Kinetic Characterization of Barley Straw Carbonization Using the Distributed Activation Energy Model (DAEM)

As a part of modeling the production process of activated biocarbon from barley straw, a model of the initial pyrolysis or carbonization stage was developed. Material samples were divided into five particle size ranges and pyrolyzed in a thermobalance at 900 °C under a nitrogen atmosphere with five different constant heating rates. For the modeling, after a brief review of the possible strategies, the Distributed Activation Energy Model (DAEM) was chosen as the most adequate. In particular, the distribution-free variant proposed by Miura and Maki was applied, allowing the activation energy distribution and the pre-exponential factor to be directly derived from experimental data without assuming a predefined analytical form for the energy distribution. The model implementation incorporates a new approximation for the temperature integral and uses five heating rates instead of the customary three. All this results in greater accuracy and detailed characterization, previously unavailable, of a widespread biomass material. A full description of the model hypotheses and procedures is given, and the results are discussed in detail, showing good agreement between experimental data and model predictions. Perspectives for the generalized use of the model, e.g., in CFD contexts, are also discussed, highlighting its robustness and computational efficiency for engineering applications.