JP2001193905A - Catalytic burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive to establish a peculiar combustion detection method because a conventional method for detecting a combustion state based on an ionic current in flame is not applicable to catalytic combustion in nonflammable combustion. SOLUTION: The catalytic burner is provided with a mixed gas feeding part 3 for mixing a fuel with air, a first catalytic body 7-a third catalytic body 11 provided on a downstream of the mixed gas feeding part, an upstream temperature sensor a16 positioned nearby an upstream surface of a catalytic combustion part, and a downstream temperature sensor b17 positioned nearby a downstream surface of the catalytic combustion part. A flow rate of the duel is detected by an output of the downstream temperature sensor b17, and a density of the mixed gas is detected by an output of the upstream temperature sensor a16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to home use,
Alternatively, the present invention relates to a catalytic combustion device applied to hot water supply and heating for business use.

[0002]

2. Description of the Related Art A catalytic combustion apparatus has been proposed in which a catalytic body in which a noble metal catalyst such as platinum or palladium is supported on a base material such as cordierite is catalytically burned, and heat generated during the combustion is used for heating or the like (eg, for example). And JP-A-6-147419).

[0003] In such a conventional catalytic combustion device, a heat exchanging section is provided on the upstream side of a honeycomb-shaped catalyst body so as to receive radiation from the catalyst body. After heating the catalyst body to the activation temperature or higher, the supply of the mixed gas is stopped, the flame of the preheating burner is misfired, and the catalytic combustion is performed by supplying the mixed gas again.

[0004]

The conventional catalytic combustion apparatus has the following problems. First, since catalytic combustion is a combustion method that does not form a flame, there is a problem that the method of detecting the combustion state based on the ion current in the flame cannot be applied as in the past, and as a result, fuel It has been considered difficult to change the flow rate (corresponding to the amount of combustion).

At the start of catalytic combustion, it is necessary to raise the temperature of the catalyst body to an activation temperature or higher. However, after the flame of the preheating burner is ignited, the exhaust gas characteristics deteriorate when the process proceeds to catalytic combustion. There was also a problem that there was something to do.

Further, catalytic combustion has a low combustion temperature,
In order to increase the amount of heat exchange, it is necessary to increase the size of the catalyst body. However, when the size of the catalyst body is large, the combustion stability tends to be insufficient particularly at a low combustion amount, and the combustion amount variable range (TDR) is increased. There is also a problem that it becomes difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and has as its object to provide a catalytic combustion device capable of detecting a fuel flow rate and rapidly increasing the fuel flow rate.

It is another object of the present invention to provide a catalytic combustion apparatus which does not deteriorate the exhaust gas characteristics at the time of transition from startup to catalytic combustion.

In addition, stable combustion can be achieved even when the combustion amount is low,
An object of the present invention is to provide a catalytic combustion device that can easily expand TDR.

[0010]

To achieve the above object, a first aspect of the present invention (corresponding to claim 1) comprises a fuel supply unit for supplying fuel and an air supply unit for supplying air for combustion. A mixed gas supply unit that mixes the fuel and the combustion air to generate a mixed gas; a catalytic combustion unit provided downstream of the mixed gas supply unit; and a vicinity of an upstream surface of the catalytic combustion unit. An upstream temperature sensor disposed and / or a downstream temperature sensor disposed in the vicinity of a downstream surface of the catalytic combustion section, wherein a concentration of the mixed gas is detected based on an output of the upstream temperature sensor; A catalytic combustion device characterized in that a flow rate of the fuel is detected by a temperature sensor.

Further, the second invention (corresponding to claim 2)
Based on the output of the upstream temperature sensor or the downstream temperature sensor, after starting the catalytic combustion device, detects an ignition phenomenon during the catalytic combustion, the catalytic combustion unit,
The present invention is characterized in that the combustion is terminated by detecting the ignition phenomenon.

