# Distillation research and models

### Sigurd Skogestad

I have worked on distillation (both batch and continuous) since about 1980 -- on design (steady-state), modelling, dynamics and control. If you do not know much about distillation, then the following paper dealing with the steady-state behavior and design of continuous distillation may be useful:
• I.J. Halvorsen and S. Skogestad, ``Distillation Theory'', Encyclopedia of Separation Science. In: D. Wilson (Editor-in-chief), Academic Press, 2000.
The following paper covers control of distillation columns:
In addition, the following paper provides an introduction to dynamics and control of distillation columns:
The following paper covers the literature up to about 1991 very well:

## Matlab files

A lot of our work has been related to the dynamics and control of "Column A" (41 stages;, relative volatility 1.5; 99% purity; liquid flow dynamics; constant pressure):
• colamod.m The basic dynamic Matlab model for column A (more details below).
In addition, there are some other column models:
• dist.m A very simple model with 3 stages + total condenser.
• dist3.m A model for closed operation (F=0, D=0, B=0) (binary mixture, two vessels).
• multicomA.m (ORIGINAL VERSION, 2003). A model for a column with any number of components (extension of colamod.m to NC components - still ideal mixture)
• multicomA.m (NEW VERSION, MARCH 2008). Also Simulink and steady-state
• colamod_nonideal.m A model for 3 components and nonideal Wilson or Uniquac liquid activity (extension of colamod.m to nonideal mixture)
• OLD: dist5.m A model for a column with varying reboiler and condenser holdup, but constant stage holdup. With PI-controllers in top. Works for closed operation (F=0)
• OLD: colap.m A first attempt at a MATLAB model for a column with pressure variations.
• Models with varying pressure and neglected vapor holdup written by Hilde Engelien
• fenske.f Steady-state model of binary distillation column based on assumption of constant molar flows and constant relative volatility (Fortran program).
• linemcmodel.mat Linear model of 5x5 column of Lundstrom in mutools format. See distillation mailbox for more details.
• Petlyuk column Dynamic model of Petlyuk column made by Ivar Halvorsen

## Speedup files

• Speedup files of B. Wittgens on multivessel batch distillation and continous distillation
• Speedup and Matlab files of E.H. Hilmen on batch distillation of nonideal mixtures
• Speedup file of P. Lundstrom of 5x5 distillation model with varying pressure and vapor holdup included

## More information on MATLAB Distillation column model ("Column A")

You can here find nonlinear and linear dynamic models of a distillation column for use with MATLAB and/or SIMULINK. The models are for the 4x4 "open-loop" (uncontrolled) column, as well as for the LV, DV, and L/D-V/B-configurations. The following assumptions are used: Binary mixture; constant pressure; constant relative volatility; equlibrium on all stages; total condenser; constant molar flows; no vapor holdup; linearized liquid dynamics, but effect of vapor flow ("K2"-effect) is included. These assumptions may seem restrictive, but they capture the main effects important for dynamics and control (except for the assumption about constant pressure).

The column has 40 theoretical stages and separates a binary mixture with relative volatility of 1.5 into products of 99% purity. It is relatively easy to change the model parameters and to simulate another column.