Gasification feasibility of polyethylene, polypropylene, polystyrene waste and their mixture: Experimental studies and modeling

Plastic waste is on the rise and continues to enter in every consumer product. Their recycling, however poses challenges due to their compositions and inhomogeneity. Gasification is an energy conversion route of hydrocarbon and is a well-developed technology for coal, but not for municipal-solid-waste (MSW) derivatives (plastic/tires/wood). Polyethylene (PE), polypropylene (PP), polystyrene (PS) holds about 12% of our daily MSW fraction and are characterized with high calorific value (~40 MJ/kg). In this work, TGA/DSC analysis was firstly done for sample plastic waste to capture their degradation kinetics needed for successful gasification. These parameters were evaluated using Arrhenius and Coat-Redfern methods. The best-fitted-values were implemented in a high-fidelity entrained-flow-gasification model for comparative analysis. Gasification was conducted based on the drop-tube-reactor (0.066 m diameter & 1.54 m length) with an equivalence ratio of 1.8. Wall temperature was fixed at 1000 °C under atmospheric pressure. Activation energy results for PE, PP, PS and their mixture are 340, 220, 320 and 85 kJ/mol, respectively and rate constants vary between E¹⁰ to E²² min⁻¹. Air gasification results in efficiencies of 59.03%, 62.73%, and 73.13% for PE, PP, and PS, respectively. Their co-gasification reached 89% due to lower activation-energy which emphasized their usage as mixture and saves their segregation.