JPH0432603A - Burner employing catalyst - Google Patents

Abstract

PURPOSE:To suppress the change with time in the surface temperature on the upstream side of a catalyst layer and provide a burner employing catalyst which is capable of maintaining a stable room heating and heating efficiency for a long time by providing a catalyst layer which forms the surface of a mixture gas channel with a catalyst metal powder carrying layer. CONSTITUTION:A catalyst layer 7 is a honeycomb-shaped substrate and has communicating holes 7a, and its surface is covered by a catalyst metal carrying layer 7b, and the catalyst metal carrying layer 7b is covered by a catalyst metal powder carrying layer 7c. With this arrangement the catalyst combustion reaction is carried out with a premixture of the fuel and air which performs gas diffusion through the catalyst metal powder carrying layer 7c, passes through it, and reaches the catalyst metal carrying layer 7b. The violent reaction heat and poisoning are eased by the catalyst metal powder carrying layer 7c. It is, therefore, possible to protect the catalyst metal from violent reaction heat, steam or poisoning.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a radiation heating type catalytic combustion device used for heating, space heating, drying, etc.

Conventional technology In general, liquid fuel such as kerosene or gaseous fuel such as city gas is mixed with air and then brought into contact with a catalyst for oxidation reaction, causing flameless catalytic combustion to occur on the surface of the so-called premixed fuel. Various catalytic combustion devices have been proposed in the past, mainly for use with gaseous fuels, and some of them have been put into practical use, but the catalysts have honeycomb-like or mat-like structures.

Alternatively, a cross-shaped catalyst was used in a single layer, and the catalytic active component was supported almost uniformly over the entire catalyst support.

In the conventional catalytic combustion apparatus described above, the fuel premixed with air undergoes a rapid oxidation reaction in the catalyst layer, generating carbon dioxide and water vapor along with reaction heat. The catalytic reaction here is initially concentrated near the upstream surface of the catalyst layer, and the reaction heat is transferred forward by radiation from the catalyst layer through a heat ray transmitter placed opposite to the front surface. supplied, heated,
Used for purposes such as heating.

Problems to be Solved by the Invention By the way, in the above-mentioned combustion, only the vicinity of the upstream surface of the catalyst layer is concentrated and used continuously at a high temperature, so catalyst deterioration in this vicinity is likely to progress.

Furthermore, the vicinity of the upstream surface of the catalyst layer is most susceptible to poisoning from fuel (for example, S poisoning of kerosene). As a result, the catalytic activity gradually decreases on the upstream side, and the center position of the catalytic reaction shifts from the upstream side to the downstream side, and at the same time, the upstream side surface temperature also decreases.

For this reason, there was a problem in that the radiant heat that was provided to the front through the heat ray transmitting body also decreased, and the heating efficiency changed significantly. Moreover, such changes in appearance tend to cause distrust among users of the catalytic combustion apparatus.

SUMMARY OF THE INVENTION An object of the present invention is to provide a catalytic combustion device that can eliminate the above-mentioned conventional drawbacks, suppress changes in heat radiation characteristics, and maintain stable heating and heating efficiency over a long period of time.

Means for Solving the Problem In order to achieve the above-mentioned object, a first means for solving the problem includes a catalyst layer provided downstream of a fuel and air mixing chamber and having a large number of communication holes, and an upstream surface of the catalyst layer. A catalytic combustion method comprising: a heat ray transmitting body disposed opposite to the catalytic combustion body; and an exhaust port provided on the downstream side of the catalyst layer; This is the configuration of the device.

In addition, as a second problem solving means, a catalyst layer having a large number of communication holes provided downstream of the fuel and air mixing chamber, and a heat ray transmitting body disposed opposite to the upstream surface of the catalyst layer. , an exhaust port provided on the downstream side of the catalyst layer, the catalyst layer has a catalytic metal unsupported layer with respect to the surface of the air-fuel mixture flow path, and the thickness of the catalytic metal unsupported layer is set on the upstream side. The structure of the catalytic combustion device is such that it becomes thinner along the downstream side.

Furthermore, in a third means for solving the problem, the catalyst layer is provided on a honeycomb-shaped substrate, a first coating layer provided on the surface of the honeycomb-shaped substrate, and a second coating provided on the surface of the first coating layer. The structure of the catalytic combustion device is such that the catalytic metal is supported only on the first coating layer.

Function The present invention forms a catalytic metal-unsupported layer on the surface of the mixture flow path of the catalytic layer, so that when the premixture of fuel and air reaches the catalytic metal-supported layer through the catalytic metal-unsupported layer, Causes a catalytic combustion reaction. Therefore, the catalyst metal can be protected from rapid reaction heat, water vapor, or poisoning compared to the conventional method. In addition, by reducing the thickness of the catalytic metal-unsupported layer from the upstream side to the downstream side in the flow path direction, it becomes possible to control the gas diffusion of the catalytic reaction rate to some extent in the catalytic metal-unsupported layer. The temperature difference between the upstream and downstream sides is significantly reduced.

