JP3050439B2 - NOx reduction method and NOx reduction device in firing furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for reducing NOx 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 from the heating burner. About.

[0002]

2. Description of the Related Art As a method of reducing NOx in a firing furnace, conventionally, generally, the amount of air supplied to fuel is extremely reduced to cause slow combustion to lower the combustion temperature to reduce NOx. A way to reduce it, ie
A method of reducing NOx by improving burner combustion has been employed.

[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 causes slow combustion to lower the combustion temperature cannot be adopted because the furnace temperature cannot be raised to a predetermined firing temperature, and thus cannot be adopted. No measures for reducing NOx were taken in a simple firing furnace. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a NOx reduction method and a NOx reduction apparatus in a firing furnace that can be adopted regardless of a firing temperature and can effectively reduce NOx. is there.

[0004]

According to a first feature of the present invention, a method for reducing NOx in a sintering furnace is a method for reducing NOx in an inlet of a furnace body.
To move the object in the furnace toward the outlet
And the exhaust gas path is directed toward the inlet through the furnace.
Only it is configured to flow through the combustion exhaust gas, the waste gas
The flue gas flowing through the flue gas contains N in the flue gas.
Supplying fuel to reduce Ox, and after the fuel is supplied
To the flue gas flowing through the flue gas passage
Combustion of unburned fuel at low temperature to suppress NOx generation
The point is to supply air so that

[0005] A NOx reduction device in a firing furnace, which is a second characteristic configuration of the present invention, is applied from the inlet to the outlet of the furnace body.
Is configured, the fired product to move through the furnace, the flue gas
A passage through which the flue gas is directed toward the inlet through the furnace.
It is configured to flow through, before flowing through the exhaust gas channel
A fuel that reduces NOx in the flue gas to the flue gas.
Fuel supply means for supplying fuel, and the fuel supply means
The fuel flowing through the exhaust gas passage after the fuel is supplied
Suppresses NOx generation of unburned fuel in combustion exhaust gas
Supply air to burn at low temperature for
The point is that a supply means is provided .

[0006]

According to the first feature of the present invention, the object to be fired is provided.
Is moved through the furnace from the inlet to the outlet of the furnace,
Exhaust gas from the combustion burner in the furnace
Flow through to the entrance. And let it flow inside the furnace
By supplying fuel for NOx reduction to combustion exhaust gas
This creates an oxygen deficient zone, which creates fuel and combustion emissions.
Reacts with NOx in the fuel to reduce NOx,
For the combustion exhaust gas flowing through the furnace after the is supplied,
In other words, after the fuel is supplied,
Of the unburned fuel in the flue gas flowing toward
Air is burned at low temperature to suppress Ox generation.
By supplying the fuel, the unburned portion of the fuel reduces the combustion temperature.
Combustion in a state where NOx generation is suppressed, and N
The fuel that is supplied to reduce Ox
The fired product can be preheated.

According to a second characteristic configuration, the object to be fired is a furnace.
Moved through the furnace from the body inlet to the outlet, the heating bar
The combustion exhaust gas from the furnace passes through the furnace, which functions as an exhaust gas passage.
Flow toward the entrance. And in the fuel supply means,
Supplying NOx reduction fuel to combustion exhaust gas flowing through the furnace
By doing so, an oxygen-deficient region is created,
Of NOx by reacting feedstock with NOx in flue gas
After the fuel is supplied by the fuel supply means, the inside of the furnace is
For the flowing flue gas, that is, when fuel is supplied
After that, the combustion exhaust gas flowing through the furnace toward the inlet
The unburned portion of the fuel with NOx
Supply air to combust at low temperature to suppress generation
By reducing the unburned portion of the fuel by reducing the combustion temperature,
Combustion in a state where generation of Ox is suppressed, and NOx
Sintered in the furnace with fuel supplied for reduction
Things can be preheated.

[0008]

According to the first characteristic configuration, as in the prior art,
Burner burns slowly to lower combustion temperature and N
Since this is not a method for reducing Ox, it can be adopted regardless of the firing temperature, and NOx in combustion exhaust gas can be effectively reduced. In addition, separate fuel for NOx reduction
But the fuel burns and moves inside the furnace
Preheating the material to be fired, thus reducing the overall fuel supply
The increase can be suppressed as much as possible, and
Then, preheating and firing are sequentially performed to perform the firing process.
While reducing NOx in flue gas
Can be reduced.

