加氢处理系统NH4Cl结晶沉积预测及优化防控

通过热力学计算获得NH₄Cl结晶反应的平衡曲线，分析冷换设备中NH₄Cl结晶沉积机理；针对某石油化工厂典型加氢反应流出物冷却分离工艺，运用Aspen仿真软件建立多相平衡体系，计算获得气相中K_p即p_HCl×p_NH3随温度的变化曲线；结合二者建立加氢反应流出物冷却分离系统NH₄Cl结晶预测模型，计算获得含不同N、Cl质量分数进料的NH₄Cl结晶温度，并提出基于NH₄Cl 结晶沉积预测的冷却分离系统注水优化方案。结果表明，冷换设备中NH₄Cl结晶沉积存在自加速过程，典型工况下NH₄Cl结晶温度在155~205℃范围，主要发生在热高压分离高压换热器和空冷器内；根据进料N、Cl的质量分数预测NH₄Cl结晶温度，并及时移动注水位置和调节注水量，可有效防止NH₄Cl结晶沉积及垢下腐蚀。

Prediction of NH4Cl Crystalline Deposition and Optimized Prevention Method in Hydrotreating Unit System

Based on the thermodynamic calculation, the NH₄Cl crystallization equilibrium curve was obtained. The deposition mechanism of NH₄Cl crystals in the heat exchanger was analyzed. The multiphase equilibrium model of typical cooling and separation system for hydrogenation reaction effluent was established by Aspen simulation software, and the K_p-Tcurve (i.e. (p_HCl×p_NH3)-T curve) was obtained. Based on the above, the NH₄Cl crystalline prediction model of cooling and separation system for hydrogenation reaction effluent was established and the NH₄Cl crystalline temperatures in the feedstock with different N, Cl mass fractions were calculated. The water injection optimization in cooling and separation system for hydrogenation reaction effluent was proposed, according to NH₄Cl crystalline prediction results. The results showed that, the NH₄Cl crystalline deposition in exchangers was a self-acceleration process. The NH₄Cl crystalline temperature ranged from 155℃ to 205℃, which were the operation temperatures of hot and high-pressure heat exchangers and air coolers. By moving injection position and adjusting the amount of wash water promptly, based on the NH₄Cl crystalline prediction results, NH₄Cl deposition and under-deposit corrosion could be effectively restrained.