JPS60202206A - Low nox combustion apparatus - Google Patents

Abstract

PURPOSE:To reduce NOX by mounting a flame stabilizing structure with a plurality of flow paths in a third stage where noncatalytic thermal combustion is conducted. CONSTITUTION:A first stage where fuel and air are mixed, a second stage where a mixed gas of fuel and air is brought into contact with a catalyst and one part of the mixed gas is burnt only by a catalytic reaction, and a third stage where fuel or a mixture mainly comprising fuel is further added to effluence from the second stage and burnt by a gas phase reaction are provided, and a flame stabilizing structure 11 with a plurality of flow paths is fitted in the third stage. A structure manufactured by bundling a plurality of pipes or a structure having honeycomb structure or the like is used as the flame stabilizing structure 11. It is preferable that a material having heat resistance and high heat capacity is employed as the quality of materials, and it is desirable that ceramics, such as Al2O3, ZrO2, etc. are used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a low NOx combustor, and particularly to a low NOx combustor using a catalytic combustion method suitable for a gas turbine combustor used in a gas turbine power generation system.

[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 alternative energy sources, but at the same time there has been a demand for efficient use of energy resources. Examples of systems that can meet these demands include gas turbine/steam turbine combined cycle power generation systems that use C natural gas as fuel, or coal gasification gas turbine/steam turbine combined cycle power generation systems, which are currently being studied. .

These gas turbine/steam turbine combined cycle power generation systems have higher power generation efficiency than conventional steam turbine power generation systems that use fossil fuels, so natural gas production is expected to increase in the future. It is expected to be a power generation system that can effectively convert fuels such as coal and gasified gas into electricity.

Conventionally, in gas turbine combustors used in gas turbine power generation systems, a mixture of fuel and air is ignited using a spark plug or the like to perform homogeneous combustion.
There is. An example of such a combustor is shown in FIG. In the combustor shown in FIG. 1, fuel injected from a fuel nozzle 1 is mixed with combustion air 3, ignited by a spark plug 2, and combusted. Then, the combusted gas, that is, the combustion gas, includes cooling air 4 and dilution air 5.
After being cooled and diluted to a predetermined turbine inlet temperature, C1 is injected into the gas turbine from the turbine nozzle 6. 8 is a swirler. One of the serious problems with such conventional combustors is that a large amount of NOx gas is generated during combustion of fuel, resulting in 'cm boundary pollution'.

The reason why the above-mentioned NOx is generated is that during fuel combustion, there is a high-temperature part that exceeds 2000° C. in the C1 combustor.

In order to solve these problems with gas turbine combustors, various combustion systems have been studied.

Recently, a heterogeneous combustion method (hereinafter referred to as catalytic combustion method) using an in-phase catalyst has been proposed.

In this catalytic combustion method, a catalyst is used to combust lean fuel that would not be combusted in a normal combustor (°C1), so the combustion temperature does not become high enough to generate NOx. Furthermore, the turbine inlet temperature can also be kept the same as in the conventional case.

FIG. 2 is a conceptual diagram of an example of a combustor used in the catalytic combustion method. Each number in the figure represents the same element as in FIG. A structural feature of this combustor is that it includes a catalyst filling section 7. The catalyst filling portion 7 is normally filled with a combustion catalyst having a honeycomb structure (1/1 C), in which a mixed gas of fuel and air is combusted.

However, this catalytic combustion method also has the following drawbacks. In other words, in the conventional C catalytic combustion method, the C fuel is combusted by both catalytic reaction and gas-phase reaction combustion in the catalyst filling section, so the temperature of the catalyst is high and the thermal deterioration of the catalyst is large, resulting in a shortened lifespan. It's short. Further, it has the disadvantage that it is difficult to cope with an increase in the gas turbine inlet temperature due to the heat resistance of the catalyst. Therefore, the present inventors decided to combust only a part of the C fuel by catalytic reaction in the catalyst-filled part, add fuel etc. further downstream of the catalyst, and use gas-phase combustion (non-catalytic thermal combustion) in that part. ) by causing ゛C
1. We have already proposed a catalytic combustion method that has a long life even in a lower catalyst temperature range than conventional ones.

