Brief introduction of working principle and form of belt dryer

According to the contact mode of drying medium and material, it can be divided into convection type and conduction type. This paper introduces the working principle of belt dryer, the characteristics and differences of convection type and conduction type belt dryer.

Brief introduction of working principle and form of belt dryer

Belt dryer is generally composed of feeding device, conveyor belt, air circulation system and heating system. The working principle is as follows: the materials are evenly distributed on the conveyor belt by the feeding device. The conveyor belt is driven by the speed regulating device to move the dried materials from the feeding end to the discharging end. The dry air is transported by the fan and passes through the material layer from top to bottom or from bottom to top. After drying, the humidity of the air increases. Part of it is discharged from the drying box, and the other part is mixed with fresh air and heated After heating to the required temperature, the device passes through the material layer vertically from the top down, and the dried product is discharged from the outlet. Belt dryer is widely used in food, chemical fiber, forestry, pharmaceutical, leather and chemical industries, especially suitable for drying granular, sheet and fibrous materials. For those materials that do not have the above shape, such as paste materials, they can be pre molded by special equipment and then dried.

Type of belt dryer:

According to the contact mode between drying medium and material, it can be divided into convection type and conduction type

Convective belt dryer

There are two types of convection belt dryer: cross flow circulation type and horizontal type. The structural characteristics of cross flow circulation belt dryer are: the conveyor belt is made of porous plate or steel mesh; the hot air passes through the porous conveyor belt and contacts with the material countercurrent to dry the material. The upper or lower part of the conveyor belt is divided into several hot air distribution areas, different areas are separated from each other, but the air volume is basically the same, and the air temperature can be set to different values according to the moisture content of the material. The difference between the horizontal belt dryer and the cross flow circulation type is that the hot air flows upstream or parallel to the material, and there is no hole in the conveyor belt.

Conduction belt dryer

In the conduction belt dryer, there are many steam boxes or steam bundles uniformly distributed along the length direction of the dryer under the material side of the conveyor belt, and the heat needed for drying is transferred to the materials by the steam side through the heat transfer wall. If the material needs to be cooled before leaving the dryer, a cooling zone can be set at the back of the dryer to provide cooling water to the tube bundle or tube box. Sometimes the infrared transmitter can be set in the dryer to strengthen the drying process. Since this kind of dryer is usually operated under vacuum, good sealing structure should be ensured at the feeding and discharging ends. Conduction type belt dryer generally has no fixed specifications and models, and is usually specially designed according to specific production conditions. The typical dryer size is 10 meters long and 2 meters wide. The conveyor belt is generally composed of 8 sections, each section is 750mm, and the diameter of driving roller is 120mm. For those heat sensitive materials or some easily oxidized materials, conduction dryer is more suitable.