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FLNG FundamentalsModule 1.1: Introduction to FLNG
LNG industry overview
Development and history
LNG properties and specifications
Opportunities and advantages of FLNG
Offshore considerations and challenges
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Most gas is transported by pipeline - Why LNG?
Volume advantage for storage and transportation Transport over wide and deep oceans
Economic advantage of LNG vs. pipeline gas dependent on distance
World Bank estimates 140 billion standard cubic metres of gas was
flared in 2011 (about 40% of the LNG traded), producing 360 million
tonnes of CO2without any beneficial heat or power production
Disadvantages of natural gas liquefaction:
Energy intensive
Capital intensive Requires specialised terminals and carriers
Purity Requirements
Cryogenic handling (materials, safety)
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Most gas is liquefied onshore -Why FLNG?
FLNG is predicted to become an important sector of the LNG
industry:
While most of the easy onshore gas fields have been tapped, there areconsiderable stranded gas reserves offshore
There is growing opposition to locating LNG plants onshore (e.g. JamesPrice Point in Australias Kimberley Region) for environmental or landuse zoning factors. Floating LNG import terminals are already gainingpopularity for this reason
Environmental impacts may be reducedone example is reduction ofdredging in harbours for laying gas pipelines and for entry of LNGcarriers
Possible cost and schedule advantages, though FLNG operatingexpense may be high
As with any novel application of technology, some risk is associated withinitial application of FLNG. Teething problems can be expected withthe first FLNG applications, but subsequent FLNG projects can beexpected to become more straightforward
Experience gained by first FLNG operators will provide a competitiveadvantage
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The cryogenic industry developed in the second half of the nineteenth
century. Among others, Dr Carl von Linde developed and patented air and
gas separation technologies in Munich, Germany. The LNG industry startedits early development in the USA by using LNG technology for natural gas
peak shaving.
1964: First base load LNG export plant begins operation in Arzew, Algeria
using a cascade process designed and constructed by Technip/Air Liquid.
Exports were initially to Canvey Island, UK and Le Havre, France.
The first LNG cargo from Arzew was transported to Canvey Island on theRiver Thames in England on board the first purpose-built LNG carrier
Methane Princess, which had a capacity of 27,000 m3.
1968: The mixed refrigerant concept was presented in a paper at the LNG-1
conference in Chicago
1969: Kenai LNG plant comes on stream in Alaska USA, designed and
constructed by Phillips Petroleum and Bechtel, exporting to Japan. The
Kenai plant was mothballed for a while in 2012 but is currently back in
production with licence to export until 2015
1970: An LNG plant using an SMR process by APCI started up in Marsa El
Brega, Libya, exporting to Italy and Spain
Development History
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Development History
Air Products developed the SMR process into the C3/MR process which
was first applied in Brunei, starting up in 1972
The C3/MR process enjoyed unprecedented success between 1972 and1999, with train sizes increasing from 1.4 MTPA (Brunei) to 3.2 MTPA
(QatarGas). The only other technology built during this 27 year period
was the Prico SMR process in Skikda Algeria by Pritchard-Rhodes (now
Black & Veatch)
In 1999, the first Optimised Cascade train (3 MTPA) started up in PortFontin Trinidad designed by ConocoPhillips and Engineered by Bechtel
The Trinidad plant reintroduced competition into the industry and
though APCI continued to dominate, both C3/MR and Optimised
Cascade technologies were successfully developed reaching train sizes
of 5 MTPA around 2005. In this period, there was a boom in
construction of LNG plants and costs began to escalate significantly
In 2004, Shell began to license its own version of the C3/MR process (a
long-held ambition) starting with the Australian North West Shelf Train 4
at 4.2 MTPA
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Development History
Linde developed the Multifluid Cascade process which was implemented in
the Norwegian Snohvit LNG plant, starting up in 2007 with a train size of
4.3 MTPA. Initially, the Snohvit plant exhibited poor availability and wasfrequently shut down for cleaning, repair or modification
Meanwhile Shell developed the Dual Mixed Refrigerant process and
successfully applied it on Sakhalin Island in Russia with train sizes of 4.8
MTPA, starting up in 2008
At Gastech in 2002, APCI rolled out its large train APX process. After
much development, the first 7.8 MTPA APX train was started up in Qatar in
2009. Six APX trains were built in total, all in Qatar, for RasGas and
QatarGas. The last, QatarGas IV, started up in 2011
Other licensors, including ConocoPhillips and Shell, have designed large
scale process, but at present there appear to be no plans to build any new
trains of significantly larger capacity than 5 MTPA Construction of new liquefaction capacity slowed, with Pluto being the only
new train added in 2012. Angola LNG joined the ranks of LNG exporters
in 2013. PNG LNG started up in 2014, along with an Algerian expansion
train and the first train using Queensland coal seam gas (QCLNG).
