JP2000186803A - Catalytic combustion equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safe or compact catalytic combustion equipment having good combustion exhaust gas characteristics. SOLUTION: A catalyst 7 carrying an oxidation catalyst component on a base material having many communicating holes and an air introducing porous material 12 made of a non-thermal conductor having many communicating holes are disposed so that downstream surfaces are opposed. The oxidation catalyst component containing a platinum as a main component is carried to the catalyst 7. An excess air coefficient of supplied premixed gas is set to 1 or below, and a total excess air coefficient added with secondary air is set to 1 or above. Both the catalyst 7 and the material 12 are disposed near at hand so that combustion exhaust gas passing the catalyst 7 and the secondary air passing through the material 12 are mixed and then brought into contact with the downstream surface of the catalyst 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic combustion device that effectively utilizes radiant heat rays generated by heat of combustion reaction.

[0002]

2. Description of the Related Art A large number of proposals have been made in a catalytic combustion apparatus using a catalyst having an oxidizing activity with respect to a fuel mainly composed of hydrocarbons, for effectively utilizing radiant heat rays generated by heat of combustion reaction. I have. Of these, only the fuel is supplied to the communication hole of the catalyst body, and oxygen in the atmosphere is diffused and supplied near the downstream surface of the catalyst body to cause a catalytic oxidation reaction, and heat rays are emitted from the exposed downstream surface of the catalyst body. A premixed mixture of fuel and air is supplied, and a contact oxidation reaction is performed mainly in the vicinity of the upstream surface of the catalyst, and heat rays are transmitted from the upstream surface through a heat ray transmission window provided opposite to the upstream surface of the catalyst. Those that emit light are well known.

Further, it is known that by performing an oxidation reaction in a reducing atmosphere using a catalyst carrying an oxidation catalyst containing platinum as a main component, the heat resistance of the catalyst can be improved (Japanese Patent Application No. 2002-214,197). Hei 10-157555). Therefore, a premixed gas having an excess air ratio of 1 or less is supplied to cause a catalytic oxidation reaction near the upstream surface of the catalyst body, and then, in a combustion exhaust gas channel installed downstream of the catalyst body, a total air excess ratio of 1 is provided. As described above, there has been proposed a method in which air is additionally supplied to cause a catalytic oxidation reaction of unburned fuel gas, carbon monoxide and intermediate products contained in combustion exhaust gas in an auxiliary catalyst.

[0004]

In the above-mentioned conventional catalytic combustion apparatus, only the fuel is supplied to the communication hole of the catalyst body, and oxygen in the atmosphere is diffused and supplied near the downstream surface of the catalyst body to perform catalytic oxidation. In the case of reacting and radiating heat rays from the downstream surface of the exposed catalyst body from the downstream surface of the exposed catalyst body, part of the heat generated in the reaction near the downstream surface of the catalyst body is radiated or conducted. The heat is transmitted to the upstream side of the catalyst body, and a part of the heat is recovered by the fuel passing through the communication hole of the catalyst body and is returned to the downstream side again. Therefore, it is possible to lower the temperature of the upstream surface of the catalyst body and the back surface of the combustion device facing the upstream surface. However, since oxygen in the atmosphere is diffused and supplied, it is difficult to supply an oxygen amount sufficient to achieve an excess air ratio of 1 or more, and to sufficiently mix fuel and oxygen before the oxidation reaction. Therefore, there has been a problem that unburned fuel gas, carbon monoxide and intermediate products are easily generated and the combustion exhaust gas characteristics are not good. Further, in addition to the reduction in the combustion rate, the heat possessed by the combustion exhaust gas generated in the combustion reaction is discharged without being recovered or used secondarily, so that the heat utilization efficiency tends to decrease. There was a problem that there is.

On the other hand, a premixed mixture of fuel and air is supplied to cause a catalytic oxidation reaction mainly in the vicinity of the upstream surface of the catalyst body, and heat rays are transmitted from the upstream surface through a heat ray transmission window provided opposite to the upstream surface of the catalyst body. In addition to transmitting the heat generated in the reaction near the upstream surface of the catalyst body to the downstream side of the catalyst body by radiation or conduction, high-temperature combustion exhaust gas passes through the communication hole of the catalyst body. In order to pass through and heat the downstream side, for example, under combustion conditions in which the temperature of the upstream surface of the catalyst body is 800 ° C. or more, the temperature of the downstream surface is raised to about 500 to 600 ° C. 30-4 of the amount of heat radiated to the side
About 0% of the heat rays are emitted from the downstream surface of the catalyst body. For this reason, the rear surface of the combustion device facing the downstream surface of the catalyst body becomes hot, and it is necessary to stack a heat insulating layer and a heat radiation layer in order to ensure safety. .

