JPS597803A - Combined cycle generating system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a combined cycle power generation system that combines a steam turbine and a gas turbine, and more particularly to an improvement of a gas turbine combustor using a catalytic combustion method.

[Technical background of the invention and its problems]

In recent years, with the depletion of petroleum resources and the like, there has been a demand for various alternative energies, and on the other hand, there has been a demand for efficient use of energy resources.

In order to meet these demands, for example, a combined cycle power generation system using a gas turbine using natural gas as fuel and a steam turbine is being considered. This combined power generation system has higher power generation efficiency than conventional steam turbine power generation systems that use fossil fuels, making it an effective way to convert natural gas fuel, whose production volume is expected to increase in the future, into electricity. It is expected to be a power generation system that can be converted.

A gas turbine combustor used in a gas turbine power generation system performs homogeneous combustion by igniting a mixture of fuel and air using a spark plug or the like. An example of such a combustor is shown in FIG. 1, where a fuel nozzle 1
The injected fuel is mixed with the combustion air 3, ignited by the spark plug 2, and combusted. The combusted gas is further added with cooling air 4 and dilution air 5 to be cooled and diluted to a predetermined turbine inlet temperature, and then injected into the gas turbine from a turbine nozzle 6. One of the serious problems with such conventional combustors is that a large amount of nitrogen oxide (NOx) gas is produced during fuel combustion.

The reason why this NOx force is generated is due to the presence of a high temperature section during combustion of the fuel. NOx
Normally, if no nitrogen components are present in the fuel,
Nitrogen and oxygen in the combustion air undergo the reaction shown in the following equation to generate nitrogen.

N2+02.2NO・・・・・・・・・・・・・・・(
1) The above reaction shifts to the right side as the temperature increases, and the amount of nitrogen monoxide (NO) produced increases. A part of the NO is further oxidized to produce nitrogen dioxide (WO2).

FIG. 2 shows the temperature distribution in the fluid flow direction in a conventional power turbine combustor.

As shown in the figure, the temperature distribution within the combustor has a maximum value, and after reaching the maximum temperature, it is cooled down to a predetermined turbine inlet temperature by cooling and dilution air. Since the maximum temperature inside the combustor can reach as high as 2000° C., the amount of NOx produced rapidly increases around this temperature. As described above, conventional gas turbine combustors have the problem of generating a large amount of NOx due to the presence of partially high-temperature parts, and for this reason, it is necessary to install exhaust gas denitrification equipment, etc. There were also problems such as the complexity of the process.

In order to solve these problems with gas turbine combustors, a two-stage combustion system has been developed in which combustion air is introduced in two stages and the fuel is combusted. However, since this method introduces air in two stages, careful attention must be paid to adjusting the amount of air introduced in each stage, and the temperature inside the combustor is relatively high, so the effect of reducing the amount of NOx is not sufficient. .

In contrast to the above-mentioned method based on a homogeneous reaction only in the gas phase, a heterogeneous combustion method using a solid phase catalyst (hereinafter referred to as catalytic combustion method) has recently been proposed. The catalytic combustion method uses a catalyst to combust a mixture of fuel and air.This method allows combustion to start at a relatively low temperature, does not require cooling air, and uses only combustion air. As a result, the maximum temperature becomes lower, and as a result, it is possible to extremely reduce the amount of NOxi generated. Furthermore, the turbine inlet temperature remains the same (as with conventional turbines), allowing complete combustion of the fuel. FIG. 3 shows such a catalytic combustion type combustor, in which a part of the fuel injected from the fuel nozzle 1 is mixed with combustion air 3, ignited by the spark plug 2, and pre-combusted. Furthermore, the remaining fuel is injected from another fuel nozzle 1, mixed with combustion air 3, and is then subjected to heterogeneous combustion in a catalyst filling section 7 filled with a precious metal-based catalyst nickel structure. Combustion progresses with homogeneous combustion occurring.

Figure 4 shows the temperature distribution inside the combustor, with curve a
is based on the conventional normal combustion method shown in Figure 1, and song #b
Curve C is for the two-stage combustion method, and curve C is for the catalytic combustion method.As is clear from the figure, the catalytic combustion method has the lowest maximum temperature and is preferable.

