Experimental characterisation of a diesel engine running on polypropylene oils produced at different pyrolysis temperatures

- Polypropylene pyrolysis at different temperatures.
- Oils tested in a four-cylinder DI diesel engine.
- Polypropylene oils showed longer ignition delay period and lower efficiency than diesel.
- Polypropylene oils produced lower CO2 emissions and higher NOX, UHC, and CO emissions than diesel.

Polypropylene is the most common type of plastic found in municipal solid waste. The production of polypropylene is expected to increase due to the widespread utilization in daily life, resulting in even higher amounts of polypropylene waste. Sending this plastic to landfill not only exacerbates environmental problems, but also results in energy loss due to the elevated energy content of polypropylene. Pyrolysis is a process that can effectively convert polypropylene waste into fuel, which can then be used to generate power and heat. In the present study, the effect of the pyrolysis temperature on the pyrolysis of polypropylene was investigated, while the oils produced at 700 °C (PP700) and 900 °C (PP900) were used to fuel a four cylinder diesel engine. The engine's combustion, performance, and emission characteristics were analysed and compared to diesel operation. The results showed that both PP700 and PP900 enabled stable engine operation, with PP900 performing slightly better in terms of efficiency and emissions. However, PP700 and PP900 were found to have longer ignition delay periods, longer combustion periods, lower brake thermal efficiencies, higher NOX, UHC and CO emissions, and lower CO2 emissions in comparison to diesel operation. Nonetheless, the addition of a small quantity of diesel improved the overall performance of the oil blends, resulting in comparable results to diesel in the case of PP900.