JPH0539908A - Radiant tube burner - Google Patents

Abstract

PURPOSE:To make the temperature distribution on the heat transfer surfaces of a radiant tube burner uniform in the up-and-down direction and in the circumferential direction. CONSTITUTION:A group 17 of particles that are heat resistant are sealed in an outer tube 2 into which inner tube 6 is concentrically inserted. Around the inner tube 6 an outside channel 7 which moves the group 17 of particles that are blown up by the combustion gas to flow upwards with the combustion gas is formed, and in the inside of the inner tube 6 an inside channel 9 is formed to receive the group 17 of particles that flow out of the upper end of the outside channel 7 and make them flow by falling down and then lead them to the lower end of the outside channel 7. In the bottom face of the outer tube 2 a dispersing and guiding face 21 that has a recessed curve shape that bends uniformly over the whole circumference round the central shaft of the bottom face is formed and leads the group 17 of particles and combustion gas flow to the lower end of the outside channel 7 by the dispersing and guiding face 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiant tube burner applied as a heat source for an atmosphere heat treatment furnace, a metal melting furnace and the like.

[0002]

2. Description of the Related Art As a conventional technique, for example, Japanese Patent Laid-Open No. 63-6 is available.
There is a publication 5217. This publication discloses a tube burner in which a heat-resistant particle group contained in an outer tube is vertically moved by combustion gas.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to make the temperature distribution on the heat transfer surface uniform in the vertical and circumferential directions in a radiant tube burner using a heat-resistant particle group as a heating medium. is there.

[0004]

A radiant tube burner according to the present invention has a heat-resistant particle group enclosed in a cylindrical outer tube having a bottom and installed concentrically in the outer tube. An outer passage is formed around the substantially cylindrical inner tube, in which the particle group blown up by the combustion gas flow that flows downward from the upper side and returns upward flows upward with the combustion gas, and the inside of the inner tube is formed. Is formed with an inner passage through which the group of particles flowing out of the outer passage are dropped and introduced into the lower end of the outer passage, and the bottom surface of the outer tube is evenly distributed around the central axis of the bottom surface. It has a configuration in which a dispersion guide surface having a concave curved surface shape is formed.

[0005]

When the combustion gas that has flowed downward flows into the outer passage around the inner tube inserted in the outer tube, the combustion gas collides with the dispersion guide surface formed on the bottom surface of the outer tube and its circumferential direction. To the U-turn, and the heat-resistant particles enclosed in the outer tube are blown up by the flow of the combustion gas that flows back and flow upward in the outer passage together with the combustion gas. From the inside to the inside passage inside the inner tube, and is introduced again to the lower end inside the outside passage by the combustion gas flow that flows back, and repeatedly circulates in the outside passage and the inside passage.

[0006]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, the combustion gas is made to collide with the dispersion guide surface evenly over the entire circumference thereof so as to be evenly distributed in the circumferential direction of the dispersion guide surface. The combustion gas can be made to flow back and flow can be made uniform and stable in the circumferential direction and the vertical direction of the outer passage while the combustion gas is ascending and flowing in the outer passage. Of the outer tube can be stabilized over the entire inside of the outer passage, and the temperature distribution in the circumferential and vertical directions of the heat transfer surface of the outer tube is made uniform, especially in the circumferential direction at the bottom of the heat transfer surface. can do.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to the drawings. In a radiant tube burner B that serves as a heat source for an atmosphere heat treatment furnace, a metal melting furnace, etc., an outer tube 2 formed of a stainless material or a ceramic material in a cylindrical shape with a bottom has a disc shape that is fastened to a mounting surface such as a furnace wall. It is vertically installed while being inserted and fixed in the center of the flange 1.

Of the outer side surface of the outer tube 2, a heat transfer surface 2a is formed below the flange 1, and the upper end of the outer tube 2 is closed by a cover plate 3, so that the outer tube 2
An exhaust gas pipe 5 is connected to the discharge port 4 opened near the upper end of the.

An upper portion of the width of the outer tube 2 has a large number of meshes for allowing gas to flow, and a peripheral edge portion is gripped by the flange 1 and a diffusion prevention net 18 is disposed near the upper end of the heat transfer surface 2a. It is installed horizontally.

At the bottom of the outer tube 2, a protrusion 2b is formed in which a central portion near the central portion descends into a conical shape concentric with the outer tube 2, the center is light-sharp, and the thickness of the skirt gradually decreases outward.
And a dispersion guide surface 21 having a concave curved surface shape that is uniformly curved over the entire circumference around the central axis 22 of the bottom surface of the outer tube 2.

The outer tube 2 is formed of a stainless material or a ceramic material in a substantially cylindrical shape, and the upper end edge 6a is disposed below the anti-scattering net 18 and the lower end edge 6b is disposed above the dispersion guide surface 21. Shaped inner tubes 6 are concentrically inserted with a gap.

An outer passage 7 is formed around the inner tube 6, and a funnel-shaped taper portion 6c having a diameter gradually increasing upward is formed near the upper end of the inner tube.

The inner tube 6 is made of a stainless material or a ceramic material and is formed into a substantially cylindrical shape.
A combustion tube 8 inserted near the upper end of the inside is inserted concentrically, and an inner passage adjacent to the inside of the outer passage 7 with the inner tube 6 interposed between the combustion tube 8 and the inner tube 6. 9 is formed.

Near the lower end of the combustion tube 8, a divergent tapered portion 8a having a diameter gradually increasing downward is formed, and between the lower end edge of the tapered portion 8a and the dispersion guide surface 21 of the outer tube 2. Has a first communication port 10 that connects the inside of the combustion tube 8 and the outer passage 7, and connects the outer passage 7 and the inner passage 9 between the tapered portion 8a and the lower end edge 6b of the inner tube 6. The second communication port 11 is formed.

