1. Dr Xuesong Zheng – Process Integration Ltd (PIL)
UoM Novel LNG Process
Dr Xuesong Zheng – Process Integration Ltd (PIL)

2. Outline LNG process review Introduction to the UoM LNG process
Case study for performance comparison
Single Mixed Refrigerant (SMR) process
UoM LNG process

3. LNG Process Review Natural Gas Liquefaction
During the natural gas liquefaction process, a large amount of shaftpower is required to run the refrigerant compressors.
Shaftpower consumption is an important performance indicator of the refrigeration process.

4. LNG Process Review Existing Liquefaction Technologies
Propane Pre-cooled Mixed Refrigerant (C3/MR) Process
Most efficient, but very complicated configuration
Optimised Cascade Cycles
Three pure refrigerant cycles in cascade
Double Mixed Refrigerant Cycles
Two mixed refrigerant cycles in cascade
Mixed Fluid Cascade Process
Three mixed refrigerant cycles in cascade
Single Mixed Refrigerant (SMR) Process
Simplest configuration, but lower efficiency
Complicated
Efficient

5. LNG Process Review SMR Process Low efficiency
Evaporation at a single pressure level
Simplest structure
Small number of design variables
Easy to optimise
Low efficiency

6. LNG Process Review
A novel LNG process was developed at the University of Manchester to:
Strike the balance on process complexity and energy efficiency
A single MR cycle with more operating variables
Simple structure but improved energy efficiency
SMR
C3/MR
UoM
Complexity
Efficiency

7. Process outline (i) The Novel UoM LNG Process:
Product streams from the flash unit are allocated to actual refrigerant streams with different flow ratio.
Light refrigerant (LR) is pre-cooled to a lower temperature.
Heavy refrigerant (HR) is compressed from the intermediate pressure level. LR HR

8. Process outline (ii) Improved efficiency
Compared with SMR, the UoM LNG process achieves:
More operating variables within a single MR cycle.
More flexible operation with flow rate allocation of LR and HR refrigerant streams.
LR and HR refrigerant streams have different composition, which is favourable for T-H profile matching in the cold box.
LR and HR evaporate at different pressure levels, which is favourable for T-H profile matching in the cold box.
Only part of the refrigerant (LR) is compressed from the low pressure end to the high pressure end.
Improved efficiency

9. Performance comparison (i)
LNG processes:
Single MR Cycle
UoM novel LNG process
Natural gas cooling profile
210 ton LNG /day

10. Performance comparison (ii)
Design Basis:
Physical property package: EOS Peng-Robinson
Minimum approach temperature: 3 oC
Temperature after ambient cooling: 35 oC
Compressor isentropic efficiency: 78%
Pump isentropic efficiency: 75%
Objective for optimisation: minimise shaft power

11. Design Scenario - 65 Bar Single MR cycle Shaft power demand: 2390 kW
Min. approach temperature: 2.6 oC

12. Design Scenario - 65 Bar Single MR cycle Shaft power demand: 2390 kW
Min. approach temperature: 2.6 oC

13. Design Scenario - 65 Bar UoM novel LNG process
Shaft power demand: 2259 kW
Min. approach temperature: 2.62 oC

14. Design Scenario - 65 Bar UoM novel LNG process
Shaft power demand: 2259 kW
Min. approach temperature: 2.62 oC

15. Design Scenario - 65 Bar UoM novel LNG process
Shaft power demand: 2259 kW
Min. approach temperature: 2.62 oC

16. Shaft Power Demand (kW)
All Design Scenarios
Energy performance comparison
Feed Pressure (Bar)
Shaft Power Demand (kW)
Relative reduction
SMR process
UoM LNG process 40
2818
2599
7.77% 65
2390
2259
5.48%
100
2084
1924
7.68%
Shaft power demand
Energy Savings

17. All Design Scenarios Energy performance comparison
For 1.0 MTPA LNG production
Feed Pressure (Bar)
Shaft Power Demand (MW)
Savings
SMR process
UoM LNG process
Shaft Power (MW)
Operating Cost (MM$/yr) 40
37.8
34.9
2.9
1.75 65
32.1
30.3
1.8
1.05
100
28.0
25.8
2.1
1.28
Annual operating hours: 8520
Power cost: 0.07 $/kWh

18. Conclusions The UoM LNG process is a simple mixed refrigerant process.
The energy efficiency of the UoM process is 5% - 8% higher than the SMR process.
The UoM process saves operating costs for LNG production.
(By 1.0 MM$/yr MM$/yr for each MTPA LNG production)
The economic benefits are more significant if the energy savings are utilised to increase LNG production.

19. Contact details Mike Murray - IP Asset Ventures Simon Clarke - UMIP
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Simon Clarke - UMIP
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Xuesong Zheng – Process Integration Ltd
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