An experimental study on the drying kinetics of lignite in high temperature nitrogen atmosphere

• The constant drying rate period is very short and can be neglected.
• The lignite drying process is characterized by a long drying rate decreasing stage.
• The mathematical model based on the shrinking core theory was developed.

The Chinese lignite upgrading process with high temperature nitrogen as a drying agent using a horizontal fixed-bed reactor was addressed and a kinetic model for the single particle lignite drying process was developed based on the experimental results. The results show that the lignite drying process consists of two stages, one is drying rate increasing stage and the other is drying rate decreasing stage. The lignite drying process can be promoted by initial nitrogen temperature increasing and lignite particle size decreasing. The effective diffusivity coefficient (De) of the moisture from the lignite particle during the drying process with different initial temperature was obtained theoretically by calculation. The activated energy of the moisture emission from the lignite with different particle size (10–25 mm) was also obtained.