Investigation of the Effect of Increasing Solvent and Demulsifier on Desulfurization of Spent Caustic from Demercaptanization Units

In this work, the separation of disulfides from spent caustic in demercaptanization units has been studied on laboratory and bench scales. The effect of increasing demulsifier on various variables such as chemical structure, concentration, solvent effect, and residence time with regards to the performance of the desulfurization of caustic has been experimentally investigated. The results show that a high efficiency of spent caustic recovery can be achieved using optimal concentrations of demulsifier and solvent. By increasing demulsifier, sulfur compounds in caustic are reduced to about 20 ppm. In this process, the best solvent for caustic desulfurization was the one similar to the original oil cut with low sulfur content. The spent caustic solution will therefore be recyclable. The operation conditions were environmentally friendly and cost effective.