Experimental Study on the Micro-Structure of Lignite and Its Explosive Solid Residue

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ABSTRACT Lignite reserves in the world’s various coal reserves in the first place. To take a qualitative and quantitative analysis on the change characteristics of the microstructure of lignite before and after explosion, the explosive tests took four lignite samples as the research object and were carried out in the 20 L spherical explosive test system. The experimental study was carried out by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectrometer to analyze the change characteristics of the surface morphology and macromolecular structure of lignite before and after explosion. The results indicated that compared with bituminous coal, the surface particles of lignite are less porous after explosion and the morphology is relatively complete. The rich aliphatic hydrocarbon and oxygen-containing structures in the range of 700–1800 cm−1 and 2800–3000 cm−1 contained in lignite were greatly reduced or disappeared after the explosion, while the mineral band at 536 cm−1 were more obvious and the band intensity became stronger. The area of D3 and D4 peak in Raman spectra decreased significantly after the explosion, which means that the CH3 and CH2 structures in the carbon structure of R-O-R’ (ether group) in lignite are significantly reduced. Besides, the intensity ratio of the sum of D3 peak and D4 peak to G peak ((ID3+ID4)/IG) of the solid product after explosion is reduced significantly, close to 0. The change can be applied of coal microstructure groups in the process of explosive reaction is helpful to reveal the reaction mechanism of pulverized coal explosion and provide a reference for identification and analysis the pulverized coal explosion accident.