JPH04297710A - Catalyst combustion apparatus - Google Patents

Abstract

PURPOSE:To provide a catalyst combustion apparatus capable of maintaining stable heating efficiency for a prolonged time by solving a problem, in which radiation heating hcaracteristics are deteriorated with time and burning characteristic are deteriorated, and improving the heat capacity and thermal conductivity of a catalyst layer in the radiation heating type catalyst combustion apparatus used for heating drying, etc. CONSTITUTION:A catalyst layer 7 is formed of heat-resistant inorganic fibers, high specific surface-area ceramic powder, on which a catalytic metal is carried, and an inorganic binder. Since heat capacity is reduced and thermal conductivity can also be deteriorated, the temperature difference on the upstream side and downstream side of the catalyst layer is increased, thus obtaining more heating radiation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation heating type catalytic combustion device used for heating, space heating, drying, etc.

0002

[Prior art] So-called premixed catalytic combustion in which 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, and flameless catalytic combustion is performed on the surface of the catalyst. Various devices have been proposed in the past, mainly for use with gaseous fuels, and some of them have been put into practical use.

0003

In catalytic combustion, fuel (for example, kerosene) 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. It is supplied and used for purposes such as heating and space heating. However, since the catalyst layer is concentrated in the vicinity of the upstream surface and is continuously used at high temperatures and in an oxidized state, catalyst deterioration in this vicinity tends to progress.

As a result, the catalytic activity gradually decreases on the upstream side, and at the same time the central position of the catalytic reaction shifts from the upstream side to the downstream side, the upstream surface temperature also decreases. In addition, the shift of the catalytic reaction center position downstream means that the effective thickness of the catalyst layer in the flow direction becomes shorter, and therefore the combustion characteristics of catalytic combustion (CO/CO2, HC
/CO2) will also gradually worsen.

[0005] Therefore, as the central position of the catalytic reaction shifts from the upstream side to the downstream side, the radiant heat that was provided to the front through the heat ray transmitter decreases, and the heating efficiency is significantly reduced. issues, and combustion characteristics (CO/C
There were issues such as deterioration of O2, HC/CO2).

The present invention solves the above-mentioned conventional problems, and provides a catalytic combustion device that can suppress changes over time in radiant heating characteristics and deterioration of combustion characteristics, and maintain stable heating and heating efficiency for a long time. With the goal.

[0007]

[Means for Solving the Problems] 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 the upstream surface of the catalyst layer. It has a heat ray transmitting body disposed facing each other and an exhaust port provided on the downstream side of the catalyst layer, and the catalyst layer is made of a high specific surface area ceramic powder supporting heat-resistant inorganic fibers and a catalyst metal. It consists of an inorganic binder for bonding ceramic powder to inorganic fibers.

[0008]

[Operation] It has been found that in catalytic combustion using kerosene as fuel, the air-fuel ratio (air/fuel) at which optimum combustion characteristics can be obtained is around 2. When combustion is carried out with the air-fuel ratio set to the optimal 2, the catalytic reaction is concentrated near the upstream surface of the catalyst layer, and downstream from that, the small amount of HC that was not completely combusted at the combustion center position. It is responsible for purifying CO. Therefore, the temperature near the upstream surface is high, and the downstream side is only affected by the heat generated at the combustion center position through heat transfer, radiation, and convection.

On the other hand, according to the present invention, since a porous material mainly composed of heat-resistant inorganic fibers is used for the catalyst layer,
Heat conductivity in the catalyst layer is suppressed, and the temperature difference between the upstream side and the downstream side of the catalyst layer becomes large. As a result, it is possible to obtain more radiation for the amount of heat used. Also, there is a small amount of H that could not be completely burned at the combustion center position.
Since the heat load on the downstream side responsible for purifying C and CO is reduced, it becomes possible to maintain good combustion characteristics over a long period of time (the ability to purify HC and CO can be maintained).

[0010] Furthermore, when operating a catalytic combustion device, it is necessary to preheat the catalyst layer to a predetermined temperature or higher, but even in this case, if the catalyst layer is made of a porous material such as the one of the present invention, the heat capacity is small and the upstream Since heat on the side is difficult to transfer to the downstream side, the upstream side is quickly preheated to the required activation temperature, which also has the effect of shortening the preheating time.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view showing the overall configuration of a catalytic combustion apparatus according to an embodiment of the present invention. In the figure, 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 opening 5, a Pt/Pd
A catalyst layer 7 supporting an active ingredient is provided upright,
A heat ray transmitting body 9 is arranged opposite to the upstream surface (front surface) thereof. 10 is an exhaust port.

