JPH05172324A - Method of reducing nox in burning furnace and nox reducing device - Google Patents

Abstract

PURPOSE:To provide a NOx reducing method and a NOx reducing device in a burning furnace which is provided with a heating burner to heat an object to be burned and exhaust gas channel to let the combustion exhaust gas of the heating burner flow through, both method and device being adoptable regardless of the burning temperature and able to reduce the NOx effectively. CONSTITUTION:The method of reducing NOx in a burning furnace is to supply to the combustion exhaust gas that flows through an exhaust gas channel H fuel that gives reducing reaction to the NOx in the combustion exhaust gas and to supply air to bun the unburned portion of the fuel at a spot on the downstream side from the fuel supply spot in the direction of the combustion exhaust gas flow. And a NOx reduction device is provided with a fuel supply means 12 that supplies fuel that gives reducing reaction to the NOx in the combustion exhaust gas to the combustion exhaust gas flowing through the exhaust gas channel H and, furthermore, an air supply means 13 is provided on the downstream side from the fuel supply means 12 in the direction of the combustion exhaust gas flow in order to burn the unburned fuel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a NOx reduction method and a NOx reduction device in a firing furnace provided with a heating burner for heating an object to be fired and an exhaust gas passage for passing combustion exhaust gas of the heating burner. Regarding

[0002]

2. Description of the Related Art As a method of reducing NOx in such a firing furnace, conventionally, by generally reducing the amount of air supplied to the fuel, slow combustion is caused to lower the combustion temperature, and NOx is reduced. How to reduce, ie
A method of reducing NOx by improving burner combustion has been adopted.

[0003]

However, for example, in a firing furnace used for firing ceramics or the like, the firing temperature is as high as 1700 to 1800 ° C.,
As described above, the NOx reduction method in which the burner is caused to slowly burn to lower the combustion temperature cannot be adopted because the furnace temperature cannot be raised to a predetermined firing temperature. NOx reduction measures have not been taken in the simple firing furnace. The present invention has been made in view of such circumstances, and an object thereof is to provide a NOx reduction method and a NOx reduction device in a firing furnace that can be adopted regardless of the firing temperature and can effectively reduce NOx. is there.

[0004]

A NOx reduction method in a firing furnace which is a first characteristic configuration of the present invention is a method for reducing NOx in the combustion exhaust gas to the combustion exhaust gas flowing through the exhaust gas passage.
Is supplied, and the air for burning the unburned portion of the fuel is supplied on the lower side of the fuel supply position in the combustion exhaust gas flow direction.

The NOx reduction device in the firing furnace, which is the second characteristic configuration of the present invention, is provided with fuel supply means for supplying the combustion exhaust gas flowing through the exhaust gas passage with fuel for reducing NOx in the combustion exhaust gas. In addition, the air supply means for supplying the air for burning the unburned portion of the fuel is provided on the lower side of the fuel supply means in the combustion exhaust gas flow direction.

[0006]

According to the first characteristic configuration of the present invention, by supplying the fuel to the combustion exhaust gas flowing through the exhaust gas passage, an oxygen deficient region is generated, and the fuel and the N in the combustion exhaust gas are generated.
By reacting with Ox to reduce NOx, and by supplying air at a location where the temperature of the combustion exhaust gas is lower on the lower side of the combustion exhaust gas flow direction than the fuel supply location, the amount of the fuel supplied to the combustion exhaust gas is reduced. The unburned content has a lower combustion temperature and N
Combustion is performed in a state in which generation of Ox is suppressed. Further, by burning the unburned portion of the fuel, it is possible to preheat the object to be fired before firing.

According to the second characteristic constitution, the fuel is supplied to the combustion exhaust gas flowing through the exhaust gas passage by the fuel supply means to generate the oxygen deficient region, and the fuel and NOx in the combustion exhaust gas are generated. To reduce the NOx and to supply air by means of an air supply means provided at a location where the temperature of the combustion exhaust gas on the lower side in the combustion exhaust gas flow direction is lower than that of the fuel supply means. The unburned portion of the fuel supplied to the fuel cell is burned in a state where the combustion temperature is lowered to suppress the generation of NOx. Further, by burning the unburned portion of the fuel, it is possible to preheat the object to be fired before firing.

[0008]

According to the first characteristic configuration, as in the conventional case,
The burner is slowly burned to lower the combustion temperature and N
Since it is not a method of reducing Ox, it can be used regardless of the firing temperature, and NOx in the combustion exhaust gas can be effectively reduced. Although a separate fuel is supplied for NOx reduction, the fuel supply amount to the burner for firing the burned material can be reduced by burning the fuel and preheating the burned material. The reduced amount can offset the increased amount of fuel supplied by the supply for NOx reduction, and the overall increase in the fuel supply amount can be suppressed as much as possible.

