JPH089526Y2 - Catalytic combustion device - Google Patents

Description

[Detailed Description of the Invention] <Industrial field of application> The present invention applies an oxidation catalyst having excellent far-infrared radiation efficiency to heating. The present invention relates to a catalytic combustion device used for drying or the like.

<Prior Art> A catalytic combustion device that mixes a gaseous fuel and a vaporized liquid fuel with air and then sends the mixture to a catalyst layer to contact the catalyst and burns flamelessly on the surface thereof does not emit nitrogen oxides. ,
Since it has excellent features such as achieving mild radiant heating by the effect of far infrared rays emitted from the catalyst layer, various proposals have been made in the past and some of them have been put into practical use. However, in all of these catalytic combustion devices, before the premixed gas is sent to the catalyst layer to start catalytic combustion, the entire catalyst layer is heated in advance and the temperature is set to a temperature at which the fuel can undergo an oxidation reaction (ignition temperature. )
Need to keep above. If the preheating of the catalyst layer takes a long time, the user feels uncomfortable. Therefore, a preheating method for minimizing the preheating time of the catalyst layer is an important problem.

Conventionally, as a preheating method for the catalyst layer, there is a flame combustion preheating method using a Bunsen burner as previously filed by the applicant. This is, on the Bunsen burner arranged on the upstream side of the catalyst layer, ignites the premixed gas only when the catalyst layer is preheated to perform flame combustion, and heats the catalyst layer located downstream by the combustion heat at this time, The flame on the Bunsen burner is extinguished when heated to a temperature above the ignition temperature, and the premixed gas is sent to the catalyst layer to start catalytic combustion.

On the other hand, a method has also been proposed in which a resistance wire heater for preheating the catalyst layer is arranged at a distance immediately before the upstream side of the catalyst layer, and the heater is energized to preheat the catalyst layer while blowing air. .

<Problems to be Solved by the Invention> The above-mentioned conventional catalyst layer preheating method has the following drawbacks. That is, in the former case, the preheating speed is faster because it can be heated with a considerably larger amount of heat using kerosene than in the latter preheating method using a heater, but the carburetor is in the stage before the Bunsen burner is ignited to preheat the catalyst layer. Requires a carburetor preheat time to heat the kerosene to a predetermined kerosene vaporization temperature, so the total preheat time including the carburetor preheat and the catalyst bed preheat is relatively long. Further, since the combustion gas is preheated, when the temperature of the catalyst layer at the initial stage of catalyst layer preheating is still low, when the combustion gas passes through this, it is cooled from the surroundings and the moisture condenses, resulting in a white air from the hot air exhaust port of the device body. It emits water vapor and is not desirable in appearance.

Further, in the latter case, the amount of heat generated by the heater is electrically limited, and a sufficiently large amount of heat cannot be obtained as in the flame combustion preheating method, so that the catalyst layer preheating time is considerably long. Also, since the heater is always exposed to a high temperature oxidizing atmosphere during operation, the heater is easily broken.

Furthermore, in both cases, the heat transfer form during catalyst layer preheating is mainly convective heat transfer using air as a heat transfer catalyst, so much heat is released outside the catalyst layer without being used for preheating the catalyst layer. , Large heat loss.

<Means for Solving the Problems> The catalytic combustion apparatus according to the present invention was made in order to solve the above problems, and has a resistance heating property formed in a honeycomb shape or a continuous foam structure as a catalyst layer carrier. An inorganic carrier is used, and a catalyst layer is formed by carrying an oxidation catalyst on the surface of this carrier directly or through a sprayed layer of aluminum oxide or the like, and electrode terminals are attached to both ends of this exothermic carrier to conduct electricity to the electrode terminals. It is characterized by connecting a control unit for controlling.

