161Process Intensification
foam layer, this should promote internal reux. In the production of nisin,
as will be described in Chapter 10, various internals were tested to improve
drainage, including metal meshes of various sizes. They were found to
marginally improve enrichment at the expense of lower recovery rates (i.e.,
alonger processing time is required to achieve the same total recovery in a
semi-batch operation).
It should be noted that Aguayo and Lemlich’s (1974) study found that
columns with perforated plates were no better than conventional columns
at low supercial gas velocities. It is possible that the bubble coalescence that
apparently caused the success of Tsubomizu’s unit was governed by inertial
effects that did not ma