The dual corona-electrostatic electrodes consist of
one or several ionizing elements (wires, needles, and blades) attached
to a metallic support. This paper analyzes the characteristic
features of a particular type of such electrodes and formulates
recommendations on their design and utilization. The experiments
focused on several models of dual corona-electrostatic electrodes,
the ionizing element being the edge of a thin metallic blade. The
tested devices had similar cylindrical metallic supports but blades
of different sizes. Thus, it was possible to investigate the influence
of electrode geometry on corona onset voltage and spark-over
threshold in configurations that are specific to industrial electrostatic
processes. Most of the experiments were performed by
using roll-type electrostatic separators. A special experimental
setup was employed for the study of the distribution of corona
current density at the surface of a plate collecting electrode. For
the model having the blade edge closer to the metallic support, the
corona onset voltage was higher, and the corona discharge affected
a smaller area at the surface of the collector. These experiments
are discussed in relation with the results of the numerical analysis
of the electric field generated by the different electrode configurations.
At a given voltage and distance between the ionizing
element and the collector, the presence of the cylindrical support
diminishes the electric field at the edge of the blade and distorts
the field lines. These effects were exploited in the design of the
electrode system of an electrostatic separator for the recycling
industry