JP3568314B2 - Heating equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heating device required for a heater, a water heater, an air conditioner, and the like.
[0002]
[Prior art]
As a heating method, it is typically known to use electric heating and combustion heating. A general method for electric heating is to generate heat by supplying electricity to a resistance wire. The combustion heating includes flame combustion and flameless combustion using a catalyst. In both cases, fuel and air are mixed and burned to generate heat. In addition, devices such as an oil fan heater that uses both an electric heater and combustion have been sold.
[0003]
[Problems to be solved by the invention]
However, when electric heating generates a large current, the cost and operating cost of the equipment increase. On the other hand, combustion heating can economically generate a large amount of heat, but has problems of generation of odor of exhaust gas, particularly odor at the time of ignition, and instability of combustion in a small combustion region. In addition, equipment using both combustion and an electric heater does not solve the problem of combustion exhaust.
[0004]
The present invention considers such a problem of the conventional heating device, and realizes a heating device that can cope with a large fluctuation of a heating load.Also, when heating is started or when the temperature is low, a high output is generated by combustion, and heating is performed. When the load is low, it is possible to heat with electric heat, clean the exhaust at the time of ignition in combustion, share the catalyst preheating power supply in catalytic combustion, and reduce the effect of low NOx. It is an object to provide a heating device for providing.
[0005]
[Means for Solving the Problems]
The present invention includes a fuel supply unit, a blower for supplying combustion air, a combustion chamber for the fuel, an electric heater provided in the combustion chamber, and a heat exchange unit provided in the combustion chamber. The heat exchange unit is heated only by the heat generated by the electric heater in the small area, and the electric heater is energized in the large heat area to heat the combustion chamber, and then the combustion is started to start the heat exchange unit. Heating was adopted.
[0006]
The reason that the odor is generated at the start of combustion is that the reaction intermediate product is discharged because the flame is cooled in a cold combustion chamber. If the combustion chamber is heated in advance by an electric heater, no odor is generated. Further, when the amount of heating is sufficient, if the combustion flame is reduced, the temperature of the flame becomes low and combustion becomes unstable. This increases the intermediate products of the exhaust and, in some cases, causes a misfire. In the conventional heating device, it was necessary to frequently turn on and off the combustion to lower the average combustion amount. However, in the present invention, when the output is low, the electric heater is heated, so that a low output can be obtained very easily. Also, when the combustion state is set again, the exhaust characteristics are not deteriorated because the heating is performed.
[0007]
Further, as shown in claim 2, the electric heater is energized and the fuel is supplied and burned in the region where the heating amount is small, and the electric heater is energized in the region where the heating amount is large to heat the combustion chamber. After that , by supplying more fuel than the region with a small amount of heating without heating the electric heater and starting combustion to heat the heat exchange part, good exhaust characteristics at ignition and stability of combustion can be obtained. Can be This is because the heat of the electric heater compensates for the decrease in the flame temperature of the small combustion. Although this method cannot cope with lower output than claim 1, the electricity bill can be saved as compared with using all electricity. It is also reasonable to use the inventions of claims 1 and 2 together.
[0008]
When a catalyst for combustion is provided in the combustion chamber, the catalyst is first heated to the activation temperature by an electric heater. This is because the catalyst does not react at room temperature. This method has safety, low NOx, and other effects because there is no flame. Even when the output is low, the catalyst is controlled to a temperature higher than the temperature at which the active temperature is maintained, and the exhaust gas is clean even when the output shifts to the high output again. The combustion may all be reacted with a catalyst, or the unburned matter of the exhaust gas after the flame combustion may be burned with the catalyst.
[0009]
Further, according to the fifth and sixth aspects of the present invention, the exhaust becomes cleaner, and the safety as if only an electric heater is provided because there is no flame can be secured.
[0010]
[Embodiment of the present invention]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0011]
(Embodiment 1)
The first embodiment of the present invention will be described with reference to FIG. An air-fuel mixture is formed in a mixing unit 3 of the fuel gas supplied from the fuel supply unit 1 and the combustion air sent from the combustion blower 2. The fuel supply amount is 5 kW, and either gaseous fuel or liquid fuel may be used. The mixture flows into a combustion chamber 4 provided downstream of the fuel mixing section 3. The combustion chamber 4 is provided with a flame hole 5, an igniter 6 by discharge, and an electric heater 7 having an output of 2 kW. A hot water pipe 9 is provided on the heat exchange fins 8 downstream of the combustion chamber 4 to recover heat. A temperature detector 10 is provided inside the combustion chamber 4. The hot water in the hot water pipe 9 is circulated by a circulation pump 11 through a hot water path 13 between the combustion chamber 4 and the heat radiation heat exchanger 12. The radiator heat exchanger 12 is provided with a blower 14 for sending warm air into the room. The hot water path 13 is provided with a hot water temperature detector 15. The heat radiating means may be such a water path or an air-cooled fin.
