ENV-00-193 WET OXIDATION OF REFINERY SPENT CAUSTIC: A REFINERY CASE STUDY

Description:

In 1995, a wet oxidation system was put into operation for treatment of refinery spent caustic from gasoline sweetening, gasoline and LPG prewashing and from gasoline and LPG mercaptans extraction at the Refinaria de Petroleos de Manguinhos, S.A. (Manguinhos) in Rio de Janeiro. Manguinhos is a producer of liquid fuels and is located near residential property within Rio de Janeiro. Prior to installing a wet oxidation system, the refinery was dependent on off-site disposal of their spent caustic. In considering on-site treatment, there was great concern for odors since the refinery was in a populated area. The refinery concluded that wet air oxidation was the best choice for their scenario, allowing for on-site treatment without the production of odorous off-gas. After treatment by wet oxidation, the oxidized spent caustic is sent to the refinery’s biological treatment system for final treatment. System performance includes complete removal of sulfides, mercaptans, and thiosulfates as well as significant reductions in phenols and overall chemical oxygen demand (COD). The oxidized spent caustic is polished in the on-site biological treatment facility before discharge.