KR100594677B1 - Combustion device - Google Patents

Abstract

A ceramic burner having a flame hole formed in the porous ceramic plate, a conductor layer formed on a surface of which the flame in the ceramic burner is formed, a conductor provided to face the conductor layer, and a voltage between the conductor layer and the conductor. And a ignition detecting means for detecting ignition by detecting a spark current flowing through the flame when is applied, wherein the conductor layer is made of an electrically conductive perovskite metal oxide.

The perovskite-type metal oxide is characterized in that La _1-x Sr _x MnO ₃ (x is 0 or less than 1).

Description

Combustion Device             

BRIEF DESCRIPTION OF THE DRAWINGS The system block diagram which shows one structural example which concerns on the combustion apparatus of this invention.

2 is a graph showing a spark current detected for a predetermined range of input between a conductor layer and a flame rod in one embodiment of the combustion apparatus of the present invention.

3 is a graph showing a change in electrical conductivity with respect to the temperature of the electrically conductive perovskite metal oxide used in one embodiment of the combustion apparatus of the present invention.

4 is a graph showing the change of the flame current with respect to the input in the ceramic burner and the other ceramic burner which concerns on the combustion apparatus of this invention.

5 is a graph showing changes over time of the flame current under various combustion conditions in a ceramic burner and another ceramic burner in accordance with the combustion apparatus of the present invention, and FIG. 5A shows the excess air ratio of 1.4 and the combustion capability of the combustion apparatus. 5b is a case where the excess air ratio is 1.4 and the combustion capacity of the combustion apparatus is minimized.

FIG. 6 is a graph showing changes over time of flame current under various combustion conditions in a ceramic burner and another ceramic burner according to the combustion apparatus of the present invention. FIG. 6A shows the excess air ratio as 1.1 and the combustion capability of the combustion apparatus. 6b is a case where the excess air ratio is 1.1 and the combustion capacity of the combustion apparatus is minimized.

Fig. 7A is a graph showing changes over time of the flame current when the combustion conditions are changed during combustion in the ceramic burner and the ceramic burner according to the combustion apparatus of the present invention.

Fig. 7B is a graph showing the change over time of the flame current when the ceramic burner and the other ceramic burner according to the combustion apparatus of the present invention are burned and re-ignited after combustion.

8 is a graph showing the relationship between the inorganic binder content of the conductor layer, the firing temperature and the electrical resistance of the conductor layer in the combustion apparatus of the present invention.

The present invention relates to a combustion apparatus having a ceramic burner.

BACKGROUND ART Conventionally, a combustion apparatus is known in which a mixture of fuel gas and combustion air mixed in advance at a predetermined ratio is supplied to a burner for primary combustion. In such a combustion apparatus, as the burner, a ceramic burner having a plurality of small diameter flame holes penetrating in the front and back directions is used in a porous ceramic plate to impart heat shock resistance.

In the combustion apparatus, ignition detection is generally performed by applying a voltage between the burner and the flame rod to detect the flame current flowing through the flame formed in the burner. The ignition detection confirms that the ignition is satisfactorily ignited by detecting the flame current of a predetermined value or more at the time of ignition, and judges that the flame ignition occurs when the flame current becomes lower than the predetermined value during combustion of the burner. However, since the ceramic burner typically does not flow as a nonconductor itself, it is difficult to detect ignition by the above-described method.

Here, it is proposed to configure the ceramic burner itself with a conductive ceramic. As the conductive ceramic, for example, a litia-based ceramic such as petalite (LiAlSi ₄ O ₁₀ ) is used.

However, according to the investigation by the present inventors, when the flame current was detected by applying a voltage between the ceramic burner made of the petalite and the flame rod, it was found that the flame current fluctuated greatly in accordance with the surface temperature of the burner. That is, the spark current between the ceramic burner made of petalite and the flame rod has a problem that it takes time until the size is detectable because the burner is low as the insulator under the condition that the surface temperature of the burner is low. In addition, the ceramic burner made of petalite has a problem that the overshoot of the spark current becomes large and requires a long time until it stabilizes when the combustion condition is changed during combustion or when the flame burner is re-ignited after the combustion stop. If the overshoot is large, the spark current for detecting ignition or misfire becomes too large, so that ignition or misfire cannot be detected until it is stabilized.

On the other hand, Japanese Patent Application Laid-Open No. Hei 1-67466 and Japanese Patent Application Laid-open No. Hei 5-18606 have proposed the formation of a conductor layer on a surface on which a flame in the ceramic burner is formed. According to the combustion apparatus described in each publication, a flame rod is provided on the side where the flame in the ceramic burner is formed to face the conductor layer, and a voltage is applied between the conductor layer and the flame rod. Alternatively, a heat exchanger is used instead of the flame rod, and a voltage is applied between the conductor layer and the heat exchanger. According to each of the above publications, it is described that by performing the above, the spark current flowing through the flame can detect the ignition.

