JPH05340273A - Combustion method for combustor - Google Patents

Abstract

PURPOSE:To maintain low NOx property at the time of a high load, and suppress increase in the discharging amount of NOx to low level at the time of a low load by increasing fuel gas in mixture gas for primary combustion by a constant amount, and reducing combustion gas in mixture gas for secondary combustion by a constant amount, when a load ratio is a prescribed value or less. CONSTITUTION:In a combustion gas discharging block 10, a fuel gas discharging hole 1 for ignition is formed on the center thereof, and an annular mixture gas discharging hole 2 for primary combustion is formed on the circumference thereof. Furthermore, an annular mixture gas discharging hole 3 for secondary combustion is formed on the circumference thereof, and a flange 4 is provided on a bulkhead between the mixture gas discharging hole 2 for primary combustion and the mixture gas discharging hole 3 for secondary combustion, so that flame formed in respective discharging holes 2, 3 are not affected each other in the root part thereof. It is thus possible to reduce concentration of NOx and enlarge the combustion range of a low noncombustible components by increasing fuel gas in mixture gas for primary combustion by a constant amount, and reducing combustion gas in mixture gas for secondary combustion by a constant amount, when a load ratio is a prescribed value or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustor combustion method for reducing the concentration of nitrogen oxides (NO _x ) in exhaust gas.

[0002]

2. Description of the Related Art In recent years, due to environmental considerations, the release of nitrogen oxides (NO _x ) generated by combustion into the atmosphere has become a serious problem. The NO _X discharged from is so-called thermal NO _X in which nitrogen in the air is oxidized in a high temperature region.

Considering a combustor for a gas turbine as one of the combustors, a conventional combustor of this type uses diffusion combustion which can obtain stable combustion.
Combustion of a fuel / air mixture produces an adiabatic flame temperature of around 2000 ° C. This high-temperature combustion gas is mixed with the air to lower the temperature, NO _X amount unacceptable for the surface of the diffusion flame is high temperature is generated. However, since the production of this thermal NO _X exponentially rises with respect to the rise in temperature, the production of NO _X can be greatly reduced by slightly lowering the temperature of the combustion flame. As one of effective means for lowering the temperature of the combustion flame, a premix combustion method is known in which fuel and combustion air are mixed before combustion and burned as a lean mixed gas.

However, in premixed combustion in which constant-edge air is supplied, such as in a combustor of a gas turbine engine,
When adjusting to achieve NO _X and complete combustion near the rated value, a rapid increase of unburned components with reduced load and flame blowout occur.

Therefore, the present inventors have filed Japanese Patent Application No. 3-3401.
In No. 75, a combustion gas injection hole for ignition is provided in the center, and an injection hole for a primary combustion mixed gas having a constant mixing ratio of air and fuel gas is provided around the injection hole, and air and fuel gas are further provided on the outer periphery thereof. In addition to proposing a combustion device that is concentrically provided with secondary combustion mixed gas ejection holes whose mixing ratio is variable,
Using this combustion device, at the time of startup, the fuel gas for ignition is ejected from the fuel gas ejection holes for ignition and burned,
A mixture gas of air and primary fuel gas is ejected from the primary combustion mixed gas ejection hole to burn, and after startup, air and secondary air having a composition ratio corresponding to the load is ejected from the secondary combustion mixed gas ejection hole. A combustion method is provided in which a mixed gas with a fuel gas is jetted and burned, then the fuel gas for ignition is narrowed down, and the mixed gas for primary combustion is constantly supplied to continue combustion.

[0006]

In the premixed combustion in which the combustion air is supplied in a constant amount, both the NO _x emission and the unburned component emission are low by the combustion device and the combustion method having the above structure. If it was possible to extend the range increases, which were both suppressed combustion emissions emissions and unburned components of the maximum load during the NO _X in the combustion device (CO), 6
As indicated by A, the air ratio of the primary combustion mixed gas is set to 1.5.
When a high air ratio such as the above is used, the uncombusted components are discharged in large amounts at a certain load factor a or less when the load is reduced, which causes a decrease in the efficiency of the combustor. Further, if the set mixing ratio of the primary combustion mixed gas is changed to a low air ratio (for example, 1.3) in order to widen the load range from the maximum load to the start of discharging unburned components, B in the figure shows As shown, the NO _X emission amount near the maximum load increases, and the low NO _X performance is impaired.

In both cases A and B, if a load range of such a level that low NO _x and low unburned components can be operated is obtained,
Although it does not pose a problem in a normal combustion device that controls both fuel gas and air according to the load, it is insufficient in a special application such as a combustor for a gas turbine engine that burns with a constant amount of air. Efficiency is reduced.

The present invention has been made in view of the above points, and it is an object of the present invention to widen the load range from the maximum load to the start of discharging unburned components (CO) while maintaining low NO _x performance.

