JPH044490B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention supplies a gaseous fuel such as city gas to a combustion catalyst, causes an oxidation reaction to occur with combustion air diffused on the surface of the combustion catalyst, This invention relates to a catalytic burner that utilizes generated heat.

Conventional technology Conventionally, as shown in Figure 2, heat-resistant ceramic fibers were molded into burner case A, which was made of heat-resistant metal with a thickness of about 0.4 to 0.6 mm, or rough material made of ordinary iron plate with heat-resistant coating. The heat insulating material B consists of a heat insulating material B, and the combustion catalyst C supporting an oxidation catalyst on a heat-resistant porous ceramic fiber aggregate is installed, and the fuel gas supplied into the burner case A is diffused through the heat insulating material B. Meanwhile, it reached the inside of the combustion catalyst body C, and was oxidized by catalytic combustion by the combustion air convecting in the combustion catalyst body C.

Problems to be solved by the invention In the case of the configuration of the conventional technology as described above, the heat insulating material B
The back side of the combustion catalyst C is kept heated by
Since the outer periphery of the combustion catalyst C is in direct contact with the burner case A, the heat generated by the catalytic reaction at the outer periphery of the combustion catalyst C is transferred to the burner case due to the good thermal conductivity of the burner case A. It passes through A and is released to the outside air. Therefore, the temperature of the outer peripheral part of the combustion catalyst C is lower than the temperature of the central part of the combustion catalyst C even during steady combustion, forming a part below the activation temperature of catalytic combustion, and this part The fuel gas that passes through is not completely oxidized and is emitted partially unburned. Therefore, from the standpoint of safety as a heating device, it cannot be used in places with closed rooms, such as living spaces, and it cannot be used unless it is in extremely well-ventilated places, such as outdoors or in large spaces. I couldn't do it.

Means for Solving the Problems The present invention solves the problems of the conventional technology, and uses Al ₂ O ₃ , SiO ₂ , ZrO on the inner wall surface of the burner case that houses the heat insulating material and the combustion catalyst. The heat-retaining coating is made of ceramics with low thermal conductivity such as grade ₂ .

Effect According to the structure of the means for solving the above problem, a heat-retaining film is formed on the inner wall surface of the burner case by ceramic coating, so that the heat generated by catalytic combustion on the combustion catalyst body is , most of it is released from the outside air open side of the combustion catalyst, and since the outer periphery of the combustion catalyst and the metal surface of the burner case are separated by a ceramic heat-retaining coating, it is conducted to the burner case and released to the outside air. The amount of heat released is less than in the prior art described above. Therefore, the proportion of unburned gas released from the outer circumference of the combustion catalyst body also decreases. Furthermore, the heat retaining effect of the heat insulating material is increased, and the catalytic reaction on the combustion catalyst body is promoted, so that the combustion performance of the catalytic burner as a whole is improved, and as a result, a wide range of combustion amount variation can be maintained.

Embodiment An embodiment of a catalytic burner according to the present invention is shown in FIG. 1, and will be described with reference to FIG.

A fuel gas inlet 3 is provided at the bottom of a burner case 2 made of heat-resistant metal and having a heat-retaining coating 1 made of ceramics such as Al ₂ O ₃ , SiO ₂ , ZrO ₂ on the inner wall surface.
On the downstream side of the fuel gas flow at the fuel gas inlet 3, there is a net-shaped spacer 4, a heat insulating material 5 made of a heat-resistant ceramic fiber molded body, a preheater 6 made of a nichrome heater wire, and a heat-resistant porous ceramic fiber aggregate. A combustion catalyst body 7 carrying an oxidation catalyst such as a platinum group metal, a holding net 8 made of a heat-resistant metal to prevent the combustion catalyst body 7 from sagging or shifting, and a presser metal fitting 9 for fixing the holding net 8. are being installed sequentially.

Next, the operation of the above configuration will be described.