In the combustion apparatus described above, it is known to form a nickel deposition coating film on the surface of the ceramic burner, for example, as the conductor layer. However, nickel has low heat resistance and cannot be used stably over a long period of time.

If platinum or palladium having excellent heat resistance is used in place of the above-mentioned nickel, it can be stably used for a long time, but since all of them are expensive as precious metals, an increase in manufacturing cost cannot be avoided.

It is also conceivable to form a silicon carbide (SiC) coated film in place of the nickel described above. Since silicon carbide has high heat resistance in air and can be used as a conductor because it is an intrinsic semiconductor, it is suitable for use in forming a conductor on the surface of a ceramic burner. The silicon carbide film is produced by, for example, reacting silicon dioxide with carbon or sintering after silicon and carbon.

However, when forming the silicon carbide coated film on the ceramic plate forming the ceramic burner, since the high temperature heat treatment is required to form the silicon carbide coated film, the porous ceramic plate is densified to provide thermal shock resistance. There is a problem of being saved. Moreover, when the baking of the said silicon carbide film is made into the temperature which the said porous ceramic plate does not compact, there exists a problem that formation of the said silicon carbide film becomes difficult.

In addition, although preparation of boron, carbon, etc. is indispensable for sintering of the said silicon carbide, the silicon carbide film formed by adding an impurity tends to reduce the strength at high temperature, and it is difficult to set sintering conditions. There is a problem. In addition, since silicon carbide deteriorates when oxidized during the sintering, there is also a problem that an increase in manufacturing cost is inevitable due to the enlargement of the apparatus such as vacuuming the inside of the apparatus to prevent this.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a combustion device in which a conductive layer is formed on a ceramic burner which is excellent in heat resistance and easy to manufacture at low cost.

The combustion apparatus of the present invention for achieving the above object is provided with a ceramic burner in which a flame hole is formed in a porous ceramic plate, a conductor layer formed on a surface on which a flame in the ceramic burner is formed, and opposite to the conductor layer. And a complex detecting means for detecting a complex by detecting a spark current flowing through the flame when a voltage is applied between the conductor layer and the conductor, wherein the conductor layer is an electrically conductive perovskite type. In the metal oxide,
The conductor layer contains an inorganic binder in the range of 1 to 20% by weight based on the total weight of the conductor layer, and is bonded to the porous ceramic plate via the binder.

The ceramic plate which forms the said ceramic burner can be manufactured inexpensively by sintering the particle | grains of the low-expansion-resistant ceramic material which has fire resistance, forming a porous body, and providing heat shock resistance. Examples of the refractory low-expansion ceramic materials include cordierite, spodumene, aluminum titanate, mullite, zirconia, zircon, magnesia (including spinel and forsterite), and alumina (corundum) Calcium cyanamide, chromium oxide, dolomite, dolomite, silicite, silica, zirconite, alumina and zirconia, mixtures of alumina and zircon, and mixtures of two or more thereof.

The ceramic burner may be formed by a dense ceramic plate. The dense ceramic plate may be manufactured by sintering particles of low-expansion ceramic materials such as petalite, spodumene, eucryptite, aluminum titanate, and potassium zirconium phosphate, but the firing temperature is relatively high. It requires energy. In addition, the dense ceramic plate may form the conductor layer by vacuum deposition, CVD, or the like, but is roughened to roughen the surface of the ceramic plate in order to improve the bondability between the ceramic plate and the conductor layer. Process is required.

Therefore, in the dense ceramic plate, the cost for manufacturing the ceramic plate itself and forming the conductor layer is increased. In the present invention, the porous ceramic plate is used for cost reduction.

The perovskite-type metal oxide is represented by general formula ABO ₃ (wherein A and B are metals and O is oxygen), and some may exhibit electrical conductivity as a metallic conductor or semiconductor. Here, in the present invention, the conductor layer is formed using a perovskite metal oxide exhibiting properties as a metallic conductor or a semiconductor. The perovskite-type metal oxide may be one in which metal A or a part of metals A and B are substituted with another metal in the above general formula.

The conductor layer is formed by applying an aqueous slurry obtained by mixing the electrically conductive perovskite metal oxide powder with a solvent such as water to the ceramic plate, followed by drying and firing to sinter.

In the present invention, the conductor layer preferably covers the surface of the porous ceramic plate uniformly, and the perovskite metal oxide penetrates into the surface pores of the porous ceramic plate.

The conductor layer may obtain uniform electrical conductivity by uniformly coating the surface of the ceramic plate. Further, since the perovskite-type metal oxide forms a solid solution at the contact surface of the ceramic plate by sintering as described above, the conductor layer and the ceramic burner are strongly bonded. Here, in the conductor layer, the perovskite-type metal oxide that penetrates into the surface pores forms the solid solution, thereby obtaining the anchoring effect, and the conductor layer is more strongly bonded to the ceramic burner.

