Overview
This wide-range TDLAS (Tunable Diode Laser Absorption Spectroscopy) moisture analyzer is a high-performance optical instrument designed specifically for processes involving significant fluctuations in moisture content. Equipped with a high-temperature heat-tracing system (capable of reaching up to 220°C), the device effectively eliminates malfunctions caused by condensation. It is widely used for batch endpoint detection in pharmaceutical or catalyst fluid-bed dryers, syngas monitoring during coal gasification, and real-time monitoring during process loop startups and steam purging.
Principle
The measurement principle of high-precision laser absorption spectroscopy is based on the absorption of light of a specific wavelength by the detected molecule.
Use laser diode light sources of different wavelengths according to the gas molecules, and then measure the intensity of the transmitted light (I) and incident light (I0) at the detector (Lambert-Beer law) to know the current gas concentration measurement chamber.
Application
• Batch Drying and Calcination Processes (Pharmaceuticals, Catalysts, Polymers)
Full-curve drying endpoint detection: In batch fluidized-bed dryers or catalyst calciners, the initial off-gas contains high levels of evaporated moisture (up to 20%–30% by volume). As the product dries, the moisture content drops sharply. Operators need to precisely determine when the moisture level falls below 1,000 ppm or 5,000 ppm to halt the batch process and prevent over-drying.
Why this range is ideal: A single TDLAS analyzer covers the entire drying curve—capable of measuring peak levels of 30% at startup without sensor saturation, while also accurately capturing the endpoint below 5,000 ppm during the drying phase, eliminating the need to switch instruments.
• Coal Gasification and Syngas Purification Loops
Wet-to-dry syngas process monitoring: Raw syngas exiting a wet scrubber is saturated with water vapor (typically 10%–30% by volume). Following cooling, gas-liquid separation, and glycol dehydration, the moisture content is reduced to dry-gas standards (5,000 ppm or lower).
Why TDLAS: TDLAS units are deployed at various stages of the purification loop. Their high-concentration measurement capability allows for monitoring raw wet gas, while the 5,000 ppm range verifies the quality of the final dry syngas; the technology also withstands contamination from high sulfur (H2S) and tar.
• Refinery and Petrochemical Unit Startup (Steam Purging and Nitrogen Blanketing)
Tracking the steam-to-dry-gas transition: Before chemical reactors (such as Fluid Catalytic Cracking units) are commissioned, gas circuits undergo steam purging to clean the lines (moisture >20%), followed by a high-purity nitrogen purge to dry the system to safe operating levels (5,000 ppm or lower).
Why other sensors are unsuitable: Standard trace moisture sensors (aluminum oxide type) cannot withstand the operating conditions of the steam purge phase and require physical isolation. This wide-range TDLAS sensor can remain online throughout the entire process, safely guiding operators as they transition from the "wet steam" phase to the "fully dry" operating phase.
Measurement components and ranges
• H2O: 0 ~ 5000ppm up to 30%
For detailed introduction, please refer to Laser Spectroscopy Analyzer.