Effect of oxygen-supply on the reburning reactivity of pyrolyzed residual from sub-bituminous coal: A reactive force field molecular dynamics simulation

Liyang Ma, Lan Zhang, Deming Wang, Haihui Xin and Qiulin Ma

Energy, 2023, vol. 283, issue C

Abstract: The lean-oxygen combustion of incompletely pyrolyzed char dominated at the combustion front of coalfield fires. Functional group distributions and carbon micro-crystal dimensions were characterized for developing the molecular model (C184H124N2O16S) of pyrolyzed coal char at 400 °C (TLG P400). The overall combustion process of TLG P400 under various oxygen/fuel ratios (Ω) were simulated in an intuitive approach with ReaxFF. The findings indicated that the primary carbon-containing intermediates transformed from large pieces of aromatic fragments C40+ with self-similarity to heavy components of C15–C40 in initial combustion stage, then to light components of C5–C14 in late stage. With Ω increasing from 1.0 to 5.0, the final carbon conversion was found to rise from 78.50% to 96.32%, while the CO/CO2 ratio in the products sharply decreased from 2.575 to 0.213. The apparent activation energy was calculated as 194.49 kJ/mol for TLG P400 combustion at Ω = 1.0. Higher oxygen concentration enhanced the adsorption proportion of edge carbon, resulting in the generation of unstable intermediates featuring meta- or para-semiquinone. These transformations promoted the detachment of edge carbon and weakened the bottle-neck effect of the single-benzene ring on rapid oxidation. This study provides valuable insights into combustion mechanism and monitoring approaches for controlling coalfield fires.

Keywords: Coalfield fires; Oxygen-supply; Coal char; Reburning reactivity; Molecular dynamics simulation (search for similar items in EconPapers)
Date: 2023
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Citations: View citations in EconPapers (1)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:283:y:2023:i:c:s0360544223025458

DOI: 10.1016/j.energy.2023.129151

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