[0009]

[Problems to be Solved by the Invention] A combustion gas injection hole for ignition is provided in the center part, and an injection hole for a primary combustion mixed gas having a constant mixing ratio of air and fuel gas is provided around the injection hole, and an air is further provided on the outer periphery thereof In a combustion method of a combustor in which a secondary combustion mixed gas injection hole having a variable mixing ratio of the fuel gas and the fuel gas is concentrically provided and burned with a constant air amount, a predetermined amount of unburned component emission increases Below the load factor of 1, the fuel gas in the primary combustion mixed gas is increased by a fixed amount and the fuel gas in the secondary combustion mixed gas is decreased by a fixed amount.

[0010]

[Action] it is possible to widen the flammable range exhibiting such both low discharge of emissions and unburned components of the NO _X control only the supply amount of the simple fuel gas according to the combustion method.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is an axial sectional view of an embodiment of a gas turbine combustor to which the method of the present invention is applied, and FIG. 2 is an end view of the combustor.

In the combustor, a combustion gas injection block 10 is supported in a front portion (on the left side in the drawing) from the center in the axial direction inside the flanged cylinder 100, and the combustion cylinder 20 is connected to the combustion gas injection block 10 and is connected to the combustion cylinder 20. Is placed in the combustion cylinder 2
The inside of 0 forms a combustion chamber 20a.

As shown in FIG. 2, the combustion gas jetting block 10 has an ignition fuel gas jetting hole 1 formed in the center thereof, and an annular primary combustion mixed gas jetting hole 2 around the fuel gas jetting hole 1.
Is formed, and an annular secondary combustion mixed gas ejection hole 3 is further formed around it. A brim 4 is provided so that flames formed in the ejection holes of the two do not affect each other at their root portions. The flange 4 forms a small combustion space S in front of the primary combustion mixed gas ejection hole 2.

Fuel gas for ignition is supplied to the fuel gas ejection hole 1 for ignition through a conduit 11, and primary fuel gas is ejected from the tip of the conduit 12 to the mixed gas ejection hole 2 for primary combustion. Secondary fuel gas is ejected from the tip of the conduit 13 to the secondary combustion mixed gas ejection hole 3. Swirlers (swirlers) 14 and 15 are attached to the opposite ends of the primary and secondary combustion mixed gas ejection holes 2 and 3 from the ejection ends.

On the other hand, an air inlet 100a is formed in the rear portion (right side in the figure) of the cylindrical body 100, and combustion air is supplied from this. Further, the ends of the primary and secondary combustion mixed gas ejection holes 2 and 3 on the opposite side to the ejection ends communicate with the inside of the tubular body 100 via swirlers 14 and 15, and air can also be introduced. It is like this.

Cooling air that dilutes the combustion exhaust gas discharged from the combustion cylinder 20 and reduces its temperature to a temperature suitable for a turbine (not shown) connected to the next stage is provided near the rear end of the fuel cylinder 20. An air hole 5 for blowing is provided.

FIG. 3 is a block diagram of a combustion control circuit of the combustor having the above structure.

In the figure, 30 is the combustor according to the present invention shown in FIG. 1, 41 is an adjusting valve for adjusting the amount of ignition fuel gas supplied to the combustor 30, and 42 is also the supply of primary fuel gas. An adjustment valve for adjusting the amount, 43 is an adjustment valve for adjusting the supply amount of the secondary fuel gas, 50 is a compressor for supplying a substantially constant amount of compressed air to the combustor 30, and 51 is combustion exhaust gas from the combustor 30. Turbine operated, 60 is turbine 5
1 is a load such as a generator, 61 is an output detector that detects the output of the load (for example, the amount of power generated when the load is a generator), 70 is a gas based on the output of the output detector 61 It is a controller that determines the supply amount and controls the opening degrees of the adjustment valves 42 and 43 to adjust the gas supply amount to the combustor 30.

Next, combustion control by the combustion control circuit shown in FIG. 3 will be described with reference to FIG.

First, at the time of start-up, the adjusting valve 41 is adjusted to supply the ignition fuel gas from the conduit 11 to the ignition fuel gas ejection hole 1 to cause diffusion combustion. The flame from the ejection hole 1 plays a role of stably igniting and burning the flame of premixed combustion generated by the primary fuel gas thereafter. Next, a constant amount of primary fuel gas is supplied from the conduit 12, and is supplied to the primary combustion mixed gas injection hole 2 at an air ratio of about 1.3, and after stable combustion, the conduit 13 is used for secondary combustion mixing. The supply of the secondary fuel gas to the gas ejection holes 3 is started, and premixed combustion is performed. Since the premixed flame acts as a pilot flame by the primary fuel gas and promotes the combustion of the premixed flame by the secondary fuel gas, the flow rate of the ignition fuel gas is reduced or the supply thereof is stopped at this point. After that, the required combustion amount is obtained by gradually increasing the supply amount of the secondary fuel gas.

