Hydrocarbon Processing - August 2022 - 64

Gas Processing & LNG Industry Spotlight
* A single analyzer can support up
to four probes, so readings can be
taken at multiple locations in the
process stream.
* Output from the probe changes
in real time, and the analyzer can
take a snapshot of the composition
in less than 20 sec, with no delay
between readings.
Compositional measurements with
Raman spectroscopy can be used to calculate
Wobbe index or calorific values,
according to International Organization
for Standardization (ISO) and Gas Processors
Association (GPA) Midstream
Association standards such as GPA 217209/GPA
2145-2009, GPA 2172-09/GPA
2145-2016, ISO 6976-1995E and ISO
6976-2016.
The Raman analyzer can detect most
natural gas components down to 200
ppm, so it is not suited for trace analysis
of LNG contaminants-such as H2
or CO2-down to regulatory levels. For
S
practicality, LNG pretreatment typically
reduces contaminant levels well below
specified thresholds. Instead, the calorific
value is the more critical measurement,
which Raman analyzers can handle within
the required ranges. If it is necessary to
measure lower contaminant levels, GC
analysis is a better solution.
Analyzer
calibration. All analyzers
require periodic calibration, but the frequency
and complexity of the calibration
process varies. GC models used for LNG
terminal service typically require daily
calibration, which is performed by feeding
a pre-measured test gas into the analyzer.
While this is not normally an arduous
process, it requires consumables and
taking the analyzer offline. Although calibration
can maintain GC measurement
accuracy, it does not solve the larger issue
with the vaporizer and sampling system.
GC can provide highly precise analysis,
but if a sample is not representative of the
LNG composition, then the underlying
problem remains unsolved.
Raman analyzers also require calibration;
however, their mechanisms for measurement
are very stable, so these analyzers
can typically operate up to 2 yr without
calibration. Because their probes are inserted
directly into an LNG stream, most
calibration requires process shutdown for
probe removal, which can be performed
during planned facility maintenance cycles.
Mounting mechanisms are available
in certain applications, enabling online
probe removal while LNG is flowing.
Analyzer validation can be performed
using a surrogate liquid sample. If the validation
result indicates that calibration is
required, standard calibration tools are
available for field calibration of the analyzer
to ensure that it is brought back to
factory specifications. The calibration
procedure tests the entire analyzer, including
the probe, fiber-optic cables and
the full analyzer.
Importance of analysis. LNG-coming
from a variety of sources, each with
unique characteristics and worth hundreds
of millions of dollars-is moved
around the world every day. While pretreatment
removes some of the variability,
even slight changes in calorific value
can change the value of a single load by
hundreds of thousands of dollars.
Analyzer technologies available today
can ensure that natural gas meets the
required quality specifications prior to
liquefaction, and then identify when it
suffers value loss during extended time in
transit. New techniques provide greater
measurement accuracy and reliability,
combined with lower lifetime costs and
maintenance, and receiving terminals
should consider all available measurement
options.
NOTES
a Endress+Hauser's SS2100 TDLAS
b Endress+Hauser's Raman Rxn5 analyzer
ALAN GARZA is the Product
Marketing Manager for the
Advanced Analysis product lines
at Endress+Hauser. He began his
career at Endress+Hauser as a
rotational engineer, developing
multiple instrumentation
technologies. His experience includes being part of
the inside sales team, where, as an applications
engineer, he developed and championed gas
analytics. His background also includes business
development and operations management. Mr. Garza
earned a BS degree in mechanical engineering
technology from the University of Houston.
SAM MILLER is the Head of
Technical Marketing for TDLAS/QF
at Endress+Hauser Optical Analysis.
He has more than 20 yr of
experience in oil and gas markets
and in the development of laserbased
products. He is a member of
the ASTM D03 standards committee and participates
in numerous natural gas conferences, including
American Gas Association (AGA) conferences, ISA
Analysis Division symposiums, and meetings for
various international hydrocarbon measurement
organizations. Mr. Miller holds a BS degree from
California Polytechnic University, Pomona, and an
MBA degree from the University of California, Irvine.
SCOTT SUTHERLAND is the Product
Manager at Endress+Hauser Optical
Analysis. He is responsible for
Raman analyzers, including the
Raman Rxn5 analyzer and its
applications in the oil and gas and
chemical industries, including
FIG. 5. The ability to insert a probe directly into the LNG stream eliminates the need for a
traditional sample handling system.
64 AUGUST 2022 | HydrocarbonProcessing.com
ammonia and methanol production, hydrogen
generation and synthetic natural gas. Dr. Sutherland
has spent more than 32 yr designing Raman analyzers
and developing Raman solutions for General Electric,
Thermo Electron, Photon Systems, Bruker Optics and
Endress+Hauser in the areas of law enforcement,
forensics, pharmaceuticals, hazardous materials and
process gas analysis. He earned BS degrees in physics
and chemistry from the University of Tennessee at
Chattanooga, and a PhD in analytical chemistry from
the University of Florida.

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Hydrocarbon Processing - August 2022

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