JP3574331B2 - Combustion burner - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a combustion burner suitable for use in a forced vaporization type combustion apparatus for vaporizing and burning a liquid fuel such as kerosene.
[0002]
[Prior art]
A conventional combustion burner of this type, for example, a combustion burner used in a forced-vaporization type combustion apparatus is configured as shown in FIGS. 7 and 8, and FIG. 7 is a schematic view of a combustion burner of a forced-vaporization type combustion apparatus. FIG. 8 is an exploded perspective view, and FIG. 8 is a schematic configuration diagram of a forced vaporization type combustion device.
[0003]
A combustion burner of a conventional forced-vaporization type combustion device will be described with reference to FIGS. 7 and 8.
[0004]
This type of combustion burner 1 includes a burner top 2, a bottom 3 combined with the burner top 2, a partition plate 4 sandwiched between the burner top 2 and the bottom 3, and a rectifying plate 5 attached to the partition plate 4. And The burner top 2 is provided with a flame net 6 having excellent heat resistance and oxidation resistance, and a back net 7 for preventing flashback and measuring static pressure of the mixed gas.
[0005]
In the combustion burner 1, the electromagnetic pump 9 that has been pumping kerosene to the vaporizer 8 during fire extinguishing is stopped, and the convection blower (not shown) is also stopped. Further, the vaporized gas remaining in the combustion burner 1 keeps burning in the combustion burner 1. As the vaporized gas remaining in the combustion burner 1 burns, the pressure of the residual vaporized gas in the vaporizer 8 also decreases, so that the injection pressure from the vaporizer 8 also decreases.
[0006]
Accordingly, the suction amount of the primary air also decreases, so that the power of the combustion flame in the combustion burner 1 gradually decreases, and the flame resistance between the flame rod 10 and the combustion burner 1 increases through the combustion flame. When the flame resistance reaches a preset value, the solenoid needle valve 11 of the carburetor 8 is operated to close the nozzle hole 12 of the carburetor 8 to prevent the residual vaporized gas in the carburetor 8 from being released. ing.
[0007]
On the other hand, in the combustion burner 1, combustion is stopped by closing the nozzle hole 12 of the carburetor 8, but a very small amount of unburned gas remains in the combustion burner 1, and the unburned gas becomes a flame of about 500 to 600 ° C. An intermediate product of aldehydes is generated by contact with the mouth net 6 and an odor accompanied by irritation is generated. Therefore, a catalyst for oxidizing unburned gas, such as platinum palladium, is applied to the flame net 6 and the back net 7. The unburned gas generated immediately after the fire is extinguished by contact with the catalyst, which has been heated to an active temperature by the combustion flame, is oxidized, so that intermediate products of aldehydes are not generated.
[0008]
[Problems to be solved by the invention]
In the combustion burner of the forced vaporization type combustion apparatus of the above-described conventional technology, at least one of the flame net and the back net of the combustion burner carries a catalyst for oxidizing unburned gas. As the temperature rises, the flame net and the back net reach and maintain a temperature at which the catalyst undergoes an oxidation reaction. Therefore, an unreacted gas, which causes odor at the time of extinguishing, is oxidized and burned to reduce odor.
[0009]
However, noble metal catalysts such as platinum show activity (oxidation reaction) from a low temperature, so that those that normally form a flame on the flame net and burn normally, due to the combustion heat over time, Reaches a high temperature, and accordingly the flame net and the back net carrying the catalyst disposed directly below it are heated to a high temperature by conduction heat or radiant heat. Before the mixed gas with the primary air oxidizes and burns on the flame net, the oxidation reaction of the catalyst with high activity occurs at a low temperature in the back net, and there is a concern that the operation may be stopped due to flashback combustion. I have.
[0010]
An object of the present invention is to provide a combustion burner that solves these problems.