Next, to explain its operation in detail, the fuel (kerosene) supplied from the fuel pump 2 and the air supplied from the fan 3 are vaporized in the mixing chamber 4 and are sufficiently premixed to be discharged from the upper part. It is sent to the auxiliary flame outlet 5. At the time of ignition, it is first ignited by the ignition electrode 6 at the auxiliary flame port 5,
At this point, flame combustion begins. The high temperature exhaust gas flows to the upper part and raises the temperature of the catalyst layer 7. The catalyst layer 7 is burnt for a predetermined period of time.
When the temperature has risen to a sufficient temperature, the fuel supply is temporarily stopped, the flame of the auxiliary flame port 5 is extinguished, and then the fuel supply is started again. At this time, the premixture that has left the mixing chamber 4 reaches the catalyst layer 7 that stands upright above, but since the temperature here has been sufficiently raised, catalytic combustion occurs mainly on the upstream (front) surface, and It flows through the hole 8 to the downstream side (rear side). Also, the catalyst layer 7
Part of the reaction heat generated on the upstream surface of the heat ray transmitter 9 passes through the heat ray transmitter 9, and another part heats the heat ray transmitter 9 and is dissipated to the front as secondary radiation from here, causing heating. It is used for heating, heating, etc.

[0013]

[Example] Alumina silica fiber (alumina 70wt)
%, silica 30wt%, fiber length approximately 10mm, fiber diameter approximately 3μm), BaO・Al2O3・CeO2 powder (
Alumina sol with a specific surface area of 120 m2/g) was corrugated by a papermaking method using a water-soluble polymer and water, and then baked at 1200°C for 2 hours to form a 150□×10
mm, 300 cells/inch2, ref thickness 0.25mm
alumina silica fiber 50wt%, BaO・Al2O3
・CeO249wt%, inorganic binder (alumina) 1
Honeycomb-shaped ceramics consisting of wt% (porosity 60%
), and then impregnated with an aqueous solution of dinitrodiammine platinum and dinitrodiammine palladium and heat-treated to produce a catalyst layer 7 supporting Pt and Pd, respectively.

(Comparative example) Honeycomb-shaped ceramics (150□×10
mm, 300 cells/inch2, ref thickness 0.25mm
, porosity 35%), BaO・Al2O3・CeO2 powder (specific surface area 120m2/g), alumina content 10wt
% washcoat binder, aluminum nitrate 9
A catalyst layer coated with 40 g of a wash coat slurry prepared by adding an aqueous salt, water, and an aqueous solution of dinitrodiammine platinum and dinitrodiammine palladium was prepared.

Using the catalyst layer 7 obtained in this way and the catalyst layer of the comparative example, a catalytic combustion device as shown in FIG. 1 was assembled.
A continuous combustion life test was conducted using Kerosene) 2.0. FIG. 2 shows the temperature distribution in the thickness direction of the catalyst layer in the examples and comparative examples at the initial stage. Further, FIG. 3 shows the results of periodic measurements of the surface temperature on the upstream side of the catalyst layer during the continuous combustion life test. Furthermore, (Table 1) shows the results of measuring the combustion characteristics after 7000 hours.

[0016]

[Table 1]

From FIG. 2, even though both the example and the comparative example were burned under the same conditions, the upstream temperature in the example was higher and the downstream temperature was lower. It can be seen that more radiation effects are obtained in the comparative example than in the comparative example. Also, as can be seen from the temperature distribution curve in Figure 2, the temperature peak and temperature curve of the comparative example were shifted to the downstream side from the beginning, and as a result, as shown in Figure 3, the catalyst The surface temperature on the upstream side of the layer decreases quickly over time, about 5% after 5000h.
While the temperature was lowered by about 0℃, in the example it was lowered by 7000 hours.
Even after that, the drop remained at about 40°C. Furthermore, in the example, the combustion center position did not shift to the downstream side compared to the comparative example, so the combustion characteristics after 7000 hours (CO/CO
2, HC/CO2), it can be seen that the examples are superior as seen in Table 1.

In the example, the catalyst layer 7 with a porosity of 60% was tested, but the present invention also produced remarkable effects on a catalyst layer with a porosity of 50%. However, in consideration of mechanical strength, the porosity is preferably 90% or less.

According to the above embodiment, the catalyst layer 7 is made of alumina silica fibers supporting Pt and Pd, BaO
, Al2O3, CeO3, alumina sol, etc., the heat radiation effect is high and the temperature drop is small in the continuous combustion life test.

[0020]

[Effects of the Invention] As is clear from the above embodiments, the present invention has the effect of suppressing changes over time in radiant heating characteristics and deterioration of combustion characteristics, and maintaining stable heating and heating efficiency for a long period of time. .

[Brief explanation of drawings]

[Fig. 1] A cross-sectional side view of essential parts showing the overall configuration of a catalytic combustion device in an embodiment of the present invention.

[Figure 2] Characteristic diagram showing temperature distribution in the thickness direction of the catalyst layer in Examples and Comparative Examples

[Figure 3] Characteristic diagram showing changes in the upstream surface temperature of the catalyst layer during continuous combustion life tests in Examples and Comparative Examples

[Explanation of symbols]

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

Claims (2)

[Claims] 1. A catalyst layer provided downstream of a fuel and air mixing chamber and having a large number of communication holes; a heat ray transmitter disposed opposite to an upstream surface of the catalyst layer; and a catalyst layer. an inorganic binder for bonding the ceramic powder to the heat-resistant inorganic fibers and a high specific surface area ceramic powder on which the catalyst layer supports heat-resistant inorganic fibers and a catalyst metal; A catalytic combustion device comprising: 2. The catalytic combustion device according to claim 1, wherein the catalyst layer is manufactured by corrugating using a papermaking method and has a porosity of 50% or more.