Further, a third aspect of the present invention (corresponding to claim 3)
Utilizes the output of the upstream sensor or the output difference between the output of the upstream temperature sensor and the output of the downstream temperature sensor to detect the concentration of the mixed gas that becomes oxygen deficient,
The present invention is the invention as described above, wherein the catalytic combustion unit terminates combustion by detecting the concentration of the mixed gas that becomes oxygen-deficient.

Further, the fourth invention (corresponding to claim 4)
Utilizes an output difference between the detection output of the upstream temperature sensor and the detection output of the downstream temperature sensor to detect at least the aging of the catalytic combustion unit, and the catalytic combustion unit
The present invention is characterized in that the combustion is terminated by detecting the aging.

Further, the fifth invention (corresponding to claim 5)
A fuel supply unit that supplies fuel, an air supply unit that supplies combustion air, a mixed gas supply unit that mixes the fuel and the combustion air to generate a mixed gas, and the mixed gas supply unit A catalytic combustion unit provided downstream of the fuel cell, and when changing the flow rate of the fuel during catalytic combustion, the flow rate of the fuel and the combustion rate at a mixed gas concentration lower than the mixed gas concentration during stable combustion. A catalytic combustion device characterized in that after starting to change the flow rate of air, a predetermined mixed gas concentration is set.

Further, a sixth aspect of the present invention (corresponding to claim 6)
When increasing the flow rate of the fuel during the catalytic combustion,
The present invention is characterized in that the flow rate of the combustion air is increased prior to the flow rate of the fuel.

A seventh aspect of the present invention (corresponding to claim 7)
When decreasing the flow rate of the fuel during the catalytic combustion,
The present invention is characterized in that the flow rate of the fuel is reduced prior to the flow rate of the combustion air.

Further, an eighth aspect of the present invention (corresponding to claim 8)
A fuel supply unit that supplies fuel, an air supply unit that supplies combustion air, a mixed gas supply unit that mixes the fuel and the combustion air to generate a mixed gas, and the mixed gas supply unit A catalytic combustion section provided downstream of the apparatus, and when starting up the catalytic combustion apparatus, a flame is formed between the mixed gas supply section and the catalytic combustion section to increase the flow rate of the combustion air. After the flame has been misfired, the mixture is set to a predetermined gas concentration and the process proceeds to catalytic combustion.

A ninth aspect of the present invention (corresponding to claim 9).
A fuel supply unit that supplies fuel, an air supply unit that supplies combustion air, a mixed gas supply unit that mixes the fuel and the combustion air to generate a mixed gas, and the mixed gas supply unit A catalytic combustion section provided downstream of the fuel cell, wherein during the catalytic combustion, the operation is continued while the fuel is intermittently delivered at a predetermined cycle or the delivery is stopped. Device.

According to a tenth aspect of the present invention (corresponding to claim 10), during catalytic combustion, the combustion air is intermittently delivered at a predetermined cycle, or the operation is continued while the delivery is stopped. The present invention is characterized in that:

According to an eleventh aspect of the present invention (corresponding to claim 11), when sending out the fuel and the combustion air during catalytic combustion, the combustion air is caused to flow before the fuel, The present invention is characterized in that when the delivery of the fuel and the combustion air is stopped, the fuel is stopped prior to the combustion air.

The twelfth aspect of the present invention (corresponding to claim 12) further comprises a heat exchange section having a heated fluid passage for passing a fluid to be heated. The present invention is characterized in that the flow rate of the heated fluid passing through the fluid passage is reduced.

[0022]

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

(Embodiment) FIG. 1 is a sectional view of a catalytic combustion apparatus according to an embodiment of the present invention. The main parts of the catalytic combustion device of the present embodiment are a fuel supply unit 1, an air supply unit 2, a mixed gas supply unit 3, a mixed gas ejection unit 4, a radiation heat receiving unit a5,
Heater 6, first catalyst body 7, radiation heat receiving section b8, second catalyst body 9, radiation heat receiving section c10, third catalyst body 11, exhaust heat recovery section 12, exhaust port 13, heat exchange section 14, heated fluid passage Fifteen
It consists of. A temperature sensor a16 is installed near the upstream surface of the first catalyst 7 and a temperature sensor b17 is installed near the downstream surface of the first catalyst 7 (between the first catalyst 7 and the second catalyst 9). .

