves 54A, 54B,
54C and flow meters 55A, 55B, and 55C are installed to detect the amount of fuel supplied by each fuel supply system FA, FB, and FC for each system, and to control the opening of each regulating valve 54A, 54B, and 54C. The amount of fuel supplied is now adjusted for each system.

High-temperature gas 56 generated in the combustor 52 is sent to a turbine 58 that is directly connected via a shaft to a driven machine 57 such as a generator, and does work there. A portion of the driving force of the turbine 58 is used to drive the air compressor 50. Exhaust gas 59 from the turbine 58 passes through a heat exchanger 60 and the like and is discharged from the stack 61 to the atmosphere.

A pressure sensor 63 that detects air column vibration and combustion vibration and a temperature sensor that detects the temperature of high-temperature gas 56 generated in the combustor 52 at the outlet of the combustor 52 are installed in the downstream gas flow path of the combustor 52. A load detector 62 consisting of a load detector 62 is provided respectively. Also,
An exhaust gas sensor 64 is installed in the downstream gas flow path of the turbine 58 to sample a portion of the turbine exhaust gas 59. The exhaust gas sensor 64 collects the sampled gas from the exhaust gas sensor 64.
The input of the calculator 66 is transmitted through an exhaust gas analyzer 65 that detects NOx and CO concentrations, respectively, and a converter 67 that converts the detection output from the exhaust gas analyzer 65 into a signal that can be read by the calculator 66. electrically connected to the port.

The input port of the calculator 66 is further electrically connected to a load detector 62 and a pressure sensor 63, respectively, via converters 68 and 69 which convert the signals into signals that can be read by the calculator 66. In addition, the input and output ports of the calculator 66 are connected to each of the regulating valves 54A, 54B, and 54C of each premixed fuel supply system FA, FB, and FC, and each flow meter 55.
A, 55B, and 55C, and this calculator 66 allows each fuel supply system FA,
The amount of fuel supplied from FB and FC to the combustor 52 is detected for each system, and each regulating valve 54A, 5
4B and 51C are appropriately controlled according to the built-in program.

The program built into this calculator 66 is
It has a fuel supply pattern configured as shown in the figure. This fuel supply pattern is a fuel schedule 70A, 70 that schedules the amount of fuel to be supplied to the combustor 52 according to the turbine load.
B, 70C to each premix fuel supply system FA, FB, FC
Each is set accordingly. Each of the fuel schedules 70A, 70B, and 70C sets the fuel supply start order in the direction of increasing turbine load.
70B and 70C are set in this order, and each system supplies them in parallel. Further, the first and second switching points C1 and C2, which are the times when fuel supply to the premixed fuel supply systems 70B and 70C are started, are set to be movable to required turbine load values, respectively. That is, at the first switching point C1, the supply amount of the fuel supply system FA that has been supplying fuel up to this point is reduced by the required amount in a stepwise manner, and this decrease is applied to the rise of the fuel supply start time of the next fuel supply system FB. After matching the supply amount, fuel will be supplied simultaneously from both systems FA and FB. Similarly, at the second switching point C2, of the premixed fuel supply systems FA and FB that have been supplying fuel up to this point, the required amount of fuel supplied by the FB system is reduced in a stepwise manner, and this reduction is applied to the next step. This is made to match the rise amount at the start of fuel supply for the FC system. Further, the total amount of each of these fuel schedules 70A, 70B, and 70C at a required turbine load matches the total fuel schedule 71 shown by the dashed line in FIG. In other words, the total fuel schedule 71 is a set of fuel supply amounts that vary depending on the type of fuel, operating method, etc., depending on the turbine load, and the total fuel supply amount FT of this total fuel schedule 71 is set for each fuel supply system.
Divide each into FA, FB, and FC in the required ratio,
The shared fuel schedules are 70A and 7.
0B, 70C. That is, the amount of each fuel schedule 70A, 70B, 70C is fa,
If fb and fc, then FT=fa+fb+fc. Therefore, if the type of fuel or the operating method differs, the total amount of fuel supplied in the total fuel schedule 71 will vary, and the respective amounts fa, fb, fc of each fuel schedule 70A, 70B, 70C will vary. Therefore, the calculator 66 has a plurality of built-in programs that set various total fuel schedules 71 depending on the fuel type, driving method, etc., and the appropriate program can be selected according to the difference in the fuel type, driving method, etc. It's becoming a matter of choice.

The built-in program of this calculator 66 has a control program configured as shown in the flowchart of FIG.
Opening control of 54B and 54C is executed.

