Dynamic Simulation of Volume Fraction and Density Solid Phase Effect on Phase Hold-Up in 3 Phase Fluidize Bed Column through CFD

The gas-liquid-solid fluidized bed has emerged in recent years as one of the most promising devices for three-phase operation. Selection and design is one of them in parameter in the performance of three phase system. This paper focuses on volume fraction and density effect on the phases hold-up in a 3 phase fluidize bed column containing liquid phase with 100 cm height and 20 cm diameter, in this case the solid phase with 0.15, 0.25, 0.35 volume fraction and density 2470, 3000, 4000, 5000 m3 dispersion into liquid phase and the gas phase enter the column through a sparger of 2 cm diameter with 0.02 m/s velocities. The results show as the solid phase volume fraction increases from 0.02 to 0.08 m/s. The gas hold-up decreases and solid hold-up increases. Solid phase density increases, so solid phase hold-up decreases and gas hold-up decreases.

Computational fluid dynamics simulation of a novel bioreactor forsophorolipid production

This paper describes three-dimensional computational fluid dynamics(CFD) simulations of gas–liquid flow in a novel laboratory-scale bioreactor contained dual ventilation-pipe and double sieve-plate bioreactor(DVDSB)used for sophorolipid(SL) production. To evaluate the role of hydrodynamics in reactor design, the comparisons between conventional fed-batch fermenter and DVDSB on the hydrodynamic behavior are predicted by the CFD methods. Important hydrodynamic parameters of the gas–liquid two-phase system such as the liquid phase velocity field, turbulent kinetic energy and volume-averaged overall and time-averaged local gas holdups were simulated and analyzed in detail. The numerical results were also validated by experimental measurements of overall gas holdups. The yield of sophorolipids was significantly improved to 484 g·L^(-1)with a 320 h fermentation period in the new reactor.

CFD Simulation of Scale Influence on the Hydrodynamics of an Internal Loop Airlift Reactor

In this work, the overall gas hold-up in the riser and down-comer of three internal airlift reactors with a working volume of 10.5, 32 and 200 l at the range of temperatures 18℃ - 21℃, under atmospheric pressure was simulated using Com-putational Fluid Dynamics (CFD). The range of superficial gas velocity was 0.5 - 3 cm/s. The three reactors geometrically were similar to each other. CFD simulation and experimental data showed that the gas hold-up in the riser and down-comer increased by increasing the reactor scale. It was concluded that the simulated data were in good agreement with the experimental ones obtained from the literature.

STUDY OF DOWNFLOW LIQUID JET LOOP REACTOR

The hydrodynamic and mass transfer characteristics of a downflow liquid jet loop reactor (D-JLR) were studied experimentally with water/air and CMC (carboxymethyl cellulose) solution/air systems. The effects of the geometry, the operating parameters and the physical properties of the liquid phase on gas hold-up and mass transfer coefficient were measuered. Compared with other types of gas-liquid reactor, D-JLR shows higher mass transfer coefficient and lower energy dissipation rate, the optimum diameter ratio was found to be about 0.42-0.6. A model for gas hold-up in D-JLR with Newtonian and non-Newtonian fluids has been developed on the basis of the equation of motion and the concept of average mixing length. The prediction of gas hold-up with the model agreed with the experimental results of this work.

Investigation of bubble diameter and flow regime between water and dilute aqueous ethanol solutions in an airlift reactor

In this study,the effect of ethanol addition into pure water and its concentration on bubble diameter,gas hold-up andflow regimes were investigated in an airlift reactor.Air and water with ethanol(concentration ranging from 0%–1%,v/v)were as dispersed and continuous phases,respectively.Superficial gas velocity was consid-ered as an effective parameter.Bubble size distribution was measured by photography and picture analysis at various concentrations of ethanol and various velocities of gas.Alcohol concentration enhancement caused bubble dia-meter to decrease.Furthermore,the bubbles diameter in pure water was nearly 4 times higher than that of ethanol with concentration of 1%(v/v)and also was 3.4 times higher than that of ethanol with concentration of 0.25%(v/v)at the highest aeration gas velocity inlet.For ethanol solutions in lower superficial gas velocity,a homogenousflow regime was observed.This trend continued to inlet gas velocity of about 0.4 cm/s.The transitionflow regime occurred after this datum although in pure water,a homogenousflow regime was observed up to a superficial gas velocity of 0.7 cm/s.The gas hold-up in dilute ethanol solutions were more than(around 2 times)that of pure water and increased with increasing concentration of ethanol in those solutions.