Kinetic modelling of waste wood devolatilization during pyrolysis based on thermogravimetric data and solar pyrolysis reactor performance

• Kinetic analysis of waste wood pellets modelling addressing solar pyrolysis products formation was presented. • TGA profiles were used in isoconversional, model-free analysis to provide initial parameters for kinetic model. • Generalised master plot methods proved deaccelerating character of wood pyrolysis obeying diffusion, contracting geometry and order based models. • Predicted reaction rates were compared with gas analyser indications obtained during solar pyrolysis experiments. • Novel approach to kinetic modelling of pyrolysis was presented and compared to three pseudo-component model results. • Validation of established models were preformed based on kinetic predictions of feedstock behaviour at heating rate of 30 K/min. Within presented paper complex kinetic analysis of waste wood solar pyrolysis with fuel characterisation has been presented. Thermogravimetric (TGA) data were obtained for heating rates denoted in solar pyrolysis experiments: 5, 10, 15 and 20 K/min. Study presents alternative approach to lignocellulosic biomass kinetics using NETZSCH Kinetics Neo (v. 2.1.2.2) software. TGA data were enriched with the gas analyser indications and experiments results from solar pyrolysis examined on self-designed laboratory reactor. Presented methodology consisted of (1) isoconversional analysis: Friedman, Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall analysis yielding apparent activation energies Eα, varying from 185.37 to 375.56 kJ/mol at reaction extent 0.1–0.9, (2) reaction model identification with generalised master plot method which showed that decomposition was driven by three-dimensional diffusion (D3) with transition to three-dimensional phase boundary (R3) and reaction order based models (F1,F2,Fn) at the end of conversion. Finally, (3) kinetic model construction was performed based on experiments observations, resulting in modelling of 3 main reactions of pyrolysis products formations. The most intensive condensable release was observed between 250 and 440 °C what correlated with CO 2 release described by dominant two-step D3-F2 consecutive reaction with activation energies and logarithmic pre-exponential factors 159.92 kJ/mol, 10.44 log(1/s) and 256.78 kJ/mol, 19.05 log(1/s) for first and second step respectively. CO formation obeyed R3 reaction mechanism with activation energy 181 kJ/mol and pre-exponential factor 12.16 log(1/s). Last stage of pyrolysis, charring, was described by two-step consecutive reaction Fn(n = 3.463)-F2 resulting in formation of CH 4 and H 2 with activation energies and pre-exponential factors of 249.72 kJ/mol, 15.87 log(1/s) and 162 kJ/mol, 6.61 log(1/s) respectively. Kinetic models and isoconversional methods results were tested using Fisher-Snedecor test. Presented methodology was compared with traditional three pseudo-component wood pyrolysis model and discussed.