What drying equipments are commonly used in industrial production? How to choose them on demand?

- May 03, 2019 -

In industrial production, due to the different shapes (bulk, granular, solution, slurry and paste) and properties (heat resistance, moisture content, dispersibility, viscidity, acid-alkali resistance, explosion-proof and humidity) of the dried materials, the production scale or production capacity are also quite different, and the requirements for drying products (such as moisture content, shape, strength and particle size) are also different. Therefore, the types of drying equipment used are also varied. Box drying equipment, also known as disk drying equipment, is one of the oldest drying equipment with intermittent operation at atmospheric pressure. Generally small is called oven, large is called oven. According to the mode of gas flow, it can be divided into parallel flow, through flow and vacuum flow.

Co-flow drying equipment is placed in shallow dish on tray 7, and the thickness of material accumulation is about 10-100 mm. Fresh air inhaled by fan 3, preheated by heater 5, sweeps horizontally along baffle 6 along the surface of materials in shallow pans, and dries the materials. Part of the exhaust gas is discharged through the exhaust pipe 2, and the rest is recycled to improve the thermal efficiency. The exhaust gas circulation is regulated by the baffle of the suction or discharge port. The flow rate of air depends on the particle size of the material. The principle is that the material should not be carried out of the drying equipment by the air flow. Generally, it is 1-10m/s. The shallow plate of the drying equipment can also be placed on the tray frame of a possible moving car to facilitate the loading and unloading of materials and reduce labor intensity. If there are special requirements for drying process, such as drying heat-sensitive materials, flammable and explosive materials or moisture recovery of materials, the box drying equipment can be operated in vacuum, which is called box vacuum drying equipment. The drying chamber is sealed. The shallow tray frame is made into a hollow one. The heating steam passes through the shallow tray. When drying, the material is heated by conduction. The water content or solvent vaporized in the tray is vaporized. The vaporized water vapor or solvent vapor is pumped out by vacuum pump to maintain the vacuum in the chamber. The material of

through-flow drying equipment is laid on a porous shallow plate (or net). The air flow passes through the material layer vertically. An inclined baffle is arranged between the two layers of material to prevent the wet air from blowing out from one layer of material from blowing into another layer. The velocity of air passing through the orifice is about 0.3-1.2 m/s. The through-flow drying equipment is suitable for granular materials with good ventilation, and its drying rate is usually 8-10 times that of the co-flow drying equipment. The flue gas can also be used as the drying medium in the box drying equipment. The advantages of box drying equipment are simple structure, less investment and strong adaptability. The disadvantage is that the labor intensity is high, the heat loss of loading and unloading materials is large, and the product quality is not uniform. Box drying equipment is generally applied to the drying of a small number of materials, especially for laboratory applications.

belt drying equipment, the cross section of drying chamber is rectangular, with a mesh conveyor belt installed inside. Material is placed on the conveyor belt. Air flow and material cross-flow. During the belt moving forward, the material is continuously contacted with hot air and dried. The conveyor belt can be single-layer or multi-layer, with a bandwidth of 1-3 m, a length of 4-50 m and a drying time of 5-120 min. Usually in the direction of material movement is divided into many sections, each section can be equipped with fans and heaters. In different sections, the direction, temperature, humidity and speed of air flow can be different. For example, in wet material section, the operating gas velocity can be higher. The conveyor belt can be made of canvas, rubber, rubber coated cloth or wire mesh according to the nature of the dried material. Material in the belt drying equipment can basically maintain its original state, but also can continuously dry a variety of solid materials, but the stacking thickness and loading density of materials on the belt should be uniform, otherwise the ventilation is not uniform, and the product quality will be reduced. The production capacity and thermal efficiency of the drying equipment are low, and the thermal efficiency is less than 40%. The belt drying equipment is suitable for drying granular, bulk and fibrous materials. Characteristics of new microwave drying equipment

Selective heating. Because water molecules absorb microwave best, the part with high water content absorbs more microwave power than the part with low water content. This is the characteristic of selective heating, which can be used to achieve uniform heating and drying.

2, energy saving and high efficiency. Microwave directly acts on the material, so there is no additional heat loss. The air in the furnace and the corresponding container will not heat, so the thermal efficiency is very high, and the production environment is also significantly improved. Compared with far-infrared heating, it can save 30% electricity.

3, short time and high efficiency. Microwave heating is a process in which the heated object itself becomes a heater without heat conduction. Microwave penetrates the interior and exterior of the object from all sides and makes the object heated uniformly in a very short time, which greatly shortens the drying time. The microwave drying equipment is easy to control and the technology is advanced. Compared with the conventional method, the equipment is ready to use; there is no thermal inertia, flexible and convenient operation; microwave power can be adjusted, transmission speed can be adjusted. In microwave heating and drying, there is no waste water and no waste gas. It is a safe and harmless high-tech.

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