It is preferable that the said conductor layer consists of a perovskite type metal oxide whose particle diameter is 0.04-5 micrometers in order to coat | cover the surface of the said ceramic plate uniformly. Here, the particle diameter of the perovskite-type metal oxide is the particle diameter after sintering as described above.

When the particle diameter after sintering of the perovskite-type metal oxide is less than 0.04 µm, it is difficult for the conductor layer to uniformly cover the surface of the ceramic plate. In addition, when the particle diameter after sintering of the perovskite-type metal oxide exceeds 5 µm, the solid solution is less likely to be formed, so that the conductor layer is easily peeled from the ceramic burner.

The conductor layer preferably has a thickness in the range of 10 to 300 μm in order to uniformly cover the surface of the ceramic plate. When the thickness of the conductor layer is less than 10 µm, the ceramic plate may be exposed and uniform electrical conductivity may not be obtained. When the thickness of the conductor layer exceeds 300 µm, the formed conductor layer may be easily peeled off due to thermal expansion during firing.

The conductor layer preferably contains an inorganic binder in the range of 1 to 20% by weight based on the total weight of the conductor layer, and is bonded to the ceramic plate via the binder. The conductive layer contains the inorganic binder so that the perovskite-type metal oxides or the perovskite-type metal oxide and the ceramic plate are strongly bonded through the binder. In addition, since the conductor layer contains the inorganic binder, the firing temperature at which the perovskite-type metal oxide can be sintered is low. Further, the width of the firing temperature at which the sintered perovskite metal oxide acts as a conductor layer is widened. Therefore, setting of baking temperature can be made easy.

As said inorganic binder, borosilicate glass, soda-lime glass, etc. can be used, for example. If the content of the inorganic binder is less than 1% by weight based on the total weight of the conductor layer, the inorganic binder cannot function as a binder. If the content of the inorganic binder exceeds 20% by weight, the resistance of the conductor layer is increased.

In the present invention, it is important that the perovskite metal oxide is selected from La _1-x Sr _x MnO ₃ because it has electrical conductivity and is easy to manufacture.

In addition, since La _1-x Sr _x MnO ₃ has a high emissivity, it is possible to lower the flame temperature by forming a conductor layer on the surface of the ceramic burner and to reduce nitrogen oxides during combustion in the ceramic burner. In addition, La _1-x Sr _x MnO ₃ catalyzes the complete oxidation of methane contained in the city gas at low temperature, and by this catalysis, nitrogen oxides can be reduced during combustion in the ceramic burner.

Next, embodiment of this invention is described in detail, referring an accompanying drawing.

As shown in FIG. 1, in the present embodiment, the combustion device 1 heats the water supplied from the ceramic burner 3 and the water supply pipe 4 into the casing 2 by the ceramic burner 3 to generate hot water. The heat exchanger 5 obtained is provided. Moreover, the combustion apparatus 1 is equipped with the hot water supply pipe 6 which supplies the hot water obtained by the heat exchanger 5 to a kitchen, a washroom, a bathroom, etc. which are not shown in figure.

The ceramic burner 3 forms a plurality of small-diameter spark holes 3a in a ceramic plate to which heat shock resistance is provided by sintering cordierite particles, which are fire-resistant low-expansion ceramic materials, to form a porous body. The ceramic burner 3 forms a conductor layer 7 made of a coating layer of electrically conductive perovskite-type metal oxide on the surface facing the heat exchanger 5.

In addition, the combustion device 1 includes a flame rod 8 between the ceramic burner 3 and the heat exchanger 5, and is provided with ignition detecting means 9 for detecting ignition of the ceramic burner 3. Doing. The ignition detecting means 9 detects ignition by applying a voltage between the conductor layer 7 and the flame rod 8 to detect the spark current flowing through the flame F when ignited in the ceramic burner 3. .

The ceramic plate obtained by sintering the cordierite particles has a good thermal shock resistance by providing a porous body having surface pores in the range of 3 to 200 µm.

As referring to the properties as metallic conductors in a buffer lobe Perovskite - Type of metal oxide of the electrically conductive, for example, _{SrTiO 3, BaTiO 3, LaTiO 3} , CaVO 3, SrVO 3, CaCrO 3, SrCrO 3, CaFeO 3, SrFeO 3 , SrCoO ₃ , LaNiO ₃ , and the like. In addition, the electrical conductivity of the perovskite-type metal oxide exhibiting properties as a semiconductor, for example, CaTiO ₃ , BaVO ₃ , LaCrO ₃ , CaMnO ₃ , LaMnO ₃ , BaFeO ₃ , LaFeO ₃ , BaCoO ₃ , SrNiO ₃ , BaNiO ₃ , LnCrO ₃ (Ln = Pr, Nd, Sm, Eu) and the like can be mentioned. In addition, a buffer lobe Perovskite - Type metal oxide showing properties as a metallic conductor to a semiconductor, for example, can listen to LaCoO _3.

