1. Laboratory for Chemical Technology, Ghent University
http://www.lct.UGent.be
Energy Efficient Light Olefin Recovery:
Absorption Versus Cryogenic Distillation
Pieter A. Reyniers, João F. dos Santos, Stephanie Saerens
Pieter Cnudde, Laurien A. Vandewalle, Thomas M. Deconinck
Steven J. Govaert, Philip de Smedt, Kevin M. Van Geem
Guy B. Marin
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014

2. Increasing propene demand
Gap between propene supply and demand is filled by production from on-purpose
routes such as propane dehydrogenation, metathesis and methanol to olefins
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
CB&I Investor / Analyst Day 2011. http://sec.edgar-online.com/chicago-bridge-iron-co-n-v/8-k-current-report-filing/2011/11/09/section6.aspx
On-purpose propene gap

3. Methanol to olefins (MTO)
Developed by UOP and Norsk Hydro A.S.
SAPO-34 catalyst operated in continuous regenerations
Combined ethene and propene yield of 75-80 wt% on feed carbon
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Senetar, J. J.; Romers, E., Scale-Up Of Advanced MTO Technology And Integrated OCP Technology. In AIChE Spring National Meeting, Chicago, IL, USA, 2011.

4. New perspectives due to MTO
Methanol to olefins clears the path for alternative separation designs
due to low light ends content (CH4, CO, H2, N2) in the reactor effluent
Engineering develops and implements this technology
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Li, L.; Ni, J. A non-cryogenic separation method for lower hydrocarbon containing light gas. WO 2009012623 A1, 2009.
Wison commercializes new methanol-to-olefins technology in China. Hydrocarbon Processing 2013.
Harris, P., UOP announces China downstream achievements. Oil & Gas Technology 23/06/2014.
Patent WO 2009/012623 A1
January 2009
Start-up of full scale plant*
September 2013
163 kt of light olefins
June 2014
* Design capacity: 300 kta light olefins

5. Separation section as a black box
Component wt% Component wt%
N2 0.40 BUTANE 1.01
H2 0.49 BUTENE 8.53
CO 0.49 2ME-PROPANE 0.25
CH4 0.59 2ME-PROPENE 2.27
ETHYNE 0.01 1,3-BUTADIENE 0.54
ETHENE 33.89 PENTANE 0.42
ETHANE 0.39 PENTENE 3.76
PROPYNE 0.05 2ME-BUTANE 0.10
PROPADIENE 0.05 2ME-BUTENE 0.94
PROPENE 45.12 DME 0.20
PROPANE 0.49
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
http://www.marler-zeitung.de/storage/pic/xmlios/zbm-import/aus-der-region/92300_1_xio-fcmsimage-20091010221603-006008-4ad0eb834d1d2.210_008_334982_Pol_Chemiep.jpg?version=1302271767
Model feed composition
19 bara, 40 °C
150 t/h - P/E = 1.5
Product specifications
Product T [°C] P [barg] Rec [%] Purity [wt%]
FUEL GAS 30 5 - -
ETHENE 30 20 99.50 99.95
ETHANE 30 5 - -
PROPENE 40 15 99.50 99.60
PROPANE 40 15 - -
C4+ 40 10 - -
Low pressure steam 6 bara
Cooling water ΔT = 15 °C
Closed loop propene refrigeration cycle
(Closed loop ethene refrigeration cycle)

6. Demethanizer first configuration
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Demethanizer first scheme as most energy efficient cryogenic
configuration
ETHENE
ETHANE
PROPENE
PROPANE
C4+
FEED
FUEL GAS
DEMETHANIZER
DEETHANIZER
DEPROPANIZER
C2-SPLITTER
C3-SPLITTER
COLD BOX
100
90
80
70
60
50
40
30
20
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
Temperature [°C]
Van Geem, K. M.; Marin, G. B.; Hedebouin, N.; Grootjans, J., Energy efficiency of the cold train of an ethylene cracker. Oil Gas-Eur. Mag. 2008, 34, (2), 95-99.

