JP2720614B2 - Catalytic combustion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiant heating type catalytic combustion apparatus used for heating, heating, drying and the like.

[0002]

2. Description of the Related Art A so-called premix type 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 for an oxidation reaction 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.

[0003]

In catalytic combustion, a fuel (for example, kerosene) premixed with air causes a rapid oxidation reaction in the catalyst layer, and generates carbon dioxide and water vapor together with heat of reaction. Initially, the catalytic reaction is concentrated in the vicinity of the upstream surface of the catalyst layer, and the reaction heat is radiated from the catalyst layer to the front through the heat ray permeable body disposed opposite the front surface. Supplied and used for heating, heating, etc. However, since only the vicinity of the upstream surface of the catalyst layer is concentrated and continuously used at a high temperature and in an oxidized state, the deterioration of the catalyst in this vicinity is apt to progress.

As a result, the catalyst activity gradually decreases on the upstream side.
Occurs, and the center position of the catalytic reaction shifts from upstream to downstream
At the same time, the upstream surface temperature also decreases.
Also, the downstream of the catalytic reaction center position is
Means that the effective flow direction thickness becomes shorter
Therefore, the combustion characteristics of catalytic combustion (CO / C
O _Two, HC / CO_Two) Also gets worse.

[0005] Therefore, when the center position of the catalytic reaction shifts from the upstream side to the downstream side, the radiant heat provided forward through the heat ray permeable body is reduced, and the heating / heating efficiency is greatly reduced. And the combustion characteristics (CO /
CO ₂ , HC / CO ₂ ) also deteriorated.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a catalytic combustion device capable of suppressing deterioration of combustion characteristics and maintaining stable heating / heating efficiency for a long time.

[0007]

In order to achieve the above object, the present invention provides a catalyst layer having a large number of communication holes provided downstream of a fuel and air mixing chamber, and a catalyst layer provided on an upstream surface of the catalyst layer. It has a heat ray permeable body disposed to face and an exhaust port provided on the downstream side of the catalyst layer, and when the cross-sectional area of the communication hole in the catalyst layer is s and the thickness in the flow direction is t, t / s = 7 (m
m ^-1 ) or more.

[0008]

In the catalytic combustion device, the deterioration on the upstream side of the catalyst layer progresses, the center position of the catalytic reaction shifts from the upstream side to the downstream side of the catalyst layer, and the thickness of the catalyst layer in the effective flow direction decreases. As a result, the combustion cannot be completed in the catalyst layer, and a small amount of CO or HC is emitted. However, according to the present invention, since the relationship between the cross-sectional area of the communication hole of the catalyst layer and the thickness in the flow direction is set to a predetermined ratio or more, the center position of the catalytic reaction is slightly shifted from the upstream side to the downstream side. Even after the transition, the combustion characteristics can be maintained in a good state.

[0009]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a main part showing an entire configuration of a catalytic combustion apparatus according to one embodiment of the present invention. In FIG. 1, 1 is a fuel tank, 2 is a fuel pump, 3 is a fan for blowing air, and 4 is a mixing chamber. An auxiliary flame port 5 is provided at the outlet of the mixing chamber 4, and an ignition electrode 6 is disposed near the auxiliary flame port 5. Above the auxiliary flame port 5, a catalyst layer 7 in which a Pt / Pd active component is carried on a honeycomb-shaped ceramic plate having a large number of communication holes 8 is provided upright, and faces an upstream surface (front surface) thereof. Then, the heat ray transmitting body 9 is disposed. Reference numeral 10 denotes an exhaust port.

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 vaporized and sufficiently premixed in the mixing chamber 4 to form an upper portion. It is sent to the auxiliary flame outlet 5. At the time of ignition, first, it is ignited by the ignition electrode 6 at the auxiliary flame port 5,
Here, flame combustion is started. The high-temperature exhaust gas flows to the upper part and raises the temperature of the catalyst layer 7. At the time when the catalyst layer 7 has been heated to a sufficient temperature by burning for a predetermined time, the fuel supply is stopped once, the flame in the auxiliary flame outlet 5 is extinguished, and then the fuel supply is started again. At this time, the pre-mixed gas that has exited the mixing chamber 4 reaches the catalyst layer 7 which stands upright. Since the temperature of the premixed gas has been sufficiently raised, catalytic combustion mainly occurs on the upstream (front) surface,
It flows to the downstream side (rear surface) via the communication hole 8. Further, the reaction heat generated on the upstream surface of the catalyst layer 7 partially transmits through the heat ray permeable body 9 and partially heats the heat ray permeable body 9 so as to emit secondary radiation from the heat ray permeable body 9 to the front side. Dissipated and provided for heating, heating, etc.

(Embodiment 1) Honeycomb-like ceramics (150 mm, 400 cells / inch ² , rift 0.15 mm thick) having a thickness of 5.0 mm, 7.5 mm, 10 mm, and 15 mm containing silica, alumina and titania as main components were applied to BaO.・ Al ₂ O ₃ .CeO ₂ powder (specific surface area 120 m ² / g) 1000 g, alumina content 10 w
Wash coat slurry obtained by adding 100 g of a t% wash coat binder, 85 g of aluminum nitrate nonahydrate, 1300 g of water, 5 g and 4 g of an aqueous solution of dinitrodiammine platinum and an aqueous solution of dinitrodiammine palladium in terms of Pt and Pd, respectively 23 g, 3 g
4 g, 45 g, and 68 g of the catalyst A for catalytic combustion (t /
s = about 4.4), B (t / s = about 6.7), C (t / s = about 8.
8), a catalyst layer 7 was prepared using D (t / s = 13.3).

