JPH0820052B2 - Radiant tube burner - Google Patents

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 simplify the structure and make the temperature distribution on the heat transfer surface more uniform in a radiant tube burner using a heat-resistant particle group as a heating medium. is there.

The radiant tube burner of the present invention has a lower end portion of a combustion tube in which a burner nozzle is inserted in an upper end portion of an inner tube inserted through a passage in a cylindrical outer tube having a bottom and installed vertically. A structure in which a heat-resistant particle group that is blown up by the combustion gas flow flowing out from the lower end of the inner tube and circulates in the passage and the inner tube is enclosed in the outer tube. Have.

[0005]

When the gas fuel is supplied to and burned in the combustion tube in which the lower end is loosely inserted in the upper end in the inner tube inserted through the passage in the outer tube, the inner tube is enclosed in the outer tube. The heat-resistant particle group is blown up by the combustion gas flow flowing out from the lower end in the inner tube and flowing into the passage to circulate and flow in the passage and the inner tube in a diffused state, and the heat transfer of the outer tube occurs. The hot surface is heated evenly.

[0006]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, it is possible to improve the durability of the burner by removing the part requiring particularly heat resistance from the combustion tube and to simplify the structure of the burner. The burner maintenance can be simplified. Further, the particle group heated by the combustion gas is diffused throughout the passage to flow upward, and while falling in the inner tube while being heated by the flame to flow and circulate in the passage and the inner tube, It is possible to uniformly and effectively heat the entire heat transfer surface of the outer tube to make the temperature distribution of the heat transfer surface uniform and stabilize the temperature of the heat transfer surface. Further, a part of the combustion gas that has passed through the passage flows into the inner tube and is mixed in the flame to promote the combustion reaction, and the radiated particles pass through the flame to increase the flame temperature. Since the NOx concentration is suppressed, the NOx concentration in the combustion gas can be reduced.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. In the radiant tube burner B, a disc-shaped flange 1 that is fastened to a mounting surface such as a furnace wall is vertically inserted by being inserted into the center of the flange 1 and is a bottomed cylinder made of stainless steel or ceramic. The outer tube 2 formed in a shape is fixed.

The inner wall surface of the bottom of the outer tube 2 is formed in a hemispherical shape, while the opening at the upper end of the outer tube 2 is closed by a cover plate 3, and a discharge port 4 opened near the upper end of the outer tube 2. An exhaust gas pipe 5 is connected to the.

Inside the outer tube 2, an inner tube 6 formed of a stainless material or a ceramic material in a cylindrical shape and having a length shorter than the length of the outer tube 2 is concentrically inserted through a passage 7. In the vicinity of the upper end of the inner tube 6, a taper portion 6a whose diameter gradually increases upward
Is formed, an outlet 6b is opened at the lower end of the inner tube 6, and a communication port 1 for communicating the inside of the inner tube 6 with the inside of the passage 7 is formed near the lower end of the outer tube 2.
0 is formed.

An anti-scattering net 18 is installed in the upper portion of the outer tube 2 and has a large number of meshes for allowing gas to flow therethrough. The outer peripheral edge of the outer tube 2 is gripped by the flange 1 and covers the passage 7 and the gap 9 above. ing. A heat transfer surface 2a is formed on the outer surface of the outer tube 2 from the position where the anti-scattering net 18 is installed to the lower end surface.

Inside the tapered portion 6a of the inner tube 6, a lower end portion of a combustion tube 8 formed of a stainless material or a ceramic material in a cylindrical shape is loosely inserted with a gap 9 therebetween.

An inlet 19 for allowing secondary air to flow 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.

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

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

When the secondary air is sent to burn the mixed gas, the combustion gas flows out from the outlet 6b of the inner tube 6 and reversely flows into the passage 7 through the communication port 10 in a folded manner to flow in the passage 7. A part of the combustion gas that has flown upward and is discharged from the discharge port 4 and that has passed through the passage 7 flows back into the inner tube 6 through the gap 9.

An inner tube 6 is provided in the outer tube 2.
A heat-resistant particle group 17 such as alumina particles capable of ascending flow due to the flow of the combustion gas flowing out of the outflow port 6a is enclosed. At the time of combustion of the mixed gas, the particle group 17 accumulated in a dense state near the bottom of the outer tube 2 flows out from the lower end of the combustion tube 8 and is blown up while being heated by the combustion gas flow that flows upward in the passage 7. Ascending flow with the combustion gas in the passage 7 in a diffused state flows into the inner tube 6 through the gap 9, falls and flows in the inner tube 6 by its own weight, is heated by the flame, and communicates from the outlet 6b of the inner tube 6. It again flows into the lower end of the passage 7 through the port 10, and repeatedly circulates in the passage 7 and the inner tube 6.

Next, the operation and effect of the embodiment having the above-mentioned structure will be described. In this example, a burner nozzle 15 for supplying gas fuel and primary air is provided in a tapered portion 6a of an inner tube 6 inserted through a passage 7 in a cylindrical outer tube 2 having a bottom and installed vertically. The lower end of the charged combustion tube 8 is loosely inserted through a gap 9 and is blown into the outer tube 2 by the flow of combustion gas flowing out from the lower end of the inner tube 6 so that the passage 7 is formed.
A heat-resistant particle group 17 that circulates and flows inside and inside the inner tube 6 is enclosed.

For this reason, the length of the combustion tube 8 can be shortened to remove the portion of the combustion tube 8 which particularly requires heat resistance, so that the durability of the burner can be improved and the structure of the burner can be improved. The burner maintenance can be simplified by simplifying the.

Further, the particle group 17 heated by the combustion gas is diffused and made to flow upward in the entire passage 7 and is made to fall and flow while being heated by the flame in the inner tube 6 to make it flow in the passage 7 and the inner tube 6. Since it circulates and flows inside, the heat transfer surface 2a of the outer tube 2
It is possible to heat the whole uniformly and effectively to make the temperature distribution of the heat transfer surface 2a uniform and to stabilize the temperature of the heat transfer surface 2a.

Further, a part of the combustion gas that has passed through the passage 7 flows into the inner tube 6 and is mixed into the flame to promote the combustion reaction, and also the particle group that has passed through the passage 7 and radiated heat. Since the heat of the flame is taken away when passing through the flame to suppress the rise of the flame temperature, the NOx concentration in the combustion gas can be reduced.

Further, since the mixed gas in which the gas fuel and the primary air are premixed 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.

[Brief description of drawings]

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

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

[Explanation of symbols]

 2 Outer tube 6 Inner tube 7 Passage 8 Combustion tube 15 Burner nozzle 17 Particle group

Claims (1)

[Claims] 1. A lower end of a combustion tube having a burner nozzle inserted therein is loosely inserted into an upper end of an inner tube inserted through a passage in a vertically-arranged bottomed cylindrical outer tube. The outer tube is filled with a heat-resistant particle group which is blown up by the combustion gas flow flowing out from the lower end of the inner tube and circulates in the passage and the inner tube. Tube burner.