In powder pneumatic conveying process, powders are highly charged due to the collisions and frictions between themselves or against the conveying pipe wall, which sometimes causes explosions and fires. In order to prevent these troubles and hazards, development of a reliable system for monitoring and controlling electrostatic charge is required.
In this study, an eletrostatic charge control system composed of corona discharge neutralizer, electrostatic field 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 process through 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 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.

View full abstract