The double blade dryer can indirectly heat or cool slurry, paste, granular and powder materials, and can complete unit operations such as drying, cooling, heating, sterilization, reaction and low temperature calcination. The device indirectly conducts heating, does not carry air to take away heat, heat is used to heat the material. The special wedge type stirring heat transfer blade in the equipment has high heat transfer efficiency and self-cleaning function of heat transfer surface, and the heat transfer area per unit effective volume is large. The heat medium can be water steam, hot water, heat conduction oil, etc., the heat transfer medium through the rotary joint, flows through the shell jacket and the hollow stirring shaft, the hollow stirring shaft has different internal structures according to the type of heat medium to ensure the heat transfer effect. The shell of the blade dryer is Ω type, and two to four hollow stirring shafts are generally arranged in the shell. The shell has a sealed end cover and an upper cover to prevent the leakage of material dust and the collection of material solvent steam. A stop plate is set at the discharge port to ensure the height of the material level, so that the heat transfer surface is covered by the material and gives full play to its function.

Pulp leaf dryer has been successfully used in food, chemical, petrochemical, dye, industrial sludge and other fields. The heat transfer, cooling and stirring characteristics of the equipment allow it to perform the following unit operations: calcination (low temperature), cooling, drying (solvent recovery), heating (melting), reaction and sterilization. The mixing blade is also a heat transfer surface, which increases the heat transfer area in the unit effective volume and shorens the processing time. The heat transfer surface of wedge blade also has self-cleaning function. Compression-expansion stirring function makes the material mix evenly. The material moves along the axial direction into a "piston flow", and in the axial interval, the temperature, humidity and mixing gradient of the material are very small. Using heat conduction oil as heat medium, pulp leaf dryer can complete low temperature calcination work. For example: calcium sulfate dihydrate (Ca2SO4·2H2O) calcined into calcium sulfate hemihydrate (Ca2SO4·1/2H2O). Sodium bicarbonate (NaHCO3) is transformed into soda ash (Na2CO3) by calcination. Through the cooling medium, such as water, cooling brine, etc., can be used for cooling. For example, the pulp leaf type alkali cooling machine used in the soda industry replaces the old air cooling alkali cooling machine, saving energy and tail gas treatment equipment, and reducing operating costs. Drying, the most important function of the equipment, does not use hot air, so that solvent recovery, energy consumption, environmental control in an ideal state of easy treatment. It is especially suitable for recyclable solvent, inflammable and easily oxidized heat sensitive materials. It has been widely used in fine chemical, petrochemical and dye industries. In the axial interval, the uniformity of temperature, humidity, and mixing degree makes the equipment usable for heating or melting, or for some solid material reactions. It has been successfully used in the industry of compound fertilizer and modified starch. Leaf dryers can be used to sterilize food and flour. The large heating area in the unit effective volume quickly heats the material to the sterilization temperature, avoiding long-term heating and changing the quality of the material.