A multi-step predictive model for the release and transformation of K-Cl-S-containing species from biomass

The release of inorganic elements, especially K, Cl, and S, can cause severe damage to biomass conversion devices, such as slagging, fouling, or corrosion. A predictive model for the release of K-Cl-S elements can be used to enhance the design and operating conditions of biomass conversion devices. In this study, a detailed model is developed that includes 12 solid species and 13 reactions, which can represent the main pathways of the release of K-Cl-S from the particle. The model is coupled to a particle model to predict the release of potassium from different types of biomass at various operating conditions. First, the types and solubility of the potassium after pyrolysis and combustion at different temperatures are compared with the experimental data from the literature. The model predictions of the H₂O-soluble, NH₄AC-soluble, stable, and total potassium are comparable to the experimental data. Second, the K, Cl, and S in two types of biomass with high and low Si content are studied and compared with the experimental data. The model is used to explain different stages of potassium, sulfur, and chlorine release, which were observed in the experiments. Finally, the concentration of gas-phase potassium-containing species, i.e., atomic K, KCl, and KOH, downstream of burning biomass particles at different temperatures are investigated and compared with experimental measurement. The model can capture the release behavior of these species at different temperatures with good accuracy. The model results are summarized to create a clearer picture of the pathways of K-Cl-S-release from biomass and their interactions with other ash elements.