蜡油加氢装置汽提塔顶后冷器腐蚀与防护

Corrosion Analysis and Countermeasures of After-cooler at the Top of Stripping Tower of VGO Hydrogenation Unit

针对某石化公司蜡油加氢装置后冷器管束的腐蚀泄漏,采用现场腐蚀调查、在线腐蚀探针监测、垢样分析及腐蚀挂片监测等手段,对管束的腐蚀泄漏情况进行了检测分析。结果表明,壳程工艺介质腐蚀性较小,其对碳钢的腐蚀速率仅为0.002 mm/a,而管程循环冷却水腐蚀性偏大,且具有较强的结垢倾向,是造成管束内壁发生穿孔泄漏的主要影响因素。腐蚀区域闭塞电池的自催化作用是促进后冷器管束腐蚀加速发展的根本原因,其与循环冷却水中的溶解氧及氯离子有密切的关系。最后,从加强冷却水系统管理、改善系统水质及涂料防护等方面提出了冷却水换热器腐蚀泄漏的防护措施。

Methods of field corrosion investigation,scale analysis,resistance probes and hanging strips monitoring were applied to investigate the corrosion of tube bundle of after-cooler at the top of stripping tower of VGO hydrogenation unit in a petrochemical company. The results show that corrosion of medium in shell side is little,and corrosion rate of carbon steel is only0. 002 mm/a,while circulating cooling water in tube side is strong corrosive and has a obvious tendency of fouling,which is the main cause of leakage in tube bundle. Self-catalysis of occluded corrosion cell in the corrosion area is the fundamental reason for the accelerated corrosion of tube,which is closely related to dissolved oxygen and chlorine ion in circulating cooling water.Accordingly,several measures are suggested to prevent the leakage of heat exchanger of cooling water,such as strengthening the management of cooling water system,improving the water quality of the system and using coating protection.