Valorization of Plastic Waste: A Lab-Scale Approach with the Aid of Solar Hydrothermal Liquefaction Technology

Hydrothermal liquefaction (HTL) technology could potentially be utilized for the conversion of non-recyclable plastics emanating from process streams into added value products, exploiting the feedstock moisture. Although solar heat and HTL coupling is a promising prospect for reducing the high energy requirements of the process, it is not sufficiently developed. The present study aims to investigate the product properties and biocrude yield resulting from HTL of plastic waste mix and polypropylene at the lab scale by conventional heating and solar energy-aided. Two different units were used and heating was provided by an electric heater and an in-house solar simulator respectively. Temperatures tested ranged from 350 to 450 degrees C with an initial pressure of 1 and 20 bar for a retention time of 30 min. A solar setup was designed and constructed including ceramic insulation and a stainless steel support shell for testing in a solar simulator. The arrangement has an 80 mm front aperture from which light rays from 4 Xenon arc lamps reached the reactor and contributed to its heating. The lamps intensity was adjusted based on the process needs through a computer interface, temperature and pressure were monitored via 4 thermocouples and a pressure transducer respectively and the whole system was monitored remotely. Biocrude yield achieved exceeded 50% in the case of polypropylene and it was increased by 5-10% when treated under the solar simulator. Higher heating values of products were increased by 30-45% compared to the feedstock for the plastic waste mix, while for the resulting PP biocrude further treatment would be needed to reach a similar increase. [GRAPHICS] .

Automated summary

This study investigates the product properties and biocrude yield resulting from the hydrothermal liquefaction (HTL) of plastic waste and polypropylene using conventional heating and solar energy-aided methods. The results show that the solar energy-aided treatment can increase the biocrude yield and improve the heating value of the products.