Study on the evolution law of oxidation characteristics of unloaded coal based on the change of buried depth

Abstract

To obtain the change law of oxidation characteristics of unloaded coal at different burial depths, the experimental coal samples were loaded and unloaded with various degrees of stress according to the in situ stress characteristics of the Changcun coal mine in China. Through low-field nuclear magnetic resonance (LNMR) and temperature-programmed experiments, the change law of oxidation characteristic parameters and pore structure parameters of unloaded coal under different stresseswas tested. The main conclusions are obtained through the analysis of the experimental results. ①With increasing burial depth, the oxidation reaction products of unloaded coal under different stresses regularly changed. ② With increasing burial depth, the oxidation characteristics of unloaded coal at different burial depths gradually increased and gradually slowed down after 1200-1600 m, and the concept of the "critical depth" of unloaded coal oxidation characteristics was proposed. ③ With increasing burial depth, the porosity of the unloaded coal body gradually decreased, the number of micropores increased, and the number of small pores, mesopores and macropores gradually decreased. It is further concluded that the difference in oxidation characteristics of unloaded coal at different depths was caused by the change in the number of micropores.