Monitoring of Multi-Phase Distribution in Packed Columns using Wire-Mesh Sensor and Update of Theoretical Models

Guanghua Zheng1, Markus Schubert2, Uwe Hampel2, Marcus Gruenewald1

1Ruhr-Universität Bochum, Institute of Thermo- und Fluid Dynamic, Universitätsstraße 150, 44780 Bochum, Germany. E-mail: zheng@fluidvt.rub.de

2Forschungszentrum Dresden-Rossendorf, Institute of Safety Research, P.O. Box 510119, 01314

Dresden, Germany. E-mail: m.schubert@fzd.de

ABSTRACT

Packing columns employing gas-liquid counter-current flow are widely used across a wide range of industries. Many correlations and models were developed to estimate the packing characteristics and process performance. Maldistribution is an unwished effect which describes non-homogeneous distribution of phases in the cross-section. It could form shortcut streams and reduce the contact area of both phases, thus lowering column efficiency. Liquid holdup is an essential parameter of hydraulic characters that influence pressure drop and load capacity of the packing column.

Traditional investigation of liquid distribution using liquid collector strongly disturbs the original conditions which make the results less reliable. In this study the local liquid holdup and their distribution was measured with the state-of-the-art wire-mesh sensor (WMS) technology installed below the packing.

To calculate separation efficiency, models were established by using process parameters, e.g. total liquid holdup. However, it was experimentally confirmed that the liquid flowing on the wall has a significant lower absorption rate compared to the flows in the packings. Furthermore, researches of distribution were focused on description of liquid phase distribution in cross-section in the literatures.

In this paper, a modified model was established to investigate the hydraulic phenomenon based on the measurements of maldistribution. The total liquid holdup was divided into two parts - the core-stream and the wall-stream - and whose ratio was analyzed. The channel model is modified with an effective liquid holdup which utilizes the effective core-stream of liquid phase. The advantage of this model is that the separation efficiency could be investigated only based on the effective stream and thus, influence of different column diameter could be eliminated. The different characteristics of new developed packing structures could be explored in percentage of effective flows and in separation efficiency of core-flows.

Keywords Wire-mesh sensor, packing column, distribution, multi-phase