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Development History (FLNG)
After years of research and development of several prototype FLNG
facilities, Shell announced FID for a floating LNG facility, Prelude, offshore
northwest Australia in 2011. Prelude will use the Shell DMR process for asingle train of 3.6 MTPA capacity. The FLNG facility is now under
construction at Samsung shipyards in Korea and will be the largest
floating structure ever constructed
In 2013, Petronas achieved FID for its PFLNG1 floating LNG project.
PFLNG1 will use a nitrogen expander process with a capacity of 1.2
MTPA and will be positioned off Sarawak Also in 2013, Exmar and Pacific Rubiales announced that construction
had started on an FLNG project for Columbia, consisting of a barge
mounted liquefaction facility in near-shore, benign waters. Capacity is 0.5
MTPA using an SMR process, but project was deferred in 2015
In 2014, Petronas announced that FID had been reached for its PFLNG2
facility to be positioned offshore Sabah with a capacity of 1.5 MTPA
Golar also announced start on conversion of an LNG carrier for FLNG in
2014. A number of other FLNG facilities are in FEED stage or undergoing
concept development or preFEED
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Refrigerant
Import
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Components of an LNG Plant
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Components Comments related to FLNG
Gas Receiving, liquids
separation and stabilisation
Onshore LNG plants often have slug catchers
with a large footprint. For FLNG, reducing deck
space is paramount
Gas TreatingRemoval of
acid gases, water and mercury
All required for FLNG. High sulphur
concentrations present a problem for floating
facilities
Heavy hydrocarbon removal
and fractionation
Dependent on feed gas composition. For
FLNG, less is better
Liquefaction SMR and expander cycle plants are simpler
with less equipment than larger plants with
multiple refrigerant cycles, but train size islimited. They may be utilised in FLNG
Hydrocarbon refrigerant cycles MRsame requirements as large scale LNG.
N2Expander cyclesadvantage of no
hydrocarbon refrigerants
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Components of an LNG Plant
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Components Comments related to FLNG
LNG Storage and
Loading
For FLNG, LNG storage will be below deck
Utilities FLNG needs to be self-contained for utility
requirements
Power Generation Power requirements need to be generated onboard for FLNG
Gas and liquid
disposal
Same requirements as for large scale LNG plants.
Location of flares on FLNG is a challenge
Other infrastructure:
buildings, drainage,
security, emergency
response, fire and gas
systems
Drainage and buildings require specific design to
suit the FLNG structure. Fire & gas and
emergency response systems require attention
due to FLNG being more congested than onshore
plants
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Components of an LNG Plant
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Equipment required for pre-treatment of feed gas is common to all
LNG process technologies (depending on feed gas composition)
Acid Gas RemovalPrevent freezing of CO2during liquefaction
Typically amine processes are used
DehydrationPrevent freezing of water during liquefactionTypically molecular sieve is used
Mercury Removalprevent Aluminium corrosion
A number of adsorbents are available
Heavy Hydrocarbon removalPrevent freezing during liquefaction
Typically distillation is used
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Gas Pre-Treatment
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LiquefactionQ: How is natural gas liquefied?
A: By using refrigeration
Q: How does refrigeration work?
A: Carnot proposes the theory
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Carnot Cycle
The Carnot cycle was proposed by Nicolas Carnot in 1823
The Carnot cycle is a theoretical thermodynamic cycle to create a temperature
difference (i.e. heat pump or, in reverse, refrigeration) by inputting work
1. Reversible isothermal expansion
2. Isentropic (reversible adiabatic) expansion
3. Reversible isothermal compression
4. Isentropic compression
A real engine (left) compared to the Carnot cycle (right). The entropy of a real material changes
with temperature.
