JP2805996B2 - Catalytic combustion device - Google Patents

Description

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

2. Description of the Related Art In general, 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 an oxidation reaction catalyst to perform flameless catalytic combustion on the surface. Conventionally, various types of combustion devices have been proposed mainly for gaseous fuels, and some of them have been put to practical use.

That is, in the catalytic combustion of this conventional catalytic combustion device, the fuel premixed with air causes a rapid oxidation reaction when guided to a catalyst layer having sufficient activity, and generates carbon dioxide and water vapor together with the heat of reaction. . The catalytic reaction here is
The reaction heat is concentrated near the upstream surface of the catalyst layer, and the reaction heat is supplied to the front by the radiation from the catalyst layer through the heat ray permeable body disposed opposite to the front surface, and is used for heating, heating, etc. Was to be offered.

However, in the configuration of the conventional catalytic combustion device described above,
If only the vicinity of the surface on the upstream side of the catalyst layer is concentrated and used continuously at a high temperature, the catalyst in the vicinity is in a state where deterioration is most likely to proceed. As a result, when the catalyst deteriorates, the activity of the catalyst gradually decreases on the upstream side, and the center position of the catalytic reaction shifts from upstream to downstream, and at the same time, the surface temperature on the upstream side also decreases. For this reason, the radiant heat provided forward through the heat ray transmitting body gradually decreases,
There was a problem that the heating / heating efficiency greatly changed.
In addition, such a change in appearance was likely to cause distrust to a user of the catalytic combustion device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a catalytic combustion apparatus which can improve the conventional disadvantages described above and maintain stable heating / heating efficiency for a long time.

Means for Solving the Problems In order to achieve the above object, the present invention provides (1) a catalyst layer having a large number of communication holes provided downstream of a fuel and air mixing chamber, and an upstream surface of the catalyst layer. A heat radiation permeable member disposed opposite to the catalyst layer, and an exhaust port provided on the downstream side of the catalyst layer, for supplying while changing the air-fuel ratio of fuel and air at a constant cycle, It is configured to perform catalytic combustion. (2) Then, the air-fuel ratio is changed to an air-fuel ratio of 1.1.
In the range of ~ 2.5, based on a certain point in the range,
The catalytic combustion is performed while periodically varying the air-fuel ratio width in the range of ± 0.05 to ± 0.3. (3) Further, the blower fan disposed upstream of the fuel and air mixing chamber is fixed, and the fuel pump disposed upstream thereof varies the supply speed to periodically vary the air-fuel ratio. The configuration is such that control is performed as described above.

Action The present invention has the above-described configuration, for example, an air-fuel ratio of 1.70
The catalytic combustion device has the same air-fuel ratio of 1.70 by changing the cycle periodically within a range of ± 0.10 (air-fuel ratio 1.60 to 1.80).
The catalyst in the catalyst layer is less deteriorated than in the case where the catalyst is fixed and the catalyst is burned, and a longer life of the catalyst layer can be achieved.

Although the reason for this is not known in detail, it is preferable that the air-fuel ratio is periodically varied and used in a dynamic state to reduce the activity of the catalyst, rather than being used in a static state in which the air-fuel ratio is constant for the catalyst layer. Conceivable. Also,
It is considered that the reaction heat load of the catalyst layer is gentler in this dynamic state.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes a fuel tank which supplies fuel to the mixing chamber 4 via a fuel pump 2 and air to the mixing chamber 4 via a fan 3 for blowing air. An auxiliary flame port 5 is provided at the outlet of the mixing chamber 4.
The ignition electrode 6 is disposed in the vicinity of. Above the auxiliary flame port 5, a catalyst layer 7 in which a platinum-group metal active component is supported on a honeycomb-shaped ceramic plate mainly composed of, for example, silica / alumina / titania, having a large number of communication holes 7a, stands upright. The heat ray transmitting body 8 is disposed so as to face the upstream surface (front surface). Reference numeral 9 denotes an exhaust port.

Next, the operation of the above configuration will be described in detail. The fuel (kerosene) supplied from the fuel pump 2 and the air supplied from the blower fan 3 are vaporized in the mixing chamber 4 and sufficiently premixed to form a mixture. Is sent to the auxiliary flame outlet 5. At the time of ignition, ignition is first performed by the ignition electrode 6 at the auxiliary flame port 5, and flame combustion is started here. Then, the high-temperature exhaust gas of this flame flows to the upper part, and the temperature of the catalyst layer 7 is raised. When the catalyst layer 7 has been burned for a predetermined time and the temperature of the catalyst layer 7 has risen to a sufficient temperature, the supply of fuel is temporarily stopped, the flame in the auxiliary flame outlet 5 is extinguished, and then the supply of fuel is started again. At this time, the pre-mixed gas that has left the mixing chamber 4 is a catalyst layer 7 that stands upright.
However, since the temperature is sufficiently raised here, the catalyst flows mainly to the upstream (front) surface, and flows to the downstream (rear) through the communication hole 7a. The reaction heat generated on the surface of the catalyst layer 7 is partially transmitted through the heat ray permeable body 8 and partially radiated to the front as secondary radiation therefrom by heating the heat ray permeable body 8. , Heating and heating.

