JPH0979524A - Single end type regenerative radiant tube burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the running cost by increasing the tube life without necessity of an expensive flame tube by simultaneously realizing energy conservation by the high-temperature preheating of combustion air by reducing NOx and recovering the exhaust heat. SOLUTION: The single end type regenerative radiant tube burner comprises a longitudinal partition 2 for partitioning a single end-type radiant tube 1 to two combustion chambers 10a, 10b communicating at the end, honeycomb-like heat storage materials 4a, 4b contained at the inlet sides of the chambers 10a, 10b, channel switching means 7 making it possible to alternately connect the chambers 10a, 10b to a fuel air supply system 8 and an exhaust system 9 via the materials 4a, 4b, and fuel pipes 5a, 5b for injecting fuel substantially in parallel with the combustion air to the chambers 10a, 10b. The combustion gas is exhausted via the other chamber and the material to be alternately switched in a short time while injecting the combustion air preheated to higher temperature than the igniting temperature of the fuel via the one material to the chamber at high speed of about 60m/sec or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-ended radiant tube burner often used in the heat treatment field and the like. More specifically, the present invention relates to a single-ended heat storage type radiant tube burner structure that can be modified into a heat storage type radiant tube by using an existing tube as it is.

[0002]

2. Description of the Related Art A single-ended radiant tube burner is used when it is difficult to install a U-shaped tube or a W-shaped tube due to a problem in the apparatus because of a limited space for mounting the tube. This conventional single-ended radiant tube burner requires an inner cylinder because of its structure. For example, as shown in FIG. 4, a conventional single-ended radiant tube burner includes a frame tube 10 that forms a combustion chamber inside a radiant tube 101.
2 is provided in the double tube structure, and the combustion gas generated in the frame tube 102 is inverted at the closed end of the radiant tube 101 to form a gap 10 outside the tube 101.
The radiant tube 101 is heated while exhausted from the inlet side of the combustion air or the fuel gas through the radiant tube 101. However, according to this burner structure, when the radiant tube 101 is heated to a required temperature, the frame tube 102 is exposed to a higher temperature than that, so that there is a problem that the life is shortened due to deformation and oxidation. Therefore, the frame tube 102 needs expensive heat-resistant cast steel or ceramic having excellent heat resistance.
In the figure, reference numeral 105 is a combustion air shroud, 106 is a fuel gas pipe, 107 is a combustion air housing, and 108 is an exhaust gas housing.

[0003]

Therefore, in the conventional single-ended radiant tube burner, the cost of replacing the frame tube (inner tube) 102 in the running cost is high, and the frame tube 102 is high.
The operating life of the car greatly affects the running cost. Further, the deformation of the frame tube 102 causes nonuniformity of the tube temperature, which also affects the life of the radiant tube 101.

Further, since the radiant tube 101 is heated and exhausted at the same temperature without sufficient exhaust heat recovery, the exhaust temperature is high and the thermal efficiency is poor. On the other hand, even if the combustion air is preheated by recovering the exhaust heat, the high temperature combustion air and the fuel gas are rapidly mixed and diffused and burned in the swirler 104, so that the flame temperature becomes high and the amount of thermal NOx increases. .

As described above, according to the conventional single-ended radiant tube burner, energy saving by high temperature preheating of combustion air by reducing NOx and recovering exhaust heat has a relationship that NOx also rises when the air temperature rises. Therefore, it could not be realized at the same time.

[0006] Therefore, an object of the present invention is to provide a single-ended radiant tube burner capable of simultaneously achieving reduction of NOx and energy saving by high temperature preheating of combustion air by recovery of exhaust heat. Another object of the present invention is to provide a single-ended radiant tube burner that does not require an expensive frame tube, has a long tube life, and can reduce running costs.

[0007]

In order to achieve the above object, a single-ended heat storage type radiant tube burner of the present invention has two combustion chambers that communicate with each other inside a single-ended radiant tube whose one end is closed. It is possible to alternately connect the combustion chambers to the combustion air supply system and the exhaust system through the longitudinal partition, the honeycomb-shaped heat storage body accommodated on the inlet side of each combustion chamber, and the heat storage body. And a fuel pipe for injecting the fuel into the combustion chamber on the side where the combustion air is injected, and the fuel pipe for injecting the fuel substantially parallel to the combustion air. Combustion air that has been preheated to a high temperature is injected into one of the combustion chambers at a high speed of approximately 60 m / sec or more for combustion, and the combustion gas is exhausted from the other combustion chamber through a heat storage body in a short time. And to perform switch to.

