JPS60186622A - Catalytic burner - Google Patents

Abstract

PURPOSE:To form a low NOx catalytic burner provided with a long-hour durability and capable of effecting a stable gaseous phase combustion in the downstream of a catalyst body by causing only a catalyst reaction combustion due to a catalytic reaction within the catalyst body to provide a non-steamlined body in the downstream of the catalyst body. CONSTITUTION:The mixing ratio, flow rate and the like of a gaseous mixture are controlled and the dimension of a catalyst body is suitably selected, whereby only the catalytic reaction combustion is caused in the catalyst body and at least a part of the fuel is burnt to generate a complex gas the temperature of which is increased. The complex gas flowing out of the catalyst body 7 is subjected to gaseous phase combustion in the downstream of the catalyst body. A non-steamlined type body 8 is placed in the downstream of the catalyst body, and the complex gas from which the catalyst body has flowed generates a vortex flow by the non-steamlined body. This vortex flow forms a closed circulating region. While a part of an ambient unburnt gaseous mixture is taken thereinto and stirred, the combustion proceeds and turned into a cumbustion gas of a high temperature. The high-temperature gas further heats the ambient unburnt gaseous mixture and simultaneously supplies active chemical pilot flame to play a role of a firing source to bring forth a flame holding effect.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a 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, various alternative energies have been required, and at the same time, efficient use of energy resources has also been required. Examples of systems that meet these demands include gas turbine/steam turbine combined cycle power generation systems that use natural gas as fuel, or coal gasification gas turbine/steam turbine combined cycle power generation systems. These power generation systems.

Its power generation efficiency is higher than that of conventional steam turbine power generation systems that use fossil fuels, so it can effectively convert fuels such as natural gas and coal gasified gas, whose usage is expected to increase in the future, into electricity. It is expected to be used as a power generation system.

BACKGROUND ART Conventionally, a gas turbine burner used in a gas turbine power generation system employs a homogeneous combustion method in which a mixed gas of fuel and combustion air is ignited by a spark plug or the like. A conceptual cross-sectional view of one 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, and then ignited by a spark plug 2 and combusted. Cooling air 4 and dilution air 5 are added to the burned gas, that is, the combustion gas, and after cooling and diluting it to a predetermined gas turbine inlet temperature,
The gas is injected from the turbine nozzle 6 into the gas turbine. In the figure, 8 is a swirler.

One of the biggest problems with the conventional combustor is:
During the combustion of fuel, large amounts of nitrogen oxides (see below) are produced.

NOx) is produced and causes environmental pollution. The reason why this NOx is generated is that a high temperature area exceeding 1500° C. exists in the combustor when fuel is combusted.

In order to solve these problems, various combustion methods have been studied, and recently, a heterogeneous combustion method using an in-phase catalyst (hereinafter referred to as a catalytic combustion method) has been proposed.

This catalytic combustion method is a method in which a mixed gas of fuel and combustion air is combusted using a catalyst. According to this method,
Combustion can start at a relatively low temperature, and compared to the combustion method shown in Figure 1, a large amount of combustion air can be mixed with the fuel for combustion, so the maximum temperature of combustion is low. However, little or no cooling and dilution air is required. Therefore, it is possible to extremely reduce the amount of NOx generated. FIG. 2 is a conceptual cross-sectional view of an example of a combustor using the catalytic combustion method described above.
Each number in the figure represents the same element as in FIG. A structural feature of this combustor is that it includes a catalyst section. This catalyst section is filled with a catalyst body 7 having a no-nicum structure.

In conventional catalytic bodies, reaction with the catalytic body typically results in phase combustion. At the inlet of the catalyst body, the temperature of the mixed gas is lower than the ignition temperature of the mixed gas, so in this region,
Gas phase combustion does not occur, only catalytic reaction combustion due to contact on the surface of the catalyst occurs, generating heat. The unburned mixed gas receives this heat and is heated. When the temperature of the mixed gas is raised to the ignition temperature, combustion occurs not only on the surface of the catalyst but also in the vicinity of the catalyst, resulting in gas phase combustion.

In this region, the υcatalyst is heated by the gas phase and reaches a high temperature, resulting in a significant decrease in catalytic activity and melting of the catalyst, significantly shortening the life of the catalyst. Become.

By the way, since the temperature of the combustion gas injected into the turbine required in a gas turbine is approximately 1100°C,
Even when all the mixed gas consisting of fuel and combustion air is combusted in the catalyst body and the temperature of the combustion gas is raised to about 1100° C., the temperature of the catalyst body becomes extremely high as described above. In experiments conducted by the present inventors, data that the temperature of the catalyst body was 1000°C to 1300°C was obtained, and it was observed that a part of the catalyst body was melted and damaged. Currently, there is no catalyst that can withstand this high temperature of 1100°C to 1300°C for a long period of time, and when such high-temperature combustion gas is required, it is difficult for conventional catalytic combustors to operate and reduce efficiency. It also had drawbacks such as being very bad.

[Purpose of the invention]

The present invention has been made in view of this point, and aims to provide a catalyst with long-term durability and to be inexpensive downstream of the catalyst.

