液体连续相撞击流反应器强化微观混合过程的机理

The micromixing process is crucial to chemical reaction, and experimental researches have shown that Liquid-continuous impinging stream reactor(LISR) has significant characteristics on enhancing micromixing process. This item is planned to, on the basis of preliminary studies and in micro-transferring point of view, put forward mechanism researches about enhancing micromixing process in LISR with the prevalent micromixing theory and numerical simulation and modern experimental techniques and so on. The main contents include those: 1) The mechanism that how impinging stream affect the macroscopic dispersion of fluid micromass in LISR. The macroscopic dispersion process of fliud micromass is basis and premise of micromixing; in LISR,obviously, macroscopic dispersion is more vigorous than in any other reactor, it is important to figure this phenomenon out 2) The mechanism that how LISR's macroscopic characteristics affect micromixing process. LISR'S macroscopic characteristics such as pressure fluctuations are the important causal factors of enhancng micromixing in LISR, and it is focused on the mechanism of quantitative affection exerted by macroscopic characteristics on the micromixing time. 3)The law of distributive formation and deformation of fluid micromass in LISR. The law of distributive formation and deformation of fluid micromass are the core of the micromixing process in prevalent theory, and in this item, will be observed by the high speed camera through the dyed-tracing method. 4) The researches on enhancement mechanism of micromixing process in LISR. It is elucidated on the basis of discussing the affection exerted by macroscopic characteristics on macroscopic dispersion and the law of distributive formation and deformation of micromass. The results of research should have a significant prospect for clarifying the enhancement mechanism of micromixing process and perfecting the micromixing theory and propelling more efficient utilization with LISR in chemical engineering domains.

微观混合过程对化学反应至关重要，实验表明液体连续相撞击流反应器（LISR）具有显著强化微观混合过程的特性，本项目拟在前期研究基础上借助微观混合理论、数值模拟及现代实验技术等手段，从微观传递角度对LISR强化机理开展基础研究。主要内容包括：(1)撞击流对流团宏观分散的影响机理。(2)LISR宏观特性对微观混合过程的影响机理。压力波动等宏观特性是LISR强化微观混合的重要因素，重点探讨宏观特性对微观混合时间的定量影响机理。(3)LISR中流体微团分布形态及形变规律。流体微团分布形态及形变规律是微观混合过程的核心，借助高速相机在染色示踪方法下观测微团分布形态及形变规律；(4)LISR强化微观混合机理研究。在讨论宏观特性与宏观分散、微团分布形态及形变规律间影响规律基础上系统阐释LISR强化微观混合机理。研究成果有助于明晰LISR强化微观混合机理、完善微观混合理论、化工领域中高效利用LISR技术。

项目组基于液体连续相撞击流反应器强化微观混合过程的思想，从撞击流反应器结构装置稳定性和混合效率出发，提出多种新型撞击流反应器。设计液体连续相撞击流反应器实验装置并搭建实验测量系统平台，制定了详细的实验实施方案，主要包括：宏观混合时间的测定；撞击区内压力波动测量；撞击流反应器中PIV速度场的测量；撞击流反应器中宏观流体团分散行为随时间和空间的变化分布等。最后利用流体动力学软件FLUENT对液体连续相撞击流反应器进行数值模拟研究，得到了将撞击流反应器内导流筒长度及直径撞击距离、桨叶形式、桨叶倾角及对置桨叶交错倾角等结构参数，以及桨叶转速、进料速度、等操作参数作为分析变量工况下流场的物料浓度分布、速度分布及混合时间等评价因子。通过本项目研究，获得结论有：1）导流筒长度的增加使导流筒内入口处轴向压力和速度增大，导流筒长度由70mm增加到85mm，撞击面中心处压力减小，中心轴向方向压力增大，但过度增大到100mm反而呈相反趋势。2）对置距离的增加，导流筒入口附近区域压力波动值和速度增大，同时也减弱了撞击取悦内压力波动和速度，桨叶对置距离增加一倍，相应压力值和速度值减小一倍。3）桨叶面积的增大有利于撞击过程中轴向压力和速度沿着径向压力和速度的转换，径向压力值相比轴向压力增加了10多倍，最大可达到20倍，压力值和速度值会随着桨叶 面积的增大而增大。4）桨叶倾角为30度时，压力波动强度与剪切应力平均值最大，桨叶倾角的改变不影响混合时间，但会局部影响流体分散效果；5）当桨叶转速为1500r/min时，其压力波动强度与剪切应力平均值最大，桨叶转速的增大会减小混合时间，促进混合；6)利用流体混合过程经验模型和现代微观混合理论模型对LISR撞击区混合时间进行理论计算，在连续稳定操作条件下，随着转速增加，经验模型与理论模型计算的宏观混合时间逐渐减小，其微观混合时间也随之下降，二者处于一种联动平衡状态；随着转速增加，两种模型计算结果趋于一致，说明两种模型更适合于在高转速撞击下的混合时间计算。研究成果有助于明晰 LISR 强化微观混合机理、完善微观混合理论、化工领域中高效利用 LISR 技术。