However, in the case of this catalytic combustion method, combustion will not proceed unless the mixed gas of fuel and air flowing into the catalyst filling part is preheated to a temperature at which the catalytic reaction is activated. Particularly when using methane as a fuel, this preheating temperature must be increased.For this reason, conventionally, a part of the fuel was normally combusted (non-uniformly combusted) using a sulfur rag before the catalyst filling section. Although the gas temperature is preheated by raising the gas temperature (system combustion), if it is normally combusted, even if it is only a part of the fuel, it becomes high temperature and generates NOx as mentioned above, and is not decomposed in the catalyst filling section.'1. However, the major problem was how to keep the temperature of this preheating combustion to a low level.

[Purpose of the invention]

The present invention provides a combined cycle power generation system that solves the problems with the catalytic combustion method and suppresses the amount of NOx generated during preheating combustion in the combustor to an extremely small amount.

[Summary of the invention]

The present invention relates to a combined cycle power generation system that rotates a generator by combining a gas turbine using natural gas as fuel and a steam turbine, in which waste heat is recovered by passing the exhaust gas of the gas turbine. A reforming reaction tube is provided in the reactor to reform part or all of the natural gas fuel, and the resulting reformed fuel with a low ignition point is fed into a combustor equipped with a catalyst together with adiabatic compressed air. It is characterized in that it is introduced into the atmosphere and then combusted through a catalytic reaction.

In the present invention, examples of natural gas used as fuel include methane, propane, etc.
In particular, methane requires a high preheating temperature for catalytic combustion. When this methane is heated and reformed with a gas containing an oxidizing agent such as steam (H2O) or oxygen gas, the following reaction proceeds and decomposes into carbon monoxide and hydrogen.

CB +MO4±CO+3H2・・・・・・・・・・・・
... (2) 2 This reforming reaction is an endothermic reaction, so it needs to be heated, but is it possible to recover waste heat from the turbine exhaust gas? By providing a reforming reaction tube within the reactor, the reaction can proceed using waste heat from the gas turbine.

The gas obtained by the reforming reaction becomes a gaseous fuel consisting mainly of -carbon oxide and hydrogen. The obtained gas is heated from room temperature to 2 (J
It is possible to ignite and catalytically burn at a temperature as low as 0°C. During steady operation of the turbine, the combustion air is adiabatically compressed to a temperature of about 300 degrees Celsius, so simply mixing it with the carbon monoxide and hydrogen obtained through reforming and supplying it to the combustor will cause no damage. Catalytic combustion proceeds without the use of an ignition device. Therefore, even if the preheating temperature of the fuel for catalytic combustion is high, such as methane, a part of the fuel is reformed in advance and the resulting fuel is catalytically combusted to generate heat, and the remaining mixture of fuel and air is preheated. By doing so, preheating by normal combustion becomes unnecessary, and the generation of NOx caused by it is also eliminated. In addition, when all of the fuel is reformed in advance and supplied to the combustor, preheating is not necessary and catalytic combustion can proceed simply by bringing the fuel into contact with the catalyst.

[Embodiments of the invention]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

5 and 6 show an embodiment of the present invention,
FIG. 5 shows the process of the combined cycle power generation system.

In the figure, 8 is a generator, and a gas turbine 9 is attached to one end of the generator.
However, a steam turbine 10 is coaxially attached to the other end. Exhaust gas 11 from the gas turbine 9 is sent to a waste heat recovery tank 12, exchanges heat with a reforming reaction tube 13 and a heat exchanger 14 provided therein, and is discharged into the atmosphere.

15 is a condenser installed adjacent to the steam turbine 10, and the water 16 obtained in this condenser 15 is transferred to the heat exchanger 14.
The water is supplied to 11. and the steam obtained by heat exchange there.
18 is supplied to the steam turbine 1.0, and this rotation causes the generator 8 to generate steam.

A part of the fuel 19 is introduced into the reforming reaction tube 13 provided in the waste heat recovery device 12 together with 18 parts of air steam, and when methane is used as the fuel 19 here, the above-mentioned (2) It is reformed and decomposed into carbon monoxide and hydrogen by the reaction of the formula. The reformed fuel 2θ is sent to the combustor 21, where it is catalytically combusted together with the adiabatic compressed combustion air 3 from the compressor 22 and the remaining fuel 19. The combustion gas 23 is sent to the gas turbine 9, which is rotated to generate electricity by the generator 8. In the figure, 24 is the reforming reaction tube 13.
This is a tank for storing reforming gas provided between the combustion chamber and the combustor 2.

An inner cylinder 26 is provided to form a flow path.