[Summary of the invention]

As a result of extensive research, the present inventors have discovered a catalytic combustor that effectively utilizes gas phase combustion downstream of the catalyst and reduces the load on the catalyst. In other words, instead of combusting all the mixed gas consisting of fuel and combustion air within the catalytic body, only catalytic reaction combustion occurs within the catalytic body, and furthermore, gas-phase combustion downstream of the catalytic body is used. By burning the unburned materials, the temperature of the catalyst body was kept below 1lli4 thermal temperature of the catalyst body, thereby suppressing deterioration of the catalyst body and extending its life. Further, downstream of the catalyst, auxiliary fuel or the like is added as necessary to promote gas phase combustion. Here, in the gas-phase combustion downstream of the catalyst, the flame is stably held, and the mixing of unburned fuel, etc. is promoted, and NOx is reduced at high temperatures due to partial increase in f% of fuel. A feature of the present invention is that a non-streamlined body is provided downstream of the catalyst body in order to avoid this occurrence.

An example of a catalytic combustor according to the present invention is shown in the conceptual cross-sectional view of FIG. There is a catalyst body 7 in the combustion chamber, and a fuel injection device i for supplying fuel is installed at the upstream end of the combustor to inject the fuel, and combustion air 3 is supplied to the injected fuel to produce a mixed gas. is doing. The mixed gas flows into the catalyst body 7, causes combustion, and increases the temperature. Here, by controlling the mixing ratio of the mixed gas, the flow rate of the mixed gas, etc., and appropriately selecting the dimensions of the catalyst body, only catalytic reaction combustion is caused in the catalyst body, and at least a part of the fuel is It is combusted to produce a heated composite gas. Then, the composite gas flowing out from the catalyst body 7 is combusted in a gas phase downstream of the catalyst body. Here, if necessary, auxiliary fuel and auxiliary combustion air can be supplied from the auxiliary fuel injection device 9 and the auxiliary combustion air injection device 10 provided downstream of the catalyst body to achieve more effective gas phase combustion. preferable. Further, since NOx rapidly increases when the combustion temperature becomes about 1500°C or more, it is necessary to adjust the amount of auxiliary fuel etc. so that the flame temperature becomes less than 1500°C.

A non-streamlined body 8 is placed downstream of the catalyst body where gas phase combustion occurs, and the composite gas flowing out of the catalyst body generates a vortex flow by the non-streamlined body. This vortex is a closed circulation area, and a portion of the surrounding unburned mixed gas is taken into this and stirred, while combustion progresses and becomes high-temperature combustion gas. This high-temperature combustion gas further heats the surrounding unburned mixed gas and at the same time supplies active chemical species, serving as an ignition source and providing a flame-holding effect.

Further, the non-streamlined body may include a heat generating means,
at the start of combustion. It can be used as an ignition source for gas phase combustion downstream of the catalyst. That is, at the start of combustion, it is possible to raise the temperature to a temperature at which the gas-phase combustion occurs downstream of the catalyst by increasing the fuel concentration only by combustion in the catalyst, but it is not possible to raise the temperature of the catalyst. increases the load on the catalyst and significantly shortens the life of the catalyst. Therefore,
Although it is desirable to provide an ignition source downstream of the catalyst, the non-streamlined body equipped with a heat generating means is preferable as an ignition source that also has a preheating effect. Even if a misfire is likely to occur due to a temperature drop due to fluctuations in the temperature, the heating means can perform heating, thereby making it possible to prevent the misfire from occurring.

On the other hand, in catalytic combustion, although it varies depending on the type of fuel, the temperature of the mixed gas flowing into the catalyst body is generally controlled in order to effectively cause a reaction with the catalyst body.

It needs to be raised to some extent. Currently, in gas turbine combustors, the temperature of the combustion air supplied from the compressor is approximately 300°C, but if a temperature higher than 300°C is required, part of the fuel is ignited and combusted in advance to raise the temperature. There is a way. However, burning part of the fuel causes a decrease in the oxygen concentration of the mixed gas supplied into the combustion chamber, which has an adverse effect on catalytic combustion, so there is a limit to the temperature rise of the mixed gas by partially burning the fuel. be. Therefore, the fourth section showing the AA' cross-sectional view in FIG.
As shown in the figure, a flow path is provided in the non-streamlined body 8, and fuel or combustion air is passed through the flow path, and heat is exchanged through the walls of the non-streamlined body to raise the temperature of the fuel or the combustion air. It is possible to supply air to the catalyst body. Of course, depending on the conditions, there may be no problem in raising the temperature of the auxiliary fuel or the auxiliary combustion air in the same way. By adjusting the flow rate, etc., a desired temperature increase can be obtained. Although not shown in FIG. 3, the non-streamlined body 8
Cooling air or the like may be introduced downstream of the combustion gas in order to obtain a predetermined combustion gas temperature. Also.

The combustion air or cooling air used in the combustion chamber may be an oxidizing gas such as concentrated oxygen, or may be further supplemented with nitrogen or other essentially inert gas. It may also be diluted.