The electrically conductive perovskite-type metal oxide may exhibit properties as a metallic conductor or a semiconductor by replacing a part of metal A or B with another metal in the above general formula, and such perovskite As a metal oxide, for example, La _1-x Sr _x MnO ₃ , La _1-x Ca _x MnO ₃ , La _1-x Sr _x CoO ₃ , La _1-x Sr _x CrO ₃ , La _1-x Ca _x CrO ₃ , La _1-x Sr _x FeO ₃ , Y _1-x Mg _x CrO ₃ , Y _1-x Ca _x CrO ₃ , Y _1-x Sr _x CrO ₃ , Y _1-x Ba _x CrO ₃ , Gd _{1 -x} Ca _x CrO ₃ , LaCr _1-y Mn _y O ₃ , LaCr _1-y Mg _y O ₃ , and the like. The perovskite-type metal oxide may exhibit properties as a metallic conductor or a semiconductor by replacing a part of metals A and B with another metal in the above general formula. Such perovskite-type metal oxides may be used. As examples, Gd _1-x Sr _x Co _1-y Mn _y O ₃ , La _1-x Ca _x Cr _1-y Co _y O _3, etc. may be mentioned. However, in the general formula, x and y are both zero and less than one.

The perovskite-type metal oxide is mixed with an oxide or a carbonate of each metal constituting the oxide such that the metal becomes an amount constituting the oxide in a stoichiometric manner, and at a predetermined temperature. It can obtain by baking at. The obtained perovskite metal oxide is pulverized to a powder having a particle diameter of 0.005 to 0.3 µm, and a predetermined amount of water is mixed into the powder to form a slurry. After spraying and applying the slurry onto the surface of the ceramic burner 3, it is dried at a predetermined temperature, and then calcined and sintered at a predetermined temperature, whereby the particle diameter of the perovskite-type metal oxide is in the range of 0.04 to 5 µm and 10 A conductor layer 7 is formed which uniformly covers the ceramic burner 3 having a thickness in the range of ˜300 μm.

The conductor layer 7 is strongly bonded to the ceramic burner 3 because the perovskite-type metal oxide forms a solid solution with the ceramic burner 3 during the sintering. At this time, the ceramic burner 3 is formed as a porous ceramic plate having surface pores in the range of 3 to 200 mu m as described above. Here, the slurry includes a perovskite-type metal oxide powder having a particle diameter of 0.005 to 0.3 µm to uniformly cover the surface of the ceramic plate 3, and the perovskite-type metal oxide powder may be used as the surface group. You can break into studying. The conductor layer 7 is obtained by the perovskite-type metal oxide penetrates into the surface pores and sintered to obtain the anchoring effect, and is more strongly bonded to the ceramic burner 3.

When the particle diameter of the perovskite-type metal oxide powder is less than 0.005 µm, it is difficult to form the conductor layer 7 having a uniform thickness because the surface pores penetrate deeply. On the other hand, when the average particle diameter of the perovskite-type metal oxide powder exceeds 0.3 μm, when sintered, it becomes difficult to obtain a particle diameter in the range of 0.04 to 5 μm, thereby reducing the anchoring effect.

In addition, instead of adjusting the particle diameter of the perovskite-type metal oxide, the conductor layer 7 may be roughened on the surface of the porous ceramic plate to adjust the roughness of the surface. Strong binding.

Next, the Example of this embodiment is shown.

(Example 1)

In this embodiment, La _0.7 Sr _0.3 MnO ₃ is used as the electrically conductive perovskite metal oxide.

In this embodiment, 200 g of ethanol is further added to a mixture of La ₂ O ₃ powder, SrCO ₃ powder, and Mn ₂ O ₃ powder by a molar ratio of 0.7: 0.3: 1, wet-mixed using a ball mill, and dried. After press molding using a uniaxial hydraulic press. Subsequently, the obtained molded product was calcined at 1100 ° C. in an electric furnace for 12 hours, and then pulverized by automatic induction to obtain a powder. Subsequently, the obtained powder was calcined at 1300 ° C. in an electric furnace for 12 hours, and then dried and ground by auto-induction to obtain a powder.

The powder after the calcination was analyzed by X-ray diffraction, and it was confirmed that the powder had a LaMnO ₃ -based bonding structure.

Subsequently, the same weight of water and 0.5 weight% of a dispersing agent (the middle diameter retainer, a brand name: Cerna D-305) of the said powder are added, wet-mixing using a ball mill, and drying it is average particle | grains. La _0.7 Sr _0.3 MnO ₃ powder having a diameter of 0.2 μm was obtained. The powder was found to be La: Sr: Mn = 0.7: 0.3: 1 (molar ratio) by an energy dispersive X-ray analyzer.

Subsequently, 20-50% by weight of water of the powder and 0.5% by weight of a dispersant (heavy oil retainer, trade name: Cerna D-305) of the powder were added to La _0.7 Sr _0.3 MnO ₃ , followed by wet mixing using a ball mill. To a slurry. Subsequently, the obtained slurry was sprayed onto the surface of the ceramic burner 3 using a commercially available odorless machine to form a coating film, and dried at 110 ° C. in a drier for 2 hours. The ceramic burner 3 having a conductor layer 7 having a thickness of 110 μm made of La _0.7 Sr _0.3 MnO ₃ having a particle diameter of 2 μm was formed by sintering by heating and firing at 1080 ° C. for 1 to 3 hours after drying. It was.