<Operation> In the above configuration, as a method of preheating the catalyst layer to the ignition temperature before the start of catalyst combustion, by adopting the method of energizing through the electrode terminals attached to both ends of the exothermic carrier to generate Joule heat, Unlike the preheating method that mainly uses convective heat transfer, the catalyst layer itself generates heat, so there is little heat loss, the energy for preheating is efficiently used, and preheating of the catalyst layer is completed in a short time. Further, unlike the case of preheating with a resistance wire heater, there is no failure due to disconnection, and since the entire catalyst layer uniformly generates heat, no odorous gas such as CO.HC is emitted during ignition. Further, the catalyst layer can be used as it is as a ceramic heater, that is, by supplying electricity to the heat-generating carrier of the catalyst layer while blowing air, it is possible to perform radiation and warm air convection heating similar to catalyst combustion.

<Embodiment> An embodiment of the present invention is shown in FIG. The following is a description with reference to FIGS. 2 and 3.

In the catalytic combustion apparatus according to the present invention, as shown in FIG. 1, a box-shaped premixed gas supply chamber 2 is incorporated inside a main body 1. On the front side of the premixed gas supply chamber 2, a catalyst layer 3 having excellent far infrared radiation efficiency is arranged. As shown in the sectional view of FIG. 2, the catalyst layer 3 is formed by forming a resistance heating inorganic material having excellent conductivity such as silicon carbide as a main component into a breathable structure such as a honeycomb or a continuous foam. The carrier 3a described above is used to carry an oxidation catalyst 3b such as a platinum group metal or a complex oxide on the surface of the exothermic carrier 3a directly or through a sprayed layer 3c of aluminum oxide. The catalyst layer 3 is formed in a rectangular shape, and the electrode terminals 4 for electricity are attached to the exposed portions of the exothermic carrier at both ends of the catalyst layer 3. Further, the periphery of the catalyst layer 3 is made of a heat insulating material such as ceramic fiber. A frame-shaped catalyst support 5 is mounted and insulated and held in the premixed gas supply chamber 2. The electrode terminal 4 is connected to the control unit 15 and a lead wire. Further, on the front side of the catalyst layer 3, a heat transmission window 6 is provided for protecting the catalyst surface and ensuring safety.

A blower duct 10 is connected to the entrance of the diffuser chamber 7 formed at the bottom of the premixed gas supply chamber 2, and the other end of the blower duct 10 is connected to a fan 12. A fuel ejection port 11 for ejecting the kerosene vaporized by the vaporizer 13 into the ventilation duct and mixing it with the combustion air is provided in the middle of the ventilation duct 10, and further the diffuser chamber 7 at the downstream portion thereof. Baffle plate 8 near the entrance,
A metal mesh 9 for rectifying is arranged near the outlet of the diffuser chamber 7. At the upper part of the combustion gas flow path formed between the catalyst layer 3 and the heat permeable window 6, a combustion gas exhaust port 17 is provided.
However, a cooling air hole 18 for supplying air for diluting and cooling the combustion gas is provided at the bottom of the combustion gas flow path, and the combustion air and Intake ports 16 for taking in cooling air into the main body are opened respectively. A temperature sensing element 14 for sensing radiant heat emitted from the back surface of the catalyst layer 3 is inserted from the back surface of the premixed gas supply chamber 2 at a position near the back surface of the catalyst layer 3. The terminal portion of the temperature sensing element 14 is connected to the control unit 15. Control unit 15
Detects the surface temperature of the catalyst layer 3 on the basis of the output of the temperature sensing element 14, as well as the exothermic carrier of the catalyst layer 3 and the fan.
The automatic control is performed on the carburetor 12, the carburetor 13, and an oil feed pump (not shown).

