JPH0139003B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion apparatus with reduced nitrogen oxide emissions.

Nitrogen oxides (hereinafter abbreviated as "NOx") are one of the air pollutants, and methods are being attempted to reduce their emissions as much as possible in various combustion devices. Methods for reducing NOx are broadly divided into methods that reduce the amount of NOx generated during the combustion stage, that is, low NOx combustion methods, and methods that reduce the NOx generated. Among these, in-furnace denitrification is one of the low NOx combustion methods. In this method, combustion is carried out at an air ratio of approximately 1 in the main burner that handles the load of the combustion device, and NOx produced in the main burner is reduced by reducing intermediate products produced in the reducing burner with a lower air ratio. harmless
_N2 . This requires good mixing of the flame generated by the main burner and the flame generated by the reduction burner.

FIG. 1 shows a conventional combustion apparatus, in which main burners 2 and 3, and a reduction burner 4 are arranged in order from the bottom of the furnace on the front wall 1a of the combustion apparatus main body 1, and an after air port 5 is arranged on the upper part. is formed.
In addition, exhaust gas G mixed with a small amount of combustion air A is supplied from the bottom of the furnace to help reduce NOx. In this combustion device, the burners and air ports are all arranged horizontally toward the rear wall, which causes the following problems. In other words, the main burner flames 7 and 8 and the reduction burner flame 9 all flow in a layered manner, and the NH, HCN, and
Reducing intermediate products such as OH and the main burner flame
Mixing with NOx will be poor, and the reduction reaction in the furnace will be insufficient. In particular, combustion air is supplied from the after-air port 5, and unburned matter produced by low-oxygen combustion is combusted, but unreacted intermediate products are oxidized by this combustion air.
A large amount of intermediate products will be inactivated and discharged without being of any use in NOx removal.

The purpose of this invention is to eliminate the above-mentioned problems, improve the mixing of the main burner flame and the reduction burner flame, and improve NOx without significantly lowering the air ratio.
The object of the present invention is to provide a combustion device capable of performing removal.

In short, this invention focuses the main burner flame on the central part of the furnace by constricting the furnace of the combustion device into a ventilary shape and arranging the reduction burner diagonally downward with respect to the entrance of the ventilary part.
The flame of the reducing burner is injected into this convergence part to improve flame mixing, and if necessary, after-air ports can be arranged in two stages on the furnace wall to precisely control the supply of combustion air. This is what I did.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, the approximate center of the furnace of the combustion apparatus main body 1 is narrowed down into a ventilate shape and the cross-sectional area of the furnace is reduced. The lower part of this ventilate part 20 serves as the main combustion chamber 10, and the upper part serves as the wide combustion chamber 11. Main burners 2 and 3 are arranged in order from the furnace bottom side on the front wall 1a of the main combustion chamber 10, and a reduction burner 4 is arranged diagonally downward at the entrance of the ventilate section. Although this reduction burner produces a considerable effect simply by installing it on the front wall 1a side, it is more effective if another reduction burner 12 is placed symmetrically with the reduction burner 4 on the rear wall 1b as shown in the figure. Reference numerals 5 and 13 indicate first-stage after-air ports, and reference numerals 14 and 15 indicate second-stage after-air ports arranged further above the first-stage after-air ports.

In the above device, the flames 7 and 8 of the main burners 2 and 3 rise in the main combustion chamber 10, but since the upper part of the main combustion chamber is the ventilate part 20, both flames move upward at the entrance of the ventilate part 20. focus towards. Since the reduction burners 4 and 12 are arranged diagonally downward at the entrance of the ventilate part 20, the reduction flames 9 and 16 are violently injected downward against the focused main burner flame, and the main burner flame that is about to rise is is influenced by this reduction flame and behaves in a complex manner, and both flames mix well. Due to good mixing of both flames, the majority of reducing intermediate products in the reducing flame are transferred to the main burner flame.
Reacts with NOx and reduces NOx to _N2 in the gas phase. Next, the unburned components mainly contained in the reduction flame are combusted in the auxiliary combustion chamber 11 by combustion air (after air) supplied from the first stage after air ports 5, 13 and the second stage after air ports 14, 15. be done. In addition, in this case, if the air supply amount can be controlled more precisely by adjusting the air supply amount of each after-air port in accordance with the amount of unburned components contained in the exhaust gas G, the amount of unburned components discharged can be reduced. It is also possible to make it smaller.

In addition, in addition to the above-mentioned two-stage combustion method, if a small amount of combustion air A is added to the exhaust gas G and supplied from the bottom of the furnace as shown in the figure, it is expected that the amount of NOx generated will be further reduced. In the figure, reference numeral 17 is an exhaust gas recirculation fan, 18 is an air supply fan, and 19 is an air heater.

By carrying out this invention, the main burner flame and the reduction burner flame can be mixed well, and the NOx reduction efficiency in the combustion stage can be significantly increased.

In addition, since the supply of after-air can be precisely controlled, the amount of unburned matter emitted can be reduced, and the amount of soot and dust generated can also be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional combustion device, and FIG. 2 is a sectional view of a combustion device according to the present invention. 1... Combustion device main body, 2, 3... Main burner,
4, 12... Reduction burner, 5, 13... First stage after air port, 10... Main combustion chamber, 11... Sub-combustion chamber, 14, 15... Second stage after air port, 20... Ventilation section.

Claims (1)

[Scope of Claims] 1. A ventilary part is formed at approximately the center in the height direction of the furnace. A combustion device with an increased NOx reduction rate, characterized in that a reduction burner is arranged diagonally downward on at least one of the walls constituting the furnace wall at the inlet, and an after air port is provided above the reduction burner. 2. Claims characterized in that the after-air ports are a first-stage after-air port and a second-stage after-air port provided above the after-air port, and the air supply amount to each after-air port can be independently controlled. A combustion device with increased NOx reduction rate as described in item 1.