The conductor layer 7 is formed by uniformly covering the surface of the La _0.7 Sr _0.3 MnO ₃ ceramic burner 3. In addition, the La _0.7 Sr _0.3 MnO ₃ which penetrates into the surface pores of the ceramic burner ₃ is sintered so that the conductor layer 7 and the ceramic burner 3 are strongly bonded.

Subsequently, when the ceramic burner 3 is mounted in the combustion apparatus 1 shown in FIG. 1, and the igniter is ignited by supplying the mixer, a voltage of 120 V is formed between the conductor layer 7 and the flame rod 8. Was applied to measure the flame current detected by the ignition detecting means 9 for the input in the predetermined range. The results are shown in FIG.

As can be clearly seen from Fig. 2, according to the conductor layer 7 of this embodiment, a spark current of 40 to 160 mA was detected by the ignition detecting means 9 for an input of 8 to 24 kw. Usually, a spark current of 1 mA is required to detect ignition by the ignition detection means 9, and a spark current of 0.1 mA is required to detect misfire, but according to the conductor layer 7 of this embodiment, The spark current obtained is far more than 1 mA, which is a range sufficient to detect ignition.

The change of the electrical conductivity with respect to the temperature of La _0.7 Sr _0.3 MnO ₃ used for the conductor layer 7 of this embodiment is shown in FIG. In Fig. 3, it is clear that La _0.7 Sr _0.3 MnO ₃ of this embodiment has a small change in electrical conductivity even at high temperatures, so that stable performance can be obtained.

Subsequently, when the ceramic burner 3 is attached to the combustion apparatus 1 shown in FIG. 1 and supplied with a mixer having an excess air ratio of 1.4 and ignited thereto, the conductor layer 7 and the flame rod 8 The voltage of 120 V was applied between the terminals to measure the flame current detected by the ignition detecting means 9 for a predetermined input. The results are shown in FIG.

Here, the "air surplus ratio" means that the stoichiometric amount of air required to completely burn a predetermined amount of fuel gas in the mixer is 1, and how many times the amount of combustion air is mixed. The indicated value. The excess air ratio is expressed as a dimensionless number having no units.

A ceramic burner 3 (conventional example) obtained in the same manner as in the present embodiment except that the conductor layer 7 was not formed was attached to the combustion device 1 shown in FIG. The spark current was measured under the conditions. In addition, a ceramic burner (comparative example) made of petalite, which is an electrically conductive ceramic, and in which the conductor layer 7 is not formed, is mounted on the combustion device 1 shown in FIG. The current was measured. A result is combined with FIG. 4 and shown.

As can be clearly seen in FIG. 4, according to the ceramic burner 3 of the present embodiment in which the conductor layer 7 is formed, the ignition irrespective of the magnitude of the input even under the condition that the mixer having the excess air ratio of 1.4 becomes an air rich. A spark current of sufficient magnitude can be detected.

On the other hand, since the ceramic burner 3 of the prior art is an insulator, the spark current is hardly detected irrespective of the magnitude of the input, as is apparent from FIG. The ceramic burner of the comparative example is the air rich, and under the condition that the temperature of the ceramic burner is relatively low, as the input increases, the detected flame current lowers to the same degree as the ceramic burner 3 of the above example.

Subsequently, when the ceramic burner 3 is mounted in the combustion apparatus 1 shown in FIG. 1 and ignited by varying the excess air ratio and the combustion capability of the combustion apparatus 1, the conductor layer 7 and the flame rod are ignited. A voltage of 120 V was applied between (8) to measure the change over time of the flame current detected by the ignition detecting means (9). The results are shown in FIGS. 5 and 6.

In addition, the ceramic burner 3 of the conventional example and the ceramic burner of the comparative example are mounted in the combustion apparatus 1 shown in FIG. 1, and the time-dependent change of the flame current detected by the ignition detecting means 9 under the same conditions as described above. Measured. The result is combined with FIG. 5 and FIG.

Here, Fig. 5A shows a case where the excess air ratio is 1.4 and the combustion capacity of the combustion device 1 is maximized. In this case, the temperature of the ceramic burner becomes relatively low. Fig. 5 (b) shows the case where the excess air ratio is 1.4 and the combustion capacity of the combustion device 1 is minimized. In this case, the temperature of the ceramic burner becomes higher than in the case of Fig. 5A.

6 (a) shows a case in which the excess gas ratio is 1.1 and the gas rich, and the combustion capacity of the combustion apparatus 1 is maximized. In this case, the temperature of the ceramic burner is higher than in the case of Fig. 5B. 6 (b) shows a case where the excess air ratio is 1.1 and the combustion capacity of the combustion device 1 is minimized. In this case, the temperature of the ceramic burner is the highest.

