The invention relates to an ultra-clean
discharge method for a
fluidized bed boiler. The ultra-clean
discharge method comprises the following steps of: carrying out in-furnace primary desulfurization in a dense-phase region of the
fluidized bed boiler; carrying out primary denitration based on SNCR on the outlet of a furnace cavity; carrying out high-temperature dust removal on a
smoke gas which is subjected to the in-furnace primary desulfurization and the primary denitration, and then carrying out secondary denitration based on SCR; carrying out heat exchange on the
smoke gas subjected to the secondary denitration to normal
smoke discharge temperature, and introducing the smoke gas into a low-temperature dust remover for secondary dust removal; delivering the smoke gas subjected to the secondary dust removal into a desulfurizing
system for secondary desulfurization. The invention also provides a corresponding
system. According to the method and the
system provided by the invention, two-stage dust removal is performed by adopting high-low temperature dust removal devices, combined denitration is performed by combining SNCR and SCR manners, desulfurizing is realized by adopting in-furnace and out-of-furnace manners and accurate control is carried out through a
combustion optimization technology and environmental-friendly system parameter, so that the discharge of
NOx and SO2 reaches the discharge standard of a gas
turbine unit in a key region of the 'fossil-fuel power
plant atmospheric
pollutant discharge standard' GB13223-2011; in addition, the corresponding system provided by the invention has the advantages of high denitration efficiency, high desulfurization effect, high system reliability, high working condition adaptability, good
NOx and SO2 discharge
controllability, long operation period, low operation cost and the like.