Hydrocarbon Processing - August 2021 - GP-19

SPECIAL FOCUS: SMALL-SCALE LNG
Medium/large-scale power production.
As power generation requirements
increase to 50 MW-300 MW, the quantity
of LNG required increases accordingly,
and the storage requirement becomes
greater than 10,000 m3
. The economics
for the storage concept change, and the
optimum solution becomes an atmospheric-type
storage.
These flat-bottomed tanks must be
built in-situ and are built according to
the relevant EN 14620 or API 620/API
625 codes. The containment type of the
tank can be defined as single, double or
full. For LNG storage of this magnitude,
the general concept is to have a full-containment
tank with a concrete outer shell
to minimize risk of leakage. However,
other concepts can be adopted depending
on the overall project safety requirements,
which may be permissible in very
remote locations.
The atmospheric LNG tanks store
the liquid at its bubble point, close to
atmospheric pressure. With the liquid
continuously boiling, the vapor (boil-off
gas) generated must be managed. The
boil-off gas can be compressed directly
to a sendout system or user. A recondenser
system used on larger regasification
terminals would not be economic in
this case. With the greater sendout rate
of LNG, options may exist for the vaporization
concept. However, it is likely that
the use of star-fin ambient air vaporizers,
albeit in a larger number, will provide an
economic solution due to low installation
and operational costs (FIG. 5).
The total solution concept. The total
solution concept combines and integrates
the power plant with an SSLNG
terminal. Depending on the size, the
power plant could be utilizing gas engines
or, as size increases, gas turbines or
combined-cycle power plants.
With a total solution concept, there is
a large potential for CAPEX savings within
the shared facility. During the plant engineering
and construction phase, common
methodologies, execution strategies
and teams not only produce cost savings
but also should limit the amount of interfaces
required between the power plant
and the LNG terminal.
All plant infrastructure can be common
and shared across the LNG storage
and power plant. This may comprise all
buildings (maintenance, control, etc.),
electrical systems, monitoring systems
(fire and gas, CCTV, etc.), as well as
other auxiliary and safety units (firefighting,
utilities, etc.), which will drive
down the overall CAPEX. The power
plant also can be designed to allow a
black start capability.
Utilizing heat integration systems
between the power plant and the LNG
terminal, the operational expenditure
(OPEX) can be reduced, but is somewhat
dependent on the type of power
generation used. With gas turbines, the
LNG cold energy can be greater utilized
with inlet air cooling. Depending on the
site location, the heat or cold from the
facility can be used within the terminal
to reduce costs, e.g., HVAC systems. At
an operational level, some reduction in
staffing costs can be achieved with operational,
maintenance and administration
teams used across the integrated facility.
With the total concept solution, the
terminal business concept can be further
extended with truck loading and road/
marine fueling facilities.
Competing offshore concepts. Competing
offshore concepts for SSLNG-topower
exist-i.e., an FSRU with onshore
power generation or a power barge.
These offshore solutions can bring
advantages in project implementation
schedule, depending on shipyard available
capacities. The FSRUs can be constructed
in a safe environment within
the shipyards. Nevertheless, the mooring
must be installed locally and under a high
CAPEX, bringing into question the biggest
advantage of an FSRU, which is flexibility
of movement to another location.
The relatively high operational costs
and operational risks due to storm and
tsunami are another disadvantage. Difficult
and extreme weather conditions may
prevent an offshore installation. Requirements
for dry dock inspections may also
interrupt the power supply.
Takeaway. The SSLNG-to-power onshore
concept is an economic and desirable
solution for power generation in remote
locations. The LNG storage concept
is flexible and scalable, depending on the
power generation required.
Technical
synergies,
such as heat
integration between the power plant and
the LNG facility, can provide an optimized
power generation efficiency. This
FIG. 4. As power generation requirements
increase up to 50 MW, the storage concept
changes to utilize vacuum-insulated bullets
with a typical capacity of 1,000 m3
.
FIG. 5. For LNG storage for large-scale
power production, the use of many
star-fin ambient air vaporizers will provide
an economic solution due to low installation
and operational costs.
total concept solution provides CAPEX
and OPEX optimization, lowers the
project risk and reduces time to commercial
operation. GP
ROBERT BRANNOCK is the
Managing Director of TGE Gas
Engineering GmbH's UK branch
and Technodyne International Ltd.
After obtaining his MS degree in
chemical engineering from UMIST
in 1996, Mr. Brannock has gained
more than 20 yr of oil and gas industry experience
in design, engineering and commissioning of gas
processing facilities and cryogenic terminals.
Working with TGE Gas Engineering since 2002,
he has occupied several positions and now manages
its UK offices. He is also a Fellow of the IChemE.
JULIAN TERPITZ is Product
Development Manager at
TGE Gas Engineering GmbH.
He is responsible for developing
and innovating TGE Gas
Engineering's offerings to the
market. He received a diplomingenieur
(master's) degree in mechanical
engineering and thermodynamics from RWTH
Aachen University in 1999. Since that time, he has
worked for many years as Project Engineering
Manager in different international projects related
to liquefied gases. He also led the department
of project engineering management at TGE Gas
Engineering for several years. During these
assignments, he gained extensive experience in
the technology, management and execution of
EPC projects from proposal to commissioning,
as well as in leading product development projects.
Gas Processing & LNG | JULY/AUGUST 2021 19
Hydrocarbon Processing - August 2021

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