Abstract:

The spent caustic oxidation unit in a 1.1 Mt/a ethylene plant adopts wet oxidation process. During 15 years of operation, there have been many operation problems such as excessive COD in high saline sewage, leakage of acid injection point elbows, and frequent blockage of the inlet filter of air compressor, which have seriously affected the long-term and stable operation of the spent caustic oxidation unit. This paper analyzes the problems in the operation of spent caustic oxidation unit, and puts forward some improvement and preventive measures. Meanwhile, based on the consumption of various working media in the spent caustic oxidation unit and combined with production and operation experience, a series of optimization measures for energy saving and consumption reduction are proposed to reduce the cost of spent caustic treatment. In combination with the current environmental protection requirements, the odor of the spent caustic oxidation unit is reduced through technological transformation measures, so as to achieve the goal of a win-win situation for long-term operation and environmental protection.

Key words: wet oxidation of spent caustic, COD, grease, acid-base corrosion, odor control