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ABSTRACT
A spontaneous combustion and oxidation simulation experiment involving coal samples from the fully mechanized top coal caving face 2308 of Getting Coal Mine was performed using a self-developed spontaneous combustion test bed. The aim was to determine the production law of spontaneous combustion products in Getting Coal Mine and provide a basis for establishing an early prediction index system for spontaneous combustion in the goaf. The law governing changes in the concentrations of CO, C2H4, and other gases with temperature in the process of coal sample heating was analyzed, and the index gas of coal sample spontaneous combustion was optimized. The experimental results showed that the shortest spontaneous combustion period was 54 days. The coal samples produced CO at a lower temperature. The absolute amount of CO production increased monotonously during the entire oxidation process, but the increase was uneven under different temperature conditions, and there was a sudden temperature point. C2H4 appeared for the first time at 110 °C, increased monotonously from 110 to 163 °C, and then fluctuated after 163 °C. Finally, CO and C2H4 were selected as the main index gases to predict spontaneous coal combustion in Getting coal mine, and C2H6 and C2H4/C2H6 were used as auxiliary index gases.
Nomenclature
| A | = | Ash content, % |
| C | = | Actual oxygen concentration at the measurement point, % |
| C0 | = | Initial oxygen concentration in the same air, % |
| Ce | = | Coal equivalent specific heat capacity, J/(g·°C) |
| Cg | = | Specific heat capacity of the air, J/(kg·°C) |
| Cm | = | Specific heat capacity of the solid coal, J/(kg·°C) |
| Ci | = | Oxygen concentration in the furnace body, % |
| Ci+1 | = | Oxygen concentration outlet gas of the furnace body, % |
| D | = | Diffusion coefficient of oxygen in pulverized coal, m2/d |
| Fi | = | Furnace height in the heating furnace body, cm |
| Fi+1 | = | Furnace height in the outlet gas of the furnace body, cm |
| M | = | Moisture content, % |
| n | = | Porosity, % |
| Q | = | Ventilation volume of the furnace body, ml/min |
| = | Air supply intensity, cm3/(s·cm2) | |
| q(T) | = | Heat release intensity, J/(s·cm3) |
| qo(T) | = | Heat release intensity of oxidation at the standard oxygen concentration, J/(s·cm3) |
| r | = | Radial coordinates of the test bench, cm |
| S | = | Cross-sectional ventilation area of the furnace body, cm2 |
| T | = | Coal temperature, °C |
| μ | = | Average velocity of air flow in the air gap, m/s |
| v | = | Voidage of the coal body in the furnace |
| V(T) | = | Oxygen consumption rate for a unit of solid coal, mol/(cm3·s) |
| V0(T) | = | Average oxygen consumption rate, mol/(cm3·s) |
| XPT | = | Crossing point temperature, °C |
| Z | = | Longitudinal coordinates of the test bench, cm |
| ρe | = | Coal equivalent density, g/cm3 |
| ρg | = | Density of the air, g/cm3 |
| ρm | = | Density of the solid coal, g/cm3 |
| τ | = | Time, s |
| λe | = | Coal equivalent thermal conductivity, J/(cm·s·°C) |
Acknowledgments
We are also grateful to editor and reviewers for their valuable comments to make our paper better.
Disclosure statement
The authors declare there is no conflict of interest.