JPH0820053B2 - 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 radiant tube burner in which a heat-resistant particle group contained in an outer tube is vertically moved by combustion gas.

[0003]

When the object to be heated in the furnace is heated by the radiant tube burner, the temperature of the combustion gas in the tube rises as the temperature in the furnace rises and is almost proportional to the rise in the temperature in the furnace. Then, there is a problem that the NOx concentration in the combustion gas increases. An object of the present invention is to make the temperature distribution on the heat transfer surface uniform and reduce the NOx concentration in the combustion gas in the radiant tube burner.

[0004]

A radiant tube burner according to the present invention has a cylindrical outer tube which is vertically installed and has a bottomed cylindrical outer tube into which a combustion gas is inserted. A combustion tube having an opening at the lower end is inserted through which an outflow port for flowing out is formed, and an outer passage formed around the inner tube is formed in the outer tube, and is formed between the inner tube and the combustion tube. An inner passage is provided in parallel, and a heat-resistant particle group that is blown up by the combustion gas flow flowing out from the outlet and circulates in the outer passage and the inner passage is enclosed in the outer tube. The combustion tube has a structure in which a large number of through holes through which the particles can pass are provided.

[0005]

The heat-resistant particle group enclosed in the outer tube is blown up by the combustion gas flow flowing out from the outlet at the lower end of the combustion tube inserted in the inner tube, and is formed around the inner tube. Part of the particle group is transferred to the combustion tube while flowing upward in the outer passage along with the combustion gas flow and then falling and flowing in the inner passage formed between the inner tube and the combustion tube. Introduced into the combustion tube through a large number of penetrating through holes, heated by the flame passing through the flame, the particle group that has passed through the flame, and the particle group that has passed through the inside passage Are merged and introduced again into the outer passage, and repeatedly circulate and flow in the both passages.

[0006]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, the particles heated by the combustion gas are caused to rise and flow while being diffused in the outer passage, and the heat transfer surface of the outer tube is set in the outer passage. It is possible to uniformly heat by the particle group diffused throughout, and it is possible to make the temperature distribution on the heat transfer surface of the outer tube uniform. In addition, a part of the particle group whose temperature has been lowered by heat radiation by heating the outer tube is introduced into the combustion tube and passed through the flame, and the heat of the flame is given to a part of the particle group that radiates heat to change the flame temperature. Since the increase is suppressed, the NOx concentration in the combustion gas can be reduced by suppressing the increase in NOx concentration accompanying the increase in flame temperature. Further, since the particles passing through the inside passage and the particles heated by the flame and heated up are mixed and flow upward in the outside passage, the heating effect on the entire particles is increased and the temperature of the heat transfer surface is increased. Can be stabilized over time.

Next, one 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 installed vertically in a state of being inserted and fixed in the central portion 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.
An exhaust gas pipe 5 is connected to the discharge port 4 opened near the upper end of the.

An anti-scattering net 18 having a large number of meshes for allowing gas to flow therethrough and having a peripheral portion gripped by the flange 1 is horizontally installed above the width of the outer tube 2.

The outer tube 2 is formed of a stainless steel or 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 bottom surface of the outer tube. 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 tapered portion 6a 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 inner passage is concentrically inserted, and between the combustion tube 8 and the inner tube 6, an inner passage 6 is provided inside the outer passage 7 with an inner tube 6 interposed therebetween. 9 is formed.

A diverging tapered portion 8a having a diameter gradually increasing downward is formed near the lower end of the combustion tube 8, and the combustion tube is provided between the lower end edge of the tapered portion 8a and the bottom surface of the outer tube 2. 8 is formed with a first communication port 10 that communicates the inner passage 8 with the inner passage 8, and a second communication that communicates the outer passage 7 and the inner passage 9 is formed between the tapered portion 8a and the lower end edge of the inner tube 6. A mouth 11 is formed.

An inlet port 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. 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 line 13 for supplying a mixed gas in which gas fuel and primary air are premixed is inserted at an upper part 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. The gas collides with the bottom surface of the outer tube 2 and flows back into the outer passage 7 in a U-turn shape, and then flows upward in the outer passage 7 and is discharged from the discharge port 4.

