加氢精制高压换热器管箱隔板脱落原因及分析

介绍了青岛石油化工有限责任公司加氢精制装置高压换热器E102管程压力差不断上升,最高至0.9 MPa,经分析后确定为氯化铵盐结垢堵塞管束,导致管程压力降异常。文章阐述了对换热器进行注水处理的过程并列举了相关化验数据,数据显示系统内Cl-质量浓度较高明显超过25 mg/L。再次投用换热器后换热温差最高仅5℃,完全没有换热效果。拆检换热器发现管箱隔板脱落,导致管程短路,造成设备失效。对连多硫酸腐蚀、Cl-应力腐蚀开裂的原理及设备故障情况进行了分析判断。该换热器故障的主要原因为奥氏体不锈钢的Cl-应力腐蚀,从而导致角焊缝处开裂,致使焊接处强度变弱,在物料的冲击下,管箱隔板脱落。针对加氢精制装置原料Cl-超标后带来的危害以及在处理过程中需要注意的问题提出了建议。

Falling of Baffle in Hydrotreater High - pressure Heat Exchanger Tube Box and Cause Analysis

In SINOPEC Qingdao Petrochemical Co., Ltd., the differential pressure of hydrotreater high - pressure heat exchanger E102 tube side increased to maximum 0.9 Mpa. The analysis identified it as abnormal pressure drop caused by fouling plugging by ammonium chlorides. The process of water injection into the heat exchanger was described, and relevant analysis data were listed, which indicated that the Cl^- concentration was too high, exceeding 25 ppm. When the heat exchanger was re - started, the heat transfer temperature was only 5 ℃, and there was no heat transfer effect. The overhaul of the heat exchanger found that the baffle of tube box fell of, which caused the short circuit of the tube side and the subsequent equipment failure. The mechanisms of polythionic acid corrosion and chloride stress corrosion cracking were described and causes of equipment failure were analyzed. It was concluded that the culprit of failure was the fillet weld cracking caused by chloride stress corrosion, which led to the reduced strength of the welded point. Under the impingement of the effluent, the tube baffle finally fell off. The hazards by the excessive Cl^- in the hydrotreater feedstock and the precautions in the treatment were presented.