JPS61147014A - Catalytic burner - Google Patents

Abstract

PURPOSE:To promote an effective oxidative reaction and reduce amount of catalysts by a method wherein a catalytic body for combustion purpose containing an oxidative catalyst in a ceramic body are divided into three layers, among them, the rear surface layer faced to a fuel supplying unit, and the other of the front surface accessed to a diffusing air, are formed with a lower rate of carrying capacities compared with the middle layer. CONSTITUTION:When a thermo-couple 12 to detect a combustion temperature detects a preheating temperature exceeding a given level an electric-magnetic valve is energized to open valve, thereby fuel is supplied. The supplied fuel gas is filled in a gas chamber 4 with a full, which is diffusing uniformly inside of a thermal insulation diffusing member 5 to reach the rear surface of combustion layer 7, where combustion gas is partly oxidized to generate a heat, thereby the both temperatures of rear surface combustion of catalyst layer 7 and the middle combustion catalyst lever 8 are increased. The fuel gas passing through the rear surface combustion catalysts layer 7, during which a partial oxidative reaction is being generated, proceeded to the middle combustion catalyst layer 8, where oxidative reaction is rapidly promoted by a combustion air internally being diffused, simultaneously the temperature of the middle combustion catalyst layer 8 is rapidly increased up to 500 deg.C. When the fuel gas, which is mostly oxidized more than half so far, has reached the front surface combustion catalyst layer 9, the fuel gas has been completely oxidized there.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention supplies gaseous fuel or vaporized liquid fuel onto a catalyst body, catalytically oxidizes the fuel with combustion air, and oxidizes the combustion produced by the reaction. This invention relates to a catalytic burner that utilizes heat and radiant heat.

BACKGROUND OF THE INVENTION Conventionally, as shown in FIG. 2, in this type of catalyst burner, a diffusion material 3, Pt, and Rh are placed in a burner case 2, which is installed from the back side into a fuel dispersion pipe 11 having a large number of small holes.

The composition includes a single combustion catalyst layer 4 that supports an oxidation catalyst using one or more platinum group metals such as P(i) at a constant loading rate, and the fuel is fed from the fuel dispersion pipe 1. The gas fuel reaches the combustion catalyst layer 4 while uniformly diffusing inside the diffusion material 3, and after being ignited by some kind of ignition means, steady catalytic combustion is performed on the surface of the combustion catalyst layer 40. (For example, Japanese Unexamined Patent Publication No. 58-213110) Problems to be Solved by the Invention However, in the above structure, the atmosphere side of the combustion catalyst layer 4,
Since the reactivity differs between the center and the back surface, the temperature of each region also differs. In particular, near the back surface of the combustion catalyst layer, the ratio of fuel gas to combustion air is very large, so only a portion of the fuel gas reacts, whereas the fuel gas reaches the center of the combustion catalyst layer. For example, the proportion of combustion air present increases, and the reaction proceeds rapidly, resulting in a rapid rise in reaction temperature. Furthermore, by the time the fuel gas reaches the part of the combustion catalyst layer 4 close to the atmosphere, the residual fuel gas that has not completely reacted in the central part is oxidized by a large amount of diffused air, so the reaction heat generated is not large. At the same time, the generated reaction heat is released, and the cooling effect of the diffused air also affects the temperature, so it forms the coldest part. Therefore, the temperature distribution of the combustion catalyst layer 4 during the steady catalytic oxidation reaction has the highest temperature at the center, followed by the back surface and the atmosphere side. Therefore, the ideal distribution of the oxidation catalyst loading rate is such that the central part requires the most amount, while the back side, where the proportion involved in one reaction is low, has a low loading rate. The loading rate is lower than that in the center. However, in a single combustion catalyst layer 4 in which the oxidation catalyst loading rate is constant in each part, a loading rate distribution that corresponds to the reactivity can be obtained, especially when an expensive oxidation catalyst such as a platinum group metal is used. However, in order to obtain the amount of oxidation catalyst necessary for combustion, it was necessary to prepare for a considerably high cost.

The present invention solves these conventional problems by making each layer of the combustion catalyst have catalytic performance according to its reactivity, allowing efficient oxidation reaction, and reducing the overall amount of catalyst. purpose.

Means for Solving the Problems In order to solve the above problems, the catalytic burner of the present invention has a combustion catalyst body in which an oxidation catalyst is supported on a heat-resistant ceramic carrier divided into three layers, and a fuel supply section. The back layer close to the central layer and the surface layer close to the diffusion air have lower loading rates than the central layer.

According to the above-described structure, the fuel gas supplied from the fuel supply section partially reacts on the back layer of the combustion catalyst body, and reaches the center layer where the oxidation catalyst is supported the highest while increasing the temperature, and rapidly The reaction progresses, and at the same time the temperature rises rapidly and reaches the surface layer. In the surface layer, most of the fuel gas is combusted, and unburned components are completely combusted. Therefore, the supporting ratio of the oxidation catalyst in the center layer is relatively higher than that in the back layer and the surface layer, resulting in an efficient and inexpensive product.

EXAMPLE Hereinafter, an example of the present invention will be explained based on the accompanying drawings.

In FIG. 1, a fuel dispersion nozzle 2 is installed through the lower part of a burner case 1 made of a heat-resistant metal.

