JPS61259013A - Catalyst combustion device - Google Patents

Abstract

PURPOSE:To provide a catalyst combustion device having such a catalyst burner that can be used in a condition in which a theoretical combustion temperature exceeds a heat-resistant allowable temperature of a catalyst carrier by a method wherein a combustion heat of the catalyst in a gas flow passage is absorbed (discharged) into a gas flow passage having no catalyst. CONSTITUTION:In a catalyst burner, combustible gas composed of mixture of fuel and fuel such as BFG or the like is uniformly supplied to gas flow passages 4A and 4B formed within a catalyst carrier frame 1 of each of the units. At this time, the combustible gas flowed into the gas flow passage 4A to which the catalyst 3 is deposited on its inner circumferential surface is completely ignited in each of the gas flow passages 4A and in turn the combustible gas flowing through the gas flow passage 4B to which not catalyst is deposited on its inner circumferential surface does not self-ignite. Therefor, the combustible gas flowing through the gas flow passage 4B may absorb the combustion heat in the gas flow passage 4A adjacent to it during its passage in the gas flow passage 4B through an hineycomb carrier 2. With this arrangement, a raising in temperature of the catalyst carrier caused by catalyst combustion can be kept at a temperature less than a heat-resistant allowable temperature of the catalyst carrier, so that it is possible to employ a low excessive rate of air (normally 1.1 to 1.2).

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a catalytic combustion device, and in particular, it is not limited by the calorie of the fuel, can burn at a low excess air rate, and can maintain the heat resistance below the allowable temperature of the catalyst carrier. The present invention relates to a catalytic combustion device suitable for.

[Background of the invention]

Catalytic combustion is a particularly effective method for stably burning low-calorie fuels such as blast furnace gas (hereinafter referred to as BFG).

However, in the catalytic combustion method, firstly, in order for the fuel to self-ignite within the catalyst layer, it is necessary to heat the combustible mixture of fuel and air to the ignition combustion temperature in advance;
Since there is a limit to the allowable heat resistance temperature of the combustion catalyst carrier, there are problems such as the need to maintain the temperature within this range during combustion.

For example, CO: 21%, CO□: 20%, H8: 3%,
The composition consists of N2 and the calorific value is 700kcaj! /
When burning BFG of Nrrr, the main component of BFG is C.
O, and the self-ignition temperature of CO is 200°C, so
To ensure safety, it is necessary to preheat to approximately 250°C. Also, the calorific value of BFG is 700kcaj! /Nn? Since BFG has a low calorie content, stable combustion is not possible without auxiliary combustion. However, stable combustion of BFG is possible with catalytic combustion. However, as is clear from Figure 11, if preheating is performed at 250°C, the theoretical combustion temperature will be approximately 1500°C.
This exceeds 1200°C, which is the allowable heat resistance temperature of the combustion catalyst carrier. It can be seen from FIG. 11 that the combustion temperature can be maintained below the allowable heat resistance temperature of the combustion catalyst carrier unless the excess air ratio is set to 2.5 times or more. However, increasing the excess air ratio requires an extremely large amount of thermal energy to heat a large amount of combustible mixture, and combustion with a high excess air ratio is unfavorable from the viewpoint of thermoeconomics of a combustion device such as a boiler.

Therefore, there is a need for a catalytic combustion method in which the excess air ratio is within the allowable temperature range of the combustion catalyst carrier and the excess air ratio is about 1.1 to 1.2.

In a conventional catalytic burner, as shown in FIG. 12, a combustible gas 26 consisting of a mixture of BFG and air is heated in advance to an ignition combustion temperature, passes through a catalyst carrier 27, and is completely combusted within a catalyst layer. Flameless combustion exhaust gas 28 is released. As shown in FIG. 13, the catalyst carrier 27 is a lattice 2 formed in the shape of a square lattice grid surrounded by a catalyst carrier frame (not shown).
A catalyst 30 is deposited on the entire inner surface of 9. When the combustible gas 26 passes through a gas flow path having a catalyst-deposited surface formed on the grid 29, it comes into contact with the catalyst 30 surface and self-ignites, and when it exits the gas flow path, combustion is usually completed. be. Therefore, since the grid 29 becomes the combustion surface as it is, the first
The catalyst carrier 27 shown in FIG. 2 is exposed to a combustion temperature higher than the allowable heat resistance temperature.

Since the honeycomb-shaped catalyst carrier 27 has a wall thickness as thin as IN or less, the catalyst carrier 27 deteriorates in a short period of time, and the catalyst carrier 27 is replaced more frequently.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a catalytic combustion device that includes a catalytic burner that can be used even under conditions where the theoretical combustion temperature exceeds the allowable heat resistance temperature of the catalyst carrier.

