JPH0227565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a means for preheating an oxidation catalyst in a domestic or industrial catalytic combustor that performs flameless combustion at 500°C or less on an oxidation catalyst supporting a catalyst. It is something.

Structure of a conventional example and its problems An example of a mechanism for igniting an oxidation catalyst body of a conventional catalytic combustor is shown in FIGS. 1 to 5.

In the case of Fig. 1, a Bunsen burner 2 is provided at the outer lower part of the oxidation catalyst body 1, and the flame of the Bunsen burner 2 heats the oxidation catalyst body 1, and after reaching a predetermined temperature, the process shifts to catalytic combustion. . In addition, as shown in Figures 2 and 3, a pilot flame 3 or ignition electrode 4 is provided in front of the oxidation catalyst 1, so that a flame is initially formed in front of the oxidation catalyst 1 and then automatically changes to catalytic combustion. It was structured like this. In the above examples, the fuel gas passes through the oxidation catalyst body 1 before the oxidation catalyst body 1 is sufficiently and uniformly heated, so the leakage of fuel gas is quite large, especially for gases that are difficult to burn, such as methane. There is a leakage of several tens of percent over several minutes. Furthermore, the ignition equipment was exposed on the front of the oxidation catalyst 1, making the design unsightly.

When using an electric heater as a means to heat the oxidation catalyst body 1, considering the safety against electric leakage,
In many cases, a sheathed heater (Fig. 4) or ribbon heater 6 (Fig. 5) is used, which increases the cost of commercialization, and also makes it impossible to arrange the heaters densely, resulting in poor thermal conductivity. It was not possible to heat the oxidation catalyst evenly and uniformly.

OBJECTS OF THE INVENTION The present invention solves the above problems and aims to uniformly and quickly preheat an oxidation catalyst body.

Structure of the Invention In order to achieve the above object, the present invention has a structure in which radiation, mainly infrared rays, is irradiated from the front surface of the oxidation catalyst to uniformly and quickly preheat the oxidation catalyst. In other words, infrared heaters that emit a large amount of radiation (usually ceramic or heat-resistant glass tubes with electrical resistance wires sealed in them) are placed above, below, or to the left and right of the front of the oxidation catalyst, with the radiation surface facing the surface of the oxidation catalyst. That's what I do. With this configuration, the entire surface of the oxidation catalyst can be uniformly preheated, and the preheating time can be considerably shortened.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 6 and 7. Identical components shown in the drawings are designated by the same numbers. In FIG. 6, a diffusion mat 5 made of mat-shaped heat-resistant ceramic fibers is provided in close contact with the rear of the oxidation catalyst body 1 carrying a rhodium catalyst made of mat-shaped alumina fibers, and wire mesh A7 and wire mesh B8 are placed in front and behind the diffusion mat 5. , and install the integrated product in the combustion device main body 9. A slight gap is made in the front part of the oxidation catalyst body 1, and electric resistance wires 11 are placed in heat-resistant ceramic tubes 10 at the upper and lower parts.
A preheating heater (infrared heater) 12 is installed. A reflecting plate 13 having a parabolic surface is attached to the infrared heater 12 so as to efficiently radiate the radiation to the front surface of the oxidation catalyst body 1. A fuel gas diffusion pipe 16 having small holes 15 for uniformly supplying fuel gas is installed in a space 14 at the rear of the diffusion mat 5, and a fuel gas supply pipe 17 is connected thereto. Further, a thermocouple 18 is inserted into the oxidation catalyst 1 from the outer wall of the combustion device main body 9.

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

First, a current is applied to the infrared heater 12 to uniformly apply infrared radiation to the surface of the oxidation catalyst 1. When the temperature of the oxidation catalyst 1 reaches a predetermined temperature (which can be detected by the inserted thermocouple 17), fuel gas is supplied from the fuel gas supply pipe 17, enters the fuel gas diffusion pipe 16, and flows through the small hole 15. It is ejected into the space 14. Furthermore, the fuel gas is sufficiently diffused by the diffusion mat 5 and reaches the oxidation catalyst body 1, where low-temperature catalytic combustion is performed by secondary air supplied from the outer surface of the oxidation catalyst body 1.

Figure 8 shows a case in which a sheathed heater (see Figure 4) is used as a mechanism for preheating the oxidation catalyst, and a case in which the surface of the oxidation catalyst according to the present invention is irradiated and heated with a quartz heater (electric resistance wire enclosed in a quartz tube). Figure 2 shows the temperature rise characteristics of the front surface of the oxidation catalyst.

The surface area of the oxidation catalyst is approximately 1000cm ² and the amount of combustion is
The sheathed heater used as a conventional preheating heater was 1300kcal/h and was about 5m long and 500W, and two 400W quartz heaters were used.

As is clear from FIG. 8, the time required for preheating is considerably shortened, and since the surface of the oxidation catalyst is heated by radiation, the start-up is particularly noticeable. Of course, there is a difference in the output of the heater used, 500W and 800W, but the effect is even greater than that. Further, in this embodiment, an example was shown in which the infrared heaters were placed above and below the oxidation catalyst, but the same effect can be obtained on the left and right sides.

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

(1) Since the oxidation catalyst is preheated uniformly from the surface, it is possible to eliminate fuel leakage at the start of catalytic combustion.

(2) Since heating is performed using radiation, the oxidation catalyst can be quickly raised to a predetermined temperature.

(3) Since preheating is performed only on the surface of the oxidation catalyst, there is no need to heat unnecessary parts such as the inside of the combustor or the back surface, and a rise in temperature of the combustor body can be prevented.

(4) Since the surface of the oxidation catalyst is irradiated with red light during preheating, a warm feeling can be visually conveyed from the beginning. (Previously, it took a considerable amount of time for the catalyst to be heated by combustion and for the radiation to actually be emitted.)

[Brief explanation of drawings]

1 to 5 show conventional catalytic combustors;
3 is a perspective view thereof, FIGS. 4 and 5 are partially sectional front views, FIG. 6 is a sectional view of an embodiment of the catalytic combustor according to the present invention, and FIG. 7 is a catalytic combustor used therein. FIG. 8, which is a block diagram of an infrared heater, is a characteristic diagram of temperature versus preheating time of the oxidation catalyst in the conventional example and the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Oxidation catalyst body, 10... Heat resistant ceramic tube, 11... Electric resistance wire, 12... Preheating heater.

Claims (1)

[Claims] 1. An electrical resistance wire is sealed in a ceramic tube, quartz tube, or heat-resistant glass tube at an angle where the radiation is irradiated on the surface of the oxidation catalyst, which has a catalyst supported on a mat of heat-resistant inorganic fibers. A catalytic combustor with preheating heaters installed at the top and bottom or left and right in front of the oxidation catalyst.