Sulfur-containing coal spontaneous combustion: A review of oxidation behavior, sulfur transformation pathways, and control strategies

Spontaneous combustion of sulfur-containing coal is a typical hazard threatening the safe and green development of the coal industry. Due to the involvement of sulfur components, the process becomes more complex and intense, making precise prevention and control significantly more difficult than that for low-sulfur coal. This paper systematically reviews the research progress on the oxidation characteristics and prevention technologies of sulfur-containing coal spontaneous combustion. It focuses on the influence of sulfur occurrence forms on the physicochemical structure of coal, reveals the transformation pathways of sulfur species during oxidation and their regulatory mechanisms on coal spontaneous combustion propensity, and elucidates the catalytic oxidation effect of pyrite and the synergistic involvement mechanism of organic sulfur, as well as the resulting macroscopic oxidative kinetic behavior and microscopic functional group response patterns. In terms of prevention and control technologies, the performance attenuation of conventional inerting and inhibition techniques in high-sulfur acidic environments is analyzed. New concepts and technological pathways for preventing sulfur-containing coal spontaneous combustion are explored, based on source control, process interruption, and intelligent early warning. Furthermore, future research directions are proposed, including the evolutionary behavior of sulfur under multi-field coupling, novel source-control inhibition methods based on in-situ regulation of sulfur elements, and intelligent monitoring and early warning technologies leveraging sulfur characteristics, with the aim of providing theoretical references and technical support for the effective prevention and control of spontaneous combustion disasters in sulfur-containing coal.