JPS6155420B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a catalyst for catalytic combustion in which various gases or evaporated liquid fuels are supplied together with combustion air onto a catalyst body, an oxidation reaction is caused on the surface, and the generated heat is utilized. The objective is to develop a catalytic combustor that prevents backfire from occurring on the surface of the red-hot catalyst and prevents combustion from moving upstream.

Conventionally, catalyst bodies for catalytic combustion have had an oxidation catalyst supported on the entire or entire surface of the catalyst carrier. Therefore, when such a catalyst body is used and fuel is delivered to the catalyst body, there is a risk of flashback whenever the airflow velocity of the fuel flowing near the catalyst body is not faster than the combustion velocity of the fuel.

Normally, in the case of this type of high-temperature catalytic combustion, the surface temperature of the catalyst body is in the temperature range of about 700°C to 1400°C, which is extremely dangerous if the fuel airflow velocity is slow. Therefore, this problem can be easily solved if the temperature can be lowered to some extent even on the side facing upstream where the airflow flows. However, in conventional catalyst bodies, in which the oxidation catalyst is supported on the entire catalyst body, the entire catalyst body becomes red hot, so we developed a method for making a catalyst body in which the catalyst is not supported only on the side into which the fuel air flows. Therefore, if this catalyst body is applied to catalytic combustion equipment, the combustion equipment can be made with less risk of flashback.

Furthermore, in the past, high-temperature catalytic combustion required a relatively high-velocity fuel airflow to be sent to the catalyst body, so its application was limited to some industrial applications. This opens the door to further application to combustion appliances.

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

1 to 4 show a catalytic combustion catalyst according to an embodiment of the present invention.

Figure 1 is an overall view of the catalyst carrier 1. The material is cordierite (2MgO ₂ 5SiO ₂ 2Al ₂ O ₃ ), and has an upper surface 2 and a lower surface 3 that are parallel to each other. has a large number of square small holes 4.

This small hole 4 has a square shape in the figure, but
The shape may be square, round, triangular, or hexagonal.

FIG. 2 is an enlarged cross-sectional view of the catalyst carrier 1 supporting a catalyst. The interior 6 of the catalyst carrier wall 5 made of porous material having micropores, its small pore surface 7, the upper surface 2, and the lower surface 3 are oxidized. A catalyst (represented by diagonal lines in the figure) is supported. Further, the lower surface 3 and the small hole surface 7 from the lower surface 3 to 1/4 of the small hole 4 are covered with a sealing ceramic cement 8 having heat resistance and fire resistance.

FIG. 3 is an enlarged cross-sectional view of another example of catalyst support, showing the inside 6 of the catalyst carrier wall 5 made of porous material having micropores, the small pore surface 7 from the top to 3/4, and
An oxidation catalyst (represented by diagonal lines in the figure) is supported on the upper surface, and 1/4 from the lower surface 3 of the lower surface 3 and the small hole 4.
Nothing is supported on the small hole surface 7 up to this point. (The manufacturing method will be described later.) FIG. 4 shows an example of a combustor constructed using the catalytic combustion catalyst according to the present invention.

Figure 4 shows an example in which the catalytic combustion catalyst according to the present invention is incorporated and applied to a hot air blower, in which a catalyst body 10 according to the present invention is installed at the tip of a horizontal cylindrical combustion tube 9 made of die-cast aluminum. On the back side, in order to prevent backfire from the red-hot catalyst body 10, a flashback prevention plate 11 made of a heat-resistant inorganic material that does not support a catalyst has micropores 12 smaller than the catalyst body 10. The flow velocity of the fuel airflow passing through the micropores 12 is set higher than the combustion velocity of the fuel. Further, on the back side of the flashback prevention plate 11, a diffusion plate 13 made of a plurality of punched metal sheets is placed to improve the mixing of fuel and air. At the rear of the combustion tube 9, there is a vaporization surface 14 for vaporizing liquid fuel on its surface, and on the outside of the vaporization surface 14, a sheathed heater 15 for heating the vaporization surface 14 in the early stage of combustion is embedded in aluminum die-casting. There is. The above-mentioned components together form the main part of catalytic combustion. A combustion air inlet 16, which is an inlet for feeding air for combustion, is opened at the rear of the combustion tube 9. Behind the combustion tube 9, a motor 17 is connected to a main shaft 18 for feeding combustion air and turning liquid fuel into fine particles.
It is installed horizontally. Motor 1
The tip of the main shaft 18 extending in front of the combustion tube 9
The tip of the combustion air inlet 16 enters a combustion air inlet 16 opened at the bottom of the liquid fuel atomization plate 1 for spraying the liquid fuel as fine particles onto the vaporization surface 14.
9. It is further connected to a liquid fuel diffusion plate 20 for widely diffusing the atomized liquid fuel in the axial direction. A truncated cone-shaped cone 21 is placed between the liquid fuel atomization plate 19 and the main shaft 18, and plays the role of smoothly guiding the liquid fuel to the liquid fuel atomization plate 19. There is a turbo fan 22 directly connected to the main shaft 18 in the center of the main shaft 18.
are provided in multiple stages, two stages in the drawing, and guide vanes 24 fixed to the burner case 23 are provided on the discharge side of each turbo fan 22. A blowing chamber 25 is configured by a combination of the turbo fan 22 and the guide blades 24, and by increasing the number of stages in the combination, the static pressure can be increased. Further, an air intake port 26 is provided in the upper part of the burner case 23. The supplied liquid fuel is delivered to the surface of the cone 21 through a fuel supply pipe 27 by an electromagnetic pump (not shown).
Immediately in front of the catalyst body 10, a heat exchange tube connecting fitting 29 to which a large number of heat exchange tubes 28 made of thin metal tubes are connected is connected to a combustion cylinder flange 30 by bolts 31 and nuts 32. The heat exchange fitting 29 is also provided with an electrode 33 for ignition.

