JP3645029B2 - Catalytic combustion device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention mainly relates to a catalytic combustion apparatus applied to domestic or business hot water supply and heating.
[0002]
[Prior art]
A catalyst that applies a precious metal catalyst such as platinum or palladium to a carrier such as cordierite that is catalytically combusted, and a heat exchanger is installed to transfer the combustion heat to a fluid to be heated such as water. Combustion devices have been proposed. Since catalytic combustion has a low combustion temperature, there is a great advantage that nitrogen oxides (hereinafter referred to as NOx) are hardly generated, lean combustion is possible, and combustion stability is excellent. At the start of catalytic combustion, the preheated burner is used to flame-combust the mixed gas of fuel gas and air to heat the catalyst body to the activation temperature or higher, and then the supply of the mixed gas is stopped to extinguish the flame of the preheated burner. Again, the air-fuel mixture is supplied and the catalyst is combusted, or as another method, the temperature of the catalyst body is raised by an electric heater or the like without causing the flame combustion, and then the air-fuel mixture is passed through the catalyst body and the catalyst is combusted. It was. In addition, in order to increase hot water supply and heating capacity, a method of increasing the temperature of the catalyst body within a range in which deterioration of the catalyst can be suppressed or increasing the red hot area of the catalyst body has been applied.
[0003]
[Problems to be solved by the invention]
However, the conventional catalytic combustion apparatus has the following problems. First, catalytic combustion has the great advantage of not generating NOx, but the combustion temperature is low, so if you try to increase the amount of heat exchange with the fluid to be heated, the catalyst body becomes large and it is difficult to downsize the entire device In the case of liquid fuel, after vaporization, the fuel was easily recondensed and tar was easily generated. In addition, after the flame combustion is performed with the preheating burner at the start of catalytic combustion, the supply of the air-fuel mixture is stopped, the flame of the preheating burner is extinguished, and the method of supplying the air-fuel mixture and catalytic combustion again tends to be complicated. In addition, when the temperature of the catalyst body is increased with an electric heater or the like without burning the flame, there is a problem that the startup time becomes long. Further, if the catalyst body is enlarged or the heat exchange amount to the fluid to be heated is increased, the combustion stability becomes insufficient particularly in the low combustion amount region, and the combustion amount variable range (hereinafter referred to as TDR) is increased. It was difficult to expand.
[0004]
In consideration of the problems of the conventional catalytic combustion apparatus, the present invention can suppress recondensation and tar generation of liquid fuel while maintaining radiant heat transfer characteristics to the radiation heat receiving body. An object of the present invention is to provide a catalytic combustion apparatus that does not hinder the combustion reaction on the upstream surface and can ensure combustion stability even when the amount of heat exchange with the heated fluid is increased. is there.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides, as a first means, a catalyst body having air permeability, a radiation heat receiving body having a heat receiving surface facing the upstream surface of the catalyst body, and a heat exchange section provided in the radiation heat receiving body. And a vaporizer for the liquid fuel to be sent to the catalyst body, and a catalyst combustion apparatus provided with a heat ray transmitting body positioned through the heat receiving surface and space on the catalyst body side of the radiation heat receiving body.
[0006]
As a second means, a catalyst body having air permeability, a radiation heat receiving body having a heat receiving surface facing the upstream surface of the catalyst body, a vaporizing portion of liquid fuel to be sent to the catalyst body, and a back surface of the heat receiving surface of the radiation heat receiving body The catalytic combustion apparatus is provided with a heat exchanging portion positioned via a thermal resistor.
[0007]
As a third means, a catalyst body having air permeability, a radiation heat receiving body having a heat receiving surface facing the upstream surface of the catalyst body, a heat exchanging portion provided in the radiation heat receiving body, and a downstream side of the catalyst body are arranged. The auxiliary catalyst body and an electric heater positioned between the catalyst body and the auxiliary catalyst body are provided, and the electric heater is energized at the start of combustion. After heating the catalyst body and the auxiliary catalyst body, the electric heater is energized. The catalyst combustion apparatus is stopped and, after a predetermined time, supplies an air-fuel mixture to perform catalytic combustion.
