Abstract: The problem of ammonium salt crystallization is very important for the safe production of the heat exchange system in hydrogenation plant, which often leads to blockage, corrosion leakage, and unplanned shutdown of the heat exchange system. It is of great significance to the study of the crystallization process and distribution characteristics of ammonium salt. In order to explore the problem of ammonium salt corrosion failure in the high pressure heat exchanger of diesel hydrogenation plant, the ammonium salt crystallization temperature was determined based on the concentration of components, and the C++ ammonium salt crystallization model and user-defined function (UDF) were written. Through isoparametric modeling of the heat exchanger, numerical simulations of the multiphase flow field, heat and mass transfer processes were carried out using ANSYS Fluent finite element analysis software and embedded UDF to analyze the intrinsic causes of corrosion failure. The mechanism of ammonium salt crystallization can be divided into heat transfer control and mass transfer control. The simulated ammonium chloride crystallization corrosion location and the actual corrosion coincided. The significant factors that influence the ammonium salt crystallization can be get through the orthogonal experimental analysis. The independence of the significant factors were analyzed to get the specific impact on the ammonium salt crystallization. Further, it provides a basis for the optimization of process device operation.

Key words: heat exchanger, ammonium salt crystallization, orthogonal analysis, numerical simulation, corrosion failure

摘要： 铵盐结晶问题对于加氢装置换热系统的安全生产至关重要，极易导致换热系统堵塞、腐蚀泄漏和非计划停车，因此，对铵盐结晶过程的研究有着重大意义。针对柴油加氢装置高压换热器铵盐腐蚀失效问题展开研究，依据组分浓度确定铵盐结晶温度，编写C++铵盐结晶模型及用户自定义函数(UDF)。通过对换热器等比建模，利用ANSYS Fluent有限元分析软件并嵌入UDF对其多相流场、传热、传质过程进行数值模拟计算，分析腐蚀失效的内在原因。结果表明，NH4Cl结晶分为传热控制和传质控制两种机理，NH4Cl结晶腐蚀的位置与实际腐蚀吻合；通过正交实验分析得到影响铵盐结晶的显著因素，并对显著因素进行独立性分析得到各因素对铵盐结晶的具体影响。本研究可为工艺装置操作优化提供依据。

关键词: 换热器, 铵盐结晶, 正交分析, 数值模拟, 腐蚀失效