Reconsidering the potential of micropyrolyzer to investigate biomass fast pyrolysis without heat transfer limitations

Commercial analytical pyrolysis systems have become increasingly used in biomass fast pyrolysis research. Establishing experimental conditions free from heat transfer limitations using these micro-rectors has not been verified. Since accurate measurement of biomass sample temperature with these devices is not possible, the isothermal character of experiments has never been verified. In this work, numerical simulations were conducted to assess the time-temperature history of both cup and different sample arrangements and to determine the overall heat transfer coefficients at the surface of the biomass samples to confirm the pyrolysis regime based on the dimensionless analysis in the micropyrolyzer. Using both a small mass of biomass sample (<= 50 mu g) carefully arranged at the bottom of the cup and a temperature below 723 K allows the complete elimination of heat transfer limitations within the micropyrolyzer. The heating time of the biomass sample was significant (4-5 s to reach 773 K), proving that the experiment is not isothermal. Thus, evaluating the kinetics of biomass fast pyrolysis requires establishing the time-temperature history of the sample, as an essential prerequesite. Both heating profiles of biomass samples arranged in thin-film and torus were found to follow that of the cup; the timetemperature history of the sample can be determined by measuring the temperature of the cup.

Automated summary

Commercial analytical pyrolysis systems are widely used in biomass fast pyrolysis research, but the experimental conditions free from heat transfer limitations have not been verified. Numerical simulations were conducted in this study to analyze the time-temperature history and heat transfer coefficients of biomass samples in micro-rectors, confirming the pyrolysis regime. The study provides a method to evaluate the kinetics of biomass fast pyrolysis.