TESTING A NEW DEVICE FOR SUPPRESSING ELECTROSTATIC CHARGES ON POLYMER GRANULES

Large discharges along the surface of the silo heap of polyethylene granules were reproducibly generated during filling of a 3 m diameter earthed metallic silo. The specific charge acquired by the granules during pneumatic transport was of the order of 2-mu-C kg-1 and the mass flow rate of the granules was approximately 1 kg s-1 (3.6 metric tons h-1). The rate of discharges depends on the height of the heap and varied from 4 to 8 discharges min-1. By operating a three nozzle injector of bipolar ions in a carefully optimized arrangement at a short distance from the granules' entry port, all discharges were immediately suppressed.