纳米流体强化蒸馏过程的传质机理研究

As the most widely used separation technology, distillation has the disadvantages of high energy consumption and low thermodynamic efficiency. Since nanofluids can enhance the heat and mass transfer performance, they are generally studied in the fields of heat transfer, absorption and extraction. However, there is a lack of systematic research in the field of distillation, and the relevant strengthening mechanism is not yet clear. This project intends to use a combination of theoretical and experimental methods to study the mass transfer mechanism of distillation enhanced by nanofluids. Molecular simulation is used to obtain the properties and microstructure characteristics of nanofluids, and the relationship between the microstructure and macroscopic properties of nanofluids is established from the microscopic scale. The lattice Boltzmann method is used for the simulation and research of interfacial Rayleigh convection and Marangoni convection in vapor-liquid mass transfer process, which reveals the effects of nanoparticles on the interfacial convection from the mesoscopic scale. To verify the accuracy of the simulation, the effects of nanoparticles on the relative volatility of binary systems are investigated by vapor-liquid phase equilibrium experiment, and the Schlieren is also used to observe the interfacial convectional structure in vapor-liquid mass transfer device. The implementation of this project will provide a new idea for energy saving in distillation process and lay a theoretical foundation for the application of nanofluids for distillation.

蒸馏作为应用最为广泛的分离技术，存在着能耗高、热力学效率低等问题。纳米流体因传热传质性能优异，在强化传热、吸收和萃取等方面研究广泛，但在蒸馏领域目前缺乏系统的研究，且相关强化机理尚不明确。本项目拟采用理论和实验相结合的方法对纳米流体强化蒸馏过程的传质机理进行深入研究。运用分子模拟获得纳米流体的物性和微观结构特征，从微观尺度建立纳米流体微观结构与宏观性质之间的关系；基于格子Boltzmann方法对汽液界面Rayleigh对流和Marangoni对流进行模拟研究，从介观尺度揭示纳米颗粒对界面对流的影响规律；通过汽液相平衡实验，探究纳米颗粒对二元体系相对挥发度的影响，并采用纹影仪观察汽液传质装置中纳米流体界面对流结构，以验证模拟结果的准确性。本项目的开展可为蒸馏过程节能降耗提供新思路，为纳米流体在蒸馏领域的应用提供理论指导。

随着节能减排成为化工行业的首要目标，蒸馏作为应用最为广泛的分离技术，存在着能耗高、热力学效率低等问题。纳米流体因传热传质性能优异，在强化传热、吸收和萃取等方面研究广泛，但在蒸馏领域目前缺乏系统的研究，且相关强化机理尚不明确。鉴于此，提出纳米流体强化蒸馏过程的新构思。.本项目主要从相平衡实验、传质实验、机理分析和传质过程建模等方面研究了纳米流体强化蒸馏过程的可行性。将不同粒径（10 nm、50 nm和60 nm）、不同浓度（0.05 wt%、0.1 wt%和0.3 wt%）的TiO2、Al2O3和SiO2纳米颗粒加入到汽液相平衡和液液相平衡体系中，并进行相平衡实验测定不同相的组成，实验结果表明纳米流体不能改变相平衡状态；采用间歇精馏实验探究纳米流体对蒸馏过程传质强化的影响，实验结果证实纳米流体对蒸馏过程的传质有一定的强化作用；同时，通过吸收实验测定不同纳米流体下二氧化碳吸收过程的增强因子和传质系数，结果证实纳米流体明显加快传质速率，并且当纳米流体中颗粒含量较小时，传质速率与颗粒粒径的大小呈负相关的关系；此外，项目还基于流体力学理论建立了精馏传质模型，模拟结果表明纳米流体提高了精馏的传质速率；为从分子层面阐明纳米流体强化传质过程的机理，基于量子力学理论计算相互作用能、径向分布函数和空间分布函数，计算结果说明纳米流体并没有改变吸收过程的相平衡，但加快了传质速率；最后，结合颗粒增强理论输运机理和流体力学作用机理，建立气液传质过程的三维非稳态数学模型，合理地预测了不同类型纳米流体对传质的影响，模型的计算结果与实验结果的最大偏差值不超过10%。.项目注重利用基础实验、理论计算和建模研究去揭示纳米流体影响传质过程的本质因素，深入认识纳米流体对传质过程中的微观机制与宏观现象，对开拓纳米流体在分离领域的应用具有重要意义。