JPH0752011B2 - Catalytic combustion device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a catalytic combustion device used for heating, heating, drying, and the like.

2. Description of the Related Art A so-called premixed catalyst in which a liquid fuel such as kerosene or a gaseous fuel such as city gas is mixed with air and then brought into contact with a catalyst layer for an oxidation reaction to perform flameless catalytic combustion on the surface thereof. Various types of combustion devices have been proposed, mainly for gas fuel, and some have been put into practical use. However, the catalyst layer is generally composed of a honeycomb, mat, or cloth-shaped one layer. Met.

In such a catalytic combustion device, the fuel premixed with air causes an oxidation reaction in the catalyst layer and produces carbon dioxide and water together with the heat of reaction. If the oxygen concentration of the air supplied here is normal (about 21% by volume), the above reaction will be complete, but if it is used continuously for a long time in a semi-enclosed room, or if other combustion equipment is used in that room. It is known that the oxygen concentration in the air gradually decreases in the case of performing the so-called oxygen-deficient state.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the conventional catalytic combustion apparatus, if the oxygen amount is equal to or more than the fuel equivalent amount (theoretical oxygen amount necessary for the reaction), the combustion has a characteristic of substantially continuing the combustion. If the amount of heat generated by the reaction is larger than the amount of heat released and the temperature of the catalyst layer is maintained at a predetermined value or higher, even if the amount of oxygen is the same, combustion will continue even if carbon monoxide and unburned gas are discharged. It has drawbacks.

Because of this, the oxygen concentration in the indoor air decreases, and 18% by volume begins to affect the sick and even the healthy.
Even if it reached 16% by volume, the combustion reaction continued, and there was a significant risk of death of livestock.

The present invention solves the above-mentioned conventional drawbacks and enables a catalytic combustion apparatus capable of detecting an oxygen deficiency state and preventing harmful or malodorous gas due to incomplete combustion, as well as preventing adverse effects on livestock due to the oxygen deficiency itself. To do.

Means for Solving the Problems In order to solve the above problems, the catalytic combustion apparatus of the present invention,
Two catalyst layers provided with temperature detecting means are provided, and a secondary air supply section opened upstream of the downstream catalyst layer is provided, and the amount of air in the air-fuel mixture to be supplied to the upstream catalyst layer is set at a predetermined interval. It is provided with a control means for reducing the inside only at a predetermined rate and stopping the fuel supply when the temperature difference of the catalyst layer detected by the temperature detecting means reaches a predetermined value or less.

Effect The present invention, by the above means, detects the oxygen deficiency state early and surely without causing incomplete combustion when the oxygen concentration in the indoor atmosphere decreases, and before reaching the limit oxygen concentration that affects the human body. It is possible to provide a highly safe catalytic combustion device by stopping combustion.

Example Hereinafter, a catalytic combustion device according to a first example of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, 1 is a fuel tank, 2 is a fuel pump,
3 is a fan for blowing air, 4 is a mixing chamber, and a flame port 5 for preheating and an igniter 6 are provided at the outlet of the mixing chamber 4. Above the flame outlet 5, a main catalyst layer 7 in which a white metal active component is carried on a honey-like ceramic plate whose main component is silica-alumina having a large number of communication holes 7a is provided upright.
A transparent window 8 made of a glass plate is arranged so as to face the upstream surface (front surface). Further, an auxiliary catalyst layer 9 having a large number of communication holes 9a is provided on the downstream side above the main catalyst layer 7. Further, thermocouples 10a and 10b for temperature detection are disposed in contact with the upstream surface of the main catalyst layer 7 and the upstream surface of the auxiliary catalyst layer 9, both of which are connected to a control circuit 11 and this control circuit At 11, the fuel pump 2 and the fan 3 are driven and controlled. A secondary air pipe 12 is provided so as to branch from the outlet of the fan 3 and is connected to a secondary air port 13 opened on the upstream side of the auxiliary catalyst layer 9.