[0012]
The operation of the present invention in such a configuration will be described. Electricity is supplied to the electric heater 7 to heat the flame hole 5 and the inner surface of the combustion chamber 4. After the inner surface of the combustion chamber 4 reaches a predetermined temperature, the energization of the electric heater 7 is stopped, and the fuel supply, the air blowing, and the operation of the igniter 6 are started. The air-fuel mixture sent from the mixing section 3 burns in the flame holes 5. At this time, since the temperature of the combustion chamber 4 has risen to 200 ° C. or higher, the ignitability is good, and the unburned gas in the exhaust gas at the time of ignition is small. When the temperature of the hot water path 13 reaches a predetermined heating temperature in such a state, the blower 14 is operated to blow hot air into the room. When the indoor temperature rises and the heating load decreases, the hot water temperature rises. This is detected by the hot water temperature detector 15, and the combustion is stopped. Electricity is supplied to the electric heater 7, and the combustion blower 2 is rotated at a low speed. The hot water maintains a predetermined heating temperature. When the heating load further decreases and the hot water temperature rises, the amount of electricity supplied to the electric heater 7 is reduced. When the heating load increases, the supply of fuel is started. Even when fuel is supplied, the combustion chamber 4 is at a high temperature, so that exhaust gas at the time of reburning is also clean.
[0013]
(Embodiment 2)
Claim 2 of the present invention will be described with reference to FIG. Even if the supply of fuel is changed, the amount of heat can be changed from 5 kW to 2 kW. If it is less than 2 kW, combustion becomes unstable, and a phenomenon such as flashback, lift or an increase in CO occurs depending on the air-fuel ratio. In the previous example, heating of 2 kW or less was performed by electric heat. However, it is also possible to energize while burning to save electricity. For example, when the combustion amount is 1 kW, the flame is cooled and the combustion becomes unstable, but when 500 W is supplied, the flame becomes stable. The total calorific value is 1.5 kW, and the range of response to the heating load is larger than when simply adjusting the fuel supply amount.
[0014]
(Embodiment 3)
Claim 3 of the present invention will be described with reference to FIG. A honeycomb-shaped purification catalyst 16 is provided downstream of the combustion chamber 4. Other configurations are the same as those of the first embodiment. At the start of combustion, an electric heater 7 heats the inside of the combustion chamber 4, particularly the purification catalyst 16. The purifying catalyst 16 has a honeycomb structure of 300 cells / square inch. The thickness in the flow direction is 20 mm. The honeycomb carrier is formed by molding cordierite or lime aluminate, and carries a platinum group metal catalyst. The honeycomb hole is a square having a side of 0.6 mm square.
[0015]
Since this is made of ceramic and has a small heat capacity, the temperature rises to 500 ° C. by the electric heater 7. For this reason, unburned gas generated when the flame hole 5 is ignited at the start of combustion reacts with this catalyst and is oxidized, so that odor is almost eliminated.
[0016]
Although a high output is obtained by combustion by 5 kW, the operation when the heating load is reduced is the same as that of the first embodiment, and the electric heater 7 is energized to output 2 kW. If such a method is applied to the second embodiment, it is possible to further reduce the combustion amount. This is because even if the flame is unstable and CO is generated, the purification catalyst heated by the electric heater 7 completely oxidizes the exhaust gas. Also, during combustion, the catalyst oxidizes the CO that generates the flame, so that the combustion exhaust gas is always clean.
[0017]
(Embodiment 4)
The invention according to claim 4 will be described with reference to FIG. A mixed air hole 17 is provided downstream of the fuel supply unit 1, the combustion blower 2, and the mixing unit 3. Although no ignition means is used, an electric heater 7 for heating the combustion catalyst 18 is provided. The combustion catalyst 18 is a honeycomb, but has a length of 200 mm, which is longer than that of the third embodiment. This is to make it possible to burn the entire amount here. Downstream of this is a hot water pipe 9.
[0018]
With such a configuration, the electric heater 7 is energized and the upstream of the combustion catalyst 18 is heated. The temperature detection unit 10 of the combustion unit detects that the catalyst 18 has reached a predetermined activation temperature, and stops energization of the electric heater 7. When the surface temperature of the electric heater 7 becomes lower than the ignition temperature, the air-fuel mixture Is supplied, the air-fuel mixture starts a catalytic reaction upstream of the combustion catalyst 18. When the amount of combustion and the amount of air gradually increase, the entire combustion catalyst 18 burns. The excess air ratio is preferably 2 or more in order to prevent deterioration of the catalyst due to high temperature.
