Slide 1
Dynamic Simulation in Design of LNG
Liquefaction Plants
Abhilash Nair, Invensys
© 2012 Invensys. All Rights Reserved. The names, logos, and taglines identifying the products and services of Invensys are proprietary marks of
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Acknowledgements
Fujii Takayoshi, JGC Corporation
Kuroda Toshiyuki, JGC Corporation
Nakagawa Tatsuji, JGC Corporation
Charles Rewoldt, Invensys
Kinya Taguchi, Invensys
Slide 3
Agenda
• Background
• LNG Liquefaction Process
• Design Challenges
• Dynamic Simulation
• Case Study - DYNSIM
 Modeling of Liquefaction process
 Controls
 Scenarios
 Results
• Benefits and Conclusion
• Q&A
Slide 4
LNG
• Natural Gas – a principle
energy source
• Supply-Demand imbalance
• Transportation requires
Liquefaction
• 1/600th volume
• High Energy Density
Image from : http://www.fossil.energy.gov
Slide 5
Natural Gas Lifecycle
Production
Liquefaction Unit
Transportation
Re-gasification Terminal
Distribution
Consumption
Images from : http://www.fossil.energy.gov
Slide 6
LNG Industry - Global
Existing:
•26 terminals –export LNG
•31 Liquefaction plants
•60 terminals –import LNG
Proposed:
•65 export(14 in NA)
•60+ Liquefaction plants
•180 import terminals(13 in NA)
Data source: Federal Energy Regulatory Commission
Slide 7
LNG Liquefaction
• Condensing Natural Gas (NG)
• Refrigeration cycles
• Four main processes
• C3MR process (APCI) – Most common
• Conoco-Philips
• Shell
• Linde
Slide 8
Design Challenges
• Unit requires high availability
• Reliable controls and Safety systems
• Expensive turbo-machinery equipments
• Natural Gas flaring
• Cryogenic service
• Expensive piping metallurgy
• Complex heat transfer equipments
• Heat integration and interaction between
refrigeration loops
Slide 9
Design Challenges
Limitations in steady state design
Impact of controls
Understanding the dynamics is critical
Dynamic Simulation - best available technology
Invensys SimSci-Esscor’s – DYNSIM
Slide 10
Dynamic Simulation - DYNSIM
• Process Simulation Tool
• System hold-up dynamics
• Control dynamics, Thermodynamics
• Process variables Vs Time
Time
• Applicable through a Project Lifecycle
Validate
Design
Checkout
Controls
PROCESS
DESIGN
DCS / PLC
CONFIGURATION
Train
Personnel
Improve
Performance
INITIAL
START
PLANT
OPERATION
Dynamic Simulation in Project Lifecycle
Slide 11
DYNSIM in LNG Applications
Production
Liquefaction Unit
Transportation
Engineering Studies
Operator Training Simulators
Re-gasification Terminal
Distribution
Consumption
Slide 12
Case Study – LNG Liquefaction Plant
• Dynamic Simulation Study - DYNSIM
• 2.1 MMTPA LNG Liquefaction Unit
• JGC Yokohama, Japan - EPC
• APCI – C3MR Process
• Mitsubishi (MHI) Compressors
• CCC Compressor Controls
Slide 13
Objectives
• Verify compressor controls
• Verify anti-surge valves’ design
• Verify cold bypass valves’ design
• Verify isolation valves’ design
• Verify settle out pressures and re-start
• Verify start-up/shutdown scenarios
• Evaluate “What-if?” scenarios
• Trip
• Discharge/Suction blockages
• Load changes etc…
Slide 14
C3MR Process (APCI)
• Feed Treatment
• Liquefaction
• Two refrigeration loops
• C3 (Propane) – Pre-cooling Natural Gas
• MR (Mixed Refrigerant) – Condensation/Sub-cooling
• Two refrigeration compressors
• Loops are heat integrated
Slide 15
C3MR Process (APCI)
• Main Cryogenic Heat Exchanger (MCHE)
• MR and Pre-cooled Natural Gas
• Condensation/Sub-cooling of Natural Gas
• Chillers
• Propane Boilers
• Pre-cooling Natural Gas feed
• Condensation of MR
Slide 16
C3MR Process (APCI)
C3 LOOP
MR LOOP
Slide 17
Modeling Notes - DYNSIM
• Compressors
• Performance maps, MW
changes
• System volume and
resistance
• Isometrics, Pipe fittings
• GA drawings, data-sheets
Curves Validation
Slide 18
Modeling Notes - DYNSIM
S07
S11
• MCHE
• Multi-exchanger,
metal mass, HMB
VL02
S06
S10
S03
VL03
VL01
S02
S09
• C3 Chillers
S01
S08
• Non-equilibrium
scenarios
• Compressor controls
• Basic CCC Controls
modeled in DYNSIM
• Non-dimensional
operating maps
Slide 19
S05
LNGHX01
S04
Scenarios
• 2 steady state ICs
• 4 startup ICs
• 35 case scenarios
• Trip cases
• Startup cases
• Load Change cases
• Process upsets
• Two Phases
List of Scenarios
• FEED
• EPC
Compressor Trip
Slide 20
Results– FEED Stage
• ASV Sizing
• Compressor trip case
• C3 MP Surge
• Original design of C3 LP ASV
was oversized
• Original design of MP ASV
was under-sized
• C3 Compressor
isolation valves
• Stroke time reduced to
route more flow to recycle
loop
Compressor coast-down
Slide 21
Results- EPC stage
• Start-up scenarios
• Available driver power verified
• Helper motor design verified
Speed
• ASV Sizing verified
• Bypass valves’ design verified
• Controls verified
Start-up scenario
Control Lines
Slide 22
Results- EPC stage
• Increase stroke time on
cold bypass (CBP) valve
• Capital Savings
• Coast-down scenarios
• Vacuum on C3 suction
• Drop C3 speed to 75% if one of
MR compressors trip
• Low Press override/ Cascade to
ASC required on C3
• HPMR Suction temperature
• Additional logics required
while opening ASV
Slide 23
Benefits and Conclusion
Dynamic Simulation in Liquefaction Plant
Design helps:
•Add exceptional value to the design
•In FEED, EPC phases and beyond…
•Identify hidden design issues in early stages
•Verify start-up and shutdown procedures
•Excellent platform for the unit OTS system
Slide 24
Q&A
Slide 25
Thank you
Abhilash Nair
Principal Consultant
Invensys SimSci-Esscor
Carlsbad, California CA 92008
+1 760-268-7748
Abhilash.Nair@invensys.com
Slide 26
C3MR Process (APCI)
ASV Opens
Hot C3 Vapor
C3 Boilers
Cryogenic C3 Liquid
Slide 27