SS2100 - LNG Product (Export/Import) Analyzer Solution

Application Note

LNG Vaporization
Liquefied Natural Gas (LNG) is produced and shipped at temperatures of approximately -160^oC, so there is little likelihood of significant water concentrations in the LNG itself. However, there are a number of different approaches for the regasification of LNG, using air, gases or liquids heated by burning the gasified LNG and one of the most common is Open Rack Vaporizers using seawater as the heating medium.

Critical Control of Moisture
Monitoring of vaporized LNG for water may be critical in some processes as an indicator of leakage across the heat exchangers. In some cases, the gasified LNG may be mixed with other fuels that are wet.

Traditional Measurement Solutions
Electrochemical and vibrating quartz crystal moisture analyzers have been the traditional method for monitoring the levels of moisture in LNG Product.

Unfortunately, trace hydrocarbons and other contaminants present in the stream contaminate the electrochemical probes. Also the probe calibration tends to drift over the lifetime of the sensor resulting in high maintenance costs due to the need to constantly replace the sensor. It’s not uncommon for moisture probes to be replaced multiple times a year. Quartz crystal moisture meters have slow wet-up and dry-down times that may distort the true moisture content during an upset.

SpectraSensors' Solution
SpectraSensors SS2100 is the ideal solution for this challenging application. Its non-contact laser and detector is impervious to damage from contaminants. Tunable Diode Laser technology means that measurement interferences from other infrared absorbing compounds are avoided. There are no wet-up or dry-down delays, resulting in fast updates even when the concentration changes dramatically. Only SpectraSensors employs Differential Spectroscopy, which incorporates a dryer using metal getter technology to subtract the spectrum of the dry gas from the wet spectrum. This allows the SS2100 to measure streams whose background gas composition changes.

Validation
Validation of low level (<10 ppm) water measurements is essential, but also extremely difficult, as certified blends at such low levels are not readily available. Some have attempted to use permeation devises, but these require regular maintenance to prevent drying out, and there is no independent way to verify the accuracy of the permeation device. SpectraSensors employs a dilution system that dilutes a relatively high concentration certified standard of H2O in Methane using dried sample gas.

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Data Sheet

Performance
Target Components	H2O in LNG Product (export/import)
Typical Measurement Ranges	0 – 10 ppm* (other ranges available upon request)
Typical Precision	±0.05ppm or 2% of Full Scale
Measurement Response Time	1 to ~60 sec*
Principle of Measurement	Tunable Diode Laser Absorption Spectroscopy Non-differential
Environmental Temperature Range	-20º to 50ºC (-4º to 122ºF) -10º to 60ºC (14º to 140ºF) optional
Sample Inlet Pressure	70 kPag (10 psig) typical 210 kPag (30 psig) maximum
Cell Temperature	Maintain at 50ºC +/- 0.2ºC
Maximum Cell Pressure	70 kPag (10 PSIg)
Sample Flow Rate	3 - 4 L/min (6.4 to 8.5 scfh)*
Validation	A certified blend of H2O in Methane balance is diluted with dried sample in the sample conditioning system under flow control
Electrical
Power	100-240 VAC, 50-60 Hz standard
Max Current	Controller: 1 A @ 120 VAC
Controller to Cell Cable Length	1m standard (3m, 5m & 10m available optionally)
Communication	Current Loop Output 4-20 mA Isolated, 1200 ohms @ 24 VDC max load Serial: ASCII Text RS232C standard Modbus RS232C
Digital Outputs	4 ea. 12 VDC for valve operations Scrubber (if required), Process/Val, Val 1, Val 2 5 SPDT (Form C) Dry Contact Alarms Common Fault, Val 1 Active, Val 2 Active, Val Fail, one user-assignable to any alarm
LCD Display	Concentration, Cell Pressure and Temperature, Diagnostic Data
Physical
Controller Enclosure	NEMA 4X - 304 Stainless Steel standard
Controller Dimensions	343mm H x 305mm W x 165mm H (13.5" H x 12" W x 6-7/16" D)*
Weight Approximately	13.1 Kg (28.6 lbs)*
Sample Cell Dimensions	28m Herriot Cell 559 mm H × 127 mm W (22” H × 5” W)
Sample Cell Construction	316L Series Polished Stainless Steel standard
Number of Sample Cells	1 (single channel SS2100) or 2 (dual channel SS2100)
Area Classification	CSA Certified for Class I, Division 2, Groups ABCD Temp Code T3C  ll 2G Ex d llB+H2 T5; Tamb : -20 ÷ +60 °C
Dimensions with Sample System	1678 mm H x 613 mm W x 427 mm D (66” H x 24-1/8” W x 16-13/16” D)
Weight with Sample System (approx.)	68 kg (150 lbs.)
* Application specific; consult factory

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