마찰하전 정전선별법에 의한 혼합플라스틱의 하전특성 및 분리효율에 관한 연구

Abstract

Charging properties and separation efficiency for the recycling of plastic wastes by triboelectrostatic separation has been studied. In the charging property study, The work function and the triboelectric series of plastics were established and a vertical-reciprocation tribo-charger was designed. Also, the charging properties that affect the charge efficiency and charging polarity of plastics were estimated and charger material was selected. In the separation efficiency study, scale-up tests for plastic wastes and the separation of plastics containing PVC, using a pipe line and a cyclone charger were performed. Using the vertical-reciprocation tribo-charger, the correlation between the work function of metals and charge density of plastics was obtained and then the work function of the plastics was established. Also, the triboelectric series which can be used as an important indicator for the separation of plastics was established according to the relationship of the charge polarity and charge density between plastics and charging materials: (negative) HPVC - SPVC - COPP - HOMOPP - LDPE - HDPE - PET - RUBBER - HIPS - Calibre - ABS - GPPS - PMMA (positive). As retention time and reciprocation numbers in the tribocharger increased, and particle size and relative humidity decreased, the charge density of plastics increased regardless of the change of charge polarity. The charge density of an ABS and PVC mixture in an equal amount was found to be about two times higher than individual ABS and PVC. In separation tests, plastic particles were charged in a fluidized bed pipeline tribocharger and then trajectory analysis was conducted in electric field of charged particles. As particle size decreased and charge density increased, the deflection toward electrode increased. It is because electrostatic force ?��? is directly proportional to the charge density of particle and electric field, and inversely proportional to particle mass. In both simulation and experimental tests for the separation of ABS from PVC, the optimum charge density and splitter position were determined to be 20∼24.5 nC/g and +2cm from the center, obtaining an ABS grade of above 99.5% and an ABS recovery of above 95%. In the 1st stage tests for separating three kinds of plastics, namely PVC, PET and ABS, using a pp cyclone charger, a 99.4% PVC grade and a 98.1% PVC recovery were successfully achieved. In the 2nd stage using a HIPS cyclone charger, a respective PET grade and recovery of 97.8% and 95.1% could be obtained. Hence, a possibility of separating PVC, PET and ABS one another in the 2-stage bench-scale triboelectrostastic tests wasverified. In separating final plastic wastes, a PET grade ranging 96.8∼98.5% using a PS, PP, or PE cyclone charger was obtained and then a possibility of plastic wastes used as reused plastic fuel of grade 2∼4 was verified. In the scale-up triboelectrostatic separation of plastic wastes from the dry processing of seaweed(sloke), a respective LDPE grade and recovery of 99.4% and 98.1% were obtained Separation efficiency for separating ABS from PVC in scale-up tests with a feed rate of 350kg/h was slightly lower than that in bench-scale tests, but a high ABS grade and recovery of 99.4% and 94.5% were successfully obtained under the optimum conditions.