Technical Disscussion

How Infrared Crystal Dryer Dry?

2021-04-04 By: OUDE

Features of infrared dryer (IRD)

The infrared crystal dryer is the latest drying technology developed at present, and the infrared crystal dryer only needs 8-20 minutes, crystallization and drying are completed at one time, saving time, electricity, good drying effect, convenient maintenance and low cost, which is the highest efficiency at present , The best choice for low energy consumption drying method.

There are three P.I.D temperature control zones, and the crystal drying temperature can be set according to the characteristics of the raw materials.

Effectively drying plastic grease: PET Flake/Pellets, PET Masterbatch,PLA,PBAT, PPS,PET composite material (G.A.G), PC, PA6(66), SURLYN etc.

Infrared principle:

The frequency of infrared is about 1012 C/S ~ 5x1014 C/S, which is part of electromagnetic wave. Near infrared wavelength is 0.75~2.5μ and travels straight at the speed of light, and it goes around the earth seven and a half times per second (about 300,000 Km/s). It can be seen from the light source It is directly transmitted to the material to be heated, causing physical phenomena of absorption, reflection, and transmission.

In addition, the infrared rays that penetrate and reflect from the material do not affect the organization of the material, but the absorbed tissue will be converted into heat energy due to molecular excitation, which causes the temperature of the material to rise. Taking PET as an example, crystallization and crystallization can be achieved in a very short time. The drying temperature can not only save energy, maintain the physical properties of liposomes and increase the IV value.

The argument to increase the IV value (intrinsic viscosity) needs to be further verified by experiments.

The working principle of infrared crystal dryer (compared with the principle of thermal convection drying)

Infrared Crystal Dryer Convective heating
Infrared drying(IR): Heat is adsorbed inside the pellets. Plastic and water are excellent IR adsorbents.
It takes about 15 to 20 seconds to heat a pellet entirely
Convecting Drying: Heat conducts into the pellet, plastic is a poor heat conductor.
It takes about 30-50 minutes to heat a pellet enturely
Water vapour moves to the coolest area, IR heating starts inside the pellets and immediately heat is conducted towards the cool ambient air.In this
phase the moisture is heated and vapourised immediately and is arracted out of the pellet into the cooler ambient air
Vapourised water moves to the coolest area, convective heating starts at the surface of the pellet and slowly heat is conducted towards the center. In this phase the moisture is attracted towards the cooler center of the pellets. Drying doesn't even start. What is more the moisture concentration inside the pellet increases
Heating difference principle explanation
The physical force for moisture diffusion is a difference in temperature and a difference in partical pressure
1)IR-provides a high vaporisationrate on moisture in the core
2)The driving force for diffusion is a difference in Temperature between the vaporised moisture and the ambient air
3)IR used cool ambient air so a permanent difference in partical pressure is always avaliable
T particle > T ambient
P particle > P ambient
when the entire pellet has reached the same temperature as the hot ambient air drying starts:
1)vaporisation rate is low
2)Vaporised water is transported from the core of the pellet to the surface
3)The driving force for this diffusion is a difference is partial pressure of the ambient air
4)To ensure this process is effective desiccant air with a low dew-point is applied generally.

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