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

Fakhari, Mona Ebrahimi; Moraveji, Mostafa Keshavarz; Davarnejad, Reza

doi:10.1016/s1004-9541(14)60050-1

Cited by 9 publications

(6 citation statements)

References 28 publications

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“…The surface tension reduction causes bubbles breaking into smaller ones, leading to a decreased bubble rise velocity, thus, the gas holdup and mass transfer increase, 16,17 Similar results are also observed when reducing liquid viscosity due to the same reason 18–20 . As the buoyancy force increases with density, which assists bubbles to leave the reactor, the gas holdup and gas–liquid mass transfer will decrease accordingly 21,22 …”

Section: Introductionmentioning

confidence: 63%

“…The oxygen in the water was first purged with Na 2 SO 3 , then, the air was pumped into the external-loop reactor, with a dissolved oxygen (DO) probe monitoring the DO concentration variation with time. From the DO profile, k l a with negligible electrode response time 21,25 is obtained:…”

Section: Experiments Setupmentioning

confidence: 99%

“…[18][19][20] As the buoyancy force increases with density, which assists bubbles to leave the reactor, the gas holdup and gas-liquid mass transfer will decrease accordingly. 21,22 In recent years, three-phase reaction has emerged as a most promising solution for the system of strong exothermic gas-phase reactions. For example, in methanol synthesis from syngas, the reaction temperature can be easily controlled by adding an inert liquid to the system.…”

Section: Introductionmentioning

confidence: 99%

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Packing size effects on the liquid circulation property in an external‐loop packed bubble column

2022

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Packing size effects on the fluid dynamics in an external-loop packed bubble column with Raschig rings of three different effective diameters (4.9, 14.1, and 40.7 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, tracer-response, and dynamic oxygen-absorption techniques. 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 in the presence of packing, however, the liquid circulating velocity and gas-liquid mass transfer coefficient are rather complicated.Specifically, the gas holdup increases with the decrease of packing size, while the liquid circulating velocity is on the contrary, and the maximal gas-liquid mass transfer coefficient is achieved under packing diameter of 14.1 mm.

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Section: Introductionmentioning

confidence: 63%

Section: Experiments Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Packing size effects on the liquid circulation property in an external‐loop packed bubble column

2022

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“…Equations from (30) to (34) presented on Table 4 correlate different parameters to determine the volumetric mass transfer coefficient in bubble column and gas-lift bioreactors, according to different authors. Fakhari et al [163] used equation (30) to determine the volumetric mass transfer coefficient in an external loop gas-lift reactor, which includes the electrode response time. In another investigation, Choi et al [164] adapted the overall mass transfer coefficient in an air-lift bioreactor to the equation (31) for a temperature of 20°C as reference.…”

Section: Mass Transfer Coefficientmentioning

confidence: 99%

Bioreactor design for enzymatic hydrolysis of biomass under the biorefinery concept

Pino

Rodríguez-Jasso

Michelin

et al. 2018

Chemical Engineering Journal

172

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The dependence on non-renewable resources, particularly fossil fuels, has awaken a growing interest in research of sustainable alternative energy sources, such as bioethanol. The production of bioethanol from lignocellulosic materials comprises three main stages, starting with a pretreatment, followed by an enzymatic hydrolysis step where fermentable sugars are obtained for the final fermentation process. Enzymatic hydrolysis represents an essential step in the bioethanol production, however there are some limitations in it that hinders the process to be economically feasible. Different strategies have been studied to overcome these limitations, including the enzyme recycling and the utilization of high solids concentrations. Several investigations have been carried out in different bioreactor configurations with the aim to obtain higher yields of glucose in the enzymatic hydrolysis stage; however, the commonest are Stirred Tank Bioreactors (STBR) and Membrane Bioreactors (MBR). In general, the key criteria for a bioreactor design include adequate mass transfer, low shear stress, and efficient mixing that allows the appropriated interaction between the substrate and the enzyme. Therefore, this review will address the main aspects to be considered for a bioreactor design, as well as, the operational conditions, some characteristics and mode of operating strategies of the two main bioreactors used in the enzymatic hydrolysis stage. Moreover, two types of pneumatically agitated bioreactors, namely bubble column and gas-lift bioreactors, are discussed as promising alternatives to develop enzymatic saccharification due to their low energy consumption compared with STBR.

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“…In the another research, Moraveji 13 studied the hydrodynamics and mass transfer characteristics in a 15.6 Â 10 À3 m 3 external loop airli reactor for oil-in-water micro-emulsions with oil-to-water volumetric ratios (4) ranging from 3% to 7% (by volume). An increase in 4 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.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics and mass transfer study of oil-water micro-emulsion in a three phase external loop airlift reactor

Moraveji

Gharib

2014

RSC Adv.

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In this study, the impact of operating conditions, liquid properties and loading of a solid phase on the hydrodynamics and mass transfer coefficient in an airlift reactor with an external loop was investigated.The gas phase sparged through the reactor was air. Oil-in-water micro emulsions containing diesel, kerosene, heavy naphtha and light naphtha made up the liquid phase with an oil concentration of 5%. The impact of the solid phase was studied with solid loadings of 0, 0.25 and 0.5 wt%. The results showed that light naphtha which had the lowest density, viscosity and surface tension had the highest mass transfer and gas holdup and the lowest liquid circulation velocity. Solid addition decreased the gas holdup and mass transfer while increasing the liquid circulation velocity. This effect was considerable on the parameters above. In addition, a correlation based on dimensionless numbers was gained to predict the Sherwood number. Good agreement was observed between the correlated and experimental values.

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

Cited by 9 publications

References 28 publications

Packing size effects on the liquid circulation property in an external‐loop packed bubble column

Packing size effects on the liquid circulation property in an external‐loop packed bubble column

Bioreactor design for enzymatic hydrolysis of biomass under the biorefinery concept

Hydrodynamics and mass transfer study of oil-water micro-emulsion in a three phase external loop airlift reactor

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