ID 26

Faradaic reactions in charging of oils in electrostatic atomizers

 

Abstract:

Electrochemical reactions cause oil electrification in electrostatic atomizers. This study investigates the effects of the electrode materials on the resultant charges carried into the spray and the leakage currents in electrostatic atomizers. Visible deposits/discolorations at the counter-electrode are found. The study also explores the fundamental electrochemical Frumkin-Butler-Volmer kinetics and physical mechanisms of oil electrification. Three different mechanisms of faradaic reactions are discussed: (i) Fatty acid dissociation resulting in proton reduction at the cathode and formation of metal salts of fatty acids there. (ii) Participation of dissociated water molecules (absorbed from the surrounding humidity) in electrode reactions. (iii) Charging neutral molecules at higher voltages at the sharp electrode (with the magnitude above about 4 kV) results in oil repulsion from the pin electrode, ultimately leading to toroidal vertical flows. The electrochemical findings are corroborated by Infrared and Raman spectroscopy of the electrode deposits. The kinetic constants of the Frumkin-Butler-Volmer law have been measured. In addition, a novel, highly sensitive method of measuring oil electrical conductivity has been introduced and verified. This lays the foundation for understanding and optimizing the electrostatic atomizer design and operation.