Multi layer mesh belt dryer is a commonly used continuous drying equipment, suitable for drying and dehydrating materials such as sheets, strips, and particles with good breathability. It is commonly used for traditional Chinese medicine decoction pieces, dehydrated vegetables, pigments, etc. At present, most of the multi-layer belt dryers produced in China have a structure of two, three, or five layers. The materials are evenly spread on the mesh belt, and the chain mesh belt slowly moves inside the drying oven under the drive of the reducer. The hot air passes through the mesh belt upwards or downwards, and after a certain drying time, the material is dried. The main drawbacks are:
(1) The belt dryer with a two-story structure occupies a large area, has high construction costs, and has a high installed power.
(2) The belt dryer with a five layer structure is difficult to evenly distribute the wind direction, and the material cannot be blown through by the wind, resulting in low drying efficiency.
(3) At present, the bottom air distribution position of the belt dryer is poor, causing the product to easily regain moisture.

Overview of multi-layer forced circulation belt dryer equipment
When adding materials, they are evenly spread on the upper mesh belt. The mesh belt slowly moves inside the drying oven under the drive of the driving sprocket and the driven sprocket. The materials fall from the tail end of the upper mesh belt to the head end of the middle mesh belt, and then from the tail end of the middle mesh belt to the head end of the lower mesh belt. Finally, they are discharged through the tail end of the lower mesh belt. During this movement, hot air enters the circulating fan through the hot air supply pipe.
The wet material conveying equipment transports the materials to the dryer chassis. The airflow entering each heating unit through the circulating fan first passes through the wind deflector into the middle chamber of the heating unit, and then heats up through the radiator. The heated air passes through the material layer to dry the materials and enters the upper chamber. It is connected to the circulating fan through the air duct and guide duct connected to the upper chamber. Most of the gas circulates, and a part of the gas with lower temperature and higher humidity content is discharged as exhaust gas through the dehumidification fan through the dehumidification outlet. The material, which has been dried at high temperature, is transported away from the outlet of the bottom conveyor belt through multiple layers of conveyor belts. This device is a fully enclosed structure with high heat source utilization, energy conservation, and the ability to achieve high-temperature uniform drying of materials with high drying efficiency, resulting in good material quality after drying.

Structural diagram of multi-layer forced circulation belt dryer equipment

Performance characteristics of multi-layer forced circulation belt dryer

(1) The multi-layer forced circulation belt dryer has good heat transfer effect, high drying efficiency, low investment, and can ensure low moisture products.
(2) One end of the dehumidification duct of the multi-layer forced circulation belt dryer is connected to the dehumidification port on the top cover of the box, and the other end is connected to the dehumidification fan. The hot air supply duct is connected to the circulating fan and the circulating fan. The reducer is connected to the mesh belt layer through the chain mesh belt, which is divided into upper, middle, and lower layers.
(3) The circulating fan of the multi-layer forced circulation belt dryer is equipped with a main return air duct and a lower circulating air duct at both ends, which are connected to the lower level air homogenizer in the lower mesh belt layer, and connected to the middle level air homogenizer placed in the middle mesh belt layer through the middle circulating air duct.
(4) The multi-layer forced circulation belt dryer adopts a three-layer structure, reducing the footprint and engineering investment; The use of two layers of air intake, the middle and lower layers, and then returning to the upper layer for circulation greatly improves the heat transfer and drying efficiency;
(5) The mesh belt movement adopts stepless speed regulation, and the material retention time can be adjusted arbitrarily to ensure low moisture requirements of the product; A very small amount of circulating air enters the lower layer to avoid product moisture regain.

Technical improvement of multi-layer forced circulation belt dryer
(1) The forced circulation multi-layer mesh belt dryer includes multiple heating units, with multiple horizontally arranged conveyor belts inside the chassis. Each unit is equipped with an independent heating device and heat exchanger, which are arranged separately from the mesh belt drying room. A heat exchanger room is also set up on the side of the drying room to effectively avoid poor contact between material particles and the heat exchanger (such as powder particles leaking onto the heat exchanger and affecting the heat transfer effect).
(2) The chassis of the forced circulation multi-layer mesh belt dryer is equipped with three horizontal conveyor belts, and the mesh belt transmission device is set as a variable frequency speed regulation device to control the speed of the conveyed equipment and ensure smooth operation. Wet materials enter the chassis from the feeding port through the conveying equipment, and are evenly laid on the conveyor belt by the fabric spreader. The materials are then transported by the conveyor belt and fall onto the lower conveyor belt from the upper conveyor belt. Each layer of conveyor belt is driven by a variable frequency speed regulating transmission motor, which can independently control and adjust the speed of each layer of conveyor belt according to the quality of each conveyed material, in order to achieve the effect of fully drying the materials.
(3) Each drying unit of the multi-layer mesh belt dryer is equipped with an independent heater and a temperature control system to control the heating temperature inside each unit. Each heating unit is controlled by an independent temperature control meter, which can independently control the temperature without interfering with each other.
(4) Each heating unit on the side of the chassis is equipped with an air duct, and the air inlet and outlet of each heating unit are connected to the circulating fan through the air duct. The bottom of the heating unit is equipped with a wind deflector inclined towards the air inlet to change the direction of the incoming airflow, allowing it to move upward and penetrate the mesh belt and material layer. Each heating unit is equipped with a dehumidification port, which is connected to a dehumidification duct and a dehumidification fan. In order to evenly eliminate the humid air inside the heating unit chamber, a dehumidification port and a dehumidification pipeline can be installed in the front, middle, and rear sections of the heating unit. Most of the airflow entering the heating unit circulates, and a portion of the airflow with lower temperature and higher humidity is discharged through the dehumidification pipeline.
(5) In order to ensure that the high temperature inside the heating unit does not dissipate, an insulation layer made of ultra-fine fiber cotton material with a thickness of 80mm is installed inside the heating unit. The unit density of the insulation cotton is small, so the entire insulation layer is tight and thick, ensuring the insulation effect. At the same time, multiple observation doors can be installed on the side of the chassis, with sealed high-temperature resistant silicone rubber strips on the side doors. The door lock adopts a lever type lock, which has a reasonable structure, easy operation, and is not easily worn.
(6) The electrical control system of the forced circulation multi-layer mesh belt dryer is an independent control cabinet, which adopts intelligent instrument control and has the advantages of high temperature control accuracy, good seismic and anti-interference performance, temperature sampling adjustment, and control output integration. The entire temperature control system is used to achieve the functions of timed constant temperature, automatic dehumidification, and timed shutdown of the dryer.

Technical parameter table of multi-layer forced circulation belt dryer

Production photo of multi-layer forced circulation belt dryer