常压塔顶系统中有机胺盐结晶风险预测

Risk prediction of amine salt crystallization in overhead systems of atmospheric towers

在炼油厂中,向常压塔顶管系注入中和剂(主要包含无机氨或各类有机胺)是解决露点腐蚀的主要措施,但中和剂的种类选择不合适及其过量使用将诱发塔顶管系的铵盐或有机胺盐结晶腐蚀。为研究不同有机胺盐的结晶特性,评估塔顶管系腐蚀风险,通过实验测定了甲胺盐酸盐、乙胺盐酸盐、二甲胺盐酸盐、吗啡啉盐酸盐和4-(2-氯乙基)吗啉盐酸盐的分解平衡压力;利用Aspen Plus对注入中和胺后的常顶工况进行了相平衡模拟。结果表明,该常顶系统中不会发生有机胺盐结晶,但会发生氯化铵结晶,结晶温度(115℃)高于水露点温度(85℃),故存在氯化铵结晶沉积垢下腐蚀风险;增加注水量至7200 kg×h-1,水露点前移至注水点,可避免露点腐蚀,氯化铵的结晶温度降至113℃,增加注水量对氯化铵结晶沉积垢下腐蚀影响不大。

Neutralizer(mainly ammonia and organic amines)injection into overhead systems of atmospheric towers is a main way to solve dew-point corrosion in refineries.However,inappropriate selection and overdose of neutralizers induce crystallization corrosion of ammonium salts or amine salts in the overhead system.In order to study the crystallization characteristics of different amine salts and evaluate the corrosion risk,the decomposition equilibrium pressures of methylamine hydrochloride,ethylamine hydrochloride,dimethylamine hydrochloride,morpholine hydrochloride and 4-(2-chloroethyl)morpholine hydrochloride were measured by experiments.In addition,the phase equilibria simulation of the overhead working condition after amine injection was performed by Aspen Plus.The results show that the crystallization of amine salts does not occur in the overhead system,but the crystallization of ammonium chloride happens.The crystallization temperature(115℃)is higher than the water dew point temperature(85℃),thus with a risk of under-deposit corrosion of ammonium chloride crystallization.Water dew point moves forward to the water injection point and the dew-point corrosion can be avoided by increasing water injection flow rate to 7200 kg×h-1,but it has little effect on the under-deposit corrosion of ammonium chloride crystallization since the crystallization temperature is reduced to 113℃.