Surrounding air method for reducing NOx emission concentration of power station pulverized coal powder plant boiler

Abstract

The invention provides a surrounding air method for reducing the NOx emission concentration of a power station pulverized coal powder plant boiler. The method includes the specific step of replacing existing secondary air with primary air high in wind pressure under the condition that it is ensured that the total air volume of a hearth is not changed, wherein the primary air is used as surrounding air of a cooling pulverized coal spray nozzle. Because the wind pressure of primary air is higher than the wind pressure of secondary air, after the existing surrounding air is replaced with primary air, the flowing speed of surrounding air is increased. It is ensured that the momentum of surrounding air is constant before and after replacement, and therefore the mass flow rate of surrounding air is correspondingly decreased after replacement. Because the momentum of surrounding air is not changed, the cooling effect the same as that of a combustor can be achieved, and rigidity of the pulverized coal jet flow is also ensured. Meanwhile, the mass flow rate of surrounding air is decreased, and therefore the excess air coefficient of the initial combustion period of pulverized coal is decreased, NO generation in the initial period of combustion is restrained, and therefore the NO emission concentration during running of the boiler is reduced.

Description

technical field [0001] The invention belongs to the technical field of power station boilers, and in particular relates to a perimeter air method for reducing the NOx emission concentration of a power station pulverized coal boiler. Background technique [0002] In 2014, coal-fired generating units accounted for about 78% of my country's total power generation, and this energy structure will not change in the future. Nitrogen oxides NO from coal combustion x (NO, NO 2 and N 2 O) is the main source of air pollutants. NO x It is toxic and can form acid rain and photochemical smog. In order to adapt to the more severe environmental situation, the new "Emission Standard of Air Pollutants for Thermal Power Plants" (GB13223-2012) will power plant boiler NO x Emission concentration is limited to 100mg / m 3 , 200mg / m for individual furnace types and regions 3 , so active coal-fired boilers need to take effective measures to reduce NO x emission. At present, the reduction of...

AI Technical Summary

Problems solved by technology

The use of low nitrogen combustion technology in power plant boilers can effectively reduce the NO in the furnace x emission concentration, but there is still a big gap to meet the increasingly stringent environmental indicators. It is necessary to run the SCR system on the unit, which can basically meet the NO x However, this will increase the operating cost of the power plant, especially under the unit load operating condition (≦65% ECR), the operating oxygen is higher than the high load, and the excess air coefficient in the main combustion area is significantly higher than the high load , which weakens the air staging effect in the furnace, increases the air / fuel ratio at the initial stage of combustion, and promotes the NO x formation reaction, which weakens the NO x reduction reaction, NO in the furnace x The emission concentration is higher, which further increases the operating cost of the SCR system and may also cause NO x Exceeding emission standards

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