Abstract: A lithium salt rotary kiln plant adopts CFB semi-dry desulfurization technology. Due to thelarge fluctuation of SO2 concentration at different mineral aggregate inlets ( 500 ~4 000 mg /Nm3) ,thebed operates unstably at the beginning,and the hourly mean concentration of SO2 at the outlet fluctuatesbetween 20 and 500 mg /Nm3. In the optimized design,the operation stability of the system was im-proved by adjusting the deflector,venturi,return inlet and spray gun. The operation results showed thatwhen the inlet gas contained medium or high concentration of SO2,the hourly mean concentration ofSO2 at the outlet was ( 20±5) mg /Nm3,which met the local standards for ultra-low emission ( hourlymean concentration of SO2≤35 mg /Nm3) . Close-