JPS5864418A - Catalytic combustor - Google Patents

Abstract

PURPOSE:To raise the outer surface temperature and enable to radiate a large quantity of heat in the form of infrared ray by a structure wherein thorium oxide and cerium oxide are borne onto the outer surface of a heat resisting inorganic tube, onto the inside surface of which catalyst is borne. CONSTITUTION:The catalytic combustor A is used for heating and the like by utilizing the heat released at the oxidation reaction performed by supplying gaseous fuel or evaporated liquid fuel together with combustion air from a feeding pipe 5 onto the catalyst 3 borne onto the inside surface of a plurality of tubes 1, which are arranged at the front of the combustor A in parallel to one another. The exhaust gas is discharged outdoors through a discharge pipe 6. In this case, the tube 1 is made of heat resisting inorganic substance such as alumina, mullite or the like with the inside diameter of 1.0-5.0mm.. The inside surface of the tube 1 is coated with undercoat such as alumina or the like and, after that, borne on with the catalyst 3. Furthermore, a layer 7 comprising in mixing thorium oxide with cerium oxide is borne on the outside surface of the tube 1 in order to complete the constitution of the tube 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalytic combustor that supplies various gases or evaporated liquid fuels together with combustion air onto a catalyst body, causes an oxidation reaction on that surface, and utilizes the amount of heat generated. The purpose of this is to efficiently convert the generated energy into infrared rays and radiate it to the outside of the tube for heating, etc., as well as to release exhaust gas outdoors.

Conventional catalytic combustors supply fuel onto a catalytic body, causing the catalytic body to generate heat, and simultaneously emit radiant heat from the catalytic body and hot exhaust gas into the room. Therefore, the indoor environment is also polluted by various exhaust components (CO+, 12, or some unburned aH, co, etc.). It is not impossible to adopt a catalytic combustion system and then pass the hot exhaust gas through a heat exchanger to exchange heat, but this method eliminates the abundant radiant heat that is the greatest advantage of the catalytic combustor. , and the device has to be complicated.

The present invention is intended to improve the various drawbacks mentioned above, and to take full advantage of the characteristics of catalytic combustion power. That is, by supporting thorium oxide and cerium oxide on the outer surface of a tube with a catalyst supported on its inner surface, the temperature of the outer surface is raised and a large amount of heat rays are emitted to the outside as infrared radiation. . The thorium oxide present on the outer surface of the tube of the catalytic combustor of the present invention coexists with a small amount of cerium oxide, so that it is easily heated to a high temperature and emits radiation including heat rays. Therefore, energy can be efficiently radiated from the outer surface of the tube. Note that the above-mentioned thorium oxide and cerium oxide do not have these properties at all by themselves; thorium oxide emits almost no thermal radiation even at high temperatures, and cerium oxide has difficulty reaching a sufficiently high temperature. Therefore, each of the above-mentioned oxides must be used as a mixture, and the ratio of cerium oxide to 100 parts of Yium oxide is appropriate in the range of 0.1 to 10 parts.
The one containing about 30% is most effective.

An embodiment of the present invention will be described below with reference to the drawings.

Multiple tubes made of inorganic heat-resistant materials such as lights (inner diameter 1
~5+nm) 1 are installed in parallel. The inner surface of the tube body 1 is coated with an undercoat 2 which has a large surface area, carries a catalyst, maintains the temperature at a high temperature, and suppresses sintering as much as possible.
Apply. The most common material for the undercoat is γ-alumina (γ-Koku2o3), which has been treated at about 1200'C for several hours, but in addition, zirconia oxide (
ZrO2) and thorium oxide (TrO2) are also good materials from the viewpoint of heat resistance. Furthermore, the catalyst body 3 is supported from above. Various materials can be used for the catalyst body 3. That is, there are many possible materials such as noble metals, transition metal oxides, rare earth element oxides, and combinations thereof, but as a result of experiments, pt-pd materials showed the best low-temperature activity and oxidation ability.

A fan 4 for blowing air is installed opposite to the rear of a group of tubes that are installed in parallel and have inner surfaces treated, and the wind helps dissipate heat from the outer surface of the tubes 1 and flows toward the front as warm air. There is. The tube bodies 1 are each brought together at both ends. That is, one side is a fuel inlet pipe 5 for feeding a mixture of fuel and combustion air, and the other side is an exhaust pipe 6 for discharging exhaust gas outdoors.

Note that a mixed layer 7 of thorium oxide and cerium oxide is supported on the outer surface of the tube 1.

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

First, the tube body 1 itself is heated by a method such as the one described above to bring it to the catalyst activation temperature. Various heating methods can be considered, such as using an electric heater or heating from outside the tube body 1 with a heating burner.

Next, the fuel and combustion air mixture is passed through the fuel inlet pipe 6 to the pipe body 1.
catalytic combustion is carried out on the catalyst body 3 supported on the inner surface of the tube body 1. Further, at the same time as combustion starts, the fan 4 rotates, and air for heat exchange is flowed forward of the tube 1 while touching the outer surface of the tube 1. Energy d generated on the inner surface of the tube body 1 is used for heating as radiation from the outer surface of the tube body 1 or as hot air after heat exchange.