An inlet port 19 through which secondary air is introduced into the combustion tube 8 is opened near the upper end of the combustion tube 8.
A secondary air supply conduit 20 is connected to the inflow port 19. An outlet 8b through which combustion gas flows out is opened at the lower end of the combustion tube 8.

A gas pipe 12 connected to a gas supply pipe 13 for supplying a mixed gas in which gas fuel and primary air are premixed is inserted at an upper portion of the combustion tube 8 with a gap therebetween. The ignition plug 14 is inserted through the central portion.

A gas pipe 1 is provided in the upper part of the combustion tube 8.
A burner nozzle 15 connected to the tip of 2 is inserted, and a secondary air flow passage 16 for supplying secondary air around the burner nozzle 15 is formed between the combustion tube 8 and the gas pipe 12.

When the secondary air is sent through the secondary air flow path 16 and the mixed gas sent to the burner nozzle 15 is burned, the combustion gas flows downward in the combustion tube 8 and flows out from the outlet 8b of the combustion tube 8. Gas is the dispersion guide surface 2
1 is guided by the dispersion guide surface 21 and is dispersed in the circumferential direction of the dispersion guide surface 21 to flow back into the outer passage 7 in a U-turn shape and flow upward in the outer passage 7 to be discharged. Discharged from.

A heat-resistant particle group 17, such as alumina particles, which can be blown up by the combustion gas flow flowing out of the outlet 8b of the combustion tube 8 and returning to the outer passage 7 is enclosed in the outer tube 2, The particle group 17 is deposited in the lower portion of the outer tube 2 before combustion.

The particle group 17 is the outlet 8b of the combustion tube 8.
Is blown up while being heated by the combustion gas flow flowing back from the outer passage 7 and introduced into the outer passage 7, and in the outer passage 7 rises together with the combustion gas in a diffused state to flow out from the upper end of the outer passage 7, It is introduced into the upper end of the inner passage 9 by hitting the scattering net 18, drops and flows in the inner passage 9 by its own weight, and flows from the lower end of the inner passage 9 to the second communication port 1.
After passing through No. 1, it again flows into the lower end of the outer passage 7 and repeatedly circulates in the outer passage 7 and the inner passage 9.

Next, the operation and effect of the above embodiment will be described. In this example, the heat-resistant particle group 17 is enclosed in the bottomed cylindrical outer tube 2 installed vertically, and the circumference of the substantially cylindrical inner tube 6 concentrically inserted into the outer tube 2 is surrounded. Is formed with an outer passage 7 for ascendingly flowing together with the combustion gas, the particle group 17 blown up by the combustion gas flow that flows downward from above and returns to the upper side, and flows out from inside the outer passage 7 inside the inner tube 6. An inner passage 9 is formed which allows the particle group 17 to fall and flow to be introduced into the lower end of the outer passage 7. The bottom surface of the outer tube has a concave curved surface shape that is uniformly curved over the entire circumference around the central axis of the bottom surface. A guide surface 21 is formed.

Therefore, the combustion gas flowing out from the outlet 8b at the lower end of the combustion tube 8 is made to collide with the dispersion guide surface 21 in a uniform state over the entire circumference thereof to be evenly distributed in the circumferential direction of the dispersion guide surface 21. In this state, the combustion gas can be made to flow backward, and the flow state when the combustion gas ascends in the outer passage 7 can be made uniform and stable in the circumferential direction and the vertical direction of the outer passage 7, The flow state of the group 17 at the time of upward flow can be stabilized over the entire inside of the outer passage 7, and the temperature distribution in the circumferential direction and the vertical direction of the heat transfer surface 2a of the outer tube 2 can be made uniform. The temperature distribution in the lower circumferential direction can be made uniform.

Further, since the mixed gas obtained by premixing the gas fuel and the primary air is supplied to the burner nozzle 15 and burned, the mixed state of the gas fuel and the air is made uniform, the ignitability is improved, and stable combustion is achieved. The state can be continued, the carbon monoxide concentration can be reduced, and the stable combustion range can be expanded.

Next, the second embodiment shown in FIG. 3 will be described. In this embodiment, the length of the combustion tube 8A is shortened to form the inner passage 9A inside the inner tube 6, and the lower end of the combustion tube 8A is The structure is the same as that of the first embodiment except that the combustion gas is inserted into the upper end of the inner tube 6 and flows downward in the inner passage 9A together with the particle group 17 to collide with the dispersion guide surface 21. ing.

Since the operation and effect of the second embodiment are almost the same as those of the first embodiment, the description thereof will be omitted.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a radiant tube burner showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a vertical sectional view of a radiant tube burner of a second embodiment.

[Explanation of symbols]

 2 Outer tube 6 Inner tube 7 Outer passage 9,9A Inner passage 17 Particle group 21 Dispersion guide surface B Radiant tube burner

Claims (1)

[Claims] 1. A heat-resistant particle group is enclosed in a bottomed cylindrical outer tube that is vertically installed, and is surrounded by a substantially cylindrical inner tube that is concentrically inserted into the outer tube. Is an outer passage that causes the particle group that is blown up by the combustion gas flow that flows downward from above and returns upward to flow upward together with the combustion gas, and inside the inner tube, the particles that have flowed out of the outside passage. A dispersion guide surface having a concave curved surface shape which is formed by dropping and flowing the group to introduce it into the lower end of the outer passage, and which is uniformly curved on the bottom surface of the outer tube around the central axis of the bottom surface. A radiant tube burner characterized by being formed.