[Summary of the invention]

The present invention provides a gas flow path that does not have a catalyst adjacent to a gas flow path that has a catalyst on the inner peripheral surface, and absorbs (releases) combustion heat in the gas flow path that has a catalyst to the gas flow path that does not have a catalyst. It was designed to do so.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 is an overall configuration diagram showing an example of a catalyst carrier in a catalytic combustion device according to the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIG. 3 is an enlarged sectional view of the main part of FIG. 1. It is.

As shown in Figs. 1 to 3, the catalyst carrier has a structure in which a honeycomb-shaped catalyst carrier 2 is arranged within a catalyst carrier frame l, and a large number of gas flow paths are formed by the honeycomb-shaped catalyst carrier 2. has been done. Among these gas flow channels, the catalyst 3 is deposited on the inner peripheral surface of the gas flow channels located alternately (staggered), and the catalyst 3 is not deposited on the inner circumferential surface of the other gas flow channels, which are made of a carrier. A surface is formed. In Figure 3, catalyst 3
The gas flow path 4A where the catalyst is deposited is particularly marked with diagonal lines for ease of illustration, and the gas flow path 4B where the catalyst is not deposited is left blank without any diagonal lines. A large number of units including the catalyst carrier frame 1 as described above are installed in a catalyst burner as shown in FIG. 12.

In this catalytic burner, combustible gas consisting of a mixture of fuel such as BFG and air is uniformly supplied to gas passages 4A and 4B formed within the catalyst carrier frame 1 of each unit. At this time, the combustible gas flowing into the gas passages 4A with the catalyst 3 deposited on the inner peripheral surface is completely combusted in each gas passage 4A, and the gas passage 4B, on which the catalyst 3 is not deposited on the one-way peripheral surface, is completely combusted in each gas passage 4A. The circulating combustible gas will not self-ignite. Therefore, gas flow path 4B
In the process of passing through the gas passage 4B, the combustible gas flowing through the gas passage 4B transfers combustion heat in the adjacent gas passage 4A to the honeycomb-shaped carrier 2.
absorb through. Since the wall thickness of the honeycomb-shaped carrier 2 is made to be about 1 mm or less, this heat exchange is easy.

FIG. 4 is a diagram schematically showing such a heat exchange mechanism. In Fig. 4, the combustible gas of the BFG preheated to 250°C generates combustion heat corresponding to the temperature shown by the two-dot chain line on the three surfaces of the combustion catalyst in the gas passage 4A where the catalyst is vapor-deposited. releases heat to the combustible gas flowing through the gas passage 4B on which it is not vapor-deposited, and the temperature actually rises as shown by the solid line, and is maintained at 1200° C. or lower, which is the allowable heat resistance temperature of the catalyst carrier. On the other hand, since there is no catalyst on the gas passage 4B side, the combustible gas flowing through the gas passage 4B absorbs heat from the gas passage 4A side and is heated to about 500 to 600° C. without being combusted.

The combustible gas that has passed through the gas flow path 4B is preheated to the verge of ignition before exiting the carrier surface, as shown in FIG.
Since it is surrounded by the catalytic combustion gas 5 at a temperature of 0.degree. C., it immediately ignites and forms a small flame 6.

In the case of the conventional catalytic burner (full surface catalyst N) shown in FIG. 12, a flameless surface is formed, but in the case of this embodiment, a slight flame surface is formed from the gas flow path 4B side where the catalyst is not deposited. It turns out.

Therefore, the combustible gas supplied to the catalytic burner is
Even when preheated to ℃, the temperature rise of the catalyst carrier due to catalytic combustion can be maintained below the allowable heat resistance temperature of the catalyst carrier, so it is recommended to adopt a low excess air ratio (normally about 1°1 to 1.2). This makes it possible to use the catalytic combustion method even for relatively high-calorie gases.

FIG. 6 and FIG. 7 each show an overall configuration diagram showing another example of the catalyst carrier in the catalytic combustion device according to the present invention,
In FIG. 6, a honeycomb-shaped carrier 8 is arranged in a catalyst carrier frame 7, and a gas passage 10A in which a catalyst 9 is deposited and a gas passage 10B in which a catalyst is not deposited are formed in each row. There is.

Also in FIG. 6, the gas flow path 10A in which the catalyst 9 is deposited
are shown with diagonal lines for ease of illustration.

In FIG. 7, catalyst carriers 12 having successively smaller diameters are arranged concentrically at predetermined intervals within a cylindrical catalyst carrier frame 11, and a thin plate-shaped catalyst carrier is arranged between each catalyst carrier 12. It has become. and a gas flow path (shaded area) 13A in which catalysts are alternately deposited in the annular gas flow path;
A gas flow path 13B is formed in which no catalyst is deposited.