The non-streamlined body may have a shape that generates a vortex flow as required downstream of the catalyst body, and the non-streamlined body 8 shown in FIGS. 3 and 4 has a cylindrical shape. In addition to this, the shapes can be selected according to various conditions, such as a sphere with a cone shape or a seven-figure shape, and the number of shapes may be singular or plural. Further, in some cases, the non-streamlined body may be located downstream of the catalytic body and before an auxiliary fuel injection device or the like. Further, the material is required to be heat resistant, and for example, a non-metal mainly composed of silicon carbide can be used.

[Embodiments of the invention]

Example 1 Combustion was carried out using a simulated combustor as shown in Figure 3, using natural gas as the fuel and a noble metal honeycomb catalyst with a diameter of 100 m and a length of 100 m as the catalyst.
A mixed gas consisting of natural gas and combustion air was heated to 450°C.
Heat to 2Q m/S to 5Qm/ in terms of 500℃.
In addition, a cylindrical non-streamlined body with a diameter of 30 am was installed downstream at a distance of 40+ m from the catalyst body, and the combustion gas sampling position was 250 m downstream of the catalyst body. did. The adiabatic flame temperature of the 1st I mixed gas is 1200°C. Table 1 shows the results when the flow rate was changed.

As a comparative example, a case where no nonlinear body was installed under the same conditions is also shown. Note that NOx during combustion was all below 3 ppm.

Table 1 The catalytic combustor of the present invention does not misfire even at the high flow velocity required for gas turbines and stably exhibits very high combustion efficiency, whereas in the comparative example, misfire occurs as the flow velocity of the mixed gas increases. have done.

Example 2 Combustion was carried out using a Moho combustor as shown in FIG. 3, using methane as the fuel and a noble metal honeycomb catalyst body similar to that in Example 1 as the catalyst body. The diameter of the catalyst body is 100m
11. The length is 10.0m. The composition of the mixed gas flowing into the catalyst body 7 is such that the molar ratio of fuel and combustion air is 1.8%.
The temperature of the mixed gas was raised to 550° C. in an electric furnace. Then, only fuel was supplied from the auxiliary fuel injection device 1t9 so that the molar ratio of the total fuel supplied to the combustion air was 2.6%. Furthermore, at the start of combustion, the non-streamlined body 8 was used as a heating element to cause combustion downstream of the catalyst. After reaching a steady state, the temperature at the rear end of the catalyst is 810℃, the combustion efficiency is more than 99℃, and the generated N
Ox content was 2 ppm or less.

On the other hand, for comparison, a non-streamlined body 8 according to the present invention was ignited using a lug and burned under the same conditions as above.
Combustion downstream of the catalyst was unstable and misfired 5 minutes after ignition. In the catalytic combustor according to the present invention, the temperature of the catalyst body 7 was approximately 800° C., which was within the allowable temperature limit of the catalyst.

〔Effect of the invention〕

In the catalytic combustor according to the invention, the life of the catalyst body is significantly extended. Furthermore, gas-phase combustion downstream of the catalyst body is flame-stabilized by the non-streamlined body installed downstream of the catalyst body, thereby preventing misfires and making it possible to perform more stable combustion even at high flow rates. In addition, since the non-streamlined body stirs, combustion on the gas phase side is more uniformly carried out, and this has the effect of preventing the rise in temperature due to partial high concentration of fuel, thereby preventing the generation of NOx. are doing.

[Brief explanation of drawings]

Fig. 1 is a conceptual sectional view showing a gas turbine combustor using a normal combustion method, Fig. 2 is a conceptual sectional view showing a gas turbine combustor using a conventional catalytic combustion method, and Fig. 3 is an example of a catalytic combustor according to the present invention. Fig. 4 is a conceptual cross-sectional view showing A in the third session.
-A' is a sectional view. DESCRIPTION OF SYMBOLS 1... Fuel injection device, 2... Ignition device, 3... Air for combustion, 4... Air for cooling, 5... Air for dilution,
6... Turbine nozzle, 7... Catalyst body, 8... Non-streamlined body, 9... Auxiliary fuel injection device, 10... Auxiliary combustion air injection device. Agent Patent attorney Kensuke Chika (and 1 other person) Figure 1

Claims (3)

[Claims] (1) means for supplying fuel and combustion air; an inlet end for receiving the fuel and combustion air; an outlet end for discharging combustion gas; and an outlet end for discharging combustion gas; A catalytic combustor having a catalyst body installed in a flow path leading to the catalyst body. By bringing the mixed gas into contact with the mixed gas while maintaining the temperature lower than the ignition temperature of the mixed gas consisting of the fuel and the combustion air, only catalytic reaction combustion occurs in the catalyst body, and further downstream of the catalyst body, A catalytic combustor that causes gas phase combustion and is characterized in that a non-streamlined body is provided in a flow path between the catalyst body and the outlet end. (2) The catalytic combustor according to claim 1, further comprising means for supplying auxiliary fuel or auxiliary fuel and auxiliary combustion air downstream of the catalyst body. (3) The catalytic combustor according to claim 1, wherein the non-streamlined body is provided with one heat generating means.