Working principle of belt dryer

The material is evenly laid on the mesh belt by the feeder, and the mesh belt is made of 12-60 mesh stainless steel wire mesh. Drag by the transmission device to move inside the dryer. The dryer consists of several units, each with independent circulation of hot air. Part of the exhaust gas is discharged by a dedicated dehumidification fan, and the exhaust gas is controlled by a regulating valve. The hot air passes through the material laid on the mesh belt from bottom to top or from top to bottom, heating and drying, and taking away moisture. The mesh belt moves slowly, and the running speed can be freely adjusted according to the material temperature. The dried finished product continuously falls into the feeder. The upper and lower circulation units can be flexibly equipped according to user needs, and the number of units can be selected according to needs.
The materials in the hopper are evenly laid on the mesh belt by the feeder, and the mesh belt is generally made of 12-60 mesh stainless steel wire mesh, which is dragged by the transmission device to move inside the dryer. The dryer is composed of several units, each with independent circulation of hot air. Some of the exhaust gas is discharged by a dedicated dehumidification fan 4, and the amount of exhaust gas emitted by each unit is controlled by a regulating valve. In the upper circulation unit, the air from the circulating fan 5 enters the lower chamber of the unit through the side air duct. The airflow is heated up by the heater 7, distributed by the distributor 6, and then blown into a jet stream towards the mesh belt. After passing through the material, it enters the upper chamber. The drying process is the process of hot air passing through the material layer, completing the transfer of heat and mass. The upper chamber is connected to the fan inlet by an air duct. Most gas cycles involve a portion of gases with lower temperatures and higher moisture content being discharged as exhaust gas through dehumidification pipes, control valves, and dehumidification fans. In the lower circulation unit, the air from the circulating fan first enters the upper chamber, is heated downwards by the heat exchanger, passes through the material layer, and enters the lower chamber. The lower chamber is connected to the fan by the side air duct and return air duct, with most of the gas circulating and some discharged. The upper and lower circulation units can be flexibly equipped according to user needs, and the number of units can also be selected according to needs.
For dehydrated vegetables, three devices are generally used in series to form the initial drying section, intermediate section, and final drying section. In the initial drying stage, due to the high moisture content of the material. Due to poor breathability, smaller paving thickness, faster running speed, and higher drying temperature are used. In the initial drying stage, the temperature of the dry gas can reach over 120oC. The retention time of materials in the final drying section is 3-6 times that of the initial drying section, and the laying thickness is 2-4 times that of the initial drying section. For the requirement of material temperature not exceeding 60oC, dry gas of around 80oC can be used. Adopting a multi-stage combination can better utilize the performance of a belt dryer and achieve more uniform drying.