In conventional catalytic combustion devices, there is a large temperature difference between the upstream and downstream sides, and the limit conditions for use are determined by the upstream surface temperature of the catalyst layer. In the present invention, the temperature difference between the upstream side and the downstream side is reduced, and when compared with the conventional combustion load at the same combustion load, the upstream side temperature can be lowered, and the load on the catalyst layer can be suppressed.

Also, if the upstream side of the catalyst is kept at the same temperature as before,
It is now possible to set the combustion load of a unit catalyst volume light much more sharply than in the past.

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

In Fig. 2, 1 is a fuel tank, 2 is a fuel pump, and 3 is a fuel tank.
is a fan for blowing air; 4 is a mixing chamber; an auxiliary flame port 5 is provided at the outlet of the mixing chamber 4; an ignition electrode θ is disposed near the auxiliary flame port 5; Above the auxiliary flame port 5, a catalyst layer 7 in which an active component of a platinum group metal is supported on a honeycomb-shaped ceramic flat plate mainly composed of silica, alumina, and titania, which has a large number of communicating holes 7a, stands upright. provided,
A heat ray transmitting body 8 is arranged opposite to the upstream surface (front surface) thereof. 9 in the figure is an exhaust port.

Next, to explain the operation in detail, the fuel (kerosene) supplied from the fuel pump 2 and the air supplied from the 77 tank 3 are
It is vaporized in the mixing chamber 4, sufficiently premixed, and sent to the upper auxiliary flame port 5.

At the time of ignition, the flame is ignited by the ignition electrode 6 at the auxiliary flame port 5, and flame combustion starts here. The high-temperature exhaust gas flows to the top and raises the temperature of the catalyst layer 7.

When the temperature of the catalyst layer 7 reaches a sufficient temperature after burning for a predetermined period of time, the supply of fuel is stopped, and after extinguishing the flame of the auxiliary flame port 6, the supply of fuel is started again. At this time, the premixture that has left the mixing chamber 4 reaches the catalyst layer 7 that stands upright, but since the temperature here has been sufficiently raised, it is mainly concentrated on the upstream side (front side).
While catalytic combustion occurs on the surface, the downstream side (
flowing to the rear). In addition, the reaction heat generated on the upstream surface of the catalyst layer 7 partially passes through the heat ray transmitter 8, and the negative part heats the heat ray transmitter 8 and is emitted to the front surface as secondary radiation from here. It is dissipated and used for heating, space heating, etc.

Here, as shown in FIG. 1, the catalyst layer 7 is a honeycomb-shaped base having communicating holes 7ai, and a catalyst metal supporting layer 7b on its surface.
Further, the surface thereof is coated with a catalytic metal non-supported layer 7C. By doing this, the catalytic combustion reaction is carried out by the premixture of fuel and air passing through the catalytic metal non-supporting layer 7C through gas diffusion and reaching the catalytic metal supporting layer 7b, resulting in rapid reaction heat and poisoning. is the catalytic metal unsupported layer 7C
plays a mitigating role.

(Example 1) Honeycomb-shaped ceramics (150 holes x 10 mm, 300 cells/1 nch2. Rib thickness 5o-25 mm) mainly composed of silica, alumina, and titania was coated with Ba0-
Al2O3・CeO2 powder (specific surface area 12 orrr'
/q) 1ooog.

5oocr of wash coat binder with alumina content of 10wt%, 107g of aluminum nitrate nonahydrate,
water 1400 (J) and a dinitrodiammine platinum aqueous solution and a dinitrodiammine palladium aqueous solution, respectively.
309 was coated with a wash coat slurry containing 10 q sq in terms of Pd. After that, add another 15g of the above wash coat slurry that does not contain Pt or Pd.
coated.

(Conventional example) BaO/Al was added to the same honeycomb-shaped ceramic as in Example 1.
2O3・CeO2 powder (specific surface area 12orrl/q) 1
ooog, wash coat binder 6009 with alumina content jQwt%. Aluminum nitrate nonahydrate 1
07q, 1400 g of water and an aqueous solution of dinitrodiammine platinum acid and an aqueous solution of dinitrodiammine palladium, respectively, in terms of P t and Pd, 10 (J).

309 was coated with a wash coat slurry containing 5q.

(Example 2) BaO/Al was added to the same honeycomb-shaped ceramic as in Example 1.
2O3, CeO2 powder (specific surface area 120m'/q) 10
00g, wash coat binder with alumina content of 10wt% 500q, nitrate eV aluminum nonahydrate 107q
, 1400q of water and dinitrodiammineplatinic acid aqueous solution and dinitrodiammineparadilam aqueous solution respectively.
30q was coated with a wash coat slurry consisting of 10 (J, 5q) added in terms of Pt and Pd. After that, Pt, Pd
An additional 16 g of the washcoat slurry containing no d was applied to the honeycomb-shaped ceramic lattice so that the thickness was different in the direction of the lattice as shown in FIG.

As described above, a combustion device as shown in FIG. 2 was assembled using the catalysts of Examples 1 and 2 and the conventional example, and the combustion rate was 2200 jtd/h.

A continuous combustion life test was conducted at an air-fuel ratio (air, kerosene) of 1.7, and temperature changes in the catalyst layer were measured. Figure 4.