Further, similarly, in the case of radiating heat rays from the upstream surface, a premixed gas having an excess air ratio of 1 or less is supplied, and a catalytic oxidation reaction is performed in the vicinity of the upstream surface of the catalyst body. In the installed flue gas flow path, air is additionally supplied so that the total air excess ratio becomes 1 or more, and unburned fuel gas, carbon monoxide and intermediate products contained in the flue gas in the auxiliary catalyst body In the catalytic oxidation reaction, the unburned fuel gas, carbon monoxide and intermediate products contained in the combustion exhaust gas, and the additionally supplied air are sufficiently mixed before the oxidation reaction in the auxiliary catalyst body. Required. If the flow path from the additional air supply position to the auxiliary catalyst body is long, it is possible to mix well, but the catalyst body and auxiliary catalyst body will be installed separately,
Since the auxiliary catalyst is less likely to receive radiant heat or the like from the catalyst, the temperature of the auxiliary catalyst tends to decrease. For this reason, carbon monoxide and intermediate products that are easily oxidized at relatively low temperatures are oxidized. Particularly, when a fuel that requires a high temperature of 600 ° C. or more for the oxidation reaction such as natural gas is used. However, there is a problem that unburned fuel gas is easily discharged. On the other hand, in order to shorten the flue gas flow path, a means for promoting mixing, such as installing a baffle plate, is required, so that the configuration of the flue gas flow path has been complicated. Further, since the combustion reaction is performed at an excess air ratio of 1 or less, the rate of reaction near the upstream surface of the catalyst body decreases, and some fuel reacts on the downstream side of the catalyst body, and the reaction heat is directly discharged. For this reason, there has been a problem that the efficiency of using the radiant heat from the upstream surface of the catalyst body is reduced.

An object of the present invention is to provide a safe or compact catalytic combustion device having good combustion exhaust gas characteristics in consideration of the problems of the conventional catalytic combustion device.

[0008]

According to the present invention, there is provided a catalytic combustion apparatus comprising: a catalyst body having an oxidation catalyst supported on a base material having a plurality of communication holes; It has a configuration in which the introduction porous bodies are arranged such that their downstream surfaces face each other, and a part of the radiant heat from the downstream surface of the catalyst body is returned to the catalyst body again by radiation from the downstream surface of the air introduction porous body. Therefore, it is possible to realize a combustion device having high utilization efficiency of radiant heat from the upstream surface of the catalyst body. Further, since direct heating due to radiation from the downstream surface of the catalyst body and contact with the combustion exhaust gas is suppressed, it is possible to lower the temperature of the back surface of the combustion device. Therefore, it is possible to provide a highly safe combustion device that does not cause a burn or the like. Further, it is possible to provide a compact and compact combustion device having a thin rear portion of the combustion device. further,
By using the radiant heat from the upstream surface of the catalyst body, the combustion exhaust gas, and the warm air at an appropriate temperature level in which the secondary air is mixed, it is also possible to realize a combustion device with high heat utilization efficiency.

Also, a catalyst body supporting an oxidation catalyst containing platinum as a main component is installed, and the excess air ratio of the premixed gas supplied is 1 or less, and the total excess air ratio including secondary air is 1 or more. And after the flue gas that has passed through the catalyst body and the secondary air that has passed through the porous body are mixed, they are arranged close to each other so as to be in contact with the downstream surface of the catalyst body. Good flue gas characteristics can be achieved without installing complicated flue gas channels with auxiliary catalysts for oxidizing unburned fuel gas, carbon monoxide, etc., and baffles for promoting mixing. A combustion device having Further, unburned fuel gas, carbon monoxide, and the like contained in the flue gas are almost completely oxidized between the catalyst body and the downstream surface of the air introduction porous body. It is possible to provide a highly safe combustion device that does not cause a problem even when leakage occurs. Furthermore, most of the reaction heat generated on the downstream surface of the catalyst body is transmitted to the upstream side by conduction, radiation, etc.,
It is possible to realize a combustion device having high utilization efficiency of radiant heat from the upstream surface of the catalyst body.

