How does rotary drum dryer work?

Rotary drum dryer, also known as drum drying equipment, is the most common and widely used type of dryer equipment in mining equipment. It is suitable for drying magnetic, heavy and floating concentrates of metallic and non-metallic ores, clay in cement industry and slime in coal mining industry.

Tumble dryers are characterized by high productivity and easy operation. The drum body of the rotary drum dryer is a horizontal rotary drum. Various types of copying boards with different staggered angles are welded inside from front to back. The rotary kiln body is inlaid with different types of refractory bricks according to the needs. The material is provided with a door ring and a spiral copy board. It has the advantages of reasonable structure, excellent production, high output, low energy consumption and convenient operation.

Internal structure of rotary drum dryer

In order to increase the good contact between each part of the material evenly distributed on the section of the drum and the drying medium, a lifting plate is installed in the drum. The types of lift boards are as follows:

1. Lifting lift plate: suitable for bulk materials or materials that are easy to stick to the cylinder wall.

2. Four-format lifting board: suitable for materials with high density, which are not brittle or difficult to disperse. The lifting plate divides the cylinder into four compartments, which are fan-shaped working chambers that do not communicate with each other. The contact surface between the material and the hot gas is larger than that of the lifting lifting plate, and it can increase the filling rate of the material and reduce the falling height of the material. And reduce dust loss and other advantages.

3. Cross-shaped or frame-shaped lifting plate: suitable for small pieces of materials that are relatively brittle and easy to disperse, so that the materials can be evenly dispersed on the entire section of the cylinder.

4. Sleeve type lifting plate: It is the lifting plate of the double heat transfer (or semi-diameter heating) tumble dryer.

5. The sub-format (fan-shaped) lifting plate is suitable for materials with very fine particles that are easy to cause powder to fly. As soon as the material is fed, it will be accumulated on the grid plate. When the cylinder rotates, the material will be flipped and continuously contact with the hot gas. At the same time, the possibility of the dry material being carried away by the gas is reduced due to the reduction of the material falling height.

Drum dryer machine drying process

If you want to understand the tumble dryer, you must start with the drying process. The entire drying process is roughly divided into three stages.

In the first stage, after the wet material enters the cylinder, in the process of moving forward, the heat is directly or indirectly supplied by the heat carrier, the temperature of the material rises rapidly, and the surface water evaporates rapidly.

In the second stage, the moisture inside the material evaporates steadily to the surface. During this period, the temperature of the material is constant and the evaporation rate is also constant.

In the third stage, the temperature of the material continues to rise, and the evaporation rate decreases. At this time, the moisture content of the material has dropped significantly, and the evaporated moisture is reduced.

Industrial rotary drum dryer heating method

The smooth progress of the drying process is inseparable from an important step: heating. There are three common heating methods for tumble dryers: direct heating, indirect heating, and composite heating.

1. Direct heating

The material in the tumble dryer is in direct contact with the hot air, and is dried by convection heat transfer. The drying speed is fast, the thermal efficiency is high, the gas and the material are fully contacted, and the dust is less. According to the flow direction of hot air, it is generally divided into two types: counter flow and downstream flow.

2. Indirect heating

Contrary to direct heating, when the tumble dryer is indirectly heated, the heating medium does not directly contact the material. All the heat required for drying the material is transferred to the material through the heat transfer wall. When drying the material, a concentric cylinder is set in the drum, the hot air passes through the inner cylinder, and the material passes through the annular space between the two cylinders. This heating method increases the heating area of the material and accelerates the drying speed.

3. Compound heating

When the rotary drum dryer is combined heating, there are both direct heating and indirect heating, and a concentric cylinder is also set in the drum. Part of the heat required for drying the material is transferred to the material by hot air through the heat transfer wall of the inner cylinder in the form of heat conduction; way to pass to the material.

Rotary drum dryer drying temperature

The heating process of the tumble dryer is inseparable from the reasonable control of the drying temperature. Although different tumble dryers may have different models and sizes, the requirements for the drying temperature are the same, and the maximum intake air temperature is the same. Generally it is 700-800℃.

When the drum dryer is working, if the temperature does not reach the expected temperature, it will affect the drying quality and drying efficiency of the material, so the operator must pay attention to the temperature of the drum.