A novel developed weighted exponential sum model for char cloud conversion behavior under air- and oxy-combustion: Experiments and kinetics modeling analysis

Comprehension of the fossil fuel chemical reaction conversion behavior benefits to insight micro physico-chemistry mechanism of burning chemical kinetics especially for conventional air-fired combustion and oxyfuel combustion. Detailed combustion reaction experiments and a novel developed kinetics model were proposed to investigate coal char conversion behavior under enriched-oxygen and high carbon diox -ide dilution environment compared with air environment in present work. Primary characteristic param-eters, i.e., combustion conversion rate, conversion ratio, burnout time, etc., mainly affected by limited chemical interactions between char oxidation reaction and gasification reaction, were studied under typ-ical environments, i.e., O-2/CO2, O-2/Ar, CO2/Ar, O-2/N-2, using detailed experiments and a novel developed kinetics model, i.e., the weighted exponential sum model (WESM). Present kinetics predictions were also compared with previous typical kinetics models, i.e., the homogeneous reaction model (HRM), the shrink-ing core model (SCM), the modified volumetric reaction model (MVRM). Results showed that present ki-netics model gave relatively more coherent predictions of the char conversion rate, conversion ratio, the maximum conversion rate and burnout time compared with those predicted by HRM, SCM and MVRM models, respectively. Meanwhile, the contribution ratio from endothermal gasification chemical reaction, i.e., C + CO2 -> 2CO, on char maximum conversion rate was 41.1% and 45.2% in 1473 K and 1663 K, re-spectively. Correspondingly, the maximum and average interaction contribution ratios (chi intmax era , chi ave intera) de-creased as 9.0% and 1.7%. The maximum rate ratio for oxyfuel combustion increased from 52.7% to 61.7%, and the average rate ratio slightly increased from 52.5% to 54.2% in these combustion reactions. (c) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

Understanding the fossil fuel chemical reaction conversion behavior provides insights into the micro physico-chemistry mechanism of burning chemical kinetics. In this study, detailed combustion reaction experiments and a novel developed kinetics model were used to investigate coal char conversion behavior in enriched-oxygen and high carbon dioxide dilution environments. The results showed that the kinetics model developed in this study gave more coherent predictions compared to previous typical kinetics models, and the contribution ratio from endothermal gasification chemical reaction on char maximum conversion rate was significant.