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

First, an electric current flows through the sheathed heater 15 embedded inside the combustion tube 9, and the combustion tube itself is heated. The temperature at the vaporizing surface 14 of the combustion tube 9 is 250°C
When the temperature reaches ~300°C, the motor 17 begins to rotate, and after a few seconds, an electromagnetic pump (not shown) for supplying liquid fuel moves through the liquid fuel pipe 27 to the tip of the main shaft 18 connected to the motor 17. It is ejected onto the side wall of the truncated cone 21 located at the truncated cone 21.
The ejected liquid fuel flows along the side wall of the rotating cone 21, moves to the liquid fuel atomization plate 19,
The centrifugal force turns the liquid fuel into fine particles from the edge of the liquid fuel atomizing plate 19 and blows them toward the vaporizing surface 14 . On the way, the blown fine particles are further spread in the axial direction than the liquid fuel diffusion plate 20, and the particles are further made finer. These liquid fuel particles hit the heated vaporization surface 14 and are vaporized there.
On the other hand, as the motor 17 rotates, the turbo fan 22 connected to the main shaft 18 is also rotated by the main shaft 18. When the turbo fan 22 generates wind pressure, the combustion air flows through the air intake port 26 → the blowing chamber 25 →
Passes through the combustion air inlet 16 and enters the combustion cylinder 9,
The liquid fuel gas evaporated by the vaporization surface 14 passes through the diffusion plate 13 and the flashback prevention plate 11, causing oxidative heat generation on the surface of the catalyst body 10.

When this burner is ignited, the electrode 33 in front of the catalyst body 10 sparks, and the combustion gas that has passed through the small holes in the catalyst body 10 is ignited, and in the initial state it emits a flame like a normal flame burner. Form and burn.
However, in a few tens of seconds, the catalyst body 10 receives radiant heat generated by the flame, and the surface temperature of the catalyst body 10 rises to reach the temperature of catalytic activation, and the process shifts to catalytic combustion. Although the temperature of the catalyst body 10 is not constant depending on its location and combustion conditions, it ranges from 700°C to 1400°C where the oxidation catalyst is supported.

Next, an example of the catalyst production method will be shown below.

Catalyst specifications (Part 1) Catalyst material: α-Al ₂ O ₃ porosity: Approx. 30% Shape: 70φ×25 Cell hole 1.5 mm square, cell thickness 0.5 mm The above α-Al ₂ O ₃ carrier is γ-Al The following mixed solution is prepared to support ₂ O ₃ fine particles. 10% alumina sol and ion-exchanged water are thoroughly stirred and mixed at a weight ratio of 1:2, and about 10% by weight of γ-Al ₂ O ₃ fine powder is added little by little into the alumina sol mixture while stirring. Dip the burner port material into the mixture, dry it in hot air, and then bake it in air at 500°C for 3 hours. After cooling this material again, it was immersed in an acetone solution of vinyl acetate polymer (approximately 20%) from one side of the carrier to a depth of 5 mm for 1 second, taken out immediately, and the acetone was evaporated with warm air (approximately 50°C). let After being placed in a drying oven at 100° C. for about 30 minutes, the carrier is taken out, and the other side of the carrier is brought into contact with an aqueous chloroplatinic acid solution to be supported within the carrier by capillary action. The concentration of the solution is adjusted so that the amount of platinum supported is 0.1 to 0.3 g per carrier. Further, after thoroughly drying the moisture at 80°C, it is fired at 600°C in air for about 2 hours. At this temperature, the portion covered with vinyl acetate resin is completely incinerated and removed, returning only the original carrier.

Catalyst Specifications (Part 2) The same catalyst carrier as above is used, and the oxidation catalyst is supported first. (The supporting method is the same as in (i)) After supporting the catalyst, dilute alumina cement (for example, Aron Ceramic manufactured by Toagosei Chemical) with water, and Dip it to a depth of 5mm, take it out immediately and dry it.

The vicinity of one surface of the catalyst body thus obtained is completely sealed, and the oxidation catalyst is not exposed.

