Inhibition of spontaneous combustion in low-rank coal by facultative anaerobic microflora: reducing oxidizer, increasing retardant and modifying coal structure

Abstract

Coal spontaneous combustion is a major mining hazard, causing casualties, economic losses, and environmental damage. Here, an eco-friendly microbial fire prevention technology was proposed. A facultative anaerobic functional microflora was cultivated from coal seam water. Its metabolic characteristics, community structure, and effects on coal properties were investigated under varying initial oxygen concentrations. The microflora rapidly consumed oxygen to below 5% within one day, reaching 1.5% under low-oxygen conditions, while CO 2 concentrations reached 7.51%-14.43%. After microbial treatment, the relative proportions of OH-O ether oxygen hydrogen bonds, alcohol and ether C-O, conjugated C=O, and carboxyl C=O decreased by 17.4%-69.1%, 29.2%-76.8%, 15.1%-81.2%, and 19.0%-36.4%, respectively. Aliphatic branching decreased whereas the relative proportion of aromatic C=C increased. Thermal analysis showed that characteristic temperatures increased by 19.65–32.81 °C, maximum heat release rates decreased by 47.8%-54.2%, and combustion-stage activation energies increased substantially. The dominant genera included Delftia , Clostridium , and Pseudomonas , which potentially involve in complex-compound degradation and support the coal-component degradation under various oxygen conditions. These results suggested that the microflora could effectively inhibit coal spontaneous combustion through oxygen consumption to decrease oxidizer availability, CO 2 production to increase retardant concentration, and coal structural modification to reduce spontaneous combustion propensity. This study established a theoretical foundation for applying microbial technology in mine fire prevention.