Abstract: At present, mature technologies on the treatment of sulfur-containing spent caustic from million-ton ethylene plants included state-owned wet oxidation technology, imported wet oxidation technology, combination of catalytic oxidation and bioaugmentation technology. Analysis showed that both wet oxidation technologies had excellent treatment effects on thiols and sulfides of ethylene spent caustic, and further the state-owned wet oxidation technology had a higher treatment efficiency, with a COD removal rate of 96.3%. In comparison, the COD removal rate of catalytic oxidation technology was only 81.1%, and GC-MS analysis showed that the effluent from catalytic oxidation still contained a large amount of organic sulfur compounds, while the direct treatment of ethylene spent caustic by bioaugmentation technology had problems such as low treatment efficiency and difficult treatment of odorous gases. Cost and economic analysis showed that state-owned wet oxidation technology had the advantages of high treatment efficiency, low operating costs, low equipment investment costs, and had great promotion and application value.

Key words: ethylene plant, spent caustic, wet oxidation, catalytic oxidation, bioaugmentation