Regeneration and treatment of sulfidic spent caustic using analytic hierarchy process

摘要

Background: Sulfur compounds must be removed from petroleum because they contribute to environmentaludpollution. A strong alkaline solution such as caustic soda is used to remove these compounds. This spentudcaustic has high values for chemical oxygen demand (COD) concentration, pH and total sulfur. In thisudstudy, the regeneration and treatment methodology of sulfidic spent caustic was investigated by applyingudthe analytic hierarchy process (AHP).udMethods: The evaluation index system developed was based on group decision-improved AHP. ExpertudChoice software was used to simplify decision-making when choosing a practical method and prioritizingudtreatment of spent caustic. Cost, environmental considerations, availability and scale-up were chosen asudcriteria and wet air oxidation and biological and catalytic methods were selected as alternative methods. Theudtreatment and regeneration of spent caustic was carried out in a batch bubble column reactor loaded withudIVKAZ catalyst and the effluent was treated in a precipitation-stirred tank reactor.udResults: Evaluation indicated that cost ranked first among criteria at 40.9%. The results showed that theudproposed process produced about 13% (wt) of caustic, 50 g/L of COD and 36 g/L of S2-.udConclusion: The results indicate that the catalytic method was more effective (0.45) than wet air oxidationudand the biological method. This process regenerated more than 85% of initial caustic and the economy ofudthe process improved by the recycling of the stream of caustic.udKeywords: Catalytic oxidation, Wastewater treatment, Recovery, Expert Choice