In the embodiments shown in FIGS. 6 and 7 as well, the gas channels 10A and 13A in which the catalyst is vapor-deposited release combustion heat to the adjacent gas channels 10B and 13B, respectively, to lower the temperature below the allowable heat resistance temperature of the catalyst carrier. Can be maintained.

In the embodiment shown in FIG.
The catalyst carrier can be manufactured easily because it is sufficient to sequentially and alternately stack a layered carrier in which a large number of 0A are formed and a layered carrier in which a large number of gas channels 10B in which no catalyst is vapor-deposited are formed. Further, in the embodiment shown in FIG. 7, an annular carrier in which a large number of gas channels 13A with a catalyst deposited thereon and an annular carrier in which a large number of gas channels 13B in which a catalyst is not deposited are alternately arranged. Since it is only necessary to fit the catalyst carrier, manufacturing of the catalyst carrier becomes simple.

In FIGS. 6 and 7, the gas flow paths in which the catalyst is not deposited are arranged in every other stage in FIG. 6 and every other ring in FIG. Therefore, depending on the dimensions of each gas flow path, a gas flow path in which no catalyst is deposited may be arranged every two stages or every two rings.

FIG. 8 is a schematic configuration diagram showing still another example of the catalytic combustion device according to the present invention, FIG. 9 is a front view of the catalytic burner shown in FIG. 8, and FIG. 10 is an example of the catalytic burner shown in FIG. 9. It is a perspective view showing a unit.

Figure 8 shows the HR3G (HeatRe
covery Steam Generation)
, that is, a heat generating boiler. In Figure 8, HR3GR
A superheater 15, a boiler 16, and an economizer 17 are installed in the upper 14 in order from the gas upstream side, and the superheater 1
A catalytic burner 18 is installed on the gas upstream side of 5. A fuel nozzle 21 is provided on the gas upstream side of the catalytic burner 18 to spray the auxiliary fuel from the auxiliary fuel supply pipe 19 via a fuel header 20 . Fuel nozzle 2 of catalytic burner 18
A debiager 22 is installed on the side opposite to 1.

The catalytic burner 18 has a structure in which several rows of honeycomb catalyst units 23 shown in FIG. 9 are stacked in multiple stages. These honeycomb catalyst units 23 are bonded and fixed to each other with ceramic cement, or are stacked with a buffer material made of ceramic fibers interposed therebetween.

In the honeycomb catalyst unit 23, honeycomb catalyst bodies 24 having the structure shown in FIG. 10 are stacked in several rows and in multiple stages. In the honeycomb catalyst unit 23 shown in FIG. 9, 24A is a honeycomb catalyst body on which a catalyst is deposited, and 24B is a honeycomb catalyst body on which a catalyst is not deposited. The honeycomb catalyst body 24 shown in FIG. 10 has a square shape with a side of about 30 to 100 m5, and the honeycomb catalyst unit 23 shown in FIG. One side of the catalyst unit 23 (indicated by a in the figure) is 12
It is 0-400m. The dimensions of the honeycomb catalyst body 24 and the number of honeycomb catalyst bodies in the honeycomb catalyst unit 23 described above are merely examples, and the dimensions and number can be arbitrarily selected.

In a waste heat boiler equipped with such a catalytic burner 18, the temperature of the gas turbine exhaust gas 25 introduced into the 5HRG duct 14 is 500 to 600'C;
5 flows through each gas flow path of the catalytic burner 18 together with the auxiliary fuel ejected from the fuel nozzle 21. The gas turbine exhaust gas 25 is heated by the combustion catalyst in the catalytic burner 18 to a temperature at which the steam temperature can be maintained in the superheater 15 (90°C).
0,~1000'C),,□14.
1. There is sufficient surplus air in the gas turbine exhaust gas 25 even without introducing air. However, the oxygen concentration in gas turbine exhaust gas is 12-12% compared to 21% in air.
Since the combustion rate is as low as 16%, the catalytic burner 18 is effective for combustion in a large amount of exhaust gas.

In the catalytic burner 18, there are a honeycomb catalyst body 24A on which a catalyst is deposited, and a honeycomb catalyst body 24A on which a catalyst is not deposited.
B are arranged alternately (staggered), forming a flame pattern as shown in FIG. However, since the honeycomb catalyst bodies 24A and 24B are a collection of gas flow paths as shown in FIG. 5, the flame is not a small flame, but a flame pattern similar to that of a normal burner is formed. .

