Hydrodynamic Flow Regimes, Gas Holdup, and Liquid Circulation in Airlift Reactors

1998 ◽  
Vol 37 (4) ◽  
pp. 1251-1259 ◽  
Author(s):  
Mohamed E. Abashar ◽  
Udi Narsingh ◽  
Andre E. Rouillard ◽  
Robin Judd
Keyword(s):  
Flow Regimes ◽  
Gas Holdup ◽  
Hydrodynamic Flow ◽  
Liquid Circulation ◽  
Airlift Reactors

scholarly journals Effect of Contaminants on the Gas Holdup and Mixing in Internal Airlift Reactors Equipped with Microbubble Generator

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Surya K. Pallapothu ◽  
Adel M. Al Taweel
Keyword(s):  
Sodium Dodecyl ◽  
Pilot Scale ◽  
Gas Holdup ◽  
Superficial Velocity ◽  
Hydrodynamic Performance ◽  
Two Phase ◽  
Liquid Circulation ◽  
Circulation Velocity ◽  
The Impact ◽  
Airlift Reactors

The impact of contaminants on the gas holdup and mixing characteristics encountered in internal airlift reactors was investigated using a 200 L pilot scale unit equipped with a two-phase transonic sparger capable of generating microbubbles. Small dosages of a cationic surfactant (0–50 ppm of sodium dodecyl sulfonate (SDS)) were used to simulate the coalescence-retarding effect encountered in most industrial streams and resulted in the formation of bubbles that varied in size between 280 and 1,900 μm. Gas holdups as high as 0.14 were achieved in the riser under homogeneous flow regime when slowly coalescent systems were aerated at the relatively low superficial velocity of 0.02 ms−1, whereas liquid circulation velocities as high as 1.3 ms−1were achieved in conjunction with rapidly coalescent systems at the same superficial velocity. This excellent hydrodynamic performance represents a 5-fold improvement in the riser gas holdup and up to 8-fold enhancement in the liquid circulation velocity and is expected to yield good mixing and mass transfer performance at low energy dissipation rates.

Unified study of flow regimes and gas holdup in the presence of positive and negative surfactants in a non-uniformly aerated bubble column

2011 ◽  
Vol 66 (18) ◽  
pp. 4047-4058 ◽  
Author(s):  
Elena M. Cachaza ◽  
M. Elena Díaz ◽  
Francisco J. Montes ◽  
Miguel A. Galán
Keyword(s):  
Bubble Column ◽  
Flow Regimes ◽  
Gas Holdup ◽  
Unified Study

Design of Venturi-tube gas distributors for bubble-type reactors

1984 ◽  
Vol 49 (9) ◽  
pp. 1939-1948 ◽  
Author(s):  
Milan Rylek ◽  
Jindřich Zahradník
Keyword(s):  
Experimental Data ◽  
Gas Holdup ◽  
Venturi Tube ◽  
Design Parameters ◽  
Dispersion Characteristics ◽  
Liquid Circulation ◽  
Bed Porosity ◽  
Gas Distributor ◽  
Liquid Dispersion

The effect of individual parts of a Venturi-tube gas distributor on quality of the gas-liquid dispersion formed was studied in a bubble-type reactor with forced liquid circulation. Gas holdup (bubble-bed porosity) was used as the dispersion characteristics, type and geometry of nozzles, suction chamber arrangement, and dimensions of the mixing tube and diffuser were chosen as variable design parameters. Experimental data of gas holdup presented in dependence on the rate of energy dissipation in the place of dispersion formation characterized then the dispersion efficiency of the Venturi tube at given conditions. Recommendations for design of Venturi-tube gas distributors are presented based upon the results of the study.

Experiment and CFD Simulation on Gas Holdup Characteristics in an Internal Loop Reactor with External Liquid Circulation

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Chunxi Lu ◽  
Nana Qi ◽  
Kai Zhang ◽  
Jiaqi Jin ◽  
Hu Zhang
Keyword(s):  
Cfd Simulation ◽  
Gas Holdup ◽  
Gas Velocity ◽  
Loop Reactor ◽  
Internal Loop ◽  
Liquid Circulation ◽  
Liquid Phases ◽  
Ansys Cfx ◽  
Other Information ◽  
Superficial Gas Velocity

An external liquid circulation is introduced into a traditional internal loop reactor in order to improve liquid circulation and increase the interface between gas and liquid phases. The effects of superficial gas velocity and external liquid circulation velocity on local and overall gas holdups are explored experimentally and numerically in the loop section of a combined gas-liquid contactor, which consists of a liquid spray, sieve plates and an internal loop with external liquid circulation. Local gas holdup is measured experimentally by a double-sensor conductivity probe. Numerical simulations are conducted in the platform of a commercial software package, ANSYS CFX 10.0. Gas holdup and other information are obtained by solving the governing equations of mass and momentum balances for gas and liquid phases in a hybrid mesh system. Both measured and simulated results indicate that local, section-averaged, and overall gas holdups increase with an increase of the superficial gas velocity. The downcomer tube for circulating external liquid has a significant influence in the gas-distributor and the downcomer-tube action regions rather than in the upper draft-tube and the gas-liquid separation regions. Good agreement between measured and predicted data suggests that CFD simulation together with experimental investigation can be employed to develop novel gas-liquid contactors with a complex geometrical configuration.

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