RECYCLING OF POLYETHENE AND POLYPROPENE IN A NOVEL BENCH-SCALE ROTATING CONE REACTOR BY HIGH-TEMPERATURE PYROLYSIS

The high-temperature pyrolysis of polyethene (PE), polypropene (PP), a nd mixtures of these polymers was studied in a novel bench-scale rotat ing cone reactor (RCR). Experiments showed that the effect of the sand or reactor temperature on the product spectrum obtained is large comp ared to the effect of other parameters (for instance, residence time). In general, it can be concluded that the amount of polymer converted, into propene and butene decreases with higher cracking severity (high er temperatures or longer residence times), while the fraction methane increases. About 80 wt % of the polymer is converted into gas at a re actor temperature of 898 K, while 20 wt % is converted into intermedia te waxlike compounds or aromatics in the case of PE. The gas yield inc reases slightly with the reactor and/or sand temperature to 88 wt % at higher temperatures. The total amount of alkenes decreases with incre asing cracking intensity, which suggests that the reactor should be op erated at the lowest possible temperature. Our results indicate that t he reactor offers a few significant advantages compared to other react ors (no fluidization gas necessary, good solid-polymer mixing, no cycl ones necessary) and a competitive product spectrum. However, significa nt improvements are still possible to make the reactor concept technic ally and economically more attractive.