Simple model for gas holdup and liquid velocity of annular photocatalytic external-loop airlift reactor under both bubble and developing slug flow

2016 ◽  
Vol 22 (3) ◽  
pp. 228-236
Author(s):  
Yiping Wang ◽  
Weiqiang Chen ◽  
Qunwu Huang ◽  
Jiahe Feng ◽  
Yong Cui
Keyword(s):  
Simple Model ◽  
Slug Flow ◽  
Liquid Velocity ◽  
Gas Holdup ◽  
Airlift Reactor ◽  
External Loop

scholarly journals The Effect of a Modified Downcomer on the Hydrodynamics in an External Loop Airlift Reactor

2006 ◽  
Author(s):  
Samuel T. Jones ◽  
Theodore J. Heindel
Keyword(s):  
Liquid Velocity ◽  
Bubble Column ◽  
Gas Holdup ◽  
Area Ratio ◽  
Airlift Reactor ◽  
Open Area ◽  
Gas Velocity ◽  
External Loop ◽  
Superficial Gas Velocity ◽  
Superficial Liquid Velocity

Gas holdup and superficial liquid velocity in the downcomer and riser are studied for an external loop airlift reactor with an area ratio of 1:16. Two downcomer configurations are investigated consisting of the downcomer open or closed to the atmosphere. Experiments for these two configurations are carried out over a range of superficial gas velocities from UG = 0.5 to 20 cm/s using three aeration plates with open area ratios of 0.62, 0.99 and 2.22%. These results are compared to a bubble column operated with similar operating conditions. Experimental results show that the gas holdup in the riser does not vary significantly with a change in the downcomer configuration or bubble column operation, while a considerable variation is observed in the downcomer gas holdup. Gas holdup in both the riser and downcomer are found to increase with increasing superficial gas velocity. Test results also show that the maximum gas holdup for the three aerator plates is similar, but the gas holdup trends are different. The superficial liquid velocity is found to vary considerably for the two downcomer configurations. However, for both cases the superficial liquid velocity is a function of the superficial gas velocity and/or the flow condition in the downcomer. These observed variations are independent of the aerator plate open area ratio. When the downcomer vent is open to the atmosphere, the superficial liquid velocity is initially observed to increase with increasing superficial gas velocity until the onset of choking occurs in the downcomer. Increasing the superficial gas velocity beyond the onset of choking increases the effect of choking and decreases the superficial liquid velocity. Once maximum choking is reached, the superficial liquid velocity becomes independent of the superficial gas velocity. When the downcomer vent is closed to the atmosphere, the superficial liquid velocity is initially observed to decrease with increasing superficial gas velocity as choking in the downcomer is immediately present. Once maximum choking occurs, the superficial liquid velocity once again becomes independent of the superficial gas velocity.

scholarly journals Sparger type influence on the gas holdup of an external-loop airlift reactor with diluted alcohol solutions

2012 ◽  
pp. 109-109
Author(s):  
Kojic Predrag ◽  
Tokic Milenko ◽  
Sijacki Ivana ◽  
Lukic Natasa ◽  
Petrovic Dragan ◽  
...  
Keyword(s):  
Gas Holdup ◽  
Airlift Reactor ◽  
External Loop

scholarly journals Mixing Characteristics of External Loop Airlift Bioreactor using Electrical Resistance Tomography

2021 ◽  
Author(s):  
Mian Hamood-Ur-Rehman
Keyword(s):  
Electrical Resistance ◽  
Liquid Velocity ◽  
Mixing Time ◽  
Perforated Plate ◽  
Packed Bed ◽  
Gas Holdup ◽  
External Loop ◽  
Gas Distributor ◽  
Airlift Bioreactors ◽  
Superficial Liquid Velocity

In the present work, a novel packed bed external loop pneumatically agitated airlift bioreactor with an internal gas distributor (perforated plate) between two rolls of packing in the riser was designed and built. This novel approach combines advantages of packed bed and external loop airlift bioreactors. The main objective of this research work was to characterize the hydrodynamic performance of this novel reactor through a non-intrusive flow visualization technique called electrical resistance tomography (ERT). The tomography images, which were generated using a linear back projection algorithm, were employed to explore the effects of different design parameters and operating conditions. These include the effect of the two packing in the riser and the internal gas distributor (perforated plate) installed between the two packing. Other parameters investigated include the effect of sparger configuration, gas flow rate, and liquid height in the bioreactor on the different hydrodynamic parameters such as gas holdup, mixing time, and liquid circulation velocity. Results showed that the gas holdup and mixing time increased in the presence of the gas distributor, while the riser superficial liquid velocity was decreased. Furthermore, gas holdup and mixing time increased, superficial liquid velocity decreased when decreasing liquid height in the reactor, and when using packing or gas distributor between two packings in the riser. These results can be used to improve mixing characteristics in external loop airlift bioreactors for wider range of applications.

