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Drum dryer is a kind of dryer which is widely used. It has the advantages of high productivity, convenient operation, reliable operation and low power consumption. It is suitable for processing fine but not too cohesive materials. It can mix dried fine clean coal and flotation clean coal, and can also dry flotation clean coal separately. This paper mainly analyzes its structure and drying principle.
Drying principle of drum dryer
The structure of drum dryer is composed of drum, stop wheel, supporting wheel, transmission device and sealing device. The supporting roller is the supporting device of the drum, with two at the front end and two at the back end, supporting the tyre. The drum is inclined installation, generally 1 ° to 5 ° in order to prevent the drum from moving down along the axial direction, a stop wheel is installed on the side of the tyre. The drum is driven by the transmission device, and the speed is generally 2 ~ 6R / min. The transmission device includes motor, reducer, small gear and big gear ring. The drum is the main body of the drum dryer. The ratio of length to diameter is generally 4:1 ~ 8:1. It is usually made of thick steel plate with two hoops on the outside. The roller is equipped with a device for conveying loose materials.
The drying principle of drum dryer: when the drying materials enter the first area of the dryer, with the rotation of the drum, and with the help of the large angle guide plate, the material is quickly guided to the inclined guide plate, which is lifted and gradually scattered to form a "material curtain", through which the high-temperature flue gas passes to preheat the material and evaporate part of the moisture. After repeated for several times, it moves to the movable grate type wing plate, and the material is mixed with the preheated grate wing plate to absorb its heat. At the same time, the material carried by the wing plate rises and falls together, and forms conduction and convective heat transfer with hot flue gas. When the material moves to the arc-shaped lifting plate with cleaning device, the chain will transfer the heat received in the upper space to the material, and the material is lifted and scattered by the lifting plate with the rotation of the drum, which can fully transfer the mass and heat with the hot flue gas, and clean the materials adhered to the inner and outer walls of the lifting plate. At the same time, the cleaning device can also crush the pellets, greatly increasing the heat exchange area and increasing the drying rate.
When the material moves to the circular arc grate type lifting plate with cleaning device, the material still carries out mass and heat transfer according to the movement law of four zones in the dryer, but there are two states of the material in this area: one is that the dry material is powdery and leaks from the gap of the grate bar with the rotation of the drum; the other is that the wet ball remains in the ring of the lifting plate and is gradually broken with the rotation of the drum The medium moisture evaporates and is finally dried. When the material moves to the sixth zone, it has become a low moisture loose state. In order to reduce dust and reduce the load of dust removal system, there is no lifting plate in the range of about 1m away from the end of the cylinder. After drying, the materials roll to the discharge box to complete the whole drying process.