The flow of combustion air injected into the radiant tube at a high flow rate of about 60 m / sec or more causes strong circulation in the radiant tube. Moreover, since the combustion air is set at a temperature higher than the ignition temperature of the fuel, for example, about 800 ° C. which is slightly lower than the temperature of the exhausted combustion gas, or higher, it is not necessary to sufficiently mix the fuel and air during combustion. Even if the high-speed high-temperature air and the fuel are injected parallel to the inside of the tube, the flame is stable and does not blow out. In addition, self-recirculation of combustion gas and exhaust gas is formed by the strong circulation generated in the radiant tube. Therefore, low NOx combustion due to slow combustion becomes possible. Here, the injection speed of the combustion air required to cause the strong circulation of the combustion gas is at least about 60 m / se.
c or more, preferably 80 m / sec or more, and most preferably 100 m / sec or more.

Further, by the high-speed jet of combustion air,
The strong circulation of combustion gas occurs in the radiant tube, and the temperature inside the tube is flattened (averaged), and the local high temperature region does not occur. Therefore, the average temperature in the tube can be raised to the vicinity of the limit temperature (Tmax), the amount of heat transfer can be increased, the temperature difference on the tube surface is small, and the thermal stress on the tube is also reduced, which is effective for extending the life of the tube. Becomes At the same time, when the high-temperature combustion gas is exhausted through the heat storage body, the sensible heat is recovered by the heat storage body, and then used again for preheating the combustion air with extremely high thermal efficiency and returned to the radiant tube. . Therefore, the temperature of the combustion air can be a high temperature close to the temperature of the combustion exhaust gas flowing out to the heat storage body,
High thermal efficiency can be maintained.

Further, since the two combustion chambers of the radiant tube are alternately burned in a short time, a non-stationary flame in which the flame position changes frequently can be obtained, and the temperature distribution in the tube can be made more uniform.

According to a second aspect of the present invention, there is provided a single-ended heat storage type radiant tube burner in which a fuel pipe housing having a flame holding cylinder at an opening end accommodates two fuel pipes and is inserted in the center of the radiant tube. And a partition for partitioning into two chambers that communicate between the two fuel pipes of the fuel pipe housing at the tip inside the radiant tube is attached to the fuel pipe housing, and a heat storage body divided into two regions around the fuel pipe housing. The fuel is alternately injected into the two combustion chambers partitioned by partitions, and the combustion air heated to a high temperature from around the fuel is passed through the heat storage body.

Therefore, the existing tube can be used as it is, and the single end type heat storage type radiant tube burner structure can be inserted thereinto for modification.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of the present invention will be described below in detail based on an example of an embodiment shown in the drawings.

FIG. 1 shows an embodiment of a heat storage type single-ended radiant tube burner of the present invention. This heat storage type single-ended radiant tube burner is a single-ended radiant tube 1 with one end closed.
The partition 2 is installed inside to form two combustion chambers 10a and 10b which communicate with each other on the tip side, and independent heat storage bodies 4a and 4b are installed on the inlet side thereof.

At the center of the radiant tube 1, a fuel pipe housing 5 containing two fuel pipes 5a and 5b is arranged. At the tip opening of the fuel pipe housing 5, there is a flame holding cylinder 12 of a pipe projecting outward.
Are provided between the flame holding cylinder 12 and the radiant tube 1, and nozzles 3a and 3b which independently function as an injection port of combustion air or an exhaust port of exhaust gas are configured.

The partition 2 may be fixed to the radiant tube 1 in advance by welding or the like, but it is preferable that the partition 2 be attached to the fuel pipe housing 5 side and simply inserted and installed in the radiant tube 1. For example, the partition 2 is attached to the fixed plate 13 that supports the ends of the two fuel pipes 5a and 5b in the fuel pipe housing 5 by welding or the like. In this case, the existing equipment can be improved by a simple operation of using the existing tube as it is and inserting the burner of the present invention therein.

