Beyond carbon capture towards resource recovery and utilization: fluidized-bed homogeneous granulation of calcium carbonate from captured CO₂

Atmospheric carbon dioxide (CO₂) imbalance due to anthropogenic emissions has direct impact in climate change. Recent advancements in the mitigation of industrial CO₂ emissions have been brought about by a paradigm shift from mere CO₂ capture onto various adsorbents to CO₂ conversion into high value products. The present study proposes a system which involves the conversion of CO₂ into high purity, low moisture, compact and large CaCO₃ solids through homogeneous granulation in a fluidized-bed reactor (FBR). In the present study, synthetic solutions of potassium carbonate (K₂CO₃) and calcium hydroxide (Ca(OH)₂) were used as sources of carbonate and precipitant, respectively. The effects of the degree of supersaturation (S) as chemical loading and influx flow rate (Q_T) as hydraulic loading on CaCO₃ granulation efficiency were investigated. In the study, S was varied from 10.2 to 10.8 and Q_T from 40 to 80 mL min⁻¹ while the operating pH and calcium-is-to-carbonate molar ratio ([Ca²⁺]/[CO₃²⁻]) were set at 10 ± 0.2 and 1.50, respectively. Results showed that carbonate ions end product distribution had a highest carbonate granulation efficiency at [Carbonate]_G of 95–96% using S of 10.6 and Q_T of 60 mL min⁻¹. Characterization of the granules confirmed high purity calcium carbonate. Overall, the transformation of industrial CO₂ emissions into a valuable solid product can be a significant move towards the mitigation of climate change from anthropogenic emissions.