^{1}

^{*}

^{1}

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.

The gas-liquid-solid fluidize bed has in emerged recent years as one of the most promising devices for three phase operation. Such a device is of considerable industrial importance as evident from its wide application in chemical, petrochemical and biochemical processing [

Even though a large number of experimental studies have been directed towards the quantification of flow structure and flow regime identification for different parameters and physical properties, the complex hydrodynamics of these reactors are not well understood due to the interaction of all the three phases simultaneously. It has been a very tedious task to analyze the hydrodynamic property experimental way of three phase fluidized bed reactor, so another advanced modeling approaches based on CFD techniques have been applied for investigation of three phases for accurate design and scale up. Basically, two approaches, namely the Euler-Euler formulation is based on the interpenetrating multi fluid model. And the Euler-Lagrangian approaches based on solving Newton Equation motion for dispersed phase are used.

Bahary et al. (1994) have used Eulerian multi-fluid approach for three phase fluidized bed [

Schallenberg et al. (2005) have used 3-D multi-fluid Eulerian approach for three phase bubble column. Gas- liquid drag coefficient based on single bubble rise modified for the effect of solid phase [

Panneerselvam et al. (2009) have work in 3-D Elerian multi-fluid approach for gas-liquid-solid fluidized bed [

Hydrodynamic equations used in this research are based on the following equations:

In the Equation (1) which is continuity equation, ρ_{k} density and ε_{k} as volume fraction of gas, liquid and solid phases. Thus the sum of volume fraction of three phases presents _{αi} for N_{p} in Naviar stock sequation. Hence, the right quotations of the Equation (2) describe those operating forces on fluidized element of phase X into the control volume. The total pressure gradient, the viscosity tensions, the gravity forces and interphase momentum forces have been mixed in M_{αi}. The Equation (3) expresses the drag force among liquid and gas phases which has different amounts in different Reynolds. The Equation (4) shows the drag force among solid and gas phases that is known as Gidaspaow [

This research has employed the multiphase model Eulerian. The model considers the phases as come turbulence environments in with the possibility of each phase existing in calculating. Range will be determined by its volume fraction and sum of the volume fractions is equal to unity. The interphase momentum appears as a drag which is a function of stumbling velocity between yhe phases. In this research, liquid acts as a continual phase and gas acts as a diffuse phase which get into the system from the bottom of column.

Boundary conditions on the wall occur as the boundary condition of inlet at the sparger, the boundary condition of outlet pressure at the top of column as well as the wall boundary condition at the walls. The model consists of a cylinder 20 cm in diameter and 100 cm in height. The gas flow lets in the bottom of column , passing through the static liquid and also the solid phase dispersed inside the liquid phase with 0.15 volume fraction, then lets out of the top. Air crosses over the fluidized column with various velocity. The research applies two dimensional simulations under condition of axis symmetry and inlet dry air.

The first step in CFD simulation of fluidized bed column is preprocessor, which has been done by GAMBIT tools, to design the problem in geometrical configuration and mesh the geometry. Before fluid flow problems can be solved, FLUENT needs the domain in which the flow takes place to evaluate the solution. The flow domains as well as the grid generation in to the specific domain have been created in GAMBIT which is shown in

^{3}.