Boiler smoke recirculation system and method

Abstract

A boiler smoke recirculation system comprises a draught fan, a main air pipe, auxiliary air pipes, spray pipe groups and the like. The draught fan is arranged on the main air pipe. The start end of the main air pipe is connected with an outlet of a dust collector. The tail end of the main air pipe is located outside the lower portion of a hearth of a boiler. The auxiliary air pipes are connected to the tail end of the main air pipe. The spray pipe groups are connected to the tail ends of the auxiliary air pipes and each comprise an upper spray pipe and a lower spray pipe. An opening of each upper spray pipe is arranged at an OFA supply opening of the upper portion of the hearth of the boiler. An opening of each lower spray pipe is arranged at a primary air opening of the hearth of the boiler. The flow of recirculation smoke is adjusted through a main air valve. The recirculation rate of the recirculation smoke is made to be 10-30%. The recirculation smoke is adjusted and distributed byan upper air valve and / or a lower air valve so that the ratio between the amount of the smoke entering the hearth via the upper spray pipes and the amount of the smoke entering the hearth via the lower spray pipes is 2:8-8:2. By the adoption of the boiler smoke recirculation system, through adjustment of the recirculation rate of the smoke and adjustment of the flow ratio between upper smoke andlower smoke of the hearth, the flame temperature and the outlet temperature of the hearth are effectively adjusted, and operation is flexible and easy; and emission of nitrogen oxides is reduced, andthe contamination problem caused by combustion of high-alkali metal fuel is relieved.

Description

technical field

[0001] The invention relates to a boiler flue gas recirculation system and a method thereof, belonging to the technical field of combustion technology. Background technique

[0002] The concentration of nitrogen oxides has a strong correlation with the generation of PM2.5, which causes smog. Most coal-fired power plants in China have completed ultra-low emission transformation, that is, nitrogen oxides (NO x ) concentration below 50mg / Nm 3 , but with the strengthening of national environmental protection efforts, it is more difficult to further reduce the concentration of nitrogen oxides in boiler flue gas. Severe contamination occurs during the combustion of high-alkali metal fuels in boilers. The current pollution prevention and control measures will greatly increase the operating costs of boilers.

[0003] A large number of practices have shown that reducing the boiler flame temperature can help reduce nitrogen oxides (NO x ), and reducing the temperatu...

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