Drying, re-adsorption characteristics, and combustion kinetics of Xilingol lignite in different atmospheres

The gasification of lignite with a moisture content of 5-10% was carried out by GSP pulverized coal gasification process(GSPPCP). An air separation unit was set up to make use of oxygen and nitrogen during lignite drying process. This was a potential approach to utilize the mixture of oxygen and moisture in lignite as a feedstock for gasification agent. In this paper, the physico-chemical properties of several lignites from Xilingol dehydrated under different atmospheres were characterized by the thermogravimetry mass spectrometry analyzer (TG-MS), fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), to investigate the impact of drying atmosphere, heating rate and particle size on drying rate, gas evolutions and drying kinetics. FWO and Vyazovkin methods were applied elaborating the drying kinetics and mechanism. The moisture in lignite decreased with the rise of drying temperature, but the dehydration rate was did not change much under different heating rate at initial stage. The distribution of energy consumption during water evaporation and water migration was determined by the fitted DTG curve. Moisture re-adsorption was greater for large particles, which correlated to the content of oxygen-containing functional groups. The combustion activation energy of nitrogen-dried lignite was larger than that of oxygen-dried lignite.