Liquid low temperature vacuum dryer manufacturers briefly describe the structure principle and equipment characteristics of the hollow paddle dryer

2023/05/05

The main structure of the hollow paddle dryer is composed of a W-shaped groove and two rotating hollow shafts installed in the groove, and hollow blades are arranged on the shaft. The heat required for drying moisture is conducted to the material through the inner wall of the W-shaped groove with jacket and the wall of the hollow blade. During the drying process of the material, the hollow shaft with hollow blades heats the material and stirs the material at the same time, thereby renewing the heating surface.

It is a continuous conduction heating dryer.
features
Compact structure, small footprint.
High heat utilization rate.


The paddle has self-cleaning ability.
The amount of gas used is small, and some auxiliary equipment can be reduced or omitted accordingly.
The material has wide adaptability and the product is dried evenly.


Suitable for a variety of drying operations.
Scope of application:
This machine is suitable for processing various paste, granular, powder and other materials with good thermal stability. Under special conditions, it can also dry heat-sensitive materials and recover solvents during the drying process.
Typical drying materials are: carbon black, light calcium carbonate, cyanuric acid, gypsum, clay, manganese dioxide, nylon and polyester chips, polyethylene, polypropylene (recycled solvent), etc.


1. Structural principle:
The hollow paddle dryer mainly consists of a W-shaped shell with a jacket, two hollow paddle shafts and a transmission device. The shaft end is equipped with a rotary joint for introducing heat medium.
The heating medium is steam, hot water or heat transfer oil.

The heating medium is passed into the shell jacket and the two hollow paddle shafts, and the material is heated and dried by conduction heating. The structure of the hollow paddle shafts is different for different materials.
The material is fed from the feed port, and the interface is renewed under the stirring action of the two hollow paddle shafts, and the material is pushed to the discharge port at the same time, and the dried material is discharged from the discharge port.
2. Equipment features:
1. The equipment has a compact structure and the device occupies a small area.

It can be seen from the structure of the equipment that the heat required for drying is mainly provided by the walls of many hollow blades densely arranged on the hollow shaft, while the heat transfer of the walls of the jacket only accounts for a small part. Therefore, the heat transfer surface of the equipment per unit volume is large, which can save the area occupied by the equipment and reduce the investment in infrastructure.
2. High utilization rate of heat.

The heat required for drying is not provided by the hot gas, which reduces the heat loss taken away by the hot gas. Due to the compact structure of the equipment and fewer auxiliary devices, heat loss is also reduced. The heat utilization rate can reach 80%-90%.


3. The wedge-shaped blade has self-cleaning ability, which can improve the heat transfer effect of the blade. The dispersion force generated by the joint movement of the inclined surface of the rotating paddle and the particle or powder layer makes it easy to automatically remove the material attached to the heating slope, so that the paddle maintains an efficient heat transfer function. In addition, due to the reverse rotation of the two-shaft blades, the material on the slope is alternately segmented (when the two-shaft blades are the closest to each other) and expanded (when the two-shaft blades are farthest from each other), making the heat transfer The material near the surface is vigorously stirred, which improves the heat transfer effect.

The heat transfer coefficient of the wedge-shaped paddle-type stirring dryer is relatively high, which is 85-350W/(M2·K).
4. The amount of gas used is small, and some auxiliary equipment can be correspondingly reduced or omitted. Since there is no need to use gas for heating, the amount of gas used in the drying process is greatly reduced. Using a wedge-shaped paddle dryer requires only a small amount of air to carry and evaporate moisture.

The amount of gas used is very small, as long as the drying system does not condense dew under the condition of dry operating temperature.
Due to the small amount of gas used, the gas flow rate in the dryer is low, and the dust carried by the gas is less, and the gas and dust in the system after drying are convenient to recover, which can reduce the size of the cyclone separator and save or reduce the bag filter. Gas heaters, blowers, etc. can be reduced in scale, saving equipment investment.


5. The material has wide adaptability and the product is evenly dried. There is an overflow weir in the dryer, which can adjust the material retention in the dryer according to the material properties and drying conditions. The material retention in the dryer can reach 70%-80% of the cylinder volume, and the residence time of the material can be increased to meet the drying requirements of difficult-to-dry materials and high-moisture materials.

In addition, it is also possible to adjust the feeding speed, the rotating speed of the shaft and the temperature of the heat carrier, etc., and the material residence time can be arbitrarily selected between a few minutes and a few hours. Therefore, it is suitable for both easy-to-dry and difficult-to-dry materials. The moisture content is only 0.1%, and there are industrial application examples.

In addition, although there are many stirring blades in the dryer, the materials are mixed evenly, but the flow of materials in the dryer from the feed port to the discharge port is basically a plug flow flow, the residence time distribution is narrow, and the product is dried evenly.
6. Suitable for various drying operations. As mentioned above, wedge-shaped paddle drying can adjust the drying process conditions through various methods, and its operation is easier to control than fluidized bed drying and airflow drying, so it is suitable for various operations.


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