Low-temperature flue gas recirculation system and method for low NOX under Pi type boiler under low load

Abstract

The invention discloses a low-temperature flue gas recirculation method for low NOX under a Pi type boiler under low load. The low-temperature flue gas recirculation method for low NOX under the Pi type boiler under the low load is characterized in that a part of flue gas is extracted from an inlet flue of a boiler economizer through a low-temperature recirculation fan to serve as low-temperaturerecirculation flue gas and is mixed with cold and hot air in a cold primary air pipe and a hot primary air pipe, then the mixed gas is introduced into a coal mill and enters into combustors by carrying pulverized coal, and volume proportions of all components in the mixed gas are adjusted through a cold primary air valve, a hot primary air valve and a low-temperature flue gas valve. The system comprises a primary fan, the low-temperature recirculation fan, a coal falling hopper, the coal mill, the combustors, a hearth, over fire air nozzles, a platen superheater, a superheater, a reheater, theeconomizer, an SCR catalyst layer, an air preheater, a temperature sensor, a mixing chamber, an oxygen meter, the hot primary air pipe, the cold primary air pipe, the low-temperature recirculation flue gas pipe, the low-temperature flue gas valve, the cold primary air valve, the hot primary air valve, an electric dust collector, an induced draft fan, a desulfurizing tower and a chimney.

Description

technical field [0001] The invention relates to the technical field of reducing NOx in π-type coal-fired boilers, in particular to a low-temperature flue gas recirculation system and method for low-NOx low-load of π-type boilers. Background technique [0002] With the increase in the installed capacity of renewable energy generators in my country, the power generation of coal-fired generators has been greatly reduced, making the load on coal-fired boilers lower and lower. Wealthy, which requires coal-fired boilers to improve peak-shaving capacity. The pulverized coal used for boiler combustion is blown into the furnace by the primary air flowing through the coal mill. However, when the boiler operates under low load conditions, in order to maintain the powder-carrying capacity, the primary air volume cannot decrease in proportion to the coal supply volume, resulting in an increase in the air-to-coal ratio of the primary air nozzle, that is, an increase in the oxygen-to-coal ...

AI Technical Summary

Problems solved by technology

[0005] In order to solve the defects that the primary air powder-carrying capacity of existing coal-fired boilers is limited during low-load operation, the oxygen-to-coal ratio is increased, and the amount of NOx generation is increased, the purpose of the present invention is to provide π-type boilers with low NOx The low-temperature flue gas recirculation system and method decouple the oxygen volume and flow rate of the primary air, and control the primary air volume and oxygen volume respectively, so as to realize the high primary air volume and reduce the oxygen volume under the low-load condition of the boiler, thereby reducing NOx The purpose of generating volume

Images