Abstract:The operation mode of SO2 fan for acid-making in Yunnan Tin Company 100000t/a copper smelting project was of soft start on power frequency, which has some problems such as low efficiency, high failure rate and large energy loss. Based on the direct relationship between the rotation speed and the frequency of power supply of asynchronous motor, high voltage frequency converter was selected to carry out speed regulation and energy-saving transformation of SO2 fan for acid-making. After transformation, the SO2 fan for acid-making was controlled by high voltage frequency converter, featured by stable and reliable performance. The annual electricity saving was 4260000kW·h, the annual economic benefit was over 1.5million CNY, indicating remarkable energy saving effect.