Evaluating the pyrolysis characteristics and gas release patterns to predict early fire warnings in coal mine conveyor belts

This study systematically investigated the pyrolysis characteristics and gas emission patterns of various types of coal mine conveyor belts using thermogravimetric-infrared spectroscopy (TG-FTIR) and energy-dispersive X-ray spectroscopy (EDS) analysis. The pyrolysis process of flame-retardant conveyor belts (PVC, PVG, SC) encompasses three stages: the preparation stage, the bond-breaking and cracking stage, and the residual decomposition stage. The bond-breaking and cracking stage exhibits dual weight loss peaks around 280-300°C and 420-460°C, corresponding to C-Cl bond cleavage (with HCl release) and C-C bond fracture (producing aliphatic and aromatic hydrocarbons), respectively. Furthermore, EDS analysis reveals that a key composition difference between conveyor belts and coal is the presence of chlorine (Cl). During pyrolysis, flame-retardant belts begin emitting HCl gas at around 170°C, which occurs significantly earlier than the peak generation temperatures (around 460°C) of CO and CO₂. Based on these findings, this study proposes a novel early fire warning strategy utilizing HCl as a signature gas. Detection of trace levels of HCl gas (e.g., 1 ppm) can indicate that the conveyor belt temperature has reached 170°C, allowing timely intervention. These results provide a promising approach for improving early fire detection and enhancing safety in coal mine operations.