An extrusion hopper dryer is a device used to pre-heat plastic pellets. It uses air heated to a low temperature to dry the pellets. It can be manually operated or automatically powered. The enthalpy rise can be achieved outside of the twin-screw extruder.
The pellets must be placed in the hopper at a controlled temperature. An auto loader is a worthwhile investment if the job is going to be large.
A non-hygroscopic resin is comparatively easy to dry.
This method is more efficient in humid climates since water molecules only collect on the surface of the pellet.
A hopper dryer consists of a heating element and a cooling system.
The air passes through a hole screen, which disperses moisture from the material.
Hot air is forced into the hopper through the air pipe.
The air circulates evenly throughout the materials.
It is best to check the moisture content of polyester pellets using a dew point meter.
This will provide an accurate indication of the drying efficiency.
The moisture level should be within the range of 0.020% to 0.03% of the weight.
If this moisture level is too high, the material may not be ready for processing.
For this reason, a dew point meter is essential. A thermometer should be attached to the extrusion hopper.