采用化学分析、宏观观察、扫描电镜及能谱分析等手段,分析了兰州石化500万t/a常减压装置常顶空冷器A-102/8出口线集合管爆管段腐蚀泄漏原因。结果表明,爆管原因是严重的酸性水腐蚀与物流的冲刷作用。该空冷器系统布置不合理造成物流偏流、分配不均,当物流通过分配管时,大量的汽相移向后程,使后程空冷器A-102/5~8中气相比例增大,由于后程空冷器供水不足,气相中H2S在冷凝、溶解过程中,形成高浓度的酸性水溶液,加之所注水溶性中和缓蚀剂在后程空冷器中缓蚀作用的弱化,酸性水溶液没有被均匀中和而形成严重了酸性腐蚀环境,并伴随物流的冲刷作用导致失效。同时,据此提出了相应的建议。

By means of macro-inspection, scanning electron microscopy and EDX, a corrosion failure analysis of broken collecting-tube in exit tube of the A-102/8 air cooler in a 5Mt/a refinery for Lanzhou petrochemical company was carried out. The results show that the reason of corrosion failure was severe acidic water corrosion and erosion-corrosion. The inconsequential design of the air cooler′s feeding tube brought out the deflection and uneven distribution of the feedstock flow, leading to enough gaseous fluid moving into later A-102/5~8 air coolers. The gaseous fluid contained much H2S, which was condensed and dissolved into the water of later air coolers and thus generated severe acidic water, but later air coolers were distributed with little water and corrosion inhibitor, whose dilution function and inhibition function were weakened, so the corrosion failure was engendered by severe acidic water corrosion and erosion-corrosion. Some improvement suggestions were pointed out.