Challenge

Refinaria de Petroleos de Manguinhos (RPDM) is a producer of liquid fuels located near residential areas within Rio de Janeiro. RPDM needed to dispose of spent caustic generated from its gasoline sweetening, gasoline and LPG prewashing, and from gasoline and LPG mercaptans extractions.

Options for spent caustic disposal included their current method of trucking the hazardous material offsite, or treating it onsite. In considering onsite treatment, RPDM was concerned about odors since the refinery was near a populated area.

Solution

After a thorough investigation, RPDM selected a Zimpro® wet air oxidation system for onsite treatment because it does not produce odorous offgas, and the effluent from the system is biodegradable.

In the wet air oxidation process, liquors are pumped to system pressure, mixed with compressed air, and brought to oxidation temperature. In the reactor, the oxidation is autothermal and destroys complex organics or reduces them to biodegradable forms or to carbon dioxide and water.

The wet air oxidation system used by RPDM was skid-manufactured in the United States and shipped to Brazil, and was designed to treat 2 gallons per minute of spent caustic.

Results

The wet air oxidation unit at RPDM has worked very well. Sulfide levels have been reduced to below detection limits, approximately 80 percent destruction of COD is achieved and near complete phenols (cresylic) destruction is achieved. No sulfide or mercaptan odor is present in the offgas or in the liquid effluent.

After treatment, the oxidized spent caustic at RPDM is sent to the conventional biological unit for final treatment.

Download the full technical paper.