Droplet Characteristics of Rotating Packed Bed in H2S Absorption: A Computational Fluid Dynamics Analysis

Dan Dan,Liu Liu,Wu Wu,Wang Wang,Yang Yang

doi:10.3390/pr7100724

Abstract

Rotating packed bed (RPB) has been demonstrated as a significant and emerging technology to be applied in natural gas desulfurization. However, droplet characteristics and principle in H2S selective absorption with N-methyldiethanolamine (MDEA) solution have seldom been fully investigated by experimental method. Therefore, a 3D Eulerian–Lagrangian approach has been established to investigate the droplet characteristics. The discrete phase model (DPM) is implemented to track the behavior of droplets, meanwhile the collision model and breakup model are employed to describe the coalescence and breakup of droplets. The simulation results indicate that rotating speed and radial position have a dominant impact on droplet velocity, average residence time and average diameter rather than initial droplet velocity. A short residence time of 0.039–0.085 s is credited in this study for faster mass transfer and reaction rate in RPB. The average droplet diameter decreases when the initial droplet velocity and rotating speed enhances. Restriction of minimum droplet diameter for it to be broken and an appropriate rotating speed have also been elaborated. Additional correlations on droplet velocity and diameter have been obtained mainly considering the rotating speed and radial position in RPB. This proposed formula leads to a much better understanding of droplet characteristics in RPB.

Highlights

An analysis on different rotating speeds and initial droplet velocities illustrates that the radial velocity is mainly affected by initial droplet velocity while the tangential velocity is related to rotating speed and radial position
A 3D CFD Eulerian–Lagrangian approach has been built by introducing a droplet breakup and coalescence model to investigate the droplet characteristics of Rotating packed bed (RPB) in H2 S selective absorption into
Droplet characteristics such as droplet velocity, average residence time and average diameter in RPB have been analyzed by diagrams and correlations, which are compared with available experimental data in the literature [14,17]

Summary

Introduction

Gas phase and liquid phase contact counter-currently in the packing by centrifugal force, and the height of mass transfer unit (HTU). In RPB can dramatically decrease by 1–3 orders of magnitude compared with that in a conventional column. RPB can enhance productivity while remarkably reducing the device size and equipment investments. RPB has been maturely applied to the traditional chemical industry [2] in processes such as distillation, absorption and extraction. It has gradually begun to play a crucial role in gas purification, especially for H2 S removal in natural gas.

Methods

Results

Conclusion