trinidad triples its lng capacity.the engineering challenges

TRINIDAD TRIPLES ITS LNG CAPACITY—THE ENGINEERING
CHALLENGES AND LESSONS LEARNED
TRIPLEMENT DE LA CAPACITE DE TRINIDAD—LES DEFIS DE
L’INGENIERIE ET LES LEÇONS TIREES
Ali Riche
Project Engineering Manager
Trinidad LNG Project
Bechtel Corporation
Tony Diocee
Engineering Manager
Trinidad LNG Project
Atlantic LNG Company of Trinidad & Tobago
William Woodard
Principal Process Engineer
Phillips Petroleum Company
ABSTRACT
Work is well underway to triple the capacity of Trinidad's LNG industry. Key
decisions to proceed with the plant expansion were made in 1999, the same year as first
LNG production. The owners, contractors, and government entities faced the challenge of
making this expansion move quickly and equitably on all sides.
There is certainly a race-to-market competition for LNG in the Atlantic basin. The
speed of this major investment decision surprised almost all interested parties. The
market, once identified, required an additional 3+ million tonnes per year in 2002 and
another 3+ million tonnes soon thereafter.
The engineering challenges in maintaining a low unit cost for LNG and still moving
quickly to more than triple the size of this facility are discussed . Lessons learned from
Train 1 are incorporated.
Little pre-investment was done with the construction of Train 1. Trains 2 and 3 were
originally expected to be duplicates of Train 1. However, the development of the
upgraded Frame 5D gas turbine provided an opportunity for increased capacity with less
incremental cost . Train 1 was "designed to capacity" and therefore the fifteen percent
additional power provided by the 5D design created numerous production bottlenecks
that had to be overcome quickly and for little added cost. Geotechnical conditions for the
expansion presented a new challenge. For Train 3 and the new LNG Tank locations, land
reclamation and soil improvement were required to establish ground and a good working
platform. With the fast track schedule dictated for the expansion, the project team worked
diligently to come up with a land reclamation plan and ground improvement technology
that will support the aggressive construction schedule.
Trinidad Train1 LNG project demonstrated the economic viability of a single train
LNG export plant - the approval of the new Trinidad LNG expansion project will achieve
a new standard of lower cost per ton of LNG.
PO-35.1
RESUME
Le projet de tripler la capacité de production de GNL à Trinidad est à un stade bien
avançé. Des décisions importantes ont été prises pour l’expansion de ce projet dès 1999,
la même année que la première production de GNL. Les propriétaires, les entrepreneurs
et les différentes entités du gouvernement ont dû relevé le défi de continuer l’expansion
de ce projet de façon rapide et équitable pour tous les partis concernés. Il y a évidemment
une compétition assez serrée sur le marché du GNL dans le bassin atlantique. La vitesse,
avec laquelle cet investissement majeur a été décidé, a donc étonné presque tous les partis
impliqués. Le marché, une fois identifié, a requis une production supplémentaire de plus
de trois millions de tonnes par an, en an 2002, suivi rapidement d’une deuxième
production de plus de trois millions de tonnes par an.
Les défis d'ingénierie, qui ont permis de maintenir un coût de revient unitaire
relativement bas pour le GNL et, en même temps, progresser rapidement afin de tripler la
taille de ce site, sont discutés avec les leçons apprises du premier train. Très peu de préinvestissements ont été nécessaires pour la construction du premier train. Les deuxième et
troisième trains devaient initialement être des répliques du premier. Cependant, le
développement de la nouvelle turbine à gaz modèle 5D représentait une occasion
tellement inespérée d’accroissement de capacité qu’elle fût retenue. Le premier train avait
été "conçu à capacité" et, par conséquent, la puissance supplémentaire de quinze pour
cent, créée par la conception de ce modèle 5D, a révélé de nouveaux problèmes limitants
la production qui ont dû être résolus rapidement et pour un faible coût ajouté. Les
conditions géo-techniques pour cette expansion ont présenté un nouveau défi, plus
spécifiquement en ce qui concerne l’emplacement du troisième train et du nouveau
réservoir GNL; la réutilisation des terres et l’amélioration du sol ont été nécessaires pour
établir une bonne plate-forme de travail au sol. Afin de maintenir un programme très
serré pour mener à bien cette expansion, l’équipe de projet a dû travailler de façon
diligente afin de proposer un plan de réutilisation des terres et une technologie
d'amélioration des sols qui supporteront le programme agressif de construction.
Le premier train GNL à Trinidad a démontré la viabilité économique d’un site GNL
avec un seul train; l’accord pour continuer l’expansion du site GNL à Trinidad va donc
réaliser un nouveau record avec un coût de revient encore plus faible de production de
GNL par tonne.
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Process Development
The liquefaction technology used for the Train 1 facility is the Phillips Optimized
Cascade LNG Process. The same technology is applied to the Expansion project. The
following schematic illustrates the major process units.
