CFD Modeling of Three-phase Bubble Column: 1. Study of Flow Pattern

Bubble column (BC) or slurry bubble column (SBC) reactor has emerged as one of the most promising devices in chemical, biochemical and environmental engineering operations because of its simple construction, isothermal conditions, high heat and mass transfer rates, and on-line catalyst addition and withdrawal. The present work has been carried out to characterize the dynamics of three-phase flow in cylindrical bubble column, run under homogeneous bubble flow and heterogeneous flow conditions using CFD (Computational Fluid Dynamics) simulation. Investigation has been done to study the flow pattern of three-phase bubble column along with parametric studies. The simulations were performed for air-water-glass beads in a bubble column of 0.6m height, 0.1m i.d. and 0.05m sparger diameter to study the flow pattern. Eulerian-Eulerian three-phase simulations with k-ε turbulence for liquid phase were carried out using the commercial flow simulation software CFX-5.6, with a focus on characterizing the dynamics properties of gas liquid solid flows. The model has been validated using available experimental data and is in good agreement. Detail study of the flow pattern in three-phase bubble column has been carried out and flow pattern has been presented in the form of contour and vector plots. The results presented are useful for understanding the dynamics of gas liquid solid flows in bubble column and provide a basis for further development of CFD model for three phase systems

CFD Modeling of Three-Phase Bubble Column: 2. Effect of Design Parameters

The effect of design parameters on the flow pattern in a three-phase bubble column by means of Computational Fluid Dynamics (CFD) has been studied. The simulations were performed for air-water-glass beads in a bubble column of H = 0.6m, D = 0.1m and ds = 0.05m to study the flow pattern. Eulerian-Eulerian three-phase simulations with k-ε turbulence for liquid phase were carried out using the commercial flow simulation software CFX-5.6, with a focus on characterizing the dynamics properties of gas liquid solid flows. The model has been validated using available experimental data and is in good agreement. Effect of design quantities such as: H/D ratio, sparger diameter, taperness on the flow pattern has been studied. The results presented are useful for understanding the dynamics of gas liquid solid flows in bubble column and provide a basis for further development of CFD model for three-phase system

Adsorption of Benzaldehyde on Granular Activated Carbon: Kinetics, Equilibrium, and Thermodynamic

Adsorption isotherms of benzaldehyde from aqueous solutions onto granular activated carbon have been determined and studied the effect of dosage of granular activated carbon, contact time, and temperature on adsorption. Optimum conditions for benzaldehyde removal were found adsorbent dose 4 g l–1 of solution and equilibrium time t 4 h. Percent removal of benzaldehyde increases with the increase in adsorbent dose for activated carbon, however, it decreases with increase in benzaldehyde mass concentration. Adsorption capacity of activated carbon for benzaldehyde removal decreases with increase in temperature, the adsorbent showing the exothermic nature of adsorption. The adsorption of benzaldehyde by granular activated carbon followed pseudo-second order kinetics. Diffusion is not the only rate-controlling step. Adsorption equilibrium data were analyzed by Langmuir, Frendlich and Temkin isotherm equation using regression analysis. Temkin found to best represent the data for benzaldehyde adsorption onto granular activated carbon. Value of the change in entropy (S°) and heat of adsorption (H°) for benzaldehyde adsorption on activated carbon were negative. The high negative value of change in Gibbs free energy (G°) indicates the feasible and spontaneous adsorption of benzaldehyde on granular activated carbon

Computer Aided Design (CAD) of a Multi-component Condenser

In the case of multi-component condensation the ‘condensing vapour contains a mixture of components having different boiling points, which condense over a wide temperature range, either in presence of or absence of non-condensing material. In this work, a design algorithm for the condensation of a multi-component vapour mixture in shell side of a shell and tube vertical condenser has been developed using Bell and Ghaly’s method. Based on this algorithm, an in-house computer code has been developed. This code was used for the design of the condenser for the condensation of a hydrocarbon vapour mixture containing propane, butane, hexane, heptane and octane in the mole composition of 0.15, 0.25, 0.05, 0.30 and 0.25, respectively. A code was also developed for the Kern’s method for the condenser design. It was found that Kern’s method provides a lesser heat transfer area because Kern’s method does not consider the mass transfer resistance, nor does it take care of handling the sensible heat transfer during condensation. These facts have been incorporated in Bell and Ghaly’s method by taking the one-phase heat transfer coefficient during vapour sensible heat transfer. The effects of operating variables viz. vapour flow rate, coolant flow rate, vapour inlet temperature, and coolant inlet temperature on the overall heat transfer coefficient, and shell side pressure drop have been studied for the wide range of parameters. The results are useful for the design of multi-component condensation

Computer Aided Design (CAD) of a Multi-component Condenser

In the case of multi-component condensation the ‘condensing vapour contains a mixture of components having different boiling points, which condense over a wide temperature range, either in presence of or absence of non-condensing material. In this work, a design algorithm for the condensation of a multi-component vapour mixture in shell side of a shell and tube vertical condenser has been developed using Bell and Ghaly’s method. Based on this algorithm, an in-house computer code has been developed. This code was used for the design of the condenser for the condensation of a hydrocarbon vapour mixture containing propane, butane, hexane, heptane and octane in the mole composition of 0.15, 0.25, 0.05, 0.30 and 0.25, respectively. A code was also developed for the Kern’s method for the condenser design. It was found that Kern’s method provides a lesser heat transfer area because Kern’s method does not consider the mass transfer resistance, nor does it take care of handling the sensible heat transfer during condensation. These facts have been incorporated in Bell and Ghaly’s method by taking the one-phase heat transfer coefficient during vapour sensible heat transfer. The effects of operating variables viz. vapour flow rate, coolant flow rate, vapour inlet temperature, and coolant inlet temperature on the overall heat transfer coefficient, and shell side pressure drop have been studied for the wide range of parameters. The results are useful for the design of multi-component condensation