Metering of Bulk Material with an Electrostatic Valve

Abstract

Several bulk materials were metered using a pulsating DC electric field through an electrostatic valve. The valve uses interparticulate clamping forces, created along the path of charge leakage, to create the equivalent of a material arch or bridge that blocks the flow channel and stops the flow of the particulate material. Turnip seed, ground soybean hulls, sand, and sugar were all successfully metered through the test apparatus. The valve was able to meter these materials at 3 to 70% of the free-flow discharge rate by changing the pulse rate and pulse width of the applied DC electric field. Soft red winter wheat, soybean, dry powdered milk, sorghum, and corn meal were not successfully metered by the electrostatic valve. Factors which affected the metering performance of the electrostatic valve were: electric properties of the material, temperature and relative humidity of the ambient air, particle size and particle distribution, moisture content of the material, and particle cohesion.