Application of distributed activation energy model to predict hydrothermal carbonization kinetics of lignocellulosic biomass

Abstract

Hydrothermal carbonization (HTC) has been established as one of the most promising techniques for producing biofuels from high moisture containing organic samples such as, biomass. However, limited progress is observed in terms of the kinetic modeling of this process. Existing kinetic models involve mechanistic and experimental shortcomings due to the nature of the non-isothermal and isothermal subsequent steps involved in the process. To address these limitations, a distributed activation energy model (DAEM) was applied to predict HTC kinetics of lignocellulosic biomass. The DAEM considered the non-isothermal temperature profile of the reactor to account for the considerable devolatilization taking place during the transient step of heating. A micro-kinetic reactor was fabricated to facilitate kinetic experiments to estimate the DAEM parameters- mean activation energy, standard deviation, and pre-exponential factor. These parameters were found to be 96.03 kJ mol−1, 3 kJ mol−1, and 5 × 108 s − 1 respectively, based on experiments at final HTC temperatures of 190 °C and 210 °C for lignocellulosic biomass. Furthermore, the parameters were used to accurately predict HTC kinetics at 230 °C using the estimated parameters at 190 °C and 210 °C. The obtained results would be valuable inputs for reactor design and large-scale simulations for HTC of lignocellulosic biomass.

Keywords

• Hydrothermal carbonization
• Kinetic modeling
• DAEM
• Lignocellulose
• Biomass
• Hydrochar