Process for drying granular polymeric material and plant operating according to said process
A process for drying granular polymeric material, includes: dehumidifying the granular polymeric material by a first flow of gas at a first temperature of between 100° C. and 150° C.; heating the dehumidified granular polymeric material to a second temperature, greater than the first temperature; drying the granular polymeric material heated to the second temperature, by applying a predefined vacuum level. The pressure-sealing elements include a filling unit, which includes a small tank blocked upstream and downstream by shut-off valves, as well as a discharge unit, which includes a small tank blocked upstream and downstream by respective shut-off valves.
1 . A plant for drying granular polymeric material, comprising:
at least one dehumidification hopper, which is connected to a dehumidification line, through which a first flow of gas for dehumidifying said granular polymeric material is introduced into said dehumidification hopper;
at least one heating hopper, which is arranged downstream of said dehumidification hopper and is provided with a heater, for heating said granular polymeric material to a second temperature that is higher than the temperature of said first flow of gas;
at least one drying hopper, which is provided downstream of said heating hopper and is connected to a depressurization circuit, for obtaining a specified vacuum level in said drying hopper and for drying said granular polymeric material;
wherein said drying hopper is separated from the other hoppers, both upstream and downstream, by pressure-sealing elements comprising a filling unit, which includes a tank blocked upstream and downstream by shut-off valves, as well as a discharge unit, which includes a tank blocked upstream and downstream by respective shut-off valves.
2 . The drying plant according to claim 1 , wherein at least one feed hopper is provided downstream of said drying hopper and upstream of a machine for working said granular polymeric material.
3 . The drying plant according to claim 1 , wherein said drying hopper has a volume of between 500 and 1000 liters and said tank of the filling unit has a volume of between 30 and 50 liters.