3.5. Mass transfer performance in countercurrent columns using
supercritical carbon dioxide as the solvent
The mass transfer performance in countercurrent columns is
commonly presented in terms of HETP. Especially of interest in
multistage gas extraction are the relations between the HETP and
the process design variables such as solvent-to-feed ratio, solventto-liquid
ratio, solvent and liquid mass velocity, reflux ratio, and
composition. The influence of design variables on HETP values can
be used to estimate the effect of scale-up on the mass transfer
efficiency of extraction columns.