Colloquia

Summary

Increasing carbon dioxide (CO2) concentrations in the atmosphere necessitate efficient carbon capture strategies. Core-shell hydrogel particles are amine-based solid sorbents that can be applied in a chemical reactor to capture CO2 with a high capacity in a wide range of environments. Furthermore, they show low degradation, are mass manufacturable, and tunable in size and composition. Freeze-drying these particles creates a porous hydrogel core, which promotes the CO2 uptake. When these particles are steamed, water enters the pores, which enhances the CO2-amine reaction. Due to the water content, the steamed particles can only be applied in a fixed bed reactor. The dry particles can be used in a fluidized bed reactor, which has improved heat and mass transfer. A deeper understanding of these particles within their respective reactors is required to optimize their implementation. In this study, coupled particle-reactor models were developed to evaluate the spatio-temporal sorption behavior of steamed and dry particles in their corresponding reactor. These models take into account the diffusion-reaction behavior on the particle scale, and the imposed hydrodynamic and mass transfer effects on the reactor scale. The models enable: 1) observation of the diffusion-reaction dynamics at both particle and reactor scale; 2) investigation on the influence of particle and reactor parameters on the sorption behavior; 3) identification of major mass transfer resistances. On a particle-scale, the steamed particles outperformed the dry particles both in terms of equilibrium capacity and sorption speed. Increasing the reactor height led to CO2 concentration differences in particles at the bottom and top of the reactors, showing sub-optimal utilization at the top. Therefore, increasing the reactor height for industrial applications is recommended, as long as the inlet gas velocity is increased accordingly to ensure a sufficient gas distribution throughout the reactors. The sorption behavior of the steamed and dry particles on a reactor scale was mostly similar to that of the particle models, as the internal resistance in the particles was dominant compared to the resistances imposed by the reactors. Therefore, future work should focus on optimizing the steamed and dry particles to reduce their internal resistance. Overall, this research enhances the understanding of the diffusion-reaction dynamics of core-shell hydrogel sorbents at both particle and reactor scales, providing insights and guidelines for its further design and implementation.