微尺度下液液体系分散与传质性能的耦合规律

In multiphase microdispersion systems with mass transfer, mass transfer processes and microdispersion characteristics are highly interrelated, and there is a strong interaction between the mechanisms involved in the process. Although most current research focuses on the role of micro-dispersion technology for the enhancement of mass transfer processes, the effect of mass transfer on the micro-dispersion process itself and synergies between the two mechanisms is still not fully understood. This study focuses on developing a more in-depth understanding of the impact of liquid-liquid mass transfer processes on micro-dispersion. Here, a phosphoric acid extraction process was used as the experimental mass transfer system. Micro-PIV, PLIF and high-precision pressure measuring devices were used to investigate the velocity field, concentration field and the energy dissipation characteristics of mass transfer during a liquid micro-dispersion process involving the generation of small dispersed phase droplets within a continuous phase flow. The influence of the flow, the mixing characteristics of the micro-dispersion process both inside and outside of the generated droplets, and the transfer of solute on the dynamic interfacial tension at the interface was investigated under different flow parameters and microdispersion modes and the data was compared. By investigating the coupled mechanisms of the combined micro-dispersion and mass transfer processes, we establish a mathematical model which links the characteristic drop size of the micro-dispersion to the liquid-liquid mass transfer, dynamic interfacial tension, and energy dissipation of the system. In doing this, our goal was to develop a better understanding of the microdispersion scaling effects and interfacial effects involved in micro-chemical processes, as well as provide a theoretical basis and an important reference for the development of new and efficient micro-dispersion techniques and devices.

对于多相微分散体系，质量传递与微分散过程间存在着较强的协同作用。现有研究大多关注于微分散技术对传质过程的强化作用，而传质过程对于微分散效果影响，以及二者之间协同作用机制的研究亟待深入开展。本项目以深入认识质量传递过程对液液微分散规律的影响为目标，采用磷酸萃取过程为研究体系，借助Micro-PIV、PLIF以及高精度压差测量装置，分别考察伴随传质的液液微分散过程速度场、浓度场以及能量耗散特性，探索液液微分散萃取过程中，液滴生成阶段分散相及连续相的流动和混合特性，以及溶质的转移对于界面动态界面张力的影响规律。对不同分散方式下液液微分散过程进行比较，揭示分散过程与质量传递的耦合机制，建立伴随传质的液液微分散尺寸、能量耗散以及动态界面张力数学模型。希望借此为深入了解微化工过程的尺度效应和界面效应，发展新型高效的微分散技术和设备提供理论依据和重要参考。

液液微分散技术是微化工领域重要研究方向之一，它可以实现微米及亚毫米级液滴的可控制备，有效的强化相间传质过程，在诸多领域有着广阔的应用前景。本课题以液液体系微分散过程与传质性能的耦合规律为主要研究对象，开展了液液微分散过程滴内流动、传质及混合行为的基础研究。借助Micro-PIV测量平台考察了不同分散方式条件下，液滴生成过程滴内流体的流动规律以及分散相通道壁面浸润性对于液滴微分散过程滴内速度分布的影响。引入涡强度参数来定量表征滴内循环的剧烈程度。综合比较三种分散方式的涡强度以及能量耗散率等参数T型结构的分散效果最好。表面浸润性对于分散液滴内部流动有着显著的影响，浸润性不同，滴内流体循环方向相反。对于伴有传质的液液微分散过程滴内流动规律开展了研究。考察了传质过程对于T型错流剪切结构通道中分散液滴内部速度分布规律。传质过程的引入使得液滴的分散尺寸有显著的降低，且滴内循环速度有所增大，液滴生成周期随传质量的增大而缩短。采用Micro-PLIF以及平行竞争反应，研究了液液微分散过程液滴生成阶段传质行为以及滴内的微观混合规律。建立了基于Micro-PLIF技术测量分散液滴生成阶段传质性能的实时测量方法。溶质的传质量随着两相流量的增加而增大，分散液滴生成阶段的传质Murphree效率高达60%-90%以上，液滴生成阶段的传质贡献是整个传质过程的50%以上，在高流量条件下甚至接近100%。建立了表征传质性能的强化因子的预测模型。两相流量的增大，微观混合效果逐渐增强，当流量进一步增大使得流动成分层流状态时，微观混合效果开始减弱。十字型结构内液液微分散过程分散相内的微观混合效果优于T型错流剪切结构通道的情况。