Further, at least one of the downstream surfaces is provided with a plurality of protruding structures, an oxidation catalyst is supported on at least a portion of the porous air-introducing body including the downstream surface, and the combustion exhaust gas and air passing through the catalyst body are supported. After the air that has passed through the porous body is mixed, the two are arranged close to each other so as to be in contact with at least one downstream surface, and the oxidation catalyst supported on the air-introduced porous body contains palladium, and Diffusion and mixing of the combustion exhaust gas and air are promoted, and the frequency of contact of the mixed gas with the catalyst surface on the downstream side of the catalyst body or the air introduction porous body increases, so that the exhaust gas can be exhausted indoors. It is possible to realize a very safe combustion device having excellent combustion exhaust gas characteristics.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

In the practice of the present invention, a catalyst body having a plurality of communication holes and having an activity of oxidizing various fuels, a heat-resistant heat ray permeable material, and an air introduction porous material having a plurality of communication holes and a poor thermal conductor. Other than body, ignition device and flow control device, fuel and air mixer, or liquid fuel vaporizer if necessary,
A temperature detecting device, a driving device, and the like are required. The catalyst body is a metal or ceramic honeycomb carrier, or a ceramic fiber braided body, a porous sintered body, etc., on which an active component mainly composed of a noble metal such as platinum or palladium is supported. Quartz glass, crystallized glass, or the like can be used as the heat ray permeable material. Further, as the air introduction porous body, a ceramic honeycomb structure, a braided ceramic fiber body, a porous sintered body, or the like can be used. Further, a manual needle valve or an electric solenoid valve is used for controlling the flow rate of air or gaseous fuel, and an electromagnetic pump or the like is used for liquid fuel. The other drive parts can be operated by manual lever operation, automatically controlled motor drive, and the like, and an electric heater, a discharge igniter, or the like can be used as an ignition device. These are all means conventionally widely used, and other known means are also possible.
Here, the description of those details is omitted. (Embodiment 1) FIG. 1 is a partial sectional configuration view of an embodiment of a catalytic combustion device according to the present invention. In FIG. 1, 1 is an air supply fan, 2 is a combustion air flow control valve, 3 is a fuel flow control valve, 4 is a fuel / air mixer, 5 is a premixed gas inlet, 6 is a premixed gas chamber, Reference numeral 7 denotes a catalyst body in which a white metal noble metal is supported on a ceramic honeycomb having a plurality of communication holes. Reference numeral 8 denotes a heat ray transmission window made of crystallized glass, which is provided at a position facing the upstream surface of the catalyst body 7. Further, 9 is a secondary air flow control valve, 10 is an air inlet, 11 is an air chamber, 12 is an air introducing porous body made of ceramic honeycomb, and is installed so that the downstream surfaces of the catalytic body 7 and each other face each other. ing. Further, 13 is an igniter comprising an electric heater, 14 is a flue gas flow path, 15
Is a combustion exhaust gas outlet.

Next, the operation and characteristics of this embodiment will be described with reference to FIG. The fuel supplied from the pipe (here, city gas is used) is flow-controlled by the fuel flow control valve 3, then supplied by the air supply fan 1, and mixed with the air flow-controlled by the combustion air flow control valve 2. In the vessel 4 are mixed. Further, the premixed gas is supplied into the premixed gas chamber 6 through the premixed gas inlet 5. On the other hand, the air whose flow rate is controlled by the secondary air flow rate control valve 8 is supplied into the air chamber 11 through the air inlet 10.

In the initial stage of the combustion, the premixed gas reaching the combustion exhaust gas passage 14 through the communication hole of the catalyst body 7 is ignited by the igniter 13.
It is ignited when electricity is supplied to. The catalyst body 7 heated by the formed flame, the vicinity of the downstream surface first rises in temperature, starts catalytic combustion here, and further heats the upstream side by the combustion heat. It shifts to catalytic combustion near the surface and becomes steady combustion.

In the steady combustion, a catalytic oxidation reaction mainly occurs near the upstream surface of the catalyst body 7. Here, by adjusting the supply amount with the fuel flow rate control valve 3, the temperature of the upstream surface has good combustion exhaust gas characteristics, 800 ° C. or more at which combustion can be continued, and 900 ° C. which is the heat resistance limit.
It is controlled as follows. At this time, an amount of heat corresponding to 50 to 60% of the calorific value of the supplied fuel is radiated to the upstream side of the catalyst body 7. Further, part of the heat generated by this reaction is mainly generated by conduction in the flow direction and radiation between the opposing partition walls inside the walls separating the communication holes of the ceramic honeycomb constituting the catalyst body 7, and thus the 7 to the downstream surface. Further, the high-temperature combustion exhaust gas generated at the reaction position near the upstream surface of the catalyst 7 heats the downstream surface when passing through the communication holes. For this reason, the temperature of the downstream surface of the catalyst body 7 reaches 500 to 600 ° C., and a heat amount corresponding to 30 to 40% of the heat amount radiated to the upstream side is also radiated to the downstream side of the catalyst body 7.

