Evaluation of Nitrous Oxide Emitted from Diesel/Biodiesel Blends during Combustion in a Diesel Engine at Laboratory Scale by a Photoacoustic Spectroscopy Technique

Abstract

The aim of this work was to evaluate the emission of nitrous oxide (N2O) using a diesel engine at laboratory scale without a catalytic converter with diesel/biodiesel blends (%) of 95:5 (B5), 90:10 (B10), 85:15 (B15), 80:20 (B20), 75:25 (B25), and 50:50 (B50). Measurements of N2O in the exhaust gas were made using an experimental setup based on photoacoustic spectroscopy using a quantum cascade laser that was validated to be selective and sensitive in the range from 1.7 to 2.72 ppmv. According to the experimental results, the lowest N2O concentration was found to be in the B5 diesel/biodiesel blend. Also, formaldehyde and methane compounds were detected qualitatively, indicating the possible presence of these chemicals in the combustion of diesel/biodiesel blends.

Photoacoustic Spectroscopy for the Quantification of N2O in the Off-Gas of Wastewater Treatment Plants

“…Costopoulos et al used a pulsed optical parametric oscillator emitting at 2.86 μm, yielding an impressive LOD of 60 ppbv. Others used a mechanically modulated continuous-wave CO 2 -laser emitting at 10.532 μm, a semiconductor laser emitting around the N 2 O absorption band at 2.292 μm, or a quantum cascade laser (QCL). , …”

“…This signal is essentially baseline-free as it is influenced neither by incoherent noise (acoustic noise from outside the PA cell) nor by coherent noise, as caused by wideband window absorption. , Detection methods with QCLs and multi pass sample cells have been developed . Only a few examples on the combination of QCLs with photoacoustic spectroscopy (PAS) are described in the literature. ,,, …”

“…Alternatively, wavelength scanning over a specific 15 or a quantum cascade laser (QCL). 16,17 Lasers with a rapid wavelength tuning capability, such as QCLs, allow for PA spectroscopy by wavelength modulation, as first proposed by Castleden et al, 18 instead of the common intensity modulation. Modulation of the wavelength over a small range around a narrow absorption peak, typically in the range of less than the fwhm of the absorption line, results in a PA signal with twice the modulation frequency, allowing for second-order detection.…”

“…21 Only a few examples on the combination of QCLs with photoacoustic spectroscopy (PAS) are described in the literature. 16,17,22,23 In this paper, we present two new PA instruments for the detection of N 2 O emissions from wastewater treatment plants (WWTPs). The instruments were combined with a dedicated sampling system to collect gaseous emissions from WWTP reactors.…”