Inhibiting effects of three commercial inhibitors in spontaneous coal combustion

Three commercial inhibitors were investigated for their suitability in preventing the spontaneous combustion of noncaking coal (NCC) and gas coal (GC), two coals of low metamorphic grades. Simultaneous thermal analysis, Fourier transform infrared spectroscopy, and kinetic analysis demonstrated that Zn/Mg/Al-CO3-layered double hydroxides (LDHs) and diammonum phosphate ([NH4]2HPO4) both exhibited substantial inhibiting effects. Therefore, Zn/Mg/Al-CO3-LDHs and (NH4)2HPO4 may be used for the prevention of spontaneous coal combustion. The reaction mechanisms and kinetic models for NCC and GC mixed with inhibitors were also determined. Na3PO4 demonstrated poor inhibiting ability in NCC and GC and even promoted the combustion of GC. Therefore, Na3PO4 is not recommended as an inhibitor for NCC and GC. Finally, the results indicated that (NH4)2HPO4 and Zn/Mg/Al-CO3-LDHs can be used to decrease CO2 release, limiting the oxidation reaction of coal and attenuating greenhouse gas emissions. This study can serve as a reference for efforts to prevent spontaneous coal combustion and for the development of new inhibitors.