JPH03241212A - Catalyst combustion device - Google Patents

Abstract

PURPOSE:To reduce a discharging of unburnt combustible gas and prevent an efficiency of combustion from being reduced by a method wherein a cross sectional area of a gas inlet part of a catalyst container is made smaller than a cross sectional area of a gas outlet port and formed to expand toward the gas outlet port. CONSTITUTION:A catalyst container 2 is comprised of a tapered pipe 11, and porous heat-resistant supporting members 12 and 13 closing both end openings capable of making a free passage of gas to constitute a gas inlet port and a gas outlet port, respectively. The tapered pipe 11 is formed such that a cross sectional area A of the gas inlet port, i.e. the supporting member 12 is smaller than a cross sectional area B of the gas outlet port, i.e. the supporting member 13 and the tapered pipe is formed to expand toward the supporting member 13 at the gas outlet port. In this way, the catalyst container 20 is formed as an expanding cylinder, thereby a tablet type combustion catalyst can be used as it is even in an application requiring a reduced pressure loss, resulting in that a discharging of the not-yet-ignited combustible gas is reduced and a combustion efficiency is prevented from being decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a catalytic combustion device that uses a combustion catalyst to combust a combustible gas containing a fuel and an oxidizer.

(Prior art) Combustible gas is generally combusted using a burner, and various types of burners are used depending on the purpose, the conditions of the combustible gas, and the use of the combustion gas. There is.

However, in recent years, it has become mandatory for this burner combustion method to reduce nitrogen oxides in the combustion exhaust gas due to environmental regulations, so even with ordinary burners, various improvements have been made and combustion conditions have changed. Efforts are being made to reduce nitrogen oxides to below regulatory limits by controlling

Among the nitrogen oxides, thermal
Nitrogen oxides are related to combustion temperature, and the higher the temperature, the more they are produced.

A catalytic combustion device shown in FIG. 6 is attracting attention as an effective means for reducing thermal nitrogen oxides. This is because the flame temperature becomes very high in normal diffusion combustion.
Nitrogen in the air exposed to this temperature generates nitrogen oxides through an oxidation reaction, whereas in the catalytic combustion device described above, flammable gas and air are premixed, and under this condition,
This is because the oxidation reaction occurs on the surface of the combustion catalyst, so the fuel burns at a relatively low temperature.

That is, a combustion catalyst 4 is housed in a catalyst container F, and a combustible gas 5 containing a mixture of fuel and an oxidizing agent is supplied to combust the fuel. The catalyst container 1o has a cylindrical body 1 and a flammable gas 5 or il! at both ends thereof. ! It consists of a heat-resistant support 2.3.

In the catalyst container 1o having such a configuration, the flow rate is Ul m/s.
ee, air containing combustible gas 5 that has been preheated to a temperature at which catalytic combustion occurs is caused to flow. Then, the combustible gas 5 passes through the 4 layers of the combustion catalyst, and catalytic combustion begins in the combustible gas 5, so the temperature begins to rise and due to thermal expansion inside the combustion catalyst 4, the superficial velocity becomes lower than U1m/see. Big U 2m
/seq speed.

In this case, when the combustible gas 5 passes through the gas outlet, that is, the support 3, the combustible gas 5 is completely combusted, the temperature further increases, and the superficial velocity becomes U10/sec. At this time, the pressure loss due to gas passing through the gas inlet and gas outlet of the supports 2 and 3 is ΔP1.

(Problem to be solved by the invention) However, even with the conventional catalytic combustion device described above,
For applications where the pressure loss ΔP1 needs to be as small as possible, the above example can be used as is, but there is a problem in that the combustion catalyst 4 must be changed from a tablet type to a honeycomb type.

Also, if the combustion catalyst 4 is changed to a honeycomb type,
Although it has the advantage of reducing pressure loss, it also has the problem that unburned combustible gas is discharged due to the flammable gas blowing through, reducing combustion efficiency.