It is important to perform gas-phase combustion in the downstream region of the catalyst, and the present inventors have already proposed a method for stabilizing the gas-phase combustion section by creating a flow retardation or reverse region in this region by increasing the diameter. I came. Therefore, the present inventors further investigated ways to further stabilize gas phase combustion in the downstream region of the catalyst in a combustor using a catalyst, and arrived at the present invention.

[Purpose of the invention]

An object of the present invention is to further stabilize non-catalytic thermal combustion (gas-phase reactive combustion) in the downstream region of the catalyst, and to provide an excellent low NOx combustor.

[Summary of the invention]

As a result of extensive research to achieve the above object, the present inventors have found that when the fuel added to the downstream region of the catalyst and the unburned fuel from the catalyst filling section are subjected to gas-phase reaction combustion in the downstream region of the catalyst, a double ligature flow is generated. It has been found that providing a flame-holding structure with channels is effective. Examples of this flame-holding structure include a plurality of pipes bundled together, a honeycomb structure, and the like.

Further, as for the material, it is preferable to use a material having heat resistance and high heat capacity, for example, it is preferable to use ceramics such as A40g and Zr01. Although the cause of the effect of the present invention is not necessarily clear, the temperature of the effluent increases in the catalyst filling section, and the combustible gas with increased fuel concentration flows into the flame stabilizing structure of the present invention. When passing through the channel, combustion is accelerated by acquiring energy through radiation and convection on the inner surface of the channel, which is thought to produce a flame-holding effect that maintains stable combustion. The energy emitted in the flow path of the flame-holding structure is caused by the high-temperature gas combusted in the rear half of the flame-holding structure heating the latter half of the body, and the heat being transferred to the front half of the flame-holding structure. conduction C
It is thought that there is a

Of course, this effect does not occur from the start of combustion; initially, it is necessary to forcibly apply energy from the outside to start combustion. The means for forcibly applying energy may be an ignition source such as a spark plug, or an auxiliary burner. Once combustion starts within this flame-holding structure with multiple flow paths, the mechanism described above will
Stable gas phase reaction combustion continues.

The equivalent diameter of the flow path provided in the flame-holding structure used in the present invention (
It is effective if the diameter (converted to a circular area) is about 5 mm to 200 mm, but if the equivalent diameter is too large, the heat transfer surface due to radiation and convection will be reduced, and if the equivalent diameter is small, the pressure loss will increase. I don't like it.

Although the above equivalent diameter depends on the operating conditions, it is practically 10 to 5.
About 0IIIll is preferable.

An example of a low NOx combustor according to the present invention is shown in FIG.

In FIG. 3, fuel is injected from the C1 fuel nozzle 1, ignited by the spark plug 2, and combusted. This part is the so-called pre-combustion part, which raises the gas temperature to the temperature at which the catalyst in the catalyst filling part 7 acts. Not necessarily necessary for invention. The fuel supplied from the fuel nozzle 9 to the catalyst filling part 7 is supplied to the mixture of pre-combusted exhaust gas and combustion air 3, which has reached the temperature at which the catalyst acts, and is mixed to obtain a desired mixture of gas. It will be done.