[0008]
As a fourth means, a catalyst body having air permeability, a radiation heat receiving body having a heat receiving surface facing the upstream surface of the catalyst body, a heat exchanging portion provided in the radiation heat receiving body, and a downstream side of the catalyst body. An auxiliary catalyst body and an ignition means positioned between the catalyst body and the auxiliary catalyst body, supplying an air-fuel mixture almost simultaneously with the operation of the ignition means at the start of combustion, and attaching a flame to the downstream surface of the catalyst body, A catalytic combustion apparatus that shifts from flame combustion to catalytic combustion is used.
[0009]
As a fifth means, the heat exchange part in the vicinity of the radiation heat receiving body and the exhaust gas heat exchange part on the downstream side of the catalyst body are made independent, and the heated fluid in the heat exchange part and the heated fluid in the exhaust gas heat exchange part are different fluids. The catalytic combustion apparatus.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
The first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the first embodiment. The main parts of the catalytic combustion apparatus of the first embodiment are a catalyst body 1, a catalyst body support 2, a combustion chamber wall 3, an electric heater 4, an electric heater support 5, an auxiliary catalyst body 6, an auxiliary catalyst body support 7, and an auxiliary combustion chamber wall. 8, a radiation heat receiving body 9, a heat exchanging portion 10, a heat ray transmitting body 11, and a heat ray transmitting body support 12. The catalyst body 1 and the auxiliary catalyst body 6 are made by supporting a noble metal catalyst such as palladium or platinum using a cordierite honeycomb having air permeability as a carrier. The auxiliary catalyst body 6 is provided on the downstream side of the catalyst body 1, and the electric heater 4 is positioned between the catalyst body 1 and the auxiliary catalyst body 6. The radiant heat receiving body 9 is provided on the upstream side of the catalyst body 1 so as to face the catalyst body 1 so that the radiant heat receiving body 9 is likely to receive radiation, and the radiant heat receiving body 9 is provided with a heat exchanging portion 10. The heat ray transmitting body 11 is made of glass, and is provided on the catalyst body side of the radiation heat receiving body 9 via a space 11a. An air-fuel mixture supply path 13, an air supply path 14, a fuel supply path 15, and a liquid fuel vaporization section 16 are provided on the upstream side of the radiation heat receiving body 9. On the other hand, an exhaust gas heat exchange section 17 and an exhaust passage 18 are provided on the downstream side of the auxiliary catalyst body 6.
[0011]
Next, the operation of this embodiment will be described. First, the electric heater 4 is energized at the start of combustion, and the catalyst body 1 or the auxiliary catalyst body 6 is heated to the activation temperature or higher, and then the energization to the electric heater 4 is stopped and the surface temperature of the electric heater 4 is set to the ignition temperature. After making it less than, the air-fuel mixture is supplied to the catalyst body 1 and catalytic combustion is performed. The air-fuel mixture is a mixture of fuel vaporized through the fuel supply passage 15 and the liquid fuel vaporization section 16 and air from the air supply passage 14, and mixing is promoted in the air-fuel mixture supply passage 13. During catalytic combustion, the upstream surface of the catalyst body 1 is heated red, and radiant energy is injected upstream. The radiant energy is absorbed by the radiant heat receiving body 9 and converted back into thermal energy, whereby radiant heat is transferred from the catalyst body 1 to the radiant heat receiving body 9, and then the radiant heat receiving body 9 is subjected to heat conduction. Heat is transferred to the fluid to be heated by the provided heat exchange unit 10. Unlike convective heat transfer, radiant heat transfer is performed without disturbing the flow of the air-fuel mixture, so that the combustion reaction on the upstream surface of the catalyst body 1 is not hindered, and the amount of heat exchange with the fluid to be heated is increased. Also, combustion stability can be ensured.
[0012]
In addition, when the heat transfer performance is improved, the temperature of the radiation heat receiving body 9 is lowered. On the other hand, it is conceivable that liquid fuel such as kerosene is allowed to flow in a vaporized state. At this time, in order to prevent the liquid fuel from condensing again on the catalyst side wall surface (heat receiving surface) of the radiation heat receiving body 9 or to easily generate tar, the heat ray transmitting body 11 is placed on the catalyst body side of the radiation heat receiving body 9 in the space 11a. Is provided. Accordingly, the temperature of the catalyst side wall surface of the heat ray transmitting body 11 is increased while maintaining the radiant heat transfer characteristics to the radiation heat receiving body 9, and the recondensation of liquid fuel and the generation of tar are suppressed. The space 11a acts as an air insulation layer. The combustion gas that has passed through the catalyst body 1 is purified by the auxiliary catalyst body 6, exhaust heat is recovered by the exhaust gas heat exchange unit 17, and then exhausted from the exhaust passage 18.
