JPS62237930A - Oven - Google Patents

Abstract

PURPOSE:To save energy by providing exhaust gas purifying catalyst with a built-in temperature sensor in an exhaust line connected to the inside of oven and using specific substance as catalyst carrier and catalyst. CONSTITUTION:An exhaust gas purifying catalyst 3 equipped with a temperature sensor is provided close to an exhaust vent of an over with an electric heater 1 to heat up the inside 1a. A catalyst 3 consists of a honeycomb molded carrier constituted with inorganic heat-resistant material such as cordierite or the like carrying Perovskite type composite oxide such as La0.9Ce0.1CoO3 and a solid electrolyte for sensing temperature connected to a temperature sensing circuit with lead. Oil adhered to the inside of oven is evaporated, decomposed into CO2 and H2O with catalyst, and senses the completing time of dry baking from lowering temperature of catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is an electric heater, an oxidation method that completely burns oil smoke and unburned hydrocarbons discharged from household and commercial ovens using a gas burner as a heat source and converts them into carbon dioxide gas and water. It relates to an oven containing a catalyst.

Conventional electric ovens and gas ovens emit steam and oil smoke or unburned hydrocarbons during cooking, causing a bad odor. In order to decompose these odors and reduce offensive odors, catalysts have recently been installed in exhaust passages.

As the catalyst, platinum group catalysts such as platinum and palladium are used. Furthermore, if the oven is used for a long period of time, oil, soot, etc. will accumulate on the inner wall of the oven, and the inner wall will become noticeably dirty. In order to remove these stains, ovens are generally equipped with a dry baking mechanism, in which the oven is heated to a temperature higher than the decomposition temperature of oil adhering to the inside of the oven using a heater or the like for a time set by a timer. In this way, the dirt inside the refrigerator is cleaned.

Problems to be Solved by the Invention As mentioned above, a dry baking mechanism is provided to remove dirt that accumulates on the inner wall of the oven when the oven is used for a long period of time. All conventional dry-firing mechanisms use a timer to set the time and perform dry-firing for a certain fixed period of time. However, it is difficult to set the truly necessary time, and there is always the problem that setting the time is too long, wasting electricity and firepower, or setting the time too short, resulting in insufficient effects. Another problem is that platinum group catalysts are generally used as conventional catalysts, but M
The medium has problems with heat resistance, especially when used at temperatures above 500°C, especially at temperatures above 700-800° (: 700° to 800°C). There is the problem of deterioration.For this reason, various methods to increase heat resistance have been proposed for months, but no satisfactory results have been obtained.Furthermore, another problem is that thermal lightning pairs are generally used to detect various temperatures. However, the heat resistance used for industrial purposes is about 500°C, and there are problems such as disconnection due to lack of durability at temperatures higher than this, so temperature detection at a practical level that can be used at higher temperatures Development of a method is desired.

Means for Solving the Problems In order to solve the above-mentioned problems, an exhaust gas purification catalyst with a built-in temperature sensor was installed in a part of the exhaust passage of various ovens. In addition, alumina is used as a catalyst for exhaust gas purification.
The catalyst carrier is made of an inorganic heat-resistant material such as silica or cordierite formed into an integrally molded mold such as a honeycomb shape, and a rare earth element such as rank 5, cerium, or alkaline earth element such as strontium or calcium is placed on the carrier. After supporting 1 to 10 weight percent of metal, the A site of the perovskite type composite oxide represented by the crystal structure formula ABO3 is composed of at least one element selected from rare earth metals such as lanthanum, neodymium, and gadolinium, and alkaline earth metals such as strontium. A catalyst is used in which the B site is selected from at least one element selected from transition metal elements such as iron, cobalt, and nickel, and the amount supported as a perovskite-type composite oxide is between 1 and 15% by weight. there was. Furthermore, as a temperature sensor, the A site of the perovskite composite oxide with the crystal structure formula ABO3 is composed of at least one element selected from rare earth elements such as lanthanum, neodymium, and gadolinium, and alkaline earth metals such as strontium, and the B site is composed of iron. The detector adopts a structure in which at least a heavy element is selected from transition metal elements such as , cobalt, nickel, etc., and is sintered at a temperature of 900' after pressurized acid form, with lead wires taken out from both ends. Shi1ko.

Operation The operation of the dry firing mechanism for removing oil stains accumulated on the inner wall of the oven having the built-in exhaust gas purification catalyst with a temperature sensor configured as described above will be described. When the oven is set to the dry baking mechanism to remove oil stains that have accumulated on the inner walls after long-term use, the inner wall temperature of the oven increases. Dirt on the inner wall is exhausted as oil mist and partially decomposed gas through the exhaust passage and out of the exhaust port. When passing through this exhaust passage, it passes through a purification catalyst installed. On the purification catalyst, the oil mist and unburned hydrocarbons are completely combusted with air and decomposed into water vapor and carbon dioxide. The heat generated at this time also heats the catalyst itself, raising its temperature. During this time, the resistance of the solid electrolyte used as the temperature sensor decreases in inverse proportion to the rise in temperature. When the inner wall is sufficiently purified by dry firing, the amount of oil mist generated is reduced, the amount of hydrocarbons passing through the catalyst is also reduced, and as a result, the amount of heat generated in the catalyst is reduced, and the temperature of the catalyst itself is also lowered. do. As a result, the resistance of the solid electrolyte of the temperature sensor also increases again. A -2 change in this resistance to 7 is detected and this is taken as the end of 7 dry firing.