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Refrigeration
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Reverse Carnot Cycle
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For liquefaction of natural gas, the
warm air in the diagram is replacedby warm natural gas which is cooled
and liquefied by the refrigerant
Refrigeration
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LNG Properties and Specifications
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For large-scale projects, LNG is stored and transported at
pressure slightly higher than atmospheric (50 to 200 mbar gauge) At these pressures, LNG is stored at its bubble point, and heat
leakage into the storage container is balanced by boil-off
LNG bubble point at these pressures is typically in the range -1650C to -160 0C, depending on composition
Low pressure storage reduces cost of containment and reduces
probability and severity of leaks
Typical insulation specifications for boil-off are 0.05% per day for
onshore storage, and 0.15 to 0.25% per day for LNG carriers (% of
LNG boiled off per day, based on total storage volume) LNG boil-off may be compressed for use as fuel, or reliquefied
Pressurised LNG storage and transport can be economic for
smaller storage vessels and trucking operations
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LNG is :
colourless odourless,
non-corrosive,
less dense than water ~ 450kg/m3
non-toxic (may cause asphyxia by excluding oxygen)
LNG vapour typically appears as a visible white cloud since its coldtemperature causes moisture in the air to condense. LNG (the liquid
itself) is not flammable or explosive
The vapours formed at an LNG liquid pool surface are always fuel rich.
Because the LNG is boiling, the pool surface vapours contain near 100
% hydrocarbons consisting primarily of methane, especially early onduring the spill
The vapours need to mix with air in order to become flammable
LNG vapours will become flammable once mixed with enough air to a
concentration ranging from 5 to 15 % by volume
LNG Properties and Specifications
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LNG Properties Video
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The ignition of LNG vapours, when in the flammable range, is relatively easy
The minimum ignition energy of LNG vapours is approximately 0.29 mJ If LNG is spilled on land or on water, some of the LNG vaporises immediately. If
ignition sources are present in locations where the vapour concentration is in the
flammable range, the most likely outcome will be an immediate ignition. The
resulting fire is sometimes termed a pool fire (even though it is the vapour which
burns, not the liquid)
LNG pool fire hazards are localized and as a result thermal radiation effects
(burns) are typically confined to within one or two pool diameters from the edge
of the flame
Thermal radiation is absorbed by water moisture and carbon dioxide present in
the air. In addition, thermal radiation intensity decays in proportion to the inverse
square of the distance from the radiation source (1/distance2)
Typically, a person exposed to a thermal radiation flux of 5 kW/m2will feel pain in
20 seconds. Second degree burns are possible. 5 kW/m2is often used as an
injury threshold
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LNG Properties and Specifications
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If ignition is not immediate, the LNG vapours will continue to evolve and will
disperse in the prevailing direction of wind If the wind speed is low and the atmosphere is stable, the vapours, being cold
and heavy, will remain close to the spill surface, and will persist for some time
until dispersed by wind. As heat is absorbed from the environment, the vapour
warms and becomes lighter than air
Cold LNG vapours drift in the direction of wind and become diluted as they mix
with more air If the vapours continue to disperse without ignition, they will ultimately become
diluted to below the lower flammability limits of 5 % and will not burn or present a
hazard anymore
Typically, 2.5 % is used as a concentration threshold (1/2 the lower flammability
limit) when estimating flammable dispersion hazard zones in order to account for
the possibility of pocketing Dilution therefore is one of the main methods used to control spills resulting
from a loss of containment of LNG
Water curtains and jets can be used to draw in air and dilute the cloud that is
generated (putting water directly onto liquid pools should be avoided)
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LNG Vapour leak showing water condensation
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If the LNG vapours encounter an ignition source and ignition occurs
without the presence of confinement, a slow-burning flash fire will occur Thermal radiation hazards are confined to the boundaries of the
flammable cloud and no appreciable overpressure is generated
provided the vapour cloud is not in a confined or congested area.
The flash fire outcome can change drastically in the presence of
significant confinement (3 walls or more), or congestion (equipment andpipe work).
This is further exacerbated by flammable gas concentration close to
stoichiometry (~9.5% of methane in air) and the presence of higher
hydrocarbon in the LNG vapour (e.g. ethane and propane).
