An experimental and numerical study of the suppression of jets, counterflow, and backflow in vortex units

Abstract

Vortex units are commonly considered for various single and multiphase applications due to their process intensification capabilities. The transition from gas-only flow to gas-solid flow remains largely unexplored nonetheless. During this transition, primary flow phenomenon, jets, and secondary flow phenomena, counterflow and backflow, are substantially reduced, before a rotating solids bed is established.This transitional flow regime is referred to as the vortex suppression regime. In the present work, this flow transition is identified and validated through experimental and computational studies in two vortex units with a scale differing by a factor of 2, using spherical aluminum and alumina particles. This experimental data supports the proposed theoretical particle monolayer solids loading that allows estimation of vortex suppression regime solids capacity for any vortex unit. It is shown that the vortex suppression regime is established at a solids loading theoretically corresponding to a monolayer being formed in the unit for 1g-Geldart D-and 1g-Geldart B-type particles. The model closely agrees with experimental vortex suppression range for both aluminum and alumina particles. The model, as well as the experimental data, shows that the flow suppression regime depends on unit dimensions, particle diameter, and particle density but is independent of gas flow rate.This combined study, based on experimental and computational data and on a theoretical model, reveals the vortex suppression to be one of the basic operational parameters to study flow in a vortex unit and that a simple monolayer model allows to estimate the needed solids loading for any vortex device to induce this flow transition. K E Y W O R D Sgas-solid vortex reactor, gas-solid vortex units, monolayer model, process intensification, vortex suppression regime Abbreviations: GSVR, gas-solid vortex reactor; GSVU, gas-solid vortex unit; GVU, gasvortex unit; HDPE, high density polyethylene.

Micromixing in a gas–liquid vortex reactor

“…A lower shear force with the wall would also lead to less turbulence. Previous research in gas–solid vortex reactor 50 also shows that the gas flow changes from “multiple rotations” to “less than one full rotation” inside the unit chamber when increasing the solid loading from zero to the maximum capacity. This is referred to as the suppression of the primary gas flow of the jets and secondary flow of counterflow and backflow.…”

Process Intensification in a Gas–Solid Vortex Unit: Computational Fluid Dynamics Model Based Analysis and Design

“…Applying a continuous solids feed with dedicated solids outlets or installing a diverging outlet could also help to improve bed stability. Another option is to inject a small amount of coarser material, which will form a monolayer near the circumferential wall; in this way breaking the gas jets so that finer material floating on top of the coarse particles’ monolayer can be contained in the unit. In contrast, there is also a maximum limit on τ p .…”

Chemisorption of CO2 in a gas–liquid vortex reactor: An interphase mass transfer efficiency assessment

“…The balance between the radially inward gas drag force and radially outward centrifugal force holds a certain amount of liquid near the outer edge of the vortex chamber, constantly refreshing the liquid into a dynamic equilibrium state and generating a large gas–liquid interfacial area 21 . It is worth mentioning that previous studies mainly focused on the vortex reactor used in gas–solid systems 23–34 . Successful experience has led to the exploration of gas–liquid systems in the reactor, and more specifically of CO 2 capture in this study.…”

“…21 It is worth mentioning that previous studies mainly focused on the vortex reactor used in gas-solid systems. [23][24][25][26][27][28][29][30][31][32][33][34] Successful experience has led to the exploration of gas-liquid systems in the reactor, and more specifically of CO 2 capture in this study.…”