Ayema Aduku Oluwaseun Harris Valerie Rivera Miguel Bagajewicz

1. Ayema Aduku Oluwaseun Harris Valerie Rivera Miguel Bagajewicz Evaluation of LNG Production Technologies University of Oklahoma

2. Outline • LNG Background • Objective • Simulation Specifications • Liquefaction Techniques • Heat Exchanger Types • Simulation Method • Results

3. Flow Diagram for a Typical LNG Plant Natural Gas CO2/H2S Removal Dehydration Heavy Component Removal Natural Gas Liquefaction Transportation

4. LNG (Liquefied Natural Gas) Basics • Combustible mixture of hydrocarbons • Dry VS. Wet • NGL Extraction • Dehydration/Scrubbing • Liquefied Natural Gas • Target temperature for Natural gas:-260°F • Reduces volume by a factor 600

5. Objective • Main Objectives • Simulate Processes • Optimize Processes • Minimize compressor work • Compare Processes based on • Capital cost • Energy cost • Total cost per capacity(Ton)

6. Liquefaction Processes * Italicized processes signify Patent searched processes. *Bolded processes signify processes not included in scope of project.

7. Flow diagrams

8. Black and Veatch’s PRICO Process AxensLiquefin Process C3MR: Air Products and Chemical Inc ExxonMobil Dual Multi-Component Cycle

9. AP-X: Air Products and Chemical Inc. Technip- TEALARC System BP- Self Refrigerated Process DMR- Dual Mixed Refrigerant

10. Linde- CO2 MFCP Linde/Statoil -Mixed Fluid Cascade Process ConocoPhilips Simple Cascade

11. Simulation Specifications • Natural Gas composition • Methane: 0.98 • Ethane: 0.01 • Propane: 0.01 • Inlet conditions • Pressure: 750 psia • Temperature: 1000F • Outlet conditions • Pressure: 14.7 psia • Temperature: -260oF • Capacity: Common min. to max. capacity of process • Common min. Capacity: 200,000 lbs/hr Beihai City, China

12. Liquefaction Techniques • Different Liquefaction techniques include: • Single Refrigeration cycle • Multiple Refrigeration cycles • Self Refrigerated cycles • Cascade Processes • The cooling of natural gas involves the use of refrigerants which could either be pure component refrigerants or mixed component refrigerants.

13. Liquefaction Techniques Schematic of a Simple Refrigeration Cycle Cooling Water low Temperature No Pressure change High Temperature refrigerant High Temperature High Pressure Compressor Expander low Temperature low Pressure Heat Exchanger refrigerant High Temperature Gas low Temperature No Pressure change

14. Liquefaction Techniques • Mixed refrigerants are mainly composed of hydrocarbons ranging from methane to pentane, Nitrogen and CO2. • Pure component Refrigerants • Specific operating ranges for each component • Mixed Refrigerants • Modified to meet specific cooling demands. • Helps improve the process efficiency

15. Liquefaction Techniques T-Q Diagrams Natural gas cooling curve The main goal is to reduce the distance between the two curves. This would signify a reduction in the work during the cooling process and an increase in efficiency. Area between curves represents work done by the system

16. Liquefaction TechniquesSingle Refrigeration Cycle • One refrigeration loop that cools the natural gas to its required temperature range. • Usually requires fewer equipment and can only handle small base loads. • Lower capital costs and a higher operating efficiency

17. Black and Veatch: PRICO Process Compressor Condenser • Single mixed refrigerant loop and single compression system • Limited capacity (1.3 MTPA) • Low capital cost • Great Pilot Process Inlet Gas Cold Box 100oC LNG Residue -260oC Expander

18. Refrigeration Cycles and Natural Gas Liquefaction Compressor Cooling Water Inlet Gas Simple Refrigeration Cycle Cold Box LNG Black and Veatch- PRICO Process Gas Liquefaction techniques take advantage of modified refrigeration cycles

19. Liquefaction Techniques Multiple Refrigeration cycles • Contains two or more refrigeration cycles. Refrigerants involved could be a combination of mixed or pure component refrigerants. • Some cycles are setup primarily to supplement cooling of the other refrigerants before cooling the natural gas. • More equipment usually involved to handle larger base loads.

20. Air Products and Chemical Inc: C3-MR LNG • APCI processes are used in almost 90% of the industry • Good standard by which to judge the other processes • Capacity of about 5 MTPA • Utilizes Propane (C3) and Mixed Refrigerants (MR) Inlet Gas Mixed Refrigerant

21. Liquefaction TechniquesSelf Refrigerated Cycles • Takes advantage of the cooling ability of hydrocarbons available in the natural gas to help in the liquefaction process. • Numerous expansion stages are required to achieve desired temperatures. • Considered as a safer method because there are no external refrigerants needing storage.

