(207c) Determination of Liquid Holdup in Structured Packing Using Neutron Radiography

Similar to x-ray radiography, neutron radiography allows for non-intrusive and non-invasive observation of the inner-workings of an operating mass transfer device, providing insight into the phase distribution of the system. Neutron scans taken at the NIST Center for Neutron Research (NCNR) of an air-water contactor were used to determine local and average liquid holdup profiles in three stainless steel structured packings (Mellapak 250Y, Mellapak 500Y, and MellpakPlus 752Y). The tests were conducted at liquid loads ranging from 2.2-20GPM/ft² and f-factors ranging from 0.5-1.3 ft/s(lb/cuft)^0.5 in a 5.75” ID column. The results for Mellapak 250Y are validated against previous studies.

Results for local holdup profiles showed a strong dependence on vertical position in the column, generating a periodic profile in all packings at all conditions examined. The largest values for holdup were seen in the joint region between two adjacent packing elements. Holdup profiles for MellapakPlus 752Y exhibited lower holdup at the joint when compared to Mellapak 500Y.