JPS5922650A - Catalyst unit - Google Patents

Abstract

PURPOSE:To remove oil mist efficiently, by laminating a metallic mesh layer, a filter layer, and a catalyst layer in a casing in this order from the upstream side of an exhaust gas. CONSTITUTION:Two sheets of catalyst layer 11 carrying platinum prepd. by immersing the surfaces of silica cloths impregnated with 5-10% gamma-alumina in advance, into an aq. soln. of chloroplatinic acid, and subjecting them to activation treatment; a mat 12 made of nonwoven fabric of silica fiber; and a stainless screen 13 are laminated, and placed in a casing 14 made of aluminum plated steel plates 14. An upper cover 15 having inside and outside diameters same as those of the casing 14 is fixed to the casing 14 by welding.

Description

[Detailed description of the invention] Industrial applications This invention relates to a catalyst unit.

Conventional configurations and their problems When cooking using electric heaters, microwaves, or gas burner cooking ovens or ranges (hereinafter, ovens will be explained as representative), odors and smoke are generated due to cooking. This is unavoidable, and in today's highly airtight houses, it often makes the living environment worse. For this reason, indoor ventilation is normally forced, but as cooking appliances become more sophisticated these days, there is a tendency to use them without limiting the location where they can be installed, increasing the relative distance between them and the ventilation equipment. It's coming. Under these circumstances, attempts have recently been made to provide the oven itself, which is the source of the odor, with a function to purify these odors and smoke. One way to achieve this type of function chemically is to use a catalytic reaction. Up until now, the inner wall of the oven chamber has been made of hollow material, and in order to make the hollow material itself have a catalytic effect, metal or other materials have been used. Products mixed with metal oxides are in practical use.

On the other hand, a method has been proposed in which combustible components that cause odor and smoke emitted from the oven are removed by catalytic reaction through a melting medium unit installed in the oven and oxidized by combustion.

Catalysts for burning off minute amounts of combustible components by catalytic oxidation include integrally molded catalysts with through holes and catalysts attached to metal nets. However, power 5 etc.
These are during an internal cleaning heat cycle that generates a large amount of smoke from a relatively low temperature (a dry-burning operation that is not used for cooking purposes to remove fats and oils attached to the internal walls of the refrigerator).
cannot effectively remove smoke. In other words, in the case of an integrally molded catalyst having a large number of through holes, the heat capacity of the catalyst itself is large, and the temperature rise of the catalyst layer due to the latent heat of the exhaust gas has a greater time delay than the temperature of the passing exhaust gas, and the reaction start temperature of the catalyst increases. Unless the temperature is sufficiently lower than the evaporation or decomposition temperature of fats and oils in the refrigerator, the catalyst layer will not perform its function at all during the period of delay in temperature rise of the catalyst layer. In addition, among the conventionally used catalysts of this type, the most effective one is one impregnated with platinum, but even in this case, the oxidative combustion of mist (steam) of animal and vegetable oils (edible oil, etc.) The starting temperature is usually the same as or higher than the evaporation temperature of the oil, and from this point of view as well, a catalyst layer with a large heat capacity is not preferred. Furthermore, in the case of a through-hole type integrally molded catalyst, in order to make efficient contact between the oil mist or oil smoke and the catalyst wall, it is necessary to have a large contact distance in the flow direction, which forces the catalyst layer to be large. There is a drawback.

On the other hand, from the viewpoint of reducing heat defects, if a suitable catalyst is attached to the thin metal plate or mesh itself or its surface, the temperature rise of the catalyst layer itself can almost follow the rise of the exhaust gas temperature. The disadvantage is that the surface is small and it is almost impossible to effectively treat large amounts of oil mist or smoke.

OBJECTS OF THE INVENTION An object of the present invention is to provide a catalyst unit for more efficiently removing oil mist and oil smoke generated from an oven.

Structure of the Invention The catalyst unit of the present invention is installed in an open refrigerator or an exhaust port, and a metal mesh layer, a filter layer, and a catalyst layer are laminated in this order in the casing from the upstream side of the exhaust gas. This is what I did.

Here, as the catalyst layer, it is possible to use a woven or nonwoven fabric of inorganic fibers such as phosphoric acid as a carrier, and support a noble metal such as platinum or a metal oxide such as copper oxide on this carrier.

