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 mo...

In this paper, we first extract a nonlinear time series from the Weierestrass function as a toy model and investigate the anti-noise ability of six different fractal scale algorithm. The results indicate that the fractal scales calculated from Detrended Fluctuation Analysis(DFA) are robust with respect to variation in noise level. Based on the conductance fluctuating signals measured from verti...

a laboratory stirred tank bioreactor with six single and dual-impeller configurations was tested to obtain the optimum operating conditions for future biological processes. six impeller combinations consisting of three basic impeller types, namely rushton turbine (rt), pitched 4blade (p4b) and pitched 2blade (p2b) downward flow were investigated in 1.77 l bioreactor working volume. power consum...

The hydrodynamics and heat transfer of cylindrical gas-solid fluidized beds for polyolefin production was investigated with the two-fluid model (TFM) based on the kinetic theory of granular flow (KTGF). It was found that the fluidized bed becomes more isothermal with increasing superficial gas velocity. This is mainly due to the increase of solids circulation and improvement in gas solid contac...

Abstract The effect of the solid–wall boundary condition on the segregation behavior of a sand ternary mixture differing in size but having the same proportion has been investigated in a gas–solid bubbling fluidized bed. A multi-fluid computational fluid dynamics model incorporating the kinetic theory of granular flow has been used. The mass fraction profiles of the different-sized partic...

Gas fluidization is widely used in industries and has been extensively studied either experimentally or mathematically. Recently, the coupled approach of discrete particle simulation (DPS) for solid phase and computational fluid dynamics (CFD) for gas phase has been proposed to study the heat transfer in fluidized beds at a particle level. The approach offers a convenient way to study the effec...

Numerical simulations of the small bubble-big bubble-liquid three phase heterogeneous flow in a square cross-sectioned bubble column were carried out with the commercial CFD package CFX-4.4 to explore the effect of superficial velocity and inlet dispersed phase fractions on the flow patterns. The approach of Krishna et al. (2000) was adopted in the Euler-Euler framework to numerically simulate ...

Bubble columns are gas- liquid contactors that are widely used in chemical and bio- chemical industries. High mixing that result in high heat and mass transfer rates are amongst their advantages. Heat transfer in a bubble column having a bundle of heaters investigated and the variation of heat transfer coefficient with variation in heaters pitch to diameter ratios in a bundle of heaters reporte...

An improved model for the production of polypropylene in a gas phase fluidized bed reactor was developed. Comparative simulation studies were carried out using the well-mixed, constant bubble size and the improved models. The improved model showed different prediction characteristics of polymer production rate as well as heat and mass transfer behavior as compared to other published models. All...