Development and Evaluation of a Batch-Reactor for Catalytic Depolymerization of Polymeric Waste for Liquid and Gaseous Fuel Production

It is postulated that waste, if managed effectively, can transform from a liability to a resource. Among various waste management techniques, such as incineration, composting, recycling, and re-use, depolymerization of municipal plastic waste demonstrated superior environmental performance by circumventing the release of harmful gases and facilitating wealth creation. A batch reactor, designed to operate at an internal pressure of 51.34 bar, a maximum temperature of 500 degrees C, and with a reactor thickness of 6 mm, was fabricated using locally available materials. Safeguards were incorporated by ring reinforcing the reactor to prevent burst incidents due to thermal expansion. Further, a sensor was integrated to stabilize the temperature, thereby enabling optimal function at a preset temperature. A shell-in-tube heat exchanger and a sub-cooler, with Log Mean Temperature Differences (LMTDs) of 280.15 degrees C and 174.53 degrees C respectively, were designed and constructed. The system's performance was evaluated by introducing approximately 2 kg of raw, washed, sun-dried, Polyethylene Terephthalate (PET) samples, and combusted in the energy conversion system for three and a half hours under a nitrogen atmosphere. For each run, 10 g of either calcium oxide (CaO) or activated carbon (AC) catalysts were added to the feedstock. Measurements of the temperature, pressure, and flow rate of the pyrolyzed product from the reactor were taken and recorded. The retention times for the depolymerization of catalyzed PET with activated carbon and calcium oxide were observed to be 38 and 45 minutes, respectively. The maximum flow rates of the vaporized product from the reactor were measured at 0.1985L/min and 0.1768L/min, at temperatures of 171 degrees C and 182 degrees C, and pressures of 37.6 kPa and 36.8kPa, respectively. Fuel conversion efficiencies of 49.2%, 66.6%, and 80.0% were recorded for uncatalyzed PET, CaO catalyzed PET, and activated carbon catalyzed PET, respectively, corroborating previous research but at temperatures below 400 degrees C.