JP3580438B2 - Gaseous fuel-oxygen burner - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a gaseous fuel-oxygen burner used in a furnace mainly for radiant heat transfer, such as a glass melting furnace.
[0002]
[Prior art]
In a glass melting furnace, a burner that burns a liquid fuel such as heavy oil or a gaseous fuel such as natural gas with preheated air is used, and is a melting method mainly using radiant heat transfer.
[0003]
When air is used as the supporting gas, thermal efficiency deteriorates because nitrogen that does not contribute to combustion occupies most of the air. For this reason, the combustion air is usually preheated using a heat storage chamber or a heat exchanger to improve the thermal efficiency, but this is not sufficient. Further, there is a disadvantage that the higher the temperature of the preheated air and the higher the thermal efficiency, the more NOx is generated. Furthermore, because of the large amount of combustion exhaust gas, a considerably large treatment facility is required for the treatment. For this reason, burners using oxygen as a supporting gas have attracted attention and have been put to practical use.
[0004]
[Problems to be solved by the invention]
As described above, when oxygen is used as a supporting gas, the amount of combustion exhaust gas can be reduced, the thermal efficiency can be improved, NOx can be reduced, and further, there are many advantages such as eliminating the need for a heat storage chamber. There are issues that need to be solved in order to use this method in a melting furnace.
[0005]
Generally, in oxyfuel combustion, the combustion speed is high and a high-temperature flame is generated. However, the brightness of the flame is usually low for the flame temperature, and there is an inconvenience in a melting furnace mainly using radiant heat transfer. The problem of such low brightness is particularly pronounced when using a low carbon content gaseous fuel such as natural gas. The term gaseous fuel as used herein means a gaseous fuel containing carbon such as methane, ethane, propane, butane and natural gas, which can generate soot.
[0006]
In order to increase the luminance of the flame, it is effective to use a laminar flame, as is well known. However, in order to satisfy the industrially practical combustion load and produce a laminar flame, it is necessary to suppress the discharge speed from the nozzle to a low speed of several m / sec or less. In a flat furnace such as a glass melting furnace, a flame extending in the horizontal direction is necessary. At that time, if the discharge speed from the nozzle is suppressed to a low speed of several m / sec or less, the propulsive force of the flame becomes insufficient, and the flame soars. It will damage the furnace ceiling. Further, in order to increase the propulsive force of the flame, it is sufficient to increase the discharge speed from the nozzle. However, as this discharge speed is increased, a turbulent flame is generated, and contradiction arises in that the luminance decreases.
[0007]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a gaseous fuel-oxygen burner that can generate a high-luminance, propulsive flame.
[0008]
[Means for Solving the Problems]
To achieve the above object, the present invention, the gaseous fuel from the center, the gaseous fuel and discharges the oxygen from its surroundings as the combustion-supporting gas - at least gaseous fuel nozzles of the oxygen burner, a gas fuel nozzle and the oxygen nozzle to near the tip, Rutotomoni includes a rectifying tube composed of a plurality of tubing, the end portion of the rectifying tube provided in the gaseous fuel nozzle, a position that has entered the inner from the discharge end of the gas fuel nozzles It is characterized by being arranged .
[0009]
In this case, it is preferable that the terminal end of the flow straightening pipe provided in the gaseous fuel nozzle is disposed at a position that is deeper than 100 mm from the discharge end of the gaseous fuel nozzle.
[0010]
Further, it is preferable to arrange eccentrically said gaseous fuel nozzle with respect to the oxygen nozzles.
[0011]
Further, it is preferable to connect a plurality of the above-described burners in parallel to the furnace wall with the discharge directions of the gaseous fuel and oxygen substantially parallel .
