Oxy-fuel combustion technology is not only an advanced carbon capture technology

but also can improve the Zhundong coal utilization rate by controlling combustion temperature through gasification reactions

which alleviates the problems of ash deposition and slagging caused by burning Zhundong coal. However

the circulating flue gas replaces air for combustion-supporting and the oxidation reaction and gasification reaction interacts with each other

which affects the reactivity of coal char. In order to ensure the combustion efficiency of coal in a limited reaction space

it is essential to study the evolution law of coal char structure for reasonably organizing combustion in the furnace and improving the combustion process of coal char. By preparing coal char in fixed bed

this paper used Raman and Fourier transform infrared spectroscopy to investigate the changes of microcrystalline structure and functional groups of the coal char. The results show that

aromatic carbon structure was easily formed when O2 or CO_2 reacted with coal alone

while aliphatic hydrogen structure was more easily formed when H_2O reacted with coal. No matter what kind of atmosphere

the coal underwent the decomposition of macromolecular structure

the formation of amorphous carbon structure and the gradual graphitization process. The change of atmosphere affected the decomposition and precipitation of organic matters. When O_2 and CO_2 coexisted

the increasing gasifying agent concentrations promoted the decomposition of aromatic structures to generate reactive aliphatic chains. However

when O_2 and H_2O coexisted

the O_2 concentration increasing accelerated the formation of stable aromatic structure

but with the H_2O concentration increasing

the reaction first consumed the aliphatic chain structure and then promoted the decomposition of aromatic structure to generate the aliphatic chain structure.