Classification of rotary dryer - Henan Hongxing

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Types of rotary dryer

 Rotary Dryer

Rotary Dryer It is a drying equipment with wide application range. Its body is a rotary cylinder, in which different forms of heat exchanger are set. Materials and hot gas for drying pass through the cylinder and conduct heat exchange to dry the materials. It is characterized by good adaptability to materials, reliable operation and large operation flexibility. It can dry materials with different moisture content, such as block, granular, powder and viscosity. According to the different classification methods, the dryer can be divided into the following types:

According to the heat transfer mode, it can be divided into:

(1) Direct heat transfer type:

In the drying process, the high temperature hot gas in the dryer directly contacts with the material in the cylinder, and transfers the heat directly to the material. This type is applicable to the condition that the material to be dried is not sensitive to high temperature and is not afraid of dust pollution. It is characterized by direct contact between hot flue gas and dried materials, high thermal efficiency and low fluid resistance. Slime dryer belongs to this type of drying equipment.

(2) Indirect heat transfer type:

This kind of dryer is suitable for drying powdery materials which are sensitive to high temperature gas or afraid of dust pollution, or easy to raise dust. Its characteristics are that the hot flue gas does not directly contact with the material, and the heat transfer efficiency and drying efficiency are relatively low, so it is rarely used in the market.

(3) Compound heat transfer type:

The drying process of this kind of dryer is that the high-temperature hot gas passes through the sleeve first, and then the hot gas is indirectly transferred to the material through the sleeve, and then the hot gas reaches the outside of the sleeve to directly heat transfer with the material. It is suitable for drying materials that are easy to ignite and explode, and can not contact with high-temperature gas and are not afraid of pollution, such as coal and other materials. The thermal efficiency is between the above two, and the fluid resistance is large. Three cylinder dryer belongs to this type of dryer.

It can be divided into two types according to the running direction of materials and high temperature hot air flow

(1) Downstream type:

In this type of dryer, the flow direction of material and high temperature hot air is consistent. The material and the high temperature gas enter the cylinder from the same end of the cylinder, and contact with the wet material immediately. Because of the large temperature difference and rapid heat exchange, the material temperature quickly rises to the wet bulb temperature of the gas, and a large amount of moisture in the material is evaporated at the feed end. The moisture content in the medium is very low, so the drying speed is very low. Therefore, it is easy to cause uneven drying rate in such dryer. This kind of rotary dryer is suitable for drying materials with high initial moisture content and low final moisture requirement; dry materials are sensitive to high temperature, such as mixture drying; for viscous materials with high plasticity, it can reduce the risk of materials sticking to the cylinder.

Note: the material should not be used when the block size is large. Because of the rapid evaporation of water, hard shell will be formed, which will affect the internal water evaporation and is not easy to dry thoroughly. It is characterized by uneven drying speed and low final moisture content.

(2) Countercurrent type:

The movement direction of the material in the dryer cylinder is opposite to that of the air flow. The wet gas flows into the low-temperature cylinder from both ends of the dryer. The dry material is in contact with the gas with high temperature and low humidity, while the wet material entering the dryer is in contact with the gas with low temperature and high humidity. The drying rate of materials in the dryer is relatively uniform, because the average temperature difference between the reverse hot air flow and the material is large, so the drying rate of the reverse hot air flow is higher than that of the forward flow drying. Sludge dryer generally belongs to this type.

The counter flow dryer is suitable for drying materials with low initial moisture content and low final moisture requirement, and materials that are insensitive to high temperature. It is characterized by uniform drying speed and high gas outlet temperature.

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