JP2000234722A - Combustor and combustion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a desired high-temperature combustion gas while the occurrence of NOx is suppressed by combining independent catalytic combustion and recombustion zones together. SOLUTION: A combustor is provided with a catalytic combustion chamber 4, a recombustion chamber 5 provided downstream the chamber 4, and a means 8 which communicates the chambers 4 and 5 with each other for fluid, burns a lean mixed gas in the combustion chamber 4, and introduces the produced combustion gas to the recombustion chamber 5. In addition, the combustor introduces fuel to the recombustion chamber 5 and burns the combustion gas mixed with the introduced combustion gas from the chamber 4, the gas already existing in the chamber 5, and the fuel introduced to the chamber 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to NOx in exhaust gas.
The present invention relates to a combustion apparatus and a combustion method capable of reducing the ratio of the combustion apparatus. The combustion apparatus and the combustion method according to the present invention are preferably employed in a gas turbine, and are expected to be used in, for example, a gas turbine for cogeneration and a giotto engine.

[0002]

2. Description of the Related Art In a conventional combustion apparatus, diffusion combustion in which fuel and air are mixed and burned is used because stable combustion can be obtained. However, according to diffusion combustion, the combustion gas temperature is locally increased. There was a problem that the temperature became extremely high and the generation of NOx was enhanced. It is known that the generation of NOx can be reduced as much as possible by employing a so-called lean premixed combustion method. However, in the lean premixed combustion method,
Since a lean gas mixture is used, there is a problem that the stable combustion range is narrow and combustion is unstable.

[0003] Techniques for solving this problem include:
There is a catalytic combustion system in which a lean mixed gas is efficiently burned using a catalyst. According to this, it becomes possible to burn the lean fuel by the catalytic action, and therefore, it is possible to perform good and stable combustion even with the lean mixed gas. However, although the reduction of NOx generation can be achieved by catalytic combustion, the catalyst in the combustion device is exposed to a severe atmosphere such as high temperature, high pressure, and high flow rate, so that the catalyst has heat resistance and the like. For that reason, it is particularly difficult to obtain the high temperatures required for gas turbines.

[0004] There is also a proposal to obtain a high-temperature combustion gas while utilizing the advantages of catalytic combustion by combining catalytic combustion with other combustion methods. JP-A-9-287740 describes that
A technique has been disclosed in which catalytic combustion is used as a main combustion method and lean direct fuel injection is used as a secondary combustion method. Also, Japanese Patent Application Laid-Open No. 7-332611 discloses a technique for introducing a mixture into a combustion region (first combustion region) of a mixture that exerts a catalytic action to perform uniform combustion (second combustion region). I have. The two applications are common in that a catalytic combustion zone and a subsequent combustion zone are provided continuously in the same chamber, and a lean mixture is introduced into the second-stage combustion zone. ing.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the problem that it is difficult to obtain a desired high-temperature gas by catalytic combustion. It is an object of the present invention to provide a combustion apparatus and a combustion method capable of obtaining a desired high-temperature combustion gas while suppressing generation of NOx by combining with a combustion zone.

[0006]

In order to achieve the above object, the technical means adopted by the present invention is to provide a combustion apparatus with:
A catalytic combustion chamber, a recombustion chamber provided downstream of the catalytic combustion chamber, and means for fluidly communicating the catalytic combustion chamber with the recombustion chamber; Burn,
The combustion gas generated in the catalytic combustion chamber is introduced into the reburning chamber through the fluid communication means, and fuel is introduced into the reburning chamber. The combustion gas, the burned gas existing in the reburning chamber, and the fuel introduced into the reburning chamber are mixed and burned.
Also, in the combustion method, a first step of catalytically combusting an air-fuel mixture using a combustion catalyst and flowing the generated combustion gas downstream, and introducing the fuel into the combustion gas generated in the first step A second step of performing combustion in the second step, wherein the combustion gas introduced from the first step, the burned gas generated in the second step, and the second step The combustion is performed while mixing with the fuel introduced in the step.