Figure 1: Process Flow Schematic
ATLANTIC LNG SIMPLIFIED PROCESS FLOW
FUEL
GAS
PROPANE
SYSTEM
INLET
FEED
INLET
SEPARATION
AND NGL
RECOVERY
GAS
TREATMENT
ETHYLENE
SYSTEM
METHANE
SYSTEM
LIQUEFACTION
VAPORS FROM
STORAGE AND
LOADING
LNG
STORAGE
NGL
STORAGE
TO NGL
PIPELINE
TO LNG
TANKER
The decision to proceed with two additional trains originally called for duplication of the
existing Train 1. Strong arguments could be made for duplication given the success of the
Train I start-up and the urgency to provide additional product to a growing market.
However, the decision was made to upgrade the refrigeration turbines from Frame 5C to
Frame 5D. The Frame 5D gas turbine offered an excellent opportunity for increasing the
capacity of the Train I design with little impact on the project schedule. It also provided
the possibility of a further reduction in the unit cost for the produced LNG.
The inclusion of an additional 10% throughput to a facility that had originally been
“designed to capacity” presented quite an engineering challenge. To facilitate the process
development a very detailed rating model of the Train I facility was developed. This
incorporated the actual compressor curves from the Train I compressors and equipment
parameters and hydraulic data from the Train I “as built”. This simulation package
quickly and accurately identified the process bottlenecks.
The process simulation was verified by performing a capacity test and the model was then
used to predict potential bottlenecks at higher capacities.
Capacity Test
A capacity test was conducted on Oct 22 to 24, 1999 to determine the ultimate capacity of
the facility and to help identify bottlenecks. The results of this work were used to
optimize the Train 2/3 designs and to lay the foundation for starting on a de-bottlenecking
exercise for Train 1. The same data points and simulations used for the performance test
were used to evaluate the overall performance against the original design. Additional
PO-35.3
information was gathered to evaluate hydraulic and equipment capacity limitations. Data
collected around the air coolers and propane condenser indicated that the fan blade
pitches could be adjusted slightly to improve the performance, this was carried out
immediately after the capacity test with very good results. Liquid lines around the
ethylene heat exchangers were identified as bottlenecks limiting some of the flexibility of
the design.
The data was then compared to simulations of the plant using Hysys which revealed
possible leaking of recycle valves and liquid carryover from the propane chillers to the
propane suction drums. Once the simulation was adjusted to account for these items the
actual measured data matched very closely to the simulation results.
The results of the capacity test indicate that in a short period after plant takeover Atlantic
LNG operations staff learned to maximize LNG production. The following table
compares the original design, performance test results and the capacity test results:
Table 1: Production Comparisons
Original
Simulation
New Simulation
Performance Test
Capacity Test
Net Guarantee LNG Production
(MMBtu/day)
Fuel Gas Consumed
(MMBtu/day)
418000
56425
416700
425239
436810
56300
55419
56312
Lessons Learned
Utilization of the “lessons learned” practice was a key work process for developing
Trains 2 and 3 design scope and in shaping the engineering, execution and construction of
the expansion project.
Meetings were held with Atlantic LNG operations staff and project E&C team early on
during the FEED phase of the project to collect lessons learned. This process was
ongoing during the early parts of the EPC phase of the project. Some key items were
identified during this period, which allowed last minute design improvements to be
incorporated. Additionally Bechtel and Phillips teams met to brainstorm and document
the lessons learned during the engineering, procurement, construction and
commissioning/startup phases Train 1 project.
The integral team reviewed recommendations and adopted solutions as the basis for train
2 and 3 design. With the 15% additional horsepower provided by the Frame 5D’s, one of
the first significant bottlenecks to be defined were the ethylene compressors. Working
closely with the compressor vendor, a new rotor was designed which required no change
to the compressor casing. This allowed the use of the additional available horsepower but
minimized the effect on the rest of the ethylene refrigeration system.
The propane condensers were also found to be a significant bottleneck due to the
significant impact on propane compressor horsepower consumption. It was possible to
increase the capacity of these air fin coolers by increasing the fan motor horsepower and
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by making modifications to fans without affecting tube bundle size. Additional bays were
added to the propane condensers to maintain condensing pressure during the hot part of
the day. This required some piping modifications
Overall plant pressure drop is very important to the efficiency of the LNG process. The
Train I design was optimized hydraulically. Trains 2 and 3 design required a few
selective changes to line sizes and, in some cases, piping layouts to efficiently allow for
the increased capacity. The project team minimized these types of changes to maintain
cost and schedule goals.
The major pressure vessels, such as the CO2 absorber, dehydrators and mercury removal
beds were determined to be adequate for the new design. However, some internal
modifications were made. Some pieces of equipment were deleted and units combined for
all three trains. These included one single defrost system for all three trains with a cleaner
fuel gas supply, and a single fuel gas system for all three trains.
