1. Evaluation of LNG
Production Technologies

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

3. Flow Diagram for a Typical LNG Plant

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
Mixed Refrigerants
Pure Refrigerants
Both
Other
Linde Process
CoP Simple Cascade
APCI C3 MR
BP Self refrigerated process
Axens Liquefin Process
CoP Enhanced Cascade
APCI AP-X
ABB Randall Turbo-Expander
Dual Mixed Refrigerant
Linde 2006
Williams Field Services co.
Technip-TEALARC
Mustang Group
ExxonMobil
Dual Multi-component
Black and Veatch Prico Process
Technip- Snamprogetti
* 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
Axens Liquefin 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
refrigerant
Expander
Compressor
Heat Exchanger
refrigerant

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

18. Refrigeration Cycles and Natural Gas Liquefaction
Cooling Water
Inlet Gas
LNG
Cold Box
Compressor
Simple Refrigeration Cycle
Black and Veatch- PRICO Process
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
Inlet Gas
LNG
Mixed Refrigerant
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)

21. Liquefaction Techniques Self 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. BP Self Refrigerated Process
Inlet gas
LNG
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

23. Liquefaction Techniques Cascade Processes
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

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 Extremely compact Compact Multiple streams
Plate-Fin-Heat-Exchangers
Coil-Wound-Heat-Exchangers
Characteristics
Extremely compact
Compact
Multiple streams
Single and two-phase streams
Fluid
Very clean
Clean
Flow-types
Counter-flow
Cross counter-flow
Cross-flow
Heating-surface
m²/m³
m²/m³
Materials
Aluminum
Stainless steel (SS)
Carbon steel (CS)
Special alloys
Temperatures
-269°C to +65 °C (150 °F)
All
Pressures
Up to 115 bar (1660 psi)
Up to 250 bar (3625 psi)
Applications
Cryogenic plants
Also for corrosive fluids
Non-corrosive fluids
Also for thermal shocks
Very limited installation space
Also for higher temperatures

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

37. Results 10

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.
Process
Cost per ton ($)
Max capacity (MTPA)
Prico
5.12
1.20
Liquefin
3.41
6.00
ExxonMobil
4.83
4.80
DMR
12.58
APX
19.20
7.80
MFCP
31.73
7.20
MFCP(CO2)
24.77
TEALARC
25.35
C3MR
12.93
Conoco
20.15
5.00

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
Temperature
Local Minimum
Global Minimum

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?