JPH0650164B2 - Catalytic combustion method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a catalytic combustion method suitable when combustion at a high temperature close to 1300 ° C. is required such as in a gas turbine combustor.

(Prior Art) In gas turbines used for power generation and other purposes, it is required to raise the temperature of combustion gas as high as possible within the range that turbine blades can withstand in order to increase the thermal efficiency. Combustion gas of about 1100 to 1300 ° C is supplied from the combustor. However, when such a high temperature combustion is performed using an ordinary burner, a high temperature region is formed in the center of the flame, and in this high temperature region nitrogen in the air combines with oxygen to generate a large amount of NO _X. I have a problem to do. Therefore, as disclosed in JP-A-58-16493 and JP-A-59-167621, catalytic combustion for reducing the amount of NO _X generated by bringing the air-fuel mixture into contact with the catalyst and catalytically burning it on the surface thereof. However, in these conventional methods, it is necessary to raise the catalyst surface temperature to be equal to or higher than the combustion gas temperature. Therefore, the catalyst deteriorates rapidly and has a life of about 100 hours. The sex was almost nothing.

Further, in Japanese Patent Laid-Open No. 60-186622, a mixture gas is passed through the inside of a precious metal honeycomb catalyst body to catalytically burn a part of the fuel to obtain a composite gas which is heated, and the composite gas is preferably an auxiliary fuel. And a device for obtaining a hot combustion gas for a gas turbine by performing gas-phase combustion in a region where the non-streamlined body is arranged after adding auxiliary air. However, in this device, as shown in the embodiment, the space velocity in the catalyst body is as large as 720,000 to 1.8 million (1 / H), and only a small part of the fuel in the air-fuel mixture is catalytically burned. Absent. Therefore, since reforming of fuel is not sufficiently performed, it is necessary to arrange a non-streamlined body on the outlet side of the catalyst body to prevent misfire, but this equipment becomes complicated and this part is very hot. Therefore, there is a problem that maintenance is not easy.

(Problems to be Solved by the Invention) The present invention solves the problems of the conventional catalytic combustion method as described above, and NO _X is generated even when high temperature combustion near 1300 ° C is performed.
The present invention has been completed for the purpose of a medium combustion method capable of extremely reducing the generation amount of hydrogen, capable of preventing catalyst deterioration and continuously used for a long period of time, and requiring no complicated device.

(Means for Solving Problems) According to the present invention, a mixture of fuel and air is supplied while being controlled, and is brought into contact with a honeycomb structure catalyst body having a combustion catalyst supported on the surface of the honeycomb structure body. A method of performing gas phase combustion in a downstream region after catalytic combustion, in which a combustor is continuously catalytically equipped with a honeycomb structure catalyst body and another flame holding means is not provided downstream thereof. Composed of a formed gas-phase combustion chamber, a honeycomb structure catalyst body having a large number of through holes having an equivalent diameter of 2.5 mm to 100 mm is used as the honeycomb structure catalyst, and the air-fuel mixture has a space velocity of 50000 (1 / H). ~ 6000
It is supplied to the honeycomb structure catalyst at 00 (1 / H) and catalytically burned inside it, and then the catalytic combustion gas is burnt in the gas phase in the downstream region without depending on other flame holding means as a flame holding source. It is characterized by that.

Hereinafter, the present invention will be described in more detail with reference to FIG.

The air-fuel mixture used in the present invention is LNG or L
It is preferable to use a mixture of hydrocarbon fuel such as PG and preheated air, the flow rate of which is controlled by the flow rate controllers (10) and (11) and the mixture of which at a predetermined ratio by the mixer (12).

In the present invention, the combustor is a catalytic combustion chamber (13) provided with a honeycomb structure catalyst body (3), and a gas phase combustion chamber (14) continuously formed downstream thereof without interposing other flame holding means. It consists of and. The air-fuel mixture is first introduced into the catalytic combustion chamber (13) provided with the honeycomb structure catalyst body (3). Honeycomb structure catalyst body
As (3), a honeycomb structure made of a heat-resistant ceramic material such as mullite or alumina having a combustion catalyst supported on the surface is used. As the combustion catalyst, at least one of platinum, palladium, and rhodium is used, and γ-Al ₂ O ₃ , Z is formed on the surface of the honeycomb structure as described above.
It is preferable that these combustion catalysts are attached after supporting rO _{2 and the} like. Among these combustion catalysts, palladium is also the most excellent in the ability to maintain the vapor phase combustion in the vapor phase combustion chamber (14) formed downstream of the catalytic combustion chamber (13).