Further, the filter layer is a temporary adsorption layer made of silica cloth or silica wool similar to the carrier. Furthermore, a perforated steel plate made of metal is placed in the preceding stage in contact with this temporary adsorption layer. A metal mesh layer, which is a lath plate or net, is provided, and these are combined and housed in a casing to form a unit.

The catalyst unit of this invention has a small heat capacity, and silica cloth and wool themselves have a large surface area, and especially those pre-supported with alumina or crystalline silica have high thermal stability on the surface. Effective as an oxidation combustion catalyst for mist and oil smoke. Furthermore, the filter layer, which is a temporary adsorption layer provided in front of the catalyst, temporarily allows oil mist with a relatively high decomposition temperature to adhere to this adsorption layer, and as the exhaust gas temperature rises, the adhering oil mist is decomposed. Then, a two-step process is carried out in which it is oxidized and burned in the catalyst layer and removed (5). Furthermore, by arranging a metal mesh layer in front of these, in addition to mechanically holding the filter material and catalyst material, it also helps to equalize heat distribution to these components, and improves the heat conduction of exhaust gas latent heat and the overall efficiency. can be made to do so.

Description of Examples Example 1: As shown in Fig. 1, 5 to 15% (wt%) of γ-alumina was preliminarily applied to the surface of a silica cloth with a porosity of 40 to 70%, which was made by weaving silica fibers. , hereinafter the same) immerse the supported material in a chloroplatinic acid aqueous solution,
Two catalyst layers 11 supporting 3-wt% of platinum Q through normal activation treatment, and a mat (filter layer) made of a nonwoven fabric made of burnt silica fibers with a density of 0.05 to O.l
2 and 10 to 50 meshes of stainless steel (gold layer mesh layer) 13, and
*It is housed in a casing 14 made of aluminized steel plate with an outer diameter of 55□I and a height of 10, and has the same inner diameter as this casing 14.
A catalyst unit was obtained by welding and fixing the casing 14 to the outer diameter upper lid 151.

(6) Example 2: As shown in Figure 2, platinum and palladium were added to the same catalyst carrier as in Example 1 at a weight ratio of 2:10 and a total amount of 0.6% based on the carrier. 20 pieces of silica-alumina (5:1 by weight) were supported on the catalyst layer 21 obtained by supporting the catalyst layer 21 and on the same silica cloth as the catalyst base material. Two to three cross-shaped filter layers 22 are stacked, and the porosity is 40 to 6.
Example 1 with 0% bottom plate (metal mesh layer) 23t''
The catalyst unit was housed in a casing 24 having approximately the same dimensions as the catalyst unit, and the upper lid 25 was welded and fixed to the casing 24 to obtain a catalyst unit.

Example 3: As shown in Fig. 3, the same catalyst layer 31 as in Example 1 was formed into a wave shape in advance, and ceramic fibers made of alumina-silica fibers as the main material and punched in advance to have an aperture of 40 to 60 inches were used. mat (filter layer) 32
are placed in a casing 34 having the same open bottom plate (metal mesh layer) 33 as in Example 2, and the upper lid 3
5 was welded and fixed to the casing 34 to form the entire catalyst unit.

The ventilation resistance of the catalyst units of Examples 1 to 3 was 5.
0! 10~60wnH3O for A'nin aeration
It was about.

Implement several to three catalyst units with an internal volume of 0.1 to 0.
In order to check the effectiveness of the catalyst, we installed several samples at the exhaust port of a 2 m3 electric oven, one at a space 10 mm away from the center of the bottom of the unit into the oven for exhaust temperature detection, and the other at the location of the catalyst inside the unit. A thermocouple was attached, and after applying 2 to 5 teaspoons of edible vegetable oil to the inner wall of the oven, electricity was turned on to raise the temperature inside the oven. At this time, the temperature changes over time of each of the catalyst layer and the exhaust gas were approximately curved as shown in FIG. 4. Here, smoke is emitted from the exhaust port at point CA, where the catalyst layer temperature and exhaust temperature intersect)
, and again the point where these surface temperature curves touch (
Odor at point B). The smoking stopped completely.

