Thermal behavior of Mongolian low-rank coals during pyrolysis

Abstract Low temperature pyrolysis behavior of four low-rank coals from the biggest deposits of Mongolia were studied using a fixed-bed reactor and Gray-King retort. The coal samples and resultant chars were analyzed using Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance (13C NMR) to explore the structure changes and thermogravimetric analyzer coupled with mass spectrometry (TG-MS) was used to investigate the pyrolysis reactivity of coal during thermal decomposition process. The results showed that the aliphatic structure in coal was significantly reduced and the carboxyl groups almost completely decomposed during pyrolysis process at 600 °C. The tar yield of Gray-king test is higher than that obtained from the fixed-bed reactor. The gaseous evolution measured by TG-MS during pyrolysis showed that the maximum peaks of evolution of CH4, H2, C2H2, C2H5, CO, and CO2 gases were well corresponded to the maximum rate of weight loss in the range 428–445 °C.