The Influence of Mass Transfer on Energy Efficient Distillation Design

The Influence of Mass Transfer on Energy Efficient
Distillation Design
Brett Walker and Dr. Ross Taylor
Department of Chemical and Biomolecular Engineering
Distillation is a process to separate compounds based on differences in boiling points; it is by far the most
used separation process. Distillation columns account for approximately seven percent of the total energy
consumed in the US. There are large overhead costs associated with building and testing these columns,
initial design is therefore done entirely using theoretical models. In standard design procedures the model
column is assumed to be operating at equilibrium. That is, the vapor and liquid phases have sufficient
time to reach their theoretical maximum separation. In this work we are able to relax the equilibrium
assumption and examine how the design changes when mass transfer limitations are considered.
Calculations are performed both in the ChemSep software package and independently programmed. We
show that mass transfer effects can have significant impacts on the optimum design, particularly in
thermodynamically non-ideal systems, situations in which small amounts of a trace compound are
desirable and in determining the height of the column. Mass transfer effects can both improve the design
effectiveness or decrease it. However, either way the influence is important. In certain cases, neglecting
the effects of mass transfer can lead to columns that cannot perform the desired separation.
2012, Chemical Engineering, Honors Program, Dr. Ross Taylor