[0007] The combustion gas generated in the catalytic combustion chamber is introduced into a reburning chamber provided separately from the catalytic combustion chamber, and fuel is injected into the reburning chamber. It burns while reacting with oxygen remaining in the combustion gas generated in the catalytic combustion chamber, and further burns in the reburning chamber (refers to the combustion gas generated in the reburning chamber).
By diluting the combustion gas introduced from the catalytic combustion chamber, dilution combustion and low-oxygen combustion are performed in the re-combustion chamber, and the generation of NOx can be suppressed while performing high-temperature combustion. The fuel introduced into the reburning chamber diffuses while being uniformly mixed with these gases, so that combustion is performed at a uniform temperature in the reburning chamber.

Preferably, the reburning chamber has an inlet for the combustion gas generated in the catalytic combustion chamber and an outlet for the combustion gas generated in the reburning chamber. By forming a circulating flow of the combustion gas introduced from the inflow port and introducing fuel into the circulating flow, the fuel is burned in the circulating flow, and the combustion gas generated in the reburning chamber is discharged to the discharge port. It is good to constitute so that it may be discharged from.

[0009] By injecting the fuel toward the circulating flow, the injected fuel diffuses along the circulating flow, and the gas forming the circulating flow is diluted by the burned gas in the reburning chamber. As such, the fuel burns while reacting slowly with the oxygen remaining in the circulation. By uniformly diffusing the fuel into the reburning chamber, the temperature distribution of the combustion gas in the reburning chamber becomes uniform, and the generation of NOx can be reduced as much as possible even during high-temperature combustion.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual diagram of a gas turbine employing a combustion device according to the present invention. The gas turbine includes a compressor 1, a combustor 2, a turbine 3
And a lean mixture obtained by mixing compressed air supplied from the compressor 1 with fuel, more preferably a lean premixed gas is burned in the combustor 2, and the combustion gas generated in the combustor 2 is burned. It is supplied to the turbine 3 at high speed, and its basic configuration is known.

The combustor 2 comprises a catalytic combustion chamber 4 and a recombustion chamber 5 disposed downstream of the catalytic combustion chamber 4.
The air that constitutes the lean mixture by the compression by the compressor 1 is preheated to a predetermined temperature at which the catalytic action is effective, and the preheated lean mixture is introduced into the catalytic combustion chamber 4. The means for maintaining the lean gas mixture supplied to the catalytic combustion chamber 4 at or above the catalyst activation temperature is not limited to compression. The means may be appropriately selected from other known means. The air may be preheated, or a preheating combustion section may be provided upstream of the catalytic combustion chamber 4.

The catalytic combustion itself is known, and is disclosed, for example, in JP-A-7-301419 and JP-A-8-252463. The combustion catalyst is, for example, a plate-like body in which a cordierite honeycomb substrate carries a combustion catalyst material such as a noble metal, and a plurality of combustion catalysts are mixed in a catalyst combustion chamber 4 at intervals. Are arranged substantially perpendicular to the direction of the flow path. So-called honeycomb catalysts are optimal for high-temperature gas generators because of their low pressure loss and high mechanical strength even when the combustion load increases. The combustion catalyst and the arrangement thereof are not limited to those described above, and the type of the combustion catalyst is appropriately selected from known catalysts. The air-fuel mixture introduced into the catalytic combustion chamber 4 is a lean air-fuel mixture. In the catalytic combustion chamber 4, when the air-fuel mixture is ignited by the ignition means, the reaction is performed relatively slowly by the action of the catalyst to generate NOx. Stable combustion is performed at a temperature that does not allow the combustion to occur.

An outlet 6 for the combustion gas generated in the catalytic combustion chamber 4 is provided downstream of the catalytic combustion chamber 4, and an inlet 7 for the combustion gas is provided upstream of the recombustion chamber 5.
The discharge port and the inflow port are fluidly communicated by the fluid communication means 8, and the combustion gas generated in the catalytic combustion chamber 4 is introduced into the downstream recombustion chamber 5 by the fluid communication means 8.