These modifications will result in a more efficient plant with easier and faster start-up and
shutdown times
Ground Improvements
Ground improvement for the expansion project presented a different type of challenge.
The proposed Train 3 and the new LNG tank were located on reclaimed land which
required extensive ground improvement technology be employed. The project team
optimized the ground improvement technique that would support the very aggressive
construction schedule. Cement Deep Soil Mixing (CDSM) technology was adopted for
the ground improvement method.
With this foundation system, cement is mixed into loose weaker soil to improve its
properties and make it a much better foundation material versus the original soils. The
CDSM technique was primarily developed in Japan for coastal structures sited on loose
materials and prone to earthquake excitation and potential liquefaction.
A CDSM foundation is constructed by making a series of interlocking rows and columns
of improved soil. A grid pattern is then obtained which prohibits the unimproved from
moving during an earthquake event. The improved cemented soil basically surrounds the
weaker unimproved soil. The soil conditions at Trains 2 and 3 were highly variable.
However, the most susceptible soil was the fill material in the upper 4 to 7 meters. The
material below the fill was marine clay deposits which are not susceptible to liquefaction
because of their cohesive behavior. The design for Trains 2 and 3 therefore required that
the CDSM columns penetrate into these cohesive marine layers. The total length of the
soil columns was about 8 to 9m.
CDSM has resulted in Train 2 and 3 ground improvement being completed in a record
four months. This has allowed the concrete placement subcontractor to mobilize and start
earlier than planned and has improved the train 2 schedule by four weeks.
PO-35.5
Figure 2: CDSM Train 2
Environmental Improvements
Due to the close location of the plant site relative to the town of Pt Fortin the project was
faced with utilizing additional measures to control noise from the facility. Bechtel
specialists predicted noise levels at the plant fence and in the community using models to
generate noise isopleths. The model was calibrated to actual operating data by conducting
a noise survey. The model was then used to predict reductions in noise levels by applying
noise mitigation measures at the sources. The three areas the project identified as targets
were:
1. Add additional exhaust silencers on the refrigeration compressor drivers.
2. Utilize low noise fans on air coolers.
3. Insulate some compressor suction and discharge piping.
Conclusion
Staying with the same liquefaction technology and duplicating the train 1 design with
some minor modifications has allowed Atlantic LNG, its shareholders and the
government of Trinidad and Tobago to move quickly to make the decision to approve the
Expansion project. Train 2 is expected to load the first ship by Dec 2002 and Train 3 by
Aug 2003 as shown in Figure 3.
The LNG production of Trains 2 and 3 is roughly 10% above train 1 capacity. This
increase was achieved by utilizing additional refrigeration compressor horsepower and
applying the lessons learned during the performance test and during the extensive
capacity test exercise.
PO-35.6
Table 2: Capacity Comparisons
Original
Simulation
Train 2 and 3
Net Guarantee LNG Production
(MMBtu/day)
418000
Fuel Gas Consumed
(MMBtu/day)
56425
460320
57900
The unit cost based on design rates and EPC contract cost of all three trains is less than
$200/mtpa. This does not include the feed gas pipelines as these are in the gas supplier’s
scope of work.
The design for the second and third trains of the Atlantic facility is believed to be an
excellent compromise providing for the additional capacity while minimizing the amount
of new engineering required and achieving a new standard of lower cost per ton of LNG
Figure 3: Project Timeline
ALNG Facilities Expansion Timeline
July
Apr
il
May
Jun
e
Dec
Jan
200
Feb 3
Mar
July
Aug
Sep
t
Oct
Nov
Apr
il
May
Jun
e
Jan
200
2
Feb
Mar
Jan
200
1
Ma
r
Apr
il
Nov
Dec
Jan
200
0
Feb
Aug
Sep
t
Oct
Mar
Apr
il
May
Jun
e
July
LNG Sales Window
FEED
Train 2
EPC
33 Months
Early
Commitments
First
Ship
Feed Gas 15 September 2002
1st LNG Ship 15 November 2002
Take Over 15 December 2002
Full Commercial Operations 15 February 2003
Feed
Gas
Plant
Takeover
Full
Commercial
Operations
Dec
Jan
200
4
Sep
t
Oct
Nov
July
Aug
Jan
200
Feb 3
Ma
r
Apr
il
Ma
y
Jun
e
Nov
Dec
Sep
t
Oct
July
Aug
Apr
il
May
Jun
e
Feb
Mar
Jan
200
2
LNG Sales Window
Train 3
EPC
Tank
42 Months
Feed Gas 1 June 2003
1st LNG Ship 1 August 2003
Take Over 1 September 2003
Full Commercial Operations 1 November 2003
PO-35.7
Feed
Gas
First
Ship
Plant
Handover.
Tank 3
Complete
Full
Commercial
Operations
Site Photos
Train 2 Compressor Area 29-Sep-00
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R S C L C o m p ressor A rea
CDSM Grid
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Overall Site Photo
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