Product Introduction
This product can indirectly heat (or cool) paste-like, granular, powder-like, and slurry-like materials, and can complete unit operations such as drying, cooling, heating, sterilization, reaction, and low-temperature calcination. The special wedge-shaped stirring heat transfer blades inside the equipment have a high heat transfer efficiency and possess self-cleaning function for the heat transfer surface.
Working Principle
The hollow shafts inside the dryer are densely equipped with wedge-shaped hollow paddle blades. The heat medium flows through the hollow shafts and the paddle blades, providing a large heat transfer area per unit effective volume. The temperature range of the heat medium is -40℃ to 320℃, which can be steam, hot water, heat transfer oil, or other liquids. The material is indirectly heated, with very little air discharged, resulting in minimal heat loss carried away by air. All the heat is used to heat the raw materials, and heat loss occurs only through the insulation layer of the equipment body, dissipating heat into the environment. The wedge-shaped paddle blades have self-cleaning functions on their heat transfer surfaces. The relative motion between the material particles and the wedge-shaped surface produces a scrubbing effect, which can remove material adhering to the wedge surface, ensuring the cleanliness of the heat transfer surface during operation. The shell of the paddle dryer is in a W-shape, and usually contains two hollow agitator shafts inside. The shell is heated via its interlayer, and is equipped with sealed end covers and top covers to prevent the leakage of material dust.
The heating medium flows simultaneously through the jacketed annular space of the cylinder and the hollow paddle on the shaft, increasing the heat transfer area. The internal structure of the hollow agitator shaft varies depending on the type of heat transfer medium to ensure optimal heat transfer efficiency.
Performance Features
1. Paddle dryer has low energy consumption: Due to the use of indirect heating, a large amount of air does not carry away heat, and insulation layers are provided on the outer wall of the dryer. For pasty materials, only 1.2 kg of steam is required to evaporate 1 kg of water.
2. Low system cost of paddle dryers: With a large heat transfer surface within the unit effective volume, processing time is shortened, and equipment dimensions are reduced, greatly saving on construction area and space.
3. Wide range of materials processed: Using different heat media, it can handle both heat-sensitive materials and materials requiring high-temperature processing. Common media include: steam, heat transfer oil, hot water, cooling water, etc.
4. It can operate continuously or intermittently and can be applied in many fields.
5. Minimal environmental pollution: Since materials are not transported by air, the amount of dust carried is extremely low. The evaporation concentration of the material solvent is very high, making it easy to handle. For materials with pollution control or solvent recovery requirements, a closed-loop circulation system can be adopted.
6. Low operating costs: The structure results in minimal wear and very low maintenance costs.
7. Stable operation: Due to the special compression-expansion stirring action of the wedge-shaped paddles, material particles are fully in contact with the heat transfer surface. The gradients of temperature, humidity, and mixing degree of the material within the axial interval are very small, ensuring the stability of the process.
Applicable raw materials
Paddle dryers have been successfully used in fields such as food, chemical, petrochemical, dye, and industrial sludge. The characteristics of heat transfer, cooling, and stirring of the equipment allow it to complete the following unit operations: combustion (low temperature), cooling, drying (solvent recovery), heating (melting), reaction, and sterilization. The stirring paddles are also the heat transfer surface, increasing the heat transfer area within the unit effective volume and shortening processing time. The wedge-shaped paddles also have self-cleaning functionality for the heat transfer surface. The compression-expansion stirring function ensures uniform mixing of materials. Materials move "piston flow" along the axis, and the gradients of temperature, humidity, and mixing degree within the axial interval are minimal. Paddle dryers using heat transfer oil as the heat medium can perform low-temperature combustion work. For example: Dihydrate calcium sulfate (Ca2SO4·2H2O) combustion is transformed into hemihydrate calcium sulfate (Ca2SO4·1/2H2O). Sodium bicarbonate (NaHCO3) is calcined to form pure soda (Na2CO3), etc. Cooling media such as water or cooled brine can be used for cooling. For example: The paddle-type cooling alkali machine used in the soda industry replaces the old air-cooled cooling alkali machine, saving energy and exhaust gas treatment equipment, and reducing operating costs. Drying, the main function of the equipment, does not use hot air, making solvent recovery, energy consumption, and environmental control easy to handle in an ideal state. It is particularly suitable for materials that require solvent recovery, are flammable, easily oxidized, and heat-sensitive. It has been widely used in fine chemicals, petrochemical, and dye industries. The uniformity of temperature, humidity, and mixing degree within the axial interval allows the equipment to be used for heating or melting, or for some solid material reactions. It has been successfully used in the compound fertilizer and modified starch industries. Paddle dryers can be used for sterilization treatment of food and flour. The large heating area within the unit effective volume quickly heats the material to the sterilization temperature, avoiding long-term heating that changes the quality of the material.
Installation Structural Schematic Diagram
Technical parameters
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