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LNG (Liquefied Natural Gas)
Chapter 18
Based on presentation by Prof. Art Kidnay
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Plant Block Schematic
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Adapted from Figure 7.1, Fundamentals of Natural Gas Processing, 2nd ed.Kidnay, Parrish, & McCartney
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Topics
Introduction
Liquefaction processes
LNG storage
Regasification
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Updated: January 4, 2019Copyright © 2017 John Jechura ([email protected])
Introduction
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Rationale for LNGLiquefying natural gas greatly reduces volume
▪ Liquid density @ 1 atm – 26.37 lb/ft³
▪ Saturated vapor volume @ 1 atm– 8.8188 ft³/lb – 230X volume
▪ Standard ideal gas vapor volume – 24 ft³/lb – 625X volume
▪ Ideal gas volume @ 1000 psia & 60oF – 0.35 ft³/lb – 9X volume
Liquefaction makes it easier to…▪ Store gas (peak shaving plants)
▪ Move gas to remote customers (base load plants)
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Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Comparison of plants
Peak shaving plants
Relatively small (~0.1x106 tpy)
70+ in US (mainly in New England region)
Facility includes:▪ Liquefaction plant
▪ Storage facilities
▪ Regasification facilities
Baseload plants
Large capacity – 3 to 10x106
tpy)
Requires large reserves to make plant economically feasible (> 1 Tscf)
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Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Schematic of peak-shaving facility
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Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Energy Transmission Efficiency Over Long Distances
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Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Schematic of a baseload plant
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Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
LNG Trade
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IGU 2018 World LNG ReportDownloaded December 24, 2018https://www.igu.org/sites/default/files/node-document-field_file/IGU_LNG_2018_0.pdf
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
LNG Trade
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IGU 2018 World LNG ReportDownloaded December 24, 2018https://www.igu.org/sites/default/files/node-document-field_file/IGU_LNG_2018_0.pdf
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
LNG Facilities & Capacities
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IGU 2018 World LNG ReportDownloaded December 24, 2018https://www.igu.org/sites/default/files/node-document-field_file/IGU_LNG_2018_0.pdf
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
LNG Liquefaction Facilities
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IGU 2018 World LNG ReportDownloaded December 24, 2018https://www.igu.org/sites/default/files/node-document-field_file/IGU_LNG_2018_0.pdf
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
LNG Regassification Facilities
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IGU 2018 World LNG ReportDownloaded December 24, 2018https://www.igu.org/sites/default/files/node-document-field_file/IGU_LNG_2018_0.pdf
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
LNG Facility Costs
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IGU 2018 World LNG ReportDownloaded December 24, 2018https://www.igu.org/sites/default/files/node-document-field_file/IGU_LNG_2018_0.pdf
Updated: January 4, 2019Copyright © 2017 John Jechura ([email protected])
Liquefaction Processes
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Typical compositions pipeline gas vs. LNG feed
Impurity Pipeline Gas LNG Feed
Water 150 ppmv (7.0 lb/MMsc) < 0.1 ppmv
Hydrogen sulfide 0.25 gr/100 scf (4.0 ppmv) < 0.25 gr/100 scf (4.0 ppmv)
Total sulfur (H2S, COS, …) 5–20 gr/100 scf < 20 ppmv
Carbon dioxide 2–3 mol% < 50 ppmv
Nitrogen < 3 mol% < 1 mol%
Mercury N/A < 0.01 μg/Nm3
Butanes N/A < 2 mol%
Pentanes+ N/A < 0.1 mol%
Aromatics < 2 ppmv
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Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Simple JT liquefaction cycle
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3 12
1 3 2
ˆ ˆ
ˆ ˆLH H qm
fm H H
− −= =
−
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0
1000
2000
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9000
10000
0 2000 4000 6000 8000
Vap
or
Qu
alit
y af
ter
JT V
alve
Tota
l Co
mp
ress
or
Po
we
r [h
p]
Max Pressure [psia]
hp
Quality
Simple JT liquefaction cycle – 500 psia inlet gas
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Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
JT liquefaction cycle with intermediate flash
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Simple closed-cycle liquefaction process
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Open-cycle expander plant
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( )4 63 12
1 3 2 3 2
ˆ ˆˆ ˆ
ˆ ˆ ˆ ˆL
e H HH H qmf
m H H H H
−− −= = +
− −
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
C3 Precooled Mixed Refrigerant
GPSA Engineering Data Book, 14th ed.
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
AP-X LNG Process
Fig. 16-37, GPSA Engineering Data Book, 14th ed.
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Cascade Refrigeration Process
Fig. 16-32, GPSA Engineering Data Book, 14th ed.
Updated: January 4, 2019Copyright © 2017 John Jechura ([email protected])
LNG storage
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Storage of LNG
Tanks can be ▪ Aboveground
▪ Below ground
Tank material is▪ Steel
▪ Prestressed concrete
▪ Hybrid (combination of both)
Typical types▪ Single-containment
▪ Double-containment
▪ Full containment
▪ Prestressed concrete
▪ Frozen-earth underground storage
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Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Single-containment tank
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Carbon Steel
Outer Tank
Perlite
Insulation
Reinforced Concrete Pad
Electrical
Heating
Elements
Suspended
Deck
Carbon Steel
Roof
9% Nickel Steel
Inner Tank
Base
Insulation
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Double-containment tank
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Carbon Steel
Outer Tank
Perlite
Insulation
Reinforced Concrete Pad
Electrical
Heating
Elements
Suspended Deck
Carbon Steel Roof
9% Nickel Steel
Inner TankBase
Insulation
Concrete
Outer
Shell
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Full-containment tank
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Carbon Steel
Outer Tank
Perlite
Insulation
Reinforced Concrete Pad
Electrical
Heating
Elements
Suspended Deck
Concrete Roof
9% Nickel Steel
Inner Tank
Base
Insulation
Concrete
Outer
Shell
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Prestressed Concrete Tank
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Earth Berm
Concrete
Select Fill
Ballast
Insulated
Roof
Insulation
and Liner
Spring-loaded
Trusses
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Figure 13.23 Frozen-earth storage container
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Spray Nozzles 9% Nickel Steel
Roof
Freeze Pipe
Insulation
LNG
Updated: January 4, 2019Copyright © 2017 John Jechura ([email protected])
Regasification
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
LNG regasification (simplified)
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~ 40 % of HHV required to heat LNG to ambient temperatures
Updated: January 4, 2019Copyright © 2017 John Jechura ([email protected])
Summary
Updated: January 4, 2019Copyright © 2019 John Jechura ([email protected])
Summary
Natural gas can be liquefied to greatly decrease its volume & make for easier long-distance transportation
Gas to be liquefied must be further processed from typical pipeline quality
Two separate steps▪ Liquefaction
• Proper heat integration necessary to minimize compression power
▪ Regasification
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