A study of gas and liquid distributions in structured packings

Abstract

This study describes the gas and liquid distributions in a column with structured packings. The column is 0.5 m in diameter. It is equipped with a total of 1289 detectors in the top and bottom cross-sections. These detectors provide a detailed picture of the gas and liquid flows through elements of only 25 x 25 mm'. The maldistribution in the gas bulk flow is negligible. Only the observed.wal1 flow can contribute to malperformance. The gas flows in parallel to sheet orientation, thus introducing a radial transport. Together with the change in the orientation of subsequent packing elements, this results in good gas mixing. It was observed that the liquid wall flow rate decreases when the gas velocity exceeds 1.7 m/s. Up to the loading point, the maldistribution of the liquid is constant. Above this point, the quality of the distribution deteriorates rapidly, due to the occurrence of large-scale liquid segregation.

Estimations of Gas Flow Maldistribution in Packed‐Bed Columns

“…Thermoanemometric measurements in gas flow are usually performed in the absence of a liquid phase, which blocks the thermal sensor. According to studies in the area [9,12], the liquid distribution and liquid holdup remain unchanged below the loading point in the common operation zone of packed-bed columns, and do not influence the gas distribution. However, at gas velocities above the loading point, the friction forces become comparable to gravitation, and the liquid holdup increases, which results in poorer liquid distribution.…”

“…Hoek et al [21] and Stikkelman et al [11,12,16] have applied a modified version of Eq. (1) to the characterization of both liquid and gas flow, Eq.…”

“…A typical example of such a scheme is shown in Fig. 2a) [11,17,18]. The column cross-section, which is 0.5 m in diameter is divided into 332 rectangular cells of size 0.025 × 0.025 m [11] or 112 cells of size 0.04 × 0.04 m [17,18].…”

“…Stikkelman et al [11,16] have run experiments in two-phase flow with a specially designed device placed over the irrigator. Both the device and irrigator smooth the gas profile, and the results do not represent the real maldistribution.…”

“…Usually the measurements follow a scheme with fixed points regardless of the type and form of the packing below, Figs. 2a) and 2b) [6,11,13]. As a consequence, it can be assumed that the measured velocity profile is not identical to this in the layer [25].…”