流动腐蚀环境下多元流体结晶相漂移沉积动力学特性研究

China is the biggest importer of crude oil, and a large number of low-priced inferior oil with strong corrosiveness is processed. The safety problem of the hydrogenated air cooling system induced by flow-induced corrosion is very prominent in petrochemical industry. In the air cooling system tube bundle, the conveying process of multiple multiphase fluid relates to complex physical processes and chemical reaction, such as component transfer, phase transition, interface generation and motion. A great deal of failure cases show that the crystallization and drifting deposition of corrosive crystalline phase is the main cause of many flow-induced corrosion failures: tube wall thinning, leakage and pipe burst, for example. Due to the unclear drifting deposition mechanism of crystalline phase, present research results cannot quantitatively describe the corresponding rule in wall damage, which makes the hydrogenated air cooling system be always in high-risk service status..Taking hydrogenated air cooling system as the research object, the project intends to deeply explore the dynamic characteristics for drifting deposition of multi fluid crystalline phase via the theoretical analysis, numerical simulation and experimental study. The primary goal is to master the crystallization rule of multiphase fluid in the flow-induced corrosion environment, and to reveal the drift and deposition mechanism of crystalline phase under fluid-thermal coupling, and to create a quantitative characterization and prediction method for the drifting deposition characteristics of crystalline phase. Then, the final goal is to reveal the internal relationship between the drifting deposition of the crystalline phase and the damage of the tube wall, and to formulate the technical standard for the active prevention and control of drifting deposition characteristics, so as to provide theoretical support for the optimal operation and risk warning of the large-scale air cooling system.

我国是原油进口第一大国，大量炼制低价腐蚀性劣质原油，石化行业的加氢空冷系统因流动腐蚀引发的安全问题极为突出。大量失效案例表明：空冷管束内多元流体输运过程涉及组分传递、相变、界面产生及运动等复杂物理过程以及化学反应产生，易结晶相的结晶及其漂移沉积是引起管壁减薄、泄漏、爆管等失效的主要原因。因结晶相漂移沉积机理不明确，现有研究成果无法定量描述与之对应的管壁损伤规律，致使加氢空冷系统始终处于高风险服役状态。.本项目拟以加氢空冷系统为研究对象，从理论分析、数值模拟和实验研究等方面对多元流体结晶相的漂移沉积动力学特性开展深入研究，掌握流动腐蚀环境下多元流体易结晶相的结晶规律，揭示流-热耦合作用结晶相的漂移沉积机理，形成结晶相漂移沉积特性的量化表征预测方法，建立结晶相漂移沉积与管壁损伤失效的内在关联，制定以漂移沉积特性主动防控为目标的技术标准，为大型空冷系统的优化运行和风险预警提供理论支撑。

我国原油对外依存度超70%，炼化企业主要炼制中东进口的高硫、高氮、含氯等劣质原油。因大量炼制腐蚀性劣质原油，炼化企业频繁发生NH4Cl颗粒漂移沉积引发的加氢空冷器管束内壁腐蚀、穿孔等泄漏事故。鉴于现有的研究成果无法定量描述NH4Cl颗粒的漂移沉积动力学特性，致使加氢空冷器始终处于高风险服役状态。.本项目以加氢空冷器为研究对象，研究NH4Cl颗粒的漂移沉积动力学特性，揭示流热耦合作用NH4Cl颗粒的漂移沉积机理，建立NH4Cl颗粒漂移沉积特性的量化表征预测方法，获得NH4Cl颗粒的漂移沉积规律。主要研究内容包括：.(1)基于加氢反应流出物的工艺流程及典型工况，构建了依据质量守恒基于逆序倒推法的工艺仿真计算模型，获得了易结晶组分NH3、HCl的物性参数随温度的变化规律；提出采用结晶温度和结晶速率表征NH4Cl的结晶特性，计算分析了氯含量、氮含量以及注水量等因素对NH4Cl结晶特性的影响规律，构建了NH4Cl结晶特性与影响因素间的关联数据库；.(2)分析了加氢反应流出物降温冷凝过程中NH4Cl颗粒的相变结晶、漂移沉积及垢下腐蚀等过程，揭示了流热耦合环境下NH4Cl颗粒的漂移沉积机理；分析了多组分流体输运过程NH4Cl颗粒的受力类型，提出采用流动场、剪切应力和颗粒沉积量表征NH4Cl颗粒的漂移沉积特性，并构建了基于CFD-DEM的NH4Cl颗粒漂移沉积数理模型；.(3)开展了变工况条件的NH4Cl颗粒漂移沉积特性实验测试，获得了介质流速、颗粒加载时间、相对湿度等对实验弯管内NH4Cl颗粒漂移沉积的影响规律；结合CFD-DEM的数值模拟，提出了适用于NH4Cl颗粒漂移沉积特性的量化预测方法，数值预测精度均在84%以上；.(4)针对实际的空冷器结构及工况参数，计算获得了空冷管束内流动参数的分布规律，以及相对湿度对颗粒黏附沉积的影响，揭示了颗粒漂移沉积与管壁损伤的内在关联关系；在此基础上，提出了适用于加氢空冷器NH4Cl颗粒漂移沉积特性控制的工艺注水、专家监管等工艺防护策略。.本研究成果可为在役加氢空冷器系统的在役检验、风险评估、优化运行和风险预警提供理论支撑，促进炼化工业的健康持续发展。