JPH04240307A - Heat generating device - Google Patents

Abstract

PURPOSE:To generate a large quantity of heat by the combustion with no flame by providing a catalyst layer that can be heated by a heater in a plurality of through-holes formed in a hot plate and on the inner wall of a mixing chamber and obtaining the state of high temperature by the reduction caused by supplying a mixture of the gas and air to the catalyst layer. CONSTITUTION:Air is drawn into a mixing chamber 4 by the drawing action of the gas flow blown out of a nozzle 2 in a liquefaction gas cylinder 1 and the air is mixed with the gas uniformly. A hot plate 5 made of aluminium is provided in the downstream of this mixing chamber 4, and into a plurality of through-holes 6 provided in this hot plate 5 the mixture gas is made to flow uniformly. A catalyst layer 7 is provided upstream of the inner wall of the mixing chamber 4 and those through-holes 6, and an electric heater 8 which is heated by a dry battery is provided near the catalyst layer 7 on the inner wall of the mixing chamber to heat the catalyst layer 7. And, the mixture gas through a valve 3 is supplied to the heated catalyst layer 7 and a reaction is made between them to obtain the state of high temperature. After that, the exhaust gas that has finished reaction by going through the through-holes 6 goes through the through-holes 6 without catalyst layer and is discharged.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to plate type cookers, heat insulators, milk boilers, portable water heaters, irons,
The present invention relates to a heat generating device that uses combustion heat as a heat source and can be applied to hair dryers, coffee makers, foot warmers, sesame roasters, sake brewers, etc.

0002

2. Description of the Related Art Stoves that combust fuel gas packed in a liquefied gas cylinder with a flame using a burner are popular and are used for outdoor cooking. Such burners are also used for soldering in piping work, etc. Furthermore, there is a pocket warmer that uses a platinum catalyst as a portable device that uses catalytic combustion. This product brings benzine into contact with a catalyst to cause a catalytic reaction, and is placed inside clothing to provide warmth.

0003

[Problems to be Solved by the Invention] Conventionally used devices using flame combustion have large flames and are suitable for applications in which objects are directly heated with flame. The temperature of the combustion flame is usually 1,200°C to 1,800°C, so it was suitable for rapidly heating objects at high temperatures. Despite these advantages, it had the disadvantage of high flame temperature and a high risk of fire. In order to avoid this danger, it may be possible to form a combustion chamber inside the device and cause the combustion to occur within the device, but this would make the device bulky and would be impractical from a practical standpoint.

On the other hand, in conventional devices using catalytic combustion, since the catalyst enables combustion at a low temperature, it has been possible to create safe devices. However, when a large amount of combustion is generated, the catalyst becomes too high and suffers thermal deterioration, so it has been possible to produce only devices with extremely low calorific value.

[0005]

[Means for Solving the Problems] In order to solve these problems, the present invention has the following configuration. A mixing part for fuel gas and air, a metal hot plate provided downstream of the mixing part, a passage hole for the gas mixed in the mixing part provided in the hot plate, and an inner wall surface of the passage hole. It is characterized by a configuration in which the area ratio of the porous catalyst layer made of a metal oxide that is in close contact with the catalyst layer and the catalyst layer on the inner wall is larger in the upstream direction of the flow of the mixed gas than in the downstream direction.

[0006] Also, in the above structure, a catalyst body is inserted into the passage hole of the hot plate, and the catalyst body faces the inner wall surface without the catalyst layer, and there is a gap between the catalyst body and the inner wall surface of the hot plate. It is characterized by a configuration in which a gas passage section is provided in the.

[0007]

[Operation] In the above structure, the reaction in the passage hole is almost completed in the upstream catalyst layer, and the exhaust gas is discharged through the downstream part of the passage hole where there is no catalyst layer. Here, the reason why a large amount of heat can be generated is that the temperature of the catalyst layer is maintained below the allowable temperature. When a mixture is supplied, the amount of reaction in the catalyst layer increases and the temperature rises, but the temperature does not rise because the hot plate removes the reaction heat of the catalyst through the thin catalyst layer. Furthermore, gas reacts violently upstream of the passage hole, but as it goes downstream, exhaust gas increases and fuel concentration decreases, so the reaction gradually ends. When the reaction is finished, the temperature of the exhaust gas is still high. Therefore, after the reaction is completed, the hot plate must receive the heat retained in the exhaust gas rather than the reaction heat. A catalyst layer downstream of the passage hole is not necessary because it inhibits heat transfer of exhaust heat. That is, the hot plate is heated by direct heat conduction from the catalyst layer upstream where the catalyst layer is at a high temperature, and the hot plate is heated by heat transfer between the exhaust gas and the metal wall inside the passage hole downstream after the reaction has finished.