A gas chamber 4 is formed by the burner case 1 and a spacer 3 in the form of a wire mesh or lath mesh having a high degree of aperture so that ventilation resistance is negligible. On the other hand, in front of the spacer 3, in the vicinity of the spacer 3, there is a heat insulating diffusion material 6 made of a heat-resistant ceramic fiber molded body, a preheater 6 in which nichrome heater wires are distributed in a fixed pattern, and a mu e203.
A heat-resistant ceramic/ac fiber molded body having micropores such as 5io2 and a high specific surface area is used as a carrier, and 0.2 to 0
．． A back combustion catalyst layer 7 having a Rh loading rate of 3%, a central combustion catalyst 118 having a Rh loading rate of 0.5 to 1 ton on a similar carrier, and a further 0.2 to 0.3 ton on a similar carrier. There is a surface combustion catalyst 1i9 having a Rh loading ratio of Protective net 1
0 is fixed at its outer periphery by a holding fitting 11. In addition, the back combustion catalyst 1ii7 and the central combustion catalyst layer 8
A thermocouple 12 for combustion temperature detection is installed between the two.

Next, the operation of the above configuration will be explained.

When the preheater 6 is energized, the generated heat is transferred from the back combustion catalyst 1ij7 to the front combustion catalyst layer 9, and the temperature between the back combustion catalyst layer 7 and the center combustion catalyst layer 8 is kept constant. The energization is continued until the temperature reaches (260 to 300'C). When the thermocouple 12 for detecting combustion temperature detects that preheating has progressed to a certain temperature or higher, a solenoid valve (not shown) for supplying fuel gas is also energized, and fuel is supplied. The supplied fuel gas fills the gas chamber 4 through the fuel dispersion nozzle 2, and while uniformly diffusing inside the heat-insulating diffusion material 6, reaches the back combustion catalyst layer 7, where a part of the fuel gas is oxidized and generated. The heat causes the temperatures of the back combustion catalyst layer 7 and the central combustion catalyst Iw8 to rise. The fuel gas that has passed through the back side combustion catalyst layer 7 while partially reacting is transferred to the center combustion catalyst layer 8.
At this point, it is rapidly oxidized by the combustion air that diffuses inside, and at the same time, the temperature of the central combustion catalyst layer 9 also increases to 500°.
It rises rapidly to about C. Further, the fuel gas, most of which has been oxidized, reaches the surface combustion catalyst +99 and is almost completely oxidized. At this stage, the preheater 6 is not required, and the power supply to the preheater 6 is stopped.

At this time, the surface combustion catalyst 19 transfers the combustion heat in the central combustion catalyst layer and obtains its own reaction heat, but it also releases heat as radiant heat and has a strong cooling effect of the diffused air. The temperature of the surface combustion catalyst layer 9 is the lowest, 260 to 350.
It will be about C. In this way, the back side combustion catalyst layer 7.
Catalytic combustion in each layer of the central combustion catalyst layer 80 and the surface combustion catalyst layer 9 reaches a steady state. The Rh loading rate of the central combustion catalyst layer 8 is higher than that of the other two layers, but as a carrier, it has a high specific surface area of 100 to 200 d/9,
Mu e2 with high heat resistance of 800-900°C
05・Sio2 is used, so the temperature is 460~550'C
Even in the central combustion catalyst layer 8 which maintains a combustion temperature of , the catalyst particles are relatively highly dispersed and can maintain a fine particle state. Furthermore, since the supporting rate of the oxidation catalyst in the surface combustion catalyst layer 9 is lower than the supporting rate of the oxidation catalyst in the central combustion catalyst layer 8, the degree of dispersion of the oxidation catalyst particles in the surface combustion catalyst layer 9 is lower than that of the central combustion catalyst layer. The degree of dispersion is higher than that in layer 8, and an extremely good state of fine particles can be maintained. Furthermore, since the reaction temperature in the surface combustion catalyst layer 9 is about 250 to 350°C, there is no fear of sintering.

Effects of the Invention As described above, the catalytic burner of the present invention provides the following effects.

(1) The combustion catalyst body is divided into three layers, and the oxidation catalyst loading rate on the front and back layers is lower than the oxidation catalyst loading rate in the middle layer, resulting in lower reactivity than in the middle layer. The amount of oxidation catalyst in the reactive surface layer and back layer can be reduced.

(2) With the above configuration, the required amount of catalyst metal can be reduced compared to the case of a single combustion catalyst body with a fixed loading rate.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a catalytic burner according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a conventional catalytic burner. 2... Fuel dispersion nozzle, 7... Back combustion catalyst layer, 8... Central combustion catalyst layer, 9...
...Catalyst layer for surface combustion. Name of agent: Patent attorney Toshio Nakao and one other name
1 figure

Claims (3)

[Claims] (1) Using one type of carrier such as a non-compression molded body made of ceramic fibers, a woven fabric, or a porous body, the combustion catalyst body carrying an oxidation catalyst is divided into three layers, and the layer near the fuel supply part and the A catalytic burner in which the oxidation catalyst loading rate in the layer facing the outside air is lower than the oxidation catalyst loading rate in the central layer located between these two layers. (2) γ-Al_2O_3 as a carrier for the combustion catalyst;
The catalytic burner according to claim 1, which uses ceramics that are porous and have a high specific surface area, such as Al_2O_3.SiO_2 and SiO_2. (3) As an oxidation catalyst, one or more of platinum group metals such as Pt, Pd, Rh, etc., or an oxide having a perovskite structure consisting of La, Co, Ce, Sr, etc. is used as the oxidation catalyst. Catalytic burner according to item 1.