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Reza Davarnejad - One of the best experts on this subject based on the ideXlab platform.
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hydrodynamics and mass transfer of oily micro emulsions in an external loop Airlift Reactor
Chinese Journal of Chemical Engineering, 2014Co-Authors: Mona Ebrahimi Fakhari, Mostafa Keshavarz Moraveji, Reza DavarnejadAbstract:Abstract This study reports an experimental investigation on hydrodynamics and mass transfer characteristics in a 15.6×10 −3 m 3 external loop Airlift Reactor for oil-in-water micro-emulsions with oil to water volume ratio (ϕ) ranging from 3% to 7% (by volume). For comparative purposes, experiments were also carried out with water. Increase in ϕ of micro-emulsion systems results in an increment in the gas holdup and a decrease in the volumetric gas-liquid oxygen transfer coefficient and liquid circulation velocity, attributed to the escalation in the viscosity of micro-emulsions. The gas holdup and volumetric mass transfer coefficient for micro-emulsion systems are significantly higher than that of water system. Two correlations are developed to predict the gas holdup and oxygen transfer coefficient.
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Hydrodynamics and oxygen mass transfer in a packed bed split-cylinder Airlift Reactor containing dilute alcoholic solutions
Heat and Mass Transfer/Waerme- und Stoffuebertragung, 2013Co-Authors: Mostafa Keshavarz Moraveji, Elmira Mohsenzadeh, Mona Ebrahimi Fakhari, Reza DavarnejadAbstract:In this article, the influences of alcohols on the hydrodynamics and oxygen mass transfer characteristics in an Airlift Reactor equipped with packing were investigated. The hydrodynamic parameters and mass transfer coefficient in 1 % (v/v) aqueous solutions of four aliphatic alcohols were tested. It was concluded that alcohols addition increased gas holdup and gas-liquid mass transfer coefficient. The packing installation increased mass transfer coefficient, gas holdup and liquid circulation velocity, as well.
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hydrodynamics and mass transfer of oil water micro emulsion in a three phase internal Airlift Reactor
Fuel, 2012Co-Authors: Mostafa Keshavarz Moraveji, Baharak Sajjadi, Mahboubeh Jafarkhani, Reza DavarnejadAbstract:In this article, the impacts of liquid properties, loading of solid phase and operating conditions on the hydrodynamic and mass transfer coefficient in a split-cylindrical Airlift Reactor sparged by air were investigated. The various oil-in-water micro-emulsion systems containing light naphtha, heavy naphtha, kerosene and diesel were used as the liquid phase with oil concentrations of 5% and the solid phase with the loading of 0, 0.25 and 0.5 wt.%. The experimental results showed that a micro-emulsion with the lowest density, viscosity and surface tension had maximum mass transfer and gas hold-up and minimum liquid circulation velocity. The gas hold-up and mass transfer decreased and liquid circulation velocity increased by solid particles addition. Further, solid loading enhancement had a dramatic effect on the mentioned parameters. Moreover, a proper correlation based on dimensionless numbers was used to predict mass transfer in this process. A very good agreement was observed between the correlated data and the experimental ones.
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effects of surfactants on hydrodynamics and mass transfer in a split cylinder Airlift Reactor
Canadian Journal of Chemical Engineering, 2012Co-Authors: Mostafa Keshavarz Moraveji, Reza Davarnejad, Mohamad Morovati Pasand, Yusuf ChistiAbstract:Effects of various concentrations (0–5 ppm) of anionic (sodium dodecyl sulfate, SDS) and non-ionic (Tween-80 and Triton X-405) surfactants on gas hold-up and gas–liquid mass transfer in a split-cylinder Airlift Reactor are reported for air–water. Surfactants were found to strongly enhance gas hold-up. Non-ionic surfactants were more effective in enhancing gas hold-up compared to the anionic surfactant SDS. An enhanced gas hold-up and a visually reduced bubble size in the presence of surfactants implied an enhanced gas–liquid interfacial area for mass transfer. Nevertheless, the overall gas–liquid volumetric mass transfer coefficient was reduced in the presence of surfactants, suggesting that surfactants greatly reduced the true liquid film mass transfer coefficient and this reduction outweighed the interfacial area enhancing effect. Presence of surfactants did not substantially affect the induced liquid circulation rate in the Airlift vessel.