The operation of the catalytic combustion device having the above-described configuration is composed of a steady combustion operation of burning the premixed gas flamelessly in the catalyst layer and a preheating operation of heating the catalyst layer to an ignition temperature or higher prior to the steady combustion operation. It

In the preheating operation, first, the electrode terminals 4 at both ends of the catalyst layer 3 are energized, and at the same time, the vaporization heater embedded in the carburetor 13 is energized to reduce the temperature of the kerosene vaporization section of the carburetor.
Heat and hold at 300 ℃. When the control unit 15 determines based on the output of the temperature sensing element 14 that the temperature of the catalyst layer 3 has reached the ignition temperature (for example, 300 ° C.) due to the energization, the catalyst layer 3 is energized. Stop and
At the same time, the fan 12 starts weak air blowing and operates the oil feeding pump. That is, the preheating operation is terminated and the steady combustion operation is started.

The kerosene is sent to the vaporizer 13 by the oil feeding pump, and the kerosene is vaporized while passing through the vaporizing portion heated and held at about 300 ° C. in the vaporizer 13, and the blowing duct 10 is supplied from the fuel jet port 11.
Is sprayed into. The atomized vaporized kerosene is mixed with the combustion air that is pressure-fed by the fan 12 to form a premixed gas, and the premixed gas passes through the baffle plate 8 and the baffle plate 8 while passing through the diffuser chamber 7 from the blower duct 10. The flow is rectified to a substantially uniform flow rate by the action of the metal mesh 9, and further supplied from the premixed gas supply chamber 2 above the diffuser chamber 7 to the catalyst layer 3. At this time, the catalyst layer 3 is preheated to a temperature equal to or higher than the ignition temperature (for example, 300 ° C.) by the preheating operation, and the catalyst layer 3 is designed to have a space velocity of 7 minutes for complete combustion of the premixed gas. Therefore, it shifts to ignition → trace temperature → steady combustion without discharging odorous gas such as CO.HC. During steady combustion, the amount of kerosene delivered and the amount of air blown by the fan 12 are controlled so that the volume ratio (ie, air ratio) of the combustion supply air amount to the theoretical air amount of the premixed gas is about 2 to 5, and the catalyst layer By controlling the back side temperature of 3 within the range of 500 to 800 ° C., it is possible to increase or decrease the combustion amount while preventing flashback and incomplete combustion of the premixed gas. In the unlikely event that the air ratio of the premixed gas is out of the set range due to some abnormality in the system, or if flashback or incomplete combustion occurs due to catalyst deterioration, etc., the control unit is based on the output of the temperature sensing element 14. Since 15 determines abnormal combustion, the combustion is stopped promptly and the emission of harmful gases such as CO.HC is prevented.

After complete combustion, the exhaust gas is discharged from the catalyst layer 3,
It is mixed with the cooling air supplied from the cooling air hole 18 to lower the temperature, and is discharged from the exhaust port 17 in the upper portion of the main body 1 as warm air. On the other hand, infrared rays are emitted from the catalyst layer 3 through the heat transmission window 6. Therefore, the convection heating by the warm air and the radiant heating by the infrared rays are simultaneously performed.

At the time of extinguishing the fire, the power supply to other devices except the fan 12 is cut off, the fan 12 alone is operated for several tens of seconds to blow air, and the system mainly including the catalyst layer 3 is cooled. At this time, since the catalyst layer 3 has a comparatively large heat capacity, even if the supply of the premixed gas is suddenly cut off, the odorous gas such as CO.HC should be discharged for a while after the extinguishing like the combustion accompanied by a normal flame. Without
It is completely oxidized on the catalyst layer 3.

Further, during steady combustion, when the control unit 15 detects the kerosene running out based on the output from the kerosene remaining amount sensor in the kerosene tank (not shown), the catalyst combustion is automatically stopped and the heat generating carrier of the catalyst layer 3 and It is possible to start the electric heating by energizing the fan 12 or select the electric heating by energizing the heat generating carrier of the catalyst layer 3 and the fan 12 from the start of the operation. It has a structure that can be used as convection heating with warm air and radiant heating with infrared rays emitted from the catalyst layer 3.

