It has long been recognized that the flow pattern,especially the velocity distribution of the fluid,is of great importance in determining the performance of the equipment using structured packing as its internals.By using three-dimensional laser Doppler velocimetry(LDV),the liquid velocity distribution of the glycerol aqueous solution was measured in a typical unit of structured packing(Mellapak 350Y).Time averaged three-dimensional velocity distributions of the unit were measured at different flow rates.The experimental data showed that the liquid velocity profile of the single phase flow was complex because of the special geometry of the unit of structured packing.In the central region of the unit,the liquid was mixed strongly and re-distributed.It was the main cause generating the vortexes and secondary flow.
The performance of sheet metal structured packing Mellapak 350Y in a pilot-scale high-pressure column(0.15 m I.D.) was investigated at 700-1900 kPa. The packing height was 2.0 m. Isobutane and n -butane was used as test mixture. The imperfect flow phenomena in column,such as maldistribution,wall flow,end effect and backmixing could be revealed by testing the composition profile along the packing. A concave or convex composition profile curve might be a result of maldistribution,and f _ max ,which was the maximum value of liquid maldistribution friction could be used to judge the sensitivity to maldistribution of a proposed packed bed. Through comparing the separation efficiency at the top section of packing with that at the bottom section would disclose the existence of wall flow and end effect in the column. Moreover,the extent of gas and liquid backmixing in packing could be estimated if the composition profile along the whole column could be obtained.
