Applications: charcoal industry, construction industry, mineral industry, chemical industry materials: river pebbles, granite, basalt, iron ore, limestone, quartz, diabase and other indirect heat dryer features: 1, equipment investment required 1/6 is imported products. 2, the material to ensure that 0.5% final moisture is dry mortar and slag powder production line product of choice. 3, cylinder self-insulation thermal efficiency up to 70% (traditional monocular dryer thermal efficiency of only 35%), to improve the thermal efficiency of 35%. 4, the fuel can be adapted to coal, oil and gas. Can bake 20mm below the block material, pellets and powder materials. 5, than monocular dryer to reduce the area of ??about 50%, lower construction investment is about 50%, 60% reduction in power consumption. 6, according to user requirements easily control the desired final moisture indicators. 7, the outlet temperature is low, long time dedusting equipment. 8, no size gear, the use of wheel drive. Works by material feeding device into the inner rotary drum and achieve downstream drying, the material in the inner constantly took a copy board, scattered spiral marching heat exchange, the material is moved to the other end of the inner enter middle, countercurrent drying, the material is repeated constantly in the middle Yang Jin, was traveling way to step back two steps forward, both fully absorb the material in the middle inner cylinder the heat, but also absorb heat the middle of the drum, while the extension the drying time, the best material in this dry state. The other end of the line to the middle of material falling into the outer layer of the material in the outer drum rectangular multi-loop approach to travel, to the drying effect of the material in the hot air discharge action fast marching drum, there is no effect of the wet material to dry weight and not due to rapid the road, the material within this rectangle copy board is fully dried, thereby completing the drying purposes.