Monitoring of multi-phase distribution in packing columns using wire-mesh sensor

Absorption packing columns employing gas-liquid counter-current flow are widely used across a wide range of industries. Maldistribution of liquid phase could reduce the contact area of both phases, thus lowering column efficiency. Liquid holdup is an essential parameter that influence pressure drop and load capacity of the packing column. Traditional measurements of local liquid holdups using liquid collector strongly disturb 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 technology using wire-mesh sensor installed below the packing.
Wire-mesh sensor contains 16x16 orthogonally arranged wires (up to 32x32), measuring the complex impedance at every sensing point which is related to the local permittivity over the whole cross section. Matrices which denote the local permittivity are obtained with a frequency up to 1000 frames per second. Knowing pure gas and liquid phase permittivity allows calculation of local phase fractions. Unlike ECT or ERT measurement, grid sensor excellently locates the liquid phase position and the area obstruction is lower than 1 percent.
Stochastic behavior of liquid flow at different time was found. It is shown that large scale of maldistribution near the wall was observed and most of liquid phase flows preferentially in the same zones.
The amount of liquid flowing along the column wall was characterized by analyzing liquid holdups of the annular grid points. It is shown that more than 27% of the liquid phase flows improperly and its amount varies dynamically.
Mesurements with wire-mesh sensor could be employed to correct essential parameters such as effective phase contact area, local liquid holdup and etc. Therefore, mass transfer laws suggested by Billet (1995) and hydraulic model by Mackowiak (2009) could be modified.