Desiccant Dryer

Operation Cycle

Dual-tower designs allow one bed of molecular sieve to dry the process air while the other undergoes thermal regeneration. Inside the desiccant dryer, the active bed adsorbs water molecules until it reaches saturation. At that point, the system switches the airflow to the second bed.

The saturated bed is then heated to release the trapped water, restoring its capacity. This alternating cycle ensures a constant flow of dry air to the resin hopper. Modern systems use dew point sensors to trigger this switch, saving energy.

Airflow System

Process air is blown through a heater to reach the drying temperature required for the specific resin. The hot air enters the bottom of the hopper and rises through the pellets, absorbing moisture as it flows. After leaving the top of the hopper, the air passes through a filter to remove dust before entering the drying bed.

This closed-loop system prevents ambient moisture from entering the drying cycle. The flow rate must be balanced to ensure even drying throughout the hopper.

Production Prevention

Underdried resin leads to cosmetic defects such as splay, bubbles, or silver streaks on the part surface. If the desiccant dryer fails, the moisture causes hydrolysis, reducing the molecular weight of the polymer. This degradation weakens the finished part, causing it to fail impact tests.

Regular maintenance of filters and desiccants prevents these issues.