The first catalyst body 7, the second catalyst body 9, and the third catalyst body 11 are made of a cordierite honeycomb having air permeability and support a noble metal catalyst such as palladium or platinum. The number of honeycomb lattices per unit area of the first catalyst body 7 is smaller than the number of honeycomb lattices per unit area of the second catalyst body 9. The base material of the first catalyst body 7 may be metal or silicon carbide instead of cordierite honeycomb.
Radiation heat receiving portion a5, radiation heat receiving portion b8, radiation heat receiving portion c10,
The exhaust heat recovery unit 12 has a large number of fins parallel to the flow direction, and is all integrated with the heat exchange unit 14.

Next, the operation of the catalytic combustion device according to the present embodiment having the above-described configuration will be described.

First, at the start of combustion, after the heater 6 is energized to raise the surface temperature so as to become an ignition source, combustion air is supplied from the air supply unit 2 and fuel is supplied from the fuel supply unit 1. A flame is formed between the mixed gas outlet 4 and the first catalyst body 7. After a few seconds (within about 5 seconds), the first catalyst body 7 is preheated to the activation temperature or higher, so that the power supply to the heater 6 is stopped, the air flow rate is increased, and the flame is misfired. The concentration is set to start the catalytic combustion in the first catalyst body 7.

At the time of catalytic combustion, the first catalytic body 7 is glowed red,
Radiant energy is emitted. This radiant energy is absorbed by the heat exchange section 14 mainly including the radiation heat receiving section a5, and is converted into heat energy again, so that radiant heat is transferred to the heat exchange section 14.

Further, the heat energy is transferred from the heat exchange section 14 through the heated fluid passage 15 by heat conduction to the heated fluid in the heated fluid passage 15 by convective heat transfer. Since the radiant heat transfer does not disturb the flow, the combustion reaction in the first catalyst body 7 is not hindered, and the combustion stability can be ensured even if the amount of heat exchange with the fluid to be heated is increased.

As the amount of combustion increases, a portion of the fuel reaches the second catalyst 9 without reacting with the first catalyst 7 and starts catalytic combustion. Further, when the amount of combustion is increased, a part of the fuel reaches the third catalyst body 11 and starts catalytic combustion.

In the radiation heat receiving portion b8 and the radiation heat receiving portion c10, the same heat transfer as in the radiation heat receiving portion a5 is promoted.
After the exhaust gas has passed through the exhaust gas recovery unit 12, the exhaust gas is exhausted to the outside through the exhaust port 13.

At the time of catalytic combustion, there is a portion showing the highest temperature inside the first catalyst body 7, so that the temperature sensor a16 and the temperature sensor b17 measuring the exhaust gas temperature show the output affected by the position of the highest temperature. Become like

When the fuel flow rate (corresponding to the amount of combustion) is increased while keeping the concentration of the mixed gas substantially constant, the position of the highest temperature moves to the downstream side, and the amount of generated heat increases. The output of the temperature sensor b17 installed near the surface increases almost in proportion to the amount of combustion. That is, the output of the temperature sensor b17 indicates a high temperature (the temperature on the downstream side is high).
It was found that when the fuel flow rate was high, the temperature was low (the temperature on the downstream side was low) and the fuel flow rate was low. At this time, the output of the downstream temperature sensor b17 is governed by the fuel flow rate and is less affected by the mixed gas concentration.

On the other hand, when the mixed gas concentration is increased while keeping the fuel flow rate substantially constant, the position of the highest temperature moves to the upstream side, so that the output of the temperature sensor a16 increases. That is, in this case, the mixed gas concentration is high when the output of the upstream temperature sensor indicates a high temperature (the upstream temperature is high), and the mixed gas concentration is low when the output indicates a low temperature (the upstream temperature is low). The relationship was found. In particular, the output of the temperature sensor a16 on the upstream side is strongly governed by the concentration of the mixed gas, and if the fuel flow rate does not change significantly, there is almost no need to consider the influence of the fuel flow rate.