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gas liquid hydrodynamics and mass transfer in aqueous alcohol solutions in a split cylinder Airlift Reactor
Chemical Engineering & Technology, 2011Co-Authors: Mostafa Keshavarz Moraveji, Baharak Sajjadi, Reza DavarnejadAbstract:The influences of aliphatic alcohols (CnH2n+1OH, n = 1–4) and their concentrations (0–1 vol.-%) on gas holdup, liquid circulation velocity, mixing time, and overall volumetric gas-liquid oxygen mass transfer coefficient were considered in a split-cylinder Airlift Reactor sparged with air. The carbon chain length of the alcohols and their concentration affect the Airlift Reactor performance. Alcohols reduced the average bubble sizes and increased the gas holdup, the interfacial area for mass transfer, and the gas-liquid mass transfer coefficient. Since butanol has the most carbon atoms in its chain, it had the most significant effect on gas holdup and mass transfer enhancement. It also decreased the liquid circulation velocity by surface tension reduction. Two correlations based on dimensionless groups were applied to investigate the effect of hydrodynamics and molecules on gas holdup and mass transfer. A satisfactory agreement between correlation and experimental results was observed.
Manindra Nath Biswas - One of the best experts on this subject based on the ideXlab platform.
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treatment of phenolic wastewater in a novel multi stage external loop Airlift Reactor using activated carbon
Separation and Purification Technology, 2008Co-Authors: Kaustubha Mohanty, Debabrata Das, Manindra Nath BiswasAbstract:In this work, a novel multi-stage external loop Airlift Reactor has been designed to remove phenol from wastewater by means of its adsorption onto the surface of activated carbons. The multi-staging has been achieved by hydrodynamically induced continuous bubble generation, breakup and regeneration. The continuous rupture and bursting of bubbles creates localized turbulence and recirculation, which helps in faster transfer of trace pollutants to the active sites of the solid adsorbents. Thus, the pollutants get adsorbed to the surface of the solid adsorbents due to continuous agitation. Different operating parameters that affect the performance of the Reactor are the superficial gas velocity, liquid circulation velocity, concentration of the pollutant present in wastewater, contact time and the carbon loading. The results show that the removal time as well as the activated carbon loading for this system were quite lower as compared to simple batch adsorption systems. The kinetic data were fitted to the models of intra-particle diffusion, pseudo-second-order and Lagergren, and followed more closely the Lagergren pseudo-first-order model. Langmuir and Freundlich models were used to study the adsorption isotherms. A correlation has been developed to predict the efficiency of percentage removal of phenol and found to be highly significant from statistical point of view.
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mass transfer characteristics of a novel multi stage external loop Airlift Reactor
Chemical Engineering Journal, 2007Co-Authors: Kaustubha Mohanty, Debabrata Das, Manindra Nath BiswasAbstract:Abstract This paper reports on the experimental investigation carried out to evaluate the interfacial area, a , and liquid-side volumetric mass transfer coefficient, k L a , to characterize a multi-stage external loop Airlift Reactor (with contraction and expansion disks), which has been conceived, designed, and fabricated as an equipment to remove trace pollutants from wastewater. In addition, it has versatile use as a gas–liquid contactor in chemical process industries. In the experimental range of gas and liquid flows investigated, the maximum interfacial area and volumetric mass transfer coefficient obtained was in the order of 300 m 2 /m 3 and 0.05 s −1 , respectively. Correlations developed for predicting the interfacial area and liquid-side volumetric mass transfer coefficient have been found to be encouraging and highly significant from statistical analysis.
