Depolymerization of polyethylene using induction-coupled plasma technology

Abstract

A significant, valuable percentage of today's municipal solid waste stream consists of polymeric materials, for which almost no economic recycling technology currently exists. This polymeric waste is incinerated, landfilled, or recycled via down-graded usage. Thermal plasma treatment is a potentially viable means of recycling these materials by converting them back into monomers or into other useful compounds. The technical, laboratory scale, feasibility of using an induction-coupled RF plasma (ICP) heated reactor for this purpose has been demonstrated in the present study. Polyethylene powder was injected axially through the center of an ICP torch. Results from the initial set of experiments, analyzed using a statistical design of experiment technique, showed that plasma plate power, central gas flow rate, probe gas flow rate, powder feed rate, and the interaction between the quench gas flow rate and power input were the key process parameters affecting the yield of ethylene in the product gas stream. The gaseous products obtained were mainly mixtures of ethylene and propylene. The amount of propylene obtained was significantly higher than anticipated and was believed to be due to β-scission reactions occurring at the higher plasma temperatures.