Aspen Plus Tutorial 5:
Preparing and Configuring a Distillation
Column using RADFRAC
We have been asked to design a C2 splitter that will give 95% recovery of the ethylene feed, as well
as a purity of 99% ethylene in the distillate.
The feed conditions are as follows:
We will use the DSTWU model to estimate the operating conditions. Run the DSTWU at P=18 bar,
RR=3.1, and basis=100 lbmol/hr. DSTWU performs a Winn-Underwood-Gilliland shortcut design
calculation for a single-feed, two-product distillation column, with a partial or total condenser.
Then we will use these results to design a RADFRAC analysis. RadFrac is a rigorous tray to tray
model for simulating all types of multistage vapor-liquid fractionation operations. Make sure that
you have a total condenser, and that you have a spec. which sets the purity of ethylene in the
Distillate to 99%.
Next week we will use a sensitivity analysis to determine the optimum feed location and number of
stages. Vary number of stages from 23-35 and feed location from 12-21. Output reflux ratio,
reboiler duty, and condenser duty.
Using the DSTWU model
1. Inset a DSTWU column, one feed to the right of the column and two product streams two the left
of the column in the flowsheet space.
2. Connect the feed arrow to the Feed on the DSTWU block.
3. Connect the top product arrow to the Distillate arrow on top of the DSTWU block.
4. Connect the bottom product arrow to the Bottoms arrow on the bottom of the DSTWU block.
Note: The stream numbers become important later, so make sure that they appear the same as the
Aspen Plus Tutorial 5
5. Hit the Next button and enter "DSTWU Distillation Example" as the title.
6. Hit the Next button and you should be at the Components-Specifications form.
7. Enter the components whi