Friction on a solid sphere exposed to gas–liquid and gas–liquid–solid flow in bubble column and fluidized bed reactors

Investigation of flow structures and transport phenomena in bubble columns using particle image velocimetry and miniature pressure sensors

Dynamics of gas–liquid flow in a rectangular bubble column: experiments and single/multi-group CFD simulations

Gas absorption is a separation process that transfers substances from gas phase to liquid phases due to the different concentrations. The operation can be applied in many treatments or purifying processes e.g. CO2 absorption from biogas or volatile organic compounds (VOCs) recovery from petroleum emission air. The conventional unit operation using for the gas absorption process are bubble column and spray column. Although there are several literatures reporting the efficiency of spray columns and bubble columns, those were done separately. Therefore, this research projected to investigate both hydrodynamics and mass transfer in both spray and bubble columns and comparing their specific power consumptions in order to develop the selection a guideline for industrial usages. The results indicated that the bubble column had larger specific interfacial area than the spray column when using at small gas loading rate. At this range of operation, the bubble column yielded higher overall mass transfer coefficient with the same specific power consumption. However, when operating at high gas loading rate, the spray column was the one better than the bubble column since the bubble column consumed larger power consumption as the pressure drop of the bubble column was mostly due to the gas flow.
 
 In addition, this research also studied the effect of solid phase on the hydrodynamics and mass transfer in the bubble column and spray column. By using the colorimetric method of “red bottle” experiment, it was found that the bubble-particles collision diminished the mass transfer of bubbles because the collision slowed down the bubbles especially for the small bubbles due to the fact that the small bubble simply lost their velocities from the collision. However, there was an advantage of introducing the particles since solid particles could obstruct the rising bubble and reduced its rising velocity. Consequently, the contact time between gas and liquid is increased and resulted in higher gas hold up and specific interfacial area. Therefore, with the appropriate conditions for which solid promoted specific interfacial area higher than diminished the mass transfer coefficient, the higher mass transfer rate was achieved. For the experimental setup using in this research, the enhance of mass transfer rate was occurred when the movable ring-shaped particles were introduced into the column that had large orifice sizes of gas sparger.
 
 In addition, this thesis also developed a colorimetric method to determine the overall mass transfer coefficient of oxygen without using other equipment rather than measuring the time which color of the solution changed from colorless to saturated red. This technique is very useful in the aspect of education since it does not require another equipment for measurement rather than visually observation. Nevertheless, the performance of optical fiber probes for hydrodynamics determination of droplets were also investigated.

Turbulent bubbly air/water two-phase up and down flows in bubble column were investigated. Important flow quantities such as local void fraction, liquid velocity and the turbulence intensity were measured using both LDV and PIV. the presence of the bubbles increased the level of turbulence in the flow. Measurements of liquid velocities in bubble columns, of different superficial gas velocities, and of different height, the flow structures show tours vortices and axisymetric flow. Key words: turbulent flow; gas-liquid flow; laser velocitymenter

Effects of hydrophilic particles on bubbly flow in slurry bubble column

Gas—liquid flow in bubble columns and loop reactors: Part II. Comparison of detailed experiments and flow simulations

Friction on a solid sphere exposed to gas-liquid and gas-liquid-solid flow in bubble column and fluidized bed reactors

Ultrafast X-ray tomographic imaging of multiphase flow in bubble columns - Part 1: Image processing and reconstruction comparison

Numerical simulation of the dynamics of two-phase gas—liquid flows in bubble columns

Quality of mixing in a downflow bubble column based on information entropy theory

Results of the development of a mathematical model of turbulent flows in bubbly media are presented. The proposed model is based on the Euler-Euler approach to the description of multiphase flows, which is supplemented by the k-ω-SST model of turbulence with some modifications that make possible (i) the generation of turbulence due to the relative motion of phases and (ii) the turbulence-induced dispersion of bubbles. Investigations performed using the proposed model and the corresponding numerical code provided detailed information on the structure of turbulent flows in bubble columns. The results of calculations show good coincidence with experimental data.

This article begins by briefly reviewing the more important contributions to the area of modeling heat and mass transfer, and particle growth during the polymerization of olefins on Ziegler–Natta catalysts. It is shown that these models are capable of identifying the critical areas involved in heat and mass transfer, and of modeling polymerizations where the observed activity is less than approximately 5,000 g of polymer per gram of catalyst per hour (g/g/h). However, it is not possible to use these models “as‐is” to model more modern catalysts whose activity levels can surpass the 50,000 g/g/h mark because they predict prohibitively large concentration gradients inside the growing particles during slurry polymerizations, and temperature gradients outside the particles during polymerization in the gas phase. An analysis of the mass and heat transfer Peclet numbers (Pe) reveals that certain simplifying assumptions may not always be valid. Pe values in the transition range suggest that convection inside the particles during polymerization in the liquid phase may help to explain why observed mass transfer rates are higher than the predicted rates. In an opposite vein, a Pe analysis shows that conductive heat transfer may play an important role at length scales characteristic of those in the early stages of polymerization. A new mechanism for heat transfer at reduced length scales is proposed. © 1995 John Wiley & Sons, Inc.

Chemical looping combustion of Victorian brown coal using Fe-based oxygen carriers

Advancements of the Fluidized Bed Fenton (FBF) Technology for wastewater treatment: Mechanism, mass and heat transfer

The present paper shows the influence of considering polydispersity of bubbly flow, simulating bubble columns with a three‐dimensional Eulerian two‐fluid model. A complete set of interfacial closure models regarding drag force, lift force, wall force, turbulent dispersion force and bubble‐induced turbulence is considered. A round bubble column of 0.288 m diameter and 2.5 m height is simulated up to a superficial gas velocity of 1 cm s–1 and compared with experimental data. It is shown that considering the polydispersity including the non‐drag forces, important flow properties of bubble columns are reproduced. Possible influences of swarm effects on the non‐drag forces are discussed and needs for further investigations are given.