In the present embodiment, as shown in FIG. 1, the heat storage bodies 4a and 4b are housed in the heat storage body case 3, and the fuel pipe housing 3 having two fuel pipes therein and the air housing 6 are integrated. This can be inserted into the radiant tube 1. In the case of the present embodiment, the heat storage case 3 and the air housing 6, which are made of, for example, heat resistant steel, are fixed to the flange portion of the radiant tube 1. The air housing 6 has two ports 6a, 6
b, and the ports 6a, 6b are connected ducts 11a,
11b are respectively connected to the switching ports of the four-way valve 7 serving as a flow path switching means, and by switching the four-way valve 7, it is possible to selectively connect to either the combustion air supply system 8 or the combustion gas exhaust system 9. ing. And one chamber 10a
(Or 10b) is supplied with combustion air through the heat storage body 4a (or 4b), while the other chamber 10b is supplied.
(Or 10a) from the heat storage body 4b (or 4a)
It is provided so as to discharge the combustion gas through.
Combustion air is supplied by a push fan or the like (not shown). Although not shown, a fuel supply system is connected to each of the fuel pipes 5a and 5b via a cutoff valve or the like, and the fuel adjusted by the fuel amount adjusting valve is selectively and alternately supplied. Further, a part of the combustion air and the fuel is distributed to a pilot burner (not shown).

Here, as the heat accumulators 4a and 4b, a material having a large heat capacity and a high durability despite a relatively low pressure loss,
For example, it is preferable to use a tubular body having a large number of honeycomb-shaped cell holes formed of ceramics. For example, for heat exchange between a high temperature fluid of around 1000 ° C. such as exhaust gas and a low temperature fluid of around 20 ° C. such as combustion air, a honeycomb manufactured by extrusion molding using a ceramic such as cordierite or mullite as a material. It is preferable to use a shape. In addition, the honeycomb-shaped heat storage material is a ceramic other than cordierite or mullite, for example, a material other than alumina or ceramics, such as a metal such as heat-resistant steel, or a composite of ceramic and metal, for example, a metal melted in the pores of a ceramic having a porous skeleton. Spontaneously penetrate,
A part of the metal may be oxidized or nitrided to form a ceramic, and the pores may be completely filled with Al ₂ O ₃ -Al composite, SiC-Al ₂ O ₃ -Al composite, or the like. The honeycomb shape originally means hexagonal cells (holes), but in the present specification, not only the original hexagonal cells but also quadrangular or triangular cells are opened innumerably. Further, the honeycomb-shaped heat storage body 1 may be obtained by bundling tubes and the like without integrally molding. Further, the shape of the heat storage body is not particularly limited to the honeycomb shape shown in the figure, and in some cases, flat plate-shaped or corrugated plate-shaped heat storage material is radially arranged in the tubular casing, or pipe-shaped heat storage material is arranged in the axial direction. It may be filled in a cylindrical casing so that the fluid may pass through. For example, although not shown, it is divided into two chambers in the circumferential direction by partition walls,
A cylindrical casing that allows fluid to pass through in the axial direction is prepared, and each chamber is filled with a lump of heat storage material such as a spherical shape, a short tube, a short rod, a strip, a nugget shape, or a net shape. It may be the one that was given.

According to the single-end heat storage type radiant tube burner system configured as described above, the radiant tube is heated as follows.

Combustion air pressure-fed from a blower (not shown) is introduced into the heat storage body 4a from the air inlet 6a of the air housing 6 through the four-way conversion valve 7 and passes through the heat storage body 4a to exchange fuel by heat exchange. Above the ignition temperature of, for example, 800 that is slightly lower than the temperature of the exhausted combustion gas
The temperature is set to about 0 ° C. or higher and is jetted from the nozzle 3a into the radiant tube 1 (combustion chamber 10a) at a high speed of at least about 60 m / sec. On the other hand, the fuel is ejected from one of the two fuel pipes 5a installed inside the fuel pipe housing 5 into the combustion chamber 6a in the tube 1 and is accompanied by the combustion air of the high-speed jet flow, and burns slowly. Here, the strong circulation of the combustion gas caused by the injection of the combustion air is better as the injection speed is faster,
At least about 60 m / sec or more, preferably 80 m
/ Sec or more, and most preferably 100 m / sec or more.

Further, the high-speed jet of the combustion air causes a strong circulation of the combustion gas in the combustion chamber 10a to average the temperature in the tube and make it flat without a local high temperature region.

