Hydrocarbon Processing - December 2021 - GP-9

EXECUTIVE VIEWPOINT
Building the foundation
for a low-emission LNG facility
JENNIFER ADAMS, Head of Decarbonization Engineering, Siemens Energy, Houston, Texas
Electric LNG (i.e.,
eLNG)
has
emerged as a powerful decarbonization
pathway for LNG project stakeholders.
However, the development of these facilities
often presents unique technical challenges
not encountered with traditional
gas turbine-driven designs.
One critical facet that needs to be adJENNIFER
ADAMS is the Head of Decarbonization
Engineering for Siemens Energy's Industrial
Applications business. In this role, she leads
the project development activities for new
markets focusing on decarbonization and
sustainable energy. Prior to joining Siemens
Energy, Ms. Adams worked with a large EPC
firm in the hydrocarbon industry, including
15 yr in a leadership role where she executed
major LNG projects. She holds a BS degree
in engineering from Texas A&M University.
dressed is integrating the onsite power
generation unit (PGU) and the liquefaction
island. Traditionally, the parties involved
with the design and engineering of
these facilities have operated in silos, often
with different mindsets and objectives. In
addition to potentially limiting opportunities
for total plant decarbonization,
this type of project approach increases
the likelihood of encountering technical
problems that can lead to costly rework. It
can also present issues if and when plant
modifications need to be made or operating
conditions change (e.g., capacity or
power demand increases, renewable energy
sources are integrated, etc.)
To ensure optimum uptime and create
the lowest possible plant emissions
profile, a more holistic design approach
is required where there is close collaboration
between the power/utility and liquefaction
design teams starting in the early
phases of the project timeline. At Siemens
Energy, we refer to this concept as " integrated
electrical and LNG plant design. " 1
eLNG vs. mechanically driven plants.
In a traditional gas turbine-driven LNG
facility, the driver selection determines
how much power is available for compressors
and dictates LNG train capacity.
While the liquefaction plant owner-operator
provides a desired nominal design
capacity for the facility based on factors
such as available feed, LNG demand,
export regulations, financial decisions,
etc., gas turbines come in discrete sizes.
As a result, the LNG capacity is usually
designed to fully utilize the site-rated gas
turbine power for maximum profit.
When designing an eLNG facility, capacity
limitations may appear superfluous
in that the operator is no longer constrained
by the gas turbine driver when
setting the capacity. However, because
electricity generation is primarily done
with gas turbines, determining the " sweet
spot " of the PGU in terms of efficiency is
essential for maximizing efficiency and
optimizing CAPEX. This sweet spot can
be determined by utilizing cogeneration
and a close match between the site-rated
power and the LNG production (FIG. 1).
Moreover, developing the liquefication
and power facilities separately results
in a highly inefficient project workflow.
In most cases, the process design team
starts by creating the electrical demand
for the main refrigeration trains and then
feeding it to the PGU team. Often, the
PGU team must feed information back to
the process team, which then initiates additional
rework.
Adopting an integrated PGU-LNG
train facility development approach
makes it possible to avoid this iterative
design process and identify issues early
on during FEED that can impact efficiency,
availability, CAPEX and overall
plant emissions.
Production and use of process heat.
With mechanically driven trains, refrigerant
compressor driver power and process
heat come from the mechanical drive gas
turbines. In an eLNG facility, however,
the paradigm is shifted. The thermal heating
required for the LNG process units
comes from the PGU through waste heat
extraction or steam. This requires evaluating
the needed heat and power during
the LNG facility's normal, steady-state
operation and during startup, shutdown
and upset scenarios.
One example of this is during startup-a
topic typically ignored in the early
Gas Processing & LNG | NOVEMBER/DECEMBER 2021 9
Hydrocarbon Processing - December 2021

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