Process intensification in small scale extraction columns for counter-current operations

This article describes a study to investigate the intensified liquid–liquid extraction by a novel, millistructured, stirred-pulsed column. The column has an inner diameter of 15 mm and is modularly designed with sections of 220 mm height consisting of 10 stirred cells. Experimental investigations were carried out in a column with five sections. The stirred cells enable high energy input, and therefore high specific surface and good extraction efficiencies. The backflow was minimized with narrow plates between the cells. Hence, the dispersed phase coalesces at the plates that separate the stirred cells. The coalescence area is destroyed by continuous pulsation of the fluid column, which transports the dispersed phase into the next stirred cell. The hydrodynamic and mass transfer inside the column was characterized with the EFCE – test system water (continuous)/acetone/n-butylacetate (dispersed). We achieved a dispersed phase hold up inside the active extraction part up to 50%, and a specific surface of over 3000 m2/m3. The extraction efficiency was measured to 17 and 25 stages per meter for the mass transfer direction (d → c) and (c → d), respectively. The comparison with other conventional pilot plant columns shows high extraction efficiency, but also a loss in total throughput.