By making the catalytic combustion chamber 4 and the reburn chamber 5 communicate with each other through the flow communicating means 8, independent combustion areas are formed in the catalytic combustion chamber 4 and the reburn chamber 5, respectively.
In the catalytic combustion chamber 4, it is desirable to perform combustion at a flow velocity as slow as possible. On the other hand, the combustion gas generated in the catalytic combustion chamber 4 is discharged at a higher velocity than the catalytic combustion chamber 4. Is desirably introduced. Therefore, it is preferable that the fluid communication means 8 has a shape in which the inner wall surface is narrowed. As a more specific example, the fluid communication means 8 is a nozzle whose inner peripheral surface is gradually reduced in diameter toward the downstream. Incidentally, the fluid communication means 8 may be integrated with the catalytic combustion chamber 4 or the re-combustion chamber 5.

Since the lean mixture is burned in the catalytic combustion chamber 4, oxygen remains in the combustion gas generated in the catalytic combustion chamber 4. Therefore, when the high-temperature combustion gas generated in the catalytic combustion chamber 4 is introduced into the reburning chamber 5 and fuel is supplied thereto, self-ignition is performed, and reburning is performed in the reburning chamber 5. Since the reburning is performed in the indoor space of the reburning chamber 5, the combustion gas generated in the reburning chamber 5 (referred to as “burned gas” in this specification) does not immediately flow downstream, but to some extent in the reburning chamber 5. It is discharged downstream while staying. Therefore, the burned gas in the reburning chamber 5 further dilutes the combustion gas introduced from the catalytic combustion chamber 4, and low oxygen combustion is performed in the reburning chamber 5 by a relatively slow reaction. Then, the burned gas in the reburning chamber 5 is discharged from a discharge port 9 provided on the downstream side of the reburning chamber 5, and if necessary, accelerated by known acceleration means and supplied to the gas turbine 3.

The combustion gas in the catalytic combustion chamber 4 is preferably introduced into the recombustion chamber 5 as a high temperature gas required for self-ignition. However, the ignition in the reburning chamber 5 is not limited to self-ignition, and a separate ignition means may be employed. The fuel injected into the reburning chamber 5 is, for example, a hydrocarbon fuel of propane or methane, but other known fuels may be used. Further, the present invention does not exclude the introduction of the fuel as a pre-mixture with air. Depending on parameters such as the amount of residual oxygen in the combustion gas generated in the catalytic combustion chamber 4, the flow rate of the combustion gas, and the injection speed of the fuel, it is preferable to directly inject the fuel.
It may be advantageous to introduce the fuel in the form of an air-fuel premix. In any case, lean combustion is performed in the reburning chamber 5. Further, the fuel introduced into the reburning chamber 5 is not limited to gaseous fuel, but may be liquid fuel spray.

In the reburning chamber 5, the fuel is diffused uniformly,
It is important to uniformly mix with the combustion gas introduced from the catalytic combustion chamber 4 and perform combustion at a uniform temperature. When the combustion gas from the catalytic combustion chamber 4 is introduced with a certain flow velocity in the reburning chamber 5, this agitates and dilutes the already burned gas present in the reburning chamber 5, and converts the fuel into the agitated gas. By introducing the fuel, it is considered that the fuel can be diffused and the combustion is performed as uniformly as possible.

According to research, in order to diffuse the fuel as uniformly as possible in the reburning chamber 5 and to perform uniform combustion, the combustion gas introduced from the catalytic combustion chamber 4 is introduced into the reburning chamber 5. It has been found to be advantageous to form a circulating flow (large-scale vortices) and inject fuel into the circulating flow. By burning the fuel while diffusing fuel in the circulation flow, the burned gas present in the reburning chamber 5 also becomes a part of the circulation flow,
In the reburning chamber 5, the combustion gas introduced from the catalytic combustion chamber 4, the burned gas present in the reburning chamber 5, and the fuel introduced into the reburning chamber 5 are burned while being uniformly mixed. .

The formation of the circulating flow in the reburning chamber 5 depends on the flow rate of the combustion gas introduced from the catalytic combustion chamber 4 into the reburning chamber 5,
Internal shape of the reburning chamber 5, position of the inlet 7 of the combustion gas into which the catalytic combustion chamber 4 is introduced, sectional shape of the inlet 7 of the combustion gas, spatial arrangement of the catalytic combustion chamber 4 and the reburning chamber 5 Parameters, such as the relationship, the position of the outlet 9 in the reburning chamber 5, and the flow rate of the combustion gas discharged from the outlet 9 (combustion gas generated in the reburning chamber 5). By selecting and combining, a good circulation flow can be formed. In order to uniformly diffuse the fuel in the reburning chamber 5, it is important to select a fuel injection position, an injection speed, an injection angle, the number of injection parts, and the like.

