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E-LNG
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Electric drive solutions
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Compressors for LNG
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Power generation
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The unique advantages of electric LNG
While today’s vast majority of refrigeration compressors in LNG liquefaction
plants are driven by gas turbines, E-LNG schemes stand out as an
economically and ecologically superior approach — despite a higher
initial investment for a larger thermal power plant. With variable-speed
electric motors available for all relevant refrigerant compressors, the
concept of electrical liquefaction of natural gas (E-LNG) can be applied
equally well to all recognized and proprietary LNG liquefaction cycles,
offering a host of benefits. The E-LNG concept has been made feasible
by Siemens’ distinctive technology position in large motors and drives,
which are available to match the top end of the refrigerant-compression
duties now demanded by the scale-up of LNG train capacities.
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One of two massive Siemens 65-megawatt variable speed drive systems
(VSDS) powering refrigerant compression at Statoil’s Melkøya Island all-electric
LNG plant. |
Dramatic boost of productivity The design concept of an E-LNG plant is to enable up to 365 days per
year of uninterrupted refrigeration-gas circulation or for periods not
limited by either the power plant or the compressor strings. This allows
for a substantial increase of productivity by eliminating downtimes of
the refrigeration compression trains. Initial additional investment costs
for the power plant are expected to be compensated within a period
of under five years, depending on the value of LNG at the time.
Significantly improved energy efficiency and reduced emissions
Combined-cycle power plants for E-LNG service provide significant
potential for improving overall thermal efficiencies. Even including distribution
losses electric drive systems achieve 96 percent efficiency,
resulting in an overall refrigeration-system efficiency of up to 45 percent,
compared to approx. 32 percent for traditional mechanical drive
solutions. Combined-cycle power plants also reduce greenhouse-gas
emissions by around 30 percent compared to traditional mechanical
compressor drives. Including process-steam supply, overall thermal
efficiency may reach 90 percent.
Increased operational safety, flexibility and asset utilizationWith E-LNG, process and compression-plant size is no longer restricted by
available mechanical drives; there is no need for fired equipment and
related scheduled maintenance inside the process plant. Associated risks
are eliminated and can reduce insurance costs. Quick and controlled
starting and re-starting of pressurized compressors minimizes downtimes
and eliminates flaring of expensive refrigerant gas, while compressor
speeds can be optimized, and target production can be reached with
smaller train capacity and unaffected by ambient temperature.
Significantly accelerated schedules
Typically, E-LNG schemes provide significant time benefits. Faster string
test programs, modular motor-drive systems, and shorter installation
times offer the potential for months of schedule reduction and a substantial
decrease in related costs.
Particularly suited for floating LNG plants (F-LNG)
The evolving concept of F-LNG plants prefers a physical separation of
combustion equipment from the process area for personnel safety
reasons. E-LNG installations can be optimally sized and located on board
a barge or ship.
 A single source from power to compression
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