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Title:: Application of toluene extraction technology for process waterin ethylene cracking unit

Author(s):: GUO Li-shi; BU Ya-kui; ZHANG Guo-dong; HUANG Chao; MA Guo-min; （No.1 Ethylene Department of Dushanzi Petrochemical Company，PetroChina，Karamay 833699，China）

Keywords:: ethylene cracking unit; light feedstock; process water; styrene; coking; toluene extraction technology

摘要:: 中国石油独山子石化公司100万t/a乙烯裂解装置原料轻质化后，致使工艺水中携带的油含量增大，尤其是苯乙烯浓度明显升高，进而形成苯乙烯结焦聚合物，使泵过滤器、换热器、塔填料等相关工艺水使用设备因结焦堵塞、腐蚀泄漏而频发运行故障，严重时导致裂解炉运行周期缩短1%，故新增应用了甲苯萃取技术，以去除降低苯乙烯含量，改善工艺水品质。结果表明：应用甲苯萃取技术后，工艺水中的苯乙烯去除效果较明显，萃取去除率达到92.50%以上；改善了工艺水品质，浊度下降率均值为98.4%，工艺水汽提塔釜工艺水中溶解携带的含油（重烃）质量浓度均值从10.20 mg/L以上下降到1.53 mg/L，最大减幅达到90.6%，塔釜工艺水泵入口滤网的清理频次从每月1次减少至每年2次，减缓了工艺水相关使用设备的结焦/泄漏运行故障及维修频次。

Abstract:: After the lightened feedstock of the 1 Mt/a ethylene cracking unit of Dushanzi Petrochemical Company，PetroChina，the oil content in the process water increased，especially the concentration of styrene. Then the styrene coking polymer was formed，which caused frequent operation failures of the pump filters， heat exchangers，tower packing and other related equipment using such process water due to coking blockage，corrosion and leakage. In the serious case，the operation cycle of the cracking furnace was shortened by 1%. Therefore，the toluene extraction technology was added to remove and reduce styrene content and improve process water quality. The results showed that after the application of toluene extraction technology，the removal effect of styrene in the process water was obvious，and the extraction removal rate was more than 92.50%. The quality of process water was improved as followed，the average turbidity reduction rate was 98.4%， the average concentration of oil in the process water stripper & kettle decreased from more than 10.20 mg/L to 1.53 mg/L，with the maximum reduction by 90.6%. The cleaning frequency of the filter screen at the inlet of the process water pump reduced from 1 time/month to 2 times/a，greatly reducing the coking/leakage operation failure and the maintenance frequency of the equipment used in the process water.