JPH1176752A - Decreasing method of nox and dioxin in waste combustion gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently perform the reduction of NOx or the suppression of the generation of dioxin in a waste combustion gas without separately preparing a reducing agent for denitrification, a dioxin decreasing agent or the like. SOLUTION: The decreasing method of NOx.dioxin in the waste combustion gas is for the reduction of NOx and the suppression of the generation of dioxin in the waste combustion gas by partially combusting a fuel containing a nitrogen portion and a chlorine portion and/or a waste containing the nitrogen portion and the chlorine portion in a gasifying furnace to turn to a combustible gas containing at least one of NH3 and HCN, completely combusting a part of the combustible gas in a complete combustion furnace 1.8 and at the same time, supplying the remaining part of the combustible gas containing NH3 and/or HCN, which is obtained by partially combusting in the gasifying furnace, into the vicinity of the outlet of the complete combustion zone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing the concentration of NOx and dioxin in combustion exhaust gas generated when burning fuel or waste containing nitrogen and chlorine.

[0002]

2. Description of the Related Art When fuel or waste containing nitrogen is burned, a part of the nitrogen is oxidized to NOx, and combustion exhaust gas containing NOx is generated. Conventionally, in order to reduce NOx in the combustion exhaust gas, NH 3 has been used as a reducing agent for denitration.
₃ and HCN were supplied from outside the system. Thus, N
H ₃ and HCN is generally known as a reducing agent for denitration, do it properly manage the temperature and oxygen concentration, it is possible to reduce the NOx generated by the combustion.

[0003] When burning fuel or waste containing chlorine, dioxins are produced from unburned aromatic hydrocarbons and hydrogen chloride in the combustion exhaust gas in the presence of oxygen. In order to reduce dioxin in the flue gas, conventionally, as described in JP-A-4-250817, NH ₃ , ammonium salt or the like was added to the flue gas from outside the system. Thus, it has recently been found that NH _{3 and the} like suppress the production of dioxins formed from unburned aromatic hydrocarbons and hydrogen chloride in the combustion exhaust gas of fuel and waste containing chlorine.

[0004]

However, in the above prior art, in order to reduce the concentration of NOx and dioxin in the combustion exhaust gas generated when burning fuel and waste containing nitrogen and chlorine, It was necessary to separately prepare a denitration reducing agent, a dioxin reduction catalyst, and the like, and it was necessary to supply a denitration reducing agent and a dioxin reduction material from outside the system.

The present invention has been made in view of the above points, and an object of the present invention is to provide a fuel containing NH ₃ and chlorine and a combustible gas containing NH ₃ and HCN obtained by partial combustion of waste. By injecting a part of the combustible gas partially burned near the outlet of the complete combustion area, NOx generated by complete combustion of the combustible gas without separately preparing a reducing agent for denitration, a dioxin reducing material, etc. And a method capable of reducing the concentration of dioxin.

[0006]

In order to achieve the above object, a method for reducing NOx and dioxin in flue gas according to the present invention comprises a fuel containing nitrogen and chlorine and / or a waste containing nitrogen and chlorine. The material is partially burned to produce NH ₃ and HC
After the flammable gas contains at least one of N, a part of the flammable gas is completely burned, and the flammable gas containing NH ₃ and / or HCN obtained by the above partial combustion near the outlet of the complete combustion region. It is characterized in that the remainder of the gas is supplied to reduce NOx in the combustion exhaust gas and suppress the generation of dioxin (see FIGS. 1 and 2).

[0007] The method of the present invention further comprises the step of partially burning a fuel containing nitrogen and chlorine or / and a waste containing nitrogen and chlorine to produce a combustible gas containing at least one of NH ₃ and HCN. After that, a part of the combustible gas is supplied to a primary combustion portion of a two-stage combustion furnace for performing primary combustion and secondary combustion to perform primary combustion, and then, the combustion gas subjected to primary combustion is supplied to a secondary combustion portion. Supply and complete combustion, and supply the remainder of the combustible gas containing NH ₃ and / or HCN obtained by the partial combustion to the vicinity of the outlet of the complete combustion area, thereby reducing NOx in combustion exhaust gas and generating dioxin. (See FIG. 1).

