氨精馏塔腐蚀失效原因分析

某炼油厂污水汽提装置氨精馏塔发生腐蚀失效，在塔的上部存在严重的冲刷腐蚀沟槽区和点蚀区，沟槽区局部腐蚀减薄穿孔，点蚀区塔壁最薄为10．73ram（最厚14．23mm）。文章从宏观腐蚀形貌、腐蚀介质、材质化学成分、金相显微观察等方面分析了腐蚀发生的原因。腐蚀主要是由塔内冷凝液的酸腐蚀和垢下腐蚀、N}{4HS的冲刷腐蚀、湿硫化氢环境下的氢损伤造成的。因此，可以采取以下预防腐蚀的措施：选用抗HIC钢板；将塔的中间冷却器改到塔外，同时控制原料中H2S质量浓度不超过设计指标3mg/L，其它杂质含量及塔污水中N｜14HS质量分数浓度不大于2％以及其他杂质含量不超标。腐蚀监控应增加塔体的定点测厚布点，并扩大腐蚀监控范围，预防相近部位腐蚀的发生。

Corrosion Failure Analysis of An Ammonia Fractionation Tower

The corrosion failure occurred in the ammonia fractionation tower in the sour water stripper of a refinery. There were serious erosion and corrosion pitting in the upper tower. Some areas in the erosion zone failed. In corrosion pitting zone, the minimum thickness was 10.73 mm, while the maximum thickness was 14.23 mm. The root causes of corrosion failure were analyzed through macro - morphology, analysis of corrosive media and chemical composition of materials as well as metallographicanalysis. The culprits of corrosion were acid corrosion and under - deposit corrosion of condensates, erosion - corrosion of NH4 HS, and hydrogen damage under wet H2 S environment. The corrosion prevention measures were adopted such as selection of anti - HIC steel, installation of inner - cooler outside of the tower, control of HzS of feed less than 3 mg/L and the concentration of NH4HS in waste water of tower to lower than 2% （wt）. The on - pot thickness measurements should be increased and the other equipment and pipelines in ammonia system should be monitored to prevent corrosion.