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

[0010]

1 to 3 show an example in which an embodiment of the present invention is applied to a tunnel type firing furnace for firing ceramics.
It will be described based on.

In FIG. 1, reference numeral 1 denotes a furnace body, and a carriage 3 on which a workpiece S is placed moves from an inlet I to an outlet O in a furnace 2 inside the furnace body 1. . The furnace body 1
It is composed of a preheating section 1A, a firing section 1B, and a cooling section 1C arranged in order from the entrance I to the exit O. The object S to be fired is placed on the carriage 3 and transported in the furnace. By doing so, a predetermined baking process is performed by sequentially passing through the preheating unit 1A, the baking unit 1B, and the cooling unit 1C.

A gas burner 4 as a heating burner for heating the object S to be fired is provided on each of the left and right sides of the firing section 1B. The exhaust gas from the gas burner 4 is supplied to the preheating unit 1 by the exhaust fan 5 in a direction opposite to the moving direction of the object S.
The furnace A is caused to flow in the direction of the inlet I to preheat the material S to be fired, and is discharged outside the furnace through the exhaust gas discharge port 6. That is, the combustion exhaust gas of the gas burner 4
The exhaust gas passage H through which the gas flows from the firing section 1B to the preheating section 1A
To the inlet I through the furnace 2 leading to the exhaust port 6 at
The combustion exhaust gas is made to flow, and the inside of the furnace 2 is also made to function as an exhaust gas passage H.

In the cooling section 1C, the cooling air supplied by the cooling fan 7 in the direction of the inlet I through the air supply nozzle 8 is supplied to the combustion air outlet 9 by the combustion air fan 9.
By discharging the cooling air through the furnace of the cooling unit 1C in a direction opposite to the moving direction of the object S to be cooled, the object S is cooled. is there. That is, the inside of the furnace 2 from the air supply nozzle 8 of the cooling unit 1C to the combustion air outlet 10 also functions as a cooling air passage R through which cooling air flows.

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

In FIG. 3, reference numeral 11 denotes a sand seal for isolating the wheel portion of the bogie 3 from being exposed to the atmosphere in the furnace. The wheel portion of the bogie 3 is exposed to a high-temperature atmosphere in the furnace or combustion exhaust gas. Prevents damage.

In the tunnel-type sintering furnace configured as described above, the sintering unit 1B is heated by the gas burner 4 to set the furnace temperature of the sintering unit 1B to about 1700 to 1800 ° C.
Also, the combustion exhaust gas from the gas burner 4 flows through the exhaust gas passage H, so that the furnace temperature of the preheating section 1A gradually increases from the inlet I to the boundary between the preheating section 1A and the firing section 1B. And the cooling air flows through the cooling air flow path R.
The temperature in the furnace of the cooling unit 1C gradually decreases from the boundary between the baking unit 1B and the cooling unit 1C to the outlet O by flowing the cooling water. That is, the furnace temperature from the inlet I to the outlet O is set to a predetermined temperature distribution, and the object S to be fired moving in the furnace is preheated, fired,
A predetermined baking process for sequentially and continuously performing cooling is performed.

Next, the 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.

At the right and left sides of the furnace body 1 where the temperature in the furnace of the preheating section 1A, that is, the temperature of the flue gas is about 1200 to 1600 ° C., the flue gas flowing through the flue gas passage H is added to the flue gas. A plurality of fuel ejection nozzles 12 as fuel supply means for ejecting and supplying a fuel gas for reducing NOx therein are arranged in parallel at a predetermined interval in the moving direction of the workpiece S. The amount of the NOx reducing fuel gas supplied from the fuel ejection nozzle 12 depends on the gas burner 4
About 5 to 30% of the amount of fuel gas supplied to the fuel cell.