As can be clearly seen in Figs. 5 and 6, according to the ceramic burner 3 of the present embodiment in which the conductor layer 7 is formed, a spark current of a magnitude sufficient to detect ignition within a very short time regardless of combustion conditions can be detected. Can be.

On the other hand, since the ceramic burner 3 of the prior art is an insulator, as can be clearly seen in Figs. 5 and 6, almost no spark current is detected regardless of the combustion conditions. In the ceramic burner of the comparative example, as can be clearly seen from Fig. 5 (a), the spark current of the same level as that of the ceramic burner 3 of the conventional example is detected only under the condition where the temperature of the ceramic burner is relatively low. The ceramic burner of the comparative example can detect a spark current of a magnitude sufficient to detect misfire and ignition under conditions in which the temperature of the ceramic burner increases as shown in FIG. 5 (b), 6 (a) and 6 (b). . However, 0.5 to 2.0 minutes are required until the spark current becomes sufficiently large.

Subsequently, the ceramic burner 3 is mounted in the combustion apparatus 1 shown in FIG. 1, and a voltage of 120 V is applied between the conductor layer 7 and the flame rod 8 to change the combustion conditions during combustion. The change over time of the flame current detected by the ignition detection means 9 was measured in case of re-ignition after extinguishing after combustion or after combustion. The results are shown in FIG.

In addition, the ceramic burner 3 of the conventional example and the ceramic burner of the comparative example are mounted in the combustion apparatus 1 shown in FIG. 1, and the aging change of the flame current detected by the ignition detecting means 9 under the same conditions as described above. Measured. The result is combined with FIG.

Here, Fig. 7 (a) shows that the excess air ratio is 1.1 and the combustion apparatus 1 is burned for 15 minutes with the combustion capacity of the combustion apparatus 1 minimized. If you change your ability to medium. In addition, Fig. 7 (b) shows combustion and extinguishing for 15 minutes under the same conditions as the first half of Fig. 7 (a), and completely cools the air excess rate to 1.1. It is a case where it re-ignites to an extent.

As can be clearly seen in Fig. 7, according to the ceramic burner 3 of the present embodiment in which the conductor layer 7 is formed, there is little overshoot regardless of the combustion conditions, and it is possible to recover to the normal spark current in a very short time. .

In contrast, the ceramic burner of the comparative example shows a large overshoot immediately after changing the combustion conditions, as can be clearly seen in FIG. In addition, the scaleover is performed for 4 seconds immediately after the change of the combustion conditions. The overshoot required 20-25 minutes to stabilize and recover to a moderate size spark current. In addition, the ceramic burner of the comparative example showed a large overshoot immediately after burning and re-ignition after combustion, and showed a large overshoot, and was restored for 20 to 25 minutes until it was stabilized by restoring to a normal-sized spark current. It was necessary. In the ceramic burner of the comparative example, no ignition could be detected until the overshoot recovered to a moderate magnitude spark current.

In addition, since the ceramic burner 3 of the prior art is a non-conductor, as is apparent from FIG. 7, almost no spark current is detected regardless of combustion conditions.

(Example 2)

In this embodiment, La _0.7 Sr _0.3 MnO ₃ is used as the electrically conductive perovskite metal oxide, and the conductor layer 7 contains borosilicate glass as the inorganic binder.

In this example, La _0.7 Sr _0.3 MnO ₃ powder was obtained in the same manner as in Example 1. The borosilicate glass was wet milled using a ball mill to obtain a powder.

Subsequently, to the La _0.7 Sr _0.3 MnO ₃ , 20-50% by weight of water of the powder and 0.5% by weight of a dispersant (heavy oil retainer, trade name: Cerna D-305) and a borosilicate glass powder were added, Wet mixing was performed to obtain a slurry. The addition amount of the said borosilicate glass powder was taken as the quantity suitable for 4 weight% with respect to the total weight of the conductor layer 7 formed by the said slurry.

Subsequently, the obtained slurry was sprayed onto the surface of the ceramic burner 3 using a commercially available odorless machine to form a coating film, and dried at 110 ° C. in a dryer for 2 hours. After drying, the substrate was heated and sintered at 950 ° C. for 1 hour in an electric furnace to form a conductor layer 7 having a thickness of 120 μm.

The conductor layer 7 is formed by uniformly covering the surface of the ceramic burner 3, and the ceramic burner 3 is sintered by the La _0.7 Sr _0.3 MnO ₃₃ sintered into the surface pores of the ceramic burner 3. Was strongly bound to. Moreover, the conductor layer 7 contained 4 weight% borosilicate glass with respect to the total weight. As a result, stronger bonding force was obtained by combining La _0.7 Sr _0.3 MnO ₃ particles or La _0.7 Sr _0.3 MnO ₃ particles with the ceramic burner 3 using the borosilicate glass as a binder.