EXAMPLE An electric oven having a built-in exhaust gas purifying catalyst with a temperature sensor manufactured using the present invention will be described as an example below.

FIG. 1 is a model diagram of an electric oven, in which an electric heater 1 on the outer periphery heats the interior 1a of the oven. An exhaust gas purification catalyst 3 with a temperature sensor is installed near the exhaust hole 2 which communicates with the interior 1a of the refrigerator. Fig. 2 is an enlarged view of the exhaust gas purification catalyst 3 with a temperature sensor, and the cordierite quality is 400cej? /? /1nch2 into a honeycomb shape, and after being impregnated with cerium nitrate aqueous solution, heated at 900℃1
After being baked for 7 hours and supported at 7% by weight, it was impregnated with an aqueous solution containing a mixture of lanthanum nitrate and cobalt nitrate in a molar ratio of 1:1.
After firing at 50° C. for 1 hour, the amount of LaCo3 supported was 8% by weight. As shown in FIG. 2, this catalyst has a solid electrolyte 4 for a temperature sensor installed in the eyes of the catalyst. Lead wires 5 are attached to both ends of the solid electrolytic Ti4 for a temperature sensor.

This lead wire 5 is connected to a temperature detection circuit (not shown). Solid electrolyte 4 for temperature sensor is Lao, 9Ce
o, 1C003 was pressure molded and then sintered at 1000°C for 10 hours. FIG. 3 shows this temperature characteristic. To carry out dry baking in an oven with a built-in catalyst for exhaust gas purification with a temperature detector, first heat the electric heater 1 and heat the oven to a temperature at which the oil adhering to the inner wall of the oven evaporates and decomposes. Raise the internal temperature. As a result, the evaporated oil passes through the exhaust gas purification catalyst 3 with a temperature sensor and is decomposed into carbon dioxide and water vapor. The resulting heat causes the catalyst temperature to rise, reaching equilibrium at a certain temperature. Thereafter, as the amount of attached oil decreases, the amount of oil that evaporates decreases, and the temperature of the catalyst also decreases. This process is shown in Figure 4. As the temperature of the catalyst changes, the resistance changes as shown in FIG. As a result, by detecting the change in ΔP using a detection circuit (not shown), it is possible to reasonably know when dry firing has ended. In addition, as another embodiment, the solid electrolyte 4 for the temperature sensor is transferred to the exhaust gas purification catalyst 39.
1. It may be buried on the outside of the building or on the wall surface.

Effects of the Invention (1) As described in (2) below, in the oven using the exhaust gas purifying catalyst with a temperature sensor according to the present invention, heating can be performed for only the time required for dry baking. That is, unlike the conventional time management system using a timer, there is no possibility of excessive dry firing or the timer turning off the dry firing even though sufficient dry firing has not been performed yet. As a result,
Energy saving effect can be obtained.

(2) By using a perovskite-type composite oxide as a catalyst or a solid electrolyte for temperature detection as used in the present invention, heat resistance and durability are improved, and there is no need to worry about thermal deterioration like with conventional platinum catalysts. It's gotten better.

Furthermore, it has become a practical temperature sensor that can be used at high temperatures.

(3) This temperature detector is a safety device that detects when something is wrong inside the refrigerator and the temperature rises, and turns off the heater.
・ ・ It can also be used as .

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an oven according to an embodiment of the present invention, Fig. 2 is a perspective view of an exhaust gas purification catalyst with a temperature sensor used in the oven, and Fig. 3 is a resistance of T-ao, 9ceo, 1Co○3. Fig. 4 is a characteristic diagram showing the resistance and temperature changes of a typical catalyst when the exhaust gas purification catalyst is used for dry firing. 2...Exhaust hole, 3...Circuit scum purification catalyst for temperature detection, 4...Solid electrolyte for temperature detector,
5...Lead wire. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2 Drop 1 Figure 3 Temp, (K) Lao, q CEO, t Temperature signature of CoO3 resistance Figure 4

Claims (2)

[Claims] (1) An oven in which an exhaust gas purification catalyst with a temperature sensor is installed in the exhaust passage communicating with the inside of the oven. (2) As a catalyst for exhaust gas purification, a catalyst carrier is made of an inorganic heat-resistant material such as alumina, silica, cordierite, etc. formed into an integrally molded mold such as a honeycomb shape, and a rare earth element such as lanthanum, cerium, or strontium is placed on the carrier. After supporting 1 to 10% by weight of an alkaline earth metal such as calcium, the A site of the perovskite complex oxide represented by the crystal structure ABO_3 is treated with at least one of rare earth metals such as lanthanum, neodymium, and gadolinium, and alkaline earth metals such as strontium. A catalyst is used in which the B site is selected from at least one element from transition metal elements such as iron, cobalt, and nickel, and the amount supported as a perovskite-type composite oxide is in the range of 1 to 15 weight percent. , crystal structure formula ABO_3 as a temperature sensor
The A site of the perovskite-type composite oxide represented by is composed of at least one element selected from rare earth elements such as lanthanum, neodymium, and gadolinium, and alkaline earth metals such as strontium, and the B site is composed of transition metal elements such as iron, cobalt, and nickel. 2. The oven according to claim 1, wherein at least one element is selected, pressure molded, sintered at a temperature of 900° C. or higher, and a detector is used with lead wires taken out from both ends.