JPH09196326A - Radiant tube burner and atmosphere sintering furnace using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiant tube burner capable of restricting a concentration of O2 in combustion discharged gas to a value less than several hundred ppm and further provide an atmosphere sintering furnace using this burner. SOLUTION: A gas burner 2 using either air of normal temperature or pre- heated air as combustion air is installed at an inlet port of a radiant tube 1, fuel gas of more than its corresponding amount is fed into combustion gas at a burner nozzle 3 installed at an outlet of the radiant tube 1, and oxygen is completely consumed. Catalyst for contact combustion may be arranged at a part of the burner nozzle 3. When such a radiant tube burner as above is installed within a sintering region, a concentration of O2 at a cooling region can be managed to a value less than several hundred ppm. In addition, if the furnace gas of high temperature is used as pre-heating air, it becomes possible to perform an irregular combustion superior in soaking heat effect.

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 capable of suppressing the O ₂ concentration in exhaust gas from the outlet side to a low level, and an atmosphere firing furnace using the same.

[0002]

2. Description of the Related Art Among various ceramics and ceramics,
In some cases, the O ₂ concentration in the furnace atmosphere in the cooling step after firing should be controlled to several hundred ppm or less. When such a fired product is fired in a gas-fired furnace using a gas burner as a heating source, a partition wall is provided between the firing zone and the cooling zone in the furnace to prevent oxygen from flowing from the firing zone to the cooling zone. In addition to suppressing as much as possible, the air-fuel ratio m of the burner at the highest temperature part of the firing zone was made as close to 1.0 as possible to reduce the O ₂ concentration in the exhaust gas discharged from the outlet side of the burner.

However, in a gas burner using normal temperature air, an air-fuel ratio of around m = 1.1 is a practical limit for the purpose of combustion stability and prevention of soot generation. If the air-fuel ratio m is lower than this, soot is produced. There is a risk that it may be generated or combustion may become unstable. Even when using preheated air, the temperature is about 400 ° C because exhaust gas sucked from the exhaust holes and heat-exchanged air are usually used, and combustion instability does not change much when using room temperature air. Therefore, the limit for practical use was around m = 1.1. For this reason, oxygen was inevitably contained in the exhaust gas of the burner in the firing zone, and the O ₂ concentration in the atmosphere at the highest temperature portion of the firing zone was limited to 2%. Therefore, in the high temperature portion of the cooling zone adjacent to the combustion zone, there is a problem that it is not possible to completely prevent the inflow of some oxygen from the combustion zone. Therefore, in an atmosphere firing furnace such as a ferrite that does not like the presence of O _{2 in} the cooling zone, it is necessary to introduce a large amount of inert gas such as N ₂ gas into the cooling zone to dilute the remaining O ₂ .

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, and a radiant tube burner capable of suppressing the O ₂ concentration in the exhaust gas from the outlet side of the burner to several hundred ppm or less, By using this, an atmosphere firing furnace capable of controlling the O ₂ concentration in the atmosphere in the furnace in the cooling step to several hundreds ppm or less is provided.

[0005]

The radiant tube burner of the present invention made to solve the above-mentioned problems is
A gas burner that uses room temperature air or preheated air as combustion air is provided at the inlet of the radiant tube, and a burner nozzle for injecting and burning fuel gas into the combustion gas of the gas burner is provided at the outlet of the radiant tube. It is characterized by being provided. Further, the atmosphere firing furnace of the present invention is characterized in that the above-mentioned radiant tube burner is installed in the firing zone, and by utilizing high temperature preheated gas, unsteady combustion that does not form a flame is performed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a view showing a typical embodiment of a radiant tube burner of the present invention, 1 is a radiant tube curved in a J shape, 2 is a gas burner provided at its inlet, 3 is a radiant tube 1 Is a burner nozzle provided at the outlet of the.

The gas burner 2 is a normal gas burner that uses room temperature air or preheated air as combustion air, and has a fuel gas inlet 4 and a combustion air inlet 5. The gas burner 2 on the inlet side of the radiant tube 1 is burned with the air-fuel ratio m in the range of 1.1 to 1.2. If the air-fuel ratio m is within such a range, the gas burner 2 will burn stably. Then, the combustion exhaust gas becomes a high temperature gas of, for example, about 1000 ° C. and flows inside the radiant tube 1 toward the outlet side, and the O ₂ concentration in this combustion gas is usually about 2 to 3%. For this reason,
As described above, conventionally, in an atmosphere firing furnace such as a ferrite that does not like the presence of O _{2 in} the cooling zone, it was necessary to introduce a large amount of an inert gas such as N ₂ gas into the cooling zone to dilute the residual O ₂ . .

However, in the present invention, the radiant tube 1
The burner nozzle 3 on the outlet side of the is equipped with a fuel gas inlet 5, which is necessary to consume oxygen in the combustion exhaust gas of the combustion gas of the gas burner 2 flowing in the radiant tube 1. At least equivalent amount of fuel gas is injected and burned. The fuel gas is raw gas, and the injected fuel gas reacts with oxygen in the high temperature combustion exhaust gas inside the burner nozzle 3 to consume oxygen in the combustion exhaust gas almost completely, and the O ₂ concentration is several hundred ppm. And

Further, if the high-temperature furnace gas is circulated in the gas burner 2 and used as preheated air, the combustion temperature of the gas burner 2 can be raised more than in the case of using normal temperature air. It becomes possible to perform unsteady combustion in which no flame is released.

