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Title:: Analysis and countermeasures of desalination water system operation problems in polypropylene plant

Author(s):: LIU Jun; WANG Yu-kun; WEI Zhen-jiang; No.3 Refinery Division of Ningxia Petrochemical Company，PetroChina，Yinchuan 750021，China

Keywords:: polypropylene; drying system; desalination water; overflowing water; washing water; recycle; energy saving

摘要:: 对中国石油宁夏石化公司10万t/a聚丙烯（PP）装置除盐水单耗高的原因进行了分析，并采取了相应的改进措施。结果表明：用于挤压造粒工段和干燥系统N2洗涤塔（T-502）的除盐水用量较大，且T-502溢流口洗涤水未得到有效回收利用是装置除盐水单耗高的主要原因；通过增设回收-过滤水箱对T-502溢流口洗涤水进行回收，同时定期用新鲜除盐水对T-502内自循环洗涤水进行补水置换，使装置除盐水单耗由0.45 t/t降至0.23 t/t，且减缓了因洗涤水杂质增多及呈弱酸性带来的设备腐蚀问题。

Abstract:: The causes of high unit consumption of desalination water in 1×105 t/a polypropylene （PP） plant of Ningxia Petrochemical Company of PetroChina were analyzed， and the corresponding improvement measures were taken. The results showed that the main reason for the high unit consumption of desalination water was that the consumption of desalination water of the N2 scrubber （T-502） of the drying system and the extrusion granulation section was large， and the washing water of T-502 overflow port was not effectively recycled. The washing water of T-502 overflow port was recovered by adding a recovery-filtration water tank， and the self-circulating washing water in T-502 was replaced with fresh desalination water regularly， so that the unit consumption of plant desalination water was reduced from 0.45 t/t to 0.23 t/t， and the corrosion problem of equipment caused by the increase of impurities in washing water and weak acidity was alleviated.