Prediction of flow behavior of particles in a tapered bubbling fluidized bed using a second-order moment-frictional stresses model

• Published in: Chemical engineering science 2012-12, Vol.84, p.170-181
• Main Authors: Liyan, Sun, Weiguo, Xu, Guodong, Liu, Dan, Sun, Huilin, Lu, Yanjia, Tang, Dan, Li
• Format: Article
• Language: English
• Subjects: Applied sciences; Bubbling; Chemical engineering; Computational fluid dynamics; Computer simulation; Cylinders; drag coefficient; Drag coefficient model; Exact sciences and technology; Fluidization; Fluidized beds; Hydrodynamics; Hydrodynamics of contact apparatus; Kinetic theory; Mathematical modeling; Mathematical models; prediction; Pressure drop; Stresses
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2012.08.002

Flow behavior of gas and particles is simulated by means of the second-order moments method (SOM) in a tapered bubbling fluidized bed. The frictional stress model proposed by Johnson et al. (1990) is used to predicate the frictional stresses of particles. A drag coefficient model for gas–monosized particles flow is proposed for predicting the interaction between gas and solid phase in the tapered bubbling fluidized beds. Distributions of concentration, velocity and moments of particles are predicted in the tapered bubbling fluidized bed. The ratio of the vertical normal second-order moment to the lateral normal second-order moment increases with the increase of tapering angle. The averaged ratios are larger than unity in the inner section (IS region) in the cylinder of the bed. It is, however, reverse in the outside of the cylinder (OS region). The second-order moments are direction-dependence, and the anisotropy of the normal components of the second-order moments is obvious in tapered bubbling fluidized beds. A comparison has been made between the simulations using proposed model and the experimental data. Simulated concentration of particles, bed pressure drop and bed expansion agreed reasonably with experimental measurements. The mean ratio of second-order moments Mzz/Mxx increases with the increase of tapered angles in the inner section (IS region). In the section outside of the cylinder (OS region), it is reverse. Such anisotropy is existed in tapered bubbling fluidized beds. [Display omitted] ▸ The drag coefficient model is proposed in the tapered bubbling fluidized beds. ▸ A second-order moments with frictional stress model is proposed. ▸ A difference of second-order moments is found in the IS and OS regions. ▸ Anisotropy of the normal components of the second-order moments is found.