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hydrodynamics of a novel multi stage external loop Airlift Reactor
Chemical Engineering Science, 2006Co-Authors: Kaustubha Mohanty, Debabrata Das, Manindra Nath BiswasAbstract:Abstract In the present investigation a novel multi-stage external loop Airlift Reactor with hydro-dynamically induced continuous bubble generation, breakup and regeneration has been proposed. The system has been designed to operate with relatively large sized bubbles, so that interfacial circulation can be induced in the liquid–bubble interfaces and faster transfer of components can take place by turbulent diffusion through the interface of the bubbles and also due to the physical rupture and reformation of the bubbles. The system was also designed to operate in three stages operating in series so that in each stage completely deaerated liquid could be brought in contact with freshly generated bubbles. Detailed studies on the gas holdup and liquid circulation velocity have been carried out with respect to various values of superficial gas as well as liquid velocities. The gas holdup of the proposed multi-stage system is 45% higher than the single stage system, which results in better mass transfer characteristics. Empirical correlations describing the performance of the proposed Reactor have been presented in this paper.
Jingqi Yuan - One of the best experts on this subject based on the ideXlab platform.
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Modeling of Mass Transfer in an Internal Loop Airlift Reactor
Chemical Engineering & Technology, 2015Co-Authors: Jingqi YuanAbstract:A complete mass transfer model was established for an internal loop Airlift Reactor. All sections of the Reactor, including bottom, riser, top, and downcomer, were taken into account. A numerical method was developed to solve the mass transfer model. The effectiveness of the model was validated by experimental measurements. Based on numerical results of the model, the dynamical mass transfer process in the Reactor was analyzed in detail. Some mass transfer characteristics of the Airlift Reactor were revealed. The results indicated that the proposed model well predicted the mass transfer in the internal loop Airlift Reactor.
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hydrodynamics and mass transfer characteristics in an internal loop Airlift Reactor with sieve plates
Chemical Engineering Research & Design, 2013Co-Authors: Lijia Luo, Jingqi Yuan, Ping Xie, Junwei Sun, Wei GuoAbstract:Abstract Effects of the sieve plate on hydrodynamics and mass transfer in an annulus sparged Airlift Reactor (0.08 m 3 , 1.3 m tall, and 0.284 m in diameter) were investigated. It is found that the sieve plate can significantly enhance gas holdup and volumetric mass transfer coefficient. The sieve pore plays an important role in breaking up bubbles. With a given free area ratio, the sieve plate with a larger sieve pore diameter is more efficient in increasing the volumetric mass transfer coefficient. Four different free area ratios between 37% and 73% are tested, and then an optimal free area ratio is determined. The effect of the sieve plate is found to be related to sparger types. The sieve plate leads to a larger increase of volumetric mass transfer coefficient with the O-ring distributor as compared to the 4-orifice nozzle. Empirical correlations and a hydrodynamic model are proposed to predict gas holdup, volumetric mass transfer coefficient and liquid velocity in Airlift Reactors with sieve plates.
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hilbert huang transform hurst and chaotic analysis based flow regime identification methods for an Airlift Reactor
Chemical Engineering Journal, 2012Co-Authors: Lijia Luo, Ping Xie, Junwei Sun, Ying Yan, Jingqi YuanAbstract:Abstract The flow regimes and their transitions in an internal loop Airlift Reactor were investigated. The Hilbert–Huang transform (HHT) was applied to analyze the energy–frequency–time distribution of the pressure signal. It was found that the Hilbert spectrum of the pressure signal was closely related to the superficial gas velocity. The stochastic behaviors of intrinsic mode functions (IMFs) extracted from the pressure signal were studied using the Hurst analysis. Two different Hurst exponents were obtained for each pressure signal: one was smaller than 0.5, while the other was larger than 0.5, representing the anti-persistent and persistent hydrodynamic behaviors, respectively. The evolution of the larger Hurst exponent clearly indicated flow regime transitions in the downcomer. The wavelet transform combined with the autocorrelation analysis were applied to extract chaotic components of the pressure signal. Two flow regime transition points were successfully detected from the evolution of chaotic parameters, i.e. the largest Lyapunov exponent, correlation dimension and Kolmogorov entropy.
