煤直接液化含固多相流分离过程煤粉漂移机理研究

Coal particles drift is a common failure mode that is general exists in particulate laden flows in the direct coal liquefaction, which is related to many factors closely, such as multiphase flow, heat and mass transfer, phase change gasification and so on. It is the source of sudden accident in these devices. The drift mechanism of coal particles in multiphase flow is unclear and current research can not describe the drift rules and effects qualitatively and quantitatively. Therefore, research in this field has been a focus in academic and engineering circles. Taking hot high pressure separator system of direct coal liquefaction as the research object, this project explores the coal particles drift mechanism under interaction of complex process, through the theoretical analysis, numerical simulation and experiment study, the drift leading failure prediction research system was established, and the drift rules of particle laden flows was also revealed. The coal particles drift mathematical model was developed and quantitative calculation method based on the coupling interaction of gas-liquid-solid phase was proposed. Through the simulation experiments, the drift characteristics of coal particles in multiphase flow was tested, and scientific coal particles drift prediction method in coal direct liquefaction system was created. The results is expected to provide theoretical basis for direct coal liquefaction system optimization design and coal particles drift scientific prevention, and to lay a foundation of relevant standards in the direct coal liquefaction demonstration engineering.

煤粉漂移是煤直接液化含固多相流输运过程普遍存在的失效形式，与多相流动、热质传递、相变汽化等复杂过程密切相关，通常是引起装置突发性事故的根源。因含固多相流煤粉颗粒相的漂移机理不明确，现有研究成果无法定性和定量描述煤粉相的漂移规律及影响因素，该领域的研究一直是学术界及工程界关注的焦点之一。本研究以煤直接液化热高压分离器系统为研究对象，开展复杂过程关联作用下煤粉漂移机理研究，通过理论分析、数值模拟和实验研究，确立煤粉漂移失效预测研究体系，揭示含固多相流体系煤粉漂移规律。构建基于气-液-固相间耦合作用的煤粉漂移数理模型，提出煤粉漂移的定量计算及表征方法；结合煤粉漂移模拟实验研究，测试含固多相流体系煤粉漂移特性，形成科学的煤直接液化煤粉漂移预测方法。研究成果有望为煤直接液化系统优化设计和煤粉漂移的科学防控提供理论支持，并可为煤直接液化示范工程相关标准和规范的完善奠定理论基础。

煤液化作为煤炭深加工的核心技术，全过程涉及煤粉及矿物质的多相流传输，特别是反应流出物分离及冷换设备，频繁因颗粒漂移引发沉积、堵塞及冲蚀磨损等失效，现有研究缺少与之相关的定性和定量的描述。.以煤液化分离冷换设备为研究对象，研究热高压分离器固相漂移特性、空冷器固相漂移沉积特性、管道冲蚀磨损特性以及液控阀节流相变过程颗粒相冲蚀磨损特性，建立颗粒漂移沉积及冲蚀磨损表征预测方法。研究内容包括：.(1)基于热高分结构和物性参数，揭示颗粒相漂移机理，建立漂移数理模型，提出漂移量化表征方法。漂移特性与进口固相质量浓度、粒径密切相关；在气-液交界面，固相平均浓度最大；小颗粒对气流跟随性好，固相漂移率与颗粒粒径呈负相关关系；进口固相质量浓度大于7%时，同一粒径的漂移率基本不变；.(2)分析流动、传热、相变、腐蚀等关联过程，揭示空冷管束内固相及腐蚀混合物的形成机理，建立漂移沉积预测方法。入口法兰处的结构突变，加剧了壁面边界层紊动状态，气液相间剪切作用对颗粒相起加速拖曳作用；提出将液相分率、颗粒停留时间和沉积速率作为表征漂移沉积特性的关键参数； .(3)采用激波脉冲式颗粒漂移及冲蚀装置，针对SiO2、SiC、Al2O3颗粒，测试了不同颗粒尺寸和冲击速度条件下材料的冲蚀磨损规律；建立了修正的冲蚀磨损数理模型，分析了弯管壁面磨损规律，磨损率高的区域与超声波测厚减薄的区域基本一致；基于人工神经网络，提出了快速磨损预测方法；.(4)开展空化水洞式实验，获得了不同空化数条件空化特征长度的变化规律；结合液控阀运行工况，构建了基于空化的冲蚀磨损预测方法；阀座和阀芯的间隙内流速急剧增加，阀芯头部和圆弧段下游存在空化区；在此基础上，获得了颗粒迹线及阀芯冲蚀磨损率分布，结合阀芯实际损伤形貌，验证了数值计算的正确性；.本课题成果可为煤直接液化分离冷换设备的在役检验、风险评估、优化设计及安全运行提供基础理论支撑，促进煤化工的健康持续发展。