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LNG Storage and Loading
TEP10 Gas Processing and LNG – Fall 2008
Jostein Pettersen
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Contents• LNG storage and loading overview
• LNG tanks
• Rollover
• Storage and loading system
• Jetty and loading arms
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LNG storage and loading schematic
Toatmosphere
LNG Tank125,000 m³
LPG Tank45,000 m³
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B.L. at Sh ip’s Manifold
B.L. between Process Plant and LNG Storage/LNG Loading
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LNG Carrier147,000 m³
Cond.Tank75,000 m³
LP Flare
Incinerator
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LNG Process Plant
LNG Tank125,000 m³
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LNG Tank125,000 m³
LPG Tank45,000 m³
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B.L. at Sh ip’s Manifold
B.L. between Process Plant and LNG Storage/LNG Loading
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1122
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LNG Carrier147,000 m³
Cond.Tank75,000 m³
LP Flare
Incinerator
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LNG Process Plant
LNG Process Plant
LNG Tank125,000 m³
2020
1 = LNG Rundown from Process Plant to Storage at B.L.2 = LNG Vapour from Storage to Process Plant at B.L.3 = Vacuum Breaker Gas for LNG Tanks from Process Plant at B.L.4 = LNG Loading from Storage to Ship at B.L.5 = LNG Vapour Return from Ship to Storage at B.L.6 = FlueGas (burned LNG Vapour) from LP Flare to atmosphere20=LNG Fuel from Storage to Process Plant at B.L.
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LNG storage tank containment principles
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• Pre-stressed concrete outer walls constructed by slipforming, sheathed internally with a gas-tight layer of nickel-alloyed steel.
• Inner tank in nickel-alloyed steel, separated from the outer walls by a layer of perlite - a variety of volcanic obsidian highly suitable for insulation
• Extra layer of steel and insulation at the transition between outer wall and tank bottom to protect it against strong local stresses should the inner tank begin to leak.
• Heating cables under the tanks will ensure that the ground remains above 0°C in order to prevent frost heaving.
Above-ground full-containment LNG tank design
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Tank safety systems• External leak
– The secondary barrier (pre stressed concrete) is made to retain the liquid (full containment definition)
• Internal leak:
– Leak protection system: Thermal Protection Barrier system, to prevent cold liquid to reduce resistance of the bottom tank,
– Leak detection system in the annular space based on thermal sensors / level detectors and continuous monitoring
• Over pressure:
– Vapor handling system,
– Safety relief valves
• Vacuum protection:
– Gas injection,
– Safety valves
• Fire and Impact:
– Pre-stressed concrete outer tank
• LNG Rollover detection system
– Measuring temperature and liquid density at different levels. Remedy: Increased circulation
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LNG/LPG/Condensate Storage - Hammerfest
Photo: Eiliv Leren
LNG 125.000
m3
LNG 125.000
m3
Condensate75.000 m3
LPG 45.000
m3
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Storage and loading system 3DHammerfest
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LNG Tank - Hammerfest
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Suspended LNG tank ceiling
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LNG tank interior
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Bermed, full containment tanksKarratha -Australia
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Rollover
• LNG composition, density and temperature will change during boil-off of gas
• If not mixed, a high density liquid will settle below the lower density liquid
• During heat leakage and evaporation the density of the upper level of liquid can become higher than the lowerlevel of liquid and a sudden rollover with mixing of the liquids may occur giving sudden evaporation and pressurebuild up, which again can lead to tank rupture
• In 1971 an rollover incident happened at the La Spezia LNG import terminal in Italy and damaged the tank roof. No ignition happend. No injuries/Fatalities
• Receving terminals have now procedures to mix old and new LNG during filling. LNG tanks have rolloverprotection systems, which include distributed temperature sensors and pump-around mixing systems
Rollover is a phenomenon that can occur when LNG at differentdensity/temperature is filled into a storage tank
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Rollover - principle
T1ρ1
T2> T1ρ2< ρ1
evaporation
heatheat
Temperature increasesDensity decreases
Light components evaporatesDensity increases
ρ2 becomes larger than ρ1A sudden change, rollover, of theliquid phases may happenA sudden pressure increase becauseof large evaporation may happen
T = Temperature (°C)ρ = Density (kg/m3)
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Tank wells
Bottom well without foot valve
Bottom well with foot valve
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LNG pumpextraction
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LNG storage and loading system (Hammerfest)
FC HCHC
HC
FCHCHC
HC
6300 m3/h 6300 m3/h
12.600 m3/h
4.200 m3/h
125.000 m3 125.000 m3
Cool down circulationCool down circulation
HC
1.240 m3/h
620 m3/hBut up to
1.240 m3/h
620 m3/hBut up to
1.240 m3/h
BL
Vapour return system
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Modus 1LNG lagring og lasting
15%
Modus 2LNG lagring
85%
Modus 3LNG lagring, LNG lasting
og fyrgassutsendelse
Modus 4LNG lagring medfyrgassutsendelse
Modus 5LNG lagring med LNG overførsel mellom tankene
< 1%
Modus 6Fyrgassutsendelseuten LNG lagring
< 1%
Modus 7LNG lagring med nedkjøling av skip
< 1% Forbered lasting Forbered lasting
Modes of operation
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Emergency disconnect:Break between two ball valves,thus sealing againstboth loadingsystem and ship(connector stays onship manifold)
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PERC (Power Emergency Release Coupler)
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Loading Jetty (Example)
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