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hydrodynamics and mass transfer characteristics in an internal loop Airlift Reactor with different spargers
Chemical Engineering Journal, 2011Co-Authors: Lijia Luo, Fengna Liu, Jingqi YuanAbstract:The effect of the sparger structure on the hydrodynamics and mass transfer characteristics of an internal loop Airlift Reactor was investigated. Three spargers with different diameters and numbers of orifices were tested. Two different flow regimes, i.e., homogenous flow and heterogeneous flow, were identified within the experimental range of superficial gas velocities. It is found that the sparger structure has more significant effect on hydrodynamic parameters in the heterogeneous flow regime than in the homogenous flow regime. The largest gas holdup and downcomer liquid velocity were obtained with the 4-orifice nozzle, followed by the O-ring distributor and the 2-orifice nozzle. The sparger structure has less effect on the oxygen transfer coefficient kL, while it strongly affects the specific interfacial area a. The 4-orifice nozzle improved the volumetric mass transfer efficiency for that it generated a smaller mean bubble diameter and therefore a larger specific interfacial area than other spargers. Based on the material conservation and pressure balance principles, a hydrodynamic model was established to predict the liquid velocity in the downcomer, as well as the liquid velocity and the cross sectional area of the up-flow in the riser. Empirical correlations were proposed for different spargers, which well predicted the gas holdup and the volumetric mass transfer coefficient.
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identification of flow regime transitions in an annulus sparged internal loop Airlift Reactor based on higher order statistics and winger trispectrum
Chemical Engineering Science, 2011Co-Authors: Lijia Luo, Jingqi YuanAbstract:Abstract Higher order statistics and Wigner higher order moment spectra were used to extract useful flow regime characteristics from wall pressure fluctuation signals in an annulus sparged internal loop Airlift Reactor. It is found that the pressure fluctuation in the Airlift Reactor is a typical nonlinear and non-stationary process, which exhibits different frequency characteristics depending on flow regimes. Analysis methods based on bispectrum and Wigner trispectrum are powerful tools to reveal frequency characteristics of pressure signals. To identify flow regime transitions in the Reactor, two new characteristic quantities, namely average bispectrum and generalized average frequency, are defined from bispectrum and Wigner trispectrum of the pressure signal, respectively. Two flow regime transition points corresponding to three flow regimes in the Reactor are successfully detected by using these two characteristic quantities.
Mostafa Keshavarz Moraveji - One of the best experts on this subject based on the ideXlab platform.
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hydrodynamics and mass transfer of oily micro emulsions in an external loop Airlift Reactor
Chinese Journal of Chemical Engineering, 2014Co-Authors: Mona Ebrahimi Fakhari, Mostafa Keshavarz Moraveji, Reza DavarnejadAbstract:Abstract This study reports an experimental investigation on hydrodynamics and mass transfer characteristics in a 15.6×10 −3 m 3 external loop Airlift Reactor for oil-in-water micro-emulsions with oil to water volume ratio (ϕ) ranging from 3% to 7% (by volume). For comparative purposes, experiments were also carried out with water. Increase in ϕ of micro-emulsion systems results in an increment in the gas holdup and a decrease in the volumetric gas-liquid oxygen transfer coefficient and liquid circulation velocity, attributed to the escalation in the viscosity of micro-emulsions. The gas holdup and volumetric mass transfer coefficient for micro-emulsion systems are significantly higher than that of water system. Two correlations are developed to predict the gas holdup and oxygen transfer coefficient.
