Ignition delay time measurements behind reflected shock-waves for a representative coal-derived syngas with and without NH3 and H2S impurities
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2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. The composition of a representative coal-derived syngas was determined by averaging 40 practical coal syngas compositions from the literature and corresponds to a departure from many recent studies which only focus on syngas blends containing just CO and H2. Ignition delay times have been measured behind reflected shock waves for this averaged mixture with an equivalence ratio of 0.5 (0.4554% CO/0.3297% H2/0.1032% CO2/0.0172% CH4/0.2407% H2O/0.8538% O2 in 98% Ar (mol.%)) at around 1.7, 13, and 32 atm. The same mixture was also investigated with impurities (200 ppm of NH3 and 50 ppm of H2S). Care was taken when working with the blends containing H2O and NH3 to avoid errors in the shock-tube composition; direct measurement of the water vapor mole fractions were performed using a tunable diode laser absorption diagnostic near 1.38 m. The effect of the various constituents on the ignition delay time was also investigated by comparing to results from a baseline mixture (H2/CO/O2/Ar) and results with this baseline mixture with only one of the other constituents of the syngas (i.e., CO2, CH4, H2S). Experimental data were compared with recent detailed kinetics mechanisms from the literature. Results showed that, under the conditions of this study, extending the mixture composition to include realistic concentrations of species beyond just the CO and H2 does not have a very large effect on the ignition delay time for a coal-derived syngas. However, a comparison of this coal-derived syngas with a syngas derived from biomass, tested in an earlier study by the authors, exhibited large differences due to the larger CH4 concentration in the bio-derived syngas. Two chemical kinetic models from the literature were found suitable to reproduce these data over most of the range of mixtures, temperatures, and pressures investigated, namely the mechanisms associated with Galway and with Princeton.
