CONTINUOUS OR BAND DRYING

The continuous or belt dryer is a drying method used in the mass production of various materials with good air permeability. For drying small parts. Such as agricultural products, soap, wool, cotton, fibers, sludge, etc.

A belt dryer can be divided into two groups; according to its composition and method of air action (dryer without porous belt and dryer with mesh belt). The first dryer belt is made of fabric (such as canvas, rubber belt, coated fabric, etc.). The heat carrier (usually hot air) passes over the layer of dry material laid evenly on the belt. The direction of the airflow is countercurrent to the direction of movement of the belt. The second type of dryer belt is made of metallic or non-metallic mesh. The hot air flows through the material layer from the bottom up or from the top down in the direction of the vertical surface of the strip. This is called a continuous flow belt dryer, which is widely used in industrial production.

Operating principle

At present, the belt dryer can be divided into single-layer, multi-layer, single-stage and multi-stage, but its working principle is basically the same. The material enters the lifting system and is distributed evenly, advancing through the conveyor belt. The hot air in the drying unit passes through the layer of material vertically to start dehydrating. The thickness of the material layer in the mesh belt is determined by the nature of the material, the way it is distributed and the drying temperature. The thickness is generally adjusted in the range of 20 - 100 mm. The drive by transmission device allows adjusting the speed with which the product advances inside the drying chamber.

Cross Flow Belt Dryer

The cross flow belt dryer is widely used in drying fiber, chemical wood pulp. food, medicine, mining, building materials and other industries. Recently, it has also been used as a sludge dryer for environmental protection.

They can be classified as follows:

1. According to the number of layers; there are individual, compound and multiple.

2. According to the ventilation direction, it can be divided into downward ventilation type, upward ventilation type or compound ventilation type.

Belt Dryer Structure

The continuous flow belt dryer mainly consists of one or more series-aligned drying machine(s), a distributing mechanism, and a discharging device. Forced ventilation is used as a drying method due to the large contact area between hot air and moist materials. allowing convection heat transfer and radiation heat transfer, and the drying intensity is high.

Cross Flow Belt Dryer Features

As the materials are stacked on a horizontal circulation conveyor made of steel wire mesh or perforated plate, the materials are not affected by vibration, breakage or other situations, and the flying dust is less.
The slurry-like materials can be suitably shaped in the feed part to form granular or rod-like materials with a diameter of 3 - 8 mm, this is done with the aim of increasing the contact area between the hot air and the materials. molded, causing a considerable increase in the drying rate.
According to the situation of the material, and in order to prevent the air pressure from compacting the materials and increasing the ventilation pressure drop, compound ventilation can be adopted to improve the uniformity of the dried materials and increase the drying rate.
In the drying process, the composite or multi-layer belt type can loosen or flip the materials, so that the air permeability is improved, thus increasing the thickness of the material layer in the slowdown drying stage. Several studies have shown that increasing the surface area of the material will increase the rate of drying. To achieve the same effect on a single-layer belt dryer, a material agitator device can be installed in the middle of the conveyor belt.
A continuous cleaning mechanism must be provided in the rotating part of the circulation conveyor to prevent the adhesion of dried materials. After cleaning the perforations on the conveyor belt, the ventilation performance and the drying rate can be kept stable.
Special attention should be paid to the sealing of the belt side and the entry and exit of the device. Otherwise, it will cause hot air short circuit or air leakage, which will greatly reduce the drying speed of materials and even prevent the drying operation.

For example, there is a need to remove surface water from 140gr lemons after a washing process. The product flow is 12,000 kg/h and they must remain in the oven for 1 min. According to the project requirements, it is recommended to use the TROCK – SP15 closed cycle model, this heat pump format is suitable for the surface drying operation of lemons. The advantage of this model is that the condenser and the dehumidification cabinet are separated from the rest of the heat pump, which provides unique installation flexibility. The purpose of the dehumidification cabinet is to remove water vapor from the air and recover heat. TROCKNNER heat pump uses an upgraded vapor injection compressor which means that in cold weather, heating efficiency can be increased by 10-20% compared to normal compressors.