Pyrolysis kinetics and reaction mechanism of waste medical masks by sectional heating process

Abstract

The COVID-19 epidemic has led to a significant upsurge in the accumulation of waste medical masks. This work focuses on the detailed examination of waste medical masks’ pyrolysis kinetic and reaction mechanism, employing a sectional heating process. The degradation properties were analyzed via thermal gravimetric analysis and pyrolysis reactor. The comprehensive kinetic process was studied using model-free and model-fitting methods, which determined the apparent activation energy and pre-exponential factor. The calculated average value for these parameters was 221.32 kJ/mol and 2.6 $\times$ 10¹⁴ min⁻¹, respectively. The pyrolysis process was carried out at three distinct temperatures: 380, 470, and 490 ℃, corresponding to the initial peak degradation rate and final degradation temperatures determined by TGA results. The total yield of oil, gas and tar was 88.6 %, 11.3 % and 0.1 %, respectively. The identification and quantification of pyrolysis products were achieved through GC–MS and FTIR. It was observed that higher pyrolysis temperature facilitated the generation of alkanes and hydrocarbons with lower carbon chain lengths in oil products and propylene monomers in gas products. The dominant pyrolysis products in oil under 380 ℃, 470 ℃ and 490 ℃ were C20, C20 and C12 with the yield of 36.17 %, 48.96 % and 43.35 %, respectively. And the corresponding dominant products in gas all were propylene with the yield of 34.74 %, 53.02 % and 54.55 %, respectively. Furthermore, a reaction mechanism was postulated to elucidate the pyrolysis process under varying temperature conditions.