Therefore, the present invention aims to provide a catalytic combustion device that can be used as a tablet-type combustion catalyst even in applications where it is necessary to reduce pressure nozzle loss, which emits less unburned combustible gas and does not reduce combustion efficiency. purpose.

[Configuration of the Invention (Means for Solving the Problems)] In order to achieve the above-mentioned object, the present invention provides a method for discharging fuel and gas from a gas inlet portion formed in a catalyst container housing a combustion catalyst toward a gas outlet portion. In the device for combusting the fuel by supplying a combustible gas mixed with an oxidizing agent, the catalyst container has a cross-sectional area of the gas inlet portion smaller than the cross-sectional area of the gas outlet portion, and a cross-sectional area of the catalyst container facing the gas outlet portion. It is shaped so that it is wide at the end.

(Function) According to the present invention, the catalyst container is formed so that the cross-sectional area of the gas inlet portion is smaller than the cross-sectional area of the gas outlet portion and widens toward the gas outlet portion. The increase in pressure loss due to the increase in flow rate due to the increase in gas amount and gas temperature as the process progresses can be prevented by widening the cross-sectional area and thereby suppressing the increase in pressure loss. Therefore, even in applications that require low pressure loss, the tablet-type combustion catalyst can be used as it is, and the combustion efficiency does not decrease due to the small amount of unburned combustible gas being emitted.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows the structure of a catalyst container 20 according to a first embodiment of the present invention, which differs from the conventional example shown in FIG. 6 in the following points.

That is, the catalyst container 20 consists of the Taber tube 1 and a porous, heat-resistant support 12 that closes the openings at both ends of the tube and forms a gas inlet and a gas outlet through which gas can freely pass. It consists of .13. In this case, in the Teva tube 1, the cross-sectional area A of the gas inlet portion, that is, the support body 2, is smaller than the cross-sectional area B of the gas outlet portion, that is, the support body 13, and the Teva tube 1 is made wider toward the support body 13 at the gas outlet portion. It was formed so that it would become so.

By forming the catalyst container 20 into a cylindrical body that widens at the end, it can be used as a tablet-shaped combustion catalyst even in applications that require low pressure loss, resulting in less unburned combustible gas being emitted and combustion efficiency not decreasing. . That is, since the cross-sectional area of the gas inlet part (support body 12) is the same as A and the conventional example shown in FIG. 6, the flow rate of the combustible gas 5 in this part is:
It is the same as U1m/see. However, the catalyst container 20
The flow rate of the combustible gas 5 becomes slower at U311/see than in the above-mentioned conventional example because it widens toward the gas outlet (support 13). in this case,
Since the pressure loss due to the passage of the combustible gas 5 is proportional to the square of the flow velocity, the pressure loss ΔP2 is equal to the pressure loss ΔP1 of the conventional example.
It is considerably smaller than .

If the inclination angle of the tapered tube 11 is, for example, 60°, ΔP
2 is approximately 1/3 to 1/4 of ΔPI.

FIGS. 2 to 4 show the results of experiments on this matter, showing the combustion gas flow rate and the differential pressure between the gas inlet and the gas outlet, that is, the pressure loss. The curves in Figure 2 are the same as those of the conventional example.
The height is 2230I11 and the volume is 839cm3), and the combustion catalyst is a circular tablet type (4.6cm in diameter and 4.6cm in thickness). In the case of this embodiment, the curve M represents the catalyst container 20 (small circular support 1
2 has a diameter of 3B, and the diameter of the large circular support 13 is 5B.
, the height is 142ca+ and the volume is 839cm3), and the combustion catalyst is tablet-shaped (diameter 4.6cm and thickness
．． 6+nm). Curve N indicates that the catalyst container is cylindrical (diameter is 3B, height is 223cm, and the volume is 839cm).
cm') and the combustion catalyst is a honeycomb type (100 meson units).

As is clear from FIG. 2, curve N has the smallest pressure loss, and curve M has a larger pressure loss than curve N, but the pressure loss is 1/4 of that of the curve.