7. Demethanizer first configuration
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Demethanizer first scheme as most energy efficient cryogenic
configuration
ETHENE
ETHANE
PROPENE
PROPANE
C4+
FEED
FUEL GAS
DEMETHANIZER
DEETHANIZER
DEPROPANIZER
C2-SPLITTER
C3-SPLITTER
COLD BOX
100
90
80
70
60
50
40
30
20
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
Temperature [°C]
Van Geem, K. M.; Marin, G. B.; Hedebouin, N.; Grootjans, J., Energy efficiency of the cold train of an ethylene cracker. Oil Gas-Eur. Mag. 2008, 34, (2), 95-99.

8. Absorption configuration
FEED
FUEL GAS
PROPENE
PROPANE
C4+
ETHENE
ETHANE
HP-DEPROPANIZER
LP-DEPROPANIZER
PRECUTTER
ABSORBER
DEETHANIZER
C2-SPLITTER
C3-SPLITTER
COLD BOX 1
COLD BOX 2
100
90
80
70
60
50
40
30
20
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
Temperature [°C]
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
“Pre-cutting and oil absorption” technology by Engineering
Li, L.; Ni, J. A non-cryogenic separation method for lower hydrocarbon containing light gas. WO 2009012623 A1, 2009.

9. Absorption configuration
FEED
FUEL GAS
PROPENE
PROPANE
C4+
ETHENE
ETHANE
HP-DEPROPANIZER
LP-DEPROPANIZER
PRECUTTER
ABSORBER
DEETHANIZER
C2-SPLITTER
C3-SPLITTER
COLD BOX 1
COLD BOX 2
100
90
80
70
60
50
40
30
20
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
Temperature [°C]
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
“Pre-cutting and oil absorption” technology by Engineering
Overall higher temperatures compared to demethanizer first configuration
Li, L.; Ni, J. A non-cryogenic separation method for lower hydrocarbon containing light gas. WO 2009012623 A1, 2009.

10. Closed propene and ethene cycles to generate cooling duty at multiple
cryogenic temperature levels
Refrigeration section
C3R1
PROPENE CYCLE
C3R2
C3R0
COOLING
WATER
C3R3C3R4C3R4'
C2R1
ETHENE CYCLE
C2R2
C2R0
C2R3
K-31K-32K-33K-34
K-21K-22K-23
X1X2X3X4
X5X6
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
mC3H6
mC2H4
Process duties mC3H6
, mC2H4
, X1..X6 m 𝑐𝑜𝑜𝑙𝑖𝑛𝑔 𝑤𝑎𝑡𝑒𝑟, Pcompressors

11. Method for techno-economic analysis
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Energy and material balances from process simulations in Aspen Plus V7.3
Pinch analysis
Feed sensitivity
Operational
expenditure
Capital
expenditure
Economic KPI
NPV, IRR, DPBT
Utility consumption
Maintenance
cost
Project
completion [%]
Technological
Economic

12. Variations on feed composition provide an indication of stability
Demethanizer first configuration is more stable than absorption configuration
CH4 has the highest effect on ethene purity in absorption configuration
Feed sensitivity
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13. Pinch analysis –composite curves
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Minimum hot and cold utility duty is comparable for the two configurations
Difference in terms of heat integration potential is minor
Kemp, I. C., Pinch Analysis and Process Integration: A User Guide on Process Integration for the Efficient Use of Energy. Elsevier Science: 2011.

14. Pinch analysis – grand composite curve
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Minimum hot and cold utility duty is comparable for the two configurations
Difference in terms of heat integration potential is minor
Kemp, I. C., Pinch Analysis and Process Integration: A User Guide on Process Integration for the Efficient Use of Energy. Elsevier Science: 2011.

