Gas generation patterns and explosive characteristics of pyrolysis gas from bituminous coal in the Linfen area

To reveal the explosion risks of gases during the pyrolysis of bituminous coal, this study focuses on the bituminous coal from Linfen, Shanxi, China. It investigates the effects of different sample scales and heating rates (0.5–2 °C/min) on the gas generation pattern during pyrolysis. Based on the evolution ranges of major gas components over the temperature interval of 400–600°C, twelve representative gas compositions were extracted using an extreme-value screening method to define the explosion risk boundaries. Subsequently, their explosion characteristics were measured using a 20 L spherical explosion test system under various equivalence ratios (φ = 0.8, 1.0, and 1.2) and initial temperatures (20–100°C). Results show that the gas generation pattern exhibits clear stages: a low-temperature degassing stage characterized by the release of CO and CO 2 ; a medium-temperature depolymerization stage marked by the concentrated release of C 2 -C 3 heavy hydrocarbons; and a high-temperature polycondensation stage with a sharp increase in H 2 content. Regarding explosion characteristics, the maximum explosion pressure P max (MPa), the maximum rate of pressure rise (dP/dt) max (MPa/s), and the deflagration index K G (MPa·m/s) all peak at the stoichiometric ratio, with explosion pressures generally higher under fuel-rich conditions than under fuel-lean conditions. Notably, the highest value of explosion severity (K G ) does not correspond to the case with the highest hydrogen content (Case 11, H 2 content 49.45%), but rather to the case with the lowest carbon dioxide content (Case 8, CO 2 content 3.00%), indicating that the dilution effect of CO 2 on explosion suppression is more significant than the promoting effect of H 2 . When the initial temperature rises from 20 °C to 100 °C, P max decreases linearly due to reduced gas density, but (dP/dt) max remains essentially constant or slightly decreases. This study clarifies the gas generation pattern and explosion characteristics of bituminous coal pyrolysis gases, providing an experimental basis for engineering safety design and risk assessment of this technology.