[0012]
[Action]
The present invention provides a gas fuel-oxygen burner that discharges gaseous fuel from a central portion and oxygen as a supporting gas from the periphery thereof, and includes a rectifying tube composed of a plurality of tubular objects at least near a distal end portion of a gaseous fuel nozzle. Because the discharge flow from the nozzle is close to laminar flow due to the presence of the flow straightening tube, the terminal end of the flow straightening tube is located at a position deeper from the discharge end of the gas fuel nozzle , The mixing of the gaseous fuel and oxygen becomes slower, and the brightness of the flame can be increased. At the same time, the driving force of the flow is also increased, so that the soar of the flame is reduced. In the present invention, the term "a plurality of tubular objects" refers to a state in which a fluid flow is close to laminar flow, in which a plurality of tubular objects such as circular or polygonal metal or ceramics are formed in a bundle or in a honeycomb shape. Should be understood to mean a group of tubing for rectifying the flow.
[0013]
Further, by supplying the oxygen and the fuel in an eccentric form, not concentrically, the mixing of the gaseous fuel and the oxygen becomes slower, and the brightness of the flame can be increased.
[0014]
Further, by connecting a plurality of the above-described burners to the furnace wall in parallel with the discharge directions of the gaseous fuel and oxygen substantially parallel to each other, the intermediate portion of each burner is in a low pressure state as compared with the surroundings. The discharge flows of the gaseous fuel and the oxygen discharged from the burner are close to each other at the tip and merge, and this confluence point is at the inner part of the furnace. And promotes the mixing of the flame, increases the brightness of the flame, burns at a high temperature, increases the amount of radiant heat transferred to the object to be melted, and improves the thermal efficiency.
[0015]
【Example】
FIG. 1 is a vertical side view of a first embodiment of a gaseous fuel-oxygen burner according to the present invention, FIG. 2 is a vertical front view taken along line AA of FIG. 1, and FIG. 3 is a vertical front view of a second embodiment of the present invention. FIGS. 4 and 5 are plan views showing a third embodiment of the present invention, FIG. 5 is a vertical sectional front view of a flow straightening tube used in the present invention, and FIG. 6 is a flow rate of a discharge fluid between a nozzle according to the present invention and a conventional nozzle. FIG. 4 is a comparison diagram showing a distribution.
[0016]
According to the study of the present inventors, in this type of gaseous fuel-oxygen burner, in order to increase the brightness of the flame, it is necessary to slow down the combustion reaction and generate a lot of soot in the flame. It is most effective to make the mixing of fuel and oxygen as slow as possible, and it has been found that a straightening tube is an effective means.
[0017]
In order to confirm the above points, as shown in FIG. 5, a nozzle 4 provided with a straightening tube 3 in which a thin metal thin tube 2 is closely arranged in a tube bundle shape in a metal outer tube 1 having a cylindrical cross section, The characteristics of the discharge flow from a nozzle without a straightening tube (not shown) were investigated. FIG. 6 shows the flow velocity distribution of the discharge flow at a position separated from the nozzle 4 by a certain distance. The solid line a shows the flow velocity distribution curve of the nozzle provided with the rectifying tube 3, and the dotted line b shows the flow rate distribution of the nozzle without the rectifying tube 3. 5 shows a flow velocity distribution curve. From FIG. 6, it can be seen that the discharge flow from the nozzle 4 having the flow straightening pipe 3 has a higher flow velocity at the center and the flow is concentrated in a narrower area. At this time, the initial discharge speed from the nozzle is the same, but it is clear that the provision of the flow straightening tube 3 has increased the propulsive force of the discharge flow. In order to make the flow velocity the same, a lower initial discharge velocity can be used, so that the Reynolds number indicating the degree of flow turbulence is reduced, and the flow can be closer to laminar flow. In addition, smoke was caused to flow in the flow, and the flow pattern was visually confirmed and compared. When the straightening pipe 3 is provided, the smoke travels straight for a relatively long time. However, when the straightening pipe 3 is not provided, the flow of the smoke is not smooth and clear, and a clear difference is recognized. Since the smoke travels straight for a relatively long time, it means that the gas mixture is slow, so the stoichiometric excess fuel-rich (oxygen-deficient) area in the center becomes large, and soot is easily generated. Therefore, the brightness of the flame increases.
[0018]
Therefore, according to the present invention, as shown in the embodiment of FIGS. 1 and 2, a nozzle 4 having the rectifying tube 3 for discharging gaseous fuel is disposed at a central portion, and a nozzle 5 for discharging oxygen is provided outside the nozzle 4. The gas fuel-oxygen burner is arranged concentrically.
