(508g) Acoustic Detection of Flooding in Absorption Columns and Trickle Beds

In many absorption columns and trickle beds, there is countercurrent flow of liquid and gas through a solid packing. If either the gas or liquid flow rate is too high, the column becomes flooded with the liquid. This change in hydrodynamic regime is associated with greatly reduced efficiency, resulting from a smaller gas-liquid interfacial area, and a dramatic increase in column pressure drop. To maximize both efficiency and productivity, many columns should be operated just below flooding conditions.

The objective of this research was to investigate the use of acoustic emissions as a method to detect the onset of flooding in absorption columns and trickle beds. Early warning of the onset of flooding would allow adjustments to be made to avoid flooding and would improve process control. Columns could, thus, be operated reliably nearer flooding conditions to maximize productivity.

Microphones were placed externally on the absorption/trickle bed column at various axial heights. Acoustic measurements were recorded with various types of solid packings, along with pressure and visual observations as the gas and liquid flow rates were adjusted over a range of flow rates leading to flooding conditions. The acoustic measurements were extensively examined using advanced signal analysis. The power of the fluctuations of frequencies from 0 ? 20 000Hz, obtained by Fast Fourier Analysis, was found to increase sharply at the onset of flooding. Acoustic measurements were therefore shown to be an effective and completely non-intrusive method of detecting the onset of flooding in absorption/trickle beds columns.