Converting Municipal Plastic Waste to Environmentally Friendly Fuel: A Process Simulation Study
Date
2022-08-31
Authors
Binekar, Ankit
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Only 9% of the total plastic is recycled, but a substantial amount cannot be recycled, and most plastic goes to landfills. In this thesis, a process simulation model is implemented in the Aspen Plus® simulator, and the technical sensitivity analysis and optimization analysis are conducted for the distillation unit of a commercial pyrolysis plant. The process simulation study was conducted for the actual plant capacity of 500 kg/hr of plastic waste under the temperature of 440°C and slight vacuum pressure of 0.998 atm to convert it into char, oil fuels, and non-condensable gases. Results show that the total oil fuel yield is 81.92% (heavy oil is 237.72 kg/hr and light oil is 171.90 kg/hr), whereas the non-condensable gases yield is 14.85%. The char yield is reduced to 3.22% due to the use of a secondary reactor that further pyrolyzes the char received from the primary reactors.
Description
The amount of municipal plastic waste increases every year. Only 9% of the total plastic is recycled, but a substantial amount cannot be recycled, and most plastic goes to landfills. In this thesis, a process simulation model is implemented in the Aspen Plus® simulator, and the technical sensitivity analysis and optimization analysis are conducted for the distillation unit of a commercial pyrolysis plant. The process simulation study was conducted for the actual plant capacity of 500 kg/hr of plastic waste under the temperature of 440°C and slight vacuum pressure of 0.998 atm to convert it into char, oil fuels, and non-condensable gases. Results show that the total oil fuel yield is 81.92% (heavy oil is 237.72 kg/hr and light oil is 171.90 kg/hr), whereas the non-condensable gases yield is 14.85%. The char yield is reduced to 3.22% due to the use of a secondary reactor that further pyrolyzes the char received from the primary reactors. The light oil and heavy oil fuel densities at 15°C are 759.36 kg/m3 and 837.16 kg/m3, similar to the density obtained from the fuel samples from the experimental runs. A technical sensitivity analysis for liquid oils was performed across the columns RC-4601 and RC-4602 with two key variables: RC-4601 condenser duty and RC-4602 condenser duty. The maximum heavy oil production of 255.76 kg/hr can be achieved at RC-4601 condenser duty of -83.48 kW. However, the light oil production decreases to 159.83 kg/hr. At the critical point of -78.16 kW, the density of the heavy oil exceeds the standard density limit (850 kg/m3). However, variations in RC-4601 condenser duty have shown no effect on the flash point of heavy oil. The optimum RC-4602 condenser duty obtained is -20.21 kW, where the light oil production rate is 182.07 kg/hr, increasing more than 5.91% over the predicted light oil production rate. At the critical point of -20.23 kW, the density of the light oil reduced to 756.17 kg/m3. The flash point of light oil decreases with the increase in condenser cooling duty; a drop of more than 46% is observed from its maximum with the increase in condenser duty. An optimization study predicted that the optimal range of condenser duty for RC-4601 is -78.21 to -78.16 kW and for RC-4602 is -23.84 to -23.85 kW. At the optimum condenser duty of -23.84 kW for RC-4602, the light oil production rate increases to 217.82 kg/hr, increasing more than 26.53% over the current operating production rate. The heavy oil production rate decreases at the condenser duty of -78.21 kW for RC-4601. However, with an increase in total condenser duty of 1.82%, the total production rate of oil fuels increases by 2.49% and the light oil to heavy oil production ratio increases from the current operating ratio of 0.72 to 1.08.
Keywords
Plastic pyrolysis process