Compared with other types of dryer, triple pass rotary drum dryer is relatively energy efficient. It features simple interior structure, small energy consumption and high labor productivity. It is primarily applied for drying of a wide variety of materials including slag, clay, coal, iron powder, mineral powder, dry-mixed motar and yellow sand, etc.

Working Principle
In triple pass rotary drum dryer, raw material will enter the interior of the inner barrel though the feeding device just like in other dryers. In the inner barrel, the material is constantly raised and scattered by the shoveling plates inside and then moves forwards in a spiral way. In this way, concurrent drying is accomplished. Then, the material goes into the intermediate barrel, where the material will still be lifted constantly and it takes two steps forward and then one step back. The material coming to the intermediate barrel has already absorbed the heat from the inner barrel and it is going to absorb the heat radiated from the intermediate barrel. Drying time is extended with the material moving forward. When the material leaves the intermediate barrel, it reaches the best drying status. Later, the material drop s into the outer barrel and moves forward in a rectangular and multiple loop way. At this time, properly dried material will quickly leave the barrel driven by the hot wind, while somehow wet material moves slower because of larger gravity. The material not dry enough will be further dried with the help of rectangular shoveling plates in the outer barrel and it will be discharged until drying process is finished.

Characteristics
1. Designed with compacting and simple structure and reasonable layout, the dryer is able to strengthen heat exchange between raw material and heat energy, thus improving drying effect.
2. The investment capital of the triple pass rotary drum dryer is just a half of that of a regular single drum dryer. Furthermore, covering area and construction investment are all decreased by about 50 percent, while power consumption is reduced by 60 percent.
3. The dryer features high reliability, low energy consumption, high thermal efficiency. Feasible fuel includes coal, oil and gas. The dryer is suitable for drying of granules , powder and lump with size less than 20mm. The rotary dryer will give best results when it is used to dry materials with certain humidity and certain size such as yellow sand, foundry sand, slag, coal cinder and fine-grained clay, etc.　　
4. Water content in finished product can be altered based on users’ requirements.
5. The temperature of finished product is not high, which is able to protect the dust removal device following from damage caused by heat. Therefore, the service time of the dust removal device is extended.
6. The transmission is achieved by the supporting wheels instead of small and large gear used in other dryers.

Technical Process
1. feed inlet
2. hot gas inlet
3. outer barrel
4. intermediate barrel
5. inner barrel
6. exhaust gas outlet
7. feed discharge outlet