Mg‐Silicate Carbonation Based on an HCl‐ and NH3‐Recyclable Process: Effect of Carbonation Temperature

A new indirect mineral carbonation process is studied which could mitigate anthropogenic CO2 emissions. In this process, magnesium silicate is dissolved in HCl and the resulting MgCl2 solution is subsequently reacted with CO2 in NH3. HCl and NH3 are recovered from NH4Cl in a two‐step thermal decomposition. Carbonation is investigated from 30 °C to 180 °C at 4 MPa CO2 pressure and Mg‐carbonate morphology transformations with increasing temperature are identified. Nesquehonite (MgCO3 · 3H2O) is obtained below 70 °C, hydromagnesite (Mg5(CO3)4(OH)2 · 4H2O) is formed at 100 °C, and further temperature increase to 180 °C leads to magnesite (MgCO3) precipitation. Nesquehonite and magnesite can fix more CO2 per mole Mg than hydromagnesite.