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J Mater Cycles Waste Manag (2009) 11:144147 Springer 2009 DOI 10.1007/s10163-008-0227-z
SPECIAL FEATURE: ORIGINAL ARTICLE Chemical Feedstock Recycling & Other Innovative Recycling
Techniques 7
Toshiro Tsuji Akito Hatayama
Gasication of waste plastics by steam reforming in a uidized bed
Received: November 30, 2007 / Accepted: October 28, 2008
Abstract The process of producing synthetic gas from waste plastics by steam reforming was investigated. To evaluate this process, the steam reforming of the oils derived from low-density polyethylene and polystyrene were carried out using a laboratory-scale uidized bed of NiAl2O3 catalysts.
The performance of gasication in terms of carbon conversion, gas yield, and gas compositions was examined. Although oils derived from plastics contain many kinds of heavy hydrocarbons and aromatics, they were well gasied at temperatures above 1023 K with a steam/carbon ratio of 3.5 and a weight hourly space velocity of 1 h1. The hydrogen content of the product gas was very high at approximately 72 vol% for polyethylene-derived oil and 68 vol% for polystyrene-derived oil. These compositions agreed well with the values calculated from chemical equilibrium.
Key words Steam reforming Waste plastics Hydrogen Coking Catalyst
Introduction
Various plastic recycling processes have been developed in Japan, based on the Package Recycling Law passed in 2000. Among these processes, the gasication of waste plastics was considered to be a promising method for feed-stock recycling, and two large commercial recycling plants were constructed and are running successfully at full operation.
However, this conventional gasication process requires large-scale facilities such as an oxygen plant because the process is based on partial combustion and it requires a large quantity of pure oxygen to keep the reaction tempera-
ture very high. The development of smaller and more efcient processes is desirable because the collection of a large amount of waste plastics is very difcult, except in areas of high population density. Therefore, we have been studying the process of gasication of waste plastics by steam reforming, which occurs at relatively low temperatures and does not require pure oxygen. The production of gas by reacting hydrocarbons with steam in the presence of a catalyst is a well-known process that was established in the 1930s. A vast number studies have focused on the steam reforming of natural gas, naphtha, and other...