JPH06300265A - Low nox gas turbine combustor - Google Patents

Abstract

PURPOSE:To contrive the reduction of NOx generated by a gas turbine by an inexpensive and simple method wherein fuel oil is mixed into water before contacting with air. CONSTITUTION:The first stage mixing of fuel oil 11 and water 14 is effected in a mixing chamber 12 and the fuel oil and water are sent into a water and oil mixing unit 2. In the mixing unit 2, the fuel oil and water are passed through three sets of orifices 15 to mix them perfectly. the mixed body of the oil and water is sent into an ejector 8 and is mixed with air, sucked in an intermediate chamber 9. Thereafter, the mixed body of oil, water and air is injected into air stream 14 through a final stage injection nozzle 5 whereby the mixed body of oil and water is dispersed into the air stream as liquid drops.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to reduction of NOx applied to an oil-burning combustor of a gas turbine.

[0002]

2. Description of the Related Art Low N emission gas from a gas turbine combustor
Although many means such as complete premixing of fuel and air and lean burn are used as means for achieving Ox conversion, the basis thereof is to lower the flame temperature. This is because NOx (thermal NOx) is hardly generated at a flame temperature of 1,600 ° C. or lower.

As a means for lowering the flame temperature, not only the above-mentioned combustion method but also a method of introducing water or steam into the flame is generally used.

In the oil fired combustor, as shown in FIG.
It is general that steam is introduced into the combustion air flowing through the air flow path 3 provided inside the combustor outer cylinder 1, and fuel oil is jetted into this from the final stage spray nozzle. However, in this case, there are the following two restrictions. (1) Completely premix air and water vapor. (2) Equal amount of a mixture of air and water vapor is dispersed in the flame. That is, unless these restrictions are solved, even if the flame temperature can be suppressed to an average low value, a high temperature may be generated locally, and there is a drawback that NOx generation cannot be suppressed there. It was

It is considered that this problem is mainly due to the difficulty of achieving the above-mentioned constraint (2), and when water vapor is injected in an actual machine, NOx does not decrease, which means an excessive amount of NOx. Water vapor is introduced into the combustor, which causes a local temperature drop and also causes combustion instability. For this reason, measures for achieving the above-mentioned problem (2) are now absolutely necessary.

It is to be noted that when steam or water is introduced into the flame, NO
There are various views other than the flame temperature reduction as a reason for reducing x, but here, only the flame temperature reduction is taken into consideration for easy understanding.

[0007]

By the way, in the conventional means for introducing steam and water into the combustion air, even if the air and steam can be completely mixed, in the case of the oil-fired combustor, Since conventional diffusion combustion is common, the mixing of oil droplets and air at the stage of burning is not always uniform, and a portion with many fuel oil droplets locally occurs to raise the flame temperature and generate a large amount of NOx. It was the cause.

The following two means can be considered to solve this defect. (A) Evaporative emission of fuel oil and air / steam mixture are completely premixed before combustion. (B) Mix fuel oil and water before contacting with air. As a fundamental measure, it is natural that the above (a) is desirable, but in the case of oil fuel, the self-ignition temperature is low and 240
If the temperature of the combustion air is as high as about 400 ° C as in a gas turbine, the use of this method (a) carries the risk of ignition in the premix chamber. is there. Therefore, the present invention provides a method for solving the above-mentioned problem (b) by a low cost and a simple method, and intends to reduce the NOx of the gas turbine combustor.

[0009]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned problems, and in an oil-fired combustor of a gas turbine,
A first mixing device for mixing fuel oil and water, a second mixing device for mixing the oil / water mixture mixed by the first mixing device and air, and the second mixing device. Oil mixed in
A low NOx gas turbine combustor, comprising a nozzle for spraying a mixture of water and air.

[0010]

According to the above-mentioned means, the fuel oil and water are first mixed in the first mixing device, and then the oil / water mixture and air are mixed in the second mixing device. Fuel oil and water are thoroughly mixed before contact with air. The oil / water mixture thus completely mixed is mixed with air by the second mixing device to be a mixture of oil / water / air, which is sprayed from the nozzle.

Therefore, the mixture of oil, water and air in the combustion stage is kept uniform, and it is possible to prevent the flame temperature from rising locally, so that a large amount of NOx is not locally generated. .

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. In the conceptual diagram of FIG. 1, 2 is a water / oil mixing section, 8 is an ejector, 9 is an intermediate chamber, 10 is a throat section, 12
Is a mixing chamber, 14 is water, 15 is an orifice,
Reference numeral 17 is a nozzle, and 18 is an ejector wall.

The combustor outer cylinder 1 and the combustor inner cylinder 6 constitute a combustor body. Inside the combustor inner cylinder 6, an orifice 15 is provided inside a pipe line 16, and an orifice 15 is 2 times the inner diameter of the pipe line 16. Water composed by installing at double intervals (3 in this embodiment)
The oil mixing section 2 and the nozzle 1 with the diameter of the downstream side of the mixing section 2 reduced
7 is attached, and the reduced diameter portion is attached to the ejector wall 18
An ejector 8 including a throat portion 10 surrounded by
Intermediate chamber 9 connected to the downstream side of the ejector 8
The final stage spray nozzle 5 is attached to the wall surface of which the diameter is reduced downstream at the tip of the chamber 9. Here, the number of the nozzles 5 is two or more (in this embodiment, four nozzles are installed so as to eject in a cross flow in the air flow), and the number is increased when the pipe diameter 16 is large. The throat section 10 and the intermediate chamber 9 determine their dimensions according to the flow rate. Further, the number of nozzles 5 may be one.