That is, as shown in FIG. 3, first, when the turbine load is set, fuel is supplied from each premixed fuel supply system FA, FB, and FC to the combustor according to the fuel pattern set by the built-in program of the calculator 66. 52 is supplied with fuel in an amount corresponding to the turbine load. Each regulating valve 54A, 54B, 54C until the supply amount from each premix fuel supply system FA, FB, FC reaches the set amount.
The opening control is repeated.

When fuel is supplied to the combustor 52 from the required premixed fuel supply systems FA, FB, and FC, this fuel is
As shown in the figure, the fuel is first fed into a premixing chamber 52C disposed in an annular space 52B on the outer periphery of the combustor inner cylinder 52A. Next, in this premixing chamber 52C, fuel is premixed with high pressure air 53 that flows around the outer periphery of the combustor inner cylinder 52A and forcibly cools it, and flows into the combustor inner cylinder 52A through the air hole 52D. do. In this combustor inner cylinder 52A, the premixed fuel supply system FA is branched from the middle and the combustion nozzle 5 is connected to the combustion nozzle 5.
Fuel is supplied through the branch path FAa connected to 2E, and diffusion combustion is already occurring. Therefore, a stable flame is formed in the backflow region 52G formed by the combustion nozzle 52E and swirler 52F for diffusive combustion. Furthermore, since the jet streams 52H of the plurality of premixed gases flow in opposition to the vicinity of the backflow region 52G as indicated by the arrows in FIG. 4, the flame is further stabilized. This flame serves as an ignition source for the premixed gas flowing into the combustor inner cylinder 52A as a jet flow 52H, and the flame is sequentially spread downstream to continue combustion. Since the equivalence ratio (φ) of this premixed gas is mixed under a fuel lean condition, for example, φ=0.7 to 0.5, the increase in flame temperature due to combustion is small. For this reason, the amount of NOx generated is extremely small compared to during diffusion combustion.

Further, since fuel lean combustion is performed using premixed gas, there is little flame radiation, and the temperature of the combustor inner cylinder 52A can be kept relatively low, so that the life of the combustor 52 can be extended.

Furthermore, since the average flow velocity of the premixed gas in the premixing chamber 52C is greater than the turbulent combustion velocity, occurrence of phenomena such as flashback can be prevented.

Furthermore, fuel is supplied to the combustor 52 from a plurality of systems, that is, three premixed fuel supply systems FA, FB, and FC. Since the second switching points C1 and C2 are set, both the NOx peak value NOxp and the CO peak value COp during partial load operation can be reduced as shown in FIG. In other words, the first and second switching points C1 and C2 are the rising points at which fuel supply by the FB and FC premix fuel supply systems starts, and since the fuel supply amount rises rapidly from zero, at the initial stage of start-up, As the fuel is burnt lean, the CO peak value COp rises rapidly as shown in FIG. 5, and as the amount of fuel supplied increases rapidly, the amount of CO generated gradually decreases. and,
As the turbine load gradually increases, the outlet temperature of the combustor 52 increases, so the amount of CO generated decreases.

On the other hand, the amount of NOx generated increases or decreases in inverse proportion to the amount of CO generated. In any case, the CO peak value COp and the NOx peak value NOxp each exhibit bimodality with two peak values, and are reduced as a whole.

The hot gas 56 with reduced NOx and CO concentrations is introduced into the turbine 58 to do work. Part of the driving force of the turbine 58 is supplied to the air compressor 5
Used to drive 0. During the introduction of the high temperature gas 56 into the turbine 58, a load detector 62 consisting of a temperature sensor detects the gas temperature, and a pressure sensor 63 detects air column vibration and combustion vibration. The detection outputs from these detectors 62 and 63 are converted into calculator signals by converters 68 and 69, and then input to the input port of the calculator 66. The calculator 66 calculates the turbine load by calculating the temperature detection value from the load detector 62,
Each premixed fuel supply system supplies fuel according to the turbine load.
It is supplied to the combustor 52 via FA, FB, and FC.
In addition, the calculator 66 compares each detected output from the pressure sensor 63 and the exhaust gas analyzer 65 with the required combustion vibration set value, NOx and CO concentration set value, and when each detected output exceeds each set value, First,
By moving the turbine load values at the second switching points C1 and C2, or adjusting the fuel supply increase/decrease at the first and second switching points C1 and C2 as appropriate, and changing the flame temperature, the combustion vibration level and turbine exhaust gas NOx and CO concentrations can be controlled.

