Optimization of Pyrolysis Oil Yield from Low and High Density Polyethylene and Polypropylene Wastes

Summary

The work explored the thermal degradation of waste plastics from Asaba metropolis in a locally fabricated batch unit for pyrolysis of
the waste feeds and the optimization of pyrolysis yield. Special attention was given to Low Density Polyethylene (LDPE), High
Density Polyethylene (HDPE) and Polypropylene (PP) because of their ability to randomly degrade, giving rise to waxy hydrocarbons
that are suitable for fuel applications. Proximate and ultimate analyses of waste samples were carried out. The effects of time and
temperature on the quantity of the pyrolysis products were studied and three (3) quadratic models were developed to explain the
process. The LDPE liquid fraction obtained was analyzed for the functional groups present using Fourier Transform Infrared
Spectroscopy (FTIR). The fuel analysis was carried out based on chemical and physical properties to characterize the liquid product
from the pyrolysis process. A 3-D plot of interaction was plotted to visualize the surface effects of these process variables. The results
of the proximate and ultimate analyses of HDPE, LDPE and PP revealed high carbon contents of 89.93%, 84.10%, 82.81%
respectively and volatile matter 96.88%, 98.10%, 82.81% respectively showing the suitability of the materials as a potential fuel
source.. The process was optimized using Response Surface Methodology with the highest yield of 62% for LDPE obtained at 600oC
and 60 minutes. The density of the fuel gotten existed in the range of regular gasoline, the fire point,120-1800C and flash point,341-
3500C were within the standard limits of regular gasoline. This research work, through pyrolysis of waste polymers, has significantly
reduced the environmental concern by turning waste polymers into wealth generating, bio-degradable and environmentally friendly
pyrolysis oil. Model equations were developed for the process and the optimum conditions were established.

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