For the supercritical 350 MW unit circulating fluidized bed(CFB) boiler in Shenhua Shendong Shanxi Hequ Power Generation plant(Hequ CFB plant)

the ultra low emission technological route is efficient desulfurization and nitrogen suppression in the furnace

selective non-catalytic reduction(SNCR) denitration and CFB flue gas desulfurization system outside the furnace. By means of site test

the influence of parameters such as bed temperature

oxygen concentration and mole ratio of calcium to sulfur inside the furnace on emission characteristics of NOx and SO2 was verified

and the effects of adding limestone into the furnace and setting pre-electrostatic dust precipitator on economy of desulfurization and denitration were also discussed. The results indicate that

the SO_2 concentration at entrance of the CFB flue gas desulfurization system outside the furnace can be controlled by adjusting the operation parameters. The optimal operation parameters were chosen after carefully comparing the boiler efficiency

limestone consumption inside and outside the furnace and urea consumption in the denitration system

then the optimum combustion efficiency and economy of desulfurization and denitration were achieved. Setting the pre-electrostatic dust precipitator at inlet of the CFB flue gas desulfurization system increased the unit economy. The research can provide references for the newly built and retrofitted large-scale CFB units with CFB flue gas desulfurization system.