FIG. 6 is a system diagram showing another embodiment of the present invention, and the difference between this embodiment and the embodiment shown in FIG. This is due to the omission of . Other than this, the configuration is almost the same as the embodiment shown in FIG.
In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals, and their explanation will be omitted. However, since the premixed fuel supply system has two systems FA and FB, the calculator 66 that controls the fuel supply operation of these supply systems FA and FB is required.
The program consists of a fuel supply pattern for two systems and a fuel supply pattern for one system.
It merely establishes two switching points.

According to this embodiment, the premixed fuel supply system FA, FB
Since there are two systems, the fuel supply pattern and control program programmed into the calculator 66 can be simplified.

〔Effect of the invention〕

As explained above, the present invention provides a plurality of premix fuel supply systems that adjustably supply fuel to a combustor and premix this fuel with air, and when the fuel supply by these premix fuel supply systems starts and The fuel supply pattern set for each system is programmed into the computer by making the fuel supply amount at the start and thereafter correspond to the turbine load. In addition to controlling the fuel supply operation, each fuel supply pattern is changed as appropriate based on the detected values of NOx and CO concentrations in the turbine exhaust gas, air column vibration, and combustion vibration.

Therefore, according to the present invention, it is possible to control the fuel supply amount etc. by the plurality of premix fuel supply systems in accordance with fluctuations in the turbine load, adjust the premix ratio as appropriate, and change the flame temperature in the combustor. This reduces the amount of gas in the turbine exhaust gas, especially during partial load operation.
It is possible to reduce NOx and CO concentrations as well as air column vibration and combustion vibration. In addition, if the type of fuel supplied from the premixed fuel supply system, the size of the gas turbine capacity, and the fuel supply pattern according to the turbine operating method are programmed into the calculator, these fuel types, etc. can be changed. Appropriate fuel supply is achieved according to the amount of fuel, which has the effect of reducing plant operating costs.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the gas turbine according to the present invention, FIG. 2 is a pattern diagram of the fuel supply pattern of each premix fuel supply system programmed into the calculator shown in FIG. 1, and FIG. The figure is a flowchart of the control program built into the calculator shown in Fig. 1, Fig. 4 is a partially detailed diagram showing the combustor shown in Fig. 1 in some detail, and Fig. 5 is the implementation shown in Fig. 1. A graph showing the NOx and CO concentration distribution in the example turbine exhaust gas in response to the turbine load, Fig. 6 is a system diagram showing another embodiment of the present invention, and Fig. 7 shows the basic configuration of a typical gas turbine. Fig. 8 is a graph showing the effect of reducing the amount of NOx generated in the combustor by increasing the premixing ratio, Fig. 9 is a system diagram of a conventional gas turbine, and Fig. 10 is a graph showing the effect of reducing the amount of NOx generated in the combustor by increasing the premixing ratio. 2 is a graph showing the amount of NOx and CO generated by a gas turbine in response to turbine load. 50...Air compressor, 51...Atmosphere, 52...
Combustor, 53...Compressed air, 54A, 54B, 5
4C... Regulating valve, 55A, 55B, 55C... Flow meter, 56... High temperature gas, 57... Driven machine, 5
8... Turbine, 59... Turbine exhaust gas, 60
... Heat exchanger, 62 ... Load detector, 63 ... Pressure sensor, 64 ... Exhaust gas sensor, 66 ... Calculator, 67, 68, 69 ... Converter.

Claims (1)

[Scope of Claims] 1. A combustor, a plurality of premix fuel supply systems that adjustably supply fuel to the combustor and premix this fuel with air, and at the start of each fuel supply of these premix fuel supply systems. A fuel supply pattern is programmed for each of the premixed fuel supply systems, in which the fuel supply amount from the start to the subsequent time corresponds to the turbine load. a calculator in which a partial load value is provided with a plurality of switching points where the fuel supply start amount of the premixed fuel supply system in the order is equal to the decrease in the preceding system; and a load detector that detects the exit temperature of the combustor. and a pressure sensor that detects air column vibration and combustion vibration downstream of the combustor, and an exhaust gas sensor that detects NOx and CO concentrations in the turbine exhaust gas, and the calculator is connected to the load detector. The turbine load is calculated from the detection output of the turbine load, and the fuel supply amount corresponding to this turbine load is determined from the fuel supply pattern and is supplied from each premix fuel supply system. A gas turbine characterized in that NOx and CO concentrations in turbine exhaust gas are appropriately controlled by adjusting the switching point of the fuel supply pattern and the fuel supply amount at this switching point accordingly. 2. The gas turbine according to claim 1, wherein each of the calculators has a built-in program that respectively sets a fuel supply pattern according to the type of fuel supplied from the premix fuel supply system and the turbine operating method.