CTA干燥机列管腐蚀机理及原因分析

摘要

在精对苯二甲酸(PTA)生产中,氧化单元的粗对苯二甲酸(CTA)干燥机列管发生严重腐蚀,影响了装置的稳定运行,对干燥机列管腐蚀的机理及原因进行了分析,并提出延长干燥机列管使用寿命的措施.结果表明:干燥机常见的腐蚀形态是点蚀、垢下腐蚀、磨损腐蚀,腐蚀形态与CTA物料中溴离子含量、物料温度以及列管材质等有关;列管表面的点蚀和垢下腐蚀以及物料对管子的冲刷磨损是CTA干燥机列管腐蚀的主要原因;控制CTA中溴离子含量、优化工艺参数、更换高性能材质的列管,可有效缓解列管腐蚀,从而提高干燥机的运转周期和运行稳定性.%The serious corrosion of crude terephthalic acid (CTA) dryer tubes of oxidation unit impacted the steady production of purified terephthalic acid (PTA).The corrosion mechanism and reasons for CTA dryer tubes were analyzed.The measures to prolong the service life of dryer tubes were put forward.The results showed that the normal corrosion morphology of the dryer in-cluded the pitting corrosion, under-deposit corrosion and abrasion corrosion and was related to the bromine ion content, feed-stocks temperature and tube material;the dominant reasons for CTA dryer tube corrosion comprised the pitting corrosion and un-der-deposit corrosion on the tube surface and scour pit of feedstocks on the tubes; the tube corrosion could be efficiently de-pressed by controlling the bromine ion content of CTA, optimizing the process parameters and applying high-performance tube, hence the operation period and stability of the dryer could be enhanced.