From Mars to the North Sea
16 Jul 2004
The measurement of water vapour in natural gas is of particular importance in assessing the likelihood of solid hydrates forming in the pipeline. Now, a technology first used on a NASA mission to Mars is being applied to this and other industrial gas applications.
Available from IMA, the tuneable diode laser (TDL) system is a near-infrared (NIR) technique that can cope with highly contaminated or aggressive gases.
Its greater accuracy (±2% of reading) than other NIR techniques means that on-line systems can approach the accuracy normally associated with transfer standard laboratory measurements made in clean gas.
Compared with dewpoint techniques, the instrument also has a very fast speed of response. It can drop from ambient conditions of around 12 000ppm to 2ppm in less than six seconds - compared with the four to six hour wait of other dewpoint systems.
What sets TDL systems apart from other NIR analysers is the spectral width of the light emitted.
Traditional NIR systems use a broad light source and filter out wavelengths above and below the wavelength of interest, but the TDL technique leaves a window of around 30 to 40nm around the target wavelength.
This extra resolution means less interference from background gases and the ability to get to down to ppm or even ppb levels.