梳理了常减压塔顶系统的腐蚀案例，介绍了塔顶系统腐蚀的主要类型：露点腐蚀与铵盐腐蚀。提出了运用多相平衡体系计算方法得到了塔顶露点温度，深入了解了露点腐蚀的规律性特点，提出了注氨、注水等切实可行的防腐蚀措施。根据案例中的具体工艺参数，通过求解热力学方程，得到了铵盐结晶平衡曲线和计算公式，判定了铵盐结晶趋势和温度范围，深入探讨了铵盐腐蚀的规律性特征。

The corrosion cases of overhead system of atmospheric and vacuum distillation unit were sorted out, and the main types of corrosion of the overhead system:dew point corrosion and ammonium salt corrosion, were introduced. Multiphase equilibrium system calculation method was used to obtain the dew point temperature at the overhead. The regular characteristics of dew point corrosion were deeply understood, and effective anti-corrosion measures such as ammonia injection (amine) and water injection were proposed. According to the specific process parameters in the case, the equilibrium curves and calculation formula of ammonium salt were obtained by solving the thermodynamic equation. The crystallization tendency and temperature range of ammonium salt were determined, and the regularity of ammonium salt corrosion was discussed in depth.