粉-粒喷动床内颗粒介尺度结构与脱硫效率构效关系理论建模及调控机理研究

During the PPSB in powder-particle spouted bed, there exists a large amount of slurry, fine powder particles and bulky particles interacting with each other, which is associated with the dynamically coupled heat and mass transfer and the desulfurization reaction. Associated with heat and mass transfer and desulfurization process in the spouted bed, the meso-scale structure of powder and forming rule has important influence on desulfurization efficiency of spouted bed, and the forming rule and regulation mechanism need to be analyzed. In addition, in view of the low gas-solid contact efficiency in traditional spouted bed annulus and its influence on desulfurization efficiency, a nozzle with a spiral blade was designed to enhance the desulfurization process in powder-particle spouted bed. . The Particle Image Velocimetry measurement (PIV) technique and measurement of particle concentration are adopted to obtain the transient flow information of multiphase in the powder-particle spouted bed. The effects of swirling flow, moisture content of the slurry and meso-scale structure of powder on the fluid flow, mixture and heat transfer characteristics of bed layer in the multiphase chemical reactions of powder and liquid drops are investigated. The discrete element method is used to simulate the heterogeneity of multiphase fluid in spouted bed, and the heterogeneous factor is used to define the heterogeneous characteristics and drag model, and the multi-scale analysis method of DEM test, non uniform drag model and multi fluid model is established to investigate the multiphase flow behavior in spouted bed. The three-dimensional numerical simulation model is built to simulate the transient process of multiphase transmission in the powder-particle spouted bed, and effects of swirl effect, slurry water content and fine powder meso-scale structure on the multi-scale regulation mechanism of desulphurization efficiency and integral energy consumption of spouted bed is investigated. This work may provide the basis for the optimum design and amplification work of powder-particle spouted bed.

粉–粒喷动床水汽化脱硫过程中存在大量含水料浆、细粉颗粒及粗大颗粒的相互作用，并伴随热、质动态耦合传递过程与脱硫反应。其中料浆含水量及细粉颗粒团的介尺度结构与形成规律关联着喷动床内的热、质传递过程与脱硫效率，需要对其形成规律与调控机制进行研究。此外，针对传统喷动床环隙区气固接触效率偏低进而影响脱硫效率的特点，本项目设计了带旋流器喷嘴来强化其脱硫过程。本研究通过粒子图像测速法及颗粒浓度测量技术获取粉-粒喷动床内的整场瞬态流动信息，考察旋流效应下喷动床内水汽化过程中料浆含水率及细粉介尺度聚团对喷动床内传递、混合与换热特性的影响规律。在理论分析方面，采用离散单元法实现喷动床内非均匀流场模拟，构建DEM试验–非均匀曳力模型–多流体模型模拟的多尺度分析方法，探讨旋流效应、料浆含水率及细粉介尺度结构对喷动床内脱硫效率、整体能耗的多尺度调控机制，为粉–粒喷动床的优化设计与放大提供依据。

喷动床作为一种新型流态化技术，因其结构简单、产物处理方便及高效处理效率被广泛应用于脱硫领域。但常规喷动床环隙区内颗粒堆积紧密，气固缺乏横向混合，存在流动“死区”等问题严重阻碍了气固流体间的质量与热量传递，影响了喷动床的处理效率。本项目基于PIV实验与数值模拟相结合的方法，探究了新型带纵向涡发生器喷动床、带旋流器喷嘴喷动床及多喷嘴喷动-流化床内各相的流场瞬态流动信息及其动态分布情况。并考察多喷嘴、纵向涡及旋流器结构对粉-粒喷动床反应器内床层尺度的传递、混合和换热特性的影响机制，获得床内脱硫反应过程规律，以期为新型喷动床技术的推广应用和运行提供理论与技术参考。研究发现新型喷动床内形成的鼓泡能够强化床内喷射区及环隙区气固两相径向混合运动，实现床体圆锥处颗粒局部流化，有效改善喷动床内流动“死区”状况。在水汽化过程中，强化构件对水汽化的促进作用由大到小依次为：旋流器＞多喷嘴＞纵向涡。在研究参数范围内，气体温度为520 K及入口气速为11.2 m/s的条件最有利于水的汽化。在脱硫反应过程中，旋流器、纵向涡及多喷嘴均能够不同程度上促进床内脱硫反应的进行。相比于常规喷动床，带旋流器喷嘴喷动床内脱硫率提高了12.2%，带纵向涡发生器喷动床提高了6.2%，多喷嘴喷动-流化床则提高了15.5%。. 此外，为进一步探讨旋流喷嘴结构对喷动床内气固两相流动的影响，开展了热风干燥实验，考察了进气温度、物料填充高度、颗粒直径对干燥性能的影响，并结合冷模实验对带旋流器喷嘴喷动床的优劣进行全方位评估。实验发现引入旋流效应后，干燥效率、干燥时间、颗粒水分扩散以及单位能耗等皆得到巨大改善。最后，基于欧拉-拉格朗日框架下的CFD-DEM方法，构建多喷嘴喷动流化床内干湿颗粒的流动和传质耦合过程的数理模型，探究干湿颗粒的流动及传热特性，发现多喷嘴喷动-流化床在处理传热系数较低、颗粒热容较小、进气温度较低的体系时优势更为明显，对床内湿颗粒的传热强化效果更优。