The development of biomass-fired circulating fluidized bed(CFB) boiler technology is critical for the energy transformation as well as and carbon neutrality in China. By arranging the high-temperature heating surfaces inside the furnace

the slagging and corrosion on surface can be effectively lightened through continuous wash and clean by solid circulating materials. Meanwhile

the ash deposition and fouling on convective heating surfaces at the tail flue can be mitigated by applying in-line tube bundles and parallel flow design

as well as increasing the tube spacing

reducing the tube diameter and lowering the gas velocity. For comprehensively solving the particle agglomeration in the whole circuit and further increasing the boiler combustion efficiency

the performance of solid circulation loop is necessary to be improved and the bed temperature should be accurately selected and controlled.Besides

properly injecting some clay carried by feeding biomass to furnace can also alleviate the agglomeration of bed materials. Three biomass-fired CFB boilers with high steam parameters were designed and constructed based on the technical routes introduced in this paper. Industrial practice showed that all of them can be operated stably in a wide load range

and no shutdown accident happened due to slagging and corrosion on heating surfaces. The boiler efficiency generally exceeded 91%

and the ultra-low NO_x and SO_2 emission standards were directly satisfied without using any flue gas denitrification nor desulfurization device. Various performance indicators basically met or even exceeded the design requirements.