(592b) Optimization Study for Wet Air Oxidation of Ethylene Plant

Authors: 
Khurram, S., Sabic
Optimization study for wet air oxidation of Ethylene plant.

Shehzada Khurram P.E Staff Scientist Olefins & Aromatics Department SABIC Saudi Basic Industries Corporation Saudi Arabia.

Abstract:

The objective of this study is to optimize the spent caustic unit in order to increase the run length. The scope of this study is to explore the opportunities and find out the short coming of the process, which cause the short length of the unit. In addition to this, suggest solutions to overcome the problem to increase overall plants efficiency, and decrease environmental impact as part of sustainability. The drive of this paper is to provide insight into the design of a wet air oxidation System, as it is applied on a full scale basis for spent caustic treatment. There are numerous design parameters, including temperature and pressure. The variations in spent caustic characteristics and treatment objectives must be carefully considered.

Red oil formation is not new for ethylene producers. For numerous years ethylene producers have been over warned with red oil associated fouling problems in oxidizers. To deal with issues normal practice is to treat the Caustic tower. In normal process there is currently no treatment in Caustic tower. Caustic towers at ethylene plants remove acid gases, hydrogen sulfide (H2S) and carbon dioxide (CO2) from ethylene gas. The spent caustic from these towers contains mercaptans and sulfides, which are reactive and odorous. Accordingly, the spent caustic requires special handling and treatment before being discharged to a conventional wastewater treatment plant. Often, the spent caustic is most commonly mated in an oxidation reactor. Also known as wet air oxidation (WAO). This process converts the sulfides into oxidation products such as sulfate ions.