Subsequently, the slurry containing La _0.7 Sr _0.3 MnO ₃ powder was manufactured by the same procedure as the above except having changed the addition amount of the borosilicate glass powder. The addition amount of the borosilicate glass powder is five kinds in an amount suitable for 0% by weight, 2% by weight, 4% by weight, 10% by weight, and 20% by weight with respect to the total weight of the conductor layer 7 formed by the slurry. A slurry of was obtained.

Subsequently, each obtained slurry was sprayed onto the surface of the ceramic burner 3 using the commercially available odorless machine, and the coating film was formed, and it dried at 110 degreeC in the dryer for 2 hours. After the drying, the mixture was heated and calcined at 880 to 1100 ° C. for 1 to 3 hours in an electric furnace. As a result, the ceramic burner in which the conductor layer 7 which does not contain borosilicate glass of 120 micrometers thick, or contains 2 weight%, 4 weight%, 10 weight%, and 20 weight% borosilicate glass with respect to the total weight, respectively is formed. (3) was obtained.

At this time, La _0.7 Sr _0.3 MnO ₃ powder and the ceramic burner (3) is bonded by sintering, and in order to investigate the range of firing temperature at which the sintered La _0.7 Sr _0.3 MnO ₃ acts as the conductor layer (7), The minimum baking temperature T ₁ for sintering so that the formed conductor layer 7 was not peeled off and the temperature T ₂ at which the resistance value of the conductor layer 7 became infinite were measured. Table 1 shows the ranges of T ₁ , T _2, and the firing temperature (d: d = T ₂ -T ₁ ).

Moreover, the change of the resistance value by baking temperature with respect to five types of conductor layers 7 which made content of borosilicate glass with respect to total weight 0 weight%, 2 weight%, 4 weight%, 10 weight%, and 20 weight%, respectively. 8 is shown.

Table 1

Addition amount (wt%) T ₁ T ₂ d           0 1060 1100          40           2          880 1000 120           4          880          990 110 10          880          970          90 20          880          920          40

As can be clearly seen in Table 1 and Fig. 8, the addition of the borosilicate glass lowers the lowest firing temperature at which La _0.7 Sr _0.3 MnO ₃ powder can be sintered. The wider the width of the firing temperature to effect the sintered La _0.7 Sr _0.3 MnO ₃ as a conductor layer (7). Therefore, setting of baking temperature can be made easy.

The conductor layer 7 can control the resistance value by appropriately setting the firing temperature if the content of the borosilicate glass to the total weight is in the range of 1 to 20% by weight. However, when the content of the borosilicate glass relative to the total weight exceeds 20% by weight, the resistance of the conductor layer 7 becomes too large regardless of the firing temperature.

In addition, although the borosilicate glass is used as the inorganic binder in the present embodiment, soda-lime glass may be used instead, and an equivalent effect can be obtained.

(Example 3)

In this embodiment, La _0.7 Sr _0.3 FeO ₃ is used as the electrically conductive perovskite metal oxide.

In this embodiment, a ceramic burner 3 having a conductor layer 7 was formed in the same manner as in Example 1 except that Fe ₂ O ₃ powder was used instead of the Mn ₂ O ₃ powder of Example 1. .

According to La _0.7 Sr _0.3 FeO _{3 used} for the conductor layer 7 of the present embodiment, when the ceramic burner ₃ on which the conductor layer 7 is formed is mounted on the combustion device 1 shown in FIG. Sufficient flame current was obtained to detect ignition between the conductor layer 7 and the flame rod 8, such as La _0.7 Sr _0.3 MnO ₃ used in.

(Example 4)

In this embodiment, La _0.5 Sr _0.5 CoO ₃ is used as the electrically conductive perovskite metal oxide.

This Example is different from Example 1 except that La ₂ O ₃ powder, SrCO ₃ powder and Co ₃ O ₄ powder are mixed in a molar ratio of 0.5: 0.5: 1, and the firing temperature of the powder is calcined to 1200 ° C. The ceramic burner 3 in which the conductor layer 7 was formed was manufactured by the exact same method.

According to La _0.5 Sr _0.5 CoO _{3 used} for the conductor layer 7 of the present embodiment, when the ceramic burner ₃ having the conductor layer 7 is mounted in the combustion device 1 shown in FIG. Sufficient flame current was obtained to detect ignition between the conductor layer 7 and the flame rod 8, such as La _0.7 Sr _0.3 MnO ₃ used in.

(Example 5)

In this embodiment, La _0.5 Ca _0.5 CrO ₃ is used as the electrically conductive perovskite metal oxide.

This Example is completely the same as Example 1 except that La ₂ O ₃ powder, CaCO ₃ powder and Cr ₂ O ₃ powder are mixed in a molar ratio of 0.5: 0.5: 1 and the firing temperature of the powder is calcined to 1500 ° C. By the same method, the ceramic burner 3 in which the conductor layer 7 was formed was manufactured.

