Kinetic study of waste turkey bone gasification: Statistical assessment of the reaction models describing Boudouard reaction in CO₂ and pressure-dependent modelling in lean air

This study presents a comprehensive multi-atmosphere kinetic analysis of turkey bone (TB) waste gasification using thermogravimetric analysis (TGA) at heating rates of 2, 4, 8, and 16 K/min. Two distinct atmospheres were investigated: pure CO₂ and lean air (O₂/N₂) at oxygen partial pressures of 8.08·10⁻³ and 1.91·10⁻² bar. The Friedman isoconversional method revealed complex activation energy profiles for CO₂ decomposition, with apparent Eₐ ranging from 103.4 kJ/mol at α = 0 to over 500 kJ/mol at α > 0.72, and an average Eₐ of 226.9 ± 18 kJ/mol (R² = 0.984). A four-stage kinetic model was developed for each atmosphere, validated through rigorous statistical analysis. For CO₂ decomposition, six reaction models were tested for the fourth stage (reverse Boudouard reaction), and Fisher-Snedecor F-test analysis at 95% confidence interval identified Avrami-Erofeev (An), autocatalytic (Cn), Šesták-Berggren (SB), and reversible nth-order (FnR) models as statistically equivalent, while contracting geometry models (R2, R3) were rejected. The optimized CO₂ model using An functions achieved R² = 0.999, with activation energies of 65.8, 141.7, 214.8, and 293.9 kJ/mol for moisture evaporation, organic matter decomposition, carbonate decomposition, and char gasification stages, respectively. For O₂/N₂ atmosphere, pressure-dependent kinetics were successfully modelled with power-law functions, revealing pressure exponents of 0.216 and 1.507 for the primary and secondary oxidation stages (R² = 0.999). This multi-atmosphere approach provides validated kinetic parameters essential for reactor modelling and CFD simulations of waste bone gasification processes.