Further, on the inlet I side of the installation position of the fuel ejection nozzle 12, the furnace temperature of the preheating section 1A is set to 700-10.
At each of the right and left sides of the furnace body 1 at a temperature of about 00 ° C., the unburned portion of the NOx reducing fuel gas is reduced in NOx generation.
Air to supply air to burn at low temperature
A plurality of air jet nozzles 13 as air supply means are
In a posture in which air is spouted and supplied upward, the objects to be fired S are juxtaposed at predetermined intervals in the moving direction. The air supplied from the air jet nozzle 13 uses the air from the cooling fan 7. The amount of air supplied from the air jet nozzle 13 is equal to or more than the theoretical amount of the NOx reducing fuel gas.

That is, with respect to the combustion exhaust gas flowing through the exhaust gas passage H, a fuel gas is supplied by the fuel ejection nozzle 12 to generate an oxygen deficient region, and the fuel gas reacts with NOx in the combustion exhaust gas. Let N
Ox is reduced to N ₂ and the fuel gas contributing to the reaction is CO. Further, the temperature of the combustion exhaust gas downstream of the fuel gas supply point for NOx reduction is 70
At a point where the temperature has dropped to about 0 to 1000 ° C., air is supplied by the air jet nozzle 13 to reduce the unburned portion of the NOx reducing fuel gas containing CO by reducing the combustion temperature to N.
Combustion is performed in a state where generation of Ox is suppressed. Further, the object 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 provided in the moving direction and the vertical direction of the material S to be fired, so that the unburned portion of the NOx reducing fuel gas is gradually reduced. The generation of NOx is further suppressed by lowering the combustion temperature by combustion.

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

Next, another embodiment will be described.

In the above-described embodiment, the case where the present invention is applied to a tunnel-type firing furnace is illustrated. However, for example, the present invention is also applicable to a firing furnace in which a preheating unit, a firing unit, and a cooling unit are vertically arranged. It is. That is, the present invention provides a firing furnace configured to form a predetermined temperature distribution along a movement path of an object to be fired moving in the furnace and to position a preheating section, a firing section, a cooling section, and the like. , And can be applied to any of them.

In the above embodiment, the case where the present invention is applied to a firing furnace having a high firing temperature, such as firing ceramics, is illustrated. However, 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 of good mixing with the combustion exhaust gas, but in addition to the gas fuel, kerosene or heavy oil Or a solid fuel such as coal.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the 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 taken in the direction of arrows AA in FIG. 1;

[Description of Signs ] 1 Furnace body 2 Furnace 4 Heating burner 12 Fuel supply means 13 Air supply means H Exhaust gas path

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F23C 11/00 318 B01D 53/56 F23J 15/00 ZAB

Claims (2)

(57) [Claims] 1. A heating burner (4) for heating an object to be fired.
And a flue gas passage (H) through which flue gas from the heating burner (4) flows, wherein the NOx reduction method is performed in a firing furnace from an inlet to an outlet of a furnace body (1). Things in the furnace
(2), and the exhaust gas passage (H) is connected to the inlet (2) through the furnace (2).
The flue gas is allowed to flow toward the mouth, and the flue gas flowing through the flue gas passage (H)
Supplying fuel to reduce NOx in the flue gas
The fuel flowing through the exhaust gas passage (H) after the
Suppresses NOx generation of unburned fuel in combustion exhaust gas
For reducing NOx in a firing furnace that supplies air so as to burn at a low temperature for the purpose . 2. A heating burner for heating an object to be fired.
When, a NOx reduction device in a kiln exhaust gas passage (H) and is provided to flow through the flue gas of the heating burner (4), be fired from the inlet to the outlet of the furnace body (1) Things in the furnace
(2), and the exhaust gas passage (H) is connected to the inlet (2) through the furnace (2).
The flue gas is allowed to flow toward the mouth, and the flue gas flowing through the flue gas passage (H)
Fuel supply for supplying fuel to reduce NOx in flue gas
Means (12) and the fuel supply means (12)
The said gas flowing through said exhaust gas channel (H) after the feed is supplied
For combustion exhaust gas, the unburned portion of the fuel is reduced in NOx generation.
Air to supply air to burn at low temperature
N in the firing furnace provided with the air supply means (13)
Ox reduction device.