Energy, Vol.169, 587-596, 2019
Assessing the effectiveness of a high-temperature-programmed experimental system for simulating the spontaneous combustion properties of bituminous coal through thermokinetic analysis of four oxidation stages
The spontaneous combustion of coal is characterized by high-temperature oxidation. This study used a self-made programmed experimental system to maintain temperature parameters at specified levels to simulate the combustion properties of coal. The oxygen concentration was determined to be inversely proportional to indicator gas concentrations. Five characteristic temperatures were achieved: critical temperature (97.45 +/- 7.15 degrees C), crack temperature (149.28 +/- 8.32 degrees C), active temperature (206.95 +/- 15.05 degrees C), speedup temperature (263.45 +/- 6.35 degrees C), and ignition temperature (390.85 +/- 27.05 degrees C). Thermal characteristics were analyzed by dividing the oxidation into the following temperature stages: the critical temperature stage, crack active speedup temperature stage, speedup ignition temperature stage, and combustion stage. Furthermore, the differential and integral kinetic methods were used to compute the apparent activation energy in the four aforementioned stages. The results indicated that the apparent activation energies decreased through the first three stages and then increased in the fourth stage. Therefore, the crack active speedup temperature stage was determined to be potentially dangerous during oxidation because gases increased rapidly at this stage; such gases included CO, which is particularly harmful to human health. The thermal energy release also increased gradually at this stage. (C) 2018 Elsevier Ltd. All rights reserved.
Keywords:Oxygen concentration;Indicator gas concentration;Characteristic temperatures;Thermal characteristic;Thermal energy release