JPS5896905A - Combustion device with high nox reduction rate - Google Patents

Abstract

PURPOSE:To improve a high rate of reduction of NOx by a method wherein a Venturi part is formed at a substantially central part of a furnace in its elevational direction, a main burner is arranged in a main combustion chamber below the Venturi part and a reduction burner is arranged at the inlet part of the Venturi in a downward inclining direction. CONSTITUTION:A Venturi part 20 is formed at a substantially central part of the furnace of the main body of a combustion device 1 so as to decrease a sectional area of the furnace. The lower part of the Venturi 20 is used as a main combustion chamber 10 and its upper part is applied as a sub-combustion chamber 11. The main burners 2, 3 are arranged in sequence from the bottom part of the furnace against the front wall 1a in the main combustion chamber 10. At the inlet of the Venturi 20 is arranged a reduction burner 4 in a downward inclining direction. An additional reduction burner 12 is arranged at the rear wall 1b in symmetrical to the reduction burner 4. At the upper part of the reduction burners 4, 12 are arranged the first and second after-air inlet ports 5, 13 and 14, 15 respectively. Thus, the main flames 7, 8 and the reduction flames 9, 16 are mixed well so as to accomplish the desired object.

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. There are two ways to reduce NOx: a method that reduces the amount of NOx generated during the combustion stage, that is, a low NOx combustion method, and a method that reduces the amount of NOx that is generated.
It is broadly divided into methods of reducing. Among these, one of the low NOx combustion methods is the in-furnace denitrification method. In this method, combustion is carried out in the main burner that receives the load of the combustion device with an air ratio of approximately 1, and the NOx produced in the main burner is reduced by reducing intermediate products generated in the reducing burner with a lower air ratio. This makes the N2 harmless.

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.
A reduction burner 4 is disposed, and an after air port 5 is formed above the reduction burner 4. Note that 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 reducing burner flame 9 all flow in a layered manner, and reducing intermediate products such as NH, HON, OH, etc. contained in the reducing burner flame 9 mix with NOx in the main burner flame. becomes defective,
The reduction reaction in the furnace becomes insufficient. In particular, combustion air is supplied from the after-air port 5 to burn unburned matter produced by low-oxygen combustion, but this combustion air oxidizes unreacted intermediate products, resulting in a large amount of intermediate products. The product will be inactivated and discharged without being of any use in removing NOx.

It is an object of the present invention to provide a combustion device that eliminates the above-mentioned problems, allows good mixing of the main burner flame and the reduction burner flame, and allows good NOx removal without extremely lowering the air ratio. It is in.

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 venturi shape and arranging the reducing burner diagonally downward with respect to a partial inlet of the venturi. The flame of the reducing burner is injected to improve flame mixing, and if necessary, after-air ports are arranged in two stages on the furnace wall to precisely control the supply of combustion air.

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

In FIG. 2, the approximately central portion of the furnace of the combustion apparatus main body 1 is narrowed down in a venturi shape so that the cross-sectional area of the furnace is reduced.

The lower part of this venturi 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 IO, and a reduction burner 4 is arranged diagonally downward at a partial venturi inlet. Although this reduction burner produces a considerable effect simply by installing it on the front wall la 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 venturi part 20, both flames move upward as they rise. focus towards the entrance. Since the reduction burners 4 and 12 are arranged diagonally downward in the venturi part 20, the reduction flames 9 and 16 are violently injected downward against this focused main burner flame, and the main burner that is about to rise is The flame behaves in a complex manner due to the influence of this reducing flame, and both flames mix well. Due to the good mixing of both flames, the majority of the reducing intermediate products in the reducing flame react with the NOx in the main burner flame, reducing the Nox in the N-noise gas phase. Next, the unburned components mainly contained in the reducing flame are subjected to combustion treatment in the sub-combustion chamber 11 by combustion air (after air) supplied from the first stage after air port 5, 13, and the second stage after air port 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 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 reducing 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. l... 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.
・・・・・・Patent attorney representing part of Venturi Oka Tagobe

Claims (1)

[Scope of Claims] 1. A part of the venturi is formed approximately at the center in the height direction of the furnace, the lower part of the venturi part is used as the main combustion chamber, the upper part is used as the auxiliary combustion chamber, and the main burner is arranged in the main combustion chamber. , a combustion system with a high NOx reduction rate, characterized in that a reduction burner is arranged at the inlet of a part of the venturi facing diagonally downward at least on the wall surface constituting the furnace wall, and an after-air port is provided above the reduction burner. Device. 2. The after-air port is 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. Range 1
A combustion device with increased NOx reduction rate as described in section 1.