Revolutionising Moisture Measurement in Natural Gas: Unveiling the Superiority of Tunable Diode Laser Absorption Spectroscopy (TDLAS)

Tunable diode laser absorption spectroscopy (TDLAS) as an analyser presents a highly effective means of measuring water content in natural gas. By employing a laser with an infrared wavelength, it is possible to isolate distinct peaks in the wavelength absorption spectrum that signify the presence of water and other components in the gas.

As an optical device, a TDLAS analyser employs mirrors and lenses to direct and focus the laser beam emitted from the source to the detector. The sample gas flows through the measurement cell, which acts as the pathway for the beam.

Consequently, the analyser can deliver an accurate measurement of water content without interference from glycol, methanol, amine, or hydrogen sulphide. This capability is rooted in the fundamental principles of physics.

TDLAS analysers are inherently stable, requiring infrequent calibration due to their resistance to drift and the absence of issues stemming from chemical contamination affecting the sensor itself.

Compared to other techniques TDLAS has a greater resistance to contaminants in the sample feed as shown in the table below:

High sensitivity and selectivity: The technique relies on the absorption of infrared light by water molecules, allowing for precise quantification of moisture content. TDLAS is capable of detecting moisture levels in the parts-per-million (ppm) range, making it suitable for applications requiring stringent moisture control. Furthermore, TDLAS can differentiate between water vapor and other gases, ensuring accurate measurements even in the presence of interfering substances. This high sensitivity and selectivity make TDLAS an ideal choice for moisture analysis in complex samples and environments.

Non-intrusive and real-time measurements: One significant advantage of TDLAS is its non-intrusive measurement capability. The technique allows moisture analysis without physical contact, minimising sample contamination and disturbance. TDLAS also enables real-time measurements, providing instantaneous feedback for process control and optimisation. This real-time capability is particularly advantageous in applications where moisture levels need to be continuously monitored and adjusted. TDLAS can facilitate rapid decision-making, allowing operators to take immediate corrective actions when moisture deviations occur, thus preventing product quality issues and minimising downtime.

Wide dynamic range: Whether the moisture content is low or high, TDLAS can accurately quantify moisture levels across a broad range of concentrations. This versatility is especially beneficial in applications where moisture content can vary significantly, such as drying processes or environmental monitoring. By covering a wide dynamic range, TDLAS eliminates the need for multiple instruments or calibration adjustments, streamlining the measurement process and reducing overall costs.

Robust and low maintenance: The absence of moving parts in TDLAS analysers minimises the risk of mechanical failures, ensuring long-term reliability. The non-contact measurement principle also eliminates the need for sample conditioning, reducing maintenance tasks and associated costs. Additionally, TDLAS analysers are often designed with self-diagnostic capabilities, enabling proactive maintenance and troubleshooting. These features make TDLAS a cost-effective solution for moisture measurement, with reduced downtime and lower overall ownership costs compared to alternative technologies.

Tunable Diode Laser Absorption Spectroscopy (TDLAS) offers numerous advantages for moisture measurement over other technologies. Its high sensitivity, selectivity, non-intrusive nature, wide dynamic range, and robustness make it a preferred choice for precise and reliable moisture analysis in various industries compared to other techniques.

Learn which moisture measurement technology is best suited for your gas application from our previous article.

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Author

Vikram Apte

Industry Manager

Endress+Hauser Australia

[email protected]