Separation of Individual Plastics from Mixed Plastic Waste by Gravity Separation Processes

In Korea, mixed plastic wastes generated from households after hand picking and/or mechanical sorting processes amount to 1,700,000 ton per year in 2005, and most of these waste are finally end up with landfill and/or incineration due to lacks of separation technologies and economical reasons. These plastic wastes can not be used as raw materials for chemical and/or thermal recycling because of their high content of PVC (upto 4.0 wt.%). In the present work, gravity separation system has been developed to remove PVC from the mixed plastic waste and recover the valuable plastics. The separation system mainly consists of air classification, magnetic separation, one-step crushing, feeding system at fixed rate and wet-type gravity separation system. The gravity system based on centrifugal separation has been developed and it consists of mixing, precleaning, separation, dewatering, recovery system, wastewater treatment system, etc. The main objective of this process to be developed is to achieve high separation efficiency of polyolefins (PE, PP, PS) with less than 0.3 wt.% PVC content and less than 10% moisture content in the final products. In addition, crushing unit with 8 rotor system is also developed to improve the crushing efficiency of soft-type plastics. The system with a capacity of 1.0 ton per hour is developed and operational results are presented.