Development of Innovative Gasification Process of Used Plastic by Using Fluidized Bed

Used plastic waste flowing into oceans has become a worldwide problem. Since international trade in used plastics has been regulated in recent years, a large amount of used plastic now requires domestic disposal. On the other hand, used plastics with a high calorific value could be used as an energy source. Therefore, the authors developed a new used plastic gasification process utilizing a fluidized bed. In this process, used plastics are decomposed in a fluidized bed reactor at around 600 °C, which is a lower temperature than that used in current commercial processes. A higher calorific value gas could be obtained by gasification reaction control at the lower temperature. Hydrogen enriched gas generated by the water-gas shift reaction (WGSR) of basic oxygen furnace gas was used as the fluidizing or gasifying agent, since hydrogen was considered to have an effect of promoting the decomposition reaction of the hydrocarbons in used plastics. As the fluid medium in the reactor, catalysts were used to improve gasification efficiency. In this study, the effect of the gasification temperature and type of catalyst on the calorific value of the produced gas and gasification efficiency were investigated. High calorific value gas (LHV: 5000 kcal/Nm³) could be successfully produced by pyrolysis of used plastics by using an appropriate gasification temperature and catalyst.