Robust Design and Capability Evaluation of a Tribo-Aerodynamic Charging Process for Fine Particles

Robustness and capability are critical issues for the industrial application of any novel electrostatic process. The aim of this paper is double: show how an experimental design methodology can contribute to assessing the robustness of a given tribo-aerodynamic charging process and validate a procedure for evaluating the capability of two tribo-aerodynamic chargers with respect to the specific requirements of electrostatic separation applications. The results of three fractional factorial experimental designs performed on starch and flour powders, in two devices similar to the triboguns employed for electrostatic powder coating, demonstrate that the tribo-aerodynamic charging is robust with respect to the three main control variables of the process: the injection and vortex pressures of the air in the pneumatic circuit and the material feed rate. The capability indexes computed for both the straight- and spiral-type tribocharges were satisfactory.