The fuel nozzle 1 and the nozzle 27 of the reformed fuel 20 are connected to the inner cylinder 26 through the closed end of the outer cylinder 25, and the end of the inner cylinder 26 facing the nozzle 27 is filled with a catalyst. A section 7A is provided. Further, a catalyst filling portion 7B is similarly provided on the turbine nozzle 6 side of this inner cylinder 26. These catalyst filling portions 7A and 7B are honeycomb structures made of ceramic and have catalysts such as precious metals supported thereon.

In this combustor 21, the reformed fuel 2
0 is injected from the nozzle 27, and this and compressor 22
The adiabatically compressed combustion air 3 is mixed with the combustion air 3 and is supplied to the catalyst filling section 7A in the previous stage. Since the combustion air 3 has been heated to a maximum temperature of about 30° C., the reformed fuel 20 is combusted by the action of the catalyst and generates heat.

In this case, since catalytic combustion is used, no NOx is generated.

Next, the unreformed fuel 19 injected from the nozzle 1 into the inner cylinder 26 is mixed with the combustion air 3, and the mixed gas rises due to the heat generated by the catalytic combustion in the previous stage of the reformed fuel 20. Warm and preheat. Even if the preheating temperature for catalytic combustion is high, such as methane, the temperature will rise sufficiently and catalytic combustion will proceed in the catalyst filling section 7B, without resorting to normal combustion that generates a lot of NOx. and is completely combusted. This combustion gas 23 is supplied from the turbine nozzle 6 to the gas turbine 9.

Furthermore, when the gas turbine 9 is started, the reforming reaction does not proceed sufficiently, so by storing the reformed fuel 19 in the tank 24 in advance and supplying it to the combustor 2, a smooth start can be achieved. can be done.

FIG. 7 shows a combustor 21 according to another embodiment of the present invention, in which a plurality of catalyst filling parts 7A are provided on the outer periphery of an inner cylinder 26, an intermediate cylinder 28 is provided to surround this, and An injection nozzle 27 for the reformed fuel 20 is attached to the opening of the intermediate cylinder 28, and an injection nozzle 1 for the unreformed fuel 19 is provided at the end of the inner cylinder 26.

Note that when the entire amount of fuel is reformed and supplied to the combustor 2, the catalyst filling section 7A at the front stage for preheating is not necessary, and only the catalyst filling section 7B at the rear stage is sufficient.

〔Effect of the invention〕

As explained above, according to the Indian cycle power generation system according to the present invention, part or all of the fuel is reformed in advance to convert it into a fuel with a low ignition point and supplied to the combustor, where it is catalytically combusted. Therefore, the amount of NOx generated can be kept extremely low compared to normal combustion.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing a gas turbine combustor using a normal combustion method. Figure 2 is a graph showing the temperature distribution of a gas turbine combustor using a normal combustion method. Figure 3 is a gas turbine combustor using a conventional catalytic combustion method. Figure 4 is a graph showing the temperature distribution of the gas turbine combustor in each combustion method, Figure 5 is a cross-sectional view of
6 and 6 show an example of the present invention, in which FIG. 5 is a process diagram showing a combined cycle power generation system, FIG. 6 is a sectional view showing its combustor, and FIG. 7 is a diagram showing the present invention. FIG. 3 is a sectional view showing a combustor according to another embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Nozzle, 2... Spark plug, 3... Combustion air, 4... Cooling air, 7.7A, 7B... Catalyst filling part, 8... Generator, 9...・Gas turbine, 1
゜...Steam turbine, 1...Exhaust gas, 12.
...waste heat recovery boiler, 13...reforming reaction tube, 14...heat exchanger, 17.18...steam,
19...Fuel, 20...Reformed fuel, 21...Combustor, 22...Compressor, 24...
...tank, 25...outer cylinder, 26...inner cylinder, 27.
··nozzle.

Claims (3)

[Claims] (1) In a combined cycle generation system that rotates a generator by combining a gas turbine and a steam turbine that use natural gas as fuel, natural gas fuel is fed into a waste heat recovery boiler that passes the exhaust gas from the gas turbine. A combined cycle power generation system comprising: a reforming reaction tube for reforming; and a combustor connected to the reforming reaction tube and provided with a catalyst between the power turbine and the power turbine. (2) The combined cycle power generation system according to claim 1, further comprising a tank for storing the reformed fuel gas between the reforming reaction tube and the combustor. (3) The combustor has a preheating section where the reformed fuel and air are mixed and catalytically combusted.
Claim 1 or claim 1, characterized in that the invention is comprised of a gas mixing section that mixes fuel and air that have not been reformed to 500 ml, and a combustion section that catalytically combusts the mixed gas. The combined cycle power generation system according to item 2.