Advanced strategies for conversing and fixing sulfur during waste resins oxidation through Ca/Zn oxides enhanced Na2CO3-K2CO3 system

Abstract

The effective reduction of sulfur pollutant emissions during the treatment of waste resins has always posed a challenge. This study put forward a solution to using the metallic oxide enhanced Na2CO3-K2CO3 system for the treatment of waste resins (CERs). Na2CO3-K2CO3 was used as a medium for heat transfer and desulfurization, while CaO or ZnO functioned as catalysts in the sulfur conversion process. The thermodynamic analysis substantiated the reliability of enhanced sulfur fixation by CaO and ZnO. H2S, SO2 and COS primarily generated during the destruction stage of -SO3H (280–500°C) and residues (∼700°C), which were largely absorbed through a vapor-liquid-solid reaction to generate CaCO3, ZnS and K2SO4. CaO improved the conversion of sulfur to sulfate and effectively mitigated the excessive emissions of CO2. SO2 generated by the oxidation of ZnS at about 800 °C could be further absorbed by molten Na2CO3-K2CO3 to form K2SO4. The proposed method exhibited in-situ desulfurization capability and effectively inhibited the sulfur migration to gaseous products. At 800°C, the sulfur retention rate, the formation rate of SO42- and the oxidation efficiency of CERs reached 91.39 %, 80.61 % and 99.99 %, respectively. The existence of CaO and ZnO facilitated the inorganic transformation of organic sulfur, and the efficient conversion of organic sulfur into inorganic compounds was achieved. This approach provides a new opportunity to improve the treatment efficiency of radioactive solid waste containing organic sulfur.