ABSTRACT
Background: sulfur compounds must be removed from petroleum because they contribute to environmental pollution. A strong alkaline solution such as caustic soda is used to remove these compounds. This spent caustic has high values for chemical oxygen demand [COD] concentration, pH and total sulfur. In this study, the regeneration and treatment methodology of sulfidic spent caustic was investigated by applying the analytic hierarchy process [AHP]
Methods: the evaluation index system developed was based on group decision-improved AHP. Expert Choice software was used to simplify decision-making when choosing a practical method and prioritizing treatment of spent caustic. Cost, environmental considerations, availability and scale-up were chosen as criteria and wet air oxidation and biological and catalytic methods were selected as alternative methods. The treatment and regeneration of spent caustic was carried out in a batch bubble column reactor loaded with IVKAZ catalyst and the effluent was treated in a precipitation-stirred tank reactor
Results: evaluation indicated that cost ranked first among criteria at 40.9%. The results showed that the proposed process produced about 13% [wt] of caustic, 50 g/L of COD and 36 g/L of S[2-]
Conclusion: the results indicate that the catalytic method was more effective [0.45] than wet air oxidation and the biological method. This process regenerated more than 85% of initial caustic and the economy of the process improved by the recycling of the stream of caustic