According to the embodiment shown in FIGS. 8 to 10, the catalytic burner 1
The combustion heat of No. 8 is about 900 to 1000°C, and does not exceed the allowable heat resistance temperature of the catalyst carrier. Further, the catalytic burner 18 is usually equipped with several tens to hundreds of honeycomb catalyst bodies 24, and the combustion catalyst uses an expensive precious metal. Since the honeycomb catalyst body 24A on which the catalyst is vapor-deposited is installed in only 1/2 of the entire catalytic burner 18, the amount of the catalyst made of expensive precious metal used can be reduced to 1/2.

In FIG. 9, honeycomb catalyst bodies 24A on which a catalyst is vapor-deposited and honeycomb catalyst bodies 24B on which a catalyst is not vapor-deposited are arranged alternately (in a staggered manner). As shown in Figure 6, the honeycomb catalyst body 24
A and the honeycomb catalyst bodies 24B may be arranged alternately in each stage.

In the above-described embodiments, an example of a gas flow path in which a catalyst is vapor-deposited is shown, but the catalyst may be supported on the inner circumferential surface of the gas flow path, and vapor deposition is a preferable example.

〔Effect of the invention〕

As described above, according to the present invention, fuel can be catalytically burned at a low excess air ratio without exceeding the allowable heat resistance temperature of the catalyst carrier, so there is no restriction due to the calorie of the fuel.
In addition, since catalytic combustion can be performed at a low excess air ratio, there is no usual stack loss, which is effective from a thermoeconomic standpoint, and can be applied to catalytic burners such as gas turbine waste heat boilers.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an example of a catalyst carrier in a catalytic combustion device according to the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIG. 3 is an enlarged sectional view of the main part of FIG. 1. , Figure 4 is the first
Figure 5 is a diagram schematically showing the heat exchange mechanism in a catalytic burner using the catalyst carrier shown in Figures 1 to 3.
FIGS. 6 and 7 are diagrams showing flame patterns on the catalyst surface of a catalytic burner using the catalyst carrier shown in the figure, respectively. FIGS. Fig. 8 is a schematic configuration diagram showing another example of the catalytic combustion device according to the present invention, Fig. 9 is a front view of the catalytic burner in Fig. 8, and Fig. 10rfA shows one unit of the catalytic burner shown in Fig. 9. A perspective view, FIG. 11 is a diagram showing the relationship between the combustion temperature and the excess rate of usable combustion air when BFG is used as fuel, FIG. 12 is a schematic cross-sectional view of a conventional catalytic burner, and FIG. FIG. 2 is an enlarged sectional view of a main part of a catalyst carrier in a conventional catalytic burner. 1.7.11...Catalyst carrier frame, 2,8.12.
... Catalyst carrier, 3.9 ... Catalyst, 4A,
IOA, 13A... Gas flow path (catalyst vapor deposition), 4
B. IOB. 13B... Gas flow path (no catalyst vapor deposition), 5...
...Catalytic combustion gas, 6...Small frame, 1
4...HR3G duct, 15...Superheater, 16...Boiler, 17...Economizer, 18...Catalytic burner, 19.・・・・・・
・Auxiliary fuel supply pipe, 20...Fuel header, 21・
...Fuel nozzle, 22, old... debut gas, 23
...Honeycomb catalyst unit, 24 Old...Honeycomb catalyst body, 24A...Honeycomb catalyst body (catalyst vapor deposition), 24B...Honeycomb catalyst body (no catalyst vapor deposition), 25. Old gas turbine exhaust gas.

Claims (5)

[Claims] (1) In a catalytic combustion device equipped with a catalyst carrier in which a large number of gas passages are formed, there is a gas passage having a catalyst on its inner peripheral surface, and a gas passage adjacent to this gas passage and having no catalyst. A catalytic combustion device characterized by comprising: (2) The catalytic combustion device according to claim 1, wherein the catalyst carrier is formed in a honeycomb shape, and gas flow paths having catalysts on the inner peripheral surface are arranged in a staggered manner within the catalyst carrier. (3) The catalytic combustion device according to claim 1, wherein the catalyst carrier is formed in a honeycomb shape, and gas flow paths having a catalyst on the inner circumferential surface are arranged at least every other stage within the catalyst carrier. . (4) A patent claim in which the catalyst carrier has a large number of concentric annular gas passages, and a gas passage having a catalyst is arranged on the inner peripheral surface of at least every other ring of these annular gas passages. The catalytic combustion device according to item 1. (5) The catalytic combustion device according to any one of claims 1 to 4, wherein the gas flow path having a catalyst on the inner peripheral surface has a catalyst deposited on the inner peripheral surface of the gas flow path.