Modeling the hydrodynamics of cocurrent gas-solid downers according to energy-minimization multi-scale theory  

作　　者：Zhixin Zhang Shanwei Hu Xinhua Liu Hui Zhao 

机构地区：[1]State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China [2]State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266555, China

出　　处：《Particuology》2016年第6期110-119,共10页颗粒学报（英文版）

基　　金：We appreciate financial support from the Strategic Prior- ity Research Program of the Chinese Academy of Sciences （No. XDA07080400） and the Natural Science Foundation of China （Nos. 21376244 and 91334107）.

摘　　要：Cocurrent gas-solid downer reactors have many applications in industry because they possess the tech- nological advantages of a lower pressure drop, shorter residence time, and less solid backmixing when compared with traditional circulating fluidized bed risers. By introducing the concept of particle clusters explicitly, a one-dimensional model with consideration of the interphase interactions between the fluid and particles at both microscale and mesoscale is formulated for concurrent downward gas-solid flow according to energy-minimization multi-scale （EMMS） theory. A unified stability condition is proposed for the differently developed sections of gas-solid flow according to the principle of the compromise in competition between dominant mechanisms. By optimizing the number density of particle clusters with respect to the stability condition, the formulated model can be numerically solved without introducing cluster-specific empirical correlations. The EMMS-based model predicts well the axial hydrodynamics of cocurrent gas-solid downers and is expected to have a wider range of applications than the existing cluster-based models.Cocurrent gas-solid downer reactors have many applications in industry because they possess the tech- nological advantages of a lower pressure drop, shorter residence time, and less solid backmixing when compared with traditional circulating fluidized bed risers. By introducing the concept of particle clusters explicitly, a one-dimensional model with consideration of the interphase interactions between the fluid and particles at both microscale and mesoscale is formulated for concurrent downward gas-solid flow according to energy-minimization multi-scale （EMMS） theory. A unified stability condition is proposed for the differently developed sections of gas-solid flow according to the principle of the compromise in competition between dominant mechanisms. By optimizing the number density of particle clusters with respect to the stability condition, the formulated model can be numerically solved without introducing cluster-specific empirical correlations. The EMMS-based model predicts well the axial hydrodynamics of cocurrent gas-solid downers and is expected to have a wider range of applications than the existing cluster-based models.

关 键 词：Mathematical modeling Hydrodynamics Fluidization Downer Cluster Multiscale 

分 类 号：O359[理学—流体力学] TM15[理学—力学]