Reduction of SO2 with CO to Elemental Sulfur in Activated Carbon Bed

To develop a new process for reducing high-concentration SO2 to elemental sulfur, the reduction of SO2 with CO and activated carbon in a fixed bed experimental system was investigated. The effects of temperature, CO/SO2 molar ratio, and reaction time on SO2 reduction were studied. The results showed that the starting temperature of SO2 reduction with activated carbon was approximately 700 degrees C and that the addition of CO decreased the starting temperature to 400 degrees C. Higher temperature led to an increase in SO2 conversion. The S yield also increased initially but then decreased when the temperature exceeded 800 degrees C, due to the formation of COS. SO2 conversion increased with an increasing CO/SO2 molar ratio, the optimum S yield being achieved at a CO/SO2 ratio of 2. However, the existence of unreacted SO2 in the product decreased the S yield and resulted in an optimum S yield occurring at a low ratio. Lower selectivity of SO2 reduction to elemental sulfur was observed if reaction time was reduced. By prolonging gas-carbon contact time, the S yield increased and gradually approached SO2 conversion at temperatures below 700 degrees C. The catalytic mechanism over activated carbon conformed to the COS intermediate mechanism, and the rate of the overall CO-SO2 reaction was determined by the Claus reaction between COS and SO2.