15. Icarus Cost Estimator
ISBL capital expenditure
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Peters, M. S.; Timmerhaus, K. D., Plant design and economics for chemical engineers. McGraw-Hill: 1991.
Total capital investment (TCI)
Fixed capital investment Working capital
Total direct cost Total indirect cost
Total installed cost
Total purchased equipment cost
Land
Engineering Contractors Contingency
Auxiliary Facilities
Installation E&I Piping
275 % of TPEC
275 % of TPEC
385 % of TPEC
462 % of TPEC

16. Total purchased equipment cost (TPEC) for the absorption configuration is
2.2 106 $ lower than TPEC demethanizer first configuration
- Lower cost for distillation columns and refrigeration
- Heat exchangers and vessels are more expensive
Difference of 10.3 106 $ in total capital investment
Capital expenditure
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17. Operational expenditure
All mechanical energy is delivered by electromotors
All thermal energy is delivered via steam generated from natural gas
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Maintenance Mechanical energy Thermal energy
Pumps Compressors Steam
Process Refrigeration
∆ = 0.19 106 $/y

18. Economic key performance indicators
Small difference in total capital investment and operational expenditure
Product price 1263 $/t
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Product Price [$/t] Wt% Ref.
Fuel gas 155.91 0.83 (1)
Ethene 1404.00 34.15 (2)
Ethane 423.56 0.51 (1)
Propene 1330.00 45.63 (3)
Propane 616.11 0.92 (1)
C4+ 934.07 17.95 (4)
Total 1263.21 100.00
(1) Natural gas price scaled with net heating value
(2) Platts Global Ethylene Price Index
(3) Platts Global Propylene Price Index
(4) Conventional Gasoline Spot Price for U.S. Gulf Coast
(a) Methanol Spot Price North America (Methanex)
Feedstock cost 500 $/t
Methanol price 482 $/t (a)
Cost contribution from MTO
reaction section is minimal

19. Economic key performance indicators
Small difference in total capital investment and operational expenditure
Construction: 1 year Operation: 20 years
Product price 1263 $/t Feedstock cost 500 $/t
Raw material cost and product revenues are dominant over operational
expenditure and depreciation costs
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Key performance indicator Demethanizer Absorber
Total capital investment (TCI) 106 $ 293.08 282.83
Operational expenditure 106 $/y 42.08 41.89
Net present value (15% discount rate) 106 $ 345.07 355.25
Internal Rate of Return % 30.85 31.85
Discounted Payback Time y 6.27 6.03

20. Feed light ends content
A lower light ends content (CH4, CO, H2, N2) in the feed is favorable for
the absorption configuration and unfavorable for the demethanizer first
configuration
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14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014
Effect of lower light ends content Demethanizer Absorber
Light ends sensitivity ≈ ↓
Pinch potential ≈ ↓
Total capital investment (TCI) ↑ ↓
Operational expenditure ↑ ↓
Net present value ↓ ↑

21. Conclusions
Comparison of two alternative configurations of a methanol to olefins
back-end section, specifically tuned for streams with low light ends
Demethanizer first configuration
 Higher stability towards variations in the light ends (CH4, CO, H2, N2) content
 Lower hot and cold utility usage upon full heat integration (∆ ≈ 1 MW)
Absorption configuration
 Lower overall operational expenditure due to lower steam demand but higher
mechanical energy demand (∆ = 0.19 106 $/y)
 Lower total purchased equipment cost due to cheaper distillation columns and
smaller refrigeration section (∆ = 2.20 106 $)
 Higher Net Present Value (∆ = 10.18 106 $)
A lower light ends content is favorable for the absorption configuration
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22. Acknowledgements
Fund for Scientific Research Flanders (FWO).
The Long Term Structural Methusalem Funding
IWT-SBO: Bioleum
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BIOLEUM
Biomass conversion

23. Laboratory for Chemical Technology, Ghent University
http://www.lct.UGent.be
Energy Efficient Light Olefin Recovery:
Absorption Versus Cryogenic Distillation
Pieter A. Reyniers, João F. dos Santos, Stephanie Saerens
Pieter Cnudde, Laurien A. Vandewalle, Thomas M. Deconinck
Steven J. Govaert, Philip de Smedt, Kevin M. Van Geem
Guy B. Marin
23
14AIChE Annual Meeting, Atlanta, GA, USA, 17/11/2014