As described above, according to the catalytic combustion device of this embodiment, the amount of combustion is detected by the output of the downstream temperature sensor b17, and the concentration of the mixed gas is detected by the output of the upstream temperature sensor a16. Thereby, the combustion state can be accurately grasped. Even with the conventional flame combustion method that detects the combustion state based on the ion current of the flame, it is difficult to accurately grasp the concentration of the mixed gas, and the combustion detection method of the present embodiment has a simple configuration. Excellent detection performance can be secured.

Further, in this embodiment, a flame is formed for preheating the catalyst at the time of startup, but no flame is formed at the time of stable combustion after the transition to catalytic combustion. However, due to abnormalities in the fuel flow rate and air flow rate, local overheating is caused. It is necessary to assume that a fire may occur and lead to ignition. Most of the ignition phenomenon occurs between the mixed gas jetting section 4 and the first catalyst body 7. However, in consideration of the case where a flame adheres near the downstream surface of the first catalyst body 7, the first catalyst body 7 The temperature near the upstream surface or near the downstream surface rises sharply. Therefore, in response to the ignition phenomenon at the time of catalytic combustion after startup, the temperature sensor a16 on the upstream side
Or the output of the temperature sensor b17 on the downstream side, and the combustion is terminated, thereby ensuring reliability.

In the catalytic combustion, lean combustion is also possible.
Although it can cope with a wide range of mixed gas concentrations, if combustion is performed at a gas concentration that causes incomplete combustion (insufficient oxygen), carbon monoxide (CO) and unburned hydrocarbons (HC) are generated even in catalytic combustion.

The present embodiment has been made in consideration of the above-mentioned problem. To avoid such a problem, the position of the highest temperature shifts remarkably to the upstream side in the mixed gas concentration where oxygen becomes insufficient. And the upstream temperature sensor a16
Or the difference between the output of the upstream-side temperature sensor a16 and the output of the downstream-side temperature sensor b17, and terminating the combustion, thereby ensuring safety. According to this method, it becomes possible to cope with an oxygen deficiency state in the room.

Also, the present embodiment focuses on the fact that the position of the highest temperature moves downstream with respect to aging of a member centering on the catalyst body such as the first catalyst body 7 and the like. Output of the temperature sensor b17 or the temperature sensor a1 on the upstream side
By detecting the difference between the output of the temperature sensor 6 and the output of the downstream temperature sensor b17 and terminating the combustion, the reliability as a combustion device can be ensured.

Further, in this embodiment, when changing the fuel flow rate during catalytic combustion, the mixed gas concentration is set to be lower than the mixed gas concentration during stable combustion, and then the fuel flow rate and the air flow rate are changed. By setting to a predetermined mixed gas concentration, the mixed gas concentration locally becomes oxygen deficient, and CO and H
By preventing C from being generated, it becomes possible to maintain good exhaust gas characteristics. Since the catalytic combustion has a wide stable combustion range on the lean combustion side, the range of change in the concentration of the mixed gas can be increased, and the control becomes easy.

For example, when increasing the fuel flow rate (combustion amount), good exhaust gas characteristics can be maintained by increasing the air flow rate ahead of the fuel flow rate.

On the other hand, when the fuel flow rate (combustion amount) is reduced, good exhaust gas characteristics can be maintained by decreasing the fuel flow rate before the air flow rate.

Further, a flame is formed between the mixed gas supply section 3 and the first catalytic body 7 which is a catalytic combustion section at the time of startup, and the flame is misfired by increasing the air flow rate. By shifting to catalytic combustion by setting to, the temperature drop of the first catalyst body 7 can be suppressed between the time when the flame is misfired and the time when the catalyst is shifted to catalytic combustion, so that CO and HC can be hardly generated. . By causing the flame to misfire by increasing the air flow rate, re-ignition of the flame can be reliably prevented.