[0019]
In the embodiment shown in FIG. 3, a nozzle 5 for discharging oxygen and a nozzle 4 provided with the rectifying tube 3 for discharging gaseous fuel are arranged not concentrically but eccentrically. When gaseous fuel and oxygen are supplied by the burner of this embodiment, the region of excess fuel (insufficient oxygen) can be further enlarged.
[0020]
The shape and installation position of the rectifier tube 3 were also examined and tested. As a result of the test, the tubule 2 constituting the rectifier tube 3 does not need to be a circle, but the inner diameter of the tubule 2 as each element is preferably 3 mm or less, and the length It was found that it was necessary to secure 30 mm or more, preferably about 100 mm. Further, the thinner the thin tube 2 constituting each element of the flow straightening tube 3 is, the better it is, but it is practically preferable to be 0.5 mm or less. It has also been found that the end of the flow straightening tube 3 needs to be installed in the vicinity of 0 to 100 mm from the discharge end of the nozzle 4.
[0021]
By providing the straightening pipe 3 as described above, the discharge flow from the nozzle 4 becomes closer to laminar flow, so that the mixing of the gaseous fuel and oxygen becomes slower, and the brightness of the flame can be increased. At the same time, the driving force of the flow is also increased, so that the soar of the flame is reduced.
[0022]
The burner of the first embodiment shown in FIGS. 1 and 2 has, for example, a gas having a rectifying tube 3 made of a bundle of heat-resistant steel thin tubes 2 having an outer diameter of 3 mm, a wall thickness of 0.5 mm, and a length of 100 mm at the center. A fuel flow path 6 is formed, and an oxygen gas flow path 7 is formed concentrically around the fuel flow path 6.
[0023]
A gas having a calorific value of 9000 Kcal / Nm ³ was burned with the same burner using the same burner except for the rectifier tube except for the rectifier tube. A comparison revealed that the burner having the rectifier tube 3 in both brightness and flame shape was clearly superior. Was confirmed.
[0024]
However, when the combustion load was increased to 600,000 Kcal / Hr or more, a decrease in luminance was observed. In practice, this may be inconvenient because a burner with a larger combustion capacity may be required.
[0025]
Therefore, two burners of the first embodiment were manufactured, and as shown in FIG. 4, a combustion test was performed adjacent to the burners. The flame shape changes depending on the arrangement of the two burners 8 and 9 with respect to the furnace wall 10. However, as long as the two flames do not collide, even if the combustion load becomes 600,000 Kcal / Hr or more as a whole, a high-luminance flame is generated. I got it. Since the preferred flame shape varies depending on the application, it cannot be determined uniformly, but it has been found that a burner having a plurality of nozzles can cope with a combustion load of 600,000 Kcal / Hr or more. In the case of the embodiment shown in FIG. 4, since the middle part of the two burners 8 and 9 has a lower pressure than the surroundings, there is a tendency that the flames approach each other at the leading end and join together. Therefore, the mixing of the gaseous fuel and oxygen is promoted in the inner part of the furnace to increase the brightness of the flame and to perform high-temperature combustion.
[0026]
Further, the gas fuel nozzle of the burner of the example was installed eccentrically with respect to the oxygen nozzle by 5 mm or 10 mm, and a combustion test was performed. As the amount of eccentricity increased, the flame shape became less axisymmetric, and the redness characteristic of incomplete combustion was partially observed, and the color tone of the flame changed. For this reason, it was difficult to evaluate the luminance, but it was found that the amount of soot generated increased, and the luminance was increased by increasing the oxygen flow rate.
[0027]
Since oxygen is expensive, it is not preferable to consume unnecessarily much oxygen. However, it may be preferable to install the nozzle eccentrically. Usually, a plurality of burners are installed in a glass melting furnace, and an exhaust gas flue is installed. Therefore, a flow of combustion gas of another burner also exists in the furnace. When a burner with a low discharge speed is used as in the burner of the present invention, such a flow of the combustion gas cannot be ignored, and particularly, oxygen on the outer periphery is easily affected. In such a case, eccentricity may be rather convenient.
