Hydrodynamic Behaviour of Helical Rings Random Packing Using CFD Simulation

Abstract

Abstract This study presented computational fluid dynamics (CFD) and experimental validation of hydrodynamic behavior of helical rings random packing. Random packings have been widely used in chemical industries in absorbers, strippers etc. Up till now, development of novel random packing structure has essentially been empirical. Even with the increased computing power, CFD simulations of random packings are hard to find in the literature. The random nature of the packing structures, and the stacked geometry make acceptable grid generation and convergence very difficult because the structure of random packing is complicated when large amounts of it are stacked in a column. In this work, a CFD model was first time developed to simulate countercurrent gas-liquid flow in random packings formed by helical rings. Gravity simulation was used to generate stacking structures. A simple feedback control scheme was applied to control the gas inlet flow rate so that a particular pressure. Multiphase model was employed to compute the gas and liquid interaction in which the surface tension and wall contact angle were found as key factors. The predictions of the CFD model were validated with a lab-scale packed-bed absorber. It was found that the helical structure did increase the interfacial area, liquid hold-up when compared to Raschig rings, and such predictions can be validated by our in-house experiment. The model also showed that helical rings will have lower pressure drop and can sustain a larger liquid-gas ratios compared to Raschig rings. In summary, our study found that CFD simulations can obtain reasonable predictions of hydrodynamic behaviour of packings, and the inclusion of microstructures into a packing element will improve its hydrodynamic properties. These results showed that CFD can be used as a basis for rational packing design.