Evaluation of Arrhenius-type overall kinetic equations for hydrothermal carbonization

- The fitting capacities of different Arrhenius-type equations, derived from the coalification model, for hydrothermal carbonization (HTC) was evaluated.
- Comparisons with other reference models revealed that the dose-response curve is the most accurate for HTC data.
- A method to predict HTC data is proposed and validated.

An Arrhenius-type overall kinetic equation was used to model hydrochar mass yield, carbon and oxygen content of hydrothermal carbonization experiments. The equation is based on the coalification model, which was earlier published, and is based on the assumptions of Arrhenius temperature behaviour. A dataset of 29 feedstock biomasses from previous studies was collected to evaluate the performance of the equation. The lowest mean absolute error (MAE) in the temperature range of 200-330 °C was found for hydrochar yield to be 1.76%, carbon content 1% and oxygen content 1.01%, respectively. It was demonstrated that not all parameters of the equation need to be specified for every feedstock. Based on this fact, a method to predict the outcome of HTC based on the lignin content of a feedstock was proposed and validated. Comparisons to other equations were performed, and the results revealed that a dose-response curve was the most accurate model for representing the experimental data.