According to La _0.5 Ca _0.5 CrO _{3 used} for the conductor layer 7 of the present embodiment, when the ceramic burner ₃ on which the conductor layer 7 is formed is mounted on the combustion device 1 shown in FIG. Sufficient flame current was obtained to detect ignition between the conductor layer 7 and the flame rod 8, such as La _0.7 Sr _0.3 MnO ₃ used in.

(Example 6)

In this embodiment, La _0.6 Sr _0.4 CrO ₃ is used as the electrically conductive perovskite metal oxide.

This Example is completely similar to Example 1 except that La ₂ O ₃ powder, SrCO ₃ powder and Cr ₂ O ₃ powder are mixed in a molar ratio of 0.6: 0.4: 1, and the firing temperature of the powder is calcined to 1500 ° C. By the same method, the ceramic burner 3 in which the conductor layer 7 was formed was manufactured.

According to La _0.6 Sr _0.4 CrO _{3 used} in the conductor layer 7 of the present embodiment, when the ceramic burner 3 formed in the conductor layer 7 is mounted in the combustion device 1 shown in FIG. Sufficient flame current was obtained to detect ignition between the conductor layer 7 and the flame pod 8, such as La _0.7 Sr _0.3 MnO ₃ used at.

(Example 7)

In this embodiment, La _0.2 Ca _0.8 MnO ₃ is used as the electrically conductive perovskite metal oxide.

This embodiment is a ceramic in which the conductor layer 7 is formed in the same manner as in Example 1 except that La ₂ O ₃ powder, CaCO ₃ powder, and Mn ₂ O ₃ powder are mixed in a molar ratio of 0.8: 0.2: 1. Burner 3 was prepared.

According to La _0.2 Ca _0.8 MnO _{3 used} in the conductor layer 7 of the present embodiment, when the ceramic burner ₃ having the conductor layer 7 is mounted in the combustion device 1 shown in FIG. Sufficient flame current was obtained to detect ignition between the conductor layer 7 and the flame pod 8, such as La _0.7 Sr _0.3 MnO ₃ used at.

(Example 8)

In this embodiment, Gd _0.8 Sr _0.2 Co _0.9 Mn _0.1 O ₃ is used as the electrically conductive perovskite metal oxide.

In this embodiment, the Gd ₂ O ₃ powder, the SrCO ₃ powder, the Co ₃ O ₄ powder, and the Mn ₂ O ₃ powder were mixed in a molar ratio of 0.6: 0.4: 1, and the firing temperature of the powder after calcining was 1200 ° C. The ceramic burner 3 in which the conductor layer 7 was formed was manufactured by the exact same method as in Example 1.

According to Gd _0.8 Sr _0.2 Co _0.9 Mn _0.1 O _{3 used} for the conductor layer 7 of the present embodiment, the ceramic burner ₃ having the conductor layer 7 is mounted on the combustion device 1 shown in FIG. 1. In the same manner as La _0.7 Sr _0.3 MnO _{3 used} in Example 1, a spark current sufficient to detect ignition between the conductor layer 7 and the flame rod 8 was obtained.

According to the above, since the perovskite-type metal oxide is itself an inexpensive price and an oxide, it is possible to reduce the manufacturing cost of the combustion device since it does not require a special device for avoiding oxidation during the firing. In addition, the perovskite metal oxide has excellent heat resistance because it is an oxide in itself.
In particular, since La _1-x Sr _x MnO ₃ has a high emissivity, by forming a conductor layer on the surface of the ceramic burner, the flame temperature can be lowered and nitrogen oxides can be reduced during combustion in the ceramic burner.
In addition, La _1-x Sr _x MnO ₃ catalyzes the complete oxidation of methane contained in the city gas at low temperature, and this catalysis can reduce nitrogen oxides during combustion in the ceramic burner. It is a useful invention.

Claims (7)

A ceramic burner having a flame hole formed in the porous ceramic plate, a conductor layer formed on a surface of which the flame in the ceramic burner is formed, a conductor provided to face the conductor layer, and a voltage between the conductor layer and the conductor. And a ignition detecting means for detecting ignition by detecting a spark current flowing through the flame when is applied, wherein the conductor layer is made of an electrically conductive perovskite metal oxide. And the conductor layer contains an inorganic binder in the range of 1 to 20% by weight based on the total weight of the conductor layer, and is bonded to the porous ceramic plate via the binder. The method according to claim 1, And the conductor layer uniformly covers the surface of the porous ceramic plate, and the perovskite-type metal oxide penetrates into the surface pores of the porous ceramic plate. The method according to claim 1, The conductor layer is a combustion device, characterized in that the perovskite-type metal oxide having a particle diameter of 0.04 ~ 5㎛. The method according to claim 1, And the conductor layer has a thickness in the range of 10 to 300 μm. delete delete The method according to claim 1, The perovskite-type metal oxide is La _1-x Sr _x MnO ₃ (x is 0 or less than 1) combustion device characterized in that

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