Here, the downstream surface of the air introduction porous body 12 made of ceramic honeycomb, which is installed so that the downstream surfaces of the catalyst body 7 and the respective downstream surfaces thereof face each other, emits radiation and contact from the downstream surface of the catalyst body 7. 500 to 600 discharged from the medium 7
Heat is received by contact with flue gas at ℃. Part of this heat is generated by conduction inside the walls separating the communication holes of the ceramic honeycomb constituting the air introduction porous body 12 and radiation between the opposing partition walls.
Is transmitted upstream. A part of the heat is recovered by the air passing through the communication hole of the air introduction porous body 12,
It is returned to the downstream side again. For this reason, the temperature of the upstream surface of the air introduction porous body 12 is 100 to 150 ° C, and the temperature of the downstream surface is 400 to 500 ° C. At this time, the amount of heat corresponding to about 50% of the amount of heat radiated to the downstream side of the catalyst body 7 is returned to the catalyst body 7 by the radiation from the downstream surface of the air introduction porous body 12. When the amount of heat radiated from the upstream surface of the catalyst body 7 is kept constant due to such a heat recirculation effect, the amount of fuel supplied (combustion amount) is determined by the case where the catalyst body 7 is installed alone and burned. Compared with this, it is possible to reduce about 10%. From this, it is possible to provide a catalytic combustion device with high utilization efficiency of the radiant heat rays emitted from the upstream surface of the catalyst body 7.

Further, in the combustion apparatus of the present embodiment,
The maximum temperature of the rear surface 20 of the combustion device facing the upstream surface could be suppressed to 80 ° C. or less and the average temperature to 65 ° C.

As described above, the air introducing porous body 12 is provided so that the radiation from the downstream surface of the catalyst body 7 and the contact with the combustion exhaust gas are not directly received on the back surface 20 of the combustion device. It is possible to lower the temperature of the back surface of the device. Furthermore, since safety can be ensured by installing only the air introduction porous body 12 and the air chamber 11, a compact combustion device having a thin rear portion can be realized.

Further, by controlling the supply amount with the secondary air flow control valve 9, the temperature of the mixed gas of the combustion exhaust gas discharged from the catalyst body 7 and the air passing through the air introduction porous body 12 is controlled. This mixed gas is discharged into the combustion exhaust gas outlet 1
5. To provide a heating device with high heat utilization efficiency that combines the radiant heat from the upstream surface of the catalyst body 7 and the hot air at an appropriate temperature level by discharging the air from the catalyst 5 to the outside and using it as hot air. Is also possible. (Embodiment 2) A second embodiment of the present invention will be described. The present embodiment has the same basic configuration as that of the first embodiment, except that an oxidizer 13 is disposed on the upstream side of the catalyst 7 in that the catalyst carries an oxidation catalyst containing platinum as a main component. That the excess air ratio of the premixed gas supplied to the catalyst body is 1 or less, and that the mixture of combustion exhaust gas passing through the catalyst body and air passing through the air introduction porous body is The difference is that the catalyst body and the air introduction porous body are arranged close to each other so as to contact the downstream surface. Therefore, the description will focus on this difference.

FIG. 2 is a sectional view of a main part of the present embodiment.
The operation and characteristics of the present embodiment will be described with reference to FIG. Fuel supplied to pipes (here city gas is used)
After the flow rate is controlled by the fuel flow control valve 3,
The air supplied by the air supply fan 1 is mixed in the mixer 4 with air whose flow rate is controlled by the combustion air flow control valve 2. Here, the flow rate is controlled so that the excess air ratio of the premixed air becomes 1 or less. Further, the premixed gas is supplied into the premixed gas chamber 6 through the premixed gas inlet 5.

On the other hand, the air whose flow rate has been controlled by the secondary air flow rate control valve 9 passes through the air inlet 10 to the air chamber 1.
1 is supplied. Here, the flow rate is controlled so that the total excess air ratio of the premixed air including the additionally supplied air is 1 or more. Further, the catalyst body 7 and the air introduction porous body 1 are arranged such that a mixture of the combustion exhaust gas passing through the catalyst body 7 and the air passing through the air introduction porous body 12 comes into contact with the downstream surface of the catalyst body 7.
2 are placed close to and opposite to a distance of 5 mm or less.

In the initial stage of combustion, a premixed gas having an excess air ratio of 1 or more is intentionally fed from the premixed gas inlet 5 and ignited by energizing the igniter 13 to form a flame at the premixed gas inlet 5. . The catalyst body 7 heated by the flame is
The temperature near the upstream surface rises first. Here, when the temperature of the upstream surface of the catalyst body 7 rises to 600 ° C. or more and the red heat is started, the fuel supply is stopped by closing the fuel flow control valve 3 once to extinguish the flame. .

