Research for the method of removing solid impurity from liquefied plastic waste using electrostatic force

• Project/Area Number: 08455482
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 資源開発工学
• Research Institution: Yamagata University
• Principal Investigator: ASANO Kazutoshi Yamagata University, Faculty of Engineering, Professor, 工学部, 教授 (30007182)
• Co-Investigator(Kenkyū-buntansha): YATSUZUKA Kyoko Yamagata University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (60210283) ; HIGASHIYAMA Yoshio Yamagata University, Faculty of Engineering, Professor, 工学部, 教授 (50144209) ; 西村 亮 山形大学, 工学部, 助手 (70261683)
• Project Period (FY): 1996 – 1997
• Project Status: Completed (Fiscal Year 1997)
• Budget Amount: ¥1,000,000 (Direct Cost: ¥1,000,000); Fiscal Year 1997: ¥1,000,000 (Direct Cost: ¥1,000,000)
• Keywords: Recycle / Plastics / Environment / Electrostatics / Electrification / Conductive particles / Insulating liquid / Petroleum

Research Abstract

In a recycling system of plastic waste, liquefaction of plastics seems the most suitable method. However, the foreign substances, such as metal particles or carbonized material, must be removed from such liquefied plastics in order to get high quality reproduction. The purpose of this research is to seek a removing method by means of electrostatic force. Since it is necessary to know the fundamental characteristics of a solid particle motion within liquefied plastics, we have simulated this system by using silicone oil and a spherical conductive particle. Carbon and steel particles of 1 to 2 mm diameter are examined. The motion of the particle was observed and record in video tape with video microscope. The DC electric field is applied to a parallel plate electrode system which is immersed in silicone oil.
The particle placed on the lower electrode is charged by the electric field, so that the force acting on the particle becomes the sum of the Coulombic force and the gravitational forc e. When the Coulombic force overcomes the gravitational force, the particle rises toward the upper electrode. The threshold voltage when the particle starts lifting agreed with the theoretical value. When the applied voltage is above the threshold the particle shows up-and-down motion. Interesting phenomenon observed is that the particle is often held on the electrode during the charge transferring. For carbon particles the velocities of upward and downward motion are almost equivalent. Although the velocity of upward motion for steel particle is slower than downward, they are getting closer with increase of the applied voltage. The elapsed time of a particle held on the electrode deviates extensively. The larger voltage is applied, the shorter the particle holding time on the electrode becomes.
The discharge current arises abruptly when the particle contacts the electrode and decreases gradually. The charge amount of a particle, which is obtained by integrating the discharge current pulse, increases with the applied voltage. Furthermore, different motion pattern was observed, that the particle moves up and down showing curved trajectory at the edge of electrodes. This has the potentiality to control the particle motion by changing the configuration of electric field. The research will continue to clarify the relation between the particle motion and the electric field configuration on the base of the knowledge gained in these experiments.