Preparation and mechanism analysis of a nano-reinforced environmentally friendly composite gel for coal spontaneous combustion prevention

Coal spontaneous combustion (CSC) has consistently been a serious safety and environmental concern in the coal industry. A nano-reinforced environmentally friendly composite gel was prepared in this study for air-leakage plugging and CSC prevention. Polyacrylamide, polydopamine, sodium lignosulfonate, phytic acid, epigallocatechin gallate and carbon nanofibers were used as raw materials. The chemical composition, crystallization and morphological structure of the novel gel were characterized. The crosslinked gel of polyacrylamide and polydopamine play a role in moisturizing and encapsulation. The expanded gel formed a carbon layer, effectively isolating the coal surface from the air. The composite gel delayed the second stage of CSC by approximately 20 %. The average heat release during the combustion stage was reduced from 8910 J/g to 7027 J/g, representing a reduction of approximately 26.8 %. The absorption intensity of the typical combustion gas products, CO₂ and CO, significantly decreased, and the rising trend was slow below 430 °C. The ultimate pressure of the air leakage plugging was 1.27 kPa. Through analyzing the inhibition and plugging mechanisms of a composite gel, this study provides a more efficient and sustainable solution for inhibiting CSC in goaf, which can enhance production safety, reduce environmental pollution, and minimize losses.