1. Terry A. Ring Chemical Engineering University of Utah
HW 6 Styrene Separation
Terry A. Ring
Chemical Engineering
University of Utah

2. Problem-Develop Separation System
Component 2 Bar(g), 425°C
Normal Boiling Point (°C)
kmole/hr
Hydrogen (H)
-252
275
Methanol (M) 65
83.594
Water (W)
100
Toluene (T)
111
Ethylbenzene (E)
136
Styrene (S)
145
Sequences
Direct and H/MWTES, MW/TES, M/W, T/ES, E/S

3. Initial Approach Just like other HW Problems Flash off H2 at -30°C
Run DSTWU columns to create the sequence
Add RadFrac columns to size the columns and HX
Cost System

4. H/MWTES, MW/TES, M/W, T/ES, E/S Sequence

5. Problems DSTWU Problems with RadFrac Problems with 1st column
2nd column
Problems fail on Rmin sometimes on NT, NFeed
RadFrac Problems with
1st column – trays dried up
2nd column – trays dried up
3rd column - Warning

6. Direct Sequence

7. Problems DSTWU Problems RadFrac Problems Columns 1,3,4 worked well
2nd column – No success to get a separation
RadFrac Problems
1st Column – Not Converged
2nd Column – Replaced with a decanter
M/T split is reasonable but dirty

8. Step Back and Review
Flash at -30°C with water in stream will freeze up unit!
Separation Difficulties with DSTWU Separations
Methanol/Water
Water/Toluene
Methanol Water/Toluene Separations
What is going on???
This looks more like a water oil separation problem than a distillation.
Decanter worked better than DSTWU in Direct Sequence for Water/Toluene.
Rethink how to make separation.

9. Rethinking the Problem
Use UNIFAC-LLE Thermopackage
Start with 3 Phase Flash at +10°C
H2 in vapor
Oil
Toluene + Ethyl Benzene + Styrene Direct Distillation Sequence
Water
Methanol + Water  Distill

10. 3 Phase Flash, M/W, T/ES, E/S
MeOH
Water

11. Results Problems DSTWU MeOH/H2O Column – Feed Tray Location RadFrac
Over come with RadFrac
RadFrac
Adjust Feed Tray location in MeOH/H2O Column
No Problems