Thereafter, when the fuel flow control valve 3 is opened again and the supply of fuel is started with the excess air ratio of the premixed air being 1 or less, catalytic combustion starts from near the upstream surface of the catalyst body 7, Eventually, steady combustion is reached.

In the steady combustion, a catalytic oxidation reaction is performed mainly in the vicinity of the upstream surface of the catalyst 7 in a reducing atmosphere. Here, by performing an oxidation reaction in a reducing atmosphere using a catalyst body 7 supporting an oxidation catalyst containing platinum as a main component, the temperature of the heat resistance limit can be increased to 1050 ° C. Hei 10-157555).
Therefore, the temperature of the upstream surface is controlled to 900 to 1050 ° C. by adjusting the supply amount by the fuel flow control valve 3. At this time, the temperature of the downstream surface of the catalyst body 7 is 600
Reaches ７750 ° C.

On the other hand, the combustion exhaust gas that has passed through the catalyst body 7 and the secondary air that has passed through the air introduction porous body 12 form a counterflow between the downstream surface of the catalyst body 7 and the downstream surface of the air introduction porous body 12. Is discharged. In the flow of the air-fuel mixture of the combustion exhaust gas and the secondary air, most of the unburned fuel gas, carbon monoxide, and intermediate products contained in the combustion exhaust gas and oxygen are diffused and mixed, and the downstream surface of the catalyst body 7 is diffused. The contact between the catalyst body 7 and the air introduction porous body 12 is repeated toward the outer peripheral direction of the catalyst body 7 and the air introduction porous body 12, and is discharged from the outermost peripheral end.
Here, since the temperature of the downstream surface of the catalyst 7 is 600 ° C. or more, even when a fuel such as natural gas that requires a high temperature for catalytic activity is used, contact with the downstream surface of the catalyst 7 At this time, all of the unburned fuel gas, carbon monoxide, and intermediate products have reached a temperature at which the oxidation reaction is performed, and the combustion device of the present embodiment emits The concentration of carbon monoxide in exhaust gas is several tens
ppm could be confirmed. As described above, by adopting a simple configuration in which the catalyst body 7 and the air introduction porous body 12 are disposed close to and opposed to each other, it is possible to achieve good combustion exhaust gas characteristics with a simple structure. That is, unburned fuel gas separately contained in the combustion exhaust gas,
There is no need to provide an auxiliary catalyst for performing the oxidation reaction of carbon monoxide and intermediate products, a baffle for promoting the mixing of the combustion exhaust gas with the secondary air, and the like. Furthermore, unburned fuel gas, carbon monoxide, and intermediate products contained in the combustion exhaust gas become almost completely carbon dioxide and water vapor between the downstream surface of the catalyst body 7 and the downstream surface of the air introduction porous body 12. From
There is no problem even if the flue gas may leak in the middle of the flue gas flow path 14 formed downstream of the flue gas.

As described above, the amount of heat corresponding to the calorific value of the fuel corresponding to the shortage of air (for example, 30% of the supply amount at an excess air ratio of 0.7) is generated by the combustion reaction on the downstream surface of the catalyst body 7. Most of these are directly supplied to the heating of the catalyst body 7, and are transmitted to the upstream side by conduction inside the partition walls or radiation between the opposing partition walls. Therefore, it is possible to provide a catalytic combustion device having a high heat utilization efficiency equal to or higher than the case where the premixed gas having an excess air ratio of 1 or more is supplied to the catalyst 7. FIG.
It is a temperature rise characteristic diagram of water when 1.5 L of water put in a 1.3 kg-weight aluminum pan is heated using the combustion device of the present embodiment. From this temperature-raising characteristic, the heating efficiency was 66% and the radiation efficiency was 50% or more, and a very high heat utilization efficiency twice or more that of the flame combustion method was obtained.

In the present embodiment, after the temperature of the vicinity of the upstream surface of the catalyst body 7 is increased by the flame formed on the upstream side of the catalyst body 7, the supply of fuel is temporarily stopped to extinguish the flame.
A method is adopted in which the supply of fuel is started again to shift to catalytic combustion, but a space sufficient to form a flame in a part near the central portion between the catalyst body 7 and the downstream surface of the air introduction porous body 12 is adopted. Is disposed, and a portion of the vicinity of the downstream surface of the catalyst body 7 is heated by the flame formed here to start catalytic combustion, and the upstream side and the outer peripheral side are repeatedly heated by the combustion heat. A method of shifting to catalytic combustion near the surface may be adopted, and the same effect can be obtained. (Embodiment 3) A third embodiment of the present invention will be described. The present embodiment has the same basic configuration as the second embodiment, except that a plurality of protruding structures are provided on the downstream surface of the air introduction porous body. Therefore, the description will focus on this difference.