Next, the operation will be described in detail. The fuel (kerosene) supplied from the fuel pump 2 and the air supplied from the fan 3 are
It is vaporized in the mixing chamber 4, and is sufficiently premixed and sent to the upper flame port 5. At the time of ignition, first, ignition is performed at the flame port 5 by the ignition device 6, and flame combustion is started there.
The high-temperature exhaust gas flows to the upper part and raises the temperature of the main catalyst layer 7 and the auxiliary catalyst layer 9. When it is detected by the thermocouple 10a that the temperature of the main catalyst layer 7 has risen to a sufficient temperature, the fuel supply is temporarily stopped, the flame of the flame outlet 5 is extinguished, and then the fuel supply is restarted. At this time, the premixed gas leaving the mixing chamber 4 reaches the main catalyst layer 7 which stands upright, but since the temperature is sufficiently raised here, while mainly causing catalytic combustion on the upstream (front) surface, It flows to the downstream side (rear surface) through the communication hole 7a. The combustion exhaust gas flows further upward, is mixed with the air supplied from the secondary air port 13 and comes into contact with the auxiliary catalyst layer 9, and if unburned components coexist, it is completely oxidized here and then cleaned. It becomes exhaust gas and is discharged to the upper part through the communication hole 9a. Therefore, even if the main catalyst layer 7 could not be completely combusted due to the deviation of the premixed state or the uneven temperature, the reaction can be completed in the auxiliary catalyst layer 9 located downstream of the main catalyst layer 7, and unburned components due to incomplete combustion can be removed. It is possible to avoid discharging it as it is. Further, the heat generated on the surface of the main catalyst layer 7 due to the combustion is partially transmitted through the transmission window 8 and part of the heat is dissipated to the front surface as secondary radiation from here by heating the transmission window 8, It is used for heating and heating.

Here, when the change of the surface temperature of the main catalyst layer 7 and the auxiliary catalyst layer 9 when the catalytic combustion of kerosene is carried out with the air ratio of 1.8 to 2.0 is observed according to the change of the oxidation concentration, it is as shown in FIG. 2 (a). It has become. That is, the combustion reaction is almost completed on the upstream surface of the main catalyst layer 7, and the catalyst surface temperature is about 860 ° C. At this time, the surface temperature of the auxiliary catalyst layer 9 is only heated by the combustion exhaust gas discharged from the main catalyst layer 7, and remains at about 550 ° C. Even if the oxygen concentration is lowered, the oxygen amount is sufficiently secured (even if the oxygen concentration is 15%, the actual oxygen excess ratio is 1.3 to 1.4). Therefore, the temperature difference between the main catalyst layer 7 and the auxiliary catalyst layer 9 (D1) hardly changes. When the amount of air supplied to the mixing chamber 4 is reduced by about 30%, the air ratio in the main catalyst layer 7 becomes 1.3 to 1.4, and the oxygen concentration is 20%.
Although complete combustion is possible with the above, the actual oxygen excess rate becomes 1.1 to 1.2 when the oxygen concentration reaches 18%, and carbon monoxide and unburned gas are generated. These combustible components are mixed with the air supplied from the secondary air port 13 and reach the auxiliary catalyst layer 9 where a combustion reaction occurs, so that as shown in FIG. The temperature of the layer 7 decreases and the auxiliary catalyst layer 9
The change that the temperature rises appears. If the oxygen concentration further decreases, the combustion amount in the main catalyst layer 7 will decrease further,
Instead, the amount of combustion in the auxiliary catalyst layer 9 increases more and more, so that the temperatures of both approaches gradually and eventually reverses. Therefore, if the temperature difference (D2) between the two is set to a predetermined value, and if the temperature difference is less than this value, the fuel supply is controlled to stop, so that it is possible to avoid continuing combustion even in the oxygen deficient state. Can be prevented from being adversely affected.

The setting conditions of the temperature difference vary depending on conditions such as the control limit oxygen concentration, the total combustion amount, the area ratio of the main catalyst layer 7 and the auxiliary catalyst layer 9, the set air ratio, etc., but they may be set according to the design conditions of the device. Good. In addition, the set value (D
The fluctuation of 2) can be easily dealt with by storing it in the control circuit 11 in advance. Further, keeping the amount of air supplied to the mixing chamber 4 always at such a limit value is unstable with respect to changes in the amount of fuel supply and the amount of air supply, and basically, complete combustion is performed in the main catalyst layer 7. It is usually preferable to supply a sufficient amount of air in order to carry out. Therefore, it is effective to perform the operation of changing the air amount for a short time of 2 to 3 minutes at a constant interval of 30 minutes or 1 hour, and the operation of reducing the air amount at a predetermined rate only within this predetermined time is constant. By repeating at intervals, it is possible to monitor the presence or absence of the oxygen deficiency state each time.

