中压湿式空气氧化装置原始开车总结

SUMMARY OF THE INITIAL START-UP OF MEDIUM PRESSURE WET AIR OXIDATION UNIT

2014年2月中国石油四川石化有限责任公司乙烯装置开车过程中,由于废碱液硫化钠含量高,氧化反应剧烈使得废碱液变酸性、废碱液萃取差造成带油,引起设备堵塞、以及总有机碳（TOC）过高及废碱氧化反应出口污水中的化学需氧量（COD）含量始终高于6 000 mg/L（超过设计值）。分析发现废碱液硫化钠含量高和带油是影响废碱液COD的主要原因。通过调整烃汽提塔的汽提蒸汽量,将洗油更换为加氢C6~C8,控制入口硫化钠含量低于4%等方法,可降低湿式空气废碱氧化装置出口污水COD。

During the start-up of the ethylene plant at Petro China Sichuan Petrochemical Co., Ltd. in February 2014, the high content of sodium sulfide in spent caustic and the fierce oxidation reaction turned the spent caustic into acidic,the poor spent caustic extraction resulted in grease formation and then equipment plugging,the TOC was too high,and the COD in the effluent from Wet Air Oxidation( WAO) unit was higher than 6 000 mg / kg,exceeding the design value. The analysis results show that the high content of sodium sulfide in spent caustic and the grease formation are the main factors influencing the COD. By adjusting the hydrocarbon stripper steam, replacing the wash oil with hydrogenated C6~ C8 from the BTX column in pyrolysis gasoline hydrogenation unit and maintaining the content of sodium sulfide at the inlet below 4%,the COD in the effluent from wet air oxidation unit can be reduced.