[0028]
Further, a burner (not shown) in which the flow straightening tube 3 was added to the oxygen flow path 7 of the burner of the above embodiment was manufactured, and a combustion test was performed. In this case, a bundle of heat-resistant steel thin tubes having an outer diameter of 3 mm, a wall thickness of 0.5 mm, and a length of 100 mm, which was the same as that used for the gaseous fuel flow path 6, was used as the flow straightening tube 3. In this case, both the luminance and the flame shape were improved.
Each of the above embodiments illustrates the case where the circular thin tube 2 is used as the rectifying tube 3. However, other tube bundle shapes, for example, an elliptical shape, a square shape, a hexagonal shape, or any other appropriate shape alone or , May be employed in combination, or may be a honeycomb shape.
[0029]
【The invention's effect】
As described above , according to the present invention, in addition to the fact that the discharge flow from the nozzle is close to laminar flow due to the presence of the flow straightening tube, the terminal end of the flow straightening tube is disposed at a position deep into the discharge end of the gas fuel nozzle. As a result , the mixing of the gaseous fuel and oxygen becomes slower, the brightness of the flame can be increased, and an improvement in energy efficiency can be expected in a furnace mainly using radiant heat transfer such as a glass melting furnace. At the same time, the propulsive force of the flow is increased, so that the soaring of the flame is reduced, and the damage to the ceiling of the furnace is also reduced, so that the effect of prolonging the life of the furnace can be expected.
[0030]
Further, if the configuration is such that the oxygen and the fuel are supplied in an eccentric form instead of being concentric, the mixing of the gaseous fuel and the oxygen becomes slower, and the brightness of the flame can be further increased.
[0031]
Further, if configured to a plurality parallel concatenated to the burner described above substantially parallel ejection direction of the gaseous fuel and oxygen to the furnace wall, a low pressure intermediate portion of each burner in comparison to ambient Therefore, the jet flows of the gaseous fuel and oxygen ejected from each burner come close to each other at the tip and join together, and this confluence point is located inside the furnace. It is possible to promote the mixing of fuel and oxygen, increase the brightness of the flame, perform high-temperature combustion, increase the amount of radiant heat transferred to the object to be melted, and improve the thermal efficiency.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional side view of a first embodiment of a gaseous fuel-oxygen burner according to the present invention.
FIG. 2 is a vertical sectional front view taken along line AA of FIG. 1;
FIG. 3 is a vertical sectional front view of a second embodiment of the present invention.
FIG. 4 is a plan view showing a third embodiment of the present invention.
FIG. 5 is a vertical sectional front view of a flow straightening tube used in the present invention.
FIG. 6 is a comparison diagram showing a flow velocity distribution of a discharge fluid between a nozzle according to the present invention and a conventional nozzle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Metal outer tube 2 Metal thin tube 3 Rectifier tube 4 Gas fuel discharge nozzle 5 Oxygen discharge nozzle 6 Gas fuel flow path 7 Oxygen gas flow path 8, 9 Burner 10 Furnace wall

Claims (4)

In a gas fuel-oxygen burner that discharges gaseous fuel from the center and oxygen as a supporting gas from the periphery, a plurality of tubular objects are provided at least near the tip of the gaseous fuel nozzle of the gaseous fuel nozzle and the oxygen nozzle. Rutotomoni includes a configured rectifying tube, the gas to the end of the fuel rectifying tube nozzle provided in the gas fuel, characterized in that the discharge end of the gas fuel nozzle was located at a position entering the back - Oxygen burner. 2. The terminal according to claim 1, wherein an end of the straightening pipe provided in the gaseous fuel nozzle is located at a position deeper within 100 mm from a discharge end of the gaseous fuel nozzle. 3. Gaseous fuel-oxygen burner. Oxygen-fuel burner - gas fuel according to claim 1, characterized in that arranged eccentrically to the gaseous fuel nozzle with respect to the oxygen nozzles. The gas fuel-oxygen burner according to any one of claims 1 to 3, wherein a plurality of burners are connected to the furnace wall in parallel with the discharge directions of the gaseous fuel and oxygen being substantially parallel.

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