FIG. 3 shows a catalytic combustion apparatus according to a second embodiment of the present invention. Here, a flow path controller 14 having an opening / closing valve is provided in the middle of the secondary air pipe 12, and at a constant time interval. It is configured to open the flow path for a short time. When the flow path controller 14 is opened, part of the air supplied to the mixing chamber 4 is supplied to the secondary air port 13 via the secondary air pipe 12. Therefore, the amount of air to the mixing chamber 4 is reduced, and at the same time, the air supply to the upstream of the auxiliary catalyst layer 9 is started, and the same effect as that of the first embodiment can be obtained.

With this configuration, no special operation is required for controlling the fan 3, and no surplus air is supplied from the secondary air port 13 during normal combustion, so that the auxiliary catalyst layer 9 is not cooled and the auxiliary catalyst layer 9 is not cooled. Since the catalyst layer 9 can be maintained at a sufficiently high temperature, it is possible to ensure complete purification performance of unburned components and carbon monoxide.

In any of the above embodiments, the thermocouples 10a and 10b are used as the temperature detecting means, but any means for detecting the temperature can be selected.
For example, a resistance thermometer such as a thermistor or a radiation thermometer using light can be used.

Further, although a ceramic honeycomb is used as a carrier for the main catalyst layer 7 or the auxiliary catalyst layer 9 here, foamed ceramic, ceramic woven cloth, non-woven cloth, or the like may be used, and the above effects are not hindered.

EFFECTS OF THE INVENTION As described above, according to the present invention, two stages of catalyst layers provided with temperature detecting means are provided, and a secondary air supply section opening upstream of the downstream side catalyst layer is provided to supply to the upstream side catalyst layer. The operation of decreasing the amount of air in the air-fuel mixture at regular intervals for a predetermined time is repeated, and when the difference in temperature of the catalyst layer detected by the temperature detecting means reaches a predetermined value or less during the decrease in the amount of air, the fuel is By providing control means to stop the supply of oxygen, when the oxygen concentration in the room atmosphere decreases, the oxygen deficiency state can be detected early and surely without causing incomplete combustion, and the limit oxygen concentration affecting the human body It is possible to provide a highly safe combustion device by stopping combustion before it becomes.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a catalytic combustion apparatus according to the first embodiment of the present invention, FIGS. 2 (a) and 2 (b) are temperature characteristic diagrams thereof, and FIG.
The drawing is a vertical sectional view of a catalytic combustion apparatus according to a second embodiment of the present invention. 2 ... Fuel pump, 3 ... Fan, 4 ... Mixing chamber, 7
...... Main catalyst layer, 9 ...... Auxiliary catalyst layer, 10a, 10b ...... Thermocouple, 11 ...... Control circuit, 12 ...... Secondary air pipe, 13 ...... Secondary air port, 14 ...... Flow path controller .

Claims (2)

[Claims] 1. A fuel and air mixing chamber, a main catalyst layer provided downstream of the mixing chamber and having a large number of communicating holes, and a large number of communicating holes provided downstream of the main catalyst layer. The auxiliary catalyst layer provided, the temperature detecting means for the main catalyst layer and the auxiliary catalyst layer, the secondary air supply section opened upstream of the auxiliary catalyst layer, and the air supplied to the mixing chamber for a predetermined period of time. A catalytic combustion characterized by having a control means for reducing only the inside at a predetermined rate, and a control means for interlocking with the temperature detecting means and for stopping the fuel supply when the temperature difference between the two reaches a predetermined value or less. apparatus. 2. A fuel and air mixing chamber, a main catalyst layer provided downstream of the mixing chamber and having a large number of communicating holes, and a large number of communicating holes provided downstream of the main catalyst layer. The auxiliary catalyst layer provided, the temperature detecting means for the main catalyst layer and the auxiliary catalyst layer, the secondary air supply section opened upstream of the auxiliary catalyst layer, and the both of the mixing chamber and the secondary air supply section are in communication. The air supply means, the flow path control means for communicating the secondary air supply part and the air supply means with each other for a predetermined time at a constant interval, and the temperature difference between the two in a predetermined value or less in conjunction with the temperature detection means. And a control means for stopping the supply of fuel when it reaches.