According to the second characteristic constitution, it is possible to obtain a preferable NOx reduction method in the firing furnace for realizing the NOx reduction method in the firing furnace described in the second characteristic constitution.

[0010]

EXAMPLES Next, examples of applying the examples of the present invention to a tunnel type firing furnace for firing ceramics will be described with reference to FIGS.
It will be explained based on.

In the figure, reference numeral 1 denotes a furnace body, and a carriage 3 on which a material S to be fired is placed is moved from an inlet I to an outlet O in a furnace 2 inside the furnace body 1. .. The furnace body 1 is
It is composed of a preheating section 1A, a firing section 1B, and a cooling section 1C which are sequentially arranged from the inlet I to the outlet O. The article S to be fired is placed on the carriage 3 and conveyed in the furnace. By doing so, the preheating unit 1A, the firing unit 1B, and the cooling unit 1C are sequentially passed to perform a predetermined firing process.

Gas burners 4 as heating burners for heating the object S to be fired are provided on both left and right sides of the firing section 1B. The combustion exhaust gas of the gas burner 4 is moved by the exhaust fan 5 in the direction opposite to the moving direction of the object S to be fired.
The inside of the furnace of A is made to flow in the direction of the inlet I to preheat the material to be fired S and to be discharged to the outside of the furnace through the exhaust gas discharge port 6. That is, the firing part 1B to the preheating part 1A
The inside 2 of the furnace reaching the exhaust port 6 is also made to function as an exhaust gas passage H for passing the combustion exhaust gas of the gas burner 4.

In the cooling unit 1C, the cooling air supplied from the cooling fan 7 through the air supply nozzle 8 in the direction of the inlet I is supplied to the combustion air exhaust port 10 by the combustion air fan 9.
The air for cooling is discharged to the outside of the furnace through the inside of the furnace of the cooling unit 1C in the direction opposite to the moving direction of the object to be fired S, so that the object to be fired S is cooled. is there. That is, the inside 2 of the furnace from the air supply nozzle 8 of the cooling unit 1C to the combustion air discharge port 10 is also made to function as a cooling air flow path R for passing the cooling air.

The cooling air flowing through the cooling air flow path R is heated by cooling the material S to be fired, and the heated cooling air is supplied to the gas burner 4 by the combustion air fan 9. The gas burner 4 is supplied as combustion air. That is, the combustion temperature of the gas burner 4 is raised by preheating the combustion air for the gas burner 4.

In FIG. 3, reference numeral 11 denotes a sand seal that isolates the wheel portion of the truck 3 from being exposed to the atmosphere in the furnace. The wheel portion of the truck 3 is exposed to the high temperature atmosphere and combustion exhaust gas in the furnace. Prevents damage.

In the tunnel type firing furnace constructed as described above, the firing section 1B is heated by the gas burner 4 to bring the temperature inside the firing section 1B to about 1700 to 1800 ° C.
Further, the combustion exhaust gas of the gas burner 4 is caused to flow through the exhaust gas passage H so that the temperature inside the furnace of the preheating section 1A gradually rises from the inlet I to the boundary between the preheating section 1A and the firing section 1B. The cooling air flow path R
The temperature inside the furnace of the cooling unit 1C is gradually lowered from the boundary portion between the firing unit 1B and the cooling unit 1C to the outlet O by flowing the gas. That is, the temperature inside the furnace from the inlet I to the outlet O has a predetermined temperature distribution, and preheating, firing,
A predetermined firing process is performed in which cooling is sequentially and continuously performed.

Next, NOx for reducing NOx in the combustion exhaust gas of the gas burner 4 in the firing furnace configured as described above.
The reduction device will be described.

In the furnace temperature of the preheating section 1A, that is, in the left and right sides of the furnace body 1 at the places where the combustion exhaust gas temperature is about 1200 to 1600 ° C., the combustion exhaust gas flowing through the exhaust gas passage H is converted into the combustion exhaust gas. A plurality of fuel ejection nozzles 12 as fuel supply means for ejecting upwardly the fuel gas for reducing NOx therein are arranged in parallel in the moving direction of the material to be fired S at predetermined intervals. It should be noted that the amount of NOx reducing fuel gas supplied from the fuel injection nozzle 12 is determined by the gas burner 4
It is about 5 to 30% of the amount of fuel gas supplied to.