When the preheater 6 is energized, the electrical heat generated from the preheater 6 is transmitted to both the heat insulator 5 and the combustion catalyst 7, and the temperature of the combustion catalyst 7 increases from 280°C to 320°C.
When the temperature at which ignition is possible is reached, a solenoid valve (not shown) is energized, and fuel gas is supplied into the burner case 2 through the fuel gas inlet 3 at a constant flow rate. While the fuel gas is uniformly diffused within the heat insulating material 5 whose temperature has been raised to a certain extent, the fuel gas itself is also heated to a certain extent and reaches the combustion catalyst body 7 . During this time, preheater 6
When fuel gas is introduced into the burner case 2, electricity is continued for a certain period of time, and it functions as an auxiliary heat source during ignition. The fuel gas that has flowed into the combustion catalyst body 7, which is maintained at the activation temperature, begins to be oxidized by the combustion air that has flowed into the combustion catalyst body 7 from the direction opposite to that of the fuel gas, and the reaction heat is As a result, the temperature of the combustion catalyst body 7 rises, and the oxidation reaction is rapidly promoted, leading to stable combustion. In a stable combustion state, most of the heat generated by catalytic combustion on the combustion catalyst body 7 is released from the open air surface of the combustion catalyst body 7, and the remaining heat is combusted by the heat insulating material 5. The fuel is accumulated in the catalyst body 7, and catalytic combustion is continuously performed. At this time, since the heat retaining coating 1 is formed on the inner wall surface of the burner case 2, both the cooling effect from the outside air into the burner case 2 and the heat dissipation effect from the outer circumference of the combustion catalyst body 7 are achieved. suppress. Therefore, since the outer circumference of the combustion catalyst body 7 can maintain a stable reaction temperature, the amount of unburned gas flowing out from the outer circumference of the combustion catalyst body 7 is extremely small.
The combustion catalyst body 7 can almost completely oxidize the fuel gas.

As an indicator of the effectiveness of the catalytic burner according to this example, the combustion performance when using CH ₄ fuel, which is the least oxidizable in catalytic combustion, is compared with that when similar combustion is performed using a conventional technology configuration. is shown in Figure 1b. The same combustion catalyst was used in both this example and the conventional example. In the figure, the combustion rate is the volume percentage of the value obtained by subtracting the amount of unburned gas from the amount of supplied fuel and the amount of supplied fuel. The black circles indicate examples of the present invention, and the white circles indicate conventional examples.

As can be seen from the figure, within the indicated methane combustion amount range, this example maintains a higher combustion rate than the conventional example, and especially around 1100 kcal/h, CH ₄ is almost It can be seen that it is completely oxidized.

Effects of the Invention According to the catalytic burner of the present invention, the effects listed below can be obtained.

(1) On the entire inner wall surface of the case made of heat-resistant metal that houses the combustion catalyst body in which the oxidation catalyst is supported on the heat-resistant porous ceramic fiber aggregate and the heat insulating material,
By forming a heat-retaining coating made of at least one type of low thermal conductivity ceramics such as Al ₂ O ₃ , SiO ₂ , and ZrO ₂ , heat radiation from the case to the outside air can be suppressed, and fuel gas can be preheated and kept warm.

(2) With the above configuration, the outer periphery of the combustion catalyst body can also be kept warm, the entire combustion catalyst body can be maintained at the activation temperature, and as a result, the combustion amount variable range can be maintained broadly.

[Brief explanation of drawings]

FIG. 1a is a longitudinal sectional view of an embodiment of a catalytic burner according to the present invention, FIG. 1b is a characteristic diagram, and FIG. 2 is a longitudinal sectional view of a conventional catalytic burner. 1... Heat retention coating, 2... Burner case, 7...
Combustion catalyst.

Claims (1)

[Claims] 1. Al ₂ O ₃ , SiO ₂ , ZrO ₂ is applied to the entire inner surface of a case made of heat-resistant metal that houses a combustion catalyst in which an oxidation catalyst is supported on a heat-resistant porous ceramic fiber aggregate.
A catalytic burner in which a heat-retaining film is formed of fine particles of low thermal conductivity ceramic using at least one type of.