FIG. 4 is a sectional view of a main part of this embodiment.
Here, 16 is a plurality of protruding structures provided on the downstream surface of the air introduction porous body 12.

Next, the operation and characteristics of this embodiment will be described with reference to FIG. The combustion exhaust gas passing through the catalyst 7 and the secondary air passing through the air introduction porous body 12
A counter flow is formed between the air and the downstream surface of the air introduction porous body 12, and the air is discharged. In the flow of the mixed gas of the combustion exhaust gas and the secondary air, most of the unburned fuel gas, carbon monoxide, and intermediate products contained in the combustion exhaust gas are diffused and mixed with the oxygen while the catalyst 7 and the air are mixed. The contact with the downstream surface of the introduction porous body 12 is repeated so as to go toward the outer periphery of the catalyst body 7 and the air introduction porous body 12. 7 or a flow in the direction of the downstream surface of the air introduction porous body 12 is formed. As a result, due to the turbulence generated thereby, diffusion and mixing of the unburned fuel gas, carbon monoxide, intermediate products and secondary air contained in the flue gas are promoted. Further, since the frequency of contact of the mixed gas with the downstream surface of the catalyst body 7 increases, it becomes possible to sufficiently mix and react at a shorter distance toward the outer peripheral direction, and the gas is discharged from the vicinity of the outermost peripheral end of the catalyst body 7. Unburned fuel gas, carbon monoxide, and intermediate products contained in the combustion exhaust gas are completely oxidized. As a result, it is possible to provide a catalytic combustion device having better combustion exhaust gas characteristics.

In this embodiment, the air introducing porous body 1
Although the plurality of protruding structures 16 are provided only on the downstream surface of the catalyst body 2, they may be provided only on the downstream surface of the catalyst body 7 or on any of the downstream surfaces, and the catalyst surface area on the downstream surface of the catalyst body 7 increases. Therefore, a more effective catalytic combustion device can be provided. (Embodiment 4) A fourth embodiment of the present invention will be described. The present embodiment has the same basic configuration as that of the second embodiment, except that an oxidation catalyst is supported on a part including the downstream surface of the air introduction porous body. The difference is that the catalyst body and the air introduction porous body are arranged close to each other so that the air-fuel mixture passing through the porous body comes into contact with at least one downstream surface of the catalyst body or the air introduction porous body. Therefore, the description will focus on this difference.

FIG. 5 is a sectional view of a main part of this embodiment.
The operation and characteristics of the present embodiment will be described with reference to FIG. Combustion exhaust gas passing through the catalyst 7 and the air-introduced porous body 1
The secondary air that has passed through 2 forms a counterflow between the downstream surface of catalyst body 7 and the downstream surface of air introduction porous body 12 and is discharged. In the flow of the mixed gas of the combustion exhaust gas and the secondary air, most of the unburned fuel gas, carbon monoxide, and intermediate products contained in the combustion exhaust gas and oxygen are diffused and mixed, and the catalyst 7 and the air are introduced. The contact with the downstream surface of the porous body 12 is repeated so that the porous body 12 is directed toward the outer periphery of the catalyst body 7 and the air introduction porous body 12 and is discharged from the outermost peripheral end. Here, since the temperature of the downstream surface of the catalyst body 7 is 600 ° C. or higher, the temperature can be set at a level downstream of the catalyst body 7 even when a fuel such as natural gas that requires a high temperature for catalytic activity is used. When contacting the surface, all of the unburned fuel gas, carbon monoxide and intermediate products have reached a temperature sufficient for an oxidation reaction to take place.
On the other hand, the temperature of the downstream surface of the air introduction porous body 12 is 550 to 7
When using a fuel such as natural gas which requires a high temperature for its catalytic activity at 00 ° C., it is difficult to completely oxidize unburned fuel gas at the time of contact, but it is difficult to completely oxidize carbon monoxide or intermediate gas. The temperature is high enough to oxidize the product.

As described above, the catalyst body 7 and the air introduction porous body 1
By supporting the oxidation catalyst on any of the downstream surfaces of (2), the surface area of the catalyst is increased, and the frequency of contact of the mixed gas with the supported portion of the oxidation catalyst is also increased. And particularly, it is possible to provide a catalytic combustion device having more excellent combustion exhaust gas characteristics from which carbon monoxide and intermediate products are completely removed.

