Diode-Laser-Based Raman Spectroscopy Applied to the Thermodynamic Characterization of Natural Gas and...

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Chemical Engineering

Background:

• Natural gas networks are increasingly heterogeneous with biomethane, LNG, and hydrogen injection.
• This necessitates advanced, continuous gas-quality monitoring solutions.
• Current methods may not meet the demands of these evolving networks.

Purpose of the Study:

• To develop and validate an industrial Raman-based instrument for in-line measurement of natural gas and hydrogen-enriched natural gas.
• To assess the system's accuracy in determining gas composition and thermodynamic properties.
• To confirm the instrument's suitability for long-term, real-world applications.

Main Methods:

• Utilized a 450 nm broadband laser diode and a custom spectrometer in a pressure-rated, ATEX-certified gas cell.
• Employed non-linear least-squares fitting with calibration spectra for gas composition retrieval.
• Calculated higher heating value (HHV) according to ISO 6976 standards.
• Validated the instrument across various pressures (1.5-17 bara) and temperatures (-20°C to 55°C).

Main Results:

• Achieved compliance with OIML R 140 Class A requirements.
• Demonstrated HHV errors below ±0.5% and repeatability within 0.1%.
• Confirmed stable performance over twelve months of field operation in pressure-reduction stations.
• Operated effectively without carrier gases or sample manipulation.

Conclusions:

• Raman spectroscopy provides a robust, low-maintenance solution for continuous natural gas quality monitoring.
• The developed instrument is suitable for controlled hydrogen-blending applications.
• The system meets stringent accuracy and reliability standards for industrial use.