Thermal decomposition and evolved gas analysis (TG-MS) of lignite coals from Southwest China

• The temperature of initial thermal decomposition differed from 256 to 315 °C in Yunnan lignite pyrolysis.
• The temperature of the maximum mass loss rate occurred at 421-453 °C in Yunnan lignite coals pyrolysis.
• CH4 generation started at approximately 200 °C as it was adsorbed into the coal structure of Yunnan lignite coals.
• Varying amounts of functional groups had influences on the weight loss and gaseous products evolution during pyrolysis.

Large amounts of lignite reserve in the southwest of China. However, there is little information about their thermal behaviors during the pyrolysis. In this work, five representative lignite samples which are characterized by high H/C atomic ratios (0.834–1.170) from Yunnan, Southwest China were investigated. The simultaneous thermogravimetry/mass spectrometry was used to study the thermal decomposition and evolved gas characteristics of the five samples. Besides, the Fourier-transform infrared (FTIR) analyzer was used to study the functional-group contents of the five samples in order to investigate the relationships between the thermal behaviors of the samples and their structures. The results revealed the influence of functional groups on the weight loss and gaseous products evolution of the lignite coals. The most prominent peaks of gaseous products were within the scope of 400–700 °C, and the maximum peaks of evolution of CO2, CO and H2O gases well corresponded to the maximum rate of mass loss in the range from 421 to 453 °C. The lignite coals from Southwest China were suitable for low temperature pyrolysis.