Furthermore, if a catalyst body is provided downstream of the passage hole in order to increase the amount of combustion, the exhaust gas containing unburned gas that has not been reacted in the catalyst layer upstream of the passage hole will react on the surface of the downstream catalyst body. do. Since the catalyst body is almost separated from the hot plate, it is difficult to be cooled even downstream, and the reaction activation temperature is sufficiently maintained, and the surface generates heat from unburned gas and becomes high temperature. That is, the inner wall surface of the downstream passage hole receives the heat of the upstream exhaust gas through convection heat transfer, and receives the heat generated by the unburned components as radiation from the high temperature surface of the catalyst. Therefore, the downstream heat exchange efficiency is extremely high, and even with a large combustion amount, the device does not become large.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a vertical sectional view (a sectional view taken along the line BB' in FIG. 2) of a heat generating device according to an embodiment of the present invention. FIG. 2 is a horizontal cross-sectional view (cross-sectional view taken along line AA' in FIG. 1). In FIG. 1, 1 is a liquefied gas cylinder such as propane or butane. A valve 3 is provided between the cylinder 1 and the nozzle 2. Air is drawn into the mixing chamber 4 by the gas flow blown out from the nozzle 2 and mixed uniformly. An aluminum hot plate 5 is provided downstream of the mixing chamber 4. The hot plate 5 is provided with five air-fuel mixture passage holes 6. The mixed gas enters the passage holes 6 evenly.

In FIG. 2, a catalyst layer 7 is provided upstream of the passage hole 6.
is formed. The catalyst layer 7 is made by bonding a fiber mat of metal oxide such as alumina or silica with colloidal metal oxide or water glass, and then attaching gamma alumina to the surface of the fiber to increase the surface area. Formed by supporting a noble metal catalyst. In order to increase adhesive strength, it is also preferable to sandblast or form a ceramic spray coating on the aluminum bonding surface. The thickness of the catalyst layer 7 is in the range of 0.5 mm to 3 mm. Passing hole 6
Such a catalyst layer 7 is formed upstream of the hot plate 5, but the inner wall of the hot plate 5 is exposed downstream.

A catalyst layer 7 is also formed on the inner wall of the mixing chamber 4, and this catalyst layer 7 is substantially continuous with the catalyst layers 7 of the five passage holes 6. An electric heater 8 heated by a dry battery is provided adjacent to the catalyst layer 7 of the mixing chamber 4. The operating state of the present invention in such a configuration will be described below.

The heater 8 is heated by the dry battery, and the temperature of the catalyst layer 7 further increases. When the catalyst layer 7 is heated to 500° C., which is the activation temperature of the catalyst, the valve 3 opens and gas is supplied from the nozzle 1. This timing may be determined by providing a thermometer such as a bimetal in the mixing chamber 4 and opening and closing the valve 3 by this operation, or by counting the time and manually opening the valve 3 by the user. The mixture starts to react in the preheated catalyst layer 7 of the mixing chamber 4. The reaction surface becomes hot and gradually spreads throughout the mixing chamber 4, and a reaction begins in the catalyst layer 7 of the downstream passage hole 6. The reaction in the passage hole 6 is almost completed at the upstream catalyst layer 7, and the exhaust gas is discharged through the downstream side of the passage hole 6 where there is no catalyst layer 7. Catalytic combustion in the catalyst layer 7 is also called flameless combustion because there is no flame and the reaction occurs on the surface of the catalyst.

The reason why a large amount of heat can be generated in such an operation is that the temperature of the catalyst layer 7 is maintained at 900° C. or lower, which is the allowable temperature limit of the catalyst metal. When a large amount of air-fuel mixture is supplied, the amount of reaction in the catalyst layer 7 becomes large and the temperature becomes high. However, since the hot plate 5 removes the reaction heat of the catalyst through the thin catalyst layer 7, the temperature does not rise. Moreover, if the catalyst layer 7 is too thin, the temperature of the catalyst will be supercooled by the hot plate 5 and the reaction will stop. This catalyst temperature mainly depends on the amount of combustion per unit area and the thickness of the catalyst layer 7.

[0014] The fibrous porous material is made of aluminum
As a result of experiments by adhering to the passage holes 6 of the hot plate 5 adjusted to 00°C, it was found that even with the adhesive method with the lowest degree of adhesion, if the thickness is 0.5 mm or less, the amount of heat conduction is large and the temperature of the catalyst layer 7 decreases, making it difficult to continue combustion. It is. In addition, the thickness is 3 mm even in the best adhesion state.
If the temperature exceeds that level, the catalyst layer 7 becomes adiabatic and a part of the surface of the catalyst layer 7 becomes too high in temperature, causing problems in terms of heat resistance. The thickness of the catalyst layer 7 is preferably within this range, but the optimal thickness varies depending on the operating temperature of the hot plate 5, so it must be selected depending on the purpose.

Upstream of the passage hole 6, the gas reacts violently, but as it goes downstream, the exhaust gas increases and the fuel concentration decreases, so the reaction gradually ends. When the reaction is completed, the temperature of the exhaust gas is as high as 500°C or higher. Therefore, after the reaction is completed, the hot plate 5 must receive the heat retained in the exhaust gas rather than the reaction heat. Therefore, the catalyst layer 7 is not required downstream of the passage hole 6 because it inhibits the heat transfer of exhaust heat. In other words, the hot plate 5 is heated by direct heat conduction from the catalyst layer 7 upstream where the catalyst layer 7 reaches a high temperature, and the hot plate 5 is heated by heat transfer between the exhaust gas and the inner wall surface of the passage hole 6 downstream after the reaction has finished. be.

