(I) Cylinder Dryer Type The cylinder dryer is the most common and widely used drying equipment in the mining industry. And a magnetic metal adapted for drying the non-metallic minerals, heavy clays and slime floating coal mining industry concentrate and cement industry and the like. It is characterized by high productivity and easy operation.
According to the heat transfer between the drying medium and the wet material, it is divided into a direct heat transfer cylinder dryer (the drying medium directly communicates with the wet material to transfer heat) and an indirect heat transfer cylinder dryer (the heat required for drying is indirectly transmitted from the cylinder wall) Wet material) two.
The direct heat transfer cylinder dryer is divided into two types: forward flow and reverse flow according to the direction in which the drying medium and the material flow.
The direct heat transfer cylinder dryer is shown in Figure 1.
The main portion of the direct heat transfer cylinder dryer is a rotating cylinder that is slightly inclined with respect to the horizontal line. The cylinder is driven by a gear, and the rotation speed is generally 2 to 6 rpm. The inclination of the cylinder is related to its length, and is usually between 1 and 5 degrees. The material is fed from the higher end of the drum and is in contact with hot air. As the cylinder rotates, the material flows to the lower end under gravity and is dried and discharged. Since the dryer is operated under negative pressure conditions, the feeding and discharge ends are sealed to prevent air leakage. The common types of sealing devices are as follows, as shown in Figure 2.
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In order to accelerate the uniform distribution of the materials on the sections of the drum section in good contact with the drying medium, a lifting plate is arranged in the cylinder. There are many forms of the riser, and the following are commonly used, as shown in Figure 3.
The lift-type lifting plate is suitable for bulk materials or materials that are easily bonded to the wall of the cylinder.
The four-format jack is suitable for materials that are dense, not brittle, or difficult to disperse. The slab divides the cylinder into four compartments, which are fan-shaped working chambers that are not connected to each other. The contact surface between the material and the hot gas is larger than that of the lift-type slab, and it can increase the filling rate of the material and reduce the falling of the material. Height and reduce the loss of dust and other advantages.
The cross-shaped or frame-shaped lifting plate is suitable for the brittle and easily dispersible small pieces of material, so that the material can be uniformly dispersed throughout the entire section of the cylinder.
The sleeve type jack is a jack of a double heat transfer (or half diameter heating) cylinder dryer.
The sub-format (fan-shaped) riser is suitable for materials with very fine particles that easily cause powder to fly. When the material is fed in, it is deposited on the grid. When the cylinder is rotated, the material is flipped and continuously in contact with the hot gas. At the same time, the height of the material falling is reduced, which reduces the possibility of the dry material being carried away by the gas.
The above various types of lifting plates can be distributed throughout the barrel. In order to enable the material to be sent to the lifting plate quickly and relatively evenly, a spiral guiding plate can be installed at the feeding end 1 to 5 meters to avoid the wetness. The material adheres to the wall of the cylinder. At the same time, the material after drying is easily lifted and taken away by the exhaust gas, and no lifting plate is installed at the discharge end 1 to 2 meters. [next]
The drying medium for direct heat transfer rotary dryers is typically flue gas. The combustion chamber of the forward-flow direct heat transfer rotary dryer is at the same end as the wet material feed, and the hot air flow is in the same direction as the flow direction. The wet material moves from the feed end to the discharge end, and the hot air also enters. The material end flows out through the discharge end under the action of the blower and the induced draft fan, and the wet material is heated and dried by the hot air during the flow. In the countercurrent mode, the wet material is fed into the dryer from the feeding end, the combustion chamber is arranged at the discharge end, and the material moves in the opposite direction to the drying medium (hot air), and the material is heated and dried during the movement. See Figure 4 and Figure 5, respectively.
Downstream drying Because the fed wet material enters the dryer, it is in contact with the drying medium with higher temperature. The initial drying driving force is larger, and the temperature of the drying medium decreases with the increase of the material temperature. Therefore, it is suitable for materials that do not require a high final water content (ie, dryness). The discharged dry material has a low temperature and is easy to transport. However, from the point of view of dust generation, fine materials are easily taken away by the airflow, and the amount of dust is large.
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