CFD study of oscillatory motion effect on liquid flow distribution into structured packed divided wall column

Abstract

Packed distillation columns are key equipment in natural gas pre-treatment process within LNG production process train operated at offshore. In this work, the impact of offshore operating conditions and that of divided wall column shape were explored via developing transient three-dimensional CFD model for a divided wall distillation column filled with structured packing. Inter-phase drag force, porous resistance force, mass transfer, and liquid dispersion were incorporated into volume averaged equations to map the distortion in liquid distribution in response to column oscillatory motion. The results show that introducing a dividing-wall into distillation column affects fluids partition and distribution. Column motions induce complex fluid flows in radial direction that result in oscillatory patterns around the steady-state solution of vertical column. Furthermore, liquid distributions in a divided wall column under influence of column motion differ with respect to column system positions throughout rotational axes, mass transfer also fluctuates according to column oscillations. A position with a dividing wall making an angle of 45˚ with rotational axis gives a scenario in which rolling motion resembles to pitching motion. The thereof position leads to moderate liquid maldistribution in comparison to liquid maldistribution from scenario with dividing wall parallel to rotational axis.