Pyrolysis of waste LDPE and waste PP plastics into fuel oil in a low-cost, lab-scale pyrolyzing unit

Abstract

Plastics cause severe environmental and societal issues when post-consumer plastics are discarded in the environment without proper management. Pyrolysis of plastic waste is a promising method for plastic waste management due to its valuable by-products such as fuel oil. The objective of the present study was to pyrolysis waste polypropylene (PP) and waste low-density polyethylene (LDPE) plastics into fuel oil in a low-cost, lab-scale apparatus at the maximum temperatures of 330°C and 355°C, respectively, and in turn to assess the physical properties, gross calorific value, density, kinematic viscosity, flash point, ash content, and sulfur content, of resultant fuel oil. Commercially available, recycled grades of LDPE and PP pellets, 70.0 g of each, were obtained, and pyrolysis was done in a lab-scale, low-cost batch reactor. The experiment was triplicated, and the resultant fuel oil was analyzed for physical properties by ASTM standard methods. The properties of resultant fuel oil were also compared with diesel grade criteria. Results revealed that the highest yield of fuel oil was obtained from waste PP at 79.57 wt.% while the waste LDPE resulted at 74.06 wt.% of fuel oil. No wax formation was observed in the waste PP pyrolysis process, unlike in the waste LDPE pyrolysis. The gross calorific values of waste PP and waste LDPE were 12 016 kcal/kg and 11 961 kcal/kg, respectively. It was higher than the standard value of commercial diesel. The distillation results indicated that short-chain hydrocarbon content is higher in the waste PP fuel oil sample than in the waste LDPE fuel oil sample. The results indicated that the resultant fuel oil samples were nearly closer to the diesel grade criteria. Therefore, the fuel oil produced from waste plastics is a viable alternative to traditional fossil fuels, with potential applications in power generation and transportation.