空冷入口管NH3-HCl-H2S结晶特性预测及注水混合数值模拟

加氢空冷器是炼油化工企业的关键设备之一.近年来中国进口原油以高硫高酸原油为主,原油种类超过150种,加工过程中还存在原油掺炼的情况,工况弹性大、风险突出,因此研究铵盐结晶规律以及注水工艺防护措施成为维护空冷器设备安全运行的重要内容.以某石油化工厂加氢空冷系统入口集合管为对象,依据质量守恒,基于逆序倒推法,建立烃、水两相...

Prediction of Crystallization Characteristics of NH3-HCl-H2S in Air-Cooled Inlet Pipe and Numerical Simulation of Water Injection Mixing

Hydrogenation air cooler is an important equipment in refineries and chemical plants. In recent years, more than 150 different kinds of crudes have been imported, and most of them are high sulfur and high acidity. Usually different crude oils need to be blended together before processing, and require great flexibility in different processes. Thus, there are some potential risks during operation. It is important to study ammonium salt crystallization fundamentals and water injection protection process to maintain air cooler equipment safe operation. Based on mass balance and inverse inversion method, inlet manifold of hydrogenation air cooling system in a petrochemical plant is studied, and simulation model of multi-component fluid process with hydrocarbon-water two-phase interaction is established. In addition, based on thermodynamics, ammonium salt crystallization temperature prediction method is proposed. A discrete model of inlet manifold with water injection structure is constructed as well. Furthermore, multi-component fluid flow characteristics in the manifold are numerically simulated by Euler two-fluid model and Ranz-Marshall interphase heat transfer model, and thus outlet water flow distribution and outlet multi-phase component temperature can be simulated under off-design conditions. Simulation results show that, for pipelines with chloride ion content greater than 1.5 mg/kg, crystallization can occur. It is also found that NH₄Cl crystallization temperature increases as chloride ion content becomes high. At the water injection rate of 30 t/h, both NH₄HS content and liquid water content can meet the specification standard. The product of water phase fraction and flowrate is the key parameter which impacts on water flow distribution. It is noticed that, for water flow uniformity, multi-point water injection has some advantages than that of single point water injection. There is no significant difference for the average temperature at all outlet sections between single-point water injection and multi-point water injection. However, due to short heat transfer time in each phase for multi-point water injection, temperature difference of materials in each phase at the outlet of pipeline is less uniform than that of single point water injection.