Also, in the present embodiment, the temperature near the first catalyst body 7 is maintained at the time of the stop by activating or stopping the fuel by intermittently flowing or stopping the fuel at a predetermined cycle during the catalytic combustion. Since the above can be maintained, when the fuel is flowed after a predetermined time, it is possible to directly shift to the catalytic combustion without energizing the heater 6. Since the catalytic combustion causes a surface reaction without forming a flame, the heat capacity of the first catalyst body 7 is increased to suppress the temperature decrease even when the supply of the fuel is stopped, and to shift the catalytic combustion during the resupply of the fuel. Can be promoted.

Furthermore, by continuing the operation while intermittently flowing or stopping not only the fuel but also the air at a predetermined cycle during the catalytic combustion, the heat retaining effect near the first catalytic body 7 is remarkably improved. Since the temperature can be easily maintained at the activation temperature or higher, if the fuel and the air are flowed after a predetermined time, it is possible to smoothly shift to the catalytic combustion without energizing the heater 6. Since the intermittent operation can substantially reduce the combustion amount without deteriorating the exhaust gas characteristics, the variable combustion amount range (TDR) can be expanded. In the flame combustion method, if the supply of fuel is stopped, the flame will be misfired.Therefore, even if the fuel is supplied after a predetermined time, the flame will not be formed, and it is necessary to start up the ignition heater and the ignition plug again to start. There is. Thus, intermittent operation is not possible with the flame combustion method,
This is a unique operation method for catalytic combustion. However, if the intermittent operation is performed under the condition that the ratio of the cycle and the stop time other than the predetermined period is too large even in the catalytic combustion, the temperature of the first catalyst body 7 becomes lower than the activation temperature, and the exhaust gas characteristics deteriorate. Since the intermittent operation cannot be continued, it is desirable that the intermittent operation cycle be within about 3 minutes. Furthermore, if it is configured such that a heat retaining region is easily formed in the vicinity of the first catalyst body 7 as in the present embodiment, it is possible to perform the intermittent operation in various modes.

As described above, when the fuel and the air flow, the air is caused to flow before the fuel, and when the fuel and the air are stopped, the fuel is stopped before the air. If the concentration of the mixed gas locally becomes insufficient for oxygen, CO
, And good exhaust gas characteristics can be maintained.

Further, the present embodiment is provided with a heat exchange section 14 having a heated fluid passage 15, and by reducing the flow rate of the heated fluid in the heated fluid passage 15 during the intermittent operation, the hot water supply device and the hot water When applied to a heating device or the like, it is possible to reduce a hot water supply output, a heating output, and the like, which are heat outputs,
As a device, a wide range of operation capability can be secured.

[0047]

As described above, according to the catalytic combustion device of the present invention, the combustion state can be accurately grasped.
Excellent precision detection performance can be secured with a simple configuration.

Further, it is possible to maintain good exhaust gas characteristics without generating CO and HC.

Further, without deteriorating the exhaust gas characteristics,
The variable combustion amount range (TDR) can be expanded, and a wide range of operation capability can be secured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a catalytic combustion device according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 3 mixed gas supply part 5 radiation heat receiving part a 6 heater 7 first catalyst body 8 radiation heat reception part b 9 second catalyst body 10 radiation heat reception part c 11 third catalyst body 12 waste heat recovery part 14 heat exchange part 15 heated fluid Passage 16 Temperature sensor a 17 Temperature sensor b

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F23N 5/00 F23N 5/00 F 5/02 341 5/02 341Z (72) Inventor Kawasaki Saki ▼ Yoshitaka 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture, Japan Matsushita Electric Industrial Co., Ltd. F term in Matsushita Electric Industrial Co., Ltd. (reference) 3K003 AA01 AB02 AC01 AC05 AC07 BA05 BB07 BC09 CA03 CC01 DA02 EA01 EA02 FA01 FA04 FB05 GA03 3K005 AA06 AA10 AB06 AB07 AB16 AB17 AB19 AC03 BA01 BA05 CA02 DA01 DA05 EA02 3 BD01 BE02 3K052 AA06 AB04 AB06 AB08 AB10 AB11 AB12 AB14 FA01 FA08 3K065 TA04 TA06 TA12 TA18 TA19 TB08 TB12 TB13 TB14 TC02 TC05 TE 01 TK02 TK04 TK09 TN01 TN04 TN13