In the present invention, when the air-fuel mixture passes through the honeycomb structure catalyst body (3), a part thereof is catalytically burned, and the catalyst combustion gas is used as a flame-holding source without depending on other flame-holding means, and the rest of the downstream region thereof. Since the gas-phase combustion is performed in the gas-phase combustion chamber (14), it is necessary to appropriately combine the equivalent diameter of the through holes of the honeycomb structure catalyst body (3) and the space velocity of the air-fuel mixture passing therethrough. . Here, the equivalent diameter is 4 × (cross-sectional area of the through hole) /
It is defined as (the inner peripheral length of the through hole), and is set to 2.5 mm or more and 10 mm or less as shown in the examples below. The space velocity is defined as (volumetric flow rate of air-fuel mixture at 0 ° C. and 1 atm) / (volume of honeycomb structure catalyst body), and is 50000 (1 / H)
/ 600000 (1 / H). When the equivalent diameter and the space velocity are smaller than the above values, most of the air-fuel mixture is completely combusted inside the honeycomb structure catalyst body (3), the temperature of the catalyst becomes high, and the gas phase combustion chamber (14 Since the gas phase combustion in (1) is not performed, the object of the present invention cannot be achieved. Further, when the equivalent diameter and the space velocity are larger than the above values, the catalytic combustion cannot be sufficiently performed, and thus the burden of gas phase combustion becomes large, and other flame holding means as in the case of the above-mentioned conventional technique. Therefore, the object of the present invention cannot be achieved.

As the honeycomb structure catalyst body (3), plural kinds of through holes having different equivalent diameters may be used in combination, and it is particularly preferable to increase the equivalent diameter toward the rear stage side.

(Operation) First, the air-fuel mixture of fuel and air mixed in a predetermined ratio by the mixer (12) is controlled by the flow control devices (10), (11) in this way first. ) Equivalent diameter of 2.5mm ~ 10mm honeycomb structure catalyst body (3) at a space velocity of 50000 (1 / H) ~ 600000 (1 / H) and catalytic combustion, a part of the mixture is 400 ~. The catalyst is combusted at a relatively low temperature of about 900 ° C., the fuel is sufficiently reformed, and the mixture of the combustion gas and the unburned mixture flows out from a large number of through holes of the honeycomb structure catalyst body (3). However, the catalytic combustion gas is used as a flame holding source for gas phase combustion in the gas phase combustion chamber (14) in the downstream region without depending on other flame holding means.
A hot combustion gas of ~ 1300 ° C is obtained. In this gas-phase combustion, the fuel dispersively flows out through a large number of through holes and burns, so there is no local high temperature region formed in the central part of the flame, and there is also the effect of the combustion catalyst. Almost no NO _X is generated. Further, since the catalytic combustion is carried out at a relatively low temperature of 400 to 900 ° C. inside the honeycomb structure catalyst body (3), the combustion catalyst is not deteriorated by heat, and as shown in the examples below, it is possible to use it for a long period of time. It is possible to maintain stable performance throughout. It should be noted that if the catalytic combustion temperature is less than 400 ° C., it will be used in the next gas phase combustion
If a high temperature combustion gas of 1200 to 1300 ° C. cannot be obtained, and if the temperature exceeds 900 ° C., the honeycomb structure catalyst body (3) deteriorates due to heat and stable combustion cannot be performed for a long period of time.

(Example) As shown in Fig. 1, a refractory (2) was inserted into a pipe (1) to form a combustion cylinder having an inner diameter of 55 mm and a total length of about 900 mm.
5 parts of a honeycomb structure catalyst body (3) having a diameter of 50 mm and a thickness of 25 mm, in which palladium was loaded at a rate of 10 g /
A catalyst combustion chamber (13) and a gas-phase combustion chamber (14) directly following the catalyst combustion chamber (13) were formed in a row and directly downstream without interposing other flame holding means. These honeycomb structure catalyst bodies (3) were prepared by supporting γ-Al ₂ O ₃ at a rate of 100 g / on a mullite honeycomb structure and firing at 600 ° C., then impregnating with a palladium chloride solution and air at 450 ° C. After baking in an atmosphere, it was further baked in a hydrogen atmosphere at 450 ° C. These honeycomb structure catalyst bodies (3) have equivalent through-hole diameters of 1.4 mm, 2.0 mm,
We prepared 7 types of 2.5mm, 4.8mm, 6.8mm, 10.0mm and 13.0mm, and used 5 of the same type in combination.

From the flow control devices (10) and (11) to natural gas fuel and 35
The air preheated to 0 ° C is sent to the mixer (12), and the natural gas whose methane concentration is 4.8% by volume is introduced into the combustion cylinder.
It is supplied to (4) and the space velocity is 30,000, 50,000, 100,000, 150,000, 60.
It was set to 800,000 (1 / H). While performing the catalytic combustion in the catalytic combustion chamber (13) and the vapor phase combustion in the vapor phase combustion chamber (14) in this manner, the temperature of each stage of the honeycomb structure catalyst body (3), the vapor phase combustion gas temperature, the outlet unburned methane concentration in (6) was measured NO _X concentration and the like.

