Effective diffusivity in a structured packed column: Experimental and Sherwood number correlating study

•Study of packing height and needle size on mass transfer coefficient.•Work done with two different surface tension chemical systems.•Study of Sherwood number of drops in a structured packed extraction column.•Correlating the experimental Sherwood number by grouping dimensionless numbers.•Development of modified correlations by application of the effective diffusivity.

Mass transfer coefficients along a structured packed column were experimentally determined to obtain a new correlation for dispersed phase Sherwood number based on molecular diffusivity. Then in a comparative investigation, the correlation was re-established based on effective diffusivity. The applied chemical systems were toluene/acetic acid/water (T/A/W) and butyl acetate/acetic acid/water (B/A/W). The effects of droplet size and packing height on experimental Sherwood number were also discussed. It was shown that local Sherwood number could be increased up to 188% with increasing the droplet size from 6 to 9 mm in fixed dispersed phase flow rate. It was also observed that when height of packing increased from 10 to 40 cm, local Sherwood number decreased by almost 48% for constant dispersed phase flow rate. The results have shown that the proposed correlation based on effective diffusivity can estimate the experimental drop Sherwood number with high accuracy (error of less than 5%). Moreover, current research shows that replacing molecular with effective diffusivity in some theoretical models can correct their estimation.