[0011]
[Means for Solving the Problems]
The combustion burner of the present invention has solved the above-mentioned problem.In a combustion burner in which a catalyst for oxidizing unburned gas is carried on a flame net and a back net of the burner, a back-fire phenomenon of steady combustion in the back net is provided. In order to eliminate the occurrence , a baking step at a baking step temperature of 800 to 850 ° C. is added.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention provides, for example, a vaporizer for vaporizing a liquid fuel such as kerosene, a burner for mixing and burning the vaporized fuel and air, an ignition heater for igniting a mixed gas to start combustion, and detecting combustion. In a forced evaporative combustion apparatus provided with a detection means for detecting the presence of a gas, at least one of a flame net and a back net of a burner is loaded with a catalyst for oxidizing unburned gas and then prefired.
[0013]
Hereinafter, a case where the embodiment of the combustion burner of the present invention is applied to a combustion burner of a forced-vaporization type combustion apparatus will be described with reference to FIGS. 1 to 6. The same reference numerals are given and the description is omitted.
[0014]
FIG. 1 is a plan view of a main part showing an embodiment of a combustion burner of the present invention, FIG. 2 is a cross-sectional view of a main part taken along line AA of the combustion burner of FIG. 1, and FIG. 4 is an explanatory view showing the relationship between the firing temperature and the firing time of the back net of the combustion burner. FIG. 5 is an explanatory view comparing the purification rate of the back net of the combustion burner and the presence or absence of the firing step. FIG. 6 is an explanatory diagram comparing the relationship between the firing temperature of the combustion burner back net and the purification characteristics.
[0015]
In the combustion burner 1 of FIGS. 1 to 3, the combustion is stopped by closing the nozzle hole 12 of the carburetor 8, but a very small amount of unburned gas remains in the combustion burner 1, and the unburned gas becomes 500 to When it comes into contact with the flame net 6 at about 600 ° C., an intermediate product of aldehydes is generated, and an unpleasant odor with irritation is generated.
[0016]
For this purpose, a catalyst for oxidizing the unburned gas, such as platinum palladium, is carried on the flame net 6 and the back net 7, and the unburned gas generated immediately after the fire is extinguished is raised to an active temperature by the combustion flame. The catalyst is oxidized by contact with the catalyst to prevent formation of an intermediate product of aldehydes.
[0017]
However, the combustion burner 1 reaches a high temperature due to the heat of combustion of the flame burner 1 which has formed a flame on the flame net 6 and burns normally with the lapse of time. Since the back net 7 supporting the catalyst disposed immediately below is also heated to a high temperature by conduction heat or radiant heat, the mixed gas of the vaporized gas of kerosene and the primary air for combustion is oxidized on the flame net 6. Before the combustion, the oxidation reaction of the catalyst having a high activity at a low temperature occurs in the back net 7, and the operation may be stopped due to flashback combustion.
[0018]
Therefore, in order to eliminate the activity in the low temperature area and maintain the activity in the high temperature area, holding at an unnecessarily high temperature and for a long time and pre-calcining will cause the catalyst itself to undergo a semi-melting phenomenon and high temperature degradation As a result, the activity is lost and the original purpose cannot be achieved, so that the setting of the pre-firing temperature requires careful control of conditions.
[0019]
When the material of the back net 7 supporting the catalyst is an austenitic stainless steel plate, when the temperature becomes 860 ° C. or higher, the material itself oxidizes to generate oxidized scale, and the catalytic effect is lost due to the falling off of the scale.
[0020]
Therefore, the preliminary firing temperature, the actual combustion test, and the material surface will be described.
[0021]
The back net 7 supporting the catalyst was baked at 650 ° C., 750 ° C., 800 ° C., and 850 ° C. for 20 minutes each, and the back net 7 was cooled at 850 ° C. and the power was turned off to cool the furnace. A combustion test was conducted by incorporating it into an actual oil fan heater. Since the temperatures of the burner and the combustion chamber were not sufficiently stable at the initial stage of ignition, flashback did not occur due to oxidation reaction of the catalyst.
[0022]
However, in the case of a fired product at a firing temperature of 750 ° C. or less, after 30 minutes of ignition, when a combustion mode in which flashback is easily performed is converted into a thermal power under the condition intentionally created, a flashback phenomenon in which most of the combustion occurs in the back net 13 is caused. It wakes up and stops operation due to flame misfire. This is because when the calcination temperature is 750 ° C. or lower, the catalyst does not sufficiently lose its activity in a low temperature range.
[0023]
Further, in the fired product at a firing temperature of 800 ° C. or higher, the above-mentioned phenomenon was not observed even after a long operation.
