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What Is The Role Of Dryer And How To Properly Maintain And Use Dryer?
May 14, 2018

A dryer is a equipment for drying wet materials. Various kinds of drying materials are required in various production processes, and the requirements for drying are different. Therefore, there are a wide variety of desiccator. According to the heating mode, there are four types as follows:

The most widely used desiccator for convective dryer, including fluidized drier, air dryer, van dryer, spray dryer, tunnel dryer and so on. The main characteristics of such desiccator are: (1) hot gas flow and solid contact directly, heat transfer from hot gas to wet solid by convection heat transfer mode, and the water vapor produced is taken away by air flow; 2. The temperature of hot gas flow can be raised to the highest temperature (about 730 C) that ordinary metal material can tolerate, and radiation heat transfer at high temperature will be the main transmission. The heat method can reach a high heat utilization rate; 3. The humidity of the air flow has an influence on the drying rate and the final water content of the product; (4) when the air flow is used at low temperature, it is usually necessary to reduce the air flow first. 5. In order to ensure the heat needed for vaporization of water, if the particle size of the dried material is very small, the dust removal device is large and expensive, and it should be operated under the condition of near atmospheric pressure.

The conduction dryer includes the spiral conveyer drier, the drum dryer, the vacuum rake dryer, the freezing dryer and so on. The main characteristics of this type of dryer are: (1) heat passes through the wall of the device (usually metal wall) to the wet material by heat conduction; the surface temperature of the material can be from below freezing point (freeze drying) to 330 degrees C; 3. It is easy to operate in a vacuum and inert atmosphere, and the volatile solvent can be recovered. It is often used for drying easily and easily decomposing materials, and is also suitable for treating powdery materials.

The radiation dryer is used to heat the wet material and dry it through radiation heat transfer. The electric heating radiant drier irradiated the dried material with infrared light bulb to make the material temperature rise and dry. The gas heating dryer will burn the gas to heat metal or ceramic radiant plates to 400~500 degrees, so that infrared rays can be generated to heat the dried materials. The radiation dryer has the advantages of large production intensity, compact equipment, flexible use, but large energy consumption. It is suitable for drying large and thin materials such as plastic, cloth, wood, painted products, etc.

The dielectric dryer is used to place the drying material in a high frequency electric field, and the object is heated and dried by the alternating action of the high frequency electric field. The characteristic of this heating is that the higher the water content in the material is, the more heat it gains. Because the water content inside the material is higher than the surface, so the energy is more and the inner temperature of the material is higher than the surface temperature, which makes the temperature gradient and the direction of water diffusion consistent. It can accelerate the vaporization of water and shorten the drying time. This dryer is especially suitable for easy crusting and internal in the drying process. A material (such as leather) that is difficult to remove. Dielectric heating and drying consume a great deal of electricity. At present, it is mainly used in food and light industry.

For desiccator design and calculation, we must first select suitable dryer type. At present, the type selection of the dryer still has a lot of empiricism, and the following aspects should be taken into consideration: (1) the characteristics of material and product, such as the form of material (such as pulp, paste, powder, block, thin slice, etc.), particle size and strength of solid particles, the form of initial water content and water content, and whether the material is poisonous and flammable It is easy to oxidize, the final water content of the product is required, whether the product is allowed to be slightly polluted, whether the form is allowed to change slightly, the maximum allowable temperature of the product and the price of the product. (II) conditions related to the production process, such as the amount of material handled, the pre-treatment and post-treatment of drying, the solvent for volatilization, and whether it is recovered or not. (3) the operating performance and economic index of the dryer. After the comprehensive consideration of the above aspects, after screening all kinds of dryers, only a few desiccator is left, and then a small test is carried out to find the most suitable operating parameters and structural parameters. Finally, according to the equipment price and the small test situation, the dryer is decided to adopt.