Pure hot air produced by the hot air furnace, hot air temperature 35 ℃ -260 ℃ controllable, using heating and ventilation drying, two drying and dehydration at the same time, to strengthen the reasonable adjustment of the amount of hot air ventilation, multi-layer drying box cycle flip, layer by layer drying, make full use of the hot air, rapid drying and dehydration, high efficiency operation.