Next, a structure in which a catalyst body 3 and a mixed layer 7 of thorium oxide and cerium oxide are supported on the inner and outer surfaces of the tube 1 will be specifically described.

Tube 1 material: inner diameter 3φ, outer diameter 4φ, length 250mm
A mullite tube was used. The material used as an undercoat on the inner and outer surfaces of the tube body 1 was adjusted as follows. Gamma alumina powder which had been previously calcined at 1200'C for 4 hours (thereby changing the surface area of the powder from about 3oom!/y to about 20m!/y) was milled into a fine powder of 10μ or less.

10% aluminium/L'30y to 100y of this powder.

305F zirconium nitrate and 2 oz of water were added and thoroughly kneaded. After the undercoat material was applied to the inner and outer surfaces of the tube 1, it was dried at 100°C for 6 hours, and then baked at 600℃ for 2 hours, and then a chloroplatinic acid solution was poured on the inner surface of the tube 1 to remove excess water. wash away t), 100
It was dried in 'C hot air for 6 hours, and further baked at 600°C for 2 hours. The concentration of the chloroplatinic acid aqueous solution was adjusted so that the supported amount was 0.1 to 0.2% by weight of platinum.

7- Finally, a solution of 100 ml of thorium nitrate and 2 y of cerium nitrate dissolved in 200 ml of water was applied to the outer surface of the tube body 1, dried in hot air at 100'C for 6 hours, and heated to 900'C.
℃? ``The undercoat described above does not need to be applied to the outer surface of the tube body 1, but it is better to apply it in order to strengthen the adhesion strength of thorium oxide and cerium oxide and to ensure uniform adhesion. .

The material of the tube 1 is made of a heat-resistant inorganic material such as a ceramic material, and infrared radiation can be efficiently obtained from the surface even with this material. Ceramic materials have better radiant heat efficiency than metal materials, and although it varies depending on the object to be heated, it is well known that, for example, when heating water, ceramic radiation is about 15 cm more efficient than metal surface radiation, resulting in energy savings. It is a fact. In this example, it was found that by coating the outer surface of the tubular body 1 made of this ceramic material with the above mixed layer 7, which is a material that easily emits radiation, the improvement was further improved by about 6%.

Moreover, the above structure prevents the catalyst body 3 from being destroyed due to excessive overheating. In other words, a catalyst body similar to this type of catalyst body 3 that uses a ceramic honeycomb cannot be put into practical use because the temperature of the catalyst body itself rises unless combustion is carried out with a considerable excess of air. However, when burned in a region close to theoretical air, 16
The temperature may even reach 00°C to 1700°C. Therefore, in the catalytic combustor according to this embodiment, heat dissipation by radiation energy and heat exchange heat dissipation by air are sufficient, so even in the region close to theoretical air, the maximum is about 110°C, and the average is about 90°C.
It can burn at temperatures of 00 to 1000°C, and can sufficiently deal with deterioration of the catalyst body 3.

Next, the effects of the catalytic combustor of the present invention will be listed.

(1) A catalytic combustor with a relatively simple configuration that can prevent exhaust gas from being released into the room and that can perform heating mainly using radiation.

(2) Sufficient heat dissipation is possible, so even if the catalyst is burned near the theoretical air amount, the catalyst body will not reach a significantly high temperature, and the deterioration life of the catalyst body can be extended, resulting in efficient combustion. becomes possible.

(3) Since the combustion part also serves as a heat exchanger, the entire device becomes compact.

(4) Although the exhaust gas is discharged outside, the composition of the exhaust gas is cleaner than in the case of general flame combustion.

In particular, compared to 1 ooppm (when converted to 0 oxygen) in the case of general flame combustion such as NOx, the catalytic combustor of the present invention has, for example, less than s ppm (when converted to 0 oxygen), and
O is also almost undetectable, making it a clean product.

[Brief explanation of the drawing]

FIG. 1... Tube body, 3... Catalyst body, 4...
...Fan, 7...Mixed layer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Scope of Claims] (1) A catalyst body is supported on the inner surface of a tube made of a heat-resistant inorganic material, into which a mixture of gas fuel or vaporized liquid fuel and combustion air is fed from one port, and this tube A catalytic combustor with thorium oxide and cerium oxide supported on its outer surface. (2) The catalytic combustor according to claim 1, wherein the heat-resistant inorganic material is at least one of alumina, mullite, cordierite, and aluminum titanate. (3) The catalytic combustor according to claim 1, wherein the inner diameter of the tube is 1.0 to 5.0 mm. (The ratio of thorium tetroxide and cerium oxide is 100:0
．． Claim 1 in the range of 1 to 1oO:10
Catalytic combustor as described in section. (5) A combustor as claimed in the claim, in which a fan is provided opposite to the pipe body.