After being crushed by coal mill, the lignite is conveyed to the feed box by belt conveyor, and then slides into the drum dryer. With the rotation and the inclination of the drum, the lignite is lifted from the bottom to the top of the drum under the action of the lifting board, forming a material curtain. The high-temperature flue gas passes through the material, preheating the wet material and evaporating part of the water. At the same time, the temperature of flue gas drops rapidly, and the preheated lignite enters the medium temperature drying stage, where most of the water is evaporated. With the repeated mixing and heat exchange of lignite and flue gas, the material is discharged from the drying drum after reaching the heat balance and meeting the lignite moisture requirements. After the heat exchange, the tail gas containing a large amount of water vapor and dust is subject to cyclone dust removal. After most of the dust is removed, it enters the bag filter for purification. The purified tail gas is directly discharged to complete the whole drying process.