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Method for reducing emission of nitrogen oxides under low load of boiler

A nitrogen oxides, low-load technology, applied in combustion methods, emission prevention, fuels burned in a molten state, etc., can solve problems such as the decline of denitration efficiency, save ash cleaning and maintenance costs, reduce waste gas and sewage costs, and solve nitrogen problems. The effect of oxides exceeding the standard

Inactive Publication Date: 2018-11-06
上海金联热电有限公司
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Problems solved by technology

[0004] When the temperature of the ammonia injection point reaches the design temperature >770°C, its denitrification efficiency can make the nitrogen oxide emission meet the national standard, but when the boiler is under low load (<70T / H), the temperature of the ammonia injection point is basically <770°C, so When the denitrification efficiency drops sharply, the average hourly emission of nitrogen oxides reaches 120-180mg / Nm3, the average emission value is 130.2mg / Nm3, and the emission of nitrogen oxides exceeds the national standard

Method used

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  • Method for reducing emission of nitrogen oxides under low load of boiler

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Embodiment 1

[0029] Embodiment 1: A method for reducing nitrogen oxide emissions under low boiler load. When the boiler load is less than or equal to 70t / h, the flue gas temperature at the boiler outlet is less than 770°C. At this time, the ammonia injection pipe 11 of the SNCR denitrification system is closed. The opening of the secondary air outlet baffle is maintained at 30%, the frequency of the secondary fan 9 is maintained at 11Hz, the boiler bed temperature is controlled at 850°C, and the oxygen content of the boiler is controlled to 3.5% by reducing the primary air volume to 5200Nm³ / H. The calcium-sulfur ratio of the limestone in the boiler is 4.5%, the desulfurizer limestone is injected continuously, and the secondary air distribution method for combustion in the boiler is: fully open the lower secondary damper 7 and fully close the secondary damper 6 , the average emission of nitrogen oxides is 112mg / Nm³.

Embodiment 2

[0030] Embodiment 2: The method for reducing nitrogen oxide emissions under the low load of the boiler is different from that of Example 1 in that the calcium-sulfur ratio of the limestone sprayed into the boiler is reduced from 4.5% to 4%, and the desulfurizer limestone After the injection method was changed to intermittent injection, the average emission of nitrogen oxides was 101.6mg / Nm³.

Embodiment 3

[0031] Embodiment 3: The method for reducing the emission of nitrogen oxides under low load of the boiler. The difference from Embodiment 2 is that the secondary air distribution method for combustion in the boiler is changed to: fully close the secondary air door 7 and fully open The average emission of nitrogen oxides is 78.7mg / Nm³ for the upper secondary damper 6.

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Abstract

The invention discloses a method for reducing the emission of nitrogen oxides under the low load of a boiler, and relates to the technical field of the energy saving and emission reduction of boilers.In the prior art, the emission of nitrogen oxides exceeds the standard during the operating of the existing boiler under the low load. A purpose of the present invention is to solve the technical problem in the prior art. According to the technical scheme, the reduction of the oxygen concentration, the reduction of the feeding amount of the desulfurizer limestone, and the change of the secondaryair distribution method are simultaneously used to reduce the emission of nitrogen oxides. With the method of the present invention, the oxygen content of the boiler is reduced so as to reduce the total electricity consumption of the three fans of the boiler, the average emission value of nitrogen oxides is effectively reduced to 71.1 mg / Nm3 from 130.2 mg / Nm3 so as to reduce the waste gas discharge cost, the ash cleaning and maintenance cost can be saved, and the boiler maintenance cost can be reduced.

Description

technical field [0001] The invention relates to the technical field of boiler energy saving and emission reduction, more specifically, it relates to a method for reducing the discharge of nitrogen oxides under low load of the boiler. Background technique [0002] In recent years, the pollution caused by nitrogen oxides (NOx) has become increasingly serious. Its hazards include: 1. Affect human health: photochemical smog has a strong stimulation and carcinogenic effect on respiratory organs; 2. Affect forest and crop growth: acid rain damage The nutrient cycle of crops and tree root systems; 3. Affect the global climate: destroy the cycle of ozone, reduce the thickness of the ozone layer, and trigger the greenhouse effect. Therefore, it is imperative to take effective control measures against it. [0003] In the prior art, the SNCR technology is generally used to reduce the emission of nitrogen oxides. SNCR denitrification technology is selective non-catalytic reduction tec...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): F23C10/28F23J15/02
CPCF23C10/28F23J15/003F23J15/02F23J2215/10F23J2219/10
Inventor 方昌军赵斌孙剑斌
Owner 上海金联热电有限公司
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