Optimizing electric field uniformity of a segmented-electrode free-fall separator using RSM-FEM coupling

Electrostatic separation enables the efficient sorting of mixed granular insulating materials by applying controlled electrical and mechanical forces. Although particle separation requires a strong electric field (E-field), a uniform field distribution is critical to achieving consistent particle deflection and high separation efficiency. This study aimed to analyze the E-field non-uniformity (NUF) in free-fall electrostatic separator design incorporating segmented electrodes and inter-electrode side openings to mitigate particle rebound. Numerical simulations were conducted to optimize critical parameters—number of electrode pairs, inclination angle, and segmented length ratio—using a coupled computational approach: finite element analysis (FEM) in COMSOL Multiphysics for field modeling, integrated with response surface methodology (RSM) via central composite design (CCD) in JMP statistical software for parametric optimization. Key performance metrics included E-field NUF and the total distance between same-polarity electrodes. Quadratic regression modeling identified the optimal configuration to be eight electrode pairs with a segment length of 4.16 cm and an inclination angle of 16.88°, achieving 86 % desirability. Simulation results showed a strong correlation with model predictions (R 2 > 0.99). Statistical analysis revealed that the number of electrode pairs was the most influential factor affecting E-field NUF, contributing to 49.75 % of the observed variance. Similarly, the segmented electrode length ratio had the strongest impact on inter-electrode distance, accounting for 65.91 % of the response variation. Compared to conventional configurations, the proposed design reduces E-field NUF by 44 %, demonstrating its potential for enhanced electrostatic separation performance. • E-field non-uniformity of free-fall separator was analyzed using RSM-FEM approach. • The effect of three geometric factors on E-field non-uniformity and inter-electrode distance was investigated. • The number of electrode pairs influences on E-field non-uniformity by 49.75 %. • The segmented electrode length ratio affects the inter-electrode distance by 65.91 %. • The proposed design reduced the E-field non-uniformity by 44 %.