The measured data after continuing combustion for 2000 hours are shown in the following table, and catalytic combustion and gas phase combustion were performed with an equivalent diameter of 2.5 mm to 10 mm and a space velocity of 50,000 to 600,000 (1 / H). Let me ○
In the case of the mark, the unburned methane concentration is 0 even after 2000 hours.
~9ppm, NO _X concentration is 4 to 6 ppm, temperature of 1,310 to 1,320 ° C.
It can be seen that the combustion gas of On the other hand, ×
In the case of the mark, most of the fuel burns catalytically, and gas-phase combustion in the downstream region hardly occurs, and the catalyst burns immediately after the start of combustion.
As it reaches a high temperature of about 1300 ° C and deteriorates and loses its function as a combustion catalyst, combustion becomes almost impossible after 2000 hours, and the mixture flows out to the outlet (6) almost as it is. became. The internal temperature of the honeycomb structure catalyst body in the table is a value measured at the central portion of the second stage honeycomb structure catalyst body.

Fig. 2 shows the temperature and gas phase combustion gas of each stage of the honeycomb structure catalyst body (3) during combustion, and ▲ is equivalent diameter 3.3m.
When the space velocity is 120,000 (1 / H), △ is equivalent to 5.0m in diameter
This is data when m and space velocity are 120,000 (1 / H). In these cases, the temperature inside the catalyst layer did not reach 900 ° C. or higher, but reached 1300 ° C. in the gas phase combustion region. On the other hand, ○ is the data immediately after the start of combustion when the equivalent diameter is 1.4 mm and the space velocity is 30,000 (1 / H), and ● is the equivalent diameter 2.0 mm and the space velocity is 50,000 (1 / H). The temperature inside the catalyst layer is
The temperature has reached 1200 to 1300 ° C, indicating that the combustion is not performed in the gas phase combustion region and the temperature is lowered. As described above, in the cases of ○ and ●, the catalyst deteriorates rapidly.

(Effects of the Invention) As described above, the present invention provides a combustor with a catalytic combustion chamber provided with a honeycomb structure catalyst body, and a gas phase formed continuously without interposing other flame holding means downstream thereof. Composed of a combustion chamber and the equivalent diameter of 2.5 m
By setting a specific range of m ~ 10 mm and space velocity of 50000 (1 / H) ~ 600000 (1 / H), preferable temperature conditions for catalytic combustion are formed and sufficient reforming of fuel is performed. , N
O _X generation amount is obtained by very little high-temperature combustion gas can be stably obtained over a long period of time.
Further, according to the present invention, since no other flame holding means is required downstream of the honeycomb structure catalyst body, the combustion device becomes simple and the maintenance becomes easy. Therefore, the present invention is extremely suitable as a catalytic combustion method suitable for a gas turbine combustor or the like that requires a stable supply of high-temperature combustion gas, and it greatly contributes to industrial development.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a graph showing a temperature distribution of each stage of the apparatus shown in FIG. (3): Honeycomb structure catalyst body, (10), (11): Flow rate control device, (12): Mixer, (13): Catalyst combustion chamber, (14): Gas phase combustion chamber.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hiroshi Mori 10-28, Takakura-cho, Atsuta-ku, Aichi Prefecture Nagoya City (72) Inventor, Kyo Fujita 20--18, Tsukimigaoka, Yatomi-cho, Mizuho-ku, Aichi Prefecture Nagoya City ( 56) References JP-A-60-186622 (JP, A) Actually developed Shou 60-95458 (JP, U)

Claims (2)

[Claims] 1. A fuel-air mixture is supplied while controlling its flow rate, and is brought into contact with a honeycomb-structured catalyst body having a combustion catalyst supported on the surface of the honeycomb-structured body for catalytic combustion,
A method of performing gas-phase combustion in the downstream region of the combustor, the gas-phase combustion being continuously formed without a catalyst combustion chamber provided with a honeycomb structure catalyst body and other flame holding means downstream thereof. And a chamber, the equivalent diameter of the honeycomb structure catalyst is a honeycomb structure catalyst body having a large number of through holes of 2.5 mm to 10 mm, and the air-fuel mixture has a space velocity of 50000 (1 / H) to 60
It is supplied to the honeycomb structure catalyst at 0000 (1 / H) and catalytically burned inside it, and then the catalytic combustion gas is burnt in the gas phase in the downstream region without depending on other flame holding means as a flame holding source. A catalytic combustion method characterized by the above. 2. The catalytic combustion method according to claim 1, wherein a honeycomb structure catalyst body in which a combustion catalyst containing palladium is carried on the surface of the honeycomb structure body is used.