bio-FLASHCHAIN® theory for rapid devolatilization of biomass. 10. Validations for agricultural residues

Abstract

This study further validates a reaction mechanism called bio-FLASHCHAIN® to simulate the rapid primary devolatilization of any agricultural residue (AgRes) at any operating conditions. The evaluations cover 42 residues with alkali and alkaline earth metal (AAEM) levels to 2.8 dry wt. % at temperatures from 200 to 1050 °C; heating rates from 1 to 5000 °C/s; contact times to 1800 s; and pressures from vacuum to atmospheric. Collectively, the test data cover the yields and elemental compositions of oils and char and the yields of CO, CO₂, H₂O, and H₂. Bio-FC™ accurately simulates complete product distributions over this domain and correctly depicts how variations in heating rate, temperature, contact time, pressure, and AAEM loading shift these distributions. Proximate and ultimate analyses, the percentages of cellulose, hemicellulose, and lignin, and AAEM loadings are required input.

This study demonstrates, for the first time, accurate extrapolations across nearly the entire range of heating rates in the target commercial applications, based on two independent kinetic aspects. First, the placement of a devolatilization history in temperature is determined by the absolute rates of depolymerization and charring for each major component in the biomass; and, second, differences in ultimate yields for multiple heating rates scale on the ratios of the rates of depolymerization and charring. The interpretations for two disparate heating rates each for four AgRes gave activation energies for both depolymerization and monomer decomposition that varied by 50 – 60 kJ/mol in each of the major components, in stark contrast with the uniform energies used to previously interpret wood devolatilization.