基于反萃-结晶的微通道规律变形液液环状流的流动和传质特性研究

As the process regulation of the stripping-crystallization process in extractant regeneration is of low accuracy with problems like burst nucleation, organic phase emulsification and low utilization of ammonia, a design to have stripping happened in microchannel with annular flow is offered. By setting spindle knots in the center of microchannel, new walls can be created and then the regularly deformed liquid-liquid annular flow. To confirm the flow regime and mass transfer of the regularly deformed liquid-liquid annular flow in microchannel, the micro-PIV and color indicator measurements are used to identify the effect of structure and operation parameters on the two-phase flow field and mass transfer coefficients. The effects of regularly deformed walls on the two-phase flow field and mass transfer are obtained and the formation of regularly deformed liquid-liquid annular flow, secondary flow and their mass transfer mechanisms can be figured out. A novel method to determine the metastable zone width under micro-scale flow is offered as well. By combining the metastable zone width, flow and mass transfer model, a coupling model of the flow regime and mass transfer of regularly deformed liquid-liquid annular flow in stripping-crystallization process can be established. we can get to know the flow and mass transfer mechanism of stripping-crystallization process in microchannel thoroughly and achieve a more controllable and effective process, which will eventually propel the application of the relevant technologies in stripping-crystallization in industry.

本项目针对萃取剂再生的反萃-结晶技术过程控制精度低，存在爆发式成核、乳化和氨利用率低的问题，提出将反萃过程置于环状流微通道中进行的思路；通过在微通道轴心安装珠串插件，引入新壁面，构建规律变形液液环状流。为探索微通道规律变形液液环状流的流动和传质特性，利用Micro-PIV技术和显色法研究微通道各种结构和操作参数对两相流场分布、传质系数的影响，从而明确规则变形壁面对两相流动和传质的作用规律，阐明规律变形液液环状流和二次循环流的形成机制及两相传质机理；提出一种新的用于微尺度流动时结晶介稳区宽度测定的方法；并将介稳区宽度与两相流动、传质模型耦合，以建立基于反萃-结晶过程的规律变形液液环状流的流动和传质耦合模型。通过研究可以深入认识反萃-结晶过程的流动和传质的基本规律，从而实现过程的可控和高效，有利于反萃-结晶过程的相关技术的工业推广和应用。

本项目针对萃取剂再生的反萃-结晶技术过程控制精度低，存在爆发式成核、乳化和氨利用率低的问题，提出将反萃过程置于环状流微通道中进行的思路；通过在微通道轴心安装珠串插件，引入新壁面，构建了规律变形液液环状流。为探索微通道规律变形液液环状流的流动和传质特性，研究了微通道各种结构和操作参数对两相流场分布、传质系数的影响。研究发现插件可以稳定流型，拓宽规律变形环状流的形成范围；变形截面插件导致流道的规则改变，使流体产生规律变形，在插件表面和流体内部形成二次循环流，可以强化传递过程；对两相流体的受力分析表明，有机相与插件的表面力是造成插件微通道内出现不同于常规微通道的双连续相流型的关键，明确了引入壁面对流动的作用规律。以甲苯-乙酸-水、D2EHPA/煤油-Cu2+-水和TBP/煤油-磷酸-水等两相体系为传质评估体系，证明了在微通道内引入变形插件是一种有效的过程强化手段。变形插件增强了对流混合和表面更新频率，充分发挥了两相界面变形和流体混沌的传质优势。基于VOF方法建立了能合理反映插件微通道内两相流动和传质特性的理论模型。利用晶核的Mie散射建立了一种新的用于微尺度流动时结晶介稳区宽度测定的方法，测定了微尺度流动时磷酸二氢钾的介稳区宽度。以氢氧化钾浓溶液处理负载磷酸的磷酸三丁酯/煤油再生的反萃-结晶过程为例，将介稳区宽度与流动、传质模型进行了耦合，可实现反萃-结晶过程的精准调控，有利于反萃-结晶过程的相关技术的工业推广和应用。本项目执行期间培养硕士研究生8名，本科生14名，发表学术论文21篇（其中SCI论文18篇），授权发明专利7篇，申请发明专利1篇。