Experimental examination of flame chemistry in hydrogen sulfide-based flames

Spectroscopic examination of the emission spectra of excited species in hydrogen/air flames both without and with H2S addition and in hydrogen sulfide/oxygen flame are conducted. The baseline case of hydrogen/air flame showed one distinct global peak of OH* at 309.13 nm. However, higher resolution spectrum analysis showed the presence of three major OH* peaks at 306.13, 309.09, and 312.9 nm. The addition of hydrogen sulfide to hydrogen/air flame resulted in the presence of a bluish cone located at inner regions of the flame. The spectrum of the blue cone showed group of peaks in the 350–470 nm spectral range. The addition of H2S drastically reduced the peak value of OH* due to extensive consumption of the hydroxyl group during H2S combustion. The group of peaks in the blue cone spectrum can be divided into three major bands. The first band is formed by SO* within 320–350 nm, the second band is attributed to SO3∗ within 350–400 nm, and the third band is caused by H* within 400–470 nm. However, the distinction of SO3∗ band and H* band around 400 nm is an issue that requires further examination. Absorption bands of SH were observed at 324.03 nm and 328.62 nm. The effect of sulfur dioxide on the spectrum was observed by neither emission bands nor absorption bands because of its reaction with elemental oxygen to produce excited sulfur trioxide. Gas chromatography analysis showed that combustion products did not contain any SO2. The spectra of H2S/O2 flame have also been examined under lean conditions (at Φ = 0.5). In contrast to H2/air/H2S flames, the spectra of H2S/O2 showed strong absorption bands of SO2 within 280–310 nm. Strong continuum was observed between 280 and 460 nm with distinct group of peaks superimposed in the spectra. The continuum is attributed to the afterglow of singlet and triplet SO2. The superimposed peaks are attributed to SO3∗ and H*.

▸ Spectroscopic examination of excited emissions of flames without/with H2S addition. ▸ Addition of H2S in H2/air flame formed a blue cone located at inner flame region. ▸ Predominant species in blue cone band (range 350–470 nm) include SO3∗, H*, and SO*. ▸ H2S/O2 flame formed continuum (range 280–460 nm) with distinct superimposed peaks. ▸ Continuum is from afterglow of SO2∗; SO2 absorption bands lies in 280–310 nm range.