In the above method of the present invention, when the flammable gas containing NH ₃ and / or HCN obtained by partial combustion is supplied to the vicinity of the outlet of the complete combustion zone, the temperature of the complete combustion zone is 850 to 1000 ° C. And the oxygen concentration is 3-6 vo
l.% is desirable. If the temperature is lower than 850 ° C., reduction of NOx or the like by NH ₃ or HCN is not performed efficiently, while if the temperature exceeds 1000 ° C., thermal NO
There is a disadvantage that x occurs. The oxygen concentration is 3v
If the amount is less than ol.%, complete combustion of the gas cannot be performed efficiently, while if it exceeds 6 vol.%, the air ratio becomes 1.3 or more, the amount of exhaust gas increases, and the thermal efficiency and the scale of equipment increase. Is not preferred.

[0009]

FIG. 1 shows a schematic system of an apparatus for carrying out a method for reducing NOx and dioxin in flue gas according to a first embodiment of the present invention. In this embodiment,
By partially burning fuel and waste containing nitrogen and chlorine,
Secondary combustion in which a flammable gas containing NH ₃ or HCN is branched, a part of the flammable gas is branched, and the remaining flammable gas is subjected to primary combustion, followed by secondary combustion, and complete combustion in this two-stage combustion. By supplying a part of the flammable gas containing NH ₃ or HCN to the combustion exhaust gas of the section, NOx in the combustion exhaust gas is reduced and generation of dioxin is suppressed.

As shown in FIG. 1, fuel / waste containing nitrogen and chlorine is supplied from a fuel / waste supply means 10 to a gasification furnace 1.
2 and partially combusted to become a combustible gas containing NH ₃ and HCN. Although not shown, the gasification residue generated by the partial combustion in the gasification furnace 12 is supplied to the gasification furnace 1.
2 to be burned (or incinerated). Part of the flammable gas containing NH ₃ and HCN obtained by the partial combustion is introduced into the flammable gas branch pipe 14, and subsequently reduces NOx in the combustion exhaust gas or suppresses generation of dioxin. Used to do. The remaining combustible gas is introduced from the combustible gas conduit 16 into the complete combustion furnace 18, where it is first combusted in the primary combustion section 20 and then completely combusted in the secondary combustion section 22. By the complete combustion (oxidative combustion) of the combustible gas, the nitrogen content in the flue gas becomes nitrogen and NOx, and dioxin is generated from the unburned aromatic hydrocarbons and hydrogen chloride in the flue gas. As described above, the production of dioxin is suppressed. 24 is a primary air supply pipe,
26 is a secondary air supply pipe.

Next, the flammable gas containing NH ₃ and HCN introduced into the flammable gas branch pipe 14 is supplied to the vicinity of the outlet of the secondary combustion section 22 of the complete combustion furnace 18, and the complete combustion is performed. It functions to reduce NOx in the generated combustion gas and to suppress the generation of dioxin. In addition,
In the present embodiment, a case is shown in which a part of the combustible gas including NH ₃ and HCN is supplied to the vicinity of the outlet of the secondary combustion part 22, but is supplied to any part near the outlet of the complete combustion region. Of course, it is possible. In this case, the temperature in the complete combustion zone is 850 to 1000 ° C., and the oxygen concentration is 3 to
It is desirable to be 6 vol.%. In this way, NO
The flue gas with reduced x and dioxin is discharged from the flue gas discharge pipe 28.

FIG. 2 shows a schematic system of an apparatus for carrying out a method for reducing NOx and dioxin in flue gas according to a second embodiment of the present invention. In the present embodiment, fuel / waste containing nitrogen and chlorine is partially burned to form a combustible gas containing NH ₃ and HCN, and a part of this combustible gas is branched to form the remaining combustible gas. The gas is completely burned in a combustion furnace, and the NH _{3 is} placed near the outlet of the complete combustion zone of the combustion furnace.
By supplying a part of the flammable gas including CO2 and HCN, NOx in the combustion exhaust gas is reduced and the generation of dioxin is suppressed.