FIG. 3 is a diagram showing a temperature change in the central portion of the catalyst layer after the energization of the catalyst layer 3 in the preheating operation according to the present invention, in the case of the conventional flame combustion preheating method and the resistance wire heater preheating method. The same temperature change of is also shown in the figure. In the case of the present invention and the resistance wire heater preheating method, the heating value is the same (600 W), and in the flame combustion preheating method, the heating value is about 1700 W, which is larger than that. . As you can see from this figure,
It can be seen that in the preheating operation, the preheating method of the present invention can heat up to the ignition temperature most quickly with a small heating value.

<Effects of the Invention> As described above, the catalytic combustion apparatus according to the present invention does not operate by supplying the premixed gas formed by mixing the combustion air and the fuel to the preheated catalyst layer to promote the oxidation reaction. In a catalytic combustion device adapted to burn by flame, a resistance heating carrier having excellent conductivity is used for the catalyst layer, and a sprayed layer of aluminum oxide is formed on the surface of the carrier and an oxidation catalyst is supported on the surface of the catalyst layer. During the preheating operation, the heating carrier of the catalyst layer is energized to generate heat in the entire catalyst layer.

 As a result, the following various effects are achieved.

(1) Since the exothermic carrier itself representing the catalyst layer generates heat, the heat loss is less than that of the conventional catalyst layer preheating method mainly for convective heat transfer, and the energy for preheating can be effectively used, and the catalyst layer The time required for the preheating operation of the is quickened, and the discomfort to the user can be reduced.

(2) Because it uses an exothermic carrier with good thermal conductivity, it has good serratic heat during preheating operation, and when premixed gas is supplied and ignited, CO.HC etc. is locally discharged from the low temperature part. Does not emit odorous gas.

(3) Heat resistance without worrying about heater wire breakage that occurs when the resistance wire heater is used for preheating the catalyst layer. It has excellent corrosion resistance.

(4) Since the catalyst layer itself generates heat during the preheating operation, there is no need for a heating means such as a resistance wire heater or a Bunsen burner for flame combustion preheating and its control device as in the conventional catalyst layer preheating method, thus simplifying the device. be able to.

(5) Since Joule heat generated by energizing the exothermic carrier of the catalyst layer can also be used as a heating means, a catalytic combustion heating with a high calorific value and a clean electric heating with a low calorific value can be selected according to preference. It is possible and widens as a heating means.

[Brief description of drawings]

FIG. 1, FIG. 2 and FIG. 3 show an embodiment of the present invention. FIG. 1 (a) is a front view showing the internal structure of the catalytic combustion device,
FIG. 1 (b) is a side view thereof. 2 (a) and 2 (b) are sectional views of the catalyst layer. FIG. 3 is a graph showing the temporal change of the temperature at the central portion of the catalyst layer during the preheating operation. 2 is a premixed gas supply chamber, 3 is a catalyst layer, 3a is a resistance heating carrier, 3b is an oxidation catalyst, 3c is a thermal spray layer, 4 is an electrode terminal, 6 is a heat transmission window, 7 is a fuser chamber, and 10 is a blower. A duct, 12 is a fan, 13 is a carburetor, 14 is a temperature sensing element, and 15 is a control unit.

Claims (2)

[Scope of utility model registration request] 1. A catalytic combustion apparatus for mixing a gaseous fuel or a vaporized liquid fuel with combustion air to form a premixed gas, and sending it to a catalyst layer for flameless combustion, wherein the catalyst layer has a conductive heat-resistant inorganic material. 1. A catalytic combustion apparatus, comprising: a resistance heat-generating carrier, which is formed into a breathable structure such as a honeycomb or a continuous foam, and an oxidation catalyst supported on the surface of the carrier. 2. A catalyst layer is heated by energizing an exothermic carrier of the catalyst layer provided with electrode terminals, and after the temperature of the catalyst layer reaches a temperature at which oxidation reaction is possible or higher, the catalyst layer is heated. The catalytic combustion apparatus according to claim 1, characterized in that energization is stopped and premixed gas is sent to start catalytic combustion.