A heat-resistant particle group 17, such as alumina particles, which can be blown up by a combustion gas flow that flows out from the outlet 8b of the combustion tube 8 and flows back into 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.

A large number of through holes are formed in the combustion tube 8 so as to face the flame in the combustion tube 8 in the vertical direction and are arranged at equal intervals in the circumferential direction so that each particle of the particle group 17 can pass through. 22 to 22 are provided so as to introduce a part of the particle group 17 falling and flowing in the inner passage 9 into the combustion tube 8 and to pass through the flame.

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 is introduced into the outer passage 7 and flows upward in the outer passage 7 together with the combustion gas in a diffused state to flow out from the upper end of the outer passage 7, It collides with the dispersion net 18 and is introduced to the upper end in the inner passage 9, and falls and flows in the inner passage 9 by its own weight. While the particle group 17 is falling and flowing in the inner passage 9, a part of the particle group 17 passes through the through hole 22 and flows into the combustion tube 8, passes through the flame in the combustion tube 8, and flows out. 8b, merges with the particle group passing through the inside passage 9 and is introduced into the outside passage 7, and the particle group 17 is in the order of the outside passage 7 → the upper portion of the inside passage 9 → the inside of the combustion tube 8 → the outside passage 7. It circulates or flows, or circulates in the order of the outer passage 7 → the inner passage 9 → the outer passage 7.

Next, the operation and effect of the embodiment having the above configuration will be described. In this example, a substantially cylindrical inner tube 6 is inserted into a vertically installed bottomed cylindrical outer tube 2, and an outlet 8a for letting out combustion gas is opened at the lower end in the inner tube 6. The inner tube 6 is inserted into the outer tube 2 through the combustion tube 8 in which the burner nozzle 15 for burning the mixed gas is charged.
The outer passage 7 formed around the inner pipe 6 and the inner passage 9 formed between the inner tube 6 and the combustion tube 8 are arranged in parallel, and the combustion gas flow flowing out from the outflow port 8a is provided in the outer tube 2. Outside passage 7 blown up by
Heat-resistant particle group 17 circulating and flowing inside and inside passage 9
And a large number of through holes 22 through which the particles can pass through are provided in the combustion tube 8.

Therefore, the particle group 17 heated by the combustion gas is caused to flow upward in the outer passage 7 while being diffused, and the heat transfer surface 2a of the outer tube 2 is diffused throughout the outer passage 7 in the particle group 17. Can be uniformly heated, and the temperature distribution of the heat transfer surface 2a of the outer tube 2 can be made uniform.

Further, part of the particle group 17 which has heated the outer tube 2 during the upward flow and whose temperature has been lowered by heat radiation is introduced into the combustion tube 8 and passed through the flame to radiate heat. Since the heat of the flame is applied to the above to suppress the rise of the flame temperature, it is possible to suppress the increase of the NOx concentration accompanying the rise of the flame temperature and reduce the NOx concentration in the combustion gas.

Further, since the particle group passing through the inside passage 9 and the particle group heated by the flame and heated up are mixed and flow upward in the outside passage 7, the heating effect on the whole particle group 17 is enhanced. Thus, the temperature of the heat transfer surface 2a can be stabilized over time.

Further, in this example, 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 to improve the ignitability, The stable combustion 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 longitudinal 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.

[Explanation of symbols]

 2 Outer tube 6 Inner tube 7 Outer passage 8 Inner passage 17 Particle group 22 Through hole B Radiant tube burner

Claims (1)

[Claims] 1. A vertically-arranged bottomed cylindrical outer tube into which a substantially cylindrical inner tube is inserted, and an outlet for discharging combustion gas is opened at the lower end of the inner tube. A combustion tube is inserted, and an outer passage formed around the inner tube and an inner passage formed between the inner tube and the combustion tube are arranged side by side in the outer tube, and the outer tube is formed. A heat-resistant particle group that is blown up by the combustion gas flow flowing out from the outlet and circulates and flows in the outer passage and the inner passage is enclosed in the tube, and the combustion tube has a passage of the particles. A radiant tube burner characterized by having a large number of possible through holes.