Thermal degradation of KN90 gauze mask rope waste : thermogravimetric and thermodynamic analyses, kinetic modeling and volatile products

Abstract

Pyrolysis is a promising thermal conversion method to dispose medical wastes. The pyrolysis behaviors, kinetics, thermodynamics and volatile products of KN90 gauze mask rope waste in nitrogen are studied under current study. The results indicate that two stages (stage 1: 0 ≤ α < 0.65 and stage 2: 0.65 ≤ α ≤ 1) mainly constitute the pyrolysis process of KN90 gauze mask rope waste in nitrogen. The average values of activation energy for stage 1, stage 2 and the entire pyrolysis process are 254.79 kJ/mol, 340.96 kJ/mol and 285.21 kJ/mol, respectively. The thermal degradation in stage 2 can be regarded as one-step reaction. The average value of pre-exponential factor for stage 2 is 1.17 × 1024 min−1 g(α)=(1-α)−2-1 can be adopted to characterize the thermal degradation in stage 2. The kinetic parameters for stage 2 can be adopted to well predict the conversion rate of stage 2. The variations of thermodynamic parameters suggest that the pyrolysis of KN90 gauze mask rope waste in nitrogen occurs more easily with the progress of thermal degradation. The total yield for the volatile products from most to least is alkanes > carbon dioxide > aromatic compounds > olefins > compounds containing carbonyl groups > alkynes > alcohols and water vapor. The possible chemical reactions to generate the specific volatile products are proposed.