Flue gas recirculation method and flue gas recirculation system capable of reducing NOx emission of circulating fluidized bed boiler

Abstract

The invention discloses a flue gas recirculation method capable of reducing the NOx emission of a circulating fluidized bed boiler. Low-temperature flue gas after dust removal treatment and before wet desulphurization is pressurized, mixed with primary air and conveyed to an air chamber in the bottom of a hearth, and the amount of the primary air for fluidization is reduced and the proportion of secondary air is increased in the case of ensuring the invariable total amount of fluidizing air, so that the staged combustion characteristic of the secondary air is enhanced, and the NOx generated by combustion in the boiler is reduced. The invention further provides a flue gas recirculation system capable of reducing the NOx emission of a circulating fluidized bed boiler. The flue gas recirculation system comprises a recirculation pipeline, a recirculation fan, a valve, a flue gas flow meter, a flue gas pressure measurement component, a flue gas temperature measurement component and the like. The system is capable of remarkably lowering the running bed temperature of the circulating fluidized bed boiler, and better realizing air staging needed for low-nitrogen combustion, thereby greatly reducing the NOx emission of the circulating fluidized bed boiler. In addition, the system is capable of being used in combination with an SNCR or SCR technology, and further reducing the NOx emission of the circulating fluidized bed boiler.

Description

technical field

[0001] The invention belongs to the technical field of boiler environmental protection, relates to the emission control of nitrogen oxides (NOx) in flue gas, and particularly relates to a flue gas recirculation method and system for reducing the NOx emission of a circulating fluidized bed boiler. Background technique

[0002] Circulating fluidized bed boiler has the characteristics of wide fuel adaptability, high combustion efficiency and low investment cost, and has been developed rapidly at home and abroad. The technologies for reducing NOx emissions from coal-fired boilers are mainly divided into three categories: low NOx combustion in the furnace, selective non-catalytic reduction flue gas denitrification (SNCR) by injecting reducing agents in the furnace, and selective catalytic reduction flue gas denitrification by injecting reducing agents in the flue behind the furnace. Gas denitrification (SCR for short), these three types of technologies can be used...

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