Claims (12)

[Claims] A fuel supply unit for supplying fuel; an air supply unit for supplying combustion air; a mixed gas supply unit for mixing the fuel with the combustion air; and a downstream of the mixed gas supply unit. An upstream temperature sensor disposed near an upstream surface of the catalytic combustion unit and / or a downstream temperature sensor disposed near a downstream surface of the catalytic combustion unit. An output of a temperature sensor detects the concentration of the mixed gas, and an output of the downstream temperature sensor detects a flow rate of the fuel. 2. The method according to claim 1, wherein an ignition phenomenon at the time of catalytic combustion after the start of catalytic combustion is detected based on an output of the upstream temperature sensor or the downstream temperature sensor, and catalytic combustion is terminated. 2. The catalytic combustion device according to 1. 3. Using the output of the upstream sensor or the output difference between the output of the upstream temperature sensor and the output of the downstream temperature sensor to detect the concentration of the mixed gas that becomes oxygen deficient, The catalytic combustion device according to claim 1, wherein the catalytic combustion is terminated. 4. An output of the downstream temperature sensor or an output difference between an output of the upstream temperature sensor and an output of the downstream temperature sensor is used to detect at least a secular change of the catalytic combustion unit. The catalytic combustion device according to claim 1, wherein the combustion is terminated by detecting an aging change. 5. A fuel supply unit for supplying fuel, an air supply unit for supplying combustion air, a mixed gas supply unit for mixing the fuel and the combustion air, and a downstream of the mixed gas supply unit. A catalytic combustion unit provided, wherein when changing the flow rate of the fuel during catalytic combustion, the flow rate of the fuel and the flow rate of the combustion air at a mixed gas concentration lower than the mixed gas concentration during stable combustion Characterized by setting a predetermined mixed gas concentration after the start of changing the temperature. 6. The catalytic combustion apparatus according to claim 5, wherein when increasing the flow rate of the fuel during the catalytic combustion, the flow rate of the combustion air is increased prior to the flow rate of the fuel. . 7. The catalytic combustion apparatus according to claim 5, wherein, when reducing the flow rate of the fuel during the catalytic combustion, the flow rate of the fuel is reduced prior to the flow rate of the combustion air. . 8. A fuel supply unit for supplying fuel, an air supply unit for supplying combustion air, a mixed gas supply unit for mixing the fuel and the combustion air, and a downstream of the mixed gas supply unit. A catalytic combustion section provided, a flame is formed between the mixed gas supply section and the catalytic combustion section when the catalytic combustion is started, and the flame is misfired by increasing the flow rate of the combustion air. A catalytic combustion device, wherein the mixture is set to a predetermined mixed gas concentration and the process proceeds to catalytic combustion. 9. A fuel supply unit for supplying fuel, an air supply unit for supplying combustion air, a mixed gas supply unit for mixing the fuel and the combustion air to generate a mixed gas, A catalytic combustion section provided downstream of the gas supply section, wherein during the catalytic combustion, the fuel is intermittently delivered at a predetermined cycle, or the operation is continued while the delivery is stopped. Catalytic combustion device. 10. The catalytic combustion according to claim 9, wherein at the time of catalytic combustion, the combustion air is intermittently delivered at a predetermined cycle or the operation is continued while the delivery is stopped. apparatus. 11. When delivering the fuel and the combustion air during catalytic combustion, the combustion air is caused to flow before the fuel, and when the delivery of the fuel and the combustion air is stopped, ,
The catalytic combustion device according to claim 10, wherein the fuel is stopped before the combustion air. 12. A heat exchange unit having a heated fluid passage through which a fluid to be heated is passed, wherein a flow rate of the heated fluid passing through the heated fluid passage is reduced during the intermittent operation. The catalytic combustion device according to claim 9 or 10, wherein the catalytic combustion is performed.