Pyrolysis of High-Density Polyethylene in a Fluidized Bed Reactor: Pyro-Wax and Gas Analysis

This study investigates the pyrolysis of high-density polyethylene (HDPE) in the fluidized bed reactor of a patented system. The experiments were performed at 500 °C, and the effect of olivine as a bed additive was studied. The HDPE material has a melting peak and crystallinity of 131 °C and 61.7%, respectively. Results revealed that wax is the dominant pyrolytic product. The addition of olivine in the fluidized bed increased the wax yield from 45.6 to 66 wt % and enhanced the formation of olefins. It was found that the pyro-wax has a high energy content (44.82 ± 0.24 MJ kg–1) and can be a potential source of fuel. The heating value is comparable to the energy content of conventional fuels. In addition, the results showed that chemicals in the pyrolytic product are dominated by aliphatic compounds. The pyro-wax has less branched alkyl chains than commercial waxes. The presence of many −C═C– groups in the pyro-wax indicates the formation of olefinic groups, and they are more than those in commercial waxes. Analysis of the pyro-gas revealed the dominance of ethylene, propylene, and hydrogen with yields of 8.68, 7.50, and 7.11 wt %, respectively, for the experiment conducted in the presence of olivine.