High Pressure Experiments and Simulations in Cocurrent Bubble Columns

Bubble column is a multiphase reactor in which gas is passes through the liquid in two phase flow. When liquid is stationary the operation is called as batch mode and co-current when both gas and liquid are moving in the same direction. The gas hold-up increases with increase in pressure for both batch & co-current column. This increment in gas holdup is very sharp initially, but soon it becomes insignificant. The increase in liquid velocity decreases the gas hold-up at all pressures. As we increase the pressure, the effect of liquid velocity is less. Three dimensional Euler-Euler two-phase fluid model has been used to simulate two-phase up-flow in bubble column (15cm diameter) using ANSYS 12.1. These experiments and simulations were operated over a range of superficial gas velocities (1 to10 cm/s) at ambient conditions as well as high pressures. The liquid velocity range was 0 to 16 cm/s. The turbulence in the liquid phase has been modeled using the standard k-ɛ model. The interactions between the two phases are described through Schiller Neumann drag coefficient formulation. The objectives are to find the effect of pressure and liquid velocity over gas holdup and to validate the CFD simulations with experimental data. Quantitatively good agreements are obtained between experimental data for hold-up and simulation values. Radial gas holdup profiles and axial liquid velocity profiles were also obtained for the simulation.