When the combustion exhaust gas generated in the combustor 30 and discharged to the rear is supplied to the turbine 51, the generator 60 as a load generates power to supply power to an electric load (not shown), and at the same time, the output detector 61. The amount of power generation is detected by. The controller 70 monitors the output of the output detector 61, and the engine load factor is determined from the output by a predetermined value C.
When it is detected that%, the opening degree of the adjusting valve 42 is decreased, and thereafter the opening degree of the adjusting valve 43 is kept constant regardless of the magnitude of the load, and the opening degree of the adjusting valve 43 is increased and then changed according to the load. As a result, the supply amount of the primary fuel gas decreases by a fixed amount (for example, about 87% until then), and the supply amount of the secondary fuel gas increases by a constant amount (for example, 114 until then).
%). The engine load factor C when switching the supply amounts of the primary fuel gas and the secondary fuel gas can be determined according to the structure of the combustor and the type of fuel gas, and as a result of the experiments by the present inventors, for example, 30%. Was found to be suitable.

5 (a) and 5 (b) show the NO _x emission amount and the unburned component emission amount in comparison with the conventional combustion method based on the results obtained by the experiments of the present inventors. It is a performance comparison chart.

As can be seen from the figure, the engine load factor is 1
In the range from 00% to the predetermined value C, the conventional low N
O _X performance is maintained, the discharge significantly suppressed as compared with the conventional the unburned component (Co) while suppressing the slight increase emissions of the NO _X in the range from the load factor C to d, NO
_The combustion range in which both the emission of _{X and} the emission of unburned components can be suppressed to low values has expanded from the conventional (ab) to (ad).

The alternate long and short dash line shown in the figure is a general NO _x emission amount (300 pp) of a conventional diffusion combustion type gas turbine combustor.
m (O ₂ 0% conversion)) is shown. According to the experiment, when the supply amount of the primary fuel gas was increased by 15% in the range of the predetermined load factor C or less, the range (a to d) satisfying the low NO _x property and the low unburnt property was the conventional range. It was confirmed that the amount increased by 60% compared to (ab).

In the above embodiment, the gas supply amounts of the primary fuel gas and the secondary fuel gas are switched once, but may be switched plural times, whereby the NO _x emission amount is increased and unburned components are removed. The increase can be further reduced, and the combustion range of low NO _x and low unburned components can be further expanded.

[0027]

As described above, according to the present invention, the supply amount of the primary fuel gas is increased by a fixed amount and the supply amount of the secondary fuel gas is decreased by the fixed amount at a predetermined load factor or less. Having to, while maintaining low nO _X resistance during high load, suppressing an increase in emissions of the nO _X in the low load low, it is possible to widen the combustion range emissions not occur unburned components. According to the present invention, it is possible to widen the combustible range with low NO _x and low unburned components only by controlling the supply amount of fuel gas, and therefore, the structure of the combustor can be changed or another device can be used. There is no need to add.

[Brief description of drawings]

FIG. 1 is an axial view of an embodiment of a combustor to which a combustion method according to the present invention is applied.

FIG. 2 is an end view of the combustor shown in FIG.

FIG. 3 is a block diagram of a fuel control circuit for implementing the combustion method according to the present invention.

FIG. 4 shows changes in the fuel gas supply amount with respect to load changes in the fuel method according to the present invention.

FIG. 5 is a diagram showing NO _X emission amount and unburned component emission amount in the combustion method according to the present invention in comparison with the conventional combustion method.

FIG. 6 is a diagram illustrating (a) NO _x emission amount with respect to engine load factor and (b) unburnt component with respect to engine load factor for explaining a combustion circuit by a conventional combustion control method.

[Explanation of symbols]

 1 Fuel Gas Injection Hole for Ignition 2 Mixed Gas Injection Hole for Primary Combustion 3 Mixed Gas Injection Hole for Secondary Combustion 5 Premixing Pipe 11, 12, 13 Conduit 20 Combustion Tube 20a Combustion Chamber 30 Combustor

Claims (1)

[Claims] 1. A combustion gas ejection hole for ignition is provided in the center,
A primary combustion mixed gas injection hole having a constant mixing ratio of air and fuel gas is provided around it, and a secondary combustion mixed gas injection hole having a variable mixing ratio of air and fuel gas is further provided on the outer periphery thereof. In a combustion method of a combustor that is concentrically provided and burns with a constant amount of air, the fuel gas in the primary combustion mixed gas is increased by a constant amount and the secondary combustion mixed gas is increased below a predetermined load factor. A method for combusting a combustor, characterized in that the amount of fuel gas therein is reduced by a fixed amount.