A pipe for supplying oil 11 is connected to the water / oil mixing section 2 in the combustor, and joins with a pipe for supplying water 14 to form a mixing chamber 12 on the way. Crossflow merging of the oil 11 toward the upstream side is adopted for the merging portion, and the angle θ in this embodiment is θ = 130 ° (normally set in the range of θ = 110 ° to 140 °). ). Both the oil 11 and the water 14 are supplied by a high-pressure pump, and the flow rate thereof can be adjusted by a valve 13 mounted on each pipe.

That is, the oil 11 and the water 14 undergo the first stage mixing in the mixing chamber 12 as shown in the basic principle diagram shown in FIG. 2, and further pass through the orifices 15 of several stages in the water / oil mixing section 2. The mixing chamber 12, the water / oil mixing section 2 and the related members thereof form a first mixing device.

Under the above structure, the oil 11 and the water 14 supplied by the respective high pressure pumps pass through the valve 13,
It is mixed by the mixing chamber 12. At this time, the water 14 forms a cross-flow merging toward the upstream side of the oil 11, so that the mixing is efficiently performed (mixing promotion by collision). The mixed fluid of oil and water that has flowed out of the mixing chamber 12 enters the mixing section 2, and the mixing of oil and water is completely performed by the vortex generated behind the orifice.

The mixed fluid of oil and water from the mixing section 2 is the second fluid.
Is ejected from the nozzle 17 of the ejector 8 serving as the mixing device of the above, and at this time, air is ejected from the peripheral air flow 4 (supplied from the compressor (not shown) through the combustion air flow path 3) through the ejector wall body 18. The negative pressure generated in the throat portion 10 is sucked into the oil / water mixed fluid. The oil / water flows including the sucked air are mixed in the intermediate chamber 9.

The mixed fluid of oil / water and air is jetted into the air stream 4 through the final stage spray nozzle 5, and the mixed fluid of oil / water is dispersed in the air stream as droplets.

A plurality of components from the oil / water mixing section 2 to the final stage spray nozzle 5 are installed in the gas turbine combustor according to the amount of fuel oil. In FIG. Conceptually shows the relationship between.

[0020]

According to the present invention described above, the following effects are exhibited. (1) Oil and water can be sufficiently mixed by the mixing chamber 12 and the water / oil mixing section 2. The mixing phenomenon of oil and water is characterized in that the density and viscosity of oil are different from those of water, but by increasing the flow velocity in the pipeline 16 and setting the value of the internal Froude number F of the pipeline to 20 or more. , It is possible to eliminate the influence of the difference in density. Also, by using light oil or heavy oil A as the type of oil, the effect of the difference in viscosity can be reduced, so that it can be treated in the same way as water and water mixing, and oil and water are sufficiently mixed. It becomes possible to tighten. The internal Froude number F is obtained by the following equation. However, u ₀ is the pipe flow velocity, D is the pipe diameter, ρ is the liquid specific gravity, and Δρ ₀ is the oil / water specific gravity difference. (2) The mixture of oil and water ejected from the nozzle 17 sucks air from between the wall 18 and the nozzle 17 by the ejector effect, but the atomization (miniaturization) effect by ejection from the nozzle 17 is small in the intermediate chamber 9. Therefore, I can hardly expect it.
However, shear force is generated due to the difference in the flow velocity between the sucked air and the oil flow, and the air is mixed in the oil / water mixture. When jetted from the final stage spray nozzle 5, the above mixture of oil and water is atomized due to the high pressure spray to be atomized.
Unlike normal oil-only atomization, it has the following effects. (A) Due to the difference in the evaporation rate of oil and water, the particle size when the oil droplets burn can be made smaller than in the case of spraying only ordinary oil, and the surface area in contact with air increases as a whole, so the flammability also increases. To do. (B) Since the atomized water along with the oil drops lowers the temperature of the surrounding gas due to the latent heat of vaporization at the time of evaporation and also lowers the oxygen partial pressure in the gas, the amount of NOx generated by combustion can be extremely reduced. (C) Since the water droplets atomized together with the oil droplets are, of course, uniformly distributed in the spatial distribution of the fuel, the effect of the above (b) appears evenly in the flame to burn steam and water. Since no local high temperature is generated in the flame as seen in the case of being placed in air, it is possible to prevent NOx generation due to this local high temperature. (3) At the time of spraying from the final stage nozzle 5, since a small amount of air is present in addition to the mixture of oil and water, the atomizing effect is improved by the expansion of this air after spraying, and the spray particle size can be reduced.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a low NOx gas turbine combustor according to an embodiment of the present invention.

FIG. 2 is a diagram showing a basic principle of the present invention.

FIG. 3 is a conceptual diagram showing a conventional example.

[Explanation of Codes] 1 Combustor outer cylinder 2 Water / oil mixing section 4 Air flow 5 Final stage spray nozzle 6 Combustor inner cylinder 7 Combustor premixing section 8 Ejector 9 Intermediate chamber 10 Throat section 11 Oil 12 Mixing chamber 14 Water 15 Orifice 16 Pipeline 17 Nozzle 18 Ejector wall

Claims (1)

[Claims] 1. An oil-fired combustor for a gas turbine, comprising: a first mixing device for mixing fuel oil and water; and a mixture of oil and water mixed by the first mixing device and air. Second
And the oil / water mixed in the second mixing device
A low NOx gas turbine combustor, comprising: a nozzle for spraying a mixture of air.