In the reburning chamber 5, a swirler may be used as a means for forming a circulating flow. The swirler is provided, for example, at the fluid communication means 8 or the inflow port 7. As a result, a spiral circulating flow with a large spiral scale can be formed in the reburning chamber 5. By injecting fuel from an appropriate portion toward the vortex circulation flow thus formed, combustion can be performed while diffusing the fuel into the circulation flow.

[0021]

FIG. 2 shows an embodiment of a combustion apparatus according to the present invention.
4 through FIG. FIG. 2 is a schematic view of a combustion apparatus, and FIG. 3 is a perspective view of a reburning chamber. This apparatus is designed mainly for various measurements, and necessarily shows an optimal design used for a gas turbine. is not. Therefore, when adopted in an actual gas turbine, an optimal design is performed without departing from the scope of the technical idea of the present invention. Although the reburning chamber 5 has a substantially cubic shape, this shape is adopted for the convenience of various measurements and is not always an optimal shape (although, as a result, a suitable shape May be.).

In the combustion apparatus shown in FIGS. 2 and 3, the upper side in the figures is the downstream side. The catalytic combustion chamber 4 includes a re-combustion chamber 5
In the figure. Catalytic combustion chamber 4 and reburn chamber 5
Are in fluid communication via a nozzle 80 which is an embodiment of the fluid communication means. The mixing chamber 1 is located upstream of the catalytic combustion chamber 4.
0, and the compressed air sent from the compressor 1;
Propane introduced from a fuel tank 11 storing propane gas is mixed in a mixing chamber 10 to form a premixed gas. The compressed air is heated by the heater 12 to about 4
Heated from 00 ° C to 550 ° C.

The combustion catalyst housed in the catalytic combustion chamber 4 is a disc-shaped platinum catalyst based on cordierite honeycomb having a diameter of 30 mm and a thickness of 8 mm. It was arranged with a gap. Note that, in the catalytic combustion chamber 4 according to the present embodiment, the number of catalysts is variable in the range of one to seven.

The combustion gas from the catalytic combustion is about 800 ° C., and this combustion gas is introduced into the downstream reburning chamber 5. The other end of the fuel supply passage 13 whose one end is connected to the fuel tank 11 is connected to the reburning chamber 5. Propane introduced from the fuel tank 11 is injected into the reburning chamber 5 and self-ignited. And combustion to obtain a combustion gas of about 1300 ° C.

The configuration of the reburn chamber 5 will be described with reference to FIG. The reburning chamber 5 is composed of a downstream upper wall 14, an upstream lower wall 15, left and right side walls 16, 17 extending from upstream to downstream, and front and rear walls 18, 19, of which The space surrounded by the wall forms a combustion space. In FIG. 3, the reburning chamber 5 is illustrated in a simplified manner for convenience of explanation, but the wall surface constituting the reburning chamber 5 actually has a predetermined thickness. The lower wall 15 is formed with a slit-like inlet 7 extending in the front-rear direction along the inner wall surface of one of the left and right side walls 16 and 17 (the right side wall 17). 14 is a slit-shaped outlet 9 which is located at the center in the left-right direction and extends in the front-rear direction.
Are formed.

By introducing the combustion gas upward at a predetermined flow rate from a position close to one side wall, the combustion gas is deposited on the inner wall surface of the right side wall 17 of the reburning chamber 5 as shown in FIG. Along the inner wall surface of the upper wall 14, flows from right to left, and flows downward along the inner wall surface of the left side wall 16 to form a circulating flow. Are discharged from the discharge port 9. By making the inflow port 7 narrow, it is possible to increase the inflow speed of the combustion gas from the catalytic combustion chamber 4 and to advantageously form a circulating flow in the recombustion chamber 5. Further, by making the discharge port 9 narrow, it is possible to prevent the combustion gas introduced into the reburning chamber 4 from being discharged as it is without forming a circulating flow.