Further, the combustion reaction on the downstream surface of the catalyst body 7 or the downstream surface of the air introduction porous body 12 generates heat corresponding to the amount of heat generated by the fuel corresponding to the shortage of air, most of which. Is supplied to the catalyst body 7 directly or by radiation from the downstream surface of the air introduction porous body 12, and is transmitted to the upstream side by conduction inside the partition wall, radiation between the opposing partition walls, and the like. Therefore, it is possible to provide a catalytic combustion device having a high heat utilization efficiency equal to or higher than the case where the premixed gas having an excess air ratio of 1 or more is supplied to the catalyst 7.

In this embodiment, the oxidation catalyst is supported on a part including the downstream surface of the air introduction porous body 12, but the oxidation catalyst may be supported on the entire air introduction porous body 12, and the above-described effect can be obtained. It does not hurt. (Embodiment 5) A fifth embodiment of the present invention will be described. This embodiment has the same basic configuration as that of the fourth embodiment, except that at least a portion including the downstream surface of the air-introducing porous body carries an oxidation catalyst containing palladium as a main component. Therefore, the description will focus on this difference.

FIG. 6 is a sectional view of a main part of the present embodiment.
FIG. 7 shows the concentration distribution of unburned fuel gas, carbon monoxide, intermediate products, and oxygen contained in the combustion exhaust gas between the catalyst body 7 and the downstream surface of the air introduction porous body 12. Here, the horizontal axis represents the air introduction porous material 12 from the downstream surface of the catalyst 7.
And the vertical axis represents the concentration of each component.

Next, the operation and characteristics of this embodiment will be described with reference to FIG. The combustion exhaust gas passing through the catalyst 7 and the secondary air passing through the air introduction porous body 12
A counterflow is formed between the downstream surface of the air introduction porous body 12 and the downstream surface of the air introduction porous body 12, and the air is discharged. In the flow of the mixed gas of the combustion exhaust gas and the additional air, most of the unburned fuel gas, carbon monoxide, and intermediate products contained in the combustion exhaust gas and oxygen are diffused and mixed. By repeatedly contacting the downstream surface of the body 12, the catalyst body 7 and the air introduction porous body 12
Toward the outer circumference, and is discharged from the outermost end. Here, the concentrations of unburned fuel gas, carbon monoxide, the combustion components of intermediate products, and oxygen contained in the combustion exhaust gas have distributions as shown in FIG. That is, the vicinity of the downstream surface of the catalyst body 7 is in an excessive combustion component state, and the vicinity of the downstream surface of the air introduction porous body 12 is in an excessive oxygen state. By the way, the oxidation reaction of unburned fuel gas or the like by an oxidation catalyst containing platinum as a main component is easily affected by the oxygen concentration, that is, the catalyst activity tends to decrease in a state of excess oxygen, whereas the oxidation reaction tends to decrease.・ Since the reaction mechanism consisting of surface reaction and desorption is different, the oxidation reaction of unburned fuel gas and the like by the oxidation catalyst containing palladium as a main component is hardly affected by the oxygen concentration. It has almost the same catalytic activity as the excess air ratio of around 1. As described above, by supporting an oxidation catalyst containing palladium as a main component on at least a part or the entire surface including the downstream surface of the air introduction porous body 12, the downstream surface of the air introduction porous body 12 in an oxygen excess state is also provided. It is possible to maintain a high catalytic activity and to provide a catalytic combustion device having more favorable combustion exhaust gas characteristics.

In the present embodiment, the oxidation catalyst is carried on a part including the downstream surface of the air introduction porous body 12, but it may be carried on the whole air introduction porous body 12, and the same effect can be obtained. Is obtained.

Although the present invention has been described above with reference to an example in which the present invention is applied to a combustion device for gaseous fuel supplied to a pipe, the present invention is, of course, not limited to this. That is, the following cases are also included in the present invention.

As a fuel type, gaseous fuel supplied from a fuel tank or liquid fuel such as kerosene can be used. In the case of gas fuel of high pressure supply such as liquefied gas fuel supplied from a fuel tank, it is not always necessary to add air supply means such as a blowing fan,
Means for sucking and introducing air using a jet pressure of fuel gas, such as a nozzle and a throat, are added. When liquid fuel is used, a means for vaporizing the liquid fuel upstream of the premixer is added.