Though it is possible to have a transition from a deflagration to adetonation, this has not been observed in practice in industrial
accidents and in experiments that simulate explosions in industrial
environment
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LNG Properties and Specifications
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LNG Properties and Specifications
During actual spills of LNG on water, a phenomenon that is
observed early on during liquid pool development is a Rapid PhaseTransition (RPT)
A rapid phase transition is the very rapid (near spontaneous)
formation of vapours as the cold LNG is vaporized from heat gained
from the underlying spill surface
Because the vapour is evolved very rapidly, localized overpressureis created. This is also sometimes described as a physical explosion
The hazard potential of rapid phase transitions can be severe, but is
highly localized within the spill area
In one large scale field trial, a rapid phase transition may have
ignited the evolved vapours
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An Example of Rapid Phase Transition
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LNG Properties and Specifications
Loss of containment leading to the formation of LNG liquid pools can also be
caused by a phenomenon called rollover
LNG rollover refers to the rapid release of LNG vapours from a storage tankcaused by stratification. The potential for rollover arises when two separate
layers of different densities (due to different LNG compositions) exist in a tank
In the top layer, the liquid becomes warmer due to heat leaking into the tank and
rises up to the surface, where it evaporates
Lighter gases are preferentially evaporated and the liquid in the upper layer
becomes denser. In the bottom layer, the warmed liquid rises towards theinterface by free convection but does not evaporate due to the hydrostatic head
exerted by the top layer
The lower layer becomes warmer and less dense
As the densities of two layers approach each other, the two layers mix rapidly,
and the lower layer which has been superheated gives off large amounts of
vapour as it rises to the surface of the tank Rollover is thought to be more likely if LNG nitrogen content is high
For FLNG, rollover is unlikely to present a problem since sloshing due to sea
state motions ensures mixing of tank contents
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LNG Tank Rollover
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LNG Properties and Specifications
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The main hazard arising out of a rollover accident is the rapidrelease of large amounts of vapour leading to potentially hazardous
situations. It is also possible that the tank pressure relief system is
not able to handle the rapid boil off rates, and as a result the storage
tank will fail and lead to the rapid release of large amounts of liquid
LNG forming a liquid pool.
LNG operators avoid rollover by carefully monitoring the
compositions, temperatures and densities and by keeping tank
contents well-mixed using mechanical means such as pumps to
circulate the liquid
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LNG Properties and Specifications
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LNG Properties and Specifications
LNG specifications are applied for different reasons:
Many of the specifications applied to LNG are relevant for the
liquefaction/transportation/regasification processes and are commonthroughout the industry. Examples are specifications for mercury, nitrogen,
water, CO2, C5+, aromatics
Other specifications are concerned with the end use of regasified LNG and are
related to pipeline specifications or the design of gas burners in the receiving
country. Examples are heating value, wobbe number, NGL/LPG content,
sulphur/H2S Receiving terminals may import LNG outside of the normal specifications (such
as heating value) but then must modify the properties in the receiving terminal
so that the gas will be suitable for in-country use. For instance to reduce
heating value, LPG components may be extracted (before regasification) or
nitrogen may be added (after regasification). To increase heating value, a
terminal may be equipped to spike the LNG with LPG in order to raise heatingvalue
Other specifications common for pipeline gas such as dewpoint are not of
concern since the liquefaction process requirements are far more stringent
than pipeline specifications
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LNG Properties and Specifications
LNG Specification for facility design:
An LNG specification is provided for design of the facilities, usually
in the Basis of Design. The design contractor must guarantee that
facilities, when built, can meet the specification
The gas treating facilities must be designed to meet the
specification for contaminants such as CO2, sulphur compounds,
water and mercury, taking account of the feed gas composition
envelope
The process design for the liquefaction facilities must ensure that
LNG can be produced to meet the specifications for properties
such as heating value and compositions of hydrocarbon
components and nitrogen
The heat and material balances and high level process design tomeet the liquefaction process requirements are usually carried out
by the liquefaction process licensor such as APCI or
ConocoPhillips
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LNG P i d S ifi i
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LNG Properties and Specifications
LNG Specifications for Sales Contracts:
LNG specifications are also provided in LNG sales contracts,
usually referred to as SPAs. These specifications are contractually
binding and failure to meet them may result in refusal to accept an
LNG cargo, or may incur a financial penalty.
The LNG export facility may have separate SPAs with a number of
different customers, so it is important that the specifications in
each of these agreements should be compatible with thespecification provided for design of the plant.
Since the marketing department of a company is often separate
from the project design department, this is not always
straightforward.
