Effects of pre-oxidized temperature and pre-oxidized oxygen concentration on burning characteristics of pre-oxidized coal

The secondary oxidation of residual coal during re-mining in goaf will seriously endanger mine safety production. To investigate the influence of the formation process of PC(pre-oxidized coal) in goaf on the secondary oxidation of coal, This paper utilized the TG-DSC analysis method to study the burning characteristics of PC under different pre-oxidized temperatures and different pre-oxidized oxygen concentrations. The results showed that both PT(pre-oxidation temperature) and POC(pre-oxidation oxygen concentration) have effects on the burning process of oxidized coal, and there is an optimal POC and the best PT. Both PT and POC only have significant effects on the characteristic temperatures before ignition temperature, and fewer effects on the ignition temperature and the characteristic temperatures after ignition temperature, and thus PT and POC only have effects on the first three stages of the secondary oxidation process of PC, i.e., water evaporation and gas desorption stage, oxygen absorption stage of weight gain, and thermal decomposition stage. The effects of PT and POC are different from each characteristic temperature, thus the effects of PT and POC are different in the first three stages. In general, the secondary oxidation process of PC Y-18 %-100 is the most dangerous when re-mining the residual coal in the goaf. However, different pre-oxidized coals have different risks in different stages of the secondary oxidation process, because the types of active structures mainly involved in the coal-oxygen reaction in each stage are different, and the PT and POC during the formation of pre-oxidized coals will affect the number of active structures involved in the coal-oxygen reaction during the secondary oxidation of pre-oxidized coals. The DSC curves of PC at 300 degrees C showed no obvious plateau of heat uptake, which was because the too high PT would decompose the steady aromatic ring structures in the coal samples. The research results can be used as the theoretical basis for the re-mining of goaf, and ensure the safety of workers and the smooth progress of re-mining.

Automated summary

This paper investigates the influence of pre-oxidization temperature and pre-oxidization oxygen concentration on the secondary oxidation of coal. The results suggest that both temperature and oxygen concentration have effects on the burning process of oxidized coal, particularly in the first three stages. Importantly, different pre-oxidized coals have different risks in different stages of the secondary oxidation process.