(Example 2) Example of honeycomb ceramics (150 mm, 300 cells / inch ² , ゛ 0.25 mm thick) having a thickness of 7.5 mm, 10 mm, 15 mm, and 20 mm containing silica, alumina, and titania as main components. 30 g, 40 g, 60 g, and 80 g of the washcoat slurry prepared in the same manner as in Example 1, respectively.
The coated catalytic combustion catalysts E (t / s = about 5.4), F (t
/ S = about 7.2), G (t / s = about 10.8), H (t / s =
About 14.4) was used to produce the catalyst layer 7. (Example 3) Thickness 10mm composed mainly of silica-alumina-titania, 15 mm, 20 mm of the honeycomb-shaped ceramic (0.99 □ mm, 200 cell / inch ^2, riffs Bu thickness 0.30 mm) was prepared in the same manner as in Example 1 Catalyst combustion catalyst I coated with 30 g, 45 g and 60 g of washcoat slurry, respectively
(T / s = about 4.7), J (t / s = about 7.0), K (t / s
= About 9.4) to produce a catalyst layer 7.

Using the catalyst layer 7 thus obtained, a continuous life test of a catalytic combustion device using kerosene as fuel was conducted. The combustion conditions were air-fuel ratio (air / fuel) 1.8, combustion amount 2
It was set to 200 kcal / h. (Table 1) Initial and 5000
h shows the combustion characteristics after h.

[0014]

[Table 1] 2 and 3 are graphs showing the results shown in Table 1. FIG. 2 shows the CO / CO ₂ characteristics, and FIG. 3 shows the HC / CO ₂ characteristics. As is clear from the figure, in the catalytic combustion apparatus with t / s = 7 (mm ^-1 ) or more, excellent combustion characteristics are maintained even after 5000 hours. Conversely, in a catalytic combustion apparatus using a catalyst layer having an insufficient ratio of the cross-sectional area of the communication hole to the thickness in the flow direction, the HC / CO ₂ characteristics particularly deteriorate after the continuous test.

For the catalyst G, combustion characteristics after 8000 hours were measured. As a result, CO / CO ₂ (× 10 ⁻⁵ ) = 4, H
C / CO ₂ (× 10 ⁻⁵ ) = 5, which was good. However, when the temperature distribution in the thickness direction of the catalyst layer 7 was measured, as shown in FIG. 4, the temperature peak position shifted to the downstream side by about 2.5 mm and the upstream temperature decreased by about 70 ° C. as compared with the initial stage. This means that the heating / heating efficiency due to the radiation from the surface of the catalyst layer 7 has decreased with time.

Therefore, if the center position of the combustion has shifted to the downstream side so far, the catalyst layer 7 has reached the end of its life without further use, even if the combustion characteristics have not deteriorated. It is desirable to make a judgment and replace the catalyst layer 7 (how many times the lower limit temperature from the initial stage at the upstream temperature is determined also varies depending on use conditions). The ratio between the cross-sectional area of the communication hole 8 and the thickness in the flow direction needs to be sufficiently large. However, as the time elapses, the upstream side of the catalyst layer 7 deteriorates, and the catalyst layer surface temperature decreases. Instead of increasing the ratio of the cross-sectional area of the communication hole 8 to the thickness in the flow direction, it is considered that t / s = about 7 to 12 (mm ^-1 ) is an effective use method of the catalyst layer 7. Can be

As described above, according to the above embodiment, the catalyst layer 7
When the cross-sectional area of the communication hole 8 is s and the thickness in the flow direction is t, by setting t / s = about 7 to 12 (mm ^-1 ), the combustion characteristics, especially the combustion characteristics when used continuously for a long time Is improved.

[0018]

As is apparent from the above embodiment, the present invention is directed to a catalyst layer having a large number of communication holes provided downstream of a fuel-air mixing chamber, and a catalyst layer facing an upstream surface of the catalyst layer. , The heat ray permeable body disposed therein, and an exhaust port provided on the downstream side of the catalyst layer. If the cross-sectional area of the communication hole of the catalyst layer is s and the thickness in the flow direction is t, t / s = 7 (mm ^-1 ) or more, so that deterioration of combustion characteristics can be suppressed and stable heating, heating, drying, and the like can be performed for a long time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional side view of a main part showing an overall configuration of a catalytic combustion device according to an embodiment of the present invention.

FIG. 2 shows the combustion characteristics (CO / C) of the catalytic combustion device of one embodiment.
Characteristic diagram showing measurement result of O ₂ )

FIG. 3 shows the combustion characteristics (HC / C) of the catalytic combustion device of one embodiment.
Characteristic diagram showing measurement result of O ₂ )

FIG. 4 shows the air-fuel ratio of the catalytic combustion device of one embodiment.
8. Characteristic diagram showing the temperature distribution in the thickness direction of the catalyst layer when burned at a burn rate of 2200 kcal / h

[Explanation of symbols]

 4 Mixing chamber 7 Catalyst layer 8 Communication hole 9 Heat ray permeable body 10 Exhaust port

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-55409 (JP, A) JP-A-1-306712 (JP, A) JP-A-2-306020 (JP, A)

Claims (1)

(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 a catalyst. And an exhaust port provided on the downstream side of the bed, where s is the cross-sectional area of the communication hole in the catalyst layer, and t is the thickness in the flow direction.
/ S = 7 (mm ^-1 ) or more.