In the process of plastic production and processing, as most plastics have hygroscopicity, it is necessary to use dehumidifying dryer for drying. The proper plastic drying process can effectively improve the drying quality of products, save costs, and reduce energy consumption. So what are the drying processes of dehumidifying dryers? Below, we will summarize and introduce them for you.
For non-hygroscopic materials, a hot air dryer can be used for drying. The principle of hot air drying is to use a fan to absorb the air in the environment and heat it to the temperature required for drying the specific material. The heated air passes through the drying hopper and heats the material by convection to remove water. Because the water is only loosely constrained by the interface tension between the material and water, it is easy to remove.
Vacuum drying, also called dehumidification drying, has also entered the field of plastic processing. This continuous operation machine is composed of three chambers installed on a rotating conveyor belt. In the first chamber, when the plastic pellets are filled, gas heated to the drying temperature is introduced to heat the pellets. The moisture is evaporated in the second chamber under vacuum. Finally, the material is sent to the third chamber and removed from the dryer. In vacuum drying, gas drying itself does not consume energy, but energy is needed to create a vacuum, and the energy consumption required to create a vacuum depends on the amount and moisture content of the material being dried.
Another drying method of dehumidifying dryers is infrared drying. In convective heating, the thermal conductivity between gas and pellets, between pellets and pellets, and inside pellets is low, so the conduction of heat is greatly restricted. When using infrared drying, the molecules are directly converted into heat vibration due to the infrared radiation received, meaning that the heating rate of the material is faster than that in convective drying. Infrared drying technology currently has broad application prospects in the plastic industry, and processes such as extrusion, hollow molding, and thermoforming can all use infrared heating.
Due to the hygroscopicity of most engineering plastics and the influence of weather and regional climate, plastic pellets are more susceptible to excessive moisture, which can lead to poor forming effects. In addition, the moisture content and hygroscopicity of plastic raw materials and the front-end pelletizing process are different, so it is easy to produce bubbles, silver streaks, poor transparency, cracks, poor stability, and other issues during forming, which seriously affects product quality. The air pipeline of the dehumidifying dryer uses a closed circulation system, which is not affected by external weather conditions. Whether it is dry or humid weather, it can dry the material well, without returning to moisture, and achieve high product forming quality.
That's all we have to introduce about the drying processes of the dehumidifying dryer. Each of the three major drying processes of dehumidifying dryers has its own benefits. Users can choose the most economical and effective drying process according to the characteristics of the materials that need to be dried.