Simultaneous analysis of particle size and electrostatic charge distribution of powder with high accuracy and precision, and its applications to electrostatic processes

Characterization of particle size and charge distribution has many applications in the fields of powder coating, electrophotography, electrostatic separation of minerals, electrostatic spray processes and pharmaceutical powder dispersion and delivery. Monitoring of the electrostatic charge and size distribution on a single particle basis can provide insight of the electrodynamics of the process, and can provide empirical tools for optimizing the process. Here, the authors present the development and performance of the newly-improved Electronic Single Particle Aerodynamic Relaxation Time (E-SPART) analyzer, that provides particle size and electrostatic charge distributions in real time and on a single-particle basis with precision and accuracy. The instrument uses an AC electric drive to oscillate the particles and to measure the particle size and distribution, as opposed to using an acoustic field superimposed on a DC electric field. Several applications, including powder coating, electrophotography, coal beneficiation and pharmaceutical powders are given as examples to demonstrate the utility of real-time analysis of size and charge distribution of airborne particles while keeping them in a suspended state.