The cycle time of traditional GC analyzers that are used for LNG analysis and energy determination is several minutes. This can be an issue if gas is being exported out of specification and needs to be diverted rapidly for further process treatment. Furthermore, for accurate accounting when metering the LNG during transfer, the LNG flow data needs to be matched to instantaneous energy data as closely as possible; a GC cannot achieve this as it leaves significant data gaps between cycles.
ASaP engineers and manufactures LNG analysis and LNG sampling systems with a wide variety of gas analyzing and LNG sampling options and solutions.
Alternative technologies like the GasPT exist which is capable of providing the accuracy required for custody transfer applications within 10 seconds. Like a GC, the GasPT does NOT require a permanent supply of support gases, such as carrier gas, calibration gas, instrument air, etc. Its compact footprint as well as significant infrastructure to protect the device from the hazardous area and marine environment.
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Background of LNG energy determination
In many countries in recent times there has been a significant shift from a single source of indigenous natural gas towards multiple sources of gas from new inter-connector pipelines and shipped LNG. The terminal operations for LNG import and export require accurate monitoring of gas quality and flow at numerous points in order to satisfy energy accounting standards and trading contracts.
The GIIGNL equation to calculate net energy transferred is: E = (V.ρ.GCV) – Egas displaced in tank ± Egas to Engine Room.
Accurate measurement of the LNG density (ρ) and Gross Calorific Value (GCV) is therefore critical and these parameters will vary as loading/unloading operations proceed and boil-off gas is released.
Solution for LNG energy determination
ASaP and Orbital joined forces and have developed an LNG Energy Determination solution using the GasPT product and the ASaP Phazer – LNG Probe-Vaporizer to provide accurate and continuous measurement of LNG properties so that operators can accurately and reliably account for every drop of LNG during transfer.
True Value™ is a unique integration of LNG sampling, LNG vaporization, gas conditioning and gas analysis which provides rapid and accurate monitoring of gas quality, with T90 response time less than 10 seconds and to a CV error of less than ±0.5%. The compact Phazer – LNG Probe-Vaporizer is linked to the system to ensure a homogenous gas mixture at its outlet. The system mounts directly onto a pipeline or can be post-mounted nearby with a short gas sample line. Best response and accuracy is gained from pipeline mounted surfaces.
Depending on the application, GasPT signal outputs can be either serial, Ethernet or analogue interfaces. Calorific Value (Gross and Net), Relative Density, Wobbe Index, Compressibility, Methane Number, Motor Octane Number and others are all standard physical properties which are output from GasPT.
In addition to ATEX, IECEx and CSA approvals, American Bureau of Shipping type approval has been obtained for GasPT marine LNG tanker applications.
The Zone 1 True Value™ has been developed specifically for LNG applications to improve speed of response and accuracy.
LNG analysis with the GasPT natural Gas Properties Transmitter
GasPT is an online transducer that provides information regarding the physical properties of natural gas – hence the name natural Gas Properties Transmitter. GasPT provides the industry critical information about the physical properties of natural gas:
- Calorific Value (CV) / British Thermal Unit (BTU)
- Wobbe Index (WI)
- Relative Density (RD)
- Compression Factor (Z)
- Methane Number (MN)
- Total Air Requirement (TAR)
- Plus others
The GasPT measures a number of easily monitored physical properties of a sample of gas from which it infers a composition. From the inferred composition GasPT uses ISO 6976 to calculate Calorific Value, Density, Relative Density and Wobbe index. Analytical Solutions and Products B.V. includes the GasPT in LNG measurement and LNG sampling systems.
The uncertainty of information of the physical properties calculated by GasPT is equal to the uncertainty when using gas chromatography. However, the speed of response will reduce the overall uncertainty. When integrated with our VE Technology® sampling system (GasPT), the total uncertainty can be reduced to 50% of that typically available with LNG analysis chromatography.
Benefits of True Value
- Proven technology.
- Full compliance with ISO 8943.
- Successful testing against EN 12838.
- Sub-cooled cold section insures 100% LNG sample transport to Vaporizer section.
- Integrated Zero Dead Volume™ accumulator.
- Unique flash vaporization and flow control design.
- No moving parts and practically maintenance free.
- Phazer – LNG Probe-Vaporizer complements the GasPT LNG instrumentation to provide LNG sampling, vaporization, conditioning and analysis in one small, easily installed system which will operate at low LNG line pressure.
- Measures at LNG pressures from 0,5 barg.
