Inhibition of spontaneous combustion for different metamorphic degrees of coal using Zn/Mg/Al–CO3 layered double hydroxides

Abstract

Abstract Layered double hydroxides (LDHs) have excellent physical and chemical properties and are thus widely and effectively used to inhibit spontaneous coal combustion. In this study, Zn/Mg/Al–CO3 LDHs, which are metal ion–LDH complexes, were prepared through coprecipitation and synthesized using three types of coal with different metamorphic degrees to form Zn/Mg/Al–CO3 LDH/coal. Additionally, the spontaneous coal combustion inhibition mechanism of added Zn/Mg/Al–CO3 LDHs was investigated using scanning electron microscopy, in situ Fourier transform infrared spectroscopy, and differential scanning calorimetry to further elucidate prevention and control measures for spontaneous coal combustion. The results demonstrated that Zn/Mg/Al–CO3 LDHs are extremely highly compatible with coal and form a crystalline structure on the surface of coal, which interrupts the diffusion of oxygen for combustion and, consequently, inhibits spontaneous coal combustion. Furthermore, the negative effects of various crucial functional groups on spontaneous coal combustion were weakened by the addition of Zn/Mg/Al–CO3 LDHs. When decomposing, Zn/Mg/Al–CO3 LDHs undergo an endothermic reaction and generate enormous amounts of CO2 and H2O, which could effectively reduce the surface temperature of coal and dilute the oxygen concentration of the environment. A novel material, Zn/Mg/Al–CO3 LDHs can be used to prevent the occurrence of severe accidents caused by spontaneous coal combustion.