加工塔河劣质稠油的常压塔塔顶工艺防腐蚀

Process Corrosion Prevention for Overhead System of Atmospheric Tower in Processing Tahe Low-quality Heavy Crude Oil

自2015年8月开始,中国石化塔河炼化有限责任公司常压塔塔顶腐蚀情况明显加剧,常压塔回流罐的铁离子质量浓度最高达到200 mg/L,平均10 mg/L,大幅超标,造成数台常压塔顶空冷器腐蚀泄漏,严重影响到装置安全稳定生产。针对该问题分析了常压塔塔顶腐蚀机理并提出相应的工艺防腐措施。通过塔顶化验数据到现场采样观察,分阶段采取了优化电脱盐操作、常压塔在线水洗、停运部分空冷、优化氨水及缓蚀剂注入量等措施,取得了阶段性性效果。通过进一步分析最终找出关键原因,即塔顶腐蚀环境p H值控制过高,氨水注入后容易形成氯化铵盐结晶,造成垢下腐蚀;中和缓释剂注入量过大,造成油水乳化。在逐渐降低常压塔塔顶氨水和中和缓蚀剂的加注量后,将塔顶系统p H值下调至7.5左右,常压塔塔顶腐蚀程度得到有效控制,常压塔回流罐的铁离子质量浓度降至3 mg/L以下。

The corrosion has been deteriorating in the overheat of atmospheric distillation tower in SINOPEC Tahe Petrochemical Company ever since August, 2015. The iron ions in the reflux drum of atmospheric tower is 200 mg/L maximum and 10 mg/L average, which exceed the required specifications. As the results, the corrosion leaking has occurred in the overhead air coolers, which has affected the safe and stable operation of the unit. Corresponding process corrosion prevention measures are proposed based upon the analysis of corrosion mechanisms. Good results have been achieved after implementation of those measures such as site sampling and analysis of atmospheric tower overhead, optimization of electro - static dosalting operation, on - line cleaning of atmospheric tower, shutdown of part of air coolers, optimization of addition of liquid amine and corrosion inhibitor, etc. The critical causes are found through further analysis, i. e the pH in the overhead corrosive environment is too high, the amine chloride crystallization can be easily formed after injection of liquid amine which results in under - deposit corrosion; The dosage of corrosion inhibitor is also too large, which leads to emulsion of oil and water. After lowering the addition of liquid amine and corrosion inhibitor in the atmospheric tower overhead and the pH value is controlled at about 7.5, the overhead corrosion of atmospheric tower is brought under effective control, and iron ion in the reflux drum of atmospheric tower is reduced to less than 3 mg/L.