As shown in FIG. 2, fuel / waste containing nitrogen and chlorine is supplied from a fuel / waste supply means 10 to a gasification furnace 1.
2 and partially combusted to become a combustible gas containing NH ₃ and HCN. NH ₃ and HC obtained by partial combustion
A part of the flammable gas containing N is introduced into the flammable gas branch pipe 14, and is later used to reduce NOx in the combustion exhaust gas and suppress generation of dioxin. The remaining combustible gas is introduced from the combustible gas conduit 16 into the combustion furnace 30 and is completely burned. By the complete combustion (oxidative combustion) of the combustible gas, the nitrogen content in the flue gas becomes nitrogen and NOx, and dioxin is produced from the unburned aromatic hydrocarbons and hydrogen chloride in the flue gas. As described above, the production of dioxin is suppressed. 32 is a combustion air supply pipe.

Next, the flammable gas containing NH ₃ and HCN introduced into the flammable gas branch pipe 14 is supplied to the vicinity of the complete combustion zone outlet of the combustion furnace 30 and the combustion gas generated by the complete combustion is produced. It functions to reduce NOx in the gas and to suppress the production of dioxin. In this way,
The combustion exhaust gas with reduced NOx and dioxin is discharged from the combustion exhaust gas discharge pipe 28. Other configurations, operations, and the like are the same as those in the first embodiment of the present invention.

[0015]

As described above, the present invention has the following effects. (1) A reducing agent and a dioxin reducing material for denitration can be manufactured from an object to be burned by a combination of partial combustion and complete combustion without separately preparing a reducing agent for denitration, a dioxin reducing catalyst, and the like. The concentrations of NOx and dioxin in the combustion exhaust gas can be efficiently reduced. (2) By applying a fuel or waste containing nitrogen and chlorine to a gasification combustion apparatus for, for example, refuse, reduction of NOx in combustion exhaust gas and suppression of dioxin generation can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a diagram showing N in combustion exhaust gas according to a first embodiment of the present invention;
It is a systematic schematic block diagram which shows the apparatus which implements the Ox / dioxin reduction method.

FIG. 2 shows N of flue gas according to a second embodiment of the present invention.
It is a systematic schematic block diagram which shows the apparatus which implements the Ox / dioxin reduction method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fuel / waste supply means 12 Gasifier 14 Combustible gas branch pipe 16 Combustible gas conduit 18 Complete combustion furnace 20 Primary combustion section 22 Secondary combustion section 24 Primary air supply pipe 26 Secondary air supply pipe 28 Exhaust gas exhaust gas Pipe 30 Combustion furnace 32 Combustion air supply pipe

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Tsutsumi 1-1, Kawasaki-cho, Akashi-shi, Hyogo Prefecture Kawasaki Heavy Industries, Ltd. Inside Akashi Plant (72) Inventor Ken-ichi Fujii 1-1-1, Kawasaki-cho, Akashi-shi, Hyogo Prefecture Kawasaki Heavy Industries, Ltd.

Claims (3)

[Claims] 1. A fuel containing nitrogen and chlorine or / and a waste containing nitrogen and chlorine is partially burned to obtain a combustible gas containing at least one of NH ₃ and HCN. Complete combustion of a part of the reactive gas,
Near the outlet of the complete combustion zone, the N
The remaining portion of the combustible gas containing H ₃ and / or HCN is supplied to reduce NOx in the flue gas and suppress the generation of dioxin.
Dioxin reduction method. 2. A fuel containing nitrogen and chlorine or / and a waste containing nitrogen and chlorine is partially burned to obtain a combustible gas containing at least one of NH ₃ and HCN. A part of the reactive gas is supplied to the primary combustion part of a two-stage combustion furnace that performs primary combustion and secondary combustion to perform primary combustion, and then the primary combustion combustion gas is supplied to the secondary combustion part for complete combustion. At the same time, the remaining portion of the combustible gas containing NH ₃ and / or HCN obtained by the partial combustion is supplied to the vicinity of the outlet of the complete combustion region to reduce NOx in the combustion exhaust gas and suppress generation of dioxin. Characteristic method for reducing NOx and dioxin in combustion exhaust gas. 3. When a flammable gas containing NH ₃ and / or HCN obtained by partial combustion is supplied to the vicinity of the outlet of the complete combustion region, the temperature of the complete combustion region is 850 to 1000 ° C., and the oxygen concentration is 3. The method for reducing NOx and dioxin in flue gas according to claim 1, wherein the amount is 3 to 6 vol.