Example of a TDL with a non-purged (NP) process adaptor and particulate filter.
Example of a folded-path TDL mounted across a 4" (DN100) pipe.
Purge gas dominates optical path with a purge-type probe, but non-purged probe offers a solution.
How beam steering affects a TDL analyzer.
A host of difficult applications for gas measurements are observed across chemical, petrochemical and other industries.
Traditional extractrive analyzers produce measurements under various difficulties that include relatively long response times or background interference in the form of various gases, dust load and moisture. Furthermore they require error-prone sampling and conditioning equipment.
With all these concerns arising from the use of extractive analyzers, Tunable Diode Laser analyzers (TDL) have garnered attention and appreciation for their utility in industrial applications: A focused and tunable laser beam is used to analzye absorption lines that are characteristic oft he particular gas species tob e measured. TDL analyzers measure in situ or directly from the gas stream without any sampling or conditioning.They are able to achieve high specificity due to the high spectral resolution available, and they provide a very fast response time. Cross interference is not a concern as the spectral lines analyzed can only be produced by oxygen, regardless of the background gas mix. As there is no requirement for sample extraction and continioning, maintenance is very low compared to extractive techniques and therefore TDL analyzers are much more cost effective than extractive analyzers.
TDL analyzers for process applications have two basic design types, namely cross-stack and probe-type. In the cross-stack design, the laser source is placed on one side oft he pipe or duct and the received on the other. In the probe type TDL analyzer, the defining feature ist he sensor probe that protrudes into the process gas stream. The laser diode and the detector are contained in a single unit, requiring a single flange connection.
Benchtop Freezer for the LabThe METTLER-TOLEDO GPro500 Is a Modern Folded-Path Probe-Type TDL Which Offers a Host of Advantages:
- Transmitter and receiver in a single unit and no need for an expensive interconnecting cable.
- Usually single flange installation.
- No tricky alignment across the pipe or vessel.
- Order of magnitude reduction in purge gas requirement.
- Small size, so easy to install in tight spaces.
- Greater accuracy (as the laser beam passes though the sample twice).
- No beam-steering-effect in hot and dusty processes as the GPro500 can also work without cold purge gas, which causes diffraction oft he laser beam and contributes to signal noise.
TDL measurements offer a lot of benefits compared to extractive analyzers. These benefits are not always mateched in practice due to the limitations oft he process interface of typical cross-stack, in situ TDL. A re-thinking of these challanges has led tot he development of a series of new innovative process adaptions for folded-path probe-type TDL. By recognizing these limitations and re-imagining a better solution, it is now possible for a compact, lightweight TDL analyzer to be utilized across a vast range of installation locations with confidence and without compromise.
Request information now or download our brochure.
We are happy to answer your questions by phone at +49 (0) 641 / 95059880