GasPT is straightforward to install, similar to a pressure or temperature transmitter. With our VE Technology sampling system it can be installed directly on the pipeline. The electrical/data connection is provided through a safety interface, which is supplied as standard, providing certification for Zone 1 hazardous areas and for certain applications Zone 0.
LNG analysis conclusion
Traditional GC analyzers and vaporizers may have issues with speed of response and gas sample partial vaporization. True Value™ provides vaporization, gas sampling, gas conditioning and analysis to give rapid and accurate CV data which can be used for custody transfer, process control and alarms on LNG terminals.
LNG measurement with Natural Gas Chromatograph NGC8206
The NGC8200 series represents the most rugged, economical, versatile, and high-precision on-line gas chromatographs in the industry. Designed with flow computer and chromatograph capabilities for energy metering, the NGC8200 series provides not only best-in-class, on-site LNG analysis, but also offers a highly versatile platform that integrates many of the functions you need to deliver greater productivity. NGC8200 models provide accurate and reliable knowledge of gas composition and other vital parameters to ensure the quality of the product, and to determine precise quantity when transferring the product for sale. With its custody-transfer and metrology quality chromatography, the NGC8200 delivers all of the measurement information you need, including:
- Relative density
- Heating value
- VOS (velocity of sound)
- GPM (gallons of liquid per thousand cubic feet)
- Wobbe index
- HCDP (hydrocarbon dew point)
- API 21.1 EFM capability
- AGA8 compressibility calculations
- H2S measurement
The NGC8206 enables you to remotely analyze natural gas composition from N2 to C6+ (optional H2S separation) and LNG analysis, and format this information for output to most third-party software systems.The unit’s integrated, 32-bit Windows® CE controller seamlessly processes all chromatograms, performs all needed calculations, and reports results in real time, for accurate and timely information on the product in process. The NGC8206 retains this as historical data, to be referred to later for custody transfer, or to verify transmitter operation performance.
The NGC8206 requires not only very little space (a mere 1.1 cubic feet) but also very little power (less than 7 watts), so it can be left continuously running.
The NGC8206 — one simple-to-operate device providing total energy measurement at every point along the natural gas supply chain, from the wellhead to the distribution market and everywhere in between.
MKS Precisive TFS Tunable Filter Spectroscopy for LNG analysis
LNG measurement Natural Gas Quality, C1-nC6 Hydrocarbon Composition, and BTU/Wobbe Monitoring
The MKS Precisive® product platform of innovative optical analyzers based on Tunable Filter Spectroscopy (TFS™) provides real-time gas and LNG analysis in the natural gas and hydrocarbon processing industries, including refineries, hydrocarbon processing plants, gas-to-power machines, bio gas processes and fuel gas transportation and metering, while delivering customers a substantially lower total cost of ownership. Analytical Solutions and Products B.V. includes the Precisive® TFS™ in LNG analysis and LNG sampling systems.
Precisive® TFS™ can be utilized from UV (Ultra-Violet) through IR (Infra-Red) spectral regions. The Precisive® TFS™ sensor platform has been on the market since 2008 with more than 2500 systems deployed.
Precisive® optical sensors are the first widely deployed hydrocarbon composition monitors to feature real-time unattended analytics with hydrocarbon speciation capability equivalent to traditional Gas Chromatography (GC) instruments yet, with much lower cost of ownership.
Now a part of MKS Instruments, the Precisive® TFS™ sensor platform will be further developed for trace/ppm through bulk/% applications where a multi-component, low-maintenance, stable analytical sensor-transmitter is required that is well positioned between traditional NDIR (Non-Dispersive Infrared) and laboratory-grade FTIR (Fourier Transform Infrared).
Gas quality monitoring on LNG export and importation terminals:
- LNG metering
- Export sales gas
- Boil-off gas recondensers inlet and outlet
- Fuel gas for revaporization heaters
Gas quality monitoring on marine LNG tankers:
- Boil-off gas prior to reliquefaction
- Ship-to-ship transfer
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ASaP delivers quality gas analyzers for natural gas
The practical solutions of ASaP are based on on decades of experience, specific education, knowledge of the team members and, last but not least, the joy in our work. The well-established and complementary ASaP package of services and products is an important contribution to the right solutions for your analytical needs. Moreover, the team spirit and the cooperation with specific partners give us the opportunity to design, build, locally install and commission tailor made analyzer systems for you. All these products and systems can be carried out according to the latest guidelines, such as ATEX.
ASaP is a reputable provider of analytical solutions; We can provide you with a full service package including analyzers, system integration etc. You are kindly invited to consult us on any analytical challenge! The Phazer is manufactured by ASaP, an ISO 9001:2015 certified company in the Netherlands.