Plastic pellets Drying: Equipment Selection

Drying plastic pellets sets two requirements that pull against each other: the surface water film has to go, and the pellets must not melt or stick together. If moisture stays on the surface, static builds up, the pellets begin to stick and ball, the conveying line bridges, and the injection or extrusion downstream comes out with surface defects. Raise the temperature and the pellets soften and go tacky, which makes the clumping worse. Controlling the temperature is therefore not about driving the water off faster, it is about keeping the pellets from softening in the first place. Our configuration is a flash airflow line.

Drying plastic pellets sets two requirements that pull against each other: the surface water film has to go, and the pellets must not melt or stick together. If moisture stays on the surface, static builds up, the pellets begin to stick and ball, the conveying line bridges, and the injection or extrusion downstream comes out with surface defects. Raise the temperature and the pellets soften and go tacky, which makes the clumping worse. Controlling the temperature is therefore not about driving the water off faster, it is about keeping the pellets from softening in the first place. Our configuration is a flash airflow line: the pellets are carried by the hot air and heat transfer completes within seconds, the contact time is too short to melt them, and a cooling section brings them back to ambient before packaging. The rotary drum is the alternative, for grades that need a longer residence time or tolerate more heat. Dust collection is the other focus: plastic powder is combustible dust, the collector has to be selected for combustible dust with explosion venting, grounding and duct bonding, as required by GB 15577-2018.

Why are dried plastic pellets still sticking?
Usually the surface water film has not been removed, and static builds up with it, so the pellets begin to cling and ball. Either the drying intensity is not enough, or air volume and temperature are not working together and the material is dwelling too long inside the machine. Adjust the drying intensity and the material temperature together rather than watching a single figure.

Can the temperature for plastic pellets be raised?
Not freely. The pellets soften and go tacky, and the clumping gets worse. The temperature has to be worked backwards from the softening point of the resin grade, and a change of grade means the parameters have to be confirmed again.

Why does plastic dust collection have to be for combustible dust?
Because plastic powder is combustible dust, and a drying system with concentrated dust, a heat source and airflow at the same time is the classic dust explosion scenario. It has to be selected for combustible dust, with explosion venting, grounding and duct bonding, as required by GB 15577-2018.