scholarly journals Effects of Sparger Design on the Gas Holdup and Mass Transfer in a Pilot Scale External Loop Airlift Reactor

2021 ◽  
Author(s):  
N. Naidoo ◽  
W.J. Pauck ◽  
M. Carsky
Keyword(s):  
Mass Transfer ◽  
Pilot Scale ◽  
Gas Holdup ◽  
Airlift Reactor ◽  
External Loop

scholarly journals Numerical study of the hydrodynamics and mass transfer in the external loop airlift reactor

2021 ◽  
pp. 34-34
Author(s):  
Predrag Kojic ◽  
Jovana Kojic ◽  
Milada Pezo ◽  
Jelena Krulj ◽  
Lato Pezo ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Airlift Reactor ◽  
Volumetric Mass Transfer Coefficient ◽  
Cfd Model ◽  
Gas Velocity ◽  
Liquid Mass ◽  
External Loop ◽  
Liquid Mass Transfer

The objective of this study was to investigate the hydrodynamics and the gas-liquid mass transfer coefficient of an external-loop airlift reactor (ELAR). The ELAR was operated in three cases: different inlet velocities of fluids, different alcohols solutions (water, 0.5% methanol, 0.5% ethanol, 0.5% propanol and 0.5% butanol) and different concentration of methanol in solutions (0%, 0.5%, 1%, 2% and 5%). The influence of superficial gas velocity and various diluted alcohol solutions on hydrodynamics and gas-liquid mass transfer coefficient of the ELAR was studied. Experimentally, the gas hold-up, liquid velocities and volumetric mass transfer coefficient values in the riser and the downcomer were obtained from the literature source. A computational fluid dynamics (CFD) model was developed, based on two-phase flow, investigating different liquids regarding surface tension, assuming the ideal gas flow, applying the finite volume method and Eulerian-Eulerian model. The volumetric mass transfer coefficient was determined using CFD model, as well as artificial neural network model. The effects of liquid parameters and gas velocity on the characteristics of the gas-liquid mass transfer were simulated. These models were compared with appropriate experimental results. CFD model successfully succeed to simulate the influence of different alcohols regarding the number of C-atoms on hydrodynamics and mass transfer.

Mass transfer in an external-loop airlift reactor: experiments and modeling

1997 ◽  
Vol 52 (21-22) ◽  
pp. 3909-3917 ◽  
Author(s):  
H. Dhaouadi ◽  
S. Poncin ◽  
J.M. Hornut ◽  
G. Wild ◽  
P. Oinas ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Airlift Reactor ◽  
External Loop

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 Predicting mass transfer in pilot scale external loop airlift reactors using neural networks

2018 ◽  
Author(s):  
◽  
Nirvana Naidoo
Keyword(s):  
Neural Network ◽  
Mass Transfer ◽  
Artificial Neural Network ◽  
Pilot Scale ◽  
External Loop ◽  
External Data ◽  
The Neural Network ◽  
Artificial Neural ◽  
Superficial Gas Velocity ◽  
Airlift Reactors

Airlift reactors are a viable means for conducting large scale mass transfer operations. However, due to the difficulty experienced in understanding the complex behavioural characteristics of these reactors, the design of airlift reactors becomes very complicated and largely empirical. Existing correlations and traditional computational fluid dynamic modelling has proven to be mostly reactor dependent and not widely applicable thereby limiting their application. There is therefore a need to develop a model that does not require prior knowledge of relationships between parameters of these reactors but instead uses an alternate method to assist with the design of airlift reactors. An artificial neural network represents this method. The aim of this investigation was to build an artificial neural network using selected input data of Newtonian fluids in pilot scale external loop airlift reactors of varying designs in order to predict the mass transfer coefficient in other external loop airlift reactors with more general geometry. To achieve this, a large base of experimental data (663) was generated using glycerine-air and water-air systems in 5 configurations of external loop airlift reactors with 3 categories of sparger design. The data was modelled using the artificial neural network software, Predict (Version 3.30) by Neuralware. The Coefficient of Correlation for the neural network model was 0.98. The neural network model was tested with unseen external data from various sources of which the R values ranged from 0.91 to 0.99. Additional external data was evaluated with the superficial gas velocity out of the range of the experimental data from this investigation and with a very different design of sparger. The R values for this additional data were 0.85 and 0.67-0.85 respectively. To achieve good correlations it was found necessary to take into account the sparger design and pore size; the actual geometric dimensions of the reactors namely the riser and downcomer diameters and heights; the visual observations of the approximate bubble size and bubble flow patterns and static liquid height in addition to the more usual data of the area and aspect ratios; the fluid properties namely, surface tension, density and viscosity; the superficial gas velocity; the downcomer superficial liquid velocity; the riser gas holdup and the downcomer gas holdup. However, some parameters like the static liquid height although considered important appeared not to be. By considering these as important input variables into the network, the artificial neural network was able to give excellent approximations for both seen and unseen data for some of the reactor configurations. However, the network also had the ability to pick up differences in the reactor configurations were it did not predict well, especially with respect to sparger design. An important conclusion arrived at in this investigation was the significant influence of the sparger and its design on the mass transfer. The sensitivity of the network to the sparger design means that a greater quantification of the influence of the sparger design is required.

scholarly journals Packing size effect on the liquid circulation property in an external-loop packed bubble column

2021 ◽  
Author(s):  
Yanling Tang ◽  
Gang Luo ◽  
Zhenmin Cheng
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Bubble Column ◽  
Gas Holdup ◽  
Oxygen Absorption ◽  
Liquid Mass ◽  
External Loop ◽  
Packing Size ◽  
Liquid Mass Transfer

Packing size effects on the fluid dynamics in an external-loop packed bubble column with Raschig rings of three different effective diameters (5, 14 and 41 mm) in the riser were investigated. The overall gas holdup, liquid circulating velocity and gas-liquid mass transfer coefficient were respectively measured by volume expansion method, tracer-response method and dynamic oxygen-absorption technique. CFD simulation with the Euler-Euler two-fluid method was used to predict the liquid circulating velocity by treating the packing as a porous medium. Compared to the empty column, the gas holdup was found to increase with the presence of packing, however, the liquid circulating velocity and gas-liquid mass transfer coefficient may increase or decrease. Specifically, the gas holdup increases with the decrease of packing size, while the liquid circulating velocity is on the contrary, which induces the maximal gas-liquid mass transfer rate at packing diameter of 14 mm.

Hydrodynamics and Mass Transfer of Oily Micro-emulsions in An External Loop Airlift Reactor

2014 ◽  
Vol 22 (3) ◽  
pp. 267-273 ◽  
Author(s):  
Mona Ebrahimi Fakhari ◽  
Mostafa Keshavarz Moraveji ◽  
Reza Davarnejad
Keyword(s):  
Mass Transfer ◽  
Airlift Reactor ◽  
External Loop
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