A Comprehensive Teaching Experiment for Energy Recovery from Waste Face Masks by Pyrolysis and CO2-Assisted Gasification

Carbon-rich organic solid wastes should be introduced to students not only as pollutants to be disposed of, but also as secondary carbon resources that can be converted into energy carriers and useful products. To connect waste valorization, low-carbon energy conversion, and experimental engineering education, this study reports a comprehensive teaching experiment based on the fixed-bed pyrolysis and CO2-assisted gasification of polypropylene-rich waste, together with the complete reference dataset and calculation workflow that accompany it. Waste face masks are used as a representative and familiar feedstock: the melt-blown filtration layer is polypropylene, whereas the spun-bonded outer layers may be polypropylene or polyethylene terephthalate, so the material is deliberately treated as a heterogeneous real waste. Every indicator reported here is defined so that it can be computed from the measured gas-phase data and the weighed feed mass alone, without elemental analysis or calorimetry of the feedstock. Students complete feedstock pretreatment, reactor operation, online micro-gas chromatography, tracer-based quantification, gas-phase mass and energy balances, uncertainty propagation, a stoichiometric oxygen balance for CO2 conversion, and a documented risk assessment. Two inert pyrolysis and two CO2-assisted gasification cases at 850 and 900 °C were implemented with 35 g of feedstock. CO2-assisted gasification raised the combustible-gas yield by about one order of magnitude: at 850 °C, the total combustible gas was 24.40 ± 0.86 g, of which strictly defined syngas (H2 + CO) was 17.87 ± 0.83 g, the combustible-gas energy 536.8 ± 12.9 kJ, and the specific energy recovery 15.34 ± 0.37 kJ g−1 feed. Evaluated over the identical 21 min window used for pyrolysis, gasification still delivered 21.87 g against 1.89 g, so the improvement is not an artefact of the longer run. Release profiles are described quantitatively by an exponentially modified Gaussian model (R2 = 0.983–0.999) with peak positions of 1.3–2.4 min and widths of 1.3–1.9 min. Using the inert run at the same temperature as a baseline. An assumption-dependent estimate indicates a CO2 conversion of 13.0 ± 0.7 g per 35 g of feedstock at both temperatures, with a possible upper estimate of approximately 26 g if the reverse water–gas shift reaction contributes. The stated uncertainty reflects the propagation of the measured gas-phase quantities but does not include the potential systematic bias associated with the unmeasured PET fraction or atmosphere-dependent behavior of oxygen-containing constituents. This estimate assumes that the CO formed from oxygen-containing minor constituents such as PET is largely removed by the baseline subtraction. The dataset comprises one run per condition; no replicate experiments were performed, so the reported uncertainties are single-run combined standard uncertainties and no claim of run-to-run reproducibility is made. The paper contributes a documented platform, a four-case reference dataset, and a fully documented calculation workflow for teaching thermochemical conversion, gas analysis, element balances, energy recovery, measurement uncertainty, and process safety.