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hydrodynamics and mass transfer of oil water micro emulsion in a three phase internal Airlift Reactor
Fuel, 2012Co-Authors: Mostafa Keshavarz Moraveji, Baharak Sajjadi, Mahboubeh Jafarkhani, Reza DavarnejadAbstract:In this article, the impacts of liquid properties, loading of solid phase and operating conditions on the hydrodynamic and mass transfer coefficient in a split-cylindrical Airlift Reactor sparged by air were investigated. The various oil-in-water micro-emulsion systems containing light naphtha, heavy naphtha, kerosene and diesel were used as the liquid phase with oil concentrations of 5% and the solid phase with the loading of 0, 0.25 and 0.5 wt.%. The experimental results showed that a micro-emulsion with the lowest density, viscosity and surface tension had maximum mass transfer and gas hold-up and minimum liquid circulation velocity. The gas hold-up and mass transfer decreased and liquid circulation velocity increased by solid particles addition. Further, solid loading enhancement had a dramatic effect on the mentioned parameters. Moreover, a proper correlation based on dimensionless numbers was used to predict mass transfer in this process. A very good agreement was observed between the correlated data and the experimental ones.
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effects of surfactants on hydrodynamics and mass transfer in a split cylinder Airlift Reactor
Canadian Journal of Chemical Engineering, 2012Co-Authors: Mostafa Keshavarz Moraveji, Reza Davarnejad, Mohamad Morovati Pasand, Yusuf ChistiAbstract:Effects of various concentrations (0–5 ppm) of anionic (sodium dodecyl sulfate, SDS) and non-ionic (Tween-80 and Triton X-405) surfactants on gas hold-up and gas–liquid mass transfer in a split-cylinder Airlift Reactor are reported for air–water. Surfactants were found to strongly enhance gas hold-up. Non-ionic surfactants were more effective in enhancing gas hold-up compared to the anionic surfactant SDS. An enhanced gas hold-up and a visually reduced bubble size in the presence of surfactants implied an enhanced gas–liquid interfacial area for mass transfer. Nevertheless, the overall gas–liquid volumetric mass transfer coefficient was reduced in the presence of surfactants, suggesting that surfactants greatly reduced the true liquid film mass transfer coefficient and this reduction outweighed the interfacial area enhancing effect. Presence of surfactants did not substantially affect the induced liquid circulation rate in the Airlift vessel.
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gas liquid hydrodynamics and mass transfer in aqueous alcohol solutions in a split cylinder Airlift Reactor
Chemical Engineering & Technology, 2011Co-Authors: Mostafa Keshavarz Moraveji, Baharak Sajjadi, Reza DavarnejadAbstract:The influences of aliphatic alcohols (CnH2n+1OH, n = 1–4) and their concentrations (0–1 vol.-%) on gas holdup, liquid circulation velocity, mixing time, and overall volumetric gas-liquid oxygen mass transfer coefficient were considered in a split-cylinder Airlift Reactor sparged with air. The carbon chain length of the alcohols and their concentration affect the Airlift Reactor performance. Alcohols reduced the average bubble sizes and increased the gas holdup, the interfacial area for mass transfer, and the gas-liquid mass transfer coefficient. Since butanol has the most carbon atoms in its chain, it had the most significant effect on gas holdup and mass transfer enhancement. It also decreased the liquid circulation velocity by surface tension reduction. Two correlations based on dimensionless groups were applied to investigate the effect of hydrodynamics and molecules on gas holdup and mass transfer. A satisfactory agreement between correlation and experimental results was observed.
Predrag S Kojic - One of the best experts on this subject based on the ideXlab platform.
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predicting hydrodynamic parameters and volumetric gas liquid mass transfer coefficient in an external loop Airlift Reactor by support vector regression
Chemical Engineering Research & Design, 2017Co-Authors: Predrag S Kojic, Radovan OmorjanAbstract:Abstract For modeling, design and scale-up of the Airlift Reactors, it is crucial to estimate hydrodynamic parameters and volumetric gas–liquid mass transfer coefficient for different flow regimes. Prediction of these variables had begun by applying empirical power low correlations and later evolved in use of the artificial neural networks (ANN) as the best option available in the literature. The objective of this study was to present the support vector regression (SVR) model that predicts the gas holdup, downcomer liquid velocity and volumetric gas–liquid mass transfer coefficient values in the external-loop Airlift Reactor better than ANN. Furthermore, to demonstrate the applicability of the SVR model, it was used on the different literature data sets with wide-ranging databanks. The statistical error analysis revealed that the proposed generalized SVR model had more precisely prediction than ANN with an average absolute relative error (AARE) of 2.17%, 1.32% and 9.64% for gas holdup, downcomer liquid velocity and volumetric gas-liquid mass transfer coefficient values, respectively.
