Experimental Investigation on Using Chloride/Hydroxide Aerosol to Control Spontaneous Combustion of Lignite in Underground Coal Mines

Abstract

To provide a sustained and reliable approach for suppressing spontaneous combustion hazard in underground goafs, chloride/hydroxide aerosols were used for the first time to inhibit spontaneous combustion of lignite. A supersonic wave generator was used to generate aerosols for continuously treating Yunnan lignite of a particle size of <1 mm. A uniform sediment of aerosols was formed when chloride and hydroxide aerosols (AlCl3–Na2SiO3, MgCl2–Na2SiO3, CaCl2–Na2SiO3, and NaHCO3–AlCl3) simultaneously flow through the coal surface. According to the oxidation experiments and microscopic tests, the controlling effect of cold aerosol was 66.28–81.28%. After treatment for 20–60 min, the produced precipitation accounted for 1.0–7.5% (by mass) of the original specimen. The TG/DSC test showed that the temperature of exothermic peak was increased by about 100 °C, and the release of heat was restrained. Infrared spectra test illustrated that the influence of cold aerosol on the organic functional groups in coal was mainly embodied in −OH, −CH2–, C–O, −COOH, etc. The superfine sediments produced by the reaction between carbonate and silicate aerosol adhere to the coal surface and continuously inhibit the oxygen absorption of coal, which offers potential as a clean, sustainable technique that can be used to prevent development of spontaneous fire.