In the above example, α-Al ₂ O ₃ was used as the carrier.
In addition to α-Al ₂ O ₃ , mullite (3Al ₂ O ₃ .
2SiO ₂ ), cordierite (2MgO・5SiO ₂・
Examples include ceramics such as 2Al ₂ O ₃ ), zirconia (ZrO ₂ ), silicon carbide (SiC), and silicon nitride (Si ₃ N ₄ ). These ceramics have excellent heat resistance (1000°C or higher) and thermal shock resistance, so they can be said to be suitable as carriers for catalytic combustion. In particular, cordierite is inexpensive, has excellent thermal shock resistance, and is the easiest material to use from a practical point of view (somewhat weak in heat resistance...maximum practical temperature of 1100-1200°C). in this way,
The carrier material can be arbitrarily selected from the above-mentioned materials depending on its intended use.

Further, as for the oxidation catalyst, Pt is used in the examples, but any catalyst can be selected as long as it exhibits oxidizing ability for hydrocarbons and is easily supported on the carrier. That is, in platinum group metals, in addition to Pt, Pd, Rh,
Ru, Ir, etc. can be used alone or in combination, and transition metal oxides such as Co, Ni,
Oxides such as Fe, Mn, Cu, Cr, and Zn can be used alone or in combination. Furthermore, a platinum group metal and a transition metal oxide may be combined. However, depending on the combination of the carrier material and the catalyst material, the catalytic activity may quickly deteriorate, so it is necessary to be careful about the combination. For example, when transition metal oxides such as Ni and Co are supported on a support that contains Al ₂ O ₃ , they will react with Al at high temperatures.
Ni, Co, etc. react to form spinel (NiAl _z O ₄ ,
CoAl _z O ₄ ) and degrade the activity. In such cases, to stabilize the transition metal oxide,
Composite with La etc. to form LaNiO ₃ or
One method is to use perovskite composite oxides such as LaCoO ₃ .

The catalytic combustion catalyst of the present invention provides the following effects.

Since the oxidation catalyst is not supported on the entire catalyst body, the temperature of the catalyst surface facing upstream into which the fuel airflow flows does not rise, so it is possible to avoid the risk of flashback to the upstream side of the fuel airflow.

The temperature of the exhaust gas discharge surface of the catalyst is higher than that of conventional catalysts, which is very advantageous for applications where infrared radiant heat is actively extracted.

There is no risk of backfire even if the speed at which the fuel gas passes through the catalyst is not high (speed higher than the combustion speed of the fuel), so it is suitable for consumer use such as household combustion equipment, which has not received attention as an application for high-temperature catalysts in the past. The possibility of application and expansion has emerged.

[Brief explanation of the drawing]

FIG. 1 is an overall view of the catalyst carrier of the catalyst of the present invention, and FIG.
3 is an enlarged cross-sectional view of a catalyst supported on a catalyst carrier in an embodiment of the present invention, and FIG. 4 is a diagram showing a case where the catalytic combustion catalyst of the present invention is applied to a practical device. 1...Catalyst carrier, 4...Small pores, 5...Carrier wall surface, 9...
Combustion tube, 10...Catalyst body, 11...Flashback prevention plate, 13
...diffusion plate, 14...vaporization surface, 15...sheathed heater,
16...Combustion air inlet, 17...Motor, 19...Liquid fuel atomization plate, 20...Liquid fuel diffusion plate, 22...Turbo fan, 26...Air intake port, 27...Fuel supply pipe, 28...Heat exchange tube.

Claims (1)

[Scope of Claims] 1. One surface of a catalyst carrier made of a heat-resistant inorganic material having substantially parallel surfaces and a large number of small pores in the thickness direction, and a predetermined length from the one surface of the inner wall of the small pores. The oxidation catalyst is supported on the other side and the other part of the inner wall of the small hole, or the oxidation catalyst is not supported on the other surface and the oxidation catalyst is supported on the oxidation catalyst with a heat-resistant and fire-resistant sealing material. A catalytic combustion catalyst characterized by being coated. 2 Mullite (3Al ₂ O ₃
2SiO ₂ ), α-alumina (Al ₂ O ₃ ), cordierite (2MgO・5SiO ₂・2Al ₂ O ₃ ), zirconia (ZrO _z ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), etc. 2. The catalytic combustion catalyst according to claim 1, characterized in that said ceramic is used. 3. As an oxidation catalyst, at least one combination of platinum group metals such as Pt, Pd, Rh, Ru, and Ir, or Co, Ni, Fe, Mn, Cu,
At least one of transition metal oxides such as Cr, Zn, etc.
The catalytic combustion catalyst according to claim 1, characterized in that a combination of two or more types or a combination of a platinum group metal and a transition metal oxide is used. 4. A water-repellent organic polymer substance that is soluble in an organic solvent is dissolved from one side of a catalyst carrier made of a heat-resistant inorganic material having substantially parallel surfaces and many small pores in the thickness direction. impregnating the surface with a solution in which the catalyst salt is dissolved so that the impregnated region remains within a certain range in the thickness direction from the one surface, and after evaporating the solvent of the solution, impregnating the other surface with a solution in which a catalyst salt is dissolved;
A method for producing a catalyst for catalytic combustion, which is characterized by evaporating water and then firing it.