Figure 5 shows the initial stage and 400°C of the catalyst layer of Examples 1 and 2 and the conventional example.
FIG. 6 shows the temperature distribution during combustion after 0 hours, and shows the change over time in the upstream surface temperature of the catalyst layer.

As is clear from Fig. 6 (in the conventional catalyst, the initial P:
When smoking, the upstream side was 900'('', but it was 300')
After 0h, the temperature drops to 845°C on the upstream side, and about 50°C.
It has changed. Such a change in the appearance of the combustion red-hot surface causes users of the catalytic combustion apparatus to feel distrustful. Furthermore, after 42 hours of combustion time, the combustion zone blew out from the catalyst layer of the combustion device, resulting in a misfire. However, in the catalyst of this example, both 5ooo
The catalyst of Example 1 showed a decrease of about 35°C after 5oooh, and the catalyst of Example 2 showed a decrease of about 20°C.
It only shows a decline in Further, as is clear from FIG. 4, it can be seen that the temperature difference between the upstream side and the downstream side of the catalyst layer is smaller in this example than in the conventional example. Furthermore, as shown in FIG. 5, it can be seen that in the conventional catalyst, the central zone of catalytic combustion progressed from upstream to downstream in the continuous combustion test for 4000 hours. In contrast, in this embodiment, even during this combustion time, the combustion does not proceed much downstream, and a normal combustion state is maintained.

Next, the catalyst of Example 2 was used to produce 28501 al/h.

Air fuel ratio 1. A continuous combustion life test was conducted at the end of the test, and temperature changes in the catalyst layer were measured. FIG. 7 shows the temperature distribution during combustion in the initial stage of the catalyst layer, and FIG. 8 shows the temporal change in the upstream surface temperature of the catalyst layer.

As is clear from these drawings, the catalyst of Example 2 can reduce the temperature difference between the upstream and downstream sides of the catalyst layer compared to the conventional catalyst. Therefore, in the conventional catalyst, the upstream surface temperature of 900'C corresponded to the combustion conditions of 22001011/h and the air-fuel ratio 1.7, but in the example 2
The catalyst showed an upstream surface temperature of 900°C when the air-fuel ratio was 2850ka/J and 1.7. As a result, we were able to increase the combustion load by approximately 30% with the same upstream surface temperature setting as before. Furthermore, even under these combustion conditions, the catalyst of the present invention was able to maintain stable catalytic combustion for a longer period of time than the conventional catalyst.

Effects of the Invention As is clear from the description of the above embodiments, according to the present invention,
It is possible to provide a catalytic combustion device that can suppress temporal changes in the upstream surface temperature of the catalyst layer and maintain stable heating and heating efficiency for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of the main part of the catalyst layer of Example 1 of the present invention,
Figure 2 is a vertical cross-sectional view showing the overall configuration of the catalytic combustion device;
The figure is an enlarged cross-sectional view of the main part of the catalyst layer of Example 2 of the present invention.
22001 m/h, air-fuel ratio 1, respectively.
．． Characteristic diagrams showing the temperature distribution during combustion at the initial stage and after 4000 hours in the catalyst layers of Examples 1 and 2 and the conventional example under 7 conditions. Figure 6 shows the upstream surface temperature of the catalyst layers of Examples 1 and 2 and the conventional example. A characteristic diagram showing changes over time, Fig. 7 is 2850-'h. FIG. 8 is a characteristic diagram showing the initial combustion temperature distribution of the catalyst layer of Example 2 under the air-fuel ratio condition of 1.7, and FIG. 8 is a characteristic diagram showing the temporal change in the upstream surface temperature of the catalyst layer of Example 2. 4...Mixing chamber, 7...Catalyst layer, 7a...
...Communication hole, 7b...Catalyst metal support layer, 7C...
... Catalyst metal unsupported layer, 8 ... Heat ray transmitter, 9
·····exhaust port. Name of agent: Patent attorney Shigetaka Awano and 1 other person
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Claims (3)

[Claims] (1) A catalyst layer having a large number of communication holes provided downstream of the fuel and air mixing chamber, a heat ray transmitter disposed facing the upstream surface of the catalyst layer, and a downstream of the catalyst layer. 1. A catalytic combustion device, characterized in that the catalyst layer has a catalyst metal-unsupported layer on the surface of the air-fuel mixture flow path. (2) A catalyst layer having a large number of communication holes provided downstream of the fuel and air mixing chamber, a heat ray transmitter disposed facing the upstream surface of the catalyst layer, and a downstream of the catalyst layer. the catalyst layer has a catalytic metal unsupported layer against the surface of the air-fuel mixture flow path, and the thickness of the catalytic metal unsupported layer is adjusted from the upstream side to the downstream side; A catalytic combustion device characterized by being thin. (3) The catalyst layer includes a honeycomb-shaped substrate, a first coating layer provided on the surface of the honeycomb-shaped substrate, and a second coating layer provided on the surface of the first coating layer, and Claim 1 characterized in that the catalyst metal is supported only on the layer.
Or the catalytic combustion device according to 2.