1. Modeling of a CO2-stripper
Marie Solvik
Supervisors : Sigurd Skogestad and Marius Støre Govatsmark

2. CO2-stripper Objectives Produce pure ethane productPC PC LC
Objectives
Produce pure ethane product
Keep the CO2 content in the sales gas within the limit.
LT, XLT FC
F, z, hf
75 stages including reboiler and reflux tank
Bottom product – purified ethane
Distillate – Offgas (CO2, ethane and some methane) QR LC
There exist a dynamic model of the system in D-spice
B, xB

3. 2-component flash tank made in Matlab
SRK equation of state with binary interaction parameter found by Kornberg (2007)
2 components- ethane and CO2
Compared to simulation done in ProSim z1
P[barg]
T[K] x1 y1 K
0.99
34.0
288.7
0.9927
0.9873
0.9946
0.90
283.8
0.9248
0.8752
0.9463
0.80
279.0
0.8428
0.7572
0.8984
0.60
271.5
0.6503
0.5497
0.8453
0.40
267.8
0.4202
0.3798
0.9039
0.20
268.0
0.1810
0.2190
1.2099 z1
P[barg]
T[K] x1 y1 K
0.99
34.0
288.7
0.9924
0.9868
0.9943
0.90
283.7
0.9231
0.8727
0.9453
0.80
278.9
0.8419
0.7561
0.8980
0.60
271.6
0.6528
0.5520
0.8455
0.40
267.8
0.4225
0.3812
0.9023
0.20
268.0
0.1780
0.2166
1.2168

4. 3-component flash tank made in Matlab
Added an extra component, methane to the model
Compared with actual process data from the top of the column and a flash tank model made in D-spice
Real time composition of ethane(red) and CO2 (green) from Aspen process explorer.

5. D-spice versus Matlab yC2 yCO2 P[barg] T[◦C] Operating point 1 (3h)
yC2
yCO2
P[barg]
T[◦C]
Operating point 1 (3h)
Aspen
0.455
0.525
34.7
-3.3
Matlab
0.528
0.458
Malab
0.443
0.527
-6.0
D-spice
-3.7
Operating point 2 (15h)
0.515
0.456
34.5
-2.0
0.556
0.420
34.6
-2.7
-3.1

6. Column model made in Matlab
SRK function of state
Builds on the flash tank model
75 stages
Time-consuming

7. Conclusion
The column model needs to be improved before finding optimal operating points
Flash tank model made in D-spice showed accurate results when comparing with actual plant data and with Matlab model.