High-Precision WMS-TDLAS Hydrogen Detection System with a Long Optical Path Length Multipass Matrix Cell
Hongyan Dong, Yiyun Gai, Zhaoyue Huang, Xue Ou, Peng Liu, Xin Zhou
Abstract
The weak absorption features of hydrogen and the coexistence of various interfering gases make it considerably challenging to achieve high-precision hydrogen detection in complex environments via tunable diode laser absorption spectroscopy (TDLAS). To address these challenges, this study employed a spectral line overlap decoupling algorithm as well as a low-pressure detection strategy and designed a TDLAS hydrogen detection system based on wavelength modulation spectroscopy and a novel long optical path length (OPL) Pickett Bradley White cell (PBWC)-PBWC multipass matrix cell (MMC), aiming to realize hydrogen sensing in biomass gasification environments. To resolve interference from coexisting methane and carbon dioxide, a reduced pressure of 200 Torr was employed to mitigate spectral line overlaps and pressure broadening effects. Additionally, a least-squares algorithm was implemented to decouple the mixed absorption spectra, enabling the high-precision retrieval of hydrogen concentration. In response to the limitation of the insufficient absorption of hydrogen, an MMC featuring a multiloop reflective architecture was designed, achieving an effective OPL of up to 314 m while possessing a high ratio of OPL to volume. The experimental results indicate that the system has good measurement linearity and accuracy, achieves a detection limit of 38.5 ppm, and can accurately measure hydrogen concentration even when interfering gases fluctuate over a wide range. This work highlights the application potential of TDLAS in hydrogen detection and fills the research gap in this field.