Proven drying methods for plastic granules

What drying system should you consider, when looking for the most cost effective solution for your needs?

Well, it depends. Because there are several factors that influence the right choice for you.

There are six categories of drying methods. Each with its own pros and cons. Lets briefly explore the advantages and disadvantages…

But first, consideration should be given to the type of plastic granules in question. Are you dealing with hygroscopic og non-hygroscopic granule?

Among the hygroscopic granule you find polymers such as nylon, ABS, polycarbonate, cellulose and polymethacrylate. These are problematic in terms of moisture content absorbed into the granule, and normally require vigorous drying to secure the right (low) moisture level.

Other polymers, such as polyethylene and polystyrene, do not normally absorb much moisture, but are able to carry significant moisture on their surface when exposed to liquid water. Typically, from condensation, or residue from cleaning regimes.

Moreover, using carbon black or pigments can cause an increase in moisture absorption.

Drying is the primary source of product failure
Given that drying is the primary source of product failure in plastic granule processing, and the fact that the moisture tolerances are so slim, that they normally are measured in parts per million (PPM), it is widely recommended to integrate drying into the plastics granule processing.

When selecting the most cost effective drying solution, there are normally six generic drying methods to be considered:

1. Compressed Air Dryers
2. Dehumidifying Dryers
3. Honeycomb Dryers
4. Hot Air Dryers
5. Rotary Wheel Dryers
6. Vacuum Dryers

In summary, Hot Air Dryers are most suitable for treatment of non-hygroscopic materials, when the challenge is to remove surface moisture from the granule. Otherwise, the right choice depends on a number of factors regarding both; the processing environment, the granule composition and the requirements to the finished products.
However, recent development in drying technology has proven to reduce the energy consumption for Dehumidifying Dryers by up to a staggering 89%. This is a real game-changer, that rearranges the priority of different drying regimes.

From more than sixty years of experience in drying technology, we at Labotek have learnt, that when it comes to drying, it is not a one-size-fits-all situation. And the right solution is best found through an exploratory dialogue, considering all your needs.

For a deeper insight into the discussion about the different drying methods, have a look at our whitepaper on the issue.