Search

Within the presented paper, different approaches to determine kinetic reaction models governing pyrolysis of three waste biomass types: waste wood (WW), waste straw (WS) and sewage sludge (SS) based on 5 dynamic heating runs (5, 10, 20, 30, 40 K/min) at TGA are presented and discussed. Fuel properties with lignocelluloses content of the investigated feedstock are presented and discussed. Ambiguous results of the generalized master-plot method draw the idea of determining actual reaction models using the isoconversional methodology. Friedman method provided apparent activation energies as a root for further calculations being the 48.1–294.3 kJ/mol for WS, 21.0–361.9 kJ/mol for WW and 58.1–484.3 kJ/mol for SS. Isoconversional pre-exponential factors were determined using linear compensation effect and were 7.2·106–1.8·1021 1/min, 1.6·104–1.2·1025 1/min, and 1.5·109–3.2·1030 1/min for WS, WW, and SS respectively. Based on isoconversional parameters, actual profiles of reaction models were estimated using the t-Students distribution for 95% confidence intervals and verified in the modelling of pyrolysis conversion profiles. Isoconversional pyrolysis models resulted in fitting to experimental profiles with non-linear coefficients of determination equal to 0.9912, 0.9876, and 0.9406 for WW, WS, and SS respectively. • Isoconversional f(α) for pyrolysis of WW, WS and SS are estimated for dynamic TGA. • A α were determined using compensation effect and E α with Friedman method. • Isoconversional kinetics resulted in fitting with R 2 0.99, 0.99, and 0.94. [ABSTRACT FROM AUTHOR]

Biomass pyrolysis is a fundamental thermal conversion method that has both industrial and economic potential. A deep knowledge of the pyrolysis character can give dramatically rise to the general development of thermal conversion methods for the effective use of biomass fuel in the incoming future. In this work, kinetic parameters estimation methods and methodology for sewage sludge pyrolysis has been presented. Special emphasis was put into combined use of the latest isoconversional methodology and model-fitting kinetics. The kinetic parameters estimation was based on a series of experiments using thermogravimetric analysis carried out for heating rates 20, 30 and 40 K/min. Complimentary use of model-based and isoconversional approach along with statistical analysis of both methods results has been presented. The proposed methodology, based on Friedman isoconversional kinetic parameters, E α 31.4–244.9 kJ/mol and A α 1.17–14.4 log(1/s), as initial guess values for optimization resulted in 10 independent reactions kinetic model, evaluating sewage sludge pyrolysis with R2 > 0.999 with activation energies E ∈ < 30.34; 259.7> kJ/mol, pre-exponential factors A ∈<1.17; 22.49> log(1/s) and reaction orders n ∈<1.17; 3>. Isoconversional methodology resulted in excellent conversion rate and mass loss fit while the order-based kinetic model simultaneously gave insight into theoretical 10 elementary sludge decomposition rates. Image 1 • Combined isoconversional and model-based approach is used to simulate SS pyrolysis. • Friedman differential method provided initial values for kinetic computations. • 10 Independent Reaction model parameters were optimized using least-squares method. • The proposed methodology resulted in modeling of SS pyrolysis with R2 > 0.999. [ABSTRACT FROM AUTHOR]

Biomass pyrolysis is a fundamental thermal conversion method that has both industrial and economic potential. A deep knowledge of the pyrolysis character can give dramatically rise to the general development of thermal conversion methods for the effective use of biomass fuel in the incoming future. In this work, kinetic parameters estimation methods and methodology for sewage sludge pyrolysis has been presented. Special emphasis was put into combined use of the latest isoconversional methodology and model-fitting kinetics. The kinetic parameters estimation was based on a series of experiments using thermogravimetric analysis carried out for heating rates 20, 30 and 40 K/min. Complimentary use of model-based and isoconversional approach along with statistical analysis of both methods results has been presented. The proposed methodology, based on Friedman isoconversional kinetic parameters, E α 31.4–244.9 kJ/mol and A α 1.17–14.4 log(1/s), as initial guess values for optimization resulted in 10 independent reactions kinetic model, evaluating sewage sludge pyrolysis with R2 > 0.999 with activation energies E ∈ < 30.34; 259.7> kJ/mol, pre-exponential factors A ∈<1.17; 22.49> log(1/s) and reaction orders n ∈<1.17; 3>. Isoconversional methodology resulted in excellent conversion rate and mass loss fit while the order-based kinetic model simultaneously gave insight into theoretical 10 elementary sludge decomposition rates. Image 1 • Combined isoconversional and model-based approach is used to simulate SS pyrolysis. • Friedman differential method provided initial values for kinetic computations. • 10 Independent Reaction model parameters were optimized using least-squares method. • The proposed methodology resulted in modeling of SS pyrolysis with R2 > 0.999. [ABSTRACT FROM AUTHOR]

• 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. [ABSTRACT FROM AUTHOR]