Effects of drying temperature on reabsorption characteristics of dried lignite

Lignite samples dried under different temperatures were prepared using a horizontal fixed-bed dryer. The ox- ygen-containing functional groups on the surface of the dried lignite samples were analyzed using Fourier-transform in- frared (FTIR) analyzer and the effective water-filled porosities of the samples were analyzed by nuclear magnetic reso- nance (NMR) spectrometer. The equilibrium moisture content of the samples was measured by a self-made reabsorp- tion device. The experimental results from the lignite samples dried at low temperature show that the drying tempera- ture has little effect on the effective water-filled porosities and the amount of the main oxygen-containing functional groups firstly decreases and then increases with the drying temperature increase. The reabsorption characteristics of lig- nite dried at low temperature was influenced by the amount of oxygen-containing functional groups. In the case of the lignite samples dried at high-temperature drying group,with the increase of drying temperature,the amount of the ef- fective water-filled porosities of the samples decreases and the amount of oxygen-containing functional groups increases and the equilibrium moisture content decreases. The effective water-filled porosity is a main factor for the lignite dried at high temperature.