[0019]
When the heating load is reduced in such a combustion section configuration, the fuel supply is reduced. Alternatively, when the heating load further decreases, the electric heater 7 is energized to heat the hot water with electric heat. At the time of re-combustion, as long as the catalyst is kept at the activation temperature, fuel can be supplied as needed to switch to high output by combustion. In this method, since there is no flame, there is no generation of combustion noise and NOx, and safety as if everything is performed by electricity can be obtained.
[0020]
(Embodiment 5)
Claim 6 will be described with reference to FIGS. As shown in FIG. 4, the fuel gas supplied from the fuel supply unit 1 and the combustion air sent from the combustion blower 2 are mixed in the mixing unit 3 to form an air-fuel mixture. The air-fuel mixture flows into the first catalytic combustion section 19 provided downstream of the mixing section 3 and reacts with the first catalytic body 22 of the first catalytic combustion section 19. That is, as can be seen from FIG. 5 showing a cross section of the first catalytic combustion section 19, a thin plate-shaped first fin 20 provided on the heat receiving fin 20 protruding from the inner surface of the first catalytic combustion section 19 via the gap 21. The mixture reacts with the catalyst 22. A first hot water pipe 24 is provided on the outer periphery of the first catalytic combustion section 19 made of an aluminum alloy to recover heat. The first catalyst body 22 is formed by coating a heat-resistant iron alloy with γ-alumina, and carrying a platinum group metal catalyst such as platinum or palladium. A second catalytic combustion section is provided downstream of the first catalytic combustion section 19, and a second catalyst body 23 having a honeycomb structure is provided here. The electric heater 7 is provided between the first catalytic combustion section 19 and the second catalytic combustion body 23. An electric heater may also be provided upstream of the first catalytic combustion section 19 so as to be linked. The inner wall of the second catalyst body 23 is lined with a heat insulating material.
[0021]
The fin 8 and the second hot water pipe 9 for exhaust heat recovery are provided downstream of the second catalyst body 23, and communicate with the first hot water pipe 24.
[0022]
The operation of the present invention in such a configuration will be described. Electric power is supplied to the electric heater 7 to simultaneously heat the first catalyst body 22 and the second catalyst body 23 to start catalyst preheating. The downstream of the first catalyst body 22 and the upstream of the second catalyst body 23 are heated. After the catalysts 22 and 23 reach a predetermined activation temperature, the power supply to the electric heater 7 is stopped, and the supply of fuel is started. The air-fuel mixture sent from the mixing section 3 passes through the first catalytic combustion section 19. The activation temperature differs depending on the type of fuel or catalyst, for example, about 300 ° C. for propane gas, higher for methane and lower for kerosene. In order to heat the catalyst to the activation temperature, the surface temperature of the electric heater is preferably 600 ° C. or higher.
[0023]
The air-fuel mixture firstly partially reacts downstream of the first catalyst 22, and the unreacted fuel that has passed through the first catalyst 22 starts to react upstream of the second catalyst 23. Since the second catalyst body 23 is at a high temperature, the unreacted gas reacts here, and the final exhaust gas contains almost no unburned gas.
[0024]
In the first catalytic body 22, the catalyst adsorbs gas and oxygen and reacts on the surface of the catalyst, so that flameless combustion occurs and the first catalytic body 22 becomes high in temperature due to the combustion heat. It is transmitted to. 75% of the energy of the fuel supplied in the first catalytic combustion section 19 is burned, and 80% of the burned energy is transferred from the fins 20 to the first hot water pipe 24. That is, 60% (= 75 × 80%) of the supplied fuel energy is transferred to water here. The exhaust gas discharged from the first catalytic combustion unit 19 has 25% (= 100% -75%) of unburned fuel and 15% (= 75% -60%) of exhaust heat with the supplied fuel energy being 100%, A total of 40% remains. When the temperature of the second catalyst body 23 becomes low, the unburned fuel hardly reacts here, so that heat exchange is not performed here. Therefore, the exhaust gas from the second catalytic combustion body 23 after all the unburned fuel has burned has 40% of the supplied energy as exhaust heat. Next, the heat is recovered by the second hot water pipe 9 having the fins 8. The heat exchange rate here was 70%. The heat recovered by the second hot water pipe 9 is 28% (= 40% × 70%). That is, the total thermal efficiency of the first hot water pipe 24 and the second hot water pipe 9 was 88% (60% + 28%) in total.