In this embodiment, the re-combustion chamber 5 is
, A straight slit is selected as the shape of the inlet 7, the vicinity of the right side wall 17 of the lower wall 15 is selected as the position of the inlet 7, and a cube is selected as the shape of the reburning chamber 5. By selecting a slit as the shape of the discharge port 9 and selecting the position of the discharge port 9 at the central portion of the upper wall 14 in the left-right direction, a circulating flow as shown in FIG. 4 is obtained. The means is not limited to this, and it is also possible to form a circulating flow by other combinations of options.

For example, with respect to the spatial positional relationship between the reburning chamber 5 and the catalytic combustion chamber 4, an arrangement relationship such as upside down or left and right direction can be selected. Regarding the shape of the reburning chamber 5, a cylindrical shape, a rectangular parallelepiped shape, a shape in which the end surface of a cylindrical main body is a curved surface, or the like may be selected. The shape of the inflow port 7 may be selected as an arc-shaped slit or an opening shape other than the slit. In short,
A suitable selection of the parameters may be made so as to form a circulating flow in the reburning chamber 5.

Above the other side wall (left side wall 16), a fuel injection port 20 which is in fluid communication with the fuel supply passage 13 is provided near the upper wall 14 so as to face the combustion space.
The fuel is injected in a substantially horizontal direction from the fuel injection port 20 toward the circulation flow. It is important to select the position of the fuel injection port 20, the injection speed, the injection angle, and the like in order to satisfactorily load the fuel in the circulation flow and diffuse and distribute the fuel to the reburning chamber 5. In particular,
It is considered that the position of the fuel injection port 20 is an important parameter for reducing the generation of NOx.
Good results have been obtained by choosing to introduce fuel from above the left side wall 16 as described above.
In the present embodiment, the injection port 20 is flush with the inner wall surface of the side wall 16, but the injection port 20 may protrude from the inner wall surface into the combustion space. Further, in order to diffuse the fuel satisfactorily throughout the reburning chamber 5, it is desirable that the circulating flow be a large-scale flow that covers the entire combustion space of the reburning chamber 5.

As described above, in the embodiment of the present invention, the combustion gas is introduced from the catalytic combustion chamber 4 as a circulating flow, and the fuel is introduced into the circulating flow. By diffusing the fuel in the reburning chamber 5 as uniformly as possible, a uniform burning temperature can be obtained as a whole. Since the first stage combustion is performed in the catalytic combustion chamber 4, even if oxygen remains in the combustion gas generated in the catalytic combustion chamber 4, its concentration is low. Moreover, the combustion gas introduced into the reburning chamber 5 is diluted with the already burned gas staying in the reburning chamber 5 in the circulating flow. Therefore, the combustion at a uniform temperature was performed by diluting and burning the high-temperature gas under a low oxygen concentration, thereby achieving low NOx combustion.

[0031]

According to the present invention, by combining the catalytic combustion and the reburning, a predetermined high-temperature combustion gas can be
Ox can be obtained while suppressing generation. Since the high-temperature combustion gas is mainly obtained by the reburning chamber, the catalyst combustion is performed without using a load on the combustion catalyst and stable catalytic combustion is performed. In the reburning chamber, so-called dilution combustion under a low oxygen concentration is performed, and generation of NOx can be suppressed while performing high-temperature combustion.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a gas turbine according to the present invention.

FIG. 2 is a view showing a combustion device according to the present invention.

FIG. 3 is a schematic perspective view of a reburning chamber constituting the combustion device in FIG. 2;

FIG. 4 is a schematic side view showing a circulation flow in a reburning chamber.

[Explanation of symbols]

 Reference Signs List 2 combustor 4 catalytic combustion chamber 5 reburning chamber 7 inflow port 8 fluid communication means 80 nozzle 9 discharge port 20 fuel injection port

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K065 TA01 TB13 TB15 TC08 TD05 TE02 TF03 TG04 TJ03 TK02 TK04 TL03 TL06 3K070 DA02 DA26 DA48 DA50 3K091 AA01 BB06 BB26 CC06 CC24 DD02 FB03 FB08 FB12 FB28 FB35 FB35

Claims (12)