Although a ceramic honeycomb is used for the carrier of the catalyst, the material and the shape are not limited as long as it has a plurality of communication holes through which a premixed gas can flow. A bonded body, a metal honeycomb, a metal nonwoven fabric, a braided body of ceramic fibers, and the like can be used.
It can be set arbitrarily according to the workability and use of the material. The active component is generally a precious metal such as platinum, palladium, or rhodium, but may be a mixture of these metals, another metal or an oxide thereof, or a mixed composition thereof, and may be a fuel. It is possible to select an active ingredient according to species and use conditions. Further, as the air introduction porous body, a ceramic honeycomb is used, but it is sufficient if the air introduction porous body has a plurality of communication holes through which air can be circulated and has poor thermal conductivity. A sintered body or the like can also be used.

A heat ray transmission window made of crystallized glass is provided at a position facing the upstream surface of the catalyst body. Any heat ray transmission window may be used, and for example, quartz glass can be used. In place of the heat ray transmission window, a secondary radiator having a high surface emissivity and a material having good heat conductivity, or a radiation heat receiving member provided with a heat medium flow path made of a copper pipe or the like may be used. It may be installed, and in any case, the same effect as described above can be obtained.

Although a direct ignition system downstream of the catalyst using an electric heater is used as an ignition means, a piezoelectric ignition device is used as an igniter for starting flame combustion. It is an effective means to make it happen.

[0043]

As is apparent from the above description, the catalytic combustion device according to the present invention has the advantages of good combustion exhaust gas characteristics, safety and compactness.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional configuration diagram of a combustion device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a main part of a combustion device according to a second embodiment of the present invention.

FIG. 3 is a graph showing a temperature rise characteristic of water during heating by the combustion device.

FIG. 4 is a cross-sectional configuration diagram of a main part of a combustion device according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing a main part of a combustion apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing a main part of a combustion apparatus according to a fifth embodiment of the present invention.

FIG. 7 is a concentration distribution of a combustion component and oxygen between a catalyst body and an air introduction porous body of the combustion apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air supply fan 2 Combustion air flow control valve 3 Fuel flow control valve 4 Mixer 5 Premixed air inlet 6 Premixed air chamber 7 Catalyst 8 Heat ray transmission window 9 Secondary air flow control valve 10 Air inlet 11 Air Chamber 12 Air-introduced porous body 13 Ignition device 14 Combustion exhaust gas passage 15 Combustion exhaust gas outlet 16 Projecting structure 20 Back of device

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Tetsuo Terashima 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 3K065 TA04 TA14 TB02 TB08 TC03 TD01 TD04 TD05 TE02 TF03 TG01 TH01 TH17 TK02 TK04 TK06 TP09 3K091 AA03 AA17 AA20 BB05 CC02 CC06 CC22 DD01 DD10 FB05 FB12 FB32 FB43 FB66

Claims (5)

[Claims] 1. A catalyst body having an oxidation catalyst supported on a substrate having a plurality of communication holes, an air introduction porous body comprising a plurality of communication holes formed of a poor thermal conductor, and an upstream surface of the catalyst body. A premixed gas chamber that forms a space for introducing a premixed gas of the covered fuel and air; a radiant heat transmitting body or a heat receiving body provided at a position of the premixed gas chamber facing the catalyst body; An air chamber that forms a space that covers the upstream surface of the introduction porous body and introduces air, and a combustion exhaust gas passage that discharges combustion exhaust gas that has passed between the catalyst body and the air introduction porous body to the outside, A catalytic combustion device, wherein a downstream surface of a catalyst body and a downstream surface of the air introduction porous body are arranged to face each other. 2. An oxidation catalyst containing platinum is carried on the catalyst body, and an excess air ratio of the premixed gas introduced into the premixed gas chamber is 1 or less and is introduced into the air chamber. The total air excess ratio to which air is added is 1 or more, and after the flue gas that has passed through the catalyst body and the air that has passed through the air introduction porous body are mixed, so as to contact the downstream surface of the catalyst body, The catalytic combustion device according to claim 1, wherein the catalyst body and the porous air body are arranged close to each other. 3. The catalytic combustion device according to claim 2, wherein a plurality of projecting structures are formed on a downstream surface of at least one of the catalyst body and the air introduction porous body. 4. An oxidation catalyst is carried on at least a part including the downstream surface of the air introduction porous body, and after the combustion exhaust gas passing through the catalyst body and the air passing through the air porous body are mixed, The catalytic combustion device according to claim 2, wherein the catalyst body and the porous air body are arranged close to each other so as to contact at least one downstream surface of the catalyst body or the porous air body. 5. . 5. The catalytic combustion device according to claim 4, wherein the oxidation catalyst supported on the air-introduced porous body contains palladium.