Integrated-path multi-gas sensor using near-infrared diode lasers: An alternative to vehicle-driven point gas analyzer
A. S. Ashik, Peter John Rodrigo, H. Larsen, Nathalia T. Vechi, Konstantinos Kissas, Anders Michael Fredenslund, Jacob Mønster, Charlotte Scheutz, Christian Pedersen
Abstract
Sensors for quantitative monitoring of greenhouse gases from high-emission facilities, such as wastewater treatment and industrial plants, are becoming essential to enforce regulatory compliance in climate action initiatives. A predominant sensing technique is the tracer-gas dispersion method (TDM) using closed-path gas analyzers typically installed in a vehicle to measure concentration as the gas plume is transected. Here, we validate for the first time the use of integrated-path gas sensors in TDM, measuring instantaneously the concentration along a predetermined laser beam path, thereby facilitating a stationary setup with orders of magnitude higher update rate and without the need for vehicles or road access. Our approach relies on a sensitive, integrated-path multi-gas sensor for real-time emission quantification using tunable diode laser absorption spectroscopy. An optical sensor head with spectral coverage from 1.52 μm to 1.65 μm is demonstrated, supporting multiplexed gas sensing in a modular fashion using low-power fiber-coupled diode lasers. The sensor measures real-time integrated-path concentrations of CO2 and CH4, and the tracer-gas C2H2 at 130 Hz with 0.5 ppm, 3 ppb, and 2 ppb sensitivity, respectively, at 1 s averaging. The integrated-path sensor is systematically benchmarked for absolute accuracy against a state-of-the-art point sensor, revealing an excellent match over 16 hours. Furthermore, the integrated-path sensor is deployed outdoors for emission quantification using TDM. A comparison to the gold-standard point sensor reveals identical results, demonstrating the integrated-path sensor as a potent substitute for vehicle-driven point sensors.