The degree of smoke generated during this period was determined by collecting exhaust gas from the vicinity of the exhaust port using a filter-type dust meter and checking the color tone of the filter. Here, the color tone was determined by a 6-step method in which total O (no coloring) was selected, and coloration due to soot generated by ignition of fats and oils in the refrigerator was set to 5.

In addition, taking advantage of the fact that the time dependence of the exhaust temperature in Figure 4, which takes the time until the smoke removal effect due to the catalytic reaction is clearly recognized, is almost the same as long as the same oven is used, the exhaust temperature It was shown in

Comparative example: The outer diameter is almost the same and the porosity is 65%.

A catalyst in which platinum was supported on a so-called monolithic carrier having a height of 10 pieces was used as a comparative example, and the degree of coloration of the filter and the exhaust gas temperature at the time of smoke reduction were measured in the same manner as described above.

The test results of Examples 1 to 3 and Comparative Examples are shown in the following table.

As is clear from the table, all of the examples (9) had a higher smoke eliminating effect than the comparative example, and the smoke eliminating effect was exhibited early after the oven was energized. This is due to the fact that the contact effect between the gas and the catalyst has been significantly improved by using the catalyst layer made of organic fibers. By providing a filter layer for temporary adsorption in front of the catalyst layer, oil mist that is generated when the exhaust temperature is relatively low is first adsorbed on the filter layer instead of directly adhering to the catalyst, thereby reducing the exhaust temperature. This is because as it rises, it decomposes and desorbs to form a gas that facilitates catalytic reactions and is brought into contact with the catalyst. Furthermore, due to the heat of reaction on the catalyst surface, the temperature of the entire unit is much higher than that of the exhaust gas. As a result, so-called functional recovery, which prevents the generation of oil smoke at low temperatures the next time, is automatically performed.

Furthermore, the heat transfer effect of the metal mesh layer at the front stage has the effect of accelerating the temperature rise of the υ catalyst layer, and also has the effect of acting as a metal filter for collecting oil mist and accelerating the decomposition of attached oil mist. The arrangement of the (10) filter layer and the gold layer mesh in the front stage of the catalyst is particularly effective when the generated substance is a liquid substance such as mist. In other words, if these mistakes occur on the surface of the catalyst, this results in so-called double poisoning, which causes the problem that the reaction cannot be fully started at the reaction starting temperature when the catalyst is in gas-solid contact. It is something that will be resolved.

In the above embodiments, the case where silica or silica-alumina fibers were used as the m'R-free fibers was explained, but other non-m'R fibers can also be used, and for example, glass fibers can also be used. It can be used as long as the catalyst unit is installed in a location where there is no problem with heat resistance. In addition, the filter layer is not necessarily limited to using fibrous fibers, but if its ventilation resistance is allowed (for example, if the exhaust gas can be forcibly exhausted by some means) , activated carbon, silica gel, etc. may also be used.

However, in these cases, of course, their heat resistance must be carefully considered, and the catalyst material does not necessarily need to be limited to noble metals as used in the examples.
Even so-called VM metal oxides have a sufficient function to completely oxidize components in exhaust gas.

Effects of the Invention As described above, the catalyst unit of the present invention has the effect of being able to remove oil mist and oil smoke generated from ovens, ranges, etc. more efficiently than conventional catalyst units.

[Brief Description of the Drawings] Fig. 1 is a sectional view showing one embodiment of the present invention, Figs. 2 and 3 are sectional views showing other embodiments of the invention, and the fourth quotient is the temperature of the catalyst layer. It is a graph showing the relationship with exhaust gas temperature. 11゜21.31...Catalyst layer, 12.22.32...
・Filter layer, 13.23.33...Metal Menyu layer Figure 1 Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) A catalyst unit in which a metal mesh layer, a filter layer for temporarily adsorbing oil mist and oil smoke, and a catalyst layer for oxidizing and burning oil mist and oil smoke are laminated in this order. (2) The catalyst unit according to claim (1), wherein the catalyst layer supports a catalyst on an inorganic fiber carrier. (3) The filter layer is formed from an inorganic fiber that is the same as or different from the carrier of the catalyst layer.
Catalyst unit described in section 1).