Effect of processing temperatures on decarbonisation of calcium carbonate in sodium hydroxide solutions at ambient conditions

Abstract The CO2 released upon calcination of limestone (process CO2 and combustion CO2) accounts for the largest portion of the emissions from the cement manufacturing industry. Our previous works highlighted the possibility for a no-combustion decarbonisation of CaCO3 through reaction with NaOH solutions to produce Ca(OH)2 at ambient conditions, while sequestrating the process CO2 in a stable mineral Na2CO3∙H2O/Na2CO3. In this study, the effect of temperature was assessed within the range of 45–80°C, highlighting a higher impact at short residence times. The proportioning of the precipitated phases Na2CO3∙H2O /Na2CO3 was also assessed at varying conditions, and the data was supported with related simulation. Experiments performed on targeted CaCO3:NaOH:H2O compositions also allowed for the detection of the Arrhenius parameters characterising each ternary system. An increasing activation energy (Ea) was found to be correlated to lower NaOH concentrations initially reacting with CaCO3. The present work offers a further understanding of the effect of temperature on the process with the potential to minimise the GHG emissions from cement and lime industries, and correctly assess eventual industrial applicability.