[0013]
Further, by pressurizing the space 11a between the heat receiving surface of the radiation heat receiving body 9 and the heat ray transmitting body 11 with a fan or the like that blows air for combustion, the mixture is prevented from flowing into the space 11a. The recondensation and tar generation of the liquid fuel in 11a can be suppressed.
[0014]
As described above, the electric heater 4 is provided between the catalyst body 1 and the auxiliary catalyst body 6, and the electric heater 4 is energized at the start of combustion to heat the catalyst body 1 or the auxiliary catalyst body 6. The energization is stopped, and after a predetermined time, the air-fuel mixture is supplied and the catalyst is combusted, so that there is no abnormal ignition or NOx in the vicinity of the electric heater 4 and the temperature between the catalyst body 1 and the auxiliary catalyst body 6 is kept as a heat retaining region. , Shortening the startup time. Furthermore, since the upstream temperature of the catalyst body 1 does not rise at the time of start-up, the heat does not move to the radiation heat receiving body 9, and the heat of the electric heater 4 can be utilized efficiently for start-up. In particular, by stopping the flow of the fluid to be heated in the heat exchanging unit 10 at the time of start-up, heat transfer to the radiation heat receiving body 9 can be suppressed, so that the start-up time can be further shortened. At the time of catalytic combustion, the auxiliary catalyst body 6 improves the exhaust gas purification performance, raises the temperature of the catalyst body 1, and improves the radiation heat transfer performance to the radiation heat receiving body 9.
[0015]
On the other hand, the air-fuel mixture can be supplied almost simultaneously with the energization of the electric heater 4 at the start of combustion, and a flame can be attached to the downstream surface of the catalyst body 1 to shift from flame combustion to catalytic combustion. In this case, since the preheating of the catalyst body 1 by the electric heater 4 is not required, the rise time for catalytic combustion can be remarkably shortened, and it is not necessary to add a preheating burner, thereby simplifying the structure and control. can do. At this time, the electric heater 4 is merely used as one of the ignition means, and other ignition means such as piezoelectric ignition may be used.
[0016]
Although the thermal efficiency can be improved by providing the exhaust gas heat exchanging portion 17 on the downstream side of the catalyst body 1, the heat exchanging portion 10 in the vicinity of the radiation heat receiving body 9 and the exhaust gas heat exchanging portion on the downstream side of the catalyst body 1 in particular. 17, and the heated fluid in the heat exchange unit 10 and the heated fluid in the exhaust gas heat exchange unit 17 are different fluids (for example, the heated fluid in the heat exchange unit 10 is used as a refrigerant, By using water as the fluid to be heated in the exchange unit 17), adaptability as a heat exchanger can be expanded, heat transfer performance and combustion stability can be easily achieved, and high TDR can be achieved.
[0017]
(Embodiment 2)
Next, a second embodiment of the present invention will be described. FIG. 2 is a cross-sectional view of the second embodiment. The catalytic combustion apparatus of the second embodiment does not have the heat ray transmitting body 11 in the first embodiment, and a thermal resistor 19 is provided between the radiation heat receiving body 9 and the heat exchanging section 10. The thermal resistor 19 suppresses heat conduction and need not be limited in shape.
[0018]
In the second embodiment, the temperature of the side wall surface of the catalyst body of the radiation heat receiving body 9 is set to a temperature at which the liquid fuel does not recondense or generate tar (about 240 ° C. or higher), and the heat exchange amount is maintained. Thus, the heat transfer area of the heat exchange unit 10 is increased. Compared with Embodiment 1, the radiant heat transfer performance from the catalyst body 1 to the radiant heat receiving body 9 is lowered, but it is not necessary to install the heat ray transmissive body 11 (glass), and the cost can be easily reduced.
[0019]
【The invention's effect】
As described above, according to the catalytic combustion apparatus of the present invention, the following effects can be obtained.
[0020]
By providing a heat ray transmitting body through the heat receiving surface and space on the catalyst body side of the radiation heat receiving body, recondensation of liquid fuel and tar generation can be suppressed while maintaining the radiation heat transfer characteristics to the radiation receiving body. . Unlike convective heat transfer, radiant heat transfer is performed without disturbing the flow of the air-fuel mixture, so that the combustion reaction on the upstream surface of the catalyst body is not hindered, and the amount of heat exchange with the fluid to be heated can be increased. Combustion stability can be ensured.