[Claims] A catalyst combustion chamber, a recombustion chamber provided downstream of the catalyst combustion chamber, and means for fluidly communicating the catalyst combustion chamber with the recombustion chamber. The fuel is burned in the catalytic combustion chamber, and the combustion gas generated in the catalytic combustion chamber is introduced into the reburning chamber via the fluid communication means, and fuel is introduced into the reburning chamber. The combustion gas introduced from the catalytic combustion chamber, the burned gas existing in the recombustion chamber, and the fuel introduced into the recombustion chamber are mixed and burned. Combustion equipment. 2. A combustion chamber comprising: a catalytic combustion chamber; a recombustion chamber provided downstream of the catalytic combustion chamber; and means for fluidly communicating the catalytic combustion chamber with the recombustion chamber. The fuel is burned in the catalytic combustion chamber, and the combustion gas generated in the catalytic combustion chamber is introduced into the reburning chamber from an inlet provided in the reburning chamber via the fluid communication means. A circulating flow of combustion gas introduced from the catalytic combustion chamber is formed, and fuel is introduced into the circulating flow to burn in the circulating flow and to generate combustion gas generated in the reburning chamber. A combustion device configured to discharge from a discharge port provided in the combustion device. 3. The reburning chamber has an inlet for the combustion gas generated in the catalytic combustion chamber, and an outlet for the combustion gas generated in the reburning chamber. By forming a circulating flow of the combustion gas introduced from the inflow port and introducing fuel into the circulating flow, the fuel is burned while diffusing in the circulating flow, and the combustion gas generated in the reburning chamber is cooled. The combustion device according to claim 1, wherein the combustion device is configured to be discharged from a discharge port. 4. The formation of the circulating flow includes selecting a flow velocity of the combustion gas introduced from the inlet into the reburning chamber, selecting a shape of the reburning chamber, selecting a position of the inlet, From the group consisting of selecting the cross-sectional shape of the inlet, selecting the spatial arrangement relationship between the catalytic combustion chamber and the reburning chamber, selecting the position of the outlet, and selecting the flow rate of the combustion gas discharged from the outlet. 4. The combustion apparatus according to claim 2, wherein the combustion apparatus is achieved by combining at least two or more. 5. The method according to claim 2, wherein the formation of the circulating flow is achieved by the fluid communication means or a swirler disposed at or near the inlet. Combustion equipment. 6. The diffusion of fuel in the circulating flow is at least one of selection of a fuel introduction position in a reburning chamber, selection of a fuel injection speed, selection of a fuel injection direction, and selection of the number of fuel introduction parts. The combustion device according to claim 2, wherein the combustion device is achieved by one of the above. 7. The reburning chamber has an upstream wall, a downstream wall, and a side wall extending from upstream to downstream, and the inflow port is formed at the upstream wall within the side wall. Along the wall,
5. The combustion device according to claim 2, wherein the combustion device is disposed close to the combustion device. 8. The fuel injection system according to claim 7, wherein the fuel is introduced from a portion adjacent to the downstream wall on an inner wall surface opposite to the inner wall surface on which the inflow port is provided. Combustion equipment. 9. The fuel supply system according to claim 7, wherein the fuel is introduced from an inner wall surface facing the inner wall surface on which the inflow port is provided and a position close to the downstream wall. Combustion equipment. 10. A first step of catalytically combusting an air-fuel mixture using a combustion catalyst and causing a generated combustion gas to flow downstream, and introducing the fuel into the combustion gas generated in the first step. And burning in a second step, wherein in the second step,
The combustion is performed while mixing the combustion gas introduced from the first step, the burned gas generated in the second step, and the fuel introduced in the second step. How to burn. 11. A first step of catalytically combusting an air-fuel mixture using a combustion catalyst and flowing generated combustion gas downstream, and introducing fuel into the combustion gas generated in the first step. And burning in a second step, wherein in the second step,
A combustion method characterized by forming a circulating flow of the combustion gas generated in the first step and introducing fuel into the circulating flow to burn the fuel in the circulating flow. 12. In the second step, a circulating flow of the combustion gas generated in the first step is formed, and fuel is introduced into the circulating flow to diffuse the fuel into the circulating flow. The combustion method according to claim 10, wherein the combustion is performed while burning.