Hydrocarbon Processing - June 2022 - GP-23

LNG
stream exiting the reactor. The CO2
can
then be removed from the product stream
by an amine system or other separation
technology, enabling a high degree of carbon
capture for both processes. The differences
between the two technologies
lie with the specific reactions involved
and the type of reactor needed. The POX
process uses a non-catalytic main reactor
and uses steam for temperature control,
while the ATR process uses a catalytic
main reactor with steam consumed as
part of the reaction.
TECHNOLOGY SYNERGIES
The pre-combustion capture processa
features several synergies gained by integrating
liquefaction, H2
production and
power generation. These synergies would
be unavailable if a plant were designed to
run on green electricity from a local grid,
or if it imported H2
for its gas turbines.
Improved liquefaction efficiency. The
proprietary process allows for a re-optimization
of the LNG liquefaction plant to
improve efficiency. Higher fuel requirements
for the H2
production facility allow
for increased end-flash flow from the
liquefaction facility, potentially increasing
LNG production by up to 2%. This may
aid in debottlenecking existing facilities
that would otherwise be limited by available
liquefaction power.
Low gas turbine NOx
emissions. With
H2-burning gas turbines, a major concern
is the generation of NOx
. The pre-combustion
capture process has several features
that help in maintaining equivalent
levels of NOx
to a typical dry low emisproducsions
(DLE) system. In the process, the
end-flash gas used to feed the H2
tion plant typically contains a significant
fraction of N2
. This N2
passes through the
plant and is sent to the power generation
system, where it serves as a diluent for the
fuel and aids in suppressing NOx
tion. Excess steam and N2
formafrom
the H2
production facility are also available for
use as additional diluents.
Retrofit considerations. The process
can be applied at both new-build sites and
in the retrofit of existing plants. Retrofitting
an existing plant to decarbonize it
comes with several unique challenges and
opportunities, as discussed here.
Pipeline
CO2
Natural gas pretreatment and LNG liquefaction
Natural gas
FIG. 3. Proprietary pre-combustion capture technologya
layout overview.
Gas Processing & LNG | MAY/JUNE 2022 23
LNG
End-flash
Power
CO2
H2 production
facility
CASE STUDIES
The following section examines three
case studies implementing the proprietary
pre-combustion capture processa
two retrofit options for existing plants
,
Gas turbine capabilities. Many gas turbines
used as compressor drivers for natural
gas liquefaction can handle a fuel that
consists of a mix of H2
and CH4
, requiring
only minor engine and package upgrades
to ensure safety and reliability while appropriately
handling the new fuel. However,
for cases where the goal is a high degree
of pre-combustion carbon capture, the gas
turbine must be capable of handling fuel
with a combustible component comprised
of 100% H2
been designed for 100% H2
and a new-build that takes full advantage
of both efficiency improvements and CO2
capture options.
All three cases and the base case used
for comparison assume an LNG liquefaction
facility that uses a proprietary LNG
technologyb
, which is
. This plant has net-in-tank
LNG production of 4.5 MMtpy. The raw
natural gas feed to the liquefaction plant
pretreatment contains 4% CO2
. Some turbines have already
fuel. For other
existing turbines, running on this fuel requires
a modification of the combustion
system to manage the unique properties of
high-H2
fuels. In either case, the gas turbine
and other site specifics-including emissions
limits and utilities availability-must
be considered when evaluating H2
as a fuel.
Offsite H2
facilities. At some sites, there
is insufficient nearby plot space for an H2
production facility. In these cases, it may
be possible to export end-flash gas via a
pipeline to a remote H2
and receive either H2
return. Alternatively, an existing LNG facility
may simply wish to replace a portion
of its fuel with a decarbonized fuel from
a third party without any major changes
to its own facility. Purchasing decarbonized
H2
change that can decrease an LNG facility's
carbon footprint.
production facility
fuel or electricity in
removed in the AGRU. Unless otherwise
stated, the liquefaction power is provided
by two directly coupled industrial
gas turbines (Frame 7E) in simple-cycle,
and an industrial gas turbine as a simplecycle
power generator for the electrical
power requirements. For the purposes of
this case study, the power generator can
be another single Frame 7E, or multiple
smaller gas turbines of similar efficiency
and total power capacity.
For each case, the power used by liquefaction
is held constant, while the total
power was varied to address the power
needs of the additional H2
facility.
production
from an external source is a simple
Retrofit (partial and full) cases. Two
options were evaluated for the retrofit
case, differing on the degree of upgrades
needed for the combustion system of the
gas turbines. The " partial H2
portion of the flash gas to the H2
tion facility, then recombines the H2
" case sends a
producproduct
with the remainder of the flash gas.
This resultant fuel stream contains approximately
20 vol% H2
. Existing industrial gas
turbines designed for use with natural gas
require only minor adjustments to handle
this new fuel stream, which avoids a significant
overhaul or extended downtime.
Power
H2
Power generation
system
Hydrocarbon Processing - June 2022

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