BASIC PERFORMANCE OF AN ELECTROSTATICALLY AUGMENTED FILTER CONSISTING OF A PACKED FERROELECTRIC PELLET LAYER

The basic performance of an electrostatically augmented filter consisting of a packed ferroelectric pellet layer has been studied. A d.c. or an a.c. voltage is applied to the pellet layer to form an electric field around each pellet. Dust particles are precharged by a d.c. corona discharge in front of the pellet layer, and are collected on the pellet surface. When an a.c. voltage is applied to the pellet layer, a stable partial discharge can be formed inside the pellet layer due to polarization of the ferroelectric pellet. By the partial discharge, sterilization can be achieved, or gas phase plasma chemical reactions can be promoted for deodorization. In order to use this filter for prevention of bio-hazard, or for deodorization, the characteristics of the partial discharge as well as its dust collection efficiency with the d.c. or the a.c. operation were measured. The ferroelectric pellets were BaTiO3-based ceramic. The larger the value of specific dielectric constant of the pellet, the lower was the initiation voltage of the partial discharge and the higher was the power of the discharge. When the filter was operated with an a.c. voltage, the dust penetration P became minimum at a certain voltage, at which the partial discharge was taking place. The minimum value of P was about 0.01% in this experimental condition. This result indicates that the filter can be used to remove dust particles and to sterilize microbes continuously. Deodorization can also be achieved continuously. When the filter was operated with a d.c. voltage, P decreased with the increase in the d.c. voltage. The minimum value of P obtained in this experimental condition was about 0.001%. © 1990.