Simultaneous measurement of SO2 and CO2 for sulfur content detection in marine diesel fuel using QCL absorption spectroscopy.

• A sensor system is developed for simultaneous measurement of SO 2 and CO 2 using mid-infrared laser absorption spectroscopy. • An enhanced broadband concentration inversion method increases detection accuracy by an average of 30.76%. • Dynamic response, accuracy, sensitivity, and detection limit are evaluated in the laboratory. • Diesel sulfur content detection was simulated by field experiments. Simultaneous measurement of CO 2 and SO 2 in ship exhaust gases is a common method for assessing compliance with sulfur emission standards. This study develops a new ship exhaust gas analyzer using time-division multiplexing of two quantum cascade lasers for simultaneous detection of the two gas species. A digital circuit integrated with a dual-channel waveform generator and a lock-in amplifier is developed to implement wavelength modulation spectroscopy (WMS) scheme. To enhance the measurement accuracy of SO 2 with broadband absorption feature, a novel WMS approach that combines first-harmonic and normalized second-harmonic detection is introduced. A Kalman filter algorithm is employed to further refine the measurement precision. Experimental results show a 30.76% increase in detection accuracy. With a 1 s time resolution, the sensitivities of 13.4 ppb for SO 2 and 9.81 ppm for CO 2 are achieved. The effectiveness of the prototype for sulfur content detection is demonstrated, aiding emission management of water transport emissions. [ABSTRACT FROM AUTHOR]