(490b) Characterization and Control of Triboelectrically Charged Particles

When two different materials are brought into contact and then separated, an electrical charge is transferred from one material to the other. This phenomenon is called contact electrification, contact charging, or tribocharging, and causes other phenomena. For instance, in pneumatic conveying applications, particles become charged and adhere to the walls. In order to improve existing processes and to develop new applications, it is important to characterize and control the electrostatic charge of particles. A particle charge increases with the number of contacts with a wall and reaches an equilibrium value. A particle charging profile can be expressed by an exponential equation with two parameters, i.e., values related to relaxation and equilibrium. To determine these parameters, two novel methods using applied electric fields have been developed. The first method characterizes the particle charging in gas-solids pipe flow. In the system, a particle charger using an electric field is applied to control the initial charge of particles. The initial charge is very important in characterizing the particle charging profiles. The second method is used for the repeated contact of particles with a flat plate. This system consists of two inclined vibrating plates and electrodes. The mass flow rate and charge of particles are controlled at the first vibrating plate. The equilibrium charge and the rate of tribocharging can be evaluated analytically from the relationship between the initial and transferred charges without changing the travel distances of the particles. This method enables the rapid and reliable analysis of the particle tribocharging process.