The combustion gas passes through one side of the partition 2 in the tube 1, reverses the flow direction at the tip of the tube, flows into the heat storage case 3 from the nozzle 3b, and passes through the heat storage body 4b. Then, the heat storage body 4b is heated and discharged from the air inlet 6b to the exhaust system 9 via the four-way valve 7.

By switching this operation to the left or right every 20 to 60 seconds, a heat storage type high speed switching combustion is realized.

The above embodiment is an example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, the flow path switching means 7 is not limited to a four-way valve, but the flow path switching means (WO94 / 02784, WO95 / 15462) of the international patent application previously proposed by the applicant of the present application.
No.) etc. may be adopted.

[0025]

As is apparent from the above description, according to the single end type heat storage type radiant tube burner of the present invention, the temperature is higher than the ignition temperature of the fuel and 60 m / sec.
The flow of the combustion air injected into the radiant tube at a high flow velocity above a certain level causes strong circulation in the radiant tube, but it does not blow out the flame, but it burns stably and reaches the tube tip on the opposite side. Since it reversely flows into the combustion chamber and is exhausted from the tube inlet side, the entire tube is heated without causing a short path. Moreover, since the strong recirculation generated in the radiant tube forms the self-recirculation of the combustion gas and the exhaust gas, the low NOx combustion due to the slow combustion becomes possible.

Further, the strong circulation of the combustion gas generated in the radiant tube by the high-speed jet of the combustion air flattens (averages) the temperature inside the tube and does not generate a local high temperature region. Therefore, the average temperature in the tube can be raised to near the limit temperature (Tmax),
The amount of heat transfer can be increased and the temperature difference on the tube surface can be reduced to reduce the thermal stress on the tube and extend the life of the tube. At the same time, when the hot combustion gas is exhausted through the heat storage body, the sensible heat is collected in the heat storage body,
It is used again for preheating the combustion air with extremely high thermal efficiency and is returned into the radiant tube. Therefore, the temperature of the combustion air can be set to a high temperature close to the temperature of the combustion exhaust gas flowing out to the heat storage body, so that the thermal efficiency can be maintained.

Further, since the two combustion chambers of the radiant tube are alternately burned in a short time, a non-stationary flame in which the flame position changes frequently can be made more uniform in the temperature distribution in the tube, and uneven heating can be reduced. The equipment is compact and easy.

According to the second aspect of the present invention, the existing tube can be used as it is, and the single-ended heat storage type radiant tube burner structure can be inserted into the tube to modify the tube.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a single-ended heat storage type radiant tube burner of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is a vertical sectional view showing a conventional single-ended radiant tube burner.

[Explanation of symbols]

 1 Radiant tube 2 Partition 3 Heat storage housing 4a, 4b Heat storage 5 Fuel pipe housing 6 Air housing 6a, 6b Air inlet 7 Four-way valve which is a flow path switching means 8 Combustion air supply system 9 Exhaust system 10a, 10b Combustion chamber 12 Insulation Flame tube

Claims (2)

[Claims] 1. A longitudinal partition that divides a single-ended radiant tube whose one end is closed into two combustion chambers that communicate with each other at the tip side, and a honeycomb-shaped heat storage body that is housed at the inlet side of each combustion chamber. A flow path switching means for alternately connecting the combustion chambers to the combustion air supply system and the exhaust system via the heat storage body, and the combustion air to the combustion chamber on the side where the combustion air is injected. And a fuel pipe for injecting fuel substantially in parallel with each other, and about 60 m / se of combustion air preheated to a temperature higher than the ignition temperature of the fuel by passing through each heat storage body.
A single-end type characterized by alternately injecting into one of the combustion chambers at a high speed of c or higher for combustion and exhausting the combustion gas from the other combustion chamber through a heat storage body in a short time. Heat storage type radiant tube burner. 2. A fuel pipe housing having a flame holding cylinder at an open end, the two fuel pipes being housed in the center of a radiant tube, and between the two fuel pipes of the fuel pipe housing. A partition that partitions the inside of the radiant tube into two chambers that communicate with each other at the tip is attached to the fuel pipe housing, and a heat storage body that is partitioned into two regions is arranged around the fuel pipe housing, and two combustion chambers that are partitioned by the partition are arranged. 2. The single-ended heat storage type radiant tube burner according to claim 1, wherein fuel is alternately injected into the chamber, and the combustion air which has passed through the heat storage body and is heated to a high temperature is injected from around the fuel.