scholarly journals Mixing Characteristics of External Loop Airlift Bioreactor using Electrical Resistance Tomography

2021 ◽  
Author(s):  
Mian Hamood-Ur-Rehman
Keyword(s):  
Electrical Resistance ◽  
Liquid Velocity ◽  
Mixing Time ◽  
Perforated Plate ◽  
Packed Bed ◽  
Gas Holdup ◽  
External Loop ◽  
Gas Distributor ◽  
Airlift Bioreactors ◽  
Superficial Liquid Velocity

In the present work, a novel packed bed external loop pneumatically agitated airlift bioreactor with an internal gas distributor (perforated plate) between two rolls of packing in the riser was designed and built. This novel approach combines advantages of packed bed and external loop airlift bioreactors. The main objective of this research work was to characterize the hydrodynamic performance of this novel reactor through a non-intrusive flow visualization technique called electrical resistance tomography (ERT). The tomography images, which were generated using a linear back projection algorithm, were employed to explore the effects of different design parameters and operating conditions. These include the effect of the two packing in the riser and the internal gas distributor (perforated plate) installed between the two packing. Other parameters investigated include the effect of sparger configuration, gas flow rate, and liquid height in the bioreactor on the different hydrodynamic parameters such as gas holdup, mixing time, and liquid circulation velocity. Results showed that the gas holdup and mixing time increased in the presence of the gas distributor, while the riser superficial liquid velocity was decreased. Furthermore, gas holdup and mixing time increased, superficial liquid velocity decreased when decreasing liquid height in the reactor, and when using packing or gas distributor between two packings in the riser. These results can be used to improve mixing characteristics in external loop airlift bioreactors for wider range of applications.

scholarly journals A Combined Numerical and Experimental Study of Hydrodynamics for an Air-Water External Loop Airlift Reactor

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Deify Law ◽  
Samuel T. Jones ◽  
Theodore J. Heindel ◽  
Francine Battaglia
Keyword(s):  
Liquid Velocity ◽  
Bubble Column ◽  
Bubble Diameter ◽  
Three Dimensional ◽  
Airlift Reactor ◽  
Cfd Modeling ◽  
Bubble Column Reactor ◽  
Ensemble Averaging ◽  
3D Simulations ◽  
External Loop

The external loop airlift reactor (ELALR) is a modified bubble column reactor that is composed of two vertical columns that are interconnected with two horizontal tubes and is often preferred over traditional bubble column reactors because they can operate over a wider range of conditions. In the present work, the gas-liquid flow dynamics in an ELALR was simulated using an Eulerian–Eulerian ensemble-averaging method in two-dimensional (2D) and three-dimensional (3D) coordinate systems. The computational fluid dynamics (CFD) simulations were compared to experimental measurements from a 10.2 cm diameter ELALR for superficial gas velocities ranging from 1 cm/s to 20 cm/s. The effect of specifying a mean bubble diameter to represent the gas phase in the CFD modeling was investigated, and 2D and 3D simulations were found to be in good agreement with the experimental data. The ELALR flow regimes were compared for the reactor operating in bubble column, closed vent, and open vent modes, and the 2D simulations qualitatively predicted the behavior of bubble growth in the downcomer. However, it was found that 3D simulations were necessary to capture the physics of the ELALR for gas holdup, bulk density differences, and riser superficial liquid velocity.

scholarly journals Hydrodynamics of a self-agitated draft tube airlift reactor

2014 ◽  
Vol 20 (1) ◽  
pp. 59-69 ◽  
Author(s):  
Miodrag Tekic ◽  
Ivana Sijacki ◽  
Milenko Tokic ◽  
Predrag Kojic ◽  
Dragan Petrovic ◽  
...  
Keyword(s):  
Draft Tube ◽  
Liquid Velocity ◽  
Mixing Time ◽  
Gas Holdup ◽  
Airlift Reactor ◽  
Hydrodynamic Characteristics ◽  
Energy Losses ◽  
Liquid Circulation ◽  
Bubble Breakup ◽  
Constructed Self

The main hydrodynamic characteristics of a novel-constructed, self-agitated draft tube airlift reactor (DT-ALR) were investigated. Ten impellers, driven only by the means of gas throughput and induced liquid circulation, were inserted in the draft tube. The insertion of impellers caused bubble breakup and reduction of both mean bubble size and coalescence, even under the conditions of high gas throughputs. Although the impellers induced energy losses, the resistance to the flow was relatively lower due to their rotation, unlike the internals used in other research reported in the literature. In comparison to the conventional configuration of a DT-ALR, it was found that the presence of impellers led to significant changes in hydrodynamics: riser gas holdup and mixing time increased, while overall gas holdup and liquid velocity in the downcomer decreased.

Sign in / Sign up

Export Citation Format

Share Document