In the catalyst filling section 7, a part of the C fuel is combusted only by the catalytic reaction, and the temperature of the gas further increases. Further fuel is added from the fuel nozzle 10, and the unburned fuel is completely combusted while passing through the flame holding structure 11 having a plurality of flow paths. In addition, in Figure 3, when starting 1 combustion, 1
Ignition ``C'' using the spark plug shown in 2. At this time, if the amount of fuel from the fuel nozzle 10 is temporarily increased, ignition is facilitated. An example perspective view is shown. This case is an example of one having a grid-like cross section. Fig. 5' shows an alumina ceramic pipe which is an element of the structure and has a plurality of flow channels parallel to the flow. It is also possible to install a flame-holding structure made by bundling a plurality of these flame-holding structures at the part 11 in FIG. 3. FIG. 6 shows another example of the present invention. In Figure 6, 'C' is
There is no pre-combustion section as shown in Fig. 5, and the fuel supplied to the catalyst filling section 7 is supplied from the fuel nozzle 9.The fuel from the fuel nozzle 10 and the effluent from the catalyst filling section 7 flow It is attached to a flame-holding structure that has multiple flow paths parallel to the .

[Embodiments of the invention]

Next, the effects of the present invention will be illustrated by an example using a simulated combustor.

Figure 7 shows a schematic diagram of the experimental apparatus. The catalyst 15 was filled with a honeycomb-shaped palladium catalyst over a length of 10 times. The diameter of the catalyst was 200 μg. A mixed gas of air 13 and fuel 14 heated to 400° C. was passed through catalyst 15 . The flame holding structure 18 has a plurality of channels parallel to the flow, and the line cross section is square and the length of the channel side is 6.
The cylindrical wall that separates the 0-1 flow path is made of ceramics (made by AztoJ) and has a thickness of 8. This was also installed.
The diameter of the part with C was 36 pieces. For comparison, an experiment was conducted with the flame holding structure 18 removed. As for the experimental conditions, the amount of air 13 was adjusted so that the flow velocity at the catalyst inlet was 35 m/sec. Natural gas was used as fuel 14.16, and the concentration was such that the theoretical adiabatic flame temperature at the catalyst inlet was 1000°C. Increase the amount of fuel 16, and after ignition, reduce this amount to "C"
The entire system when the combustion efficiency is less than 97% during running.
The theoretical adiabatic flame temperatures of C were compared and shown in Table 'C. The combustor of the present invention uses a catalyst that has been heated for 4000 hours in an electric furnace at 1000°C to forcibly deteriorate the catalyst. It can be seen that this method is effective in stabilizing gas phase reaction combustion from carbon, and stable combustion can be obtained under a wide range of operating conditions.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a typical gas turbine combustor. Figure 2 on the right is a schematic cross-sectional view of a conventional catalytic combustion filter type gas turbine combustor. FIG. 3 is a schematic cross-sectional view of a gas turbine combustor according to the present invention. FIG. 4 is a perspective view showing an example of a flame-holding structure used in the present invention. FIG. 5 is a perspective view showing a unit constituting the flame stabilizing structure used in the present invention. FIG. 6 is a schematic cross-sectional view showing an example of a gas turbine combustor according to the present invention. FIG. 7 is a schematic cross-sectional view of the combustor used in the simulation experiment of the example. 1, 1', 9.10.16. ...Fuel nozzle. 2, 12.17. ...Spark Grab. 3... Combustion air, 4... Dilution air. 5... Cooling air, 6... Turbine nozzle. 7... Catalyst filling part, 8... Swirler-911, 18,
...A structure with multiple channels parallel to the flow. 13...Air, 14...Fuel. 15...Catalyst. Agent: Patent attorney Kensuke Chika (and 1 other person) Figure 5 Figure 7

Claims (1)

[Scope of Claims] 1) A first step of mixing fuel and air; bringing the mixed gas of the fuel and air into contact with a catalyst to convert a portion of the mixed gas into carbon by only a catalytic reaction; a second stage of combustion;
a third stage in which a fuel or fuel-based mixture is further added to the effluent from the second stage; A low N03C combustor, characterized in that a flame holding structure having a plurality of flow paths is provided in the stage. 2) Claim 1, characterized in that an ignition source is provided in the third stage. Low NOx combustor as described in section. 3) The low NOx combustor according to claim 1, wherein the flame stabilizing structure installed at the third stage is made of ceramic having a plurality of flow paths parallel to the flow.