Computational Fluid Dynamics Simulation of Hydrodynamics in a Two-Stage Internal Loop Airlift Reactor with Contraction-Expansion Guide Vane

Abstract

Global circulation and liquid back mixing adversely affect the continuous production of a multistage internal airlift loop reactor. A contraction-expansion guide vane (CEGV) is proposed and combined with a two-stage internal loop airlift reactor (TSILALR) to suppress the liquid back mixing between stages. A computational fluid dynamics (CFD) simulation is conducted to evaluate the performance of the CEGV in the TSILALR. The bubble size distribution and turbulent flow properties in the TSILALR are considered in the CFD simulation by using the population balance model and RNG k - ε turbulence model. The CFD model is validated against the experimental results. The deviations in the gas holdup and mean bubble diameter between the simulation and experimental results are less than 8% and 6%, respectively. The streamlines, flow pattern, bubble size distribution, and axial liquid velocity in the TSILALRs with and without the CEGV at superficial velocities of 0.04 and 0.08 m/s are obtained by CFD simulation. It has been shown that the CEGV generated local circulation flows at each stage instead of a global circulation flow in the TSILALR. The average global gas holdup in the TSILALR with a CEGV increased up to 1.98 times. The global gas holdup increased from 0.045 to 0.101 and the average axial velocity in the riser decreased from 0.314 to 0.241 m/s when the width of the CEGV increased from 50 to 75 mm at the superficial gas velocity of 0.08 m/s.

The Influence of Draft Tubes on the Mass Transfer and Mixing Performance of a Pilot-Scale Internal-Loop Airlift Reactor

“…Segmenting the draft tube could significantly increase the gas holdup in the downcomer. This conclusion is also consistent with relevant research [15].…”

“…This study provided valuable insights for optimizing the structure of two-stage ILAR through CFD simulation, which is helpful in developing more efficient bioreactors. To inhibit liquid back mixing between the stages of a twostage ILAR, Shi et al [15] proposed a contraction-expansion guide vane. CFD simulation and experimental results showed that the internals generated local circulation flows at each stage rather than overall circulation flow, which increased the overall gas holdup by 1.98 times.…”

“…Therefore, in order to better explore the substantive effect of multistage structure, comparative analysis and further research should be conducted on different reactor configurations, such as multistage, single-stage, and bubble columns. Additionally, some internals were designed and developed to enhance the performance of multistage ILARs [15,24]. However, their more complex geometric structures may lead to energy consumption, as well as installation and operational difficulties in industrial applications.…”

Characteristics of Bubbly Flow, Mass Transfer, and CO2 Absorption in a Two-Stage Internal Loop Airlift Reactor Assembly with a Diamond-Shaped Guide Baffle

“…It was confirmed that the gas holdup and k L a increased in the ILALRs with HFPs. Shi et al 41 attempted to suppress the liquid back-mixing in a two-stage ILALR by installing a contraction−expansion guide baffle between the first and second stages. It was found that local circulations in the first and second stages were generated, and local gas holdup increased as compared to a regular twostage ILALR.…”

The Study of Fluid Dynamics Simulation of the Internal Flow Field in a Novel Airlift Oscillation Loop Bioreactor

“…The internal components of the airlift loop reactor can improve the transfer performance. Shi et al [17] studied hydrodynamics in a two-stage internal loop airlift reactor with contraction-expansion guide vane. The two-stage had better performance improvement.…”