Influence of mass transfer in distillation: Feasibility and design

Abstract

AbstractThe influence is considered of mass transfer on distillation column design. The column design equations incorporating mass‐transfer effects are similar to the conventional design equations and are as easy to solve numerically. Mass‐transfer effects do not influence pinch‐point curves and pitchfork distillation boundaries. Mass transfer does, however, change the composition trajectories, which might thus cross the pinch‐point curves. Inclusion of mass transfer in the design equations allows us to estimate the actual number of stages (or the column height). The curvature of composition trajectories may have a significant impact on the total number of stages and on the feed stage location. Mass‐transfer effects do not influence the minimum reflux for columns involving a very sharp split. However, and contrary to previous reports, mass‐transfer effects may strongly affect the minimum reflux for less than very sharp separations. Mass‐transfer effects should be taken into consideration when trace components are a concern. A feasible design based on residue curve maps might be rejected by a design method based on mass transfer. More important, however, the converse also is true. © 2005 American Institute of Chemical Engineers AIChE J, 51: 854–866, 2005