加氢装置高压换热器失效分析及铵盐腐蚀结晶温度的变化规律研究

通过分析某煤柴油加氢装置高压换热器（E-104）管束失效案例，初步判断系统存在铵盐垢下腐蚀风险。建立了反应流出物系统的仿真模型，由此分别计算失效换热器管程、壳程发生铵盐结晶的风险，结果表明：所研究系统中不存在NH₄HS结晶风险；系统铵盐结晶温度随腐蚀性元素含量的提高稍有提高；在原工况、新工况下，热高压分离气系统的NH₄Cl结晶温度分别为177℃和181℃，冷低压分离油系统的NH₄Cl结晶温度分别为178℃和182℃，在原工况操作条件下，E-104的管、壳程均存在NH₄Cl结晶的风险。通过正交试验确定各因素对NCl结晶温度的影响程度由高到低的顺序为：Cl元素含量＞N元素含量＞系统气相流量＞系统操作压力，并进一步得到NH4Cl结晶温度随Cl、N含量的变化规律，利用此规律进行预测将大大提高对NH4Cl结晶温度的预测效率。

FAILURE ANALYSIS OF HIGH PRESSURE HEAT EXCHANGER OF HYDROTREATING UNIT AND STUDY ON CHANGE RULE OF AMMONIUM SALT CORROSION AND CRYSTALLIZATION TEMPERATURE

The failure cases of the E-104 tube bundles was analyzed and preliminarily judged that the system had corrosion under the ammonium salt scale. Then a simulation model of the reaction effluent system was established through software simulation. The risk of ammonium salt crystallization in the tube side and shell side of the failed heat exchanger was calculated. It was found that there was no risk of NH₄HS salt formation in the studied system. The ammonium salt crystallization temperature of the system increased slightly with the increase of the content of corrosive elements. The crystallization temperature of NH₄Cl in the hot high gas separation system in the original working condition and under new conditions were 177 ℃ and 181 ℃ respectively，and the NH₄Cl salt formation temperature of the cold low oil separation system were 178 ℃ and 182 ℃ respectively，which showed that under the original operating conditions，there was a risk of NH₄Cl crystallization in both the tube and shell side of E-104. Furthermore，the order of the factors affecting the crystallization temperature of NH₄Cl was determined as follows：content of Cl>content ofN >system gas flow rate>system operating pressure through the design of orthogonal experiments.What’s more，athree-dimensional map to predict the content change pattern was obtained，which will greatly improve the prediction efficiency of the NH4Cl salt temperature.