[0025]
When the catalytic combustion device is operated at the same combustion load factor (the amount of combustion per combustion chamber volume) as the flaming combustion device, the temperature of the catalyst becomes 1200 ° C. or more, and the heat resistance life of the catalyst is significantly shortened. Therefore, in Embodiment 4, a large catalyst is used. However, in the present embodiment, the first catalyst body 22 has a relatively low temperature because the fin 20 which is the heat exchange section is directly covered by the catalyst body, and heat is directly transferred from the heat generated by the catalyst to the heat receiving section. Get higher.
[0026]
Also in this embodiment, if the heating load decreases and the hot water temperature rises too high, the fuel supply amount must be reduced. The lower limit of combustion is 2 kW at which the catalyst becomes lower than the activation temperature. Here, the combustion is stopped and the electric heater 7 is energized again to heat the hot water. Since the electric heater can control from 2 kW to 0, it can cope with a large fluctuation of the heating load. However, if the activation temperature of the reburning catalyst is maintained, the combustion can be restarted at any time, and a rapid increase in the heating load can be handled. Even if the temperature is lower than the activation temperature, clean exhaust during reburning will not be impaired if a slight preheating time is provided by re-energization.
[0027]
The control of switching between combustion and electricity according to the first to fourth embodiments is performed based on the outside air temperature and the indoor temperature. Alternatively, it may be selected according to the application, such as by detecting the temperature of hot water.
[0028]
【The invention's effect】
The effects of the present invention described above are as follows. By realizing a heating device that can cope with a large fluctuation in the heating load, it is possible to generate a high output by combustion at the start of heating or when the temperature is low, and to heat with electric heat when the heating load is low.
[0029]
In addition, since the exhaust gas at the time of ignition in combustion can be made clean, adverse effects peculiar to combustion are reduced.
[0030]
Further, in the catalytic combustion, the preheating power source for the catalyst can be shared and the effect of low NOx is brought about.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a combustion apparatus according to one embodiment of the present invention.
FIG. 2 is a longitudinal sectional view showing a combustion apparatus according to a third embodiment of the present invention.
FIG. 3 is a sectional view of a fourth embodiment of the present invention.
FIG. 4 is a sectional view of a sixth embodiment of the present invention.
FIG. 5 is a sectional view of a first catalytic combustion section according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel supply part 2 Combustion blower 3 Mixing part 4 Combustion chamber 5 Flame hole 6 Igniter 7 Electric heater 8 Heat exchange fin 9 Hot water pipe 10 Temperature detection part 11 Circulation pump 12 Radiation heat exchanger 13 Hot water path 16 Purification catalyst 17 mixed pores 18 combustion catalyst 22 first combustion catalyst 23 second combustion catalyst 24 second hot water pipe

Claims (6)

A fuel supply unit, a blower for supplying combustion air, a combustion chamber for the fuel, an electric heater provided in the combustion chamber, and a heat exchange unit provided in the combustion chamber; A heating unit that heats the heat exchange unit only by the heat generated by the electric heater and, when the amount of heating is large, burns after energizing the electric heater to heat the heat exchange unit. A fuel supply section, a blower for supplying combustion air, a combustion chamber for the fuel, an electric heater provided in the combustion chamber, and a heat exchange section provided in the combustion chamber, wherein the heating amount is small. Heats the heat exchange section by energizing the electric heater and supplying and burning fuel, and when the heating amount is large, energizes the electric heater and then heats without energizing the electric heater. A heating device characterized in that the heat exchange section is heated by supplying more fuel than in the case of a small amount and performing combustion. The combustion chamber includes a flame hole and an ignition means, the electric heater is provided downstream of the flame hole, and further includes a purifying catalyst downstream of the electric heater. 3. The heating device according to claim 1, wherein the heating device is provided downstream of the medium. The heating device according to claim 1, further comprising a combustion catalyst downstream of the electric heater, wherein the combustion catalyst is heated by the electric heater to start a catalytic reaction with the combustion catalyst. 5. The heating device according to claim 3, wherein the combustion chamber temperature when the combustion amount is small is substantially the same as the combustion chamber temperature before the start of combustion heated by the electric heater. A first catalytic combustion section provided in the combustion chamber, a first heat exchange section provided in the first catalytic combustion section, a heat receiving fin provided in the first catalytic combustion section, and a fin provided in the fin. A first catalytic body, a second catalytic combustion section provided downstream of the first catalytic combustion section, and a second catalytic body having a larger geometric surface area than the first catalytic body provided in the second catalytic combustion section. A second heat exchange unit communicating with the first heat exchange unit provided downstream of the second catalyst body; an electric heater provided downstream of the first catalyst body; A heating unit for supplying fuel after heating the first and second catalyst bodies to start catalytic combustion.

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