Isothermal kinetics based on two-periods scheme for co-drying of biomass and lignite

• Effects of temperatures, sample kinds and blend ratios on co-drying kinetics.
• The mechanism functions of the biomass/lignite blends in two falling rate periods.
• The activation energy of the biomass/lignite blends and their individuals.
• Significant interactions between lignite and Bermuda grass or red pine.
• The blending of lignite with grass or pine improves drying of their individuals.

Thermal gravimetric analysis (TGA) was applied to investigate the co-drying kinetics of biomass (Bermuda grass and red pine) with lignite. The drying rate of the lignite was much higher than that of the pure Bermuda grass and red pine. The drying of samples presented two distinctive falling rate periods. The activation energy of the pure Bermuda grass and red pine were higher than those of the grass/lignite and pine/lignite blends, respectively. In the first falling rate period, the dominant mechanism functions for the lignite, red pine and their blends were 1−(1−α)1/31−(1−α)1/3, and the functions were 1 −(1 − α)0.5 in the Bermuda grass and its blends, while in the second falling rate period, the functions of the blends and their parent samples were −ln(1 − α). The drying kinetics of blends had no linear relation with blend ratios. The blending of the lignite with the grass or pine could improve the drying of the individuals.