Analysis of dissipative mechanisms of cluster heterogeneous structures in gas–solid riser

• Published in: Chemical engineering science Vol. 246; p. 116878
• Main Authors: Xiaoxue, Jiang, Shuyan, Wang, Baoli, Shao, Huilin, Lu
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 31.12.2021
• Subjects: Collision mechanism; Drag model; Fluidized bed riser; Kinetic theory of granular flow; Particle clusters, Drag mechanism; Fluidized bed riser; Particle clusters, Drag mechanism; Collision mechanism; Drag model; Kinetic theory of granular flow
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2021.116878

The reduction of relative velocity of the gas phase and the solids phase and granular temperature promotes the aggregation of particles. The increasing relative velocity and granular temperature restrains the formation of clusters. [Display omitted] •The criterion distinguishing homogeneous flow from heterogeneous flow is proposed.•The gas viscous energy dissipation rate is low and even negligible.•The influence of dissipative drag mechanism is critical on formation of clusters.•The reduction of granular temperature leads to enhancing occurrence of clusters. In present study, a model of the criterion for cluster heterogeneous flow is presented in terms of the rates of hydrodynamic and collisional energy dissipations of the occurrence of particle clusters. The dynamic threshold distinguishes homogeneous flow from heterogeneous flow according to the collisional and hydrodynamic energy dissipations. Computation simulations indicate that the gas viscous energy dissipation rate is low about one to two order of magnitudes in comparison to hydrodynamic and collision energy dissipation rates. The energy dissipation of interface interaction is large in comparison to the energy dissipations of the dilute and dense phases. The dilute and dense collisional energy dissipations play different roles at the low and high solids volume fractions. As the relative velocity of gas and particles decreases, particle clusters are formed because the hydrodynamic energy dissipation becomes dominant. With the decrease of granular temperature, the formation of particle clusters is induced by collisional energy dissipation.