FIG. 2 is a view showing another embodiment of the radiant tube burner of the present invention. In this case, the catalytic combustion catalyst 7 is provided inside the burner nozzle 3 on the outlet side of the radiant tube 1 together with the fuel gas inlet 6. The structure of this catalytic combustion catalyst 7 is not particularly limited, but if a catalyst such as platinum is supported on the surface of a honeycomb ceramic carrier, for example,
The pressure loss can be reduced.

The radiant tube burner of FIG. 2 is shown in FIG.
However, since the catalytic combustion catalyst 7 is provided inside the burner nozzle 3,
The fuel gas injected from the fuel gas injection port 6 can be burned more completely by the catalytic action of the catalytic combustion catalyst 7, and the O ₂ concentration can be further lowered than that of FIG. 1.

FIG. 3 is a view showing an atmosphere firing furnace using the radiant tube burner of the present invention described above. As shown in the figure, the inside of the furnace is divided into a pre-tropical zone 8, a firing zone 9 and a cooling zone 10 from left to right, and a partition wall 11 extending from the road wall to the vicinity of the conveyance path for the fired products suppresses the gas flow in the furnace. Has been done. The radiant tube burner B of the present invention is provided at least in the highest temperature portion of the firing zone 9.
Reference numeral 12 is an ordinary gas burner, and 13 is an inert gas supply nozzle provided in the cooling zone 9. Although the furnace shown is a roller hearth kiln, the structure of the furnace itself is not limited to this.

The atmosphere firing furnace of FIG. 3 constructed in this manner transfers the fired product to the right and fires it according to the temperature curve shown in the upper graph of FIG. 3, but the radiant tube of the present invention is used. At the highest temperature portion of the firing zone 9 where the burner B is provided, the O ₂ concentration in the furnace atmosphere can be drastically reduced compared to the portion before that.
In the cooling zone 10 provided with the inert gas supply nozzle 13, it is possible to completely control the O ₂ concentration in the atmosphere in the furnace to a level of several hundred ppm or less. Therefore, the furnace is suitable for firing the fired product, in which the O ₂ concentration in the atmosphere in the cooling step should be controlled to several hundred ppm or less. Further, as described above, when the high-temperature furnace gas is circulated through the gas burner 2 and used as preheated air, the radiant tube burner B is allowed to perform unsteady combustion without releasing flame into the furnace. Is possible. Such unsteady combustion is also excellent in soaking effect, and can evenly heat the inside of the furnace to suppress variations in the quality of the fired product. As such preheated air, it is preferable to use the exhaust gas sucked from an ordinary exhaust hole, which is heat-exchanged and reheated to 400 ° C. or higher, preferably 600 ° C. Further, it is more preferable to suck the exhaust gas of 600 ° C. or higher from the rear part of the firing zone and utilize this gas.

Incidentally, what is indicated by a chain line in the upper graph of FIG. 3 is the O ₂ concentration of the conventional atmosphere firing furnace described in the section of the prior art. Thus, conventionally, in the high temperature part of the cooling zone 9 adjacent to the combustion zone 8, the O ₂ concentration is several hundred pp due to the influence of oxygen flowing from the combustion zone.
It could not be managed below m.

[0015]

As described above, the radiant tube burner of the present invention can reduce the concentration of O _{2 in} combustion exhaust gas to several hundreds.
The atmospheric firing furnace of the present invention using the same can control the O ₂ concentration in the furnace atmosphere in the cooling step to several hundreds ppm or less while using the gas burner. Further, the radiant tube burner of the present invention is also excellent in soaking effect because it can perform unsteady combustion that does not form a flame, and can evenly heat the inside of the furnace to suppress variations in the quality of the fired product. it can.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing another radiant tube burner of the present invention.

FIG. 3 is a plan view of an atmosphere firing furnace of the present invention, a temperature curve thereof, and a graph of O ₂ concentration.

[Explanation of symbols]

1 radiant tube, 2 inlet gas burner, 3
Exit burner nozzle, 4 Fuel gas inlet, 5 Combustion air inlet, 6 Fuel gas inlet, 7 Contact combustion catalyst, 8 Pre-tropical zone, 9 Firing zone, 10 Cooling zone, 11 Partition wall, 12 Normal gas burner , 13 Inert gas supply nozzle, B Radiant tube burner of the present invention

Claims (6)

[Claims] 1. A gas burner using room temperature air or preheated air as combustion air is provided at the inlet of the radiant tube, and fuel gas is injected into the combustion gas of the gas burner at the outlet of the radiant tube for combustion. Radiant tube burner characterized by having a burner nozzle for. 2. The radiant tube burner according to claim 1, wherein high-temperature furnace gas is used as preheated air. 3. The radiant tube burner according to claim 1 or 2, wherein the combustion gas of the gas burner is injected with a fuel gas in an amount equal to or more than the equivalent O ₂ of the residual O ₂ in the combustion gas for combustion. 4. The radiant tube burner according to claim 1, wherein a catalytic combustion catalyst is provided in the burner nozzle portion. 5. The radiant tube burner according to any one of claims 1 to 4, wherein the combustion form is an unsteady combustion that does not form a flame. 6. An atmosphere firing furnace, characterized in that the radiant tube burner according to any one of claims 1 to 5 is installed in a firing zone to perform unsteady combustion that does not form a flame.