Aluminum can be used at a maximum temperature of about 350°C due to its heat resistance, but when used as an iron to generate steam, the temperature is about 120°C, and when the hot plate 5 is used as a cooking device, the temperature is about 200°C. Such temperature adjustment is possible by opening and closing the valve 3 according to the signal from the temperature detection section 9.

Next, FIGS. 3 and 4 regarding different embodiments
I will explain it together. In the configuration shown in FIGS. 1 and 2 described above, when the opening degree of the valve 3 is increased in order to further increase the combustion amount, the flow rate of the gas passing through the passage hole 6 increases. As a result, the amount of fuel gas that cannot be fully reacted in the catalyst layer 7 increases. Furthermore, the heat exchange efficiency also decreases in the downstream exhaust heat recovery section. Therefore, both the catalyst layer 7 and the downstream exhaust heat recovery section must be made longer in proportion to the flow velocity.

This embodiment aims to increase the amount of combustion without increasing the length of the passage hole 6, and to prevent the heat exchange efficiency from decreasing. A catalyst body 10 is provided downstream of the passage hole 6, and this catalyst body 10 is provided at the center of the passage hole 6, opposite to the upstream catalyst layer 7, and the exhaust gas is discharged between the catalyst body 10 and the inside of the hot plate 5. Pass between walls. The catalyst body 10 is partially supported by a support body 11 that is separate from the hot plate 5 but does not impede the flow. The effects of such means are as follows. Exhaust gas containing unburned gas that has not been reacted in the catalyst layer 7 upstream of the passage hole 6 reacts on the surface of the catalyst body 10 downstream. Since the catalyst body 10 is almost separated from the hot plate 5, it is not easily cooled downstream and maintains the reaction activation temperature, and the surface thereof generates heat due to unburned gas and becomes high temperature. That is, the inner wall surface of the downstream passage hole 6 receives the heat of the upstream exhaust gas by convection heat transfer, and receives the heat generated by unburned components as radiation from the high temperature surface of the catalyst body 10. Therefore, the downstream heat exchange efficiency is high and the device does not become large even with a large combustion amount.

Furthermore, if the cross-sectional area of the flow path formed by the hot plate 5 and the catalyst body 10 downstream is smaller than that of the flow path formed by the catalyst layer 7 upstream of the passage hole 6, the catalyst layer 7 radiation is easily transmitted to the hot plate, and the heat transfer of the exhaust gas is also improved. The downstream gas temperature is lower and the flow rate is smaller than the upstream, so there is less resistance to passage, so the resistance does not increase.

Furthermore, if an infrared absorbing coating, for example a ceramic coating having a thickness of about 10 to 50 μm, is formed on the downstream inner wall surface heated by this radiation, the radiant heat transfer is further improved. Moreover, the support body 11 may protrude from the inner wall surface. In this case, since the protrusions play the role of fins, recovery of exhaust heat is further promoted, and the heat of the catalyst body 10 can also be recovered through thermal conduction through the protrusions, resulting in higher efficiency.

In the above embodiment, the aluminum hot plate 5 and mixing chamber 4 are divided into appropriate blocks to facilitate manufacturing. Alternatively, a heat sink may be attached to the outer periphery of the heat plate 5 depending on the purpose. Alternatively, by installing a re-combustion catalyst downstream of the outlet of the passage hole 6 and adding a function to purify the CO emitted when the air ratio falls below the equivalence point, a safer, more efficient and more compact structure can be created. It becomes a heat generating device.

[0022]

As described above, according to the present invention, it is possible to react a large amount of fuel gas in an extremely small hot plate without producing a flame. Therefore, it is possible to provide a small and safe heat generating device with high thermal efficiency that can be applied to portable heating appliances.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view (BB' in FIG. 2) showing the configuration of a heat generating device according to an embodiment of the present invention.

[Figure 2] Horizontal cross-sectional view of the device (A-A' in Figure 1)

[Figure 3
] A vertical sectional view (BB' in FIG. 4) showing a heat generating device according to another embodiment of the present invention.

[Figure 4] Horizontal cross-sectional view of the device (A-A' in Figure 3)

[Explanation of symbols]

1 Cylinder 4 Mixing chamber 5 Hot plate 6 Passing hole 7 Catalyst layer 10 Catalyst body

Claims (2)

[Claims] 1. A mixing part for fuel gas and air, a metal hot plate provided downstream of the mixing part, a passage hole for the gas mixed in the mixing part provided in the hot plate, and a through hole for the gas mixed in the mixing part, and a metal hot plate provided downstream of the mixing part. A heat generating device in which the area ratio of a porous catalyst layer made of a metal oxide that is in close contact with an inner wall surface of a hole and the catalyst layer on the inner wall is larger in an upstream direction in a flow direction of a mixed gas than in a downstream direction. 2. A catalyst body is inserted into a passage hole of a hot plate, the catalyst body faces an inner wall surface without a catalyst layer, and a gas passage portion is provided between the catalyst body and the inner wall surface of the hot plate. The heat generating device according to claim 1, further comprising: