Feedback Control of Electrification in Powder Pneumatic Conveying Process [Translated]^†

Abstract

In a powder pneumatic conveying process, powders are remarkably charged due to the collisions and frictions between themselves or against the conveying pipe, which sometimes causes explosion and fire. In order to prevent these troubles and hazards, development of a reliable system for monitoring and control of electrification (electrostatic charge) is strongly required.In this study, an electrostatic charge control system composed of corona discharge neutralizer, electrostatic filed strength sensor and computer control system was newly developed and applied to the powder pneumatic conveying process. Dynamic characteristics of electrostatic charge and its elimination by the corona discharge neutralizer were analyzed. Based on the characteristics, a simplified transfer function composed of first order lag element including dead time was proposed and optimal control parameters for the digital PID control was determined. Performance of the control system was also investigated experimentally under various control parameters. It was found that the electrostatic charge during powder pneumatic conveying process was favorably self-controlled by means of the newly developed control system.

Control of electrostatic charge for powder by using feedback control-type ionizer system

“…Since the output values of I e are nonlinear with I o , PID (proportional, integral, and derivational) control using practical feedback is not easily introduced (Watano et al, , 2003. As a trial and for stability in tests of long operation, we employed a new and simplified formula (1) using fuzzy control, as follows,…”

“…Such a discharging phenomenon may cause an explosion or fire when an explosive dust cloud is present simultaneously. From the viewpoint of safety engineering and within the background reported above, experimental studies related to hazardously charged powders have widely been conducted for years (Choi, Yamaguma, Kodama, Suzuki, & Mogami, 2005;Kodama, Suzuki, Nishimura, Yagi, & Watano, 2002;Kodama, Suzuki, & Mogami, 2003;Watano, Saito, & Suzuki, 2003). We developed a nozzle-type electrostatic ionizer with an electrostatic detection meter to reduce the charge of pellets before they enter a silo in a pneumatic transport system (Watano, Saito, & Suzuki, 2002).…”