Experimental and modelling study of syngas combustion in CO2 bath gas

Abstract

Syngas produced from coal and biomass gasification has been proposed as a potential fuel for direct-fired supercritical power cycles. For instance, the Allam-Fetvedt cycle can offer price-competitive electricity production with 100 % inherent carbon capture while utilizing CO2 dilution of about 96 %. In this work, ignition delay times (IDTs) of syngas have been measured in CO2 diluted conditions using a high-pressure shock tube at two pressures (20 and 40 bar) over a temperature range of 1100 – 1300 K. Syngas mixtures in this study were varied in equivalence ratio and H2:CO ratios. The datasets were compared against the predictions of AramcoMech 2.0 and the University of Sheffield supercritical CO2 2.0 (UoS sCO2 2.0) kinetic models. Quantitative comparative analysis showed that the UoS sCO2 2.0 was superior in its ability to predict the experimental IDTs of syngas combustion. We found that the reaction of CO2 and H to form CO and OH caused the separation of H2 and CO ignition in two events, which increased the complexity of determining the IDTs. We investigated this phenomenon and proposed a method to determine simulated IDTs for an effective comparison against the experimental IDTs. The chemical kinetics of syngas combustion in a CO2 and N2 bath gas are contrasted by sensitivity and rate-of-production analyses. By altering the ratio of H2 and CO as well as mixture equivalence ratio, this work provides vital IDT data in CO2 bath gas for further development and validation of relevant kinetics mechanisms.