Further, the temperature inside the furnace of the preheating section 1A is 700 to 10 on the inlet I side of the installation location of the fuel injection nozzle 12.
A plurality of air ejection nozzles 13 as air supply means for ejecting upwardly the air for combusting the unburned portion of the NOx reducing fuel gas are provided on each of the left and right sides of the furnace body 1 at a temperature of about 00 ° C. The objects to be fired S are arranged in parallel in the moving direction with a predetermined interval. As the air supplied from the air ejection nozzle 13, the air from the cooling fan 7 is used. The amount of air supplied from the air ejection nozzle 13 is equal to or more than the theoretical amount of air of the NOx reducing fuel gas.

That is, the fuel gas is supplied from the fuel injection nozzle 12 to the combustion exhaust gas flowing through the exhaust gas passage H to generate an oxygen-deficient region, and the fuel gas reacts with NOx in the combustion exhaust gas. By letting N
Ox becomes N ₂ and is reduced, and the fuel gas that has contributed to the reaction becomes CO. Further, the combustion exhaust gas temperature downstream of the NOx reduction fuel gas supply point in the combustion exhaust gas flow direction is 70
By supplying air from the air ejection nozzle 13 at a location where the temperature drops to about 0 to 1000 ° C., the combustion temperature of the unburned portion of the NOx reducing fuel gas containing CO is lowered to N.
Combustion is performed in a state in which generation of Ox is suppressed. Further, the material S to be fired is preheated by burning the unburned portion of the NOx reducing fuel gas.

The air is supplied by a plurality of air ejection nozzles 13, ... Dispersed in the moving direction and the vertical direction of the material to be fired S, so that the unburned portion of the NOx reducing fuel gas is gradually increased. Combustion is performed to further lower the combustion temperature to further suppress the generation of NOx.

The NOx reduction device is constructed as described above, and NOx is provided at about 5% of the amount of fuel gas supplied to the gas burner 4.
By supplying the reducing fuel gas, NOx in the combustion exhaust gas can be reduced by about 15%. It should be noted that the NOx reduction becomes more effective as the supply amount of the NOx reducing fuel gas is increased, and by supplying about 20% of the fuel gas amount supplied to the gas burner 4, the NOx reducing fuel gas in the combustion exhaust gas is supplied. NOx can be reduced by about 50%.

[Other Embodiments] Next, other embodiments will be listed.

In the above embodiment, the case where the present invention is applied to the tunnel type firing furnace is illustrated, but it is also applicable to a firing furnace configured by arranging the preheating section, the firing section, and the cooling section side by side in the vertical direction. Is. That is, the present invention is a firing furnace configured to position a preheating unit, a firing unit, a cooling unit, etc. by forming a predetermined temperature distribution along the moving path of the object to be fired moving in the furnace. , Can be applied to both.

In the above embodiment, the case where the present invention is applied to a firing furnace having a high firing temperature such as firing a ceramic is illustrated, but the present invention can be applied regardless of the firing temperature.

As the fuel for NOx reduction, it is preferable to use the gas fuel exemplified in the above embodiment because it is well mixed with the combustion exhaust gas, but in addition to the gas fuel, kerosene or heavy oil. Liquid fuels such as, or solid fuels such as coal can also be used.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a plan view of a tunnel-type firing furnace to which the present invention is applied.

FIG. 2 is a side view of a tunnel type firing furnace to which the present invention is applied.

FIG. 3 is a view on arrow AA of FIG.

[Explanation of symbols]

 4 Heating Burner 12 Fuel Supply Means 13 Air Supply Means H Exhaust Gas Path

Claims (2)

[Claims] 1. A heating burner (4) for heating an object to be fired.
And a method for reducing NOx in a firing furnace provided with an exhaust gas passage (H) for allowing combustion exhaust gas of a heating burner (4) to flow through the combustion exhaust gas flowing through the exhaust gas passage (H). A NOx reduction method in a firing furnace in which a fuel for reducing NOx in the combustion exhaust gas is supplied, and air for burning an unburned portion of the fuel is supplied on the lower side of the fuel supply position in the combustion exhaust gas flow direction. 2. A heating burner (4) for heating an object to be fired.
And a NOx reduction device in a firing furnace provided with an exhaust gas passage (H) for allowing combustion exhaust gas of the heating burner (4) to flow therethrough, wherein the combustion exhaust gas flowing through the exhaust gas passage (H) is Fuel supply means (12) for supplying fuel for reducing NOx in the combustion exhaust gas is provided, and the fuel supply means (1)
Air supply means (13) for supplying air for burning the unburned portion of the fuel to the lower side in the combustion exhaust gas flow direction than 2).
NOx reduction device in a firing furnace provided with.