Ignition delay time measurements behind reflected shock-waves for a representative coal-derived syngas with and without NH3 and H2S impurities

Abstract

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 H 2. 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% H 2 / 0.1032% CO 2 / 0.0172% CH 4 / 0.2407% H 2 O / 0.8538% O 2 in 98% Ar (mol. %)) at around 1.7, 13, and 32 atm. The same mixture was also investigated with impurities (200 ppm of NH 3 and 50 ppm of H 2 S). Care was taken when working with the blends containing H 2 O and NH 3 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 (H 2 /CO/O 2 /Ar) and results with this baseline mixture with only one of the other constituents of the syngas (i.e. CO 2 , CH 4 , H 2 S). 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 H 2 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 CH 4 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.

Reactivity of CO/H2/CH4/Air Mixtures Derived from In-Cylinder Fuel Reformation Examined by a Micro Flow Reactor with a Controlled Temperature Profile

“…However, experimental investigations on the reactivity of reformate gases including small hydrocarbons are still quite limited while many studies have assessed the reactivity of pure CO/H 2 mixtures (Dryer and Chaos 2008;Frassoldati, Faravelli, Ranzi 2007;Nakamura et al 2016;Natarajan, Lieuwen, Seitzman 2007;Petersen et al 2007;Walton et al 2007). In order to compare target mixture conditions investigated in the present study and earlier works considering the reactivity of CO/H 2 mixtures with small hydrocarbons (Gersen, Darmeveil, Levinsky 2012;Liu et al 2018;Mansfield and Wooldridge 2015;Mathieu et al 2015;Mathieu, Kopp, Petersen 2013), a CO-H 2 -CH 4 ternary diagram is introduced (Figure 3). CH 4 is selected as a representative small hydrocarbon because it is the simplest hydrocarbon and the most likely to be included in reformate products besides CO and H 2 .…”

“…CH 4 is selected as a representative small hydrocarbon because it is the simplest hydrocarbon and the most likely to be included in reformate products besides CO and H 2 . For each plot in Figure 3, the mole fractions of CO, H 2 and CH 4 are extracted from the literatures (Gersen, Darmeveil, Levinsky 2012;Liu et al 2018;Mansfield and Wooldridge 2015;Mathieu et al 2015;Mathieu, Kopp, Petersen 2013) and normalized. As might be readily apparent, most cases are located on several specific regions in the chart.…”

“…As might be readily apparent, most cases are located on several specific regions in the chart. The mixture conditions around CO/H 2 = 50/50 (the green shaded region) are intended for mixtures from coal and biomass reforming (Mansfield and Wooldridge 2015;Mathieu et al 2015;Mathieu, Kopp, Petersen 2013). The conditions including a large amount of CH 4 (the yellow shaded region) are considered for the utilization of synthetic natural gas (Gersen, Figure 2.…”

Auto-ignition of biomass synthesis gas in shock tube at elevated temperature and pressure

“…Results were compared with previous work of Peschke and Spadaccini [21] indicating that their variations of ignition delay times over time agreed well, but there are deviations between experimental results and predictions. Mathieu et al [22,23] studied the ignition delay times of syngas derived from coal and biomass in a shock tube. The effects of other components (CH 4 , CO 2 , H 2 O, NH 3 , H 2 S) other than CO and H 2 on the ignition delays were investigated.…”

Shock-tube water time-histories and ignition delay time measurements for H2S near atmospheric pressure

“…of a large fraction of natural gas resources (so-called sour natural gas) [1]. Syngas blends produced from either coal or biomass can also contain H 2 S, up to 1.3% mol [2], and it has been shown that H 2 S, even in small proportion, can have a noticeable effect on important combustion properties such as ignition delay time ( ign ) [2,3] and flame speed [4] for hydrogen-based mixtures. For these reasons, H 2 S combustion chemistry has been the topic of several recent studies [1,3,[5][6][7][8][9].…”