FIG. 3 shows the combustion gas flow rate and the differential pressure between the gas inlet and the gas outlet, that is, the pressure loss.

The curve shows that the combustion catalyst is a circular ring-shaped tablet type (outer diameter is 8.8 m, inner diameter is 267 m, and thickness is 8.6 m).
m), in which the catalyst container 10 is a cylindrical body (same dimensions as in FIG. 2). Curve M indicates that the combustion catalyst is a circular ring-shaped tablet (outer diameter is 8.8+am, inner diameter is 2.7mm, thickness is 8°6mm), and the catalyst container 2
0 is the case where a cylinder body (same dimensions as in FIG. 2) that widens toward the end is used. In this case as well, the pressure loss of the curve M is smaller than that of the curved line.

FIG. 4 shows the combustion gas flow rate and the differential pressure between the gas inlet and the gas outlet, that is, the pressure loss.

The curve has a combustion catalyst in the form of a spherical tablet (about 6 m in diameter).
m), in which the catalyst container 10 uses a segmented body (same dimensions as in FIG. 2). Curve M is a combustion catalyst or spherical (
This is a case where the catalyst container 20 is a cylindrical body (same size as in FIG. 2) that widens at the end. In this case as well, the pressure loss is smaller in the curve gM than in the curve.

In the first embodiment, flashback, which seems to be a problem, does not occur if the flow velocity at the gas inlet is greater than the combustion velocity, so in this respect it is the same as the conventional example. Therefore, catalytic combustion can be maintained with low pressure loss even at relatively high space velocities without any problems.

FIG. 5 shows a second embodiment of the present invention, in which the basic configuration of the previously described embodiment includes one catalyst container 20 and one combustible gas introduction header 6; An example is a plurality of divided catalyst containers 20a, 20b, 20c, 20d,
This is a case where one combustible gas introduction header 6 is installed to supply flammable gas to these.

In the case of this embodiment, it has been experimentally determined that the pressure loss is reduced to 1/2/3 of the divided number of catalyst containers 20a to 20d (four in this case) at the same space velocity compared to the previous embodiment. It is clear from the results.

In this case, given a constant cross-sectional area for the combustible gas passages, compared to the case described above with a single combustion catalyst layer,
The cross-sectional area of each combustion catalyst layer can be reduced, and pressure loss can be further reduced. Furthermore, in this embodiment, each catalyst container 20
Since the combustion catalyst 4 rises in the center within a~2Od, the resistance when the flammable gas passes through the combustion catalyst becomes uniform, and the combustible gas flows uniformly into the combustion catalyst 4. The combustion efficiency of flammable gas is improved. In addition,
The problem of flashback is exactly the same as in the previous embodiment.

[Effects of the Invention] According to the present invention described above, the catalyst can be used as a tablet-type combustion catalyst even in applications that require low pressure loss, and the catalyst emits less unburned combustible gas and does not reduce combustion efficiency. A combustion device can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the first embodiment of the catalytic combustion apparatus of the present invention, and FIGS. 2 to 4 are diagrams for explaining the effects of the embodiment of FIG. A diagram showing the relationship between pressure (pressure loss), FIG. 5 is a diagram for explaining the second embodiment of the catalytic combustion device of the present invention, and FIG. 6 is a diagram for explaining an example of the conventional catalytic combustion device. It is a diagram. 4... Combustion catalyst, 5... Flammable gas, 6... Flammable gas introduction header 11... Tapered pipe, 12.13.
・Support, 20, 20a, 20b, 20c, 20d...
-Catalyst vessel.

Claims (1)

[Claims] A combustible gas containing a mixture of fuel and an oxidizer is supplied from a gas inlet portion formed in a catalyst container housing a combustion catalyst toward a gas outlet portion to combust the fuel, the catalyst container comprising: A catalytic combustion device, characterized in that the cross-sectional area of the gas inlet portion is smaller than the cross-sectional area of the gas outlet portion, and is formed to widen toward the gas outlet portion.