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

Abstract

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 (QT) as hydraulic loading on CaCO3 granulation efficiency were investigated. In the study, S was varied from 10.2 to 10.8 and QT 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 QT 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.