JPS58138906A - Low nox combustion device - Google Patents

Abstract

PURPOSE:To mix sufficiently NOX in main burner flames with reducing intermediate products in reducing burner flames so as to augment denitrating efficiency, by arranging main burners around reducing burners so that the reducing burner flames may be surrounded by the main burner flames. CONSTITUTION:Part of combustion air 10 flowed in a blast box 7 reaches the reducing burners 2 via an air register 6, and fuel jetted from the burners 2 is burnt to produce reducing flames. In this case, as the purpose of the reducing flames is to produce reducing intermediate products such as CN, CO, etc., the opening of the air register 6 is narrowed so that the air-fuel ratio becomes on the order of 0.1 to 0.5. In the case of the main burners 1 which assume heat load, the burning is effectd with the air-fuel being 1 or above, and the main burner flames are jetted into the furnace in such a way that they enclose the reducing burner flames. Thus, the chance of contact of the reducing intermediate products in the reducing flames with the main burner flames is substantially increased, and as a result, successful denitration can be effected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion device that significantly reduces nitrogen oxide emissions.

BACKGROUND OF THE INVENTION Nitrogen oxides (hereinafter abbreviated as NOx) are one of the air pollutants, and various combustion methods or denitrification devices for reducing the amount of nitrogen oxides emitted have been provided and put into practical use. Among these methods, methods to reduce NOx by improving combustion methods include the two-stage combustion method, exhaust gas recirculation method, and flame splitting method, but each has advantages and disadvantages, such as a decrease in thermal efficiency and an increase in unburned content. A problem has arisen. In such a situation, a combustion method called in-furnace denitrification method has recently been attracting attention.

This method generates intermediate products that have reducing properties in some burners by extremely lowering the air-fuel ratio in these burners, and this intermediate product harmlessly removes NOx generated in burners that mainly receive heat loads. This reduces the amount of energy to N2. In order to carry out this method efficiently, it is a prerequisite that the amount of reducing intermediate products produced must be kept at the amount necessary and sufficient for reducing NOx, and it is necessary to avoid producing intermediate products unnecessarily. This will reduce combustion efficiency and increase unburned matter. However, in the conventional in-furnace denitration method, the proportion of intermediate products generated that can be used for NOx denitration is not necessarily high, and there is a desire to develop a combustion device that can perform more efficient denitration.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a combustion device that increases denitrification efficiency.

In short, this invention has a configuration in which a plurality of main burners are installed around a reducing burner so that the shoulder burner flame is covered by the main flame, and the NOx in the main burner flame and the reducing property in the reducing burner flame are reduced. / to ensure good mixing of the products.

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

In FIGS. 1 and 2, a flame holding plate 3 is arranged at the center of the burner throat 4 formed on the front wall 5 of the furnace.
A plurality of reduction burners 2 (four in the illustrated case) are arranged around the flame stabilizing plate 3. 8 is a manifold for fuel 11 (for example, natural gas), and each reduction burner 2
supply fuel. Reference numeral 1 designates a plurality of main burners arranged around the reduction burner 2, and 9 a manifold that supplies fuel 12 (which may be similar to the fuel 11) to the main burner 1.

In this combustion device, combustion air 1 flowing into the wind box 7
A part of 0 passes through the air register 6 and reaches the reduction burner 2,
A reduction flame is formed by burning the fuel injected from the burner 2.

In this case, the purpose of the reducing flame is to generate reducing intermediate products such as (!N, Co, etc.), so the opening degree of the air register 6 is narrowed and the air-fuel ratio is extremely low, for example 0.1 to 0.5.
degree. On the other hand, in the main burner 1 which receives a heat load, combustion is performed at an air-fuel ratio of 1 or more, and this main burner flame is injected into the furnace so as to surround the reduction burner flame. This greatly increases the chance of contact between reducing intermediate products in the reducing flame and the main burner flame, and good denitration can be achieved with less intermediate products.

In other words, in the past, since the mixing of the two was not necessarily good, it was necessary to increase the amount of intermediate products produced, and for this reason, the air-fuel ratio of the reduction burner was often set to 0, but in the case of this invention, NOx Since the efficiency of contact between the fuel and intermediate products is high, the air-fuel ratio in the reduction burner can be set relatively high, stabilizing combustion and preventing a decrease in thermal efficiency.

3 and 4 show another embodiment.

In this embodiment, an air boat 13 is further formed around the main burner 1, and the remaining unburned matter is burned in the main burner flame and the reduction burner flame. If desired, one or more sets of burners shown in FIG. 4 can be provided on the furnace wall.

Originally, in the main burner, the air-fuel ratio was high because it was necessary to burn the unburned matter in the reducing flame, and it was often set to about 1.4 to 1.5, for example, but when the air-fuel ratio is raised like this, NOx also increases. It becomes a trend.

In other words, it is preferable that the unburned content in the reduction flame be combusted by combustion air supplied from a source other than the main burner.In the case of this embodiment, since the air boat 13 is formed separately, the air-fuel ratio of the main burner l is approximately 1. Can be held in the main burner 1
It is possible to reduce the amount of NOx generated.

By carrying out this invention, reducing intermediate products and NO
Since the nitrogen and nitrogen are well mixed, the efficiency of denitration in the furnace increases, and the air-fuel ratio of the reduction burner can also be increased accordingly, making it possible to stabilize combustion.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a combustion device showing a first embodiment of the present invention, FIG. 2 is a view taken along line A-A in FIG. 1, and FIG. 3 is a sectional view of a combustion device showing a second embodiment. The sectional view, FIG. 4, is a view taken along the line B-E in FIG. 3. 1... Main burner 2... Reduction burner 5... Furnace front wall 10... Combustion air 13... Air boat

Claims (1)

[Claims] 1. In a device that reduces nitrogen oxides produced by combustion in a main burner with reducing intermediate products produced by combustion in a reduction burner, a reduction burner is disposed on the wall of the furnace, and the reduction burner is A low NOx combustion device characterized in that one or more burner devices are disposed on a furnace wall surface, the burner device being configured such that the main burner is arranged around the main burner so that the main burner flame surrounds the reducing burner flame. 2. Low NOx according to claim 1, characterized in that an air boat is formed on the furnace wall surface around the main burner.
Combustion device.