JPS6128886B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel combustion device for a boiler equipped with a NOx reduction function.

As shown in Fig. 1, in a conventional boiler fuel combustion system, the individual capacity of a plurality of main burners 01 is reduced by applying a bias to the upper and lower stages, for example, to reduce the individual capacity of the main burners 01.
A common implementation method is to provide an overfire air port 02 at the top of the combustion chamber 1 for two-stage combustion, and further provide a circulation path 03 for recirculating exhaust gas into the combustion air.

There is a limit to the amount of NOx that can be reduced with such equipment, and generally only a reduction rate of about 30 to 40% can be achieved.

Therefore, the present invention has been made for the purpose of providing a fuel combustion device attached to a boiler that can further reduce NOx. A main combustion device that performs two-stage combustion includes a burner, a main air register that supplies air from around the main burner, and an overfire nozzle that is arranged above the main burner. , an afterburner equipped with an exhaust gas circulation nozzle for supplying exhaust gas to the surroundings, and an afterair nozzle disposed above the afterburner are provided on the furnace wall, and the fuel from the main burner is transferred to the main air register and the overflow. The air from the fire air nozzle performs two-stage combustion to suppress the generation of NOx, which is generated after the two-stage combustion.
NOx is converted to _N2 by fuel from afterburner,
After converting to HCN, NH ₃ , etc., and converting HCN and NH ₃ to N ₂ using a small amount of O ₂ in the exhaust gas, the residual amount is burned by after-air.
It can effectively reduce the generation of NOx.

Next, the present invention will be specifically explained based on an embodiment shown in FIGS. 2 to 4.

In FIGS. 2 to 4, the outlet side of the fan 1 communicates with an air preheater 3 through a duct 2, and the air preheater 3 communicates with a mixing device 5 through a duct 4. The outlet side of the mixing device 5 is connected to a wind box 7 provided on the outside of the furnace wall of the furnace 8 via a duct 6.
It communicates with The main burner 2 is installed on the furnace wall inside the wind box 7.
4-1 and 24-2 are provided, and the main burner 24-
1 and 24-2 are flow rate regulating dampers 6- and 24-2, respectively.
Main burner air register 6- with 4, 6-6
3 and 6-5, and an overfire air nozzle 6-7 equipped with a flow rate regulating damper 6-8 is provided above the main burner 24-2. Wind box 7
is divided into an upper part and a lower part via an air conditioning damper 7-1 on the upper side of the overfire nozzle 6-7, an afterburner 25 is arranged on the upper side, and the afterburner outer cylinder 2 surrounds the afterburner 25.
3 is provided. Further on the outer periphery of the afterburner outer cylinder 23, an afterburner air register 6-9 equipped with a flow rate regulating damper 6-10 is arranged, and further above the afterburner 25 is an afterburner nozzle 6-11 equipped with a flow rate regulating damper 6-12. is installed. The upper part of the furnace 8 is provided with convection heat surfaces 9 and 10, and the exhaust gas from the furnace 8 is guided to a chimney 13 via a duct 11, an air preheater 3 duct 12. The middle of the duct 11 and the mixing device 5 are connected to the duct 14, the ventilation fan 15, and the damper 1.
7, and the middle of the duct 16 and the afterburner outer cylinder are connected to each other by a damper 1.
9 is connected by a duct 18.

Combustion air that has been pressurized through the ventilation fan 1 passes through a duct 2 and reaches an air preheater 3 where it is heated.
The heated air passes through a mixing device 5 from a duct 4, has its oxygen concentration reduced, passes through a duct 6, and is then introduced into a furnace 8 from a bar wind box 7.

The high temperature gas burned in the furnace 8 is transferred to the convection heat transfer surface 9,
The air passes through a duct 10 through a duct 11 to an air preheater 3, where it is cooled, and is then discharged into the atmosphere through a chimney 13 from 12.

In addition, the exhaust gas is branched from the duct 11, and the ventilator 15, duct 16, and damper 1 are sent from the duct 14.
7, the line reaches the mixing device 5, branches off from the duct 16, passes through the duct 18 and the damper 19, and reaches the afterburner outer cylinder 23. Fuel is introduced into the furnace 8 from the main burners 24-1, 24-2 and the afterburner 25.

In the above device, the main burners 24-1, 24-2, the mixing device 5 attached thereto, and the overfire air nozzle 6-7 are a method conventionally implemented as a NOx reduction measure, for example, to reduce NOx from 250ppm to 150ppm. I can do it.

In such a state, the afterburner 25 in this device
and afterburner outer cylinder 23, afterair 6-
The effect of the combination of 11 can further enhance the NOx reduction effect.

The NOx generated by the combustion of fuel supplied from the main burners 24-1 and 24-2 is transferred to the afterburner 2.
After being reduced by the fuel from 5 and transferred to HCN, NH ₃ , etc., and further converted to HCN and NH ₃ by the low partial pressure O ₂ in the exhaust gas from the afterburner outer cylinder 23, the after air nozzle 6-11 The air from the fuel burns the unburned matter, effectively reducing NOx.

Figures 5 and 6 show the NOx reduction effect of this device.
This will be explained using a specific experimental example shown in the figure.

Figure 6 shows an example of an experiment using a burner using this device. In other words, by increasing the amount of afterburner fuel, for example, NOx can be reduced by increasing the amount of afterburner fuel by 10 to 15%.
If the reduction rate increases further by 40-50%, it will be an after-cost expense.
It was confirmed that there was a reduction effect of 60% or more at 20% or more. In addition, by increasing the combination of afterburner and afterair to two or three stages in this way, a synergistic effect can be obtained, and as shown in Figure 5, the initial
Estimated NOx can be reduced to 20ppm by combining three stages.

After-air occurs when after-euel is introduced.
Used to reduce CO and emissions and maintain effective combustion.

As described above, it can be seen that the present device can effectively reduce NOx.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional boiler fuel combustion device, Fig. 2 is a drawing showing one embodiment of the present invention, Fig. 3 is a detailed view of section A in Fig. 2, and Fig. 4 is a diagram showing a part A in Fig. 2. The block diagram in FIG. 3, and FIGS. 5 and 6 are graphs showing the NOx reduction effect of one embodiment of the present invention. 1, 15... Ventilator, 2, 4, 6, 11, 1
2, 14, 16, 18... Duct, 3... Air preheater, 5... Mixing device, 6-3, 6-5...
...Air register for main burner, 6-4, 6-6, 6
-8,6-10,6-12,7-1...Damper for flow rate adjustment, 6-7...Overfire air nozzle,
6-9...Air register for afterburner, 6-1
1... After air nozzle, 7... Wind section, 8... Furnace, 9, 10... Convection heat transfer surface, 13... Chimney, 1
7, 19... Damper, 23... Afterburner outer cylinder, 24-1, 24-2... Main burner, 25...
Afterbana.

Claims (1)

[Claims] 1. A furnace wall forms a furnace, and a main burner is arranged in multiple stages vertically on the furnace wall, a main air register that supplies air from around the main burner, and an overfire air nozzle arranged above the main burner. an afterburner equipped with an exhaust gas circulation nozzle disposed above the overfire air nozzle to supply exhaust gas to the surroundings of the main combustion device that performs two-stage combustion, and an afterair nozzle disposed above the afterburner; A fuel combustion device for a boiler characterized by being installed on the furnace wall.