[0024]
Next, the surface of the back net 7 fired at each temperature was examined by SEM observation and EDX analysis. In the fired product having a firing temperature of 850 ° C. or lower, the presence of pt and the oxide film formed on the surface No abnormality was observed, but in the fired product at a firing temperature of 860 ° C., peeling occurred in the formed oxide film.
[0025]
Next, the relationship between the sintering temperature and the purification rate will be described. FIG. 4 is a diagram showing the relationship between the sintering temperature and the sintering time. FIG. 5 is a graph showing the relationship between the presence / absence of a baking step and the purification rate. After the baking temperature in FIG. 4 was raised to 850 ° C., the power was turned off, and the furnace was cooled in a furnace. It is something.
[0026]
As shown in FIG. 5 , when pre-firing is not performed, an oxidation reaction appears at about 160 ° C., and almost complete reaction is observed at 250 ° C., indicating activity from a low temperature. On the other hand, in the fired product, a reaction is observed from about 350 to 400 ° C., and a complete oxidation reaction starts from about 430 ° C. or more.
[0027]
From the above results, it can be seen that the firing (oxidation reaction) in the low temperature range is eliminated by firing.
[0028]
FIG. 6 shows the relationship between the sintering temperature and the purification characteristics. The relationship between the sintering temperature and the purification characteristics was measured using a propylene evaluation gas. The lower the sintering temperature, the better the purification rate. At a temperature of 850 ° C., the temperature is worse than at other temperatures, and calcination at a high temperature may cause catalyst poisoning.
[0029]
However, when the power is turned off after the firing temperature reaches 850 ° C., the same performance as when firing at a low temperature (600 ° C.) is exhibited, and the effect of thermal degradation is also avoided when the firing is held for a moment. be able to.
[0030]
From the above results, after supporting the catalyst on a back net, for example, a metal net, by performing a pre-firing step for a predetermined time at a firing temperature in the range of 800 to 850 ° C., the occurrence of a flashback phenomenon in steady-state combustion is reduced. Can be eliminated.
[0031]
【The invention's effect】
Since the combustion burner of the present invention has the above-described structure, there is a risk that flashback may occur before the steady combustion of the noble metal catalyst on the back net, but a step of pre-firing at 800 to 850 ° C is added. By doing so, the activity in the low temperature range is eliminated, the risk of flashback is eliminated, and the effect is exhibited by reducing the odor at the time of ignition / extinguishing.
[Brief description of the drawings]
FIG. 1 is a plan view of a main part of a combustion burner according to an embodiment of the present invention.
FIG. 2 is a sectional view of an essential part taken along line AA of FIG. 1;
FIG. 3 is a sectional view of an essential part taken along line BB of FIG. 1;
FIG. 4 is an explanatory diagram showing a relationship between a firing temperature and a firing time.
FIG. 5 is an explanatory diagram comparing a purification rate and the presence or absence of a firing step.
FIG. 6 is an explanatory diagram comparing the relationship between the firing temperature and the purification characteristics.
FIG. 7 is a schematic exploded perspective view of a combustion burner of a conventional forced-vaporization type combustion device.
FIG. 8 is a schematic configuration diagram of a conventional forced vaporization type combustion device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Burner 2 Burner top 3 Bottom 4 Partition plate 5 Rectifier plate 6 Flame net 7 Back net 8 Vaporizer 9 Electromagnetic pump 10 Frame rod 11 Solenoid needle valve 12 Nozzle hole

Claims (2)

In a combustion burner in which a catalyst for oxidizing unburned gas is carried on a flame net and a back net of a burner, a firing process temperature of 800 to 850 ° C. is used in order to eliminate the occurrence of a flashback phenomenon in steady combustion on the back net. A combustion burner characterized by adding a firing step. In a combustion burner carrying a catalyst for oxidizing unburned gas in the flame net and back net of the burner,
The catalyst is a noble metal catalyst, the back net is an austenitic stainless steel material,
Combustion burner characterized in that the baking step temperature is added baking step of 800 to 850 ° C. in order to eliminate the occurrence of backfire phenomena of the steady combustion in the backstop.

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