超声微反应器内介尺度行为及调控机制

Both microreactor and sonochemistry are important process intensification technologies. Microreactor has advantages such as small volume, fast heat/mass transfer, stable multiphase flow pattern, safety and easy to scale up, but also disadvantages like easy to get clogged, relatively week advective mixing and poor operating flexibility. Similarly, sonochemical technology also has its problems of uneven sound/bubble field distribution, acoustic cavitation process difficult to control and scale up. Introducing ultrasound into microreactor can not only solve the clogging problem, but also intensify the mixing process and increase the operational flexibility for microreactor; on the other side, utilizing microreactor’s advantages can also achieve stable, controllable and quick scaling up acoustic cavitation processes. It is of great significance to realize the synergistic effects of ‘Sonochemical Microreactor'—synergistic combination of sonochemistry and microreactor, utilizing one’s advantages to solve the other’s problems. .Microreactor is an ideal platform to study the cavitation behavior due to its uniform and controllable sound field. The intensification of ultrasound originates from the induced secondary flow including accoustic streaming, shock wave or micro-jetting. During cavitation, the structure of bubble surface, as well as its vibration and evolution behavior is a typical meso-scale structure. This project proposes to study the meso-scale behavior of cavitation bubbles and its regulation mechanism in microreactors. The formation, evolution and regulation of the structures of bubble surface and the neighbouring flow field/concentration field are systematically investigated. The interactions between the meso-scale behavior and transport and reaction, as well as the regulation mechanism are also investigated. This program plans to reveal the coupling law between the transport and reaction during intensification of ultrasound, and to provide fundamental basic for the development of reaction technology and new processes in ultrasonic microreactors.

微化工和声化学都是化工过程强化的重要技术。微反应器具有体积小、传递速率快、流型稳定、易放大等优点，但也存在对流混合弱、操作弹性差、易堵塞等问题；声化学技术也存在声场和气泡场分布不均、声空化过程难以调控、放大困难等问题。将微反应器和超声结合，利用彼此之优势以解决彼此之劣势，实现协同强化作用，具有重要意义。.微反应器内声场分布可控，是研究空化行为的理想平台。超声强化机理源自于气泡发生振动、生长和崩溃等空化过程所引发的声流、冲击波或微射流等现象。空化过程中气泡表界面结构及其振动、演化规律是典型的介尺度行为。本项目针对微通道内空化气泡表界面介尺度行为，系统研究气泡界面结构及其附近流场等衍生结构的形成、演变和调控机理，深入研究气泡界面介尺度结构与界面上传递、反应的相互作用关系及调控规律，揭示超声强化过程中的传递与反应耦合机制，为超声微反应系统中化学反应的强化及新工艺过程开发奠定理论基础。

微化工和声化学都是化工过程强化的重要技术。将微反应器和超声集成，既能利用超声效应提高微反应器的对流混合性能和操作弹性，也能在微通道内对声场及声空化过程进行调控，实现二者优势互补与协同强化，具有重要的研究价值。超声强化机理源自于气泡发生振动、生长和崩溃等空化过程所引发的声流、冲击波或微射流等现象。空化过程中气泡表界面结构及其振动、演化规律是典型的介尺度行为。.本项目围绕“微反应器内超声空化过程中气泡表界面介尺度结构形成机制、演变规律与调控机理”和“空化气泡界面流动-传递-反应的多机制耦合与调控”两个关键科学问题开展研究工作。.优化设计和制造了稳定高效的新型超声微反应器作为研究平台。利用高速摄影等实验技术，系统研究了超声条件、通道尺寸、流体性质、温度等因素作用下，微通道内自由、受限气泡的声空化过程介尺度结构的形成机制和演变规律；基于声压和表面张力的竞争协调机制，建立了微反应器内气泡空化过程的调控理论。利用荧光、变色成像等在线/局部表征技术，研究了空化气泡振动过程中的限域效应和界面流动-传递的耦合过程行为，揭示超声空化在均相和多相体系下的流动-传质的耦合强化机制。基于超声气泡动力学理论构建了CFD模拟方法，揭示了空化过程中气泡的特殊介尺度结构Faraday表面波的形成原因以及对流场的周期性扰动规律。.利用超声微反应器过程强化特性实现了单硝基甲苯等高效连续制备，研究了空化过程对于快速强放热反应的作用规律；开发了用于纳米颗粒连续化制备的超声微反应系统，实现了纳米药物等的高效连续可控制备，形成具有自主知识产权的工艺技术，拓展了声化学技术应用范围。项目成果丰富了介尺度科学的基本理论，并为超声微反应技术在化工过程强化中的应用和发展奠定了基础。 .项目执行期间培养博士研究生7名、硕士研究生1名，在AIChE J.，Chem. Eng. Sci.等化工核心刊物和会议上发表学术论文26篇、其中SCI论文22篇、EI论文4篇，授权发明专利6件、申请发明专利1件。.