The performance of rotary concentric cylinder fractionating columns—1

Abstract

A type of laboratory fractionating column is described, consisting essentially of two concentric glass cylinders of which the inner one rotates. This apparatus is of general use in preparative work, giving an exceptionally low hold-up, pressure drop and H.E.T.P., and having no bearings or shaft seals in the working section. It also offers a convenient means of studying the general properties of film-type rectifying systems ; it functions as a wetted-wall column in which the vapour flow regime may be changed in a predictable way without alteration of throughput by changing the form and speed of the rotor. A technique is described for determining liquid and vapour side mass transfer resistances. In experiments at atmospheric pressure with a mixture of n-heptane and methyl cyclohexane it is shown that the separating power of the column is controlled by the vapour phase mass-transfer resistance, the liquid side resistance being negligible. Attempts are made to relate the overall column characteristics to the fluid mechanical properties of the vapour stream under various conditions of operation.