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enhanced mass transfer in a novel external loop Airlift Reactor with self agitated impellers
Biochemical Engineering Journal, 2017Co-Authors: Natasa Lj Lukic, Predrag S Kojic, Ivana M Sijacki, Svetlana S Popovic, Miodrag N Tekic, Dragan Lj PetrovicAbstract:In the present study a novel type of internals, self‐agitated impellers, were inserted in the riser section of an external‐loop Airlift Reactor to intensify mass transfer rates. The performance of self‐agitated impellers was evaluated through comparative analysis of the obtained volumetric mass transfer coefficient values with regard to liquid phase properties and sparger types. Compared to the configuration without impellers, self‐agitated impellers considerably improved Reactor characteristics by increasing volumetric mass transfer coefficient up to 82% at smaller superficial gas velocities. At higher gas velocities, corresponding to aeration conditions operated in most cultivation, values of volumetric mass transfer coefficient were 20–30% higher with the insertion of impellers. The effective viscosity played a key role in defining the magnitude of the impellers’ effect on the improvement of volumetric mass transfer coefficient. Superficial gas velocity and sparger design influenced impellers efficiency as well. The highest improvements of volumetric mass transfer coefficient were achieved in the most viscous carboxylmethylcellulose solution by using the least effective type of sparger. Besides proposed empirical correlations, which gave an average relative error of 9.1%, an artificial neural network was also successfully developed to estimate the volumetric mass transfer coefficient. The results showed that neural network model was able to predict volumetric mass transfer coefficient with an average relative error of 4.8%.
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volumetric gas liquid mass transfer coefficient in an external loop Airlift Reactor with inserted membrane
Chemical Industry & Chemical Engineering Quarterly, 2016Co-Authors: Predrag S Kojic, Ivana M Sijacki, Natasa Lj Lukic, Dragica Z Jovicevic, Svetlana S Popovic, Dragan Lj PetrovicAbstract:The effects of the inserted membrane in the downcomer of an external-loop Airlift Reactor, the gas sparger type (single orifice and sinter plate) and added alcohol (ethanol, n-butanol, or n-hexanol) on the volumetric gas-liquid mass transfer coefficient (kLa) were studied. Due to the presence of the membrane in the downcomer, kLa did not change significantly; the differences were smaller than 10%. The highest values of the kLa were obtained using the sinter plate. It was found that the addition of small amounts of alcohol increased the mass transfer. Using our experimental results and the data of other authors, the feed-forward back propagation neural network for prediction of kLa in external-loop Airlift Reactors with alcohol solutions was proposed. [Projekat Ministarstva nauke Republike Srbije, br. 172025]
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influence of the sparger type and added alcohol on the gas holdup of an external loop Airlift Reactor
Chemical Engineering & Technology, 2015Co-Authors: Predrag S Kojic, Milenko Tokic, Ivana M Sijacki, Natasa Lj Lukic, Dragan Lj Petrovic, Dragica Z Jovicevic, Svetlana S PopovicAbstract:The influences of alcohol adding and three different gas spargers (single orifice, perforated plate, and sinter plate) on the gas holdup in an external-loop Airlift Reactor were studied. The experimental results show that the gas holdup can be increased by mutual influence of both the alcohol adding and the sparger type. The presence of small amounts of normal aliphatic alcohols caused an increase of the gas holdup compared to the air-water system, due to their coalescence-inhibiting nature. The sinter plate was the most efficient sparger, followed by the perforated plate and the single orifice. A proposed artificial neural network (ANN) has the potential to predict gas holdup values in Airlift Reactors for various alcohols and types of gas spargers.