In addition to specifying the allowable ranges for LNGcompositions and properties, the SPA will typically also specify
calculation methods or international standards to determine exactly
how the properties will be calculated
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LNG P ti d S ifi ti
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LNG Properties and Specifications
Sample LNG specification for a typical liquefaction plant
High Heating Value (ideal) 1050 - 1150 BTU/ Scf
Composition
Nitrogen 1.0 % mol maximum
Methane 85.0 % mol minimumButanes and heavier 2.0 % mol maximum
Pentanes and heavier 0.1 % mol maximum
Impurities
Hydrogen Sulphide 5.0 mg/Nm3 maximum
Total Sulphur 30 mg/Nm3 maximum
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Examples of LNG Characteristics (from GIIGNL)
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Opportunities / Advantages of FLNG
World Energy Outlook (International Energy Agency)
The share of natural gas in the global energy mix increases from 21% to 25%
in 2035, pushing the share of coal into decline and overtaking it by 2030
Trade between the main world regions more than doubles, with the increase of
around 629 bcm split evenly between pipeline gas and Liquefied Natural Gas
An increase in production equal to about 3 times the current production of
Russia will be required simply to meet the growth in gas demand by 2035
All predictions are for natural gas usage and LNG trade to grow substantiallyover the coming decades. With recent developments, it seems increasingly
likely that FLNG will become a major contributor to the predicted increases in
LNG trade and production
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Opportunities / Advantages of FLNG
Drivers for FLNG
Proven technology is available (although building an LNG plant on a floating
platform still involves novelties and challenges)
A floating LNG vessel is potentially re-deployable (although modifications
may be required when feed gas composition varies significantly - a fully
flexible design to accommodate all feed gas compositions is not practical)and therefore may be viable for smaller gas reserves
Cost effective way of monetising smaller and more remote gas reserves
Cost savings can be realised e.g. by eliminating long subsea pipelines,
offshore processing and compression
Potential to avoid problems with land-based LNG plants such as land
access, delays in obtaining permits, eliminating need for new infrastructure
and influx of construction workers when the LNG plant is in a remote
location
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Opportunities / Advantages of FLNG
Some of the factors likely to be critical for success of the first FLNGventures are:
Combination of LNG knowhow, FPSO experience and LNG shipbuilding
expertise e.g. Shell/Technip/Samsung or Linde/SBM/Daewoo
Recognition of novel aspects (risks); willingness, methodology and
knowhow to address them
Research and design development to address novel aspects such as
effect of motion on LNG equipment, LNG offloading at sea
Financefinancial backers are harder to find until the technology
application is regarded as proven
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Offshore Considerations and Challenges
LNG plants are relatively complex to operate and maintain, and doing this
in a marine environment with less available space adds additional
complexity Motion of the FLNG carrier due to sea state makes operation and
maintenance operations more difficult, e.g. working on rotating equipment
and other machinery with precise tolerances
Emergency operations such as fire fighting become more difficult in a
floating environment
A marine atmosphere can be more corrosive for equipment and pipework
(including stress corrosion cracking), though this is already well-known
since many LNG plants are located in tropical coastal environments
Compared with onshore LNG plants, staff live and work in a relatively
confined space
Escape and evacuation procedures and drills are more complex and
assume more importance compared with onshore plants
Major turnaround maintenance may require additional accommodation for
maintenance personnel e.g. separate floating accommodation vessels
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Off h C id ti d Ch ll
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Offshore Considerations and Challenges
(according to TOTAL)
The challenges of floating LNG (FLNG) derive mainly from the need to fit process
operations that typically have a very extensive onshore footprint into a small space
offshore. This raises numerous issues, especially with regard to:
The size of the FPSO,which must have room to accommodate the gas production,
processing and liquefaction facilities as well as living quarters for a crew of 200 to 300
people. However, due to economic considerations as well as construction constraints,
its dimensions must be as compact as possible
Integration, because the space limitations of a floating plant dictate a specific process
layout that requires some stacking of equipment. Installing the production facilities on
deck and the LNG storage in the hull of the vessel creates some architectural
challenges as well
Marinisation of equipment,because process installations must be designed to
withstand wave action. This is especially important to ensure proper processing of the
gas prior to liquefaction, as the feed gas for the liquefaction process must comply with
stringent specifications
Safety, because the close proximity of process units - and above all the living quarters
just adjacent to them - make safety issues even more acute than for an onshore plant.
Safety is also a central focus when it comes to offloading the LNG onto methane
carriers, and innovative transfer systems are being developed for this context
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