SIMULATION AND OPTIMIZATION OF LOW DENSITY POLYETHYLENE PLASTIC WASTE PYROLYSIS FOR LIQUID FUEL PRODUCTION USING ASPEN HYSYS

Plastic waste pollution is a critical global environmental challenge. In developing countries like Nigeria, adequate plastic waste valorization strategies are key to mitigating plastic pollution, advancing circular economy principles and encouraging sustainability. This study presents an Aspen HYSYS steady-state simulation and optimization of a 1,000 kg/h pyrolysis process of sachet water nylon plastic wastes modelled as Low Density Polyethylene (LDPE) plastic. The simulation model incorporates a multi-unit flowsheet, hypothetical pseudo-component modelling of LDPE with literature-validated thermophysical properties, and the Peng-Robinson equation of state as the thermodynamic fluid package. A three parameter sensitivity analysis was carried out to deduce optimization conditions for optimum liquid fuel yield. At base-case conditions of 450°C reactor temperature and atmospheric pressure, the simulation yielded 516.9 kg/h of pyrolysis oil and 483.1 kg/h of fuel gas, with pyrolysis oil comprising 80.2% C5–C10 liquid fuel range hydrocarbons, consistent with experimentally reported yields of 70–80%. The sensitivity analysis examined reactor temperature (400–550°C), condenser outlet temperature (25–60°C), and feed preheater ∆T (275–450°C). Reactor temperature showed a direct proportional relationship with oil yield, peaking at 460°C. Condenser temperature demonstrated a strong inverse relationship, with oil yield declining from 58.7% at 25°C to 26.9% at 60°C. Feed preheater temperature exerted no discernible influence on product yields over the inspected temperature range. The study identified suitable optimization conditions favoring sustainable liquid fuel yield in pyrolysis process and thus provides a basis for advancing circular economy and reducing plastic pollution (sachet water nylon waste) in Nigeria.