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Tunable Diode Laser Spectroscopy in Critical Applications

By Mettler Toledo CE |

Accurate and continuous O2 determination plays a pivotal role in achieving safety and process reliability in a wide range of manufacturing processes. Harsh process conditions and maintenance requirements of sampling and conditioning systems can present challenges in procuring accurate and reliable measurements.


Problems with Extractive Oxygen Analyzers

Traditional extractive oxygen analyzers such as paramagnetic analyzers are often required to, produce measurements in various challenging situations that include harsh environment conditions, background interference in the form of various gases, dust load, and moisture. Shortcomings that can be attributed to the use of extractive oxygen analyzers include:

• Erroneous measurements – In unique applications, such as where propionic acid is present, paramagnetic analyzers might produce errors even with the presence of a drop of condensate of propionic acid. Mistakenly low oxygen values can be measured due to “eating” of oxygen by the propionic acid in the sampling line.

• Suboptimal performance -In the VCM production process, the response time of the an extractive analyzer might be too slow. In incinerators, suboptimal performance of extractive measurement systems in terms of interference from NOx emissions, presence of HCl, and excess air are observed via comparative studies.

• Cross interference: The presence of undesirable particles such as dust and moisture in the measurement cell can significantly hinder the performance of extractive oxygen analyzers.

• High costs of maintenance: Extractive oxygen analyzers require error-prone sampling and conditioning equipment. Also, they have to face the toughest process conditions. Such systems require extensive maintenance and therefore incur high costs


With all the disadvantages and concerns arising from the use of extractive oxygen analyzers, Tunable Diode Laser (TDL) analyzers have garnered attention and appreciation for their utility in industrial applications. TDL analyzers work on the principle of laser absorption spectroscopy. A focused and tunable laser beam is used to analyze absorption lines that are characteristic of the particular gas species to be measured. TDL oxygen analyzers measure oxygen in situ or directly from the gas stream without any sampling or conditioning.

Some of the benefits of TDL Analyzers:

TDL analyzers offer the following advantages over extractive analyzers:

- High resolution and accuracy:

- Speed

- Resistance against cross interference:

- Resistance against corrosion

- Recalibration

- Cost

To see the details get the White Paper

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