高密度差低界面张力体系RBM效应及其液液传质机理研究

Liquid-liquid extraction is a widely used and efficient separation technology. The development of an energy-effective and efficient separation equipment or technology and the depth study of liquid-liquid dispersion have become urgent tasks in chemical industry. Because liquid - liquid two-phase flow involves complex interface behaviors, its theoretical research has always been a major difficulty and focus in the chemical disciplines. Expecially, in a high-density difference and low-interfacial tension system, a fundamental knowledge of the relevant physical phenomena during mass transfer is not fully understood. In this project, the high-density difference and low-interfacial tension systems, such as chloroform- DMF- water, chloroform- ethanol- water, and trichloroethane - water - acetone, will be taken as the research object, and liquid-liquid mass transfer kinetics experiments will be performed, the effect of density difference and interfacial tension on the growth, deformation, and movement of single droplet are studied, as well as the effect of the temperature of the flow field, concentration, the geometry characteristics, and other factors on the Rayleigh-Benard-Marangoni Rayleigh-Benard-Marangoni（RBM）effect will be investigated. A CFD model will be created to explore the development and evolvement of RBM effect. And a mechanism model will be proposed in order to describe the prossess of liquid-liquide mass transfer in high-density difference and low-interfacial tension system, thus the coupling relationship amond mass transfer, heat transfer, and fluid flow will be revealed. The regulation methods of the RBM effects will be presented basic on the study of the mechanisms of liquid-liquid mass transfer, which provides a theoretical basis for the development of process intensification technology.

液液萃取是一种应用广泛的分离技术。开发高效、低能耗的传质分离技术和设备，深入进行液液分散体系的基础研究，已成为化工学科一个重要任务。由于液液两相涉及复杂的界面行为，其理论研究一直是本领域的难点，而有关高密度差低界面张力体系中液液传质的基础研究仍是空白。本研究针对高密度差低界面张力体系，以三氯甲烷萃取废水中的N,N-二甲基甲酰胺为研究对象，进行液液传质动力学实验，研究密度、界面张力等参数对液滴的生长、形变、运动以及液液传质的影响规律。建立能够描述高密度差低界面张力体系下Rayleigh-Benard-Marangoni（RBM）效应的计算流体力学模型，探讨RBM效应发生与发展过程。建立能够描述高密度差低界面张力体系下液液传质过程的机理模型，研究传质、传热与流动相互耦合作用关系。通过高密度差低界面张力体系中液液传质的微观机理研究，提出 RBM效应的调控方法，为传质过程强化技术提供理论基础。

液液萃取是一种应用广泛的分离技术。开发高效、低能耗的传质分离技术和设备，深入进行液液分散体系的基础研究，已成为化工学科一个重要任务。由于液液两相涉及复杂的界面行为，其理论研究一直是本领域的难点，而有关高密度差低界面张力体系中液液传质的基础研究仍是空白。本研究针对高密度差低界面张力体系，首先测定了三氯甲烷-DMF-水三元体系的液液相平衡数据，并用NRTL和UNIQUAC模型进行关联。采用单液滴法测定了氯仿-DMF-水高密度差体系的传质系数，探究了分散相浓度、液滴粒径、温度等条件对萃取传质过程的影响。建立能够描述高密度差低界面张力体系下Rayleigh-Benard-Marangoni（RBM）效应的计算流体力学模型，探讨RBM效应发生与发展过程。由于Marangoni效应和Rayleigh-Bénard效应的作用增强，高密度差体系更易发生界面不稳定性现象，从而提升液滴的传质系数。采用OCA20光学接触角测量仪观测了液滴的不稳定性，分别考察了分散相浓度和液滴粒径对液滴不稳定性的影响。基于VOSET模型捕捉液液两相运动界面，对高密度差低界面张力体系中单液滴运动及传质过程进行了数值模拟。通过分析不同时刻的表面图和流线图及瞬态速度变化图研究了单液滴运动过程的速度变化及形变，以及导致发生这种现象的关键因素（密度差和分散相浓度）。Marangoni效应和Rayleigh-Bénard效应的相互叠加效应，使得液滴在运动过程中易于变形。通过高密度差低界面张力体系中液液传质的微观机理分析，研究了Marangoni效应对传质过程的影响规律。到目前为止，本项目共发表论文4篇，参加国内外学术会议4次，申请1项国家发明专利，培养研究生3名。通过该项目的研究，我们对高密度差低界面张力体系中的液液传质和液滴运动过程有更加深入认识，达到了项目预期目标。