Determination of liquid hold-up and flow distribution inside modular catalytic structured packings

This paper presents the results of a study carried out to examine liquid hold-up and flow distribution in a 0.1 m internal diameter column filled with catalytic structured packing Katapak-SP.Information has been gathered at local scale by means of a non-intrusive high energy X-ray tomograph. Measurements have been carried out in a large number of packing cross sections situated at different heights between the top and bottom of the packed column, giving access to the evolution of axial profiles of liquid hold-up in the open channels (separation zone) and in the catalytic baskets (reaction zone) as a function of the liquid load. The total hold-up, evaluated by averaging local tomographic values over the packed volume, was compared with global hold-up data obtained by traditional methods, like draining and RTD measurements.A method was also proposed to deduce the distribution of liquid flowrate, between the reaction and the separation zones, from hold-up distribution measured by tomography. The methodology was validated by comparison with experimental data obtained by collecting separately the liquid flowing out of the two zones at the bottom of the packed bed. The obtained results are invaluable to improve the description of hydrodynamics in rate based performance models.

Research highlights
► Liquid hold-up and flow distribution inside the catalytic structured packings Katapak-SP 11 and 12, gathered at local scale by using X-ray tomography.
► Axial profiles of liquid hold-up in the open channels (separation zone) and in the catalytic baskets (reaction zone) and their evolution as a function of the liquid load.
► Total hold-up from tomographic measurements compared with global hold-up data obtained by traditional draining and RTD measurements.
► A method is proposed to deduce the liquid splitting factor between the different zones using X-ray tomography data and applying hydrodynamic models adapted to the packing geometry.
► Experimental findings presented in form of correlations which can be used in design of catalytic distillation.