Synchronous thermal analyses and kinetic studies on a caged-wrapping and sustained-release type of composite inhibitor retarding the spontaneous combustion of low-rank coal

•A sustained-release type of inhibitor for coal spontaneous combustion was prepared.•Changed TGA-DSC parameters and ignition behavior caused by inhibitor were analyzed.•Variations of apparent activation energy caused by prepared inhibitor were computed.

In this paper, a novel type of composite inhibitor (PAA/SA-CC) was developed and characterized with the aim of achieving sustained and highly effective inhibition on spontaneous combustion of low-rank coal. A concept of realizing the caged-wrapping and sustained-releasing function of polymer as regard to high-activity chemical inhibitor was proposed, basing on which the composite inhibitor was prepared with poly(acrylic acid)/sodium alginate super absorbent and (+)-catechin. Subsequently, synchronous thermal analysis was carried out to investigate the influence of inhibitors on the tendency of coal to spontaneous combustion, which was characterized by four characteristic temperatures and three other characteristic parameters marked. Furthermore, hot-surface ignition tests were conducted to validate the inhibition on coal ignition behavior. Finally, non-isothermal isoconversional methods were performed by Starink model and Friedman-Reich-Levi model, respectively. The results demonstrate that PAA/SA-CC synergizes the inhibiting characteristics of the two distinctive inhibitors, especially exerts a continuously high-efficiency inhibition on the coal-oxygen chemisorption, which performs better than the case of mechanically blending. Besides, both the two kinetic analysis approaches agree on the results that the incorporation of 3 wt.% PAA/SA-CC shifts the apparent activation energy-temperature evolution to higher levels.