22. BPSelf Refrigerated Process • Neither refrigerants, compressor, nor expanders present in setup. • Cost include mainly capital costs and electricity. • Low Production rate (51%) • Capacities of over 1.3MTPA attainable . Residue Gas Inlet gas LNG

23. Liquefaction TechniquesCascadeProcesses • A series of heat exchangers with each stage using a different refrigerant. • Tailored to take advantage of different thermodynamic properties of the refrigerants to be used. • Usually have high capital costs and can handle very large base loads.

24. ConocoPhilips Simple Cascade • 3 stage pure refrigerant process • Propane • Ethylene • Methane • 5 MTPA Capacity Methane • Ethylene • Propane Residue Gas Sub-Cooling Inlet Gas Pre- Cooling Liquefaction LNG

25. Equipment

26. Plate Fin Heat Exchanger Very compact design but limited in operating range

27. Spiral Wound Heat Exchanger Large operating range but robust design

28. Spiral Wound Heat Exchanger Tube bundles wrap around central hollow tube

29. Equipment Comparison

30. Our Evaluation Methods • Data on operating conditions (Temperatures, Pressures, Flowrates, etc) for all these processes is not widely available (Only some is reported). • We decided to perform simulations using our best estimates. • We used minimum compression work as guide. • We identified non-improvable points

31. Details of methodology • Conditions after each stage of refrigeration were noted • After making simple simulations mimic real process, variables were transferred to real process simulation • Optimization- Refrigerant composition • Optimization- Compressor work • Restriction needed- Heat transfer area • All cells in LNG HX must have equal area • Restriction needed- Second law of thermodynamics • Check temperature of streams • Utilities • Obtain cooling water flow rate

32. CO2 Pre-cooled Linde Process • Modification of the Mixed Fluid Cascade Process • Three distinct stages using 3 mixed refrigerants with different compositions • Carbon dioxide is sole refrigerant in pre-cooling stage • Separate cycles and mixed refrigerants help in the flexibility and thermodynamic efficiency • Process is safer because hydrocarbon inventory is less • 8 MTPA Capacity Inlet Gas 100oC Pre- Cooling -70oC Liquefaction High Pressure -140oC Low Pressure Sub-Cooling -260oC LNG

33. TQ diagrams from PRO II simulation

34. Results

35. Cost Basis • Economic Life of 20 years • New train required at the documented maximum capacity of each specific process. • Average cost of electricity and cooling water throughout the US used in analysis. • Energy cost evaluated at a minimum capacity of 1.2 MTPA

36. Results 10 Spikes in chart represent points at which new train of process is installed

37. Results 10 Energy cost includes electricity and cooling water cost

38. Results The Liquefin Process is reported as fast becoming a popular LNG technique. The Prico process results were expected. Numerous equipment usually leads to higher overall costs.

39. Analysis • Our results may not match market trends • Operating temperature and pressure range as well as flowrate information unavailable • Precedents to compare results unavailable • Information on cost to use process unavailable (licensing, proprietary production fees, etc.)

40. Analysis • We may be trapped in local minima and failed to identify better conditions Work Local Minimum Global Minimum Temperature

41. Conclusions • We successfully simulated several LNG production plants • We obtained capital and operating costs and determined a ranking • Some connection with existing trends were identified, but other results do not coincide with market trends • We discussed why discrepancies may arise.

42. Questions?

43. References "Overview: LNG Basics." Center for Liquefied Natural Gas. 2008. Center for Liquefied Natural Gas. 3 Feb 2008. <http://www.lngfacts.org/About-LNG/Overview.asp>. http://www.globalsecurity.org/military/systems/ship/tanker-lng-history.htm www.fpweb.com/200/Issue/Article/False/67449/Issue Fossil Energy Office of Communications. U.S. Department of Energy: Fossil Energy. 18 Dec 2007. U.S. Department of Energy. 3 Feb 2008. .<http://www.fossil.energy.gov/programs/oilgas/storage/index.html>. "Mustang receives U.S. patent for LNG liquefaction process." Scandanavian Oil and Gas Magazine. 14 Dec 2007. 3 Feb 2008. <http://www.scandoil.com/moxie-bm2/news/mustang-receives-us-patent-for-lng-liquefaction-pr.shtml>. Spilsbury, Chris; Yu-Nan Liu; et al. "Evolution of Liquefaction Technology for today's LNG business." Journees Scientifiques Et Techniques (2006) Process Selection is Critical to onshore LNG economics.” World-Oil Magazine. February 2006 com <http://www.worldoil.com/Magazine/MAGAZINE_DETAIL.asp?ART_ID=2808&MONTH_YEAR=Feb-2006> Flynn, Thomas N. “Cryogenic Engineering.” Second edition. Marcel Dekker. New York- NY. 2005