[0021]
In addition, an electric heater is provided between the catalyst body and the auxiliary catalyst body, the electric heater is energized at the start of combustion, the catalyst body or the auxiliary catalyst body is heated, the energization to the electric heater is stopped, and after a predetermined time, By supplying the air-fuel mixture and performing catalytic combustion, there is no abnormal ignition or NOx in the vicinity of the electric heater, so that the temperature can be kept between the catalyst body and the auxiliary catalyst body, and the startup time can be shortened.
[0022]
Also, by attaching a flame to the downstream surface of the catalyst body and shifting from flame combustion to catalyst combustion, preheating of the catalyst body becomes unnecessary, so the rise time to catalyst combustion can be significantly shortened, and the preheating burner Therefore, the structure and control can be simplified.
[0023]
In addition, by making the heat exchange part near the radiant heat receiver and the exhaust gas heat exchange part downstream of the catalyst body independent, the heated fluid in the heat exchange part and the heated fluid in the exhaust gas heat exchange part are different fluids. In addition to being able to expand the adaptability as a heat exchanger, it is easy to achieve both heat transfer performance and combustion stability, and a high TDR is also possible.
[Brief description of the drawings]
FIG. 1 is a sectional view of a catalytic combustion apparatus according to a first embodiment of the present invention. FIG. 2 is a sectional view of a catalytic combustion apparatus according to a second embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 Catalyst body 4 Electric heater 6 Auxiliary catalyst body 9 Radiation heat receiving body 10 Heat exchange part 11 Heat ray transparent body 16 Liquid fuel vaporization part 17 Exhaust gas heat exchange part 19 Thermal resistor

Claims (7)

A catalyst body having air permeability, a radiation heat receiving body located on the upstream side of the catalyst body and having a heat receiving surface facing the catalyst body, a heat exchanging portion provided in the radiation heat receiving body, and the catalyst body A catalytic combustion apparatus, comprising: a vaporizing unit for liquid fuel to be sent; and a heat ray transmitting member disposed at a predetermined distance from the heat receiving surface on the catalyst body side of the radiation heat receiving member and transmitting heat rays. The catalytic combustion apparatus according to claim 1, wherein a space between a heat receiving surface of a radiation heat receiving body and the heat ray transmitting body is pressurized. A catalyst body having air permeability, a radiant heat receiver located on the upstream side of the catalyst body and having a heat receiving surface facing the catalyst body, a vaporization portion of liquid fuel to be sent to the catalyst body, and the radiant heat receiver A catalytic combustion apparatus comprising: a heat exchanging portion provided on a back surface of a heat receiving surface via a thermal resistor. A catalyst body having air permeability, a radiation heat receiving body located on the upstream side of the catalyst body and having a heat receiving surface facing the catalyst body, a heat exchanging portion provided in the radiation heat receiving body, and the catalyst body An auxiliary catalyst body disposed on the downstream side, and an electric heater disposed between the catalyst body and the auxiliary catalyst body, energizing the electric heater at the start of combustion, the catalyst body and the auxiliary catalyst body After heating, the energization to the electric heater is stopped, and after a predetermined time, an air-fuel mixture is supplied to perform catalytic combustion. A catalyst body having air permeability, a radiation heat receiving body located on the upstream side of the catalyst body and having a heat receiving surface facing the catalyst body, a heat exchanging portion provided in the radiation heat receiving body, and the catalyst body An auxiliary catalyst body disposed on the downstream side, and ignition means disposed between the catalyst body and the auxiliary catalyst body, supplying an air-fuel mixture substantially simultaneously with the operation of the ignition means at the start of combustion, A catalytic combustion apparatus characterized in that a flame is attached to a downstream surface of a medium to shift from flame combustion to catalytic combustion. The catalytic combustion apparatus according to claim 1, 3, 4 or 5, wherein an exhaust gas heat exchanging portion is provided downstream of the catalyst body. The heat exchange part near the radiant heat receiver and the exhaust gas heat exchange part downstream of the catalyst body are independent systems, and the heated fluid in the heat exchange part and the heated fluid in the exhaust gas heat exchange part are different fluids. The catalytic combustion apparatus according to claim 6.

Images