In the present invention, the blower fan 3 operates at a predetermined fixed value at the same time that the catalyst layer starts catalytic combustion, and the supply speed per unit time is changed only for the fuel supplied from the fuel pump 2. As a result, control is performed so that the air-fuel ratio of air and fuel can be periodically changed based on a certain point as a reference.

The details of the experimental comparison with the conventional example will be described below together with the experimental example of the above-described embodiment.

That is, in this embodiment, the catalyst layer 7 is formed of a honeycomb-shaped ceramic (15%) mainly composed of silica, alumina, and titania.
0 □ × 10mm, 300 cells / inch _^2, BaO · Al ² to rib thickness 0.25 mm)
A wash made by adding 1000 g of O ₃ · CeO ₂ powder (specific surface area: 120 m ² / g), 400 g of a wash cord binder having an alumina content of 10 wt%, 120 g of aluminum nitrate nonahydrate, 1400 g of water and 10 g of an aqueous solution of dinitrodiammine palladium in terms of Pd. Obtained by coating 45 g of the slurry with a coat slurry. Using this catalyst layer 7, a combustion device was assembled with the configuration as shown in FIG. 1, and a life test of the catalyst combustion device was performed.

The test conditions at this time were a combustion amount of 2200 kcal / h and an air-fuel ratio of 1.
The cycle was changed so that one cycle of 1.70 → 1.60 → 1.70 → 1.80 → 1.70 was 2 seconds at ± 0.10 based on 70.

In the experiment in the conventional example, the same catalyst layer 7 and catalytic combustion device as in the example were used, and the test condition was a combustion amount of 2200 kcal / h.
The air-fuel ratio was fixed at 1.70.

FIG. 2 shows the change over time of the catalyst layer upstream surface temperature (when measuring the upstream surface temperature of the catalyst layer 7 in this embodiment,
Only then was the air-fuel ratio fixed at 1.70).

As a result, the catalyst in the conventional experiment had a temperature of 900 ° C. on the upstream side during the initial combustion, but dropped to 860 ° C. after 3000 hours, and further dropped to 800 ° C. after 6000 hours. Such a change in appearance on the combustion red hot surface causes distrust to the user of the catalytic combustion device. But,
In this example, the temperature was 885 ° C. on the upstream side at 3000 h, and decreased to 845 ° C. at 6000 h. Therefore, according to the present embodiment, it is possible to achieve a life extension of about 1.5 times compared to the conventional example.

In this example, the test was performed at an air-fuel ratio of 1.70 ± 0.10, but the surface temperature of the catalyst layer changes slightly by about 20 ° C. by changing the air-fuel ratio from 1.60 to 1.80. This temperature difference is received by the apparatus user as fluctuation of the catalytic combustion surface. Therefore, if the fluctuation width of the air-fuel ratio is too large, the fluctuation of the temperature difference also increases, and the flickering of the glowing surface gives the user a feeling of discomfort. Therefore, it is preferable that the periodic fluctuation of the catalyst layer surface temperature resulting from the air-fuel ratio fluctuation be about 20 to 30 ° C. or less. For this purpose, when the reference air-fuel ratio point is small, the fluctuation width can be small (about ± 0.05), and as the air-fuel ratio point increases, the fluctuation width can be increased (up to about ± 0.30).

In addition, it is considered that about one cycle in which the air-fuel ratio is varied is preferably about 1 to 3 seconds, which does not matter to the user of the apparatus and is reasonable for the apparatus.

Effects of the Invention As is clear from the above description of the embodiment, according to the present invention, there is provided a catalytic combustion device capable of maintaining stable heating / heating efficiency for a long time by supplying the air-fuel ratio while changing it at a constant cycle. Can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a catalytic combustion apparatus according to one embodiment of the present invention, and FIG. 2 is a characteristic diagram of a change with time of the surface temperature on the upstream side of the catalyst layer of the embodiment of the present invention and a conventional example. 2 ... Fuel pump, 3 ... Blower fan, 4 ... Mixing chamber, 7 ... Catalyst layer, 7a ... Communication hole, 8 ... Heat permeable body,
9 ... Exhaust port.

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masato Hosaka 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Hirohisa Kato 1006 Odaka Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-1-306712 (JP, A) JP-A-1-306711 (JP, A) JP-A-61-246508 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) F23D 11/40 F23C 11/00 306 F23C 11/00 312 F23N 1/02

Claims (3)

(57) [Claims] 1. A catalyst layer having a plurality of communication holes provided downstream of a fuel and air mixing chamber, a heat ray permeable member disposed opposite to an upstream surface of the catalyst layer, and the catalyst layer A catalytic combustion apparatus having an exhaust port provided on the downstream side of the fuel cell and supplying the fuel and air while changing the air-fuel ratio at a constant cycle, and causing the catalyst layer to perform catalytic combustion. 2. In the air-fuel ratio range of 1.1 to 2.5, catalytic combustion is performed while periodically varying the air-fuel ratio range of ± 0.05 to ± 0.3 with respect to a certain point in this range.
A catalytic combustion device according to any of the preceding claims. 3. A blower fan arranged upstream of the fuel and air mixing chamber is fixed, and a fuel pump arranged upstream of the mixing chamber varies its supply speed so that the air-fuel ratio changes periodically. 3. The method according to claim 1, wherein the control is performed.
A catalytic combustion device according to any of the preceding claims.